Reduction of lean NOx by ethanol over Ag/Al2O3 catalysts in the presence of H2O and SO2

The reduction of lean NOx using ethanol in simulated diesel engine exhaust was carried out over Ag/Al(2)O(3) catalysts in the presence of H(2)O and SO(2). The Ag/Al(2)O(3) catalysts are highly active for the reduction of lean NOx by ethanol but the reaction is accompanied by side reactions to form CH(3)CHO, CO along with small amounts of hydrocarbons (C(3)H(6), C(2)H(4), C(2)H(2) and CH(4)) and nitrogen compounds such as NH(3) and N(2)O. The presence of H(2)O enhances the NOx reduction while SO(2) suppresses the reduction. The presence of SO(2) along with H(2)O suppresses the formation of acetaldehyde and NH(3). By infrared spectroscopy, it was revealed that the reactivity of NCO species formed in the course of the reaction was greatly enhanced in the presence of H(2)O. The NCO species readily reacts with NO in the presence of O(2) and H(2)O at room temperature, being converted to N(2) and CO(2) (GO). Addition of SO(2) suppresses the formation of NCO species and lowers the reactivity of the NCO species. However, the reduction of NOx is still kept at high conversion levels in the presence of H(2)O and SO(2) over the present catalysts. About 80% of NOx in the simulated diesel engine exhaust was removed at 743 K.