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a b s t r a c tNanocrystalline CeO 2 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/CeO 2 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 • 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 CO 2 (15 vol.%) and H 2 O (10 vol.%) in the reaction mixture on the performance of CuO-CeO 2 catalysts was also investigated. The addition of CO 2 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 CO 2 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 Ce 4+ species before reaction.

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