纳米银催化的甲烷选择还原NO反应研究

Selective Catalytic Reduction of NO by Methane over Nano-silver Catalysts

采用浸渍方法制备银担载量为 3%～ 15 %的Ag/H ZSM 5催化剂 ,考察其在CH4选择还原NO反应中的活性和选择性 .结果表明分子筛中 3%～ 5 %银的引入对催化剂活性提高较小 ;在银担载量高于 7%的催化剂样品上 ,NO转化率显著提高 .通过XRD、UV vis和TEM技术对催化剂样品的表征 ,发现在担载量高于 7%的催化剂样品上有聚集的纳米银颗粒的形成 ,并且银颗粒的大小随银担载量增加而增大 .将表征结果与反应数据相结合 ,说明了分子筛外表面纳米银颗粒的形成 ,提高了银催化剂在CH4选择还原NO反应中的活性 .银催化剂上NO/O2 共吸附后的TPD和TPR研究揭示了纳米银颗粒参与选择还原反应的机制 .

Silver impregnated H ZSM 5 catalysts with various silver loading (3% 15%) were investigated for the selective catalytic reduction (SCR) of NO by methane.The NO reduction activities were greatly increased on the catalysts with silver loading higher than 7% samples.Characterization results by XRD,UV vis and TEM indicated that silver species were incorporated in the zeolite channels on low Ag loading samples,while nano sized silver particles were formed over Ag loading higher than 7% samples.Combined characterization results with activity measurements,it was concluded that the catalytic activities were apparently enhanced by the nano silver particles formed.TPD and TPR studies revealed the catalytic roles of nano silver particles in the SCR reaction.