| Most of volatile organic compounds(VOCs) emitted from industrial and transportation activities are harmful to the atmosphere and human health. can cause serious environmental problems. Therefore, it is of significance to strictly control the emissions of VOCs. Catalytic oxidation is considered to be one of the most effective pathways to remove VOCs, in which the key issue is the availability of high-efficiency catalysts. Perovskite-type oxides are low in cost, high in thermal stability, and good in anti-poisoning ability. If perovskite-type oxides were prepared to be three-dimensionally ordered macroporous(3DOM), their surface areas would be increased, and hence their catalytic performance would be improved. Loading transition-metal oxide and/or gold nanoparticles on the surface of a porous perovskite-type oxide might further enhance its catalytic activity. In this thesis, the yAu/zMnOx/3DOM La0.6Sr0.4MnO3(yAu/zMnOx/3DOM LSMO; y = 1.76?6.85 wt%, z = 8.0 wt%; MnOx was mainly Mn2O3 nanoparticles) and yMnOx?zAu/3DOM La0.6Sr0.4CoO3(yMnOx?zAu/3DOM LSCO; y = 1.76?6.85 wt%, z ? 2.0 wt%; MnOx was mainly Mn3O4 nanocubes) catalysts were prepared using the(in situ) polymethyl methacrylate(PMMA)-templating and polyvinyl alcohol(PVA)-protected NaBH4 reduction methods. Physicochemical properties of these porous materials were characterized by means of the techniques, such as inductively coupled plasma atomic emission spectroscopy(ICP?AES), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), nitrogen adsorption?desorption(BET), X-ray photoelectron spectroscopy(XPS), and hydrogen temperature-programmed reduction(H2-TPR). Catalytic activities of the samples were evaluated for the oxidation of toluene, and the relationship between physicochemical properties and catalytic performance of the materials was established. The main results obtained in the thesis are as follows: 1. The 3DOM LSMO support, 8MnOx/3DOM LSMO, and yAu/8MnOx/3DOM LSMO catalysts were prepared via the in situ PMMA-templating and PVA-protected NaBH4 reduction routes, respectively, in which the LSMO possessed a rhombohedral crystal structure and a high-quality 3DOM structure. The 3DOM LSMO and yAu/8MnOx/3DOM LSMO samples displayed a surface area of 22?25 m2/g, with the MnOx and Au nanoparticles(3.2?3.8 nm in size) being highly dispersed on the 3DOM LSMO surface. The 5.92Au/8MnOx/3DOM LSMO sample exhibited the highest adsorbed oxygen species concentration and the best low-temperature reducibility, and the highest catalytic activity for toluene oxidation: the T50% and T90%(temperatures required for achieving toluene conversions of 50 and 90 %) were 205 and 220 oC at a space velocity(SV) = 20,000 mL/(g h), respectively. The apparent activation energies obtained over the yAu/8MnOx/LSMO samples were in the range of 52.8?68.5 kJ/mol. 2. The 3DOM LSCOsupport, 2Au/3DOM LSCO, and yMnOx?2Au/3DOM LSCO catalysts were prepared using the PMMA-templating, PVA-protected NaBH4 reduction, and physical adsorption methods, respectively. The LSCO was of rhombohedral crystal structure. The 3DOM LSCO and yMnOx?2Au/3DOM LSCO possessed a high-quality 3DOM structure, a surface area of 18?33 m2/g, with the MnOx(5?12 nm in size) and Au(3?4 nm in size) nanoparticles being well dispersed on the surface of 3DOM LSCO. There was a good relationship between adsorbed oxygen species concentration or low-temperature reducibilityand catalytic performance. Among all of the catalysts, 1.67MnOx?2Au/3DOM LSCO performed the best: the T50% and T90% were 214 and 230 oC at SV = 20,000 mL/(g h), respectively. 3. The excellent catalytic performance of 5.92Au/8MnOx/3DOM LSMO or 1.67MnOx?2Au/3DOM LSCO was associated with its larger surface area, higher oxygen adspecies concentration, and better low-temperature reducibility as well as the stronger interaction between Au or MnOx nanoparticles and 3DOM LSMO or 3DOM LSCO. |
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