Abstract
ABSTRACTThe synthesis of aluminum oxide grafted on silica gel surface was carried out by the reaction of a suitable aluminum precursor with the surface hydrolysis of the oxide support. The chemical and physical properties of the attached oxide, SiO2/ Al2O3, can be quite different than those found for bulk Al2O3. The advantage of this preparation method, compared to the conventional ones (impregnation, precipitation and calcination), is that the oxide is highly dispersed on the surface (monolayer or submonolayer). We characterized the surface oxides treated at the temperature range of 423 to 1573 K employing X-ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance spectroscopy (NMR), and diffuse reflectance spectroscopy (DRS). XPS was used to identify the oxidation states and atomic ratios. Al27 NMR detected two species for samples heated up to 1023 K, and another one above this temperature. DRS, using pyridine as a molecular probe, showed that both Lewis and Brönsted acid sites are stable up to 1023 K. We concluded that the aluminum oxide is highly dispersed on the silica gel surface and it remains stable up to 1023 K.
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