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采用共沉淀法制备了Ce Zr YLa+La Al纳米复合载体,以三种方法制备了一系列Pt-Rh/Ce Zr YLa+La Al催化剂.对所制样品进行了N2吸附-脱附、粉末X射线衍射、X射线光电子能谱和H2程序升温还原的表征.并考察了三种方法所制得催化剂的理论空燃比天然气汽车尾气净化性能.结果表明,三个催化剂的活性顺序为Cat3≈Cat2>Cat1,其中Cat3具有最低的CO和NO起燃温度(T50),分别为114 oC和149 oC,最低的CH4和CO完全转化温度(T90),分别为398 oC和179 oC,以及最佳的CH4和CO温度特性,ΔT(T90–T50)值分别为34 oC和65 oC.Cat2具有最低的CH4起燃温度(342°C)和最低的NO完全转化温度(174°C).Cat1具有最差的转化活性,说明物理混合法制备的催化剂(Cat3和Cat2)性能优于共浸渍法制备的催化剂(Cat1).这是由于物理混合法制备的催化剂,Pt和Rh均匀分散在载体表面,两者物理接触共同参与CH4/CO/NO三种污染物的转化.相反,共浸渍法制备的催化剂,Pt和Rh之间存在较强的相互作用,改变了Pt的电子状态,而且形成了表面Pt富集的Pt-Rh双金属颗粒覆盖了Rh活性位,从而降低催化活性;同时,对于通过物理混合法并进一步添加助剂所制备的Cat3,XRD结果显示助剂Zr4+进入了铈锆固溶体晶格,产生晶格缺陷;XPS结果显示Cat3具有最高的Ce3+/Ce比例.这些都有利于提高催化剂的氧流动性,从而提高催化剂活性并拓宽空燃比窗口.
Ce Zr YLa + La Al nanocomposite was prepared by co-precipitation method and a series of Pt-Rh / Ce Zr YLa + La Al catalysts were prepared by three methods.The samples were characterized by N2 adsorption-desorption, Ray diffraction, X-ray photoelectron spectroscopy and temperature programmed reduction of H2 were investigated. The purification performance of the theoretical AFR natural gas vehicle with three catalysts was investigated. The results showed that the activity order of the three catalysts was Cat3≈Cat2> Cat1 with Cat 3 having the lowest CO and NO light-off temperatures (T50) of 114 oC and 149 oC, respectively, with the lowest CH4 and CO complete conversions (T90) of 398 oC and 179 oC, respectively, and the best CH4 And CO temperature characteristics, the ΔT (T90-T50) values were 34 oC and 65 oC, respectively.Cat2 had the lowest CH4 ignition temperature (342 ° C) and the lowest NO complete conversion temperature (174 ° C) (Cat3 and Cat2) prepared by the physical mixing method is better than the catalyst prepared by the co-impregnation method (Cat1) .The catalyst prepared by the physical mixing method, Pt and Rh uniformly dispersed on the surface of the carrier, both Physical contact to participate in the conversion of CH4 / CO / NO three pollutants.In contrast, co-impregnation Preparation of the catalyst, there is a strong interaction between Pt and Rh, changing the electronic state of Pt, and the formation of surface Pt-enriched Pt-Rh bimetallic particles covered Rh active sites, thereby reducing the catalytic activity; the same time, For Cat3 prepared by physical mixing method and further adding additives, XRD results showed that Zr4 + enters the lattice of cerium-zirconium solid solution, resulting in lattice defects; XPS results show that Cat3 has the highest Ce3 + / Ce ratio. Improve the catalyst oxygen flow, thereby increasing the catalyst activity and broaden the air-fuel ratio window.