CO oxidation over CuO/ZrO2 catalysts: effect of loading and incorporation procedure of CuO

CuO/ZrO2 catalysts were prepared by in situ sol-gel and impregnation methods, with CuO concentrations of 1 and 3.6 mol.-% calcined at 400 degrees C. The catalysts were characterised by SBET, XRD, diffuse reflectance ultraviolet-visible spectroscopy and temperature programmed reduction (H-2). The catalytic activity was performed in the CO oxidation. The XRD, diffuse reflectance ultraviolet-visible spectroscopy and temperature programmed reduction results showed that the dispersion of Cu species depends on the method of preparation and on the copper loading. The CuO/ZrO2 catalysts prepared by impregnation procedure showed higher catalytic activity than those prepared by the in situ sol-gel method. This observation can be explained by the presence of small particles of CuO on the catalyst prepared by impregnation (higher dispersion), which does not occur in the catalysts obtained by the in situ sol-gel method due to an important amount of Cu-2+ ions that were incorporated into the support network, which are considered catalytically inactive.