Determination of Transient Reaction Kinetics for Unsteady-State Methanation of CO2 on Ruthenium Catalysts using Periodic Experimentation

将可再生能源纳入化学价值链需要设计能够灵活应对原材料供应、质量和组成的时间波动的化学反应器。一方面，应实现恒定的产品质量，另一方面，即使在高度动态的条件下，也应确保安全运行。在固体催化剂上进行的化学过程尤其重要，因为就价值创造而言，它们在化学工业中所占份额最大。化学反应器的设计和尺寸设计的关键是反应动力学，反应动力学是在适当的数学反应器模型中实现的，并代表固体表面的催化过程。现在使用反应器模型来模拟和优化反应器的负荷特性、产品产率和其他方面。对于高度动态的操作模式，动力学也需要充分反映催化剂的瞬时行为。然而，在大多数情况下，这种瞬时反应动力学是未知的，或者在一定程度上是未知的，因为到目前为止，通常进行稳态实验来获得动力学信息。该项目旨在通过高动态周期性实验和基于模型的实验数据评估来获取暂态动力学信息。在相关技术条件下，在Ru基催化剂上二氧化碳加氢制甲烷是一个具有技术相关性的反应范例。将证明化学反应器的周期阶跃响应包含相应的动力学信息，并且这些信息可以根据动态反应器模型的实验结果来确定。特别是，将调查在周期运行期间建立的极限环。重点是开发一种从周期性阶跃响应确定暂态动力学的方法，其中包括适当的实验程序和基于模型的评估策略。为此，选择了一类多相催化的气相反应中与应用相关的示例反应，它相对于所涉及的基本反应提供了足够的复杂性，以提供可推广的结论。

The integration of renewable energies into the chemical value chain requires the design of chemical reactors that can respond flexibly to temporal fluctuations in the availability, quality and composition of the raw materials. On the one hand, a constant product quality should be achieved and, on the other hand, safe operation should be guaranteed even under highly dynamic conditions. Chemical processes that take place on solid catalysts are particularly relevant, as they account for by far the largest share in the chemical industry in terms of value creation. Essential for the design and dimensioning of chemical reactors are the reaction kinetics, which are implemented in suitable mathematical reactor models and represent the catalytic processes at the solid surface. The reactor models are now used to simulate and optimize the reactors with regard to load characteristics, product yield and other aspects. For highly dynamic operation mode, kinetics are required that also adequately represent the transient behavior of the catalysts. However, in most cases, such transient reaction kinetics are not known or only to some extent, since steady-state experiments have usually been performed to obtain kinetic information so far. The proposed project aims to obtain transient kinetic information by means of highly dynamic periodic experiments and model-based evaluation of experimental data. The hydrogenation of CO2 to methane on ruthenium-based catalysts under technically relevant conditions serves as an example reaction with technical relevance. It will be demonstrated that the periodic step response of a chemical reactor contains the corresponding kinetic information and that such information can be determined from the experimental results on the basis of a dynamic reactor model. In particular, the limit cycle that is established during periodic operation will be investigated. The focus is on the development of a methodology for the determination of the transient kinetics from periodic step responses, which includes an adequate experimental procedure and a strategy for model-based evaluation. For this purpose, an application-relevant example reaction from the class of heterogeneously catalyzed gas phase reactions is selected, which offers sufficient complexity with respect to the elementary reactions involved to provide generalizable conclusions.