In-situ FTIR and XAS study of the evolution of surface species during transient Co oxidation on supported Au/Tio₂

Transient experiments involving the saturation of the catalyst either with CO or O₂, followed by admission of O₂ or CO, were performed. Exposure of the activated catalysts to 10 mbar of CO at -60°C led to the formation of CO adsorbed species over only 13% of the gold. Admission of 25 mbar of O₂ to the CO-saturated catalyst induced drastic changes on the nature and population of surface species. CO₂ was readily formed at the expense of the highly active CO-Au species (2091/cm), at a turnover frequency (TOF) of 1.4 mole/mole Au-min. CO₂ production was spread over a longer time scale, with a maximum TOF of 1 mole/mole Au-min. Whether the catalyst is initially saturated with CO or O₂ before admitting the other reactant did not affect the total amount of CO₂ generated. Transformation of CO into CO₂ entailed a hydroxocarbonyl intermediate characterized by an absorption band at 1240/cm. Its rate of disappearing correlated with the rate of formation of CO₂. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 1/04/2005).