Development of DeNO_x Catalysts for Diesel Engine Exhaust

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This study has been devoted to 1) collection of fundamental data for applying the selective catalytic reduction of NO with hydrocarbons, 2) clarification of the reaction mechanism, and 3) relation between NO_2 formation and catalytic activity for the eduction of NO.1) Pt-ZSM-5 showed the highest catalytic activity for the conversion of NO into N_2 among various catalysts in H_2O and SO_2 at low temperature. Pt-ZSM-5 showed high durability during the continuous service of 1000 h in H_2O and SO_2.2)The formation of N_2 in the selective catalytic reduction of NO over Cu-ZSM-5 was clarified to proceed through the reaction of NO+O_2 with surface adsorbates of C_2H_4. The redox properties of Cu ions in Cu-ZSM-5 were greatly dependent on the oxidation or evacuation temperature. In addition, it followed that there were three kinds of Cu^+ species with different adsorption properties in Cu-ZSM-5.3) To divide the consecutive reactions of NO oxidation and NO_2 reduction, two reactors were used and hydrocarbons as reactant were introduced between them (IAR method). It was confirmed that this method was very effective for the selective reduction of NO when Pt- and In- catalysts were applied in the first and second reactor, respectively.