Effect of Ce and La on the structure and activity of MnOx catalyst in catalytic combustion of chlorobenzene

Abstract

Mn-based oxide-mixed catalysts modified with Ce and La, which were prepared by complexation method, were tested in the catalytic combustion of chlorobenzene (CB) as a model of chlorinated aromatics. The characterization by XRD, XPS, TPR and Raman shows that the addition of Ce makes a large portion of Mn species enter CeO2 fluorite, leading to the formation of MnCeOx solid solution. The structure to be composed of MnOx and MnCeOx solid solution is highly active for CB oxidation due to the presence of a large amount of active oxygen species. The addition of La can promote the thermal stability of MnCeOx solid solution during calcination up to 750°C, and accordingly the catalyst presents high activity. The study on reaction kinetics shows zero order on CB concentration in the presence of the catalysts except for MnCe-550, indicating that adsorption strength of Cl species produced during the reaction is critical to CB combustion because the adsorbed Cl species can decrease the reducibility of Mn species, thus the mobility of oxygen. Nevertheless, high activity, good selectivity and desired stability were observed over MnCeLa catalysts at 350°C.