催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (6): 898-907.DOI: 10.1016/S1872-2067(15)61052-X

• 论文 • 上一篇    下一篇

酸预处理对于Fe-ZSM-5和Fe-beta分子筛催化消除N2O的影响

吴敏芳a,b, 王慧b, 钟良枢b, 张新艳c, 郝郑平d, 沈群b, 魏伟b,e, 钱光人a, 孙予罕b,e   

  1. a 上海大学环境与化学工程学院, 上海 200444;
    b 中国科学院上海高等研究院低碳转化科学与环境工程重点实验室, 上海 201210;
    c 长春理工大学化学与环境工程学院, 吉林长春 130022;
    d 中国科学院生态环境研究中心环境纳米材料实验室, 北京 100085;
    e 上海科技大学, 上海 201210
  • 收稿日期:2016-01-11 修回日期:2016-02-01 出版日期:2016-05-30 发布日期:2016-05-30
  • 通讯作者: Qun Shen, Wei Wei
  • 基金资助:

    国家自然科学基金(21307144, 21307007); 吉林省科技发展计划项目(20140520150JH).

Effects of acid pretreatment on Fe-ZSM-5 and Fe-beta catalysts for N2O decomposition

Minfang Wua,b, Hui Wangb, Liangshu Zhongb, Xinyan Zhangc, Zhengping Haod, Qun Shenb, Wei Weib,e, Guangren Qiana, Yuhan Sunb,e   

  1. a School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China;
    b CAS Key Laboratory of Low-Carbon Conversion Science & Engineering, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China;
    c School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, Jilin, China;
    d Department of Environmental Nano-materials, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China;
    e ShanghaiTech University, Shanghai 201210, China
  • Received:2016-01-11 Revised:2016-02-01 Online:2016-05-30 Published:2016-05-30
  • Contact: Qun Shen, Wei Wei
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21307144, 21307007) and Science of Technology Development Plan of Jilin Province of China (20140520150JH).

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摘要：

作为六大温室气体之一, N2O 的增温潜能是 CO2 的 310 倍, 甲烷的 21 倍, 目前仍然以 0.80 ppb/年的速度增长, 但是减排成本很低, 因此对 N2O 的消除具有重要意义. 在工业中金属修饰的微孔分子筛因其优良的催化活性, 高水热稳定性, 低成本等优点而成为研究重点. 但是微孔分子筛狭窄的微孔孔道限制了金属前驱体的进入, 导致活性金属含量低, 进而限制了活性的提高. 因此采用一定的改性手段减小分子筛颗粒尺寸, 缩短微孔孔道长度或者扩大微孔孔道来增加活性铁物种的含量进而提高分子筛催化活性.
本文选用商用的 ZSM-5 和 beta 分子筛作为母板分子筛, 按照 3 g : 50 mL 比例将分子筛母板与 1.0 mol/L 的 HNO3 在室温下混合, 分别搅拌 0, 2 和 24 h, 然后采用液相离子交换法负载金属铁制备得到 Fe-ZSM-5 和 Fe-beta. 通过 X 射线衍射、N2 物理吸吸脱附、电感耦合等离子原子发射光谱仪、扫描电镜、透射电镜、NH3 程序升温脱附及紫外漫反射 (UV-vis) 等手段对不同时间处理的分子筛的形貌、酸性和铁物种等物理化学性质进行表征. 对两种催化剂催化消除 N2O 的反应性能进行了测试. 结果显示, 温和的酸处理下分子筛脱除了部分 Al, 其中, ZSM-5 分子筛的表现为由外向内逐层刻蚀, 颗粒尺寸减小, 孔道长度缩短, 但是由于 MFI 型分子筛较高的稳定性, 酸处理对分子筛孔道大小的改变并不明显, 而对于 beta 分子筛, 首先是其中大量无定形物种的去除, 然后对孔道进行修饰, 使之略微扩大, 但是对颗粒尺寸的影响不大.
ICP 结果显示, 商用 ZSM-5 和 beta 分子筛经过温和的酸处理改性后, Si/Al 比增大, 负载 Fe 的含量明显增加, 各催化剂催化消除 N2O 的活性也出现了不同程度的提高. Fe-ZSM-5 和 Fe-beta 分子筛上 N2O 完全转化温度分别向低温段移动了 10-15 和 30 ℃. UV-vis 谱图显示, 分子筛中存在着不同种类的铁物种, 通过分峰计算发现, 孤立的 Fe3+铁离子和低聚态的 Fex3+Oy 均是催化活性铁物种, 其含量的增加部分也解释了活性提高的原因.

关键词: 金属铁修饰的分子筛, 氧化亚氮, 催化性能, 酸浸, 活性位

Abstract:

Two series of ZSM-5 and beta zeolites were pretreated in 1.0 mol/L HNO3 solution at room temperature for various time periods. The catalytic performances of their Fe-exchanged products in N2O decomposition were evaluated. The Fe-zeolite catalysts were characterized using N2 adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, ultraviolet-visible spectroscopy, temperature-programmed desorption of NH3, and scanning and transmission electron microscopies. For the ZSM-5 zeolite, acid leaching primarily takes place on the crystal surface and the particle size is reduced, therefore the pore channels are shortened. However, because of the good stability of MFI zeolites, the acid does not greatly penetrate the pore channels and new mesopores are not created. For the beta zeolite, because the amorphous material is inclined to dissolve (deagglomerate), some of the micropores are slightly dilated. The improved catalytic activities can be explained by the increased active Fe loading as a result of structural changes.© 2016, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Key words: Iron-containing zeolite, Nitrous oxide, Catalytic performance, Acid leaching, Active site