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Title: Formation of NO + and its possible roles during the selective catalytic reduction of NOx with NH 3 on Cu-CHA catalysts

Abstract

The catalytic activities of small-pore Cu-CHA and large-pore Cu-BEA catalysts for the selective catalytic reduction of NO with NH 3 were measured at a very high flow rate. Cu-CHA clearly exhibited much higher intrinsic SCR activity and lower N 2O selectivity. In situ DRIFT spectra were recorded during the adsorption and desorption following NO and (NO+O 2) exposure to fully oxidized samples in a flow cell. The results are in agreement with what we have reported previously based on in situ transmission IR studies of partially reduced samples. Both suggest that different SCR reaction pathways might exist on these two catalysts and that NO + could be an important reaction intermediate for Cu-CHA. Detailed IR studies with various isotopically labeled gas mixtures of (NO+O 2), ( 15NO+O 2), (NO+ 18O 2) and ( 15N 18O+O 2) were conducted to understand the origin of the surface adsorption complexes on Cu-CHA. Formation of NO + was not the consequence of a simple charge transfer reaction, NO+Cu 2+=NO+ + Cu +. Instead, O 2 was found to be essential in changing the oxidation state of N from +2 to +3 although it did not participate in new N$-$O bond formation. In conclusion, themore » majority of the adsorbed NO + maintained its isotopic origin of the feed gas.« less

Authors:
 [1];  [2];  [3];  [2];  [2];  [2];  [2]
  1. Johnson Matthey Inc., Wayne, PA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Inst. for Integrated Catalysis
  3. Johnson Matthey Inc., Wayne, PA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Inst. for Integrated Catalysis
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
1415772
Report Number(s):
PNNL-SA-129558
Journal ID: ISSN 0920-5861; PII: S0920586117308441
Grant/Contract Number:
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Catalysis Today
Additional Journal Information:
Journal Name: Catalysis Today; Journal ID: ISSN 0920-5861
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Zeolite supported Cu catalysts; Cu-CHA catalysts; Selective catalytic reduction of NOx; NO+ formation; Surface NO adsorption complexes

Citation Formats

Chen, Hai-Ying, Kollar, Marton, Wei, Zhehao, Gao, Feng, Wang, Yilin, Szanyi, János, and Peden, Charles H. F. Formation of NO+ and its possible roles during the selective catalytic reduction of NOx with NH3 on Cu-CHA catalysts. United States: N. p., 2017. Web. doi:10.1016/j.cattod.2017.12.022.
Chen, Hai-Ying, Kollar, Marton, Wei, Zhehao, Gao, Feng, Wang, Yilin, Szanyi, János, & Peden, Charles H. F. Formation of NO+ and its possible roles during the selective catalytic reduction of NOx with NH3 on Cu-CHA catalysts. United States. doi:10.1016/j.cattod.2017.12.022.
Chen, Hai-Ying, Kollar, Marton, Wei, Zhehao, Gao, Feng, Wang, Yilin, Szanyi, János, and Peden, Charles H. F. 2017. "Formation of NO+ and its possible roles during the selective catalytic reduction of NOx with NH3 on Cu-CHA catalysts". United States. doi:10.1016/j.cattod.2017.12.022.
@article{osti_1415772,
title = {Formation of NO+ and its possible roles during the selective catalytic reduction of NOx with NH3 on Cu-CHA catalysts},
author = {Chen, Hai-Ying and Kollar, Marton and Wei, Zhehao and Gao, Feng and Wang, Yilin and Szanyi, János and Peden, Charles H. F.},
abstractNote = {The catalytic activities of small-pore Cu-CHA and large-pore Cu-BEA catalysts for the selective catalytic reduction of NO with NH3 were measured at a very high flow rate. Cu-CHA clearly exhibited much higher intrinsic SCR activity and lower N2O selectivity. In situ DRIFT spectra were recorded during the adsorption and desorption following NO and (NO+O2) exposure to fully oxidized samples in a flow cell. The results are in agreement with what we have reported previously based on in situ transmission IR studies of partially reduced samples. Both suggest that different SCR reaction pathways might exist on these two catalysts and that NO+ could be an important reaction intermediate for Cu-CHA. Detailed IR studies with various isotopically labeled gas mixtures of (NO+O2), (15NO+O2), (NO+18O2) and (15N18O+O2) were conducted to understand the origin of the surface adsorption complexes on Cu-CHA. Formation of NO+ was not the consequence of a simple charge transfer reaction, NO+Cu2+=NO+ + Cu+. Instead, O2 was found to be essential in changing the oxidation state of N from +2 to +3 although it did not participate in new N$-$O bond formation. In conclusion, the majority of the adsorbed NO+ maintained its isotopic origin of the feed gas.},
doi = {10.1016/j.cattod.2017.12.022},
journal = {Catalysis Today},
number = ,
volume = ,
place = {United States},
year = 2017,
month =
}

Journal Article:
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  • A comparative study was carried out on a small-pore CHA.Cu and a large-pore BEA.Cu zeolite catalyst to understand the lower N2O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH3. On both catalysts, the N2O yield increases with an increase in the NO2/NOx ratios of the feed gas, suggesting N2O formation via the decomposition of NH4NO3. Temperature-programmed desorption experiments reveal that NH4NO3 is more stable on CHA.Cu than on BEA.Cu. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysismore » using isotope-labelled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, CHA.Cu is shown to be considerably less active than BEA.Cu in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on CHA.Cu, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N2O formation on this catalyst as compared to BEA.Cu. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.« less
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