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  • 1
    Electronic Resource
    Electronic Resource
    Nature of the metal-support interface in supported metal catalysts: Results from X-ray absorption spectroscopy (1992)
    Springer
    Catalysis letters 14 (1992), S. 271-277 
    Details
    ISSN: 1572-879X
    Keywords: Nature metal-support interface ; hydrogen pretreatment ; EXAFS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract X-ray absorption spectra characterizing the metal-support interface in supported metal complexes and supported metal catalysts are summarized and evaluated. Single-metal-atom transition metal complexes on non-reducible metal oxide supports are bonded with metal-oxygen bonds with metal-oxygen distances of approximately 2.15 A; the bonding distance is only weakly sensitive to the oxidation state of the metal. Nearly this same metal-oxygen distance is characteristic of the metal-support interface in metal-oxide-supported metal clusters following high temperature reduction in H2 (HTR:T 〉 450 °C). The metals at the interface may be polarized sufficiently that they bond with the oxygen of the support much as the cations in mononuclear complexes bond with it. When the supported metals are treated in H2 at low temperatures (LTR:T 〈 350 °C) or are prepared under He with partially hydroxylated supports, a longer metal-support oxygen distance is observed, typically 2.5–2.7 Å. This distance is suggested to characterize interactions between zero-valent metals and support oxygen. Changes in the performance of supported metal catalysts resulting from differences in the temperature of pretreatment in H2 are attributed to changes in the electronic properties and/or morphology of the metal clusters, which are suggested to be related to the concomitant changes in the structure of the metal-support interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769664
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Highly dispersed MgO-supported model Pd-Mo catalysts prepared from bimetallic clusters: Chemisorption and selective catalytic reduction of NO (1996)
    Springer
    Catalysis letters 38 (1996), S. 57-61 
    Details
    ISSN: 1572-879X
    Keywords: bimetallic clusters ; NO reduction ; Pd-Mo catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Model supported palladium and palladium-molybdenum catalysts prepared from organometallic precursors and previously characterized by a variety of chemical and physical methods were examined by IR spectroscopy of NO chemisorption and tested for their activities as catalysts in the competitive NO + CO + O2 reaction. The IR results reveal distinctive behavior of the catalyst made from a bimetallic precursor, and the activity results show that this catalyst is more selective for NO reduction than the other catalysts, but its stability is vulnerable to the reaction conditions. The high selectivity is attributed to Pd-Mo interactions, which are inferred to be stronger in the catalyst prepared from a bimetallic precursor than in catalysts prepared from monometallic precursors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806900
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Pt clusters in BaKL zeolite: Characterization by transmission electron microscopy, hydrogen chemisorption, and X-ray absorption spectroscopy (1990)
    Springer
    Catalysis letters 6 (1990), S. 369-381 
    Details
    ISSN: 1572-879X
    Keywords: Zeolite L ; platinum ; hexane to benzene ; EXAFS ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Platinum supported on BaKL zeolite was characterized by Transmission Electron Microscopy (TEM), hydrogen chemisorption, and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results of all three techniques indicate the presence of highly dispersed platinum in the zeolite pores. There is no evidence of platinum outside the zeolite pores. The EXAFS data determine a Pt-Pt coordination number of 3.7, suggesting that the average platinum cluster in the zeolite consists of 5 or 6 atoms, consistent with the TEM and chemisorption data. The EXAFS data also provide evidence of the platinum-zeolite interface, indicated by Pt-O contributions at 2.14 and 2.70 Å, and a Pt-Ba contribution at 3.8 Å. The Pt/BaKL zeolite is one of the most highly dispersed supported platinum samples and one of the most structurally uniform supported metal catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764004
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    Paper (German National Licenses)
    Fulltext
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