Highly selective oxidation of cyclohexene to 2-cyclohexene-1-one in water using molecular oxygen over Fe–Co–g-C3N4

Abstract

Efficient and greener oxidation of cyclohexene to 2-cyclohexene-1-one is an interesting topic. In this work, we prepared a series of Fe–Co doped graphitic carbon nitride (Fe–Co–g-C₃N₄) catalysts through simple impregnation and calcination methods. The catalysts were characterized by different techniques, such as transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption–desorption measurement, powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The selective oxidation of cyclohexene to 2-cyclohexene-1-one was carried out in different solvents over the catalysts using molecular oxygen as an oxidant. The influence of supports, solvents, Fe/Co molar ratio in the catalysts, pressure of oxygen, reaction temperature and time of the reaction was investigated. It was revealed that the bimetallic Fe–Co–g-C₃N₄ catalysts were very efficient for the reaction. More interestingly, the selectivity of the reaction in water was much higher than that in other solvents. Under optimized conditions, the selectivity to 2-cyclohexene-1-one could reach 95% at a cyclohexene conversion of 36%. The Fe–Co–g-C₃N₄ catalyst could be reused at least four times without obvious loss of efficiency.