ROLE OF COBALT MOLECULAR-SIEVES IN THE LIQUID-PHASE OXIDATION OF CYCLOHEXANE TO ADIPIC ACID

The catalytic activity of CoAPO-5 in the oxidation of cyclohexane to a dipic acid has been re-examined in order to specify the actual role of the solid. It was shown that the catalytic activity in acetic acid wa s ascribable to the leaching of cobalt. The activity of CoAPO-5 was co mparable to that of cobalt(II) acetate at very low concentration. Surp risingly, a maximum of activity was found at 0.17 mmol dm(-3), which c orresponds to the concentration of cobalt leached from the solid in th e reaction. Such a concentration is far below the concentration usuall y used for homogeneous catalysis. Variations in adipic acid selectivit y, which followed the variations in activity, were interpreted by chan ges in mechanism.