核壳结构锰铈基催化剂的构建及其低温SCR选择性和抗硫性的研究

MnCe-based catalysts show promising catalytic properties and hold great potential for selective catalytic reduction (SCR) of NOx at low temperature, but still suffer from the following major obstacles: (1) poor low temperature N2 selectivity and weak SO2-resistance ability, (2) the limited understanding of the interfacial active sites and the redox couple cycle mechanism, and (3) the catalyst deactivation/poisoning and SO2-resistance mechanisms in different temperature remain disputable. In this proposed project, we expect to achieve a breakthrough to solve aforementioned problems through the proposed catalyst structure and mechanism innovations. First, we will for the first time construct a novel core-shell hetero-structured Mn@Ce catalysts, i.e., MnOx nanoflakes grafted CeO2 nanorods with {110} exposed plane. Subsequently, coat the surface of Mn@Ce with ultrathin SnOx thin layers that serve as additional acid sites and protecting barriers, and further couple with N-doped graphene to enhance the electron migration between the redox couples. All the components will interact with each other and generate a synergy to enhance the low temperature N2 selectivity and improve the tolerance to SO2 and durability. Second, deeply gain insights into the hetero-structured catalyst interface and electron transfer mechanism between redox couples by various ex-situ and in situ spectroscopic techniques. Finally, comprehensively evaluate the low temperature SCR performance for NOx removal, such as NO conversion efficiency, N2 selectivity, and long-term SO2 durability, and further understand the catalyst deactivation and SO2-resistance mechanism in different temperatures, so that we can establish the correlations between catalysts structure-property-activity. The findings in this project will provide fundamental principles and viable options to develop novel, efficient, and stable catalysts for deNOx at low temperatures, and to advance the understanding of the heterojunction interface and deactivation mechanism.

目前锰铈基催化剂在低温SCR脱硝方面表现出良好的应用前景，但依然面临挑战：(1)低温N2选择性和抗硫性差；(2)其界面化学和氧化还原电对之间电荷转移机制不明确；(3)催化剂失活中毒和抗中毒机理尚存争议。本项目拟从催化剂结构和机理出发，首先合成多孔核壳结构MnOx@CeO2异质催化剂：将MnOx纳米片嫁接到CeO2纳米棒上，再在其表面涂SnOx薄膜形成保护层和提供酸性位，并与N-掺杂石墨烯耦合以提高Mn、Ce、Sn电对循环之间电子转移。各组分产生协同效应，从而提高催化性能，然后采用先进的准原位和原位谱学与表面技术阐明异质催化剂的界面结构和电对之间的相互作用；最后系统评价催化剂在低温SCR反应性能和抗硫耐久性，并探索催化剂的失活和抗中毒机制，建立锰铈基催化剂结构和性能之间的构效关系。该项目实施将为开发新型高效稳定低温SCR脱销催化剂、加深对催化剂结构和抗中毒机理的认识提供理论依据和技术支持。

针对当前大气污染的严峻形势，结合锰铈基催化剂在低温SCR脱硝方面表现出良好的应用前景，以研究 NOx 催化消除的高效催化剂为目的。本项目根据研究存在的(1)低温 N2选择性和抗硫性差；(2)其界面化学和氧化还原电对之间电荷转移机制不明确；(3)催化剂失活中毒和抗中毒机理尚存争议这几个方面的问题。拟从催化剂结构和机理出发。①考察了不同掺杂元素，制备方法，形貌等因素对掺杂改性的铈基催化剂的性质和 NH3-SCR 催化性能的影响规律；② 阐明了载体改性等手段对活性组分的的影响以及铈基载体与活性组分之间相互作用的变化；为科学调变铈基催化剂的性质提供了科学依据。③ 借助于多种原位表征手段追踪吸附物种和催化剂表面在反应中的变化历程，揭示了催化剂与反应物分子之间的相互作用及其与反应活性之间的关系；构建“载体表面结构-负载活性物种-反应物分子”的内在联系，从分子层面探讨了铈基催化剂 NO 消除反应的微观过程及催化作用机制。最后系统评价催化剂在低温SCR反应性能和抗硫耐久性， 并探索催化剂的失活和抗中毒机制，初步建立了组成、结构与催化性能之间的构效关系，为开发设计高效实用的 NOx 净化催化剂，加深对催化剂结构和抗中毒机理的认识提供相关的理论参考。已发表相关研究论文 7 篇。