Effect of Platinum Poisoning on DeNOx Performance of SCR Catalyst

YU Jintao; MAN Hengxiao; ZHANG Yu; QI Junxue; ZHANG Ruxiao; WANG Jiandong

Vehicle Engine ›› 2022, Vol. 0 ›› Issue (1) : 1-6.

Effect of Platinum Poisoning on DeNO_x Performance of SCR Catalyst

YU Jintao^1,2,MAN Hengxiao³,ZHANG Yu³,QI Junxue³,ZHANG Ruxiao³,WANG Jiandong³

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Abstract

With the increasingly stringent emission regulations, the DOC-DPF-SCR aftertreatment system is more widely used in diesel engine. The main active components of DOC catalyst located upstream of SCR catalyst are noble metals of platinum and palladium. The oxidized noble metals can be gasified at high temperature and can migrate and deposit on the SCR catalyst with the flow of exhaust gas, which results in noble metal poisoning of SCR catalyst. The poisoned catalyst after the bench test was prepared into small samples and the performance of catalyst was investigated. It was found that the poisoning of noble metal mainly affected the efficiency of DeNO_xin the high temperature stage of above 300 ℃. At the same time, two simulated poisoning samples were prepared in the laboratory,namely inner coating sample and surface coating sample. The Pt poisoning phenomenon of SCR catalyst was studied and the reaction mechanism after poisoning was analyzed. The experimental results of inner coated with 500×10^－6 sample showed that the oxidation capacity of catalyst increased significantly and the ammonia leakage reduced to 0 at 350 ℃ after the noble metal poisoning occurred. However, the selective reduction ability decreased significantly and the NO_x conversion efficiency decreased to 56.3% at 450 ℃. The surface coated with 50×10^－6 sample had the similar experimental results with 500×10^－6 sample. The two different coating methods showed that the poisoning mainly occurred in the surface layer and hence the utilization rate of inner catalyst was low. The adsorbed ammonia was difficult to enter the inner catalyst layer and was directly oxidized to NOx and N₂O, which resulted in reduction of NO_x conversion efficiency.

Key words

noble metal / catalyst poisoning / SCR / nitrogen oxide

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YU Jintao,MAN Hengxiao,ZHANG Yu,QI Junxue,ZHANG Ruxiao,WANG Jiandong. Effect of Platinum Poisoning on DeNO_x Performance of SCR Catalyst[J]. Vehicle Engine. 2022, 0(1): 1-6