Investigation of vapor-liquid surface tension for carbon dioxide and hydrocarbon mixtures by perturbed-chain statistical associating fluid theory combined with density-gradient theory

The perturbed-chain statistical associating fluid theory (PC-SAFT) and density-gradient theory (DGT) are used to construct an equation of state (EOS) applicable for the phase behaviors of supercritical carbon dioxide (CO2) and hydrocarbon binary mixtures. In the bulk phases, the nonuniform EOS reduces to PC-SAFT, which is able to accurately describe the vapor-liquid equilibria (VLE) below the critical region. In the vapor-liquid surface, this EOS is able to predict the surface tensions for binary mixtures with the bulk properties and the influence parameters of pure components as input. The surface tensions Of CO2-butane, CO2-decane, CO2-benzene, CO2-cyclohexane, and CO2-tetradecane binary mixtures are predicted, and the results are satisfactory compared with the experimental data.