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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 14 (1992), S. 339-348 
    ISSN: 1572-879X
    Schlagwort(e): Ammonia synthesis ; Ru-zeolite ; metal clusters ; conversion measurements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Na-Y zeolite was cation exchanged with Ru(NH3)6Cl3 yielding at 25% exchange level a light-purple solid which was active in ammonia synthesis at atmospheric pressure. Pulse conversion experiments show that the catalyst stores nitrogen as it was observed with the conventional iron catalyst. At 810 K the conversion reached about 20% of the maximum conversion of the iron catalyst. The catalyst deactivated reversibly within 30 h due to agglomeration. The active species in the catalyst is most likely a cluster-like Ru metal particle prevented from sintering under the reducing conditions of catalysis by the zeolite framework.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1572-879X
    Schlagwort(e): Ammonia synthesis ; supported ruthenium catalyst ; dispersed ruthenium ; instationary kinetics ; lifetime effects ; ruthenium oxidation ; surface analysis ; XPS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Reaction of Ru(NH3)6Cl3 with Na-A and K-A zeolites yielded oligomeric amino-oxo-complexes supported on the zeolite. Controlled thermal activation under hydrogen converted the precursor in a two-step reaction into an active catalyst with good long-term stability and resistance against small doses of oxygen poison. Several nanometers sized Ru metal particles are chemically bonded to the zeolite surface which provides in the K form an alkali promoter at the metal-zeolite interface. Extensive oxidation breaks the metal-support anchoring and re-reduction produces Ru metal particles sintering rapidly into large metal crystals with only small residual catalytic activity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 650-654 
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Na—Y zeolite was cation exchanged with Ru and tested in ammonia synthesis at atmospheric pressure. Activities up to ∼10% of the commercial iron catalyst scaled by the active surface area were observed. Characterization of the zeolites with XPS was complemented with reference thermal desorption spectroscopy data on a polycrystalline Ru metal surface. The catalysts showed high thermal stability in in situ reduction-oxidation cycles. The chemical state of the Ru will be discussed. From shift measurements the Ru is metallic in the active state, but line shape arguments point to a cluster-like particle morphology. The location of the Ru inside or outside the zeolite framework will be discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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