Continuous synthetic method of p-phenylenediamine

Abstract

The invention provides a new process for producing p-phenylenediamine through a continuous method. The process comprises: taking p-nitroaniline, a solvent and hydrogen as main raw materials, in a fixed bed reactor or shell-and-tube reactor and in the presence of a catalyst, carrying out a hydrogenation reaction to prepare a p-phenylenediamine crude product, performing rectification recycling to the crude product to obtain high-purity p-phenylenediamine, and recycling excess hydrogen and solvent for cyclic application. According to the process, the p-phenylenediamine conversion rate can reach 100%, and the purity of p-phenylenediamine can reach no less than 99.9%. The process is green, eco-friendly and new.

Description

technical field [0001] The invention belongs to the field of fine chemical industry and relates to a method for preparing high-purity p-phenylenediamine through hydrogenation reduction of p-nitroaniline. Background technique [0002] P-phenylenediamine is an important organic chemical raw material, which is generally used in the production of dyes, rubber antioxidants, etc. The traditional production method of p-phenylenediamine is to use p-nitrochlorobenzene as raw material, react with ammonia water (or ammonia gas) under high temperature and high pressure conditions to prepare p-nitroaniline, and p-nitroaniline is then reduced to produce p-nitroaniline by alkali sulfide or iron powder The crude p-phenylenediamine is purified by recrystallization to prepare high-purity p-phenylenediamine. The biggest defect of this process is that there is a lot of industrial wastewater, and the reduction of iron powder will also produce a large amount of iron sludge, which seriously pollu...

AI Technical Summary

Problems solved by technology

The outstanding advantage of this process is that there are no three wastes, but the technical difficulty is relatively high, and production control is relatively difficult. This method also has many other disadvantages, such as expensive metal catalysts, easy to be poisoned and difficult to recycle, polar solvent dimethyl sulfoxide (DMSO), The price is expensive, and dimethyl sulfoxide is easy to poison the hydrogenation catalyst, resulting in high product cost