Phase equilibria, PVT behavior, and critical phenomena in carbon dioxide plus n-alkane mixtures using the perturbed-chain statistical associating fluid theory approach

The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state was shown to be suitable for pure components and mixtures of solvents and gases as well as for liquid-liquid and vapor-liquid equilibria of polymer systems. In this work, the ability of PC-SAFT to predict the complex phase behavior that can be found in carbon dioxide + n-alkane systems was analyzed. The pure-component parameters were taken from the literature, and the k(ij) binary interaction parameter was calculated by using the experimental vapor-liquid-liquid equilibria of CO2 + n-tridecane at several temperatures. From the different but close k(ij) values, k(ij) = 0.12 was selected. This value allowed one to obtain that a CO2 + n-tridecane mixture exhibits type IV phase behavior, which is in agreement with the experimental results. The k(ij) = 0.12 interaction parameter was transferred to the other CO2 + n-alkane systems for the calculation of mixture properties such as phase equilibria, densities, critical lines, and critical end points, which determine the types of phase behavior. PC-SAFT predictions are in good agreement with experimental data.