Phase Equilibria and Excess Properties of Short-Alkane Mixtures Estimated Using the SAFT-VR Equation of State

Abstract

Excess thermodynamic properties constitute excellent and valuable experimental information for determining if a theory or molecular model is able to predict the solution thermodynamic behavior of a given fluid mixture. Phase equilibrium, which is often used to test the applicability of a formalism in this context, does not always constitute a strong enough test to determine if the model or theory provides a sufficiently realistic description of the global thermodynamic behavior of the system. In this work we use a version of the statistical associating fluid theory (SAFT) to show how a simple model of alkanes, with a reduced number of molecular parameters, is able to predict simultaneously the general trends of phase equilibria and excess properties of mixtures of short n-alkanes. Despite the fact that alkane molecular models are simple, they are able to describe most of the features of phase and excess behavior of the mixtures considered. Theoretical predictions, at different thermodynamic conditions, are compared with experimental data taken from literature. Agreement between both results is at least qualitatively correct for a wide range of conditions, although deviations increase at higher temperatures and when pure compound critical points are approached.