XPS characterization of cobalt impregnated SiO2 and γ-Al2O3

SiO2 and gamma-Al2O3 impregnation with nominal 10 and 20% of cobalt was examined using wet impregnation method starting with Co(NO3)(2)center dot 6H(2)O. The samples were dried and analyzed by XPS prior to calcination to study the surface species in the solids and the role of the support in the processing of supported cobalt catalysts. The results showed that cobalt introduction alters the few top nanometers of the support materials as there are significant changes recorded in the XPS spectra. Most importantly, there is a remarkable similarity between the O 1s XPS signal of SiO2 and gamma-Al2O3 following Co 20% impregnation, which suggests that these materials could have similar properties in terms of the oxidation ability and the general redox behavior. The shift of Al 2p peaks to higher binding energy (BE) in the XPS investigations and the shift of Si 2p peaks to lower BE were observed for high nominal cobalt loading. These results suggest that the choice of the support in cobalt-based catalysts would tune the chemical characteristics of cobalt in the final materials.