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Issue 10, 2019
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Temperature-programmed reduction with NO as a characterization of active Cu in Cu-CHA catalysts for NH3-SCR

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Abstract

Temperature programmed reduction with NO (NO-TPR) is introduced as a characterization method, by monitoring the reduction of CuII to CuI in a mixture of NH3 and NO. Since the NO-TPR method is based on the oxidation and reduction half cycles of the NH3-SCR reaction, quantitative information about the amount of active Cu in Cu-CHA is obtained. Furthermore, information on the stability and reactivity of reaction intermediates in the NH3-SCR cycle is obtained as well. The reduction of the Cu is followed by monitoring the consumption of NO, after oxidation of the catalyst in O2 or a mixture of NO and O2 to form the CuII state. Two distinct states of the Cu are revealed. The first state, corresponding to the reduction of a Cu-oxide species, is reduced around 130 °C and is observed at low Cu content only. The second state corresponds to the reduction of a Cu-nitrate species around 200–230 °C. The low-temperature activity of Cu-chabazite catalysts with low Cu content show the same trend as the Cu-nitrate species observed in NO-TPR. The fraction of Cu-oxide in NO-TPR decreases with increasing Cu content, leading to a non-linear dependence of the NH3-SCR activity on the Cu-content. At high Cu content, all Cu forms a stable Cu-nitrate species, and the NH3-SCR activity becomes proportional to the Cu content. This agrees well with the known behavior of Cu-CHA catalysts, indicating that NO-TPR seems to be a viable method for the characterization of Cu-CHA materials as NH3-SCR catalysts.

Graphical abstract: Temperature-programmed reduction with NO as a characterization of active Cu in Cu-CHA catalysts for NH3-SCR

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Publication details

The article was received on 21 Feb 2019, accepted on 22 Apr 2019 and first published on 23 Apr 2019


Article type: Paper
DOI: 10.1039/C9CY00358D
Catal. Sci. Technol., 2019,9, 2608-2619

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    Temperature-programmed reduction with NO as a characterization of active Cu in Cu-CHA catalysts for NH3-SCR

    P. S. Hammershøi, C. Negri, G. Berlier, S. Bordiga, P. Beato and T. V. W. Janssens, Catal. Sci. Technol., 2019, 9, 2608
    DOI: 10.1039/C9CY00358D

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