Heterogeneous Catalysis in the Liquid-phase Oxidation of Olefins. IV. The Activity of a Supported Vanadium or Chromium Oxide Catalyst in the Decomposition of t-Butyl Hydroperoxide

Abstract

Abstract The liquid-phase decomposition of t-butyl hydroperoxide (t-BuOOH) has been carried out in benzene under an N2 atmosphere using a vanadium or chromium oxide, supported on γ-Al2O3 or SiO2 as the catalyst, for the purposeof clarifying the reaction mechanism of the cyclohexene oxidation. The decomposition of t-BuOOH on the supported oxide catalyst was a first-order reaction; the main products were t-butyl alcohol, di-t-butyl peroxide, and acetone, suggesting that t-BuOOH is decomposed homolytically on the catalyst by the Haber-Weiss mechanism. The effect of the vanadium–chromium binary system formation was small, but the interaction between metal oxides and the supports appeared to be important in the t-BuOOH decomposition. Tetrahedrally co-ordinated vanadium species were formed on SiO2 and showed the highest activity, followed by the chromium co-ordinated tetrahedrally on SiO2 or on γ-Al2O3, while an octahedrally co-ordinated vanadium or chromium showed low activity. Such order of the activity was in good agreement with that obtained in the liquid-phase oxidation of cyclohexene. We observed a relatively good correlation between the catalytic activity and the acidity of the supported binary metal oxides. The V2O5–SiO2 system showed an especially large acidity; here t-butyl alcohol was dehydrated into di-t-butyl ether and 2-methyl propene.