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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 11 (1991), S. 253-265 
    ISSN: 1572-879X
    Keywords: Silver ; oxygen ; selective oxidation ; thermal desorption ; subsurface compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polycrystalline Ag treated with O2 at pressures up to 1 bar and at temperatures up to 920 K was examined by TDS. It was found that the peak commonly observed at 595±25 K and assigned to adsorbed atomic oxygen (Oa) is shifted to higher desorption temperatures with rising dosing temperatures. Since saturation of the uptake was not possible either, this peak was identified as dissolved atomic oxygen (Od). The existence of a maximum for the O2 uptake after exposure at 820 K was found. Hence, under conditions of formaldehyde synthesis (≈ 920 K) the ability of the catalyst to dissolve oxygen is near its maximum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 22 (1993), S. 215-225 
    ISSN: 1572-879X
    Keywords: Ion-scattering spectroscopy (ISS) ; methanol oxidation ; oxygen ; Raman spectroscopy ; reflection electron microscopy (REM) ; silver ; X-ray photoelectron spectroscopy (XPS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Under the applied high reaction temperatures (∼900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (Oγ) apart from O atoms dissolved in the bulk (Oβ). Methanol oxidation to formaldehyde proceeds through this Oγ species as demonstrated by application of a variety of spectroscopic techniques.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-879X
    Keywords: oxygen ; partial oxidation ; reconstruction ; reflection electron microscopy ; Raman spectroscopy ; silver ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Interaction of water with an oxygenated Ag(111) surface leads to an enhancement of the surface restructuring and an activated formation of hydroxyl groups (OH) located stably on the surface and incorporated in the subsurface region, as evidenced by means of reflection electron microscopy (REM) and in situ Raman spectroscopy. Dehydroxylation of OHads at elevated temperatures releases the strongly bound oxygen species labelled Oγ at the surface, and offers an alternative to the energetically less favorable pathway for the direct formation of the Oγ species from molecular oxygen.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Topics in catalysis 14 (2000), S. 95-100 
    ISSN: 1572-9028
    Keywords: ruthenium ; ruthenium dioxide ; oxide ; CO oxidation ; oxygen ; chemisorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract CO oxidation over ruthenium dioxide (RuO2) dominates the CO/CO2 conversion rate over the catalytically active oxygen-rich Ru(0001) surfaces. In sharp contrast, chemisorbed O overlayers on Ru(0001) (with and without dissolved oxygen) are virtually inactive with respect to CO oxidation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 12 (1992), S. 331-344 
    ISSN: 1572-879X
    Keywords: XPS of Pt black catalyst ; UPS of Pt black catalyst ; surface state of Pt black ; catalytic properties of Pt black
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract XPS and UPS of a Pt black catalyst after customary H2-O2 regeneration shows considerable amounts of residual C as well as surface OH/H2O species. Surface C could not be removed even by O2 at 800 K. Oxygenates are stable even after H2 treatment up to 750 K. Their chemical state has been tentatively identified by comparing XPS and UPS results. Catalytic transformations of n-hexane on Pt black treated analogously is reported and the effect of surface species on catalytic properties discussed. Possible consequences of the presence of stable surface OH/H2O species on H2-O2 titrations are mentioned.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-879X
    Keywords: Ammonia synthesis ; iron catalyst ; surface characterization ; promoter effects ; nitrides ; ion scattering spectroscopy ; XPS ; HRTEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Industrial doubly-promoted iron catalysts and model systems of singly-promoted K- and Al-iron catalysts were characterised by their catalytic performance at 1 bar pressure. The relevance of bulk nitrogen for catalytic performance is shown. The catalysts were also activated in an in-situ reaction chamber of a He-ion scattering spectrometer (ISS) and their top atomic layer elemental composition was determined after they had reached similar performance as in the microreactor tests. The bulk microstructure of these samples was investigated by high resolution transmission electron microscopy (TEM) and microdiffraction. All evidence indicates that small highly crystalline α-Fe platelets act as active phase. Their surfaces are covered to a large extent by promotor compounds which are partly present as poorly crystalline aggregates with iron oxide leaving only a small fraction of elemental iron directly exposed to the gas phase. The intimate contact between iron crystals and promoters particles prevents recrystallisation and is the key to the understanding of the structural stability of the catalyst system.
    Type of Medium: Electronic Resource
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