X‐ray photoelectron spectroscopy investigation of pumice‐supported nickel catalysts

Abstract

Abstract Pumice‐supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x‐ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica‐ and alumina‐supported nickel catalysts, a preferential interaction of Ni 2+ with Al 3+ of the support has been determined. A quantitative XPS analysis indicated large segregation of nickel to the surface. The treatment with H 2 at 673 K and 1073 K produced a partial reduction of Ni +2 to Ni 0 . The extent of the reduction was largest at 1073 K and in this case the reduced Ni in the metallic phase was detectable by x‐ray diffraction. A decrease of the Ni 2p/Si 2p intensity ratio occurring in the lower temperature H 2 ‐treated catalysts was attributed to diffusion of nickel as Ni 2+ , as a consequence of a solid‐state reaction between nickel ions and support oxides, whereas the decrease of the intensity ratio in the high‐temperature reduced catalysts was attributed to sintering of the nickel particles and to diffusion of nickel atoms interacting with oxygen vacancies of the support.