A comparison of Huron-Vidal type mixing rules of mixtures of compounds with large size differences, and a new mixing rule

A comparison is made of a number of Huron and Vidal-type mixing rules for mixtures of molecules with large differences in size, and a new mixing rule of this class is introduced. In particular a comparison is made of the PSRK, MHV1, MHV2, LCVM and HVOS models which combine equations of state with activity coefficient models. The new mixing rule introduced here has a well defined reference pressure and performs equally well in comparison to the other models for VLE correlation-prediction of mixtures of molecules with large size differences. Such mixtures were the focus of this study since for these significant differences between the mixing rules are observed. The models considered here have not been tested on an identical basis before as we do here, which is to use the same EOS (Soave-Redlich-Kwong), the same excess energy model (UNIQUAC) and the same size and shape parameters for light compounds in each of the mixing rules. This test reveals that while there are differences between the models, none was clearly superior to the others for all mixtures, though the MHV2 model was the least accurate.