Abstract
Preferential oxidation of CO in H 2 was studied over a series of CuO x –CeO 2 mixed oxide catalysts with differing Cu loadings and preparation techniques to elucidate structure and mechanism parameters required to achieve high selectivity. Using in situ diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS), CO oxidation activity is linked to Cu + carbonyl species (∼2110 cm −1), while catalyst deactivation is associated with catalyst hydration. Active sites for both reactions are found to be reducible oxygen from highly dispersed or surface incorporated CuO x species in proximity to Ce, and are quantified utilizing anaerobic titrations. Active site concentrations (2.1–3.5 × 10 −6 mol O ∗ m −2) are correlated with surface copper content, as determined by X-ray photoelectron spectroscopy (XPS). High reaction selectivity towards CO oxidation (100% selectivity above 200 ppm CO at 333 K) is attributed to preferential adsorption of CO as well as inhibited H 2 dissociation due to oxidized copper sites. A detailed Mars and van Krevelen mechanism for CO and H 2 oxidation is proposed and supported by comparing the model to the experimental data.
Published Version
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