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|Type:||Artigo de periódico|
|Title:||Aluminum Oxide Grafted On Silica Gel Surface: Study Of The Thermal Stability, Structure And Surface Acidity|
De Castro S.C.
|Abstract:||The synthesis of aluminum oxide grafted on silica gel surface was carried out by the reaction of a suitable aluminum precursor with the surface hydroxyl groups, ≡SiOH, of the oxide support in non-aqueous solvent. The advantage of this preparation method, compared to the conventional ones (impregnation or precipitation and calcination), is that the oxide is highly dispersed on the surface (monolayer or submonolayer). The resulting material, SiO2/Al2O3, was heat treated at temperature range of 423 to 1573 K. The Al/Si atomic ratios, determined by X-ray photoelectron spectroscopy (XPS), showed that aluminum is less mobile up to heat treatment of 1173 K and above this temperature part of it diffuses to the interior of the matrix. 27Al solid state nuclear magnetic resonance spectroscopy (NMR) showed two different environments, tetrahedral and octahedral for sample calcined up to 1023 K and above this temperature, aluminum in a trigonal bipyramidal environment was also detected. Pyridine adsorbed on a Lewis acid sites were observed for samples calcined up to 1023 K, and above this temperature they were not detected.|
|Editor:||Kluwer Academic Publishers, Dordrecht, Netherlands|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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