物理化学学报 >> 2015, Vol. 31 >> Issue (12): 2375-2385.doi: 10.3866/PKU.WHXB201510201

催化和表面科学 上一篇    下一篇

MnSAPO-34分子筛的制备、表征及其NH3-SCR活性

陈锋1,黄碧纯1,2,*(),杨颖欣1,刘小青1,喻成龙1   

  1. 1 华南理工大学环境与能源学院,广州510006
    2 华南理工大学,工业聚集区污染控制与生态修复教育部重点实验室,广州510006
  • 收稿日期:2015-04-28 发布日期:2015-12-04
  • 通讯作者: 黄碧纯 E-mail:cebhuang@scut.edu.cn
  • 基金资助:
    国家自然科学基金(51478191);广东省省级科技计划项目(2014A020216003)

Synthesis, Characterization and NH3-SCR Activity of MnSAPO-34 Molecular Sieves

Feng. CHEN1,Bi-Chun. HUANG1,2,*(),Ying-Xin. YANG1,Xiao-Qing. LIU1,Cheng-Long. YU1   

  1. 1 School of Environment and Energy, South China University of Technology, Guangzhou 510006, P. R. China
    2 Key Laboratory of the Ministry of Education for Pollution Control and Ecosystem Restoration in Industry Clusters, South China University of Technology, Guangzhou 510006, P. R. China
  • Received:2015-04-28 Published:2015-12-04
  • Contact: Bi-Chun. HUANG E-mail:cebhuang@scut.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(51478191);Guangdong Provincial Science and TechnologyProject, China(2014A020216003)

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摘要：

采用水热合成方法制备含锰的SAPO-34分子筛(MnSAPO-34)催化剂,考察了锰投加量、焙烧温度及晶化时间对催化剂氨选择性催化还原(SCR)氮氧化物反应活性的影响,并通过X射线光电子能谱(XPS)、程序升温还原(TPR)、程序升温脱附(TPD)等多种分析手段对催化剂进行表征.活性测试结果表明,当MnO与P2O5的摩尔比n(MnO)/n(P2O5)= 0.1,采用6 h晶化时间, 550 ℃焙烧制备的MnSAPO-34分子筛具有最佳SCR活性, NOx转化率接近100%, N2选择性高于80%.分析结果表明, Mn的引入对分子筛的晶体及多孔结构有较大影响,过多的引入会降低结晶度及产生非骨架锰氧化物,同时还会降低分子筛的比表面积和孔容,但焙烧温度的降低以及晶化时间的缩短可以提高分子筛的比表面积和孔容.高温焙烧后分子筛表面出现了高氧化态锰物种,以Mn4+为主,而提高Mn3+的比例则有利于提高催化活性.在适当的合成条件下, Mn的引入可增强分子筛对NO和NH3分子的吸附,而强吸附态NO及强吸附态NH3的相互作用可能是催化活性快速提高的原因.

关键词: 选择性催化还原, 氮氧化物, 锰, SAPO-34分子筛, X射线光电子能谱, 程序升温还原, 程序升温脱附

Abstract:

A series of MnSAPO-34 molecular sieves were synthesized by a hydrothermal method for selective catalytic reduction (SCR) of NO with NH3 and characterized using X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Three factors were studied, including Mn-loading, calcination temperature, and synthesis time. The MnSAPO-34, which was synthesized in 6 h and calcined at 550 ℃ with the Mn-loading (n(MnO)/n(P2O5)= 0.1), exhibits the highest activity among all the samples, with NOx conversion of almost 100% and N2 selectivity higher than 80%. The results show that the porous and crystalline structures of MnSAPO-34 are greatly affected by addition of manganese, and excessive Mn-loading could result in lower crystallinity and the generation of nonframework manganese oxides. Meanwhile, a decrease in specific surface area and pore volume are observed in MnSAPO-34 with higher Mn-loading; however, the opposite characteristics are observed with a decreasing calcination temperature and shorter synthesis time. Manganese species of high oxidation state, mostly Mn4+, are shown to be on the catalysts surface after high temperature calcination, and the increase ratio of Mn3+ could help to improve the catalytic activity. Under proper synthesis conditions, the incorporation of manganese could improve the adsorption of nitric oxide and ammonia, and the interaction between the strongly adsorbed NO and strongly adsorbed NH3 might be the reason for the enhancement in their catalytic efficiency.

Key words: Selective catalytic reduction, Nitrogen oxide, Manganese, SAPO-34 molecular sieve, X-ray photoelectron spectroscopy, Temperature-programmed reduction, Temperature-programmed desorption