Co3O4/CeTiOx多级结构微纳米材料的光助NH3-SCR催化性能及反应机理研究

Selective catalytic reduction of NOx with NH3 (NH3-SCR) is considered as a potential technology for the removal of NOx from diesel vehicles, whereas the V-based catalysts under investigation still have some problems, such as the unsatisfied low-temperature activity and N2 selectivity, and the narrow temperature window. The project in application proposes to use photo-assisted NH3-SCR technology to solve these problems. In this project, Co3O4/CeTiOx materials with hierarchical structures possessing some special microstructures and orientation of crystal face will be fabricated on the molecular level, and the photo-catalysis will be utilized as an assistant method to produce hydroxyl and oxygen radicals, which could be beneficial for the activation of gas-phase NOx and NH3 on the surface of catalyst, and therefore improve the performance of traditional NH3-SCR reaction. Furthermore, the kinds and behaviors of surface adsorbed species will be investigated combined with various in situ spectroscopies (in situ FTIR/ DRIFT, in situ MS and in situ ESR) and DFT calculations. Based on the analysis, the structure-property relationship between the active sites and catalytic activation and the specific mechanism of photo-assisted NH3-SCR reaction will be clarified, and these results will be helpful for the improvement of the catalysts. The execution of this project will provide some new thoughts for the promotion of the traditional NH3-SCR reactions and the applicative catalysts, and it has great meaning for the solution of the predicament of the NOx abatement from diesel vehicles.

NH3选择性催化还原（NH3-SCR）技术在柴油机动车尾气NOx催化净化中具有良好的应用前景，但是目前钒基催化剂普遍存在低温活性不足、高温区N2选择性较低以及反应温度窗口较窄等问题。针对上述问题，本申请项目拟采用光助NH3-SCR技术，通过在分子水平上构建具有特殊微观结构和晶面取向特性的Co3O4/CeTiOx多级结构微纳米催化材料，利用光激发辅助方式产生羟基自由基及氧自由基等活性物种促进NOx和NH3分子在催化材料表面的活化，以改善传统NH3-SCR反应性能。在此基础上，将采用多种表征手段并结合多种原位谱学技术以及量子化学计算方法，考察催化材料表面吸附态物种的种类及其反应行为，建立催化剂活性位点与催化活性的构效关系，阐明光助NH3-SCR反应机理。本项目的实施能够为传统NH3-SCR反应及其适用催化剂的设计改良提供新思路，对于解决目前柴油机动车尾气NOx催化净化所面临的困境具有重要意义。

NH3选择性催化还原（NH3-SCR）技术在柴油机动车尾气NOx催化净化中具有良好的应用前景，但是目前钒基催化剂普遍存在低温活性不足、高温区N2选择性较低以及反应温度窗口较窄等问题。针对上述问题，本项目采用光助NH3-SCR技术，利用光激发辅助方式产生羟基自由基及氧自由基等活性物种促进NOx和NH3分子在催化材料表面的活化，以改善传统NH3-SCR反应性能。.本项目通过构建具有多级微纳米结构的Co-Ce-Ti复合催化材料、Mn-Ni-Ti固溶体催化剂等，有效提高了TiO2基脱硝催化剂的低温活性、拓宽了反应窗口。催化材料中M1-O-M2（M1、M2为不同掺杂金属元素）复合键的生成增强了催化剂的晶格缺陷和表面缺陷，并通过调控Co、Ce、Mn等元素价态和表面吸附氧浓度，促进了反应物种NO和NH3分子在催化剂表面的吸附和活化。在光协同条件下，光辐射作用可进一步促进NO分子的活化，从而促进了NH3-SCR反应的发生。上述催化剂的NH3-SCR或光助NH3-SCR反应机理通过原位红外谱学技术得以验证。本项目通过原位红外实验，充分考察了催化材料表面吸附态物种的种类及其反应行为，建立了催化剂活性位点与催化活性的构效关系。此外，依托本项目，项目组构建了多种具有良好光催化或催化氧化性能的Co基纳米催化材料，包括Co3O4 QDs/g-C3N4、Co/AC、Co-Mn/AC等，为设计适用于光助NH3-SCR反应催化剂拓宽了思路。本项目的研究成果可为传统NH3-SCR反应及其适用催化剂的设计改良提供新思路，对于解决目前柴油机动车尾气NOx催化净化所面临的困境具有重要意义。