Method of preparing xylene by alkylation of benzene and methanol

Abstract

The invention relates to a method of preparing xylene by alkylation of benzene and methanol. Two fixed bed alkylation reactors are adopted. The first reactor adopts new benzene, circulated benzene and methanol as raw materials and prepares toluene and the xylene through alkylation. The second reactor adopts the benzene and the methanol in reaction products of the first reactor as raw materials and prepares the xylene through alkylation. The benzene, the toluene and the crude xylene in the two reactors are separated by a benzene-toluene fractionating tower. The separated benzene and the separated toluene are circulated and respectively returned to the first reactor and the second reactor to be adopted as the raw materials. A xylene mixture product and heavy aromatics are separated from the crude xylene by a xylene rectifying tower. The method reduces loss of the raw materials and increases the xylene yield. The method adopts a single tower for separating the benzene, the toluene and the crude xylene, and is short in process and simple in equipment.

Description

technical field [0001] The invention belongs to the field of organic chemical synthesis, in particular to a method for producing xylene by alkylation of benzene and methanol. Background technique [0002] Xylene is mainly composed of p-xylene, o-xylene and m-xylene. It is an important chemical raw material and has a wide range of uses. Among them, p-xylene (PX) is an important organic chemical raw material, which can be used to produce purified terephthalic acid (PTA) or dimethyl terephthalate (DMT), and PTA or DMT reacts with ethylene glycol Polyethylene terephthalate (PET), namely polyester, is further processed and spun to produce polyester fiber and polyester cord for the tire industry; in addition, PX is also used in medicine. Meta-xylene is used to produce isophthalic acid, and o-xylene is used to produce phthalic anhydride, which in turn produces various plastic plasticizers. [0003] Xylene used to come mainly from the coking industry. Now it mainly comes from the...

AI Technical Summary

Problems solved by technology

Due to the different feed ratios and operating conditions of the alkylation reaction of benzene, toluene and methanol, the one-step process of benzene-methanol to xylene has a large loss of raw materials, low conversion rate, resulting in large circulation, high energy consumption and high yield of heavy aromatics. shortcoming

[0011] This patent uses double reactors to react benzene and toluene with methanol to produce xylene respectively, which can flexibly adjust the ratio and reaction conditions of benzene-methanol and toluene-methanol, and adopts the method of separating benzene, toluene and crude xylene in a single tower. No similar reports or patents

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