Accurate computer simulation of phase equilibrium for complex fluid mixtures. Application to binaries involving isobutene, methanol, methyl tert-butyl ether, and n-butane

We have developed a new method, called the reaction Gibbs ensemble Monte Ca rlo (RGEMC) method, for the computer simulation of the phase equilibria for multicomponent mixtures, given an intermolecular potential model for the c onstituent molecular species. The approach treats the phase equilibrium con ditions as a special type of chemical reaction and incorporates knowledge o f the pure-substance vapor pressure data into the simulations. Unlike macro scopic thermodynamic-based approaches like the Wilson and the universal qua sichemical functional group activity coefficients (UNIFAC) approximations, no experimental information concerning the mixtures is required. In additio n to the PTxy phase equilibrium data, the volumetric properties of the mixt ure are calculated. We developed intermolecular potential models based on t he optimized potentials for liquid simulations (OPLS) of Jorgrensen and use d the RGEMC method to predict phase equilibrium data for the binary systems isobutene + methyl tert-butyl ether (MTBE) and the binaries formed by meth anol with isobutene, MTBE, and n-butane. The predictions are excellent, and of comparable accuracy to those obtained using the Wilson and the UNIFAC t hermodynamic-based approaches, even though such approaches use experimental mixture information.