The method of producing styrene

 

(57) Abstract:

Usage: petrochemistry. Ethylbenzene is subjected to catalytic dehydrogenation in the multi-zone reactor at an elevated temperature in the presence of water vapor by heating the reaction products between zones due to the indirect contact of the products of the dehydrogenation reaction and the reaction mass oxidation neskondensirovannyh gas. The technical result - improving the efficiency of the process of dehydrogenation of ethylbenzene. table 1.

The invention relates to a method for the dehydrogenation of alkylaromatic hydrocarbons, in particular to a method for dehydrogenation of ethylbenzene to obtain styrene, and can be used in the petrochemical industry.

A known method of producing styrene (U.S. Pat. USA 3755482, MKI C 07 C 15/10) catalytic multistage dehydrogenation of ethylbenzene by which the average temperature of each stage at least at the 10oC higher than at the previous stage.

The process is endothermic and requires wiring heat. Therefore, the reaction products before entering the next stage of dehydrogenation to increase the conversion of ethylbenzene heated water vapor through the separating wall, which results in the project hydrocarbons (U.S. Pat. USA 4435607, MKI 07 WITH 5/40, C 07 C 5/48, NCI 585/443) with intermediate oxidation of the formed hydrogen. By this method the hydrocarbons interact with the dehydrogenation catalyst containing activated compound of an alkali metal compound of iron, in the first dehydrogenation zone in the presence of water vapor with the formation of the outgoing stream containing unreacted hydrocarbon products of the dehydrogenation, hydrogen and water vapor. The resulting mixture is introduced into the second oxidation reaction zone, which impose additional oxygen-containing gas to the selective oxidation of hydrogen on a catalyst containing platinum and potassium deposited on highly porous aluminum oxide. Due to the exothermic oxidation of hydrogen flow temperature rises to the specified stream enters the next area dehydrogenation of hydrocarbons. The reaction is carried out at a temperature of 500-700°C and a pressure of 0.1-10 at using ethylbenzene as a source of hydrocarbon to obtain styrene. Thus the selectivity of the oxidation reaction with oxygen to co and CO2is 21-26%, the conversion of oxygen 59-66% and the number of ethylbenzene to styrene, converted to carbon dioxide at the stage of oxidation, Costa from the first dehydrogenation zone increases the temperature of the stream before the subsequent dehydrogenation zone, to increase the total conversion.

In the catalytic oxidation zone in the presence of oxygen-containing gas along with hydrogen partially oxidize unreacted aromatic hydrocarbons from the previous dehydrogenation zone, which reduces the selectivity of transformation to the target product and leads to the formation of undesirable oxygen-containing impurities, reducing quality product.

The oxidation of hydrogen and other products of the dehydrogenation, as well as the dehydrogenation of ethylbenzene is determined by the activity, selectivity and temporal drift - aging catalysts, and requires selection of the two catalysts, working steadily during the same time: one in the dehydrogenation process, and the other in the oxidation process. However, it is known that the catalytic dehydrogenation of ethylbenzene work continuously without overload and shutdown regeneration 16000-20000 hours. While oxidation catalysts require regeneration or overload through 2000-4000 hours of the race. The creation of two catalysts, dehydrogenation and oxidation with identical characteristics for the duration of the work is technically challenging. In addition, the use of oxygen vastly energy consumption with the same degree of condensation. Therefore, the known process is economically not efficient enough.

The objective of the invention is to increase the efficiency of the process of dehydrogenation of ethylbenzene to obtain styrene.

Features a method of producing styrene by catalytic dehydrogenation of ethylbenzene, implemented in a multi-zone reactor at an elevated temperature in the presence of water vapor by heating the reaction products between zones due to the oxidation of oxygen-containing gas formed during the dehydrogenation of the hydrogen-containing gas with subsequent condensation of the products of dehydrogenation and Department neskondensirovannyh gas in which heat between zones carry out the indirect contact of the products of the dehydrogenation reaction and the reaction mass oxidation neskondensirovannyh gas.

Ethylbenzene is mixed with water vapor, enters first into the first dehydrogenation zone, where due to the endothermic nature of the dehydrogenation reaction of ethylbenzene and heat loss into the environment, the flow of reagents is cooled and goes into the heating zone, which is sent to the second dehydrogenation zone and then, after teplooborudovanie, on condensation. When decanting khlebodarova condensate styrene. Part neskondensirovannyh gas selected with dekantatsii condensate is directed into the reactor between zones dehydrogenation, where in a special device carry out the oxidation neskondensirovannyh gas oxygen.

Heat oxidation neskondensirovannyh gas by indirect contact is used to heat the reaction products from the first dehydrogenation zone in front of the entrance to the second dehydrogenation zone to increase the conversion of ethylbenzene and increase the yield of styrene. Reaction mass oxidation neskondensirovannyh gas from the oxidation zone is also not in contact with the reaction products from the dehydrogenation zone. Neskondensirovannyh gas, unused to heat flow between zones dehydrogenation, take away the fuel network.

Given the conversion of ethylbenzene in the second dehydrogenation zone is supported by the change in the flow rate neskondensirovannyh gas and therefore of oxygen for oxidation.

Improving the efficiency of the process of dehydrogenation of ethylbenzene to obtain styrene in multi-zone reactor for the proposed method, in comparison with the known, provided a supply of heat between zones dehydrogenation due to indirect tile content browser to maintain the predefined conversion without reducing the selectivity of the process, to exclude the formation of oxygen-containing impurities and corrosion of the equipment, to avoid the loss of aromatic hydrocarbons in the oxidation by air oxygen. In addition, the proposed method provides reliability management process and the change in the conversion of ethyl benzene by dehydrogenation zones in a wide range.

Use for oxidation neskondensirovannyh gas due to the presence of carbon monoxide, which reduces the possibility of formation of explosive mixtures.

Example 1. (The prototype)

Dehydrogenation of ethylbenzene is carried out in an adiabatic reactor with two zones dehydrogenation and enclosed between the zone of oxidation of hydrogen. The dehydrogenation catalyst contains Fe2O3- 68-72; Cr2O3- 4-6; K2CO3- 19-21 and other additives to 4 wt. %. The oxidation catalyst prepared on the basis of Al2O3contains 0,79% Pt and 2,78% K.

Ethylbenzene fed to the dehydrogenation with a bulk velocity of the liquid 0,4 h-1. Dilution of the raw water steam 1 : 3,3 weight. The temperature at the inlet into the first dehydrogenation zone 600°C.

Due ekzotermicheskoi reaction of dehydrogenation of ethylbenzene and heat in the environment is I, containing hydrogen, methane, carbon oxide, reacted and unreacted aromatic hydrocarbons, enters the zone of oxidation on the oxidation catalyst, where due to the exothermic oxidation of hydrogen and reacted and unreacted aromatic hydrocarbon flow temperature at the inlet to the second dehydrogenation zone is increased to B16°C. In the zone of oxidation of the supplied air with speed, providing 65% conversion of oxygen. The catalyst of the second dehydrogenation zone similar in composition to the catalyst in the dehydrogenation zone. The reaction products from the second dehydrogenation zone condense and of the hydrocarbon part of the produce styrene.

Conversion agilmente after the second dehydrogenation zone amounted to 56.8 and selectivity to styrene and 88.8 wt. %. The content of carbonyl compounds in the styrene selected from the condensed hydrocarbons amounted to 0.022%, which is higher than the stipulated GOST 10003-90 for styrene. Condensed products after the second dehydrogenation zone had a pH of 5.8. The heat consumption in the second dehydrogenation zone with consideration of heat for heating of the reaction products from the flow temperature at the outlet of the first zone to a temperature of 616°C input is

Dehydrogenation of ethylbenzene is carried out according to the proposed method in the adiabatic reactor with two zones dehydrogenation and enclosed between the heating zone flow from the first dehydrogenation zone in front of the entrance to the second dehydrogenation zone due to the heat of oxidation neskondensirovannyh gas oxygen. The dehydrogenation catalyst has a composition as in example 1. Ethylbenzene, mixed with water vapor, is fed to the catalyst in the dehydrogenation zone at a temperature of 600oC. the Volumetric feed rate of the liquid is maintained 0,4 h-1and dilution of the raw water steam 1:3,3 weight. Due to the endothermic dehydrogenation reaction of ethylbenzene and heat loss to the environment temperature of the flow at the exit from the first dehydrogenation zone is reduced. To improve the conversion ethylbenzol and to increase the yield of styrene the reaction stream from the first zone before entering the second dehydrogenation zone is heated to a temperature of 616oC in a special device that is enclosed between zones dehydrogenation> due to the heat of the exothermic oxidation neskondensirovannyh gas oxygen. The heat flow is through dividing the degree of the current from the second dehydrogenation zone after heat recovery is condensed. If dekantatsii condensate allocate neskondensirovannyh gas composition: hydrogen - to 91.6; methane - 1,9; carbon monoxide - 6,5 vol.%. Part neskondensirovannyh gas selected with dekantatsii condensate is directed in the agreement between zones dehydrogenation special device oxidation zone neskondensirovannyh gas to heat flow from the first dehydrogenation zone to supply the second dehydrogenation zone, and the remainder in the fuel network. To bear at the entrance to the second area temperature 616oC spent 38% neskondensirovannyh gas from the total amount. It is obvious that changing consumption neskondensirovannyh gas for oxidation, it is possible to provide the desired conversion of ethylbenzene on the second level.

Under the conditions of example, the conversion of ethylbenzene after the second dehydrogenation zone amounted to 57.0 and selectivity to styrene by 89.5 wt. %. The content of carbonyl compounds in the styrene - rectified, isolated from the condensed hydrocarbons, was 0,006%, which is lower than that provided by GOST 10003-90 for styrene higher grade. Condensed products after the second dehydrogenation zone had a pH equal to 7. The heat consumption in the second dehydrogenation zone with heat metering heating products is gidrirovaniya was 53350 kcal/kg mol converted ethylbenzene. Heat oxidation products neskondensirovannyh ethylbenzene gas after overheating flow from the first dehydrogenation zone is used to heat the air and neskondensirovannyh gas from the zone of oxidation.

The quality of styrene obtained by the proposed method are given in the table.

The proposed method for the dehydrogenation of ethylbenzene to obtain styrene in comparison with the known can improve the efficiency of the process and to avoid the loss of aromatic hydrocarbons, the formation of carbonyl compounds, corrosion of the equipment.

The method of producing styrene by the catalytic dehydrogenation of ethylbenzene, implemented in a multi-zone reactor at an elevated temperature in the presence of water vapor by heating the reaction products between zones due to the oxidation of oxygen-containing gas formed during the dehydrogenation of the hydrogen-containing vapor with subsequent condensation of the products of dehydrogenation and Department neskondensirovannyh gas, characterized in that the heat between zones carry out the indirect contact of the products of the dehydrogenation reaction and the reaction mass oxidation neskondensirovannyh gas.

 

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