Effects of pretreatment conditions on CO oxidation over supported Au catalysts

Supported gold catalysts were prepared by a deposition-precipitation method and characterized to understand the different activities for CO oxidation with different pretreatment conditions. Gold catalysts supported on Fe2O3, TiO2, and Al2O3 Showed decreasing activity with increasing calcination temperatures, with the Al2O3-supported catalyst showing activity substantially lower than that of the other two catalysts. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) studies showed the phase transition of gold from Au(OH)(3) through Au2O3 to metallic gold with increasing calcination temperatures for all catalysts. In addition to the particle size of metallic gold, the oxidation states of gold were proven to be important for CO oxidation. The oxidized gold species were more active than metallic gold. Furthermore, facile formation of the interface between gold and support appears to be critical for high CO oxidation activity of supported gold catalysts. (C) 1999 Academic Press.