Study On The Crystallization Process Of Glycine With Additives And Molecular Simulation

As an important fine chemical intermediate,glycine is widely used in the pesticide,pharmaceutical,food,feed,photoelectric material,daily chemical industries and other fields.At present,the domestic production of glycine has these problems,such as mixed crystal,which consists of alpha form and gamma form glycine,poor crystal habit,non uniform distribution of particle size and caking when glycine is stored at a long time,which seriously affect the production,sale and use of glycine.In this paper,a systematic study on the crystallization process of glycine based on the research background was conducted.Study on the crystallization thermodynamics of glycine with additives.The solubility of glycine in water with different additives was measured under normal atmospheric pressure across the temperature range of(293.15-343.15)K by using a dynamic laser method.The effects of additive variety,additive addition and temperature on the dissolution behavior of glycine were studied.Nonlinear regression fitting was performed to calculate the solubility data with the modified Apelblat model,NRTL model and ?h model,thus the correlative model parameters were obtained,and the mathematical models of dissolution behaviors of glycine in water with different additives were established.The thermodynamics properties of glycine in the dissolution process were systematically analyzed.The values of apparent standard enthalpy,entropy,and Gibbs free energy changes,relative enthalpy contribution,relative entropy contribution,enthalpy-entropy compensation,and excess enthalpy of solution were calculated,which provided basic data and theoretical support for the research of crystallization technology and crystallization kinetics.Study on the crystallization metastable property of glycine in water with additives.The supersolubility of glycine in water with different additives was systematically measured,and the metastable zone of solution crystallization was obtained,in which the effects of additive variety,additive addition and temperature for metastable zone width of glycine were studied.The temperature of appeared crystal point was measured during cooling crystallization process of glycine under different variety of additives,additive addition,cooling rate and stirring rate using EasyMax device,and the regulation of law was determined.Study on the crystallization technology of glycine in water with additives.Single factor control was employed to systematicly study the effects of different additives on crystallization process of glycine.With crystal form,crystal habit and particle size distribution of glycine crystal product being the research targets,the effect and control law of additives on the quality of glycine crystal product were analysised and identified.Study on the crystal morphology of glycine.With glycine,which was the crystal product from cooling crystallization in water with additives,being the research object,Materials Studio molecular simulation software was employed to index the X-ray powder diffraction data of different form glycine to get the corresponding crystal cell parameters,and then the microscopic structures of the two forms glycine was determined.The theoretical crystal habit of glycine was simulated by using BFDH model.