Selective Catalytic Reduction of Nitric Oxide with Propene and Diesel Fuel as Reducing Agents over Anodic Alumina Catalyst

摘要

A novel metallic monolith anodic gamma-alumina catalyst,prepared through anodization of aluminum,hot water treatment and active metal impregnation,was employed to investigate the selective catalytic reduction of NO under oxygen-rich conditions with propene and diesel fuel as reducing agents.Using propene as a reducing agent,Pt/Al_2O_3/Al offered the best low-temperature SCR activity(about 573 K),and was resistant to SO_2 poisoning.However,a high undesired selectivity to N_2O and a narrow operating-temperature window were two major disadvantages.At a moderate temperature(about 673 K),Cu-Ce/Al_2O_3/Al showed a favorable de-NO_x activity comparable to Pt/Al_2O/Al,a higher N_2 selectivity and a wider operating-temperature window than Pt/Al_2O_3/Al.In particular,adding SO_2 into feedstream dramatically promoted the de-NO_x activity of Cu-Ce/Al_2O_3/Al,and this increase was unchanged with time-on-stream.Among the catalysts tested in this paper,the highest de-NO_x activity was obtained on the alumite support,but at a high temperature(about 773 K).Although the presence of SO_2 strongly inhibited the NO_x reduction of the alumite support,NO_x conversion of 80% could still be maintained in the coexisting SO_2 and H_2O.When introducing diesel fuel instead of propene as a reducing agent,the over-oxidation of diesel fuel by oxygen remarkably decreased the NOT reduction of Pt/Al_2O/Al and Cu-Ce/AljO/Al.The alumite support became a promising choice,due to the stable 67% of de-NO_x activity achieved under the same redox conditions.However,the presence of a high concentration of SO,substantially depressed the de-NO activity of the alumite support.On the contrary,a significant promotional effect of SO,on the de-NOx activity was also observed over Cu-Ce/Al_2O_3/Al,when using diesel fuel as a reducing agent,as observed in the SCR-NO-C3H6.