Modeling the excess Gibbs free energy for selected binary and ternary alcohol-water mixtures.

Abstract

The excess Gibbs free energy provides a useful means for the analysis of the non-ideality of chemical solutions. Several models [Margules, van Laar, Wilson, and non-random two liquid (NRTL)] are used to predict the behavior of isothermal vapor liquid equilibrium data for binary mixtures of methanol + water, ethanol + water, methanol + ethanol, and the ternary system methanol + ethanol + water at 323.15 K, 328.15 K, and 333.15 K. Only the Wilson and the NRTL equations have the ability to give good fit for the activity coefficients over the entire composition range. Nonlinear regression techniques are used to fit the Wilson and NRTL models. The experimental data are checked for thermodynamic consistency.