Esterification kinetics of free fatty acids with supercritical methanol for biodiesel production

Non-catalytic esterification of Free Fatty Acids (FFA) with supercritical methanol was studied under reaction conditions of (250–320 °C) at 10 MPa. A detailed experimental programme was implemented to investigate the influence of temperature, stirring rate and the molar ratio of methanol to FFA in the feed in a batch-type reaction vessel. The esterification products of FFA with supercritical methanol are Fatty Acids Methyl Esters (FAME; biodiesel) and water. The yield of FAME was found to increase with an increase in temperature, and with an increase in the molar ratio of methanol to FFA. At >850 rpm the yield of FAME was not affected by stirring rate. The rate constants and energy of activation have been numerically evaluated by solving an ordinary differential equation that describes the reaction kinetics. The proposed kinetic model shows a reversible second order reaction and represents all the experimental data satisfactorily, providing deeper insight into the kinetics of the reaction.