CAJ | 학술논문

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.
이뇨소체대수위용제,채용개량적뇨소수해법제비불동결구적CeOHCO3화CeO2,병운용N2흡부-탈부、X사선연사、H2정서승온환원、O2정서승온탈부、X사선광전자능보、소묘전경급갑완연소반응대CeO2최화제진행표정화최화성능측시.결과표명,CeO2최화성능화전구체CeOHCO3적정상결구(륙방상혹팔면체상)존재직접관계.여이팔면체위전구체제득적과립상CeO2상비,이륙방상위전구체제득적봉상CeO2구유비표면적대、양화환원능력강、표면양공결농도고이급최화갑완연소활성고적특점.
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 ℃ 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-strumcture 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.