Stability Mechanism of Low Temperature C2H4-SCR with Activated-Carbon-Supported MnOx-Based Catalyst

Manganese-based catalysts have shown great potential for use as a hydrocarbon reductant for NOx reduction (HC-SCR) at low temperatures if their catalytic stability could be further maintained. The effect of CeO2 as a promoter and catalyst stability agent for activated carbon supported MnOx was investigated during low temperature deNOx based on a C2H4 reductant. The modern characterization technology could provide a clear understanding of the activity observed during the deNOx tests. When reaction temperatures were greater than 180 degrees C and with ceria concentrations more than 5%, the overall NO conversion became stable near 70% during long duration testing. In situ DRIFTS shows that C2H4 is adsorbed on the Mn3Ce3/NAC catalysts to generate hydrocarbon activated intermediates, R-COOH, and the reaction mechanism followed the E-R mechanism. The stability and the analytical data pointed to the formation of stable oxygen vacancies within Ce3+/Ce4+ redox couplets that prevented the reduction of MnO2 to crystalline Mn2O3 and promoted the chemisorption of oxygen on the surface of MnOx-CeOx structures. Based on the data, a synergetic mechanism model of the deNOx activity is proposed for the MnOx-CeOx catalysts.