Dawson-type polyoxometalates as green catalysts for adipic acid synthesis

Article abstract of DOI:10.1016/j.molcata.2015.12.014

Dawson-type POMs series of formula α- and β-K₆P₂W₁₈O₆₂ isomers, α1- and α2-K₆P₂Mo₅W₁₃O₆₂ isomers, α-K₆P₂Mo₆W₁₂O₆₂ isomer and α1-K₇P₂Mo₅VW₁₂O₆₂ isomer, have been used as catalysts for the liquid phase oxidation of cyclohexanol, cyclohexanone and cyclohexanol/cyclohexanone mixture to form adipic acid in presence of hydrogen peroxide without solvent, without phase-transfer agents and without adding acid. ³¹P NMR spectroscopy of different POMs after cyclohexanol oxidation showed the formation of new active species that can be attributed to "peroxo-POMox" form. An adipic acid yield of 69% was obtained from the oxidation of a mixture of cyclohexanol (50%) and cyclohexanone (50%) with α-K₆P₂Mo₆W₁₂O₆₂ isomer.