On the mixing rules matter: The VLE predictions for binary systems

Abstract Mixing rules are used to extend the range of applicability of both equations of state and excess Gibbs energy models. The equations of state are limited by the molecules complexity, whilst the excess Gibbs energy constraint is the range of temperature and pressure. Mixing rules allow the coupling of both types of thermodynamics models to overcome such limitations. In this work, the analysis of the performance of 5 excess Gibbs energy models using the Peng-Robinson equation of state and two of its variants with 3 different mixing rules – VDW1, HVOS, and WS. Great accuracy of the UNIFAC and UNIFAC(Do) models, especially when using the VDW1 mixing rule to couple with either PRSV or PRSV2, was obtained. The F-SAC model has provided reliable results as well. In addition, evaluations over the performance of the excess Gibbs energy, the equations of state, and the mixing rules were made separately, in order to better analyze their results. The COSMO-SAC model was greatly affected by the HVOS mixing rule, leading to very high objective function values.