3-D flower like Ce-Zr-Cu mixed oxide systems in the CO preferential oxidation (CO-PROX): Effect of catalyst composition

Ce-Zr-Cu mixed oxide systems, with different contents of ZrO2 and CuO, were prepared by slow co-precipitation method, leading to the formation of materials with a flower-like morphology. It was evaluated both the role of CuO loading (3-7 wt%), by maintaining constant the amount of ZrO2 (7 wt%), and the role of ZrO2 (2-10 wt%)witha fixed amount of CuO (7 wt%). The prepared catalysts were characterized by means of ICP-OES, SEM, N-2 physisorption, quantitative XRD, H-2-TPR, and XPS. Their catalytic performances in the preferential oxidation of CO in excess of H-2 (CO-PROX) were evaluated, in the 40-190 degrees C temperature range. Characterization and catalytic results showed that an optimum Zr/Ce molar ratio and CuO loading are required to attain the best catalytic performance over the studied nanostructured Ce/Zr/Cu oxide system. Characterization results revealed that, regardless of the sample composition, all of them presented similar flower-like morphology and textural properties. Instead, the catalyst composition determined the crystalline phases formed, their reducibility and surface distribution. The catalyst containing an intermediate ZrO2 loading (7 wt%) and the highest studied CuO amount (7 wt%), FCZCu77, showed the higher fraction of undetectable CuO from XRD, that is the highest proportion of highly dispersed Cu species also observed from H-2-TPR. These characteristics justify how FCZCu77 catalyst exhibited a quite higher catalytic activity than the others samples. (C) 2014 Elsevier B.V. All rights reserved.