Catalysts anatase

Catalyst Anatase (%) BET surface area (m /g) Particle size (nm) Purity as TiOz (%) Band-gap energy (eV)... 

Naphthaleneamine. 1-Naphthylamine or a-naphth5iamine/7i5 -i2- can be made from 1-nitronaphthalene by reduction with iron—dilute HCl, or by catalytic hydrogenation it is purified by distillation and the content of 2-naphthylamine can be reduced as low as 8—10 ppm. Electroreduction of 1-nitronaphthalene to 1-naphthylamine using titania—titanium composite electrode has been described (43). Photoinduced reduction of 1-nitronaphthalene on semiconductor (eg, anatase) particles produces 1-naphthylamine in 77% yield (44). 1-Naphthylamine/7J4-J2-. can also be prepared by treating 1-naphthol with NH in the presence of a catalyst at elevated temperature. The sanitary working conditions are improved by gas-phase reaction at... 

Elucidation of reduction behaviors for Co/Xi02 catalysts with various rutile/anatase ratios... 

The present study revealed effects of various rutile/anatase ratios in titania on the reduction behaviors of titania-supported cobalt catalysts. It was found that the presence of rutile phase in titania could facilitate the reduction process of the orbalt catalyst. As a matter of fact, the number of reduced cobalt metal surface atoms, which is related to the overall activity during CO hydrogenation increased. 

The present research showed a dependence of various ratios of rutile anatase in titania as a catalyst support for Co/Ti02 on characteristics, especially the reduction behaviors of this catalyst. The study revealed that the presence of 19% rutile phase in titania for CoATi02 (C0/RI9) exhibited the highest number of reduced Co metal surface atoms which is related the number of active sites present. It appeared that the increase in the number of active sites was due to two reasons i) the presence of ratile phase in titania can fadlitrate the reduction process of cobalt oxide species into reduced cobalt metal, and ii) the presence of rutile phase resulted in a larger number of reduced cobalt metal surface atoms. No phase transformation of the supports further occurred during calcination of catalyst samples. However, if the ratios of rutile anatase were over 19%, the number of active sites dramatically decreased. 

The band gap energy of modified catalysts decreased down to 1.6 eV, and the basic structure and physical properties of the catalysts were not changed during modification process. All of the synthesized Ti02 were anatase structure but commercial Ti02 were contained 30% rutile structure. However, the catalytic activity of modified catalysts using two different Ti02 were almost the same in this reaction conditions. 

The commonly used catalyst today is a vanadia on a titania support, which is resistant to the high SO2 content. Usually the titania is in the anatase form since it is easier to produce with large surface areas than the rutile form. Several poisons for the catalyst exist, e.g. arsenic and potassium. The latter is a major problem with biomass fuel. In particular, straw, a byproduct from grain production, seems to be an attractive biomass but contains potassium, which is very mobile at reaction tern-... 

A 0.5 wt% Pt/Ti02 catalyst was prepared by the photodeposition method. A 100 mg Ti02 (Aeroxide P25S Degussa, 50 m /g, approximately 70% anatase and 30% mtile) were suspended in 30 mL aqueous solution with 1.4 mg chloroplatinic acid... 

The process has been commercially implemented in Japan since 1977 [1] and a decade later in the U.S., Germany and Austria. The catalysts are based on a support material (titanium oxide in the anatase form), the active components (oxides of vanadium, tungsten and, in some cases, of molybdenum) and modifiers, dopants and additives to improve the performance, especially stability. The catalyst is then deposited over a structured support based on a ceramic or metallic honeycomb and plate-type structure on which a washcoat is then deposited. The honeycomb form usually is an extruded ceramic with the catalyst either incorporated throughout the stmcture (homogeneous) or coated on the substrate. In the plate geometry, the support material is generally coated with the catalyst. 

Heat-flow calorimetry may be used also to detect the surface modifications which occur very frequently when a freshly prepared catalyst contacts the reaction mixture. Reduction of titanium oxide at 450°C by carbon monoxide for 15 hr, for instance, enhances the catalytic activity of the solid for the oxidation of carbon monoxide at 450°C (84) and creates very active sites with respect to oxygen. The differential heats of adsorption of oxygen at 450°C on the surface of reduced titanium dioxide (anatase) have been measured with a high-temperature Calvet calorimeter (67). The results of two separate experiments on different samples are presented on Fig. 34 in order to show the reproducibility of the determination of differential heats and of the sample preparation. 

The three TS-1 catalysts with similar Ti contents have cuboidal morphology with comparable particle sizes of 0.2-0.3 pum (as shown in SEM pictures, Fig. 53). The EPR spectra of the samples in contact with aqueous H202 (46%) (Fig. 54) indicate that the ratio of the A to B superoxo species in various TS-1 samples increases in the order TS-1 (fluoride) < TS-1 (with anatase) < TS-1 (without anatase). Catalytic activity for phenol hydroxylation and allyl alcohol epoxi-dation (Table LIII) was found to parallel the A/B ratio of the oxo-Ti species (TS-1 (fluoride) < TS-1 (with anatase) < TS-1 (without anatase)). 

In a follow-up study, the authors498 probed the mechanism over Pt/Ti02 rutile and anatase catalysts. The authors could see OCO stretching bands clearly upon CO adsorption, but had difficulty observing the C-H stretching bands to identify them as bidentate formates (rutile—OCO bands at 1374 cm-1 for symmetric and 1599 cm-1 for asymmetric anatase—OCO bands at 1362 cm-1 for symmetric and 1561 cm-1... 

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