Activity coefficients of associating mixtures by group contribution

A group contribution model is presented for the prediction of activity coef ficients in associating mixtures. An association term has been added to the traditional UNIFAC residual and combinatorial contributions to the activit y coefficients. The association term, is based on Wertheim's theory for flu ids with highly directed attractive forces, as applied in the SAFT equation , and it follows the group contribution approach proposed by Gros et al. in the GCA-EOS model. Good predictions of both vapor-liquid and liquid-liquid equilibria are achieved, with a set of group interaction parameters determ ined from infinite dilution activity coefficients. (C) 1999 Elsevier Scienc e B.V. All rights reserved.