Development of an enthalpy-based group-contributionGmEmodel

Abstract

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 description of excess molar enthalpies. In a first step the interaction parameters were optimized to excess enthalpy data following the group identification of Wu and Sandler. Furthermore, the interaction parameters of two modified UNIFAC models (Weidlich and Gmehling and Larsen and Fredenslund) were fitted to the same data base in order to obtain comparable results. Although 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 be transferred into theGmEform. In this second step, activity coefficients at infinite dilution were used to fit the interaction parameters of the 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 infinite dilution were used simultaneously to determine the interaction parameters. By doing so, the thermodynamic consistency of the interaction parameters should increase.