The liquid-phase oxidation of cyclohexanone with oxygen, catalysed by Keggin-type polyoxometalates. A cleaner alternative to the current process for adipic acid synthesis

The principal industrial process for adipic acid production is done in two-steps. The first step is the oxidation of cyclohexane with air to a mixture of cyclohexanol and cyclohexanone, the second step is the oxidation with a large excess of HNO3. The co-product of the oxidation with nitric acid are nitrogen oxides; NO and NO2 can be reoxidized and recycled, whereas N2O is a pollutant gas that has to be abated before emissions of tail gases into the atmosphere. The study of an alternative synthethic pathway in which air is the oxidising agent is a fascinating challenge of the modern chemistry. In the present communication, we report about a study on the reactivity of Keggin-type P/Mo/V polyoxometalates (POMs) in the oxidation of cyclohexanone to AA with oxygen.