REDUCTION OF LEAN NOX BY ETHANOL OVER AG AL-2O3 CATALYSTS IN THE PRESENCE OF H2O AND SO2/

The reduction of lean NOx using ethanol in simulated diesel engine exh aust was carried out over Ag/Al2O3 catalysts in the presence of H2O an d SO2. The Ag/Al2O3 catalysts are highly active for the reduction of l ean NOx by ethanol but the reaction is accompanied by side reactions t o form CH3CHO, CO along with small amounts of hydrocarbons (C3H6, C2H4 , C2H2 and CH4) and nitrogen compounds such as NH3 and N2O. The presen ce of H2O enhances the NOx reduction while SO2 suppresses the reductio n. The presence of SO2 along with H2O suppresses the formation of acet aldehyde and NH3. By infrared spectroscopy, it was revealed that the r eactivity of NCO species formed in the course of the reaction was grea tly enhanced in the presence of H2O. The NCO species readily reacts wi th NO in the presence of O-2 and H2O at room temperature, being conver ted to N-2 and CO2 (GO). Addition of SO2 suppresses the formation of N CO species and lowers the reactivity of the NCO species. However, the reduction of NOx is still kept at high conversion levels in the presen ce of H2O and SO2 over the present catalysts. About 80% of NOx in the simulated diesel engine exhaust was removed at 743 K.