采用等体积浸渍法制备了以改性氧化铝为载体材料的Pd/Al2O3密偶催化剂,并采用H2程序升温还原(H2-TPR),CO化学吸附和X射线光电子能谱(XPS)对催化剂进行了表征.在模拟尾气条件下对催化剂的总包反应及与C3H8相关的单反应活性进行了测试.结果表明,老化处理后活性PdOx数量下降,并伴随有金属态Pd0的产生.老化后,起燃温度(T50)和完全转化温度(T90)分别提高了76和64℃,即催化剂低温活性比高温活性下降明显.对比新鲜和老化催化剂上单反应活性,结果表明,老化后无水条件下有NO参与的反应的低温活性下降显著.老化处理过程突出了NO对低温活性的抑制作用和H2O对高温活性的促进作用.
The Pd/Al2O3 close-coupled catalysts supported on modified alumina were prepared by an impregnation method,and then characterized by H2-temperature programmed reduction (H2-TPR),CO chemisorption,and X-ray photoelectron spectroscopy (XPS).Both total catalytic activity and single reactions in related to C3H8 conversion were tested in simulated exhaust gas.The results show that the amount of active PdOx decreases and negative metallic Pd0 appears during aging treatment.The light-off temperature (T50) and complete conversion temperature (T90) increase by 76 ℃ and 64 ℃,respectively.After aging treatment,signifying that the low-temperature activity decreases more obviously than high temperature property.The results of comparison among single reactions indicate that the light-off activity of reactions which occur in atmosphere with the participation of NO but without H2O injection decreases dramatically after the aging treatment.The inhibitive effect of NO on light-off activity and the positive effect of H2O on high temperature property become obvious during the aging treatment.
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