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Title: NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations

Abstract

The locations and energies of Cu ions in a Cu/SSZ-13 zeolite catalyst were investigated by density functional theory (DFT) calculations. For 'naked' Cu2+ ions (i.e., Cu2+ ions with no ligands in their coordination spheres other than zeolite lattice oxygen atoms), the more energetically favorable sites are within a 6-membered ring. However, with the presence of various adsorbates, the energy difference between 6- and 8-membered ring locations greatly diminishes. Specifically, Cu2+ ions are substantially stabilized by -OH ligands (as [CuII(OH)]+), making the extra-framework sites in an 8-membered ring energetically more favorable than 6-membered ring sites. Under fully dehydrated high vacuum conditions with different Si/Al and Cu/Al ratios, three chemisorbed NO species coexist upon exposure of NO to Cu/SSZ-13: NO+, Cu2+-NO and Cu+-NO. The relative signal intensities for these bands vary greatly with Si/Al ratios. The vibrational frequency of chemisorbed NO was found to be very sensitive to the location of Cu2+ ions. On the one hand, with the aid from DFT calculations, the nature for these vibrations can be assigned in detail. On the other hand, the relative intensities for various Cu2+-NO species provide a good measure of the nature of Cu2+ ions as functions of Si/Al and Cu/Al ratios andmore » the presence of humidity. These new findings cast doubt on the generally accepted proposal that only Cu2+ ions located in 6-membered rings are catalytically active for NH3-SCR.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1166879
Report Number(s):
PNNL-SA-102388
Journal ID: ISSN 2155-5435; 47953; VT0401000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 4; Journal Issue: 11; Journal ID: ISSN 2155-5435
Country of Publication:
United States
Language:
English
Subject:
Cu-Chabazite; selective catalytic reduction; infrared spectroscopy; DFT calculations; Environmental Molecular Sciences Laboratory

Citation Formats

Zhang, Renqin, McEwen, Jean-Sabin, Kollar, Marton, Gao, Feng, Wang, Yilin, Szanyi, Janos, and Peden, Charles HF. NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations. United States: N. p., 2014. Web. doi:10.1021/cs500563s.
Zhang, Renqin, McEwen, Jean-Sabin, Kollar, Marton, Gao, Feng, Wang, Yilin, Szanyi, Janos, & Peden, Charles HF. NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations. United States. https://doi.org/10.1021/cs500563s
Zhang, Renqin, McEwen, Jean-Sabin, Kollar, Marton, Gao, Feng, Wang, Yilin, Szanyi, Janos, and Peden, Charles HF. 2014. "NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations". United States. https://doi.org/10.1021/cs500563s.
@article{osti_1166879,
title = {NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations},
author = {Zhang, Renqin and McEwen, Jean-Sabin and Kollar, Marton and Gao, Feng and Wang, Yilin and Szanyi, Janos and Peden, Charles HF},
abstractNote = {The locations and energies of Cu ions in a Cu/SSZ-13 zeolite catalyst were investigated by density functional theory (DFT) calculations. For 'naked' Cu2+ ions (i.e., Cu2+ ions with no ligands in their coordination spheres other than zeolite lattice oxygen atoms), the more energetically favorable sites are within a 6-membered ring. However, with the presence of various adsorbates, the energy difference between 6- and 8-membered ring locations greatly diminishes. Specifically, Cu2+ ions are substantially stabilized by -OH ligands (as [CuII(OH)]+), making the extra-framework sites in an 8-membered ring energetically more favorable than 6-membered ring sites. Under fully dehydrated high vacuum conditions with different Si/Al and Cu/Al ratios, three chemisorbed NO species coexist upon exposure of NO to Cu/SSZ-13: NO+, Cu2+-NO and Cu+-NO. The relative signal intensities for these bands vary greatly with Si/Al ratios. The vibrational frequency of chemisorbed NO was found to be very sensitive to the location of Cu2+ ions. On the one hand, with the aid from DFT calculations, the nature for these vibrations can be assigned in detail. On the other hand, the relative intensities for various Cu2+-NO species provide a good measure of the nature of Cu2+ ions as functions of Si/Al and Cu/Al ratios and the presence of humidity. These new findings cast doubt on the generally accepted proposal that only Cu2+ ions located in 6-membered rings are catalytically active for NH3-SCR.},
doi = {10.1021/cs500563s},
url = {https://www.osti.gov/biblio/1166879}, journal = {ACS Catalysis},
issn = {2155-5435},
number = 11,
volume = 4,
place = {United States},
year = {Fri Nov 07 00:00:00 EST 2014},
month = {Fri Nov 07 00:00:00 EST 2014}
}