Sulfonic acid-functionalized platelet SBA-15 materials as efficient catalysts for biodiesel synthesis

Sulfonic acid-functionalized platelet SBA-15 materials (SA-SBA-15-p) with ordered short mesochannels (150-350 nm) and acid capacities up to 1.2 mmol H+ g(-1) were synthesized by one-pot co-condensation of tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of appropriate amounts of Zr(IV) ions and H2O2. The SA-SBA-15-p materials were efficient catalysts for biodiesel synthesis through esterification of long chain carboxylic acids with methanol. The short-channel SA-SBA-15 materials showed higher catalytic activities than the conventional rod-like or fiber-like analogues, due to better molecular diffusion. Moreover, the used SA-SBA-15-p materials could be easily regenerated by ethanol extraction and the catalytic activities were retained after several recycle runs. In comparison to Amberlyst 15 resin, SA-SBA-15-p materials were superior considering the reaction rates per acid site because of the high accessibility of the sulfonic acid sites in the well-ordered large mesopores (ca. 7 nm) to the reactant molecules. Moreover, SA-SBA-15-p also showed better tolerance to small amounts of water in the reaction system than Amberlyst 15 resin.