Oxidation of cyclohexanone and/or cyclohexanol catalyzed by Dawson-type polyoxometalates using hydrogen peroxide

The oxidation of cyclohexanone, cyclohexanol or cyclohexanone/cyclohexanol mixture using as catalyst, Dawson-type polyoxometalates (POMs) of formula, α- and β-K 6 P 2 W 18 O 62 , α-K 6 P 2 Mo 6 W 12 O 62 and α1-K 7 P 2 Mo 5 VW 12 O 62 and hydrogen peroxide, carried out at 90 °C with a reaction time of 20 h, led to a high number of mono- and di-acids which were identified by GC-MS. Levulinic, 6-hydroxyhexanoic, adipic, glutaric and succinic acids, major products were evaluated by HPLC. Regardless of the substrate nature, all POMs exhibited high catalytic activity with 94–99% of conversion, whereas the formation of the different products is sensitively related to both the composition and symmetry of the POMs and the substrate nature. The main products are adipic acid in the presence of α-K 6 P 2 Mo 6 W 12 O 62 and α1-K 7 P 2 Mo 5 VW 12 O 62 , levulinic acid in the presence of α1-K 7 P 2 Mo 5 VW 12 O 62 and β-K 6 P 2 W 18 O 62 and 6-hydroxyhexanoic acid in the presence of α- and β-K 6 P 2 W 18 O 62 . Graphical abstract High catalytic activity was observed with α- and β-K 6 P 2 W 18 O 62 , α-K 6 P 2 Mo 6 W 12 O 62 and α1-K 7 P 2 Mo 5 VW 12 O 62 Dawson-type for the oxidation of cyclohexanone, cyclohexanol or cyclohexanone/cyclohexanol mixture, in the hydrogen peroxide presence, to several oxygenated products. Adipic, levulinic and 6-hydroxyhexanoic acids are the main products. The peroxo- species formed in situ could be the active sites.