Catalytic oxidation with air of cyclododecanone and 3,3,5-trimethylcyclohexanone to the corresponding linear dicarboxylic acids over synthetic carbons

Cyclododecanone and 3,3,5-trimethylcyclohexanone were oxidised with air in an attempt to prepare 1,12-dodecanedioic and 2,2,4- or 2,4,4-trimethyladipic acids, respectively. These long-chains dicarboxylic acids are useful for polymer synthesis. Oxidation was conducted on metal-free and platinum-loaded carbon catalysts activated in air or CO2. The influence of catalyst preparation and of reaction parameters on the activity and selectivity to the corresponding linear diacids has been studied. In parallel with oxidation reaction giving the long-chain C12 diacids, oxidative cleavage reactions occur leading to C4-C11 dicarboxylic acids. The air-activated carbon SA yielded the best selectivity to the desired long-chains diacids (25-30%). Selectivity was also improved by operating at 125 °C and 40 bar of total air pressure and by diluting the cyclic ketones in acetic acid, pure or containing 20% water.