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  • Artikel: DFG Deutsche Nationallizenzen  (5)
  • Digitale Medien  (5)
  • 1995-1999  (5)
  • 1
    Digitale Medien
    Digitale Medien
    The activation of O2 and the oxidative dehydrogenation of C2H6 over SmOF catalyst (1996)
    Springer
    Catalysis letters 40 (1996), S. 101-104 
    Details
    ISSN: 1572-879X
    Schlagwort(e): ethane oxidative dehydrogenation ; O2 activation ; SmOF ; dioxygen species and mono-oxygen species
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The activation of O2 over SmOF was studied by in situ laser Raman spectrometry and temperature programmed desorption (TPD). When the hydrogen- and helium-treated (1 h for each gas at 973 K) SmOF sample was cooled to 303 K in oxygen, Raman bands which correspond to the existence of O 2 2− , O 2 n− (2 〉n 〉 1), O 2 − and O 2 δ- (1 〉δ 〉 0) species were observed. From 303 to 973 K, there was no O2 desorption but the Raman bands observed at 303 K reduced in intensity and vanished completely at 973 K, even though the sample was under an atmosphere of oxygen. We suggest that as the sample temperature increased, dioxygen species were converted to mono-oxygen species such as O− which were undetectable by Raman spectrometry. O2 desorption occurred above 973 K, giving a TPD-peak at 1095 K. When C2 H6 was pulsed over the sample pretreated with oxygen and helium at 973 K, C2H4 selectivity was 91.8%. We conclude that the mono-oxygen species is responsible for the oxidative dehydrogenation of ethane to ethene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807464
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  • 2
    Digitale Medien
    Digitale Medien
    Methane activation over unsupported and La2O3-supported copper and nickel catalysts (1996)
    Springer
    Catalysis letters 36 (1996), S. 159-163 
    Details
    ISSN: 1572-879X
    Schlagwort(e): methane activation ; Cu/La2O3 and Ni/La2O3 catalysts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Methane was pulsed over pure CuO and NiO as well as Cu/La2O3 and Ni/La2O3 catalysts at 600° C. Results indicate that the mechanisms for methane activation over copper and nickel are quite different. Over CuO, methane is converted to CO2 and H2O, most likely via the combustion mechanism; whereas metallic copper does not activate methane. Over NiO in the presence of metallic nickel sites, methane activation follows the pyrolysis mechanism to give CO, CO2, H2 and H2O. Similar results were obtained over the Cu/La2O3 and Ni/La2O3 catalysts. XRD investigations indicate that copper and nickel existed as CuLa2O4 and LaNiO3 respectively in the La2O3-supported catalysts. The effect of La2O3 on the activation of methane is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807613
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  • 3
    Digitale Medien
    Digitale Medien
    Preparation and characterization of rare earth orthovanadates for propane oxidative dehydrogenation (1996)
    Springer
    Catalysis letters 37 (1996), S. 241-246 
    Details
    ISSN: 1572-879X
    Schlagwort(e): rare earth orthovanadates ; citrate method ; propane oxidative dehydrogenation ; redox property
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract High purity rare earth orthovanadates (REVO4), YVO4, LaVO4, CeVO4, NdVO4, SmVO4 and EuVO4, were prepared by the citrate method. XRD, FT-IR, LRS and TPR techniques were employed to characterize these orthovanadates. The catalytic performance of SmVO4, LaVO4 and YVO4 in the oxidative dehydrogenation of propane can compete with that of Mg3V2O8. The selectivity of propene over CeVO4, NdVO4 and EuVO4 was relatively lower. The correlation between the reducibility and the selectivity of the catalysts implied that the V4+/V3+ couple might be involved in the dehydrogenation process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807761
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  • 4
    Digitale Medien
    Digitale Medien
    Pulse study of methane partial oxidation to syngas over SiO2-supported nickel catalysts (1996)
    Springer
    Catalysis letters 41 (1996), S. 159-163 
    Details
    ISSN: 1572-879X
    Schlagwort(e): methane oxidation ; syngas ; SiO2-supported nickel (Ni/SiO2) ; deuterium isotope effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The reaction behaviors of CH4/O2 (2/1) with unreduced and reduced SiO2-supported nickel (10 wt% metal) catalysts were investigated in a pulse micro-reactor at temperatures ranging from 600 to 800° C. In the interaction of CH4/O2 with unreduced NiO/SiO2, the products are exclusively CO2 and H2O at or below 700°C. At 800° C, besides CO2 and H2O, CO and H2 are formed. The reactivity at 800°C can be ascribed to the net generation of metallic nickel site at this temperature. In the reaction of CH4/O2 over reduced Ni/SiO2, the main products are CO and H2 with CO2 and H2O being the minor ones. The results indicate metallic nickel is the active site for methane partial oxidation to syngas. Normal deuterium isotope effects of similar magnitude were observed on the overall, as well as on the CO and CO2 formation reactions with insignificant change in the product selectivities when CD4 was used instead of CH4, indicating that methane dissociation is a key step and that CO and CO2 are formed via some common intermediates which are subject to kinetic deuterium isotope effect. The results of deuterium isotope effects can be reasonably explained based on the methane pyrolysis mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00811484
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  • 5
    Digitale Medien
    Digitale Medien
    An ab initio study of methane activation on lanthanide oxide (1997)
    Springer
    Catalysis letters 49 (1997), S. 53-58 
    Details
    ISSN: 1572-879X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Ab initio MP2 calculations have been carried out to study the activation of methane on lanthanide oxide La2O3. O- and O2 2- are assumed to be the active species on the oxide surface. The possible roles of O2- and O2 4- on the oxide surface in C-H bond activation are also investigated. It is shown that the CH4 oxidative dehydrogenation occurs much more readily on O- and O2 2- than on O2- and O2 4-. The results indicate that O- and O2 2- are the active species and therefore support the O- and O2 2- mechanisms assumed for the reactions. The promoter compound containing Br- is found to be favorable for the methane activation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019040902099
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