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  • 1
    Electronic Resource
    Electronic Resource
    Surface and subsurface products of the interaction of O2 with Ag under catalytic conditions (1991)
    Springer
    Catalysis letters 11 (1991), S. 253-265 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00764316
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the nature of the active state of silver during catalytic oxidation of methanol (1993)
    Springer
    Catalysis letters 22 (1993), S. 215-225 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00810368
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The dissociative adsorption of N2 on a multiply promoted iron catalyst used for ammonia synthesis: a temperature-programmed desorption study (1994)
    Springer
    Catalysis letters 24 (1994), S. 317-331 
    Details
    ISSN: 1572-879X
    Keywords: Nitrogen adsorption ; N2 TPD ; iron-based catalyst ; ammonia synthesis ; microkinetic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The temperature-programmed desorption (TPD) of N2 from a multiply promoted iron catalyst used for ammonia synthesis has been studied in a microreactor system at atmospheric pressure. From TPD experiments with various heating rates a preexponential factorA = 2 × 109 molecules/site s and an activation energyE = 146 kJ/mol was derived assuming second-order desorption. The observed dependence of the TPD peak shapes on the heating rates indicated the influence of readsorption of N2 in agreement with the results obtained for various initial coverages. Simulating the N2 TPD curves using the model by Stoltze and Nørskov revealed that the calculated TPD curves were not influenced by the molecular precursor to desorption. However, the calculated rate of readsorption was found to be overestimated at high coverage compared with the experimental results. A coverage-dependent net activation energy for dissociative chemisorption (E*) was introduced as the simplest assumption rendering the dissociative chemisorption of N2 activated at high coverage. The best fit of the experimental data yieldedE* = (−15+30θ) kJ/mol using only a single type of atomic nitrogen species. These findings are in satisfactory agreement with the parameters underlying the Stoltze-Nørskov model for the kinetics of ammonia synthesis as well as with the data reported for Fe(111) single crystal surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811804
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    Paper (German National Licenses)
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