催化学报

催化学报 ›› 2025, Vol. 69: 185-192.DOI: 10.1016/S1872-2067(24)60161-0

• 论文 • 上一篇    下一篇

一氧化碳在铁-β沸石催化剂上选择性还原N2O机理的原位/Operando光谱研究

钱宇澄a, Shunsaku Yasumurab, 张宁强a, Akihiko Anzaia, Takashi Toyaoa, Ken-ichi Shimizua,*()   

  1. a北海道大学催化研究所, 札幌, 日本
    b东京大学工业科学研究所, 东京, 日本
  • 收稿日期:2024-09-13 接受日期:2024-10-08 出版日期:2025-02-18 发布日期:2025-02-10
  • 通讯作者: 电子信箱: kshimizu@cat.hokudai.ac.jp (K. Shimizu).

Mechanism of selective reduction of N2O by CO over Fe-β catalysts studied by in-situ/operando spectroscopy

Yucheng Qiana, Shunsaku Yasumurab, Ningqiang Zhanga, Akihiko Anzaia, Takashi Toyaoa, Ken-ichi Shimizua,*()   

  1. aInstitute for Catalysis, Hokkaido University, N-21, W-10, Sapporo 001-0021, Japan
    bInstitute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro, Tokyo 153-8505, Japan
  • Received:2024-09-13 Accepted:2024-10-08 Online:2025-02-18 Published:2025-02-10
  • Contact: 电子信箱: kshimizu@cat.hokudai.ac.jp (K. Shimizu).

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摘要：

随着温室气体排放的增加, N2O作为一种具有高全球变暖潜力的温室气体, 亟需有效控制其排放. 现有的N2O分解技术虽能在无还原剂情况下将其分解, 但由于需要高温条件且在过量氧气存在下效率较低, 限制了其广泛应用. 相比之下, 使用CO作为还原剂进行选择性催化还原的反应温度低、低温活性好, 有望成为一种更具N2O去除效率的途径. 然而, 现有的非贵金属催化剂在氧气环境下活性较差. 本文研究了铁交换沸石(Fe-β)催化剂在过量氧气条件下通过CO选择性还原N2O的催化机理, 揭示了铁在氧化还原循环中的状态变化, 旨在为开发高效N₂O还原催化剂提供理论依据和实验数据支持.

本文创新性的对Fe-β催化剂在过量氧气环境下促进N2O选择还原反应的机理进行了系统研究. 通过紫外-可见光谱(UV-vis)和X-射线吸收光谱(XAS)研究了Fe0.9β催化剂在250‒500 °C范围内CO还原N2O的反应机理. 结果发现, Fe0.9β催化剂表现出较好的催化性能, 表观活化能为38 kJ/mol, 显著低于N2O直接分解所需的99 kJ/mol. 在300 °C下, N2O还原速率比直接分解速率的16倍. 此外, CO与N2O的反应速率是CO与O2反应速率的两倍, 表明N2O而非氧气在该催化反应中优先与CO发生反应. 采用原位UV-vis光谱研究了N2O选择还原反应的氧化还原循环机制: 反应初始时, Fe(III)-αO物种被CO还原生成CO₂和Fe(II)物种, 随后N2O将Fe(II)物种重新氧化为Fe(III)-αO物种. 实验结果表明, N2O相较于O2在该循环中具有更高的反应活性. 具体而言, 尽管O2的浓度是N2O的100倍, N2O氧化速率仍然是O2的4倍, 这表明了N2O在Fe位点上的反应更为迅速. 通过XAS光谱进一步确认了Fe在催化反应中的氧化态变化, 证明了Fe在N2O氧化过程中经历了Fe2+与Fe3+之间的氧化还原循环. TOF数据表明, 低Fe含量催化剂Fe0.9β的单个Fe位点表现出更高的催化活性, 这进一步强化了该催化剂在过量O2环境下的优越性. 基于此, 本文提出了Fe-β催化剂在N2O还原中的高效选择性还原反应机理, 并为开发更高效的非贵金属催化剂提供了新思路.

未来, 随着全球对温室气体减排的需求增加, 研究开发新型、高效、稳定的N2O还原催化剂将成为重要方向. 本文通过揭示Fe-β催化剂的氧化还原机制, 为该领域的研究提供了重要的理论支持与实验数据, 有助于推动更高效的N2O还原技术的实际应用.

关键词: 铁交换沸石, 一氧化二氮, 选择性还原, 原位紫外-可见光光谱

Abstract:

Selective reduction of N2O by CO under excess O2 was effectively catalyzed by Fe(0.9 wt%)-exchanged β zeolite (Fe0.9β) in the temperature range of 250-500 °C. Kinetic experiments showed that the apparent activation energy for N2O reduction with CO was lower than that for the direct N2O decomposition, and the rate of N2O reduction with CO at 300 °C was 16 times higher than that for direct N2O decomposition. Reaction order analyses showed that CO and N2O were involved in the kinetically important step, while O2 was not involved in the important step. At 300 °C, the rate of CO oxidation with 0.1% N2O was two times higher than that of CO oxidation with 10% O2. This quantitatively demonstrates the preferential oxidation of CO by N2O under excess O2 over Fe0.9β. Operando/in-situ diffuse reflectance ultraviolet-visible spectroscopy showed a redox-based catalytic cycle; α-Fe-O species are reduced by CO to give CO2 and reduced Fe species, which are then re-oxidized by N2O to regenerate the α-Fe-O species. The initial rate for the regeneration of α-Fe-O species under 0.1% N2O was four times higher than that under 10% O2. This result shows quantitative evidence on the higher reactivity of N2O than O2 for the regeneration of α-Fe-O intermediates, providing a fundamental reason why the Fe0.9β catalyst selectively promotes the CO + N2O reaction under excess O2 rather than the undesired side reaction of CO + O2. The mechanistic model was verified by the results of in-situ Fe K-edge X-ray absorption spectroscopy.

Key words: Fe-exchanged zeolites, N2O, Selective catalytic reduction, In-situ ultraviolet-visible