Centre for Catalysis Research, Dept of Chemistry, University of Glasgow, Glasgow, UK.
Selective Hydrogenation of PyGas over Palladium
CatalystsS David Jackson
by-product of high temperature naphtha cracking, highly unsaturated mixture
(carbon range ~C5-C12).
PyGas Components Weight percent (wt %)
Benzene, toluene and xylenesOlefins and dienesStyrene and other aromaticsParaffins and naphthenics
50251510
Typical composition of Pyrolysis Gasoline
Pyrolysis Gasoline
Pyrolysis Gasoline Composition
PyGas Components Weight percent (wt %)
TolueneStyrene1-penteneCyclopentene1-octeneHeptaneDecane
55101010102.52.5
Composition of our model Pyrolysis Gasoline
Reaction Conditions
Continuous flow fixed bed reactor
Catalysts:
16 wt.% Ni/Al2O3
1 wt.% Pd/Al2O3
Reaction Temperature:140C - 200C
Hydrogen Pressure :1 - 20 barg
WHSV: 4 h-1
Catalyst weight:0.5 g
Potential reactions of PyGas
Styrene Ethyl Benzene Ethylcyclohexane
Toluene Methycyclohexane
Cyclopentene Cyclopentane
1-Pentene 2-Pentene
Pentane
2-Octene
3-Octene
4-Octene
Octane
1-octene
0.0E+00
5.0E-07
1.0E-06
1.5E-06
2.0E-06
2.5E-06
0 5 10 15 20 25
Rat
e of
form
atio
n ( r
) M
oles
g-1
s-1
Hydrogen pressure ( PH2 ) barg
Praffins
Internal olefins
EB
Saturated compound from aromatics (MCH, ECH)
0
0.2
0.4
0.6
0.8
1
0
20
40
60
80
10 28 52 76
Yiel
d ( %
) [
MC
H ]
Con
v ( %
) [
Tolu
ene
]
Time of Reaction ( Hours )
Toluene(Conv) MCH
Carbon Balance
Reaction Temperature:140C - 200C
Hydrogen Pressure :20 bar
WHSV:4 h-1
Pd/Al2O3
Percent Carbon Balance of each species in synthetic PyGas hydrogenation
Reaction Temperature:140 C
Hydrogen Pressure :1 - 20 bar
WHSV:4 h-1
Percent Carbon Balance of each species in synthetic PyGas hydrogenation
Pd/Al2O3
Carbon Balance
0.0E+00
2.0E‐10
4.0E‐10
6.0E‐10
8.0E‐10
1.0E‐09
1.2E‐09
0
50
100
150
200
250
300
350
400
450
500
0 50 100 150 200 250 300
Ion curren
t
Tempe
rature (C)
Time (min)
Temp CO2 H2O
Pd/Al2O3, WHSV 4h-1, 140C, 5barg H2
Pd/Al2O3, WHSV 4h-1, 140C, 5barg H2
0
50
100
150
200
250
300
350
400
450
500
0.0E+00
5.0E‐12
1.0E‐11
1.5E‐11
2.0E‐11
2.5E‐11
3.0E‐11
3.5E‐11
0 20 40 60 80 100 120 140 160 180 200
Tem
pera
ture
(C
)
Ion Cu
rren
t ( n A)
Time ( mins)
92 104 78 106 Temp
78, benzene92, toluene104, styrene106, EB
-7.00E-04
-6.00E-04
-5.00E-04
-4.00E-04
-3.00E-04
-2.00E-04
-1.00E-04
0.00E+00
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 100 200 300 400 500 600 700 800 900 1000
Ion
curr
ent (
a.u.
)
Der
ivat
ive
wei
ght (
%/C
)
Temperature [C]
Deriv weight m/e 44
Pd/alumina, cyclopentene
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
-6.0E-04
-5.0E-04
-4.0E-04
-3.0E-04
-2.0E-04
-1.0E-04
0.0E+00
0 100 200 300 400 500 600 700 800 900 1000
Der
ivai
tve
Wei
ght (
%/o
C)
Ion
Cur
rent
(mA)
Temperature (oC)
m/e 44 Deriv weight
Carbon laydown Toluene
3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
Intensity (arb. units)
Raman Shift (cm‐1)
Raman Spectra for Pd/alumina after Toluene
Carbon laydown Toluene
0
0.2
0.4
0.6
0.8
1
0
20
40
60
80
10 28 52 76
Yiel
d ( %
) [ M
CH
]
Con
v ( %
) [ T
olue
ne ]
Time of Reaction ( Hours )
Toluene(Conv)
MCH
5 barg H2 WHSV 4 h-1
0
10
20
30
40
0
20
40
60
80
100
120
10 28 52 76
Yiel
d (%
) [ T
rans
/Cis
-oct
enes
]
Yiel
d (%
) [ O
ctan
e ],
Con
v (%
) [ 1
-oct
ene
]
Time of Reaction ( Hours )
1-octene(Conv) OctaneTrans-2-octene Cis-2-octeneTrans-4-octene Trans/Cis-3-octene & Cis-4-octene
5 barg H2 WHSV 4 h-1
0
7
14
21
28
35
0
20
40
60
80
100
10 29 53 76
Yiel
d ( %
) [ O
ctan
e, T
rans
/Cis
-oct
enes
]
Con
v ( %
) [ 1
-oct
ene
]
Time of Reaction ( Hours )
1-octene(Conv) Octane Trans-2-octene Cis-2-octene
Trans-3-octene Cis-3-octene Trans-4-octene Cis-4-octene
5 barg H2 WHSV 8 h-1
0
8
16
24
32
40
0
20
40
60
80
100
120
10 29 53 76
Yiel
d ( %
) [O
ctan
e, T
rans
/Cis
-oct
enes
]
Con
v ( %
) [
1-oc
tene
]
Time of Reaction ( Hours )
1-octene(Conv) Octane Trans-2-octene Cis-2-octene
Trans-3-octene Cis-3-octene Trans-4-octene Cis-4-octene
1 barg H2 WHSV 4 h-1
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 Orders of reactions wrt H2
Reactants 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)
PH2 = 10 barg, PT = 20 barg
(50% 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 Ethylbenzene 1.0 1.2
Ethylbenzene Ethylcyclohexane - - Toluene Methylcyclohexane - -
PyGas PyGas for aromatics extraction (aromatic + saturated paraffins)
PyGas for gasoline pool (aromatic + internal olefins)
Hydrogenated PyGas (saturated paraffins + saturated
compounds of aromatics)
Stream cracker plant
Aromatic
Gasoline pool
H-PyGas-III H-PyGas-II
H-PyGas-I
PyGas PyGas for aromatics extraction (aromatic + saturated paraffins)
PyGas for gasoline pool (aromatic + internal olefins)
Hydrogenated PyGas (saturated paraffins + saturated
compounds of aromatics)
Stream cracker plant
Aromatic
Gasoline pool
H-PyGas-III H-PyGas-II
H-PyGas-I
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.
Acknowledgements
Kohat University of Science and Technology (KUST), Kohat, Pakistan
Javed AliMartin MacIntosh