Modeling Phase Equilibria Relevant to Biodiesel Production: A Comparison of g^E Models, Cubic EoS, EoS−g^E 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 (g E) models, cubic equations of state (EoS), equations of state with EoS−g E 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.

Heterosegmental Modeling of Long-Chain Molecules and Related Mixtures using PC-SAFT: 1. Polar Compounds

“…Regarding the binary methyl alkanoate + water mixtures, Oliveira et al measured the solubility of water in some methyl alkanoates based on even-numbered n -alkyl carboxylic acids, namely, from methyl hexanoate to methyl octadecanoate. Additionally, they used CPA, UNIFAC, and soft-SAFT to model the measured solubilities with good agreement with the experimental data. − As experimental solubility data for these mixtures are scarce, other works made use of the experimental data of Oliveira et al and described them using UNIFAC, PHSC, and COSMO-SAC. ,− However, no previous works dealing with the thermodynamic modeling of the solubility of methyl alkanoates in water could be found in the literature.…”

The prediction multi-phase, multi reactant equilibria by minimizing the Gibbs energy of the system: Review of available techniques and proposal of a new method based on a Monte Carlo technique

“…In many industrial fields, the spreading of robust and low-cost computer resources is massively used to foster innovation across many technical fields (Council, 1999). It is true also for the chemical industry where numerical tools and models are used to predict phase equilibrium, (Oliveira et al, 2011) solubility (Cañas-Marin et al, 2006), even some complex catalytic reactions (Masel, 2001). A somewhat recent branch is molecular modeling which, based on an improved understanding of microscopic and molecular behaviors, could help in designing new molecule and predicting some of their properties via an ab-initio approach (Edgar, 1999; the chemical equilibrium in a multiphase reactive mixture.…”

Comparison of the Osmotic Virial Equation with the Margules Activity Model for Solid–Liquid Equilibrium

“…However, the problem is in developing appropriate mixing rules. 8 Different types of equations of state have been used to model activity coefficients based on type of mixtures, such as the Soave− Redlich−Kwong equation and the Peng−Robinson equation for vapor−liquid equilibrium of petrochemical mixtures 9 and the osmotic virial equations of state for aqueous mixtures. 10−18 Among the above-mentioned three types of activity coefficient models, the goal of this article is to compare the general polynomial form of the osmotic virial equation of state and the empirical Margules model for obtaining activity coefficients.…”

“…However, the problem is in developing appropriate mixing rules . Different types of equations of state have been used to model activity coefficients based on type of mixtures, such as the Soave–Redlich–Kwong equation and the Peng–Robinson equation for vapor–liquid equilibrium of petrochemical mixtures and the osmotic virial equations of state for aqueous mixtures. − …”