High Catalytic Activity in CO Oxidation over MnO
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Nanocrystals |
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Authors: | Viacheslav Iablokov Krisztina Frey Olga Geszti Norbert Kruse |
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Affiliation: | 1. Chemical Physics of Materials, Université Libre de Bruxelles, CP 243, Brussels, 1050, Belgium 2. Department of Surface Chemistry and Catalysis, Institute of Isotopes, Konkoly Thege Miklós út 29/33, 1121, Budapest, Hungary 3. Research Institute for Technical Physics and Materials Science, Konkoly Thege Miklós út 29/33, 1121, Budapest, Hungary
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Abstract: | Manganese oxides of various stoichiometry were prepared via Mn-oxalate precipitation followed by thermal decomposition in the presence of oxygen. A non-stoichiometric manganese oxide, MnO x (x = 1.61…1.67) was obtained by annealing at 633 K and demonstrated superior CO oxidation activity, i.e. full CO conversion at room temperature and below. The activity gradually decreased with time-on-stream of the reactants but could be easily recovered by heating at 633 K in the presence of oxygen. CO oxidation over MnO x in the absence of oxygen proved to be possible with reduced rates and demonstrated a Mars—van Krevelen—type mechanism to be in operation. A TEM structural analysis showed the MnO x phase to form microrods with large aspect ratio which broke up into nanocrystalline manganese oxide (MnO x ) particles with diameters below 3 nm and a BET specific surface area of 525 m2/g. Annealing at 798 K rather than 633 K produced well crystalline Mn2O3 which showed lower CO oxidation activity, i.e. 100% CO conversion at 335 K. The catalytic performance in CO oxidation of various Mn-oxides either studied in this work or elsewhere was compared on the basis of specific reaction rates. |
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