In order to investigate the influence of MnO2 modification methods on the catalytic performance of CuO/CeO2 catalyst for NO reduction by CO, two series of catalysts （xCuyMn/Ce and xCu/yMn/Ce） were prepared by co-impregnation and step- wise-impregnation methods, and characterized by means of X-ray diffraction （XRD）, Raman spectra, H2-temperature programmed reduction （H2-TPR）, in situ diffuse reflectance infrared Fourier transform spectra （in situ DRIFTS） techniques. Furthermore, the cata- lytic performances of these catalysts were evaluated by NO＋CO model reaction. The obtained results indicated that： （1） The catalysts acquired by co-impregnation method exhibited stronger interaction owing to the more sufficient contact among each component of the catalysts compared with the catalysts obtained by stepwise-impregnation method, which was beneficial to the improvement of the reduction behavior; （2） The excellent reduction behavior was conducive to the formation of low valence state copper species （Cu＋/Cu0） and more oxygen vacancies （especially the surface synergetic oxygen vacancies （SSOV, Cu＋-n-Mn（4-x）-）） during the reaction process, which were beneficial to the adsorption of CO species and the dissociation of NO species, respectively, and further promoted the en- hancement of the catalytic performance. Finally, in order to further understand the difference between the catalytic performances of these catalysts prepared by co-impregnation and stepwise-impregnation methods, a possible reaction mechanism （schematic diagram） was tentatively proposed.
The CuO/CeO2 catalysts were investigated by means of X-ray diffraction （XRD）, laser Raman spectroscopy （LRS）, X-ray photoelectronic spectroscopy （XPS）, temperature-programmed reduction （TPR）, in situ Fourier transform infrared spectroscopy （FTIR） and NO＋CO reaction. The results revealed that the low temperature （〈150℃） catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu＋/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO＋CO reaction.
采用浸渍法以Cu(CH3COO)2为前驱体,在N2气氛下于不同温度下焙烧,制备了CuOx/CeO2催化剂。结合XRD,H2-TPR,XPS等表征技术,以及CO-PROX(Preferential Oxidation of CO)反应测试,获得了CuOx/CeO2催化剂中不同Cu物种随焙烧温度变化的分布信息及其对CO-PROX催化活性的影响。结果表明:CuOx/CeO2催化剂CO-PROX催化活性变化的趋势与催化剂表面分散态Cu+物种变化趋势一致,随着焙烧温度从200℃升至500℃,催化剂表面的分散态Cu+先增加后减少,当分散态Cu+在焙烧温度250～400℃达到最多时,其催化活性最好,随后下降,说明分散态Cu+对CO-PROX反应活性起关键作用。
