Nickel Nanoparticles Supported on Silica of Low Surface Area. Hydrogen Chemisorption and TPD and Catalytic Properties

Nickel metal nanoparticles supported on silica of low surface area (15 m 2 g -1 ) were prepared by reduction of nickel acetate by hydrazine in aqueous medium. Their gas-phase stability and surface properties depended on thermal pre-treatment under H 2 or air atmosphere. Small nickel particles (<10 nm), in oxidized or reduced state, are strongly resistant to reductive or oxidative treatment respectively. For H 2 -treated catalysts, H 2 chemisorption and TPD results suggested the occurrence of spillover hydrogen between the metal nickel phase and silica. For air then H 2 treated catalysts, hydrogen spillover seemed to involve the NiO phase. The activity of the catalysts in gas-phase benzene hydrogenation also depended on the thermal pre-treatment. Pre-calcined then reduced catalysts exhibited higher TOFs than non pre-calcined catalysts, suggesting that the presence of NiO phase may have influenced the hydrogenation process.