Process for preparing phenylhydrazine sulfate by continuous method

Abstract

The invention discloses a process for preparing phenylhydrazine sulfate by a continuous method, which comprises the following steps: reducing a phenyl diazonium salt solution by using a NaHSO3 solution to generate phenylhydrazine sulfate, the molar ratio of diazonium salt to NaHSO3 being 1: (2.5-5.5); and respectively pumping a phenyl diazonium salt solution and a sodium hydrogen sulfite solution into a pipeline reactor by a metering pump under the condition that the mixing temperature is 5-30 DEG C, controlling the temperature of the pipeline reactor in a sectional manner, performingfront stagecontrolling at 50-80 DEG C for retention time of 5-10 minutes, adding a dilute sulphuric acid solution into a reaction pipeline, performing rear stage controlling at 80-100 DEG C forretention time of 15-25 minutes, then introducing into a crystallization kettle, cooling to 0-5 DEG C, crystallizing, and centrifuging. A continuous method is used for replacing traditional intermittent operation, the operation efficiency and safety are greatly improved, workshops are saved, equipment investment is reduced, energy consumption is reduced, and manpower is reduced.

Description

technical field [0001] The invention relates to the field of chemical synthesis, in particular to a preparation method of phenylhydrazine sulfate. Background technique [0002] Phenylhydrazine salts (including hydrochloride, sulfate, etc.) have an extremely important position in the fields of fine chemicals and organic synthesis, especially as important raw materials and intermediates for medicines and pesticides, and can synthesize a series of medicines, dyes, and azo compounds And other raw materials of fine chemicals, such as pyrazolone pesticides, celecoxib and its similar series of APIs, etc. [0003] The synthetic method of phenylhydrazine salt is mainly through three steps of diazotization, reduction and acidification hydrolysis. Since the diazonium salt synthesized during the diazotization reaction is unstable and highly active, it can be decomposed and exploded by heat, friction, or impact, and the diazonium salt can be decomposed at room temperature, so the diazot...

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Problems solved by technology

[0005] However, the reaction of the subsequent reduction step is slow, and it often takes several hours to complete the reaction, which seriously restricts the equipment efficiency, such as the methods reported in the literature such as Organic Syntheses, 1941, 1,442, CN101928246, European Journal of Medicinal Chemistry, 2016, 120, 37-50, etc. Subsequent reduction and hydrolysis take more than 3 hours, and a large amount of wastewater is generated

The advantages of the continuous preparation of diazonium salts in the early stage are greatly reduced, and the yield obtained is often not high

In addition, most of the reduction methods reported in the literature are traditional batch reactions, and the temperature difference between different reaction areas such as the wall and the center of the kettle is large, and slight changes in the process conditions during the preparation of phenylhydrazine often lead to large fluctuations in the yield. poor reproducibility

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