LEAN SELECTIVE CATALYTIC REDUCTION OF NO2 BY METHANE OVER CO-ZEOLITES

The reaction of NO2, CH4 and O-2 was studied using low levels of metha ne compared to NO2 and O-2 over protonic and cobalt-exchanged ferrieri te, ZSM-5 and mordenite zeolites. Results suggest that two reaction pa thways at low and high temperatures may be involved in the lean select ive catalytic reduction (SCR) of NO2 by methane. At low temperatures, the reduction of NO2 to NO and N-2 might be the initial reaction step. It is likely that NO2 or its adsorbed precursors initiate the reactio n of methane at low temperatures. At high temperatures, the oxidation of NO and combustion of methane with oxygen might be involved. No appr eciable differences were observed in the reduction of NO2 over Co-zeol ites as compared to known results of NO reduction over these materials . However, enhanced N-2 formation rate was observed on H-zeolites star ting from NO2 instead of data reported for NO. Furthermore, it appears that the active sites for SCR are both acid and metal sites.