Method for preparing p-aminophenol from nitrobenzene

Abstract

The invention discloses a method for preparing p-aminophenol from nitrobenzene, which mainly comprises the following steps: carrying out hydrogen reduction reaction in a CO2 / H2O system in a high-pressure reaction kettle at 100-150 DEG C for 4-7 hours by using Pt as a main active component and Mg, Cr and Ni as assistants under the conditions that the H2 pressure is 0.5-2 MPa and the CO2 pressure is 4-6 MPa; after the reaction is finished, filtering the catalyst out and drying the same for continuous use, wherein the selectivity of the p-aminophenol can reach 85% or above. According to the reaction, a CO2 / H2O system is used for replacing a traditional sulfuric acid system, the problems of sulfuric acid pollution to the environment and aftertreatment are solved, meanwhile, the problem of corrosion of sulfuric acid to equipment is avoided, the catalyst with the HZSM-5 molecular sieve as the carrier can adjust the acidity of the carrier, meanwhile, the defect that the acidity of the CO2 / H2O system is insufficient is overcome, and the stability of the catalyst is good.

Description

technical field [0001] The invention belongs to the field of catalytic hydrogenation and relates to a method for preparing p-aminophenol from nitrobenzene. Background technique [0002] p-Aminophenol (p~Aminophenol, referred to as PAP), is an important organic intermediate and chemical raw material, widely used in medicine, rubber, dyes and other industries. In the pharmaceutical industry, p-aminophenol is mainly used in the production of paracetamol and other drugs. Paracetamidyl acetylsalicylate), vitamins, compound nicotinamide, clofibrate, 6-hydroxyquinoline, salaminophen, etc., are very important pharmaceutical intermediates; in the dye industry, PAP can be used as As an intermediate of dyes, p-aminophenol can also be used in the dye industry to produce various dyes such as dispersants, acid dyes, direct dyes, sulfur dyes and fur dyes; in the rubber industry, PAP is mainly used to produce p-phenylenediamine Anti-aging agent, with non-toxic, low pollution, high efficie...

AI Technical Summary

Problems solved by technology

However, there is still a problem of sulfuric acid corrosion in the reaction process; the invention patent CN103357407A discloses a preparation method and application of a catalyst for the preparation of p-aminophenol by a one-step method of nitrobenzene. The method is: pretreatment of activated carbon, loading of platinum salt, vanadium Loading of acid salt and reduction of catalyst; the mass percentage of platinum in the catalyst is 0.5% to 5%, and the mass percentage of vanadium is 0.05% to 2%.

By adding a certain amount of metal vanadium to the Pt / C catalyst, this invention reduces the poisoning effect of sulfide on platinum in the nitrobenzene raw material, prolongs the service life of the catalyst, and improves the catalytic activity and selectivity of the catalyst at the same time. The catalyst has stable performance and good reproducibility. It can be used to catalyze nitrobenzene to prepare p-aminophenol in one step, which reduces the purity requirements of raw material nitrobenzene and reduces the cost of catalysis. Although the yield of this patent is high, but It is because sulfuric acid is used as the reaction medium, which causes serious environmental pollution, and the sulfuric acid is difficult to handle after the reaction is completed.

Invention patent CN103553943A discloses a method for preparing p-aminophenol by hydrogenation of nitrobenzene, using pressurized CO 2 / H 2 The carbonic acid formed in O promotes the Bamberger rearrangement of the intermediate N-phenylhydroxylamine formed in the hydrogenation reaction of nitrobenzene to generate p-aminophenol. After the reaction, CO is released. 2 The system is self-neutralizing, which fundamentally avoids the pollution of the environment by adding alkali to neutralize the generated salt wastewater in the traditional reaction process, but the yield of p-aminophenol is not high

Images