Preparation of mesoporous stannosilicates SnTUD-1 and catalytic activity in levulinic acid esterification

The direct synthesis of SnTUD-1 with different Si:Sn ratios (100, 50 and 25) by using non-surfactant template triethanolamine (TEA). It functioned as a structure-directing agent and assisted to graft the Sn ions into the TUD-1 silica layer. The physicochemical properties of these materials were examined with XRD, N-2 sorption, DR UV-Vis, NH3-TPD, Si-29-NMR, HRTEM, XPS and pyridine adsorbed FT-IR studies, which indicated highly interconnected mesoporous structure with wormhole like morphology. Sn4+ ions were mainly tetrahedrically coordinated with silica; while increase of loading lead to the formation of nanocrystalline SnO2 with different sizes. Materials showed acidity in the range of 0.13-0.31 mmol/g. Synthesized catalysts were tested in the esterification of levulinic acid (LA) with various aliphatic alcohols and exhibited excellent activity. The catalyst was recycled five times without loss of its activity.