CONICET | Buscador de Institutos y Recursos Humanos

In a recent work from our group [1], three different equations of state(EoS) were compared in predictive mode for the computation of activitycoefficients in nearly athermal mixtures, using null kijs as it is typicallyused in any of those models for alkane mixtures, at least when the firstlighter compounds of the series are not involved. The chosen equationsof state represented three different classes: the Peng-Robinson (PR) [2]for two-parameter cubic EoS, the GeneralizedRedlich-Kwong-Peng-Robinson (RKPR) [3] as a three-parameter cubicEoS and the PC-SAFT [4] as a representative of the SAFT family ofthree-parameter EoS when applied to non-associating systems. It wasshown that, contrary to what was believed by an important part of thethermodynamic community, the cubic nature of PR is not the reason forthe incorrect trend of positive deviations from ideality observed for thepredicted γinf, since the RKPR with the same repulsive term does notsuffer from this limitation. The results indicated that when using eitherthe PC-SAFT EoS or the RKPR EoS with a recent parameterization forn-alkanes [5], both models qualitatively predict appropriate behaviors,being in general RKPR predictions closer to reported experimental data.In a later communication, Jaubert and Privat [6] proposed to godeeper in a discussion or debate around the following main issues:- The possible implications of different pure compound parameters inequations of state, beyond the repulsive and the attractive ones, anda comparison between cubic and SAFT type models.- The role of the kij parameter and whether it is appropriate or not touse zero values as default in nearly athermal systems like mixtures ofalkanes.- The question of whether two-parameter EoSs, like SRK or PR, areable to represent the behavior of asymmetric mixtures of alkanes.

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