MnOx/WO3/TiO2低温选择性催化还原NOx机理的原位红外研究

doi:10.11949/j.issn.0438-1157.20160953

化工学报 ›› 2016, Vol. 67 ›› Issue (12): 5031-5039.DOI: 10.11949/j.issn.0438-1157.20160953

• 催化、动力学与反应器 • 上一篇下一篇

MnO_x/WO₃/TiO₂低温选择性催化还原NO_x机理的原位红外研究

廖永进¹, 张亚平², 余岳溪¹, 李娟², 郭婉秋², 汪小蕾²

1 广东电网有限责任公司电力科学研究院, 广东广州 510080;
2 东南大学能源与环境学院, 能源热转换及其过程测控教育部重点实验室, 江苏南京 210096

收稿日期:2016-07-08 修回日期:2016-08-25 出版日期:2016-12-05 发布日期:2016-12-05
通讯作者: 张亚平。amflora@seu.edu.cn
基金资助:
国家自然科学基金项目（51306034）；江苏省重点研发计划项目（BE2015677）。

In situ FT-IR studies on low temperature NH₃-SCR mechanism of NO_x over MnO_x/WO₃/TiO₂ catalyst

LIAO Yongjin¹, ZHANG Yaping², YU Yuexi¹, LI Juan², GUO Wanqiu², WANG Xiaolei²

1 Electric Power Research Institute of Guangdong Power Grid Co. Ltd., Guangzhou 510080, Guangdong, China;
2 Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, Jiangsu, China

Received:2016-07-08 Revised:2016-08-25 Online:2016-12-05 Published:2016-12-05
Supported by:
supported by the National Natural Science Foundation of China(51306034) and the Key R & D Projects of Jiangsu Province(BE2015677).

摘要/Abstract

摘要：

浸渍法制备15% MnO_x/5% WO₃/TiO₂低温脱硝催化剂，利用原位傅里叶变换红外（in situ FT-IR）设计包括多种吸附反应以及不同预处理方式的微观暂态试验与微观稳态试验，研究其NH₃-SCR脱硝反应机理，并推测反应路径。结果表明，催化剂的NH₃-SCR反应主要以Eley-Rideal机理方式进行，仅在一定温度条件下可以看到Langmuir-Hinshclwood反应路径。催化剂表面Lewis酸位的NH₃吸附是还原剂的主要来源，Brønsted酸位吸附的NH₄⁺随温度上升参与反应的比例略有提高。NH₃的吸附活化是整个反应的控制步骤，吸附态NH₃更易与NO₂发生反应，NO与催化剂表面的相互作用明显弱于NO₂。NO会在催化剂表面氧化活性中心形成大量双齿配位型硝酸盐，阻碍NH₃的吸附和活化，O₂存在条件下促进NH₃-SCR反应进行，阻止NO在催化剂表面形成双齿硝酸盐。NO与NH₃在催化剂表面存在吸附竞争，NO的吸附作用强于NH₃，温度达到100℃后吸附的NH₃方可大量活化并与NO_x发生进一步反应。

关键词: MnO_x/WO₃/TiO₂催化剂, 原位红外, NH₃-SCR脱硝机理, 制备, 吸附, 活化

Abstract:

15% MnO_x/5% WO₃/ TiO₂ catalyst for low-temperature selective catalytic reduction of NO_x was synthesized by an impregnation method. NH₃-SCR mechanism was explored systematically and possible pathway was proposed through in situ FT-IR study on microscopic transient and steady states under various conditions of single or mixed gas feed with multiple pre-treatment. The results revealed that NH₃-SCR reaction over the 15%MnO_x/5%WO₃/TiO₂ catalyst proceeded mainly by the Eley-Rideal mechanism with the Langmuir-Hinshclwood pathway only at certain temperature. NH₃ adsorbed on the Lewis acid sites of the catalyst surface was the main source of reductant; however, more NH₄⁺ adsorbed on the Brønsted acid sites of the catalyst surface involved in the NO_x reduction with increase of reaction temperature. The adsorption and activation of NH₃ was key step for the whole SCR reaction. NO₂ easily reacted with adsorbed NH₃ with stronger affinity to catalyst surface than NO. The bidentate nitrate, which formed considerably at oxidation active centers of the catalyst by NO adsorption, didn't participate in NH₃-SCR reaction but obstructed adsorption and activation of NH₃. O₂ could promote NH₃-SCR by blocking formation of bidentate nitrate. The adsorption of NO and NH₃ on the catalyst surface was competitive at room temperature, which NO adsorption was higher than NH₃ at O₂ absence. The absorbed NH₃ could be massively activated and reacted with NO_x upon temperature reached to 100℃.

Key words: MnO_x/WO₃/TiO₂ catalyst, in situ FT-IR, NH₃-SCR mechanism, preparation, adsorption, activation

中图分类号:

TB34

廖永进, 张亚平, 余岳溪, 李娟, 郭婉秋, 汪小蕾. MnO_x/WO₃/TiO₂低温选择性催化还原NO_x机理的原位红外研究[J]. 化工学报, 2016, 67(12): 5031-5039.

LIAO Yongjin, ZHANG Yaping, YU Yuexi, LI Juan, GUO Wanqiu, WANG Xiaolei. In situ FT-IR studies on low temperature NH₃-SCR mechanism of NO_x over MnO_x/WO₃/TiO₂ catalyst[J]. CIESC Journal, 2016, 67(12): 5031-5039.

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MnO_x/WO₃/TiO₂低温选择性催化还原NO_x机理的原位红外研究

In situ FT-IR studies on low temperature NH₃-SCR mechanism of NO_x over MnO_x/WO₃/TiO₂ catalyst

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