Development of DeNO_x Catalysts for Diesel Engine Exhaust

本研究的主要目的是：（1）收集烃类选择性催化还原NO的基础数据;（2）阐明反应机理;（3）NO_2生成与催化剂脱氮活性的关系。（1）Pt-ZSM-5在低温H_2O和SO_2中对NO转化为N_2的催化活性最高。Pt-ZSM-5在H_2O和SO_2中连续使用1000 h后，仍显示出很好的稳定性。2）在Cu-ZSM-5上选择性催化还原NO反应中，N_2的生成是通过NO+O_2与C_2H_4表面吸附物的反应进行的。Cu-ZSM-5分子筛中Cu离子的氧化还原性质与氧化温度或真空温度有很大关系。3）为了区分NO氧化和NO_2还原的连续反应，采用了两个反应器，并在两个反应器之间引入烃类作为反应物（IAR法）。实验结果表明，在第一反应器和第二反应器中分别使用Pt-和In-催化剂时，该方法对NO的选择性还原是非常有效的。

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.