Preparation method of p-aminodiphenylamine

Abstract

The invention relates to a method for preparing p-aminodiphenylamine, which comprises the following: (1) a step of condensation, in which, nitrobenzene and aniline produce condensation reaction in the presence of a catalyst to generate condensation solution including 4-nitrodiphenylamine and 4-nitrosodiphenylamine; (2) a step of extraction, in which, water phase and organic phase in the condensation solution are separated by an extracting method; (3) a step of reduction, in which, hydrogen and the organic phase of the condensation solution produce reduction reaction in the presence of the catalyst to generate reduction solution including the p-aminodiphenylamine; (4) a step of separation, in which, the p-aminodiphenylamine is separated from the reduction solution to form crude p-aminodiphenylamine feed liquid; and (5) a step of rectification, in which, the p-aminodiphenylamine is separated from the crude p-aminodiphenylamine feed liquid in a rectification mode to form a p-aminodiphenylamine product. The method is suitable for serialized industrialized production in large scale, and has the advantages of low reduction reaction temperature, mild reaction condition, few side products, high conversion rate and selection, low labor intensity and no corrosive liquid, thereby reducing pollution to environment.

Description

Technical field [0001] The invention relates to a method for preparing p-aminodiphenylamine, which uses nitrobenzene and aniline as raw materials, adopts two composite catalysts and a cyclic operation process to continuously prepare p-aminodiphenylamine. Background technique [0002] P-aminodiphenylamine is an intermediate product for the manufacture of p-phenylenediamine antioxidants and stabilizers. It is an important chemical product in the rubber industry and polymer industry. According to different raw materials, there are many methods for producing p-aminodiphenylamine. , Which includes: [0003] 1) Formanilide method: aniline reacts with formic acid to form formanilide, and then condenses with p-nitrochlorobenzene to produce N-formyl dianiline, decarbonylation produces p-nitrodiphenylamine, and then reduces with alkali sulfide to produce P-Aminodiphenylamine. The advantages of the formanilide method are lower reaction temperature and short reaction time. The disadvantage i...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that a large amount of hydrochloric acid and liquid caustic soda are used, the pollution of "three wastes" is serious, and nitroso compounds are also carcinogenic

[0005] 3) o-sulfonic acid method: produce p-aminodiphenylamine with o-sulfonic acid method, the quality is better, and the yield is relatively high, but this method has a long process flow, consumes a large amount of acid, seriously corrodes the equipment, and produces a large amount of " "Three wastes"

But there are some common shortcomings: first, the mixture used for reduction is used under strong alkaline conditions, and a hydrogenation solvent must be added, resulting in incomplete reduction, strict requirements on conditions, and low product yield; The second is that there are many processes and cumbersome operations, which is not conducive to large-scale industrial production; the third is that the product quality is not high

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