Prediction of water solubilities in hydrocarbons and oils using F-SAC coupled with SRK-EoS

In the present work, the F-SAC (Functional-Segment Activity Coefficient) model was used to predict the water solubility at high temperatures (and pressures) of defined hydrocarbons and non-defined oil fractions. Since in the F-SAC model no pressure effects are considered, the model was coupled with the Soave-Redlich-Kwong (SRK) equation of state by means of the Self-Consistent Mixing Rule (SCMR) in order to properly compute high-pressure data. The F-SAC parameters for hydrocarbon-water systems were revised using the combined model SRK + SCMR(F-SAC) and a data set with 648 infinite-dilution activity coefficient (IDAC), and 589 liquid-liquid equilibrium (LLE) points, including high temperature and pressure data. For defined hydrocarbon-water systems, calculated absolute average deviation (AAD) in logarithm units for IDAC and LLE were 0.12 and 0.29 respectively. The determination coefficients were close to 1.0, which indicates a strong correlation between the calculations and the experimental data. For the non-defined oil predictions, the F-SAC group fragmentation was simply determined by assuming a linear alkane structure. In spite of this crude approximation, for the studied petroleum fractions, the proposed model was capable of satisfactory represent the experimental water solubility data, with an overall AAD 0.088 for the logarithm of molar fractions.