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  • 2000-2004  (3)
  • 2000  (3)
  • oxidative dehydrogenation  (2)
  • Chebyshev polynomials  (1)
  • 1
    ISSN: 1572-879X
    Schlagwort(e): gallium oxide ; titanium oxide ; carbon dioxide ; oxidative dehydrogenation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Annals of the Institute of Statistical Mathematics 52 (2000), S. 557-573 
    ISSN: 1572-9052
    Schlagwort(e): Chebyshev polynomials ; convex combination ; extremal problems for polynomials ; Lagrange interpolation polynomial ; optimal discrimination designs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The extrapolation design problem for polynomial regression model on the design space [−1,1] is considered when the degree of the underlying polynomial model is with uncertainty. We investigate compound optimal extrapolation designs with two specific polynomial models, that is those with degrees |m, 2m}. We prove that to extrapolate at a point z, |z| 〉 1, the optimal convex combination of the two optimal extrapolation designs |ξ m * (z), ξ2m * (z)} for each model separately is a compound optimal extrapolation design to extrapolate at z. The results are applied to find the compound optimal discriminating designs for the two polynomial models with degree |m, 2m}, i.e., discriminating models by estimating the highest coefficient in each model. Finally, the relations between the compound optimal extrapolation design problem and certain nonlinear extremal problems for polynomials are worked out. It is shown that the solution of the compound optimal extrapolation design problem can be obtained by maximizing a (weighted) sum of two squared polynomials with degree m and 2m evaluated at the point z, |z| 〉 1, subject to the restriction that the sup-norm of the sum of squared polynomials is bounded.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1572-879X
    Schlagwort(e): dehydrogenation ; oxidative dehydrogenation ; cumene ; α-methylstyrene ; vanadium oxide ; activated carbon ; temperature-programmed reduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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