Choojun, Kittisak

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Choojun, Kittisak
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kittisak.ch@kmitl.ac.th

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    Item type:Publication,
    Effect of cobalt complex precursors on reactivity of cationic cobalt catalysts: Cyclohexane dehydrogenation
    (2019-05-10)
    Choojun, Kittisak
    ;
    Worathanaseth, Arucha
    ;
    Kuhatasanadeekul, Satu
    ;
    Kurato, Teeraporn
    ;
    Ketaniruj, Supanut
    Effect of the cobalt precursors, including [Co(bipy)<inf>3</inf>](NO<inf>3</inf>)<inf>2</inf>, [Co(NH<inf>3</inf>)<inf>5</inf>Cl]Cl<inf>2</inf>, [Co(NH<inf>3</inf>)<inf>6</inf>]Cl<inf>3,</inf> and [Co(en)<inf>2</inf>Cl<inf>2</inf>] Cl, on reactivity of the cationic Co/SiO<inf>2</inf> prepared by strong electrostatic adsorption (SEA) was investigated for the dehydrogenation of cyclohexane as a model reaction. According to the charge density of the cobalt complex, highly dispersed Co<sup>2+</sup> species and/or Co<sup>3+</sup> oxide can be obtained on the silica surface. The dehydrogenation activity is in the order of Co/SiO<inf>2</inf> catalysts prepared by [Co(bipy)<inf>3</inf>](NO<inf>3</inf>)<inf>2</inf> > [Co(NH<inf>3</inf>)<inf>5</inf>Cl]Cl<inf>2</inf> > [Co(NH<inf>3</inf>)<inf>6</inf>]Cl<inf>3</inf> > [Co(en)<inf>2</inf>Cl<inf>2</inf>] Cl, correlating to the Co<sup>2+</sup> content of the final catalysts. The cationic cobalt catalysts are more active than the pre-reduced one. Although metallic cobalt is found to be less active, the activity of cationic cobalt catalyst is enhanced under H<inf>2</inf> flow, presumably due to the formation of cobalt hydride intermediate. The inter-conversion of Co<sup>2+</sup>/cobalt hydride intermediate is readily reversible and regulated by presence of hydrogen.