Isobaric vapor–liquid equilibria for the binary and ternary mixtures of 2-propanol, water, and 1,3-propanediol at P = 101.3 kPa: Effect of the 1,3-propanediol addition

Isobaric vapor–liquid equilibrium (VLE) at P = 101.3 kPa have been measured for the ternary system of 2-propanol + water + 1,3-propanediol and its constituent binary systems of 2-propanol + water and 2-propanol + 1,3-propanediol using an equilibrium still with circulation of both vapor and liquid phases. The ternary system of 2-propanol + water + 1,3-propanediol was prepared with three mass fractions (0.10, 0.30, and 0.50) of 1,3-propanediol in the overall liquid mixtures. The equilibrium compositions of mixtures were analyzed by gas–liquid chromatography. The liquid activity coefficients were obtained using the modified Raoultʹs law. The relative volatilities of 2-propanol to water were also determined. The results showed that the azeotropic point of 2-propanol + water can be eliminated when the mass fraction of 1,3-propanediol in the liquid phase is up to 0.50. Thermodynamic consistency tests were performed for the VLE data of these two binary systems. The new binary and ternary VLE data were successfully correlated with the Wilson, non-random two-liquid (NRTL), and universal quasi-chemical activity coefficient (UNIQUAC) models. The models with their best-fitted interaction parameters of the binary systems were used to predict the ternary VLE data. A comparison of model performances was made by using the criterion of mean deviations in boiling point and in vapor-phase composition.