STUDIES OF SUPPORTED NICKEL CATALYSTS BY X-RAY PHOTOELECTRON AND ION SCATTERING SPECTROSCOPIES

Supported nickel catalysts, prepared by impregnation, were studied by two surface sensitive techniques: X-ray photoelectron spectroscopy (ESCA or XPS) and ion scattering spectroscopy (ISS). The nature of the nickel species on the surface was analyzed by ESCA when the support was changed. ESCA-H2 titrations were used to systematically characterize the nickel species as a function of calcination temperature and nickel content. The relationship between the signal intensity ratio of Ni/Al and the bulk nickel content was examined and compared by ESCA and ISS, which have different sampling depths. Nickel shows little interaction with silica but strong interaction with γ-alumina in the impregnated catalysts after calcination. In unreduced silica supported catalysts, the nickel species is NiO. At low nickel content of the unreduced γ-alumina supported catalysts, there are two forms of the nickel present on the surface. At high nickel content, a third species of nickel (NiO) appears after the surface sites of γ-alumina have been filled. The results demonstrate that comparative studies by ESCA and ISS can potentially provide valuable information about the character of surface species on supported catalysts. © 1979 American Chemical Society.