SELECTIVE OXIDATION OF CYCLOHEXANE BY AN IRON PALLADIUM BICATALYTIC SYSTEM UNDER MILD CONDITIONS - IRON-OXIDE SILICA CATALYSTS

In situ oxidation of cyclohexane to cyclohexanol and cyclohexanone was investigated with hydrogen peroxide produced from hydrogen and oxygen at a temperature of 30-degrees-C and under atmospheric pressure. Three kinds of iron oxide/silica catalysts were prepared from ferric chloride, ferric nitrate and ferric hydroxide and the catalysts were characterized by X-ray fluorescence, X-ray diffraction and X-ray photoelectron spectroscopy and their activities were examined. The effective species of catalyst was found to be Fe2O3 on silica. Changing the iron starting materials affects the dispersity of iron oxide on silica, thereby resulting in a difference of catalytic activity. The catalyst originating from ferric hydroxide shows the highest dispersity and activity per unit atom of iron. The formation of a fine crystallite of iron oxide is important to increase the activity of the catalyst as is shown by the fact that catalytic activity is increased by decreasing the iron content of the catalyst.