Method for improving 4-amino diphenylamine yield

Abstract

This invention provides a method for improving the yield of 4-aminodiphenylamine, comprising: use nitrobenzene and phenylamine as raw material to conduct condensation and hydrogenation reactions, where the nitrobenzene is added in to start the condensation reaction when the mole ratio of water and alkaline in the catalyst is 4-6:1, and stop the reaction when the mass percentage of the alcohol compounds in the reaction solution becomes less than 0.3%. This invention is characterized in that it can precisely control the water content by detecting the alcohol compounds during the condensation reaction, so as to efficiently prevent the decomposition of condensing catalyst, obtain a high production yield, and accomplish the repeated use of the catalyst.

Description

technical field [0001] The invention relates to a method for increasing the yield of 4-aminodiphenylamine, in particular to the preparation process of 4-aminodiphenylamine using nitrobenzene and aniline as raw materials. Background technique [0002] 4-Aminodiphenylamine is the main intermediate of rubber antioxidants and dyes. Its production methods mainly include: (1) Diphenylamine method, that is, using diphenylamine and nitrous acid as raw materials to obtain N-nitroso Diphenylamine is reacted with anhydrous hydrogen chloride alcohol solution to obtain 4-nitrosodiphenylamine, which is hydrogenated and reduced to obtain the product; (2) the aniline method is formed by condensation of p-chloronitrobenzene and aniline in the presence of an acid-binding agent 4-nitrodiphenylamine, hydrogenation reduction to obtain 4-aminodiphenylamine; (3) formanilide method, that is, formanilide and p-chloroaniline are used as raw materials to react to generate 4-nitrodiphenylamine, hydroge...

AI Technical Summary

Problems solved by technology

Too much water in the reaction will lead to an increase in side reactions, but too little water in the reaction will cause the catalyst to decompose. On the one hand, the selectivity of the condensation catalyst will decrease when it is returned to use. On the other hand, it will poison the hydrogenation catalyst when it is brought into the hydrogenation stage. , affecting the product yield

The problem of the decomposition of the condensation catalyst is discussed in detail in CN1307556A, thus the patent proposes to control the molar ratio of water and alkali to be not less than 4:1 before the condensation reaction starts, and the molar ratio of water to alkali to be not less than 0.6 at the end of the condensation reaction: 1, to prevent the decomposition of the condensation catalyst, better realize the recovery and reuse of the catalyst, it provides in embodiment 1 and adopts this control method, the condensation intermediate product (4-nitrodiphenylamine+4-nitroso Diphenylamine) the selectivity of p-nitrobenzene can reach 94% or 95.1%, but the productive rate of 4-aminodiphenylamine after hydrogenation is not described; In embodiment 3A, adopt two kinds of condensation catalysts of reuse Carrying out the reaction, the selectivity of the obtained condensation intermediate product p-nitrobenzene reaches 93.7% and 89.3% respectively, and the hydrogenation conversion rate is only 70% and 48%, which is much worse than the fresh condensation catalyst effect