化工进展 ›› 2019, Vol. 38 ›› Issue (04): 1611-1623.DOI: 10.16085/j.issn.1000-6613.2018-1195

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选择催化还原(SCR)反应机理研究进展

张道军1(),马子然2,孙琦2,徐文强2,李永龙2,竹涛3,王宝冬2()   

  1. 1. 北京化工大学化工资源有效利用国家重点实验室,北京100029
    2. 北京低碳清洁能源研究所,北京 102211
    3. 中国矿业大学(北京)化学与环境工程学院,北京 100083
  • 收稿日期:2018-06-07 修回日期:2018-12-03 出版日期:2019-04-05 发布日期:2019-04-05
  • 通讯作者: 王宝冬
  • 作者简介:张道军(1989—),男,博士,主要研究方向为大气污染控制。E-mail: <email>zhangdaojun@nicenergy.com</email>。|王宝冬,教授级高级工程师,青年千人计划专家,主要研究方向为大气污染控制。E-mail: <email>wangbaodong@nicenergy.com</email>。
  • 基金资助:
    中组部青年千人启动经费-洁净煤(燃煤电厂)污染物控制(GB9300120001);北京低碳清洁能源研究所科技项目(CF9300171821)

Progress in the mechanism of selective catalytic reduction (SCR) reaction

Daojun ZHANG1(),Ziran MA2,Qi SUN2,Wenqiang XU2,Yonglong LI2,Tao ZHU3,Baodong WANG2()   

  1. 1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
    2. National Institute of Clean-and-Low-Carbon Energy,Beijing 102211,China
    3. School of Chemical & Environmental Engineering,China University of Mining & Technology Beijing, Beijing 100083,China
  • Received:2018-06-07 Revised:2018-12-03 Online:2019-04-05 Published:2019-04-05
  • Contact: Baodong WANG

摘要:

简述了NH3和NO在催化剂表面吸附、转化活化和反应历程及H2O和SO2对以上反应行为的影响。分析表明,NH3氧化脱氢进而与NO反应是决定NH3反应性和最终产物的关键。NO以气态(Eley-Rideal机理)或硝基类物质等吸附态(Langmuir-Hinshelwood机理)形式参与选择催化还原(SCR)反应。提高催化剂酸性和氧化还原循环性能,利于NH3和NO吸附和转化及相互间反应。高温时,H2O影响轻微,而SO2增强催化剂酸性,提高脱硝活性。低温时,H2O和SO2抑制NO吸附和转化活化,导致硫铵盐累积和活性位转变为硫酸盐使催化剂失活。因此,提高抗H2O、抗SO2性能是低温脱硝催化剂研发的重要方向。而发展在线升温等再生工艺以解决硝酸盐或含硫化合物导致的失活问题,对保障低温脱硝系统长期稳定运行具有重要意义。

关键词: 选择催化还原, 催化剂, 氨气, 氮氧化物, 吸附, 活化, 活性

Abstract:

In this work, adsorption, activation, and reactivity of NH3 and NO on the selective catalytic reduction (SCR) catalysts and the effects of H2O and SO2 on the reaction behaviors of NH3 and NO were reviewed. The analysis shows that the co-reaction between the H-abstraction products of the adsorbed NH3 and the adsorbed NO species (or gas phase NO) is the key to determine the NH3 reactivity and the final SCR product. The gas phase NO could react with the H-abstraction products of the adsorbed NH3 directly (Eley-Rideal mechanism). In addition, a lot of conversion products, such as nitrites and nitrates species, could form after NO was adsorbed and activated on the catalyst surface. These species could also react with adsorbed NH3 species (Langmuir-Hinshelwood mechanism). This is another important pathway for NO to participate in the SCR reaction, especially at low temperature. It is beneficial for the adsorption and conversion of NH3 and NO to enhance the catalyst acidity and redox ability. The effects of H2O and SO2 on the catalyst are influenced by the temperature. At high temperature, the effect of H2O on the catalyst is very little, while the catalyst acidity could be enhanced by SO2, which enhance NH3 adsorption. At low temperature, however, the adsorption and conversion of NO could be inhibited severely by H2O and SO2, especially the SO2. The accumulation of ammonia sulphate and the conversion of active sites to sulphate could result in severe deactivation of the catalyst. Therefore, it is still a severe challenge to improve the H2O and SO2 resistance ability for developing low temperature SCR catalyst. It is of great significance to increase the catalyst temperature to decompose the nitrate and sulfate to regenerate the catalyst in operation.

Key words: selective catalytic reduction (SCR), catalyst, ammonia, nitrogen oxides, adsorption, activation, reactivity

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