Titania removal

NO, however, can only be removed by adding a reductant, ammonia, and using a catalyst. The process is called selective catalytic reduction, or SCR. The catalyst consists of vanadia and titania and works in the temperature interval 600-700 K according to the overall reaction ... 

In the area of pollution control, file removal of NOx from stationary sources effluents, such as power plant stack gases, has been accomplished by use of titania-vanadia catal)rsts, which promote the reduction of NOx with NH3 to produce nitrogen and water. 

Baiju, K.V., Shukla, S., Biju, S., Reddy, M.L.P., and Warrier, K.G.K. (2009) Morphology-dependent dye-removal mechanism as observed for anatase-titania photocatalyst. Catalysis Letters,... 

Ordered mesoporous materials of compositions other than silica or silica-alumina are also accessible. Employing the micelle templating route, several oxidic mesostructures have been made. Unfortunately, the pores of many such materials collapse upon template removal by calcination. The oxides in the pore walls are often not very well condensed or suffer from reciystallization of the oxides. In some cases, even changes of the oxidation state of the metals may play a role. Stabilization of the pore walls in post-synthesis results in a material that is rather stable toward calcination. By post-synthetic treatment with phosphoric acid, stable alumina, titania, and zirconia mesophases were obtained (see [27] and references therein). The phosphoric acid results in further condensation of the pore walls and the materials can be calcined with preservation of the pore system. Not only mesoporous oxidic materials but also phosphates, sulfides, and selenides can be obtained by surfactant templating. These materials have pore systems similar to OMS materials. 

Phosphates and sulfates correspond to chemical groups which are difficult to photodegrade due to the fact that they adsorb strongly on semiconductor surfaces, particularly titania, even at concentrations as low as 1 mM. In the case of phosphates, the binding with the oxide is so strong that removal with water is inefficient and alkali washing is necessary. Phosphates and sulfates may, however, display singular features as they form reactive species under UV illumination in accordance with eqns (4) and (5) ... 

We are developing a new method for preparing heterogeneous catalysts utilizing polyamidoamine (PAMAM) dendrimers to template metal nanoparticles. (1) In this study, generation 4 PAMAM dendrimers were used to template Pt or Au Dendrimer Encapsulated Nanoparticles (DENs) in solution. For Au nanoparticles prepared by this route, particle sizes and distributions are particularly small and narrow, with average sizes of 1.3 + 0.3 nm.(2) For Pt DENs, particle sizes were around 2 nm.(3) The DENs were deposited onto silica and Degussa P-25 titania, and conditions for dendrimer removal were examined. 

Crooks and coworkers, who studied Pd and Au DENs immobilized in sol-gel titania, similarly reported the onset of dendrimer mass loss at relatively low temperatures (ca. 150 °C). Pd helped to catalyze dendrimer decomposition in their system, as well. Temperatures of 500 °C or greater were required to completely remove organic residues from their materials. (10) This treatment resulted in... 

Atoms in the free surface of solids (with no neighbors) have a higher free energy than those in the interior and surface energy can be estimated from the number of surface bonds (Cottrell 1971). We have discussed non-stoichiometric ceramic oxides like titania, FeO and UO2 earlier where matter is transported by the vacancy mechanism. Segregation of impurities at surfaces or interfaces is also important, with equilibrium and non-equilibrium conditions deciding the type of defect complexes that can occur. Simple oxides like MgO can have simple anion or cation vacancies when surface and Mg + are removed from the surface,... 

Applying fins coated with titania is an effective way to enhance the formaldehyde removal performance (Mo et al., 2008b). In order to compare the formaldehyde removal performance of annular photocatalytic reactors with and without the aforementioned fins, the PCO reactors without and with the fins operated in a sealed stainless steel chamber with formaldehyde in its air, respectively. Figure 4.15 shows the chamber formaldehyde concentration decay curves (a) an annular PCO reactor without fins, (b) an annular PCO reactor with six fins. It can be seen that the reactor with fins is more efficient than that without. The reason and the analysis are presented by Mo et al. (2008b) in detail. 

---