Prediction of Infinite-Dilution Activity Coefficients in Binary Mixtures with UNIFAC. A Critical Evaluation

Using an extensive data base, several UNIFAC-type activity coefficient models have been compared with respect to their accuracy in the prediction of infinite-dilution activity coefficients in binary mixtures. In the case of aqueous mixtures, the correlation of Pierotti, Deal, and Derr (PDD) has also been included in the comparison. For athermal alkane/alkane asymmetric mixtures the modified UNIFAC-type models perform very well, while the original UNIFAC ones give poor results. For nonaqueous polar mixtures, the modified UNIFAC of Gmehling et al. gives satisfactory results. For the highly nonideal aqueous systems, the PDD correlation is the best method. When the PDD correlation is not available, order of magnitude estimates can be obtained from the UNIFAC-LLE of Magnussen et al. Finally, for the hydrocarbon/water mixtures, the modified UNIFAC-type model of Hooper et al. should be used since it was specially developed for such systems.