催化学报 ›› 2017, Vol. 38 ›› Issue (11): 1831-1841.DOI: 10.1016/S1872-2067(17)62897-3

• 论文 • 上一篇    下一篇

F127辅助制备介孔Fe/TiO2催化剂用于中温NH3选择性催化还原反应

李昱琳a,b, 韩小金a, 侯亚芹a, 郭耀萍a,b, 刘勇进a,b, 向宁a,b, 崔燕a, 黄张根a   

  1. a 中国科学院山西煤炭化学研究所煤炭转化国家重点实验室, 山西太原 030001;
    b 中国科学院大学, 北京 100049
  • 收稿日期:2017-06-12 修回日期:2017-07-29 出版日期:2017-11-18 发布日期:2017-11-24
  • 通讯作者: 黄张根
  • 基金资助:

    中国科学院战略性先导科技专项(XDA07030300).

In situ preparation of mesoporous Fe/TiO2 catalyst using Pluronic F127-assisted sol-gel process for mid-temperature NH3 selective catalytic reduction

Yulin Lia,b, Xiaojin Hana, Yaqin Houa, Yaoping Guoa,b, Yongjin Liua,b, Ning Xianga,b, Yan Cuia, Zhanggen Huanga   

  1. a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Shanxi, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-06-12 Revised:2017-07-29 Online:2017-11-18 Published:2017-11-24
  • Contact: 10.1016/S1872-2067(17)62897-3
  • Supported by:

    This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA07030300).

摘要:

NOx是大气污染物的重要组成部分,能够造成酸雨、光化学烟雾和臭氧层破坏等一系列环境问题,严重危害人类健康.选择性催化还原(SCR)是控制NOx排放的主要技术,当前工业上普遍采用的是钒钛催化剂,然而该催化剂活性温度窗口较窄(300-400 ℃),N2选择性较低,而且钒物种本身有毒.因此开发新型SCR催化剂成为研究热点.
Fe/TiO2催化剂具有稳定的化学性质,环境污染少且价格低廉,近年来受到广泛关注.为了提高Fe/TiO2催化活性,人们采用了各种不同的制备方法.本文以F127作为结构导向剂,结合溶胶-凝胶法原位合成了具有介孔结构、工作温度在150-300 ℃的Fe/TiO2脱硝催化剂,并与普通浸渍法和共沉淀法制备的催化剂进行了对比.利用N2吸附脱附、紫外-可见光谱、X射线电子能谱、NH3程序升温脱附和原位红外光谱等技术研究了制备方法对Fe/TiO2催化剂物理结构及脱硝性能的影响.结果表明,相较于浸渍法和共沉淀法,模板法制备的催化剂具有较高的脱硝效率和抗H2O和SO2性能.作为结构导向剂,F127能够诱导催化剂形成均匀的介孔结构,有利于提高催化剂比表面积,促进反应物分子的扩散和转移,从而提高催化剂脱硝效率.
进一步研究发现,模板法能够明显促进活性组分Fe物种的分散和NH3吸附,载体与活性组分具有较强的相互作用,因而有利于催化剂产生较多的活性位.结合XPS结果,较多的活性位点有利于表面吸附氧(Oα)在催化剂表面的吸附.Oα有利于NO到NO2的转化,从而促进快速SCR反应:NO+NO2+2NH3→2N2+3H2O.通过原位红外机理分析证明,吸附在模板法制备的催化剂表面的NO物种具有较强的稳定性,当温度超过200 ℃时,仍然保持一定的吸附强度;吸附NH3红外结果表明,Lewis酸性位比Brønsted酸性位具有更强的稳定性,当温度超过150 ℃仍然具有较强的Lewis酸吸附.催化剂表面稳定的NO物种和Lewis酸位上强的NH3吸附是催化剂催化活性增加的重要原因.

关键词: Fe/TiO2, 介孔结构, 相互作用, 中温氨选择催化还原

Abstract:

An Fe/TiO2 catalyst with uniform mesopores was synthesized using Pluronic F127 as a struc-ture-directing agent. This catalyst was used for selective catalytic reduction of NO with NH3. The catalytic activity and resistance to H2O and SO2 of Fe/TiO2 prepared by a template method were better than those of catalysts synthesized using impregnation and coprecipitation. The samples were characterized using N2-physisorption, transmission electron microscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fouri-er-transform spectroscopy. The results showed that Pluronic F127 acted as a structural and chemi-cal promoter; it not only promoted the formation of a uniform mesoporous structure, leading to a higher surface area, but also improved dispersion of the active phase. In addition, the larger number of Lewis acidic sites, indicated by the presence of coordinated NH3 species (1188 cm-1) and the N-H stretching modes of coordinated NH3 (3242 and 3388 cm-1), were beneficial to mid-temperature selective catalytic reduction reactions.

Key words: Fe/TiO2, Mesopore structure, Interaction, Mid-temperature NH3 selective catalytic reduction