水热老化对含钯La_0.9)Sr_(0.1)CoO_(3-δ)/α-Al_2O_3催化性能的影响  

Influence of Hydrothermal Aging on Catalytic Performance of α-Al_2O_3-Supported Pd-Containing La_(0.9)Sr_(0.1)CoO_(3-δ)Oxides for CO-NO Reaction

作　　者：赵峰[1] 李能[1] 李国英[1] 刘希尧[1] 李士杰[1] 林炳雄[1] 

机构地区：[1]北京大学物理化学研究所,北京100871

出　　处：《催化学报》2003年第7期525-530,共6页

基　　金：国家自然科学基金资助项目 (2 0 0 730 0 1)

摘　　要：以浸渍法制备了α Al2 O3 负载的含钯La0 9Sr0 1CoO3 δ钙钛矿样品 ,探讨了水热老化对样品催化CO NO反应性能的影响 ,并以XRD ,TPR和XPS等对样品在水热老化前后的结构进行了表征 .结果表明 ,钯的引入方式直接影响样品的水热性能 .掺钯样品 (LaSrCoPd)具有良好的水热性能 ,经水热老化后 ,其催化活性显著提高 ,显示出最好的催化性能 ;样品中钯离子位于钙钛矿晶相内 ,形成α Al2 O3 负载的La0 9Sr0 1Co0 95Pd0 0 5O3 δ.La0 9Sr0 1CoO3 δ/α Al2 O3 负载钯的样品 (Pd/LaSrCo)具有最高的初活性 ,但经水热老化后 ,其催化活性明显降低 .在水热老化过程中 ,La0 9Sr0 1CoO3 δ钙钛矿的结构稳定 ,但含钯钙钛矿晶相中的钯离子迁移聚集成独立的PdO颗粒 ,较小的PdO颗粒聚集成较大的颗粒 .水热老化后 ,Pd/LaSrCo样品表面裸露的钯原子数目减少 ,导致其催化活性降低 ;而LaSrCoPd样品表面裸露的钯原子数目增多 ,导致其催化活性升高 .Al 2O 3-supported Pd-containing La 0.9Sr 0.1CoO 3-δ oxides were prepared by impregnation and their catalytic performance for CO-NO reaction was measured. XRD, XPS and TPR techniques were used to characterize these catalyst samples. Compared with La 0.9Sr 0.1CoO 3-δ/α-Al 2O 3(LaSrCo), the Pd-containing samples had higher catalytic activity, showing that Pd is the active component. Pd-doped sample (LaSrCoPd) showed good hydrothermal property and, compared with other samples, gave the best performance after hydrothermal aging. The fresh LaSrCo-supported Pd sample (Pd/LaSrCo) gave the best performance, but hydrothermal aging evidently reduced its activity, and its light-off temperature increased by 20 ℃ after hydrothermal aging. In fresh Pd/LaSrCo sample, Pd ions existed as the form of PdO, while in fresh LaSrCoPd sample, Pd ions existed in the lattice of perovskite. As a result, the Pd 3d 5/2 binding energy of these two samples is 337.0 and 337.5 eV respectively. After hydrothermal aging, the Pd 3d 5/2 binding energy of both the samples located near 336.5 eV, suggesting that Pd ion states are very similar and exist as the form of isolated PdO particles. The reduction peaks of Pd ions in fresh LaSrCoPd and Pd/LaSrCo samples appeared at 220 and 200 ℃ respectively. After hydrothermal aging, these two peaks disappeared completely; for Pd/LaSrCo sample, a new reduction peak could be observed at 60 ℃, while for LaSrCoPd sample, two new reduction peaks at 60 and 110 ℃ appeared instead. During hydrothermal aging, near all of the Pd ions in bulk phase of perovskite were dislodged from the lattice and existed as the form of PdO particles. Small PdO particles also tended to agglomerate into large ones. Therefore, a shift of Pd 3d 5/2 binding energy towards lower value was observed after hydrothermal aging. The hydrothermal aging increased the amount of naked surface Pd ions of LaSrCoPd, but decreased that of Pd/LaSrCo.

关 键 词：钙钛矿 钯 水热老化 催化活性 一氧化碳 一氧化氮 

分 类 号：O643.3[理学—物理化学]