Extraframework aluminum species in zeolites: Ab initio molecular dynamics simulation of gmelinite

Lubomir Benco, T. Demuth, Juergen Hafner, Francois Hutschka, Hervé Toulhoat

    Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

    Abstract

    The dynamical behavior of extraframework aluminum particles (EFAL) in zeolites has been investigated using a first-principles molecular dynamics technique. Small clusters of hydrated aluminum hydroxide Al(OH)3(H2O)3 and Al(OH)3(H2O) are located both in the main channel and in the cage. The simulation of the hexacoordinated cluster at T = 300 K shows an overcoordination of the central atom and a release of H2O molecules. When placed in the main channel both the EFAL and the noncoordinated H2O molecules are mobile. When placed in the cage, a network of hydrogen bonds is established, occluding the EFAL and suppressing its mobility. The basic character of the EFAL causes an exchange of Brønsted acid protons between the zeolite and the EFAL particle. In a high-acidity zeolite a multiple, simultaneous proton exchange is observed, leading to a separation of charges (EFAL2+, zeolite2-). The calculated stretching OH frequencies of the EFAL are ?60 cm-1 higher than those of the Brønsted OH, in good agreement with IR measurements. Œ 2002 Elsevier Science (USA).
    OriginalspracheEnglisch
    Seiten (von - bis)480-488
    Seitenumfang9
    FachzeitschriftJournal of Catalysis
    Jahrgang209
    Ausgabenummer2
    DOIs
    PublikationsstatusVeröffentlicht - 2002

    ÖFOS 2012

    • 1030 Physik, Astronomie

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