Selective oxidation of CO in excess hydrogen over CuO/CexSn1−xO2 catalysts

CexSn1−xO2 (1 − x = 0.1–0.5) mixed oxides were prepared as supports of CuO/CexSn1−xO2 catalysts. They were characterized and used in the selective oxidation of CO in excess hydrogen. Incorporating Sn4+ into CeO2 not only increased the mobility of lattice oxygen but also promoted the activity of the selective CO oxidation. These promoting effects were attributed to the redox behaviors of Ce4+/Ce3+ and Sn4+/Sn2+ in CexSn1−xO2 mixed oxides and to the interfacial interaction between fine clusters of CuO and CexSn1−xO2. Of these CuO/CexSn1−xO2 catalysts, 7% CuO/Ce0.9Sn0.1O2 catalyst was the most active one; it was and more active than the 7% CuO/CeO2 catalyst, with a T100 temperature (80–85 °C) for complete conversion that was about 15 °C less than that of 7% CuO/CeO2 (95–100 °C). The selective oxidation of CO was still promoted as the incorporated amount of Sn4+ exceeded 10%, which is different from the result of incorporating Zr4+ in CexZr1−xO2 (1 − x > 0.1). Such incorporation of Zr4+ in CexZr1−xO2 weakened the selective oxidation. The 7% CuO/Ce0.9Sn0.1O2 catalyst was almost inactive in H2 oxidation below 110 °C, and it achieved a selectivity of approximately 100%. The activity of the 7% CuO/Ce0.9Sn0.1O2 catalyst was weakened in the feed in the presence of CO2 and H2O, but the stability of the catalyst was maintained. The 7% CuO/Ce0.9Sn0.1O2 catalyst exhibited a good activity that was comparable with that of the noble metal catalyst of 5% Pt/Al2O3 and a good selectivity of much greater than 5% Pt/Al2O3.