Researchers Are Turning CO2 Into High-purity Carbon

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-06-05 00:21

CO ₂ filter from the air and convert it into an industrially usable raw material - it is currently researching the Karlsruhe Institute of Technology (KIT) in the project "Necoc" - " Ne gative C arb o n dioxide to C arbon". A globally unique test facility on a container scale produces the high-purity carbon powder "Carbon Black" from the CO ₂ contained in the ambient air, which is to be used industrially as a raw material

In order to implement the goals of the Paris climate agreement of 2015, not only the CO ₂ emissions have to be reduced, but already emitted CO _{2 has to be} removed from the atmosphere.

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Prof. Thomas Wetzel from the Institute of Thermal Process Engineering (TVT) at KIT explains: "The approach pursued in our project is to separate CO2 from the atmosphere and convert it into carbon black, a powdery, high-purity carbon." This is how a harmful greenhouse gas becomes a raw material for high-tech applications. Carbon black can be used in the electronics, printing or construction industries.

CO ₂ becomes methane and water

In the Necoc research project, a corresponding test facility is to be created in which the following process steps are combined: With the help of an adsorber, CO _{2 is} first filtered from the ambient air (direct air capture method, DAC). It is then converted into methane and water together with renewable hydrogen in a microstructured reactor.

The methane produced serves as a carbon carrier for the further process and is fed into a bubble reactor filled with liquid tin. In the rising methane bubbles there is a pyrolysis reaction in which methane breaks down into its components. These are, on the one hand, hydrogen, which is returned directly to the methanation, and solid carbon in the form of microgranular powder, the carbon black.

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All process steps have already been developed and investigated by the researchers involved up to the laboratory scale. "We know the individual building blocks well," says NECOC project coordinator Dr. Benjamin Dietrich (TVT). "However, they have never been implemented in a network in an integrated system, this is a world premiere." The skilful integration of the process components and the correct process control are crucial for the energy efficiency of the process and the quality of the product Carbon Black.

The decisive advantage over the previously proposed concepts for reducing atmospheric CO ₂ - such as carbon capture-and-storage methods (CCS), in which the storage of CO ₂ is intended in deep rock layers - lies primarily in this end product: “Solid carbon is much less complex to handle than CO ₂ and even useful as a raw material. So far, carbon black has mainly been made from fossil oil. In this respect, the process is a technological approach for a sustainable future in several respects: It combines the direct contribution to solving the climate problem with a component of a post-fossil raw material supply,”says Dietrich.

Cooperation with industrial companies

The test facility will be built on the KIT site. The aim is to demonstrate operation over a longer period of time. In future stages of expansion, both the performance per container will be increased and the parallel operation of many systems will be possible.

The construction of the new test facility is made possible by the close cooperation with two industrial partners who are each responsible for specific modules within the container facility. Climeworks Deutschland GmbH focuses on the DAC process: “Our know-how relates to CO ₂ filtering from the ambient air. But of course there is always the question of what happens to the CO ₂ after filtering,”says Dr. Dirk Nuber, head of Climeworks Deutschland GmbH. "The conversion of CO ₂ into a storable material comes very close to an ideal solution."

The company Ineratec GmbH, in turn, specializes in microstructured reactors, in which otherwise regeneratively produced synthesis gases are converted into climate-neutral liquid fuels or chemical products. "Necoc's goal is to permanently remove CO ₂ from the atmosphere," says Dr. Tim Böltken, one of the founders of the start-up. "With our reactor technology, we are helping to make this new process path for negative emissions possible," says Böltken.

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