Bismuth-containing SBA-15 mesoporous silica catalysts for solvent-free liquid-phase oxidation of cyclohexane by molecular oxygen

Bismuth (Bi)-containing SBA-15 mesoporous silica catalysts, Bi/SBA-15, with different Bi loadings were synthesized by a direct hydrothermal method. The materials were characterized in detail by various techniques. Powder-X-ray-diffraction (PXRD), N-2-adsorption/desorption, and transmission-electronmicroscopic (TEM) analyses revealed that the well-ordered hexagonal structure of SBA-15 is maintained after Bi incorporation. Diffuse-reflectance UV/VIS, Raman, and X-ray photoelectron spectroscopy (XPS) showed that the incorporated Bi-atoms are highly dispersed, most of them entering the internal surface of SBA-15. The new, very stable catalysts were found to be highly efficient for the oxidation of cyclohexane in a solvent-free system, molecular oxygen (02) being used as oxidant.