Additive Manufacturing for Process Intensification: Tailor-Made Design of Catalyst Supports for Single Phase and Multiphase Reaction Systems

Open cellular structures are promising novel catalyst supports as they combine the advantages of randomly packed fixed-bed reactors (radial mixing, tortuosity of the flow) and honeycombs (high geometric specific surface area, low pressure drop) owing to their high porosities and their characteristic 3D cellular architecture. Open cellular structures are manufactured mainly by means of a replication technique, which results in an irregular architecture of the structure, and consequently of the open porous system.

With the rise of additive manufacturing techniques it is nowadays possible to manufacture periodic open cellular structures (POCS) by, e.g., selective electron beam melting (SEBM) with well-defined geometrical properties. In this regard, a new degree of freedom in the design is unlocked as metal-based open cellular structures of nearly arbitrary geometrical complexity can be manufactured in a well-defined and highly reproducible manner.

We have extensively investigated open cellular materials with both periodic [1,2] and random [3] cell geometries regarding their performance as catalyst support. These structures were characterized with respect to their morphological/geometrical properties, fluid dynamic behavior and mass and heat transport properties. Models for the estimation of properties important for reactor design such as, e.g., specific surface area and pressure drop [1, 2] were developed and validated by experiments.

Detailed numerical studies of such geometries and the 3D flow field along with mass and heat transport processes as well as studies on the effective heat conductivity in POCS of different configurations were carried out [3, 4]. The established models allow for the design and optimization of POCS that are tailor-made according to the needs of the reaction system, representing a new class of superior catalyst supports.

The tailor-made POCS were manufactured, functionalized by catalytic coating, and then applied in two case studies for demonstration. In the first case study, the focus is on the optimization of heat transport in a highly exothermic gas phase reaction for enhancing the selectivity, where the oxidation of methanol to formaldehyde serves as example system. In the second case study the phase contacting, i.e. the gas-liquid distribution in a trickle-bed reactor was optimized [5]. As example reaction system, the hydrodesulfurization (HDS) of gas oil was investigated.

For both reaction systems, the tailor-made POCS were benchmarked against a traditional randomly packed bed reactor, and clearly a great potential for process intensification could be demonstrated.

References

[1]       Inayat, A.; Schwerdtfeger, J.; Freund, H.; Koerner, C.; Singer, R.F.; Schwieger, W.; Chem. Eng. Sci. 66(12) (2011) 2758-2763.

[2]       Klumpp, M.; Inayat, A.; Schwerdtfeger, J.; Koerner, C.; Singer, R.F.; Freund, H.; Schwieger, W.; Chem. Eng. J. 242 (2014) 364-378.

[3]       Bianchi, E.; Groppi, G.; Schwieger, W.; Tronconi, E.; Freund, H.; Chem. Eng. J. 264 (2015) 268-279.

[4]       Bianchi, E.; Schwieger, W.; Freund, H.; Adv. Eng. Mater. 18(4) (2016) 608-614.

[5]       Laemmermann, M.; Schwieger, W.; Freund, H.; Catal. Today 273 (2016) 161-171.