(264c) Catalytic Activity of Mixed Mesoporous Gallium-Niobium Oxides

Mesostructuring mixed metal-oxide systems offers the possibility to design novel catalytic phases with high surface areas, controlled porosities, tunable surface compositions, and improved catalytic performance. Herein we present the synthesis and characterization of semi-crystalline mesoporous gallium-niobium mixed oxide phases prepared via Self-Assembly Hydrothermal-Assisted (SAHA) method in the presence of non-ionic structure directing agents. These mesophases displayed surface areas as high as 360 m²/g and unimodal pore size distribution in the 3-6 nm range. Due to their high surface areas, tunability of pore sizes and their acidic nature the mixed mesoporous gallium-niobium oxides were employed as catalysts for the hydrolysis of carboxylic acid esters and isomerization of olefins. The mixed gallium-niobium oxides were catalytically active in acid?catalysed reactions like (1) the hydrolysis of carboxylic acid esters (methyl oleate), (2) the double bond and skeletal isomerisation of olefins (hexadecene), and linear, unsaturated esters (methyl oleate and linoleate). Their catalytic activity in these acid-catalysed reactions was correlated to their surface acidity as measured by the adsorption of dipropylamine and their niobium content. Furthermore, these novel catalysts have potential in the preparation of biofuels from lipid feedstocks like vegetable and animal oils and fats.