An interpretation of the behavior of EoS/GE models for asymmetric systems

The recently developed EoS/G(E) models are mixing rules for the equations of state energy parameters based on the equality of the G(E,)s as Obtained from the EoS and from an explicit G(E)/activity coefficient model, e.g. UNIFAC, NRTL. This equality is, depending on the model, postulated at infinite or zero pressure or at other conditions (system's pressure, constant volume packing fraction). In a number of publications over the last years, the achievements and the shortcomings of the various EoS/G(E) models have been presented via phase equilibrium calculations. This short communication provides an explanation of several literature EoSIGE models, especially those based on zero-reference pressure (PSRK, MHV1, MHV2), in the prediction of phase equilibria for asymmetric systems as well as an interpretation of the LCVM and kappa-MHV1 models which provide an empirical - yet as shown here theoretically justified - solution to these problems. (C) 2000 Elsevier Science Ltd. All rights reserved.