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Oxidative dehydrogenation of ethylbenzene on vanadium-magnesium oxide catalysts
144
R.N. VOLKOVet aL
9. J. KNOTERUS J. Inst. Petrol. 43, 307, 1957 10. A. A. POLYAKOVA, Molekularnyi mass-spektral'nyi analiz neftei, p. 130, Nedra, Moscow, 1973 11. AI. A. PETROV, Khimiya alkanov, pp. 204, 213, Nauka, Moscow, 1974 12. N. B. VASSOYEVICH, A. N. GUSEVA and I. E. LEIFMAN, Geokhimiya, 7, 1075, 1976 13. G. BREI and G. EVANS, Uglevodorody v materinskikh ottozheniyakh. Symp.: Organicheskaya geokhimiya, pp. 2, 93, Nedra, Moscow, 1970 14. G. EGLINTON, Organicheskaya geokhimiya (Ed. G. Eglinton and T. M. G. Murphy) p. 29, Nedra, Leningrad, 1974
Petrol. Chem. U.S.S.R. Vol. 25, No. 3, pp. 1'44-148, 1985 Printed in Poland
0031-6458/85 $10.00 + .00 © Pergamon Journals Ltd.
OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE ON VANADIUM-MAGNESIUM OXIDE CATALYSTS* R. N. VOLKOV, V. P. PANOVA, I. P. BELOMESTNYKI-I,G. V. SHAKHNOVICHand
~. V. ISAGULYANTS N. D. Zelinskii Institute of Organic Chemistry, U.S.S.R. Academy of Sciences Voronezh Branch of the S. V. Lebedev All-Union Scientific Research Institute of Synthetic Rubber Manufacture (Received 2 January 1984)
PREVIOUS studies [1, 2] showed that vanadium-magnesium oxide catalysts are highly active and selective for the oxidative dehydrogenation of ethylbenzene to styrene. The present work investigates catalyst stability under conditions of continuous operation without recovery. EXPERIMENTAL
Oxidative dehydrogenation was carried out in an adiabatic reactor consisting of five sections (50 x 1850 mm), each section carried an electrically heated lining, a thermocouple and connecting pipes for the supply of air, steam and for sampling; the first section was filled with Raschig rings and served as a mixer. The vanadium-magnesium oxide catalyst prepared by mixing a m m o n i u m metavanadate or vanadium pent0xide, modifying components and magnesium oxide, * Neftekhimiya 25, No. 4, 468--471, 1985.
Oxidative dehydrogenation of ethylbenzene
145
followed by calcination of the component" mixture at 550°C and forming pellets (d 5 ram), has the following characteristics: specific surface 110 m2/g, overall pore volume 0.7 cma/g, the predominant dimensions being 150 to 500 fit and strength100 kg/cm 2. Equal volumes of the catalyst were placed into each section (overall catalyst volume being 1600 ml) or a continuous layer used (2200 ml). Ethylbenzene and steam were led into an evaporator, where the steam mixture was heated to approximately 400°C, then channelled ilato the first section of the reactor. The content gas was cooled stepwise with water and salt ice (at - 5°C); the hydrocarbon/water layer was then separated and uncondensed gases discarded to atmosphere. The hydrocarbon cat alysate and gaseous reaction components were analysed chromatographically [2]. After vacuum distillation of volatile hydrocarbons the content of "heavy residue" in the catalysate [3] was determined gravimetrically. The catalysate "heavy residue" later determines the "vat residue of styrene rectification" (VRSR), an important economic indicator of styrene production. The aqueous layer of the catalysate was examined by UV [4] to find the content of aromatic hydrocarbons and oxygen-containing compounds. RESULTS
Oxidative dehydrogenation experiments were carried out while varying the space velocity of ethylbenzene (Veb being 0.35 to 1.2 hr -1, the molar ratio of oxygen and steam to ethylbenzene ranging from 0.8 to 1-2 and from 7 to 20, respectively) with different sectional distribution of oxygen. Product composition (Table 1) indicates that by-products (carbon dioxide, benzene, methane and unsaturated light hydrocarbons) are formed in small quantities. Only low levels of phenol (less than 0.2 wt. in terms of ethylbenzene) are present in the aqueous condensate. Two series of experiments were carried out with different amounts of catalyst, differing space velocities of ethylbenzene and dilution of ethylbenzene with steam. In the second column of Table 2, where experimental results are shown, the temperature ranges in the catalytic zones are indicated, the maximum corresponds to the temperature of the second and third sections, while in the remaining sections it is nearer to the minimum. Catalytic product yield is close to the theoretical value (considering COz). In the first series of experiments (1-5) where ethylbenzene was diluted with steam (1 : 7) and at space velocities of ethylbenzene of 0.7 to 1-2 hr -1, the temperature briefly increased spontaneously in the catalyst layer (above 560°C), particularly in the start-up period; styrene yields were high and the catalyst worked constantly for a long period of time. Increasing the temperature of the first catalytic zone to 580°C (experiment 4), increased the amount of "heavy residue", styrene content in the catalysate did not increase and process selectivity decreased. Increasing the oxygen to ethylbenzene ratio from 1.1 to 1.3 reduced process selectivity both as a result of accelerated formation of CO2 and due to benzene (to 3 wt. ~o). With an ini-
146
R . N . VOLKOVe t aL
TABLE 1. COMlaOSITIONOF PRODUCTS OF OXIDATIVEDEHYDROGENATIONOF ETHYLBENZENE Composition of gaseous products, vol.
Composition Of the catalysate, I
benzene
0.6 1"0 2"4 2"7 3"1
TABLE 2.
oxygen-conethylstyrene i taining comtoluene benzene pounds 58"0 0'2 0"1 41.1 62"3 0"3 0"2 36;2 62"7 0-2 0"2 34"5 74.8 0"3 0'1 22.1 •77"8 0"2 0"1 18.8
EFFECT OF EXPERIMENTAL
C02
02
5'0 6"7 8'4 10'0 8'0
3"6
CONDITIONS ON OXIDATIVE
3"1 1"6 2"0 3"6
CO
0"4 ---
Heavy C1-C2 residue, hydro- wt. 7o carbons 0.4 2'2 2.9 0.4 1"0 0.2 2"2 0-5 1"6 0"4
DEHYDROGENATION OF ETHYL-
BENZENE
No. of expt. 1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
°C t,
Vob. h r - 1
560--480 I 0"7 560--480 0"7 560-480 "0"7 580--480 0"7 560--480 ti 1"2 490-470 0"35 490-470 0"35 490-470 0.35 490-470 I 0"35 530-470 0"35 490-470 0"35 490-470 0'35 490-470 0"35 490-470 0-35 590-470 0"5 590-470 0"5
Eb : O2 : H20 (mole) 1:0'8:7 1:1"1:7 1:1.3:7 1:1'1:7 1:1"0:7 1 : 1"0 :.13 1 : 1 : 17"6
1:1:20 1:1:20 1 : 1 : 22"5 1 : 0"7 : 20 1:0"8:20 1:I:20 1 : 1'2:20 1:1.2:15 1:1:15
Styrene yield, wt. ~
Heavy residue, wt. ~
55 68 64 62 57 50 55 61 6O 65 48 5O 61 74 71 65
0"4 0"3 0"8 0"8 0"4 0-3 0"3 0"3 0'3 0"2 0"1 0"2 0"2 0"3 0-4 0"4
Selectivity, 93 91 86 86 92 89 89 89 91 90 92 91 91 90 89 90
Note. In experiments 1-5 the catalyst sample weighed 1600ml, in other experiments- 2200 ml. In experiments 9 and 12 air distribution was in sections ( 2 5 ~ o f the total amount), in other experinaents---40, 30, 20 a n d 107o in seetons 2 to 5, respectively.
tial c o m p o n e n t r a t i o (of ethylbenzene, oxygen a n d steam) o f 1 : 1, 1 : 7 a n d a s p a c e velocity o f 0.7 h r -1, t h e s t y r e n e c o n t e n t in the catalyst l a y e r i n c r e a s e d i r r e g u l a r l y a n d was d i s t r i b u t e d in the sections as follows: in the s e c o n d section 15-20 wt. 70, in the t h i r d 25-30 w t . ~ , in the f o u r t h 12-15 w t . ~ a n d the fifth 10-12 w t . ~ a n d a styrene c a t a l y s a t e c o n t e n t o f 70-75 wt. ~ . T h e catalyst survived u n d e r these c o n d i tions f o r m o r e t h a n 5000 h r w i t h o u t r e g e n e r a t i o n a n d activity a n d selectivity s h o w e d no reduction. T h e s e c o n d series o f e x p e r i m e n t s (see e x p e r i m e n t s 6 t o 16) was c a r r i e d o u t a t l o w e r space velocities o f e t h y l b e n z e n e a n d h i g h e r dilutions o f e t h y l b e n z e n e with steam, w h e n t e m p e r a t u r e in the catalyst l a y e r c h a n g e d slightly.
Oxidative dehydrogenation of ethylbenzene
147
As the reaction mixture was diluted further with steam (experiments 6 to 9) when veb was 0.35 hr- 1 the conversion to styrene increased, however, it only reached maximum value, with a simultaneous increase of oxygen concentration, at an oxygen to ethylbenzene ratio of 1-2 (experiment 14). Changing oxygen distribution in the catalytic zones from steady to a distribution decreasing in the layer in a ratio of 4 : 3 : : 2 : 1 had practically no effect on process indices. Simular results were obtained under these conditions also at a space velocity of ethylbenzene of 0.5 hr -1 (experiment 15). Tests in the second series of experiments took 1600 hr, and catalyst activity remained constant during this time. Therefore, during oxidative dehydrogenation of ethylbenzene in a pilot plant using a vanadium-magnesium oxide catalyst, styrene was obtained with a yield of up to 74 wt. ~ at a selectivity of 90 ~. The catalyst worked steadily without marked evolution of heat for a prolonged period of time. Reaction conditions for oxidative dehydrogenation (space velocity of ethylbenzene, ratio of ethylbenzene and steam) were similar to conditions for industrial synthesis of styrene on an iron-chromiumpotassium catalyst [5], but contact temperature was much lower (480°-500°C instead of 600°-620°C). During oxidative dehydrogenation with a dilution of initial components steam was used at 400°C instead of 650°-700°C, required for catalytic preparation of styrene. Results of testing the catalyst using a pilot plant and the kinetic model of the process previously obtained using this catalyst [6], formed the basis for simulating an industrial adiabatic, large capacity, four-section reactor [7]. Calculations show that carrying out the reaction under conditions corresponding to the first series of experiments (initial component ratio 1 : 1 : 7), in a large capacity reactor seems to increase temperature considerably, for practically all conditions examined (above 650°C) at the outlet from the second section of the reactor. This is undesirable since previous process studies showed a reduction in activity and selectivity for catalysts subjected to high temperature. Calculation of temperatures in the catalyst layer by the simulation of an industrial reactor using data obtained for the second test series showed that no adiabatic heating resulting in a marked temperature rise takes place in this case. Calculations enable conditions (1 : 1 : 7 ratio) to be recommended as optimum even for large capacity reactors, which had been adopted in the second series of tests. SUMMARY
1. Oxidative dehydrogenation of ethylbenzene to styrene at 470°-500°C was studied on a vanadium-magnesium oxide catalyst : at an ethylbenzene s.v. of 0.35 to 1"2 hr -1 and ratios ofethylbenzene: oxygen : steam of 1 : 0.8 to 1.3 : 7 to 20. Stlcrene yield reached 74 ~ , with a process selectivity of 90 ~ . 2. The catalyst showed a high operating stability during 5000 hr without regeneration. 3. The following is recommended for simulating an industrial reactor: ethylbenzene : 02 : H 2 0 ratio of 1:1 : 7, C8 s.v. =0"35 hr -~ at 470°~90°C.
148
O.M. RI~VENKOet al. REFERENCES
1. L P. BELOMESTNYKH, O. K. BOGDANOVA and G. V. SHAKHNOVICH, A.c. SSSR, No. 522851, Claim submitted on 21.05.75, Pub1. in Byul. izobr., No. 28, 7, 1976 2. I. P. BELOMESTNYKH, G. V. SHAKHNOVICH, O. K. BOGDANOVA, R. N. VOLKOV and V. P. PANOVA, Neftekhimiya 17, 6, 829, 1977 3. N. V. GARMANOV, Analiz produktov proizvodstva sinteticheskikh kauchukov, p. 239, Khimiya, Leningrad, 1957 4. E. SHTERN and K. TIMMONS, Elektronnaya adsorbtsionnaya spektroskopiya v organicheskcSi khimi~, p. 295, Mir, Moscow, 1974 5. Ch. TOMAS, Promyshlennyye kataliticheskiye protsessy i effektivnyye katalizatory, p. 77, Mir, Moscow, 1973 6. G. V. SHAKHNOVICH, I. P. BELOMESTNYKH, N. V. NEKRASOV, M. M. KOSTYUKOVSKII, R. N. VOLKOV, V. P. PANOVA and S. L. KIPERMAN, Kinetika i kataliz 24, 4, 870, 1983 7. N. V. KOL'TSOV, S. A. GRIN' and I. P. BELOMESTNYKH, Mater. Vsesoyuz. konf. "Khimreaktor-8", Chimkent, 1, p. 182, 1983
Petrol. Chem. U.S.S.R. Vol. 25, No. 3, pp. 148-154, 1985 Printed in Poland
0031-6458/85 $10.00+ .00 © Pergamon Journals Ltd.
OXIDATIVE METHYLATION OF TOLUENE* O. M. REVENKO, KH. YE. KHCHEYAN, M. P. TIKHONOVAand A. V. BORISOGLEBSKAYA All-Union Scientific Research Institute of Organic Synthesis (Received i0 August 1984)
T n s oxidative methylation of toluene is a radical-chain reaction, which takes place by a system with degenerate branching [1-3]. In the initial stage toluene consumption and the formation of end products such as benzene, styrene and phenols, increases by the principle e -or. The entire reaction over a period of time in relation to overall toluene conversion, is described by N. N. Semenov's equation for nonsteady-state branched reactions and reactions with degenerate branching. A l d e h y d e s - b e n z a l d e h y d e and formaldehyde, as well as other end-products are present in the condensate. A parallel is observed between the current concentration of aldehyde and the variation of reaction rate. Maximum rate is achieved by establishing fixed concentration of bot h benzaldehyde and formaldehyde. The presence o f two aldehydes which, according to generally accepted theories, are formed by * Neftekhimiya 25, No. 4, 475--480, 1985.
R.N. VOLKOVet aL
9. J. KNOTERUS J. Inst. Petrol. 43, 307, 1957 10. A. A. POLYAKOVA, Molekularnyi mass-spektral'nyi analiz neftei, p. 130, Nedra, Moscow, 1973 11. AI. A. PETROV, Khimiya alkanov, pp. 204, 213, Nauka, Moscow, 1974 12. N. B. VASSOYEVICH, A. N. GUSEVA and I. E. LEIFMAN, Geokhimiya, 7, 1075, 1976 13. G. BREI and G. EVANS, Uglevodorody v materinskikh ottozheniyakh. Symp.: Organicheskaya geokhimiya, pp. 2, 93, Nedra, Moscow, 1970 14. G. EGLINTON, Organicheskaya geokhimiya (Ed. G. Eglinton and T. M. G. Murphy) p. 29, Nedra, Leningrad, 1974
Petrol. Chem. U.S.S.R. Vol. 25, No. 3, pp. 1'44-148, 1985 Printed in Poland
0031-6458/85 $10.00 + .00 © Pergamon Journals Ltd.
OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE ON VANADIUM-MAGNESIUM OXIDE CATALYSTS* R. N. VOLKOV, V. P. PANOVA, I. P. BELOMESTNYKI-I,G. V. SHAKHNOVICHand
~. V. ISAGULYANTS N. D. Zelinskii Institute of Organic Chemistry, U.S.S.R. Academy of Sciences Voronezh Branch of the S. V. Lebedev All-Union Scientific Research Institute of Synthetic Rubber Manufacture (Received 2 January 1984)
PREVIOUS studies [1, 2] showed that vanadium-magnesium oxide catalysts are highly active and selective for the oxidative dehydrogenation of ethylbenzene to styrene. The present work investigates catalyst stability under conditions of continuous operation without recovery. EXPERIMENTAL
Oxidative dehydrogenation was carried out in an adiabatic reactor consisting of five sections (50 x 1850 mm), each section carried an electrically heated lining, a thermocouple and connecting pipes for the supply of air, steam and for sampling; the first section was filled with Raschig rings and served as a mixer. The vanadium-magnesium oxide catalyst prepared by mixing a m m o n i u m metavanadate or vanadium pent0xide, modifying components and magnesium oxide, * Neftekhimiya 25, No. 4, 468--471, 1985.
Oxidative dehydrogenation of ethylbenzene
145
followed by calcination of the component" mixture at 550°C and forming pellets (d 5 ram), has the following characteristics: specific surface 110 m2/g, overall pore volume 0.7 cma/g, the predominant dimensions being 150 to 500 fit and strength100 kg/cm 2. Equal volumes of the catalyst were placed into each section (overall catalyst volume being 1600 ml) or a continuous layer used (2200 ml). Ethylbenzene and steam were led into an evaporator, where the steam mixture was heated to approximately 400°C, then channelled ilato the first section of the reactor. The content gas was cooled stepwise with water and salt ice (at - 5°C); the hydrocarbon/water layer was then separated and uncondensed gases discarded to atmosphere. The hydrocarbon cat alysate and gaseous reaction components were analysed chromatographically [2]. After vacuum distillation of volatile hydrocarbons the content of "heavy residue" in the catalysate [3] was determined gravimetrically. The catalysate "heavy residue" later determines the "vat residue of styrene rectification" (VRSR), an important economic indicator of styrene production. The aqueous layer of the catalysate was examined by UV [4] to find the content of aromatic hydrocarbons and oxygen-containing compounds. RESULTS
Oxidative dehydrogenation experiments were carried out while varying the space velocity of ethylbenzene (Veb being 0.35 to 1.2 hr -1, the molar ratio of oxygen and steam to ethylbenzene ranging from 0.8 to 1-2 and from 7 to 20, respectively) with different sectional distribution of oxygen. Product composition (Table 1) indicates that by-products (carbon dioxide, benzene, methane and unsaturated light hydrocarbons) are formed in small quantities. Only low levels of phenol (less than 0.2 wt. in terms of ethylbenzene) are present in the aqueous condensate. Two series of experiments were carried out with different amounts of catalyst, differing space velocities of ethylbenzene and dilution of ethylbenzene with steam. In the second column of Table 2, where experimental results are shown, the temperature ranges in the catalytic zones are indicated, the maximum corresponds to the temperature of the second and third sections, while in the remaining sections it is nearer to the minimum. Catalytic product yield is close to the theoretical value (considering COz). In the first series of experiments (1-5) where ethylbenzene was diluted with steam (1 : 7) and at space velocities of ethylbenzene of 0.7 to 1-2 hr -1, the temperature briefly increased spontaneously in the catalyst layer (above 560°C), particularly in the start-up period; styrene yields were high and the catalyst worked constantly for a long period of time. Increasing the temperature of the first catalytic zone to 580°C (experiment 4), increased the amount of "heavy residue", styrene content in the catalysate did not increase and process selectivity decreased. Increasing the oxygen to ethylbenzene ratio from 1.1 to 1.3 reduced process selectivity both as a result of accelerated formation of CO2 and due to benzene (to 3 wt. ~o). With an ini-
146
R . N . VOLKOVe t aL
TABLE 1. COMlaOSITIONOF PRODUCTS OF OXIDATIVEDEHYDROGENATIONOF ETHYLBENZENE Composition of gaseous products, vol.
Composition Of the catalysate, I
benzene
0.6 1"0 2"4 2"7 3"1
TABLE 2.
oxygen-conethylstyrene i taining comtoluene benzene pounds 58"0 0'2 0"1 41.1 62"3 0"3 0"2 36;2 62"7 0-2 0"2 34"5 74.8 0"3 0'1 22.1 •77"8 0"2 0"1 18.8
EFFECT OF EXPERIMENTAL
C02
02
5'0 6"7 8'4 10'0 8'0
3"6
CONDITIONS ON OXIDATIVE
3"1 1"6 2"0 3"6
CO
0"4 ---
Heavy C1-C2 residue, hydro- wt. 7o carbons 0.4 2'2 2.9 0.4 1"0 0.2 2"2 0-5 1"6 0"4
DEHYDROGENATION OF ETHYL-
BENZENE
No. of expt. 1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
°C t,
Vob. h r - 1
560--480 I 0"7 560--480 0"7 560-480 "0"7 580--480 0"7 560--480 ti 1"2 490-470 0"35 490-470 0"35 490-470 0.35 490-470 I 0"35 530-470 0"35 490-470 0"35 490-470 0'35 490-470 0"35 490-470 0-35 590-470 0"5 590-470 0"5
Eb : O2 : H20 (mole) 1:0'8:7 1:1"1:7 1:1.3:7 1:1'1:7 1:1"0:7 1 : 1"0 :.13 1 : 1 : 17"6
1:1:20 1:1:20 1 : 1 : 22"5 1 : 0"7 : 20 1:0"8:20 1:I:20 1 : 1'2:20 1:1.2:15 1:1:15
Styrene yield, wt. ~
Heavy residue, wt. ~
55 68 64 62 57 50 55 61 6O 65 48 5O 61 74 71 65
0"4 0"3 0"8 0"8 0"4 0-3 0"3 0"3 0'3 0"2 0"1 0"2 0"2 0"3 0-4 0"4
Selectivity, 93 91 86 86 92 89 89 89 91 90 92 91 91 90 89 90
Note. In experiments 1-5 the catalyst sample weighed 1600ml, in other experiments- 2200 ml. In experiments 9 and 12 air distribution was in sections ( 2 5 ~ o f the total amount), in other experinaents---40, 30, 20 a n d 107o in seetons 2 to 5, respectively.
tial c o m p o n e n t r a t i o (of ethylbenzene, oxygen a n d steam) o f 1 : 1, 1 : 7 a n d a s p a c e velocity o f 0.7 h r -1, t h e s t y r e n e c o n t e n t in the catalyst l a y e r i n c r e a s e d i r r e g u l a r l y a n d was d i s t r i b u t e d in the sections as follows: in the s e c o n d section 15-20 wt. 70, in the t h i r d 25-30 w t . ~ , in the f o u r t h 12-15 w t . ~ a n d the fifth 10-12 w t . ~ a n d a styrene c a t a l y s a t e c o n t e n t o f 70-75 wt. ~ . T h e catalyst survived u n d e r these c o n d i tions f o r m o r e t h a n 5000 h r w i t h o u t r e g e n e r a t i o n a n d activity a n d selectivity s h o w e d no reduction. T h e s e c o n d series o f e x p e r i m e n t s (see e x p e r i m e n t s 6 t o 16) was c a r r i e d o u t a t l o w e r space velocities o f e t h y l b e n z e n e a n d h i g h e r dilutions o f e t h y l b e n z e n e with steam, w h e n t e m p e r a t u r e in the catalyst l a y e r c h a n g e d slightly.
Oxidative dehydrogenation of ethylbenzene
147
As the reaction mixture was diluted further with steam (experiments 6 to 9) when veb was 0.35 hr- 1 the conversion to styrene increased, however, it only reached maximum value, with a simultaneous increase of oxygen concentration, at an oxygen to ethylbenzene ratio of 1-2 (experiment 14). Changing oxygen distribution in the catalytic zones from steady to a distribution decreasing in the layer in a ratio of 4 : 3 : : 2 : 1 had practically no effect on process indices. Simular results were obtained under these conditions also at a space velocity of ethylbenzene of 0.5 hr -1 (experiment 15). Tests in the second series of experiments took 1600 hr, and catalyst activity remained constant during this time. Therefore, during oxidative dehydrogenation of ethylbenzene in a pilot plant using a vanadium-magnesium oxide catalyst, styrene was obtained with a yield of up to 74 wt. ~ at a selectivity of 90 ~. The catalyst worked steadily without marked evolution of heat for a prolonged period of time. Reaction conditions for oxidative dehydrogenation (space velocity of ethylbenzene, ratio of ethylbenzene and steam) were similar to conditions for industrial synthesis of styrene on an iron-chromiumpotassium catalyst [5], but contact temperature was much lower (480°-500°C instead of 600°-620°C). During oxidative dehydrogenation with a dilution of initial components steam was used at 400°C instead of 650°-700°C, required for catalytic preparation of styrene. Results of testing the catalyst using a pilot plant and the kinetic model of the process previously obtained using this catalyst [6], formed the basis for simulating an industrial adiabatic, large capacity, four-section reactor [7]. Calculations show that carrying out the reaction under conditions corresponding to the first series of experiments (initial component ratio 1 : 1 : 7), in a large capacity reactor seems to increase temperature considerably, for practically all conditions examined (above 650°C) at the outlet from the second section of the reactor. This is undesirable since previous process studies showed a reduction in activity and selectivity for catalysts subjected to high temperature. Calculation of temperatures in the catalyst layer by the simulation of an industrial reactor using data obtained for the second test series showed that no adiabatic heating resulting in a marked temperature rise takes place in this case. Calculations enable conditions (1 : 1 : 7 ratio) to be recommended as optimum even for large capacity reactors, which had been adopted in the second series of tests. SUMMARY
1. Oxidative dehydrogenation of ethylbenzene to styrene at 470°-500°C was studied on a vanadium-magnesium oxide catalyst : at an ethylbenzene s.v. of 0.35 to 1"2 hr -1 and ratios ofethylbenzene: oxygen : steam of 1 : 0.8 to 1.3 : 7 to 20. Stlcrene yield reached 74 ~ , with a process selectivity of 90 ~ . 2. The catalyst showed a high operating stability during 5000 hr without regeneration. 3. The following is recommended for simulating an industrial reactor: ethylbenzene : 02 : H 2 0 ratio of 1:1 : 7, C8 s.v. =0"35 hr -~ at 470°~90°C.
148
O.M. RI~VENKOet al. REFERENCES
1. L P. BELOMESTNYKH, O. K. BOGDANOVA and G. V. SHAKHNOVICH, A.c. SSSR, No. 522851, Claim submitted on 21.05.75, Pub1. in Byul. izobr., No. 28, 7, 1976 2. I. P. BELOMESTNYKH, G. V. SHAKHNOVICH, O. K. BOGDANOVA, R. N. VOLKOV and V. P. PANOVA, Neftekhimiya 17, 6, 829, 1977 3. N. V. GARMANOV, Analiz produktov proizvodstva sinteticheskikh kauchukov, p. 239, Khimiya, Leningrad, 1957 4. E. SHTERN and K. TIMMONS, Elektronnaya adsorbtsionnaya spektroskopiya v organicheskcSi khimi~, p. 295, Mir, Moscow, 1974 5. Ch. TOMAS, Promyshlennyye kataliticheskiye protsessy i effektivnyye katalizatory, p. 77, Mir, Moscow, 1973 6. G. V. SHAKHNOVICH, I. P. BELOMESTNYKH, N. V. NEKRASOV, M. M. KOSTYUKOVSKII, R. N. VOLKOV, V. P. PANOVA and S. L. KIPERMAN, Kinetika i kataliz 24, 4, 870, 1983 7. N. V. KOL'TSOV, S. A. GRIN' and I. P. BELOMESTNYKH, Mater. Vsesoyuz. konf. "Khimreaktor-8", Chimkent, 1, p. 182, 1983
Petrol. Chem. U.S.S.R. Vol. 25, No. 3, pp. 148-154, 1985 Printed in Poland
0031-6458/85 $10.00+ .00 © Pergamon Journals Ltd.
OXIDATIVE METHYLATION OF TOLUENE* O. M. REVENKO, KH. YE. KHCHEYAN, M. P. TIKHONOVAand A. V. BORISOGLEBSKAYA All-Union Scientific Research Institute of Organic Synthesis (Received i0 August 1984)
T n s oxidative methylation of toluene is a radical-chain reaction, which takes place by a system with degenerate branching [1-3]. In the initial stage toluene consumption and the formation of end products such as benzene, styrene and phenols, increases by the principle e -or. The entire reaction over a period of time in relation to overall toluene conversion, is described by N. N. Semenov's equation for nonsteady-state branched reactions and reactions with degenerate branching. A l d e h y d e s - b e n z a l d e h y d e and formaldehyde, as well as other end-products are present in the condensate. A parallel is observed between the current concentration of aldehyde and the variation of reaction rate. Maximum rate is achieved by establishing fixed concentration of bot h benzaldehyde and formaldehyde. The presence o f two aldehydes which, according to generally accepted theories, are formed by * Neftekhimiya 25, No. 4, 475--480, 1985.