Stability Mechanism of Low Temperature CH-SCR with Activated-Carbon-Supported MnO -Based Catalyst.

Manganese-based catalysts have shown great potential for use as a hydrocarbon reductant for NO reduction (HC-SCR) at low temperatures if their catalytic stability could be further maintained. The effect of CeO as a promoter and catalyst stability agent for activated carbon supported MnO was investigated during low temperature deNO based on a CH reductant. The modern characterization technology could provide a clear understanding of the activity observed during the deNO tests. When reaction temperatures were greater than 180 °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 CH is adsorbed on the MnCe/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 Ce/Ce redox couplets that prevented the reduction of MnO to crystalline MnO and promoted the chemisorption of oxygen on the surface of MnO -CeO structures. Based on the data, a synergetic mechanism model of the deNO activity is proposed for the MnO -CeO catalysts.