Investigating the Low Temperature Formation of CuII-(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx

Chiara Negri, Peter Sams Hammershøi, Ton V. W. Janssens, Pablo Beato, Gloria Berlier, Silvia Bordiga*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of CuII‐(N,O) species on Cu exchanged chabazite zeolites (Cu‐CHA), active for the selective catalytic reduction of NOx with NH3 (NH3‐SCR). In particular, we investigated the reaction of NO and O2 at low temperature (200 and 50 °C) on a series of Cu‐CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C. At lower temperature a mixture of chelating and monodentate nitrates are formed, together with the nitrosonium ion NO+, whose amount was found to be proportional to the zeolite Brønsted site concentration. Nitrates were found to mainly form with CuII ions stabilized by one negative framework charge (Z), Z‐[Cu(OH]I or Z‐[Cu(O2]I, without involvement of Z2‐CuII ones. This evidence, together with the absence of bridging nitrates in samples with high probability for Cu–Cu pairs, indicate that the nitrate ligands are not able to mobilize copper ions, at variance with what recently reported for NH3. Finally, water was found to replace preformed chelating copper nitrates and deplete NO+ (though with different kinetics) at both temperatures, while favouring the presence of monodentate ones.
Original languageEnglish
JournalChemistry: A European Journal
Volume24
Issue number46
Pages (from-to)12044-12053
Number of pages10
ISSN0947-6539
DOIs
Publication statusPublished - 2018

Keywords

  • FTIR
  • Nitrates
  • NO oxidation
  • Spectroscopy
  • Zeolites

Cite this

Negri, Chiara ; Hammershøi, Peter Sams ; Janssens, Ton V. W. ; Beato, Pablo ; Berlier, Gloria ; Bordiga, Silvia. / Investigating the Low Temperature Formation of CuII-(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx. In: Chemistry: A European Journal. 2018 ; Vol. 24, No. 46. pp. 12044-12053.
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title = "Investigating the Low Temperature Formation of CuII-(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx",
abstract = "In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of CuII‐(N,O) species on Cu exchanged chabazite zeolites (Cu‐CHA), active for the selective catalytic reduction of NOx with NH3 (NH3‐SCR). In particular, we investigated the reaction of NO and O2 at low temperature (200 and 50 °C) on a series of Cu‐CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C. At lower temperature a mixture of chelating and monodentate nitrates are formed, together with the nitrosonium ion NO+, whose amount was found to be proportional to the zeolite Br{\o}nsted site concentration. Nitrates were found to mainly form with CuII ions stabilized by one negative framework charge (Z), Z‐[Cu(OH]I or Z‐[Cu(O2]I, without involvement of Z2‐CuII ones. This evidence, together with the absence of bridging nitrates in samples with high probability for Cu–Cu pairs, indicate that the nitrate ligands are not able to mobilize copper ions, at variance with what recently reported for NH3. Finally, water was found to replace preformed chelating copper nitrates and deplete NO+ (though with different kinetics) at both temperatures, while favouring the presence of monodentate ones.",
keywords = "FTIR, Nitrates, NO oxidation, Spectroscopy, Zeolites",
author = "Chiara Negri and Hammersh{\o}i, {Peter Sams} and Janssens, {Ton V. W.} and Pablo Beato and Gloria Berlier and Silvia Bordiga",
year = "2018",
doi = "10.1002/chem.201802769",
language = "English",
volume = "24",
pages = "12044--12053",
journal = "Chemistry: A European Journal",
issn = "0947-6539",
publisher = "Wiley - V C H Verlag GmbH & Co. KGaA",
number = "46",

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Investigating the Low Temperature Formation of CuII-(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx. / Negri, Chiara; Hammershøi, Peter Sams; Janssens, Ton V. W.; Beato, Pablo; Berlier, Gloria; Bordiga, Silvia.

In: Chemistry: A European Journal, Vol. 24, No. 46, 2018, p. 12044-12053.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Investigating the Low Temperature Formation of CuII-(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx

AU - Negri, Chiara

AU - Hammershøi, Peter Sams

AU - Janssens, Ton V. W.

AU - Beato, Pablo

AU - Berlier, Gloria

AU - Bordiga, Silvia

PY - 2018

Y1 - 2018

N2 - In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of CuII‐(N,O) species on Cu exchanged chabazite zeolites (Cu‐CHA), active for the selective catalytic reduction of NOx with NH3 (NH3‐SCR). In particular, we investigated the reaction of NO and O2 at low temperature (200 and 50 °C) on a series of Cu‐CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C. At lower temperature a mixture of chelating and monodentate nitrates are formed, together with the nitrosonium ion NO+, whose amount was found to be proportional to the zeolite Brønsted site concentration. Nitrates were found to mainly form with CuII ions stabilized by one negative framework charge (Z), Z‐[Cu(OH]I or Z‐[Cu(O2]I, without involvement of Z2‐CuII ones. This evidence, together with the absence of bridging nitrates in samples with high probability for Cu–Cu pairs, indicate that the nitrate ligands are not able to mobilize copper ions, at variance with what recently reported for NH3. Finally, water was found to replace preformed chelating copper nitrates and deplete NO+ (though with different kinetics) at both temperatures, while favouring the presence of monodentate ones.

AB - In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of CuII‐(N,O) species on Cu exchanged chabazite zeolites (Cu‐CHA), active for the selective catalytic reduction of NOx with NH3 (NH3‐SCR). In particular, we investigated the reaction of NO and O2 at low temperature (200 and 50 °C) on a series of Cu‐CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C. At lower temperature a mixture of chelating and monodentate nitrates are formed, together with the nitrosonium ion NO+, whose amount was found to be proportional to the zeolite Brønsted site concentration. Nitrates were found to mainly form with CuII ions stabilized by one negative framework charge (Z), Z‐[Cu(OH]I or Z‐[Cu(O2]I, without involvement of Z2‐CuII ones. This evidence, together with the absence of bridging nitrates in samples with high probability for Cu–Cu pairs, indicate that the nitrate ligands are not able to mobilize copper ions, at variance with what recently reported for NH3. Finally, water was found to replace preformed chelating copper nitrates and deplete NO+ (though with different kinetics) at both temperatures, while favouring the presence of monodentate ones.

KW - FTIR

KW - Nitrates

KW - NO oxidation

KW - Spectroscopy

KW - Zeolites

U2 - 10.1002/chem.201802769

DO - 10.1002/chem.201802769

M3 - Journal article

VL - 24

SP - 12044

EP - 12053

JO - Chemistry: A European Journal

JF - Chemistry: A European Journal

SN - 0947-6539

IS - 46

ER -