Experimental study of Fe modified Mn/CeO2 catalyst for simultaneous removal of NO and toluene at low temperature

Abstract

A series of Mn/CeO2 catalysts modified with different Fe contents were prepared by impregnation method and tested for their low-temperature performance for simultaneous de-nitrification and toluene removal. It was found that the Fe5Mn/CeO2 catalyst showed the best catalytic performance and the conversion efficiency of toluene reached 90% at 175 °C and NO conversion reached 90% at 95−300 °C. The physical and chemical properties of the catalysts were characterized by BET, SEM, XRD, XPS, H2-TPR, NH3-TPD and O2-TPD. XPS results showed that the increased content of Ce3+ and Mn4+ in the Fe5Mn/CeO2 catalyst promoted the formation of oxygen vacancies and unsaturated chemical bonds, providing more active sites, thus facilitating the efficient removal of NO and toluene at low temperatures. Compared with other catalysts, H2-TPR, NH3-TPD and O2-TPD indicate that Fe5Mn/CeO2 catalyst has great redox ability, stronger acidity and better oxygen migration ability. In addition, this paper explores the effects between selective catalytic reduction (NH3-SCR) and catalytic oxidation reaction of toluene over Fe5Mn/CeO2 catalyst. NH3 preferentially reacts with the active site on the catalyst to inhibit the toluene oxidation process, while NO promotes the toluene removal process. Toluene can promote the NH3-SCR process in a certain temperature range. While NO promotes the formation of NO2, NO2 effectively promotes the combination of toluene and active sites, which is conducive to the catalytic oxidation of toluene; The inhibition of toluene on the NH3-SCR process weakens with the increase of temperature. At 100 °C, the inhibition of toluene on the NH3-SCR process disappears. When the temperature exceeds 225 °C, toluene reacts with NO as a reducing agent and promotes the formation of NO2, thus promoting the NH3-SCR reaction.