An efficient catalyst of manganese supported on diatomite for toluene oxidation: Manganese species, catalytic performance, and structure-activity relationship

Abstract

The work reports the preparation of diatomite-supported manganese catalysts by deposition-precipitation method, and their application for toluene oxidation. Microstructure and morphology of catalysts were investigated by Powder X-ray diffraction pattern (PXRD), thermogravimetric (TG), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen (N2) adsorption-desorption isotherms. Temperature-programmed reduction (TPR) and temperature-programmed surface reaction (TPSR) were used to analyze the reducibility of Mn species and the reactivity of surface oxygen species, respectively. The characterization results reveal that the manganese species were mainly in the phase of amorphous MnO2 and Mn2O3 on the diatomite, and the manganese species were successfully loaded on diatomite surface and filled in pores. With the increase of Mn content, the catalytic activity enhanced, due to the increase of surface oxygen species as adsorption-reaction sites. The Mn4+ played an important role in the superior catalytic activity towards toluene. The catalyst also displays high stability and superior activity towards toluene oxidation, which presents an applied interest. The effect of Mn content on the catalytic activity of catalysts was discussed in view of reaction mechanism and variations of physicochemistry properties.