Selective catalytic reduction of NOx with NH3 over Cu-SSZ-13 catalysts: Studies on the pronounced dual-maxima profile of the NOx-conversion

Cu-SSZ-13 催化剂上 NH3 选择性催化还原 NOx：NOx 转化的显着双最大值曲线的研究

• 批准号: 325032706
• 负责人: Professor Dr. Jan-Dierk Grunwaldt
• 金额: --
• 依托单位: Institut für Technische Chemie und Polymerchemie (ITCP)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/325032706?language=en
• 关键词: Selective; catalytic; reduction; NOx; NH3

Cu-containing zeolites with chabazite structure such as Cu-SSZ-13 and Cu-SAPO-34 have recently attracted much interest due to their excellent activity for selective catalytic reduction of NOx with NH3 and also because of their remarkable hydrothermal stability and resistance towards HC poisoning. Numerous studies have been published during the last years which deal with systematic research on preparation methods, performance and deactivation, reaction mechanism and kinetics. The main difficulty in obtaining in-depth knowledge of the reaction mechanism results from the very dynamic change of the Cu sites which involves variation of the oxidation state, location within the zeolite framework and also interaction with the reactants (NOx and NH3) and spectator species (H2O). This requires characterization under operating conditions (often called "operando"). With the present proposal we aim at the understanding of these aspects and especially at uncovering the origin of a two-maximum profile (so-called "seagull shape") of the standard SCR reaction, which has been reported for model and commercial Cu-SSZ-13 catalysts. For this purpose, systematic kinetic studies performed in our laboratories for well-defined Cu-SSZ-13 catalysts will be supported by operando spectroscopic investigations with the aim at obtaining relevant structure-reactivity correlations. Additionally, the still strongly debated redox steps (e.g. Cu+ reoxidation) of the SCR related reactions will be investigated. The research will be sustained throughout by targeted variation of the preparation method (e.g. Cu loading, Si:Al ratio) and comprehensive material characterization. Due to their outstanding potential, particularly operando X-ray photon-in/photon-out techniques such as high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD-XAS) and X-ray emission spectroscopy (XES) will be exploited for uncovering reaction mechanism intermediates, as for example the interaction mode of NOx and NH3 with the Cu sites at different temperatures along the seagull SCR profile. Moreover, while exposing the catalyst to realistic gas mixtures and temperatures, spatially (micrometer range) and time resolved (ms range) X-ray absorption spectroscopy (XAS) will be applied for uncovering the dynamics of the electronic structure and local coordination during the different SCR redox steps. The significance of the proposed project lies in providing essential mechanistic details obtained under operando conditions. Understanding the reasons leading to catalyst deactivation at intermediate temperatures as well as obtaining a complete overview on the redox chemistry at the Cu sites during SCR is of significant importance for the further development of this class of catalysts and for generating improved microkinetic models.

具有菱沸石结构的含铜沸石如Cu-SSZ-13和Cu-SAPO-34由于其优异的用NH3选择性催化还原NOx的活性以及还由于其显著的水热稳定性和抗HC中毒性而最近引起了广泛的兴趣。在过去的几年中，已经发表了大量的研究，涉及制备方法，性能和失活，反应机理和动力学的系统研究。在获得深入的知识的反应机理的主要困难的结果从非常动态的变化的Cu网站，其中涉及的氧化态的变化，在沸石框架内的位置，也与反应物（NOx和NH3）和旁观者物种（H2O）的相互作用。这需要在操作条件下进行表征（通常称为“operando”）。通过本提案，我们的目标是了解这些方面，特别是揭示标准SCR反应的两个最大值曲线（所谓的“海鸥形状”）的起源，该曲线已针对模型和商业Cu-SSZ-13催化剂进行了报道。为此，在我们的实验室进行的系统动力学研究明确的Cu-SSZ-13催化剂将支持操作光谱调查，目的是获得相关的结构-反应性的相关性。此外，仍然强烈争论的SCR相关反应的氧化还原步骤（例如Cu+再氧化）将进行研究。该研究将通过有针对性地改变制备方法（例如Cu负载，Si：Al比）和全面的材料表征来持续进行。由于其突出的潜力，特别是可操作的X射线光子输入/光子输出技术，如高能量分辨率荧光检测的X射线吸收光谱（HERFD-XAS）和X射线发射光谱（XES）将被用于揭示反应机理中间体，例如，在不同温度下的NOx和NH3与Cu位点的相互作用模式沿着海鸥SCR曲线。此外，在将催化剂暴露于真实的气体混合物和温度的同时，将应用空间（微米范围）和时间分辨（毫秒范围）的X射线吸收光谱（XAS）来揭示不同SCR氧化还原步骤期间的电子结构和局部配位的动态。建议项目的意义在于提供在操作条件下获得的基本机械细节。了解的原因导致催化剂失活在中间温度下，以及获得一个完整的概述在SCR过程中的Cu网站的氧化还原化学这类催化剂的进一步发展，并产生改进的微观动力学模型是非常重要的。