前驱体CeOHCO_3的结构对CeO_2催化性能的影响(英文)  

Effect of Structure of CeOHCO_3 Precursor of CeO_2 on Its Catalytic Performance

作　　者：孙明娟[1,2] 邹国军[1] 许珊[1] 王晓来[1] 

机构地区：[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

出　　处：《催化学报》2012年第8期1318-1325,共8页

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.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 orthorhombie form （CeOz-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 CeOz-D. Hz-TPR showed a much lower reduction temperature and enhanced re- ducibility with CeO2-A. XPS and O2-TPD results demonstrated there were more oxygen vacancies on the surface of CeOz-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.

关 键 词：六方相 碱式碳酸铈 氧化铈 棒状结构 甲烷燃烧 

分 类 号：O643.36[理学—物理化学]