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  • SiO2-supported nickel (Ni/SiO2)  (1)
  • citrate method  (1)
  • ethane oxidative dehydrogenation  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 40 (1996), S. 101-104 
    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
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 37 (1996), S. 241-246 
    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
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 41 (1996), S. 159-163 
    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
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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