In-situ characterization of supported Au catalysts for CO oxidation

Au/γ-alumina prepared by deposition-precipitation was characterized by in-situ XANES and TPR to determine changes in the an oxidation state during activation for CO oxidation. As prepared, the sample was inactive without activation. It could be activated by various methods, e.g., heating at 100°C in H ₂ followed by H ₂ + H ₂O. Treatment in dry H ₂ at 100°C caused some reduction to Au(0) but with minimal increase in CO oxidation activity. Subsequent treatment with H ₂O, however, caused further reduction of gold and the catalyst became quite active. Additional reduction and increase in activity occurred during reaction. The presence of Au(0) was thus necessary for activity. However, the presence of Au(0) alone was insufficient for high CO oxidation activity. In-situ XANES results showed no detectable differences among the active, thermally deactivated, and the regenerated samples. Thus, the degree of reduction of gold is an incomplete indication of activity. Water is also an important factor. This is an abstract of a paper presented at the 227th ACS National Meeting (Anaheim, CA 3/28/2004-4/1/2004).