Performance of Mn-Ce catalysts supported on different zeolites in the NH₃-SCR of NO_x

With various zeolites such as β, ZSM-5 and USY as the support, a series of Mn-Ce catalysts were prepared by impregnation method and characterized by XRD, BET, NH₃-TPD, H₂-TPR and XPS; their catalytic performance in the NH₃-SCR of NO_x at low temperature was investigated. The results show that all these catalysts are highly active in the NH₃-SCR reaction at low temperature; especially, over the Mn-Ce/USY catalyst, the conversion of NO_x reaches 90% at 107℃. After loaded of manganese and cerium, the specific surface area and pore volume of supported catalysts are decreased. Amorphous MnO_x as the active component and crystalline CeO₂ are detected on the surface of ZSM-5 zeolite. The weak acid sites on the catalyst surface probably play an important role in the NH₃-SCR at low temperature. Meanwhile, a high atomic ratio of Mn⁴⁺/Mn³⁺ and concentration of adsorbed oxygen may also promote the NH₃-SCR reaction at low temperature.