Investigation of Vapor−Liquid Equilibria for Supercritical Carbon Dioxide and Hydrocarbon Mixtures by Perturbed-Chain Statistical Associating Fluid Theory

The perturbed-chain statistical associating fluid theory (PC-SAFT) is used to investigate the vapor−liquid equilibria for binary supercritical carbon dioxide (CO 2 ) and hydrocarbon mixtures. The molecular parameters m, σ, and ε / k for pure CO 2 and hydrocarbons with carbon number n ≤ 20 are taken from the work of Gross and Sadowski. m, σ, and ε / k for n -alkanes with n > 20 are obtained by extrapolation from the linear relationships between molecular parameters and molecular weight M w . The binary interaction parameters ( k ij ) are regressed by using the experimental data. Investigation shows PC-SAFT is able to accurately describe the vapor−liquid-phase equilibria for both CO 2 −light hydrocarbon and CO 2 −heavy n -alkane (up to C 44 ) binary mixtures. When the carbon number n in each hydrocarbon ranges from 1 to 20, the regressed k ij increases monotonically with the increase of n . However, when n is greater than 20, there is a unique binary interaction parameter ( k ij = 0.16) that can well describe the vapor−liquid-phase equilibria for CO 2 −eicosane, CO 2 −octacosane, CO 2 −hexatriacontane, and CO 2 −tetratetracontane binary mixtures.