CO oxidation over Co-catalysts supported on silica-titania – The effects of the catalyst preparation method and the amount of incorporated Ti on the formation of more active Co3+ species

Herein, a sol-gel one-pot methodology to tune the activity of Co-catalysts supported on silica-titania to CO oxidation is described. SEM, TEM, EDS, XPS and H2-TPR evidenced a higher Co dispersion from that method when compared to catalysts prepared by impregnation. Furthermore, the simultaneous addition of cobalt oxalate during the incorporation by sol-gel of a controlled low Ti amount into the silica (Si/Ti = 5.7) was determinant to improve the Co dispersion and to avoid the formation of Co-species with strong support interaction. Moreover, XPS analyses evidenced that the mentioned low Ti amount favoured a higher formation of superficial Co3+ and lattice O2− species, which promoted a higher CO oxidation specific activity and, more importantly, strongly decreasing the light-off temperature. On the other hand, Rietveld analyses, Raman spectroscopy, H2-TPR and XPS data showed that the incorporation of higher amounts of Ti into the silica (Si/Ti = 0.2) led to the formation of cobalt titanate, decreasing the concentration of superficial Co3+ and lattice O2− species and, consequently, decreasing the specific activity toCO oxidation.