• activity, propene poisoning resistance and hydrothermal stability of copper exchanged chabazite-like zeolite catalysts for scr of no with ammonia in comparison to cu/zsm-5

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    • تاریخ ارائه: 1392/07/24
    • تاریخ انتشار در تی پی بین: 1392/07/24
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     copper, iron, and mixed copper/iron exchanged zeolites containing zsm-5 and chabazite-like zeolites (ssz-13, sapo-18 and sapo-34) were studied for selective catalytic reduction (scr) of no with nh3 with or without propene. cu/zsm-5, cu/ssz-13, cu/sapo-18 and cu/sapo-34 exhibited high no conversions without propene. however, as compared to cu/zsm-5, no conversions over cu/ssz-13, cu/sapo-18 and cu/sapo-34 were more stable with propene, due to coke formation over cu/zsm-5. the results of n2-adsorption/desorption and xps showed that the surface area, cu+/cu2+ ratio and the surface amount of cu content of cu/zsm-5 catalysts changed from 324 m2/g, 0.03 and 11.5 wt% for the fresh cu/zsm-5 catalyst to 68 m2/g, 0.34 and 5.3 wt% for the used sample. however, there were little changes between fresh and used cu/ssz-13, cu/sapo-18 and cu/sapo-34 catalysts. moreover, cu/zsm-5 catalyst showed a larger decline in no conversion with time on stream and a higher adsorption amount of propene compared to cu/ssz-13, cu/sapo-18 and cu/sapo-34 catalysts. the resistance to hydrocarbon poisoning depended on the pore geometry of the zeolites. during nh3-scr, the presence of medium-pore sizes in cu/zsm-5 led to hydrocarbon deposition, which blocked the active sites and also decreased the active intermediates needed for no conversion. cu/ssz-13, cu/sapo-18 and cu/sapo-34 catalysts, on the other hand, with small pores and cage diameters and with one-dimensional channel structures, showed higher hydrocarbon poison resistance. moreover, these copper exchanged small-pore zeolites showed much higher hydrothermal stability than the medium-pore cu/zsm-5.

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