Co助剂对稀燃NO_x阱Pt/Ba-Al-O结构和性能的影响  

Effect of Cobalt Promoter on Structure and Properties of Lean-Burn NO_x Trap Pt/Ba-Al-O

作　　者：李新刚[1] 孟明[1] 林培琰[1] 陈加福[1] 伏义路[1] 俞寿明[1] 谢亚宁[2] 胡天斗[2] 

机构地区：[1]中国科学技术大学化学物理系,安徽合肥230026 [2]中国科学院高能物理研究所,北京100039

出　　处：《催化学报》2002年第5期417-420,共4页

基　　金：国家自然科学基金 ( 2 99730 37);教育部优秀青年教师资助计划 (EYTP);安徽省自然科学基金 ( 990 45 42 9)资助项目

摘　　要：采用共沉淀 浸渍法制备了Pt/Co Ba Al O催化剂 ,用X射线衍射、X射线吸收近边结构和扩展X射线吸收精细结构等手段表征了催化剂的微观结构 ,并在连续流动微型反应器上测定了催化剂对NOx 的储存性能 .载体经过 80 0℃焙烧后 ,Co物种主要以四面体配位的铝酸钴相存在 .在富氧条件下 ,高分散的小颗粒铝酸钴相促进了NO向NO2 的转化 ,大大改善了催化剂对NOx 的储存性能 .铂物种则以小的金属原子簇形式存在 ,分散度很高 .钴助剂的添加改善了氧化铝相的分散度 ,抑制了金属铂原子簇与载体的相互作用 ,使铂在催化剂表面分散得更均匀 ,从而有利于NOxUnder lean-burn conditions, the NO, trap Pt/Ba-Al-O can store NO, as nitrates or nitrites. Successive sequences of lean and rich operating periods provide a high efficiency for NO, reduction. On addition of the Co promoter, the NO, storage capacity of the trap is improved remarkably. In this paper, the NO, trap Pt/Co-Ba-Al-O with an Al:Ba:Co molar ratio of 32:2: 1 and a Pt:Co-Ba-Al-O mass ratio of 1.0% was prepared by the coprecipitation-impregnation method. X-ray diffraction, X-ray absorption near edge structure and extended Xray absorption fine structure were used to characterize the microstructure of the samples. After calcination at 800degreesC I cobalt species react with alumina to form CoAl2O4, in which cobalt is present in the form of tetrahedrally-coordinated Co2+ ions. The well-dispersed CoAl2O4 phase can promote the conversion of NO to NO2 through reactions of 2Co(2) + 1/2O(2) --> 2Co(3) + [O2-] and 2Co(3+) + [O2-] + NO --> 2Co(2+) + NO2 under lean-burn conditions. This results in an enhancement of the NO, storage capacity. Pt species mainly exist as well-dispersed small atomic clusters. Compared with the sample Pt/Ba-Al-O, Pt/Co-Ba-Al-O shows a higher alumina dispersion and the strung interaction between Pt species and supports is inhibited. This leads to the adequate distribution of fine-grained platinum species over the NO, trap and is favorable for NO, storage. A NO, storage capacity of 372 mumol/g is obtained over Pt/Co-Ba-Al-O at 200 degreesC, which is about 21.6% higher than that over Pt/Ba-Al-O.

关 键 词：氮氧化物阱 铂 负载型催化剂 钴 助剂 X射线吸收精细结构 污染物治理 

分 类 号：O643.3[理学—物理化学]