Improved models for the prediction of activity coefficients in nearly athermal mixtures 1 Part II. A theoretically-based GE-model based on the van der Waals partition function

 
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1997 (EN)
Improved models for the prediction of activity coefficients in nearly athermal mixtures 1 Part II. A theoretically-based GE-model based on the van der Waals partition function (EN)

Tassios, DP (EN)
Fredenslund, A (EN)
Nikolopoulos, GI (EN)
Kontogeorgis, GM (EN)

N/A (EN)

This work, which is a continuation of a recent publication on the same topic (G.M. Kontogeorgis, P. Coutsikos, P. Tassios and Aa. Fredenslund, Fluid Phase Equilibria, 92 (1994) 35), presents a new theoretically-based GE-model (Chain-FV) for alkane systems. The model is based on a modified form of the generalized van der Waals partition function and attempts to account for all non-energetic effects of solutions of both short- and long-chain alkanes, including alkane polymers. Both the free-volume effects and the density-dependent rotational degrees of freedom are considered. The resulting GE-model which, despite its derivation from a partition function resembles the Flory-Huggins formula, is suitable for vapor-liquid and solid-liquid equilibrium calculations for nearly athermal polymer solutions as well as for alkane systems. We show that using plausible assumptions for the free-volume and the external-degree-of-freedom parameter, very good predictions are obtained for activity coefficients of asymmetric alkane systems at both concentration ends, for solid-liquid equilibrium calculations, as well as in extreme cases (polymer solutions, activity coefficients of heavy model alkane polymers in short-chain compounds recently available from molecular simulation studies). The predictions of the Chain-FV model are better than the Flory-Huggins and Elbro terms and equivalent to the recently proposed empirical R-UNIFAC and p-FV models. However, unlike the latter two models, the one proposed in this work offers a successful combination of simplicity and accuracy, with a solid theoretical basis. (EN)

journalArticle

Paraffins (EN)
Mixtures (EN)
Alkane polymers (EN)
Functions (EN)
Flory-Huggins formula (EN)
Free-volume (EN)
Forecasting (EN)
Excess properties (EN)
van der Waals partition function (EN)
Activity coefficients (EN)
Polymer solutions (EN)
Density (specific gravity) (EN)
Degrees of freedom (mechanics) (EN)
Calculations (EN)
Phase equilibria (EN)
Mathematical models (EN)
Statistical mechanics (EN)
Polymers (EN)
Free volume effect (EN)
Thermodynamic properties (EN)
Alkane solutions (EN)

Εθνικό Μετσόβιο Πολυτεχνείο (EL)
National Technical University of Athens (EN)

Fluid Phase Equilibria (EN)

1997


N/A (EN)



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