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

本项目致力于负载型VOX催化剂的现场/操作研究。结合对这些材料的新见解，将使用新开发的装置，在BAM小组同时进行时间和空间分辨率的XAFS测量。这促进了本申请的新颖性。这种装置的吸引人的特点是：a)探测更大部分的样品，对化学不均匀材料尤其重要，同时识别不同的氧化状态；b)无扫描和c)第二尺度的时间分辨率。鉴于本项目的重点，通过杂原子掺杂改变载体材料应该会导致活性VOx中心的不同氧化还原活性。因此，需要研究的关键参数是V物种的氧化态和配位几何的局部和随时间的变化。根据结果，将研究对催化剂性能的影响，并将在催化剂和反应器装置的进一步开发中考虑。负载型VOx催化剂作为甲烷直接制取甲醛的替代催化剂是非常有吸引力的。计划在该项目中使用/测试的物种(介孔二氧化硅材料)特别适合Vox所需的结构特性。这些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，以便与催化参数直接相关(操作法)。在该项目中，BAM的同步加速器技术和LIKAT在催化研究方面的经验完美地相辅相成。目前，时间分辨XAFS实验和横向分辨XAFS实验是分开存在的。据我们所知，同时提供这两种设施的设施尚未有报道。特别是在催化领域，这种实验在催化剂与合适的反应器设计相结合的开发方面开辟了新的机会，例如单床与多床。这种综合的实验方法使我们对一些具有挑战性的问题有了新的认识，例如热点的形成以及催化活性中心的结构动力学。这有助于为潜在问题找到新的解决方案。甲烷部分氧化制甲醛是检验这种方法的一个合适的反应，这是学术界和工业界都非常感兴趣的。此外，该方法还可以用于其他具有挑战性的甲烷催化反应的催化剂的结构研究，如全氧化、氧化和非氧化偶联、直接合成甲醇等，甚至可以用于催化中一系列悬而未决的结构问题。

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.