物理化学学报 >> 2001, Vol. 17 >> Issue (12): 1072-1076.doi: 10.3866/PKU.WHXB20011204

研究论文 上一篇    下一篇

NOx储存催化剂Pt/BaAl2O4-Al2O3的XAFS研究

李新刚;孟明;林培琰;黄志坚;伏义路;谢亚宁;胡天斗   

  1. 中国科学技术大学化学物理系, 合肥　230026；中国科学院高能物理研究所,北京　100039
  • 收稿日期:2001-04-16 修回日期:2001-07-20 发布日期:2001-12-15
  • 通讯作者: 孟明 E-mail:mengm@ustc.edu.cn

The Study of XAFS for the NOx Storage Catalyst Pt/BaAl2O4-Al2O3

Li Xin-Gang;Meng Ming;Lin Pei-Yan;Huang Zhi-Jian;Fu Yi-Lu;Xie Ya-Ning;Hu Tian-Dou   

  1. Department of Chemical Physics, University of Science and Technology of China, Hefei　230026;Synchrotron Radiation Laboratory, Institute of High Energy Physics, Beijing　100039
  • Received:2001-04-16 Revised:2001-07-20 Published:2001-12-15
  • Contact: Meng Ming E-mail:mengm@ustc.edu.cn

PDF

3454

赞

摘要： 采用共沉淀-浸渍法在不同载体焙烧温度下,制备了不同Al/Ba原子比的Pt/BaAl2O4-Al2O3系列样品.用XRD， XANES， EXAFS，以及NSC (NOx storage capacity）测定等手段对样品的微观结构和NOx储存性能进行了详细的表征.样品中Ba物种是以BaAl2O4和BaCO3两种混合物相的形式存在，且伴随着载体焙烧温度和Ba含量的降低， BaAl2O4物相的分散度变高， NOx储存活性也随之提高，这表明BaAl2O4相的分散度与样品的NOx储存性能密切相关，小颗粒的BaAl2O4相是NOx的主要储存活性中心.在样品中， Pt物种以金属原子簇形式存在，分散度很高，其Pt－Pt壳层配位数较标样Pt粉有显著下降， Pt－Pt键长变短，出现了纳米收缩现象.高分散的小颗粒金属Pt原子簇为捕获和氧化NOx的主要活性中心.

关键词: NOx, Pt/BaAl2O4-Al2O3, 储存, XAFS

Abstract: A series of Pt/BaAl2O4-Al2O3 NOx trap samples were prepared by coprecipitation-impregnation method. The supports BaAl2O4-Al2O3 were calcined at 800 ℃ and 1000 ℃, respectively. X-ray Diffraction(XRD), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure(EXAFS) were used to characterize the microcosmic structure of barium and platinum species in the samples. It is shown that the barium exists in the forms of BaAl2O4 and BaCO3 crystallites. With the decreasing of calcination temperature and barium content, the dispersion of BaAl2O4 phase becomes higher. Platinum in the samples mainly exists as small atomic clusters, which possess very high dispersion. In comparison with the standard compound of platinum, the magnitude for Pt－Pt coordination shell is significantly decreased, and the coordination distance is also shortened about 0.01 nm. All the results suggest that the BaAl2O4 crystallites should be the centers for NOx storage, while the fine-grained platinum species with high dispersion are deduced as the centers for the capture and oxidation of NOx species.

Key words: NOx, Pt/BaAl2O4-Al2O3, Storage, XAFS