硅铝比对Cu/SSZ-13SCR活性位的影响  

Effect of Si/Al ratio on the SCR active sites of Cu/SSZ-13

作　　者：秦萱 尹德嘉 余丽泽 张涛[1] 常化振 朱燕[1] 刘国华[1] 李俊华[2] QIN Xuan;YIN De-jia;YU Li-ze;ZHANG Tao;CHANG Hua-zhen;ZHU Yan;LIU Guo-hua;LI Jun-hua(School of Environment&Natural Resource,Renmin University of China,Beijing 100872,China;School of Environment,Tsinghua University,Beijing 100084,China)

机构地区：[1]中国人民大学环境学院,北京100872 [2]清华大学环境学院,北京100084

出　　处：《中国环境科学》2020年第2期591-599,共9页China Environmental Science

基　　金：中国人民大学2019年度‘中央高校建设世界一流大学(学科)和特色发展引导专项资金’资助项目。

摘　　要：采用固态离子交换法制备了不同硅铝比(Si/Al=5,10,25)的Cu/SSZ-13分子筛催化剂,探究硅铝比对其NH3选择性催化还原(NH3-SCR)活性位的影响规律,并通过X射线衍射(XRD),H2程序升温还原(H2-TPR),NOx程序升温脱附(NOx-TPD),NH3程序升温脱附(NH3-TPD),原位红外实验(in situ DRIFTS)等手段进行物化性质表征.活性测试结果表明,当Cu负载量为4wt%时,不同硅铝比的Cu/SSZ-13具有显著差异的SCR活性;其中,Cu/SSZ-13(10)的SCR活性最佳,200~450℃温度范围内NO转化率均大于80%.XRD和H2-TPR结果表明,硅铝比会影响Cu/SSZ-13的Cu物种的分布和氧化还原性.NOx-TPD和NH3-TPD结果表明,3种催化剂中Cu/SSZ-13(10)具有最多Cu2+离子,Cu2+离子可以为Cu/SSZ-13(10)提供更多的NOx吸附位点和Lewis酸性位点,而Lewis酸性位是Cu/SSZ-13主要的低温SCR活性位点,因此有利于NH3-SCR反应的进行.当硅铝比增加到25时,Cu/SSZ-13(25)的Lewis酸性位大量损失,导致其SCR活性明显下降.Cu/SSZ-13catalysts with different Si/Al ratio were prepared by a solid-state ion exchange method,which were used for selective catalytic reduction of NOx with NH3(NH3-SCR)reaction.Various characterization methods,including X-ray diffraction(XRD),temperature programmed reduction with H2(H2-TPR),temperature programmed desorption(TPD)of NOx,temperature programmed desorption(TPD)of NH3,and in situ diffuse reflectance FTIR spectroscopy(in situ DRIFTS),were used to elucidate the different catalytic performance over these Cu/SSZ-13catalysts.Compared with Cu/SSZ-13(25)and Cu/SSZ-13(5),Cu/SSZ-13(10)showed relatively superior SCR activity,with more than 80%NO conversion between 200 and 450°C.The XRD and H2-TPR results suggested that Si/Al ratio could influence the dispersion of Cu species and redox property of Cu/SSZ-13 catalysts.The XRD and H2-TPR results indicated that there were the most isolated Cu2+ions existed in Cu/SSZ-13(10).Cu2+ions could provide NOx-adsorbed sites and Lewis acid sites over Cu/SSZ-13,which mainly account for its low-temperature SCR activity.However,the NO conversion of Cu/SSZ-13(25)decreased obviously in the whole temperature range,due to the significant loss of Lewis acid sites.

关 键 词：氮氧化物 NH3-SCR Cu/SSZ-13 硅铝比 活性位点 

分 类 号：X505[环境科学与工程—环境工程]