Prediction of liquid-liquid equilibria of multicomponent fatty systems using the ASOG method

Abstract

Purification steps, as solvent extraction, play an important role in biodiesel and edible oil processing. Their continuous improvement relies on predictive tools for computing liquid-liquid equilibria (LLE), and among these tools, group contribution methods, such as the UNIQUAC Functional-group Activity Coefficients (UNIFAC) method and its variants, and the Analytical Solutions of Groups (ASOG) method, are commonly used. In this work the ASOG method was evaluated for predicting LLE of 372 multicomponent fatty systems from the literature. The ASOG method, although quite unexplored, in particular for fatty systems, performed satisfactorily well, resulting in a global deviation of 9.27%. The Solution Structure of Isoactivity Equations (SSIE), a recently published procedure for computing LLE based on the solution of the isoactivities was adopted as the calculation strategy. The predictive capacity of the ASOG method was also improved by means of readjustment of interaction parameters related to functional groups of fatty acid (COOH), ester (COO), aldehydes (COH), water (H2O), and unsaturation (CC). The new parameters allowed prediction of solubility of fatty acid, alcohol and aldehyde in both fatty and solvent phases more precisely, diminishing deviations between calculated and experimental compositions.