Nitrate-nitrite equilibrium in the reaction of NO with a Cu-CHA catalyst for NH3-SCR

The equilibrium reaction between NO and Cu-nitrate, Cu(ii)-NO3- + NO(g) Cu(ii)-NO2- + NO2(g), has been proposed to be a key step in the selective catalytic reduction of NO by ammonia (NH3-SCR) over Cu-CHA catalysts and points to the presence of Cu-nitrites. Whereas the formation of gaseous NO2 has b...

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Bibliographic Details
Published in:Catalysis science & technology 2016-01, Vol.6 (23), p.8314-8324
Main Authors: Tyrsted, C, Borfecchia, E, Berlier, G, Lomachenko, KA, Lamberti, C, Bordiga, S, Vennestroem, PNR, Janssens, TVW, Falsig, H, Beato, P, Puig-Molina, A
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Ammonia
Catalysts
Conversion
Fourier transforms
Infrared spectroscopy
Selective catalytic reduction
Zeolites
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Summary:The equilibrium reaction between NO and Cu-nitrate, Cu(ii)-NO3- + NO(g) Cu(ii)-NO2- + NO2(g), has been proposed to be a key step in the selective catalytic reduction of NO by ammonia (NH3-SCR) over Cu-CHA catalysts and points to the presence of Cu-nitrites. Whereas the formation of gaseous NO2 has been observed, a direct observation of Cu-nitrite groups under conditions relevant to NH3-SCR has been so far unsuccessful. In an effort to identify and characterize Cu-nitrites, the reaction between Cu-nitrates hosted in the CHA zeolite and NO is investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) and X-ray absorption spectroscopy (XAS). We find that NO reacts with Cu-nitrates and that about half of the Cu-nitrate species are converted. After the reaction, the Cu(ii) state is different from the original oxidized state. Analysis of XAS data indicates that the final state of the Cu-CHA catalyst is consistent with the partial conversion of the Cu-nitrate species to a bidentate Cu-nitrite configuration.
ISSN:2044-4753
2044-4761
DOI:10.1039/c6cy01820c