SBA-15 mesoporous silica modified with rhodium by MDD method and its catalytic role for N2ON_2O decomposition reaction

SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N2O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)3 as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified with metals were characterized with respect to metal loading (EPMA), structure (XRD), texture (BET), morphology (SEM), Rh dispersion (oxygen chemisorption), surface acidity (pyridine adsorption) and chemical nature of introduced copper and iron species (UV-vis-DRS). The rhodium-containing SBA-15 samples were found to be active catalysts for the N2O decomposition reaction. Deposition of Al on the Rh-loaded catalyst increased its activity. An opposite effect was observed for the samples modified with Cu and Fe

Characterization and quantification of the NH3 modification of a BCl3-treated silica gel surface

The reaction of NH3 with a well characterized silica surface containing =SiOBCl2 surface species has been studied using FTIR photoacoustic spectroscopy and quantitative boron, chloride and ammonia analysis. The influence of reaction time and temperature on the reaction was studied. Characterization of the reactions occurring and the surface species formed was carried out. Both surface siloxane groups and =SiOBCl2 species interact with NH3, resulting in the formation of NH4Cl, chemisorbed amine groups and =SiOH groups. Borazine-like surface species are formed at higher temperatures. A quantitative description of the grafted groups has been obtained as a function of reaction temperature

Characterization of a TiCl4-modified silica surface by means of quantitative surface analysis

The reaction of TiCl4 with the surface of a silica gel has been investigated in detail using Fourier-transform IR photoacoustic spectroscopy (FTIR PAS) and elemental analysis. The hydroxy groups on the silica react with the TiCl4 giving rise to both monodentate and didentate surface groups. The parameters influencing the relative distribution of these groups have been studied. A quantitative description of the chemisorbed species has been obtained as a function of the pretreatment and the reaction temperatures

Preparation of supported vanadium oxide catalysts : adsorption and thermolysis of vanadyl acetylacetonate on a silica support

Adsorption and subsequent thermolysis of vanadylacetylacetonate [VO(acac)(2)] on a silica support yields supported V-O structures. The initial concentrations of the complex, the drying temperature and the calcination are the factors with the highest impact on the nature of the vanadium oxide coating. Too high initial concentrations of the complex induce coalescence and clustering of the adsorbed product. During the drying or curing step, important rearrangements occur in the adsorbed layer, creating additional covalent bonds between the complex and the substrate. Calcination is accompanied by thermolysis: a conversion of the supported VO(acac)(2) towards supported vanadium oxide. The evolved products were identified and a conversion mechanism is suggested. The thermolysis of adsorbed VO(acac), is a fast and effective way to create supported vanadium oxide catalysts with a high surface area