Copper Site Motion Promotes Catalytic NOx Reduction under Zeolite Confinement

Dongdong Chen; Abhishek Khetan; Huarong Lei; Valentina Rizzotto; Jia-Yue Yang; Jiuxing Jiang; Qiming Sun; Baoxiang Peng; Peirong Chen; Regina Palkovits; Daiqi Ye; Ulrich Simon

doi:10.1021/acs.est.3c03422

Copper Site Motion Promotes Catalytic NO_x Reduction under Zeolite Confinement

Environ Sci Technol. 2023 Oct 24;57(42):16121-16130. doi: 10.1021/acs.est.3c03422. Epub 2023 Oct 16.

Authors

Dongdong Chen¹, Abhishek Khetan², Huarong Lei^{1

3}, Valentina Rizzotto³, Jia-Yue Yang⁴, Jiuxing Jiang⁵, Qiming Sun⁶, Baoxiang Peng⁷, Peirong Chen¹, Regina Palkovits⁸, Daiqi Ye¹, Ulrich Simon³

Affiliations

¹ National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, School of Environment and Energy, South China University of Technology, 510006 Guangzhou, China.
² Multiscale Modelling of Heterogeneous Catalysis in Energy Systems, RWTH Aachen University, Schinkelstrasse 8, 52062 Aachen, Germany.
³ Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen Germany.
⁴ Optics & Thermal Radiation Research Center, Shandong University, 266237 Qingdao, China.
⁵ MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, 510275 Guangzhou, China.
⁶ Innovation Center for Chemical Sciences, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China.
⁷ Laboratory of Industrial Chemistry, Ruhr University Bochum, 44780 Bochum, Germany.
⁸ Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany.

PMID: 37842921
DOI: 10.1021/acs.est.3c03422

Abstract

Ammonia-mediated selective catalytic reduction (NH₃-SCR) is currently the key approach to abate nitrogen oxides (NO_x) emitted from heavy-duty lean-burn vehicles. The state-of-art NH₃-SCR catalysts, namely, copper ion-exchanged chabazite (Cu-CHA) zeolites, perform rather poorly at low temperatures (below 200 °C) and are thus incapable of eliminating effectively NO_x emissions under cold-start conditions. Here, we demonstrate a significant promotion of low-temperature NO_x reduction by reinforcing the dynamic motion of zeolite-confined Cu sites during NH₃-SCR. Combining complex impedance-based in situ spectroscopy (IS) and extended density-functional tight-binding molecular dynamics simulation, we revealed an environment- and temperature-dependent nature of the dynamic Cu motion within the zeolite lattice. Further coupling in situ IS with infrared spectroscopy allows us to unravel the critical role of monovalent Cu in the overall Cu mobility at a molecular level. Based on these mechanistic understandings, we elicit a boost of NO_x reduction below 200 °C by reinforcing the dynamic Cu motion in various Cu-zeolites (Cu-CHA, Cu-ZSM-5, Cu-Beta, etc.) via facile postsynthesis treatments, either in a reductive mixture at low temperatures (below 250 °C) or in a nonoxidative atmosphere at high temperatures (above 450 °C).

Keywords: Cu mobility; GFN-xTB simulations; XAS; in situ IS-DRIFTS; molecular dynamics.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Ammonia / chemistry
Catalysis
Copper
Nitrogen Oxides / chemistry
Temperature
Zeolites* / chemistry

Substances

Zeolites
Copper
Ammonia
Nitrogen Oxides