Enhanced performance of Pd nanoparticles on SBA-15 grafted with alkyltrialkoxysilane in 2-ethyl-anthraquinone hydrogenation

Pd catalysts on mesoporous silica SBA-15 functionalized with alkyltriethoxysilane (alkyl = methyl, ethyl, propyl and isobutyl) were prepared. The effects of grafting sequence on the grafting amount were studied. The catalysts were characterized by XRD, FT-IR, elemental analysis, thermogravimetric analysis, nitrogen adsorption-desorption, TEM and XPS, and evaluated using catalytic hydrogenation of 2-ethyl-anthraquinone. The grafting amount increases with increasing the alkyl chain length of alkyltriethoxysilane. The highest grafting amount with the carbon content of 1.56% is obtained using an ante-grafting procedure where the grafting is performed prior to the removal of template, and this catalyst shows the highest activity and selectivity (98.3%). The accordant relationship between the activity of Pd/SBA-15 catalysts and their grafting amount indicates a positive effect of hydrophobicity of SBA-15 created by grafting on the catalytic hydrogenation of 2-ethyl-anthraquinone.