Selective Hydrogenation
of PyGas over Palladium
Catalysts
S David Jackson
Centre for Catalysis Research, Dept of Chemistry, University of Glasgow, Glasgow, UK.
Jean-Marc Bader and Gildas Rolland, (Axens), International Petroleum Refining, July 2013
Pyrolysis Gasoline
by-product of high temperature naphtha cracking,
highly unsaturated mixture
(carbon range ~C5-C12).
Typical composition of Pyrolysis Gasoline
PyGas Components
Benzene, toluene and xylenes
Olefins and dienes
Styrene and other aromatics
Paraffins and naphthenics
Weight percent (wt %)
50
25
15
10
Jean-Marc Bader and Gildas Rolland, (Axens), International Petroleum Refining, July 2013
Pyrolysis Gasoline Composition
Composition of our model Pyrolysis Gasoline
PyGas Components
Weight percent (wt %)
Toluene
Styrene
1-pentene
Cyclopentene
1-octene
Heptane
Decane
55
10
10
10
10
2.5
2.5
Reaction Conditions
Continuous flow fixed bed reactor
Reaction Temperature:
140C - 200C
Hydrogen Pressure :
1 - 20 barg
WHSV: 4 h-1
Catalyst weight:
0.5 g
Catalysts:
16 wt.% Ni/Al2O3
1 wt.% Pd/Al2O3
Potential reactions of PyGas
1-Pentene
2-Pentene
Cyclopentene
Cyclopentane
Pentane
2-Octene
1-octene
3-Octene
Styrene
Ethyl Benzene
Ethylcyclohexane
4-Octene
Octane
Toluene
Methycyclohexane
Rate of formation ( r ) Moles g-1 s-1
2.5E-06
Praffins
2.0E-06
Internal olefins
EB
1.5E-06
Saturated compound from
aromatics (MCH, ECH)
1.0E-06
5.0E-07
0.0E+00
0
5
10
15
Hydrogen pressure ( PH2 ) barg
20
25
1
80
Toluene(Conv)
0.8
MCH
0.6
40
0.4
20
0.2
0
0
10
28
52
Time of Reaction ( Hours )
76
Yield ( % ) [ MCH ]
Conv ( % ) [ Toluene ]
60
Carbon Balance
Pd/Al2O3
Percent Carbon Balance of each species in synthetic PyGas hydrogenation
Reaction Temperature:
140C - 200C
Hydrogen Pressure :
20 bar
WHSV:
4 h-1
Carbon Balance
Pd/Al2O3
Percent Carbon Balance of each species in synthetic PyGas hydrogenation
Hydrogen Pressure :
1 - 20 bar
Reaction Temperature:
140 C
WHSV:
4 h-1
Time
FLOW
YIELD
100 %
100 %
90%
10%
FLOW
GC/TPO
GC/TPO
Pd/Al2O3, WHSV 4h-1, 140C, 5barg H2
500
1.2E‐09
450
1.0E‐09
400
350
300
250
6.0E‐10
200
4.0E‐10
150
100
2.0E‐10
50
0
0.0E+00
0
50
100
150
200
Time (min)
Temp
CO2
H2O
250
300
Ion current
Temperature (C)
8.0E‐10
Pd/Al2O3, WHSV 4h-1, 140C, 5barg H2
3.5E‐11
500
450
3.0E‐11
400
78, benzene
92, toluene
104, styrene
106, EB
2.0E‐11
350
300
250
1.5E‐11
200
150
1.0E‐11
100
5.0E‐12
50
0.0E+00
0
0
20
40
60
80
100
120
140
Time ( mins)
92
104
78
106
Temp
160
180
200
Temperature (C)
Ion Current ( n A)
2.5E‐11
0.014
0.00E+00
0.012
-1.00E-04
0.01
-2.00E-04
0.008
-3.00E-04
0.006
-4.00E-04
0.004
-5.00E-04
0.002
-6.00E-04
0
0
100
200
300
400
500
600
Temperature [C]
Deriv weight
m/e 44
700
800
900
-7.00E-04
1000
Ion current (a.u.)
Derivative weight (%/C)
Pd/alumina, cyclopentene
Carbon laydown Toluene
0.0E+00
0.018
0.016
-1.0E-04
Ion Current (mA)
-2.0E-04
0.012
0.01
-3.0E-04
0.008
-4.0E-04
0.006
0.004
-5.0E-04
0.002
-6.0E-04
0
100
200
300
400
500
600
Temperature (oC)
m/e 44
Deriv weight
700
800
900
0
1000
Derivaitve Weight (%/oC)
0.014
Carbon laydown Toluene
Raman Spectra for Pd/alumina after Toluene
4000
3900
3800
Intensity (arb. units)
3700
3600
3500
3400
3300
3200
3100
3000
1000
1100
1200
1300
1400
1500
1600
‐1
Raman Shift (cm )
1700
1800
1900
2000
5 barg H2 WHSV 4 h-1
1
80
Toluene(Conv)
MCH
0.8
0.6
40
0.4
20
0.2
0
0
10
28
52
Time of Reaction ( Hours )
76
Yield ( % ) [ MCH ]
Conv ( % ) [ Toluene ]
60
5 barg H2 WHSV 4 h-1
100
1-octene(Conv)
Trans-2-octene
Trans-4-octene
Octane
Cis-2-octene
Trans/Cis-3-octene & Cis-4-octene
40
30
80
60
20
40
10
20
0
0
10
28
52
Time of Reaction ( Hours )
76
Yield (%) [ Trans/Cis-octenes ]
Yield (%) [ Octane ], Conv (%) [ 1-octene ]
120
5 barg H2 WHSV 8 h-1
Conv ( % ) [ 1-octene ]
1-octene(Conv)
Octane
Trans-2-octene
Cis-2-octene
Trans-3-octene
Cis-3-octene
Trans-4-octene
Cis-4-octene
80
28
60
21
40
14
20
7
0
0
10
29
53
Time of Reaction ( Hours )
76
Yield ( % ) [ Octane, Trans/Cis-octenes ]
35
100
1 barg H2 WHSV 4 h-1
120
1-octene(Conv)
Octane
Trans-2-octene
Cis-2-octene
Trans-3-octene
Cis-3-octene
Trans-4-octene
Cis-4-octene
Conv ( % ) [ 1-octene ]
100
32
80
24
60
16
40
8
20
0
0
10
29
53
Time of Reaction ( Hours )
76
Yield ( % ) [Octane, Trans/Cis-octenes ]
40
1-alkene reacts at edges/corners
2-alkene reacts on faces
For ring hydrogenation, the ring prefers
a flat, parallel adsorption mode rather than an
edge-on adsorption
Reactions
Orders of reactions wrt H2
Reactants
Products
PH2 (1-5 barg)
PH2 (5-20 barg)
1-pentene
Pentane
1.6
0.3
1-pentene
Trans-2-pentene
-1.1
-
1-pentene
Cis-2-pentene
-1.2
-
1-octene
Octane
1.6
0.3
1-octene
Trans-2-octene
-0.7
-
1-octene
Cis-2-octene
-0.8
-
Cyclopentene
Cyclopentane
1.6
0.2
Reactions
Reactants
Orders of reactions wrt H2
Products
PH2 (1-20 barg)
Styrene
Ethyl benzene
0.1
PH2 (1-5 barg)
PH2 (5-20 barg)
Toluene
Methylcyclohexane
-
2.4
Ethylbenzene
Ethylcyclohexane
-
2.9
Reactions
Orders of Reactions
wrt PyGas (WHSVPyGas 4-8 h-1)
Reactants
Products
PH2 = 5 barg,
PT = 20 barg
(25% hydrogen gas)
1-pentene
Pentane
-0.3
0.7
1-pentene
Trans-2-pentene
3.4
-
1-pentene
Cis-2-pentene
3.6
-
1-octene
Octane
-0.7
0.3
1-octene
Trans-2-octene
2.6
-
1-octene
Cis-2-octene
2.9
-
Cyclopentene Cyclopentane
0.0
0.8
Styrene
1.0
1.2
Ethylbenzene Ethylcyclohexane
-
-
Toluene
-
-
Ethylbenzene
Methylcyclohexane
PH2 = 10 barg,
PT = 20 barg
(50% hydrogen gas)
Stream cracker plant
Hydrogenated PyGas
(saturated paraffins + saturated
compounds of aromatics)
PyGas
PyGas for aromatics extraction
(aromatic + saturated paraffins)
H-PyGas-II
H-PyGas-III
PyGas for gasoline pool
(aromatic + internal olefins)
H-PyGas-I
Gasoline pool
Aromatic
H-PyGas-I gives a high octane mixture which can be utilised as a gasoline
blending mixture
 mild reaction parameters [T ≈ 140oC, PT ≈ 20 barg, PH2 ≈ 1-5 barg,
WHSVPyGas ≈ 4-8 h-1].
 Reactive species like styrene and alkadienes are selectively hydrogenated.
 High selectivity to internal olefins
 No significant hydrogenation of the aromatic compounds.
H-PyGas-II gives a feed for aromatics extraction.
 Uses moderate reaction conditions
[T ≈ 140oC, PT ≈ 20 barg, WHSVPyGas ≈ 4 h-1, PH2 ≈ 5-20 barg].
 Selective hydrogenation of styrene and olefins
 No hydrogenation of aromatics.
H-PyGas-III gives a low aromatic gasoline pool mix.
 Uses more forcing hydrogenation reaction conditions [PH2 ≈ 20 barg, PT ≈ 20
barg, WHSVPyGas ≈ 4 h-1 T ≈ 140-200oC].
 Can be coupled to acid catalyst to get ring opening and iso-alkanes for the
production of the high-octane components (iso-alkanes) for the gasoline pool
mixture.
1-alkene reacts at edges/corners
2-alkene reacts on faces
Acknowledgements
Javed Ali
Martin MacIntosh
Kohat University of Science and Technology (KUST),
Kohat, Pakistan