Liquid-liquid equilibrium constant for acetic acid in an epoxidized soybean oil-acetic acid-water system

Abstract

Dependency of the liquid-liquid equilibrium constant for acetic acid (A) in a system of epoxidized soybean oil-acetic acid-water from temperature and composition was experimentally determined. To estimate the liquid-liquid equilibrium constant for acetic acid (K A ), the interaction parameters of the Wilson, NRTL (non-random two liquid) and UNIQUAC (universal quasi chemical) models for the activity coefficient were calculated by fitting the experimental values of the equilibrium constant for acetic acid. The Marquardt method was used to fit the data. In spite of all applied simplifications, small deviations of the calculated values from those experimentally determined indicate the adequacy of all three models for the prediction of the liquid-liquid equilibrium constant for acetic acid. Comparison of the experimentally determined values of the equilibrium constant for acetic acid in the investigated system with those reported in the literature for the system with soybean oil, shows that the value of the liquid-liquid equilibrium constant for acetic aid in the system of epoxidized soybean oil-acetic acid-water is about 1.5 times higher than in the system of soybean oil-acetic acid-water for the same temperature and similar composition. For the investigated conditions, the influence of the changing of the oil phase composition on the equilibrium constant for acetic acid is more prominent than the influence of the temperature or the total acetic acid content in the system. © 2009 AOCS.