Prediction of hydrocarbon solubility in water under vapor-liquid-liquid conditions

Prediction of the solubility of hydrocarbons in water under vapor-liquid-liquid equilibria conditions was accomplished by the used of a modified equation of state approach. The method is based on previous equation of state work by Kabadi and Danner (1986) as refined in the API Technical Data Book (Danner and Daubert, 1998). A simple generalized group contribution model is recommended for the prediction of the water effects on the Soave energy parameter. In addition, a similar model is added to approximate activity coefficients in the aqueous phase. The use of generalized binary interaction parameters is also recommended.; The analysis of this project was based on a critically evaluated literature database. The method is compared to the API method and to a method that combines the API method with the UNIFAC model for activity coefficients. The generalized method improves the prediction of solubility of hydrocarbons in water over the other tested methods. The average bias is 1.83 x 10-3 mole fraction compared to 1.82 x 10-2 for the API method and 8.50 x 10-3 for the API-UNIFAC combination. The generalized method is also preferred because it converges for more data points and requires fewer input parameters than the UNIFAC method. The generalized method only requires the carbon number and a selection from five hydrocarbon functional groups whereas UNIFAC contains 85 functional groups and in excess of 200 interaction parameters.