THE KINETICS OF HYDRODEMETALLATION
OF
METALLOPORPHYRINS
BY
CHI-WEN HUNG
B. Ch. E., National Taiwan University
(1974)
Submitted in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy
at the
Massachusetts Institute of Technology
August, 1979
-I
signature of Author
Department of Chemical Engineering
August, 1979
Certified by
James Wei, Thesis Supervisor
Accepted by
G. C. Williams, Chairman, Departmental
Committee on Graduate Thesis
ARCHIVES
OF
2i:cf ncY
LIBRARIES
THE KINETICS OF HYDRODEMETALLATION
OF
METALLOPORPHYRINS
BY
CHI-WEN HUNG
Submitted to the Department of Chemical Engineering
on August
3
1979 in partial fulfillment of the
,
requirements for the Degree of Doctor of Philosophy.
ABSTRACT
The kinetics of hydrodemetallation of nickel etioporphyrin I (Ni-Etio),
nickel tetraphenylporphine
(Ni-TPP), and vanadyl etioporphyrin I (VO-Etio)
have been studied in batch autoclave experiments, with white oils as
solvents, and CoO -MoO 3 /Al 2 03 as catalyst without presulfiding.
The effects of hydrogen pressure up to 12-500 KPa and temperature
between 287-357 C were studied.
Up to 90% metal removal,
described by fractional order kinetics.
the data can be
The activation energy is from
27-37 kcal/g mole, and the hydrogen pressure dependence is from 1.2-2.2
order.
Vanadium removal tends to have larger activation energy and smaller
hydrogen pressure dependence.
A few runs on mixed vanadyl and nickel etioporphyrins showed that
while the presence of vanadyl compounds will suppress the nickel removal
reaction,
the reverse is
less significant.
Few runs on free base etio-
porphyrin and tetraphenylporphine show that free base porphyrins quickly
disappear in the autoclave.
Catalyst with different propotion of cobalt and molybdenum have
been prepared to catalyze nickel etioporphyrin as reactants.
The result
.shows that order of impregnation has no effect on hydrodemetallation
activity, and MoO 3/Al
Thesis Supervisor:
2
0 3 catalyst is
more active than CoO/Al 2 0 3 catalyst.
James Wei
Professor and Department Head
of Chemical Engineering
ACKNOW:EDGEMENTS
I would like to express my appreciation and gratitude to my
advisor, Dr. James Wei, for the guidance and support given to me
over these years.
The useful discussion with Drs. Putnam,
Satterfield, and
Vayenas of the M.I.T. Chemical Engineering Department, and Dr. Peter
Hambright of Howard University are greatly appreciated.
My colleague, Rakesh Agrawal, has been of invaluable help to me.
I would also like to thank my friends for their helping hands and
advice regarding my research.
Cocchetto,
Among them are Kelvin Chew, Joe
Selahattin Gultekin, George Huff Jr., Jen-Jiang Lee, and
Cherng-Chiao Wu.
This work is dedicated to my parents, Dr. and Mrs. Tsu-Pei Hung,
and especially to my wife, Shu-Fang, for her assistance in typing the
manuscript and for her understanding and compassion.
-5TABLE OF CONTENTS
Page
1.
INTRODUCTION
18
2.
BACKGROUND AND LITERATURE SURVEY
21
2.1
Metal Compounds in Petroleum
2.1-1
2.1-2
2.1-3
2.2
3.
24
2.1-1.a
Porphyrins
24
2.1-1.b
Metalloporphyrins
27
Geochemistry of Porphyrins
35
35
2.1-2.a
Types of Porphyrins in Petroleum
2.1-2.b
Origin of Porphyrin and Metalloporphyrin
Nonporphyrin Metal Compounds
37
40
Hydrodemetallation Reaction
45
2.2-1
46
2.2-2
2.3
Properties of Porphyrins and Metalloporphyrins
21
Kinetics
2.2-1.a
Thermal Demetallation and Nonhydrogenative Demetallation
46
2.2-1.b
Hydrodemetallation
48
Deposition of Metals on Hydrodesulphurization
Catalysts
58
2.2-2.a
Concentration Distribution of Vanadium
and Nickel on Spent Catalysts
58
2.2-2.b
Amount of Deposition
61
2.2-2.c
Catalyst Aging
62
2.2-2.d
Distribution along the Reactor Bed
64
Research and Development on Metal Removal Processes
MATERIALS AND EXPERIMENTAL PROCEDURES
66
69
3.1
Equipment for Hydrodemetallation Study
69
3.2
Materials
77
3.2-1
Catalyst
77
3.2-2
Solvent
85
3.2-3
Gas
85
3.2-4
Model Porphyrins and Metalloporphyrin; Com-pounds
87
-6Table of Contents (cont'd)
3.3
3.4
Experimental Procedures
90
3.3-1
Dissolving Model Compounds in Nujol
90
3.3-2
Pretreatment of Catalyst
94
3.3-3
Demetallation Experiment
94
3.3-4
Self Preparation Catalyst
98
101
Analysis
3.4-1
Liquid Sample
101
3.4-2
Solid Sample
107
3.4-3
Gas Sample
107
109
4. RESULTS
4.1
Page
Nickel Porphyrin Runs for Commercially Available HDS 9A
109
or HDS 16A Catalyst
4.1-1
4.1-2
4.2
Air Prepared Ni-TPP Runs
109
4.1-l.a
General Observations
109
4.1-1.b
Kinetics
112
4.1-1.c
Catalyst Effects
117
Helium Prepared Nickel Porphyrin Runs
124
4.1-2.a
General Observations
124
4.1-2.b
Kinetic Order
129
4.1-2.c
Catalyst Effects
135
Vanadyl Porphyrin Runs
140
4.2-1
General Observations for VO-Etio Runs
140
4.2-2
Kinetic Order
144
4.2-3
Catalyst Effects
148
4.3
Free Base Porphyrin Runs
149
4.4
Mixed Nickel and Vanadyl Porphyrin Runs
152
4.4-1
General Observations
152
4.4-2
Kinetics
152
-7Page
Table of Contents (cont'd)
4.5
5.
162
Self Preparation Catalyst Runs
4.5-1
General Observations
162
4.5-2
Effect of Cobalt or Molybdenum on Demetallation
Activity of Ni-Etio
166
170
DISCUSSION OF RESULTS
5.1
170
Diffusion Effects
5.1-1
Nickel Porphyrin Runs
170
5.1-2
Vanadyl Porphyrin Runs
174
5.1-3
Mixed Ni-Etio and VO-Etio Runs
175
5.2
Hydrogen Consumption
178
5.3
Intermediates and Products in Liquid Phase
180
5.3-1
Intermediates
180
5.3-2
Products
189
5.4
5.5
192
Intermediatea and Products on Catalyst
5-4-1
Intermediates
192
5.4-2
Products
192
Discussion on Kinetic Model and Possible Mechanism
19
5.5-1
Background
199
5.5-2
Results and Discussion
205
5.6
Catalyst Deactivation
218
5.7
Comparison among Nickel Runs
219
5.7-1
Between Air Prepared Ni-TPP and Helium Prepared
219
Nickel Porphyrin Runs
5.7-2
Comparison between Helium Prepared Ni-TPP and
220
Ni-Etio Runs
5.7-3
5.8
5.9
Comparison between CoO-MoO3 /A
Catalysts for Ni-Etio Runs
2 03
and NiO-MoO /Al 2 0
223
Comparison between Nickel and Vanadyl Porphyrin Runs
227
Comparison between Individual Ni-Etio, VO-Etio Runs
229
and Mixed Ni-Etio, VO-Etio Runs
-8Table of Contents (cont'd)
6.
Page
5.10
Comparison with Previous Work
231
5.11
Differentiating between Two First-Order Reactions and
a Single Second-Order Reaction
235
CONCLUSIONS AND SUGGESTIONS
247
6.1
Conclusions
247
6.2
Suggestions
250
7.
BIBLIOGRAPHY
252'
8.
NOMENCLATURE
266
APPENDIX
Experimental Data
268
-9LIST OF FIGURES
Number
Title
Page
2-1
Nomenclature of Porphyrin System
25
2-2
The UV-Visible Absorption Spectrum (in CH Cl 2 ) of Etioporphyrin-I and DPEP (Deoxophylloerythroe ioporphyrin).
(Alturki et al. (1971)).
28
2-3
Visible Spectra of Porphyrins: (a)
30
-Phylloporphyrin
XV;
(b) Etioporphyrin I; (c) Rhodoporphyrin XV; (d) Deoxophylloerythroetioporphyrin. (Baker et al. (1978)).
2-4
Absorption Spectra for DPEP (Deoxophylloerythroetioporphyrin) Type of Vanadyl Porphyrin (Top),
Porphyrin (Bottom).
33
and Nickel
The curves that show Soret band
peaks have been diluted from the others that show visible
peaks.
(Hodgson, et al. (1967)).
2-5
Absorption Spectra for Nickel Etioporphyrin I (Top) and
Vanadyl Etioporphyrin I (Bottom).
Samples were Dissolved
in Nujol First and Then Diluted by Xylene. Background:
Xylene.
34
2-6
Scheme for The Transformation of Chlorophyll Qk to Stable
Vanadyl Porphyrins.
38
2-7
41
Examples for Nonporphyrin Metal Compounds: (1) Highly
Aromatic Porphyrin Chelates; (2) Porphyrin Decomposition
Ligands, (Metals will Fill Up to the Center); and (3) Simple
Complexes from Resin Molecules. (Yen (1975)-(a)).
2-8
Cross Sectional View of an Asphaltene Model.
2-9
Defect Site in an Aromatic Sheet of the Asphaltene
Structure. (Yen (1974)).
2-10
Qualitative Changes in Asphaltenes and Surrounding
49
Resins During HDS Processing. (Beuther and Schmid (1963)).
2-11
Sulphur Removal Versus Nickel Removal and Vanadium
Removal for Several Vacuum Gas Oil.
(Yen (1977)). 43
43
56
(Massagutov et al.
(1967)).
2-12
Concentration Profile of Vanadium and Nickel on the
Desulphurization Catalyst after 50hrs Reaction.
(Sato et al. (1971))
60
-10-
List of Figures (cont'd)
Title
Number
Page
2-13
Concentration Profile of Carbon, Vanadium, and Nickel
(Sato et al. (1970)).
Along with the Reactor Bed.
65
3-1
Schematic of High Pressure Autoclave Reactor System for
Hydrodemetallation Study.
70
3-2
Autoclave Batch Reactor System.
71
3-3
List of Components for Figure 3-2.
72
3-4
Schematic of Main Body of 1-Liter Autoclave.
73
3-5
Schematic of Catalyst Loader and Porous Filter.
75
3-6
Pore Size Distribution for HDS-16A CoO-MoO 3 /Al 2 03
Catalyst.
80
3-7
Pore Size Distribution for HDS-9A Ni0-Mo0 /Al 2 03
82
Catalyst.
3-8
Pore Size Distribution for VI-Alumina Catalyst Carrier.
84
3-9
Structure of Model Compounds: (1) TPP; (2) Etio-I;
(3) Ni-TPP; (4) Ni-Etio I; (5) VO-TPP; (6) VO-Etio I.
88
3-10
Structures of Chlorins (TPP type).
89
3-11
Apparatus for Removing Air from Nujol.
92
3-12
Apparatus for Dissolving Model Compounds in Nujol.
93
3-13
Absorption Spectra of Ni-TPP and VO-TPP.. Samples were
Dissolved in Nujol First and then Diluted by Xylene.
Background: Xylene.
103
3-14
Absorption Spectra of Free Base Etio I and Free Base TPP.
Samples were Dissolved- in Nujol First and then Diluted by
Xylene. Background: Xylene.
104
-11-
List of Figures (cont'd)
Title
Number
Page
3-15
Soxhlet Extraction Apparatus.
108
4-1
Dependence of Noncatalytic Disappearance of Air Prepared
Ni-TPP on the Operating Temperature.
113
4-2
First 'Order Plot for Air Prepared Ni-TPP Run (Run NT4).
114
4-3
First Order Plot for Air Prepared Ni-TPP Run (Run NT6).
115
4-4
Arrhenius Plot for Air Prepared Ni-TPP Runs.
118
(6995 1Pa
Hydrogen, Oil/Catalyst=650 cc/g).
4-5
Effect of Catalyst on Air Prepared Ni-TPP Hydrodemetallation Reaction.
119
4-6
The Dependence of First Order Rate Constant in Fast
121
Reaction Region on the Oil/Catalyst Ratio. (Run NT6-
NT9).
4-7
The Relationship between the Amount of Nickel Deposited
122
on the Catalyst when the Shift from Fast Region to Slow
Reaction Region Occurs and the Oil/Catalyst Ratio.
4-8
(a) Zero Order Plot; (b) First Order Plot; (c) Second
Order Plot; (d) Half Order Plot for Run NEY4.
130
4-9
Effect of Temperature on Half Order Rate Constants for
Nickel Porphyrin Disappearance Rate. P: 6995 IPa
H2'
133
4-10
Effect of Temperature on Half Order Rate Constants for
Total Nickel Removal Rate. P: 6995 KPa H2'
134
4-11
Pressure Dependence of Half Order Rate Constants.
T: 3160C. (Ni-Etio Runs).
136
4-12
Comparison between Hydrodemetallation (NEll) and Nonhydrogenative Demetallation (NE16H) Reaction.
137
4-13
Effect of Catalyst on Hydrodemetallation Reaction.
139
-12List of Figures (cont'd)
4-14
Page
Title
Number
Comparison of Vanadium and Nickel Runs (Run VE8 and
142
Run NE18) over Alumina Support.
4-15
Comparison of Vanadium and Nickel Runs (Run VE9H, NE16H,
143
and NT18H) under Helium Pressure.
4-16
Half Order Plot for VO-Etio Run.
4-17
Effect of Temperature on Half Order Rate Constants for
VO-Etio Runs.
4-18
(Run VE3).
145
P: 6995 KPa.
Pressure Dependence of Half Order Rate Constants for
VO-Etio Runs.
146
147
T: 316 0 C.
4-19
Half Order Plot for Mixed VO-Etio and Ni-Etio Run. (Run
NVE5).
154
4-20
Half Order Plot for Mixed VO-Etio and Ni-Etio Run. (Run
156
NVE3).
4-21
Dependence of Half Order Rate Constants on the Ratio
of Ni-Etio and VO-Etio Initial Concentrations.
157
T:316 C;
P: 6995 KPa.
4-22
Absorption Spectra of Mixed VO-Etio and Ni-Etio Run.
(Run NVE2). Top: Fresh Sample. Bottom: Sample Collected
1.6 hrs after Injection of Catalyst. All were Diluted
by Xylene.
158
4-23
Effect of Temperature on Half Order Rate Constants for
Mixed VO-Etio and Ni-Etio Runs. P: 6995 KPa; C /CNo
2.12.
159
4-24
Pressure Dependence of Half Order Rate Constants in Mixed
Ni-Etio and V-Etio Runs. T: 316 C; C vo/CNio: 2.11.
161
4-25
Effect of Molybdenum on Half Order Rate Constants of
167
Ni-Etio Runs.
4-26
Dependence of Half Order Rate Constants on Cobalt Addition
for Ni-Etio Runs.
168
-13List of Figures (cont'd)
5-1
Page
Title
Number
Scanning Electron X-Ray Microanalyzer Indication of
Nickel Distribution for Spent Catalyst of Run NT25,
172
and Fresh Catalyst.
5-2
Weight Percent of Nickel Deposited on the Designated
Spots of the Catalyst Pellet Described in Figure 5-1.
173
5-3
Scanning Electron X-Ray Microanalyzer Indication of
Vanadium Distribution for Spent Catalysts of Run VE3,
176
and Run VT1.
5-4
5-5
Weight Percent of Vanadium Deposited on the Designated
Spots of the Catalyst Pellets Described in Figure 5-3.
177
Indication of Intermediates (Run NE14): (Left): Plot
181
of Concentration Difference between Total Nickel and
(
Ni-Etio -Versus Time. (Right): Plot of Absorption
Arbitary Unit) of 6 16nm Peak Versus Time.
5-6
Absorption Spectrum of Ni-TPP and Ni-Etio During Reaction. 182
For Run NT20, and NE14.
5-7
Absorption Spectrum of VO-TPP and VO-Etio During Reaction. 184
For Run VT1 , and VE3.
5-8
Color Pictures of Ni-Etio Sample (NE14), and VO-Etio
Sample (VE3).
185
5-9
Color Pictures of Ni-TPP Sample (NT15), and VO-TPP
Sample (VT3).
186
5-10
Temperature Dependence of k, K1 , and Kp for Ni-Etio Runs.
206
5-11
Temperature Dependence of k, K 1 , and Kp for VO-Etio Runs.
207
5-12
Experimental and Theoretical Concentration Versus Time
Data for Run NE4.
209
5-13
Experimental and Theoretical Concentration Versus Time
Data for Run VE3.
210
5-14
Comparison between Experimental Data and Theoretical
Values of Spent Oil Run. (NE15).
215
-14-
List of Figures (cont'd)
Title
Number
Page
5-15
Comparison between Air Prepared Ni-TPP Run (NT6) and
Helium Prepared Ni-TPP Run (NT20).
222
5-16
The Range of Parameter Values of A and B Suitable for
239
Two First Order Kinetics to Simulate Second Order
Kinetics, and the Dependence on Conversion Level.
5-17
The Range of Parameter Values of A and B Suitable for
Two First Order Kinetics to Simulate Second Order
Kinetics, and the Dependence on Conversion Level.
240
(In Log-Log Scale).
5-18
The Dependence of~b(Minimum of
m
) and A on E (Con-
241
version).
5-19
The Dependence of B and kN on E (Conversion).
242
5-20
Comparison between Concentration D, Obeying Second
Order Kinetics, and Two First Order Kinetics, Cf and C
244
-15LIST OF TABLES
Number
Title
Page
2-1
Distribution of Trace Elements in Components of
California Crude Oil. (Filby, (1975)).
22
2-2
Distribution of Nickel and Nickel Porphyrin.in Crude
Oil Fractions. (Filby, (1975)).
23
2-3
Structures of Selective Porphyrins of The Four Basic
29
Types. (Baker and Palmer (1978)).
2-4)
Molecular Weight of Homologues Series of Porphyrins.
36
2-5
Kinetic Order, Activation Energy, and Rate Constants
for Thermal Demetallation of Vanadium and Nickel in
Residual or Crude Oils.
47
2-6
Summary of Previous Studies on Kinetics of Catalytic
52
Hydrodemetallation.
3-1
List of Major Components in Figure 3-4.
74
3-2
Physical and Chemical Properties for American Cyanamid
79
HDS 16A CoO-MoO3 /Al 2 03 Catalyst.
3-3
Physical and Chemical Properties for American Cyanamid
HDS 9A NiO-MoO3 /Al 2 03 Catalyst.
81
3-4
Physical and Chemical Properties for Norton SA-6273
83
Alumina Catalyst Carrier.
3-5
Specifications of Nujol.
86
3-6
Operating Conditions for Demetallation Experiments.
97
3-7
Absorption Peaks for Model Compounds.
105
3-8
Peaks Used for Quantitative Analysis.
105
4-1
Operating Conditions for Air Prepared Ni-TPP Runs.
110
-16List of Tables (cont'd)
Page
Title
Number
4-2
Operating Conditions for Each Nickel Rune
125
4-3
Reproducibility of Nickel Runs.
128
4-4
Dependence of Kinetic Order on Temperature and
Pressure.
132
4-5
Operating Conditions for Each Vanadium Run.
141
4-6
Operating Conditions for Free Base Porphyrin Runs.
150
4-7
Operating Conditions for for Mixed VO-Etio and Ni-Etio
153
Runs.
4-8
Composition of Self Preparation Catalysts.
163
4-9
Operating Conditions for Self Preparation Catalyst Runs.
164
4-10
Comparison between Self Preparation Catalysts and
Commercial Catalysts on Hydrodemetallation Activity
of Ni-Etio.
165
5-1
Duration of Each Sample Shown in Figure 5-8 and Figure
187
5-9.
5-2
Concentration of C, H, N, V, and Ni on Spent Catalysts
of Different Runs.
194
5-3
Metal
Rate Values (R ) as a Function of Initial
Initial
Concentration or Hydrogen Pressure for Ni-Etio Runs.
211
5-4
Initial
Rate Values (R
0
)
as a Function of Initial
Metal
213
Concentration or Hydrogen Pressure for VO-Etio Runs.
5-5
Comparison of Pseudo First Order Rate Constants of Air
Prepared Ni-TPP and Helium Prepared Ni-TPP Hydrodemetallation Runs.
221
5-6
Comparison between VO-Etio, Ni-Etio, and Ni-TPP Demetallation Runs.
225
-17List of Tables (cont'd)
Number
5-7
5-8
Title
Page
Comparison between CoO-MoO /Al
Catalysts for Ni-Etio Runs
2
03 and NiO-Mo0 /Al2 03
230
Comparison between Individual Ni-Etio, VO-Etio, and
Mixed Ni-Etio, VO-Etio Runs.
226
(Total Metal Removal).
5-9
Comparison of First Order Demetallation Rate Constants
between Previous Literature and This Study.
5-10
Values of A, B,0 , and K
version).
for a Given Value of G
(
Con-
232
243
-
1.
18-
Introduction:
Due to the shortage of crude oil supply, there has been a rapid
expansion in demand for upgrading residual oils in the past few years.
This tendency is expected to be continued in the years to come.
(Penick (1977),
Johnson et al. (1975)).
Although nearly half of the elements in the periodic table have
been identified in crude oils (Smith et al. (1959)),
are commonly the most abundant metals.
distillation,
substantially all
section (Nelson (1976)).
nickel and vanadium
During atmospheric or vacuum
of the metals are left
in the residual
The concentration of vanadium plus nickel in
residual oils ranges from less than 10 ppm (Such as Murban Crude) to
more than 1700 ppm (Boscan Crude from Venezuela), commonly they are
within the range of 30 to 200 ppm (Nelson (1976)).
With few exceptions,
there appears to be more vanadium than nickel in the residual oils.
(Yen (1975)-(a)).
As the presence of these vanadium and nickel compounds will cause
many problems during upgrading or burning of residual oils, they have to
be removed:
(1)
The metal compounds will react with hydrogen at the presence of
hydrodesulphurization (HDS)
(HDM) reaction.
catalyst in the so-called hydrodemetallation
The final metal sulfides will deposit on the catalyst
and deactivate the HDS catalyst.
While the initial deactivation of
-19-
HDS catalyst is due to coke deposition which can be removed by com-
bustion; the ultimate life of the catalyst is primarily controlled by
the irreversible deposition of metals.
(1975),
and McColgan and Parsons,
(Brunn et al. (1975), Newson
(1974)).
This results in higher
catalyst replacement rate, larger reactors, and higher temperature of
HDS operation (Hastings et al.
(1975)).
In addition to these, higher
hydrogen pressure, lower space velocities, and higher hydrogen recycle
rates are also required (Billon et al. (1977)).
Based on the price
of $1.20/lb for Co-Mo HDS catalyst, the catalyst cost increase from as
low as 4#/bbl for low-metal feeds to as high as 400/bbl for medium-metal
(150
ppm vanadium plus nickel) feeds; it
is
usually not feasible to
desulphurize the residual oils that contain more than 200 ppm of vanadium
plus nickel due to the catalyst cost (Nelson (1976)).
The higher
hydrogen consumption for high metal content residual oils has also being
metioned by Nelson (1977).
(2) When desulfurized residual oils are sent to cracking unit for further
upgrading to make gasoline or kerrosene, the left over metals will
deposit on and deactivate the cracking catalyst (Ritter et al. (1974)).
The deposted metals will increase hydrogen, lights gas, coke yields,
and decrease the gasoline yield; nickel in the charge caused 4.5 times
the increase in coke yield, and
7.9 times the decrease in gasoline
yield as did an equal amount of vanadium in the charge.
(Dale and
-20-
Mckay (1977),
Habib et al. (1977),
and Donaldson et al. (1961)).
An
example given by Edison et al. (1976) shows that for a 50,000 b/d
Cat cracker with 50 ppm vanadium plus nickel in the feed, about
40 tons/day of fresh catalyst must be added to prevent the metal level
from exceeding 1%.
(3) During combustion of these hydrotreated residual oils, the metals
will form ashes in combustion; while nickel oxide will have erosion
effect, the vanadium oxide will have corrosion effect to the furnace
linings and turbine blades.
(4) If trace amounts of oxides of vanadium and nickel escape to the
atmosphere during combustion, they will be harmful to humans, animals,
and plants (Smith (1975)).
A better understanding of the hydrodemetallation reaction and the
laws of metal deposition would lead to better designs of catalysts and
reactors, and to longer economic life of the catalyst.
As in residual oils, there are many metal compounds of unspecified
nature and quantity; also, sulphur compounds, nitrogen compounds, and
asphaltenes are available.
All these species will make the study of
hydrodemetallation difficult.
This study used pure model metal compounds
of known structure dissolve in white oil, so that kinetics of hydrodemetallation can be studied for each compound individually.
By this
way, the kinetic result will not be affected by other metal compounds,
sulphur compounds, and other materials commonly occuring in residual
oils.
-212.
2.1
Background and Literature Survey:
Metal Compounds in Petroleum:
Metal compounds in petroleum are usually been placed into two
categories, metalloporphyrins and nonporphyrin metal compounds.
As
the study of porphyrins can contribute to broaden our knowledge about
the origin and history of petroleum, the metalloporphyrins have been
studied extensively in the past.
have not been well characterized.
The nonporphyrin metal compounds,
The ratio of metalloporphyrins to
nonporphyrin metal compounds varies from 0.01 to 1, depends on the
source of crude oils.
(Dean and Whitehead (1963), Costantinides and
Guido (1963),Baker (1978),
Hodgson et al. (1963)).
The distribution
of vanadium and nickel in crude oils is determined by separating the
crude oils into three compounds: (1)
Methanol soluble fraction, (2)
Resin: methanol insoluble and n-pentane soluble, and (3) Asphaltenes:
n-pentane insoluble.
Table 2-1 (Filby (1975))
shows the distribution
of several trace metals in different fractions of California crude
oils, Table 2-2 shows the distribution of nickel and nickel porphyrin
in different fractions.
It appears that most of the metals (especially
nonporphyrin metal compounds) occur in the asphaltene fraction.
The vanadium present in crude oils has been shown to exist entirely
+2
in the vanadyl state (V=0)+2.
nickel appears to be Ni+2
(Yen (1977), and Saraceno et al. (1961));
-22-
Table 2-1:
Distribution of Trace Elements in Components of California Crude Oil.
(Filby, (1975))
Concentration
9,g/g)
rude oil(%)
Crude Oil
Methanol
Soluble
100.0
57.5
Resins
37.5
Asphaltenes
R
C
A
C
4.99
v
7.5
0.82
12.4
61.6
1.65
8.2
Ni
93.5
7.21
147.0
852.0
1.57
9.1
Co
12.7
0.8
10.7
122.0
0.84
9.6
Fe
73.1
1.95
66.4
895.0
0.91
12.2
Hg
21.2
0.686
29.6
140.0
1.40
6.6
1.41
11.9
0.95
11.7
Cr
o.634
0.300
0.894
Zn
9.32
0.74
8.86
Sb
0.0517
0.0033
0.0130
1.22
0.25
23.6
As
0.656
0.546
0.290
2.25
0.44
3.4
7.540
109.
R ratio of metal concentration in resins to that in crude
-d=
ratio of metal concentration in asphaltenes to that in crude
-23-
Table 2-2:
.
Distribution of Nickel and Nickel Porphyrin in Crude-Oil Fractions,
(Filby, (1975))
Fraction
Crude Oil
Methanol Soluble
Resins
Asphaltenes
57.5
37.5
4.99
1.590
0.123
2.500
14.500
Ni.
Porphyrin
(pmol/g)
1.050
0.142
1-60o
7.130
Ni as Ni
Porphyrin
66.o
100.0
64.0
49.2
34.0
0
36.0
51.8
Crude Oil
100.0
(%)
Ni
Concentration
(Amol/g)
(%)
Nonporphyrin
Ni (%)
-24-
Properties of Porphyrins and Metalloporphyrins:
2.1-1
There are two books that deal with porphyrins and metalloporphyrins
and are of great value in this study: (1)
Vol VII, by Dolphin D. (1978),
"The Porphyrins", Vol I to
and (2) "Porphyrins and Metallopor-
phyrins", by Smith K.M. (1975).
2.1-1.a
Porphyrins:
The compound formed from four pyrrole groups linked via the c(-
positions through four methine groups is known as
which is the basic skeleton of porphyrins.
porphine,
(C
20
H
N
Porphyrins have various
substituents replacing the pyrrolic hydrogens
(position 1-8),
the
methine hydrogens (ok, P, 9 and 6 positions), or the imine hydrogens.
Other parent macrocycles are chlorin, phorbin, tetrahydroporphyrin with
opposite rings reduced is called bacteriochlorin, and hexahydropor-
phyrin (called porphyrinogen).
Figure 2-1.
Porphine
All these structures are shown in
itself does not occur in nature, but porphyrins
are found in nature both in the free form and as complexes with iron
(hematins, hematin enzymes such as the cytochromes, hemoglobin).
Substituted dihydroporphyrins called chlorins occur in the photosynthetic pigment, chlorophyll.
Due to its
stable.
This is
highly aromatic character, porphyrin ring is very
one of the reasons why they are of interest to
geochemists.
The most obvious physical property of porphyrins is
their intense
color which shows absorption bands in the visible and ultraviolet range.
-25-
6
/
NN
N
N
NH
N
6
N
HN
N
NN
5/
Porphin
Phlorin
N
-N
H
H
N
H
H
N
N f-N
Phorbin
Fig. 2-1 Nomenclature of Porphyrin System.
Chiorin-Phiorin
-26(Continued)
NH
/N
HH/
N/w
N
H
H/
N
N
N
Dihyroporphyrin
Dihydroporphyrin
/
(Chlorin)
\N HHN
NN
H
Bacteriochlorin
(Tetrahydrochlorin)
Fig.2-1
H-
Porphyrinogen
(Hexahydroporphyrin)
Nomenclature of Porphyrin System.
-27The molar extinction coefficients range from 100 to about 5 x 105.
The
The spectra can be separated into two parts, visible and near UV.
free-base porphyrins have four bands in visible range, an other band
near UV is the largest peak, usually near 400 nm, and is called the
Soret band.
Some spectra of porphyrins are given in Figure 2-2.
(Alturki et al. (1972)).
There are four major types of porphyrins: (1)
throetioporphyrin) Type, (2) Etio Type,
DPEP (Deoxophylloery-
(3) Rhodo Type,
(4) Phyllo Type.
Table 2-3 shows the structures of selected porphyrins of the four types
(Baker and Palmer (1978)).
four types of porphyrins.
Figure 2-3 shows the visible spectra of the
(Baker and Palmer (1978)).
The peaks in the
visible region are numbered I-IV, beginning at the longest wavelength.
The differences in relative heights of the visible peaks are a function
of the type of side chain substitution of the molecule.
Take for
example, the order of peak heights for etio-type is IV>-III-II-I.
More
details about discussion of these four types of porphyrins can be found
in the aformentioned two books about porphyrins.
2.1-1.b
Metalloporphyrins:
The chelation of a metal ion by a porphyrin involves the incorporation of the metal ion into the center of the tetrapyrrole nucleus
with the simultaneous displacement of two protons from the secondary
(pyrrole type) nitrogen atoms. Porphyrins form tetradentate chelates of
the inner complex type; this with a divalent metal ion of the positive
charges on the metal ion are exactly compensated by the negative charges
-28-
-
w
ETIOPORPHYRIN
0.4
x4
z
30
I
622
4O
'A
0
VI)
399
*1,
DPEP
CIO
09
x64.
X11
:0
40
WAVELENGTH
Fig. 2-2
616
SSI0
(nm)
The UV-Visible Absorption Spectrum (in CH2 Cl 2 ) of Etioporphyrin-I (C: 167.5x1 o3) and DPEP (Deoxophylloerythroetioporphyrin) (e: 296.7x103).
(Alturki et al. (1971)).
-29Table 2-3:
Structures of Selective Porphyrins of the Four Basic Types. (Baker
et al. (1978)).
Rs
.
R,
R,
R,
NH
N
N
HN
R.
.
R
R,
R.
V
Substituentso
Compound
H
H
H
H
H
H
H
H
H
H
H
M
H
M
H
H
H
H
H
H
H
H
H
H
H
Rhodo
H
H
H
DPEP
H
H
H
DPEP
R3
R4
Rs.
M
M
M
E
M
M
. M
E
E
E
M
E
E
E
M
E
M
M
M
M
M
E
M
E
E
E
H
H
M
M
M
M
M
M
M
E
E
E
E
H
E
E
M
E
E
E
P
M
M
E
M
M
M
M
H
H
H
H
H
H
H
H
M
Rhodoporphyrin XV
M
E
M
E
M
C
P
M
Dcoxophylloerythrin methyl
ester
Deoxophylloerythroetioporphyrin
M
E
M
E
M
CH2 CH 2 PMe
M
M4
E
M
E
M
M
Etioporphyrin I
Etioporphyrin 1i
Etioporphyrin III
Etioporphyrin IV
y-Phylloporphyrin XV
Deuteroctioporphyrin II
a, y-Dimethyldeuteroctioporphyrin II
*M
=
CH 3 ; E
=
CH 2 CH 3 ; P
=
- CH 2CH,
E
CH2CH 2 COOH; me - methyl ester; C - COCH.
type
a
R2
R,
Spectral
y
R,
R
Etio
Etio
Etio
Etio
Phyllo
Etio
Phyllo
-4
-30-
a
1.6
b
1.6
1.4
1.4
1.2
1.0
1.2
1.0
0.8
0.8
0.6
0.6
60.4
x
0.2
0.4
02
I
I
I
I
I
- - 20
c 1.6
1.4
-
Q.
1.4
1.2
-
t.o
5.220
1.0
-
1.0
0.8
0.80.6
0.6-
0.4
0.4
0.2
0
I
I
I
I
I
500
530
560
590
620
6W
470
50
530
560
590
620
650
Wav' Ienglh, nm
Fig. 2-3
Visible Spectra of Porphyrins: (a) c-Phylloporphyrin XV;
(b) Etioporphyrin I; (c) Rhodoporphyrin XV; (d) Deoxophylloerythroetioporphyrin. ( Baker et al. (1978)).
-31on the porphyrin nucleus, so that in the absence of ionized substituents
on the porphyrin the resulting chelate has no net charge.
While the molecule can be regared for most purpose as essentially
planar, with a diameter of approximately 8.5
.
and a thickness of
approximately 4.7R, there are significant deviations from planarity.
Fleischer (1962) found that in respect to the plane formed by the four
methene bridge-carbon atoms, two of the pyrrole rings are tilted
and two downwards.
upwards
In the case of nickel porphyrins, nickel sits
in the
middle of porphyrin plane; for vanadyl porphyrins, x-ray diffraction
data shows that vanadium atom lies out of the basal plane of the ligand
macrocycle,
the distance between the vanadium atom and the ligand basal
plane ranges from 0.3-0.6A, (Yen (1975)).
As mentioned earlier, vanadyl
porphyrins always require vanadium atom to connect to an oxygen atom
whi ch is perpendicular to the porphyrin plane.
The UV/visible spectra of metalloporphyrins are different from free
base porphyrins, usually there exist only two bands in visible range in
addition to the Soret band.
It is believed that if
the complex is highly
stable the visible peak at longer wavelength (0( band) will be higher
than the peak at shorter wavelength (P band).
and
P
(Falk (1964)).
The 0(
bands for nickel etioporphyrin in neutral solvents are at 550
and 514
n with d/J
intensity ratio of about 3.
phylloerythroetioporphyrin (DPEP), the
For nickel deoxo-
/p ratio is about 2.0.
etioporphyrins have peaks at 570 and 531 nm with the 4/l
ratio for vanadyl DPEP is 1.3.
Vanadyl
ratio 2, the
The reason for vanadyl porphyrins to
shift to longer wavelengths and reduced a/e ratio are considered to be
-32due to the additional coordination with the oxygen to yield a pentacoordinate complex.
(Baker and Palmer (1978)).
Figure 2-4 shows the
visible spectra for vanadyl and nickel DPEP (Hodgson et al. (1967));
and Figure 2-5 shows the visible spectra for vanadyl and nickel
etioporphyrins I.
-33-
SI
400
I
500
700
600
WAVELENGTH- Ytm
z
0
I
400
I
I
700
500
600
WAVELENGTH- tyxv\
Fig. 2-4 Absorption Spectra for DPEP (Deoxophylloerythroetioporphyrin)
Type of Vanadyl Porphyrin (Top), and Nickel Porphyrin (Bottom).
The curves that show Soret band peaks have been diluted from the
others that show visible peaks.
(Hodgson, et al.
(1967)).
-34-
z
0
I-a.
0
V)
CO
391
0.6
553
0.4
0.2
517
0
400
520
460
WAVELENGTH
i
580
(nm)
I
I
I
I
Pure Vo Etio
.
08F-
407
z
0
571.5
P0.
0
0.4
(in
534
CO3
4
I
i
0
380
420
460
500
WAVELENGTH
Fig. 2-5
540
5Z0
620
(n m)
Absorption Spectra for Nickel Etioporphyrin I (Top) and
Vanadyl Etioporphyrin I (Bottom).
Samples Were Dissolved!
in Nujol First and Then Diluted by Xylene.
Xylene.
Background:
-352.1-2
Geochemistry of Porphyrins:
2.1-2.a
Types of Porphyrins in Petroleum:
Most of the studies made in the past regarding porphyrins in
petroleum were done on the free base porphyrins.
The reason is that
in general the position and intensity of the metalloporohyrin visible
absorption bands are much less sensitive to alterations by substituents than are the spectra of the free base porphyrins; acid extraction
(demetallation) is usually taken to covert metalloporphyrins
to free
base porphyrins before study.
Special method for isolation of metalloporphyrins from petroleum
has been developed, but tends to be laborious.
(Baker and Palmer
(1978)).
The two most important types of porphyrins found in petroleum
are DPEP and Etio types, generally there appears to be more DPEP than
Etio in petroleum..
Rhodo type of porphyrin has also been found.
(Yen (1975)-(a), Sugihara et al. (1970), Baker (1969), and Didyk et al.
(1975)-(a)).
All three types of porphyrins exist
methylene homologues.
as series of
(Dean and Whitehead (1963)).
Table 2-4 shows the molecular weights of homologues series of
porphyrins.'
The molecular weight range for free base porphyrins in
petroleum appear to be among 394 and 562, the weight average mass are
about 420-490 for different crudes.
(Baker and Palmer (1978)).
1w
Table 2-4
Molecular Weight of Homologues Series of Porphyrins
Vanadyl
DPEP series
Rhodo series
BenzDPEP
Nickel
DPEP series
DPEP + 56
310 + 14n
DPEP
series
308 + 14m
8
422
420
428
485
476
9
436
434
442
499
490
10
450
448
456-
513
504
11
464
462
470
527
518
12 b
478
476
484
541
532
13
492
490
498
555
546
14
506
504
512
569
560
15
520
518
526
583
574
16
534
532
540
597
588
Etio and Phyllo
series
n or m
DPEP + 65
456 + 14n
aNumber of methylene groups attached to the porphyrin nucleus.
bEtioporphyrin and DPEP have an equivalent of 12 methylene group substituents.
(Baker and Palmer (1978)).
0'
-37Moleular weight higher than the above range have also been found,
and porphyrin dimers, trimers were also found.
(Blumer and Rudrum
(1970)).
Porphyrins have also been found in other materials: Hodgson et
al. (1963)
and Alturki et al. (1971)
sands; Hodgson et al. (1968)
studied the porphyrins in oil
studied the porphyrins in soils,
and sedimentary rocks; Hodgson et al. (1967)
sediments,
also examined porphyrins
in oil sand, solid hydrocarbons (Gilsonite and Grahamite), oil shales,
rocks, and coal; porphyrins in sediments have also received attention
by Baker and Saith (1974),
(1961);
oil, oil
Baker et al. (1970),
and Blumer and Omenn
Morandi and Jensen (1966) compared the porphyrins in shale
shale and petroleum by absorption and mass spectroscopy; and
finally, porphyrins in meteorites have been studied by Hodgson and
Baker (1969).
2.1-2.b
Origin of Porphyrin and Metallo Porphyrin:
The oldest and by far the most popular explanation for the
existence of metals in petroleum is that proposed by Treibs (1936).
His theory assumes that porphyrins (and possibly non-porphyrins) are
derived from chlorophylls of aquatic life.
Treibs suggested a series
of chemical reactions that could account for this transformation.
After some additions and modifications, Yen (1973)
came up a scheme
for the transformation of chlorophyll to vanadyl DPEP and other stable
vanadyl chelates.
This scheme is
shown in Figure 2-6.
A similar
scheme starting from hemin and yielding etioporphyrins was also
-38CIHLOROPHYLL a
O4.CM
PHEOP*4YTIN as
a
PHEOPHORBIDE
H3
2
C.M
CA
M+
M
+
,
CAC3
C.H
+RON
M
M
C"4M
C414
0
Ito
C-
OOIO
0CM 3
-cmi-CM.C-C
1-0,- HOCC,64"
PHEOPORPHYRfN
C3C
og
1
c3
H
3
4
OZ
=0C
C
CM 3
C-2 5,3
4
'O
CM3
j:,\
CM 3
CM 3
\C
C4 N 2
CM
CH
-,
C2 M5
N4\
Fig. 2-6M SceefrTeTasomto0fClrpyld
Vanadyl Porphyrins.
\
CH
C 2 H5
CH37
C 6M 3
17
0+
CM 3
ms-a- NAPHTHYLPORPI{YRIN
CM 3
3
/-H
M
RHODO t(BENZOPORPHYRIN)
(
CH
C 2 MZ 4
Z 2 5 H2 M
N
+
,
CMH 5
C94
4,
COT4
-
ETIO (ETIOPORPHYRIN)
C~ 5
-4.
C
0.0
C'Oz
HS
C2 M
2P-0-Co
++\
H
2 4
OPEP
5
+
C"3
ICM
DEOXOPHYLLOERYTHRIN
CM
3
0
-CM
OR
~)
PIIYLLOERYTHRIN
3
.0
+XI
oSal
C
3fI
-39proposed by Treibs, but is now rejected based on the findings that
there are not enough hemin exists in aquatic life
to the etioporphyrins.
(Corwin (1959)).
to contribute
One important fact from
the aformentioned scheme is that the Etio type of porphyrins were
derived from DPEP type of porphyrins; it
of geothermal maturation.
(1973), and (1969)
actually became an indiactor
(Didyk et al. (1975)-(b)).
Yen (1975)-(a),
studied the correlation of the ratio of DPEP/Etio
to the depth of burial for a number of petroleum deposits.
The source of metals in porphyrins is
not conclusive.
Some
proposed that vanadyl and/or nickel chlorins exist in living organisms
and that petroleum porphyrins are derived directly from such biogenic
metal complexes.
(1970))
(Hodgson et al. (1967)).
Others (Sugihara et al.
claimed that vanadium in non-porphyrin complexes such as
asphaltenes were the source of vanadium in porphyrin.
mentioned about the source of nickel in porphyrins.
Few were
-40Nonporphyrin Metal Compounds:
2.1-3
The study of nonporphyrin metal compounds is very important as
(1)
For many crude oils, there appear to be more nonporphyrin metal
compounds than metalloporphyrins.
(2) It is believed that the metals
in metalloporphyrins came from nonporphyrin metal compounds.
(Sugihara et al. (1970)).
Yen (1975)-(a) classified nonporphyrin metals into the following
groups : (a) Chlorophyll o( and other hydroporphyrins,
(b) Highly
aromatic porphyrin chelates, (c) Porphyrin decomposition ligands,
(d) Transition metal complexes of tetradentate mixed ligands such
as V, Ni, Fe, Cu, Co, and Cr.
two parts,
the first
is
and the other part is
This can be further separated into
the simple complexes from resin molecules,
chelates from asphaltene sheets.
metallic compounds such as Hg, Sb, As.
(e)
O gano-
(f) Carboxylic acid salts
of the polar functional groups of resins, such as Mo and Ge.
Colloidal minerals, such as silica and Nacl.
are of importance.
(g)
Only (b), (c) and (d)
Figure 2-7 shows the example for the (b), (c),
and simple complexes from resin molecules of (d) types of nonporphyrin
metals.
The most important nonporphyrin metal compounds are the ones
appear in the asphaltene fraction.
The reasons are substantial
amount of metal compounds appear in this fraction (Table 2-2).
Crudes high in metals are high in asphaltenes, and 50-99% of them are
nonporphyrin metal compounds.
(Yen, et al. (1968)).
-41-
N
N
/v 0
N
N
(-1)
V
M
v
M
ON1HO
H HO
MN
/
M
y
p
Y
P
P
p
(2)
0
o
V-*-
0
jm. -Va
0
65,
Ni
L0Q
(3)
Fig. 2-7
Examples for Nonporphyrin Metal Compounds: (1) Highly Aro*matic Porphyrin Chelates; (2) Porphyrin Decomposition Ligands,
(Metals Will Fill Up to the Center); and (3) Simple Complexes
from Resin Molecules.
(Yen (1975)-(a)).
-42Asphaltenes contain highly condensed aromatic and heterocyclic
The
rings with oxygen, nitrogen, and sulfur (Ball et al. (1959)).
asphaltene molecules associate in dilute solutions at low temperatures,
but dissociate at high temperatures.
The molecular weights of asphal-
tenes depend on the methods of measurement, they range from 1,000
to 500,000, Dickie and Yen
(1967) published the tabulation of methods
and results; they also proposed a macrostructure of asphaltene.
et al. (1961),
(1962),
Yen
(1970), (1974) studied the asphaltene in petro-
leum extensively by x-ray diffraction and electron spin resonance.
The conclusion is that asphaltenes exists as clusters of sheets,
each
sheet is made up of individual molecules of aromatics, paraffins,
naphthenics, macrocyclics, and heterocyclics, the bridges or links
can be cleaved under selective chemical or physical conditions.
Each sheet has a graphite-like aromatic plate with a diameter of 8-151,
connects to the other
type of aformentioned hydrocarbons.
distance between parallel plates is
3.55-3.7a,
The
and generally an average
cluster consists of 4-5 plates with an overall thickness of 14-28R.
One of the characteristics of the single sheet in asphaltenes is
that
they can stack one above the other, bound together either through
interactions of the polynuclear aromatic centers or through
heteroatoms in the sheets.
It is also possible that increase the
metal content will increase the tendency of the particles to associate
further.
(Dickie et al. (1969)).
model based on x-ray diffraction.
Figure 2-8 shows the asphaltene
(Yen (1977)).
-43Sheet
SLe
8-15E
dm 3.55 - 3.70 A
dy 5.5-6.0 A
L6 -14-28 A
Fig. 2-8
Cross Sectional View of an Asphaltene Model. (Yen (1977)).
/yAJ\M
Represents the Zig-Zag Configuration of a Saturated.
Carbon Chain or Loose Net Naphthenic Rings.
Represents the Edge of. Flat Sheets Condensed Aromatic Rings.
Fig. 2-9
Defect Site in an Aromatic Sheet of the Asphaltene
Structure., (Yen (1974)).
-44It
is
known that many of the aromatic portions of the sheets have
defective centers (gaps and holes), these defects are formed as a
result of the incomplete graphitization of benzenoid rings by donor
atoms such as N, S, and 0.
It
is
believed that these defective
centers are the coordination centers of metals.
the example of defect site for metals.
Figure 2-9 shows
(Yen (1974)).
Finally, one thing very interest is that Sugihara et al. (1970)
mentioned that crudes with high vanadium content are high in sulfur,
and crudes with high nickel content are high in nitrogen.
He further
mentioned that oxovanadium is known to prefer to coordinate to ligands
with the decreasing order of 0"S -N,
nickel.
which it
is
N -S
-0
for
2.2
Hydrodemetallation Reaction:
As in addition to metal compounds, sulphur and nitrogen compounds
are available in residual oils, hydrodemetallation (HDM) always occur
along with hydrodesulphurization (HDS)
and hydrodenitrogenation (HDN)
reaction during hydroprocessing of residual oils.
Riley (1978)
(1971),
mentioned that HDM is
Oxenreiter et al. (1972),
faster than HDN; Frost et al.
Oleck and Sherry (1977)
showed that
Audibert and Duhaut
HDS is
faster than HDM in typical HDS units.
(1970)
also reported that the ratio of vanadium removal to sulphur
removal decrease with space velocity.
The chemistry of hydrodemetallation reaction is
not well known,
but both hydrogen and catalyst are required for the reaction to occur.
As sulphur compounds are available in residual and catalyst were
presulphided in commerical runs, the final metallic products deposited
on the catalyst are beleived to be inorganic metal sulphides.
tings, et al. (1975),
(Has-
Dautzenberg et al. (1978), Newson (1975), and
Schuit and Gates (1973)).
Under commercial conditions, hydrodemetallation typically takes
place at 4000C (750 0F) and 14MPa (2000 psig) of hydrogen by using
Coo-Moo 3 /Al 2 03 as catalyst.
2.2-1
Kinetics:
2.2-l.a
Thermal Demetallation and Nonhydrogenative Demetallation:
Wooldle and Chandler (1952) mentioned that vanadium and nickel
are thermally stable up to 3700 C(700 0 F), and at temperatures
approaching 3700C, these molecules exert very small but significant
vapor pressures.
Hodgson and Baker (1957)
studied the thermal behavior
of vanadium, nickel, and porphyrin contents in McMurray crude oil
(Athabaska) in connection with their studies of the petroleum
maturation process.
Constantinides and Guido (1959)
examined the
thermal behavior of vanadium, nickel in Kuwait residual.
Thermal
degradation for both vanadul and nickel porphyrins from Wyoming
reduced crude has been investigated by Rosscup and Bowman- (1967).Hodgson (1973)
used the above literature for his discussion about
the geochemistry of porphyrins.
All of them reported that the thermal
decomposition of the metal compounds in oil obeys first order kinetics,
with activation energy from 43 to
57 kcal/g-mole.
Nonhydrogenative
demetallation was studied by Fischer et al. (1976) for Wilmington
Residual, Agha Jari residual, and San Joaquin residual at the presence
of manganese nodules.
As their results were consistent with previous
studies on thermal demetallation, they suggested that nonhydrogenative
demetallation with manganese nodules is of thermal and not of catalytic
character.
A summary from the above literature regarding the kinetic
order, activation energy, and rate constent is shown in Table 2-5.
-47Table 2-5
Kinetic Order, Activation Energy, and Rate Constants for Thermal
Demetallation of Vanadium and Nickel in Residual or Crude Oils:
Author
Kinetic
order
(1) Hodgson and
Baker (1957)
Activation
Energy (Kcal/g mole)
52.5
(Porphyrin )002
Degradation
58.6
(m
(Nickel)
Removal(38C
57.5
(2) Costantinides
et al.
Rate
Constant (1/hr)
1_
(Porphyrin
(1959)
Degradation
(3) R;sscup and
Bowman (1967)
(4) Fischer et al-
(1976)
45.6
0.013 (3580 C)
0.012 (3580 C)
0.41 (3900 C)
-Vanad-
0.068 (3900 C)
(Nickel
0.070 (39000)
Vanadium
Removal
46
)
(3580C)
( Nickel
0.21 (3900C)
0.12 (3900 C)
Vanadium
Removal
0.28 (3900C)
( Neoal)
0.23 (3900C)
2,2-1.b
Hydrodemetallation:
Beuther & Schmid (1963) studied the kinetics of vanadium and
nickel removal for Middle East (Kuwait) reduced crudes and found
that the kinetic order is second order with respect to metal compounds.
They also found that vanadium removal rate is faster than nickel
removal rate.
By using the structure of asphaltene proposed by
Yen et. al. (1961)
which has also been shown in Figure 2-8, they
postulated that nickel concentrates on the interior of the asphaltene
"molecule", while vanadium concentrates on the exterior of the
molecule.
This is
one of the reason they believed to be the faster
vanadium removal rate.
Another reason they believed is that the valence
state of vanadium ih vanadium complex is +4, while nickel is +2.
As
the vanadium does not have its valences satisfied in the basal plane,
it is also bound to an oxygen atom.perpendicular to the planer structure
of complex such as porphyrin.
The tendency of atoms to project from
the plane (see 2.1-1.b) for vanadium complexes may take the metal
atom more accessible to the catalyst through the projecting hetero-atom.
In another word, they believed that it is the polarity and accessibility
at the periphery of the asphaltene molecule that makes the ease of
vanadium removal relative to nickel.
Figure 2-10 shows their
description about the qualitative changes in asphaltenes during HDS
processing.
Larson and Beuther (1966) examined the hydrodemetallation
of vanadium and nickel in varous fractions of crude oils, and fit
-49-
A. Before HDS
-- s
Resin-like
Molecules
B. After HDS
S
a
Sulfur
Vanadium
0 Nickel
AN
Fig. 2-10
Aromatic Rings
Naphthenic Rings
Qualitative Changes in Asphaltenes and Surrounding
Resins During HDS Processing.
(Beuther and Schmid (1963)).
-50their data by first order kinetics.
removal rate of vanadium.
They also reported the higher
Some experiments to proved that vanadium
complexes have higher polarity and concentrate more on the edge of
asphaltene moleale were also conducted by them to support the earlier
theory proposed by Beuther and Schmid (1963)
vanadium removal rate.
Arey et al.
(1967)
that explained the higher
reported nickel is charac-
teristically more difficult to be removed than vanadium and the hydrodesulfurized product of Kuwait Atmospheric Residuals tends to be
relatively rich in nickel.
porphyrin in residual oil is
Kwan and Sato (1970) proposed that vanadylthen
directly adsorbed to the catalyst,
the porphyrin ring is broken down, the material is transformed into
non-vandyl compound, and finally deposited on the catalyst.
and Duhaut (1970)
Audibert
studied the commercial hydrodesulfurization of
residuals from several Middle-Eastern oils.
They found that demetall-
ation reaction for vanadium to be 15-20% faster than nickel, and
reaction ratio are roughly linear with hydrogen pressure.
Inoguchi
et al. (1971)-(a) maintained that the hydrodemetallation rate can be
described equally well in terms of either first
The activation is
than nickel,
10 kcal/g mole.
or second order kinetics.
Although vanadium removal is
faster
the selectivity for vanadium removal and nickel removal
varied with the reaction temperature; when reaction temperature is
creased,
in-
the selectivity for nickel removal also increase and reached a
maximun at 400 0 C then decreases as temperature is further increased.
-51An investigation made by Oxenreiter et al. (1972)
on the hydrodesulphuri-
zation of some redisuals shows that at their operating conditions,
is
there
66% vanadium and 56% nickel removal for Gach Saran residual, 63%
vanadium and 36% nickel removal for Khafji residual.
They also showed
that the demetallation rate for resin fraction of residuals is faster
than the asphaltene fraction.
tallation over manganese
tant of 5-12
Chang
and Silvestri (1974) found deme-
modules to be first
hr at 750OF (40000), which is
-
mentioned in section (2.2-1.a).
order,
much
with a rate cons-
higher than a thermal rate
They believed that the mechanism of
hydrodemetallation involves reduction and deposition, plus hydrogenation
of the hydrocarbon moiety.
Shah and Paraskos (1975) indicated the higher
vanadium removal rate for Kuwait crude oil.
In the publication of 1976,
Chang and Silvestri maintained their earlier statement in 1974, and also
used Co0-MoO3 /Al 20 3 for comparison.
Oleck and Sherry (1977) claimed
that up to about 83% metals removal, demetallation reaction are best
described by second order kinetics.
The activation energy for vanadium
removal is 38.2 kcal/g mole for CoO-MoO 3 /Al 2 03 catalyst and 26 kcal/g mole
for manganese nodules, the hydrogen pressure dependence is
one for both vanadium and nickel.
larger than
Riley (1978) supported the first
order kinetics as well as the higher removal rate for vanadium.
A
summary of these studies is shown in Table 2-6.
By comparison, the related hydrodesulphurization reaction is also
often described as either first order with respect to the sulphur compounds (Frost and Cottingham (1971),
Schuit and Gates (1973),
and
Schuman and Shalit (1970)) or second order (Watanabe et al. (1970),
T1able 2-6
Summary of Previous Studies on Kinetics of Catalytic Hydrodemetallation
Kinetic
Catalyst
Used
Authors
Crude
Order
E
V removal rate
(kcal/g mole)
Ni removal rate
Order of
Dependence
on H2
(1) Beuther &
Schmid
HDS
Catalyst
Kuwait
Reduced
2
----
----
I
----
----
----
----
----
1
Crude
(1963)
&
(2) Larson
Beuther
(1966)
Kuwait
Atmospheric
Residual
(3) Arey
et al.
(1967)
(4) Audibert
(5)
Middle
& Duhaut
Eastern
(1970)
Oils
Inoguchi
et al.
Khafji
Atmospheric
(1971)-(a)
Residual
(6) Oxenreiter
et al.
Khafji
& Gach
(1972)
Saran
1 or 2
----
----
----
----
10
-
1
Function of
Temperature
----
Residual
(to be continued)
MW
Catalyst
Crude
Used
Authors
Kinetic
Order of'
Order
Dependence
E
(kcal/g mole)
V removal rate
Ni removal rate
on H
2
&
(7) Chang
Silvestri
(1
Agha Jari
Topped
Manganese
Nodules
9 7 4)
HDS
Catalyst
Kuwait
Crude
Chang
Silvestri
Manganese
Nodules,
(1976)
Co-Mo/Al
Kuwait
Residual,
Agha Jari
&
(8) Shah
Paraskos
7 1
I
Crude
--
--
---
1
-
(11)
Manganese
Nodules,
(1977)
Co-Mo/Al20
Kuwait
Lagomedio
Atmospheric
Residual
Riley
Co-Mo/Al2
(1978)
1
03
2
Residual
Co-Mo/Al
<1 for 2 0 3
Manganese Nodule
Safania
Atmospheric
for
Co-Mo/Al 2 03
Smaller 2__for Others
1 for
&
Sherry
Oleck
>1
1
38.2
(Co-Mo/Al 2 03
)
,
Topped Crude
&
(10)
9
& PoroceI 3P
&
(9)
&
(1975)
26
(Nodule)
>1'
-54Massagutov et al. (1967), Beuther and Schmid (1963), and Oleck and
Sherry (1977)).
Riley (1978).
Fractional order (1.5 order) is also described by
The activation energy for hydrodesulphurization appears
to be in the range of 27 to 45 kcal/g mole (Oleck and Sherry (1977),
Schuman and Shalit (1970),
Cottingham (1971)).
Watanabe et al. (1970),
and Frost and
Although Audibert and Duhaut (1970)
claimed
that metal removal has higher activation energy than sulphur removal,
it
is not generally true.
The hydrogen dependence for sulphur removal
appear to be first order (Oleck and Sherry (1977),
Watanabe et al. (1970),
Schuit and Gates (1973)).
For hydrodenitrogenation which might occur along with hydrodemetallation and hydrodesulphurization, Flinn et al. (1963) reported that
the total nitrogen removal from quinoline in a paraffin oil over
NiO-W/Al203 catalyst was first order with respect to quinoline.
Aboul-
Gheit and Abdou (1973) also claimed first order kinetics with respect
to total nitrogen content.
Shih et al. (1977)
also fitted their data
with first order kinetics in their study of hydrodenitrogenation of
quinoline in white oil over NiO-MoO3 /Al 2 03 catalyst, their report also
show that hydrogen dependence is less than first order and the
apparent activation energy for total nitrogen removal is 25 kcal/g mole.
There appears to be a relationship between the metal removal rate
(especially vanadium) and the sulphur removal rate.
Massagutov et al.
(1967) studied the relationship between sulphur removal and vanadium
removal, sulphur removal and nickel removal respectively.
A very good
-55linear relationship was obtained between sulphur removal and vanadium
removal.
Their result is shown in Figure 2-11.
also reported by Richardson and Alley (1975),
(1971),
Similar result was
Frost and Cottingham
This clearly shows that metal
Inoguchi et al. (1971)-(b).
(especially vanadium) compounds and sulphur compounds are closely
related in residual oils, which is
Figure 2-10.
Yen (1977)
consistent to the model shown in
mentioned that one of the reason for the
association of asphaltene sheets is due to O=V ..... X (X=0,N,S) or
0=V ..... 7C
from resin and asphaltene sheets.
The processing of
residual oils requires hydrogenation.
As the association of X
V=0 (X especially S) and
as well as,-7lt-bond should be
IT.....
V=0,
...
overcome to let the sheets accessible for hydrogen attack, this will
result in the proportionality of vanadium removal to sulphur removal.
Although there has been a deviation regarding the kinetic order
of hydrodemetallation, almost all of the authors who claimed second
order kinetics agreed that the metal complexes can be divided into
two groups, each following a first order kinetics with different rate
constant and perhaps different initial concentration; the result of
conversion versus residence time would be difficult to distinguish
from the results of a second order reaction.
(1963),
(Beuther and Schmid
Inoguchi et al. (1971)-(a), Oleck and Sherry (1977), and Mosby
et al. (1973)).
Similar thing for hydrodesulphurization were metioned
by Schuman and Shalt (1970), Riley (1978), de Bruijn (1976), and Arey
et al. (1967).
We have shown that the two first order kinetics can
be used to approximate a second order
kinetics only at less than 92%
I00-
Q
& oo
PA.
0 60
0
U'8
12
-
60 ---
-
IX
~60 i
-
-2
0
0
z0
GO
00V,0
I~
20
IN
6u
so
20
IOU
S ULPHUR REMOVAL,/.
-Nickel removal versus vacuum gas oil
desuiphurization level.
60
s0
reioval i'crsus vacuun gas oil
desuipliurization level.
V: vacuum gas oil from Chckmagush crude oil; 0: vacuum gas
oil from Arlan crude oil: x vacuum gas oil from mixture of
Tuimaza and Arlan crude oils; 0: data reported by Connally';
0: data reported by Eberlinc'O; +: data rcported by Lewis";
A: data reported by Abbott 1 2 ;
Sulphur Removal Versus Nickel Removal (Left) and Vanadium Removal (Right)
(Massagutov et al. (1967)).
S
.
for Several Vacuum Gas Oil.
too
-Vanadiun
V: vacuum gas oil from Chcknmagush crude oil; 0: vacuum gas
oil from Arlan crude oil; x : vacum gas oil from mixture of
Tuimaza and Arlan crude oils; 0: data reported by Connally';
0: data reported by LbEhrlinc10; &: data reported by Abbott";
Fig. 2-11
90
SULPH UR RE MOVAL,O/.
-57conversion, and only when the ratios of the parameters of the two
first
within very narrow ranges, the result
order reaction fell
is shown in Chapter
5.11.
There has been some study on the effect of composition of catalyst
on hydrodemetallation, Chang and Silvestri (1974) compared two ocean
nodules catalysts which contain substantial amount
of Ni, Mo and Co
with fresh water nodule which has only trace amount of Ni, Mo and Co,
and found the ocean
nodules.
nodules are not more active than fresh water
In their publication of 1976, they compare- comercial available
Coo-Moo 3 /Al 2 03 with Lake Michigan Nodules and porocel on hydrodemetallation, and found that for hydrogen pressure higher than 800 psig,
2
0
is
more active than the other .two; while for pressure
lower than 800 psig, nodules is
Oleck and Sherry (1977)
more active than CoO-MoO 3/Al
2
03
'
Coo-Moo /Al
shows CoO-MoO /Al203 is always more active
than manganese nodules; while Riley (1978)
claimed that vanadium
removal activity is independent of the loading of Co and Mo on alumina.
As in the previous studies the demetallation reaction is either
diffusion limited or on the verge of diffusion limited, no conclusive
statements can be made if there exists deviation about the pore
structure of different catalysts.
Oleck and Sherry (1977) explained
the higher activity of CoO-MoO 3/A1 2 0 3 by larger pore size.
Chang and Silvestri (1974)
showed that the effectiveness factors
for demetallation with manganese catalyst is 0.55 when average catalyst
size is 1 mm, and 0.95 when it is 0.2 mm.
Shah and Paraskos (1975)
argued that the effectiveness factor for demetallation reaction can
-58not exceed 0.4.
Riley (1978) showed that vanadium removal activity
Similar
actually increases as the pore diameter of catalyst increases.
results were observed by Shah and Paraskos (1975), Spry and Sawyer
(1975),
Inoguchi et al. (1971)-(c), and Hardin et al. (1978).
As
Hardin et al. (1978) observed that more coke is formed on catalysts
while less metals per unit area are formed on catalyst that has larger
pores, it was proposed that there exists an optimum pore size for the
design of hydrodesulphurization catalyst.
As previously mentioned, substantial amount of metal compounds
exist in the asphaltene fraction of residual oils; in order for the
metals to be removed from asphaltene molecules, the large asphaltene
molecules have to diffuse into the catalyst.
asphaltene, only 10~7-10
obtained (Newson (1975)).
Due to the size of
cm /sec of effective diffusivity can be
This will explain the low effectiveness
factors for demetallation reactions.
As shown in Table 2-6, except the kinetic order, no sufficient
information were given to led to an understanding of demetallation;
a study based on model metal compounds dissolving in clean oils and
diffusion free conditions would provide useful kinetic data.
Deposition of Metals on Hydrodesulphurization Catalysts.
2.2-2
2.2-2.a
Concentration Distribution of Vanadium and Nickel on
Spent Catalysts:
Scanning electron x-ray microanalyzer was used for the study of
the deposition of metals on catalyst.
Arey et al. (.1967) mentioned
-59that nickel tends to be deposited throughout the desulphurization
catalyst particules whereas vanadium is concentrated in the outer
These metallic deposits many render the inner portions of the
layers.
catalyst particle inaccessible to the feed stock.
Audibert and
Duhaut (1970) showed that while vanadium has diffused into the
pellets up to 650 micron depth only, most of the nickel concentration
has been measured inside the pellets;
deeply than vanadium.
Kwan and Sato (1970)
Inoguchi et al. (1971)-(a)
tion.
that is,
nickel diffuses more
shared the same observa-
found that though nickel is
similar
in behavior to vanadium which tends to deposit more on the edge of the
catalyst than at the center, it spreads out more widely on the whole
catalyst than vanadium does.
Todo et al. (1971) observed that both
vanadium and nickel only deposited on the edge of the catalyst; that
is, the concentration profiles for both nickel and vanadium are of
U-shape.
Sato et al. (1971) claimed that while vanadium deposition
is of U shape, nickel tends to be uniformly distributed.
shows their result.
(1972)
Figure 2-12
Finally, an investigation made by Oxenrieter et al.
shared the same view as Sato et al. (1971).
The general observation from aformentioned references is
that
vanadium always distributed more on the edge of the catalyst while
nickel tends to be more uniformly distributed.
The deviation may
be due to different particle size and pore structure of the catalysts
used in different studies.
Although in section 2.2-1 we have mentioned
that vanadium removal rate is always higher than nickel removal rate'
-60-
8
WV
6CQ 5W0
300
400
2W
100
0
NO 220 300 400 5W0- C.W
0
.o6 0 403 300 200 100
0 100 200 300 400 5O0
DISTANCE FROM CENTER OF CATALYST (/')
AFTER
Fig 2-12
50
HRS ON STREAM
Concentration Profile of Vanadium (up) and Nickel (Down)
on the Desulphurization Catalyst after 50hrs Reaction.
(Sato et al. (1971))
-61-
and also learned that both reaction might be diffusion limited.
However, the higher vanadium removal rate is not sufficient to explain
the big difference between the concentration profile of vanadium and
nickel shown in Figure 2-12.
Sato et al. (1971) did theoretical
calculation and showed that in order to achieve the big difference
of concentration profiles shown in Figure 2-12,
the effective
for vanadium has to be less than 10% of nickel, which is
impossible.
diffusivity
highly
There exists some unrevealed phenomena other than metal
removal activity and effective diffusivity that causes the big difference
in Figure 2-12.
2.2-2.b
Amount of Deposition:
From the information concerning the distribution of deposition of
metals on the catalyst layer, Kwan and Sato (1970) also found that the
deposition of carbonaceous substance takes place consecutively whereas
that of vanadium or nickel simultaneously.
The amount of vanadium and nickel deposited on the catalyst
depends on the duration of catalyst on stream and the amount of
metals in feed stocks.
As high as 56 wt% for vanadium,
17 wt% for
nickel were observed by Oxenreiter et al. (1972), while as low as
0.1 wt% for vanadium and 0.05 wt% for nickel were observed by Kwan
and Sato (1970).
While the amount of deposition for vanadium and nickel on the
catalyst will increase with time of operation, coke deposition appears
to reach a saturation concentration and never increases again.
Kwan
-62and Sato (1970) found that there is no difference for the amount of
coke deposition between 50 hours and 1000 hours on stream.
phenomena were observed by Beuther and Schmid (1963),
(1970),
Dautzenberg et al. (1978),
Silvestri (1976),
2.2-2.c
Sato et al. (1970),
Similar
Sato et al.
Chang and
and Inoguchi et al. (1971)-(b).
Catalyst Aging:
Kwan and Sato (1970),
Sato et al. (1971),
Inoguchi et al. (1971)-
(a), Chang and Silvestri (1976), and Dautzenberg pointed out that the
initial fast deactivation of catalyst is caused by the coke deposition.
Beuther and Schmid (1963) found that when hydrogen partial pressure is
increased, the saturation level of coke is decreased, however, the
initial rapid rate of coke formation has not been eliminated.
They
also observed that while pore volume and surface area were decrease&
by initial coke deposition, the average pore radius was reduced only
slightly, and pore size distribution was not changed.
was reported by Richardson and Alley (1975).
Similar result
Riley (1978) concluded
that the coking tendency of resid HDS catalysts is controlled by
intrinsic surface properties rather than the pore size distribution
of the catalysts.
Brunn et al. (1975) developed several coke resistant
catalysts and showed that longer catalyst life were obtained.
The
chemical modification of the catalyst surface and the effect of hydrogen
on coke deposition are discussed in the book by Gates et al. (1978).
Unlike coke that has upper limit, vanadium and nickel tend to
deposit on the catalyst with no limit, Sato et al (1970), Inoguchi et al.
(1971),
Kwan and Sato (1970), McColgan and Parsons (1974), Brunn et al.
(1975), and Dautzenberg et al. (1978) concluded that the slow deactivation rate of catalyst following initial coke deposition is caused by
the deposition of metals.
Brunn et al. (1975) found that the ultimate
life of the catalyst is controlled by the rate of metals deposition
during processing and the maximum capacity of the catalyst for metal
deposition which can also be function of feedstocks and severity of
operation.
Sato et al. (1971) agreed that vanadium deposition will cause
pore plugging of the catalyst and eventually deactivate the catalyst,
but they were reluctant to
say nickel would do the same thing.
Oxenreiter et al. (1972) found that while after reaction, surface area
and pore volume of catalyst were substantially reduced, the pore size
distribution of the remaining pores was not significantly altered.
They suspected that pore mouth plugging is the way for the coke and
metal deposition to deactivate the catalyst.
By accepting the concept
that the pore plugging is due to coke deposition and metal sulfides,
Newson (1975) proposed a pore plugging model to describe catalyst
deactivation in axial flow trickle-bed reactor.
Recently, Dautzenberg
et al. (1978) developed a two parameter model to describe the deactivation of residual desulphurization catalyst which was caused by the
pore plugging of metal deposition.
As a summary, deposition of coke will cause loss of catalyst
activity by chemical modification of the surface and by physical
plugging of the pores; the deposition of metal sulfides cause loss of
-64-
catalyst activity by physical plugging of the pores, it is not clear
whether it will cause chemical modification of the surface or not,
but the possibility can not bd excluded.
2.2-2.d
Distribution along the Reactor Bed:
In top feed fixed bed hydrodesulphurization unit, Audibert and
Duhaut (1970) found that the concentration of metal deposition varies
linearly from the top to the bottom.
Sato et al.
(1970) reported that
the coke deposition increases along with the bed, while metal deposition
decreases from the inlet to the outlet.
By comparing with vanadium
profile, the nickel profile appears to be mild along with the bed;
this behavior results in the increasing ratio of
Ni- along with the bed.
These findings are consistent with the earlier statements made in
2.2-1.b and 2.2-2.a that vanadium removal is faster than nickel, and
while coke was formed consecutively, vanadium and nickel were formed
simultaneously.
Figure 2-13 shows the concentration profile of nickel,
vanadium, and carbon along with the reactor bed.
(Sato et al. (1970)).
It clearly shows that coke reaches saturation concentration after
50 hours on stream, while vanadium and nickel keep on increasing.
Similar result was reported by Inoguchi et al. (1971)-(a),
Sato (1970),
and Oxenreiter et al. (1972).
Kwan and
-6512
10
C
8
lot
0.81.
0.61-
v
0.4
0.2
-
Ni
-
0
50
HRS ON STREAM
12
10
C
9
"i. 6
4.
H
2
Ni
0
Inlet
Center
Outlet
1000 HRS ON STREAM
Fig. 2-13
Concentration Profile of Carbon, Vanadium, and Nickel
Along with the Reactor Bed.
(Sato et al. (1970)).
-662.3
Research and Development on Metal Removal Processes:
As hydrodemetallation occurs along with hydrodesulphurization, a
major part of available investigations have been devoted to studying
process variables influence on HDS process results, to testing new
HDS catalysts, and developing new direct HDS process technology.
Most
of the aforementioned references in section 2.2 are of this category.
Some of the available processes that involves metal removing in
direct hydrodesulphurization unit are: "Resid HDS", developed by Gulf
(Brunn et al. (1975);
"RDS and VRDS hydrotreating"by Chevron; "RCD
Unibon" by UOP; and "Resid Ultrafining" by Amoco.
(Mosby et al. (1973))
More details can be found in "Hydrocarbon Processing", September (1978).
When the vanadium plus nickel contents in feedstocks are over
200 ppm, the direct hydrodesulphurization is usually not economical.
As a result, an alternate scheme of demetallation/desulfurization is
necessary.
In the U.S. alone over 300 patents have issued dealing
with the removal of metal contaminants from various petroleum fractions.
Some of the representative demetallation which do not take place
in hydrodesulphurization reactor are briefly described as follows:
(Reference:
Hydrocarbon Processing, September, (1978)).
(1) Extraction:
UOP has developed Demex process, which is using low-molecular
weight paraffinic solvents to demetallize vacuum residuals.
The
process has the ability of spliting high metal content residuals
into a demetallized oil (DMO) of relatively low metal level and an
asphalt with a high metal content.
A typical 130 ppm nickel and
-67-
vanadium yield DMO which is under 30 ppm nickel and vanadium.
Kerr-McGee Refining Corp. came up with another process called
"Residuum Oil Supercritical Extraction (ROSE)",
extraction.
The result is
which use pentane for
that about 70%-90% of metals in residuals are
removed.
Other related processes like solvent deasphalting,
propane
deasphalting were also metioned in the above reference.
(2) Scavenging:
to remove metals via relatively inexpensive,
occuring agents.
natural
Use of pretreatment guard chambers containing these
solid absorbents are usually required.
Cities Service Research
&
This is
Development Co. uses an ebullating bed reactor ahead of a hydrotreater
when porcessing a residual containing large amount of metal (200-300
ppm).
The reactor is loaded with an undisclosed natural agent, which
cost 5-10% as much as CoO-MoO 3 /Al 2 03 catalyst used in the hydrotreater.
(LC-Fining Process).
Shell's Hydrodesulphurization process features an
unidentified agent said to have a high affinity for metals and low
activity for sulphur.
The company employs a moving bed reactor with
special internals to prevent plugging and maintain even distribution
of liquid over the full vessel cross section.
Fresh supplies of the
scavenger are added and spent material withdrawn at a rate that
optimizes the efficiency of vanadium removal.
Hydrocarbon Research, following tests it conducted for the U.S.
Environmental Protection Agency, favors activated bauxite impregnated
-68with a small amount of molybdenum for scavenging.
An ebullating bed
is used for the metal removal process, and it is known as H-Oil process
when combine with other desulphurization process. (Chervenak et al.
(1973), (1976), and Rovesti and Wolk (1973)).
Other available processes are Exxon's "RESIDfining" process
(Moritz et al. (1971)), and the Unicracking/HDS process by Union Oil
Co. (Young and Richardson (1977)).
(3) Fluid Catalyst Cracking (FCC) Developments:
Another approach is to send the residuals into FCC units, and to
remove the metals with cat-cracking catalyst.
ARCO developed the Demet III process, and claimed to have a low
cost catalyst regeneration system that has the ability of removing
metals from cracking catalysts.
Both chemical and physical treatments
are used in regenerating the catalyst.
(Edison et al. (1976)).
Other process regarding metal removal with FCC units is Pullman-
Kellogg's "Heavy Oil Cracking".
-693.
3.1
Materials and Experimental Procedures:
Equipment for Hydrodemetallation Study:
As the main objective in this study is to study the intrinsic
(diffusion free) kinetics of hydrodemetallation reaction.
batch reactor system will meet the need.
A schematic of the autoclave
batch reactor system is shown in Figure 3-1.
Figure 3-2 shows the
picture of this autoclave batch reactor system.
are given in Figure 3-3.
An autoclave
The specifications
The 1-liter autoclave (Autoclave Engineers,
is designed to stand 37325 KPa (5400 psi)
Erie, Penn., Model AFP 1005),
and 480 0 C, which is much higher than our operating conditions.
In order to disperse the hydrogen into the autoclave effectively
and to prevent catalyst particles froin entering into the sampling line,
0.5 micron stainless steel porous filter with 3/16 inch in diameter and
1/2 inch in length (New Met Inc., Pequabuck, Conn.) were attached at
the end of hydrogen inlet line and at the beginning of liquid sampling
line respectively.
In addition, a special catalyst loader at essentially
room temperature was designed to store the mixture of the catalyst and
metal dissolving white oil.
when it
This mixture was injected into the autoclave
reached reaction temperature.
This design will prevent hydro-
demetallation reaction from occuring during the heating period.
3-4
Figure
shows a close look of the main body of the 1-liter autoclave.
The specifications are given in Table 3-1.
As the porous filter and
the catalyst loader are of special design in this study, they are shown
in more details in Figure 3-5.
For safety reasons, a 1/8 inch steel plate barricade was built to
Pt/A 12 03
Water
Ox ygjen
( Removal/
Removal
Z eolite
Catalyst
Looder
Motor
Ball
0
Valve
Pressure
He
Gaoug e
Liquid
Sampling
Linq
I
I
I
I
I
S
I
I
S
I
i
I
I
I
I
I
-- >Vq nt
I
----
I
I
I
H2
..
Im p alI e
tr
Porous Filter
1 Liter Autoclovq
Fig. 3-1
Schematic of High Pressure Autoclave Reactor System for Hydrodemetallation Study.
-71-
Fig. 3-2
Autoclave Batch Reactor System.
-72-
1
6
5
i
I
R=
.4
10
9
m.-m
16
15
-
14
13
List of Components for Figure 3-2.
(1) Catalyst Loader; (2) Extension Handle; (3) Ball Valve;
(4) Cooling Coils for Cooling Jacket; (5) Belt; (6) MagneDrive; (7) 1/4" O.D. Tube to Pressure Gauge; (8) Cover of
Autoclave;
(9) Body of Autoclave; (10)
Motor; (11)
& (12)
&
Fig. 3-3
12
(13) Thermocouples; (14) Vent Line; (15) Insulation Material;
(16) Furnace; (17) Stand.
-73-
i7-
2 -I- I +",aP.
31 mm~L~2~
4
\kZ
~
0
1-
I
;I
9
______
-
k
5
6
V6.
rfr
0
7
17
1
9
2/
.~-
9
3
1
L
L
11
133
I
Fig. 3-4
--
4.
M
M
0
Zr
4
-4
14
,-15
(A
437
0
0
Cl
V 3.001 DPIA
-
8 //
I 7tb
UNIT: INCH
Schematic of Main Body of 1-Liter Autoclave.
-74Table 3-1
List of Major Components in Figure 3-4:
Maximum Allowable Working Pressure: 5400 PSI at 900 F
Hydrotest Pressure : 9100 PSI at R.T.
Components
Specifications
1
Cooling Jacket
With 1/4
2
Gas Input Line
1/8
3
Sampling Line
1/16" O.D.70.030 I.D. 316 S.S. Tube
4
Hex. Soc. Cap 'Screw
7/8
5
Cover of Autoclave
316 S.S.
6
Gasket
316 S.S.
7
Body
316 S.S.
8
Stand
9
Cooling Coil
3/16" O.D.,1/8" I.D. 316 S.S.
10
Thermowell
3/16" O.D.,1/8" I.D. 316 S.S.
11
Shaft
316 S.S.
12
Locknut
316 s.s.
13
Impeller
1-1/4" Dia., 316 S.S.
14
Furnace
High Temp. Max. Operating Temp.: 1000 F,
115V. -1 - 50/60 HZ-1.7 K.W., Type K
Thermocouple
15
Transite Plate
16
Catalyst Charge Line
1/4" 0.D.,0.180
17
Coupling
For 1/16" to 1/8", 316 SS.
18
Porous Filter
3/16" Dia., 1/2" Long, 1/2A- Openings.
O.D. Tubing Cooling Water System
0.D.,0.062
316 S.S. Tube
Dia.
I.D. 316 S.S. Tube
-75.
'
-
1.3.
1
11'D
F~i'
C
4
-4
U
(.
*--
jd
n
11
5
).
Components
Specifications
1.
1/8" o.D. Inlet
316 s.s.,o.o62"
I.D..
2.
Adapter
316
Coupling
O.D. (F) to
1/2" O.D. (M).
316 S.s., 1/2"
3.
.
3
O.D. to 1" O.D...
4.
Nipple
316 S.S.,o.688"
I.D..
5.
316 S.S.,1" onD.
Coupling
to 1"O.D..
6.
Adapter
316 S.S.,1" o.D
(M) to 1/4" OD.
(F).
6
7
7.
Ball Valve
316 S.S,For
1/4" Ofl, Tube.
8.
Extension Handle
Brass
9.
1/4" o.D.
316 S.S.,O.180"
Outlet
I.D..
10. 1/8" O.D. Tube
316 s.s.,o.o62"
I.D..
11. 1/2 Micron
Porous Filter
Fig.
3-5
Schematic of Catalyst Loader
316 S.S.
(Left) and Porous Filter (Right).
-76surround the autoclave, and a rupture disc with 22677 KPa specification was installed.
About the temperature control and indication system, there is an
temperature indicator (Model 2170 A, Omega Engineering, Stamford,
Conn.) with an independent thermocouple (Item 11 in Figure 3-3) placed
in thermowell to take the temperature reading during reaction.
As the
temperature controller (Model 238-13, Type K Thermocouple, P/N
H8-4002-0600, LFE Corp., Waltham, Mass.) is installed to control the
temperature of the furnace, the thermocouple (Item 13 in Figure
3-3)
was connected to the furnace.
For further safety insurance, an on-off temperature controller
(Model 232-F, P/N H2-1022-4100, LFE Corp., Waltham, Mass.) with an
independent thermocouple (Item 12 in Figure
3-3)
attached to thermowell
was placed in addition to the main temperature controller; this on-off
controller will shut off the furnace in case of failure of the main
controller thermocouple.
-773.2
Materials:
Catalyst:
3.2-1
Commercially available CoO-MoO3 /Al 2 0 3 catalyst, NiO-MoO /Al 0
3
2 3
catalyst, and alumina catalyst carriers were used for our study.
They were described as follows:
(1) CoO-MoO 3 /Al 2 0 3 Catalyst:
As in commercial, most of the hydrodesulphurization units use
CoO-MoO /Al 20
study.
as HDM/HDS catalyst, it
was also used for most of the
The catalysts were HDS 16A catalyst, and were obtained from
American Cyanamid (Bound Brook, N.J.).
The physical and chemical pro-
perties for HDS 16A catalyst are shown in Table 3-2.
Figure 3-6
shows
the pore size distribution.
(2) NiO-MoO3 /Al 2 03 Catalyst:
Few runs on NiO-MoO /Al 2 03 were also made by using HDS 9A catalyst
from American Cyanamid.
Table 3-3 shows their properties, and Figure
3-7 shows the pore size distribution.
(3) e-Alumina Catalyst Carrier:
This catalyst carrier was used for comparison and was also used
as the carrier for self preparation catalyst.
from Norton Company (Akron, Ohio).
The carrier was obtained
Again, Table 3-4 shows the properties,
and Figure 3-8 shows pore size distribution.
(4) Other Catalysts:
The oxygen removal catalyst in the hydrogen line was 0.5 wt% Pt
on alumina, 1/8 inch pellets type M catalyst (Engelhard Industries,
Newark, N.J.).
The oxygen removal catalyst in the helium line was the
-78mixture of (a) Copper catalyst, with 10% CuO on alumina (Cu-0803 T 1/8
inch, Harshaw Chemical Co., Cleveland, Ohio), and (b) Zinc catalyst, 100%
ZnO (Zn-0401 E 3/16 inch, Harshaw Chemical Co., Cleveland, Ohio).
The
water removal catalyst was typical zeolite.
(5) Self Preparation Catalyst:
The procedure to prepare catalyst will be mentioned in section 3.3-4.
The effect of self preparation catalysts on demetallation reaction will
be discussed in section 4.5.
-79Table 3-2
Physical and Chemical Properties for American Cyanamid HDS 16A
2 03
CoO-MoO 3/Al
Catalyst:
Lot. No. MTG-S-0573
(1) Chemical Compositions:
5.7
Coo
:
MoO
: 12.2
3
Na2
:
0.03
Fe
:
0.04
(wt%)
(2) Physical Properties:
Apparent bulk density, g/cm 3
0.737
Average diameter, cm
Average length, cm
0.152 (0.06 inches)
0.432 (0.17 inches)
Average crush strength, g
6350.4 (14 lbs)
Fines, wt%
0.2 (-16 mesh)
Pore volume (H2 0),
Pore volume (Hg),
cc/g
cc/g
2
Surface area, m /g
0.43
0.50
Density, g/cc
176
0.67*
Average pore diameter,
1) 80.4 angstron*
2) 97.7 angstron
*1):
The density is obtained by crushing the catalyst into 0.074-0.088 mm
average diameter (170-200 mesh), and then preheat at 400 0 C for 24
hours to remove water trap in the catalyst before it was placed in
measuring bottle.
*2): 80.4 1 is the value taken as that corresponding to 50% of the total
pore volume, 97.7 R is the value taken by dividing the value of pore
volume by surface area and multiply by 4.
Pressure (PSIA)
0
0
80q
0
0
I
00
4
I*
~l
I
I
I
I
0
I
0
0
0
0
0
0
0
0
0
00
~-1
c; I
C)
4
.0
C.>
I,
N
cN
0
0
0
c
p
c
442
1767.6
Fig. 3-6
I
1
176.8
117.8
Pore Dihmeter (Angstrons)
I
88.4 70.7 59-0 44.2
Pore Size Distribution for HDS-16A CoO-MoO 3/Al 20
Catalyst.
35.4
OD
-81Table 3-3
Physical and Chemical Properties for American Cyanamid
HDS 9A NiO-MoO3 /Al 2 03 Catalyst
Lot. No. MTG-S-0155
(1) Chemical Composition:s s
Ni0
MoO3
3.2
17.5
Na2 0
0.03
Fe
s04
0.03
0.4
Si02
0.5
(wt%)
(2) Physical Properties:
Average diameter, cm
0.155 (0.061 inches)
Average length, cm
0.457
Poured bulk density, g/cm3
0.769
3
Compacted bulk density, g/cm
0.833
Crush strength, g
6350.4
Fines, U.S. Std. Sieve
-16 mesh, wt%
0.1
Loss on abrasion, wt%
1.0
Loss on Ignition at
900 0 F,wt%
1.2
0.42
Pore volume (Hg), cc/g
Surface area, m2/g
Density, g/cc*
0.52
170
0.69
Average pore diameter
1) 88
*
Pore volume (H20), cc/g
*1, *2:
(14 lbs)
see footnotes in Table 3-2.
A
2) 85
A
I
0
8
2I
2000
i
5000
10000
Pore Diameter (Angstrons)
1000
I I
I
200
1 I
1III
100
50
O
a
\0
0
0
.H
0I
0:
0
j
C\J
Cq
0
0
I
I
I
i
I I
100
10
I
I
*
0
IW
I
e-
I
I I I I
I
I
fr
I
I I
1000
Pressure (PSIA)
Fig. 3-7
Pore Size Distribution for HDS-9A NiO-MoO 3 /Al 2 03 Catalyst.
III
10000
t
.
I
I
0
-83Table
3-4
Chemical and Physical Properties for
Norton SA-6273 Catalyst Carrier
Lot. No. 63012
(1) Chemical Compositions:
Al20
Na 0
So2
si0 2
Fe2 0
: > 99.85
-< 0.015
: 0.09
:
(wt%)
0.06
(2) Physical Properties:
Size and shape
8-14 mesh (ave. 0.159 cm) spheres.
Crush strength, g
2404
Crystal phase, XRD
Gamma alumina
Pore volume, H2 0, cc/gm
0.662
Pore volume, Hg, cc/gm
0.719
218.73
1) 68A
Surface area, m 2 /g
Average pore diameter
* see footmole 2 of Table 3-2.
2) 65.7A
4
IW
qw
Pore Diameter (Angstrons)
o
o
o
00
0
00
0
0
0
0
0
-
0
a>>
'c;
\o
HU)
80
-
000
c
ro
Pressure
Fig.
3-8
(PSIA)
Pore Size Distribution for lr'-Alumina Catalyst Carrier.
-85Solvent:
3.2-2
White Oil (Nujol) was purchased from Plough Inc.,
Tenn.).
(Memphis,
Nujol is a mixture of liquid hydrocarbons obtained from
petroleum.
It is a colorless, transparent, oily liquid, free from
fluorescence.
It is odorless and tasteless at room temperature.
It should be free from sulphur and nitrogen compounds.
From the
average molecular weight and viscosity data, it is believed that
Nujol consists only of naphthenes, paraffins, and isoparaffins, with
naphthenes dominating.
The average number of naphthene rings should
be about 2.5 - 4.0, and should be about 40% of carbon in naphthene
rings.
Table 3-5 shows the properties of Nujol.
More details about
typical white oils can be found from Franks (1964)-(a), (1964)-(b),
Steenbergen (1974), Fiero (1965), and Meyer (1968).
3.2-3
Gas:
Hydrogen is ultra high purity with less than 3 ppm oxygen and at
least 99.999% hydrogen.
Helium is 99.995% purity in 3500 psig cylinder.
Oxygen used in the preparation of catalyst is research purity with
99.99% of oxygen.
All were purchased from Matheson Gas Products
(Gloucester, Mass.).
-86Table 3-5
Specifications of Nujol:
Specific Gravity
: 0.875 to 0.885
Density by Own Measurement at 24.670 C
Viscosity at 1000 F
: 0.8763 g/cc
: 360 to :390 SSU
Viscosity at 2100F
: 54 SSU
Net Optical Density
: 0.100 maximum
Flash Point, Pensky-Martin Open Cup
: 420 0 F
Pour Point
: 25 0 F
1.48
Refractive Index at 20 0
7.5 % Absorbance
U.V. Absorption at 275 run
15.0 % Absorbance
10.0 % Absorbance
295/299 run
299 rnm up
B.P. Range at Atmospheric Pressure
IBP
% % %
50
90
95
FBP
at 10 mm
IBP
%
5
% %
%
10
50
90
95
676 0 F
8050 F
878 0 F
903 F
927 F
4o6 T
464 F
485 F
a 5260F
: 5810 F
a 603 0 F
624 0 F
%
6
:
:
:
:
:
FBP
Average Formula
: 30H 57
Average Molecular Weight
417
Description, Solubility, Acidity or
Alkalinity, Readily Carbonizable Substances,
Solid Paraffin, Sulphur Compounds, and
Cloud Point
: all passes U.S.P.
test
-87Model Porphyrins and Metalloporphyrins Compounds:
3.2-4
All the model compounds were purphased from Man-Win Coordination
Chemicals (Washington D.C.).
The molecular structures of free base
tetraphenylporphine (TPP), free base etioporphyrin I (Etio I),
nickel tetraphenylporphine, vanadyl tetraphenylporphine (VO-TPP),
nickel etroporphyrin I (Ni-Etio I), and vanadyl etioporphyrin I
(VO-Etio I) are shown in Figure
(1975),
and Sugihara et al.
3-9.
Baker and Palmer (1978),
Yen
(1970) mentioned that the metallo etio-
porphyrin series are available in nature.
Metallo tetraphenyl-
porphines do not occur in nature, they were used to compare the
demetallation activity with metallo etioporphyrins.
Free base TWP
and Etio are notfound in nature either, they were used for special
study.
(Section 4.5).
While Etio and metallo-Etio are pure, TP
and metallo-TPP are reported to have less than 5% of chlorin and
metallo-chlorin.
The structures of chlorins are shown in Figure 3-10.
Method for the preparation of these porphyrins and metalloporphyrins can be found in the book of Smith (1975),
and Dolphin (1978);
and also the publications by Dorough and Miller (1952),
Rousseau and
Dolphin (1974), Erdman et al. (1956), Adler et al. (1967), Adler
et al. (1970), Rislove et al. (1968), Eisner and Harding (1964),
Bluestein and Sugihara (1973).
-88C2H5
CH3
H3 c.N.N
N
/
\
C 2 H5
N
N
H5 C2-
CH3
CH 3
2H
(2)
C2H5
H3
N
N
CH3
.-- N
N
c 2H 5
)
3
H52-N
CH 3
(3)
2H5
(4)
N/
N%
CH3
H3
CH2H5
CH
..-- N
N
/
2H 5
/
N
6CH3
CH3
C2 H5
(5)
Fig. 3-9
Structures of Model Compounds:
(2) Etio-I: MW=474, C32N H3
(i) TPP: MW=614.67,
(3) Ni-TPP: Mw=671.38, C4N4 H 2 8 Ni.
(4) Ni-Etio I: MW=530.71, C32 N4 H32 Ni.
C4NH 2 8 VO.
C4N4 H3 0
(6) VO-Etio I: NW=538.94,
(5) VO-TPP: MW=679.61,
C3 2 N4 H3 2 VO. (q:Phenyl Gruop.)
-89-
N
N
N
N-
Chlorin
No
N
N
(N
Niekel Chilorin
(A
-- N.
b
N
=O
N
N
Vanadyl Chlorin
Fig. 3-10
Structures of Chlorins (TPP type).
-903.3
3.3-1
Experimental Procedures:
Dissolving Model Compounds in Nujol:
As all the model compounds are solids at room temperature and
have poor solubility, heating is needed to dissolve these compounds
into Nujol.
The method of dissolving model compounds in Nujol was
developed by Rakesh Agrawal.
Nujol was placed in funnel originally, and
was vacuum pumped to remove air dissolved.
The air removed Nujol would
then mix with appropriate amount of either porphyrins or metalloporphyrins in the filtering flask.
The apparatus of removing air from Nujol
is shown in Figure 3-11.
After all the Nujol has been transferred to the flask, the
apparatus shown in Figure 3-11 was quickly changed to the one as
shown in Figure 3-12.
(Note that the funnel, filter was replaced by
valves and helium line).
The mixture of model compounds and Nujol
were then heated under positive helium pressure and with proper mixing;
frequently the helium supply was cut and the vacuum pump was applied
to remove any oxygen that may still exist in Nujol.
The temperature
applied to the heater was 315 0 C, although lower temperature (204 0 C)
is also adequate for dissolving metalloetioporphyrins in Nujol, 315 C
was generally applied.
The peak heating period was three hours; by
including the preheating and postcooling periods, the total duration
under heat could be six hours.
A batch of 1300 c.c. to 1600 c.c.
model compounds containing Nujol can be prepared each time.
-91-
After the solution was cooled to room temperature,
placed in the funnel.
they were
Vacuum pump was then applied to filter the
solution through 0.5 micron membrane filter disc to remove any larger
undissolved porphyrin particles.
The apparatus used was essentially
the same as the one shown in Figure 3-11.
The filtered solution
was finally placed in glass jar for storage.
Solubility limits the concentration to less than 40 ppm nickel
in Nujol, also 500 ppm TPP or Etio in Nujol.
While vanadyl etio-
porphyrin appears to have similar solubility in Nujol as nickel
porphyrin, vanadyl tetraphenylporphine is less soluble.
It was unable
to obtain more than 20 ppm of vanadyl tetraphenylporphine in Nujol.
1w
Imw
Iw
1. Nujol
2. Aluminum Clamp
3. Filtering Flask
4. Spinbar
5. Model Compounds
6. Hot Plate/Stirrer
7. Funnel,
To Vacuum Pump
10
8L
1000 co
8. 0.5 Micron Membrane
Filter Disc
9. 1/4" O.D.
I\
Tygon Tube
10. Vacuum Traps
11. Liquid Nitrogen
2-
00
U
Fig. 3-11
Apparatus for Removing Air from Nujol.
0
0
1. Valves
2. Mixture of Nujol an4
Model Compounds
3. Spinbar
Helium Supply
4. Hot Plate/ Stirrer
6
5. 1/4" O.D. Tygon Tube
6. vacuum Traps
7.
Liguid Nitrogen
To Vacuum Pump
4(
I
If
Fig.
3-12
Apparatus for Dissolving Model Compounds in Nujol.
1
-943.3-2
Pretreatment of Catalyst:
The catalyst was crused into 170-200 mesh (0.074-0.088 mm
diameter) before use.
The measured catalyst was preheated at 44000
for 24 hours in tubular furnace.
Experiment showed that there was 11%
loss of weight for HDS 16A Co0-MoO 3 /Al 2 03 catalyst and Norton alumina
carrier, 6% for HDS 9A NiO-MoO 3 /Al 2 03 catalyst, and only
3%
for self
preparation catalysts; the loss of weight is believed to be loss of
water during the first 24 hours.
As no further decreasing of weight
after 24 hours was observed, 24 hours should be enough to removed the
water that originally trapped in the catalyst.
The deviation about
the loss of weight during heating period is due to the fact that each
type of catalyst has been exposed to atmosphere for different period
of time; self preparation catalysts have least amount of water because
they have been heated before and during calcination.
The heated
catalyst was quickly weighted and placed in the catalyst loader with
approximately 25 gram of Nujol with dissolved metal.
3.3-3
Demetallation Experiment:
Measured metal (either nickel or vanadium) containing solution
prepared from the method cited in 3.3-1 was placed inside the autoclave.
After all the parts were assembled, pressure test was conducted under
helium pressure.
Usually 7000 KPa (1000 PSI) higher than the operating
pressure was used for pressure test.
Before heating was started, the
-95reactor was purged by low pressure helium and followed by hydrogen for
one hour to remove the air in the reactor.
Experiment shows that there
is no need to remove the air remain in the catalyst loader.
The reactor
and catalyst loader was then filled up with hydrogen, the pressure was
preset to a value that it would reach reaction pressure when the reactor
reached reaction temperature.
The hydrogen line was cut after both
places reached desired pressure.
The reactor was heated to 250 0 C overnight to ensure no failure
on temperature controling system or reactor system.
It was then
heated to the desired temperature, usually it took 150 minutes to
reach desired temperature and stay steady.
The reactor was then
depressurized to less than 700 KPa (100 PSI).
By connecting hydrogen
line at 6995 KPa (1000 PSIG) to the catalyst loader and. by opening the
ball value at the bottom of the loader, the catalyst/solution mixture
was quickly injected into the reactor,
again.
and the ball valve was closed
The procedure was repeated three times to ensure complete
injection of catalyst.
The hydrogen supply line was then connected
to the reactor to let the pressure in reactor reach the desired
pressure, and then the supply line was cut.
This procedure usually took three minutes.
As the reactor tem-
perature was decreased due to the injection of cold catalyst/solution
mixture and hydrogen,
it
usually took
to reach desired temperature again.
6 more minutes for the temperatures
Time zero was set at the time the
-96catalyst was first
Table
3-6.
injected.
The operating conditions are listed in
The liquid samples were collected by sample vials
periodically from the liquid sampling line, they were then quenched in ice
water to reduced the temperature to room temperature.
After the reaction, cooling water was connected to cool the reactor
to lower than 800.
/solution
The reactor was opened, and the mixture of catalyst
filtered to recover the spent catalyst.
The reactor
was then cleaned by acetone for the usage of next run.
-97Table 3-6
Operating Conditions for Demetallation Experiments:
Oil u sed
: 420g (,--25g in loader and ---395g in
reactor originally)
Catal yst
Oil/Catalyst (cc/g)*
: 0.5 to 2g (dry)
300-1000, with 700 as standard ratio.
(This is based on a previous test that
about
95% of the catalyst was injected
successfully into the reactor.).
Hydrogen pressure
Temperature
Impeller speed
4237-12509 KPa. (600-1800 PSIG).
: 287-357 0 C. (550-675*F).
500 RPM
The volume of Nujol at reaction temperature was calctilated
based on: density (g/cc) = 0.876 x (1-0.000705 (T(C0 )-24.67))
-983.3-4
Self Preparation Catalyst:
The method for the preparation of catalyst was obtained through
private discussion with C.P. Cheng of the University of Delaware
More details about the methods of preparation, and the structures
of HDS catalyst can be found from his Master's thesis (Cheng (1978)).
The procedures for preparation of catalyst include: (1)
Pre-
treatment of catalyst carriers; (2) Dissolving metal salts in water
to make solution; (3) Impregnation and Drying; (4) Calcination.
They are described briefly as follows (2 grams of dried alumina was
used as the basis of calculation):
(1)
Pretreatment of catalyst carriers:
The catalyst carrier (Norton, SA-6273
s-Alumina) was crushed
into 170-200 mesh size (0.074-0.088 mm in diameter), and then placed
in tubular furnace at 440 0C for 24 hours to remove the water.
(2)
Making solutions:
Molybdenum solutions were prepared from ammonium molybdate,
(Fisher Scientific Co., Fair Lawns, N.J.; (NH)6 Mo 7 0 24 . 4H20
F.W. = 1235.86; Moo 3 = 81.9%.).
To prepare a solution which would
give 15% MoO 3 when impregnated on I'-alumina carrier,
ammonium molybdate
1.38g of
was dissolved in 5 ml of distilled water.
Cobalt solutions were prepared from cobalt nitrate, (Fisher
Scientific Co., Fair Lawns, N.J.; Co(NO 3 )2 .6H2 0; F.W. = 291.04;
-99COO = 25.76%.).
To prepare a solution which would give 7% CoO
on
VJ-alumina carrier, 2.05g of cobalt nitrate was dissolved in 5cc
distilled water.
Nickel solution were prepared from nickel nitrate, (Fisher
Scientific Co., Fair Lawns, N.J.; Ni(NO 3 )2 . 6H2 0; F.W. = 290.81;
NiO = 25.69%).
on 9
To prepare a solution which would give 7% NiO
-alumina support, 2.05g of nickel nitrate was dissolved in
5cc distilled water.
(3)
Impregnation and Drying:
Catalysts were prepared by impregnation of cobalt and molybdenum
solutions or nickel and molybdenum solutions on the carrier using the
"dry impregnation" method as described in Chapter 2 of Cheng's (1978)
thesis.
The dried carrier (2g) was placed in 20 ml beaker.
Molybdenum
solution in ammount equal to the pore volume of the support (1.32c.c.)
was added using a pipette.
to ensure proper mixing.
5
The mixture was then stirred for 20 minutes
It was then placed in oven at 110 0 C for
hours to evaporate the water.
Impregnation with cobalt or nickel
solution followed the same procedure.
The impregnated sample was
then placed in desicator overnight for cooling.
-100-
(4)
Calcination:
The sample was taken out from desicator and placed in a special
made quartz tube.
It was then calcined in a preheated tubular
furnace at 500 C for 6 hours under a slow flow of oxygen (0.5-1 cc/sec).
The catalyst was removed immediately after six hours and placed
in small bottles for cooling.
It was then remeshed to secure the
desired size (0.074 mm/0.088 mm diameter).
Standard procedures
mentioned in section 3.3-2 and 3.3-3 were followed when the prepared
catalyst was used for demetallation experiment.
MoO 3 catalyst, CoO catalyst, different Co/Mo ratio of CoO-MoO 3
catalyst, and NiO-MoO
catalyst were prepared by the above procedures.
variation of the above method was also studied by impregnating first
with cobalt solution then with a molybdenum solution, and by calcine
at 600 C; however, no difference on demetallation activity has been
found.
Details about the composition and result of these self pre-
paration catalyst will be shown in Chapter 4.
-101-
3.4
Analysis:
3.4-1
Liquid Sample:
About 0.3 to 1.5g of liquid was taken out from the sample vials,
it
was then placed in 10 me volume flask.
After it
was weighted, xylene
( 4 x-5-s, ACS certified, Fischer Scientific, Fair Lawns, N.J.) was
placed into the flask to ditute the sample; the ratio of sample to
xylene was 1:5 to 1:25, depend on the concentration of the original
sample.
When atomic absorption spectrophotometer is used for analysis,
too low xylene proportion would increase the scattering of reading; and
too high xylene proportion would lead too low reading.
Slavin (1964), and Kerber (1966)).
(Trent and
Atomic absorption spectrophotometer
(Perkin-Elmer 403) was used to find the total concentration of nickel or
vanadium in the sample.
The standard solutions for nickel or vanadium
were purchased from Conostan Division, Continental Oil Company, Ponca
City, Oklahoma.
Each standard contains either 5000 ppm of nickel or
vanadium dissolved in paraffinic hydrocarbons (21 cst at 100OF for
viscosity, and 4000F for flash point).
Approximately 200 ppm standard
solution was prepared by diluting the original standard with Nujol and
stored for use.
When each time on analysis, 5 ppm standard was prepared
by diluting the 200 ppm standard by xylene.
Standard addition method
(as described by Trent and Slavin (1964)) was taken to obtain the
calibration curve for analysis.
It appears that for nickel analysis,
the detection limit was about 0.05 ppm for nickel in xylene, and the
-102-
calibration curve was linear up to 1.5 ppm; in the case of vanadium,
the detection limit was about 0.15 ppm, and calibration curve was
linear up to 1.5 ppm.
Compare with nickel, the vanadium analysis
is more difficult and less accurate.
For vanadium analysis, special
burner has to be placed for nitrous oxide-acetylene flames, these were
mentioned by Manning (1965), and Lang et al. (1975).
The detail
procedure of using atomic absorption spectrophotometer for analysis
was developed by Rakesh Agrawal and myself.
As mentioned in Chapter 2, porphyrins have intensive absorption
peaks in visible bands; visible spectrophotometers were also used to
find the concentration of free base porphyrins or metalloporphyrins
in liquid sample.
Cary 14 visible spectrophotometer was used to
obtain the absorption spectra in the visible range for some of the
samples.
The spectra for Ni-Etio I and VO-Etio I have been shown
in Figure 2-5.
Figure 3-13 shows the visible spectra for Ni-TPP
and VO-TPP, and Figure 3-14 shows the visible spectra for free base
TPP and Etio I.
Table 3-7 shows a summary of the absorption peaks
for the model compounds used.
By comparing vanadyl porphyrins with
nickel porphyrins, it is clear that all the major peaks for vanadyl
porphyrins have shifted to longer wavelength, and the ratio of
571.5/534 peaks for VO-Etio is smaller than 553/517 peaks for Ni-Etio.
This is consistent with the finding of Baker and Palmer (1978), which
was also mentioned in section 2.1-1.b.
For quantitative analysis of metalloporphyrins, Coleman 111
(Perkin-Elmer) visible spectrophotometer was used.
The sample analyzed
-103SI
z
-
-
F
I
414
0
O.6-
0
o
0.4
U)
0.2
0
I
380
42a
I
I
I
t
46o
5o
$40
WAVELENGTH
(nm)
1 -1
I
so
620
548
z
0
423
0
0.4~
508
583
0
3b0
420
460
500
WAVELENGTH
Figure 3-13
540
580
620
(nm)
Absorption Spectra of NI-TPP (Top) and VO-TPP (Bottom).
Samples were Dissolved in Nujol First and Then Diluted
by Xylene.
Background: Xylene.
-104-
j
I
I
I
400
Etio
z
0.8
0
Cr
0
01
498.5
0.4
530.5
623.5
569
380
420
-
I
SI
0
460
500
540
WAVELEN GTH (nm)
580
660
620
T PP
0.8
z
418
--
0
CL
514
0
V)
CO
0.4
-54B
590
64G
4802
o" oooo"o44,
0
380
Fig. 3-14
420
460
500
WAVELENGTR
540
580
620
(nm)
Absorption Spectra of Free Base Etio I (Top) and Free
Base TPP (Bottom). Samples were Dissolved in Nujol First
and Then Diluted by Xylene.
Background:
Xylene.
6 G0
-105Table 3-7
Absorption Peaks for Model Compounds:
Soret Peak (n)
Compounds
Visible Peaks (nm)
Free Base TPP
418
480, 514, 548, 590, 646
Free Base Etio I
400
498.5, 530.5, 569, 623.5
Nickel TPP
414
527.5
Vanadyl TPP
423
508, 548, 583
Nickel Etio I
391
517, 553
Vanadyl Etio I
407
534, 571.5
Table 3-8
Peaks Used for Quantitative Analysis:
Compounds
Peak Used
Absorption Constant
(
Absorption/ppm Metal)
Nickel TPP
527.5
0.287 + 0.019
Vanadyl TPP
548
0.424 t 0.020
Nickel Etio I
517
0.164 + 0.007
Vanadyl Etio I
534
0.242 t 0.011
were essentially the same samples prepared for atomic absorption analysis
(in xylene diluted form).
The peak used and the absorption constant
found from calibration curve are shown in Table
limit is about
As (1)
3-8.
The detection
3.8% absorption.
the deviation of absorption constant found for each time of
analysis; (2) the background change during reaction;
(3) the possibly
transalkylation of porphyrins during reaction were expected to affect
the quantitative analysis of visible spectrophotometer rather than
atomic absorption spectrophotometer.
This study use atomic absorption
spectrophotometer as the main tool for analysis.
-107Solid Sample:
3.4-2
After each run, the spent catalyst was placed in Soxhlet extractor
(Fischer Scientific, Fair Lawns, N.J.) for 24 hours to remove the oil
trapped in the catalyst by xylene.
Figure 3-15 shows the Soxhlet
Then it was dried in a furnace at 110 0C for
extractor apparatus.
5 hours to vaporize the xylene.
Part of the sample was sent to Galbraith
Laboratories (Knoxville, Tenn.).for carbon, nitrogen,
and vanadium analysis.
resin and polished.
hydrogen, nickel,
The rest of the sample was then mounted on epoxy
Scanning electron x-ray microanalyzer
Model 5 Electron Microprobe Computer Automation,
(ETEC
(MAC)
Hayward, CA.) was used
to find the concentration of nickel or vanadium deposited on the catalyst,
and to see whether nickel or vanadium was uniformly distributed on the
The voltage used was 15 KV, and the current was 30 nanoamps.
catalyst.
Usually ten spots were taken for each particle examined; each spot was
approximatsly with the dimension of 3/(width) x 5/.(length) x 5/4
(depth).
Several particles in the same sample were examined to offset
the possibly experimental error.
3.4-3
Gas Sample:
The spent gas has been sent to Matheson Gas Products (Gloucester,
Mass.) for hydrogen analysis to ensure that the hydrogen consumption is
negligible.
Some fresh gas tanks have also been sent to them to check
the oxygen content.
The hydrogen analysis was
done by gas
chromatography; the oxygen analysis was done by Trace Oxygen Analyzer.
108-
To Vent
Cooling Water
Out
Condenser
Cooling Water
In
Soxhlet Extraction Tube
Thimble
500 cc Flask
Xylene
Hot Plate_
Fig. 3-15
--0
Soxhlet Extraction Apparatus.
-1094.
4.1
Result:
Nickel Porphyrin Runs for Commercially Available HDS 9A
or HDS 16A Catalyst:
Air Prepared Ni-TPP Runs:
4.1-1
This is
properties.
4.1-l.a
an early series,
which turn out to be of peculiar
We do not depend too much on it.
General Observations:
Ten experiments (Run NT1 to NT9, NT31) were carried out with
Al 0
23
as catalyst.
Except NT1, all the others use HDS 16A CoO-MoO
/
air prepared Ni-TPP.
In these ten runs, the solution was prepared in a
beaker so that the solution was exposed to the air
The temperature of heating was 250 C.
during heating.
Table 4-1 shows operating
conditions for each run.
By comparing the concentration of total nickel with that of NiTPP (Helium Prepared), it
as Ni-TPP.
appears that only 85% of the nickel remained
The rest of the 15% nickel is
not Ni-TPP or Ni-Chlorin,
and are believe to be either nickel oxide or organo-nickel compounds
which results from oxidation and degradation of porphyrins.
At the presence of oxidation agents,
porphyrins will be able to
degrade irreversibly to maleimides, which are fragments of porphyrins,
(Baker and Palmer (1978)).
Porphyrins also has the ability of rever-
sibly transfered to other type of compounds,
Starodubova et al. (1975)
had studied the oxidative-reducing properties of petroleum porphyrins.
-110Table 4-1
Operating Conditions for
Air Prepared Ni-TPP Run:
Catalyst
Initial Cat.
Conc. of Quantity
Total Ni
(P. P. M.
(g)
)
Run#
Oil
Temp.
Pressure
Duration
of
Reaction
(g)
(0 C)
(KPa)
(Hr.)
Quantity
NT 1
none
23.2
0
430.0
329.0
NT 2
HDS 16A
21.9
1.13
426.7
331.7
I,
9.4
NT 3
I
18.3
1.12
423.5
355.9
'I
7.1
NT 4
"t
30.4
2.58
431.6
294.7
I,
11.8
NT 5
"f
30.1
2.17
408.4
261.1
'I
27.3
NT 6
"t
25.6
1.02
428.3
342.4
'I
NT 7
"t
27.4
0.46
418.6
342.5
NT 8
"t
26.9
1.70
440.5
342.8
NT 9
"f
27.3
0.72
421.1
342.1
NT31
"f
30.0
1.16
385.7
329.0
6995
26.0
9.9
24.7
"o
9.6
21.5
I
9.5
*(1) Unless otherwise mentioned, the catalyst is fresh and the size is
0.074-0.088 mm in diameter.
HDS 16A is CoO-MoO 3 /Al 2 03 catalyst.
*(2) Run NT31 used HDS 16A with the size 0.149-0.177 mm in diameter.
*(3) For catalytic runs, time zero was the time catalyst was injected.
*(4) Initial concentration was the concentration of sample collected
at reaction temperature before catalyst was injected; in the case
of non-catalytic runs, it was collected after temperature reached
reaction temperature for 10 minutes.
-111Costantinides et al. (1959) studied the rate of oxidation of porphyrin,
and showed that it is function of air flow rate as well as temperature.
More details about the oxidation reactions and products of porphyrins
can be found from the books of Smith (1975) and Dolphin (1978).
In order to show that it is oxygen rather than nitrogen in the
air that reacts with porphyrin during the preparation period, two
experiments were made:
(1) Ni-TPP solutions in glass liner were placed in autoclave under
positive helium pressure at 200 0 C for 24 hours.
nickel nor loss of Ni-TPP were observed.
out and replaced with air.
Neither loss of total
The helium was then purged
After another 24 hours at 1600 C, it
was
found that while total nickel did not change, only 21% of nickel
remained as Ni-TPP.
This experiment shows that light is not needed for
the degradation of porphyrin to occur, but air is necessary.
(2) Two runs (NT1O,
NT11) of nitrogen prepared Ni-T2P solution were
made, and comparison with that of helium prepared Ni-TPP solution shows
no difference in demetallation activity.
However, as it
will be shown,
the air prepared Ni-TWP does not have the same demetallation behaviors
as helium prepared Ni-TTP.
These experiments show that it might be
oxygen but definitely not nitrogen that cause the change of Ni-TTP
during the preparation period.
In demetallation runs, it
is observed that 10 to 40% of total
nickel and Ni-TPP would disappear from the solution during the preheating period, that is, between the time the furnace was turned on
and the time the catalyst was about to be injected.
This disappearance
-112of total
nickel and Ni-TPP is believed to be either adsorbed on the
stainless steel wall of autoclave or evaporate to the gas phase, However, a run made without catalyst (Run NT1)
is
simply shows that there
no further drop after the concentration of nickel decrease from
28.1 to 23.2 ppm; this simply indicates that equilibrum has reached
either with the gas phase or the reactor wall. Same run (NT1) also
shows that most of the drop occurred during the period the reactor
was heated from 250 C to the desired temperature, this also indicates
that the rate of this drop is temperature dependent.
Figure 4-1
shows the percentage drop of total nickel and Ni-TPP as a function
of final reactor temperature.
The initial concentration is the con-
centration of nickel in the reactor before heating, the final concentration is the one taken before catalyst was injected (Which is exactly the initial concentration of hydrodemetallation study cited in
Table 4-1).
4.1-1.b
It
is
Kinetics:
observed that for lower temperature runs, the! reaction can
be correlated by two consecutive first
order plot: a slow first
order
reaction followed by a fast first order reaction (see Figure 4-2 for
run NT-4).
For higher temperature runs, two consecutive first
order
kinetics also follows, but it is fast reaction followed by a slow
reaction instead.
(see Figure 4-3 for run NT6).
whole reaction should contain three section:
(1)
Initial slow reaction region:
It
shows that the
0
I
I
I
I
I
I
Total Nickel
10 1
Ni-TPP
20 1
disappearanco
30
~A)
40
501-
601
250
I
275
I
300
I
I
325
350
I
400
I
375
To C
Fig. 4-1 Dependence of Non-Catalytic Disappearance of Air Prepared Ni-TPP
on the Operating Temperature.
MW
3.4
I
w
i
I
I
I
I
I
I
A
A
0
Total Nickel
A
Ni-TPP
3.0
A
2.6
1.8
ln C
-
2.2
4::-
1.4
Ae
1.0
0.6
0.2
-0 2
I
i
2
F
El
0
4I~
Iv
Time (hour)
Fig. 4-2
First Order Plot for Air Prepared Ni-TPP Run (Run NT 4).
C in ppm.
4'Tl
-115-
o Total
Nickel
Ni- T PP
3
2
In C
0-
0
Fig. 4- 3
2
6
4
TIME (hrs)
First Order Plot for Air Prepared Ni-TPP Ran.
(Run NT6). C in ppm.
10
-116This region is very clear at low temperature runs: NT4 (294.70),
and NT5 (261.1 C), it shows up at high temperature runs only when the
oil-catalyst ratio is high (That is, the amount of catalyst is small.).
Among Run NT6-NT9, which were four runs made at the same temperature but
different amount of catalyst (Run NT6-NT9),
region but not Run NT6 and NT8.
Run NT7
and NT9 shows this
Probably initially some compounds such
as porphyrin degradation products would chemisorbed on the catalyst, and
not until certain amount of these materials were transformed to other
compounds, will the hydrodemetallation reaction occur effectively.
If chemisorption follow exothermic process, it would explain why lower
temperatures would show up and less clear at high temperatures.
Also,
at higher catalyst concentration, the amount of these materials per
gram of catalyst is less, this would also explain why this region is
less obvious for higher catalyst concentration runs.
(2) Fast reaction region: This region appear clearly throughout all
the temperature range.
(3)
Final slow reaction region:. Only observed for higher temperature
runs; it
is very clear at 340 0 C Runs (NT6-NT9)
not found at 294.7 0 C (NT4) or 261.10 C (NT5).
and 357C Run (NT3) but
As it will be shown in
Figure 4-6 that at least one mole % of nickel per gram of catalyst has
to be deposited before the reaction would transfer from fast reaction
region to this slow region, it
is not surprised that NT4 and NT5 do not
show this region; the amount of nickel deposited on the catalyst for these
-117two runs never exist 0.8 mole %.
Another important observation is that both total nickel and Ni-TPP
follow the some trend, and they all shift to another region at the
same time.
(Figure 4-2 and 4-3).
The Arrhenius plot at 6995 1Pa and Oil/Catalyst=650 is shown in
Figure 4.4.
The activation energy for Ni-TPP disappearance is 20.45
As no straight line can be obtained for total nickel re-
kcal/g mole.
moval, probably the non-porphyrin nickel compounds follow different activation energy.
Here the first order rate constants refer to the rate
constants in the fast reaction region.
4.1-1.c
Catalyst Effects
It has been mentioned in section 4.1-1b
run (NT1),
that for non-catalytic
there exist a decline of nickel concentration in heating
period, but this decline would stop shortly and no further decreasing
was observed when the temperature reached steady operating temperature.
When CoO-MoO 3 /Al 2 0 3 was used, the nickel concentration keeps on decrease
as time goes.
run (NT1)
Figure 4-5 shows the difference between non-catalytic
and catalytic run (NT2).
An very important observation about the catalyst effect is that the
first order rate constant in the aformentioned fast region is function
of oil to catalyst ratio; for same amount of oil used, the first order
rate constant would increase as the amount of catalyst increased.
-118-
7.0-
7 Total Nickel Removal
Ni-TPP Disappearance
*
6.0
5-0 --
5.0
ln k
4.0-
.I
1-55
Fig. 4-4
I
I
1.6o
1.65
1/T
*
3.0
1.70
1.75
(1/ko
x 1000)
1.80
Arrhenius Plot for Air Prepared Ni-TPP Runs.
(6995 KPa Hydrogen, Oil/Catalyst= 6 50 cc/g)
1.85
-11932
I
I
I
I
A Run NT 1
Total Nickel Removal;
28
A Run NT 2
24
A
A
A
A
A
ME
A
A
A
U
.20
M
16
C
M
12'
M
8
0
M
U
U
4
U
0
0~
I
2
I
I
4
6Time.
Fig, 4-5
I
I
10
12
(hour)
Efect of Catalyst on Air Prepared Ni-TPP Hydrodemetallation Reaction.
C in ppm.
-120Figure 4-6 shows the result.
(Run NT6-NT9).
Same trend was observed
for the first rate constant of final slow reaction region, as there
were too few data points in this region, they are not shown here-.
Another interesting finding from Figure 4-6 is that the difference
between the rate constant of total nickel removal and Ni-TWP is constant regardless of the oil/catalyst ratio.
The difference is 159.4 for
run NT6; 161.8 for N7; 172.3 for NT8; and 170.3 for NT9.
Qualitative
explanation is that some materials formed adsorbed on the catalyst (can
either be nickel compounds or nonmetallic compounds) and affect the
hydrodemetallation activity.
As the more the catalyst, the less the
materials per gram of catalyst, so the hydrodemetallation activity
would increase as the oil/catalyst ratio decreases.
The rate cons-
tants shown in Arrhenius plot of Figure 4-4 have been corrected to oil/
catalyst=650 based on Figure 4-6.
If the amount of nickel deposited on the catalyst was calculated
for the time the reaction shift from fast reaction region to final
slow reaction region from the typical log C Versus time plot by intrapolation; the result shows that these amount of nickel per gram of catalyst is linear function of oil/catalyst ratio.
The same linear
relationship is not obtained by calculating from the Ni-TPP desappearance.
See Figure 4-7.
Due to the findings that: (1)
The air prepared Ni-TWP is not pure;
(2) The hydrodemetallation activity depends on oil/catalyst and the
reaction activity seems to change during reaction; the air prepared NiTPP runs received no further attention.
-121-
-
500
* Total Nickel
*
Ni- TPP
400
I
300
k
(cc/g-hr)
-200
U-
100
I
0
I
400
I
oil/catalyst
I
800
I
I
1200
(cc/g)
Fig. 4- 6 The Dependence of First Order Rate Constant in Fast
Reaction Region on the Oil-Catalyst Ratio. (Run NT 6-9).
-122-
M
Total Nickel
*
Ni-TPP
3
4
C
0
2.
0
1
I
100
I
500
900
oil/catalyst
1300
(cc/g)
Fig. 4- 7 The Relationship between the Amount of Nickel Deposited on
the Catalyst when the Shift from Fast Reaction Region to
Slow Reaction Region Occurs and the Oil- Catalyst Ratio.
-123In this thesis, only run NT1 to Nt9, and run NT31 used air pre-
pared Ni-TPP.
Run NT1O and NT11 used nitrogen prepared Ni-TPP.
All the other runs (include Ni-TPP, Ni-Etio, VO-TPP, VO-Etio, free
base porphyrin runs) were made by using helium prepared porphyrins
when
(the method described in section 3.3-1).
For simplification,
no method of preparation is mentioned, it
simply refers to helium
prepared porphyrins.
-1244.1-2
Helium Prepared Nickel Porphyrin Runs:
4.1-2.a
General Observations:
Twenty one experiments were carried out with Ni-TPP, and twenty
six with Ni-Etio.
A summary of the operating conditions for each run
is given in Table 4-2.
Several runs at the same pressure and temperature were made for
Ni-TPP and Ni-Etio individually to test the reproducibility.
sult are shown in Table 4-3.
The re-
Except NT12, NT14, NT15, and NT26 runs,
all others are within + 15% deviation from the mean rate constants calculated from each group of particular metallic compounds, pressure,
and temperature reproducibility runs.
In freshly prepared nickel solution in Nujol, the concentration
measured by atomic absorption agree with that of visible spectrophotometer.
After reaction, the atomic absorption concentration (total
nickel) is always higher than the' visible spectrophotometer concentration (nickel porphyrin).
Perhaps there are intermediates which show
up in atomic absorption, but not in visible spectrophotometer.
In the first ten minutes after catalyst injection, there is a
transient period of rapid concentration decline by up to 8 ppm for
Ni-Etio on HDS 16A, 11 ppm on HDS 9A catalyst.
When alumina is used,
and when helium is used, the transient in concentration decline is
only one tenth as large.
Unlike air prepared Ni-TPP, there were no
drop of concentration during heating period for helium prepared nickel
porphyrins.
-125Table 4-2
Operating Conditions for
Each Nickel Runs:
Run#
Catalyst
Initial
Conc. of
Total Ni
(ppm)
Cat.
Quantity
(g)
Oil
Temp.
Pressure
(0C)
(KPa)
Quantity
(g)
6995
Duration
of
Reaction
(Hr.)
NT1O
HDS 16A
11.7
1.18
423.8
343.3
NT11
"f
15.6
0.22
422.3
342.7
8.9
NT12
34.1
0.45
415.0
343.2
6.3
NT13
33.6
0.48
423.9
315.0
24.7
1.5
9.3
NT14
",
35.3
0.96
420.5
315.6
NT15
"I
35.7
0.85
424.4
342.2
5.0
NT16
21.8
0.85
426.9
342.0
2.8
NT17
30.2
0.89
428.4
290.3
23.0
NT18H
26.8
0.88
429.9
357.4
29.1
NT19
31.4
0.90
422.1
316.3
8.1
35.3
0.87
418.4
343.8
5.2
NT21
35.4
0.88
418.3
287.9
26.4
NT22
34.0
0.87
418.7
302.0
31.6
35.6
0.89
425.4
329.8
4.6
NT24
35.0
0.88
428.4
329.8
4.6
NT25
30.0
0.83
420.8
357.4
3.0
NT26
27.3
0.88
430.4
315.6
5.8
NT20
NT23
",
"'
"I
(to be continued)
-126Run#
Catalyst
Initial
Conc. of
Total Ni
(ppm)
(cont.)
Cat.
Quantity
Oil
Quantity
Temp.
Pressure
(g)
(g)
(OC)
(KPa)
Duration
of
Reaction
(Hr.)
NT27
HDs 16A
26.6
0.88
430.3
316.0
4237
23.2
NT28
"
26.0
0.88
423.0
313.4
9752
3.8
NT29
"
24.4
0.88
428.4
316.0
12509
3.7
NT30
"
24.3
0.88
430.9
316.1
9062
4.2
NE 1
"
39.0
0.88
417.0
316.0
6995
6.3
NE 2
"t
33.5
0.88
434.0
316.0
975Z
3.9
NE 3
"
34.3
0.89
432.2
343.6
6995
3.4
NE 4
"
35.5
0.88
438.2
316.0
"
6.9
NE 5
"
35.4
0.73
375.3
315.9
"
7.2
NE 6
"
34.8
0.88
429.8
315.3
12509
3.3
NE 7
"
35.3
0.88
427.3
329.7
6995
3.6
NE 8
"
34.7
0.98
420.5
288.1
NE 9
33.9
0.88
424.8
315.7
4237
12.9
NE10
34.1
0.91
428.5
302.0
6995
12.6
NE11
36.9
0.88
416.2
357.8
1.85
NE12
37.5
0.89
425.0
315.7
7.9
NE13
38.7
2.01
436.9
315.9
4-55
NE14
37.4
0.89
426.7
344.2
NE15
36.7
0.89
425.1
316.7
"
28.0
0.89
419.7
357.1
"
9.0
NE17
none
37.7
0
431.4
344.2
"
7.4
NE18
Alumina
33.7
0.84
421.2
342.7
NE16H
"
"
21.6
2.95
7.25
(to be continued)
7.55
-127Run#
Catalyst
Initial
Conc. of
Total Ni
(ppm)
Cat.
Quantity
Oil
Quantity
Temp.
Pressure
Duration
of
Reaction
(g)
(g)
(0 C)
(KPa)
(Hr.)
NE19
HDS 16A
29.3
0.43
183
340.7
6995
2.8
NE20
HDS 9A
30.5
0.94
426.4
315.9
11475
6995
2.65
4.9
NE21
"
30.4
0.94
433.4
316.0
NE22
"
30.5
0.93
429.5
343.6
"
2.05
NE23
HDs 16A
14.7
0.90
423.3
343.2
"
1.2
NE24
"
14.9
0.92
412
344.2
"
0.95
NE35
"
27.8
0.90
425.2
343.4
"
2.0
NE36
"
24.8
0.88
428.3
344.1
"
3.2
*(1)
In the run No. such as "NE16H", "N" represents nickel,
Ni-Etio,
"E" for
"T" for Ni-TPP; the digits "16" represent run number,
"H" for those runs under helium pressure,
nothing for runs under
hydrogen pressure.
*(2) NE5 used the spent catalyst of run NBJ4.
Alumina is
2 03
catalyst, HDS 16A is CoO-MoO 3 /Al 20
,
*(3) HDS 9A is NiO-MoO 3/Al
Norton SA 6273 ''-Alumina.
*(4) The size of catalyst used is 0.149-0.177 mm for run NE12,
0.074-0.088 mm for all
the other runs.
and
All in diameter.
*(5) NE15 used 50% of the spent oil of NEll and 50% of fresh Nujol
by dissolving new batch of Ni-Etio.
*(6)
Time zero and initial concentration were defined in Table 4-1.
*(7) Run NE19 has been placed in glass liner to avoid contact with
stainless steel wall.
*(8)
The feedstock of run NE36 was mixed with 0.188g of pyrrole.
-128Table 4-3
Reproducibility of Nickel Runs
Run #
Deviation from
Mean
%
Half Order Rate Constants
of Total Nickel Removal
fJ i-cc oil
g cat *hr
NT12
NT15
NT16
NT20
1081.0
617.9
679.8
72 .4
mean:
776.0
std. dev.: 20.8
NT23
NT24
618.6
668.2
643.4
mean:
std. dev.: 35.1
NT13
NT14
NT19
NT26
231.2
188.1
272.1
8.8
260.1
mean:
std. dev.: 68.4
11.1
27.7
4.6
34.1
NT17
NT21
59.5
52.6
mean:
56.1
std. dev.: 4.9
6.1
6.1
NE 1
NE 4
NE13
426.5
472.0
373.8
424.1
mean:
std. dev.: 49.1
0.6
11.3
11.9
NE 3
NE14
1010.7
1094.9
mean: 1052.8
std. dev.: 42.1
4.0
4.0
39.3
20.4
12.4
6.5
3.85
3.85
-129Kinetic Order:
4.1-2.b
The kinetics describe below refer to the period after the rapid
transience.
Unlike air
prepared runs, the data here fits
a fractional
order kinetic model at up to 90% conversion much better than zero,
first,
or second order kinetics.
4-8 where the data from
See Figure
run NE4 were plotted as C, ln C, 1/c and
JT
vs t which should yield
straight lines for zero, first, second and half-order kinetics.
The kinetic data for all the runs can be well represented by half
order kinetics, but the best fit kinetic order is a function of temperature and hydrogen pressure.
At a constant pressure of 6995 KPa,
the best fit kinetic order increases from 0.1 at 288.1 0 C to 0.93 at
357.80C.
0
At a constant temperature of 316.0 C, the best fit kinetic
order decreases from 0.5 at 4237 K1a to 0.27 at 12509KPa.
This is
shown in Table 4-4.
The temperature and pressure dependence of kinetics can be expressed in terms of half order rate constants.
The Arrhenius plots for HDS 16A catalyst runs at
shown in Figure 4-9
and Figure 4-10.
nstants were obtained from
6995 KPa are
For Figure 4-9,, the rate co-
;C Vs time plot where C was measured by
visible spectrophotometer; these rate constants represent the disappearance rate constants of Ni-Etio or Ni-TPP.
For Figure 4-10,
as the concentration was measured by atomic absorption spectrophotometer which shows the total nickel concentration; the rate constants
qW
1w
W
I
i
I
Zero Order
Order
1st
(a)
3 '-
0
(b)
0
0
0
0
2
30 0
C
0
LNC
0e
0
13
I '-
201
'-A)
0
0
0
0
10h-
0
13
0
03
0
0
Ii
II
2
4
6
TIME (hrs)
Fig. 4- 8
I
in
-1
iI
0
2
Ii
4
iI
6
TIME (hrs
)
0
It
(a) Zero Order Plot, and (b) First Order Plot for Run NE 4. C in ppm.
-W
6
(c)
(d)
5
I
4
3
Tot al
Nic kel
1.5
2
NI- Etio
-
1
ocn0 0
0
I 1
I
I
I
1
2
3
1
-
0
2
4
TIME ( hrs.)
Fig. 4-8
6
0
4
5
6
TIME ( hrs.)
(c) Second Order Plot, and (d) Half Order Plot for Run NE 4. C in ppm.
7
k~A)
-132Table 4-4
Dependence of Kinetic Order on Temperature and Pressure
A)
Pressure effect: (T = 316.0 0 C)
P (KPa) Run #
_
B)
Best Fit
Correlation
Kinetic Order
Coefficient
Correlation Coefficient
of Half Order Fit
4150
-NE9
0.5
0.9998
0.9998
7560
7560
NE1
NE4
0.5
0.9990
0 .9990
0.5
0.9995
0.9995
7560
9650
12408
NE13
NE2
NE6
0.5
0.39
0.27
0.9993
0.9993
0 .9983
0.9942
0.9991
0.9987
Temperature effect: (P = 7560KPa)
T (0 C)
Run #
Best Fit
Correlation
Correlation Coefficient
_
Kinetic Order
Coefficient
of Half Order Fit
288.1
NE8
0.1,
0.9946
0.9832
302.0
NElO
0.29
0.9990
0.9967
316.0
NEl
0.5
0.9990
0.9990
316.0
NE4
0.5
0.9995
329.7
0.4
0.62
0.9981
343.6
344.2
NE7
NE3
NE14
0.9995
0.9993
0.9998
0.63
0.9993
0.9969
357.8
NE11
0.93
0.9991
0.9881
0 .9982
1w
I
8
I
0
0
I
0
-
Iw
71-
7
LNK
0
LNK
0
6
61-
00
0
5[
Ni -TPP
4
33693
E
I
1.6
Ni- Et Jo
E=28077
CAL
G-MOLE
I
1.7
I/T *K x 1000
Fig. 4- 9
4
CAL
G-MOLE
1.8
1.6
I
1.7
1.8
1/T *K x 1000
Effect of Temperature on Half Order Rate Constants for Nickel Porphyrins
Disappearance Rate.
k:gp~~i~- cc oil/g cat * hr; Pi 6995 KPa.
w
1w
i
i
I
I
I
I
0
7H
7
LNK
0
LNK
00
6
61
0
I-
5t
Ni -T P P Runs
(Total
Ni)
~ E=34035
4
CAL
G MOLE
17
1,6
1/T'K x1000
Fig. 4- 10
Ni -ETIO Runs
( Total NI
)
51
E a27617
18
CAL
G-MOLE
1.6
1/T*K
1.7
x1000
I
1.8
Effect of Temperature on Half Order Rate Constants for Total Nickel
Removal Rate.
k:fvliii *cc oil/g cat* hr; P: 6995 xPa.
-135represent the overall nickel removal rate constants of Ni-TPP or
Ni-Etio runs.
For both Ni-TPP and Ni-Etio, the difference of ac-
tivation energy between Ni-Porphyrin disappearance and total nickel
removal is not great.
For Ni-TPP demetallation, it is 34.0 kcal/
g-mole for total nickel removal and
33.7
kcal/g.-mole for Ni-TTP
disappearance; for Ni-Etio it is 27.6 kcal/g-mole for total nickel
removal and 28.1 kcal/g-mole for Ni-Etio disappearance.
Runs with
temperature higher than 357.2 0 C were not made as Nujol cracks at
temperatures above 371 0 C.
Two runs (NE21, NE22) use HDS 9A NiO-
Moo 3 /Al 2 03 catalyst were made to compare the activation energy with
the runs on CoO-MoO3 /Al 2 03 catalyst.
The activation energies found
are 26.1 kcal/g mole for Ni-Etio disappearance and 27.4 kcal/g mole
for total nickel removal.
The pressure dependence at
316 0 C of half order rate constants
of Ni-TPP and Ni-Etio are given in Figure 4-11 (for HDS 16A catalyst).
which is more pressure dependence than the 1.5 power of Ni-Etio
.
Ni-TPP demetallation depends on hydrogen pressure to the 2.2 power,
The pressure dependence for Ni-Etio on HDS 9A catalyst is 1.4 (run
NE20 and NE21),
which is very close to Ni-Etio HDS 16A catalyst.
When hydrogen pressure is replaced by helium, there is essentially
no reaction, this is shown in Figure 4-12.
4.1-2.c
Catalyst Effects:
On experiments where no catalyst is used, and where alumina alone
is used, the reaction rate is negligible in comparison with experi-
w
qw
1w
I
I
I
I
Run
I
Nr- TPP RUNS
Ni-Etio Runs//
NI
8
uro
N[-Etio
11.658
1
0 Total Ni
0
0
0
0
-
72
oTota
1.342-
N .
2.26
7~
LNK
o
6.5
LNK
66
I
4
8.3
Fig. 4- 11
8.9
LNP
I
I
I
9.5
8.3
I
8.9
LNP
Pressure Dependence of Half Order Rate Constants.
k:jpipm *cc oil/g cat -hr; P: KPa; T: 3160C.
-
5-
9.5
-137-
I
I
32
0
0
03
0
0
0
0
03
0
24 -o
C
0
Ni-ETIO Runs:
0
16
0
Total Nickel
vs Time
O
He, Run NE 16H
o
H2 , Run NE 11
0
0
0
0
0
0
0
I
I
0
Fig. 4- 12
2
4
TIME (hrs)
I
6
Comparison between Hydrodemetallation (NE 11) and Nonhydrogenative
Demetallation (NE 16H) Reaction.
C in ppm.
-138ments where CoO-MoO 3 /Al 20 3 was used. (See Figure 4-13).
In order to
study the effect of stainless steel wall of autoclave on the hydrodemetallation reaction, one run (Run NE19) uses Ni-Etio in glass
liner was made; the result shows that both the activity and the
kinetics are same as previous runs at same conditions (NE3 and NE14).
Different oil-catalyst ratio has also been studied for Ni-Etio
on HDS 16A catalyst.
(NE1, NE4, and NE13).
The result show-that
unlike previous air prepared Ni-TPP runs, the demetallation activity
of helium prepared nickel porphyrins are not function of oilcatalyst ratio.
-139I
I
I
V
40
V
V
v
V
000 0
32
0
0
0
E0
0
0
0
C
24
Ni-ET10
Runs: Total Nickel
Time
0
P R M.
0
6
0
vs
V
Non-Catalytic, Run NE 17
El
Alumina, Run NE 18
0
CoO-MoO3 /Al 2 03 , Run NE 3
0
0
0
8
0
0
0
0
0
S0i
2
0
1
I
I
4
6
8
TIME (hrs)
Fig. 4- 13
Effect of Catalyst On Hydrodemetallation Reaction.
C in ppm.
-140Vanadyl Porphyrin Runs:
4.2
Ten experiments were carried out with VO-Etio, three with VO-TPP.
a summary of the operating conditions for each run is
given in Table
4-5.
4.2-1
General Observations for VO-Etio Runs:
Just as previous nickel runs, the atomic absorption concentration
is
always higher than the visible spectrophotometer concentration
during reaction.
However, the difference for vanadium runs is
not
as big as nickel runs.
In the first ten minutes after catalyst injection, there is also
a transient period of rapid concentration decline of up to 10 ppm,
which is larger than nickel runs.
When alumina or helium is used, as
the oil/catalyst ratio for the two vanadium runs (VE8 and VE9H) are
smaller than similar runs for nickel (NE16H, NT18H, and NE18), the
decline in concentration is about
7.5 ppm per gram of catalyst for
vanadium runs and only 1.4 ppm per gram of catalyst for nickel runs.
This might indicate that vanadyl porphyrins adsorbed stronger than
catalyst.
2
03
)
nickel porphyrins on either alumina or HDS 16A (CoO-MoO 3/Al
Figure 4-14 shows the comparison between Ni-Etio and the
higher activity VO-Etio runs over alumina.Figure 4-15 shows the comparison
among
Ni-Etio, Ni-TPP, and VO-Etio runs under helium pressure.
It is clear from the Figures that the initial drop of the concentration is
runs.
very large for vanadium runs and insignificant for nickel
-141-
Table 4-
Run#
Catalyst
5 Operating Conditions for Each Vanadium Run:
Cat.
Quantity
Initial
Conc. of
Total V
(ppm)
(g)
Oil
Quantity
(g)
Temp.
Pressure
Duration
of
Reaction
(OC)
(IKPa)
(Hr.)
6995
10.0
40.5
0.89
426.4
315.5
31.9
29.4
1.71
0.89
420.0
299.9
422.5
348.8
27.6
424.4
315.7
4237
31.5
1.30
0.90
315.1
11820
VE 6
19.3
1.11
423.6
425.0
9752
VE 7
20.0
1.08
419.6
315.8
332.5
344.3
343.7
13.6
6.4
6.25
6995
2.9
VE 3
"'
"
VE 4
VE 5
Hms 16A
11.6
"
VE 2
HDS 16A
"
VE 1
3.0
Alumina
28.5
1.31
425.6
VE9HI
HDs 16A
22.5
1.17
15.6
0.90
426.3
432.0
VE1 1
24.1
0.91
424..3
343.6
VT 1
14.7
0.84
427.5
332.2
0.65
VT 2
11.0
1.18
427.2
317.1
0.95
VT 3
15.5
0.91
414.0
316.5
2.2
VE10
"
VE 8
*(1) In the run No. such as "VE9H",
represents nickel,
"
7.0
7.0
344.2
"V" represents vanadium,
1.3
2.1
"N"
"E" for ratio, "T" for TPP; the digits "9"
represent run number,
"H" for those runs under helium pressure,
nothing for runs under hydrogen pressure.
*(2) The catalyst is fresh and the size is 0.074-0.088 mm in diameter.
*(3) For catalyst runs, time zero was the time catalyst was injected.
*(4)
Initial concentration was the concentration of sample collected
at reaction temperature before catalyst was injected.
-142-
)000
32 0-0
000
0
0
0
28
0 Ni-Etio=Run NE 18
24
-
VO-Etio =Run VE 8
20
C
12
4
I
I
I
I
4
5
6
7
SI
0
0
1
2
3
TIME (hrs)
Fig. 4- 14
Comparison of Vanadium and Nickel Runs (Run VE8 and
NE18) over Alumina Support.
8
-143-
36-
I
I
I
.1
o VO-Etio
32
I
I
I
Run VE 9H
A Ni - Etio Run
o Ni- TPP Run
NE 16 H
NT18H
28
0
n6
0
A
24
A
0
0
0
)
20
0
0
12
8
4
0
0
'I
I
I'
2
II
II
3
4
TIME
Fig. 4- 15
I
I
I
II
5
6
7
8
( hrs
)
C
0
Comparison of Vanadium and Nickel Runs (Run VE9H, NEI6H,
and NT18H) under Helium Pressure.
9
-1444.2-2
Kinetic Order:
The kinetics of VO-Etio runs follow fractional order kinetic
model at up to 90% conversion.
plot of run VE3.
Figure 4-16 shows the half order
As the correlation coefficients to fit
half order
kinetic order for all the eight VO-Etio runs were above 0.9970 and
the scatter of data was rather random, no attempt was made to find
the best fit kinetic order as the function of temperature or pressure.
The temperature and pressure dependence of kinetics is expressed
in terms of the half order rate constants.
KPa hydrogen is shown in Figure 4-17.
The Arrhenius plot at 6995
VO-Etio demetallation has an
activation energy of 37.1 kcal/g-mole for total vanadium removal,
and 35.8 kcal/g-mole-for VO-Etio disappearance; both of them are
larger than Ni-Etio.
It can also be seen from Figure 4-17 that the
difference between the two types of rate constants are very small.
The finding of higher total vanadium removal rate constants than
VO-Etio disappearance constant for some of the runs
(VE3
and VE?) is
believed to be experimental errors.
The pressure dependence at
316 0 C for
of VO-Etio runs is given in Figure 4-18.
half order rate constants
The result shows that the
order of dependence is about 1.2, which is smaller than 1.5 power for
Ni-Etio.
No demetallation reaction was found under helium pressure
(see Figure 4-15).
-145-
I
I
I
Run VE3
0 Total Vanadium
AVO-Etio
-
4
3
C= P. PM.
2
-0
1
f
0
I
1
TIME
Fig. 4-16
2
(hrs)
I
3
Half Order Plot for VO-Etio Run. (Run VE3).
8
I
I
i
8
8
1
Total Vanadium
E 2 3714 2
I
I
'
.8
Vo - Etlo
e- llmanm
cal /g-mol e
I- I-
- I'
7
71
1
6h-
G
In k
In k
0\
4
4
1/T
1/ 0 k x 1000
l/T
I
1.6
1.6 5
1.7
1.75
1.6
I
1.65-
Fig. 4- 17 Effect of Temperature on Half Order Rate Constants for VO-Etio Runs:
Removal. (Right): VO-Etio Disappearance Rate.
1/ok x 1000
I
1.7
I
1.75
(Left): Total Vanadium
ktjsp-p.cc oil/g cat.hr; P:6995 KPa.
I--
I-IJ.
I
I
,
I
1
Vo
-
Total Vonadium
Etlo
6.2 1-
642
1.23.
1.16
5.8H-
5.8
In -k
In k
5.4
5.4 [-
5.0
5.0
4.6
I
8.3
-I
I
8.7
I
I
9.1
In P
Fig. 4-18
I
I
9.5
4.6
II
8.3
II
1
I
8.7
Pressure Dependence of Half Order Rate Constants.
kfipmo.cc oil/g cat.hr, P in KPa, T: 3160C.
I
1
I
9.1
In P
I
I
9.5
I
-1484-
The results on VO-TP are not satisfactory due to the following
two reasons:
(1)
It was unable to prepare high enough solution concentration of
VO-TPP for use.
The sensitivity of analytical equipment would not
allow us to obtain accurate kinetic data, starting from such low initial concentration.
(2) Three runs of VO-TPP at low concentration
(10-15 ppm) show that
the observed rate is at least seven times faster than VO-Etio at
identical conditions.
Diffusion limitation might occur, so intrinsic
(diffusion free) kinetic data can not be obtained.
4.2-3
Catalyst Effects:
When alumina is used alone for VO-Etio, some demetallation reaction
also occur.
(See Figure 4-14).
However, the rate constant found in
term of half order kinetics is only 8% of typical CoO-MoO 3 /Al 2 03 run
at identical conditions.
As the kinetic order of VO-Etio and Ni-Etio runs are virtually
the same, and the demetallation activities are not far away from each
other; the fact that the demetallation activities is not function of oil/
catalyst ratio for nickel runs should also hold for vanadium runs.
-1494.3
Free Base Porphyrin Runs:
In previous demetallation studies (section 4.1 and 4.2), no peaks
for free base porphyrins were found by visible spectrophotometer.
In order to further verify this, free base porphyrins were used as the
model compounds; if they are the final products of demetallation runs,
at least part of them should remain in the solution when free base
porphyrins are used as the sole model compounds.
The free base porphyrins are prepared under helium pressure,
is
the procedure mentioned in section 3.3-1.
which
The concentration here
refers to 10-6 gram of free base porphyrins per gram of oil.
451 ppm,
the initial concentration of free base Etio, corresponds to 55.8 ppm
of Ni-Etio (55.8 x 10-6 gram of nickel per gram of oil) if
were transformed to Ni-Etio.
to 30 ppm of Ni-TPP.
all of them
For free base TPP, 366 ppm corresponds
The operating conditions are shown in Table 4-6.
Run El was made by following the procedures of previous metalloporphyrin runs.
It was found that even before injection of catalyst,
all the etioporphyrins disappeared (No peaks like Figure 3-14 were
found from visible spectrophotometer), and both atomic absorption and
visible spectrophotometer show the formation of 12 ppm of Ni-Etio.
After injection of catalyst, this new formed Ni-Etio also demetallized,
but with slower rate than previous typical Ni-Etio runs.
Probably
some compounds have formed from free base porphyrins to suppress
demetallation reaction of Ni-Etio.
It is believed that the nickel
came from the 316 stainless steel wall, normally contains about
10-14% of nickel.
(Clark and Varney (1962)).
Theoretical calculation
-150Table 4-6 0perating Conditions for Free Base Porphyrins:
Catalyst
Cat.
Initial
Conc. of Quantity
Porphyrins
(ppm)
(g)
Oil
Quantity
Temp.
Pressure
(g)
(0 C)
(KPa)
E 1
HDS 16A
451
0.88
432.4
316.2
6995
7.5
E 2
"
451
0.88
315.8
"
8.7
T 1
"
366
0.89
313.7
"
4.1
Duration
of
Reaction
-
Run#
-293
-273
(Hr.)
*(1)
E represents free base etioporphyrin,
T represents free base TPP.
*(2)
The catalyst is fresh and the size is 0.074-0.088 mm in diameter.
*(3)
The time zero was the time catalyst was injected.
*(4)
Initial coacentration was the concentration before heating.
(Different from demetallation runs).
*(5) Run E2 and TI have been placed in glass liner to avoid contact
with the stainless steel wall.
-151shows that only 1.2 x 10
cm thickness of the nickel in stainless steel
wall has been extracted out, which is negligible.
Run E2 was made by
placing the metal dissolving oil in glass liner to minimize the contact of solution with stainless steel wall; the reactor was also
heated in the maximum speed to shorten the period of heating.
By doing this, no nickel was found before injection of catalyst.
The first sample collected 18 minutes after injection of catalyst showed
no evidence of either free base porphyrins by visible spestrophotometer
or nickel by atomic absorption spectrophotometer.
However, visible
spectrophotometer picked up Ni-Etio peaks which should be equivalent
to 19 ppm of Ni-Etio; this "Ni-Etio" peaks were believed to be "Cobalt
Etio" peaks as they have very similar peaks in visible range.
(Hambright (1978), Dorough et al. (1951), and Smith (1975)).
The same
sample was sent to Galbraith Inc. (Knoxville, Tenn.) for cobalt analysis,
which showed that 15 ppm of cobalt actually appears in the solution.
These Co-Etio eventually disappeared from solution as reaction went on.
Another run by using tetraphenylporphine (Run TI) in glass liner also
has similar result to run E2.
Although the free base porphyrin runs show that nickel in stainless steel wall can be extracted out by free base porphyrins.
The
stainless steel wall apparently has no effect on demetallation runs,
this has been shown in section 4.1-2.c which concluded that glass
liner (NE19)
run is
the same as ordinary demetallation runs.
-1524.4
Mixed Nickel and Vanadyl Porphyrin Runs:
As both vanadium and nickel are available in petroleum, it is
important to study whether there is any difference between the individual vanadium or nickel runs (section
vanadium and nickel runs.
4-1 and 4-2) and mixed
(this section).
Eleven runs on mixed VO-Etio and Ni-Etio runs have been made.
The operating conditions for each run is shown in Table 4-7.
4.4-1
General Observations:
In the first fifteen minutes after injection of catalyst, the
ratio of concentration decline for vanadium to nickel is roughly from
2.5:1 to 9.4:1, which depends on the initial
metal ratio.
This shows
that vanadyl porphyrins have stronger affinity to the catalyst than
nickel porphyrins.
The vanadium removal rate in the mixed run was
much the same as individual vanadium runs.
The beginning nickel
removal rate was suppressed by the presence of vanadium compounds,
the rate was then increased to 60% or 85% of the removal rate as
individual nickel runs when the concentration of vanadium in the
bulk was less than 4 ppm.
4.4-2
Kinetics:
Figure 4-19 shows the half order plot of run NVE5,
the fast
reaction region for nickel is close to 60% of the reaction rate
of individual nickel run, the slow reaction region for nickel is
-153Operating Conditions for Mixed VO-Etio and Ni-Etio Runs:
Table 4-7
Run#
Catalyst
Initial
Conc. of
Cat.
Quantity
Oil
Quantity
Temp.
Pressure
Duration
of
Reaction
(Hr.)
Ni or V
(g)
(g)
(OC)
(1Pa)
0.91
427.1
316.1
6995
V: 18.4
Ni: 16.3
0.89
424.7
342.8
V3 8.7
Ni: 25.2
0.89
422.7
343.4
3.1
V: 19.6
1.79
424.0
315.7
8.5
V: 30.9
0.91
439.3
343.4
6.0
5.25
(ppm)
NVE1
HDS 16A
V: 19.5
9.2
NVE2
NVE3
I
NVE4
"
Ni: 15.5
3.85
Ni: 19.9
NVE5
I,
Ni: 26.9
NVE6
6W
V: 30.8
Ni: 14.1
0.91
436.7
343.4
NVE7
II
V: 27.2
Ni: 13.0
0.90
425.4
316.0
NVE8
'I
V: 27.3
0.86
425.4
315.9
12509
10.5
V: 6.4
Ni: 29.7
0.90
428.3
343.7
6995
3.2
V: 27.1
0.86
427.1
315.8
9752
12.5
0.89
427.5
329.4
6995
9.0
14.0
Ni: 12.8
NVE9
'I
NVE10
'9
Ni: 12.9
NVE11
'I
V: 27.4
Ni: 13.1
-154-
-
-
6
Run NVE5
Slow
OTotal Vonadium
ATotal Nick el
5
4fost
C=PPM
0
30
2-
o
2
3
4
5
6
TIME (hrs)
Fig. 4- 19 Half Order Plot for Mixed VO-Etio and Ni-Etio Run.
(Run NVE 5).
-155only 16% of the individual one; the reaction rate for vanadium is 93%
of the individual vanadium run.
By changing the ratio of initial
concentration of VO-Etio to Ni-Etio from 1:1 (Run NVE5) to 1:3
(Run NVE3), the suppression effect of vanadium on nickel has been
minimized.
While the vanadium rate remains the same, the slow reaction
region for nickel in run NVE3 is now 52% of individual nickel run; and
the fast reaction region is 85%.
(See Figure 4-20).
Figure 4-21 shows
the dependence of half order rate constants on the ratio of Ni-Etio
and VO-Etio initial concentrations.
Note that vanadium removal rate is
not obviously affected by the presence of nickel, but the reverse is
not true.
Figure 4-22 shows the visible spectra of run NVE2 before in-
jection of catalyst and 1.6 hour after injection of catalyst, which
clearly show that the ratio of VO-Etio peaks (407 and 571.5 rum) to
Ni-Etio peaks (391 and 553 m) decreased during the reaction.
As in most of the crude, there are more vanadium than nickel (section 2.1-2.b); the temperature and pressure dependence of half order
rate constants were studied by setting the ratio of initial
concentration of VO-Etio to Ni-Etio to be 2.12.
the Arrhenius plot at 6995 KPa hydrogen.
Figure 4-23 shows
The activation energy (total
metal removal) for VO-Etio is 37.0 kcal/g-mole, which is close to 37.1
kcal/g-mole for individual run (Figure 4-17); the activation energy for
fast reaction rate constant of Ni-Etio is 26.2 kcal/g-mole, again
is not far away from 27.6 kcal/g-mole for individual Ni-Etio runs
(Figure 4-10).
The activation energy for slow reaction rate constant
- -156-
51
slow
Run
NVE 3
oTotal Vanadium
A Total Nickel
4
fast
3
C=PPM
2j
I
I
0
1
2
I
3
TIME (hrs)
Fig. 4- 20 Half Order Plot for Mixed VO-Etio and Ni-Etio Run.
(Run NVE 3).
-157I
I
A
I.
A
900
I
I-
I4I
a
&-
*
kI
IE/
Z4Pm.* cc oil
g cat a hr
/ /
A
-
700
A
I.
(Total Metal Removal)
500
Ni-Etio (Fast)
/
A
--
-Ni-Etio
--
/
300
(Slow/
E
I
/
100
I
I
0
0.4
0.2
C
I
o.6
0.8
1.0
/(CNio+C)Vo
Fig. 4- 21 Dependence of Half Order Rate Constants on the Ratio of
Ni-Etio and VO-Etio Initial Concentrations.
P: 6995 KPa.
T, 3160 C;
-
158-
NVE 2
0.8
2
O
0.4
~
0
tn0.4
CO
407
553 571.5-
391
534
I
I
370
410
I
I
450
I
490
WAVELENGTH
530
570
610
(nm)
NVE 2
0.8
553
z
0
391
I-
ce0.4
0
0)
407
517
370
Fig. 4-22
410'
450
490
530
WAVELENGTH (nm)
616~
571.5
570
~
610
Absorption Spectra of Mixed VO-Etio and Ni-Etio Run.
(Run NVE 2). Tbp: Fresh Sample. Bottom: Sample Collected
1.6 hrs after Injection of Catalyst. All were Diluted by
Xylene.
-159I
I
I
I
I
(Total Metal Removal)
Ni-Etio (Fast), E=-26.2
A
VO-Etio,
*
Ni-Etio (Slow), B=40.4
E=37.0
E (Act. Ener.) in Kcal/g mole.
6.0 1
5.0
ln k
4.0 k
3. O I ~L6o
i. 6o
Fig. 4-23
I
1.62
1. 62
I
1.64
1.64
I
1.66
I
1.68
I
1.70
I
1.72
1.66
1.68
1.70
1.72
l/T (1/K 0 x 1000)
Effect of Temperature on Half Order Rate Constants for
Mixed VO-Etio and Ni-Etio Runs.
cat *h0oil
g cat
ehr
g
C V/cNio=2.12;
P=6995 1ea;
-160of Ni-Etio is
40.4 kcal/g-mole.
dependence at 316 0 C.
Figure 4-24 shows the hydrogen pressure
It is 1.11 for VO-Etio and 1.29 for fast Ni-Etio
removal rate constants; they are not far away from 1.16 for VO-Etio
(Figure 4-18) and 1.34 for Ni-Etio (Figure 4-11) individual runs.
It is 0.24 for slow Ni-Etio removal rate constants.
-161-
I
I
I
i
I
(Total Metal Removal)
6.5
A
Ni-Etio in Fast Reaction Region
SVO-Etio
6.0
-
Ni-Etio in
U
Slow Reaction Region A
5.5
5.0
ln k
eU
4.5 -(0.24)
4.0
(2
3.5
3.0
6.8
I
I
I
6.9
7.0
7.2
7.1
I
I
7.3
7.4
in P
Fig. 4- 24 Pressure Dependence of Half Order Rate Constants in Mixed
Ni-Etio and VO-Etio Runs.
c
oil
M
g;P
g cat -hr
In 1a.
C
/CNio2. 11; T3160 C;
7.5
-1624.5
Self Preparation Catalysts Runs:
Ten runs of self preparation catalysts were made by using Ni-Etio
as model metal compounds.
in section 3.3-4.
The method of preparation has been mentioned
Table 4-8 shows the composition of these catalysts.
A list
of operating conditions is shown in Table 4-9.
4.5-1
General Observations:
The results show that half order kinetic model fits
all the runs
pretty well. Two different calcination temperature runs (NE25 and NE26)
show that temperature of calcination makes no difference on demetallation activity (within 10% deviation).
Order of impregnation also
shows no effect on demetallation activity (NE25 and NE32).
This finding
is consistent to the previous literature which mentioned;that order
of impregnation makes no difference on hydrodesulphurization activity.
(Mccolgan et al. (1973), Part 5; and Mone and Moscou (1975)).
By comparing with commercial catalysts (HDS 16A and HDS 9A) runs,
the self preparation catalysts show lower demetallation activity.
The self preparation catalysts show only 60-80% activity of commercial
catalysts; by correcting with the difference of surface area, they
show only 50-70%.
Probably the method of preparation or the PH en-
vironment during preparation would affect the demetallation activity.
Table 4-10 shows the comparison of hydrodemetallation activity between
self preparation catalysts and commercial catalysts.
-163-
Table 4-8
Run#
NE25
Composition of Self Preparation Catalysts:
Composition
.5.5% Co
10.1% Mo
NE26
5.6% Co
10.1% Mo
NE27
10.0% Mo
NE28
5.7% Co
NE29
15.0% Mo
NE30
5.0% Mo
NE31
5.6% Ni
10.0% Mo
NE32
5.5% Co
10.0% Mo
NE33
NE34
9.0% Co
10.0% Mo
3.64% Co
10.1%
Mo
*(1) The support used is s-Alumina obtained from Norton (SA-6273).
*(2) Weight percent was balanced by Alumina (Al2 0).
*(3) Most of catalysts were prepared by calcination at 5000C, and
by impregnation of molybdenum first and then cobalt (or nickel).
The exceptions are run NE26 in which the calcination temperature
was 600 0 C, and run NE32 in which cobalt was impregnated first.
-164Table 4-9
Opera-ting Conditions for
Self Preparation Catalysts Runs:
Run#
Initial
Conc. of
Total Ni
(ppm)
Cat.
Quantity
Oil
Temp.
Pressure
Duration
of
Quantity
Reaction
(g)
(g)
(OC)
(10a)
6995
(Hr.)
2.85
NE 25
28.2
0.97
427.3
343.9
NE 26
29.5
0.97
423.9
343.5
NE 27
27.3
0.98
425.4
343.8
NE 28
28.7
0.98
426.8
343.3
NE 29
28.5
0.96
427.1
343.4
NE 30
28.0
0.98
428.1
343.7
NE 31
28.8
0.97
431.2
343.6
NE32
28.8
0.97
425.2
343.8
NE 33
28.5
0.96
431.4
343.7
2.95
NE34
28.2
0.97
434.8
343.7
3.0
V1
it
3.8
9.2
"
it
2.9
of
2.1
to
10.0
2.1
"
,
2.9
-165Table 4-10
Comparison between Self Preparation Catalysts
and Commercial -Catalysts on Hyd~fodemetallatiori Activity of
Ni-Etio:
Catalyst
Run#
Half Order Rate Constant
)
(Total Nickel Removal
pp-m-.cc oil
g cat.hr
NE 3
HDs 16A
NE14
HDS 16A
(CoO-Mo0 /Al 2O3 )
1010.7
1094.9
NE25
Self Prepared
NE22
HDS 9A
NE1
Self Prepared
829.4
(Ni-Mo0 3/Al2 05 )
1430.8
895.0
*(1) The composition of commercial catalysts are shown in Table
3-2 to Table
3-4, and of self preparation catalysts are shown
in Table 4-9.
*(2)
The operating conditions are shown in Table 4-3 and Table 4-10.
-1664.5-2
Effect of Cobalt or Molybdenum on Demetallation Activity
of Ni-Etio:
It was found that MoO3 /Al 2 03 itself is a very good hydrodemetalFigure 4-25 (Run NE18, NE27, NE29, and NE30) shows
lation catalyst.
that as the weight
also increases.
% of molybdenum increases, the demetallation activity
As the solubility of ammonium molybdate in water is
limited; more than 20 wt% of molybdenum on alumina could not be prepared.
However, it is expected that the demetallation activity should not
increase anymore when molybdenum trioxide covers a monolayer on alumina
carrier, which is equivalent to 30 wt% of molybdenum on alumina.
Normally, commercial catalyst has about 50% of monolayer of MoO3 on
catalyst.
More than this quantity may not increase the activity.
The
reason is that not all surface can accept MoO , and 50% monolayer appears
to be enough.
(Schrader
(1979)).
Figure 4-26 (Run NE25, NE27, NE28, NE33, and NE34) shows the effect
of cobalt on hydrodemetallation activity.
based on per gram mole of Mo plus Co.
The rate constants here are
This Figure shows:
(1)
The
addition of cobalt actually decreases the demetallation activity; (2)
CoO/Al 2 03 (Run NE28) is inferior to MoO3 /Al 2 03 (Run NE27) in demetallation
on alumina is
black; which is believed to be the formation of Co 0
(Mone and Moscou (1975).
blue color.
slightly yellow color, pure cobalt
However, the CoO-MoO /Al203 catalyst is
The difference of colors simply shows that there are
.
Pure molybdenum on alumina is
1120
960
Total Nickel Removal
K
A
-
800
Ni-Etio Disappearance
640
#- cc
G
HR
480
0\
-
320
____
1 60
A
10
5
0
Wt
*.
Mo
15
on ALUMINA
Fig. 4- 25 Effect of Mo on Half Order Rate Constants of Ni-Etio Runs.
-168-
600
NE27
500
NE P
NE25
400
k
-
300
NE33
ONE28
_
200
-
100
0
0
0.2
I
o.4
Co/Co+Mo
Fig. 4-26
I
o.6
o.8
(Mole Ratio)
Dependence of Half Order Rate Constants
(
4Tpp.cc oil/g mole Co+Mo' hr) on Cobalt
Addition.
(Total Nickel Removal).
1.0
-169some interactions between cobalt and molybdenum in addition to the
interactions between cobalt-alumina, and molybdenum-alumina.
CoAl 2 0
(Mone and Moscou (1975)) and CoMo0
to be found in CoO-MoO3/Al 20
catalyst.
4
Both
(Cheng (1978)) are believed
5.
5.1
Discussion of Results:
Diffusion Effects:
Nickel Porphyrin Runs:
5.1-1
Despite the fact that the kinetic order increases with increasing
temperature.
There are negligible diffusion effects.
(1) Although the kinetic order increases with temperature, it also
decreases with pressure.
For half order kinetics, the diffusion
controlled kinetic order should theoretically be no more than 0.75
order.
This was obtained by applying half order rate equation into
the generalized Thiele modulus defined by Bischoff (1965)
to the region of strong pore resistance.
and extend
However, in the Ni-Etio run,
the kinetic order reached 0.93 order at 357.8 C (Run NE11) already.
(2) Different size catalysts (0.149-0.177 mm and 0.074-0.088 mm)
have been studied at the same standard condition for Ni-Etio, and this
kinetic order remains at half order for both runs.
There was only
less than 10% decrease of the half order rate constant for the large
size run (Run NE12) which is within reproducibility range.
(3) Scanning electron x-ray microanalyzer has been used to find
the concentration profile of nickel deposited on the catalyst shown
in Figure 5-1 for both Ni-TPP run at 357.20 c, 6995 KPa (Run NT25)
and fresh CoO-MoO 3 /Al 2 03 catalyst.
The concentration of nickel which
was represented by the brightness of the spots is quite uniform all
-171over the catalyst.
Figure 5-2 shows the weight percent of nickel
deposited on the designated spots of the catalyst pellet,
which
conconfirms that nickel deposited uniformly all over the catalyst.
In the case of fresh catalyst, there is no big difference about
brightness of spots between the catalyst and expoy resin.
Several
other catalyst particles at the same run and other runs (Both Ni-Etio
and Ni-TPP) were also examined,
and all
of them showed the same uni-
form distribution.
(4) Theoretical Calculation of Thiele Modulus:
The viscosity of
Nujol at reaction temperature can be calculated from the data shown
in Table
3-5
by using the equation cited in the book of Nelson (1974)
for unit conversion, and the equation in the book of Reid, Prausnitz,
and Sherwood (1977) for temperature correction.
The density of Nujol
at reaction temperature can be calculated from the data and equation
given in Table
3-6.
Einstein-Stoke equation was then used to cal-
culate the bulk diffusivity of Ni-porphyrin in Nujol.
Effective
diffusivity was then calculated from the equation shown by Spry
and Sawyer (1975).
diameter,
The necessary parameters such as the average pore
density and pore volume of catalyst are given at Table 3-2
for HDS 16A catalyst.
Tortuosity was taken as 4, which was recommended
by Satterfield (1978).
The diameter of Ni-Etio was calculated to be 14.2A based on the
information from Fleischer (1963).
The diameter for Ni-TPP is around
4K)
Fig. 5-1
Scanning Electron X-Ray Microanalyzer Indication of Nickel Distribution.
Left: Ni-TPP Run at 357 0 C (NT25), wt% of Nickel Deposited on the catalyst
was 1.44% (500x); Right: Fresh Catalyst. (700x)
-173-
Run NT25
Position
wtfo Ni
1
2
1.36
1.58
3
1.50
11
-1.40
4
5
6
7
8
9
10
1.48
1.41
1.41
1.39
1.53
1.46
1.38
%
1.44 0.07
0
07
03
8
12
04
W
0O
10
05
0
06
Fig. 5-2
Weight Percent of Nickel Deposited on the Designated Spots
of the Catalyst Pellet Described in Figure 5-1.
-174The effective diffusivity for Ni-Etio at 357.20 C in CoO-MoO 3
/
19R.
Al203 is calculated to be 2.66 x 10-6 cm2 /sec.
The theoretical
calculation of Thiele modulus was calculated to be 0.59.
Inter-
polation of effectiveness for half order was taken from the book of
Satterfield (1970) which showed the relationship between effectiveness
factor and Thiele modulus for both first order and zero order.
The
result showed that effectiveness factor for Ni-Etio run at 357.2 0 C
and 6995 IPa should be higher than 0.95 which will ensure diffusion free
kinetics.
Based on the above findings,
tioned operating ranges,
it
is
concluded that in the aforemen-
the kinetics of nickel porphyrin runs was not
affected by diffusion processes.
5.1-2
Vanadyl Porphyrin Runs:
Same as nickel porphyrin runs, VO-Etio runs show no diffusion
effect in the operating range.
However,
VO-TPP runs shows some diffu-
sion limitation:
(1)
All the VO-Etio runs follow very well with 0.5 kinetic order.
If diffusion effect exists, the kinetic order should be increased with
either operating pressure or temperature.
For VO-TPP runs, the initial
concentration was too low to take accurate kinetic data.
VT3 shows that the best fit
kinetic order is
only 20% time to reach complete conversion,
However, run
close to 0.7, and it
compared to Ni-TPP at
takes
-175identical operating conditions.
This is one of the indication that
diffusion limitation might occur for VO-TPP runs.
(2) Scanning electron x-ray microanalyzer has been used to find the
concentration profile of vanadium deposited on the spent catalyst.
The concentration of vanadium was represented by the brightness of the
In Figure
spots.
5-3, the photo on the right shows the concentration
profile of vanadium for VO-Etio run (Run VE3), and the left shows the
concentration profile of vanadium for VO-TPP run (Run
concentration profile for VO-Etio run is
VT1).
While the
quite uniform, there is
slightly concentration gradient for VO-TPP run.
Figure
5-4 shows the
concentration of vanadium on each designated spot for the two spent
catalyst pellets.
5.1-3
Mixed Ni-Etio and VO-Etio Runs:
The spent catalysts for the mixed Ni-Etio and VO-Etio runs were
also examined by scanning electron x-ray microanalyzer,
the result
also shows that no diffusion limitation occur for both vanadium and
nickel.
IN
Fig. 5-3
Scanning Electron X-Ray Microanalyzer Indication of Vanadium Distribution.
(Right): Run VE3, wt% of VAnadium on Catalyst is 1.47%.
(Left): Run VT1, wt% of Vanadium on Catalyst is 0.60%.
(700x).
(700x).
Run VE3
Run VT1
Position
1
2
3
4
Position
wt% V
7
0.28
0.84
0.95
8
0.81
5
6
0.65
0.55
0.43
0.28
wt% V
Position
1
2
3
4
5--
wt% V
Position
wt/ V
1.50
1.39
6
7
1.45
1.56
1.54
1.43
8
1.48
9
1.53
1.47
10
Averages 1.47 0.05 wt%
1.43
01
01
02
02
03
07
04
0708
08
05
06
Fig. 5-4
03
04
010
05
09
06
Weight Percent of Vanadium Deposited on the Designated Spots of the Catalyst
Pellets Described in Figure 5-3.
-K,
-K,
-1785.2
Hydrogen Consumption:
Solubility of hydrogen in tetralin, diphenylmethane, creosote
Simnick
oil and hexadecane was available by Simnick et al. (1977),
et al. (1978),
spectively.
Cukor and Prausnitz (1972)
Prather et al. (1977),
The general observations are: (1)
re-
There was linear rela-
tionship between the hydrogen pressure and the mole fraction of hydrogen
in liquid phase.
(2) The solubility of hydrogen is larger for paraffin
than for aromatic, with naphthene in the middle. (3) If the solubility
of hydrogen in Nujol was assumed to be the same as that in tetralin,
diphenylmethane or creosote oil respectively, the mole ratio of hydrogen
to nickel porphyrin or to vanadyl porphyrin in liquid phase in our
operating range is
of the range from 150 to 2000.
(4) It
takes only
seconds for hydrogen in oil to reach equilibrium concentration.
Based on the above observations, it
is
concluded that:
(1)
The
effect of hydrogen on half order rate constant can be described by
hydrogen pressure directly instead of by the mole fraction of hydrogen
in Nujol which is
unknown.
(2) It
is
safe to assume that as the mole
ratio of hydrogen to nickel or vanadyl porphyrin is very high, if Nujol
itself does not consume hydrogen severely, the hydrogen concentration
in Nujol can be taken as constant.
To ensure that this actually
happens, gas sample was collected after three hours reaction time
at 357 0 C and 6995 KPa H2 for Ni-Etio run (Run NE11), and was sent to
Matheson Gas Product (Gloucester, Mass.) for hydrogen analysis, the
-179result showed that the purity of hydrogen remained more than
99%,
which ensure that the concentration of hydrogen in liquid phase
remained constant during reaction.
-180Intermediates and Products in Liquid Phase:
5.3
5.3-1
Intermediates:
There are several evidences for the existence of intermediates:
(1) From the half order plot of Figure 4-8, the rate constants for
the disappearance of Ni-Porphyrins tend to be larger than those of
the rate constants for total nickel removal.
This was found for all
the runs.
(2) The concentration difference between total nickel and nickel
porphyrins increases to a maximum, then decreased during reaction.
This points to a built-up of intermediates that eventually disappear,
shown in the left part of Figure
5-5.
Although less clear in the
case of vanadium runs, the concentration difference between total
vanadium and vanadyl porphyrins also increased to a maximum, then
decreased during reaction.
(3)
The color of the sample collected change from red to violet to light
yellow for Ni-Etio runs, and from red to reddish violet to light yellow
for VO-Etio runs after the catalyst was injected.
The absorption spectra
of the samples collected during reaction showed the presence of a new
peak at 616 nm and a shoulder at
runs, the new peak is 631 nm.
Ni-Etio run (NE14),
595
nm for Ni-Etio runs; as for VO-Etio
The spectra is shown in Figure 5-6 for
and Figure 5-7 for VO-Etio run
(VE3).
In comparison
with Figure 2-5 which shows the visible spectra of fresh VO-Etio and
Ni-Etio, the new peaks at 595 rum and 616 =m for Ni-Etio, and 631 nm
5 5
I
5
5
I
I
I
0
0
0
AC
Abs.
0
PPM.
3
3
S
0
0
2 [-
0
I
F-L
00
0
Ih
-
I
0
O'
.C
0
II
I
2
TIME (hrs)
Fig. 5-5
0
I
0
I
2
TIME ( hrs)
Indication of Intermediates (Run NE14): (Left): Plot of Concentration Difference
between Total Nickel and Ni-Etio Versus Time. (Right): Plot of Absorption (Arbitary
Unit) of 616 nm Peak Versus Time.
-1820.8
7-
'414
z
0
I
0.4
Ai
IIIII
0
V')
95616
s9
sh tilc
0
360
400
440
520
480
WAVELENGTH
0.8
560
600
640
(nm)
r-
39 1
z
~553
0
616
0.4
0
517
VI)
595
Shouldqr
0
360
400
440
480
WAVELENGTH
Fig. 5-6
520
560
600
640
(nm)
Absorption Spectrum of Ni-TPP and Ni-Etio During Reaction.
(Top): Run NT20 Collected at 0.7 Hrs Reaction Time; (Bottom):
Run NE14 Collected at 0.75 Hrs Reaction Time. Samples were
Diluted by Xylene.
Background: Xylene.
-183I
i
z
407
407
0.8
I
I
I
VE 3
571.5
0
I0O
0r
0
LO
0.4
534
631
0
410
530
590
WAVELE NGTH (nm)
450
490
I
I
423
650
I
I
VT 1
O,8
632-
-
z
I
610
0
548
0
0.4
VI)
583 592
0
410
Fig. 5-?
I
I
I
I
450 490
530 590'
WAVELEN GTH (nm)
I
610
650
Absorption Spectra of VO-Etio and VO-TPP Runs During Reaction.
(Top): Run VE3 Collected at 0.6 Hrs Reaction Time; Diluted by
Xylene and with Xylene as Background.
(Bottom): Run VT1 Colle-
cted at 0.2 Hrs Reaction Time; Without Dilution, with Nujol
as Background.
-184for VO-Etio are clearly shown in Figure 5-6 and 5-7.
For Ni-Etio
run, as the shoulder was not observed for all the runs while 616
n
occurred each time, it is believed that they are of different compounds.
The 616 nm peak in the right part of Figure 5-5 reflects an intermediate
in which absorption peak of 616 nm reached maximum and decreased during
reaction.
The 631 rnm peak for VO-Etio runs has similar trend to 616 nm
peak for Ni-Etio runs.
The color of the sample collected change from brown to green to light
yellow for Ni-TPP runs; and from reddish brown to green to light yellow
for VO-TPP runs during catalytic reaction.
The absorption spectra of the
samples collected during reaction showed the presence of new peak at
616 nm and a shoulder at 595 nm for Ni-TPP runs; and a new peak at 632 nm
with minor shoulder at 592 nm for VO-TPP runs.
Again, Figure 5-6 shows
Ni-TPP run (NT20), and Figure 5-7 shows VO-TPP run (VT1).
In comparison
with Figure 3-13 which shows'the spectra of fresh Ni-TPP and VO-TPP,
the
new peaks occurred during reaction are clearly shown in Figure 5-6 and
Figure 5-7.
Same as metalloetioporphyrin runs, these new peaks are
believed to be the formation of intermediates.
Figure 5-8 shows the color pictures of Ni-Etio and VO-Etio runs,
Figure 5-9 shows VO-TPP and Ni-TPP runs; and Table 5-1 states the duration
for each samples in Figure 5-8 and 5-9.
While we failed to take better
picture for Ni-TPP run so that the color change can be clearly shown;
VO-TPP, Ni-Etio, and VO-Etio pictures show clearly the color change.
From the study of previous literature: Albers and Knorr (1941),
Peychal-Heiling and Wilson (1971), Whitlock (1969), Dorough and
-185-
Figure 5-8
Color Pictures of Ni-Etio Sample (NE14), and VO-Etio (VE3).
Sample.
-186-
Fig. 5-9 Color Pictures of Ni-TPP Sample (NT15), and VO-TPP Sample (vT3).
-187-
Table 5-1
Duration of Each Sample Shown in
Figure 5-8 and Figure
5-9
(1) Figure 5-8:
(a) Ni-Etio run (NE14) from left to right:
1.3,
Fresh sample, and 0.3, 0.75,
1.95, 2.6,
2.95 hours
after injection of catalyst.
(b) VO-Etio run (VE3)
from left
Fresh sample, and 0.15,
to right:
o.6, 0.9, 1.55, 2.3, 3.0 hours
after injection of catalyst.
(2) Figure 5-9:
(a) Ni-TPP run (NT15)
from left
to right:
Fresh sample, and 0.13, 0.33,
1.0,
1.9, 2.92, 5.03 hours
after injection of catalyst.
(b) VO-TPP run (VT3) from left to right:
Fresh sample, and 0.15, 0.45, 0.9, 1.22,
after injection of catalyst.
1.65, 2.2 hours
-188Huennekens (1952),
It is possible
and Miller and Dorough (1952).
that 616 nm is Ni-Chlorin (either TPP type or Etio type) in which one
of the pyrrole group was hydrogenated.
The structure of TPP type of
Ni-Chlorin has been shown in Figure 3-10, corresponds to the 616 rnn
peak in Ni-TPP or Ni-Etio runs.
The 631 nm peak for VO-Etio runs and
The
632 nm peak for VO-TPP runs are believed to be vanadyl chlorins.
structures of TPP type vanadyl chlorin has also been given in Figure
3-10.
Ni-chlorin or VO-chlorin may not be the only intermediate.
volume 2, Chapter 1 of Dolphin's book (1978),
some
In
forms of metallo
dihydroporphyrins and tetrahydroporphyrins have been suggested and are
certainly possible to be existed as intermediates of demetallation
reaction.
Both the carbon in methine bridge (0(,
,1
, andS) or
pyrrolic position (position 1-8) are entitled to accept hydrogen.
A schematic of these positions as well as some of the free base
dihydroporphyrins and tetrahydroporphyrins have been given in Figure
2-1.
In the operating condition of hydrodemetallation runs, transalkylation reaction is highly possible.
These products of trans-
alkylation would be a homologous series of metalloporphyrins (Baker
and Palmer (1978)),
and they are expected to change either the molar
extinction coefficient or peak wavelength of porphyrins.
(1978)).
(Hambright
Run NE17 and NE18 show the peak wavelength shift during
reaction: 517 nm peak shifted to 513 ram, 553 ram peak shifted to
5 49
rnm,
and 616 rum shifted to 612 rim, all these might result from transalkylation
reaction.
Similar result were observed in CoO/Al203 catalyst run (NE28).
-189As there is no simple way to synthesize pure compounds of afomentioned possible intermediatesand except chlorin, all
other forms
do not have intensive absorption peaks in visible range;
neither quan-
titive nor qualitative analysis can be made for these possible
intermediates.
Due to the existence of CoO-MoO3 /Al 2 03 or NiO-MoO 3 /Al 2 03 catalyst,
the inherited cracking activity of these catalysts might also break
some carbon-carbon bonds in the reduced porphyrins.
quite stable, but the stability is
of porphyrins occurs, which is
Porphyrins are
expected to be destroyed if
reduction
possible in hydrodemetallation study.
Bond breaking of carbon-carbon bond as well as nickel-nitrogen bond
would then be feasible.
Some forms of nickel or vanadyl chelates
which consist nickel or vanadium with fragments of porphyrins and partly
with the catalytic surface can also be possible intermediates.
Although not conclusive,
in Chapter 14 of Smith's book (1975),
Fuhrhop mentioned the instability of the porphyrin after saturation
of an pyrrolic carbon atom (such as formation of chlorin),
he also pointed
out the possibility of opening of the porphyrin macrocycle after
addition reactions to pyrrolic carbon atoms.
5.3-2
Products:
As it will be shown in section
5-4 that because all the metal
eventually will adsorbed on the catalyst, the final products in the
liquid phase do not contain metals.
-190At the very beginning of this study, it
was thought that the final
products might be free base porphyrins or their reduced forms such as
dihydroporphyrins,
tetrahydroporphyrins (Their parent structures were
shown in Figure 2-1).
However,
this speculation was rejected by the
following findings:
(1) Free base porphyrin (section 4-3) runs show that free base porphyrins are extremely unstable at the presence of metals (either Ni,
V, Co, or Mo).
If free base porphyrins ever formed, they would
transform to metalloporphyrins right away.
As cobalt are available
on the catalyst surface, and nickel are available in stainless steel
wall, at least some of them should show up as cobalt or nickel porphyrins
during vanadyl porphyrin runs.
However,
atomic absorption analysis
shows that neither nickel porphyrins nor cobalt porphyrins were found
in the vanadyl porphyrin runs; and no cobalt porphyrins were found
in nickel porphyrin runs.
Thus free base porphyrins are neither the
intermediates not the products of hydrodemetallation.
(2) The absorption peaks for free base tetraphenylporphine (TPP),
tetraphenylchlorin (TPB), and tetraphenylbacteriochlorin
are known.
(Peychal-Heiling and Wilson (1971)).
(TPC)
They are 418, 480,
514, 548, 590, and 646 ran for TPP (Figure 3-7), 418, 517, 542, 597 and
651 rim for TPC, and 356, 378, 521, and 742 nm for TPB.
were observed for both vanadyl and nickel TPP runs.
None of them
More than this,
if the reduced porphyrins (such as dihydroporphyrins, tetrahydroporphyrins) are formed, they would reoxidized gradually to free base por-
phyrin when they were exposed to air (Hambright (1978)).
However,
-191neither free base Etio nor free base TPP were observed for samples
that have been exposed to air for more than 250 days.
From the above findings, it
is
believed that neither free base
porphyrins nor their reduced forms can be the final metal free products
of hydrodemetallation reaction.
As previously mentioned, both CoO-MoO /Al 0
3
2
and NiO-MoO 3 /Al2 03
catalysts have cracking activity; probably the final products in the
liquid phase are a series of nitrogen containing hydrocarbons.
They
can be family of pyrroles (see book of Badger (1961) for detail), or
system with two pyrrole rings (book of Dolphin (1978),
Bullock et al. (1958)),
Chapter 1).
Chapter 1, and
or even more pyrrole rings (Dolphin
This speculations is
(1978),
supported by the experiments of
free base porphyrin runs (section 4-3) which show that less than 25%
of free base porphyrins formed metalloporphyrins
(either Co or Ni),
and more than 75% just show no properties of porphyrin related compounds.
An intensive study about metal free products could lead to a
better understanding about the mechanism of hydrodemetallation.
-192-
5.4
5.4-1
Intermediates and Products on Catalyst:
Intermediates:
All the possible intermediates mentioned previously in liquid
phase (section
5.3)
are certainly possible to be presented on the
catalysts; especially for those metal chelates that partially connect
to fragments of porphyrins and partially connect to catalyst surface.
5.4-2
Products:
The aformentioned nonmetallic products (section 5.3) are also
possible to be existed on catalyst.
Here the focus will be placed
on the metals (either nickel or vanadium) that deposited on the
catalyst.
The amount of deposition for nickel, vanadium, carbon, and
nitrogen are important in the study about the final form of nickel or
vanadium on the catalyst.
Table 5-2 shows the result of the spent
catalysts for different elements deposited.
All the sample were
analyzed by Galbraith Lab. Inc. (Knoxville, Tenn.).
The observations
are summarized as follows:
(1) Carbon deposition: For Ni-TWP runs, the carbon ranges from 2.10
to 4.67%.
For Ni-Etio runs, alumina run (NE18) has little
carbon
built up, but helium run (NE16H) almost have the same amount of
carbon as typical Ni-Etio run (NE14).
NiO-MoO /Al203 run (NE20)
more carbon than CoO-MoO 3 /Al 2 03 run (NE14).
has
As for vanadyl porphyrin
runs, helium run (VE9H) also has the same amount of carbon as
-193hydrogen runs (VT2, VE3); and alumina run (VE8) has less carbon.
The
mixed VO-Etio and Ni-Etio runs and free base porphyrin runs always
built up 2 to 4% of carbon.
From the above data, it is clear that
carbon built up is about 2.0-4.7% for hydrodemetallation runs, and
similar for helium runs; but less for alumina runs.
A special run made
by pure Nujol without dissolving any porphyrins (marked as Run Nujol)
also show 1.44% of carbon built up.
It is thus speculated that the
carbon deposition was not solely result from hydrodemetallation reaction;
even no porphyrin run (Run Nujol), alumina runs,
or helium runs would
have contributed to carbon deposition.
(2) Hydrogen deposition: By reviewing all the data, it shows that
hydrogen built up is from 0.45 to 1.27%.
(Run NE18,
It seems that alumina runs
VE8) have more hydrogen.
(3) Nitrogen deposition: The concentration of nitrogen ranges from
0.09 to 0.72%.
Both helium and alumina (NE18,
built up than hydrodemetallation
runs, this is
VE8) have less nitrogen
quite reasonable as the
helium and alumina runs have little nickel or vanadium built up, and
should not have nitrogen built up either.
However, pure Nujol run
has same amount of nitrogen as hydrodemetallation
run.
Probably the
sample for Nujol run was contaminated somehow.
(4) Nickel deposition: Both helium run and alumina run show only trace
amount of nickel (<0.15%), which can be experimental errors.
All the
other hydrodemetallation runs show that nickel indeed deposited on
-194Table 5-2
Concentration of C, H, N, V, and Ni
on Spent Catalysts of Different Runs:
Run#
NT 4
4.67
1.16
0.28
NT 8
2.10
1.13
0.34
NT19
---
0.54
0.54
---
1.22 (1.37)
1.50 (1.70)
1.37 (1.62)
---
0.85 (0.95)
---
NT31
3.29
0.93
0.50
0.45
NE14
2.51
0.87
0.53
---
1.71 (1.72)
NE16H
2.94
0.81
0.10
---
0.10 (0.11)
NE18
1.31
1.27
0.09
NE20
4.15
1.05
0.71
---
0.08 (0.15)
3.89 (3.90)
VT 2
3.41
0.82
0.38
0.39 (0.40)
---
VE 3
2.78
0.94
0.48
1.22 (1.39)
--
VE 8
1.51
1. 16
0.18
VE9H
2.29
0.66
0.08
0.32 (0.325) --0.07 (0.055) ---
NV 2
2.95
0.58
0.78(0.86) 0.69 (0.74)
Nv 5
3.79
0.75
0.90
0.72
1.35(1.49) 1.33 (1.25)
E I
0.92
0.55
0.34 (0.46)
E 2
3.29
2.65
0.94
0.50
0.08
Nujol
1.44
0.78
0.51
NT20
2.82
NT23
(to be continued)
-195(cont.)
*(I) The numbers in parenthesis are the theoritical value calculated
from mass balance.
*(2) Run Nujol is the run specially made by placing Nujol (420g)
in the reactor at the presence of KDS 16A catalyst (0.88g),
with 6995 KPa H2 , and 343 C temperature.
were same as demetallation runs.
All the procedures
-196-
the catalyst as final products; all the values were consistent to those
calculated from theoretical mass balance by assuming all the nickel
disappeared from liquid would go to catalyst.
values were shown in Table 5-2).
(These theoretical
Scanning electron x-ray microanalyzer
were used to further verify the amount of nickel deposition.
For run NE14,the portion of nickel in the spent catalyst that is
xylene extractable amounts to 1.4 x 10-2wt% of dried catalyst, which
shows that very little nickels are weakly adsorbed on the catalyst.
amount of nickel by scanning electron x-ray microanalyzer is
The
1.75 wt%
of catalysts, which agrees well with the material balance calculation
of 1.72 wt%.
The spent catalyst was also analyzed by Galbraith
(Knoxville, Tenn.) to show 1.71 wt% nickel.
From nickel deposition of run El and E2, it shows that in free
base porphyrin runs, if
the solution was contacted with stainless steel
wall, nickel porphyrin would be formed and be demetallized later
(Run El); if the solution was protected by glass liner, a small amount
of nickel porphyrin (<I ppm) was formed nevertheless by contact with
the stainless steel cooling coil and impeller (Run E2).
It
is
concluded that nickel would adsorbed on the catalyst as a
hydrodemetallation product.
(5)
Vanadium deposition: It
has been shown in Figure 4-14 and Figure
4-15 that VO-Etio runs have a huge initial
concentration drop even
in the case of alumina carrier or helium pressure.
that disappeared initially
All these vanadium
are believed to be due to reversible ad-
sorption of metalloporphyrins on catalysts.
The reasons are: (a)
-197In run VE8,
the amount of vanadium that is
0.27 wt% of dried catalyst.
similar to 0.33 wt%, the amount
This is
In run VE9H, the amount of
of vanadium lost in transient period.
xylene extractable is
vanadium that is
xylene extractable is
0.31 wt% of dried catalyst.
This is again similar to 0.34 wt%, the amount of vanadium lost in
transient period.
(b) After xylene extraction, the spent catalysts
show little amount of vanadium deposition from the analysis made
by Galbraith.
(Table 5-2).
As for the hydrodemetallation runs of vanadyl porphyrins, similar
result to nickel runs was observed.
For run VE3, the portion of
vanadium that is xylene extractable also amounts to 1.4 x 10-2 wt%
of dried catalyst.
microanalyzer is
The amount of vanadium by scanning electron x-ray
1.35 wt% of catalyst,
and is
1.22 wt% from the
analysis made by Galbraith (Knoxville, Tenn.); all these are close
to the theoretical mass ballance calculation of 1.39 wt%.
It is doubtful that the form of these vanadium or nickel can be
all
metalloporphyrins or their reduced forms.
ratios of atoms Ni:C:H:N are
For Ni-Etio,
1:6.54:0.55:0.95.
the weight
However, for run
NE14, the ratio is only 1:1.46:0.51:0.31 (Table 5-2).
What even
more is, as carbon and hydrogen can also be formed from Nujol itself,
the actual ratio of Ni:C and Ni:H should be even higher. Similarly
for VO-Etio, the atomic ratios V:C:H:N are 1:7.54:0.63:1.1,
and run
VE3 shows only 1:2.0:0.68:0.35.
Through the comparison of typical hydrodemetallation run (NE14 or
VE3), alumina run (NE18 or VE8), and helium run (NE16H or VE9H),
-198quantitatively it
deposit
is conclude that all the metals (Ni or V) would
on the catalyst;
qualitatively it
is
suggested that carbon
and hydrogen deposition is independent of hydrodemetallation reaction,
while nitrogen deposition is dependent on hydrodemetallation reaction.
An attempt was made to try to use ESCA (Electron Spectroscopy for
Chemical Analysis) to study the chemical forms of deposited vanadium
or nickel.
Unfortunately, it was found that unless the amount of metal
deposition is larger, and unless other species on the catalyst are well
understood; very limited information can be obtained from ESCA study.
A very accurate carbon, hydrogen, and nitrogen analysis would be
a prerequirement
to make a more powerful statement about the final form
of nickel and vanadium on catalyst.
At present, one can only speculate
that most probably either elementally metals or metal oxides would be,
the best candidates.
-199-
5.5 Discussion on Kinetic Model and Possible Mechanism:
5.5-1
Background:
The fractional order (half order) kinetic model is empirical,
and is useful in the discussion of pressure, temperature dependence,
and in the comparison of demetallation activity (such as between vanadium
and nickel, between CoO-MoO 3/Al 2 03 and NiO-MoO3 /Al 2 03 ). However, it
does not tell much about the mechanism.
It will be helpful to proposed
a kinetic model which is based on feasible mechanisms, and will also
demonstrate the half order observed kinetics.
The kinetic model proposed in this section is based on the phenomena observed in the previous experimental runs.
Although it
shows
good data fits, reasonable Arrhenius plots, and initial rate expressions; it
is premature to say that this mechanism is correct.
More
information is needed to prove or disprove the mechanism, and they will
be discussed in Chapter 6.
The useful observations from previous experimental runs are
summarized as follows:
(1)
The kinetic order is fractional order, between zero and one.
The
hydrogen pressure dependence is alway between 1 and 2 for metalloetioporphyrins, and between 2 and 3 for Ni-TPP.
(2) CoO-MoO 3 /Al 2 03 or NiO-MoO 3/Al 20 3 are essential for effective
demetallation reaction, which need the active sites provided by them.
-200These catalysts are known to have hydrogenation activity; in addition
to this, the presence of Al203 plus S102, and possible interactions
between Al20
and metal oxides might also contribute to some acid sites.
It is reasonable to proposed that demetallation reaction would need both
hydrogenation and acid sites.
(3) Free base porphyrin runs show that free base porphyrin is very
As none-of its hydrogenated free base forms were observed,
it is conceivable that the structure of porphyrins were destroyed
during demetallation reaction.
in the porphyrin plane.
,
unstable.
This would involved C-C bond breaking
(Section 4-3).
(4) Intermediates are formed during demetallation,
and it
that probably hydrogenative metalloporphyrins were formed.
is suspected
As visible
spectra show multiple new peaks which seems to be independent to
each other, more than one intermediate are suspected.
(section
5-3).
(5) The demetallized metals were permanently adsorbed on catalyst
surface and could not be extracted out by xylene.
Carbon, nitrogen,
hydrogen analysis on spent catalysts suggest that elemental metals
or metal oxides are the most probable forms of the metals on catalyst.
(Section 5-4).
Since Ni-Etio and VO-Etio are the main model compounds for study,
the mechanism and kinetic model proposed here are for the demetallation
of Ni-Etio VO-Etio only.
The following steps for demetallation reaction are speculated:
-201NiL + A M NiLA
K1
(5-1)
NiLA + H2;=a 2NiLH2A
2
K
2
(5-2)
NiLH2A + H2=&NiLH A
K3
(5-3)
NiLH2A
NiLH2 + A
1/K4
(5-4)
NiLH 4A%
NiLH4 + A
1/K 5
(5-5)
K6
(5-6)
K7
(5-7)
K8
(5-8)
B + NiLH 4A 3==* NiPB + RA
RA
NiPB
R + A
NiB + P
(Rate Controlling)
Ni here represents nickel; NiL is the initial compound Ni-Etio;
A is the active site that has hydrogenation activity and cracking activity,
which might be mixture of CoO or Moo ; H2 is
hydrogen;
NiLH2 and NiLH4
are hydrogenated nickel porphyrins, may be Ni-chlorin and Ni-tetrahydroporphyrins; B consists of A and C where A has been defined, and C is the
site
that only has cracking activity; NiPB is
tear the porphyrin into two parts, and is
the product of step 6 that
on the catalyst surface; R is the
other fragment of decomposed porphyrin, L actually consists of P and R;
(
NiB is the final product of nickel that permanently adsorbed on site B
It is assumed that the final metal form is elemental nickel); and finally
P is
the part of NiP that lose nickel during step 8.
All the species end
with "A", such as NiLA, are the species that adsorbed on A site.
Eq. (5-1) is the adsorbing step of Ni-Etio on site A; eq. (5-2) and
eq. (5-3) are hydrogenation reactions; eq. (5-4) and (5-5) are the desorption of hydrogenated nickel porphyrin intermediates;
that involves bond breaking of porphyrin; eq.
eq.
(5-6) is the step
(5-7) is the rate controlling
step, it can be a combination of further bond breaking and desorption
-202processes,
whether this is
a single step or multiple steps would not
affect the overall kinetic expression provided each intermediate is
of negligible amount;
equation (5-8)
is
the step form nickel that
peranently adsorbed on the site B.
It
assuming that equation (5-7) is
is
irreveisible one, all
letter
"K" is
rate controlling and
the other steps are at equilibrium.
equilibrium constant and "k" is
rate constant.
The rate of disappearance of RA can then be equation
d (RA
dt
k (RA}
Capital
(5-9):
(5-9)
7
Mass balance of A and B would follow eq. (5-10) and eq. (5-11):
(A1 = (A) + (NiLA)+ (NiLH2 ) + (NiLH 4 ) + (RA)
(B) = (B) + (NiPB) + (NiB)
A)
(5-10)
.
(5-11)
and (B0 ) are the initial concentrations of site A and B.
Although intermediates were found in demetallation reaction,
in here for simplicity it
intermediate species
is assumed that all
the concentration of
are very small compare with initial
compound
(NIL) or final compound (R).
Eq. (5-10)
and eq. (5-11) can then be simplified to eq. (5-12)
and eq. (5-13):
(A0 ) = (A) + (NiLA)
(B 0 ) = (B) + (NiB)
+ (RA)
(5-12)
(5-13)
It has been calculated that even all the nickel would adsorbed
on the catalyst, it
catalyst.
would occupied less than 5% of total surface of
Since B is the site that only the acidity is required, it
-203-
In here it is assumed that NiB only
could be all over the catalyst.
occupy limited surface of B so the total concentration of B site
Eq. (5-14) would then hold throughout
will not change during reaction.
the reaction:
(5-14)
B)
After algebraic derivations, eq.
(5-9) would be transformed to (5-15):
k7KIK 2K 3 K6 K8 Ao) (BO) (NiL} (H
2
)NiB
(P) + K INiB)JP)[NiL) + KjK2 K3 K6K8LAO) [NiL) [H
2
dt
(5-15)
(
(Bd
NiB is considered as solid, so its chemical potential is constant.
Three parameters are assigned to eq. (5-15):
k7KjK2KK6K(Aoj
(NiB)
I
P2
(Bo)
KI
K3 K2
K 6 K8(Bo)
(NiB)
S3
Eq. (5-15) can then be substituted into eq. (5-16) by PI, P ,'
2
P,
(NiL) (H2
.2
3
(5-16)
[P) + P 2 (P][NiL) + P 3 [NiL}(H2 2
dt
If all the intermediates are of negligible amount compare with
initial reactant (NiL) and final products (R) and (P), eq . (5-17)
and eq. (5-18) would be available:
=)
-
-
dt
Where(Ni)
is
(NiL) '= (Ni]
d(NiLL_
dt
_
d(BA]
dt
()(
dt
the concentration of total nickel compounds.
(5-18)
17)
-204-
Further more, it is assumed that the concentration of P is equal
to the disappearance amount of total nickel compounds (eq. (5-19)):
(P) = (Ni0 ) - (Ni)
Where
(5-19)
Ni0 ) is the initial nickel concentration.
eq. (5-17), eq. (5-18), and eq.
By substituting
(5-19) into eq. (5-16), eq. (5-20)
is obtained:
(Ni)
(5-20)
2H2
(Ni)
(NiJ] - (Ni) +
d(Ni)
dt
1
P2 (tNi3- (Ni))
should be replaced by (V)
+ P2(NiH
for VO-Etio.
The concentration versus time data for each Ni-Etio and VO-Etio
run is
used to find the rate (d(Ni) /dt) versus time data.
concentration is
The initial
obtained by extrapolation of concentration versus
time data to zero time.
For a particular run as hydrogen consumption is negligible,
H2
is constant;
(Nid or (Vo) will also be obtained.
By using non-linear
least square subroutine through
computer, the best fit Pi, P '
2
will be obtained.
Eq. (5-21) to eq. (5-23) are used to find the
equilibrium and rate constants:
S3
= k7 (A)
P2 =K
p ~
P3
=
k
(5-21)
(5-22)
-K
2 =
2 K5 K6 K8 (BQ
K
(NiB 3
K
(5-23)
3
-205While P 2 '
3/P2 should be independent of oil/catalyst ratio,
P I/P3 will depend on it;
oil/catalyst is multiplied by P /P
to a new assigned value "k''.
or k
A
(k = k7 (A) x oil/catalyst). The unit of
pressure used here is MPa (10 3 KPa), ppm for metal concentration,
and unit of time is hour.
5.5-2
Results and Discussion:
(1)
The Arrhenius plot for k, Ki, K is shown in Figure 5-10 for
p
Ni-Etio, and Figure 5-11 for VO-Etio- Very good straight lines are
obtained for both model compounds.
For Ni-Etio, the activation energy
is 22.5 kcal/g mole for k, heat of reaction is 58.1 kcal/g mole for
K1 , and 35.3 for K . For VO-Etio, the activation energy is
p
23.7 kcal/g mole for k, heat of reaction is 23.6 kcal/g mole for Ki,
and 28.9 for K energy of k; K
Both compounds show reasonable values for activation
decreases with temperature,
higher value of heat of reaction,
is
the magnitude of K 1 for vanadium
larger than nickel for temperature over
term of K
3K
6K 8
although Ni-Etio has
3050 C.
K , a combining
p
are increasing with temperature.
While K 2 ,
5
should decrease with temperature as they are equilibrium constants
of hydrogenation reaction which should be exothermic; K6, K8 might
increase with temperature and result in the
increase with temperature.
net value of K
p
that would
-206-
ek
U
1
*K
AK,
11-
0
10
9
-- 1
ln
ln k
-- 4
1.58
1.62
|
11
1.66
1/T
Fig. 5-10
11
1.70
i
i
1.74
J-5
1.78
1/ko x 1000
Temperature Dependence of k, K1 , and K
for Ni-Etio Runs.
-207-
I
I
I
I
|
I
I
0
m
A
10
-1
9
-1-2
pA
ln K
ln k
-1-3
8
k
AK
7
I
1.6
I
1.64
1.68
1/T
i
I
1.7
'I
1.76
1/K0 x 1000
Fig. 5-11 Temperature Dependence of k, K1 , and K
for VO-Etio Runs.
-5
-208(2)
The concentration versus time plots for both experimental run
and theoretical calculation are shown in Figure 5-12 for Ni-Etio
Run (NB4) and Figure 5-13 for VO-Etio Run (VE3).
The dots represent
the experimental data, the solid curves represent the theoretical
calculation values from model presented in this section, the dotted
curves are those calculated from half order kinetic model.
As three
parameters are used in this kinetic model, it is not surprised that
such a good fit
can be obtained.
(3) From eq. (5-16),
one learns that at the very begining of the
reaction very little
P are formed.
If CP ] or CNij - (NiJ
is assumed to be zero, then eq. (5-20) would become eq. (5-21):
d(Nil
dt )
I
0
dt jtO
(NiJ (H 2
P 1 (Ni
H
-P3 ( Ni 0) CH2]
= k
7
A
(5-21)
Eq -(5-21)simply means that the initial rate should be independent
of initial
concentration of nickel or vanadium and hydrogen pressure.
The magnitude of this initial rate should also be equal to k 7 (A ).
As in autoclave batch reactor system, initial rate is impossible
to obtain unless by extrapolation;
lots of errors are expected.
Table 5-3 shows the experimental initial rate
(R0 = d(Nig /dt x oil/
catalyst) and the ,theoretical initial rate for the different initial nickel
concentration, but same hydrogen pressure runs (Run NE3, NE4, NE23,
NE24, NE35); or same initial concentration,
but different hydrogen
pressure runs (NEI, NE2, NE4, NE5, NE6, NE9).
same thing for VO-Etio runs.
Table 5-4 shows the
Both Tables show that for most runs,
the experimental initial rate is lower than theoretical rate, this
-209i
II
I
I
I
I
Run NE4
30
0kxperiental Data
Theoretical Calculatio n
from EQ. 5-20
25
-
-
Theoretical Calculatio n
from Half Order Kineti C
Model
20 1
C
(ppm)
10
-
15
00
1
2
3
Time
Fig. 5-12
4
5
r-
8
(hour)
Experimental and Theoretical Concentration Versus Time
Data for Run NE4.
-210-
Run VE3
*
Experimental Data
Theoretical Calculation
from Half Order Kinetic
Model
20
Theoretical Calculation
from EQ. 5-20
15-
C
(ppm)
10.
5
oN
0
2
01
Time
Fig. 5-13
(hour)
Experimental and Theoretical Concentration Versus Time
Data for Run VE3.
-211Table 5-3
Initial Rate Values (R0 ) as a Function of Initial Metal
Concentration or Hydrogen Pressure for Ni-Etio Runs:
A. Different Initial Ni-Etio Concentration Runs:
Run#
Initial Ni-Etio
Experimental Value
Concentration,
C 0 (ppm)
R
0
(ppmcc oil
g cat.hr
Theoretical Value
R (ppm-cc oil) = k
0
g cat.hr
NE 3
30.2
14360
18662
NE14
34.0
16692
18662
NE35
25.0
13353
18662
NE23
11.8
13520
18662
NE24
11.5
16156
18662
0
Dependence: R OC C00.026
B. Different Hydrogen Pressure Runs:
PH2((MPa)
Experimental Value,
R
0
Theoretical Value
k
R0
NE 9
4.237
5400
7855.4
NE 1
6.995
5649
7855.4
NE 4
i
7157
7855.4
"
Run#
7385
7855.4
NE 5
NE 2
9.752
6070
7855.4
NE 6
12.509
7672
7855.4
(to be continued)
-212-
(Cont.)
Dependence: R 0 0
P
0.249
*The initial concentrations are the concentrations obtained
from C versus time plot by extrapolation, which are different
from the one cited in Table 4-2.
-213Table 5-4
Initial Rate .Values (R -) _as Function of Initial Metal
Concentration or Hydrogen Pressure for VO-Etio'Runs:
A. Different Initial VO-Etio Concentration Runs
Run#
Initial Conc.
of VO-Etio,
CO(ppm)
Experimental Value
R (ppm cc oil
o g cat.hr
Theoretical Value
R
o
= k(pPm cc oil)
g cat.hr
VE10
7.15
5906
6449
VEIl
15.30
6028
6449
Dependence: R
C00.026
B. Different Hydrogen Pressure Runs:
Experimental Value
R (pPm cc- oil)
o g cat.hr
Theoretical Value
R = k(PPm cc oil
g cat.hr
o
Run#
Initial Conc.
of VO-Etio,
Co (ppm)
VE 4
4.237
2750
2591
VE 1
6.995
2402
2591
VE 5
9.752
2933
2591
VE 6
11.820
2646
2591
Dependence: R 0
P H20.02
-214-
could be due to the direction of extrapolation of C VS t is
the low concentration side.
expected to be very large.
from
The errors of taking initial rate are
Identical condition runs (NEI,
show that standard deviation is
-
15% of mean value.
NE4, NE5)
Nevertheless,
results show that for Ni-Etio the concentration dependence is
0.026,
pressure dependence is 0.25; for VO-Etio, it is 0.026 and 0.02
respectively.
All these values are closer to zero than 0.5 or 1.
By taking the experimental and plotting errors of initial
rate into
account, the closeness of aformentioned numbers to zero should be
satisfactory.
(4) A special run (NE36) was made by adding 0.188g pyrrole in the
catalyst loader and keeping other operating conditions constant.
If
P is pyrrole or its degraded products, then the added pyrrole should
be equivalent to (P) = 392 ppm; which is high enough to inhibit the
demetallation reaction greatly (needs 17 hours for 80% conversion).
Nevertheless, the result of run NE36 shows that the demetallation
rate is only slightly inhibited by adding pyrrole and hence P should
not be pyrrole.
Another run (NE15) by dissolving Ni-Etio in the mixture of 200g
of spent oil of run NEll and 220g of fresh Nujol was made under
coo-mo3/Al203
catalyst, 6995 KPaH2 , and 316 0 C.
initial product P should be 16 ppm.
The concentration of
Figure 5-14 shows the comparison
of the experimental result with that of theoretical calculation,
shows fairly well match.
which
If one repeats the same procedure by dis-
solving metal compounds in older spent oils, the product inhibition
-215I
I
I
I
I
I
-
30
U
Run NE15
Experimental Data
25
-
20
-
Theoretical Calculation
Assumes (Po)=- 1 6 ppm
Assumes (P)
14ppm
C
15
-
(ppm)
10
5
*N
0
I
0
I
2
I
I
I
4
Time
6
8
(hour)
Fig.: 5-14 Comparison between Experimental Data and Theoretical Values
of Spent Oil Run. (NE15).
-216effect should be clearer.
The observations of the two special runs can be summarized as
follows:
(a) From run NE15, it
looks like there exists some products
that will inhibit the demetallation reaction.
This observation supports
the proposed mechanism which has a product inhibition term (P) in the
(5-16)).
rate equation (eq.
(b) From run NE36, it is observed that
whatever product P isit should not be pyrrole or its degraded products.
(5) This mechanism has several weakness:
except eq.
(5-7), all
might not be so.
the other steps are of equilibrium, which
(b) The model proposed assume that whatever the
intermediates form,
5-5
(a) The model assumed that
they are of only negligible amounts,
but Figure
shows that the amount of intermediate could be more than 4ppm.
Though modification should have been done to understand more about
the mechanism, lack of accuracy of quantitative analysis on visible
spectrophotometer prevents one from doing such modification.
(6)
Other mechanisms may result in the same rate expression as shown
in eq. (5-20).
The points can be made from this study are: (a) Whatever
the reasonable mechanism will be, the resulting rate expression should
be between 0 and 1 order with respect to metal concentration,
between 1 and 2 order with respect to hydrogen.
and
This also implies
that one metal molecule needs two hydrogen molecules to demetallize.
(b) Initial rate data implies that both the pressure and initial metal
concentration dependence should be zero order.
Whatever the mechanism
-217proposed, the above two observations should be satisfied.
(7) To prove whether porphyrin is really destroyed or not during
hydrodemetallation reaction would require a design of pure hydrogenation
catalyst that does not have acid site.
catalysts to eluciate the mechanism.
It
will be useful to use such
As Nujol would contribute carbon
deposition in blank run (Run Nujol in Table 5-2). it is
not a real
"inert"; the possibility of Nujol to involve in demetallation mechanism
can not be excluded.
Nujol is
Runs with other suitable solvent would show whether
inert in hydrodemetallation reaction.
S
-2185.6
Catalyst Deactivation:
There is no appreciable catalyst deactivation during the courses, of
an experiment.
The spent catalyst from run NE4, after 7 hours of
operation, was used for run NE5.
No appreciable change of half order
kinetics or rate constant was noticed.
There is no contradiction between our findings and previous literatures which mentioned the deactivation of hydrodemetallation and hydrodesulphurization reactions by the deposition of coke and metals.
The
spent catalyst of Run NE5 has less than 3.5% of nickel and less than 3%
of carbon (not necessarily coke) deposited on the spent catalyst.
The low metal and coke deposited on the catalyst is due to short
operation hours and probably the absence of aromatic compounds in
Nujol; it is not surprising that the rate of deactivation is not
detectable.
The kinetics and activity of VO-Etio runs are close to that of
Ni-Etio or Ni-TPP runs.
Since we have shown that the rate of deac-
tivation is insignificant for nickel runs, the rate of deactivation
is not significant in the case of vanadyl porphyrin runs either.
-219Comparison among Nickel Runs:
5.7
Most of the materials used for discussion here can be found in
section 4.1.
Between Air Prepared Ni-TPP and Helium Prepared Nickel
5.7-1
Porphyrin Runs:
The difference are summarized as follows:
(1)
The kinetics for air prepared Ni-TPP follows slow first order region,
fast first order region, and then go back to slow first order region
(Figure 4.2, 4.3); the kinetics for helium prepared Ni-TPP and Ni-Etio
follow fractional order (half order) kinetics (Figure 4-8 (d)).
The
kinetics of nitrogen prepared Ni-TPP is the same as helium prepared
Ni- TPP.
(2) While there is an appreciable decline of concentration for air prepared
Ni-TPP runs during the preheating period (Figure 4-1); they show no initial
drop after the catalyst is injected.
On the contrary, the helium prepared
nickel porphyrins do not disappear during preheating period; but there
is a transient period of rapid concentration decline for the first ten
minutes after the catalyst is injected.
(3) The demetallation rate constants for air prepared Ni-TPP depends
on the oil/catalyst ratio, and there is a linear relationship between
the amount of nickel deposited on the catalyst when the shift from
fast reaction region to slow reaction region occurs and the oil/catalyst
ratio.
(Figure 4-6 and Figure 4-7).
oil/catalyst dependence at all.
Helium prepared runs shows no
-220(4) The demetallation activity of the air prepared Ni-TPP was less
than 40% of helium prepared Ni-TPP.
Table 5-5 shows the comparison
by forcing helium prepared run (NT2O) to fit first order.
Figure 5-15
shows the C Vs t plots for run NT6 and NT20, which clearly shows the
faster demetallation rate for helium prepared Ni-TPP.
5.7-2
Comparison between Helium Prepared Ni-TPP and Ni-Etio Runs:
(i) The solubility of
metallotetraphenylporphines
than metalloetioporphyrins,
in Nujol is
poorer
higher temperature has to be used to dis-
solve metallotetraphenylporphines
in Nujol (section 3.3-1).
Probably
the more aromatic nature of TPP type of porphyrins decrease the solubi-
lity in Nujol.
(2) Both Ni-TPP and Ni-Etio fit
than zero order, first
4-8).
order,
fractional order kinetics,- better
and second order kinetics.
(Figure
However, from the reproducibility runs (Table 4-3), it
is
clear that Ni-TPP runs have larger fluctuation than Ni-Etio runs.
Roughly speaking, the difference between total nickel removal half
order rate constant and nickel porphyrins disappearance half order
rate constant is
bigger for Ni-TPP runs than it
is
for Ni-Etio runs.
Probably more intermediates were formed for Ni-TPP runs.
(3) Ni-TPP runs have higher activation energy than Ni-Etio runs,
and their hydrogen dependence is larger than second order.
hydrogen dependence for Ni-Etio runs is only 1.5 order.
The
The possible
-221-
Table '5-5 Comparison of Pseudo First Order Rate Constants
of Air-Prepared Ni-TPP arid Helium-Prepared Ni-TPP.
Air-Prepared (Run# NT6)
kfast
kslow
*
1
202
cc/g.hr
82
cc/g.hr
Helium-Prepared (Run# NT20)
k*
:
424.5
cc/g.hr
: k was found from the slope of lnC vs t plot by
linear regression.
-222I
I
D
I
I
32
I
o Run NT20
0
28 -Q
Run NT6
24
0
20
U
C
(ppm)
16
12
0
U
0
0
U
U
0
81-
U
0
N
0
41*-
U
aU.
0
0t
0
I
I
2
4
I
6
Time
Fig. _5-1_5
I
8
I
10
(hour)
Comparison between Air Prepared Ni-TPP Run (NT6)
and Helium Prepared Ni-TPP Run (NT20).
12
-223mechanism proposed in section 5.5 was focused on metalloetioporphyrins; for Ni-TPP runs, three hydrogen molecules should be required
to demetallize one molecule of Ni-TPP.
of more intermediates
,
This supports the speculation
and the observation of larger than second order
hydrogen dependence for Ni-TPP runs.
(4) Generally speaking, for total nickel removal rate, the magnitude
of half order rate constant is smaller for Ni-TPP run than it
Ni-Etio run at 316 0 C, and 6995 KPa hydrogen pressure.
disappearance, it
is for
For nickel porphyrin
is larger for Ni-TPP run rather than it
is for Ni-Etio
run.
The comparison between Ni-TPP and Ni-Etio runs for activation
energy, hydrogen dependence, and calculated half order rate constants
at 316 0 C, and 6995 KPa hydrogen pressure are shown in Table 5-6.
5.7-3
Comparison between CoO-MoO /Al.0
and NiO-MoO /Al 0
Catalysts for Ni-Etio Runs:
(1)
Same as Ni-Etio runs for CoO-MoO /Al
3
2 03
catalyst, NiO-MoO 3 /Al 2 0 3
catalyst runs also fit half order kinetics. Although the difference
is not big, the half order rate constant for NiO-MoO3 /Al2 03 catalyst
is always larger than CoO-Mo03/Al2 03 catalyst at the same operating condition.
The half order rate constant for total nickel removal at 316 0 C, and 6995 KPa
.
hydrogen is 403 for CoO-MoO /Al2 03 , but it is 481 for NiO-MoO /A1 2 0
The same observation is also made in self preparation catalyst runs
-224(Run NE25 and run NE31); for run NE25 (CoO-MoO3 /A
2 03 )
the half order
rate constant is 829, while for NE3i (NiO-MoO3 /Al 2 03 ) it is 895.
(2) The activation energy, hydrogen dependence for NiO-MoO /Al
2 03
catalyst on Ni-Etio runs are very similar to CoO-Mo0 /Al2 03 catalyst.
The comparison is shown in Table 5-7, which clearly shows that the
difference is very small.
-225Table 5-6
Comparison between VO-Etio, Ni-Etio and Ni-TPP Demetallation Runs:
VO-Etio
Ni-Etio
Ni-TPP
(a) Activation
energy for
total metal
37.1
27.6
34.0
35.8
28.1
33.7
removal
(kcal/g mole)
(b) Activation
energy for
metalloporphyrin
disappearance
(kcal/g mole)
(c) Hydrogen
pressure dependence
for total
1.16
1.34
2.26
1.23
1.66
2.13
metal removal
(d) Hydrogen
pressure dependence
for metalloporphyrin
disappearance
(e) Half order rate
constant at 3160 C,
6995 ICa H for
202.2
403.4
249.5
205.7
440. 9
450.3
total metaI removal
49TM cc oil
g cat hr
(f) Half order rate
constant at 3160C,
6995 KPa H2 for
metalloporphyrin
disappearance
zp-m cc oil
g cat hr
Table 5-7 .Comparison between CoO-MoO /Al 0
and NiO-MoO /Al 0 Catalysts for Ni-EtIo Runs:
NiO-MoO3 /Al 2 03 (HDS 9A)
Coo-Moo 3 /Al 2 03 (HDS 16A)
(a) Activation
energy for
total nickel
removal
(kcal/g mole)
27.4
27.6
(b) Activation
energy for Ni-Etio
disappearance
(kcal/g mole)
26.1
28.1
(c) Hydrogen
pressure dependence
for total nickel
removal
(d) Hydrogen
pressure dependence
for Ni-Etio
disappearance
1.45
1.34
1.41
1.66
-2275.8
(1)
Comparison between Nickel and Vanadyl Porphyrin
For metallotetraphenylporphine runs, it
Runs:
has been mentioned
(section 4.2) that VO-TPP runs is seven times faster than Ni-TPP
runs.
Also, as VO-TPP runs would enter into diffusion limited
region, no kinetic data were obtained for VO-TPP runs.
(2) In the Ni-Etio and VO-Etio runs, the reaction rate for VO-Etio
is
slower than Ni-Etio at 316 0 C, and 6995 KPa.
However, as VO-Etio
has higher activation energy than Ni-Etio, they show higher activity
than Ni-Etio at higher temperature.
By combining with the observation
that vanadium would retard nickel removal, our finding is consistent
to the previous literatures (Oleck and Sherry (1977),
Chang and
Silvestri.(1974, 1976), Riley (1978), Oxenreiter et al. (1972), and
'Larson and Beuther (1966))
that mentioned vanadium has higher activity.
Table 5-6 summarized the activation energy, hydrogen pressure dependence,
and the calculated half order rate constants at 316 0 C, 6995 KPa
hydrogen of VO-Etio, Ni-Etio, and Ni-TPP runs.
(3) The kinetic order of vanadium and nickel runs are similar; both
fit
well with 0.5 kinetic order.
However, the dependence of
kinetic order on temperature and hydrogen pressure for vanadium runs
are less significant.
(4) Vanadium adsorbs on the catalyst stronger than nickel.
The
-228concentration decline in transient period for vanadium runs is
than that for nickel.
has to be removed first
larger
In mixed vanadium and nickel runs, the vanadium
before nickel can be removed effectively.
This is supported by the previous literature by Larson and Beuther
(1966)
that claimed vanadium-containing molecule is more polar and
surface active than nickel-containing molecule in general.
(5) For both nickel and vanadium runs, the information on the deposition
of vanadium or nickel, carbon, hydrogen, and nitrogen on spent catalyst
indicates that only a small portion of vanadium or nickel on catalyst
can be metalloporphyrins.
(6) Except VO-TPP runs which show higher activities and was somewhat
affected by diffusion processes, all the other three series, VO-Etio,
Ni-Etio, and Ni-TPP appear to be diffusion free.
-2295.9
Comparison between Individual Ni-Etio, VO-Etio Runs
and Mixed Ni-Etio, VO-Etio Runs:
(1)
Same as individual runs, the mixed Ni-Etio and VO-Etio runs also
fit
half order kinetic model.
While demetallation activity of VO-Etio
is not affected by the presence of Ni-Etio, the reverse is not true.
The kinetics of Ni-Etio in mixed runs can be fitted by a slow half
order followed by a fast half order.
Both of the half order rate
constants for Ni-Etio in mixed runs are lower than individual Ni-Etio
runs, and the values depend very much on the ratio of- initial concentrations of vanadium to nickel.
(Section 4-4, Figure 4-19 to Figure
4-21).
.
(2) The comqparison of activation energy, hydrogen dependence, and tota
metal removal half order rate constants for individual VO-Etio, Ni-Etio
and mixed VO-Etio, Ni-Etio
uns is shown in Table 5-8.
As the rate
constants of Ni-Etio in mixed run would depend on initial concentration
ratio of VO-Etio to Ni-Etio, the activation energy, hydrogen dependence,
rate constants shown in Table 5-8 for mixed runs is based on C o/c Nio=2.1.
Table 5-8
Comparison between Individual Ni-Etio, VO-Etio,
and Mixed Ni-Etio, VO-Etio Runs (Total Metal Removal)a
Individual
VO-Etio
Mixed
VO-Etio
Individual
Ni-Etio
Mixed
Ni-Etio
Fast
slow
26.2
40.4
(1) Activation
energy
37 .1
37.0
27.6
(kcal/g mole)
(2) Hydrogen
pressure
dependence
1.16
1.11
1.34
1.29
0.24
0
(3) Half order
rate constant
at 316oC, 6995 KPa
ipm. cc oil
H2 ,
g Cat. hr.
*
202.2
Calculated
value
190.8
403.4
235.5
35.7
(Run
NVE 7
Calculated)
value
Run
NVE?
Run)
NVE?
The initial concentration ratio for VO-Etio to Ni-Etio is 2.1.
-231Comparison with Previous Work:
5.10
(1)
While the previous literature show that the kinetics of hydro-
demetallation reaction is
2-6),
either first
order or second order (Table
this study found that the apparent kinetic order is always
less than first order, and is a function of temperature and pressure.
These apparent fractional order can be well explained by either
Eley-Rideal or Langmiur type kinetics, which was proposed in section
5.5.
(2) The demetallation rate in this study is much faster than previous
investigators.
The comparison is made by the following procedure: (a)
The data reported by Oleck and Sherry (1977) was used for comparison.
They operated at an oil/catalyst ratio of 20,
and pressure at 13888 KPa, the initial
vanadium and 19 ppm for nickel.
temperature at 398.9 0 C
concentration was 195 ppm for
Their second order data can be con-
verted to two first order rate constants, which are shown in Table
5-9.
(b) For this study, the expected first order rate constants at 398.90C,
13888 KPa H2 were calculated from the more sophieticated model shown in
section 5.5 by extrapolation the temperature to 398.9 0C.
After C Vs t
data are obtained from this model, first order constant can then be
obtained by finding the slope of lnC Vs t plots.
The first order rate
constant for nickel removal then was corrected by Figure 4-21 to account
for the retarding effect of vanadium compound on nickel.
they were transformed from cc oil
g cat hir
for oil is 0.88.
Finally,
assuming the density
to gby
g cat hryasuigte
The values are also shown in Table
5-9.
est
It's not
difficult to explain why the calculated vanadium removal rate constant
TEable 5-91
Comparison of First Order Demetallation Rate
Constants between Previous Literature and This Studyi
Vanadium Removal
g oil
Nickel Removal
g oil
g cat.hr
g cat.hr
Previous Study
Fasts 62.4
Fast: 26.9
(Oleck and Sherry)
Slow s 11.52
Slow t
3.84
(1977)
This Study:
452
Fasts 840
Slows 240
*Temperatures 398.80C; Pressure: 13888 KPa; Initial Concentration of Vanadium: 195 ppm,
Initial Concentration of Nickels 19 ppm.
-233is
lower than the fast nickel removal rate constant.
The fast removal
nickel rate constant could only occur when the concentration of vanadium
in the bulk is very low, it is thus believed that during most of the
time, nickel removal rate would follow the slow rate constant (240)
rather than fast rate constant (840) due to the high initial concentration of vanadium.
It is clear from Table
5-9 that our rate constants are roughly
a order of magnitude higher than the rate constants reported by Oleck
and Sherry.
This difference in activity can be due to a number of factors.
The system used in this study is clean without
compounds.
The nickel and vanadium are all
sulphur and nitrogen
porphyrins, without the more
refractory asphaltene compounds. The catalyst has not been presulphided.
All these may contribute to the greater activity.
(3) Since this study has shown that vanadium removal rate has higher
activation energy, and it
will not be suppressed by the presence of
nickel compound, the general statements about the higher vanadium removal rate made by the previous investigators (Table 2-6) are qualitatively true.
The ratio of vanadium/nickel removal rate would be function
of initial concentration of vanadium, initial of concentration nidkel,
temperature, pressure, and the concentration of vanadium during reaction.
-234This study does not support the speculation made by Sato et al.
(1971)
that claimed the effective diffusivity for vanadium has to be
less than 10% of nickel.
If this was true, one should expect some
diffusion limited reaction in VO-Etio runs; but no such thing was
observed.
(section 5.1).
(4) The activation energy for vanadium removal found by Oleck and
Sherry (1977)
is
was 38.2 kcal/g mole for CoO-MoO /Al203
catalyst, this
very close to the value found in this study: 37.1 kcal/g mole.
The pressure dependence found by them was 1.77 and 1.50 order for
vanadium and nickel removal respectively,
of 1.16 and 1.34 done by this study.
which are larger than that
-2355.11
Differentiating between Two First-Order Reactions and a
Single Second-Order Reaction:
In section 2.2-1.b,
it
was mentioned that in some cases,
hydrodeme-
tallation or hydrodesulphurization can be described as either second
order kinetics or two parallel first order kinetics.
In this study, the approximation of second order kinetics,
kD 2
dD
~Tk
D
(5-22)
(1 + D kt)
by two parallel first order kinetics was studied.
dCf
df=
dt
-k
C
ff
dC
=t-ksC s-
C =
f + Cs
oCe-k t + C
e-ks
(5-23)
The goodness of the approximation can be measured by the maximum
percentage over the range of conversions:
max
Max. I
It was found that I
C
X
100
(5-24)
Lxis the function of the following three
parameters:
A =C so/C f
ratio of initial concentrations
B = ks/k
ratio of rate parameters
-236-
6 % (Conversion) = 100 x (C - C)/C0
For
max
=
5%, it will be shown that the values of A and B needed
to fit the second order kinetics are restricted to narrow regions inside
a contour; as C increases, the available region will shrink.
As the
conversion level increases to 92%, the available region becomes a single
Beyond 92% conversion, the sum of two first order kinetics cannot
point.
approximate second order kinetics at less than 5% error.
The "normalized" first
order concentration C
N
is
defined
in equation (5-25):
CN
tN is
N + Ae-BtN
(5-25)
the normalized reaction time or residence time in the reactor.
The "normalized" forms enable one to study this topic based on the
relative values of rate constants, initial concentrations, and time
(such as A, B, tN) only.
The relationship between the normalized values
and those of the absolute concentrations, time, rate constants can be
found in the following analysis.
The "nomalized" second order concentration DN is also defined
in equation (5-26):
DN = (A
+
1)/(1 + kNN (A + 1))
(5-26)
kN here is normalized second order rate constant.
For a given values of A and B, the normalized time required (TN)
to reach the final conversion (E) can be calculated from equation (5-25).
Then, kN can be obtained by using least square method from the values
of TN, A, and B.
-237The least square method is designed to find kN that allow the
minimum of equation (5-27) to occur:
J
(1/CN
(5-27)
1/DN)dtN
-
After few mathematical manipulations, kN can be calculated from
equation (4-7):
k fTN
)
3
N+ Ae-BtN dtN ~ 2(A +1)) N
(e
o
N
t
-
TN 2
(5-28)
After kN is obtained, DN can be calculated for a
given time tN
from equation (5-26).
In order to show the deviation between CN and DN
for a given time tN; the deviation term,
-
CN
-
DNI
N Max is the maximum of
N' is defined in equation (5-29):
(5-29)
N for a given set of A, B, andCG.
As the initial concentration C., the sum of C
0fo
and C
so
,
should be
equal to D0 , equation (5-22) can be transformed to equation (5-30):
D = D0 /(I
+ D0 kt) = C0/(I + C0 kt) = Cf(A + 1)/(i + C f(A + 1) kt)
(5-30)
Similarly, equation (5-23) can be rearranged to equation (5-31):
C = Cfoe-kft + ACf e-Bkft
(5-31)
-238By using equation (5-30) and (5-31), it can be shown that the
following relationship exists:
kI
k C fo/kf
(5-32)
TN = k t
N max
(5-33)
CN
max
C
max
max
(5-34)
These equations allow one to transfer all the normalized values
back to the absolute values.
Through the help of IBM 370 Computer,
a datafile by using A, B, and & as independent variables, and kN Imax
as dependent variables was established.
Figure 5-16 shows the contours of 5% max by using 4- (Conversion)
as parameter, and A, B as X aid Y axis respectively.
with log-log scale, is shown in Figure 5-17.
Same plot, but
For a given value of G,
the set A, B, and kN that would give the minimum value of I max
as the symbol) is shown in Figure 5-18, Figure 5-19, and Table 5-10.
Based on the above Figures, the following things are observed:
(1) By setting max = 5% as acceptable deviation, it
is observed that
for a true second order reaction, it can always be simulated by two
first order kinetics up to 92% conversion.
In a semi-log plot of
C versus t, with conversion below 90%, the integral of equation (5-22)
can be approximated very well by two straight lines, with A = 0.40 and
B = 0.12.
See Figure 5-20.
When conversion increases to 99%, clearly
no two straight lines can represent the integral, which has become
highly curved.
0.2
I
I
I
I
1
II
/
I
78 0o
-
0.16
A
\84
o
880%0
90* 00
0.12H-
92%/
/k
I
I
0.081-
/
B =k
Conversion Level
/
/ '
I
\.0
-~---78
I/
II
---
I,
0.041-
0/0
84 0/%
88 0/0
------ 90 00
o 92 %Do
Boundary : -\m ax=- 5
I
0
0
I
0.4
I
I
I
0.8
I
1
1.2
A=
0/0
I
1.6
I
I
2.0
I
2.A
Cso/Cfo
Fig. 5-16 The Range of Parameter Values of A and B Suitable for Two First Order Kinetics
to Simulate Second Order Kinetics, and the Dependence on Conversion Level.
II
II
II
II
II
I
I
I
I
I
I
0.3-
60%
B
0.2-
70%
78%
%
88
92%6
0.1-
%
50
%.1
0.2
0.4
1
4
2
10
20
40
100
A
Fig.
5-17 The Range of Parameter Values of A and B Suitable for Two First Order Kinetics to Simulate
Second Order Kinetics, and the Dependence on Conversion Level. (In Log-Log Scale).
-241-
25
1.2
200.9
A
15-
x
-- 0.6
z
~10'
-0.3
5
10
0
02
68
Fig. 5-18
The Dependence of q (Minimum Of
74
80
86
CONVERSION%
(Conversion).
max
92
)
and A on
9-8
E
-242-
0.17 F
1.2
0.14-
0.9
B
Km,
0.11-
0.6
0.08 -
0.3
68
86
80
74
CONVERSION
%
0.2
Fig. 5- 19 The Dependence of B and kN on 6 (Conversion).
92
98
-243Table5-10, Values of A, B,f), and k. for
a Given Value of C (Conversion):
(Minimum
max)%
kN
E (Conversion)%
A
B
76
1.12
0.151
0.671
0.2801
78
1.02
0.148
0.835
0.3071
80
0.94
0. 146
1.045
0.3340
82
0.86
0.142
1.338
0.3617
84
0.76
0.139
1.651
0.4092
86
o.68
0.135
2.151
0.4535
88
0.6
0.129
2.860
0 .5029
90
0.52
0.123
3.959
0.5680
92
0.42
0.118
5.04
0 .6922
94
0.34
0.108
7.11
0.8123
96
0.24
0.093
10.61
1.0374
98
0.16
0.075
17.85
1.3939
-2444-
1.0
o
t
2
4
8
10
Cf 0
C
Cs=CSO 2kst
0.1
Cf = Cf o
-k f t-
Do
-=
0.01
1.[Do kt
I
60
1
o
20
40
80
100
t
Fig.
-
Comparison between Concentration D, Obeying Second Order
Kineties, and Two First Order Kinetics,
C
and Cs'
-245(2) If the kinetics is two parallel first order, then it can be simulated
by second order kinetics only when A and B fall in the contours as
described in Figure 5-16 and Figure 5-17.
Although when the conversion
drops to 50%, almost any value of A between 0.01 and 25, B between 0.01
and 0.95 of first order kinetics will be able to be simulated by second
order kinetics (Figure 5-17); it simply shrinks to a single point when
conversion is increased to 92%, and hence no second order kinetics will
be able to approximate the two first order kinetics above 92% conversion.
(3) Roughly speaking, for G between 70% and 92%, the values of A and
B that can be approximated by second order will fall in the region:
0 .4
A<2, and 0 .053 B3.0 .2.
It
is
suggested that if
two pa.al1el first
one desires to tell
the difference between
order and single second order kinetics,
periment should be run over 92% conversion.
If
this is
not feasible,
As C0
D0 = C
+ C o, equation (5-35) is obtained:
= C0/(1 + A)
C
(5-35)
To match the initial rates at zero conversion:
k C
f fo
+k
C
sS
2
0o
= kC
After substitution,
kg
(I + A)
kCo (1+
one many re-
.
as measurements at -low concentrations can be difficult,
sort to dilution of the petroleum residual to reduce
C
the ex-
(5-36)
-246The apparent first order rate constant (to approximate second
constant is independent
of C
.
order kinetics), is dependent on C 0 ,. but a true first order rate
-247-
6
6.1
(1)
Conclusions and Suggestions:
Conclusions:
In this kinetic study, almost all
made under diffusion free condition,
are intrinsic kinetics.
the experimental runs were
so that the kinetic data obtained
The only exception is
vanadyl tetraphenylporphine
(VO-TPP) runs that were diffusion limited.
(2) The demetallation kinetics for the solution prepared under air is
different from the solution prepared under helium.
solution was used for the main kinetic study.
Helium prepared
The conclusions made
hereafter reflect the findings from helium prepared solutions only.
(3) Both hydrogen and catalyst are necessary for demetallation reaction.
Hydrogen consumption is negligible in the batch reactor system used,
and no appreciable deactivation of catalyst was observed due to its
relatively lower metal and carbon deposition.
(4) From individual nickel (Ni-Etio or Ni-TPP) or vanadium (VO-Etio)
hydrodemetallation runs, it is observed that all the demetallation
kinetics follow fractional order (half order) kinetic model.
By
fitting the data into half order kinetic model, the activation energy
for demetallation reaction is from 27-37 kcal/g mole, and the hydrogen
pressure dependence is from 1.2-2.2 order.
Vanadium removal tends to
have larger activation energy and smaller hydrogen pressure dependence.
For demetallation reaction of Ni-Etio in the operating range used,
NiO-MoO /Al 20
catalysts are more active than CoO-MoO /Al 20
catalyst;
-248but have similar activation energy and hydrogen pressure dependence.
It is probable that intermediates were formed during demetallation reaction.
When hydrogen is
replaced by helium,
or catalyst is
replaced by
demetallation reaction was observed.
alumina carrier, very little
Nickel
would not, but vanadium would reversibly adsorbed on the catalyst or
carrier due to its higher adsorption ability.
(5)
When VO-Etio and Ni-Etio were mixed together for study, the vanadium
demetallation rate would not be affected by the presence of nickel;
however, nickel demetallation rate would be suppressed by the presence
of vanadium.
The reason for vanadium suppression of nickel is
be due to its
higher absorption ability in catalyst.
believed to
(6) Free base porphyrin is not stable at the presence of catalyst and
hydrogen.
Less than 25% of free base porphyrins formed metalloporphyrins
(either Co or Ni), and more than 75% just disappeared.,
This finding implies
that free base porphyrins or their related reduced forms can not be the
final products of demetallation reactions.
(7) Either cobalt or molybdenum alone would be a good demetallation
catalyst.
Molybdenum tends to be better than cobalt.
Order of impreg-
nation for cobalt and molybdenum does not affect the demetallation activity.
(8) A three parameter kinetic model developed from an Eley-Rideal type
mechanism fit
the data for Ni-Etio and VO-Etio runs very well regardless
of the pressure, temperature, and initial concentration range.
(9) At identical operating conditions,
in this study is
a orer
-of magnitude faster than previous literature
that use crude oil for study.
presence of asphaltenes,
the demetallation rate found
The reason could be explained by the
sulphur, and nitrogen compounds in petroleum.
-249(10) If in crude oil there are two metal complexes, and each follows a
first order kinetics but with different rate constants, the concentration
versus time data can also be represented by a second order kinetic model
up to 92% conversion provided both the ratio of the initial concentrations of two metal complexes and the ratio of the two first order rate
constants are within certain narrow ranges.
-250-
6.2
Suggestions:
(1) As this work did not involved much in elucilating the possible
mechanisms, it is suggested that a full scale investigation be done
to find the possible mechanisms.
The mechanism proposed earlier is
over simplified, and would have to be modified by the existence
of intermediates.
As most of the speculated intermediates and
products are not commercially available, organic synthesis should
be expected.
Gas chromatography,
liquid chromatography,
and/or
mass spectrometer would be necessary to identify those possible
intermediates and products.
nitrogen,
it
If the quantitative analysis of carbon,
nickel, and vanadium on spent catalysts can be improved,
would also help in finding the final forms of metal on spent
catalyst.
Initial
of mechanism.
range is
concentration is
an important factor in the study
As Nujol has limited solubility, the initial concentration
too narrow.
To find other solvents that will have higher
solubility of model compounds as well as high boiling point will be
very helpful.
It will. also ibe useful to use- other solvent to find
out whether Nujol is
inert to demetallation reaction or not.
A better
understanding of the mechanism could lead to a better design of process
parameters in HDS or HDM processes, and lead to the development of
regeneration of spent catalysts.
(2) Although it
has been observed that vanadium would suppress nickel
removal reaction, the details are not yet known.
It would be useful
to develop a kinetic model of nickel removal that contains vanadium
suppression term.
Better understanding of the interaction between
-251vanadium and nickel could lead to better design of metal removal
catalysts.
adsorb
Typical example is that since vanadium would physically
on alumina, and it
would suppress nickel removal, may be
one can use cheap adsorbing materials to remove vanadium before more
expensive and more active materials are used to remove nickel.
(3) It has been found that MoO /Al203 is a very good demetallation
catalyst.
If the, self preparation catalyst experiments are continued
and each catalyst is
well characterized,
one might be able to find a
better metal removing catalyst, it would also be helpful to the study
of understanding demetallation mechanism.
A working example is
a
development of catalyst that has hydrogenation activity but not cracking
activity,
this would prove or disprove the two sites theory.
(4)'Crude oils has sulphur and nitrogen compounds, and the catalysts
are presulphided before used in commercial HDS unit.
It
useful to presulphide the catalyst in the future study.
would be
By comparing
them with the unpresulphided runs, one would know the effect of
presulphiding catalyst on demetallation reaction.
By adding sulphur
or nitrogen compounds in solution would lead to an understanding about
the effect of these two compounds on demetallation reaction.
Finally,
a study of dissolving model metal compounds in crude
oil that has been demetallized will be a pre-step toward the understanding
of demetallation of residual oils itself.
-252-
7
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-266-
8
A.
Nomenclature:
In Chapter 5.5:
A3 Active site that has both hydrogenation and cracking activity.
B: Active site that consists of A and C types of active site.
C: Active site that has cracking activity but not hydrogenation activity.
H2 : Hydrogen.
K: Equilibrium constant.
k: Rate constant.
L: Initial
reactant (Porphyrin),
NiL would be nickel porphyrin.
LH 2: Intermediate (Hydrogenated porphyrin),
LHg
such as chlorin.
Intermediate (Hydrogenated porphyrin), such as tetrahydroporphy;;n.
Ni: Nickel.
P: Product.
Pi, P2 ' 3: Parameters used in eq. (5-20).
R: Product.
t: Time.
V: Vanadium.
Subscript:
1, 2, etc. : For various equilibrium constants.
o
: For initial properties.
p
: For K , a notation used to represent P
-267B.
In Chapter 5.11:
A: Ratio of initial concentrations.
B: Ratio of rate parameters.
C: Total concentration of first order model.
D: Total concentration of second order model.
k: Rate constant.
T: Time needed to reach conversion G.
t: Time.
Subscript:
f: Refers to fast reaction part of first order model.
fo: Refers to initial properties of
"f".
max.: Maximum.
N: "Normalized" value.
o: Initial property.
sa Refers to slow reaction part of first order model.
so: Refers to initial properties of "s".
Greek Letters:
: Deviation between two first order model and single second order model.
(1f% = ID-Cl/C
x
100)
Minimum of
.
)
6 : Conversion. (C = (C0-C)/C
-268APPENDIXz EXPERIMENTAL DATA
(1)
Only concentration versus time data will be given here, the operating
conditions for every specific run can be found in Table 4-1,Table 4-2,
Table 4-5, Table 4-6, Table 4-7 or Table 4-9.
(2) t
N
represents the time after injection of catalyst (hr).
represents the total concentration of nickel in solution during
reaction (ppm)
NS represents the concentration of nickel porphyrins in solution
during reaction (ppm).
V
represents the total concentration of vanadium in solution
during reaction (ppm).
VS represents the concentration of vanadyl porphyrins in solution
during reaction (ppm).
A
represents the absorbance of new peak (616 nm for nickel runs,
631 nm or 632 nm for vanadium runs) formed during reaction.
(Absorbance/g sample).
Run NT2
Run NTl
A
21.1
t
0.12
21.8
18.5
0.65
23.5
20.7
0.45
21.9
18.8
o.68
2.08
22.8
19.3
0.92
21.0
19.8
0.81
3.53
22.3
22.5
19-0
1.50
16.1
1.0
19.9
2.25
19.3
14.1
15.4
1.01
21.6
17.5
10.5
18.2
6.9
4.5
0.96
22.3
3.08
4.03
5.12
5.78
6.58
6.5
7.83
3.7
9.42
2.8
0
NN
23.2
1.08
t
t
5.08
6.66
7.83
9.25
21.6
NS
18.8
A
N
8.0
5.4
4.5
NS
0.82
('3
3.1
2.5
0.37
1.8
0.24
1.2
0.12
6' 0
90' 0
.
9 0T
ZT 00
9064/
903
4*6
zz1 0
0
CT
N
/1
9
11' 0
C9z
69*o
6919
q06
47 47
6T oT
90 9T
69'0
02T
9'ac
4710
4790
/59*9
90T
9Cz
94C
459;
T
/5'ITT
ge 9T
Nog
680o
Z490
v
C *.'0
ag/
9680
o06
z OT
C49~*0
49.00
13* 00
COO
9400
0
v
SN
17N
SN
rIN
una
N
I:j
ung~
Run NT6
Run NT5
N
NS
A
t
N
NS
A
0.38
29.0
25.8
21.6
o.96
28.5
o.64
0.61
0.61
0.08
0.95
1.58
2.33
25.5
25.3
25.3
25.1
0.33
0.70
24.7
23.4
20.9
o.98
19.0
1.08
o.61
1.17
18.9
1.14
3.33
4.5
6.03
27.9
28.5
24.4
0.62
1.75
14.6
15.0
10.7
24.9
o.64
2.28
12.3
7.6
1.11
27.9
25.1
0.62
2.92
28.0
24.8
28.2
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19.0
16.8
2.82
0.55
0.75
0.95
12.1
8.5
7.6
5.2
16.5
14.4
2.42
1.05
4.4
6.1
14.1
12.1
2.02
1.2
7.35
8.75
11.6
8.3
1.02
1.4
9.2
5.6
0.72
1.6
7.3
5.6
3.8
3.0
10.4
5.9
2.8
1.85
2.0
12.57
2.5
o.6
A
29.7
23.6
13.6
2.8
1.4
0.9
\0
Run NE13
Run NE12
NN
NS
27.9
29.2
0.3
0.55
22.5
22.3
19.1
17.8
18.7
0.8
16.9
15.4
19.1
14.8
1.1
14.3
13.1
3.07
3.75
4.55
16.5
13.1
10.2
1.35
12.6
11.0
1.63
10.3
9.1
9.5
7.5
4.8
1.95
8.3
7.5
5.55
6.7
6.1
2.6
2.5
5.3
4.4
3.0
0.9
7.88
1.3
3.05
3.8
4.55
3.2
1.1
3.0
1.4
t
N
NS
0.3
0.75
1.2
31.2
29.2
26.6
31.2
23.2
22.6
1.77
23.2
2.42
A
tt
0.1
0.2
A
0
Run NE15
Run NE14
t
N
NS
0.283
30.3
30.3
24.6
0.7
28.4
27.1
18.9
1.2
25.3
24.9
1.7
22.4
21.4
2.3
19.7
16.6
17.2
12.2
15.2
11.3
8.8
1.6
9.1
6.5
3.8
1.95
3.6
2.3
5.9
3.9
2.6
2.8
1.1
4.75
6.o
6.95
2.95
1.6
t
N
0.15
0.3
0.5
0.75
1.05
1.3
30.4
27.8
23.6
19.6
15.4
NS
29.9
2.1
A
3.0
7.25
13.8
10.2
6.8
3.8
2.6
13.6
10.6
7.0
3.4
1.2
A
Run NE17
Run NE16H
N
NS
25.4
0
0.53
1.67
3.08
37.7
37.4
36.8
36.6
36.3
34.7
34.9
36.3
25.8
26.2
25.6
26.8
4.6
6.12
36.0
35.7
35.1
33.0
7.5
25.7
25.5
7.38
33.2
31.9
9
25.5
26.0
N
N9
0.3
1
2
26.9
26.4
26.5
26.4
26.7
26.6
3
25.9
4.35
6
t
A
t
A
Run NE19
Run NE18
N
NS
A
0.15
24.2
22.3
1.9
0.4
19.9
3.1
34.0
0.8
14.1
34.3
1.2
9.8
17.3
9.5
6.5
32.1
1.6
6.4
31.3
2.0
3.7
4.1
1.8
31.8
29.6
27.8
2.4
2.0
1.1
2.8
0.9
t
N
NS
0.,15
32.5
0.4
32.9
33.5
33.7
0.7
2.15
33.2
32.6
31.5
30.7
2.9
30.4
3.883
31.5
5.25
30.8
28.8
1.1
1.6
7.45
7.55
30.4
26.9
29.2
A
t
t
2.2
1.5
0.9
0.4
0.2
Run NE21
Run NE20
tt
N
NS
A
19.5
16.4
0.15
21.8
1.64
0.45
19.3
19.3
16.3
12.8
0.85
1.35
5.7
7.4
4.6
2.08
17.1
13.8
10.4
2.2
2.8
2.6
2.9
7.1
2.65
0.5
3.95
4.9
3.9
1.2
N
NS
0.2
20.8
o.4
18.4
0.8
13.7
9.1
t
1.3
1.75
A
2.39
11.5
2.49
2.22
7.5
5.3
1.4
0.92
3.2
o.54
14.o
r')
4::-
Run NE23
Run NE22
t
N
15.9
2.57
0.067
11.4
12.4
2.58
0.15
0.35
0.55
0.75
1.05
8.5
6.0
7.2
4.6
0.82
3.4
2.5
2.0
1.2
0.52
0.19
0.6
0.5
1.2
0.2
NN
0.15
0.35
19.5
14.9
0.6
10.6
0.85
7.8
4.9
5.9
3.7
1.9
1.8
1.15
1.55
1.86
0.5
2.05
0
A_
A
tt
1.93
1.27
0.79
0.35
10
0.90
Run NE25
Run NE24
t
N
0.067
io.6
NS
A
t
N
NS
A
0.15
21.5
21.0
2.31
0.35
16.6
3.11
o.6
18.9
16.0
13.6
9.7
7.6
3.19
2.64
6.1
1.47
3.7
o.85
0.34
0.19
0.1
9.0
0.25
6.4
9.8
9.2
6.7
0.4
4.3
4.4
o.85
13.0
o.6
2.2
2.7
10.3
0.8
0.7
1.15
1.5
0.95
o.2
1.85
7.4
5.0
2.2
3.5
1.3
2.55
2.6
1.6
1.0
2.85
2.09
N
Run NE27
Run NE26
NS
A
19.0
22.2
2.61
16.5
14.7
2.75
14.4
2.82
12.2
11.8
10.2
9.6
8.2
2.19
2.1
8.2
6.3
5.7
4.4
2.5
4.5
3.2
2.2
0.7
0.4
1.52
1.05
0.69
2.9
2.3
1.8
0.2
3.4
3.8
3.2
2.4
t
N
NS
A
t
0.15
0.35
0.55
22.2
19.2
2.3
19.3
16.1
3.0
16.7
13.3
0.8
14.1
11.2
3.1
2.9
0.15
0.35
0.63
0.9
1.1
1.45
1.85
11.5
8.6
8.4
2.3
1.7
1.2
2.2
3.7
6.8
5.4
3.5
1.3
1.7
2.55
2.9
2.9
2.1
5.9
N
1.5
1.2
2.71
0.45
0.21
10)
nRunNE29
Ran NE8
N
NS
A
0.15
0.35
0.6
16.2
13.0
2.50
13.2
10.1
10.2
2.58
2.14
5.47
0.93
6.7
14.6
4.46
1.1
5.4
11.5
6.0
3.39
4.8
18.4
14.3
5.98
12.0
4.7
1.97
1.41
1.3
1.55
1.85
7.1
9.4
2.7
0.90
2.1
8.5
7.2
6.3
2.4
0.62
1.5
0.52
N
NS
A
0.15
0.45
27.8
27.0
1.1
26.7
23.6
4.06
0.8
25.7
22.5
1.35
24.4
19.3
2.25
22.1
3.45
t
9.2
* While total nickel fits
model, Ni-Etio does not.
half order
t
7.6
4.6
1.34
3.9
3.7
3.0
1.03
0.75
2.7
2.2
0.49
1.7
1.1
o.6
0.19
1
0
Runn NE31
Run NE3
t
N
NS
A
17.2
15.1
12.2
2.84
21.2
0.15
0.35
20.9
18.5
0.6
12.1
9.3.
2.24
15.3
6.2
1.36
6.3
4.5
o.89
4.0
12.4
8.3
0.95
1.25
1.55
8.3
3.0
17.6
14.9
4.1
2.8
0.47
5.0
10.4
5.6
1.85
3.2
1.1
0.16
6.0
8.1
3.5
2.1
2.4
7.0
2.1
8.5
5.9
3.5
10.0
1.8
t
N
NS
0.15
0.65
24.8
23.5
22.6
1.35
2.1
12.3
0.5
A
14.7
2.82
\~0
lw
Run NE33
Thin NE32
t
N
NS
0.15
0.35
0.55
20.8
19.2
18.2
16.4
13.7
12.3
1.1
15.8
13.7
11.4
1.45
8.6
1.85
5.9
0.8
2.2
2.55
3.7
2.5
2.9
1.4
A
N
NS
A
0.15
0.35
o.6
21.3
2.73
18.0
17.8
14.4
15.3
11.2
0.9
12.4
9.9
3.02
2.71
9.7
7.6
6.5
1.59
1.48
5.2
5.2
4.0
3.6
2.0
0.52
2.7
1.3
0.32
t
9.4
6.8
1.25
3.8
2.1
1.95
2.35
2.65
2.95
1.1
1.6
2.2
3.24
1.15
~A)
C
a
Run NE35
Run NE34
t
N
NS
A
t
N
0.15
0.35
21.3
20.2
2.09
0.15
21.8
18.4
16.5
2.86
o.6
13.4
2.96
17.8
14.6
0.9
15.8
13.1
0.3
0.5
2.61
0.8
9.0
1.2
11.2
2.27
1.1
6.1
1.55
1.95
8.8
6.7
10.9
9.6
6.8
4.5
1.7
2.35
4.7
3.6
1.17
0.82
3.6
1.8
2.0
1.0
2.7
3.3
2.4
3.0
2.6
1.0
1.57
0.47
0.23
NS
A
0
Run NE36
t
N
NS
0.15
21.7
19.8
0.3
0.5
0.73
1.15
21.7
21.7
20.3
15.3
14.6
1.6
11.5
8.2
2.05
18.7
16.o
2.85
5.9
3.7
3.2
2.1
2.4
A
8.0
4.3
3.0
0
t\)
Run
Run
n VE2
VE
V
14.3
14.1
0.45
13.3
13.5
o.6
12.8
12.8
2.79
0.85
12.2
2.42
1.88
1.35
11.7
10.6
2.2
9.3
9.8
8.4
1.17
3.35
8.0
7.0
4.8
6.1
5.3
5.95
4.2
4.1
8.6
2.3
2.1
11.6
1.0
0.9
V
Vs
A
0.95
2.15
29.9
26.5
25.3
3.95
22.6
17.6
3.0
3.33
3.30
5.22
17.8
6.38
15.2
11.2
13.4
10.8
8.0
10.0
7.1
21.4
8.2
4.9
Vs
tt
0.25
t
t
A
0
9,.
Run VEh
Run VE3
tt
0.15
0.35
0.6
0.9
1.2
1.55
1.9
Vv
A
-I;
t
Vv
vs
A
17.3
16.0
0.29
20.0
18.3
1.21
18.2
16.2
2.35
0.15
0.3
15.3
13.5
10.5
2.43
2.15
0.85
1.45
14.8
17.0
15.9
13.7
12.9
11.8
8.2
1.84
2.45
10.1
5.9
3.3
1.39
0.82
3.57
4.8
11.4
10.0
12.4
9.8
6.5
2.7
3.7
1.5
0.3
3.0
0
2.3
Vs
1.7
0.42
8.3
6.6
4.9
6.3
7.9
5.9
8.23
4.0
9.55
2.8
3.2
2.2
12.0
1.4
0.9
13.6
0
1.45
1.46
1.58
1.45
1.26
~A)
1.00
o.68
o.46
0
4::-
Run vE6
Run VE5
V
Vs
A
t
V
0.3
19.1
15.1
1.12
14.0
0.7
16.5
12.4
2.22
1.2
14.0
10.9
2.33
0.15
0.3
0.7
1.85
11.8
2.18
2.77
9.1
9.1
6.4
3.6
4.5
5.8
t
5.5
3.7
2.1
6.4
0.9
12.5
A
13.8
12.0
9.9
1.40
1.2
11.0
9.2
8.8
1.55
1.69
1.8
6.7
6.3
1.2
5.1
3.5
1.38
o.96
2.6
4.6
4.4
0.9
2.9
2.4
2.0
0.56
3.5
4.4
1.6
1.3
0.54
0.29
1.4
0.37
5.0
5.7
6.3
1.1
0.5
0.4
0
0
17' Z
T OCT
9o9T
"*9T
v
9HA
001T
900
9 CT
9' ~I
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9011
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9004O
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9'819
A
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v
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6' 0
ga
9,6
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Too
:I
SA
Urig
,w
Run VE10
Run VE9H
t
V
Vs
13.8
0.083
6.4
6.3
15.1
14.8
0.15
5.5
4.6
5.4
0.55
14.3
14. 1
14.1
14.4
13.9
14.2
t
V
Vs
0.25
13.3
13.7
0.6
1.4
2.5
3.5
4.5
5.5
7.0
13.8
14.2
A
0.32
4.2
2.8
0.87
3.1
1.6
14.8
1.1
0.9
0.7
14.3
1.3
0.2
14.4
A
1.2
I
1w
Run VT1
I
Run VEi
0.15
0.35
14.2
13.8
0.2
Vv
2.3
12.0
11.7
0.5
0.2
0.6
9.7
o.65
0
0.9
10.1
8.3
1.2
5.5
5.4
1.5
4.4
1.8
2.8
4.2
2.8
2.1
1.4
1.3
t
A
V
tt
Vs
A
1.5
8.0
0
Run VT3
Run VT2
t
V
0.07
8.9
vs
8.0
0.25
4.7
0.6
1.3
0.1
t
0.95
A
t
v
vs
8.1
0.15
9.2
3.8
0.3
4.8
0.7
0.45
7.3
5.4
3.7
2.8
0.9
0.65
0.9
1.22
1.65
1.5
o.4
2.2
0.1
A
2.5
1.4
I~A
Ran
n E2
Run E
t
'
0.55
0.9
*
N
NS
10.5
10.0
14.5
15.6
15.1
1.5
9.7
9.4
2.1
8.9
13.2
11.9
2.7
8.3
11.7
3.4
8.0
9.6
4.2
7.4
8.1
5.1
6.3
6.8
7.4
4.7
4.1
7.5
2.9
2.6
The higher value of NS is
A
due to the
t
N
NS
0.3
0.4
o.65
0.7
19.2
1.15
1.85
0.3
19.5
1.1
16.0
2.7
0.84
12.5
3.7
4.95
6.38
8.65
0.9
0.6
10.3
7.9
0.5
5.0
A
0.7
* NS is actually Co-Etio, the sample
formation of Co-Etio, Co-Etio would
collected at 0.65 hrs has 15ppm of
show up at NS but not N.
cobalt.
1
Run TI
N
NS
0.2
41
0.35
o.65
<1
10.5
9.0
6.9
1.05
<1
<1
<11.6
t
1.55
2.35
<:
A
4.7
4.2
3.33
4.07
*
NS is actually Co-TPP, the sample
collected at 0.2 hrs has 12 ppm
of cobalt.
Run NVE2
Run NVE1
t
N
V
t
N
V
0.25
14.4
9.7
0.2
16.1
10.6
0.5
14.0
9.2
0.45
14.4
8.0
0.85
14.0
8.8
0.75
5.6
1.2
13.9
1.75
2.5
13.5
14.0
8.1
6.9
1.1
1.6
13.7
13.0
11.2
2.25
6.6
3.5
4.8
13.8
12.7
2.65
4.2
3.1
2.0
6.65
10.2
5.3
3.5
2.3
0.9
1.5
0.7
0.3
3.85
o.6
8.0
8.2
0.4
9.2
5.4
t
N
3.6
~~A)
,w
Run NVEY4
Run NVE3
t
t
N
V
t
0.2
N
V
4.6
0.2
22.4
0.45
21.4
1.3
0.55
17.4
16.1
0.75
1.1
19. 1
0.4
1.0
14-3
15.2
10.9
0.2
1.55
13.1
11.8
3.2
10.4
8.6
1.6
6.0
0.4
3.8
0.4
1.5
1.9
2.3
7.5
4.7
2.7
2.7
3.1
1.2
2.2
2.95
3.9
4.9
5.9
6.9
8.45
2.0
0.4
3.9
3.5
2.0
1.1
'YA
Run NVE6
Run NVE5
t
N
V
N
V
o.2
25.2
22.9
0.2
13.2
21.3
0.5
25.1
18.4
23.5
16.3
13.4
12.7
18.4
0.85
0.5
0.9
1.25
22.9
11.0
1.3
12.0
11.2
1.75
21.9
19.6
14.3
7.0
11.3
10. 1
7.4
5.1
1.8
2.45
2.0
3.15
9.9
o.2
3.85
4.55
7.3
4.0
t
2.4
3.1
3.9
4.65
5.4
6.0
5.2
2.4
1.1
5.25
1.9
0.7
14.4
3.5
1.6
o.4
0~A
Ruin NVE8
Run NVE?
N
V
0.2
12.0
22.7
19.4
0.65
11.8
20.7
1.25
11.4
12.2
17.2
16.2
1.95
3.5
11.7
12.7
3.5
11.3
10.9
17.1
14.3
4.8
6.8
11.3
10.6
10.0
10.1
4.9
8.9
2.5
9.2
9.6
7.9
4.0
5.0
6.5
7.7
6.3
0.9
11.5
7.9
1.8
9.07
2.7
12.0
7.2
1.5
1.4
14.0
3.8
9.55
10.5
N
V
0.2
12.8
20.8
0.7
12.9
1.45
2.35
12.2
t
t
0.3
9.4
U'
Run NVEIO
Run NVE9
N
V
0.5
12.3
19.8
1.0
11.6
18.5
18.2
2.0
11.4
1.3
1.55
13.2
3.0
1o.6
4.0
11.5
10.8
15.2
11.1
1.85
7.9
5.0
10.4
6.3
2.2
5.4
6.0
10.2
4.2
2.65
2.6
7.0
9.8
3.2
0.6
8.0
9.0
9.3
6.8
3.1
1.6
10.0
4.5
11.2
2.0
12.5
0.2
N
V
0.2
25.5
1.3
0.5
0.9
22.3
0.8
N
t
,
t
8.4
0.6
ON\
N
A
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1"9
zoo
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0 "4
0
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