摘要
Cu-ZSM-5分子筛因具有高的催化脱除NO活性和对环境友好等优点而引起广泛关注。本文从NO分解反应、以NH3为还原剂选择性催化还原NO(NH3-SCR-NO)和以碳氢化合物为还原剂选择性催化还原NO(CH-SCR-NO)三个方面综述了Cu-ZSM-5分子筛催化脱除NO反应机理和催化剂改进方面的研究进展,并对该领域存在的问题和发展前景做了总结和展望。Cu-ZSM-5分子筛催化分解NO被认为是最具有吸引力的脱硝方法,其通过Cu+的氧化还原过程和N2O的生成来实现;Cu-ZSM-5分子筛上NH3-SCR-NO反应具有较高的NO脱除效率,NO首先被氧化为NO2,NO2再与NH3结合为NH4NO3,NH4NO3再进一步与NO反应生成N2;CH-SCR-NO反应是利用贫燃发动机尾气中未完全燃烧的碳氢化合物为还原剂,一般认为碳氢化合物与氮氧化物生成硝基烷或亚硝基烷,再经异氰酸酯或氰化物生成终产物N2。Cu-ZSM-5分子筛存在水热稳定性差和易发生二氧化硫中毒等缺点,通过引入第二金属组分和制备整体式催化剂方法可显著改善Cu-ZSM-5分子筛的催化性能。系统了解NO脱除反应机理和活性位的作用机制可为催化剂的改进奠定理论基础,同时也有助于设计合成新型高效、环境友好的脱硝催化剂体系。
More attention to Cu-ZSM-5 zeolite has been NO, and the process it concerned is non-polluting paid due to its excellent catalytic activities in removal of In this review, the reaction mechanism and catalyst improvement of NO decomposition, selective catalytic reduction of NO with ammonia （ NH3-SCR-NO） and with hydrocarbons （CH-SCR-NO） over Cu-ZSM-5 zeolite are summarized. The possible developing orientations in the field of removal of NO over Cu-ZSM-5 zeolite are also prospected. Direct catalytic decomposition of NO to N2 and 02 has been recognized as the most attractive method for removal of NO, which involves redox process of Cu ＋ and formation of N20. NH3-SCR-NO reaction is one of the most efficient and widely-used techniques. Firstly, NO is oxidized to NO2, and then NH4NO3 is formed from the reaction of NO2 and NH3. Finally, NH4NO3 reacts with NO generating N2. CH-SCR-NO reaction over Cu-ZSM-5 zeolite is an efficient way for the treatment of automobile-exhaust pollution. The formation of key intermediates such as isocyanate and cyanide species is a necessary process during CH-SCR-NO reaction. However, Cu-ZSM-5 zeolite suffers from poorhydrothermal stability and high sulfur dioxide （SO2） poisoning property which have suppressed its industrial applications. Introduction of a second metal and fabrication of monolithic catalyst can significantly improve the catalytic performance of Cu-ZSM-5 zeolite. The systematic understanding of reaction mechanism is beneficial to the improvement of Cu-ZSM-5 zeolite and also important for the design of novel, efficient, environmentally- friendly catalysts.
出处
《化学进展》
SCIE
CAS
CSCD
北大核心
2014年第2期248-258,共11页
Progress in Chemistry
基金
国家自然科学基金项目(No.20806070)资助~~
