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Abstract

Highly ordered mesoporous Cu–Ce–O catalysts with different Cu contents have been synthesized by using ordered mesoporous silica KIT-6 as a hard template. The mesostructural order of the negative replica is influenced by the ratio of Cu to Ce. Using XRD, HR-SEM, TEM and EDX analysis, it was found that the ordered mesostructures of the nanocomposites degenerate with increasing Cu concentration, due to CuO leaching during the template removal process and a phase separation at high Cu concentration. Cu ions can replace Ce-ion in the structure of CeO₂ at Cu concentrations below 40 mol%. However, the Cu concentration in the final materials is lower than expected from the ratio used in the synthesis. The activity in preferential oxidation of CO in H₂-rich gases (PROX) was tested at a space velocity of 60,000 mL h⁻¹ g_cat⁻¹. The activity of the mesoporous catalysts increases with the concentration of Cu and becomes stable for Cu concentrations higher than 20 mol%. A CO conversion around 100 % can be attained with Cu_0.20Ce_0.80O₂ as catalyst at 160 °C. The exit CO concentration can be as low as 70 ppm under these conditions. The CO₂ selectivity can reach 100 % at low temperature (60 – 80 °C). Direct loading of CuO on the surface of mesoporous CeO₂ leads to large CuO crystals and correspondingly low activity. The influence of the pretreatment atmosphere on activity was also studied. Oxidation–reduction–reoxidation cycling can improve the catalytic activity of the catalysts.