Cyclohexanone from Cyclohexane and O2 in a Zeolite under Visible Light with Complete Selectivity

Irradiation of a cyclohexane and O2-loaded zeolite NaY with green or blue light resulted in oxidation of the alkane to cyclohexyl hydroperoxide and cyclohexanone (plus water) as the sole products. The hydroperoxide was found to rearrange thermally to cyclohexanone without side reaction. Complete selectivity in terms of the final oxidation product cyclohexanone persists even at high (>40%) conversion of cyclohexane. The chemistry was monitored by in-situ FT-infrared spectroscopy and the visible reactant absorption by diffuse reflectance spectroscopy. The absorption is attributed to the cyclohexane·O2 charge-transfer transition, which is shifted from the UV into the visible by the very high electrostatic field of the zeolite matrix cage. At elevated temperature, cyclohexane is thermally oxidized by O2 to the same products.