Comparison of different cubic equations of state and combination rules for predicting residual chemical potential of binary and ternary Lennard–Jones mixtures: Solid-supercritical fluid phase equilibria

Abstract

Molecular simulation data of binary and ternary mixtures were used to study the capability of cubic equations of state (CEOS), Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK), and Peng–Robinson (PR), to predict the residual chemical potential of a heavy solid compound in a supercritical fluid when molecules interact each other with a simple Lennard–Jones (LJ) potential. The chemical potential of the solid compound is calculated directly from the Lennard–Jones parameters of the involved molecules. It was found that if appropriate combination rules are used, van der Waals one fluid theory (vdW-1f) allows CEOS to reproduce accurately the molecular simulation data without any adjustable parameter, even if asymmetries in molecular size and energy are considerable. For the supercritical binary systems analyzed in this work, it was observed that the relation of the parameters of energy influences more the performance of vdW-1f theory (and as a consequence the performance of the CEOS), than the relation of the parameters of size.