[Optimization of Promoter and Support for Co-based/zeolites Catalysts in Catalytic Reduction of NO by CH].

Catalytic behavior of Co-based/zeolites catalysts was investigated in NO reduction by CH. Optimization of promoter and support was investigated by catalytic tests, and the relationship between catalytic activity and catalyst structure was illustrated by catalyst characterization. Co-Fe/SAPO-34 exhibited the highest activity among various Co-base/zeolites catalysts. The maximum conversion of NO with 52.7% was obtained on Co-Fe/SAPO-34 at 450℃. The inhibition of activity of Fe/zeolites became severe in the presence of SO, CO, and HO. CO exerted virtually no effect on the SCR activity of Co-Fe/zeolites. The inhibition of NO conversion by HO was reversible for Co-Fe/zeolites catalysts. Cobalt species were mainly present in CoO and Co(OH) states in Co-Fe/SAPO-34. CoOand Co(OH) were the main cobalt species of Co-Fe/ZSM-5, while CoO, CoAlO and CoO might be present in Co-Fe/Beta. The ratio of Fe/Fe in the surface layer of Co-Fe/zeolites decreased in the order of Co-Fe/ZSM-5(3.98) > Co-Fe/SAPO-34(0.52) > Co-Fe/Beta(0.43). The active states of cobalt species and suitable ratio of Fe/Fe were important for the activity of Co-Fe/zeolites in CH-SCR. CH-SCR over Co-Fe/zeolite catalysts started with the adsorption of NO and CH on Brønsted acid sites of the zeolite to produce NOand carbon-containing species(-C=O and -COO) in the presence of oxygen, respectively. Subsequently, the important intermediates of nitrate species were generated from NO at the active sites. Finally, nitrate species reacted with carbon-containing species to form N and CO.