Numerical Model And Analysis For Crystallization Thermodynamics And Nucleation Kinetics

As an important means of separation and purification,crystallization has been widely used in the fields of chemistry,physics,materials and life science.Crystallization process not only affects the product purity,crystal size distribution(CSD),but also determines the crystal habit and form.In order to optimize the crystallization process,the industrial crystallization process is often controlled in the metastable zone,which is closely related to crystallization thermodynamics(dissolution process)and nucleation kinetics(nucleation process).In this paper,the mathematic method is adopted to study three different crystalline systems,dicyandiamide is a typical small molecule compound,paracetamol is a typical drug molecule with polymorph,and potassium sulfate is a typical inorganic salt.1)Crystallization Thermodynamics Study:the study of thermodynamic phase equilibrium characterized the starting point and limit of crystallization process.The solubility of three systems(dicyandiamide,paracetamol form Ⅰ and Ⅱ,potassium sulfate)at different temperatures was determined.The phase equilibrium of organic and electrolyte solution was established.Moreover,an effective method was put forward to predict the solubility of polymorph by acitivity model and thermal property.2)Nucleation Potential Model:In order to establish a unified model relating primary nucleation dynamical experiments(metastable zone and induction time),the nucleation potential model with clear physical significance was derived based on the classical nucleation theory.The validity of the nucleation potential model is verified by dicyandiamide experiments and 45 sets of survey data.3)Nucleation Kinetics Study:nucleation kinetics characterizes the boundary and the operational limit of crystallization process.Based on its great understanding of the crystallization process,the nucleation potential model can better correlate the metastable zone with different temperature,explore the mechanism of nucleation process,and predict the polymorph nucleation region by coupling with polymorph phase equilibrium.This model has excellent application prospect.