A team of researchers led by Meenesh Singh of the University of Illinois at Chicago has discovered a way to convert 100% of the carbon dioxide captured by industrial waste into ethylene, a building block for plastic products.
Their results are published in Cell Reports Physical Science.
While researchers have been exploring the possibility of converting carbon dioxide to ethylene for more than a decade, the UIC team’s approach is the first to achieve nearly 100% use of carbon dioxide to produce hydrocarbons. Their system uses electrolysis to transform captured carbon dioxide gas into high-purity ethylene, with other carbon and oxygen-based fuels as by-products.
The process can convert up to 6 tons of carbon dioxide to 1 ton of ethylene, recycling nearly all the carbon dioxide captured. Since the system runs on electricity, the use of renewable energy can make the process carbon negative.
According to Singh, his team’s approach surpasses the net zero carbon emissions goal of other carbon capture and conversion technologies, effectively reducing the total carbon dioxide production from industry. “It’s a net negative,” he said. “For every ton of ethylene produced, you are taking in 6 tons of CO2 from point sources that would otherwise be released into the atmosphere “.
Previous attempts to convert carbon dioxide to ethylene relied on reactors that produce ethylene within the source carbon dioxide emission stream. In these cases, only 10% of CO2 emissions typically convert to ethylene. Ethylene must subsequently be separated from carbon dioxide in an energy-intensive process that often involves fossil fuels.
In the UIC approach, an electric current is passed through a cell, half of which is filled with captured carbon dioxide, the other half with a water-based solution. An electrified catalyst attracts 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 of the carbon dioxide molecules to form ethylene.
Among the world’s manufactured chemicals, ethylene ranks third in carbon emissions after ammonia and cement. Ethylene is used not only to make plastic products for packaging, the agricultural and automotive industries, but also to make chemicals used in antifreeze, medical sterilizers, and vinyl siding for homes.
Ethylene is usually produced in a process called steam cracking which requires huge amounts of heat. Cracking generates about 1.5 tons of carbon emissions per ton of ethylene created. On average, producers produce around 160 million tons of ethylene every year, which translates to over 260 million tons of carbon dioxide emissions worldwide.
In addition to ethylene, UIC scientists have been able to produce other carbon-rich products useful to industry with their approach to electrolysis. They also achieved very high solar energy conversion efficiency, converting 10% of the energy from solar panels directly into producing carbon products. This is well above the state-of-the-art 2% standard. For all the ethylene produced, the solar energy conversion efficiency was approximately 4%, approximately the same rate as photosynthesis.
- Aditya Prajapati, Nishithan C. Kani, Joseph A. Gauthier, Rohan Sartape, Jiahan Xie, Ivan Bessa, Miguel T. Galante, Samuel L. Leung, Marcio HS Andrade, Robert T. Somich, Márcio V. Rebouças, Gus T. Hutras , Nathalia Diniz, Meenesh R. Singh. CO2-free high purity ethylene from CO2 electro-reduction with efficiencies of 4% from solar to ethylene and 10% from solar to carbon. Cell Reports Physical Sciences, 2022; 101053 DOI: 10.1016 / j.xcrp.2022.101053
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