MgAl and ZnAl layered double hydroxides modified with molybdate and tungstate anions as catalysts for oxidation of cyclohexane
Résumé
Catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone with H 2 O 2 was performed at a mild temperature of 40 °C and atmospheric pressure, using ZnAl or MgAl layered double hydroxides (LDHs) modified with tungstate and molybdate anions as catalysts in heterogeneous medium. The catalysts were prepared by direct anion exchange reactions of tungstate and molybdate on LDHs intercalated with chloride/carbonate anions. All the solids showed catalytic activity in the cyclohexane oxidation, with slight selectivity for the ketone product. The catalytic efficiency was sensitive to the M 2+ present in the composition of the LDH as well as to the anions. ZnAl-modified with WO 4 was more active and more selective for ketone than the MgAl-modified WO 4 or any molybdate-based LDH catalysts.
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