Noble Metal (Pt, Rh, Pd) Promoted Fe-ZSM-5 for Selective Catalytic Oxidation of Ammonia to N2 at Low Temperatures

We have reported previously the excellent performance of Fe-exchanged ZSM-5 for selective catalytic oxidation (SCO) of ammonia to nitrogen at high temperatures (e.g., 400-500 °C). The present work indicates that the reaction temperature can be decreased to 250-350 °C when a small amount of noble metal (Pt, Rh or Pd) is added (by both doping and ion exchange) to the Fe-ZSM-5. The SCO activity follows the order: Pt/Fe-ZSM-5 > Rh/Fe-ZSM-5 > Pd/Fe-ZSM-5. The noble metal promoted Fe-ZSM-5 catalysts also show higher activity for NH3 oxidation than Ce-exchanged Fe-ZSM-5 at low temperatures. On the Pt promoted Fe-ZSM-5, near 100% of NH3 conversion is obtained at 250 °C at a high space velocity (GHSV = 2.3 × 105 h-1) and nitrogen is the main product. The presence of H2O and SO2 decreases the SCO performance only slightly. This catalyst is a good candidate for solving the ammonia slip problem that plagues the selective catalytic reduction (SCR) of NO with ammonia in power plants.