Preparation Of CuO-NiO/CeO₂ Catalyst And Its Catalytic Performance For Hydrogen Purification

In order to keep from poisoning of the electrode in proton exchange membrane fuel cell（PEMFC）, a purified H2-rich gas fuel with CO concentration below 10 ppm is required. Preferential oxidation and methanation of CO in H2-rich gas are effective for purification of industrial H2-rich gas.In this thesis, the following work was completed.（1） Simple metal oxides MOx（M = Cu, Ni, Co, Fe, Ce） were prepared by thermal decomposition of the corresponding nitrates and used for hydrogen purification process. Co₃O₄ catalyst showed the best performance for CO removal. At lower reaction temperatures, preferential oxidation of CO took place; at higher reaction temperature, CO methanation reaction occurred due to the formation of metallic cobalt. The Ni O catalyst also catalyzed CO methanation at higher reaction temperatures due to formation of metallic Ni.（2） Binary metal oxide catalysts MOx/Ce O2（M = Cu, Ni, Co, Fe） were prepared with impregnation method. Cu O/Ce O2 catalyst showed the best catalytic activity at the low temperatures. While, as reaction temperature increased, catalytic activity was decreased significantly. This is because metallic Cu formed at high reaction temperatures promoted H2 oxidation and decreased CO conversion. Ni O/Ce O2 catalyst showed the best catalytic activity at high reaction temperatures. This is ascribed to the metalicl Ni formed at the high reaction temperatures, which catalysed CO methanation reaction.（3） Ternary metal oxide catalysts Cu O-Ni O/Ce O2 were prepared to take advantages of catalytic performances of Cu O/Ce O2 and Ni O/Ce O2. And high catalytic activity in the whole reaction temperature range of 100-260 oC was thus obtained. At lower reaction temperatures preferential oxidation of CO took place; at higher reaction temperatures CO methanation reaction occurred due to formation of metallic Ni. Analytical techniques including XRD, TPR and XPS were used to analyze valence state changes of the catalysts before and after the reaction. It is confirmed that the catalysts were changed into lower valence states during the catalytic reaction process.