Heterogeneous oxidation of cyclohexane and ethylbenzene by transition metal-incorporated catalysis

Abstract

This study is to focus on the preparation of heterogeneous catalysts with high catalytic activities for oxidation of cyclohexane and ethylbenzene. Three classes of materials were studied: layered double hydroxides (LDHs) and their corresponding mixed metal oxides, polyoxometalates and metal incorporated xerogels. Transition metals chosen for the study are Co, Cu, Ni, Cr and Mn. The LDHs and mixed metal oxide catalysts were utilized for the oxidation of ethylbenzene with tert-butylhydroperoxide. The use of other oxidants such as hydrogen peroxide or air are also investigated. The Ni [subscript 4.8 ] Al and Cu [subscript1.0] Mg[subscript 2.9] Al oxide catalysts showed high activity with high acetophenone selectivity and they can be reused. Polyoxometalate catalysts possessing acid, alkali and alkyl ammonium cations were compared their activity towards oxidation of cyclohexane and ethylbenzene with hydrogen peroxide. The catalyst with alkyl ammonium showed the highest activity. Metal incorporated xerogel catalyst was appropriate to catalyze oxidation of cyclohexane in tert-butyl hydroperoxide as well as in air without any solvent. The activity order is Co > Cu > Mn > Cr > Ni. They showed no leaching into the reaction mixture