Study On Single Crystal Growth And Crystallization Process Of Glycine

Glycine is the simplest non-essential amino acid and can be applied in many fields. Most of glycine are compounded by chloroacetic acid ammonolysis, and it is hard to remove the impurities, so the purity is not good. Its CSD (calculation the particle size of distributions) also can't reach the grade that we required, in addition, there is caking phenomenon while in the process of storing and transporting. Based on the deficiency stated above, the crystallization process of glycine was investigated and analyzed systematically.The solubility of glycine in pure water and water-acetone of different ratio was measured by dynamics laser method, and the results showed that it increased with the temperature rises and fitted better by Apelblat equation. The dissolving entropy and dissolving enthalpy data were calculated by the Van't Hoff equation. The solubility in acetone-water was fitted linear with the temperature. The metastable zone was also measured by dynamic laser method and the width of the metastable zone in different solution was analyzed theoretically.The densities of glycine in different mass ratio of acetone-water at 25? at the atmospheric pressure were measured by the buoyancy densitometer, and were fitted by the Vogel-Tamman-Fulcher (VTF) equation preferably. The data of apparent molar volume, limiting partial molar volume and transfer partial molar volume of glycine in water-acetone solution were calculated according to the densities data, and the results showed that the transfer partial molar volumes were positive and increased with the acetone content.The size variation of glycine single crystal in different directions in the supersaturated solution and supersaturated acetone-water solution was measured by the XDS-1B inverted microscope, and was fitted by linear to calculate the growth rate. The growth rate constants Kg and crystal growth activation energy Ea of glycine crystal in the supersaturated solution were calculated according to the dynamics equation.The crystallization process is the important purification of glycine. Based on cooling crystallization, the cooling-antisolvent crystallization process was investigated systematically and the anti-solvent used in the experiment was acetone. In the experiment, the impacts of crystal seed, the anti-solvent dripping speed rate, stirring intensity and cooling rate to the glycine crystal production were discussed, and the glycine crystallization process operational conditions were determined finally.