Clean Oxidation of Cyclohexanone to Adipic Acid Catalyzed by Ammonium Phosphomolybdate with Dawson Structure under Microwave Irradiation

Ammonium Phosphomolybdate with Dawson structure was prepared by hydrothermal synthesis and characted by means of FT-IR, UV-Vis,XRD and SEM. The synthesis of adipic acid with cyclohexanone and 30 percent hydrogen peroxide under microwave irradiation was carried out as a probe reaction to study the catalytic activity. Effects of catalyst amount,30wt.% H2O2 amount,microwave power, reaction time were investigated and optimized with orthogonal experiments and simple fact experiments. The results show that under the optimal condition, i.e. the mole ratio of C6H10O: H2O2:H2C2O4•2H2O:(NH4)6P2Mo18O62•nH2O =100:500:2.0:0.087, the reaction temperature was 100°C, microwave power was 400W, irradiation time was 3.5 h，the isolated yield of adipic acid could reach 72.5%．The catalyst could be reused for 5 times and the isolated of adipic acid was still above 43.2%.