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  • 1
    ISSN: 1572-879X
    Keywords: methanol synthesis ; copper catalyst ; oxygen coverage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The coverage of oxygen formed on the surface of catalysts during methanol synthesis from CO2 has been measured for copper-based catalysts including various metal oxides using a method called reactive frontal chromatography (RFC). An excellent correlation between the specific activity for methanol synthesis and the oxygen coverage (θ) was obtained, where the activity increased linearly with oxygen coverage atθ〈0.16 and then decreased atθ〉0.18. The results strongly indicate that the support effect or addition of metal oxides revealed in methanol synthesis over copper catalysts is ascribed to the ratio of Cu+ to Cu0 on the surface of copper particles.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-879X
    Keywords: methanol synthesis ; copper catalyst ; role of ZnO ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methanol synthesis by the hydrogenation of CO2 over Zn-deposited polycrystalline Cu was studied using surface science techniques. The Zn sub-monolayer was oxidized by the reaction mixture during the reaction at 523 K, leading to the formation of ZnO species. The kinetic results definitely showed that the ZnO species on the Cu surface promoted the catalytic activity of methanol formation, where the activity of Cu increased by a factor of 6 at the Zn coverage of 0.17. A volcano-shaped curve was obtained for the correlation between the Zn coverage and the catalytic activity, which was very similar to the correlation curve between the oxygen coverage and the specific activity for methanol formation previously obtained for the Cu powder catalysts. The role of ZnO in Cu/ZnO based catalysts was ascribed to the stabilization of Cu+ species by the ZnO moieties on the Cu surface.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-6079
    Keywords: 34.50.Hc ; 32.80.Hd ; 32.80.Kf ; 32.30.Rj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the target thickness dependence ofK-vacancy production probabilities and total cross sections for 40.6 MeV Ar ions hitting Ca and Cu targets. The probabilities were measured as a function of the scattering angle between 0.13° and 1.4° by means of aK x-ray-particle coincidence. By integrating the measured probabilities over the impact parameter a significantly lower total cross section was obtained than the directly measured value. The maximum seen in the impact parameter dependent probability varies with decreasing target thickness towards the results obtained with molecular and atomic gas targets. From these observations a multiple collisionL-vacancy process prior to 2pπ-2pσ rational coupling is concluded.
    Type of Medium: Electronic Resource
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