Oxidation of Cyclohexanone/Cyclohoxanol to Adipic Acid with H_2O_2 Using Phosphotungstic Acid as Catalyst

Cyclohexanone or the mixture of cyclohexanone and cyclohoexanol can be directly oxidized to adipic acid with 30% H_2O_2 in the presence of Na_2WO_4·2H_2O or H_7[P(W_2O_7)_6]·xH_2O without any phase transfer catalyst and organic solvent.The effects of amount of 30% H_2O_2,reaction time,temperature,amount of the catalyst,proportion of cyclohexanone to cyclohoexanol and oxalic acid on the oxidation reaction are investigated.The yield of adipic acid is 71.8% with Na_2WO_4·2H_2O as catalyst and oxalic acid as ligand at(90°C).When using H_7[P(W_2O_7)_6]·xH_2O as catalyst,95.1% yield of adipic acid can be reached at(90°C).In the absence of acidic ligand,H_7[P(W_2O_7)_6]·xH_2O can still perform very well in the oxidation of cyclohexanone or the mixture of cyclohexanone and cyclohoexanol.The yield of adipic acid can reach 87.5% or 82% under optimum conditions.