Preparation and characterization of a copper oxide nanoparticle-supported red-mud catalyst for liquid phase oxidation of ethyl benzene to acetophenone

Abstract

In this study, liquid phase oxidation of ethyl benzene to acetophenone was widely investigated using a new recyclable supported catalyst of CuO nanoparticles impregnated over activated red-mud (CuO_AARM). The catalyst was prepared using a hydrothermal reaction procedure. A catalytic conversion process was carried out in the presence of H₂O₂ as an oxidant. Material characterization was performed using various instrumentation techniques such as FTIR, TGA, XRD and TEM. The H₂-TPR results indicate the reducible properties of the catalyst at low temperatures, attributed to the presence of largely scattered small-sized CuO species on the support material. The progress of the catalytic reaction was found to follow the pseudo 1st order kinetics. The proposed mechanistic pathway, in an optimized geometrical structure, was found to favor the reaction via hydroperoxyl radical formation following an endergonic process, evident from the correction to Gibbs free energy. A selectivity of 74.0% is achieved with this catalyst in the oxidation of ethyl benzene to acetophenone. The synergy between the atomically dispersed CuO nanoparticles and the components in the red-mud support promotes a facile and robust approach towards the development of a recyclable and reusable heterogeneous catalyst with 86.0% conversion efficiency.