Solubility of succinic acid, glutaric acid and adipic acid in propionic acid + ε-caprolactone + water mixtures: Experimental measurement and thermodynamic modeling

The solubilities of succinic acid, glutaric acid and adipic acid in propionic acid + water solvent mixtures at 304.25–354.65 K, and in propionic acid + ε-caprolactone + water solvent mixtures at 297.65–351.25 K were determined by the synthetic method at atmospheric pressure. The experimental data in propionic acid + water solvent mixtures were correlated by the modified Apelblat equation and modified nonrandom two-liquid (NRTL) activity coefficient model. The results showed that the calculated solubility data by the modified NRTL models had a better agreement with the experimental data, and the value of average relative deviation was 1.923%. And the solubilities of succinic acid, glutaric acid and adipic acid in ternary propionic acid + ε-caprolactone + water solvent mixtures predicted by the modified NRTL model agree with the experimentally determined results satisfactorily, which showed that the modified NRTL model would be suitable model for predicting the solubilities of succinic acid, glutaric acid and adipic acid in propionic acid + ε-caprolactone + water. Furthermore, the thermodynamic functions including dissolution enthalpy, entropy and Gibbs energy were obtained from the solubility data by using the van't Hoff equation.