Cu-exchanged chabazite zeolites (Cu-CHA) are effective catalysts for the NH3-assisted selective catalytic reduction of NO (NH3-SCR) for the abatement of NOx emission from diesel vehicles. However, the presence of a small amount of SO2 in diesel exhaust gases leads to a severe reduction in the low-temperature activity of these catalysts. To shed light on the nature of such deactivation, we characterized a Cu-CHA catalyst under well-defined exposures to SO2 using in situ X-ray absorption spectroscopy. By varying the pretreatment procedure prior to the SO2 exposure, we have selectively prepared Cu-I and Cu-II species with different ligations, which are relevant for the NH3-SCR reaction. The highest reactivity toward SO2 was observed for Cu-II species coordinated to both NH3 and extraframework oxygen, in particular for [Cu-2(II) (NH3)(4)O-2](2+) complexes. Cu species without either ammonia or extraframework oxygen ligands were much less reactive, and the associated SO2 uptake was significantly lower. These results explain why SO2 mostly affects the low-temperature activity of Cu-CHA catalysts, since the dimeric complex [Cu-2(II) (NH3)(4)O-2](2+) is a crucial intermediate in the lowtemperature NH3-SCR catalytic cycle.

SO2 Poisoning of Cu-CHA deNO x Catalyst: The Most Vulnerable Cu Species Identified by X-ray Absorption Spectroscopy

Borfecchia, Elisa;Martini, Andrea;Bordiga, Silvia;Berlier, Gloria;
2022-01-01

Abstract

Cu-exchanged chabazite zeolites (Cu-CHA) are effective catalysts for the NH3-assisted selective catalytic reduction of NO (NH3-SCR) for the abatement of NOx emission from diesel vehicles. However, the presence of a small amount of SO2 in diesel exhaust gases leads to a severe reduction in the low-temperature activity of these catalysts. To shed light on the nature of such deactivation, we characterized a Cu-CHA catalyst under well-defined exposures to SO2 using in situ X-ray absorption spectroscopy. By varying the pretreatment procedure prior to the SO2 exposure, we have selectively prepared Cu-I and Cu-II species with different ligations, which are relevant for the NH3-SCR reaction. The highest reactivity toward SO2 was observed for Cu-II species coordinated to both NH3 and extraframework oxygen, in particular for [Cu-2(II) (NH3)(4)O-2](2+) complexes. Cu species without either ammonia or extraframework oxygen ligands were much less reactive, and the associated SO2 uptake was significantly lower. These results explain why SO2 mostly affects the low-temperature activity of Cu-CHA catalysts, since the dimeric complex [Cu-2(II) (NH3)(4)O-2](2+) is a crucial intermediate in the lowtemperature NH3-SCR catalytic cycle.
2022
2
4
787
792
https://pubs.acs.org/doi/10.1021/jacsau.2c00053?ref=PDF
selective catalytic reduction; Cu-CHA; deNO(x) catalysis; sulfur poisoning; X-ray absorption spectroscopy; X-ray adsorbate quantification; XAS; XAQ
Molokova, Anastasia Yu; Borfecchia, Elisa; Martini, Andrea; Pankin, Ilia A; Atzori, Cesare; Mathon, Olivier; Bordiga, Silvia; Wen, Fei; Vennestrøm, Peter N R; Berlier, Gloria; Janssens, Ton V W; Lomachenko, Kirill A
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1878641
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