A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

Hai Ying Chen; Zhehao Wei; Marton Kollar; Feng Gao; Yilin Wang; Janos Szanyi; Charles H.F. Peden

doi:10.1016/j.jcat.2015.06.016

A comparative study of N₂O formation during the selective catalytic reduction of NOx with NH₃ on zeolite supported Cu catalysts

Hai Ying Chen, Zhehao Wei, Marton Kollar, Feng Gao, Yilin Wang, Janos Szanyi, Charles H.F. Peden

Research output: Contribution to journal › Article › peer-review

128 Scopus citations

Abstract

Abstract A comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA 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 Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO₂ + O₂) and (¹⁵NO + NH₃ + O₂) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH₄NO₃. Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH₄NO₃ on Cu-CHA, 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 Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH₄NO₃ on the catalysts.

Original language	English
Article number	11797
Pages (from-to)	490-498
Number of pages	9
Journal	Journal of Catalysis
Volume	329
DOIs	https://doi.org/10.1016/j.jcat.2015.06.016
State	Published - Jul 14 2015
Externally published	Yes

Funding

HYC is grateful to Johnson Matthey for the support of this collaboration work and to PNNL for an Alternate Sponsored Fellowship. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

Funders	Funder number
Energy Efficiency and Renewable Energy, Vehicle Technologies Office
U.S. Department of Energy
Pacific Northwest National Laboratory

Keywords

NHNO decomposition
NO formation mechanisms
Pore restriction effect in zeolites
Selective catalytic reduction of NOx
Surface nitrate groups
Zeolite supported Cu catalysts

Access to Document

10.1016/j.jcat.2015.06.016

Cite this

@article{508695af50ab4de395096ba03b05fee3,

title = "A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts",

abstract = "Abstract A comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA 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 Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on Cu-CHA, 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 Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.",

keywords = "NHNO decomposition, NO formation mechanisms, Pore restriction effect in zeolites, Selective catalytic reduction of NOx, Surface nitrate groups, Zeolite supported Cu catalysts",

author = "Chen, {Hai Ying} and Zhehao Wei and Marton Kollar and Feng Gao and Yilin Wang and Janos Szanyi and Peden, {Charles H.F.}",

note = "Publisher Copyright: {\textcopyright} 2015 Elsevier Inc.",

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doi = "10.1016/j.jcat.2015.06.016",

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T1 - A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

AU - Chen, Hai Ying

AU - Wei, Zhehao

AU - Kollar, Marton

AU - Gao, Feng

AU - Wang, Yilin

AU - Szanyi, Janos

AU - Peden, Charles H.F.

PY - 2015/7/14

Y1 - 2015/7/14

N2 - Abstract A comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA 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 Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on Cu-CHA, 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 Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.

AB - Abstract A comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA 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 Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on Cu-CHA, 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 Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.

KW - NHNO decomposition

KW - NO formation mechanisms

KW - Pore restriction effect in zeolites

KW - Selective catalytic reduction of NOx

KW - Surface nitrate groups

KW - Zeolite supported Cu catalysts

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