Reaction Mechanism of Aerobic Oxidation of Alcohols Conducted on Activated-Carbon-Supported Cobalt Oxide Catalysts

Authors

  • Dr. Junjiang Zhu,

    Corresponding author
    1. Department of Chemistry, Technical University of Berlin, Englische Str. 20, 10587 Berlin (Germany), Fax: (+49) 30-314 29271
    • Department of Chemistry, Technical University of Berlin, Englische Str. 20, 10587 Berlin (Germany), Fax: (+49) 30-314 29271
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  • Prof. Joaquim L. Faria,

    1. Laboratory of Catalysis and Materials (LCM), Associate Laboratory (LSRE/LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal), Fax: (+351) 22-5081449
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  • Prof. José L. Figueiredo,

    Corresponding author
    1. Laboratory of Catalysis and Materials (LCM), Associate Laboratory (LSRE/LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal), Fax: (+351) 22-5081449
    • Laboratory of Catalysis and Materials (LCM), Associate Laboratory (LSRE/LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal), Fax: (+351) 22-5081449
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  • Prof. Arne Thomas

    1. Department of Chemistry, Technical University of Berlin, Englische Str. 20, 10587 Berlin (Germany), Fax: (+49) 30-314 29271
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Abstract

Catalytic performances and the reaction mechanism of Co3O4/AC (AC=activated carbon) for aerobic oxidation of alcohols carried out in the liquid phase were investigated. Co3O4/AC shows a high activity for aerobic oxidation of benzyl alcohol, comparable to noble metal catalysts (e.g., Au/AC) even in the absence of additives or promoters (e.g., NaOH). Changing preparation conditions, such as treatment temperature and/or time, can affect the catalytic performances of Co3O4/AC, due to decomposition of surface groups of the carbon support. Careful studies show that low alcohol conversions are obtained with either Co3O4 or AC alone, which indicates that the high conversion observed over the Co3O4/AC is due to a synergistic effect between Co3O4 and AC. Parallel experiments using a high-surface-area covalent triazine framework or oxygen-inert carbon nitride as support for the Co3O4 catalyst also show lower conversions, which suggest that the ability of AC (in Co3O4/AC) to activate molecular oxygen is essential for the reaction. FTIR and XPS spectra taken from catalysts before and after the reaction confirm that oxygen activation proceeds mainly on the carbon support. As a result, it can be assumed that the alcohol dehydrogenation step proceeds on the metal oxide, whereas the oxygen activation step occurs mainly on the carbon support.

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