Vapor‐liquid equilibria at high pressures: Calculation of partial molar volumes in nonpolar liquid mixtures

Abstract

AbstractThermodynamic analysis of high‐pressure vapor‐liquid equilibria requires information on the effect of pressure on liquid phase fugacities; this information is given by partial molar volumes in the liquid mixture. A method for predicting these partial molar volumes is presented here. First, molar volumes of saturated liquid mixtures are computed by extending to mixtures the corresponding states correlation of Lyckman and Eckert. These mixture volumes are then used to calculate partial molar volumes with an expression based on a modification of the Redlich‐Kwong equation. At high pressures partial molar volumes are strong functions of the composition and in the critical region, may be positive or negative. Calculations are sensitive to the characteristic energy between dissimilar molecules; this energy is generally lower than that given by the geometric‐mean rule. Calculated results are in good agreement with experimental data for seven systems containing paraffinic and aromatic hydrocarbons, carbon dioxide, and hydrogen sulfide.