Turning CO₂ into fuels: Chemists solve a key scaling problem
LIKAT Technical Center produces catalyst on kilogram scale for the first time for a pilot plant
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Chemists at the LIKAT Technical Center in Rostock have succeeded for the first time in producing a new catalyst on a pilot scale. The first ten kilograms of the substance have now been delivered to research partners in Hamburg and Vienna. The catalyst, developed at LIKAT as part of an earlier collaborative project, is intended to produce CO₂-neutral fuels in Vienna and demonstrate its practical suitability for larger plants. It is the centerpiece of a modern form of the Fischer-Tropsch Synthesis (FTS), which was developed a hundred years ago by two German chemists to liquefy coal and natural gas. Instead of fossil raw materials, this new FTS variant now liquefies the greenhouse gas CO2.
Dr. Christoph Wulf and Dr. Simon Haida (from left) present a portion of the synthesized material
Rachow, LIKAT
The new version of this Fischer-Tropsch catalyst was developed at the Leibniz Institute for Catalysis. The process converts carbon dioxide (CO₂, together with sustainably produced hydrogen (H₂), into climate-friendly synthetic fuels. These fuels can power conventional internal combustion engines and, unlike gasoline or diesel, contain no sulfur or nitrogen compounds whatsoever. “The research aims for sustainable, CO₂-neutral mobility, which is also a focus of the national high-tech agenda,” says Dr. Christoph Wulf, group leader at the LIKAT Transfer Technical Center.
Successor to InnoSyn
Like the classic process, the modern method takes place in so-called bubble column reactors, but under much milder reaction conditions. In long vertical tubes, all the substances involved work their way through a viscous liquid from the bottom to the top: on the one hand, the “bubbles”—that is, the gaseous starting materials CO2, H2 and, subsequently, carbon monoxide (CO). On the other hand, there are all the liquid intermediate and final products, as well as the catalyst in the form of fine iron oxide-based beads.
This catalyst was developed as part of the federally funded InnoSyn consortium project—a component of the “Hydrogen Republic of Germany” initiative—in conjunction with an AI model for the CO₂-FTS, under the direction of LIKAT chemist Dr. David Linke (see also https://idw-online.de/de/news851343 ). Partners at the Engler-Bunte Institute of the Karlsruhe Institute of Technology (KIT) demonstrated the feasibility of this process in a multiphase reactor system on a gram scale. In a follow-up project, Green Fuel and Chemicals, the process is now to be prepared for industrial application. This includes a demonstration on the kilogram scale in a pilot plant at the Vienna site of Bioenergy and Sustainable Technologies GmbH (BEST). There, several kilograms of CO₂ are to be converted into sustainable fuels and chemicals by early 2027.
Catalyst Formulation for Up-Scaling
When new catalysts leave the research laboratory, they typically function in quantities of just a few milligrams. For upscaling—as chemists call it—to scales of several kilograms and solution volumes of up to 100 liters, the catalyst requires a different formulation. The goal of the new research collaboration was to find the appropriate approach. Dr. Christoph Wulf and Dr. Simon Haida took on this task at the LIKAT Transfer Technical Center.
As both chemists explain, this also involved developing a practical production technology for the catalyst. The catalyst for the new Fischer-Tropsch synthesis is formed from metal salts in a precipitation reaction, producing a rust-red “cake” of iron oxide—a kind of paste that is subsequently spray-dried and thermally treated. The result is particles with a virtually perfect spherical shape. The beads vary in size and must therefore be fractionated—that is, sorted by size.
Particle size determines function
“The crux of the matter is that the behavior of a catalyst cannot be predicted on a large scale,” says Simon Haida. Stirring and thoroughly mixing a 100-milliliter solution may seem simple. “On a 50-liter scale is , the particular processing—specifically the filtration , that separates the crude product from the reaction solution —a challenge.” This requires systematic experiments in which the reaction volumes are gradually increased.
This work was carried out in close collaboration with LIKAT chemist Dr. Aleksandr Fedorov, who had originally developed the catalyst. With each new step, he readjusted the catalyst and tested its performance. The chemists then had to plan the equipment for their next step.
In this way, they progressed from a batch of a few milliliters to 50 liters, which can be used to supply pilot plants. One finding from the experiments is that particle size significantly influences the catalyst’s performance. Dr. Wulf: “The iron oxide beads must not be too large so that they can continue to float— , so to speak— in the subsequent bubble column reactor. However, if they are too small, they clump together and clog the filter at the reactor outlet or even end up in the product and contaminate it.”
Pilot Plant Enables Up-Scaling
LIKAT is one of the first scientific institutions in Germany capable of producing new catalysts for its research on a pilot scale. While other institutes do have pilot plants for testing catalysts, Christoph Wulf notes: “But they lack the equipment to produce the test substances on the necessary scale.” At LIKAT, the Catalysis2Scale technical facility has now been well-equipped with instruments and equipment thanks to grant-funded projects and research collaborations. With the first ten kilograms of their iron oxide catalyst for the new Fischer-Tropsch synthesis, Dr. Wulf and Dr. Haida now aim to draw the attention of potential research partners to this opportunity.
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