Industrial & Engineering Chemistry Research, Vol.55, No.8, 2426-2437, 2016
Process for Glycine Production by Antisolvent Crystallization Using Its Phase Equilibria in the Ethylene Glycol-NH4Cl-Water System
A new process for the production of glycine by using antisolvent crystallization with the mixture of ethylene glycol (MEG) and water as a substitute for methanol has been developed on the basis of chemical modeling phase equilibria for the glycineNH(4)ClMEGH(2)O system. MEG is considered as a green solvent because it has great higher boiling point up to 470 K and thus is almost nonvolatile compared with methanol. We discovered that the solubility of glycine, NH4Cl and their mixtures can be greatly changed by altering the composition of the mixed MEG-H2O solvents and realized the complete separation of glycine and NH4Cl by water evaporation. Phase equilibria for the glycine NH4Cl-MEG-H2O system were measured from 278 to 353 K. The mixed-solvent electrolyte (MSE) model was applied with new binary interaction parameters obtained from regressing experimental and literature data. This newly modified model accurately predicted the solubilities in the quaternary glycine NH4Cl-MEG-H2O system with average absolute relative deviations of 5.84% and 1.03% for glycine and NH4Cl, respectively. Simulation for the new process was performed by the model to investigate its operating conditions, from which the optimal composition of antisolvent was determined to be 50 wt % of MEG solution. Under this condition, glycine and NH4Cl were successfully separated from their solid mixtures in batch crystallization experiments, validating the feasibility of the proposed process for glycine production.