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.