Heteropolyoxometalate Catalysts for Oxidation of Alcohols with H2O2 Under Green Condition

This work describes the use of hydrogen peroxide as an oxidant for the selective oxidation of cyclohexanol and benzyl alcohol under green condition using heteropolyoxometalates catalysts. The results showed that catalytic activity depended on types of countercation and metal of the catalysts. For transition metal-substituted polyoxotungstates [(n-C4H9)4N]4H[PW11M(H2O)O39], the catalytic order is Ni > Co > Mn. For a series of vanadium(V)-substituted polyoxotungstates [(n-C4H9)4N)]3+x[PW12-xVxO40], the catalytic activity decreased with increasing numbers of vanadium atoms in the catalyst. Using the [(n-C4H9)4N]4H[PW11Ni(H2O)O39] as a catalyst, cyclohexanol was oxidized to cyclohexanone with 98% yield and 100% selectivity at 90 °C in 5 h whereas benzyl alcohol was oxidized to benzaldehyde with 96% yield and 37% selectivity to benzaldehyde and 63% selectivity to benzoic acid at 90 °C in 12 h.