The Research Of Solid-liquid Equilibrium Based On Three Organic Benzoates

Crystallization technology is a basic unit operation of Chemical Engineering.As a separation and purification method,it has high separation efficiency and low energy consumption.Solid-liquid equilibrium,the important theoretical basis of crystallization technology,are of the great significance for judging the feasibility of crystallization process and the end point of separation,and also for optimizing the crystallization process.As the organic chemical raw materials and intermediates,Benzoates are widely used in the fields of fine chemicals such as medicine,daily chemical,food,etc..However,there are rarely reports in the literature relate to it,which greatly limits the optimization of production processes,the improvement of products quality,the reduction of energy consumption and other aspects.The study focuses on the research of solid-liquid equilibrium of Methyl 3,4,5-Trimethoxybenzoate,Dimethyl terephthalate(DMT),and Ethyl p-Hydrobenzoate.The main work includes:(1)Determined the solubility data in common industrial solvents by gravimetric analysis,summarized the law of dissolution with temperature,solvent composition and other influencing factors,and discussed the co-solvent effect in mixed solvent;(2)Obtained the thermodynamic parameters in the dissolution process by using the modified Van't Hoff equation.Analysis of the dissolution thermodynamic behavior reveals that all processes are endothermic,entropy increasing,and non-spontaneous.Besides,the intermolecular force is the main driving force in all dissolution processes;(3)Seven solid-liquid equilibrium models were used to correlate the solubility data,including the Apelblat equation,Van's t Hoff equation,?h equation,JA-Apelblat,Wilson equation,NRTL equation,and UNIFAC equation,and obtained the model parameters of related models.Compared the fitting effects of various models,the average relative deviation(ARD)of the Apelblat equation and Van's t Hoff in different dissolution system is less than 2%,which is slightly better than the activity coefficient model,but both of them are satisfactory;(4)Defined two new UNIFAC groups,namely methoxy(CH3O-)b and phenolic hydroxyl(HO-)b,and the volume and surface area parameters of the new groups were calculated and applied to the UNIFAC model.The fitting results of methyl 3,4,5-trimethoxybenzoate and Ethyl p-Hydrobenzoate.In this study,the basic data of solid-liquid equilibrium and related thermodynamic parameters of three substances were obtained.The database was supplemented,and a suitable thermodynamic model was selected to describe and predict the dissolution process,which reduced a lot of experimental costs,and provided reliable support for theoretical research and industrial optimization.