Modeling of solid-supercritical fluid phase equilibria with a cubic equation of state-G(ex) model

Equations of state (EOS) are an important tool for the correlation and pred iction of thermodynamic properties and phase behavior of pure substances an d mixtures. Therefore EOS are widely used in design, simulation and optimiz ation of chemical processes. In particular, cubic EOS are routinely used in the chemical and petrochemical industries to calculate phase equilibria an d thermophysical properties. This approach proves to be simple and accurate for engineering calculations. However, when these equations are used with the classical van der Waals mixing rules they do not perform well for highl y polar, asymmetric and/or associating mixtures. Consequently, numerous mix ing rules have been proposed to extend the capabilities of cubic EOS. Recen tly, several mixing rules have been developed that contain excess Gibbs ene rgy (G(ex)) models. The Wong-Sandler mixing rule belongs to this group, and has been successfully used to describe the phase behavior of mixtures that involve both polar and associating fluids. Here we consider the applicatio n of this mixing rule to solid-supercritical fluid phase equilibria as solv ent extraction with supercritical or near-critical fluids has been proposed as an alternative to conventional separation processes. While these system s generally involve constituents that are of very different molecular natur e (i.e. asymmetric mixtures), the EOS model considered here successfully de scribed binary and ternary solid-supercritical fluid mixtures. (C) 2001 Els evier Science B.V. All rights reserved.