摘要
在富氧且有催化剂存在条件下以NH3或尿素为还原剂选择性地还原NOx为N2的技术,即NH3/Urea-SCR技术,是去除固定源和移动源NOx最为有效且应用最广的技术之一,其中最重要的催化剂体系是钒基催化剂。本文从钒基催化剂的组成及其NH3-SCR反应性能、钒基催化剂的活性改进以及钒基催化剂上的NH3-SCR反应机理三个方面对该领域的研究进展做了较为全面的综述,并对NH3-SCR领域可能的发展方向做了展望。传统的V2O5-WO3(MoO3)/TiO2催化剂以及改性后的钒基催化剂在中温段具有优异的NOx净化效率和抗SO2中毒性能,其中高分散的V5+物种以及多聚的钒酸盐物种为NH3-SCR反应的活性中心。针对采用不同方法制备的或具有不同组成的钒基催化剂体系,多数学者认为NH3-SCR反应按照Eley-Rideal(E-R)机理进行,部分学者认为按照Langmuir-Hinshelwood(L-H)机理进行,这可能与催化剂的钒负载量以及反应温度区间相关。在后续工作中研究者应结合多种测试手段,具体问题具体分析,综合考虑温度的动态影响以及表面酸碱性对反应物的吸附活化,以得出更为全面、真实的反应机理。系统了解前人在钒基NH3-SCR催化剂领域的研究进展有助于现阶段开发高效稳定、可适应复杂工作条件的钒基SCR催化转化器,同时也对设计合成新型高效、环境友好且抗中毒的非钒基SCR催化剂体系具有一定的参考价值。
Selective catalytic reduction of NOx with NH3 or urea （NH3/Urea-SCR） as reducing agents over catalytic materials in oxygen-rich conditions is one of the most efficient and widely-used techniques for the removal of NOx from stationary and mobile sources. The most important catalyst system for NH3-SCR process is vanadium- based catalyst. In this review, the composition and NH3-SCR performance, the activity improvement of vanadium- based catalysts and the corresponding NH3-SCR reaction mechanisms are summarized. The possible developing orientations in the field of NH3-SCR technique are also prospected. The conventional V2O5-WO3 （ MoO3 ）/TiO2 catalyst and corresponding improved vanadium-based catalysts usually show excellent deNOx efficiency and SO2 durability in the medium temperature range. On these catalysts, the highly dispersed V^5＋ species and poly-vanadate species are confirmed to be the active phases for NH3-SCR reaction. Over vanadium-based catalysts prepared by different methods or with different compositions, a majority of researchers consider that the NH3-SCR reaction follows an Eley-Rideal （E-R） mechanism and some researchers prefer to a Langmuir-Hinshelwood （L-H）mechanism, which might be related to the vanadium loading amount and reaction temperature. During the subsequent work in further study, the researchers should combine multiple characterization methods aiming at different catalyst systems, and pay more attention to the influence of temperature on the reaction mechanism together with the effect of surface acid/basic property on the adsorption and activation of NH3NOx. Accordingly, much more comprehensive and authentic reaction mechanism can be concluded. The systematic understanding of the research progress in vanadium-based catalysts is beneficial to the development of highly efficient, stable vanadium-based SCR catalytic converters at the present stage, and also important for the design and synthesis of novel, efficient, environmentally-friendly vanadium-free SCR catalysts with
出处
《化学进展》
SCIE
CAS
CSCD
北大核心
2012年第4期445-455,共11页
Progress in Chemistry
基金
国家自然科学基金项目(No.51108446)
国家高技术研究发展计划(863)项目(No.2009AA064802
2010AA065003)
中国科学院优秀博士学位论文
院长奖获得者科研启动专项资金资助
关键词
钒基催化剂
NH3-SCR
烟气脱硝
柴油车尾气净化
反应机理
非钒基催化剂
vanadium-based catalysts
NH3-SCR
flue gas denitration
diesel exhaust purification
reactionmechanism
vanadium-free catalysts
