Vanadia-silica

Active heterogeneous catalysts have been obtained. Examples include titania-, vanadia-, silica-, and ceria-based catalysts. A survey of catalytic materials prepared in flames can be found in [20]. Recent advances include nanocrystalline Ti02 [24], one-step synthesis of noble metal Ti02 [25], Ru-doped cobalt-zirconia [26], vanadia-titania [27], Rh-Al203 for chemoselective hydrogenations [28], and alumina-supported noble metal particles via high-throughput experimentation [29]. 

Fujdaia. K. L Tilley. T. D. New vanadium tris(terf-butoxy)siioxy complexes and their thermolytic conversions to vanadia-silica materials. Chem. Mater. 2002. 14, 1376-13B4. 

The vanadia/silica system [53] is another one in which Si NMR data, at least for the sol-gel derived glasses on which such data have been reported, provide only rough qualitative support for conclusions based primarily on other types of data [53f]. In the V203/Si02 system, NMR results have been more useful to date [53a,b]. Figure 34.43 shows NMR spectra, both MAS and static-sample results, on a 10% vanadia/silica system under ambient (wet) conditions... 

Parvuleseu, V, Paun, C., Parvuleseu, V, et al. (2004). Vanadia-silica and Vanadia-cesium-sUica Catalysts for Oxidation of SO2, J. Catal., 225, pp. 24-36. 

Planar model catalysts with similar compositions (such as vanadia-silica, vanadia-alumina on NiAl(l 10), and vanadia on Ce02(l 11) monocrystal faces) have been recently investigated with surface science techniques such as infrared reflection absorption spectroscopy Although the authors claim that these studies... 

Busca, G., (1989). On the mechanism of methanol oxidation over vanadia-based catalysts A FTIR study of the adsorption of methanol, formaldehyde and formic acid on vanadia and vanadia-silica, J. Mol. Catal., 50, pp. 241-249. 

R. Rulkens, T.D. Tilley - A Molecular Precursor Route to Active and Selective Vanadia-Silica-Zirconia Heterogeneous Catalysts for the Oxidative Dehydrogenation of Propane, J. Am. Chem. Soc. 120, 9959,1998. 

Oyama and Somorjai have studied the oxidation of ethanol and ethane over vanadia supported on silica.33 Ethane oxidation yielded ethylene and acetylene with considerable CO2 for highly dispersed catalysts. Ethanol oxidation to acetaldehyde, on the other hand was shown to be structure insensitive. Conversions and selectivities for reaction of ethanol are shown in Table III.33... 

Hess C, Wild U, Schlogl R. The mechanism for the controlled synthesis of highly dispersed vanadia supported on silica SBA-15. Microporous and Mesoporous Materials. 2006 95(l-3) 339-349. 

This description is consistent with the results of TPR/TPO-Raman investigations of supported vanadia on silica. 

The group 5-7 supported transition metal oxides (of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and rhenium) are characterized by terminal oxo bonds (M =0) and bridging oxygen atoms binding the supported oxide to the cation of the support (M -0-MSUpport). The TOF values for ODH of butane or ethane on supported vanadia were found to depend strongly on the specific oxide support, varying by a factor of ca. 50 (titania > ceria > zirconia > niobia > alumina > silica). 

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