Integrated DeNO x –DeSoot Catalytic Systems with Improved Low-Temperature Performance

Abstract

Performance of the combined catalysts [CeO2–ZrO2 + FeBETA] and [Mn/CeO2–ZrO2 + FeBETA], prepared by mechanical mixing of the component powders, was studied in soot oxidation and NH3-SCR. [CeO2–ZrO2 + FeBETA] catalyst (with component volumetric ratio of 3/1) demonstrated efficient soot oxidation at 400–450 °C and DeNOx performance similar to that of FeBETA catalyst, despite the fact that the amount of zeolite was reduced by four times indicating a strong synergistic effect between the components. Low-temperature DeNOx performance of the [CeO2–ZrO2 + FeBETA] system can be additionally enhanced by doping the CeO2–ZrO2 with Mn. It was found that NOx conversion over [Mn/CeO2–ZrO2 + FeBETA] at 150–250 °C was steadily improved by increasing the Mn loading, and [5.4 % Mn/CeO2–ZrO2 + FeBETA] attained NOx conversion above 90 % at Treact ~190 °C. Comparative studies of soot oxidation and NH3-SCR over combined catalysts and individual components indicated that the soot oxidation activity is assigned to the soot oxidation over ceria–zirconia component, while enhanced low-temperature SCR performance is a result of a “bi-functional” SCR mechanism comprising NO oxidation to NO2 over CeO2–ZrO2 component followed by fast-SCR over FeBETA.