Selective catalytic reduction of NOₓ with NH₃ over different copper exchanged zeolites in the presence of decane
2011
Sultana, Asima | Nanba, Tetsuya | Sasaki, Motoi | Haneda, Masaaki | Suzuki, Kunio | Hamada, Hideaki
Copper-exchanged in to zeolites containing large, medium and small pores were studied for selective catalytic reduction (SCR) of NO with NH₃ in the presence and absence of decane. Cu/ZSM-5 and Cu/ERI exhibited higher NOₓ conversion compared to Cu/FER and Cu/MOR. On the other hand NOₓ conversion over Cu/FER was more stable in the presence of decane compared to Cu/MOR and Cu/ZSM-5 catalysts. Fresh and used Cu/zeolite catalysts were analyzed by H₂-TPR, NH₃-TPD, ESR and TGA. Copper species with different reducibility and isolated Cu²⁺ ions in different coordinations were identified by H₂-TPR and the ESR techniques respectively. The initial NOₓ conversion activity of Cu/zeolites seems to depend on the number of isolated Cu²⁺ species, which were affected by the zeolite structure. Whereas, the catalysts resistance to hydrocarbon poisoning depended on the pore geometry of the zeolites. During NH₃-SCR, the presence of large pores and cages in the zeolite lead to hydrocarbon deposit and retention by the zeolites which blocks the active sites and also decreases the active intermediates needed for NOₓ conversion. Cu/ZSM-5 with higher number of isolated Cu²⁺ species showed higher initial NOₓ conversion compared to other Cu/zeolite catalysts. Cu/FER on the other hand with small pore and cage diameter with one-dimensional channel structure showed higher hydrocarbon poisoning resistance.
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