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Mr. Sebastian Webel

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Pictures of the Future
The Magazine for Research and Innovation
 

Materials Science and Processing

Putting Carbon Dioxide to Work

Two research projects that are being conducted jointly by Siemens and Evonik are designed to produce valuable substances from carbon dioxide. Silver-based electrodes enable an electrolytic process to produce carbon monoxide, which is a feedstock for specialty chemicals, while copper-based electrodes enable it to create ethylene.

With its reputation as a top greenhouse gas, carbon dioxide doesn’t have a very positive image. However, not all the news is bad. In two government-funded projects that Siemens is conducting in cooperation with German chemical company Evonik, researchers are using CO2 to produce valuable basic and specialty chemicals for industry. The scientists expect to gain important insights that will enable them to gradually implement electrochemical synthesis processes for large-scale industrial applications.

Rheticus: Converting CO2 into Specialty Chemicals

In January Siemens and Evonik presented a new joint research project called Rheticus. In the project, approximately 20 experts from both companies are working to generate specialty chemicals from CO2. The first phase of the project will end in 2019, and plans call for the completion of an initial test facility at Evonik’s headquarters in northwestern Germany two years later.

How will the process envisioned by the two companies work? In the first step, a Siemens electrolyzer uses energy from renewable sources to convert carbon dioxide and water into metabolizable carbon monoxide (CO). Next, a fermentation process from Evonik very selectively converts the gases containing CO into valuable substances with the help of specialized microorganisms. The end products are chemicals such as butanol and hexanol, both of which are feedstocks for products such as specialty plastics and food additives.

“We are operating experimental setups,” says Günter Schmid, who is responsible for electrolyzers at Siemens Corporate Technology. “This is where we can test and optimize our electrolysis cells and gas diffusion electrodes.” The aim of the project is to scale the technology from lab dimensions to those of a testing facility by 2021. The Rheticus facility is expected to have a production capacity of 10 to 20 tons per year. This would set the stage for building an industrial plant with a production capacity of up to 20,000 tons of butanol or hexanol per year. “We’re also discussing the possible production of other specialty chemicals or even fuels,” Schmidt adds. Depending on the needs of future customers, the dimensions of the Rheticus platform could also be expanded.

Rheticus is part of the Copernicus Initiative for Germany’s energy transition. The initiative is designed to find new solutions for converting the country’s energy supply system. The German Federal Ministry of Education and Research (BMBF) is providing Rheticus with €2.8 million in funding.

Siemens researchers in the Rheticus research project are working to generate specialty chemicals from carbon dioxide. Elena Volkova is preparing electrodes, a cell, and a set of operating parameters for a new series of tests.

eEthylene: CO2-neutral Production

In the government-funded eEthylen project, experts from Siemens are working together with scientists from Evonik, Berlin Technical University, Ruhr University Bochum, and the Helmholtz Institute Erlangen-Nuremberg to study how carbon dioxide can be converted into ethylene. “We are convinced that not only will CO2 help to produce coveted materials, but that it will also open up new business opportunities for Siemens,” says Dan Taroata, a project manager at Siemens, the consortium’s leader.

The researchers are using electricity in a direct, single-stage electrolysis system to synthesize ethylene out of carbon dioxide and water. Their work focuses on electrocatalysts because these materials can charge inert CO2 with energy-rich electrons in order to create ethylene. If the electrons cluster in the surrounding water instead, the process creates hydrogen. That’s why the catalyst plays a decisive role in the method’s success. However, it is a great technological challenge to find a stable cupriferous electrode for the production of ethylene.

The use of an appropriate catalyst ensures the electrochemical synthesis of ethylene from carbon dioxide and water; otherwise electrolysis produces only hydrogen.

Electrolyzers: A Core Area of Expertise at Siemens

For the CO2-to-ethylene production process, Siemens is contributing a system from one of its key areas of expertise: an electrolysis facility for continuous operation. It is based on electrolyzers for hydrogen production, which are part of the company’s current product range.

The three-year project, which was launched in October 2016, is receiving funding from the German Ministry of Education and Research and is part of the CO2Plus research initiative for the use of CO2 to broaden the production base for raw materials. Siemens is the leader of the project consortium.  With a total budget of €2.9 million, the eEthylen project could revolutionize ethylene production. Its goal is to find out how  carbon dioxide can be efficiently converted into ethylene.

Economical Ethylene Production

Ethylene is currently used in a wide variety of ways. For one thing, it is the feedstock for the production of polyethylene, polyvinylchloride, and polyester. As such, it is contained in most plastics. Ethylene also helps to make fruits and vegetables ripen at precisely the right time — an important application in a world of globalized food-supply chains.

If the electrolytic production process can be optimized, it might be able to compete with the conventional manufacturing method. In addition to the fact that the process would use atmospheric CO2 and thus be desirable from an environmental perspective, it would also be worth pursuing from a business point of view. That’s because one ton of ethylene costs between €850 and €1,200 — a hefty sum, considering that around 180 million tons are used annually worldwide.

Ulrich Kreutzer
Picture credits: from top: 1. Evonik, Video: ERBSE DESIGN