AA Various Oxidants Included

2 Heterogeneous Catalysis for Cyclohexane Oxidation to Either Ol/One or AA (Various Oxidants Included) 

With MnAPO-5, the activity in the aerobial oxidation of cyclohexane to Ol/One increased linearly with the number of redox-active sites, since the reaction involves cycling between Mn(II) and Mn(III). Therefore, the reaction requires cation sites able to reversibly form charge-balancing cationic species [24f[. 

Besides MeAPO, several heterogeneous systems have been proposed for the oxidation of cydohexane vith various oxidants [2c], but almost all of them yield 01/ One as the main reaction products, with AA being only a minor product. Heterogeneous catalysts can be either oxides or metal cations and complexes incorporated on inorganic matrixes, such as active carbon, zeolites, aluminophosphates or conventional supports such as alumina and silica. The activity of these systems is greatly affected by the choice of solvent, which determines the polarity of the medium. In addition, the hydrophobicity of the support is important, since a hydrophobic environment rapidly expels the oxidized products from the reaction zone. When oxygen is used as the oxidant, these systems often need small amounts of hydroperoxides as co-catalysts. 

Examples of heterogeneous catalysts for the oxidation of cyclohexane to Ol/One or to AA with various oxidants include [25-27]  

Nano Au particles supported on mesoporous materials (SBA-15, MCM-41), which catalyze the oxidation of cyclohexane to Ol/One with oxygen, without solvent (conv. 18%, selectivity 93%) [25a]. Similar performance is obtained when Au is dispersed over other supports, for example, silica, alumina or titania [25b, c, d[. 

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