Preferential CO oxidation (CO-PROX) catalyzed by CuO supported on nanocrystalline CeO2 prepared by a freeze-drying method

• CuO supported on nanocrystalline CeO2 is highly active and selective in CO-PROX.
• In spite of their low surface area, the prepared catalysts are active and selective.
• The good CO-PROX catalytic performance is due to the high dispersion of the active phase.
• The presence of CO2 and H2O in the gas stream partially deactivate the catalysts.

Nanocrystalline CeO2 with a regular size of 9.5 nm was prepared by a freeze-drying method, and subsequent impregnated with a Cu(II) acetate solution, varying the loading of Cu (3, 6, 12 wt.%). The resulting CuO/CeO2 materials were characterized by N2 physisorption at −196 °C, HRTEM, H2-TPR, X-ray diffraction, Raman spectroscopy and XPS and tested as catalysts in the preferential CO oxidation in a H2-rich stream (CO-PROX) in the temperature range 40–190 °C. In spite of their low specific surface areas the catalysts exhibited a good catalytic performance, resulting active and selective in the CO-PROX reaction at low temperatures. The inhibiting effect of the simultaneous presence of CO2 (15 vol.%) and H2O (10 vol.%) in the reaction mixture on the performance of CuO-CeO2 catalysts was also investigated. The addition of CO2 and water in the gas stream depressed CO oxidation up to 160 °C, its effect being negligible at higher temperatures. Nevertheless, despite these expected deactivation phenomena, a CO conversion value higher than 90% and a CO2 selectivity of about 90% was achieved for all the samples at 160 °C. The excellent performance, especially shown by the catalyst with 6 wt%. of copper, has been related to the wide dispersion of the copper active sites associated with the high amount of Ce4+ species before reaction.

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