The Preparation and Characterization of Manganese Oxides/Rice Husk Silica Nanosized Catalysts for CO Oxidation

Abstract

In this work, nanosized manganese catalysts were prepared by incipient wetness impregnation of manganese salt on nanosilica. The nanosilica was thermally extracted from rice husk. The effect of metal oxide loading on the physico-chemical features and the catalytic activities of the catalysts towards the oxidation of carbon monoxide were investigated. Nanocatalyst loaded with 20.1 wt% manganese oxide (Mn20) was distinguished by the high surface area accompanied by the creation of new mesopores with respect to parent nanosilica. The X-ray diffraction and H₂-temperature programmed reduction analyses indicated that the Mn₅O₈ phase was the predominant phase in Mn20 catalyst. The presence of the Mn₅O₈ phase, in addition to the high surface area of Mn20 catalyst, resulted in decreasing the conversion temperature of CO oxidation (T₅₀), where the CO oxidation may follow the Mars-van-Krevelen route, i.e., redox mechanism.

Keywords:

• carbon monoxide
• manganese
• nanosilica
• oxidation
• rice husk

Notes

^a S _BET is the BET surface area, S_micro is the micropore surface area, and V_MP is the total micropore volume.