新型铁基小孔分子筛的制备及其脱硝反应过程与机理研究

Environmental-friendly removal of NOx from mobile sources such as diesel exhaust is a research hotspot in the field of air pollution control. At present, the selective catalytic reduction of NO with NH3　(NH3-SCR) is one of the most promising techniques for NOx removal from diesel exhaust. Due to some inevitable disadvantages of the present vanadium based catalyst, this research combined the great potential HCs tolerance of small-pore zeolites and the great catalytic performance of Fe-zeolites, such as good medium-high temperature activity, broad operating temperature window, stability, good H2O/SO2 durability, et al. and studied the controllable synthesis of novel small-pore Fe-based zeolites with high Fe loading and high dispersivity. This research aimed at improvement of low temperature activity of Fe-zeolites and focused on the development of novel, highly efficient, stable, environmental-friendly NH3-SCR catalysts, and discussed their feasibility industrial use. Furthermore, the research placed emphasis on the gas-solid interface and the interference relationship between the physicochemical states of materials and their catalytic performance with various advanced characterization and in-situ reaction techniques. The effect of catalyst structure, reaction process and reaction mechanism were revealed. Also, the poisoning resistance performance and catalytic stability of the catalysts for simulated diesel exhaust elimination were studied and their potential application was revealed. This research integrated poriferous materials and catalytic removal of NOx. The implement of this project would provide new materials and new ideas for NOx control.

柴油车尾气等移动源NOx的环境友好消除是当前大气污染控制领域的研究热点，氨选择性催化还原 (NH3-SCR)技术是最有希望实际应用于柴油车NOx尾气控制的技术之一。针对传统钒基催化剂体系应用于柴油车尾气净化存在诸多问题，本课题结合小孔分子筛优异的抗HCs中毒潜质和铁分子筛良好的中高温活性、宽操作温度窗口、较好的热稳定性和抗H2O/SO2等性能，开展新型高负载量、高分散的铁基小孔分子筛催化材料的合成规律研究，提高其低温活性，开发具有高NH3-SCR活性、水热稳定、环境友好的催化剂体系，探讨其高效消除NOx尾气的工业应用前景。在此基础上采用原位技术及先进的表征手段重点研究NH3-SCR反应过程中气-固界面过程及材料物化性质与催化性能的内在关联，揭示NH3-SCR反应的构效关系、反应过程及反应机理。本项目是孔材料与NOx污染控制领域的交叉与结合，项目的实施将为NOx的控制提供新材料和新思路。

本项目针对柴油车尾气中NOx的环境友好消除，结合小孔分子筛优异的抗HCs中毒潜质和铁分子筛良好的中高温活性，采用离子交换法成功制备了八元环小孔Fe-LTA、Fe-ABW和Fe-SSZ-13分子筛，发现分子筛负载铁含量、铁物种分布及催化性能都与分子筛载体结构密切相关。三种铁分子筛中，铁含量顺序为Fe-LTA＞Fe-ABW＞Fe-SSZ-13。催化活性顺序为Fe-SSZ-13＞Fe-LTA＞Fe-ABW。结合表征结果发现， Fe-LTA和Fe-ABW分子筛孔道中存在大量的铁氧化物团簇和纳米铁氧化物，而Fe-SSZ-13分子筛中主要存在的铁物种为孤立的铁离子。因此，孤立的铁离子是NOx催化还原反应的活性物种，而分子筛孔道中铁氧化物团簇次之，而纳米铁氧化物活性很低。同时所制备的Fe-SSZ-13具有优异的催化活性和稳定性，并且具有非常强的抗CHx中毒能力，非常具有应用前景和研究价值。.在此基础上，开展采用无有机模板剂条件下的晶种导向法合成Fe-SSZ-13分子筛，以减少价格昂贵的模板剂N,N,N-三甲基金刚烷氢氧化铵的使用，促进其实际工业应用。最佳的合成条件是未焙烧的ssz-13作晶种，晶种量15%，晶化温度100℃、4d，Si/Al比为20条件下，能合成最高含量的SSZ-13。采用晶种合成的SSZ-13负载金属离子Fe和Cu以后，催化活性与以金刚烷为模板剂合成的SSZ-13活性相当，且价格低廉，具有很强的应用前景。.本项目采用超声辅助浸渍法成功合成了高铁含量的FeMOR-5%-UV催化剂，并且发现其具有很高的NO催化还原活性，且显著高于传统的浸渍法和离子交换法所制备催化剂。FeMOR-5%-UV优异的催化性能主要归因于在超声过程中引入了更多的离子交换位上的孤立的Fe3+离子。活性最高的FeMOR-5%-UV催化剂在添加SO2等多种气氛时，催化活性下降不显著。在持续100 h的汽车尾气条件下进行稳定性实验，FeMOR-5%-UV的催化活性没有明显下降。FeMOR-5%-UV的优异的催化活性和稳定性非常具有应用前景和研究价值。.并通过量子化学计算设计含铁有机胺络合物作模板剂设计合成分子筛研究，为相关分子筛的合成过程提供理论依据和实验指导。研究结果对汽车尾气中氮氧化物的控制和消除具有理论价值和实际意义。