In-situ studies of oxidation/reduction of copper in Cu-CHA SCR catalysts: Comparison of fresh and SO2-poisoned catalysts

• Published in: Applied catalysis. B, Environmental Vol. 269; p. 118722
• Main Authors: Bergman, Susanna L., Dahlin, Sandra, Mesilov, Vitaly V., Xiao, Yang, Englund, Johanna, Xi, Shibo, Tang, Chunhua, Skoglundh, Magnus, Pettersson, Lars J., Bernasek, Steven L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.07.2020; Elsevier BV
• Subjects: Absorption spectroscopy; Catalysts; Copper; Cu-SSZ-13; Deactivation; Heating; In-situ XANES; Metal clusters; NH -SCR 3; NH3-SCR; Oxidation; Regeneration; SO /sulfur poisoning 2; SO2/sulfur poisoning; Species; Spectrum analysis; Sulfur dioxide; Temperature dependence; Time dependence; Wavelet transforms; X ray absorption; X-ray absorption spectroscopy; Cu-SSZ-13; NH3-SCR; In-situ XANES; regeneration; SO2/sulfur poisoning
• ISSN: 0926-3373; 1873-3883; 1873-3883
• DOI: 10.1016/j.apcatb.2020.118722

[Display omitted] •Cu-SSZ-13 catalysts for SCR were studied as fresh and SO2-poisoned samples.•In-situ Cu K-edge XANES studies of the oxidation/reduction of Cu in these catalysts was correlated with SCR performance and catalyst characterization.•H2-TPR was used to determine Cu sites present in the catalyst.•Cu K-edge XANES spectra were used to follow oxidation and reduction of these Cu ion sites for fresh and SO2-poisoned samples.•Differences in the ease of Cu ion reduction is observed for fresh vs. SO2-poisoned samples in different temperature regions. SO2-poisoning results in deactivation of Cu-CHA SCR under standard SCR conditions; however regeneration at 700 °C completely restores the SCR performance. To understand the nature of these effects, Cu-species in the fresh and poisoned catalysts were characterized by in-situ temperature-dependent time-resolved Cu K-edge X-ray absorption spectroscopy using the multivariate curve resolution alternating least squares (MCR-ALS) approach and continuous Cauchy wavelet transforms. The extracted chemically-meaningful reference spectra of Cu-species were analyzed by DFT-assisted XANES calculations. Cu-bisulfates were found as the most energetically favorable poisoned Cu-species. The response of Cu-species to a reducing environment differs in the fresh and SO2-poisoned catalysts. Differences in reducibility are related to the formation of quasi-linear Cu-complexes in the SO2-poisoned catalyst formed during heating in H2/He. Heating in H2/He leads to partial desulfurization of the poisoned catalyst. Cooling in H2/He after heating results in more facile formation of Cu-metal clusters in fresh catalyst than in SO2-poisoned.