Alkali- and nitrate-free synthesis of highly active Mg–Al hydrotalcite-coated alumina for FAME production

Abstract

Mg–Al hydrotalcite coatings have been grown on alumina via a novel alkali- and nitrate-free impregnation route and subsequent calcination and hydrothermal treatment. The resulting Mg–HT/Al₂O₃ catalysts significantly outperform conventional bulk hydrotalcites prepared via co-precipitation in the transesterification of C₄–C₁₈ triglycerides for fatty acid methyl ester (FAME) production, with rate enhancements increasing with alkyl chain length. This promotion is attributed to improved accessibility of bulky triglycerides to active surface base sites over the higher area alumina support compared to conventional hydrotalcites wherein many active sites are confined within the micropores.