- Email: [email protected]
Electropyrolysis of low-octane gasoline vapours
ELECTROPYROLYSIS OF LOW-OCTANE GASOLINE VAPOURS* V. S. AL'TStIULEI~, V. I. SOI%OKINand G. S. S~tFra I~lstitute of Mineral Fuels (Received 11 November 1969)
THERMAL pyrolysis of hydrocarbon raw material in tube heaters is widely used in modern industry to obtain gaseous olefins. This method, however, has several disadvantages: its efficiency is not high enough, heat transfer through the walls is limited. In addition, the method is intermittent because of the need for burning out coke, particularly when using heavy types of raw material and requires high-alloy steel apparatus. A promising trend in developing new methods of preparing gaseous olefins uses electrical energy and processes are carried out in a micro-spark discharge and an electric field is applied on a fluidized layer of conducting material particles. Studies of propane pyrolysis in micro-spark discharge [1] show that this method has numerous advantages: 1) a large number of spark discharges helps to achieve local high temperatures with low wall temperature and allows rapid quenching of products; 2) the process is not accompanied by the separation of free carbon; 3) the relative contents of ethylene and propylene in the pyrolytic gas can be adjusted b y varying specific energy; 4) simple apparatus is required for the process; 5) the degree of conversion of the initial product is high and specific input moderate. These aspects of the process induced the authors to investigate the treatment of low-octane straight-run gasoline in micro-spark discharge. EXPERIMENTAL
Experiments were carried out in a laboratory apparatus (Fig. 1). The reactor consists of three metal cylinders connected in series (external diameter 76 mm, height 275 mm). A metal grid was welded on to the lower part of each cylinder, on which a layer of conducting particles was arranged and functioned as an electrode. A quartz vessel (internal diameter 45 ram, height 180 mm) was placed in the metal cylinder. The gap between the vessel and the cylinder was filled with crushed fire brick. Electrode charcoal or siliconized graphite comprised the conducting particles 1-2 mm in diameter; a second electrode was placed over the particle layer which was able to move automatically and * Neftekhirniya 10, No. 5, 666 671, 1970. 194
Eleetropyrolysis of low-octane gasoline vapours
195
vertically during the experiment. Externally each cylinder was heated electrically to compensate for heat losses. A thermocouple was placed at the gas outlet from each cylinder. The reactor enabled us to carry out experiments at a pressure higher t h a n atmospheric. Alternating current of up to 1000 V w~s supplied to the electrodes. To stabilize the spark discharges, three special chokes were arranged in the high voltage line. Energy consumption was recorded by a meter. Low-octane gasoline was pumped from a graduated burette into an evaporator, into which steam was simultaneously passed. The steam-gas mixture flowed into a steam superheater, from which it entered the reactor.
~E
8
£ /0
i!
Jii r~ l h-~atmos,ohe,~e
Fie. 1. Layout of laboratory apparatus. 1--Cylinder contaitfing nitrogen; 2--choke; 3-thermoeouple; 4--small steam boiler; 5--measuring tank; 6--mixer; 7--super heater; 8--reactor; 9--tubular cooler; 10--condensate tank;//--glass trap; 12--gas meter; 1 3 assembly of droppers. The steam-gas mixture was fed at a rate required to maintain regular bubbling of the particle layer. When bubbling evenly under steady conditions the voltage supplied was 1000 V, and current 2-3 A. At the outlet from the third phase of the reactor the gas and vapour mixture passed through a tubular cooler, a condenser, traps which were arranged in a jacket containing ice, gas meter, an assembly of droppers and then passed into the atmosphere. The gas obtained was analysed in a KhT-2M chromatograph and an IGI combined chromatograph and resin was separated from water; to determine the group composition of substances contained, the resin was analysed in a "Tsvet" chromatograph. The experiments were carried out with a 0.4 : 0-45 ratio of steam to gasoline.
196
V.S. AL'TSHULERet al.
I t has been pointed out [2, 3] t h a t steam promotes reduction in coke formation during pyrolysis of hydrocarbon raw material. Low-octane straight run gasoline obtained from the Moscow Oil Refinery was the raw material. Characteristics of the gasoline were: I.B.P. 42°; F.B.P. 153 ° (96% boils away); iodine number 1.2; n~° 1.4007; d24° 0.6898; average molecular weight 83; aromatic hydrocarbon content 12.84% wt. Two series of experiments were carried out: with carbon particles and with particles having conducting and catalytic properties. Gas formation under different conditions of electropyrolysis of gasoline was determined according to specific electricity consumption. The retention time of the steam-gas mixture in the zone of discharge varied little in practice in the experiments and was 0-05-0.08 sec. RESULTS
F i r s t series of experiments. Results of the first series of experiments (Figs. 2 and 3) indicate t h a t with an increase in specific energy ethylene, pro-
zgLk.g
%w/ 12
~aSOllt'le
-0"15 -01
8
zt
9"O5
o
0
k [k5
%~.
Oasolihe !
16 ~
o
gO°
o
~
l'----"
0'2
o
-101 o5
o
0"I
10
,..~.)~Y~x-..-'x)O<~Xx 0
I
f
I
I
I
0
F
2
OIitll 02
O'3
30
O
o
o
~
!
0"2 0'I
10 0!
20~
30=
I
I
I
I
I
o5
oz
o.B
1.1
FIG 2
I
PS ,wh/kg
03
~5
~7
~8
~'lkWh/kq
FIG 3
FZG. 2. Dependence of the content and yield of unsaturated hydrocarbons on specific energy. Temperature 350°: 1--C2H4; 2--C3He; 3--C4Hs-bC4H6. FIG. 3. Dependence of the content and yield of unsaturated hydrocarbons on specific energy. Temperature 560°: 1 - C2H~; 2 - C3He; 3 - C,Hsq-C4H6.
197
Electropyrolysis of low-octane gasoline vapours
pylene, butadiene and b u t e n e contents increased in the v a p o u r m i x t u r e a n d gas and u n s a t u r a t e d h y d r o c a r b o n yields, calculated per kg gasoline increased. A t t h e same t i m e p r o p y l e n e c o n t e n t in gas increased at a lower r a t e t h a n ethylene c o n t e n t and the overall contents of butenes and butadiene. T h e a m o u n t and quality of p y r o l y t i c p r o d u c t s was considerably influenced b y t h e heating t e m p e r a t u r e of the raw material. gaco!~ne
%v@. [2
o
O15
o
O.t
c2H~:csH6 (,,oz) -
!
0
/4
qV'~o o
0
1
~b.
Ol - ~ e ~ l ~ I
I
I
I
,
,
, 0 03
20 _ o
o
2
Og o.f
I
I
I
I
]
I
3
.
0
I
I
I
l
r
I
tl O,3
1 ...9-
2
2oh
/ ×
! 0
,
2
!
,, 0.!
OOg
3O
z
0
o
O.2 04
I
I
I
I
0.3
0"5
0.7
0"9
FIG. 4
I
H
I
1"3kWh/kg
0|~.
04
- ~ " , -- ,
0-2
l}3
0.14 05
i o O.G O.7AWh/k9
Fzo. 5
FI¢. 4. Dependence of the C2tt< : C~H6 ratio on specific energy. Temperature, °C: 1 -- 3507 2--560; 3--450-500 (with a catalyst). Fie. 5. Dependence of the content and yield of unsaturated hydrocarbons on specific energy with a catalyst. Temperature 450-500°: 1--C2H4; 2--C8H6; 3--C4Hs~-C4H6. Figures 2 and 3 show t h a t on changing t h e t e m p e r a t u r e of heating the raw material t h e same c o n t e n t of u n s a t u r a t e d c o m p o u n d s was o b t a i n e d in gas with different specific energies. Thus, at a heating t e m p e r a t u r e of 350 ° and a specific e n e r g y of 1.3 k W h / k g gasoline, ethylene content in gas was 29~o wt., p r o p y l e n e c o n t e n t 20~o wt., overall c o n t e n t of C 4 H s ÷ C 4 H 6 = 1 3 - 8 % wt., g a s yield being 0-66 nm3/kg (Fig. 2). The same lower olefin c o n t e n t could be obrained with a specific e n e r g y of 0-45 kWh/kg, if the heating t e m p e r a t u r e o f t h e initial gas m i x t u r e was increased to 560-570°C (Fig. 3). An increase in the t e m p e r a t u r e of the steam-gas m i x t u r e increased the, e x t e n t of gas f o r m a t i o n a n d the yield of u n s a t u r a t e d hydrocarbons.
198
V.S.
AL'TSHULER et al.
On heating the steam-gas mixture to 560 ° and with a specific energy of 0.5 kWh/kg a high overall yield of unsaturated hydrocarbons was obtained: 650/0 wt., or calculated in terms of gasoline, about ao/b -~o~ wt. In addition to ethylene and propylene, the gas contained a significant i)roportion of butenebutadiene fraction (13.5% wt.), which is of considerable interest for rubber production. A comparison of results and the composition of gas obtained by pyrolysis of gasoline in tube heaters indicates that in our experiments the gas produced had a higher propylene content (l 5 /6°,/o vol. instead of' 10 I 1°/o vol.) and a lower methane content (20% vol. instead of 2 4 ° vol.). Figure 4 shows t h a t with an increase in specific energy the C a l l 4 : C a l l 6 ratio increased slightly, this ratio increasing with an increase in heating temperature (other conditions being the same). Electropyrolysis of gasoline took place under mild conditions which is proved by the low waste gas temperature {about 475-525 °) short retention time (0.04-0.08 see) and the composition of liquid products.obtained. In gasoline pyrolysis on heating to 350 ° resin is a slightly aromatic product which hardly differs in composition from the initial gasoline, This is particularly true for resin prepared with low specific energies. With an increase of specific energy, the percentage of gasoline, toluene and xylenes increased. It is evident that to obtain aromatized resin, pyrolysis shouht be c~rried out with increased contact, time. Characteristics of liquid products are described below. CHARACTERISTICS OF L I Q U I D PRODUCTS
W(~raperature of r a w m a terial in e x p e r i m e n t s without a catalyst
Indices
i Experiments a, cat,ai w i t h Ix-st i
] R e s i n y ' e l d , k g / k g gasoline C o n t e n t of a r o m a t i c h y d r o c a r b o n s , (~) wt.: benzene toluene ethylbenzene xylenes Total
350 °
560 °
0.6",)
0._13
3.57 6.18 2.14 4.70 18.()1)
9.56 12.0 J~, 3.74 9.86 44.38
[ ~
0.2.0
8.65 10.41 3.05 8.02 33.97
Waste gas temperature has a significant effect on the variation of resin .composition in the direction of aromatization. Thus, an increase in outlet gas temperature to 550-600 ° increased the yield of aromatic compounds in resin to 44-4% wt. This resin is of considerable interest as a raw material for the preparation of high-octane gasoline and aromatic hydrocarbons. Experiments on eleetropyrolysis of. low-octane gasoline show t h a t lower
Electropyrolysis of low-octane gasoline vapours
199
olefins can be obtained at regular rates from gasoline vapour in micro-spark discharge. The composition and the proportion of gaseous and liquid products obtained depends on the specific energy and heating temperature of the raw material. By adjusting the specific energy and temperature, gas with different lower olefin content, different C2H4 : C3H 6 ratio and resin with different contents of aromatic compounds can be obtained. This process may be of special interest when ethylene, propylene and a butylene-butadiene fraction are (~onsidered as intermediate products. Second series of experiments. It was of interest to explain the possibility of using a conducting material, which catalyses pyrolysis of gasoline in discharge. The use of ~ catalyst during pyrolysis of hydrocarbon raw material helps to increase considerably the selectivity of dehydrogenation, compared with thermal reactions in which comparatively intensive cracking takes place. in industrial equipment used for paraffin dehydrogenation alumina-chromium oxide catalysts are used. Alumina is normally used as a Catalyst car?ier. When the catalyst must also be conductive, alumina is inapplicable. We therefore used electrode carbon and siliconized graphite as carrier. An impregnated chromium oxide-potassium oxide catalyst was made according to a former study [4]. Results of this series of experiments are shown in Fig. 5. which confirms the results of the first series of experiments, i.e. with an increase in speeific energy unsaturated hydrocarbon content and yield increase. With low specific energy (0.6 kWh/kg) gas yield is high (0.66 nm3/kg gasoline) and so is the overall contents of unsaturated compounds (60% wt.). The resin obtained contains 34~/o wt. aromatic compounds. Temperature at the inlet in the first part of the reactor is 450-500 °. It is therefore natural to expect that with an increase in the heating temperature of the initial vapourgas mixture, the unsaturated hydrocarbon content in pyrolytic gas would increase. Experiments indicate that it is possible, in principle, to carry out electropyrolysis of low-octane gasoline in micro-spark discharge using an impregnated catalyst as conducting material. Investigations should be continued in this direction, in order to increase the selectivity of the process. SUMMARY
1. With an increase in specific energy lower olefin yield and gas yield increase.
2. With an increase in the temperature of heating of the raw material, ethylene, propylene, butane and divinyl contents and gas yield and, in resin, the content of aromatic hydrocarbons increase. 3. A conducting material can be used as catalyst in pyrolysis. 4. With a specific energy of 0.5 kWh/kg gasoline the extent of gas formation is 79°//o and ethylene content in the final gas (% wt.) is 31, propylene 25, butenes and divinyl 13.
200
V . S . AL'TSI:[ULER et al.
REFERENCES 1. V. S. AL'TSHULER, G. S. SHAFIR and V. I. SOROKIN, Sb. Gazovye protscssy, (Gaseous Processes). Nauka, Moscow, 1967 2. M. A. DALIN, T. N. MUKHINA, T. V. PItOKOF'EVA and L. V. TALISMAN, Khimicheskaya pererabotka neftyanykh uglevodorov (Chemical Treatment of' Petroleum Hydrocarbons), Tr. Vses. soveshehaniya (Proceedings of All-Union Conference). Izd. AN SSSI¢, Moscow, 1956 3. I. N. MORINA, Khimicheskaya pererabotka n e f t y a n s k h uglevodorov (Chemical Treatment of Petroleum Hydrocarbons), Tr. Vess. soveshchaniya (Proceedings of All-Union Conference). Izd. AN SSSR, Moscow, 1956 4. Auth. Cert. U.S.S.R. 215888. Otkr,. izobr., prom. obraztsy, tov.znaki, No. 14, 13, 1968
THERMAL pyrolysis of hydrocarbon raw material in tube heaters is widely used in modern industry to obtain gaseous olefins. This method, however, has several disadvantages: its efficiency is not high enough, heat transfer through the walls is limited. In addition, the method is intermittent because of the need for burning out coke, particularly when using heavy types of raw material and requires high-alloy steel apparatus. A promising trend in developing new methods of preparing gaseous olefins uses electrical energy and processes are carried out in a micro-spark discharge and an electric field is applied on a fluidized layer of conducting material particles. Studies of propane pyrolysis in micro-spark discharge [1] show that this method has numerous advantages: 1) a large number of spark discharges helps to achieve local high temperatures with low wall temperature and allows rapid quenching of products; 2) the process is not accompanied by the separation of free carbon; 3) the relative contents of ethylene and propylene in the pyrolytic gas can be adjusted b y varying specific energy; 4) simple apparatus is required for the process; 5) the degree of conversion of the initial product is high and specific input moderate. These aspects of the process induced the authors to investigate the treatment of low-octane straight-run gasoline in micro-spark discharge. EXPERIMENTAL
Experiments were carried out in a laboratory apparatus (Fig. 1). The reactor consists of three metal cylinders connected in series (external diameter 76 mm, height 275 mm). A metal grid was welded on to the lower part of each cylinder, on which a layer of conducting particles was arranged and functioned as an electrode. A quartz vessel (internal diameter 45 ram, height 180 mm) was placed in the metal cylinder. The gap between the vessel and the cylinder was filled with crushed fire brick. Electrode charcoal or siliconized graphite comprised the conducting particles 1-2 mm in diameter; a second electrode was placed over the particle layer which was able to move automatically and * Neftekhirniya 10, No. 5, 666 671, 1970. 194
Eleetropyrolysis of low-octane gasoline vapours
195
vertically during the experiment. Externally each cylinder was heated electrically to compensate for heat losses. A thermocouple was placed at the gas outlet from each cylinder. The reactor enabled us to carry out experiments at a pressure higher t h a n atmospheric. Alternating current of up to 1000 V w~s supplied to the electrodes. To stabilize the spark discharges, three special chokes were arranged in the high voltage line. Energy consumption was recorded by a meter. Low-octane gasoline was pumped from a graduated burette into an evaporator, into which steam was simultaneously passed. The steam-gas mixture flowed into a steam superheater, from which it entered the reactor.
~E
8
£ /0
i!
Jii r~ l h-~atmos,ohe,~e
Fie. 1. Layout of laboratory apparatus. 1--Cylinder contaitfing nitrogen; 2--choke; 3-thermoeouple; 4--small steam boiler; 5--measuring tank; 6--mixer; 7--super heater; 8--reactor; 9--tubular cooler; 10--condensate tank;//--glass trap; 12--gas meter; 1 3 assembly of droppers. The steam-gas mixture was fed at a rate required to maintain regular bubbling of the particle layer. When bubbling evenly under steady conditions the voltage supplied was 1000 V, and current 2-3 A. At the outlet from the third phase of the reactor the gas and vapour mixture passed through a tubular cooler, a condenser, traps which were arranged in a jacket containing ice, gas meter, an assembly of droppers and then passed into the atmosphere. The gas obtained was analysed in a KhT-2M chromatograph and an IGI combined chromatograph and resin was separated from water; to determine the group composition of substances contained, the resin was analysed in a "Tsvet" chromatograph. The experiments were carried out with a 0.4 : 0-45 ratio of steam to gasoline.
196
V.S. AL'TSHULERet al.
I t has been pointed out [2, 3] t h a t steam promotes reduction in coke formation during pyrolysis of hydrocarbon raw material. Low-octane straight run gasoline obtained from the Moscow Oil Refinery was the raw material. Characteristics of the gasoline were: I.B.P. 42°; F.B.P. 153 ° (96% boils away); iodine number 1.2; n~° 1.4007; d24° 0.6898; average molecular weight 83; aromatic hydrocarbon content 12.84% wt. Two series of experiments were carried out: with carbon particles and with particles having conducting and catalytic properties. Gas formation under different conditions of electropyrolysis of gasoline was determined according to specific electricity consumption. The retention time of the steam-gas mixture in the zone of discharge varied little in practice in the experiments and was 0-05-0.08 sec. RESULTS
F i r s t series of experiments. Results of the first series of experiments (Figs. 2 and 3) indicate t h a t with an increase in specific energy ethylene, pro-
zgLk.g
%w/ 12
~aSOllt'le
-0"15 -01
8
zt
9"O5
o
0
k [k5
%~.
Oasolihe !
16 ~
o
gO°
o
~
l'----"
0'2
o
-101 o5
o
0"I
10
,..~.)~Y~x-..-'x)O<~Xx 0
I
f
I
I
I
0
F
2
OIitll 02
O'3
30
O
o
o
~
!
0"2 0'I
10 0!
20~
30=
I
I
I
I
I
o5
oz
o.B
1.1
FIG 2
I
PS ,wh/kg
03
~5
~7
~8
~'lkWh/kq
FIG 3
FZG. 2. Dependence of the content and yield of unsaturated hydrocarbons on specific energy. Temperature 350°: 1--C2H4; 2--C3He; 3--C4Hs-bC4H6. FIG. 3. Dependence of the content and yield of unsaturated hydrocarbons on specific energy. Temperature 560°: 1 - C2H~; 2 - C3He; 3 - C,Hsq-C4H6.
197
Electropyrolysis of low-octane gasoline vapours
pylene, butadiene and b u t e n e contents increased in the v a p o u r m i x t u r e a n d gas and u n s a t u r a t e d h y d r o c a r b o n yields, calculated per kg gasoline increased. A t t h e same t i m e p r o p y l e n e c o n t e n t in gas increased at a lower r a t e t h a n ethylene c o n t e n t and the overall contents of butenes and butadiene. T h e a m o u n t and quality of p y r o l y t i c p r o d u c t s was considerably influenced b y t h e heating t e m p e r a t u r e of the raw material. gaco!~ne
%v@. [2
o
O15
o
O.t
c2H~:csH6 (,,oz) -
!
0
/4
qV'~o o
0
1
~b.
Ol - ~ e ~ l ~ I
I
I
I
,
,
, 0 03
20 _ o
o
2
Og o.f
I
I
I
I
]
I
3
.
0
I
I
I
l
r
I
tl O,3
1 ...9-
2
2oh
/ ×
! 0
,
2
!
,, 0.!
OOg
3O
z
0
o
O.2 04
I
I
I
I
0.3
0"5
0.7
0"9
FIG. 4
I
H
I
1"3kWh/kg
0|~.
04
- ~ " , -- ,
0-2
l}3
0.14 05
i o O.G O.7AWh/k9
Fzo. 5
FI¢. 4. Dependence of the C2tt< : C~H6 ratio on specific energy. Temperature, °C: 1 -- 3507 2--560; 3--450-500 (with a catalyst). Fie. 5. Dependence of the content and yield of unsaturated hydrocarbons on specific energy with a catalyst. Temperature 450-500°: 1--C2H4; 2--C8H6; 3--C4Hs~-C4H6. Figures 2 and 3 show t h a t on changing t h e t e m p e r a t u r e of heating the raw material t h e same c o n t e n t of u n s a t u r a t e d c o m p o u n d s was o b t a i n e d in gas with different specific energies. Thus, at a heating t e m p e r a t u r e of 350 ° and a specific e n e r g y of 1.3 k W h / k g gasoline, ethylene content in gas was 29~o wt., p r o p y l e n e c o n t e n t 20~o wt., overall c o n t e n t of C 4 H s ÷ C 4 H 6 = 1 3 - 8 % wt., g a s yield being 0-66 nm3/kg (Fig. 2). The same lower olefin c o n t e n t could be obrained with a specific e n e r g y of 0-45 kWh/kg, if the heating t e m p e r a t u r e o f t h e initial gas m i x t u r e was increased to 560-570°C (Fig. 3). An increase in the t e m p e r a t u r e of the steam-gas m i x t u r e increased the, e x t e n t of gas f o r m a t i o n a n d the yield of u n s a t u r a t e d hydrocarbons.
198
V.S.
AL'TSHULER et al.
On heating the steam-gas mixture to 560 ° and with a specific energy of 0.5 kWh/kg a high overall yield of unsaturated hydrocarbons was obtained: 650/0 wt., or calculated in terms of gasoline, about ao/b -~o~ wt. In addition to ethylene and propylene, the gas contained a significant i)roportion of butenebutadiene fraction (13.5% wt.), which is of considerable interest for rubber production. A comparison of results and the composition of gas obtained by pyrolysis of gasoline in tube heaters indicates that in our experiments the gas produced had a higher propylene content (l 5 /6°,/o vol. instead of' 10 I 1°/o vol.) and a lower methane content (20% vol. instead of 2 4 ° vol.). Figure 4 shows t h a t with an increase in specific energy the C a l l 4 : C a l l 6 ratio increased slightly, this ratio increasing with an increase in heating temperature (other conditions being the same). Electropyrolysis of gasoline took place under mild conditions which is proved by the low waste gas temperature {about 475-525 °) short retention time (0.04-0.08 see) and the composition of liquid products.obtained. In gasoline pyrolysis on heating to 350 ° resin is a slightly aromatic product which hardly differs in composition from the initial gasoline, This is particularly true for resin prepared with low specific energies. With an increase of specific energy, the percentage of gasoline, toluene and xylenes increased. It is evident that to obtain aromatized resin, pyrolysis shouht be c~rried out with increased contact, time. Characteristics of liquid products are described below. CHARACTERISTICS OF L I Q U I D PRODUCTS
W(~raperature of r a w m a terial in e x p e r i m e n t s without a catalyst
Indices
i Experiments a, cat,ai w i t h Ix-st i
] R e s i n y ' e l d , k g / k g gasoline C o n t e n t of a r o m a t i c h y d r o c a r b o n s , (~) wt.: benzene toluene ethylbenzene xylenes Total
350 °
560 °
0.6",)
0._13
3.57 6.18 2.14 4.70 18.()1)
9.56 12.0 J~, 3.74 9.86 44.38
[ ~
0.2.0
8.65 10.41 3.05 8.02 33.97
Waste gas temperature has a significant effect on the variation of resin .composition in the direction of aromatization. Thus, an increase in outlet gas temperature to 550-600 ° increased the yield of aromatic compounds in resin to 44-4% wt. This resin is of considerable interest as a raw material for the preparation of high-octane gasoline and aromatic hydrocarbons. Experiments on eleetropyrolysis of. low-octane gasoline show t h a t lower
Electropyrolysis of low-octane gasoline vapours
199
olefins can be obtained at regular rates from gasoline vapour in micro-spark discharge. The composition and the proportion of gaseous and liquid products obtained depends on the specific energy and heating temperature of the raw material. By adjusting the specific energy and temperature, gas with different lower olefin content, different C2H4 : C3H 6 ratio and resin with different contents of aromatic compounds can be obtained. This process may be of special interest when ethylene, propylene and a butylene-butadiene fraction are (~onsidered as intermediate products. Second series of experiments. It was of interest to explain the possibility of using a conducting material, which catalyses pyrolysis of gasoline in discharge. The use of ~ catalyst during pyrolysis of hydrocarbon raw material helps to increase considerably the selectivity of dehydrogenation, compared with thermal reactions in which comparatively intensive cracking takes place. in industrial equipment used for paraffin dehydrogenation alumina-chromium oxide catalysts are used. Alumina is normally used as a Catalyst car?ier. When the catalyst must also be conductive, alumina is inapplicable. We therefore used electrode carbon and siliconized graphite as carrier. An impregnated chromium oxide-potassium oxide catalyst was made according to a former study [4]. Results of this series of experiments are shown in Fig. 5. which confirms the results of the first series of experiments, i.e. with an increase in speeific energy unsaturated hydrocarbon content and yield increase. With low specific energy (0.6 kWh/kg) gas yield is high (0.66 nm3/kg gasoline) and so is the overall contents of unsaturated compounds (60% wt.). The resin obtained contains 34~/o wt. aromatic compounds. Temperature at the inlet in the first part of the reactor is 450-500 °. It is therefore natural to expect that with an increase in the heating temperature of the initial vapourgas mixture, the unsaturated hydrocarbon content in pyrolytic gas would increase. Experiments indicate that it is possible, in principle, to carry out electropyrolysis of low-octane gasoline in micro-spark discharge using an impregnated catalyst as conducting material. Investigations should be continued in this direction, in order to increase the selectivity of the process. SUMMARY
1. With an increase in specific energy lower olefin yield and gas yield increase.
2. With an increase in the temperature of heating of the raw material, ethylene, propylene, butane and divinyl contents and gas yield and, in resin, the content of aromatic hydrocarbons increase. 3. A conducting material can be used as catalyst in pyrolysis. 4. With a specific energy of 0.5 kWh/kg gasoline the extent of gas formation is 79°//o and ethylene content in the final gas (% wt.) is 31, propylene 25, butenes and divinyl 13.
200
V . S . AL'TSI:[ULER et al.
REFERENCES 1. V. S. AL'TSHULER, G. S. SHAFIR and V. I. SOROKIN, Sb. Gazovye protscssy, (Gaseous Processes). Nauka, Moscow, 1967 2. M. A. DALIN, T. N. MUKHINA, T. V. PItOKOF'EVA and L. V. TALISMAN, Khimicheskaya pererabotka neftyanykh uglevodorov (Chemical Treatment of' Petroleum Hydrocarbons), Tr. Vses. soveshehaniya (Proceedings of All-Union Conference). Izd. AN SSSI¢, Moscow, 1956 3. I. N. MORINA, Khimicheskaya pererabotka n e f t y a n s k h uglevodorov (Chemical Treatment of Petroleum Hydrocarbons), Tr. Vess. soveshchaniya (Proceedings of All-Union Conference). Izd. AN SSSR, Moscow, 1956 4. Auth. Cert. U.S.S.R. 215888. Otkr,. izobr., prom. obraztsy, tov.znaki, No. 14, 13, 1968