Method for preparing p-phenylenediamine through hydrogen reduction

Abstract

The invention discloses a method for preparing p-phenylenediamine through hydrogen reduction. The method specifically comprises the following steps: (1) adding deionized water, absolute ethyl alcoholand catalyst into two serially connected reactors; (2) controlling temperature of reactors, keeping stirring and continuously introducing hydrogen into the reactors, and controlling inner pressure ofthe reactors; (3) continuously adding deionized water and paranitroaniline into a first level reactor when the inner pressure of reactors meets the requirement; (4) opening a discharging port of the first level reactor and discharging into a second level reactor, and meanwhile, opening the discharging port of the second level reactor and discharging into a catalyst settling tank, while carrying out steps (1), (2) and (3); (5) opening the discharging port of the catalyst settling tank and discharging into a separation device, after the material in the catalyst settling tank settles down; (6) removing solvent and vacuum-drying, thereby acquiring an end product of p-phenylenediamine. According to the invention, green and environment-friendly solvent and catalyst are used for preparing p-phenylenediamine through hydrogen reduction, product yield is high and purity can reach up to 100%.

Description

technical field [0001] The invention relates to a method for preparing p-phenylenediamine through hydrogen reduction, and belongs to the technical field of p-phenylenediamine production. Background technique [0002] p-Phenylenediamine is one of the simplest aromatic diamines, and it is also a widely used intermediate, which can be used to prepare azo dyes, high molecular polymers, and can also be used to produce fur dyes, rubber antioxidants and photo In addition, p-phenylenediamine is a sensitive reagent commonly used to detect iron and copper. [0003] At present, the traditional process of domestic production of p-phenylenediamine is obtained by using p-nitroaniline as raw material, and then reducing it with iron powder or lead chloride. The biggest defect of this process is that there is a lot of industrial waste water, which seriously pollutes the environment, and the product yield is low. , the total yield is less than 85%, and the purity is relatively low, generally...

AI Technical Summary

Problems solved by technology

[0003] At present, the traditional process of domestic production of p-phenylenediamine is obtained by using p-nitroaniline as raw material, and then reducing it with iron powder or lead chloride. The biggest defect of this process is that there is a lot of industrial waste water, which seriously pollutes the environment, and the product yield is low. , the total yield is less than 85%, and the purity is low, generally around 95%

In recent years, there have been many studies on the new synthesis process of p-phenylenediamine, but the catalytic reduction process proposed on the basis of the traditional process has the prospect of industrial application, that is, using methanol as a solvent and carrying out hydrogenation under the action of a supported noble metal catalyst Reaction to prepare p-phenylenediamine, this process effectively solves the problem of environmental pollution, but the disadvantage of this process is that the noble metal catalyst is expensive, and at the same time, the loss of the separation solvent methanol is high, and methanol is toxic, so the production cost of the entire process is very high and it is not environmentally friendly.