Development of an enthalpy-based group-contribution G(m)(E) model

The enthalpy-based group-contribution model (EBGCM) presented in this work represents a group-contribution model based upon the three-parameter Wilson equation and the EBLCM (enthalpy-based local composition model) for the de scription of excess molar enthalpies. in a first step the interaction param eters were optimized to excess enthalpy data following the group identifica tion of Wu and Sandler. Furthermore, the interaction parameters of two modi fied UNIFAC models (Weidlich and Gmehling and Larsen and Fredenslund) were fitted to the same data base in order to obtain comparable results. Althoug h the EBGCM was developed primarily for the prediction of excess enthalpies , the excess Gibbs free energy can be calculated too. For that purpose, the equations of the EBGCM (as well as for the modified UNIFAC versions) can b e transferred into the G(m)(E) form. In this second step, activity coeffici ents at infinite dilution were used to fit the interaction parameters of th e new model as well as the parameters of the two modified UNIFAC models. In a third step, both excess enthalpy data and activity coefficients at infin ite dilution were used simultaneously to determine the interaction paramete rs. By doing so, the thermodynamic consistency of the interaction parameter s should increase. (C) 1999 Academic Press.