Vapor-liquid equilibria for polyatomic fluids from site-site computer simulations: pure hydrocarbons and binary mixtures containing methane

Abstract

de Pablo, J.J., Bonnin, M. and Prausnitz, J.M., 1992. Vapor-liquid equilibria for polyatomic fluids from site-site computer simulations: pure hydrocarbons and binary mixtures containing methane. Fluid Phase Equilibria, 73: 187-210. Densities and enthalpies of vaporization for several alkanes have been calculated by dividing the molecules into sites (or groups) and then using Monte Carlo simulation with site-site Lennard-Jones potential energy functions. The properties of uniphase systems have been determined from simulations in the isobaric-isothermal ensemble. The properties of saturated (two-phase) systems have been computed by simulations in the Gibbs ensemble. The intermolecular potential energy functions used in these simulations are similar to those presented by Jorgensen, Madura and Swenson (1984, J. Am. Chem. Soc., 106: 6638). However, to cover an appreciable range of external conditions, the characteristic energy ϵ used here is a linear function of site density. Site-site potential functions provide the microscopic analog of group contribution methods for estimation of thermodynamic properties. Good agreement with experiment is achieved for several pure hydrocarbons and for a few binary mixtures containing methane.