Comparison of cubic- and hard-sphere-based equations of state for associating fluid mixtures

Abstract

Recently obtained enthalpy and phase behavior data at elevated pressures and temperatures for both pure fluids and binary and ternary mixtures of m-cresol, quinoline, and tetralin, combined with phase behavior data for mixtures of methanol, n-pentane, and acetone, were used to compare variations of perturbed hard sphere (PHS) equations of state for mixtures with a typical cubic equation of state, a modified Soave-Redlich-Kwong (SRK) equation, for estimating properties of these highly nonideal systems. By fitting pure fluid vapor pressures, attractive terms, a(T), were determined for the PHS equations of state, which are much more consistent with the original temperature-independent attractive parameters as suggested by van der Waals. Experimentally determined binary interaction parameters resulted in comparable phase behavior fits and predictions for both equations. However, the PHS equations of state yielded much more accurate predictions of ternary enthalpy differences than the SRK equation of state