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

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 N-2 physisorption at 196 C, HRTEM, H-2-TPR, X-ray diffraction, Raman spectroscopy and XPS and tested as catalysts in the preferential CO oxidation in a H-2-rich stream (CO-PROX) in the temperature range 40-190 degrees 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 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.