高性能多级结构Ce基SCR催化剂的可控制备及反应机理研究

Selective catalytic reduction (SCR) of nitrogen oxides (NOx) is one of the most efficient techniques for eliminating NOx, the key issue is the development of high performance catalysts. However, SCR catalysts usually suffer from problems, such as narrow active temperature window and poor sulfur resistance at low temperature. Ce-based catalysts are shown to exhibit good performance for SCR reaction, and superior sulfur resistance at low-temperature can be expected by carefully controlling the microstructure and surface acid/alkaline sites of the catalysts. In this study, we attempt to prepare CeaR1-aOb (R = Cu or Mn or Co)@CexA1-xOy (A = Ti or W) catalysts with interesting surface/inner multilevel structures by using co-axial electrospinning, in which the inner structures are dominated by oxidation sites while the inner by acid/alkaline sites. Meanwhile, the composition and microstructure as well as surface acid/alkaline sites will be adjusted, to construct high efficient low-temperature SCR catalyst with strong sulfur resistance. A systematic characterization of catalysts would be performed to get information about the composition, structure and performance, being aimed to disclose structure-activity relationship, and clarify the regulatory mechanism over microstructure controlled SCR catalysts by using co-axial electrospinning. The regulatory mechanism of catalyst surface acid/alkaline sites and the reaction mechanism will be disclosed. It is envisioned that the results obtained in the proposed project will provide a useful guidance on the synthesis and design of highly efficient SCR catalysts for NOx removal.

选择性催化还原(SCR)是最有效脱除氮氧化物(NOx)的技术之一，高性能催化剂的研发是实现该过程的关键，但SCR催化剂普遍存在活性温度窗口窄和易硫中毒问题。Ce基催化剂对SCR反应呈现出良好的催化性能，通过微观结构和表面酸/碱性位的调控是改善催化剂低温抗硫性能的关键。本项目拟采用同轴静电纺丝技术，制备具有多级结构的CeaR1-aOb(R = Cu,或Mn或Co)@CexA1-xOy(A = Ti或W)催化剂，内部多层次结构以氧化功能位(CeR)为主，表面多极结构以酸/碱性功能位(CeA)为主。同时通过催化剂组成、微观结构和表面酸/碱性位的调控，构筑高效低温、抗SO2中毒的SCR催化剂。通过各种表征揭示催化剂的组成-结构-催化性能间的构效关系，探明同轴静电纺丝技术对微结构可控SCR催化剂的调控规律，并建立表面酸/碱性位调控机制，阐明催化反应机理，为发展高效SCR催化剂提供理论基础和原型技术。

项目负责人针对低温SCR催化剂存在着温度窗口窄，脱硝效率受逃逸氨等指标制约，应用于广大燃煤工业锅炉存在烟气适应性差（抗特征污染物性能，烟温匹配性）等存在的科学及技术难题， 通过发展多种Ce基催化剂微观结构可控的制备新技术，包括微波单模﹑轴静电纺丝技术等方法， 获得了Ce基催化剂的不同微观 (Chemical Engineering Journal, 2020, 382, 122910; Ind. Eng. Chem. Res. 2017, 56, 14980−14994, Dalton Trans., 2017, 46, 16967; Nanoscale, 2019, 11, 4794), 不同金属和载体间相互作用(Catal. Sci. Technol. 2018, 8, 4494-4502; Ind. Eng. Chem. Res. 2019, 58, 17692−17698) 对催化性能的影响规律，并结合W和 Fe等不同活性金属，调节催化剂氧化还原性质及表面碱性位的数量和分布强度，通过非稳态TPSR和TPD等技术结合原位红外谱，获得催化剂表面的氧化还原性能及酸碱性位，关联L酸和B酸性位的数量与强度与SCR性能间的构效关系，从而揭示了微观结构对表面酸碱性位及氧化还原性能影响的作用机制，获得了催化剂的组成-微观结构-表面酸碱性位-催化性能间的关系，阐明了NH3-SCR催化剂的反应原理..在上述研究的基础上，改变催化剂配方，预处理条件，沉淀方式，成型过程的成型添加剂，干燥和焙烧工艺的深入探究，获得了Ce基催化剂的放大效应和使役特性（授权发明专利：ZL201710677887.1, 一种Ce基氧化物催化剂及其制备与应用; 发明专利：201910600945X)，为进一步实现催化剂的放大化制备提供了原型技术。在该项目的实施过程中，共发表SCI论文8篇，申请发明专利5件，授权专利1件，培养硕士研究生4名。