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为研究纳米钙钛矿型稀土氧化物ABOx中A、B组合对NO+CO催化活性的影响规律及机理,采用柠檬酸溶胶-凝胶法制备了6个钙钛矿型稀土复合氧化物LaMnOx、YMnOx、LaCoOx、YCoOx、LaNiOx、YNiOx,用X射线衍射(XRD)、扫描电镜(SEM)、比表面积(BET)、X射线光电子能谱(XPS)对其进行了表征,测试了它们对CO+NO的催化活性。所得催化剂对CO的催化活性顺序为:LaNiOx>YCoOx>YNiOx>YMnOx>LaCoOx>LaMnOx,对NO的催化活性顺序为:LaNiOx>YCoOx>YNiOx>LaCoOx>YMnOx>LaMnOx。LaNiOx的催化活性最好,350℃时NO和CO转化率均为100%。结果表明,B位Mn、Co、Ni离子的价态和外层d电子数、催化剂的比表面积及其氧的存在形式是影响催化活性的重要因素。而价态相同、半径不同的La3+或Y3+通过对晶格氧和B位Mn、Co、Ni价态的影响,从而对催化活性也有较大的影响。
In order to study the regularity and mechanism of the catalytic activity of A and B in ABOx nano-perovskite oxides for NO + CO, six perovskite rare earth oxides LaMnOx were prepared by citric acid sol-gel method. YMnOx, LaCoOx, YCoOx, LaNiOx and YNiOx were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET) and X-ray photoelectron spectroscopy (XPS) Catalytic activity of NO. The order of catalytic activity of the obtained catalyst to CO is: LaNiOx> YCoOx> YNiOx> YMnOx> LaCoOx> LaMnOx, and the order of catalytic activity for NO is LaNiOx> YCoOx> YNiOx> LaCoOx> YMnOx> LaMnOx. The catalytic activity of LaNiOx is the best. The conversion of NO and CO is 100% at 350 ℃. The results show that the valence of Mn, Co and Ni ions at B site, the number of d electrons in the outer layer, the specific surface area of the catalyst and the presence of oxygen are important factors affecting the catalytic activity. However, La3 + or Y3 + with the same valence and different radius have a great influence on the catalytic activity through the influence on the valence states of Mn, Co and Ni in the lattice oxygen and B sites.