How can the chemical industry operate more energy-efficiently in the future while also utilizing renewable energy? This is precisely the question addressed by the AMAZING research project—Additive Manufacturing for Zero-emission Innovative Green Chemistry.
The goal of this German-Dutch project was to develop a novel ceramic membrane reactor. In such a reactor, chemical reactions and mass separation can be directly combined. For example, hydrogen is produced during the dehydrogenation of alkanes into important chemical feedstocks such as ethylene. If this hydrogen is removed directly from the reaction chamber via a ceramic membrane, the chemical equilibrium can be influenced and the process made more efficient.
The manufacturing of the ceramic membranes played a key role in this process. While Forschungszentrum Jülich contributed an established manufacturing process—film casting—as a reference, WZR’s task was to explore the possibilities of additive manufacturing for such membrane systems.
A Direct Comparison of Four 3D Printing Methods
At the start of the project, it was by no means clear which additive manufacturing process would be best suited for producing the complex membrane structures. That is why we at WZR first investigated four different processes: binder jetting, material jetting, material extrusion, and 3D screen printing.
The goal was not simply to use existing printers with a new ceramic material. For each process, suitable inks, pastes, or powder mixtures had to be developed, and the respective process parameters had to be adjusted. Using all four processes, we were ultimately able to produce test specimens from the LWO material (lanthanum tungstate) used in the project and then sinter them.
Among other things, we evaluated microstructure, strength, and sintering shrinkage. Shrinkage is particularly critical for a multilayer ceramic component: the membrane and the support structure must shrink as uniformly as possible during firing to prevent the component from warping or cracking.
Following the screening, two processes were selected for further development: material extrusion (MEX) and 3D screen printing.
3D Screen Printing: Membrane and Support Structure Manufactured Using Additive Manufacturing
3D screen printing proved to be particularly interesting, as this process can be used to build both very thin, dense ceramic layers and three-dimensional support structures.
However, this required extensive development work. An existing screen printing system at WZR underwent significant technical upgrades. Among other things, a movable and heated build platform was installed. In addition, we developed a control system that automatically synchronized the movement of the build platform, the drying intervals, and the individual printing processes.
An even greater challenge was the development of the ceramic screen-printing paste. Conventional paste systems could not be readily adapted to the LWO material used in the project. Therefore, numerous different formulations and additives were investigated. In particular, the rheology, drying behavior, and subsequent helium leak tightness of the ceramic membrane had to be taken into account simultaneously.
The result was a stable paste with suitable rheological properties.
This made it possible to fabricate the membrane and support structure immediately one after the other. First, five membrane layers were printed. After changing the screen, 70 layers of the structured support geometry were printed. In this way, fully additively manufactured supported membranes were produced.
The subsequent heat treatment was also optimized. After sintering, the membrane and support structure were bonded together without a discernible interface. The residual porosity of the membrane layer was very low. Tests conducted by the project partners at Forschungszentrum Jülich and in the membrane reactor at hte GmbH confirmed the gas tightness. The ceramic membranes achieved thicknesses of only about 30 to 60 µm.
Material Extrusion: 3D Printing Meets Film Casting
At the same time, a second manufacturing method was developed at WZR. Material extrusion allows a complex support structure to be built up relatively quickly. However, this process is less suitable for producing a very thin, gas-tight membrane.
Therefore, the advantages of the two technologies were combined: The thin membrane was produced at Forschungszentrum Jülich using film casting, after which WZR used material extrusion to print the three-dimensional support structure directly onto it.
Numerous development steps were also necessary for this. On the one hand, the MEX paste had to be reliably fed through the 3D printer’s nozzle, and on the other hand, it had to adhere sufficiently well to the delicate membrane film. In early trials, drying stresses still led to deformations, delamination, and in some cases even cracks in the membrane.
These problems were resolved by further developing the paste formulation and modifying the extrusion unit. At the same time, the solid content of the paste was adjusted so that the shrinkage of the printed support structure could be matched to that of the membrane.
The result: planar, monolithic sintered composite components consisting of a film-cast membrane and a 3D-printed support structure.
More Than Just a New Manufacturing Process
Throughout the project, the geometry of the membranes was also continuously refined. The active membrane area was enlarged, integration into the metal frame was improved, and gas tightness was further enhanced. At the same time, the proton flux through the membranes was increased.
This marked the achievement of an important project goal: Both fully 3D-printed membrane-support structures and hybrid components made using film casting and material extrusion were successfully produced.
For WZR, however, the results extend beyond the specific application in the AMAZING project. The use of functional ceramic materials in 3D printing, the combination of different microstructures within a single component, and the optimization of materials for a common sintering process significantly expand our capabilities in additive manufacturing.
Now that the project has been completed, WZR plans to expand its existing product and development portfolio to include laboratory-scale membrane modules that can be used, for example, in industrial or academic research projects.
From the Research Project to the Next Development Step
AMAZING was deliberately positioned at a relatively early stage of technological maturity. Nevertheless, by the end of the project, the process feasibility of the concept had been confirmed.
The overall process also demonstrated interesting prospects for more sustainable chemical production. For example, if the hydrogen separated by the membrane is used on the second side of the reactor for a reverse water-gas shift reaction, CO₂ can be converted into synthesis gas at the same time. In this way, the concept combines electrification, process intensification, and carbon utilization.
The results from AMAZING therefore not only mark the conclusion of a research project but also lay the foundation for the next steps in development. A follow-up project has already been initiated by the consortium.
For us at WZR, one thing is particularly valuable: AMAZING has demonstrated that additive manufacturing can go far beyond simply producing complex geometries, even when it comes to highly functional ceramic components. Through the targeted combination of material, microstructure, and 3D printing process, functions can be integrated directly into a ceramic component.
