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Influence of the fractional composition of gasolines on the products of their pyrolysis
INFLUENCE OF THE FRACTIONAL COMPOSITION OF GASOLINES ON THE PRODUCTS OF THEIR PYROLYSIS* T. N. MUKHINA and S. YE. ITSEK Scientific Research Institute for Synthetic Alcohols and Organic Products
(Received 29 April 1962) IN VIEW of the use of gasoline fractions of various molecular weights as raw materials for the production of ethylene, propylene, and butylene, the elucidation of the influence of the fractional composition of the initial raw material on the distribution of the products of its pyrolysis is an important question. There is some information in the literature on the influence of the fractional composition of the raw material on the yield of pyrolysis products. Thus, on the basis of laboratory investigations a series of relationships for the conversion and distribution of the gaseous products obtained as functions of the velocity and temperature of the pyrolysis process for different types of raw materials has been given [1-13]. Literature data on the pyrolysis of hydrocarbon fractions in semi-industrial tube furnaces show that under the optimum conditions for each type of raw material the yield of olefms does not substantially depend on the fractional composition of the raw material. The yield varies within the range of one order of magnitude and the course of the reaction depends in the first place on the parameters of the process [14-15]. Analogous relationships have been obtained in a high-velocity cracking apparatus with an internal heater [16-18]. Generalized results characterizing the approximate yields of ethylene, propylene, and resin in the pyrolysis of various types of raw material in tube furnaces are given in Table 1 [19]. The data clearly show a tendency for a reduced yield of olefins as the raw material becomes heavier. Contradictory results have been obtained on the influence of the fractional composition of the raw material pyrolysed on the yield of pyrolysis gas and the composition of the final products from investigations carried out in tube furnaces in the presence of superheated steam [20, 21]. In one case, the yield of C2 gases first rose as the number of carbon atoms in the raw material increased (up to about C10) and fell gradually only for v e r y long chains. In the other case it was found that the maximum yields of gas, olefins, and ethane were greater when light gasoline was pyrolysed; when * Neftekhimiya 2, No. 5, 723-729, 1962.
481
482
T. N. MUKHINAand S. YE. ITSEK TABLE I. YIELDS OF THE PYROLYSIS PRODUCTS IN THE TREATMENT OF DIFFERENT TYPES OF RAW MATERIALS
Raw material
Ethane Propane n-Butane Natural gasoline Gas condensate Crude petroleum
Yield, calculated on the raw material passed, % by weight Ethylene
Propylene
Pyrolysis resin
50-55 44-45 32-35 27-30 20-25 6-11
1-2 15-20 17-22 12-16 10-12 6-12
0 5-15 6-9 25-30 35-40 30-40
h e a v i e r fractions were pyrolyscd higher yields of methane, acetylene, divinyl, l i q u i d products, and coke were obtained. I n the production of acetylene by the method given by P a t t o n et al. [22], in addition to ligroin, in m a n y experiments liquid hydrocarbon fractions with a wide boiling range, and also propane, were used. The composition and yield of the products were similar in all cases. The pyrolysis of gasoline fractions with different C/H ratios has been investigated in a number of industrial systems: by the Catarol method [23], t h e Lurgi-Ruhrgas-Bayer method [24], by high-velocity cracking methods [25], and by the Farbwerke Hoechst method [26]. I t was found that the composition of the gases was approximately constant for different types of raw material when the processes were carried out under similar conditions. These results are isolated, relate to dissimilar industrial systems, and give no clear and unambiguous idea of the main features of the distribution o f the products in the pyrolysis of raw materials of different fractional corn, positions. T h e necessity of establishing definite results on the pyrolysis o f raw materials of different fractional compositions expressed graphically in the form of the composition of the pyrolysis products as functions of the molecular weight or the C/H ratio and of the parameters of the process was the reason for the present investigation.
EXPERIMENTAL
The raw materials used were 30-70 °, 70-120 ° , 120-140 ° , and 140-170 ° fractions isolated by the distillation of gasoline from straight-distilled Ro~ mashkin0 petroleum in a rectifying column with an efficiency of 40 theoretical plates. The characteristics of these fractions are given in Tables 2 and 3. The fractions had similar chemical compositions, corresponding to the following contents of different types of hydrocarbons: paratrms--63% by weight, n a p h t h e n e s - - 3 1 ~ by weight, a r o m a t i c s - - 6 ~ by weight.
Influence of gasoline composition on pyrolysis products
483
i
TABLE 2. FRACTIONAL00ilil~ITION (ENOLER DISTILLATION) Fraction, °C ~o Distilled Initial boiling point 10 20 30 40 50 60 70 80 90 Final boiling point
30-70° I 70-120° I 120-140° I 140-170 ° Temperature, °C 31.0 49.0 51.0 53-0 55.0 57.0 60.0 61-0 64.0 66.2 70.0
70.0 81.5 86.5 88.0 90.5 92.5 96.0 98-5 103.5 108.0 120.0
120.0 126.5 127.0 127.5 128.0 128.5 129.5 130.5 132.0 138.0 140-0
139-0 146.0 147.0 148-0 149.0 150.0 152.0 154.0 157.0 161.0 170.0
TABLE 3. CHARACTERISTICSOF THE FRACTIONS Fraction, °C Molecular weight Specific gravity C/H ratio
30-70 ° 80.5 0.668 5.39
70-120 ° 97-8 0.713 5-6
120-140 ° 117.0 0.743 5.73
140-170 ° 131-5 0.761 5.82
The fractions were subjected to pyrolysis in a q u a r t z r e a c t o r placed in a t u b e furnace. Before passing into the reactor, t h e raw material a n d w a t e r were e v a p o r a t e d in a q u a r t z e v a p o r a t o r . T h e pyrolysis was carried o u t a t t e m p e r a t u r e s o f 700-800 ° w i t h a c o n t a c t t i m e o f 0.2 to 1.0 sec, using 25°/o b y weight o f steam, calculated on the raw material. T h e pyrolysis gas was a n a l y s e d c h r o m a t o g r a p h i c a l l y on a K h P A - 2 apparatus. F o r convenience in comparison, t h e e x p e r i m e n t a l results on t h e yields o f p r o d u c t s o b t a i n e d in t h e pyrolysis o f raw materials o f different fractional compositions were r e p r e s e n t e d as a f u n c t i o n of the s e v e r i t y f a c t o r o f t h e process. T h e s e v e r i t y f a c t o r characterizes t h e d e p e n d e n c e o f the composition o f t h e pyrolysis gas o n t h e p a r a m e t e r s o f t h e p r o c e s s - - t e m p e r a t u r e a n d c o n t a c t time. I t was f o u n d t h a t the s e v e r i t y is expressed in the f o r m o f the equation It ==tT0"06 , where t is the t e m p e r a t u r e in °C a n d ~ is t h e c o n t a c t t i m e in sec. Table 4 gives t h e calculated values o f t h e s e v e r i t y tt for each set o f conditions for c a r r y i n g o u t t h e pyrolysis process.
484
T. N. MUKHINAa n d S. YE. ITSlZK
On analysing the relationship between the change in the concentration of the components of the pyrolysis gas and the C/H ratio in the raw material (Fig. 1, a, b) it can be seen that the composition of the pyrolysis gas changes only slightly. Thus, as the molecular weight of the initial raw material changes from 80.5 to 131.5 (which corresponds to an increase in the C/H ratio from
2
6"~
6.6
C/x rat~ @ ~ t / n
5'B
5.82
t ~ raw
FIG. 1. Dependence of the composition o f the pyrolysis gas on the C/H ratio in the raw material at the values of the severity factor ~t: a--713; b--765.
5.39 to 5.82) the concentration of hydrogen falls from 19-3 to 15.5% by col. at a severity ~=765 and from 17.1 to 13.0~ by volume at ~=713. The concentration of methane and of the propane-propylene and butane-butylene fractions falls slightly as the C/H ratio in the raw material increases. The content of ethane and ethylene in the gas increases as the raw material becomes heavier. Thus, the concentration of ethylene in the pyrolysis of a
Influence of gasoline composition on pyrolysis products
485
gasoline with a molecular weight of 80.5 amounts to 27.8~/o and that of ethane to 3 . 9 ~ by vol.; in the pyrolysis of a gasoline with a molecular weight of 131.5 the amount of ethylene in the gas is 29.2~ by vol. and the amount of ethane is 4.9% by vol. By comparing the amounts of gas formation obtained in the pyrolysis of gasoline fractions at different values of the severity of the process, i~, it is possible to show a decrease in the gas formation on passing from a lighter to a heavier raw material. Thus, at a severity 1~----765, the yield of gases from the pyrolysis of the 30-70 ° fraction is 8 7 ~ by weight, from the 70-120 ° fraction it is 83~/o by weight, from the 120-140 ° fraction 77°/o by weight, and from the 140-170 ° fraction 75% by weight. In the pyrolysis of different hydrocarbon fractions, a considerable change in the amount of gas formed, with its composition remaining approximately constant, leads to a change in the yields of the components calculated on the raw material passed. These changes are illustrated in Fig. 2, a, b, c, which gives the dependence of the changes in the yields of the components on an increase in the C/H ratio at severity factors 1~--~690, 765, and 797. At these values of the severity factor the distribution of the pyrolysis products is constant. From an analysis of the data corresponding to severity p=765 (Fig. 2c) it follows that the yields of pyrolysis products depend on the fractional composition of the raw material. On comparing the yields obtained in the pyrolysis of the 30-70 and 140-170 ° fractions (with C/H ratios of 5.39 and 5-82, respectively), a fall in the yield of the methane-hydrogen fraction from 20.7~ by weigt to 18.4~o by weight is found. At the same time, the yield of ethylene falls from 3 0 ~ by weight to 27.2~ by weight, the yield of propylene from 18.5 to 14.6 ~ by weight, and the combined yield of butylenes from 8.5 to 5 . 0 ~ by weight. On passing from a light to a heavier raw material a marked rise in resin formation is found. A consideration of Figures 3a, b, c, and d, which show the yield of olefins as a function of the severity factor for gasoline of various fractional compositions, permits the optimum conditions for a pyrolysis process directed to the production of either ethylene or propylene or the butylenes to be selected. By analysing the graphs given above it is possible to state that the curves of the yields of the components of the pyrolysis gas pass through a maximum corresponding to a single value of the severity factor of the process for different hydrocarbon fractions. Thus, it follows from Fig. 3a that the maximum yield of ethylene is obtained at the same value of the severity factor 11-~785 for all the fractions pyrolysed. The maxim u m yield of propylene (Fig. 3b) is considerably displaced to the left (in comparison with the maximum for ethylene) in the direction of milder conditions and corresponds to a severity 11=735. The maximum yields of the butylenes are obtained at it----720 (Fig. 3c). The optimum figures for the combined unsaturated hydrocarbons are obtained at a severity ~= 755 (Fig. 3d).
486
T . N . MUKHINA and S. Y z . ITSZK
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FIG. 3. Izffluence o f t h e s e v e r i t y factor in t h e pyrolysis o f various gasoline f r a c t i o n s ' o n t h e yield of olefins: a - - e t h y l e n e ; b - - p r o p y l e n e ; c - - b u t y l e n e s ; d - - t o t a l u n s a t u r a t e d h y d r o carbons. 1 - - 3 0 - 7 0 ° fraction; 2 - - 7 0 - 1 2 0 ° fraction; 3 - - 1 2 0 - 1 4 0 ° fraction; 4 - - 1 4 0 - 1 7 0 ° fraction.
It follows from the Figures that the severity figures mentioned for each fraction correspond to the optimum yields given in Table 5. TABLE 4. DEPENDENCE OF THE SEVERITY FACTOR ~t ON THE PARAMETERS OF THE PYROLYSIS PROCESS
T e m p e r a t u r e , °C C o n t a c t time, sec Severity factor
800
750
700
0.28 0.57 0.94 740 765 797
0.25 0.43 0.74 690 713 736
0-18 0-30 0.52 630 650 674
488
T . N . MUKHINA a n d 8. Y E . ITSEK
TABLE 5. OPTIMUM YIELDS OF UNSATURATEDHYDROCARBONS OBTAINED IN THE PYROLYSIS OF GASOLINES OF DIFFERENT FRACTIONAL COMPOSITIONS, CALCULATED ON T H I RAW MATERIAL PASSED (% B y WEIGHT)
Fr. 30_70 °
Components Ethylene Propylene Butylenes C H2~
! !
30"3 19"3 10.2 57.0
Fr. 70__120°
Fr. 120__140°
Fr. 140_170 °
29"2 16"9 7"8 52"2
28-0 15"1 6'5 47"6
26"2 14"2 5"7 45"5
785 735 720 755
SUMMARY 1. An investigation has been carried o u t of the pyrolysis o f t h e following fractions o f straight-distilled gasoline: 30-70 °, 70-120 °, 120-140 °, a n d 140170°C. 2. Certain features o f the influence o f the fractional composition o f the initial raw material on the n a t u r e o f t h e distribution o f their pyrolysis p r o d u c t s h a v e b e e n established: (a) the composition o f the gas changes o n l y slightly with a v a r i a t i o n in the fractional composition o f the initial raw material; (b) t h e fractional composition o f the initial raw material has a considerable influence o n t h e a m o u n t o f gas formed, which decreases w h e n t h e molecular weight o f t h e initial raw material increases u n d e r similar process conditions; (c) the yield o f c o m p o n e n t s o f the pyrolysis gas decreases on passing f r o m lighter t o heavier r a w material; a n d (d) as t h e C]H ratio in the raw material rises, the f o r m a t i o n o f coke considerably increases. 3. T h e results o b t a i n e d m a k e it possible, w i t h o u t c a r r y i n g o u t a n y supp l e m e n t a r y e x p e r i m e n t a l investigations, to establish t h e possible distribution o f t h e pyrolysis p r o d u c t s o f a raw material o f a n y p a r t i c u l a r fractional composition. Translateat by B. J. HAZZARD REFERENCES 1. H. R. LINDEN and R. pEglq~ Industr. Engng. Chem. 47, No. 12, 2470, 1955 2. H. R. LINDEN and J. M. RigID, Chem Engng. Progr. 55, No. 3, 71, 1959 3. J. M. REID and H. R. LINDEN, Chem. Engng. Progr. 56, No. 1, 47, 1960 4. H. R. LINDEN, Petrol. Process. 6, 1389, 1396, 1951 5. H. R. LINDEN, High Temperature Vapor Phase Cracking of Hydrocarbons Dissertation. Institute of Technology, Chicago, 1952 6. H. R. LINDEN, N. G. BAIR and E. S. PETTYJOHN, Amer. Gas. Assoc. Prec., 616, 1954 7. H. R. LINDEN and E. S. PETTYJOHN, Amer. Gas Assoc. Prec. 553, 1951 8. H. R. LINDEN and E. S. PETTYJOHN, Inst. Gas Technology Research Bull. No. 2 (April, 1952), No. 9 (March, 1952) 9. H. R. LINDEN and J. M. REID, Petrol. Refin. 35, No. 6, 189, 1956
Influence of gasoline composition on pyrolysis products
489
10. E. B. SCHULTZ and H. R. LINDEN, Industr. Engng. Chem. 49, No. 12, 2011, 195 11. S. ANDO a n d M. UCHIDA, Ann. Rept. Engng Res. Inst. Fac. Engng Univ., Tokyo, 16, No. 1, 72, 1957 12. M. KOSHINO and H. IMAI, Repts. Govt. Industr. Res. Inst., Nagoya, No. 7, 771, 1958; No. 11,847, 1958 13. M. KOS/HNO and H. IMAI, Repts. Govt. Industr. Res. Inst., Nagoya, No. 4, 179, 1960 14. J. PROCHAZKA and P. MIKULAS, Chem. prdmysl, 10 (35), No. 2, 59, 1960 15. M. A. D~,IJIN, R. S. BURMISTROVA and K. D. TANIYANTS, Khim. prom. No. 6, 9, 1958 16. S. D. MEKHTIYEV and Yu. G. KAMBAROV, Dokl. Akad. Nauk Az SSR 15, No. 2, 125, 1959 17. S. D. MEKHTIYEV and Yu. G. KAMBAROV, Azerb. khim. zh. No. 5, 13, 1959 18. Yu. G. KAMBAROV, Isslvdovaniye termicheskogo razlozheniya nekotorykh individ u a l ' n y k h uglevodorodov i neftyanykh fraktsii. (Investigation of the Thermal Decomposition of some Individual Hydrocarbons and Petroleum Fractions.) Author's abstract, Baku, 1960 19. R. DENVENPORT, Petrol. Refin. 39, No. 3, 126, 1960 20. G. KRECELER, ErdS1 u. Kohle, 12, No, 5, 353, 1959 21. G. WENGLER and H. ZEININGER, Chem.-Ing.-Tech. 33, No. 5, 301, 1961 22. J. H. PATTON, G. C. GRUBL and K. F. STEPHENSON, Petrol. Refin. 37, No. 11, 180, 1958 23. G. GEISELER, R. KUSCHMIERS and H. REINHARD, Chem. Technik 11, No. 12, 656, 1959 24. World Petrol 30, No. 6, P a r t 2, 62, 1959 25. K. P. LAVROVSKII and A. M. BRODSKII, Khim. n a u k a i prom. 2, No. 2, 189, 1957 26. G. KRECELER, Petrol. Refin. 34, No. 10, 139, 1955
(Received 29 April 1962) IN VIEW of the use of gasoline fractions of various molecular weights as raw materials for the production of ethylene, propylene, and butylene, the elucidation of the influence of the fractional composition of the initial raw material on the distribution of the products of its pyrolysis is an important question. There is some information in the literature on the influence of the fractional composition of the raw material on the yield of pyrolysis products. Thus, on the basis of laboratory investigations a series of relationships for the conversion and distribution of the gaseous products obtained as functions of the velocity and temperature of the pyrolysis process for different types of raw materials has been given [1-13]. Literature data on the pyrolysis of hydrocarbon fractions in semi-industrial tube furnaces show that under the optimum conditions for each type of raw material the yield of olefms does not substantially depend on the fractional composition of the raw material. The yield varies within the range of one order of magnitude and the course of the reaction depends in the first place on the parameters of the process [14-15]. Analogous relationships have been obtained in a high-velocity cracking apparatus with an internal heater [16-18]. Generalized results characterizing the approximate yields of ethylene, propylene, and resin in the pyrolysis of various types of raw material in tube furnaces are given in Table 1 [19]. The data clearly show a tendency for a reduced yield of olefins as the raw material becomes heavier. Contradictory results have been obtained on the influence of the fractional composition of the raw material pyrolysed on the yield of pyrolysis gas and the composition of the final products from investigations carried out in tube furnaces in the presence of superheated steam [20, 21]. In one case, the yield of C2 gases first rose as the number of carbon atoms in the raw material increased (up to about C10) and fell gradually only for v e r y long chains. In the other case it was found that the maximum yields of gas, olefins, and ethane were greater when light gasoline was pyrolysed; when * Neftekhimiya 2, No. 5, 723-729, 1962.
481
482
T. N. MUKHINAand S. YE. ITSEK TABLE I. YIELDS OF THE PYROLYSIS PRODUCTS IN THE TREATMENT OF DIFFERENT TYPES OF RAW MATERIALS
Raw material
Ethane Propane n-Butane Natural gasoline Gas condensate Crude petroleum
Yield, calculated on the raw material passed, % by weight Ethylene
Propylene
Pyrolysis resin
50-55 44-45 32-35 27-30 20-25 6-11
1-2 15-20 17-22 12-16 10-12 6-12
0 5-15 6-9 25-30 35-40 30-40
h e a v i e r fractions were pyrolyscd higher yields of methane, acetylene, divinyl, l i q u i d products, and coke were obtained. I n the production of acetylene by the method given by P a t t o n et al. [22], in addition to ligroin, in m a n y experiments liquid hydrocarbon fractions with a wide boiling range, and also propane, were used. The composition and yield of the products were similar in all cases. The pyrolysis of gasoline fractions with different C/H ratios has been investigated in a number of industrial systems: by the Catarol method [23], t h e Lurgi-Ruhrgas-Bayer method [24], by high-velocity cracking methods [25], and by the Farbwerke Hoechst method [26]. I t was found that the composition of the gases was approximately constant for different types of raw material when the processes were carried out under similar conditions. These results are isolated, relate to dissimilar industrial systems, and give no clear and unambiguous idea of the main features of the distribution o f the products in the pyrolysis of raw materials of different fractional corn, positions. T h e necessity of establishing definite results on the pyrolysis o f raw materials of different fractional compositions expressed graphically in the form of the composition of the pyrolysis products as functions of the molecular weight or the C/H ratio and of the parameters of the process was the reason for the present investigation.
EXPERIMENTAL
The raw materials used were 30-70 °, 70-120 ° , 120-140 ° , and 140-170 ° fractions isolated by the distillation of gasoline from straight-distilled Ro~ mashkin0 petroleum in a rectifying column with an efficiency of 40 theoretical plates. The characteristics of these fractions are given in Tables 2 and 3. The fractions had similar chemical compositions, corresponding to the following contents of different types of hydrocarbons: paratrms--63% by weight, n a p h t h e n e s - - 3 1 ~ by weight, a r o m a t i c s - - 6 ~ by weight.
Influence of gasoline composition on pyrolysis products
483
i
TABLE 2. FRACTIONAL00ilil~ITION (ENOLER DISTILLATION) Fraction, °C ~o Distilled Initial boiling point 10 20 30 40 50 60 70 80 90 Final boiling point
30-70° I 70-120° I 120-140° I 140-170 ° Temperature, °C 31.0 49.0 51.0 53-0 55.0 57.0 60.0 61-0 64.0 66.2 70.0
70.0 81.5 86.5 88.0 90.5 92.5 96.0 98-5 103.5 108.0 120.0
120.0 126.5 127.0 127.5 128.0 128.5 129.5 130.5 132.0 138.0 140-0
139-0 146.0 147.0 148-0 149.0 150.0 152.0 154.0 157.0 161.0 170.0
TABLE 3. CHARACTERISTICSOF THE FRACTIONS Fraction, °C Molecular weight Specific gravity C/H ratio
30-70 ° 80.5 0.668 5.39
70-120 ° 97-8 0.713 5-6
120-140 ° 117.0 0.743 5.73
140-170 ° 131-5 0.761 5.82
The fractions were subjected to pyrolysis in a q u a r t z r e a c t o r placed in a t u b e furnace. Before passing into the reactor, t h e raw material a n d w a t e r were e v a p o r a t e d in a q u a r t z e v a p o r a t o r . T h e pyrolysis was carried o u t a t t e m p e r a t u r e s o f 700-800 ° w i t h a c o n t a c t t i m e o f 0.2 to 1.0 sec, using 25°/o b y weight o f steam, calculated on the raw material. T h e pyrolysis gas was a n a l y s e d c h r o m a t o g r a p h i c a l l y on a K h P A - 2 apparatus. F o r convenience in comparison, t h e e x p e r i m e n t a l results on t h e yields o f p r o d u c t s o b t a i n e d in t h e pyrolysis o f raw materials o f different fractional compositions were r e p r e s e n t e d as a f u n c t i o n of the s e v e r i t y f a c t o r o f t h e process. T h e s e v e r i t y f a c t o r characterizes t h e d e p e n d e n c e o f the composition o f t h e pyrolysis gas o n t h e p a r a m e t e r s o f t h e p r o c e s s - - t e m p e r a t u r e a n d c o n t a c t time. I t was f o u n d t h a t the s e v e r i t y is expressed in the f o r m o f the equation It ==tT0"06 , where t is the t e m p e r a t u r e in °C a n d ~ is t h e c o n t a c t t i m e in sec. Table 4 gives t h e calculated values o f t h e s e v e r i t y tt for each set o f conditions for c a r r y i n g o u t t h e pyrolysis process.
484
T. N. MUKHINAa n d S. YE. ITSlZK
On analysing the relationship between the change in the concentration of the components of the pyrolysis gas and the C/H ratio in the raw material (Fig. 1, a, b) it can be seen that the composition of the pyrolysis gas changes only slightly. Thus, as the molecular weight of the initial raw material changes from 80.5 to 131.5 (which corresponds to an increase in the C/H ratio from
2
6"~
6.6
C/x rat~ @ ~ t / n
5'B
5.82
t ~ raw
FIG. 1. Dependence of the composition o f the pyrolysis gas on the C/H ratio in the raw material at the values of the severity factor ~t: a--713; b--765.
5.39 to 5.82) the concentration of hydrogen falls from 19-3 to 15.5% by col. at a severity ~=765 and from 17.1 to 13.0~ by volume at ~=713. The concentration of methane and of the propane-propylene and butane-butylene fractions falls slightly as the C/H ratio in the raw material increases. The content of ethane and ethylene in the gas increases as the raw material becomes heavier. Thus, the concentration of ethylene in the pyrolysis of a
Influence of gasoline composition on pyrolysis products
485
gasoline with a molecular weight of 80.5 amounts to 27.8~/o and that of ethane to 3 . 9 ~ by vol.; in the pyrolysis of a gasoline with a molecular weight of 131.5 the amount of ethylene in the gas is 29.2~ by vol. and the amount of ethane is 4.9% by vol. By comparing the amounts of gas formation obtained in the pyrolysis of gasoline fractions at different values of the severity of the process, i~, it is possible to show a decrease in the gas formation on passing from a lighter to a heavier raw material. Thus, at a severity 1~----765, the yield of gases from the pyrolysis of the 30-70 ° fraction is 8 7 ~ by weight, from the 70-120 ° fraction it is 83~/o by weight, from the 120-140 ° fraction 77°/o by weight, and from the 140-170 ° fraction 75% by weight. In the pyrolysis of different hydrocarbon fractions, a considerable change in the amount of gas formed, with its composition remaining approximately constant, leads to a change in the yields of the components calculated on the raw material passed. These changes are illustrated in Fig. 2, a, b, c, which gives the dependence of the changes in the yields of the components on an increase in the C/H ratio at severity factors 1~--~690, 765, and 797. At these values of the severity factor the distribution of the pyrolysis products is constant. From an analysis of the data corresponding to severity p=765 (Fig. 2c) it follows that the yields of pyrolysis products depend on the fractional composition of the raw material. On comparing the yields obtained in the pyrolysis of the 30-70 and 140-170 ° fractions (with C/H ratios of 5.39 and 5-82, respectively), a fall in the yield of the methane-hydrogen fraction from 20.7~ by weigt to 18.4~o by weight is found. At the same time, the yield of ethylene falls from 3 0 ~ by weight to 27.2~ by weight, the yield of propylene from 18.5 to 14.6 ~ by weight, and the combined yield of butylenes from 8.5 to 5 . 0 ~ by weight. On passing from a light to a heavier raw material a marked rise in resin formation is found. A consideration of Figures 3a, b, c, and d, which show the yield of olefins as a function of the severity factor for gasoline of various fractional compositions, permits the optimum conditions for a pyrolysis process directed to the production of either ethylene or propylene or the butylenes to be selected. By analysing the graphs given above it is possible to state that the curves of the yields of the components of the pyrolysis gas pass through a maximum corresponding to a single value of the severity factor of the process for different hydrocarbon fractions. Thus, it follows from Fig. 3a that the maximum yield of ethylene is obtained at the same value of the severity factor 11-~785 for all the fractions pyrolysed. The maxim u m yield of propylene (Fig. 3b) is considerably displaced to the left (in comparison with the maximum for ethylene) in the direction of milder conditions and corresponds to a severity 11=735. The maximum yields of the butylenes are obtained at it----720 (Fig. 3c). The optimum figures for the combined unsaturated hydrocarbons are obtained at a severity ~= 755 (Fig. 3d).
486
T . N . MUKHINA and S. Y z . ITSZK
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FIO. 2. Influence of the C/H ratio by ~ i g h t on the yields of pyrolysis products at the following values of the severity factor ~: a--797; b--690; e--765.
Influence of gasoline c o m p o s i t i o n on pyrolysis p r o d u c t s 20
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FIG. 3. Izffluence o f t h e s e v e r i t y factor in t h e pyrolysis o f various gasoline f r a c t i o n s ' o n t h e yield of olefins: a - - e t h y l e n e ; b - - p r o p y l e n e ; c - - b u t y l e n e s ; d - - t o t a l u n s a t u r a t e d h y d r o carbons. 1 - - 3 0 - 7 0 ° fraction; 2 - - 7 0 - 1 2 0 ° fraction; 3 - - 1 2 0 - 1 4 0 ° fraction; 4 - - 1 4 0 - 1 7 0 ° fraction.
It follows from the Figures that the severity figures mentioned for each fraction correspond to the optimum yields given in Table 5. TABLE 4. DEPENDENCE OF THE SEVERITY FACTOR ~t ON THE PARAMETERS OF THE PYROLYSIS PROCESS
T e m p e r a t u r e , °C C o n t a c t time, sec Severity factor
800
750
700
0.28 0.57 0.94 740 765 797
0.25 0.43 0.74 690 713 736
0-18 0-30 0.52 630 650 674
488
T . N . MUKHINA a n d 8. Y E . ITSEK
TABLE 5. OPTIMUM YIELDS OF UNSATURATEDHYDROCARBONS OBTAINED IN THE PYROLYSIS OF GASOLINES OF DIFFERENT FRACTIONAL COMPOSITIONS, CALCULATED ON T H I RAW MATERIAL PASSED (% B y WEIGHT)
Fr. 30_70 °
Components Ethylene Propylene Butylenes C H2~
! !
30"3 19"3 10.2 57.0
Fr. 70__120°
Fr. 120__140°
Fr. 140_170 °
29"2 16"9 7"8 52"2
28-0 15"1 6'5 47"6
26"2 14"2 5"7 45"5
785 735 720 755
SUMMARY 1. An investigation has been carried o u t of the pyrolysis o f t h e following fractions o f straight-distilled gasoline: 30-70 °, 70-120 °, 120-140 °, a n d 140170°C. 2. Certain features o f the influence o f the fractional composition o f the initial raw material on the n a t u r e o f t h e distribution o f their pyrolysis p r o d u c t s h a v e b e e n established: (a) the composition o f the gas changes o n l y slightly with a v a r i a t i o n in the fractional composition o f the initial raw material; (b) t h e fractional composition o f the initial raw material has a considerable influence o n t h e a m o u n t o f gas formed, which decreases w h e n t h e molecular weight o f t h e initial raw material increases u n d e r similar process conditions; (c) the yield o f c o m p o n e n t s o f the pyrolysis gas decreases on passing f r o m lighter t o heavier r a w material; a n d (d) as t h e C]H ratio in the raw material rises, the f o r m a t i o n o f coke considerably increases. 3. T h e results o b t a i n e d m a k e it possible, w i t h o u t c a r r y i n g o u t a n y supp l e m e n t a r y e x p e r i m e n t a l investigations, to establish t h e possible distribution o f t h e pyrolysis p r o d u c t s o f a raw material o f a n y p a r t i c u l a r fractional composition. Translateat by B. J. HAZZARD REFERENCES 1. H. R. LINDEN and R. pEglq~ Industr. Engng. Chem. 47, No. 12, 2470, 1955 2. H. R. LINDEN and J. M. RigID, Chem Engng. Progr. 55, No. 3, 71, 1959 3. J. M. REID and H. R. LINDEN, Chem. Engng. Progr. 56, No. 1, 47, 1960 4. H. R. LINDEN, Petrol. Process. 6, 1389, 1396, 1951 5. H. R. LINDEN, High Temperature Vapor Phase Cracking of Hydrocarbons Dissertation. Institute of Technology, Chicago, 1952 6. H. R. LINDEN, N. G. BAIR and E. S. PETTYJOHN, Amer. Gas. Assoc. Prec., 616, 1954 7. H. R. LINDEN and E. S. PETTYJOHN, Amer. Gas Assoc. Prec. 553, 1951 8. H. R. LINDEN and E. S. PETTYJOHN, Inst. Gas Technology Research Bull. No. 2 (April, 1952), No. 9 (March, 1952) 9. H. R. LINDEN and J. M. REID, Petrol. Refin. 35, No. 6, 189, 1956
Influence of gasoline composition on pyrolysis products
489
10. E. B. SCHULTZ and H. R. LINDEN, Industr. Engng. Chem. 49, No. 12, 2011, 195 11. S. ANDO a n d M. UCHIDA, Ann. Rept. Engng Res. Inst. Fac. Engng Univ., Tokyo, 16, No. 1, 72, 1957 12. M. KOSHINO and H. IMAI, Repts. Govt. Industr. Res. Inst., Nagoya, No. 7, 771, 1958; No. 11,847, 1958 13. M. KOS/HNO and H. IMAI, Repts. Govt. Industr. Res. Inst., Nagoya, No. 4, 179, 1960 14. J. PROCHAZKA and P. MIKULAS, Chem. prdmysl, 10 (35), No. 2, 59, 1960 15. M. A. D~,IJIN, R. S. BURMISTROVA and K. D. TANIYANTS, Khim. prom. No. 6, 9, 1958 16. S. D. MEKHTIYEV and Yu. G. KAMBAROV, Dokl. Akad. Nauk Az SSR 15, No. 2, 125, 1959 17. S. D. MEKHTIYEV and Yu. G. KAMBAROV, Azerb. khim. zh. No. 5, 13, 1959 18. Yu. G. KAMBAROV, Isslvdovaniye termicheskogo razlozheniya nekotorykh individ u a l ' n y k h uglevodorodov i neftyanykh fraktsii. (Investigation of the Thermal Decomposition of some Individual Hydrocarbons and Petroleum Fractions.) Author's abstract, Baku, 1960 19. R. DENVENPORT, Petrol. Refin. 39, No. 3, 126, 1960 20. G. KRECELER, ErdS1 u. Kohle, 12, No, 5, 353, 1959 21. G. WENGLER and H. ZEININGER, Chem.-Ing.-Tech. 33, No. 5, 301, 1961 22. J. H. PATTON, G. C. GRUBL and K. F. STEPHENSON, Petrol. Refin. 37, No. 11, 180, 1958 23. G. GEISELER, R. KUSCHMIERS and H. REINHARD, Chem. Technik 11, No. 12, 656, 1959 24. World Petrol 30, No. 6, P a r t 2, 62, 1959 25. K. P. LAVROVSKII and A. M. BRODSKII, Khim. n a u k a i prom. 2, No. 2, 189, 1957 26. G. KRECELER, Petrol. Refin. 34, No. 10, 139, 1955