Accurate vapour-liquid equilibrium calculations for complex systems using the reaction Gibbs ensemble Monte Carlo simulation method

The reaction Gibbs ensemble Monte Carlo (RGEMC) computer simulation method [J. Phys. Chem. B 103 (1999) 10496] is used to predict the vapour-liquid eq uilibrium (VLE) behaviour of binary mixtures involving water, methanol, eth anol, carbon dioxide, and ethane. All these mixtures contain molecularly co mplex substances, and accurately predicting their VLE behaviour is a consid erable challenge for molecular-based approaches, as well as for traditional engineering approaches. The substances are modelled as multi-site Lennard- Jones (LJ) plus Coulombic potentials with standard mixing rules for unlike site interactions. No adjustable binary-interaction parameters and no mixtu re experimental properties are used in the calculations; only readily-avail able pure-component vapour-pressure data are required. The simulated VLE pr edictions are compared with experimental results and with those of two typi cal semi-empirical macroscopic-level approaches. These latter are the UNIFA C liquid-state activity-coefficient model combined with the simple truncate d virial equation of state, and the hole quasi-chemical group contribution equation of state. The agreement of the simulation results with the experim ental data is generally good and also comparable with and in some cases bet ter than those of the macroscopic-level empirical approaches. (C) 2001 Else vier Science B.V. All rights reserved.