Modeling binary mixtures of n-alkanes and water using PC-SAFT

Modeling and measuring the mutual solubility in binary n-alkane + water mixtures is very challenging due to their low order of magnitude. Consequently, experimental data regarding mutual solubilities of these systems scatter remarkably. In this work, the PC-SAFT equation of state has been applied to model liquid-liquid and vapor-liquid-liquid equilibria of binary n-alkane + water mixtures. For this purpose, temperature-dependent binary interaction parameters have been fitted to the n-alkane solubility in the aqueous phase for n-alkanes ranging from n-pentane to n-undecane. Furthermore, these binary interaction parameters have been correlated with the carbon number of the n-alkane in order to predict phase equilibria of binary n-alkane + water mixtures for n-alkanes ranging from n-propane to n-pentadecane. Excellent agreement between modeling results and available experimental data has been observed for the liquid-liquid equilibria including the description of the minimum of n-alkane solubility in water as a function of temperature. Even the prediction of the vapor-liquid-liquid equilibria of the respective mixtures showed remarkably good results compared to experimental data.