催化学报

催化学报 ›› 2012, Vol. 33 ›› Issue (8): 1318-1325.DOI: 10.1016/S1872-2067(11)60409-9

• 研究论文 • 上一篇    下一篇

前驱体 CeOHCO3 的结构对产物 CeO2 催化性能的影响

孙明娟1,2, 邹国军1, 许珊1, 王晓来1,*   

  1. 1中国科学院兰州化学物理研究所羰基合成与选择性氧化国家重点实验室, 甘肃兰州 730000; 2中国科学院研究生院, 北京 100049
  • 收稿日期:2012-04-02 修回日期:2012-05-03 出版日期:2012-08-01 发布日期:2012-08-01

Effect of Structure of CeOHCO3 Precursor of CeO2 on Its Catalytic Performance

SUN Mingjuan1,2, ZOU Guojun1, XU Shan1, WANG Xiaolai1,*   

  1. 1State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China; 2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2012-04-02 Revised:2012-05-03 Online:2012-08-01 Published:2012-08-01

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摘要： 以尿素替代水为溶剂, 采用改良的尿素水解法制备不同结构的 CeOHCO3 和 CeO2, 并运用 N2 吸附-脱附、X 射线衍射、H2 程序升温还原、O2 程序升温脱附、X 射线光电子能谱、扫描电镜及甲烷燃烧反应对 CeO2 催化剂进行表征和催化性能测试. 结果表明,CeO2 催化性能和前驱体 CeOHCO3 的晶相结构 (六方相或八面体相) 存在直接关系. 与以八面体为前驱体制得的颗粒状 CeO2 相比, 以六方相为前驱体制得的棒状 CeO2 具有比表面积大、氧化还原能力强、表面氧空缺浓度高以及催化甲烷燃烧活性高的特点.

关键词: 六方相, 碱式碳酸铈, 氧化铈, 棒状结构, 甲烷燃烧

Abstract: A modified hydrothermal process method based on using urea instead of water as the solvent was used to prepare CeOHCO3. Pure CeOHCO3 with a single crystalline structure was produced by varying the experimental conditions. CeO2 particles obtained from these CeOHCO3 precursors were tested for CH4 oxidation. The temperatures for 90% methane conversion were 604 and 647 °C for CeO2 catalysts obtained from hexagonal and orthorhombic CeOHCO3, respectively, indicating that the CeO2 catalyst from hexagonal CeOHCO3 (CeO2-A) was more active than that from the orthorhombic form (CeO2-D). The specific surface area and pore volume of CeO2-A were 45 m2/g and 0.35 cm3/g, respectively, which were higher than those of CeO2-D. H2-TPR showed a much lower reduction temperature and enhanced reducibility with CeO2-A. XPS and O2-TPD results demonstrated there were more oxygen vacancies on the surface of CeO2-A than on CeO2-D, which implied increased oxygen mobility. The CeOHCO3-structure dependent activity was investigated and found to originate from the morphologies of the CeOHCO3 precursors. Hexagonal CeOHCO3 had a rod-like shape while orthorhombic CeOHCO3 had a sphere-like morphology. After calcination, the obtained CeO2 had the morphology of the precursor. The difference in morphology gave CeO2 catalysts with different texture, structure, reducibility, and thus catalytic activity.

Key words: hexagonal, cerium hydroxide carbonate, cerium oxide, rod-like, methane oxidation