Novel and efficient cobalt encapsulated SBA-15 catalysts for the selective oxidation of cyclohexane

Co-SBA-15 catalysts were synthesized by direct synthesis and post-synthetic impregnation methods at two different loadings of Co viz., 1.2 and 2 wt%. The structure of SBA-15 was found to remain intact even after the incorporation of Co in either of the two methods of catalyst preparation, which was confirmed by low-angle XRD. The existence of Co2+ species were confirmed by characteristic absorption bands of Co in the UV–vis spectra and XPS results. The encapsulation of Co in SBA-15 was found to be highly advantageous in yielding significant amounts of the desired products viz., cyclohexanone and cyclohexanol in the oxidation of cyclohexane in liquid phase without using any solvent under moderate pressure of O2 at 433 K. The catalysts showed high turn over numbers towards the oxidation of cyclohexane to cyclohexanone and 2%CoSYN (2 wt% Co-SBA-15) catalyst showed a maximum of 9.4% conversion of cyclohexane and 78% selectivity towards the formation of cyclohexanone.