Silica, titanium containing

Ti-SBA-15 mesoporous, titanium-containing silica self-assembly-15 (with uniform, hexagonal, tubular channels) synthesized by using a triblock organic copolymer as a template... 

The titanium-containing silicas were also employed in the epoxidation of a series of FAME mixtures obtained directly from vegetable oils, namely high-oleic (HO) sunflower oil, coriander oil, castor oil and soya-bean oil, by esterification with so-... 

Titanium containing pure-silica ZSM-5 (TS-1) materials are synthesized using different methods. The activity of the titanium containing catalysts for the oxidation of alkanes, alkenes and phenol at temperatures below 100 °C using aqueous H2O2 as oxidant is reported. The relationships between the physicochemical and catalytic properties of these titanium silicates are discussed. The effects of added duminum and sodium on the catalytic activity of TS-1 are described. The addition of sodium during the synthesis of TS-1 is detrimental to the catalytic activity while sodium incorporation into preformed TS-1 is not. The framework substitution of aluminum for silicon appears to decrease the amount of framework titanium. 

New plants are successfully operating with clean and efficient process technologies. This is the most significant development made possible by the discovery, in 1983, of titanium-containing crystalline silicas and their unique catalytic properties, especially in selective oxidation reactions with H202 as the oxidant. 

The synthesis of methyl /-butyl ether (MTBE) from isobutylene and methanol on TS-1 has been investigated. This reaction is catalyzed by acids and the industrial production is carried out with sulfonic acid resin catalysts. It has been reported that at 363-383 K the reaction proceeds in the presence of the acidic HZSM-5, but also on TS-1, which is much more weakly acidic. However, the characterization of the catalysts used is not completely satisfactory for instance, the IR spectra reported do not show the 960-cm 1 band that is always present in titanium-containing silicas. It is therefore possible that the materials with which the reaction has been studied are not pufe-phase TS-1. The catalytic activity for MTBE synthesis is, in any case, an interesting result, and further investigations with fully characterized catalysts are expected to provide a satisfactory interpretation of these results (Chang et al., 1992). 

Shan, Z., Gianotti, E., Jansen, J. C., Peters, J. A., Marchese, L. and Maschmeyer, T. One-step synthesis of a highly active, mesoporous, titanium-containing silica by using bifunctional templating, Chem. Eur. J., 2001, 7, 1437-1443. 

For redox catalysis, efforts have been spent on preparing transition metal modified mesoporous materials. These materials are capable of extending the catalytic oxidation chemistry to large molecules. The selective catalytic activity has also been demonstrated, for example, in the oxidation of aromatic compounds by using titanium-containing mesoporous silica (Ti-MCM-41 and Ti-HMS). ... 

Titanium-containing pure-silica ZSM-48 (e.g., [71, 72]), a unidimensional medium pore zeolite, and titano-aluminosilicates with the structure of zeolite Beta [72-74] are materials which are currently scrutinized in catalytic oxidation reactions [75]. In the latter case, however, residual acidity created by framework aluminum leads to undesired side reactions. Since, so far, the direct synthesis of Al-free pure titaniumsilicate Beta was not successful, van Bekkum et al. [76] developed a special post-synthesis modification technique. The three-step procedure... 

Si MAS-NMR spectra were reported for a new zeolite, ITQ-13. 19F NMR data enabled the distribution of F and Ge atoms in the structure to be understood.513 13C CP/MAS-NMR and 29Si MAS-NMR spectra were used to characterise titanium-containing mesoporous silica SBA-15, formed in the presence of -(trimethoxysilylpropyl)ethylenediamine triacetic acid.514 1H, 19F and 29Si MAS-NMR spectra were reported for the fluoride-containing zeolite SSZ-44.515... 

Fig. 2. UV-Vis spectra of titanium containing mesoporous silica materials.

High-temperature treatment of silicon- or titanium-containing alloys leads to the formation of crystalline titania or silica surface layers with thicknesses in the micrometer range, as demonstrated by Seo et al., who used these materials for the construction of heat exchangers with catalyti-cally active surfaces [166]. However, the thermal treatment of nickel alloys that also contain iron leads to a layer of amorphous iron oxide, which is not suitable for depositing catalytic materials [167]. 

Results of another experiment support this interpretation. An attempt was made to extract the titanium from a cogelled catalyst and from a titanated silica, each containing the same amount of Ti (2 wt%) and calcined at the same temperature, 600 °C. Presumably, if the titanium were in the bulk it would not be leached out readily. An acidic solution of hydrogen peroxide was used to perform the extraction. More than 90% of the titanium could be removed from the titanated silica, but only 58% could be extracted from the cogel. Thus, cogelled titania was less accessible, but even in the cogel most of it could be removed. Apparently, even in cogel, the titanium has some preference for the surface. 

A liner for a gas storage tank contains a polymer composition comprising a polyamide A, a nucleating agent in an amount of 0.05 to 0.15 wt%, and an impact modifier in an amount of at least 7 to 20 wt%. Suitable nucleating agents include talc, carbon black, silica, titanium dioxide, and nanoclay. ... 

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