Heteropolyoxometalate Catalysts for Oxidation of Alcohols with H2O2 Under Green Condition

Abstract

This work describes the use of hydrogen peroxide as an oxidant for the selective oxidation of cyclohexanoland benzyl alcohol under green condition using heteropolyoxometalates catalysts. The results showed thatcatalytic activity depended on types of countercation and metal of the catalysts. For transition metal-substitutedpolyoxotungstates [(n-C4H9)4N]4H[PW11M(H2O)O39], the catalytic order is Ni > Co > Mn. For a series ofvanadium(V)-substituted polyoxotungstates [(n-C4H9)4N)]3+x[PW12-xVxO40], the catalytic activity decreasedwith increasing numbers of vanadium atoms in the catalyst. Using the [(n-C4H9)4N]4H[PW11Ni(H2O)O39] as acatalyst, cyclohexanol was oxidized to cyclohexanone with 98% yield and 100% selectivity at 90°C in 5 hwhereas benzyl alcohol was oxidized to benzaldehyde with 96% yield and 37% selectivity to benzaldehyde and63% selectivity to benzoic acid at 90°C in 12 h. Key Words: Heteropolyoxometalate; Oxidation; Alcohols; Hydrogen peroxide