Catalytic Oxidation of Cyclohexene to Adipic Acid over Heteropolyacids

The oxidation of cyclohexene to adipic acid catalyzed by heteropolyacids has been investigated, using 30% aqueous hydrogen peroxide as an oxidant, and dicarboxylic acids or 8 hydroxyquinoline as cocatalyst. Adipic acid in yield up to 75 0% was obtained in 6 h, in the presence of 8 hydroxyquinoline. When oxalic acid was used as cocatalyst in condition of 92 ℃, 6 h, n (cyclohexene)∶ n (H 3 PW 12 O 40 )∶ n (H 2 C 2 O 4 )∶ n (H 2 O 2 )=100∶1∶1∶538, the yield of adipic acid was 70.1%. When cetyltrimethyl ammonium bromide or cetylpyridinium bromide was used as phase transfer catalyst, the yield of adipic acid was 73 1% and 71 6% respectively. Catalytic oxidation of cyclohexene oxide or trans 1,2 cyclohexanediol to adipic acid over tungtophosphoric acid were also carried out in order to confirm the reported mechanism of the reaction.