Development of a Universal Group Contribution Equation of State. 2. Prediction of Vapor−Liquid Equilibria for Asymmetric Systems

Abstract

The PSRK method is a well-established group contribution equation of state (GCEOS) for the prediction of vapor−liquid equilibria (VLE) and other properties. A generalized GCEOS has been developed to overcome the still remaining weaknesses of the PSRK model, which is of great interest for industrial chemistry. A generalized volume-translated Peng−Robinson (PR) equation of state (EOS) has been combined with the group contribution method UNIFAC by means of a simple gE mixing rule, derived from the PSRK one. In this new GCEOS, the Flory−Huggins term of the PSRK mixing-rule and the combinatorial part of the UNIFAC model are skipped simultaneously, which leads to a much better description for asymmetric systems. The predictions are further improved by using a quadratic mixing rule for the parameter b with an exponent of 3/4 for the binary parameter bij in the combination rule. Temperature-dependent group interaction parameters are fitted to VLE over a wide range of temperature and pressure. The results of the n...