Energy conservation and emission reduction process for producing p-xylene through alkylation of tolylcarbinol

Abstract

The invention discloses an energy conservation and emission reduction process for producing p-xylene through alkylation of tolylcarbinol, and belongs to the field of petrochemical industry. The process is divided into a reaction part and a separation part. A plurality of ZSM-5 catalyst fixed bed reactors are adopted in the flow; the temperature rise of the reactors is controlled by direct chilling of methanol among the reactor sections, so that the conversion rate of toluene is increased; the temperature after heat exchange between materials at outlets of the reactors and raw materials in front of a heating furnace is increased through compression of a compressor; then heat exchange is performed many times to increase the heat recovery; and meanwhile, power is provided for flowing of the materials in the flow, and the amount of a low-grade refrigerant required for flash separation is reduced, so that heat work integration is realized; and finally, a p-xylene product is obtained through coupling operation of rectification and melt crystallization. Carrier gas required by the process and unreacted toluene are mostly recycled in the flow. The energy conservation and emission reduction process has the effects and benefits of being a new energy conservation and emission reduction process for producing the p-xylene and producing obvious economic and social benefits.

Description

technical field [0001] The invention belongs to the field of petrochemical industry, and relates to an energy-saving and emission-reduction process for producing p-xylene (PX) by alkylating toluene with methanol, wherein the alkylation is a low-pressure and high-temperature reaction carried out on a ZSM-5 molecular sieve catalyst. The process particularly involves technologies such as thermal power integration, carrier gas recovery, toluene recovery, and p-xylene purification. Background technique [0002] Of the three isomers of xylene, para-xylene (PX) has the largest market. PX is mainly used in the production of refined terephthalic acid (PTA) and terephthalate (DMT) for the preparation of various polymers such as polyethylene terephthalate or PET, polypropylene terephthalate ester or PPT, and polybutylene terephthalate or PBT. There are two main ways to obtain aromatics in industry: catalytic reforming and cracking, both of which contain part of p-xylene, and the prod...

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Problems solved by technology

The process does not consider heat recovery, resulting in high energy consumption

[0006] Similarly, Chinese patents CN 102464558 A, CN 102463072 A, CN 1037499A, etc. all have relevant descriptions of the production and separation technologies in this technical field, but fail to propose a complete process for the production of p-xylene by alkylation of toluene and methanol; US patent US 20110092755 and others also describe some technologies in this technical field, but none of them realize energy integration

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