Low-temperature SCR of NO with NH3 over noble metal promoted Fe-ZSM-5 catalysts

We have reported previously the excellent performance of Fe-exchanged ZSM-5 for selective catalytic reduction (SCR) of NO with ammonia at high temperatures ( 300 - 400 degrees C). In this work, we found that the reaction temperature could be decreased to 200 300 degrees C when a small amount of noble metal (Pt, Rh, or Pd) was added to the Fe-ZSM-5. The SCR activity follows the order Pt/Fe-ZSM-5 > Rh/Fe-ZSM- 5 > Pd/Fe-ZSM-5 at 250 degrees C. On the Pt promoted Fe-ZSM-5, 90% NO conversion was obtained at 250 degrees C at GHSV = 1.1 x 10(5) h(-1). Moreover, the noble metal improved the resistance to H2O and SO2. The presence of H2O and SO2 decreased the SCR performance only very slightly.