J. Abildskov et al., TOWARDS THE DEVELOPMENT OF A 2ND-ORDER APPROXIMATION IN ACTIVITY-COEFFICIENT MODELS BASED ON GROUP CONTRIBUTIONS, Fluid phase equilibria, 118(1), 1996, pp. 1-12
A simple modification of group contribution based models for estimatio
n of liquid phase activity coefficients is proposed. The main feature
of this modification is that contributions estimated from the present
first-order groups in many instances are found insufficient since the
first-order groups do not provide all the important molecular structur
al information. Therefore, addition of second-order terms, which provi
de the needed extra molecular structural information, is proposed. The
scope of the new approach is demonstrated through the well-known UNIF
AC model in terms of improved correlation/prediction capabilities, dis
tinction between isomers and ability to overcome proximity effects.