Study On The Catalytic Oxidation Of Formaldehyde And Carbon Monoxide At Low Temperature Over Over Supported Pt Catalysts

Formaldehyde is one of the most serious indoor air pollutants, which is emitted from building and furnishing materials and is harmful to human health. Thus, elimination of indoor formaldehyde at room temperature has attracted much attention. Pt catalysts show high reactivity for catalytic formaldehyde oxidation, with some catalysts (e.g Pt/TiO2) could decompose formaldehyde completely to CO2 and H2O at room temperature. Furthermore, CeO2 and CeO2-based mixed oxides are widely applied in catalysis due to their unique properties such as fast Ce3+/Ce4+redox cycle and oxygen storage capacity (OSC). Therefore, in this thesis, we prepared a series of Pt/CeO2 catalysts and tested for formaldehyde and carbon monoxide oxidation. The main results are as follows:1. Pt catalysts supported on CeO2 were prepared by impregnation method and tested for formaldehyde oxidation. The effects of different Pt precursors and Pt loading on the catalytic properties of the catalysts were investigated. XRD, TEM and CO chemisorption results indicated that the Pt particles were highly dispersed in the catalysts. Catalyst with H2PtCl6 as the precursor exhibited lower reactivity than that with Pt(NO3)2 as the precursor, due to the suppressed redox ability of the catalyst in the presence of Cl- ions. It was also found that the reactivity increased with increasing Pt content in the catalyst, and a catalyst with 3.0 wt% Pt loading exhibited the highest activity, with a 80% conversion of formaldehyde at 30℃. The possible reaction mechanism for the catalytic of formaldehyde over Pt/CeO2 catalyst. It was proposed that the HCHO molecule adsorbed on the catalyst, then reacted with the active oxygen species to form carbonate species; finally, the carbonates could be decomposed into gaseous CO2 and H2O in the mild temperature.2. The effect of support on the catalytic properties of Pt catalysts. It was found that the reactivities of carbon monoxide and formaldehyde oxidation were influenced by the properties of the supports. Inert support did not catalyzed the activation of oxygen, because it did not take part in the oxidation reaction. At the same time we founded that the specific surface area of CeO2 also influence the catalytic properties of Pt/CeO2 catalyst. For example, on the 2.0 Pt/CeO2 (34) catalyst, formaldehyde and carbon monoxide were completely oxidation respectivily at 90℃,140℃. Maybe its high activities are infulunced by the strong interaction between metal and carrier.3. A series of Pt catalysts were prepared by a method of impregnation on different metal oxides (CeO2 and Ce1-xLaxO2-d) and tested for low temperature formaldehyde and carbon monoxide oxidation. It was found that the catalysts with La,Nd,Sm doped ceria show decreased activity compared to undoped catalyst. This indicate that more work is needed to explain the effect of support on the catalytic of Pt catalysts.