Abstract: In this paper, a new “green” route to the synthesis of adipic acid is reported. This environmentally benign synthesis of adipic acid involves in the direct oxidation of cyclohexene catalyzed by Na₂WO₄·2H₂Owith 27.5% aqueous hydrogen peroxide using alkyl ammonium sulfate as a phase transfer agent. The results show that N,N-dimethyl-dodecylammonium sulfate, dodecylammonium sulfate and tri-n-octylammonium sulfate can be used as efficient phase transfer agents for this reaction under refluxing temperature. After the reaction is stopped, the homogeneous solution was cooled to 0 ℃ for 12 h. Then the crystalline product was collected by filtration and dried in air, a colorless, analytically pure product adipic acid was obtained in_52.1%—94.1% yields. The catalyst in concentrated filtrate can be reused.

Key words: Adipic acid, Cyclohexene, Catalytic oxidation, Phase transfer agent