A green method of adipic acid synthesis: organic solvent- and halide-free oxidation of cycloalkanones with 30% hydrogen peroxide

Cyclohexanone and cyclohexanol are oxidized to adipic acid in high yield with aqueous 30% H2O2 in the presence of H2WO4 as a catalyst under organic solvent- and halide-free conditions. It is important that no solvent is used in order to achieve high reactivity in this heterogeneous reaction. The use of t-butyl alcohol or dioxane as a solvent (homogeneous conditions) significantly decreases the yield of adipic acid from cyclohexanone. This ketone-to-dicarboxylic acid conversion is applicable to five- to eight-membered cyclic ketones. No operational problems are foreseen for a large-scale version of this green process.