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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 13 (1992), S. 143-152 
    ISSN: 1572-879X
    Keywords: Methane ; conversion ; oxidative dehydrogenation ; cations ; sulphates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidative coupling of methane has been studied on Mg, Ca, Sr and Ba sulphate. The conversions and selectivities are found to be dependent on the nature of the cation and to be approximately correlated with their electronegativities, thus implying that the C-H bond scission in CH4, at least with these catalysts, is heterolytic, is rate determining, and further, that the formation of C2+ hydrocarbons is dependent, among other factors, on the concentration of methyl radicals.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-879X
    Keywords: metal-oxygen cluster compounds ; heteropoly acids ; stability ; pH ; aqueous solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The stabilities of the solid superacids H3Mo12O40, H3PW12O40, H4SiMo12O40 and H4SiW12O40 in aqueous solution have been measured at various values of pH by use of ion chromatographic analyses. The aforementioned acids are completely decomposed at values of pH, 4.0, 5.2, 7.0 and 11.0, respectively. The stabilities in aqueous solution with respect to pH follow the order H4SiW12O40 〉 H3PW12O40 〉 H4SiMo12O40 〉 H3PMo12O40.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 16 (1992), S. 389-398 
    ISSN: 1572-879X
    Keywords: Methane ; oxidative dehydrogenation ; zirconium oxide ; hydroxyl ; steaming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zirconium oxide is shown to be capable of catalyzing the conversion of methane to ethane at temperatures as low as 530 °C. The lowest temperature at which ethane is produced is found to be dependent upon the method employed for the preparation of the catalyst. The presence of surface hydroxyl groups appears to be necessary for the production of ethane at these low temperatures.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 42 (1996), S. 105-111 
    ISSN: 1572-879X
    Keywords: 1-butene ; isomerization ; isobutene ; 12-tungstophosphoric acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract On 12-tungstophosphoric acid (HPW) supported on silica, 1-butene is isomerized to cis- and trans-2-butene at 100°C and higher while a temperature of 150°C is required to form isobutene. While the conversion remains at 80–90% regardless of the loading of HPW on the support and the reaction temperature, the selectivity to isobutene reaches a maximum of 33% at a loading of 23% HPW/SiO2 and 300–350°C. Small quantities of C n (n = 3,..., 8) species are also formed. These results together with those from ammonia poisoning, temperature-programmed desorption of ammonia,1H MAS NMR and infrared spectroscopy show that HPW/SiO2 possesses sites of strength as high as or higher than those on HZSM-5, that such sites are required for the skeletal isomerization process and that both mono- and bimolecular processes are occurring on the catalyst. The absence of dependence of conversion of 1-butene and selectivities to cis- and trans-2-butene on loading and reaction temperature can best be rationalized on the basis of a rapid attainment of an equilibrium between the aforementioned three species and sec-butyl carbenium ions from which pool the energy barrier to the primary butyl carbenium and hence to isobutene is surmounted, given appropriate conditions.
    Type of Medium: Electronic Resource
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