期刊
CHEMOSPHERE
卷 250, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2020.126272
关键词
In situ DRIFTS; Cu redox; Nitrogen oxides; Zeolite catalyst; DFT calculation
资金
- National Natural Science Foundation of China [21976058, 21806039]
- Natural Science Foundation of Guangdong Province [2018A030313302]
- German Federal Ministry of Education and Research (BMBF) [13XP5042A]
- Excellence Initiative of the German federal and state governments
- Xinghua Talent Program of South China University of Technology
Reduction of harmful nitrogen oxides (NOx) from diesel engine exhausts is one of the key challenges in environmental protection, and can be achieved by NH3-assisted selective catalytic reduction (NH3-SCR) using copper-exchanged chabazite zeolites (i.e. Cu-CHA, including Cu-SSZ-13 and Cu-SAPO-34) as catalysts. Understanding the redox chemistry of Cu-CHA in NH3-SCR catalysis is crucial for further improving the NOx reduction efficiency. Here, a series of Cu-SSZ-13 catalysts with different Cu ion exchange levels were prepared, thoroughly characterized by different techniques such as X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy and temperature-programmed desorption using NH3 as a probe molecule, etc., and tested in NH3-SCR reactions under steady-state conditions. In situ studies by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), supplemented with densityfunctional theory calculations, provided solid evidence for the formation of ammonium ion (NH4+) intermediates resulting from the reduction of Cu2+ to Cu+ by co-adsorbed NH3 and NO molecules on CuSSZ-13. Catalytic relevance of the NH4(+) intermediates, as demonstrated by an increase of NO conversion over Cu-SSZ-13 pre-treated in NH3/NO atmosphere, can be attributed to the formation of closely coupled Cu+/NH4(-) pairs promoting the Cu- re-oxidation and, consequently, the overall NH3-SCR process. This study thus paves a new route for improving the NH3-SCR efficiency over Cu-CHA zeolite catalyst. (C) 2020 Elsevier Ltd. All rights reserved.
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