Oxidation of 2-hydroxycyclohexanone (2-HCO) which can be synthesized from both petroleum and biomass was investigated with heteropolyacids and oxygen as catalysts and oxidant, respectively. 2-Hydroxyadipic acid (2-HAA) was obtained in moderate yields, and H 4 PVW 11 O 40 gave the highest yield (39 %). 2-HAA is a dicarboxylic acid expected to be a monomer, and this work is the first report for production of 2-HAA by catalytic oxidation reactions. The oxidation of 1,2-cyclohexanedione (CHDO), which is a potential intermediate of 2-HCO oxidation, produced similar yield of 2-HAA even without catalyst. The effects of catalyst amount (first order), oxygen pressure (almost zero order) and the addition of radical scavenger (no effect) on the 2-HCO oxidation with H 4 PVW 11 O 40 catalyst were similar to those in a related case of 2-methoxycyclohexanone oxidation to adipic acid with heteropolyacid catalyst. 2-HCO is proposed to be oxidized to CHDO as a precursor of 2-HAA in a similar mechanism to 2-methoxycyclohexanone oxidation.
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