不同晶粒Cu/SAPO-34 SCR催化剂可控制备及构效关系和反应机理研究

Cu/SAPO-34 catalysts have become the focus in SCR research due to its superior SCR activity, excellent N2 selectivity, high hydrothermal durability and carbon deposition prevention.Presently, the controllable preparation of different particle sizes have not been reported. The structure-activity relationship of Cu/SAPO-34 catalyst need to be deepened. And the SCR reaction mechanism is still unclear. In this project, using high-throughput screening technology, we will achieve controllable one-step synthesis method of Cu/SAPO-34 for different particle sizes. The structure-activity relationship between particle size, acidity, active species and catalytic activity, high/low temperature hydrothermal stability, resistance to poisoning (sulfur poisoning, coke and alkaline metal poisoning) will be systematic investigated. By pre-poisoning of acid site and active site method combining in-situ technology and kinetics analysis, the complex SCR reaction process will be revealed. The cause of saddle-shaped curve during NH3-SCR reaction process will be intensively studied. The SCR reaction mechanism of copper-based small pore zeolite will be further improved. It will provide basic data and theoretical guidance for high-performance materials development.

Cu/SAPO-34具有优异的富氧条件下NOx催化脱除能力、高温水热稳定性及抗积碳能力，已成为车用脱硝催化剂的研究热点。但关于不同晶粒Cu/SAPO-34催化剂的可控制备还未见报道，构效关系研究有待深入，NH3-SCR催化反应机理尚未明确。本课题通过采用高通量筛选技术，实现不同晶粒Cu/SAPO-34的可控制备；阐明Cu/SAPO-34晶粒、酸性及活性物种等结构参数与催化活性、高/低温水热稳定性及抗中毒（硫中毒、积炭、碱金属中毒）等性能之间的构效关系；利用酸性位/活性中心预毒化方法，结合原位EPR、原位DRIFTS、原位XRD及动力学表征等多种手段，揭示酸性、活性物种对氨吸附/迁移的影响机制，解析Cu/SAPO-34催化剂NH3- SCR催化反应马鞍形活性曲线的形成原因，完善铜基小孔分子筛SCR催化反应机理，为高性能材料的开发提供基础数据和理论指导。

铜基CHA型分子筛催化剂因具有优异的NH3-SCR催化性能而备受关注，但水热稳定性问题、硫中毒问题及碱金属中毒问题的存在制约了其商业化应用。本课题研究内容包括1）不同晶粒Cu/SAPO-34和Cu/SSZ-13催化剂合成；2）不同晶粒CHA型SCR催化剂构效关系研究；3）Cu/CHA SCR催化剂应用研究。通过优化原位水热合成工艺，实现了不同晶粒尺寸、结构和酸位性质均一的Cu/SAPO-34和Cu/SSZ-13催化剂的可控制备；研究发现晶粒尺寸影响Cu/SAPO-34中Si元素的分布，晶粒尺寸越大，表面的Si-O-Al键越富集，低温水热稳定性越差；动力学结果表明，不同粒径的Cu/SSZ-13样品表现出了相同的Ea以及TOF值，NH3-SCR反应不受晶内扩散控制；应用研究表明，Cu/CHA催化剂在硫中毒过程中，均发生Cu2+数量下降，生成硫酸铜物种，使NH3-SCR的催化性能降低，但Cu/SSZ-13催化剂的耐酸能力强于Cu/SAPO-34，分子筛骨架结构受到硫中毒影响较小；碱金属中毒研究表明，Na离子能置换Cu/SAPO-13中的H+和孤立态Cu2+，形成SiO2/AlPO4和“类CuAl2O4”等新物种，导致NH3-SCR活性降低。K离子对Cu/SSZ-13催化剂的毒化机理类似，活性位降低和CHA骨架结构破坏导致了催化剂的SCR反应活性下降。