Densities, surface tensions, and isobaric vapor–liquid equilibria for the mixtures of 2-propanol, water, and 1,2-propanediol

Abstract

Densities and surface tensions of the ternary system (2-propanol+1,2-propanediol+water) at T=298.15K and its constituent binary systems (2-propanol+1,2-propanediol and 1,2-propanediol+water) at T=298.15, 308.15, 318.15, and 328.15K were measured under atmospheric pressure. Densities were determined using a vibrating-tube densimeter. Surface tensions were determined by the Wilhelmy-plate method. From the experimental binary and ternary data, the excess molar volumes and deviations in surface tension were calculated. These excess quantities were fitted to the Redlich–Kister equation, a simple equation based on Connors and Wright, and a modified equation of Cibulka, respectively. The results were used to study the nature of mixing behaviors between mixture components.Isobaric vapor–liquid equilibrium (VLE) at P=101.3kPa have been measured for the ternary system of 2-propanol+water+1,2-propanediol using an equilibrium still with circulation of both vapor and liquid phases. The effect of 1,2-propanediol on the VLE of 2-propanol+water was studied with three mass fractions (0.10, 0.30, and 0.50) of 1,2-propanediol in the overall liquid mixtures. The equilibrium compositions of mixtures were analyzed by gas–liquid chromatography. The results showed that the azeotropic point between 2-propanol and water can be eliminated when the mass fraction of 1,2-propanediol in the feed is up to 0.50. The relative volatilities of 2-propanol with respect to water were also determined. The new ternary VLE data were successfully correlated with the Wilson, NRTL, and UNIQUAC models, for which the binary interaction parameters are reported. The comparison of the volatility effect of 1,2-propanediol with that of 1,3-propanediol on 2-propanol+water was illustrated.