Modeling of Vapor-Liquid Equilibria for CO2 + 1-Alkanol Binary Systems with the PC-SAFT Equation of State Using Polar Contributions

In this work, we present the modeling of the vapor-liquid equilibria for the binary systems CO2 + 1-alkanol (from methanol to 1-nonanol) using the PC-SAFT equation of state as the thermodynamic model for the liquid and vapor phases. Four different versions of the PC-SAFT model were compared: the quadrupolar version for the CO2 molecule, the dipolar version for alkanols, a dipolar + quadrupolar version for CO2 and alkanols without considering cross-interactions, and the original version of the PC-SAFT equation. For the modeling of these systems, binary interaction parameters were fitted to experimental binary vapor-liquid equilibrium data of the form k(ij) = k(ij)(0) + k(ij)(1)/T. The results obtained showed that, for pure compounds, the inclusion of the dipolar term improved the predictions of the saturation region slightly, whereas for binary systems, the PC-SAFT model with dipolar and quadrupolar contributions yielded the best predictions of the experimental behavior, mainly because of the quadrupolar contribution for the CO2 molecule. The dipolar version of the PC-AFT equation gave no better predictions than those obtained with the original PC-SAFT model with an association contribution.