Building of a sulfonyl-group-functionalized monomer whose polymer is able to catalyze biodiesel formation

Abstract

A linear polymer containing sulfonyl groups was synthesized from a vinyl monomer to use its acid group as a catalyst of the esterification of oleic acid to form biodiesel. First, synthesis optimization of the monomer was carried out in an aqueous system. This molecule was obtained in an excellent yield, where the pH and reaction time were decisive factors in the synthesis performance. The vinyl monomer was then polymerized, and the catalytic activity of the sulfonic acid could be demonstrated in the esterification of oleic acid with short-chain alcohols. The increase in the catalyst content resulted in a higher concentration of the carbonyl group activated, and this was followed by faster esterification kinetics. The highest yield (98 mol %) was reached after 20 min when 10 mol % catalyst was used. A larger size alcohol led to slower esterification kinetics because its ability as a nucleophile was decreased by steric impediment. The sulfonyl group in polymer 4 proved to be an acid almost as efficient as sulfuric acid, although the former worked in a heterogeneous system.