Mutual solubilities of hydrocarbon–water systems with F-SAC

• The F-SAC model is extended with a new temperature correction for hydrogen bonding systems.
• The modified model is able accurately correlate the very small mutual solubilities of hydrocarbon–water systems.
• The minimum solubility of hydrocarbons in water around room temperature is well represented.

In this paper, the F-SAC model was extended in order to better represent the mutual solubility of hydrocarbons (alkanes, cycloalkanes, alkenes, cycloalkenes and aromatics) in water. Aqueous mixtures of hydrocarbons exhibit an extremely non-ideal behavior, resulting in very low solubilities. A new parameter for the computation of the association energy was proposed, enabling a better agreement with temperature dependent experimental data in wide temperature ranges. Infinite-dilution activity coefficient as well as liquid–liquid equilibrium data were considered. The results were compared with some UNIFAC variants, found in the literature. For the studied systems, the proposed method performed better, including the quantitative representation of the experimentally observed minimum solubility point of hydrocarbons in the water-rich phase, while none of UNIFAC models tested were capable of predicting such behavior. Further, improved high-pressure results were obtained when the proposed model was coupled with a cubic equation of state through the SCMR mixing rule.