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  • 2000-2004  (2)
  • 1995-1999  (2)
  • 1965-1969
  • monomolecular reaction  (2)
  • oxidative dehydrogenation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Promoting effect of carbon dioxide on the dehydrogenation and aromatization of ethane over gallium‐loaded catalysts (2000)
    Springer
    Catalysis letters 64 (2000), S. 215-221 
    Details
    ISSN: 1572-879X
    Keywords: gallium oxide ; titanium oxide ; carbon dioxide ; oxidative dehydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ga2O3 and Ga2O3/TiO2 catalysts were found to be effective agents for the dehydrogenation of ethane to ethene in the presence of carbon dioxide at 650 °C. The activity of the Ga2O3 and Ga2O3/TiO2 catalysts in the presence of CO2 was 2–4 times higher than that without CO2. Ethene yields reached ca. 20–25% and selectivity was ca. 70–90% at 650°C in the 17% ethane and 83% CO2 feed at an SV of 9,000 ml/(g‐cat h). The presence of CO2 markedly promoted dehydrogenation of ethane over Ga2O3 and Ga2O3/TiO2 catalysts. Furthermore, the promoting effect of CO2 on the aromatization of ethane and ethene over a Ga2O3+H/ZSM‐5 catalyst was also observed above 650 °C. Aromatics yields were higher than those without CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019047306179
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Skeletal isomerization of 1-butene over mesoporous materials (1999)
    Springer
    Catalysis letters 57 (1999), S. 209-215 
    Details
    ISSN: 1572-879X
    Keywords: 1-butene ; skeletal isomerization ; mesoporous material ; acid site concentration ; monomolecular reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract On the skeletal isomerization of 1-butene, mesoporous materials with mesopores too large to expect any shape selectivity have been used in order to investigate the effects of the concentration of acid sites on the conversion of 1-butene and the selectivity for isobutene. The concentrations of acid sites can be varied through the control of the Si/Al ratio. The conversion of 1-butene increases with increasing the aluminium content of mesoporous materials, while the selectivity for isobutene decreases. The results of ammonia TPD, IR measurement of 1-butene adsorption, and TG analysis of used catalysts indicate that distant location of activated 1-butene molecules induces the monomolecular reaction over the mesoporous materials with low aluminium content, resulting in high selectivity for skeletal isomerization. On the mesoporous material with high aluminium content, however, the high concentration of activated 1-butene molecules accelerates the multimolecular oligomerization and, thus, reduces the selectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019028522765
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of the fluorine loading level on the skeletal isomerization of 1-butene over fluorine-modified alumina (1998)
    Springer
    Catalysis letters 51 (1998), S. 101-107 
    Details
    ISSN: 1572-879X
    Keywords: 1-butene ; skeletal isomerization ; fluorine-modified alumina ; acid site concentration ; monomolecular reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract γ-alumina catalysts modified with different weight loadings of fluorine have been used for skeletal isomerization of 1-butene in order to investigate the effects of the fluorine loading level on the conversion of 1-butene and the selectivity to isobutene formation. Increasing the actual loading of fluorine up to 0.012 wt% led to an increase in conversion of 1-butene over fluorine-modified γ-alumina catalysts, while the high selectivity to isobutene remains almost unchanged. On the other hand, a clear trend of increasing 1-butene conversion with a decreasing selectivity to isobutene is observed for the γ-alumina catalysts with higher loadings of fluorine. An analysis of the results from the thermal analysis, NH3 temperature-programmed desorption, infrared and the 1-butene sorption measurments clearly indicates that the number of strong acid sites in the modified γ-alumina catalysts is greatly enhanced at fluorine loadings higher than 0.012 wt%, leading to the acceleration of 1-butene oligomerization followed by cracking to light hydrocarbons. Therefore, the 1-butene isomerization selectivity from fluorine-modified γ-alumina catalysts can be understood in terms of a competition between the monomolecular and bimolecular reaction pathways, which highly depend on the concentration of strong acid sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019037017971
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dehydrogenation of isopropylbenzene with vanadium-oxide-loaded activated carbon catalyst in the presence of carbon dioxide (2000)
    Springer
    Catalysis letters 69 (2000), S. 59-64 
    Details
    ISSN: 1572-879X
    Keywords: dehydrogenation ; oxidative dehydrogenation ; cumene ; α-methylstyrene ; vanadium oxide ; activated carbon ; temperature-programmed reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dehydrogenation of isopropylbenzene to α-methylstyrene was carried out using various supported metal oxide catalysts in the presence of carbon dioxide. An activated carbon-supported vanadium oxide catalyst afforded a high activity in carbon dioxide atmosphere: the α-methylstyrene yield in carbon dioxide atmosphere was two times greater than that in an argon atmosphere at 723 K. In order to investigate the role of carbon dioxide in this reaction, we carried out temperature-programmed reduction (TPR) studies using both fresh and used catalysts. The TPR profiles clearly indicate that carbon dioxide could keep the surface of vanadium oxide at a high oxidation state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019084915149
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    Paper (German National Licenses)
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