The method of producing styrene

 

(57) Abstract:

The invention relates to the petrochemical industry and can be used to obtain styrene by dehydration of methylphenylcarbinol during the joint production of propylene oxide and styrene. The essence of the invention is the implementation of evaporation of liquid raw materials and overheating directly in the reaction zone due to the heat of the water vapour coming from superheater gas contact, and from the superheater furnace, and high-boiling products comprising methylphenylcarbinol, pre-evaporation are not separated and decomposed into a number of valuable products in the reactor together with the bulk of the raw materials. 4 tab., 1 Il.

The invention relates to cyclic compounds, in particular, to dehydration methylphenylcarbinol in styrene in the joint process of obtaining propylene oxide and styrene.

Known methods of dehydration alkylaromatic alcohols in the vapor phase in the adiabatic reactor using a catalyst of titanium oxide, thorium, aluminum at a temperature of 180-280oC [1, 2].

The disadvantage of these methods is the low yield of the target products and vyskytla of methylphenylcarbinol in styrene with water vapor in the presence of a catalyst based on aluminum oxide in a two-stage adiabatic reactors with intermediate heating of the contact strip, providing equality of the temperatures at the inlet to each stage of contact [3]. The disadvantage of this method is also insufficient conversion methylphenylcarbinol and selectivity, as well as increased heat loss of water vapor on the stages of overheating of the charge and hydrocarbons in the selection of the high-boiling products from the evaporator, the burning of which affects the sanitary and technical condition of production. To this we must add the need for periodic cleaning of the superheater charge from the polymer deposits, which leads to unplanned production stops.

The proposed method devoid of the above disadvantages, because it allows completely excluded from the process schema nodes evaporation and overheating of the mixture to 320oC and, consequently, to reduce heat loss and hydrocarbons avoid stopping systems associated with the cleaning of the superheater charge.

The aim of the invention is the reduction of energy consumption, raw material consumption and stabilization of production and the improvement of sanitary and technical condition of production.

This goal is achieved by the described method, whereby the evaporation of liquid raw materials and overheating conduct C is Aza, and from the superheater furnace, and high-boiling products comprising methylphenylcarbinol, pre-evaporation are not separated and decomposed into a number of valuable products in the reactor together with the bulk of the raw materials.

Studies have shown that decomposition of high boiling point selected from the evaporator at a temperature of 280-320oC, is formed mainly of styrene and ethylbenzene.

In the drawing is given of the proposed scheme dehydration.

In this way raw methylphenylcarbinol fraction is fed through line 1 into the convection part of the oven 2, where it is heated to a temperature of 180-190oC due to the heat from flue gases and line 3 in liquid form is directed to mix with water vapor and further along the line 4 with a temperature of 270-320oC in the reactor of the first stage 5.

Contact the gas line 6 enters the interstage superheater 7, where it is superheated to a temperature of 270-320oC, then line 8 is directed into the reactor of the second stage 9. Contact the gas after the reactor through line 10 is directed to the cooling and rectification.

Water vapor flows through line 11 into the furnace 2, where it is superheated to a temperature of 500-700oC and on line 12 enters partially on line 13 is on line 15.

Regulating the amount of steam coming from the superheating-chamber of the furnace, is produced in the reactor 5 and the interstage superheater 7 a flap with incomplete cover 14 that can withstand the required temperature in each of the reactors.

Every 400-1000 hours of work is the regeneration of the catalyst vapor mixture.

The invention is illustrated by the following inventions.

Example 1. Fraction of methylphenylcarbinol is fed into the evaporator, where mixed with water vapor in the vapor phase enters the heat exchanger for indirect overheated water vapor coming from the interstage superheater, to a temperature of 270-320oC and is directed in the first stage of contact. Contact the gas at the outlet of the first stage is heated to the reaction temperature in the interstage superheater and enters the second stage contacting. Taglocity residue selected from the evaporator is sent to incineration.

Dehydration is carried out at two values of the volumetric velocity on the catalyst alumina (10 l) under the following conditions (see tab. 1).

Thus the following results are obtained (see tab. 2).

Example 2 (offers the superheating furnace to a temperature of 180-190oC in liquid form without separation from it storable. The evaporator and the superheater charge of technological schemes are excluded.

If this is observed the following mode of dehydration (see table. 3).

Thus the following results are obtained (see tab. 4).

Thus, the introduction of this scheme in the current production of propylene oxide together with styrene at JSC "Nizhnekamskneftekhim" will allow you to:

to exclude from the process schema nodes evaporation and overheating of raw materials and thus reduce heat loss by evaporation and overheating in devices and pipelines due to the feed in the reaction zone liquid raw material;

to increase the productivity of the reactors styrene by increasing conversion and decomposition of IFC and taglocity previously withdrawn from the evaporators;

accordingly reduce consumption of raw materials and water vapor;

to improve the sanitary condition of production by eliminating the operation of the combustion taglocity drawn from the evaporator.

The method of producing styrene by dehydration of methylphenylcarbinol in a two-stage reactor on the catalyst is aluminum oxide in the presence of water vapor heated flow coming from the first the action methylphenylcarbinol in liquid form, pre-heated in the convection part of the superheating furnace up to 180 - 190oAnd mixed before entry into the catalyst bed of the first stage reactor at a mass ratio of 1 : 1,0 - 1,2 with water vapor coming from the interstage superheater and directly from the superheater furnace.

 

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