Effect of Metal Groups in Transition Metal Alkoxide Catalysts on Transesterification

Abstract

Transesterification is a widely used chemical reaction in chemical industry. The use of common homogeneous catalysts that comprise of alkali metal hydroxides/alkoxides and inorganic acids lead to intricacies associated with post reaction separation of catalysts from products. On the other hand, heterogeneous catalysts possess the drawback of limiting mass transport due to the presence of a three phase system that is inherently immiscible in each other with liquid/liquid/solid (L/L/S) interfaces. With the intention of ameliorating conditions for a reaction system containing L/L immiscible reactants, the ability of select metal alkoxides to act as a phase transforming advanced catalytic materials were studied. In this regard, the ability of transition-metal alkoxides to initially act as a homogeneous catalyst and then phase-separate into a heterogeneous form was elucidated. Specifically, the study targeted ascertaining the effects of different metal groups of alkoxide catalysts on the performance (yield and selectivity) toward transesterification. Eight different metals were tested. Transesterification was done using identical weights of metal alkoxides, i.e., 1% of the total weight of the reactants. Studies confirm that active sites of metal alkoxides can catalyze the transesterification reaction. It was observed that, a maximum ester yields were observed with titanium isopropoxide and yttrium isopropoxide catalysts. The selectivity of all transition metal alkoxide catalysts toward component fatty acid methyl esters was the same