Liquid–liquid equilibrium of fatty systems: A new approach for adjusting UNIFAC interaction parameters

Along the refining process of vegetable oils the removal of free fatty acids is the most important purification step. The deacidification by liquid–liquid extraction using an alcoholic solvent has been shown to be a viable alternative from a technical point of view. In prior studies reported in the literature, the equilibrium data were determined and correlated for each different type of edible oil and they are most often represented in terms of mass fractions of pseudocomponents. However, to obtain a better predictive tool, it is necessary to consider the true compositions of these mixtures. In this work, several data for real multicomponent systems available in the literature were used to readjust group interaction parameters of the UNIFAC (Universal Quasi-Chemical Functional-group Activity Coefficients) method. A new group has also been proposed in order to simplify the description of the triacylglycerols. The deviations found using the original groups and parameters of UNIFAC were considerably higher than the deviations found in both alternative procedures, indicating that the correlation and prediction of this type of systems were significantly improved. The developed procedures were further tested using data measured for two validation systems, which confirmed the improvement in the predictive power of the UNIFAC method.