Thermodynamic equilibrium of hexamethylenediammonium glutarate in mono-solvents and binary solvent systems

Abstract

Hexamethylenediammonium glutarate was synthesized by glutaric acid recovered from mixed dibasic acid and 1, 6- hexanediamine in aqueous solution and characterized by fourier transform infrared spectroscopy and nuclear magnetic resonance. Its thermal properties were evaluated via differential scanning calorimetry. At the same time, the solubility of hexamethylenediammonium glutarate in four mono-solvents (water, methanol, acetic acid and ethylene glycol) and four binary solvents (methanol + ethanol/2-propanol/1-butanol/DMF) were determined by dynamic method at atmospheric pressure. It turns out that the solubility of hexamethylenediammonium glutarate in the selected solvents increases with the temperature rising in the investigated temperature range. Moreover, the solubility data was correlated by the modified Apelblat model, the λh model, the e-NRTL model and the Jouyban–Acree model. The results showed that the experiment data was better in agreement with the values calculated by the modified Apelblat model in mono-solvents and binary mixed solvents. In addition, the dissolution thermodynamics were based on the van't Hoff equation. The results demonstrated that the dissolution processes of hexamethylenediammonium glutarate in the selected binary solvents were the non-spontaneous and endothermic processes. Therefore, the solubility data and the dissolution thermodynamic properties provide the basis for the separation and purification of hexamethylenediammonium glutarate by crystallization.