Methanolysis of triacylglycerols by organic basic catalysts

Abstract

AbstractMethanolysis of rapeseed and soybean oil was studied using organic basic catalysts at boiling with reflux. The molar ratio methanol/free fatty acids (FFA) amounted to approx 2.8 : 1. The catalyst (guanidine carbonate) is used at concentrations between 0.5 and 1.3 wt‐% with respect to the oil. During boiling at reflux, guanidine carbonate disintegrates into guanidine and gaseous carbon dioxide. This is a very special reaction; other alcohols such as ethanol, propanol, etc. do not react in this way with guanidine carbonate. Under these conditions, the reaction mixture consists of two phases. The catalyst is mainly dissolved in the methanol phase. The rate of the phase transfer reaction is increased by stirring. With guanidine carbonate as a catalyst, neutralized rapeseed oil yielded, within 45 min and in one step, a product that meets the European Norm for biodiesel. Degummed and dried crude rapeseed oil contains ca. 1 wt‐% FFA, whereas crude degummed and dried soybean oil contains 0.3–0.7 wt‐% FFA. During catalysis with guanidine carbonate, the FFA are transformed into their methyl esters to about 60–70% at low concentrations in the crude oil (approximately up to 1–1.5%). Neutralization of the degummed and dried crude oil proved to be unnecessary in such cases.