Development of GEQUAC as a new group contribution method for strongly non-ideal mixtures

The reliable prediction of fluid-mixture behavior is essential in applied thermodynamics. Current group-contribution methods have proven to be widely applicable and sometimes, but not always successful in describing thermophysical properties. Since these semi-empirical methods are lacking a theoretical basis for the definition of functional groups, they often deliver unreliable predictions. Previous work has demonstrated that the physically consistent excess Gibbs energy model Group-surface Explicit QUAsiChemical (GEQUAC) theory allows the thermodynamic description of associating as well as non-associating liquid mixtures by explicitly accounting for different poles of the molecular surface between which strong interactions take place. Fitting of the model parameters to carefully selected binary VLE and hE data of alcohol+alkane and ketone+alkane mixtures in homologous series suggests that GEQUAC represents a very promising new group-contribution method. In addition to an excellent simultaneous description of mixture phase behavior and excess properties, the resulting model parameters display physical relevance allowing data extrapolation. Differences in molecular structure are exclusively considered by exchange-entropy parameters ωjis.