Prediction of infinite dilution activity coefficients in aqueous solutions by group contribution models. A critical evaluation

Based on an extensive database, the predictive accuracy of the ASOG and several UNIFAC-type models has been critically evaluated for infinite dilution activity coefficients in aqueous solutions. In general, all the models give rather poor results with mean relative deviations of 45–72% (except the cases where the relative deviations are higher than 100%), whereas the modified UNIFAC (Dortmund) performs well for most of higher polar compounds (e.g., ethanol, acetone, acetic acid) in water mixtures. The UNIFAC–LLE of Magnussen et al. may provide order of magnitude estimates for some lower polar compounds (e.g., aldehydes or 2-ketones with carbon number of 6–9), although it gives poor results for the higher ones. In the particular case of alkanes in water mixtures, the specially developed model of Hooper et al. provides comparatively fair results, but the predicted mean relative deviations of 36% are still large. In this work, an improved UNIFAC will be proposed by using mixture-type groups to account for the specially hydrophobic effects in systems including water, satisfactory results are obtained.