Highly Selective Preparation of Cyclohexanone Oxime from Liquid-Phase Catalytic Oxidation of Cyclohexylamine with Molecular Oxygen over Glucose-Modified TiO2 under Solvent-Free Conditions

A simple and highly efficient method for manufacturing cyclohexanone oxime from solvent-free liquid-phase aerobic oxidation of cyclohexylamine over a glucose-modified TiO2 catalyst had been developed under mild reaction conditions. The results indicated that glucose-modified TiO2-enriched surface hydroxyl groups as an efficient catalyst played a crucial role in activating cyclohexylamine, and 59.8% conversion and 88.6% selectivity to cyclohexanone oxime were achieved. The characterization results by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques indicated that the introduction of glucose effectively improved the surface areas, and the amounts of surface hydroxyl groups of the catalyst and the new C–O–Ti bonds were formed. Finally, combined with the experimental results, the possible catalytic oxidation pathway over the glucose-modified TiO2 catalyst was deduced. This work employing inexpensive and highly reactive glucose-modified TiO2 as the catalyst and molecular oxygen as the oxidizer for preparing cyclohexanone oxime from aerobic oxidation of cyclohexylamine is promising and has extensive prospects in industrial applications.