Thesis (M.Eng.)--Chulalongkorn University, 2008

A novel method for preparation of Au/TiO2 and Ag/TiO2 catalysts via a deposition technique assisted by supercritical carbon dioxide was investigated. Supercritical carbon dioxide was employed as a solvent to dissolve the metal compound and to deposit metal on two type of TiO2 (Degussa P-25 and solvothermal) supports. The catalysts were characterized by XRD, Nitrogen Physisorption, TEM, ICP-OES and XPS. The catalytic activity of the supported metal catalysts was measured for CO oxidation reaction. For Au/TiO2 catalysts, several solvents were employed to dissolve gold precursor including water, methanol, and acetylacetone. The highest catalytic activity was obtained when used acetylacetone as a solvent, producing a light off temperature at 367 °C. For Ag/TiO2 catalysts, various preparation parameters were investigated, including amount of silver loading, holding time, pressure, and type of TiO2 supports. The highest activity was obtained for the catalyst that was prepared with amount of silver loading of 20 wt%, holding time of one hour, pressure of 20 MPa, and TiO2 support prepared by solvothermal method. The light off temperature for that catalyst was 78 °C.