Catalytic Carbon Monoxide Oxidation Over Copper/Silica Nanocatalysts

In this work, the catalytic activity of copper/silica nanocatalysts (prepared by incipient wetness impregnation of the metal salt on nanosilica, thermally extracted from rice husk) on the oxidation of carbon monoxide is investigated. The effect of metal loading on the physico-chemical features of the prepared catalysts has been investigated by X-ray diffraction, differential thermal analysis, transmission electron microscopy, nitrogen adsorption-desorption at −196°C, and temperature programmed reduction. The nanocatalyst loaded with 30.7 wt% CuO showed the highest surface area having newly created mesopores, with respect to the parent nanosilica. The temperature programmed reduction analysis indicated the presence of different types of copper species, including variation in their oxidation states, on the surface of the Cu20 and Cu30 catalysts. The catalytic activity on carbon monoxide oxidation at temperatures between 125 to 500°C was enhanced associated by increasing both copper oxide loading and the reaction temperature. The activity of the Cu30 catalyst at low temperatures attributed to the presence of the bulky cupric oxide species with a polar oriented (111) surface, which subsequently enhanced the catalyst surface adsorption efficiency; also, the presence of the cuprous oxide species can precede the carbon monoxide oxidation reaction through the associative (Langmuir-Hinshelwood) mechanism.