The method of producing styrene

 

(57) Abstract:

The invention relates to catalytic processes, in particular the obtaining of styrene by the catalytic dehydrogenas ethylbenzene on iron oxide catalysts at a temperature of 560 - 640oC in the presence of water vapor, followed by separation of styrene from the products of dehydrogenation of ethylbenzene (furnace oil) by multistage distillation with sequential allocation benzatropine faction, return ethylbenzene and styrene-rectified. The invention consists in that, to increase the conversion of ethylbenzene under dehydrogenation of ethylbenzene on iron oxide catalyst, the content of styrene in etilbenzene the charge coming into the dehydrogenation reactor, is maintained at a level no higher than about 0.15 wt.%, it allows you to increase the conversion of ethylbenzene with 62,9 to 67.9 wt.%.

The invention relates to the field of catalytic processes, namely the obtaining of styrene by catalytic dehydrogenation of ethylbenzene, and can be used in the petrochemical industry.

Known methods for producing styrene by catalytic dehydrogenation of ethylbenzene on iron oxide catalysts at temperatures of benzene by multistage distillation with sequential allocation benzatropine faction, return of ethylbenzene and styrene-rectified. CBM product of the column selection styrene-rectified subjected to additional distillation with return of distilled styrene in the column selection styrene-rectified.

P. Kirpichnikov, A. and others "Album of technological schemes of the main production of the synthetic rubber industry", HP, "Chemistry", 1980, S. 100.

Oil, gas and petrochemicals abroad, 1991, 8, S. 100 - 102.

In known methods for producing styrene content of the styrene in return ethylbenzene reaches up to 1.5 wt.%, which results when it is mixed with fresh ethylbenzene to styrene content in etilbenzene the charge coming into the dehydrogenation reactor, in the range of 0.4 - 0.4 wt.%. The conversion of ethylbenzene in this way is usually not more than 60 wt.%

U.S. patent N 3326996, CL 260-669, publ. 1967.

E. M. PR and other "styrene", M, Tsniiteneftehim, 1996, S. 38.

The objective of the invention is to increase the efficiency of the process, which consists in increasing the conversion of ethylbenzene at the stage of dehydrogenation.

This object is achieved by the described method of producing styrene by catalytic dehydrogenation of ethylbenzene in the presence of water vapor with posledney faction, etilbenzene fraction of recycling that is returned to the mixing with the original fresh ethylbenzene at the entrance of the reactor block, and styrene - rectified, by maintaining the concentration of styrene in etilbenzene charge at no more than about 0.15 wt.%.

Studies have shown that the decrease in the content of styrene in etilbenzene charge up to a level of 0.15 wt.% allows to significantly improve the conversion of ethylbenzene, because, apparently, the inhibitory effect of styrene in raw materials, as a result of adsorption on his catalytic centers because of differences in the absorption coefficients of styrene and ethylbenzene. The decrease in the concentration of styrene in etilbenzene charge below the specified limit does not lead to a significant change in the conversion of ethylbenzene, but causes considerable technical difficulties in implementing the invention.

It is known that for splitting a pair of ethylbenzene - styrene close boiling points required columns with a large number of plates. So, in practice, in the industry at a residual styrene content in return ethylbenzene at 1.5 wt.% use columns with at least 70 plates. Therefore, the column selection return ethylbenzene often perform a "split" consisting ofits spontaneous polymerization", M, Tsniiteneftehim, 1974, S. 23.

The implementation of the present invention, namely, maintaining the concentration of styrene in etilbenzene the charge level of 0.15 wt.%, will require reducing the amount of styrene in return ethylbenzene to less than 0.5 wt.%. The decrease in the concentration of styrene in return ethylbenzene to such a level using conventional distillation columns would require significant capital and energy costs, which would reduce the effectiveness of this invention.

The full effectiveness of the implementation of the present invention is achieved by using special regular nozzles installed in the separation columns instead of the usual distillation plates. Use regular packing, for example of the type intalox company Norton, allows after the replacement of the existing plates in the current column to dramatically improve the efficiency of the column, to reduce the hydraulic resistance at the same capacity, to reduce the temperature in the cube columns and loss of styrene in the polymer. Thanks for such a replacement of the styrene content in the return ethylbenzene can be reduced to the desired according to this invention without significant capital e invention is illustrated by the following examples:

Example 1 (comparative). Acibenzolar the mixture obtained after mixing of the fresh and return ethylbenzene, styrene content in a mixture of 0.5. %, was subjected to dehydrogenation on the oxide catalyst MST-75 in an isothermal reactor. The process was carried out at a temperature of 600oC, the mass ratio of raw materials : water vapor equal to 1 : 2, and a space velocity of etilbenzene charge 1 hour - 1. The conversion of ethylbenzene was 62.9 wt. % with a selectivity of conversion of ethylbenzene to styrene 96,7%.

Example 2. Acibenzolar the mixture obtained after mixing of the fresh and return ethylbenzene, styrene content in a mixture of 0.15 wt.% were subjected to dehydrogenation on the oxide catalyst MST-75 in an isothermal reactor. The process was carried out at a temperature of 600oC, the mass ratio of raw materials : water vapor equal to 1 : 2 and a space velocity of etilbenzene charge 1 hour - 1. The conversion of ethylbenzene amounted to 67.9 wt.% when the selectivity of the conversion of ethylbenzene to styrene 96,7%.

Thus, as can be seen from the presented data, the decrease in the concentration of styrene in etilbenzene charge up to a level of 0.15 wt.% increases the conversion of ethylbenzene to styrene.

The way in which the group benzatropine faction, return etilbenzene faction and styrene-rectified, characterized in that the concentration of styrene in etilbenzene the charge coming into the dehydrogenation reactor, is maintained at a level no higher than about 0.15 wt.%

 

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