荧光XAFS表征Pt/BaAl_2O_4-Al_2O_3催化剂中的微量铂物种  

Fluorescence-XAFS Characterization on the Small Amount of Platinum in Pt/BaAl_2O_4-Al_2O_3 Catalysts

作　　者：孟明[1] 张忠和[1] 罗金勇[1] 林培琰[2] 伏义路[2] 

机构地区：[1]天津大学化工学院催化科学与工程系,天津300072 [2]中国科学技术大学化学物理系,合肥230026

出　　处：《无机化学学报》2006年第2期298-302,共5页Chinese Journal of Inorganic Chemistry

基　　金：国家博士点专项基金(No.20040056028);天津市自然科学基金(No.05YFJMJC09700);天津大学'985教育振兴行动计划'资助项目

摘　　要：随着稀薄燃烧（1ean—burn）发动机的推广使用和环保法规的日趋严格．消除稀燃尾气中的氮氧化物（NOx）已刻不容缓。NOx储存还原技术被认为是最具应用前景的方法之一。目前，对Pt／BaAl2O4－Al2O，体系中NOx储存与还原机制的研究较多，但对该体系中微量铂物种微观结构及其与性能的关系研究较少．这主要是由于Pt含量（0．1wt％～0．5wt％）太低，分散度较高，使表征方法受到很大限制。The support BaAl2O-Al2O3 and the catalysts Pt/BaAl2O4-Al2O3 were prepared by co-precipitation and impregnation method, respectively. The NOx storage capacities （NSC） of the samples were investigated. The fluoreseence-XAFS technique was employed to characterize the fine structures of the small amount of platinum. The results show that after calcination in air, the platinum mainly exists as chloride, and the rest is in the form of oxyehloride, however, after reduction by H〉 the most platinum species transform into highly dispersed metallic erystallite （2-3 nm） with a very small residual amount of chloride. After aging treatment, a small part of platinum in the reduced sample is oxidized into oxide. Combined with the results of the NOx storage capacities, it is indicated that for NOx storage, highly dispersed metallic platinum erystallites are the most active phase, while the chloride species of platinum have much weaker effect on NO~ storage. The growth of Pt erystallite size and the partial oxidation of metallic Pt are the main reasons for the decrease of NOx storage capacity of the aged sample.

关 键 词：Pt/BaAl2O4-Al2O3催化剂 氮氧化物储存 XAFS 

分 类 号：O643[理学—物理化学]