Non-catalytic biodiesel fuel production with supercritical methanol technologies

Study presents that supercritical methanol has the ability to convert oils/fats consisting of triglycerides and free fatty acids (FFAs) into fatty acid methyl esters through transesterification and methyl esterification, respectively, without any catalyst. This one-step method (Saka process) is simpler process realizing shorter reaction time and higher yield of methyl esters than those of the conventional alkali-catalyzed method. To improve the biodiesel quality that satisfies the standard specification, another reaction route was also developed by the two-step method (Saka-Dadan process), which consists of hydrolysis step for oils/fats in subcritical water and subsequent methyl esterification of the hydrolyzed products of fatty acids from oils/fats in supercritical methanol. These new methods are highly tolerant against the presence of FFAs and water in oils/fats. Therefore, compared to the alkali-catalyzed method, proposed methods can be applied for various types of oils/fats and their wastes as raw materials to produce biodiesel fuel.