Preparation and catalytic properties of single-phase Ni-Sn intermetallic compound particles by CVD of Sn(CH3)4 onto Ni/silica

The particles of each single-phase Ni-Sn intermetallic compound (IMC), Ni3Sn, Ni3Sn2, and Ni3Sn4, have been formed on silica by chemical vapor deposition (CVD) of Sn(CH3)(4) onto Ni/SiO2. The prepared Ni-Sn IMC/SiO2 was characterized by chemical analysis, X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The results clarified that the particles on silica had the same stoichiometric Ni/Sn atomic ratio and specific bulk and surface structure as those of corresponding unsupported IMCs prepared by melting the mixture of pure Ni and Sn powder. The Ni-Sn IMC/SiO2 was used as a catalyst for the dehydrogenation of cyclohexane. The catalytic activity of each Ni-Sn IMC/SiO2 was much higher than that of the unsupported IMCs, whereas it was lower than that of the Ni/SiO2 catalyst. The catalytic activities of Ni-Sn IMCs increased with the increasing Ni/Sn ratio. The selectivity of Ni3Sn/SiO2 and Ni3Sn2/SiO2 for the formation of benzene was almost 100 C-%, even at higher conversions. The unsupported IMC catalysts also showed high selectivity to benzene, whereas Ni catalyst gave almost exclusively methane at higher conversions. (C) 2001 Academic Press.