Comparison of SAFT-VR-Mie and CP-PC-SAFT in predicting phase behavior of associating systems I. Ammonia–water, methanol, ethanol and hydrazine

Abstract

This study evaluates the accuracy of SAFT-VR-Mie coupled with the new association treatment of Dufal et al. [Mol. Phys. 113 (2015) 948] and CP-PC-SAFT in modeling ammonia(1)–water(2), –methanol(2), –ethanol(2) and –hydrazine(2) systems and the pertinent pure compounds, while considering the entire thermodynamic phase space and various thermodynamic properties. The binary adjustable parameters have been set to zero in all the cases. Although SAFT-VR-Mie is the more sophisticated model having a stronger molecular background, it does not exhibit an over-all advantage over CP-PC-SAFT. Specifically, the latter approach is more accurate in predicting phase equilibria, densities at very high pressures and, usually, sound velocities in the entire pressure range. At the same time, SAFT-VR-Mie is typically a better estimator of the available density and isochoric heat capacity data at moderated pressures. In addition, it is demonstrated that the sophisticated rigorous cross-association scheme attached to SAFT-VR-Mie does not have an over-all advantage in comparison with the simplified approach of Kraska. The results of this study indicate that solely an advanced molecular background does not necessarily guarantee over-all robustness and reliability of EoS models. Not less important role should be attributed to the parametrization strategies and their fitness at the key states, such as the critical points and the co-volumes.