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Cellular Catalyst Supports

Cellular structures as novel catalyst supports

The realization of optimal reaction conditions requires the possibility to control the effective transport properties of the catalytic bed. In this context the use of structured catalyst supports offers a high degree of freedom for a more efficient geometry design. However, to fully exploit the potential of structured catalysts at first a detailed understanding of the interaction between geometric features and transport properties is necessary.

In the “Catalytic Reactors and Process Technology” group detailed numerical simulations in 3D models are used to investigate the transport properties of open cellular structures. This is, in addition to the kinetic investigations (kinetic modeling) carried out in the group, a first step to assess the potential of these novel supports in catalytic reactors.

To obtain a numerical representation of the catalyst support geometry real samples (e.g., open-cell foams) can be digitized using X-rays micro computed tomography (μ-CT), a non-destructive technique enabling resolutions in the order of microns. This allows a detailed characterization of the geometry and the comparison with further experimental results.

Furthermore, depending on the application, the random geometry of the open-cell support can be simplified as a uniform matrix of equal cells. In such a way, the complexity of the problem is decreased to a single cell, which is the representative elementary volume (REV) of the material. In this case the geometry of the solid matrix can be constructed with CAD tools or result from a rigorous optimization with a desired objective. Also, it is possible to generate a catalyst support structure numerically from scratch to have full control over its detailed properties (e.g., porosity and surface area) for the examination of new structuring concepts.

The heat transfer in the 3D models can be investigated by numerical simulations (e.g. Finite Volume Analysis) to gain information about hot/cold spots and the different influence of conduction and convection. This allows identifying designs that reduce heat transport limitations and thermal stress on structure and catalyst. Similarly, the properties with respect to fluid flow (e.g., pressure drop, velocity distribution) and mass transport (e.g., residence time distribution, dispersion) can be studied numerically. Achieving improved mass transport and lower pressure drop can considerably reduce operating costs of a chemical plant. Additionally, the improved control of the flow regime, the temperature distribution and residence time can increase selectivity and yield, and thereby the overall reactor performance.

For the detailed simulations several different numerical methods (e.g., Finite Volume, Lattice Boltzmann) and tools (open source codes, in-house developments) are applied. Due to the detailed simulations and the investigated geometry size it is often necessary to conduct the simulations on high performance compute clusters to obtain suitable results in a reasonable time frame.

Using selective electron beam melting (SEBM) the optimized geometries can be manufactured in the facilities for additive manufacturing of process engineering components at VerTec. The realized geometries can then undergo testing and experiments.

Taking all the obtained information into account, the influence of different geometric properties on the overall reactor performance can be identified. Owing to the short feedback loop between geometrical parameters and relevant physical properties (numerical experiment), various classes of structures can systematically be investigated, evaluated and new structures for improved reactor performance can be proposed.

 


Fundings and Cooperations

Cluster of Excellence “Engineering of Advanced Materials” (EAM)

Central Institute for Scientific Computing (ZISC)

Chair of Applied Mathematics 2 (Prof. Dr. Michael Stingl)

Chair of Metals Science and Technology (Prof. Dr.-Ing. Robert F. Singer, Prof. Dr.-Ing. habil. Carolin Körner)

Chair of Theoretical Physics 1 (Prof. Dr. Klaus Mecke)

Laboratory of Catalysis and Catalytic Processes, Politecnico di Milano (Prof. Enrico Tronconi, Prof. Gianpiero Groppi)

 

 


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