Titanium oxide/highly dispersed

The aim of this work is to develop new Fe-Mo containing mixed oxides highly dispersed in a titania matrix, prepared by the sol-gel method, and to compare these materials to those of iron molybdate prepared by conventional methods (i.e. impregnation). Here, we report the preparation of sol-gel derived iron molybdenum titanium mixed oxides. The bulk composition and the textural properties of these materials are investigated by elemental chemical analysis and N2 adsorption, respectively. 

Titanium dioxide supported gold catalysts exhibit excellent activity for CO oxidation even at temperatures as low as 90 K [1]. The key is the high dispersion of the nanostructured gold particles over the semiconducting Ti02 support. The potential applications of ambient temperature CO oxidation catalysts include air purifier, gas sensor and fuel cell [2]. This work investigates the effects of ozone pretreatment on the performance of Au/Ti02 for CO oxidation. 

Propose a way to apply titanium oxide in very highly dispersed form onto an alumina support. 

Lee et al. s study also investigates the hydrophilicity of the heterocatalyst. They mention that the highly acidic surface of the material is more hydrophobic than the pure titanium oxide surface. They theorize that this is because the acidic surface results in fewer adsorbed OH ions and thus a weaker interaction with water. As expected, this increased hydrophobicity leads to an increase in the stability of dispersions of nanoscale powders of this material. Saltiel et al. showed that WOs-coated titanium oxide powders were much more stable than their uncoated counterparts. Even after agglomeration, the agglomerates of the coated powders were more porous than those of pure titanium oxide (the coated powders had a fractal dimension of 1.55 while the pure titanium oxide powders had a fractal dimension of 1.60). 

Figure 12 shows the XANES and FT-EXAFS spectra of the titanium oxide catalysts chemically doped with Cr ions (a and A) and physically implanted with Cr ions (b and B). Analyses of these XANES and FT-EXAFS spectra show that in the titanium oxide catalysts chemically doped with Cr ions by an impregnation or sol-gel method, the ions are present as aggregated Cr oxides having an octahedral coordination similar to CriOs and tetrahedral coordination similar to CrOs, respectively. On the other hand, in the catalysts physically implanted with Cr ions, the ions are present in a highly dispersed and isolated state in octahedral... 

In the present work the synthesis of highly dispersed niobium or titanium containing mesoporous molecular sieves catalyst by direct grafting of different niobium and titanium compounds is reported. Grafting is achieved by anchoring the desired compounds on the surface hydroxyl groups located on the inner and outer surface of siliceous MCM-41 and MCM-48 mesoporous molecular sieves. Catalytic activity was evaluated in the liquid phase epoxidation of a-pinene with hydrogen peroxide as oxidant and the results are compared with widely studied titanium silicalites. The emphasis is directed mainly on catalytic applications of niobium or titanium anchored material to add a more detailed view on their structural physicochemical properties. 

FIGURE 3 Selectivity for N2 formation as a function of the coordination number of Ti determined by EXAFS in the photocatalytic decomposition of NO into N2 and 02 on various titanium oxide catalysts including highly dispersed, chemical mixture and bulk Ti02 powder. (Reproduced with permission from Yamashita and Anpo (2004).)... 

As shown in Fig. 29, highly dispersed titanium oxide anchored onto Vycor glass exhibits a photoluminescence spectrum that has a peak near 485 nm when excited by U V light at about 300 nm this is attributed to the radiative deactivation of the charge-transfer excited state of the titanium oxide species 168, 212) ... 

Titanium oxides anchored to transparent Vycor glass and titanium oxides dispersed into Si02 carriers or matrices exhibit extremely high photocatalytic activity due to the high activity of the highly dispersed tetrahedral titanium oxide species (168, 200, 201). The sol-gel method was found to be... 

As shown in Fig. 65, titanium-silicon binary oxides prepared by the sol-gel method exhibit a characteristic photoluminescence spectrum near 480 nm upon excitation at 280 nm. The absorption and photoluminescence spectra are attributed to the charge-transfer processes on the highly dispersed tetrahedral titanium oxide species embedded in the Si02 matrices (168, 200, 201). When the titanium content of the oxides was decreased, the intensity of the photoluminescence spectrum increased, and its peak wavelength shifted to shorter wavelengths. 

In the present study, highly dispersed titanium oxides included within the zeolite cavities (Ti-oxide/Y-zeolite) and framework (Ti-MCM-41,-48) were prepared using an ion-exchange method and hydrothermal synthesis to be used as photocatalysts for the reduction of CO2 with H2O at 328 K. The characterization of these catalysts by means of in situ photoluminescence, diffuse reflectance absorption, XAFS (XANES and FT-EXAFS), and ESR measurements have been carried out and special attention has been focused on the relationship between the structure of the titanium oxide species and the reaction selectivity in the photocatalytic reduction of CO2 with H2O to form CH3OH. 

UV irradiation of the anchored titanium oxide catalyst in the presence of CO2 and H2O at 77 K led to the appearance of ESR signals due to the Ti3+ ions, H atoms, and carbon radicals [5,6]. From these results the reaction mechanism in the photocatalytic reduction of CO2 with H2O on the highly dispersed titanium oxide catalyst can be proposed in the following way. CO2 and H2O molecules interact with the excited state of the photoinduced (Ti3+— 0") species and the reduction of CO2 and the decomposition of H2O proceed competitively. Furthermore, H atoms and OH radicals are formed from H2O and these radicals react with the carbon species formed from CO2 to produce CH4 and CH3OH. 

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