Predicting Mixture Phase Equilibria and Critical Behavior Using the SAFT-VRX Approach

• Published in: The journal of physical chemistry. B 2005-05, Vol.109 (18), p.9047-9058
• Main Authors: Sun, Lixin, Zhao, Honggang, Kiselev, Sergei B, McCabe, Clare
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp044413o

The SAFT-VRX equation of state combines the SAFT-VR equation with a crossover function that smoothly transforms the classical equation into a nonanalytical form close to the critical point. By a combinination of the accuracy of the SAFT-VR approach away from the critical region with the asymptotic scaling behavior seen at the critical point of real fluids, the SAFT-VRX equation can accurately describe the global fluid phase diagram. In previous work, we demonstrated that the SAFT-VRX equation very accurately describes the pvT and phase behavior of both nonassociating and associating pure fluids, with a minimum of fitting to experimental data. Here, we present a generalized SAFT-VRX equation of state for binary mixtures that is found to accurately predict the vapor−liquid equilibrium and pvT behavior of the systems studied. In particular, we examine binary mixtures of n-alkanes and carbon dioxide + n-alkanes. The SAFT-VRX equation accurately describes not only the gas−liquid critical locus for these systems but also the vapor−liquid equilibrium phase diagrams and thermal properties in single-phase regions.