Mesoporous Sn-TiO2 Catalysts by Molecular Protection Strategy for the Baeyer-Villiger Oxidation of Cyclohexanone with Molecular Oxygen

摘要

In order to improve the catalytic performance of tin-doped samples in the Baeyer-Villiger oxidation of cyclohexanone with molecular oxygen as oxidant, the mesoporous Sn-TiO2 catalysts with more incorporation of tin species were successfully prepared via a simple vapor-phase self-assembly method followed by molecular protection strategy treated with ethyl-enediamine solution. The physical and chemical properties of these prepared samples can be characterized by different methods including XRD, N2 sorption, Raman, ICP, UV-vis DRS, pyridine-adsorbed IR, SEM and TEM. The characterization results indicated that the ethylenediamine can protect the ordered mesopores of anatase TiO2, which would be beneficial to the more tetrahedrally homogeneous incorporation of tin species resulting in the promotion of Lewis acidity. The ordered mesoporous 18Sn-TiO2-EN catalyst with highest surface areas, pore volume and appropriate Lewis acidity showed the highest catalytic performance, whose cyclohexanone conversion, capro-lactone selectivity and TON value were up to 94.1%, 95.2% and 3.7, respectively, and it showed good catalytic stability.