Selective oxidation of cyclohexane to KA-oil with oxygen over active Co₃O₄in a solvent-free system

Abstract

Heterogeneous oxidation of liquid cyclohexane with molecular oxygen was carried out in a solvent-free system initiated by various catalysts and additives. Among those catalysts tested, the Co₃O₄ catalyst prepared by a simple calcination at 550 °C was relatively active for the oxidation of cyclohexane to KA-oil (a mixture of cyclohexanone and cyclohexanol), and could achieve about 9.2 mol% conversion of cyclohexane and 92.7 % selectivity of KA-oil at 130 °C under the pressure of 1.0 MPa O₂ for 2 h, comparable to those of Co₃O₄ nanocrystals and Co/ZSM-5. This would help to widen the scope of the catalysts available for the titled oxidation. The use of peroxides and NHPI as the initiators without any catalyst could lead to the occurrence of non-catalytic oxidation of cyclohexane as well.