Propylene conversion on tungsten-alumina catalysts

0031-6458/78/0101-0001$07.50/0

Petrol. Chem. U.S.S.R. Vol. 18, pp. 5--8.

(~) PergamonPressLtd. 1979.Printed in Poland

PROPYLENE CONVERSION ON TUNGSTEN-ALUMINA CATALYSTS* F. K . SHI~IIDT, YE. A. GRECttKIlVA, YU. S. LEVKOVSKII, O. I. SIIMIDT a n d V. ]3. LAVRENT'YEVA Irkutsk Polytechnic A. A. Zhdanov State University, Irkutsk

(Received 26 3lay 1976) A CO~BI~cATrO~r of disproportionation with oligomerization of lower olefins enables unsaturated hydrocarbons required for industry to be synthesized. The development of bifunctional catalysts, in the presence of which oligomerization and disproportionation of olefins take place simultaneously, therefore acquires considerable practical significance. Results are given of a study of propylene conversion in the presence of alumina-tungsten catalysts, from which we developed a method for the single-stage joint preparation of pentenes and hexenes from propylene [1]. EXPERIMENTAL

The catalyst was prepared by the saturation of A-64 industrial alumina (a fraction of 30-40 mesh) with tungstic acid in a concentrated solution of ammonia. After two hours' agitation at room temperature and impregnation for 24 hr the catalyst was filtered, dried at 120 ° and calcined for 5 hr at a ~emperature of 550-570 °. WO a content was 10.6~/o, Ssp=183 m2/g. The catalyst was activated and regenerated in a reactor immediately before the experiment by calcination in dry air at 550 ° for 3 hr and in argon, for 2 hr. Experiments of propylene conversion at atmospheric pressure were carried out in a quartz reactor in a device used in our previous studies [2, 3]. At a propylene pressure higher than atmospheric experiments were carried out in a stainless steel reactor. An LKhM-7A chromatograph with a packed column 6 m long was used for the analysis of products; fl, fl'-oxydipropionitrile was the liquid phase and helium, the carrier gas. The isomeric composition of Ca-Ca olefins was determined in a "Khrom-2" chromatograph using two capillary columns 100 m long with dinonylphthalate and vacuum oil as stationary phases. Analysis was carried out at a temperature of 50 °. With a capillary column a flame-ionization detector was used and with a packed column--a katharometer was used. * Neftekhimiya 18, 51o. I, 23-29, 1978.

2

F.K. S~T

et a~.

RESULTS

Main p r o d u c t s o f p r o p y l e n e conversion on a l u m i n a - t u n g s t e n c a t a l y s t s in t h e t e m p e r a t u r e r a n g e studied are: h y d r o g e n , ethylene, p r o p a n e , b u t e n e s , p e n t e n e s , h e x e n e s a n d h e p t e n e s (Table 1). T r a c e s o f paraffins were also found. TABLE 1. EFFECT OF TEMPERATURE 0~¢ T~E COMPOSITION OF CONVERSIONPRODUCTS OF PROPYLENE, MOL. %

v=240 hr-*; PCsH6-----1arm, duration of experiment 3 hr

T, °C

Average ! degree of !conversion of propylene,

! 200 300 400 500

I

H~-FC1-C8 paraffins

C4H,

C,H+

C~Hlo /

C+H1, I C,Ht,

!

% 4.3 12.6 28.0 19.5

0.5 0.9 1.4 3"3

2t.6 14.1 11"6 17.6

37.1 34.4 32.1 36.6

20.3 21.8 22.7 20-4

20.1 26.9 29-4 20.0

0.4 1-9 2-8 2-1

I t should b e n o t e d t h a t a c c o r d i n g to t e m p e r a t u r e e t h y l e n e c o n t e n t is 1.7-3 t i m e s lower t h a n b u t e n e c o n t e n t , i.e. d i s p r o p o r t i o n a t i o n o f p r o p y l e n e t o e t h y l e n e a n d b u t e n e s is n o t t h e r~ain r e a c t i o n on t h e a l u m i n a - t u n g s t e n c a t a l y s t . T h e overall c o n t e n t of e t h y l e n e a n d p e n t e n e s is a b o u t t h e s a m e as b u t e n e c o n t e n t , i n d e p e n d e n t o f t e m p e r a t u r e , space v e l o c i t y a n d p r o p y l e n e pressure. F i g u r e l a shows t h e v a r i a t i o n o f t h e degree o f p r o p y l e n e conversion o v e r a period of t i m e a t different t e m p e r a t u r e s . T h e a c t i v i t y o f t h e a l u m i n a TABLE 2. EFFECT OF TEMPERATURE ON THE COMPOSITION OF BUTENES AND PENTENES, MOL. °/0

v = 240 hr-*; pc3Ee= 1 arm

T,

°C

250 300 350 420

But - 1-

But -2 -

eno

eno

8"1 12"7 11"0 11"8

23'9 23"8 29"5 29"6

Isobutene

Pent - 1ene

68"0 63"5 59"5 58"6

17.9 22.2 16.3 21-9

Pent-2ene

I

35.2 30-8 24.2 16.1

3 -Moth - 2-Methylbut - ylbut. 1-ene l -ene 2.4 1.4 1.2 1.5

,

14.1 11.5 17.7 22.3

2-Methylbut 2-ene 30.4 35.1 40.6 38.2

t u n g s t e n c a t a l y s t decreases w i t h t i m e , e v i d e n t l y d u e to b l o c k i n g of a c t i v e eentres b y p r o d u c t s o f i n t e n s i v e p o l y m e r i z a t i o n o f p r o p y l e n e ; c a r b o n a n d h y d r o g e n c o n t e n t in t h e c a t a l y s t a f t e r t h r e e h o u r s ' e x p e r i m e n t a t 420 ° is 11.24 a n d 1.25%, respectively.

Propylene conversion on tungsten-alumlna e a t a l y ~ T h e extremal de13endence of the degree of propylene conversion on tem-

perature is probably also due to an increase in the rate of deactivation of the catalyst on increasing process temperature (;Fig. lb). It was established tha~ after oxidizing recovery with air, catalyst activity is completely restored. mole %

JO

20

§ ~ I0

3 ° I

0

I

O0

I

I 80

[

I I20

Time, rain

I

I0 I 160

0

/Q h

I

I

200

300

I 000 T,°C

I 500

I.. 600

I~G. 1. Relation between the degree of conversion of propylene and time (a) and temperature (b): catalyst WOa-}-Al=Oa; v=240 hr-Z; pcstr6--~1 atm; 1-=275°; 2--420°; 3--500°. Figure 2 shows the effect of propylene pressure on catalysate composition. An increase in propylene pressure increases the degree of conversion and hexerie content; the contents of other components, butenes in particular, decreases. An increase (four-fold) in space velocity from 240 to 960 hr -1 with pe,~, of 9 arm reduces the degree of conversion of propylene (from 38.5 to 34.2%), whereby the proportion of hexenes slightly increases in the catalysate and t h e proportion of ethylene and butenes decreases. Pentene content does not change noticeably and is about 20% in terms of conversion products of propylene. The isomeric composition of butenes, pentenes and hexenes depends on temperature (Table 2, Fig. 3). It follows from results of hexene composition and its dependence on process parameters that propylene dimerization cannot take place by the classical carbcnium-icnic mechanism. In fact, if propyiene dimerization would only take place by a carbonium-ionie mechanism, 3-methylpentenes, linear hexenes, 2,3- and 2,2-dimethylbutenes would only be obtained as a result of secondary reactions of skeletal isomerization of 4-methylpentenes. In this case a significant reduction would be expected in the contents of products of isemerization of 4-methylpentenes with a reduction of prccess temperature, which is not observed (Fig. 3). In addition, in a special experiment of isomerization of 4-methylpent-2-ene at 300 ° it was shown that the proportion of isomers obtained in this case (about 10%) is less than in the catalysate of propylene at the same temperature. The composition of hexenes also does not agree with the mechanism of dimerization by the type of degenerat~ polymerization with addition--ellmination of metal hydride [4].

4

F.K.

SHM'IDT et G~.

The formation of 3-methylpentenes is a fundamentally important fact, their contents in the hexene fraction, independent of process conditions, is close to the thermodynamic equilibrium. 3-Methylpentenes are therefore primary products of dimerization of propylene. qg o

3

mole %

mole %

~30 I 0

~ 30

o

3

5

I

I

I

I

I

7

B afro

260

300

350

~aHe FIG. 2

03

'

I

I

ztO0 " ¢50 7:,°C

FIG. 3

FIG. 2. Effect of pressure on the degree and composition of conversion products of propylene: v~--240hr-l: /--linear hexenes; 2--4-methylpent-2-ene-F2-methylpent-l-ene and -2-ene; 3--3-methylpent-l-ene and -2-ene~-2-ethylbut-l-ene; 4--2,3 and 3,3-dimethylbutenes. FIG. 3. Effect of temperature on hexene composition: v----240hr-1; /--linear hexenes; 2--4-methylpent-2-ene~2-methylpent-l-ene and .2-ene; 3--3-methylpent-l-ene and -2-ene-~2-ethylbut-l-ene; 4--2,3 and 3,3-dimethylbutenes. As indicated, at all temperatures, space velocities and pressures investigated ethylene content is 1.7-3 times lower than that of butenes, which could be due to dimerization of ethylene. However, the catalyst used is practically inactive during dimerization of ethylene. When passing through an ethylenepropylene mixture (1 : 1) no marked increase in pentene yield was observed either. It is clear that pentene formation in the process studied is not the result of codimerization of ethylene with propylene. These results are in agreement with results of another study [5], in which it was shown that codimerization of ethylene with propylene takes place only on alumina-tungsten catalysts activated with nickel. Isobutene content in the butene fraction is higher than the thermodynamic equilibrium consequently, isobutylene is the primary product of propylene conversion. I f reactions of metathesis of propylene and co-disproportionation of laropylene with hexenes were the main reaction resulting in butene formation, it could be expected that linear butenes would be formed. Special features established in this study about the composition of conversion products of propylene can be explained if we accept the hypothesis t h a t on heterogeneous catalysts, as with homogeneous systems of rectathesis, olefin conversion takes place via c£rbene complexes. The significant

Propylene conversion on tungsten-alumina catalysts

5

role of carbene complexes as active particles in reactions of metathesis and polymerization of cyclo-olefins by the action of homogeneous catalytic s y s t e m s first noted in studies [6, 7], has been convincingly confirmed in recent years by direct experimental results obtained by Dolgoplosk et al. [8, 9] and a number of other scientists [10-15]. It should be emphasized in particular that by the interaction of carbene complexes with mono- and di-substituted olefins, as well as products of transfer of alkylidene groups to carbene, corresponding cyclopropane derivatives are formed [16-18]. Cyclopropane derivatives may therefore be formed not only by the interaction of free carbenes with olefms, but also by complex combination with metal. However, the rupture of C--C bonds by metathesis is, apparently, only typical of carbenes combined in a complex manner with the metal. The formation of cyclopropane and methylcyclopropane from ethylene a t low temperatures on a Mo(CO)6/A1203 catalyst may be regarded as indirect evidence of the participation of carbenes as intermediate products in t h e metathesis of olefins on heterogeneous catalysts [19]. Metathesis of olefms in the presence of homogeneous catalysts takes place as a chain process, in which carbene complexes of transition metals (Mo, W, Re) are the kinetic chain transfer agents. Possible methods of forming carbene complexes have been examined previously [7, 20, 21]. For heterogeneous catalysts of metathesis unpromoted by organo-metallie compounds carbenes may be formed as a result of a-elimination of the hydride or proton, respectively in the allyl or carbonium-ionic derivative of the transition metal [22]. These complexes are obtained by well-known reactions of introducing olefin at t h e metal--hydrogen bond in the hydride complex formed as a result of protonization of the reduced form of metal alongside the Bronsted acid centre or by protonization of propylene that had formed a complex with the transition metal. A layout is given of the reactions taking place: _~14Me,~T__~ / .~j A1

0

\l

H

~+2 Me

H

+

CH2--CH--CH 3 ~

- /O\l ~+~ ,C,lt~ AI Me

OH H~C~CH--CH a

,1

-,c., -

OH

C~CH 3

\all a

where A1--OH is the Bronsted type acid centre, Me +n, the transition metal with a lower degree of oxidation n.

6

F.K. SHMIDT ~.~ ~.

On the catalyst surface therefore there are at least two types of complex (A) and (C) or (B) and (C), the interaction of which with a second propylene molecule results in hexenes. It should be noted that the formation of small amounts of hydrogen and saturated hydrocarbons confirms the slight role of hydrogen redistribution which probably takes place via C --H forms of propylene adsorbed by dissociation. It has been impossible so far to evaluate the effect of surface complexes (A), (B) and (C) on propylene dimerization. However, the assumption concerning the predominance of carbene complexes (C) is in satisfactory agreement with the formation of 3-methylpentenes and linear hexenes as primary products in proportions close to thermodynamic equilibrium. As noted previously, the possibility of forming eyclopropane by interaction of carbene metal complexes with olefins is an experimental fact [16-18]. Naturally, at high temperatures on acid t y p e catalysts such as aluminatungsten catalysts one bond in the cyclopropane ring is ruptured at high rates to form hexenes, all skeletal isomers being primary products. The transfer of alky]idene groups by metathesis to form pentenes, or butenes including isobutene is the second course of carbene conversion. The formation of pentenes, or butenes is determined by propylene coordination in relation to carbene in the transition metal complex and the structure of the intermediate cycloCH3

/

butane metal complex; for example for carbene of type Me=C following complexes are formed: /CH3

t

\ CHa

M,,--c

"=c/c" 7

the

[

I\c.,

I

I\ CII'

Me

[[ + l'so-C,H,o

c.,

\CH3 CHs--CH---CH~

II + i=o-c,n, CH'"CH,

These reactions may be regarded as a stage of chain extension. Finally, the interaction of carbenes eombine~ with the metal by coordination : CH~ and :CH--CH 3 with propylene producing butenes and pentenes, is a stage of chain rupture. It is easy to show within the framework of the mechanism discussed that tho composition of products of metathesis of propylene is determined by chain length. If chain length is one, butenes and pentenes are only obtained from propylene in equimolecular quantities; if chain length is eqaal to two, ethylene, butenes and pentenes are formed, butene and pentene yield being

Propylene conversion

on t u n g s t e n - a l u m i n a catalysts

7

three times and twice as high as that of ethylene, respectively. As chain length increases, pentene yield decreases and the ratio between ethylene and butenes approximates the equimolecular. For example, with a chain length of a hundred the ratio of C~ : C4= 0.98 and pentcne content in conversion products of propylene is less than one per cent. We note that the overall contents of ethylene and pentenes will be equal to butene content, ind3pendent of chain length. As shown by Table 1, in the temperature range studied this ratio is satisfactorily maintained, although the degree of propylenc conversion changes almost seven times. Chain length was evaluated from C~:C4 and C5:C ~ ratios in conversion products of propylene. It appeared that as temperature increased, chain length decreased: 3.3 (200°); 2.5 (300 °) and 2 (400°), i.e. on increasing temperature, the probability of chain rupture increases. The increase of hexene yield on increasing temperature to 400 ° is in qualitative agreement with the dependence of chain length on temperature. At 500 ° hexene yield decreases, which is first of all due to the increase in the rate of catalytic cracking of hexenes. Under the conditions examined on an alumina-tungsten catalyst propylene metathesis therefore takes place with comparatively short chain length and conversions of propylene to ethylene, hutches and pentenes arc of the type of degenerate metathesis. Conversions of ethylene to propylene and butene on a metathesis catalyst Mo(CO)dy-Al~03 [23] may be explained by a similar mechanism. The causes of a marked difference in catalytic properties of the catalyst used and those of other catalysts of metathesis, e.g. alumina-molybdenum, molybdenum- and tungsten-silicate catalysts are so far not clear, although isobUtylene and pentenes are always formed in these catalysts in larger or smaller proportions [24]. It may be assumed that Bronsted type acid centres, which determine the direction of conversion of carbene complexes are of significance. In fact, after the treatment of the alumina-tungsten catalyst with organic aluminium or magnesium compounds reacting with acid ccntres, propylene metathesis takes place basically to ethylene and butenes [25]. SUMMARY

A study was made of propylene conversion on tungsten-alumina catalysts over a wide range of temperature, pressure a~d space velocity. It was estabfished that dimerization and metathesis to ethylene, butenes and pentenes are the main reactions of propylene conversion. REFERENCES

1. Auth. Cert. U.S.S.R. 429049; 25.05.1974. Otkr., izobr., prom. obr. i toy. znaki No. 19, 75, 1974 2. F. K. SHMIDT~ V. G. LIPOVICH and Ye. A. G R E C ~ I N A , l~eftekhimiya 11,850, 1971

8

T. Yu. FRID et aS.

3. F. K. SHM1DT, Ye. A. GRECHKINA, V. V. SARAYEV a n d V. G. LIPOVICH, Neftekhimiya 14, 41, 1974 4. G. LEFEVRE a n d J. CHAUVIN, Aspekty gomogennogo kataliza (Aspects of Homogeneous Catalysis). Mir, Moscow, 1973 5. E. ECHIGOYA a n d A. KOBAYASHI, Chem. Letters, No. 4, 277, 1972 6. J. L. HERISSON and J. CHAUVIN, Makromolek. Chem. 141, 161, 1971 7. B. A. DOLGOPLOSK, K. L. MAKOVETSKII and Ye. I. TINYAKOVA, Bold. A N SSSR 202, 871, 1972 8. B. A. DOLGOPLOSK, T. G. GOLENKO, K. L. MAKOVETSKII, I. A. ORESHKIN a n d Ye. I. TINYAKOVA, Dokl. AN SSSR 216, 807, 1974 9. B. A. DOLGOPLOSK, K. L. MAKOVETSKII, T. G. GOLENKO, Yu. V. KORSHAK a n d E. I. TINYAKOVA, Eur. Polymer J. 10, 901, 1974 10. R. H. GRUBBS, P. L. BURK a n d D. D. CARR, J. Amer. Chem. Soc. 97, 3265, 1975 11. T. J. KATZ a n d J. I~ICGINNES, J. Amer. Chem. Soc. 97, 1592, 1975 12. J. MCGINNES, T. J. KATZ a n d S. HURWITZ, J. Amer. Chem. Soc. 98, 605, 1976 13. T. J. KATZ a n d R. ROTHCHILD, J. Amer. Chem. Soc. 98, 2519, 1976 14. W. S. GREENLEL a n d M. F. FARONA, Inorgan. Chem. 15, 2129, 1976 15. N. C~I.DERON, E. A. OFSTEAD and W. A. JUDY, Angew. Chem. 88, 433, 1976 16. C. P. CASEY and T. J. BURKHARDT, J. Amer. Chem. Soc. 96, 7809, 1974 17. C.P. CASEY, H. E. TUINSTRA and M. C. SAEMAN, J. Amer. Chem. Soc. 98, 608, 1976 18. P. G. GASSMAN and T. H. JOHNSON, J. Amer. Chem. Soe. 98, 6055, 6057, 6058, 1976 19. R. L. BANKS and G. C. BAILEY, Ind. Eng. Chem. Prod. Res. Dev. 3, 170, 1964 20. E. L. MUETTERTIES, Inorgan. Chem. 14, 951, 1975 21. I. A. ORESHKIN, K. L. MAKOVETSKII, B. A. DOLGOPLOSK, Ye. I. TINYAKOVA, I. Ya. OSTROVSKAYA, I. L. KERSHENBAUM and G. M. CHERNENKO, Vysokomol. soyed. XIXB, 55, 1977 22. D. T. LAVERTY, J. J. ROONEY a n d A. STEWART, J. Catalysis 45, 110, 1976 23. P. P. O'NEILL a n d J. J. ROONEY, J. Amer. Chem. Soc. 94, 4383, 1972 24. J. C. MOL and J. A. MOULIJN, Advances in Catalysis 24, 131, 1975 25. F. K. SHMIDT, Yu. S. LEVKOVSKII, B. V. TIMASHKOVA, V. B. LAVRENT'YEVA and E. A. GRECHKINA, Reaction Kinetics and Catalysis Letters 3, 385, 1975

Petrol. Chem.U.S.S.R. Vol. 18, pp. 8-14. ~) PergamonPress Ltd. 1979.Printed in Poland

0031-6458/78/0101-0008507.50/0

ALKYLATION ON ADAMANTANE WITH ISO-OCTANE IN THE PRESENCE OF ALUMINA CATALYSTS* T. ¥ c . FRID, V. •. SOLOV'YEV,V, G. ZAIKI~, ¥E. I. BAO~n and P. I. SxNt~ I n s t i t u t e of Petrochemical Synthesis, U.S.S.R. Academy of Sciences (Received 3 June 1977)

THE interest in adamantane derivatives is first of all due to the possibility of using its derivatives as pharmaceutical preparations and polymers [1]. Alkyladamantanes may be used as components of synthetic lubricants [2]. * Neftekhimiya 18, No. 1, 39-43, 1978.