Selective Oxidation of Cyclohexane over Transition-Metal-Incorporated HMS in a Solvent-Free System

Mesostructure materials A-HMS (A = Ce, Ti, Co, Al, Cr, V, Zr) were synthesized with cetylamine as the structure director and tetraethyl orthosilicalite as the silica source. CeO2/V-HMS and CeO2/Al-HMS were prepared by dipping-calcination method. The materials were characterized by X-ray diffraction (XRD), UV−vis, Fourier transform infrared (FT-IR), N2 adsorption−desorption, inductively coupled plasma−atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). The incorporated ions were mostly in the framework of the mesoporous materials, which were confirmed by the XRD, FT-IR, UV−vis, and 27Al MAS NMR analyses. The solids obtained were employed as heterogeneous catalysts for the selective oxidation of cyclohexane with oxygen (O2) as oxidant in a solvent-free system. The material CeO2/V-HMS exhibited the highest activity with about 18% conversion of cyclohexane but 68% total selectivity to cyclohexanol and cyclohexanone...