Lean selective catalytic reduction of NO2 by methane over Co-zeolites

The reaction of NO2, CH4 and O2 was studied using low levels of methane compared to NO2 and O2 over protonic and cobalt‐exchanged ferrierite, ZSM‐5 and mordenite zeolites. Results suggest that two reaction pathways at low and high temperatures may be involved in the lean selective catalytic reduction (SCR) of NO2 by methane. At low temperatures, the reduction of NO2 to NO and N2 might be the initial reaction step. It is likely that NO2 or its adsorbed precursors initiate the reaction of methane at low temperatures. At high temperatures, the oxidation of NO and combustion of methane with oxygen might be involved. No appreciable differences were observed in the reduction of NO2 over Co‐zeolites as compared to known results of NO reduction over these materials. However, enhanced N2 formation rate was observed on H‐zeolites starting from NO2 instead of data reported for NO. Furthermore, it appears that the active sites for SCR are both acid and metal sites.