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 predi ction of infinite-dilution activity coefficients in binary mixtures. I n the case of aqueous mixtures, the correlation of Pierotti, Deal, and Derr (PDD) has also been included in the comparison. For athermal alk ane/alkane asymmetric mixtures the modified UNIFAC-type models perform very well, while the original UNIFAC ones give poor results. For nona queous polar mixtures, the modified UNIFAC of Gmehling et al. gives sa tisfactory results. For the highly nonideal aqueous systems, the PDD c orrelation is the best method. When the PDD correlation is not availab le, order of magnitude estimates can be obtained from the UNIFAC-LLE o f Magnussen et al. Finally, for the hydrocarbon/water mixtures, the mo dified UNIFAC-type model of Hooper et al. should be used since it was specially developed for such systems.