A modification of the Wilson equation with only binary parameters for ternary liquid—liquid equilibria

Abstract

While predicting the liquid—liquid equilibria of Type I partially miscible ternary mixtures with the commonly used excess Gibbs energy models based on a local composition model such as UNIQUAC, it is found that noticeable discrepancies exist between the predicted and experimental values. To obtain a better prediction, a modified Wilson equation containing only two binary parameters and an empirical parameter k accompanying every constituent component is proposed in this paper. This empirical parameter plays an important role in the estimation of ternary LLE for systems including at least one water—nonpolar or alcohol—nonpolar constituent binary system. The equation can also be easily extended to multicomponent systems merely by using binary pair parameters. To test this model, the LLE of ten Type I ternary mixtures are estimated using only the parameters of three binary pairs. Comparisons are made with the experimental data from the literature, and the estimated results of the models of UNIQUAC and Wang and Chao (1983) [Wang, W. and Chao, K.C., 1983. Chem. Eng. Sci., 38: 1483–1492] which are applicable to partially miscible mixtures.