Modeling Phase Equilibria Relevant to Biodiesel Production: A Comparison of gE Models, Cubic EoS, EoS−gE and Association EoS

Abstract

Liquid−liquid equilibrium (LLE) and vapor−liquid equilibrium (VLE) data of binary and ternary systems formed at the biodiesel production and purification industrial units were used to evaluate the performance of commonly used excess Gibbs energy (gE) models, cubic equations of state (EoS), equations of state with EoS−gE mixing rules, and association equation of state models. The models used in this study are the UNIFAC, Soave−Redlich−Kwong (SRK) EoS, the SRK-MHV2, the Peng−Robinson (PR) EoS using the MHV2 mixing rule, the predictive Soave−Redlich−Kwong (PSRK) EoS, and the Cubic-Plus-Association (CPA) EoS. All models were used with previously established parameters, and the applicability of each model to the various systems investigated and the quality of the description of the phase equilibria are discussed. The results obtained show that the CPA EoS is the most adequate model to be used for the description of the phase equilibria of importance for the design and optimization of biodiesel production plants.