首页|The effects of SO2 exposure on three-way catalysts for passive SCR operation
The effects of SO2 exposure on three-way catalysts for passive SCR operation
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NSTL
Efficient lean-burn gasoline engines cannot employ traditional three-way catalysts(TWCs)to control NOx emissions due to excess oxygen.Passive selective catalytic reduction(pSCR)is a process designed to control NOx by generating NH3 over the TWC during fuel-rich operation,storing it on a downstream SCR,and then converting NOx during fuel-lean operation.This work is focused on studying sulfur effects on this promising strategy.Two hydrothermally-aged commercial catalysts were studied for their effectiveness in the presence of SO2:a Pd-based TWC and a TWC with NOx storage.The sulfated samples were evaluated in a flow reactor under pSCR conditions and with targeted reactions.SO2 inhibited the water gas shift and steam reforming reactions,decreasing(but not eliminating)NH3 production; however,initial activity is recoverable after a simple thermal treatment at 650 ℃.This work will prove valuable in understanding,mitigating,and even reversing the effects of SO2 inhibition on real pSCR systems.
NSTL
