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Effects of Acidity and Pore Size Constraints on Supported Niobium Oxide Catalysts for the Selective Formation of Glycerol Monolaurate

Supported niobium oxide catalysts with 5–30 wt. % Nb2O5 were prepared by grafting niobium ethoxide onto MCM‐41 and hydrous zirconia. The supported samples contain Brønsted‐acid sites, whereas bulk niobium oxide has predominantly Lewis‐acid sites. In the esterification of glycerol with lauric acid, good activity and a high glycerol monolaurate selectivity was achieved when the active niobium oxide phase was coated within the pore channels of an MCM‐41 support, which has a mean pore diameter of 2.2 nm. Phosphated Nb2O5/MCM‐41 showed an even higher activity without any penalty in selectivity, enabling monolaurate yields of 89–90 %. Glycerol monolaurate is an important ingredient in the food, pharmaceutical, and cosmetic industries. A key feature of these pore confined catalysts is the sustained high selectivity to monolaurate even at high conversions. In contrast, niobium oxide supported on wide‐pored hydrous zirconia showed lower selectivity. The catalysts are active in the solventless esterification of a number of alcohols and acids and can be easily recycled for subsequent batch reactions, making them attractive as green catalysts for sustainable processes.