Phase Equilibria,PVTBehavior, and Critical Phenomena in Carbon Dioxide +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 CO 2 + 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 CO 2 + 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 CO 2 + 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.