Liquid-liquid equilibria with an equation of state based on the significant structure model

Abstract

Liquid-liquid equilibrium data for class II + class V, class I + class II, and class I + class V mixtures were correlated with a recently proposed equation of state (EOS) and local composition mixing rules. It was found the Suzuki EOS with the local composition mixing rules was successful in correlating liquid-liquid equilibrium data for mixtures of an alcohol and shorter chain hydrocarbons (class II + class V) with two interaction parameters, k ij and l ij, which correct the interaction energy and the local composition terms. However, for alcohol and long chain hydrocarbon mixtures, we found that only qualitative agreement was possible for the more polar phase. This can be explained in terms of the dielectric constants of the pure components. For class I + class II mixtures and class I + class V mixtures, the local composition mixing rules gave fair agreement with the data. Correlation of the data with random mixing rules is also shown for comparison along with the Soave EOS equation. It was found that both the Soave EOS and Suzuki EOS produced similar results with random mixing rules and that the liquid density had little effect on the calculations.