Method for recycling aniline in phenyl carbamate preparation process by urea coupling method

Abstract

The invention discloses a method for recycling aniline in a phenyl carbamate preparation process by a urea coupling method, belonging to the technical field of non-phosgene synthesis of phenyl carbamate. Under the catalytic action of a bifunctional catalyst, a crude product N,N'-diphenylurea containing a small amount of aniline, which is obtained by an improved urea method and is not washed by methanol or any other solvent, is used as a raw material to directly react with carbonate to prepare the phenyl carbamate, i.e. the N,N'-diphenylure and residual aniline in the N,N'-diphenylure simultaneously react with dimethyl carbonate to efficiently synthesize the phenyl carbamate. The invention has the advantage of mild reaction conditions, uses the high-activity bifunctional catalyst, does not need to separate the small amount of aniline in the N,N'-diphenylure, and uses the aniline as the reaction raw material, thereby implementing aniline recycling at low cost, and solving the problem of difficulty in separating and recycling aniline in the transfer process.

Description

technical field [0001] The invention belongs to the technical field of non-phosgene synthesis of aniline carbamate, in particular to a method for recycling aniline in the process of preparing aniline carbamate by a urea coupling method. Background technique [0002] Isocyanate is an important class of organic synthesis intermediates, widely used in polyurethane, coatings, dyes and pesticides and other fields. In the traditional isocyanate synthesis industry, most products are synthesized by the phosgene method. With the increasing environmental protection requirements, the development of non-phosgene synthesis methods has become a very important topic in the chemical industry. Phenyl carbamate is a very key intermediate in the process of non-phosgene synthesis of isocyanate, and its non-phosgene synthesis process has become a research hotspot. [0003] The non-phosgene synthesis of phenylcarbamate mainly includes oxidative carbonylation of aniline, reductive carbonylation o...

AI Technical Summary

Problems solved by technology

In the reaction process, under the action of the bifunctional catalyst, the crude product of diphenylurea does not need to be washed, and diphenylurea and the residual aniline therein react with dimethyl carbonate to efficiently synthesize methyl phenylcarbamate at the same time, realizing the Low-cost aniline recycling, which solves the problem of difficult separation and reuse of aniline in the transfer process