Fluid Catalytic Cracking
A.Meenakshisundaram
Chennai Petroleum Corporation Limited
Worldwide Petroleum Product Distribution
OIL USE – SECTOR WISE
(million tons oil equivalent)
1985
1995
2000
2010
Transportation
1180
1600
1870
2320
Petrochemical
140
192
250
300
Heating and
Industrial
1340
1216
1265
1430
Other
140
192
215
250
Total
2800
3200
3600
4300
Share of Transport
42
50
52
54
WORLD CRUDE OIL
QUALITY
PROPERTIES OF
CRUDE OIL
1985
1990
1995
1999
2010
(PROJECTED)
'S' IN CRUDE
WT% (AVG.)
1.14
1.12
1.31
1.41
1.51
API GRAVITY
32.7
32.6
32.4
32.2
31.8
METALS IN RESIDUE
(PPM WT)
275
286
297
309
320
19.4
19.8
20.2
21.3
3.61
3.91
4.0
RESIDUE IN CRUDE
OIL (VOL%)
"S" IN RESIDUE
19.0
3.07
3.26
Petroleum Refining
• Crude as obtained can not be used as fuel products as it is a
complex mixture of various light and heavy hydrocarbons
• Refining involves separation of light fractions by
distillation to produce distillate fuels.
• Heavier fractions are converted into useful fuel products
by secondary processing such as FCC,Hydrocracking etc..
• Environmental and Engine requirements require further
transformations to make improved quality fuel products
(e.g Reforming, Hydrotreating etc.)
Catalytic Processes in Refining
• Processes for Secondary Conversion - converting heavier fractions
into lighter products - FCC, Hydrocracking etc..
• Processes for meeting fuel engine requirements - Catalytic
Reforming, Alkylation, Catalytic Dewaxing etc..
• Processes for meeting Environmental requirements of fuels - HDS,
Oxygenates Production, Benzene /Aromatics reduction etc.
• Processes for Production of Lubes - Catalytic Dewaxing, Catalytic
Iso Dewaxing , Hydrocracking, Hydrofinishing etc..
• Apart from the above, catalytic processes are also used in
refineries for Hydrogen Production, Petrochemical Feedstocks and
Speciality Products etc..
World Catalyst Market
Sales in Billion US $
Catalyst use by
Industry
1997
1999
2001
2007
Environmental
1.63
2.61
2.88
4.05
Refining
2.07
2.17
2.32
2.84
Polymers
1.70
2.06
2.22
2.97
Petrochemicals,
Fine Chemicals
2.00
2.16
3.17
3.64
Total
7.40
9.0
10.59
13.51
Refining Catalyst Market
FCC
OTHERS 5%
ALKYLATION 15%
FCC 40%
HYDROPROCESSING
REFORMING,ISOME
RISATION
ALKYLATION
OTHERS
REF.,ISOMERIATION 15%
HYDROPROCESSING 25%
Petroleum Refining - Effect of
Catalysis Innovations
% oil converted to
1990
2000
Gasoline
29%
29%
Middle Distillates
34%
37%
Other Products
17%
18%
Fuel Oil
20%
16%
Source ; BP Statistical review of world energy, EIA
FLUID CATALYTIC CRACKING
Fluid Catalytic Cracking
• Refinery process that “cracks”high molecular weight
hydrocarbons to lower molecular weight.
•Refinery process that provides ~50 % of all transportation
fuels indirectly.
•Provides ~35 % of total gasoline pool directly from FCC
produced naphtha.
•~80 % of the sulfur in gasolines comes from the FCC
naphtha.
FLUID CATALYTIC CRACKING
• MAJOR SECONDARY REFINING PROCESS
• CONVERSION OF HEAVY FRACTIONS ( VGO -370 C+)INTO
LIGHTER FUEL PRODUCTS(LPG,GASOLINE,DIESEL)
• CIRCULATING FLUID BED REACTOR SYSTEM (REACTORREGENERATOR CONFIGURATION )
• MULTI COMPONENT CATALYST SYSTEM
• CATALYST TAILORED FOR EACH UNIT BASED ON UNIT
OBJECTIVES AND CONSTRAINTS
• FCC IS THE WORKHORSE FOR REFINERY - MOST
PROFITABLE TOO!
FLUID CATALYTIC CRACKING
Main Reactions in FCC
• Cracking of Paraffins,Naphthenes and
side chain of aromatics
• Isomerisation of olefins
• Dehydrogenation of Naphthenes and
Olefins
• Hydrogen Transfer
• Cyclization and condensation of olefins
• Alkylation and dealkylation
FLUID CATALYTIC CRACKING
CATALYSTS
INDIAN GASOLINE SPECIFICATIONS
S.No.
Characterstics
1
Density @15 C
2
Distillation
Unit
kg/m3
Recovery upto 180 C Min.Vol%
3
RON min
4
Sulfur Total Max.
5
Benzene Content Max
%Vol
6
Olefins max.
7
8
%Mass
Bharat Stage II
710-770
Euro III
Euro IV
720 - 775 720 - 775
90
75
75
88
91
91
0.05
0.015
0.005
1.0
1.0
%vol
21
18
Aromatics Max.
%vol
42
35
RVP Max
kPa
60
60
3.0(Metro)
35-60
ADDITIVES IN FCC UNIT
FCC ADDITIVES
• ZSM-5 Additive for boosting octane number and light
olefins yields (C3/C4)
• Alumina micro Spheres with dispersed Pt for
enhancing CO oxidation in Regenerator dense bed (CO
Promoter)
• Bottoms Cracking Additive – Alumina Matrix with
tailored pores and acidity for cracking heavier
fractions of the feed.
• Gasoline sulfur reduction additive
• SOx Reduction Additive for reducing SOx emissions
• Metal Passivators – Sb/Bi liquid compounds for Ni
Passivation, Vanadium Trap for V passivation
ZSM-5 Additive
• ZSM-5 Additive - Reactant shape selectivity is in play whereby
molecules are sterically discriminated based on their ability to
enter the pores of the zeolite for cracking
• Intermediate pore size of ZSM-5 restrict the access of highly
branched and cyclic hydrocarbons to the interior of the zeolite for
cracking. Thus Higher Octane molecules are retained in the
gasoline range
• Only lower octane normal and monomethyl aliphatics enter the
pores and preferentially cracked to lighter products
• Increases the iso/normal paraffin and olefin ratio
• Results in higher RON , higher Propylene/Butylene yields, lower
Gasoline yield
• About 2 to 5% dosage of additive is used with ZSM-5 crystal
content of 25 – 40wt%
Bottom Cracking Additive
• Bottom Cracking Additive (BCA) in
general facilitates cracking of heavy ends
of the feed into intermediate range
molecules suitable for further cracking
by the host catalyst.
• Use of BCA in some units is preferred to
high activity matrix especially units with
coke burning limitation
Options for Gasoline Sulfur Removal
•
•
•
•
Pretreatment of FCC Feed
Treatment of FCC Naphtha
Undercutting FCC Gasoline
FCC Gasoline Sulfur Additive
Catalyst for Sulfur Reduction in Gasoline
CO Promoter
• Promotes combustion of CO to CO2(200 ppm of CO in
flue gas for a 50 000 bpd FCC unit or 1.5 – 2.0 tpd)
• Eliminates the need for CO boiler and improves the
environment by reducing CO in flue gas.
• Lower Carbon on Regenerated Catalyst will increase
activity and better coke-conversion selectivity.
• Pt at 1 PPM level in the unit will promote CO
oxidation.
• Normally a separate additive containing 500 –1000
ppmw Pt on Gamma Alumina is used.
• Pt catalysed CO combustion occurs readily in the dense
phase at temp. 650 – 700 C
Refinery CO Control
C + O2 = CO2 H = -94 Kcal/mole
C +1/2 O2 = CO H = -26.4 Kcal/mole
CO +1/2 O2 = CO2 H = -67.6 Kcal/mole
Reduction of After Burn Temperature with Promoted CO
Combustion
Component
Temperature C
Without Promoter With Promoter
Typical Flue Gas
700
650
Dense Phase
660
675
After-burn  T
+40
-15
De SOx Additive
• About 10% Sulfur in FCC feed gets deposited in the
coke
• This sulfur in coke is oxidised to SO2(90%) and
SO3(10%) in the FCC regenerator.
• Sulfur in Flue Gas Emissions are stringently restricted
by emission norms
• DeSOx Additives help in reducing emissions of SOx
• An effective Sox reduction catalyst must oxidize SO2 to
SO3 and form a sulfate. This sulfate has to be stable
under regenerator conditions and be able to release the
sulfur as sulfide in the reactor
Chemistry of SOx Reduction
Reactions in Regenerator
S(in coke) + O2 = SO2
2SO2 + O2 = 2SO3
SO3 + MO = MSO4
Reactions in the Reactor
MSO4 + 4H2 = MO + H2S + 3H2O
MSO4 + 4H2 = MS + 4H2O
Stripper:
MS + H2O = MO + H2S
MS + H2O = MO + H2S
MSO4 + 4H2 = MO + H2S + 3H2O
MSO4 + 4H2 = MS + 4H2O
S(in coke) + O2 = SO2
2SO2 + O2 = 2SO3
SO3 + MO = MSO4
SOx Reduction Catalysts
• MgO,Al2O3,MgAl2O4, La2O3 and CeO2
based catalysts are suitable for FCC unit
DeSOx
• Ceria oxidises SO2 to SO3
• SO3 is picked up as sulfate on MgO and Mg
spinels
• Sulfur picked up in regenerator is stripped in
the reducing atmosphere of the reactor.
Feed Metal Deactivation
• Ni and V present in heavy ends of the feed end
in the catalyst
• Both Ni and V function as dehydrogenation
catalysts in FCC reactor
• Relative dehydrogenation activity is expressed
in terms of 4Ni+V
• Vanadium reacts destructively with zeolitic
component of FCC catalyst
• Ni alters the selectivity to coke and gas yields
FCC Passivation Additives
• Ni Passivation is effective with only
Antimony,Bismuth and Cerium based
compounds.
• Compounds with active ingredients in Organic
or Aqueous solvent is generally used
• XRD results suggest that Sb forms Ni-Sb solid
solutions with high level of Sb on the Ni surface
thus causing the passivation effect.
• Sn reduces the deletirious effect of V by
forming inert compounds on the FCC catalyst
surface.Sn/V complex is formed
FCC – Recent Trends
Changes in FCCU yields over the years
Time Period
1960
1970
1980
1990
Design Features
Cracking Mode
Bed
Riser
Riser
Riser with Rapid
disengaging
Combustion
Mode
Partial
Partial
Complete
Complete
Feed – Catalyst
Mixing
Poor
Poor
Poor
Good
Catalyst Type
Amorphous
RE Y Zeolite
USY Zeolite
USY Zeolite with
active Matrix
Yields Wt%
C2LPG
Gasoline
Cycle oils
Coke
RON
5.0
18.7
45.4
21.5
9.4
92.0
3.8
17.3
49.8
21.7
7.4
91.0
4.0
17.9
50.9
21.8
5.4
92.5
3.3
17.9
52.5
21.5
4.8
93.0
IMPROVEMENTS IN FCC
Year
Avg.Feed
processed (in
tons)per kg of
catalyst
Max.
Concarbon
of feed
Avg.
conversion
for VGO
1950
0.5
1%
62%
1975
1.1
2.5%
73%
2000
2.0
7.5%
79%
Source : Akzo Nobel (Albemarle) catalyst data
Fluid Catalytic Cracking Catalysts– Future Trends
• More Resid Cracking and Deep Catalytic
Cracking application will require new zeolite
materials with larger pores – metal tolerance
required
• More FCC units will be designed for
Petrochemical feedstocks – Additive usage will
increase - More selective Additive for
Propylene/Butylene will be required.
• Development of Newer Additives for meeting
product quality will be required –
Sulfur/Olefins