ABSTRACT: Cu-exchanged chabazite is the catalyst of choice for NOx abatement in diesel vehicles aftertreatment systems via ammonia-assisted selective catalytic reduction (NH3-SCR). Herein, we exploit in situ X-ray absorption spectroscopy powered by wavelet transform analysis and machine learning-assisted fitting to assess the impact of the zeolite composition on NH3-mobilized Cu-complexes formed during the reduction and oxidation half-cycles in NH3-SCR at 200 °C. Comparatively analyzing well-characterized Cu-CHA catalysts, we show that the Si/Al ratio of the zeolite host affects the structure of mobile dicopper(II) complexes formed during the oxidation of the [CuI(NH3)2]+ complexes by O2. Al-rich zeolites promote a planar coordination motif with longer Cu-Cu interatomic distances, while at higher Si/Al values, a bent motif with shorter internuclear separations is also observed. This is paralleled by a more efficient oxidation at a given volumetric Cu density at lower Si/Al, beneficial for the NOx conversion under NH3-SCR conditions at 200 °C.

Assessing the Influence of Zeolite Composition on Oxygen-Bridged Diamino Dicopper(II) Complexes in Cu-CHA DeNOx Catalysts by Machine Learning-Assisted X-ray Absorption Spectroscopy

Martini, Andrea
First
;
Negri, Chiara;Deplano, Gabriele;Bordiga, Silvia;Berlier, Gloria;Borfecchia, Elisa
Last
2022-01-01

Abstract

ABSTRACT: Cu-exchanged chabazite is the catalyst of choice for NOx abatement in diesel vehicles aftertreatment systems via ammonia-assisted selective catalytic reduction (NH3-SCR). Herein, we exploit in situ X-ray absorption spectroscopy powered by wavelet transform analysis and machine learning-assisted fitting to assess the impact of the zeolite composition on NH3-mobilized Cu-complexes formed during the reduction and oxidation half-cycles in NH3-SCR at 200 °C. Comparatively analyzing well-characterized Cu-CHA catalysts, we show that the Si/Al ratio of the zeolite host affects the structure of mobile dicopper(II) complexes formed during the oxidation of the [CuI(NH3)2]+ complexes by O2. Al-rich zeolites promote a planar coordination motif with longer Cu-Cu interatomic distances, while at higher Si/Al values, a bent motif with shorter internuclear separations is also observed. This is paralleled by a more efficient oxidation at a given volumetric Cu density at lower Si/Al, beneficial for the NOx conversion under NH3-SCR conditions at 200 °C.
2022
13
26
6164
6170
https://pubs.acs.org/doi/10.1021/acs.jpclett.2c01107?ref=PDF
Cu-Chabazite, Selective Catalytic Reduction, deNOx catalysis, X-ray Absorption Spectroscopy, EXAFS Wavelet Transform, Machine Learning-assisted EXAFS fitting
Martini, Andrea; Negri, Chiara; Bugarin, Luca; Deplano, Gabriele; Abasabadi, Reza K; Lomachenko, Kirill A; Janssens, Ton V W; Bordiga, Silvia; Berlier, Gloria; Borfecchia, Elisa
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1878640
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