The oxidation with air of cyclohexanone was conducted in the presence of synthetic carbons catalysts. The effect of carbon activation treatment (CO2 or air burnoff), phosphorus additive, platinum loading, and nature of the solvent (water or water/acetic acid mixture) were studied. Cyclohexanone oxidation at 140 degrees C yielded a mixture of C6, C5, and C4 dicarboxylic acids. Air activated carbons, including those containing phosphorus or those supporting platinum, resulted in a higher yield of adipic acid. The activity and selectivity was associated with the oxygenated functional groups, essentially carbonyl/quinone groups, created during air activation of the carbon. The incorporation of phosphorus into the carbon increased slightly the selectivity to 34.3%, probably because this additive increased the density of oxygenated functional groups. The deposition of platinum by impregnation and liquid-phase reduction with formaldehyde increased the reaction rate and improved the selectivity to adipic acid, where the highest figure was 38.8%. It was suggested that platinum contributed to molecular oxygen activation. In contrast platinum deposition by cationic exchange followed by reduction under H2 resulted often in a detrimental effect probably because the density of the oxygenated groups on carbon is decreased upon H2 reduction in the presence of platinum. When the oxidation of cyclohexanone was carried out in mixtures of water/acetic acid, the selectivity given by the different samples were quite close and generally smaller than those obtained in water which indicates that acetic acid interacts with the oxygenated surface functional groups responsible for the activity and selectivity. Oxidation experiments with methyl-labeled 4-methylcyclohexanone indicated that glutaric acid was produced by oxidative decarbonylation of both the C1 and C2 carbon atoms of the molecule.

The gas-phase epoxidation of propylene using N 2 O, air and air-ammonia mixture as an oxidants was studied. Propylene can be epoxidized by nitrous oxide with a yield as high as 13.3% over silica supported iron oxide catalysts modified by amines. The iron oxide dispersion, the acidity of the support and the nitrogen-containing modifiers are the key factors determining the catalytic performance. We suggest a reaction pathway involving two concurrent mechanisms: the radical oxidation of propylene to acroleine, hexanediene, etc., and a non-radical oxidation leading to epoxide. Propylene is epoxidized with air over silica-supported iron oxide catalysts at a conversion of about 0.2%. Using air as an oxidizing agent, the presence of gaseous ammonia improves the propylene conversion by 10-fold preserving the considerable selectivity (up to 60%). This observation suggests a reaction mechanism involving the oxidation of ammonia to nitrous oxide in the first step, which subsequently produces active oxygen species, which selectively oxidize propylene to propylene oxide (PO).

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