GC-PPC-SAFT Equation of State for VLE and LLE of Hydrocarbons and Oxygenated Compounds. Sensitivity Analysis

Abstract

Group-contribution polar versions of SAFT equations of state are very useful for predictive calculations of mixtures containing diverse polar molecules. In this work, we have evaluated the predictive performance of one such model, the so-called polar perturbed-chain (PPC) SAFT model for phase-equilibrium properties of 290 hydrocarbons and monofunctional oxygenated compounds. Emphasis has been given on carrying out an extensive evaluation considering diverse types of phase behavior (vapor–liquid and liquid–liquid equilibria) and properties/conditions (Henry’s law constant for H2, N2, and CH4; infinite-dilution activity coefficient in water; solubility in water; infinite-dilution n-octanol/water partition coefficient). In general, considering the predictive nature of the calculations, encouraging results were obtained. For pure-component vapor pressures and liquid molar volumes, the deviations are very small, at 20% and 3%, respectively. The deviations in the prediction of the Henry’s law constants are within a factor of 2, with the best results found for the methane and nitrogen solubilities. For solubilities in water and, consequently, for infinite-dilution n-octanol/water partition coefficients, deviations are within a factor of 2 for hydrocarbons and within a factor of 4 for alcohols and aldehydes, but they are large for the other oxygenated families. To identify paths for improvement, a sensitivity analysis was performed, indicating that all of the parameters make large contributions to almost all properties. In addition, the sensitivity of the infinite-dilution activity coefficient in water to the molecular size parameters was extremely high. This suggests that a small change in these parameters might improve the results significantly.