高等学校化学学报

高等学校化学学报 ›› 2009, Vol. 30 ›› Issue (6): 1177.

• 研究论文 • 上一篇    下一篇

熔铁催化剂还原过程的原位XRD研究及活性相的形成机理

郑遗凡1,2, 刘化章1, 李小年1   

  1. 1. 浙江工业大学化学工程与材料学院,
    2. 分析测试中心, 杭州 310014
  • 收稿日期:2008-10-27 出版日期:2009-06-10 发布日期:2009-06-10
  • 通讯作者: 刘化章, 男, 教授, 博士生导师, 主要从事合成氨催化剂研究, E-mail: cuihua@zjut.edu.cn; 郑遗凡, 男, 博士, 副教授, 主要从事材料微结构研究, E-mail: zhengyifan@zjut.edu.cn
  • 基金资助:

    基金项目： 国家自然科学基金(批准号: 2047307)和浙江省科技计划项目(批准号: 2007F70039)资助.

In situ X-ray Diffraction Investigation on Reduction Process of Ammonia-synthesis Fused-iron Catalysts and the Formation Mechanism of Its Active Phase

ZHENG Yi-Fan1,2*, LIU Hua-Zhang1*, LI Xiao-Nian1   

  1. 1. College of Chemical Engineering and Material Science,
    2. Research Center of Analysis and Measurement, Zhejiang University of Technology, Hangzhou 310014, China
  • Received:2008-10-27 Online:2009-06-10 Published:2009-06-10
  • Contact: LIU Hua-Zhang, E-mail: cuihua@zjut.edu.cn; ZHENG Yi-Fan, E-mail: zhengyifan@zjut.edu.cn
  • Supported by:

    基金项目： 国家自然科学基金(批准号: 2047307)和浙江省科技计划项目(批准号: 2007F70039)资助.

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被引次数

7

摘要：

选择Fe1-xO基和Fe3O4基氨合成熔铁催化剂ZA-5和A110, 采用XRD原位反应器模拟真实的还原条件进行原位XRD实验. 通过对还原过程的物相跟踪分析和对前驱体、活性相的XRD微结构动态演化分析表明, ZA-5和A110的还原温度区间分别为300~362 ℃和343~450 ℃, 前者比后者具有更快的还原速度及更低的还原温度; ZA-5和A110在(211)和(110)方向的晶粒度比值(D(211)/D(110))分别为0.7014和0.8631, ZA-5催化剂具有更好的高活性(211)晶面, 其活性相微观应力明显比A110大, 且随着温度升高逐渐减小; 采用Rietveld全谱拟合结构分析和Popa模拟技术对活性相晶形进行模拟, 得到A110活性相晶形为凹陷立方体, ZA-5为立方体和球形的混合晶形, ZA-5的高活性晶面(111)和(211)晶面比A110生长更好; ZA-5催化剂活性相晶形从低温的类八面体向高温球形演化, 在355 ℃时有比较完善的八面体晶形, 此温度下(111)晶面生长得最好; ZA-5催化剂活性相与前驱体的八面体晶形结构匹配性好, 比A110更容易还原.

关键词: 熔铁催化剂, 原位XRD, 活性相, 微观应力, 形成机理

Abstract:

Two types of ammonia-synthesis fused-iron catalysts, A110 and ZA-5, which based on Fe3O4 and Fe1-xO precursors respectively, were investigated by simulating actual reduction conditions of their preparation with in situ X-ray diffraction. During in situ X-ray diffraction, the transformation of crystal phase, the structures of their precursors and active phase based on X-ray diffraction data were analysed. The results show that the reduction temperature ranges of ZA-5 and A110 are 300—362 ℃ and 343—450 ℃, respectively; the reduction temperature of Fe1-xO-based catalyst ZA-5 is lower than that of Fe3O4-based catalyst A110; the reduction rate of Fe1-xO-based catalyst ZA-5 is faster than that of Fe3O4-based catalyst A110; crystallite size ratios of D(211)/D(110) estimated from (211) and (110) crystal planes of catalysts ZA-5 and A110 are 0.7014 and 0.8631 respectively; catalyst ZA-5 owns more developed high active (211) crystal plane, the value of the microstrain of its active phase is stronger than that of catalyst A110, and the value decreases gradually as the temperature increasing. The morphology simulation of active phase based on Popa technology by Rietveld ana-lysis show that the morphology of the active phase of catalyst A110 is cupped cubic, and that of catalyst ZA-5 is a mixture of cube and globe; high active crystal planes (111) and (211) of catalyst ZA-5 develop better than that of catalyst A110; the morphology of active phase crystal of catalyst ZA-5 is well developed octahedron at 335 ℃, and compared with at other temperatures, its crystal plane (111) is the most developed at this temperature; the morphology of active phase of catalyst ZA-5 transforms from octahedron to globe as the temperature increasing gradually; the match of octahedral structure catalyst ZA-5 is better than that of its precursors, and catalyst ZA-5 can be reduced more easily compared with catalyst A110.

Key words: Fused-iron catalyst, In situ X-ray diffraction, Active phase, Microstrain, Formation mechanism

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