PREDICTION OF VAPOR-LIQUID-EQUILIBRIA AT LOW AND HIGH-PRESSURES USINGUNIFAC-BASED MODELS

Four recently developed models involving equations of state combined w ith the UNIFAC G(E) expression: MHV2, PSRK, LCVM, and the Wong-Sandler models are compared with respect to their performance in the predicti on of vapor-liquid equilibria (VLE). The following cases are considere d: (a) polar mixtures with components of similar size at low and high pressures; (b) asymmetric systems containing supercritical gases and n -alkanes; (c) infinite dilution activity coefficients in asymmetric hy drocarbon mixtures. All models perform satisfactorily in the VLE predi ction of symmetric systems (case a), but only the LCVM model for asymm etric ones (cases b and c). The conventional gamma-phi approach has al so been included in the comparison when applicable; i.e., low-pressure VLE.