SCR-catalyzed diesel particulate filters (SDPFs) filter particulate matter, convert them periodically, and reduce NOx in the exhaust gas. Two important reactions are:
• Without NO2: Standard SCR:Â
4 NH3 + 4 NO + O2 → 4 N2 + 6 H2O
• With NO2: Fast SCR:Â
4 NH3 + 2 NO + 2 NO2 → 4 N2 + 6 H2O