Counting of Oxygen Defects versus Metal Surface Sites in Methanol Synthesis Catalysts by Different Probe Molecules

Authors

  • Matthias B. Fichtl,

    1. Catalysis Research Center and Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching bei München (Germany)
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  • Julia Schumann,

    1. Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
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  • Igor Kasatkin,

    1. Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
    2. Saint Petersburg State University, Research Centre for X-ray Diffraction Studies, 199155 Decabristov lane 16, St. Petersburg (Russia)
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  • Nikolas Jacobsen,

    1. Clariant Produkte (Deutschland) GmbH, BU Catalysts, Waldheimer Strasse 13, 83052 Bruckmühl (Germany)
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  • Malte Behrens,

    1. Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
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  • Robert Schlögl,

    1. Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin (Germany)
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  • Martin Muhler,

    1. Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Universitätsstrasse 150, 44780 Bochum (Germany)
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  • Olaf Hinrichsen

    Corresponding author
    1. Catalysis Research Center and Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching bei München (Germany)
    • Catalysis Research Center and Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching bei München (Germany)

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  • Financial support was provided by the Bayerisches Wirtschaftsministerium (NW-0906-0002) and Clariant Produkte (Deutschland) GmbH. M.B.F. gratefully acknowledges the support of the TUM Graduate School.

Abstract

Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N2O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N2O, temperature programmed desorption of H2, and kinetic experiments. The presence of ZnO dramatically influences the N2O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu-ZnO interface and can be used to easily quantify the intensity of Cu-Zn interaction. N2O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H2.

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