Synthesis And Characterization Of Titanium Oxide Based Catalysts And Their Application In The Environmental Catalysis

Part Ⅰ:TiO2-ZrO2 (hereafter denoted as TZ) binary oxides with different Ti:Zr ratios were obtained by co-precipitation method and CuO-TZ catalysts were prepared via wet-impregnation method. It is found that catalysts show better activity in the NO+CO reaction when Zr:Ti ratios are low, and the Ti:Zr=20:1 sample shows the highest activity. CuO catalysts supported on TZ (Ti:Zr=20:1) and pure anatase TiO2 were studied by HRTEM, XRD, UV-Vis DRS, TPR, XPS, in situ FT-IR and activity test for the removal of NO by CO. The results indicate that:(1) CuO species can be highly dispersed on the surface of TZ support, and the dispersion capacity (DC) is about 1.1mmol/100m2 TZ, which can be explained by the incorporation model. (2) The reduction temperature of CuO supported on TZ is lower than that supported on pure anatase TiO2, ZrO2 and ZrO2 surface-modified anatase TiO2 supports. Furthermore, the activity of Cu-TZ is also the highest among them measured by a relative turn over frequency (TOF) value of NO. (3) The ZrO2 doping into TiO2 improves the adsorption stability of NOx (especially the bridged nitrate/nitro) and decreases the active temperature of Cu+-CO species, both of which are the key intermediates for NO conversion. On the other hand, the ZrO2 doping into TiO2 promotes the formation of Cu+/Cu0 species at high temperatures, which has a crucial effect on N2O reduction. Part Ⅱ:ZrO2-doped TiO2 hollow nanospheres with anatase-phase are efficiently fabricated via functionalized negatively charged polystyrene (PS) spheres without any surfactant or polyelectrolyte. The resulting Ti1-xZrxO2 (hereafter denoted as TZ) hollow nanospheres are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), nitrogen sorption, and UV-visible diffuse reflectance spectroscopy (UV-vis). The Zr4+ incorporation decreases the anatase crystallite size, increases the specific surface area and changes the pore size distribution. Furthermore, it induces increased amounts of surface hydroxyl groups, enrichment of electron charge density around Ti4+ ions, and blue shift of adsorption edges. The TZ hollow nanospheres doped with moderate ZrO2 (molar ratio, Ti:Zr=10:1) exhibit better photocatalytic activity than the other samples for the degradation of rhodamine B in aqueous solution, which is correlated with the effect of Zr4+ doping on the physicochemical properties in terms of surface structures, phase structures and the electronic structures. Part Ⅲ:Binary metal oxides V2O5-WO3 supported on Tio.5Sn0.5O2 (hereafter denoted as TS) catalysts have been characterized by XRD, LRS, TPR, NH3-TPD, NH3 adsorption in situ FT-IR, and the micro-reactor test for the removal of NO by NH3. The results suggest that:(1) Both vanadium oxide and tungsten oxide (loadings< 0.5 mmol/100m2 TS) are highly dispersed on TS support. (2) The reduction temperature of vanadium species becomes higher due to the formation of the V-O-W bonds. (3) With the loading amounts of WO3 increasing, the amounts of the Br(?)nsted acid sites increase, while the amounts of Lewis acid sites decrease. The strength of Br(?)nsted acid sites is little influenced by the tungsten species which is further proved by the density functional theory (DFT) calculation results. Further increase of WO3 (loadings ≥ 1.0 mmol/100m2 TS) results in the formation of crystalline WO3 and they will cover the vanadium oxide species on the surface of the catalysts. (4) The activity of "NO+ NH3+O2" reaction is tightly related to the amounts of the Br(?)nsted acid sites:the higher SCR activities should be attributed to the larger amounts of Br(?)nsted acid sites when WO3 are highly dispersed. When the crystalline WO3 form, they cover the surface of the catalysts, and lead to the decrease of the activities.