Study Of The Separation And Purification Of M-cresol And P-cresol By Dissociation Extractive Crystallization

As a pair of isomers with close boiling points,m-crsol and p-cresol are difficult to separate by traditional technology.Because highly purified m-cresol and p-cresol are important fine chemical intermediates,researchers has been focusing on the separation of m-cresol and p-cresol for decades.The purpose of this paper is to investigate the separation and purification of m-cresol and p-cresol by using dissociation extractive crystallization.Dissociation extractive crystallization combines complexation reaction with crystallization in order to purify the target product selectively.This technique is extremely potential for separating azeotropic mixtures.On the basis of dissociation extractive crystallization,DABCO?6H₂O and CH₃COONa are employed as neutralizing agents to purify p-cresol and m-cresol respectively.Through experiments,it was proved that this strategy could successfully accomplish the separation of cresol isomers.For the purpose of optimal operating conditions,the effect of some factors such as types of solvent,mass of neutarlizing agent,volume of solvent,reactive temperature,reactive time,crystallization temperature and washing times on purities and yields of product were investigated by single factor experiments.As a result,the optimal values and appropriate range of single factors have been determined.Based on the results,orthogonal experiments were designed to get the optimum experimental conditions which could realize the highest purities and yields of products.A green process for separation of m-cresol and p-cresol using dissociation extractive crystallization was presented in this paper.Namely,DABCO?6H₂O method was used to purify p-cresols firstly,and then the filtrate of this step was served as raw materials for CH₃COONa method to separate m-cresols from the mixtures.The filtrate of CH₃COONa method was recycled to mix up with raw materials of DABCO?6H₂O method,so that the overall yields of this process were raised significantly.This process was validated by experiments.In the experiments,the raw materials were from the distillates of industrial cresols.The results showed that purified p-cresol and m-cresol were produced by DABCO?6H₂O-CH₃COONa coupling method.Also,there was no discharge of the three wastes,because all the solvents,neutralizing agents and extraction solvent could be recycled and reused within the process.Because of the circulation of raw materials,there is no loss of m-cresol and p-cresol in the process theoretically.This study provides a high recovery and environmental-friendly strategy for separation of m-cresol and p-cresol.