A kinetics study of the simultaneous methanolysis and hydrolysis of triglycerides

Abstract

Transesterification of triglycerides (oils and fats) catalyzed by bases is a common method for production of fatty acid methyl esters (FAME) - a renewable fuel (biodiesel) and basic oleochemical. Hydrolysis of esters - saponification - represents the main side reaction. Saponification leads to catalyst deactivation and impedes products purification. In this work, kinetics of the competing triglyceride hydrolysis and methanolysis (i.e. transesterification) is investigated. Furthermore, an alternative organic catalyst - tetramethylammonium hydroxide (TMAH) - is compared with potassium hydroxide and sodium methoxide. TMAH is less active but the methanolysis is more selective towards FAME formation and hydrolysis proceeds at a slower rate in comparison to the inorganic catalysts. FAME are less susceptible to hydrolysis than glycerides. A simple mathematical model assuming irreversibility of all reactions is capable to describe the measured data well (40-60°C, TMAH concentration 0.5-1.5wTMAH/woil, molar ratio methanol:oil=6). © 2015 Elsevier B.V..