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 = kij₀ + kij₁/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-SAFT equation gave no better predictions than those obtained with the original PC-SAFT model with an association contribution.