Time- and lateral-resolved X-ray Absorption Fine Structure spectroscopy in a single-shot - A new concept for characterizing catalyst materials at work

本计画系针对负载型氧化钒触媒之原位/操作性研究。与对这些材料的新见解一起，将使用新开发的装置，该装置将BAM组的时间和空间分辨XAFS测量同时结合起来。这促进了本申请的新奇性。该装置的吸引人的特点是：a）探测样品的较大部分，这对于化学异质材料尤其重要，同时辨别不同的氧化态; B）无扫描和c）第二尺度的时间分辨率。考虑到本项目的重点，通过杂原子掺杂改变支撑材料应导致活性VOx位点的不同氧化还原活性。因此，调查的关键参数是局部和时间依赖性的变化，氧化态和配位几何的V-物种。根据结果，将研究对催化剂性能的影响，并考虑进一步开发催化剂和反应器装置。负载型VOx催化剂的案例研究是非常有吸引力的甲烷直接生产甲醛的替代品。计划在该项目中使用/测试的物种（中孔二氧化硅材料）特别适合VOx的所需结构特性。测量将在反应池中进行，在出口处进行产物分析，以评估催化剂的结构变化，从而与催化参数直接相关（操作方法）。在该项目中，BAM在同步加速器技术方面的经验和LIKAT在催化研究方面的经验完美地相互补充。目前，时间分辨和横向分辨XAFS实验分别存在。据我们所知，目前还没有报告提供两者结合的设施。特别是在催化领域，这种实验为催化剂与合适的反应器设计的组合开发开辟了新的机会，例如单床与多床。这种集成的实验方法允许新的洞察到一些具有挑战性的问题，例如热点形成以及催化活性位点的结构动力学。这有助于为根本问题找到新的解决办法。用于测试这种方法的合适的反应是甲烷部分氧化成甲醛，这在学术界和工业界都引起了极大的兴趣。此外，该方法可用于催化剂的结构研究，用于其他具有挑战性的催化反应与甲烷，如全氧化，氧化和非氧化偶联，直接甲醇生产等，甚至为一堆未解决的结构问题在催化。

This project addresses to the in situ/operando investigation of supported VOx catalysts. Together with the new insights about these materials, the newly developed set-up that combines time- and spatial-resolved XAFS measurements simultaneously at the BAM group will be used. This promotes the present application to novelty. Attractive features of this set-up are: a) probing a larger portion of the sample, especially important for chemically heterogeneous materials, discerning different oxidation states simultaneously; b) scanningless and c) time resolution in the second scale. Given the focus of the present project, varying the support materials by heteroatom doping should result in different redox activities of the active VOx sites. Hence, the key parameters to investigate are local and time dependent changes in oxidation state and coordination geometry of V-species. Depending on the results, the influence on the catalyst performance will be investigated and will be considered for further developments on the catalysts and the reactor set-up. The case study of supported VOx catalysts is very appealing as an alternative for the direct production of formaldehyde from methane. The species planned to be used/tested in this project (mesoporous silica materials) are especially well suited for the desired structural properties of VOx. The measurements will be carried out in a reaction cell with a product analysis at the exit, in order to evaluate the structural changes of the catalyst to correlate directly with the catalytic parameters (operando approach). In the project the experiences at BAM with synchrotron techniques and at LIKAT in catalytic research ideally complement each other. Nowadays, time- and lateral-resolved XAFS experiments exist separately. Facilities offering a combination of both have not yet been reported, to the best of our knowledge. Especially in the field of catalysis, such experiment opens up new opportunities in the combined development of catalysts with a suitable reactor design, e.g. single-bed vs. multi-bed. This integrated experimental approach allows new insight into some challenging problems, e.g. hot spot formation as well as structural dynamics of catalytic active sites. This can help to find new solutions for underlying problems. A suitable reaction for testing such approach is the partial oxidation of methane to formaldehyde which is of great interest in both academia and industry. Moreover, the approach could be used for the structural investigation of catalysts used for other challenging catalytic reactions with methane, e.g. total oxidation, oxidative and nonoxidative coupling, direct methanol production etc. or even for the bunch of unsolved structural questions in catalysis.