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Laurent Delannoy Norbert Weiher Nikolaos Tsapatsaris Angela M. Beesley Luanga Nchari Sven L. M. Schroeder Catherine Louis 《Topics in Catalysis》2007,44(1-2):263-273
The origin of CO oxidation performance variations between three different supported Au catalysts (Au/CeO2, Au/Al2O3, Au/TiO2) was examined by in situ XAFS and DRIFTS measurements. All samples were prepared identically, by deposition-precipitation of an aqueous Au(III) complex
with urea, and contained the same gold loading (~1 wt %). The as-prepared supported Au(III) precursors exhibited different
reduction behaviour during exposure to the CO/O2/He reaction mixture at 298 K. The reducibility of the Au(III) precursor was found to decrease as a function of the support
material in the order: titania > ceria > alumina. The as-prepared samples were inactive catalysts, but Au/TiO2 and Au/CeO2 developed catalytic activity as the reduction of Au(III) to metallic Au proceeded. Au/Al2O3 remained inactive. The developed catalytic CO oxidation activity at 298 K varied as a function of the support as follows:
titania > ceria > alumina ~ 0. The EXAFS of samples pretreated in air at 773 K and in H2 at 573 K reveals the presence of only metallic particles for Au/TiO2 and Au/Al2O3. Au(III) supported on CeO2 remains unreduced after calcination, but reduces during the treatment with H2. CO oxidation experiments performed at 298 K with the activated samples show that the presence of metallic gold is necessary
to obtain active catalysts (Au/CeO2 is not active after calcination) and that the reducible supports facilitate the genesis of active catalysts, while metallic
gold particles on alumina are not active. 相似文献
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