Impact of the surface hydrophobicity/hydrophilicity ratio on the catalytic properties of Ni nanoparticles/MCM-41 system used in the hydrogenation of acetophenone

Three nickel catalysts were prepared supporting pre-synthetized monodisperse Ni nanoparticles of 16 nm. As support, nanospheres of MCM-41 were used. Two batches of these supports were superficially modified by silylation treatments with different functionalizing agents: methyltrimethoxysilane and hexamethyldisilazane. These procedures led to three catalysts whose only structural differences were the surface hydrophobicity degrees. These catalysts were tested in chemoselective hydrogenation of acetophenone and the conversion level was increased by effect of the silylation. Instead, selectivity to 1-phenylethanol, the product of interest, stayed at very similar and high values, about 95 %. The sequence of activity levels was explained considering local effects (steric and energetic) of the different functionalizing groups.