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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 57 (1999), S. 209-215 
    ISSN: 1572-879X
    Schlagwort(e): 1-butene ; skeletal isomerization ; mesoporous material ; acid site concentration ; monomolecular reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1572-879X
    Schlagwort(e): 1-butene ; skeletal isomerization ; fluorine-modified alumina ; acid site concentration ; monomolecular reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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