Novel CoMn2O4 as a highly efficient catalyst for the oxidation of o-, m-, p-xylene: Preparation and kinetic study

Abstract

In this research, a novel CoMn2O4 catalyst was prepared for the removal of o-xylene, m-xylene, and p-xylene. The catalyst showed better activity than that of MnO2 and Co3O4. The better activity of CoMn2O4 was attributed to the abundant concentration of Co2+, Mn3+, and lattice oxygen. Kinetic studies were carried out for the catalytic oxidation of three xylenes over the CoMn2O4 catalyst based on the Power-Low model, the Mars-van Krevelen model, the Eley-Rideal model, and the Langmuir-Hinshelwood model. All the three reactions could be most accurately described by the Mars-van Krevelen model, which suggested that the isomers of xylene had very little effect on the mechanism of xylene oxidation over the CoMn2O4 catalyst. The activation energies of the oxidation processes of o-xylene, m-xylene, and p-xylene were 94.64 kJ/mol, 78.46 kJ/mol, and 57.13 kJ/mol, respectively. The proposed mechanism based on the Mars-van Krevelen model suggested that xylene molecules reacted with the Co3+ and Mn4+/Mn3+ on the CoMn2O4 catalyst and participated in the cycle of adsorption, redox, and desorption.