Green and efficient catalytic oxidation of ethylbenzene to acetophenone over cobalt oxide supported on a carbon material derived from sugar

Abstract

The use of biomass as a carbon source to support metal oxides has significant advantages in environmental protection and reducing the cost of the catalyst. The critical point lies on the development of highly active and recyclable catalysts. In this study, sugar was used as a carbon source, and cobalt oxide was loaded via an in situ method and an impregnation method to prepare the catalyst, respectively. The catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman, in situ electron paramagnetic resonance (in situ EPR) and N₂ adsorption–desorption. The characterization results show that the macroporous carbon-supported cobalt oxide catalyst prepared by the in situ method contains CoO_x nanoparticles on the support, but the dispersion of cobalt oxide on the support is more uniform compared with the catalyst prepared by the impregnation method. The catalytic performance of the prepared catalyst was evaluated through the oxidation of ethylbenzene (EB) to acetophenone (AP) as a probe reaction. Under the optimized reaction conditions, temperature (T) = 80 °C, m(catalyst) : m(EB) = 0.15, n(H₂O₂) : n(EB) : n(KBr) = 14.4 : 1 : 0.1, t = 8 h, and V(EB) : V(CH₃COOH) = 1 : 10, the conversion of EB and the selectivity of AP were 84.1% and 81.3%, respectively. CoO_x/SC-10-in situ exhibits improved reactivity of EB oxidation owing to cobalt ions on the carbon support that promote the free radical and acid catalytic reaction pathway. The cobalt oxide catalyst supported by biomass carbon has decent recycling and regeneration ability, which provides a new idea for the application of biomass.