Aerobic oxidation of cyclohexene catalyzed by NiO/MCM-41 nanocomposites in the gas phase

Abstract

The nanoparticles of NiO supported on mesoporous MCM-41 were synthesized and characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this study, catalytic activities of the supported NiO nanoparticles for oxidation of cyclohexene to 2-cyclohexene-1-ol and 2-cyclohexene-1-one with air in the gas phase were considered. These nanoparticles of NiO supported on mesoporous MCM-41 were effective catalysts in a temperature range of 220–310 °C at 1 atm of air. Under these reaction conditions, the activity of the catalysts decreases in the following order: 5 wt.% NiO/MCM-41 > 7.5 wt.% NiO/MCM-41 > 2.5 wt.% NiO/MCM-41. With 5 wt.% NiO supported on mesoporous MCM-41 and under our experimental conditions, the conversion percent of cyclohexene is 62.3% with 65.9% selectivity of 2-cyclohexene-1-ol + 2-cyclohexene-1-one and 12.2% cyclohexadiene at 280 °C. To achieve higher conversion of cyclohexene and better selectivity towards 2-cyclohexene-1-ol + 2-cyclohexene-1-one, factors such as reaction temperature, loading amount of nickel oxide and space velocity were studied, and optimized conditions were investigated. The nanoparticles of NiO supported on mesoporous MCM-41 were effective catalysts of cyclohexene oxidation in a temperature range of 220–310°C under atmospheric pressure of air and under these reaction conditions, the order of catalytic activities are as follows: 5 wt.% NiO/MCM-41 > 7.5 wt.% NiO/MCM-41 > 2.5 wt.% NiO/MCM-41.