Thesis (D.Eng)--Chulalongkorn University, 2009

This research is to study the effect of surface modification of TiO₂ support on the catalytic activity in CO oxidation. Two methods were employed for surface modification of TiO₂ support: the creation of defective sites on TiO₂ surface and the modification with trace element. The results found that the presence of higher amount of Ti³⁺ on the larger crystallite size TiO₂ stabilizes small metal particles during impregnation, calcination, and reduction steps via stronger metal-support interaction; hence higher CO oxidation activities. In addition, the modification of TiO2 support with trace element can improve the CO oxidation activity. All of element dopants (i.e., Al, Si and P), the Si-modified TiO₂ showed the highest catalytic performance of Ag/TiO₂ catalyst. However, there existed an optimum content of Si/Ti molar ratio at ca. 0.05-0.1 which resulted in an improved catalytic activity of Ag/TiO₂ in CO oxidation. There was no improvement in CO oxidation activity of the Ag/TiO₂ catalyst when the Si/Ti was further increased to 0.3 due probably to the formation of amorphous SiO2 instead of the Ti-O-Si bond. The P-modified TiO₂ supported Ag catalysts using phosphorus precursor in the form of oxide promoted the weak adsorbed oxygen species and resulted in catalytic activity improvement in CO oxidation