Effect of the CeO2 content on the surface and structural properties of CeO2-Al2O3 mixed oxides prepared by sol-gel method

Mixed xCeO(2)-Al2O3 oxides with different CeO2 content (x = 1-20 wt%) were prepared by sol-gel method. The effect of the CeO2 content, atmosphere and temperature treatment during synthesis on the structure and properties of the xCeO(2)-Al2O3 was investigated. xCeO(2)-Al2O3 xerogels prepared from aluminum trisec-butoxide and Ce(III) nitrates have a pseudo boehmite-like structure. The Ce(III) ions stabilized under a reductive atmosphere randomly occupy vacant sites in tetrahedral and octahedral positions of Al2O3. The crystallization of gamma-Al2O3 is suppressed and the textural properties of the mixed xCeO(2)-Al2O3 oxides are stabilized at high temperature. Conversely, the treatment xCeO(2)-Al2O3 xerogels in an oxidative atmosphere shows a progressive oxidation of Ce(III) to Ce(IV) with crystallization of gamma-Al2O3 and formation of CeO2 with fluorite-like structure as the temperature rises. The effect of CeO2 on the catalytic performance xCeO(2)-Al2O3-supported Pt catalysts in partial oxidation of methane reaction was tested. The Pt catalysts were obtained by two methods: (i) impregnation of the xCeO(2)-Al2O3 supports with H-2 PtCl6 center dot 6H(2)O and (ii) one-step preparation by addition of Pt precursor during the sol-gel synthesis. CeO2-containing catalysts showed higher stability than Pt/Al2O3 catalyst obtained by impregnation method. The effect of the support was less evident when the catalysts were obtained by the one-step method. Pt catalysts based on sol-gel oxides preparation show higher thermal stability and result in higher Pt sintering resistance than conventional ones. (C) 2010 Elsevier B.V. All rights reserved.