Oxidation of carbon monoxide in the presence of hydrogen on the CuO, CoO, and Fe2O3 oxides supported on ZrO2

Abstract

The catalytic activity of the CuO/ZrO 2 , CoO/ZrO 2 , Fe 2 O 3 /ZrO 2 , and CuO/(CoO, Fe 2 O 3 )/ZrO 2 systems in the reaction of selective CO oxidation in the presence of hydrogen was studied at 20–450°C over the oxide concentration range of 2.5–10 wt % on the surface of ZrO 2 . The conversion of CO on the CoO/ZrO 2 systems was almost independent of the concentration of CoO: 88 or 90% for 2.5 or 10% CoO, respectively. TPR data allowed us to relate the catalytic activity of CoO/ZrO 2 to Co-O-Zr clusters, the amount of which was almost constant over the test range of CoO concentrations. The conversion of CO on 2.5% CuO/ZrO 2 was 32% (190°C) or 62–66% on 5–10% CuO/ZrO 2 (170°C). According to TPR data, clusters like Cu-O-Zr occurred on the surface of ZrO 2 , and the amount of these clusters reached a maximum upon supporting 5% CuO. The catalytic properties of 5% CuO/5% CoO/ZrO 2 and 5% CoO/5% CuO/ZrO 2 samples were identical to those of 5% CuO/ZrO 2 samples. It is likely that the formation of active reaction sites upon consecutively supporting the oxides occurred on the same surface sites of ZrO 2 . In this case, Co and Cu oxides competed for cluster formation, and the copper cation can displace the cobalt cation from the formed clusters. The Fe 2 O 3 samples were inactive; a maximum conversion of 34% (290°C) was observed on 10% Fe 2 O 3 /ZrO 2 . The catalytic properties of CuO/Fe 2 O 3 /ZrO 2 were also identical to those of CuO/ZrO 2 , and they depended on the presence of Cu-O-Zr clusters on the surface.