Microwave-assisted removal of benzene with high efficiency on cobalt modified copper-manganese spinel oxides

Abstract

Microwave-assisted process has been demonstrated to have immense potential for promoting chemical reactions and reducing energy consumption. In this study, catalytic oxidation of benzene was carried out over Co-Cu-Mn mixed oxides (CoxMn1−xCuOy) under microwave irradiation. The spinel-type mixed oxides were mainly formed for the Co-Cu-Mn mixed oxides with different Co/Mn ratios. The substitution of Mn sites by Co was confirmed by Fourier and Wavelet transformed extended x-ray absorption fine structure spectra. As the Co/Mn ratio increased, the heating characteristics of the catalysts under microwave irradiation monotonically improved. The benzene oxidation activity increased on the Co/Mn ratio of 2/3 due to the enhanced specific surface area, benzene adsorption properties, and lattice-oxygen reactivity. Microwave inducing significantly lowered the reaction temperature required for benzene oxidation. Co0.4Mn0.6CuOy completely oxidized benzene at a relatively low microwave power compared to pristine Cu-Mn oxides. The Co-Cu-Mn oxides showed high activity and stability for benzene oxidation even under humid conditions. Combining pre-adsorption and thermal oxidation processes on Co0.4Mn0.6CuOy improved the low concentration of benzene oxidation efficiency by rapid microwave heating. The compound of Co0.4Mn0.6CuOy and Co0.8Mn0.2CuOy mixed at 3:1 showed even higher activity than Co0.4Mn0.6CuOy.