双活性组分小孔分子筛用于脱硝反应中的构效关系及抗中毒性能研究

Oxides of nitrogen (NOx) in the atmosphere, as key precursory pollutants, induce the formation of haze. The selective catalytic reduction of NOx by NH3 (NH3-SCR) is one of the most promising technologies for NOx emission control from diesel engines. Compared with other NH3-SCR catalysts, Fe-Cu-SSZ-13, bimetallic-based small-pore zeolites, showed higher hydrothermal stability and better sulfate and water durability. The study on its structure-activity relationship and resistance to poisoning is very important for the further catalytic performance improvements. In this study, many characterization methods will be used for probing the state of active species and interaction caused by bimetal, and the results will be correlated to their catalytic performance. The relationship will provide a guideline for designing catalysts with excellent NH3-SCR activity, high hydrothermal stability and good sulfate and water durability. Based on the effect of water and sulfate on the physiochemical properties and active species, poisoning mechanism of SO2 and H2O on NH3-SCR reaction over the optimized Fe-Cu-SSZ-13 catalyst will be investigated. The effect of NO2 on the poisoning resistance of Fe-Cu-SSZ-13 catalyst will be also studied. These results will provide theoretical basis and basic data for the developments of new catalysts used for diesel engines exhaust purify.

氮氧化物（NOx）是灰霾形成的重要前体污染物，NH3选择性催化还原NOx（NH3-SCR）是目前柴油车尾气NOx去除的主流技术。相比于其他NH3-SCR催化剂，双活性组分小孔分子筛Fe-Cu-SSZ-13具有更为优异的水热稳定性和抗硫抗水中毒能力，其构效关系和抗中毒机制的研究对催化剂的进一步改良具有十分重要的意义。本项目采用多种表征手段，探讨Fe-Cu-SSZ-13催化剂表面双活性组分物种的存在状态、相互作用等对催化剂催化性能的影响规律，制备催化活性优异、水热稳定性高、抗硫抗水能力强的Fe-Cu-SSZ-13催化剂；通过解析水、硫共存对催化剂理化性质和活性物种的影响，揭示催化剂的抗硫抗水中毒机制；调变反应气氛，剖析NO2对催化剂抗硫抗水中毒能力的影响规律；以上研究成果将为研制可满足柴油车尾气净化需求的新型催化剂提供科学依据和技术储备。

氮氧化物（NOx）是灰霾形成的重要前体污染物，NH3选择性催化还原NOx（NH3-SCR）是目前柴油车尾气NOx去除的主流技术。Cu-SSZ-13催化性能优异，但抗硫中毒能力有待提高。本项目以提高该系列催化剂的催化性能为目标，研究第二金属元素Fe的掺杂方式、制备环境以及焙烧条件等对该催化剂水热稳定性及抗硫中毒能力的影响。探讨CuFe-SSZ-13催化剂表面双活性组分物种的存在状态、相互作用等对催化剂催化性能的影响规律，制备催化活性优异、水热稳定性高、抗硫抗水能力强的Fe-Cu-SSZ-13催化剂；揭示催化剂的抗硫抗水中毒机制。研究结果表明，采用液相离子交换法、固相离子交换法以及均匀沉淀法均可制备催化活性优异的CuFe-SSZ-13催化剂。Fe的掺杂均显著提高催化剂的抗硫中毒能力，不同掺杂方式之间无显著差异，但Fe的掺杂方式显著影响催化剂的水热稳定性。综合考虑催化剂NH3-SCR催化性能，液相离子交换法是制备Fe-Cu-SSZ-13催化剂的最佳制备方法。进一步对液相离子交换法的制备步骤进行优化，制备出催化活性、水热稳定性和抗硫中毒能力都显著高于Cu-SSZ-13的催化剂。对优选后的Fe-Cu-SSZ-13进行反应机理的研究发现CuFe-SSZ-13同时具有Cu-SSZ-13和Fe-SSZ-13反应的特征。在硫中毒条件下，Fe物种的存在不仅降低Cu物种的中毒程度，也影响了硫化后催化剂的反应路径，最终提高了硫化条件下的低温活性。项目的研究成果对柴油车尾气NOX催化净化后处理系统有较好的理论及技术指导意义。