ZrO2晶相对锰铈系SCR催化剂脱硝活性的影响  

Effects of Zirconia Crystallite Phases on MnO_x-CeO_2 SCR De NO_x Catalysts

作　　者：叶飞[1,2] 刘荣[1,2] 贡湘君 管昊[1,2] 

机构地区：[1]南京师范大学地理科学学院,江苏省物质循环与污染控制重点实验室,江苏南京210023 [2]江苏省地理信息资源开发与利用协同创新中心,江苏南京210023

出　　处：《环境科学研究》2015年第11期1720-1727,共8页Research of Environmental Sciences

基　　金：江苏省环境保护厅基金项目(2013032);江苏高校优势学科建设工程项目

摘　　要：采用浸渍法制备了以nm级c-Zr O2(立方相Zr O2)、t-Zr O2(四方相Zr O2)和m-Zr O2(单斜相Zr O2)为载体的负载型Mn Ox-Ce O2/Zr O2催化剂,并在连续流动固定床反应器上考察了催化剂的NH3-SCR低温脱硝性能.结果表明,催化剂脱硝性能良好,当Mn Ox负载量(以w计)为15.0%时,以c-Zr O2为载体的催化剂脱硝效率在103℃即可达到100%.在相同活性组分负载量和反应温度条件下,各催化剂的低温脱硝活性体现出Mn Ox-Ce O2/c-Zr O2>Mn Ox-Ce O2/t-Zr O2>Mn Ox-Ce O2/m-Zr O2的规律,因此对Mn Ox负载量为5.0%的Mn Ox-Ce O2/Zr O2系列催化剂进行进一步表征,以探究该规律的内在影响因素.BET测试结果表明,以c-Zr O2为载体的催化剂的比表面积最大,达到39.67 m2/g,更有利于气体和催化剂表面活性位的接触.XPS测试结果表明,以c-Zr O2为载体的催化剂表面晶格氧含量最丰富,有助于Lewis酸性位的形成.TPR和TPD测试图谱中的峰强及峰面积表明,以c-Zr O2和t-Zr O2为载体的催化剂表面主要存在Lewis酸性位;而在以m-Zr O2为载体的催化剂表面,Lewis酸性位较多,同时还存在少量的Brnsted酸性位.研究显示,Zr O2晶型结构变化引起Mn Ox-Ce O2/Zr O2催化剂的比表面积、表面活性酸性位的不同是产生晶型效应的原因所在;采用Zr O2作为负载型低温SCR催化剂载体时,以立方相晶型结构为最佳.A series of catalysts with manganese oxide and cerium oxide supported on monoclinic zirconia（ m-ZrO2）,tetragonal zirconia（ t-ZrO2） and cubic zirconia（ c-ZrO2） were prepared by the wet impregnation method. SCR activity measurements were carried out in a fixed-bed reactor. The results revealed that all prepared catalysts showed good catalytic activity. The catalyst with 15. 0% Mn Oxsupported on c-ZrO2 got 100% NO conversion at 103 ℃. The activity of all prepared catalysts decreased in the following sequence： Mn Ox-CeO2/c-Zr O2 Mn Ox-CeO2/t-ZrO2 Mn Ox-CeO2/m-ZrO2. To explain this phenomenon,catalysts with 5. 0% Mn Oxsupport on m-,t- and c-ZrO2 were chosen to be further characterized. BET results suggested the surface area of the catalyst supported by c-ZrO2 was 39. 67m2/g,which was the biggest and best one for contact between gas and active sites. XPS analytical outcomes indicated the concentration of lattice oxygen on the surface of the catalyst supported by c-ZrO2 was the highest,which was helpful for the formation of Lewis acid sites.The total area and intensity of TPR and TPD peaks indicated that there were only Lewis acid sites on the surface of catalysts supported by c-ZrO2 and t-ZrO2,while both Lewis and Brnsted acid sites appeared on the surface of catalysts supported by m-ZrO2（ though the latter was predominant）. Crystal effect was attributed to the difference of surface area and acidity for different structures of ZrO2. Cubic zirconia is the best choice for SCR catalyst support.

关 键 词：晶型效应 立方相ZrO2 四方相ZrO2 单斜相ZrO2 脱硝活性 

分 类 号：X701[环境科学与工程—环境工程]