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New System Captures Carbon From Flue Gas And Makes Ethylene
January 4, 2023 | Leave a Comment
Engineers at the University of Illinois Chicago have built a machine that captures carbon from flue gas and converts it to ethylene. The device integrates a carbon capture system with an ethylene conversion system for the first time.
The system not only runs on electricity, but it also removes more carbon from the environment than it uses for power – making it what scientists call net-negative on carbon emissions.
Among manufactured chemicals worldwide, ethylene ranks third for carbon emissions after ammonia for fertilizer and cement for concrete. Ethylene is used not only to create plastic products for the packaging, agricultural and automotive industries but also to produce chemicals used in antifreeze, medical sterilizers and vinyl siding for houses as examples.
Meenesh Singh, UIC assistant professor in the department of chemical engineering said, “This is the first demonstration of a net-negative, all-electric integrated system to capture carbon from pollutants and create a highly valuable resource. There is an urgent need to develop efficient technologies for integrated carbon capture and conversion to sustainably producible net-negative fuels. Currently, integrated carbon capture and conversion systems are highly energy-intensive and work in a discontinuous cycle of carbon dioxide capture and reduction. Efficiently integrating carbon capture with the conversion system eliminates the need for transportation and storage, and thereby increasing its energy efficiency.”
The integrated carbon capture and conversion system developed at UIC continuously captures carbon dioxide from flue gas to produce high-purity ethylene.
Schematic of the integrated system with migration-assisted moisture-gradient CO2 capture and electrochemical CO2 reduction reaction. Image Credit: Meenesh Singh, et al. University of Illinois Chicago. For the largest image click the press release link.
To capture carbon from the air or flue gas, Singh’s lab modified a standard artificial leaf system with inexpensive materials to include a water gradient – a dry side and a wet side – across an electrically charged membrane.
On the dry side, an organic solvent attaches to available carbon dioxide to produce a concentration of bicarbonate, or baking soda, on the membrane. As bicarbonate builds, these negatively charged ions are pulled across the membrane toward a positively charged electrode in a water-based solution on the membrane’s wet side. The liquid solution dissolves the bicarbonate back into carbon dioxide, so it can be released and harnessed for CO2 conversion.
The system uses a modular, stackable design that allows the system to be easily scaled up and down.
To convert captured carbon dioxide to ethylene, Singh and his colleagues used a second system in which an electric current is passed through a cell. Half of the cell is filled with carbon dioxide captured from a carbon capture system, the other half with a water-based solution. An electrified catalyst draws charged hydrogen atoms from the water molecules into the other half of the unit separated by a membrane, where they combine with charged carbon atoms from the carbon dioxide molecules to form ethylene.
The UIC researchers integrated the two systems by feeding the captured carbon dioxide solution to the carbon conversion system and recycling it back. The closed-loop recycling of solution ensures a constant supply of carbon dioxide from flue gas and its conversion to ethylene.
To test their integrated system, the researchers implemented a 100-square-centimeters bipolar membrane electrodialysis unit to capture carbon dioxide from the flue gas and hydraulically connected it to the 1-square-centimeter electrolysis cell to produce ethylene.
They were able to test the system continuously, 24 hours per day for seven days. The system was not only stable the entire time, it also captured carbon at a rate of 24 grams per day and produced ethylene at a rate of 188 milligrams per day.
“In the journey to make ethylene production green, this is a potential breakthrough,” Singh said. “Our next step is to scale up the integrated carbon capture and conversion system to produce ethylene at higher rates – a rate of 1 kilogram per day and capture carbon at a rate higher than kilograms per day.”
Co-authors of the study include Aditya Prajapati and Rohan Sartape of UIC, and Miguel Galante, Jiahan Xie, Samuel Leung, Ivan Bessa, Marcio Andrad, Robert Somich, Marcio Reboucas, Gus Hutras and Nathalia Diniz of Braskem.
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This innovative invention just might have some legs! The world economy uses a lot of ethylene that is either extracted from natural gas or reformed from heavier molecules. The products and parts of products involved are so numerous a counting defies reason, as they must measure in the millions worldwide.
The real interest is getting a reuse or recycling of the CO2. For now the beneficiary of the CO2 output is the plant kingdom. That’s great as link one in the food chain is plants. The likelihood a system like this would be prevalent isn’t high, but getting a product of value from large concentrated CO2 producers instead of an effluent is very attractive, indeed.
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