Characterization of Alumina, Silica, and Titania Supported Cobalt Catalysts

A multiple technique approach was used to characterize the structural, chemical, and electronic properties of Co catalysts supported on Al2O3, SiO2, and TiO2 as well as Co/Mn catalysts on TiO2. The morphology of the catalysts was studied by transmission electron microscopy followed by X-ray diffraction to determine the phase composition and the distribution of the crystallite size. The electronic properties of the calcined catalysts were investigated by X-ray photoelectron spectroscopy. Comparison with reference data allows identification of the cobalt-containing species in the surface. In agreement with adsorption experiments, the signal intensities yield the dispersion of the applied catalysts in the sequence Co/Al2O3>Co/TiO2>Co/SiO2. Temperature-programmed reduction and oxidation reveal the formation of various oxides in dependence on temperature as well as, in case of the alumina- and titania-supported cobalt catalysts, the formation of high-temperature compounds CoAl2O4 and CoTiO3, respectively. Dynamic and static adsorption studies and BET measurements complete the characterization of the supported catalysts.