Solid-Liquid Phase Equilibrium and Determination of Excess Enthalpy, Entropy and Gibbs Free Energy of Androstenedione in Lower Alcohols

Solid-liquid phase equilibrium is the basis of crystallization. To choose the proper solvent and to design an optimized crystallization processs, the solubilities of androstenedione (AD) in methanol, ethanol, isopropanol, and n-butanol were measured at the temperature range from (278.15 to 323.15) K using a multiple reactor set up. The temperature (clear point) at which the suspension turns into a clear solution was taken as the saturation temperature of AD. The experimental data were modeled by van’t Hoff equation and activity coefficient models (Wilson, NRTL and UNIQUAC models), and the NRTL equation was able to estimate the solubility with the best accuracy. Based on the NRTL model and experimental data, the excess enthalpies, entropies, and Gibbs free energies of solutions and activity coefficients of AD were determinded in different alochols. Futhermore, other thermodynamic properties (infinite-dilution activity coefficients and excess enthalpies) were derived as well. The intermolecular interactions and structural effects were analyzed on the basis of these obtained properties.