层嵌主客体钼铁复合材料构建及主客体间相互作用对催化消除NOx性能与机理的影响研究

V2O5-WO3/TiO2 catalyst has been used commercially, while it has many shortcomings in practical application, such as the narrow temperature window, poor thermal stability and biological toxicity, the high manufacturing costs. To solve these problems, a series of environmental-friendly and low cost catalysts with wide operating temperature window and excellent thermal stability need be developed for NH3-SCR reaction. Using a two-dimensional layered structure of α-MoO3, host (α-MoO3) guest (Fe) composites formed through lamellar intercalation will be synthesized, and "subject—object" relationship model will be built. The design of this lamellar intercalation functional composite is conducive to strengthening the interaction between these two metal elements, regulating the surface geometry and electronic structure of each metal element, improving the physical and chemical properties of the catalyst and obtaining the properties of the host-guest interaction, which will further enhance NH3-SCR reaction performance. In-situ mass spectrometry and DRIFTS are combined to elucidate the dynamic relationship between the composite and the adsorption-activation of the reaction molecules. The NH3-SCR reaction pathway of the catalyst is also proposed, and the relationship model of "structure—NH3-SCR activity—reaction mechanism" is established, which will provide the theoretical and experimental basis for the development of efficient NH3-SCR catalysts.

针对柴油机NOx选择催化消除中商业V2O5-WO3/TiO2催化剂操作温度窗口窄、生产成本高、热稳定性差、生物毒性等不足，研究开发具有宽操作温度窗口和优良热稳定性的环境友好型高效廉价的NH3-SCR催化剂。利用α-MoO3的二维层状结构，设计合成一种特殊的层状主(α-MoO3)客(Fe)体嵌入型复合材料，建立“主体—客体”关系模型。这种层嵌钼铁功能复合材料的设计，有利于加强两种金属元素之间的相互作用，调控各金属元素的表面几何和电子结构，改善催化剂的物理、化学等性质，进而提高催化剂NH3-SCR反应性能。将原位质谱与原位红外光谱技术相结合，阐明层嵌钼铁复合氧化物与反应分子吸附活化之间的动态关系，并提出该催化剂的NH3-SCR反应路径，建立“催化剂结构—NH3-SCR活性—反应机理"三者之间的关系模型理，为开发高效NH3-SCR催化剂提供理论和实验基础。

针对柴油机NOx选择催化消除中商业V2O5-WO3/TiO2催化剂操作温度窗口窄、生产成本高、热稳定性差、生物毒性等不足，研究开发具有宽操作温度窗口和优良热稳定性的环境友好型高效廉价的NH3-SCR催化剂。本项目基于Fe3+与Mo6+之间的相互作用，形成具有Fe2O3-Fe2(MoO4)3结构的FeMo复合氧化物催化剂，其展现出优良的脱硝性能(在225-425oC温度范围内，NOx转化率能达到80%以上)。Fe2O3和Fe2(MoO4)3产生界面相互作用，有利于物种间形成电子相互作用，进而使得Fe物种呈现缺电子状态而Mo物种呈现富电子状态。一方面，缺电子状态的Fe物种和界面间电子相互作用使得亲电性质的Lewis酸增多。另一方面，Mo(VI)由MoO3的八面体结构变化为MoO42-中的四面体结构导致不饱和Mo=O键的形成，从而导致Mo-OH结构的形成增加了Brønsted酸性位的数量。两者之间的电子相互作用也在一定程度上抑制了NO2/NO2-进一步氧化生成NO3-。此外，利用原位质谱与原位红外光谱技术相结合，提出了该催化剂的NH3-SCR反应路径。吸附NH3物种不仅可以通过Eley-Rideal反应路径与气态NO2反应，而且还可以与被吸附的NO2-和NO3-物种通过Langmuir-Hinshelwood反应路径发生反应而生成中间物质，然后分解为N2和H2O。NO2和NO2-的形成促进了反应过程，且为NH3-SCR反应的速控步骤。基于研究结果，建立了“催化剂结构--SCR活性-反应机理"三者之间的关系模型理，为开发高效NH3-SCR催化剂提供了新策略。