Effect of alkali metal promoters on natural manganese ore catalysts for the complete catalytic oxidation of o-xylene

Abstract

A series of alkali metal doped natural manganese ore (NMO) catalysts were prepared by an impregnation method, and tested for the complete catalytic oxidation of o-xylene. The effects of alkali metal on the catalytic performance and structural properties of NMO were examined. Alkali metals were found to enhance the activity of NMO in the following order: Li < Na < Rb < K, Cs. The experimental results showed that NMO-K(Cs)-0.07 could convert o-xylene (0.055 vol.%) into CO 2 and H 2O at 240 °C, which was 60 °C lower than that of NMO. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) measurements revealed that the primary component of NMO and NMO-K-0.07 were MnO 2. It was found that K 2O was highly dispersed onto the NMO surface. The addition of K 2O did not increase the BET surface area of the NMO. However, it resulted in the binding energy of the Mn 2p of NMO-K-0.07 shifted to a lower value. The results suggested that alkali metals act as electronic promoters, indicating that alkali metal doped NMO are promising catalyst candidates for the catalytic oxidation of VOCs.