Selective CO oxidation in excess of H2 over high-surface area CuO/CeO2 catalysts

The influence of the surface area, crystal size of the support and the Cu loading (3–9 wt.%) on the catalytic behavior of CuO/CeO2 catalysts was investigated in the preferential CO oxidation (PROX) reaction. Two ceria samples were used: a high-surface area one (SCe) prepared by the templating technique and a low surface commercial one (ACe). Copper was incorporated to the calcined support by classical impregnation. Techniques were used to characterize the textural, structural and chemical properties of the catalysts (BET, XRD, HRTEM, and TPR). For catalysts supported on SCe these techniques evidenced highly dispersed copper species in strong interaction with nanosized CeO2 crystals. The enhanced redox properties of the CuO–support interface sites at low temperature evidenced by TPR in CuSCe catalysts play a fundamental role in the catalytic behavior for the CO oxidation in presence of excess H2 (PROX). CuSCe catalysts showed excellent catalytic activity compared to catalysts supported on the commercial CeO2. Total conversion of CO is obtained at 125 °C with 100% selectivity to CO2. In the presence of CO2 and H2O the maximum CO conversion for temperatures higher than 125 °C was 95%. Selectivity also decreased being more pronounced when H2O was present. This negative effect was reversible since the original activity and selectivity were practically restored upon elimination of these components from the feed. Partially reduced Cu+ species seem to be present in the catalysts according to CO adsorption followed by DRIFT.