(426a) Study on the Adsorption Performance of Fe/Zsm-5 and Influence of Reaction Conditions in Scr of Nox with Propylene

The adsorption performance of Fe/ZSM-5 catalyst has been investigated in the SCR of NOx with propylene as the reducing agent. Freudlich equation was found to fit the adsorption isotherm satisfactorily if the system dispersion is considered. Fe/ZSM-5 catalyst showed reasonable NO adsorption capacity. The adsorption capacity and breakthrough time of Fe/ZSM-5 catalyst, which will be used for the design of the novel dual zone reactor system, can be predicted by the Freudlich equation at a given temperature and inlet NO concentration. However, the predicted breakthrough time must be corrected by a factor of 0.8 to account for the influence of the system dispersion.

The study on the influence of reaction temperature, gas space velocity and gas composition on the Fe/ZSM-5 catalyst activity showed that, the catalytic activity of Fe/ZSM-5 catalysts was sensitive to the reaction temperature and space velocity. To keep a long-term stable catalytic activity, the reaction temperature must be kept at T=350^oC or higher, while the space velocity GHSV<=5000h^-1. To reach a high NO conversion, a high HC to NO ratio was needed. Considering both the economic aspect and the reduction efficiency of NO, a HC to NO molar ratio of 2 is recommended. O₂ concentration played an important role in the SCR of NO with propylene as the reducing agent. The catalyst exhibited acceptable activity when O₂ concentration was controlled at some low level (<=1% at 350^oC).

Those performance data may be used for design the operating conditions of a newly proposed dual-zone continuous reactor for catalytic reduction of NOx under lean operating conditions.