2019-Sustainable Industrial Processing Summit
SIPS2019 Volume 11: New and Advanced Materials, Technologies, and Manufacturing

Editors:F. Kongoli, F. Marquis, N. Chikhradze, T. Prikhna
Publisher:Flogen Star OUTREACH
Publication Year:2019
Pages:174 pages
ISBN:978-1-989820-10-0
ISSN:2291-1227 (Metals and Materials Processing in a Clean Environment Series)
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    A Convenient Way to Synthesize of Nanosized Catalysts in Quasi-intramolecular Solid Phase Redox Reactions

    Laszlo Kotai1; Fernanda Paiva Franguelli2; Kende Beres3; Hanna Solt1; Peter Nemeth1; Zoltan Homonnay4; Istvan E. Sajo5;
    1RESEARCH CENTRE FOR NATURAL SCIENCES, HUNGARIAN ACADEMY OF SCIENCES, Budapest, Hungary; 2HUNGARY AND BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS, Budapest, Hungary; 3HUNGARY AND INSTITUTE OF CHEMISTRY, ELTE EOTVOS LORAND UNIVERSITY, Budapest, Hungary; 4INSTITUTE OF CHEMISTRY, ELTE EOTVOS LORAND UNIVERSITY, Budapest, Hungary; 5JANOS SZENTAGOTHAI RESEARCH CENTRE, UNIVERSITY OF PECS, Budapest, Hungary;
    Type of Paper: Keynote
    Id Paper: 289
    Topic: 43

    Abstract:

    Nanosized mixed-metal-oxide catalysts are used in various industrially relevant processes like Fischer-Tropsch synthesis or NOx removal from gases. Transition metal ions, coordinated by reducible ligands (NH3, pyridine or urea) that make salts with oxometalate anions (MnO4-, CrO42-, Cr2O72-), are used to prepare nano-sized mixed spinel-type metal-oxides with pre-selected composition, properties, and structure. The applicability of a mixed oxide catalyst is determined by the distribution of the two metals among valence states, and crystallographic positions (in spinels T-4 and OC-6). The methods currently used for the synthesis of mixed metal-oxides do not allow the control of these properties. This is because the methods used for synthesis of mixed metal-oxides include processes that take place at high temperatures, where the mobility of atoms leads to the formation of a thermodynamically stable structure. This stable structure is characterized by its unique distribution of metal atoms among positions and valence states. The unique feature of the catalyst synthesis method developed by us [1-4] is based on the thermal decomposition of tetraoxometalates of transition metal ions, coordinated by reducible ligands at relatively low temperatures (100-200 oC). The thermal decomposition of tetraoxometalates then releases gas-phase products formed from the ligands. This is a solid-phase reaction which forms mixed oxides with metastable structures because at low temperatures, the metal ions remain in the crystallographic positions of the precursor salt. For example, hexaaquairon(III) permanganate results in (Fe,Mn)O type and (Fe,Mn)3O4 type mixed oxides, depending on the atmosphere and temperature of decomposition. Furthermore, the original spinel structure can be oxidized into defect-spinel structures and finally to (Fe,Mn)2O3 type oxides.

    [Fe(urea)6(MnO4)3] --> (Fe,Mn)3O4 --> (Fe,Mn)3O4.5 --> (Fe,Mn)2O3
    --> (Fe,Mn)O

    Due to a large number of crystal defects, nanocrystallites are formed which is favorable for catalysis. Our method enables one to set the ratio of the metal ions arbitrarily by starting from an isomorphous solid solution in which we partially replaced the metal ion by another one, and/or the anion by another tetraoxometalate or by an "innocent" anion (which forms gaseous products due to the lack of metal atoms, e.g., MnO4- by ClO4-).
    [Fe(urea)6](MnO4)3 -- (Fe,Mn)-oxides with Fe:Mn=1:3 overall ratio
    [Fe(urea)6(MnO4)2(ClO4)2 -- (Fe,Mn)-oxides with Fe:Mn=1:2 overall ratio
    [Fe(Urea)6](MnO4)(ClO4)2 -- (Fe,Mn)-oxides with Fe:Mn=1:1 overall ratio
    [(Fe0.5Cr0.5)(urea)6](MnO4)0.5(ClO4)2.5 -- (Fe,Cr,Mn) oxides with Fe:Cr:Mn=1:1:1 overall ratio

    Keywords:

    Nanocomposites; Nanomaterials; New and advanced materials;

    References:

    [1] Sajó I.E., Bakos P. Szilágyi I.M., Lendvay Gy., Magyari J., Mohai M., Szegedi A., Farkas A., Jánosity A., Klébert Sz., Kótai L., Inorg. Chem., 2018, 57(21), 13679-13692.
    [2] Kotai, L., Banerji, K. K., Sajo, I., Kristof, J., Sreedhar, B., Holly, S., Keresztury, G., Rockenbauer, A.
    Helv. Chim. Acta, 2002, 85(8) 2316-2327F
    [3] Kotai L., Fodor J., Jakab E., Sajo I., Szabo P., Lonyi F., Valyon J., Gacs, I., Argay G., Banerji K., Trans. Metal Chem., 2006, 31(1) 30-34
    [4] Sajó I. E., Kotai L., Keresztury G., Gacs I., Pokol Gy., Kristóf J., Soptrayanov B., Petrusevski V. M., Timpu D., Sharma P. K., Helv. Chim. Acta 2008, 91, 1646

    Cite this article as:

    Kotai L, Franguelli F, Beres K, Solt H, Nemeth P, Homonnay Z, Sajo I. (2019). A Convenient Way to Synthesize of Nanosized Catalysts in Quasi-intramolecular Solid Phase Redox Reactions. In F. Kongoli, F. Marquis, N. Chikhradze, T. Prikhna (Eds.), Sustainable Industrial Processing Summit SIPS2019 Volume 11: New and Advanced Materials, Technologies, and Manufacturing (pp. 73-74). Montreal, Canada: FLOGEN Star Outreach