双金属交换的Cu-Mn/SSZ-39催化剂的NH_(3)-SCR脱硝性能

NH_(3)-SCR denitrification performance over bimetal exchanged Cu-Mn/SSZ-39 catalyst

以SSZ-39为载体,采用离子交换法制备不同铜锰物质的量比的Cu-Mn/SSZ-39分子筛催化剂,并考察其在以NH3为还原剂的选择性催化还原NO反应(NH3-SCR)中的脱硝活性。通过XRD、SEM、N_(2)吸脱附、NH_(3)-TPD、H_(2)-TPR、XPS、ICP等对催化剂的结构、形貌、表面酸性等进行表征。结果表明,Cu^(2+)提供主要的反应活性位,使催化剂具有良好的脱硝活性和N_(2)选择性;Mn^(2+/3+)交换提高了催化剂的表面酸性,特别是增加了弱Lewis酸的含量;Cu^(2+)、Mn^(2+/3+)双金属交换的Cu-Mn/SSZ-39催化剂具有良好的低温脱硝活性和水热稳定性。当Cu与Mn的物质的量比为1∶0.6时,Cu-Mn(0.6)/SSZ-39具有最低的起燃温度(T_(50)为125℃),在184~433℃的宽温度范围内NO转化率达到90%以上,并在450℃内保持90%以上的N_(2)选择性。水热老化后的Cu-Mn/SSZ-39-A基本保持了原有的晶型、形貌和脱硝活性,体现了良好的水热稳定性。

Cu-Mn/SSZ-39 zeolite catalysts with different Cu/Mn molar ratios were prepared by ion-exchange method using SSZ-39 as support for selective catalytic reduction of NO by NH_(3)(NH_(3)-SCR).The structures, morphologies and surface acidity of the catalysts were characterized by XRD, SEM, N_(2) adsorption-desorption, NH_(3)-TPD, H_(2)-TPR, XPS and ICP techniques. The results showed that Cu^(2+) provided the major active sites, which made the catalyst have good denitration activity and N_(2) selectivity. The exchange of Mn^(2+/3+) increased surface acidity of the catalysts, especially the content of weak Lewis acid. The Cu-Mn/SSZ-39 catalysts with bimetallic exchange of Cu^(2+) and Mn^(2+/3+) showed good low temperature NH_(3)-SCR activities and hydrothermal stability. When the molar ratio of Cu to Mn was 1∶0.6, the prepared Cu-Mn(0.6)/SSZ-39 exhibited the lowest light-off temperature(T_(50)=125 ℃), the NO yield was above 90% at a wide temperature window from 184 ℃ to 433 ℃, and the N_(2) selectivity reached above 90% at below 450 ℃. After hydrothermal aging, the Cu-Mn/SSZ-39-A basically maintained its original crystal form, morphology and denitration activity, showing a good hydrothermal stability.