Synthesis of adipic acid catalyzed by surfactant-type peroxotungstates and peroxomolybdates

Four surfactant-type peroxotungstates and peroxomolybdates have been synthesized and characterized. Their catalytic activities for 30 wt.% H2O2 oxidation of cyclohexene, cyclohexanol, cyclohexanone and 1,2-cyclohexanediol to adipic acid were evaluated without organic solvent and phase-transfer catalyst. The surfactant-type polyoxoperoxometalates act as not only a catalyst but also a phase-transfer agent, which can form the emulsion droplets. The emulsion droplets are in the highly dispersed form and behave like homogeneous catalysts with high activities. Long carbolic chain cation assembled in the interface of the emulsion droplets, peroxotungsten anion-containing catalysts exhibited high activities. However, peroxomolybdenum anion-containing catalysts exhibited low activities.