2 5 I H I G H L I G H T S 2 0 2 2
It was possible to verify the presence of Cu-N and Cu-O bonds in the [CuII2(NH3)4O2]2+ complex by X-ray emission spectroscopy (XES) measurements taken at beamline ID26 (Figure 15). These measurements independently confirmed the formation of the [CuII2(NH3)4O2]2+ complex, and also showed the absence of a direct Cu-S bond after the interaction with SO2, indicating that SO2 binds to Cu via an O-atom.
This study finds that the [CuII2(NH3)4O2]2+ complex is the most reactive Cu-species to SO2. This complex is formed via the reaction of O2 with the CuI(NH3)2-complex, which is a crucial step in the catalytic cycle for NH3-SCR. Therefore, it is concluded that the reaction of the [CuII2(NH3)4O2]2+ complex with SO2 is responsible for the poisoning of Cu- CHA catalysts in NH3-SCR by SO2.
Fig. 14: Cu K-edge XANES (a) and FT-EXAFS spectra (b) collected in situ during the exposure of Cu species to SO2 at 200 °C. c) The S/Cu ratio in the samples after exposure to SO2 obtained from SO2-TPD and XAQ.
PRINCIPAL PUBLICATION AND AUTHORS
SO2 poisoning of Cu-CHA deNOx catalyst: the most vulnerable Cu species identified by X-ray absorption spectroscopy, A. Yu. Molokova (a,b), E. Borfecchia (b), A. Martini (b,c), I.A. Pankin (c), C. Atzori (a), O. Mathon (a), S. Bordiga (b), F. Wen (d), P.N.R. Vennestrøm (e), G. Berlier (b), T.V.W. Janssens (e), K.A. Lomachenko (a), J. Am. Chem. Soc. Au 2,4, 787-792 (2022); https:/doi.org/10.1021/jacsau.2c00053 (a) ESRF (b) Department of Chemistry and NIS Centre, University of Turin (Italy) (c) The Smart Materials Research Center, Southern Federal University, Sladkova (Russia) (d) Umicore AG & Co, Hanau (Germany) (e) Umicore Denmark ApS, Hørsholm (Denmark)
 C.K. Lambert et al., React. Chem. Eng. 4(6), 969-974 (2019).  R. Gounder et al., React. Chem. Eng. 4(6), 966-968 (2019).  P.S. Hammershoi et al., Appl. Catal. B-Environ. 238, 104-110 (2018).  P.S. Hammershoi et al., Appl. Catal. B-Environ. 226, 38-45 (2018).  K.A. Lomachenko et al., J. Phys. Chem. C 126, 11, 5175-5179 (2022).
Fig. 15: Background- subtracted Cu Kβ
valence-to-core XES spectra for
different stages of the formation of [CuII2(NH3)4O2]2+ complex and its
exposure to SO2.