Modeling Phase Equilibria for the Glycine–NH4Cl–Methanol–Water System and Its Application for the Industrial Monochloroacetic Acid Process

Abstract

As a continuation of our previous study, this work focuses on the determination and modeling of phase equilibria for the mixed-solvent electrolyte system containing glycine, ammonium chloride (NH4Cl), methanol, and water. This electrolyte is used in the monochloroacetic acid (MCA) process for glycine production. The solubilities for the NH4Cl–methanol–water and glycine–NH4Cl–methanol–water systems were determined from 283.15 to 323.15 K. The MSE model embedded in the OLI platform was modified by regressing experimental data through adjustment of the UNIQUAC and the middle-range interaction parameters. With the new model parameters, solubilities in the quaternary system were predicted with excellent agreement. The average absolute deviations between the prediction and the experimental solubility are 3.46 and 0.54% for glycine and NH4Cl, respectively. OLI Stream Analyzer 9.1 was used with this new MSE model to investigate the effect of the methanol composition and temperature on the yield of glycine crystallization in the MCA process. It was found that a methanol mole fraction of 0.65–0.70 at ambient temperatures was optimal for enhancing the theoretical yield of glycine to 96.5% while minimizing the methanol consumption.