CO preferential oxidation over CuO–CeO2 catalysts synthesized by the urea thermal decomposition method

CuO–CeO2 catalyst precursors were synthesized by the homogeneous thermal decomposition of urea. Catalysts containing different Cu/Ce ratios were obtained by calcinating the precursors at 450 °C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX) and temperature-programmed reduction (TPR) measurements. Catalytic tests were performed in the temperature range 100–300 °C to evaluate the activity, selectivity and stability of these samples for the preferential oxidation of CO (CO PROX) reaction. The effect of the presence of H2O and/or CO2 in the feed stream on both the structure and the catalytic behaviour of the samples were also analysed. The catalytic activity of the samples for both CO and H2 oxidation reactions increases as the copper loading increases and H2 oxidation competition becomes more important when the available oxygen in the gas phase is scarce. During the first 24 h of CO PROX operation, catalysts with low copper content are perfectly stable but the sample with the highest copper content has shown an irreversible deactivation, probably due to a partial reduction of the segregated CuO phase present in the fresh sample. The presence of both water and carbon dioxide in the feed gas stream has a negative effect on the catalytic activity of CuO–CeO2 catalysts.