The Study On Crystallization Process Of M–aminophenol

M-aminophenol(MAP)is a widely used organic chemical raw material and pharmaceutical intermediate.Its main applications include dyes,pharmaceuticals,petrochemicals,etc.There are various methods for producing m-aminophenol,such as nitrobenzene,resorcinol ammonolysis,and aniline hydroxylation.However,there are a series of problems such as complex process,large pollution and high cost.Hydrolysis of m-phenylene diamine has become a hot spot for many scholars due to its cheap raw materials,simple process,and clean production,which have the dual advantages of low production cost and perfect technical cost.However,in this method,the separation of the product MAP and the raw materials phenylene diamine is hard to avoid and very difficult,and it has become the key to the failure of this process.Based on the differences in the solubility of MAP and m-phenylene diamine,the cooling crystallization process of m-aminophenol was systematically studied.The main research content is as follows:(1)The solubility data of m-aminophenol were measured using a laser-monitoring observation under the atmospheric pressure.The solubility data were fitted by empirical data?Apelblat model and ?h model,and the Apelblat model fitted the best results.The super solubility of m-aminophenol was determined by the laser dynamic method,combining with the solubility data to ascertain its metastable zone.At the same time,the effects of temperature,stirring rate and cooling rate on the width of metastable zone were investigated.(2)The intermittent dynamite method was used to determine the cooling crystallization kinetic data of m-aminophenol and apply the method of moment transformation and particle size independent growth model to process and analyze the dynamic data,so that we can regress the nucleation rate equation and the growth rate equation of m-aminophenol crystals.Meanwhile,the effects of supersaturation and suspension density on the nucleation and growth rate were analyzed.(3)The solubility and supersolubility of m-aminophenol with different content of m-phenylene diamine were determined by laser dynamic method.The effect of m-phenylene diamine on the purity of MAP cooling crystal was analyzed.Experiments show that the presence of m-phenylene diamine makes crystallization of MAP more difficult.It can still meet the crystallization purity requirement when the content of m-phenylene diamine is 20%,and when the content reach to 30%,it will cause the purity of the clean product to fall below 99%.In this paper,the solubility,metastable zone and crystallization kinetics of MAP were studied systematically.At the same time,the effect of m-phenylene diamine on the crystallization process of MAP was also studied.There were no reports in the literature at home and abroad.This study provides basic data and theoretical support for the cooling and crystallization process of MAP,providing reliable technical support for the industrialization of m-phenylene diamine hydrolysis.