A groundbreaking discovery in the conversion of carbon capture for ethylene production

Abstract illustration of atoms passing through water and an electrified membrane under a bright sun. Credit: Meenesh Singh

A team of researchers led by Meenesh Singh of the University of Illinois Chicago has discovered a way to convert 100% of the carbon dioxide captured from industrial exhaust into ethylene, a key building block for plastic products.

Their findings have been 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% utilization of carbon dioxide for hydrocarbon production. Their system uses electrolysis to convert captured carbon dioxide gas into high-purity ethylene, with other carbon-based fuels and oxygen as by-products.

The process can convert up to 6 tons of carbon dioxide into 1 ton of ethylene, recycling nearly all of the carbon dioxide captured. Since the system runs on electricity, the use of renewable energy can make the process CO2 negative.

According to Singh, his team’s approach exceeds the net-zero carbon target of other carbon capture and conversion technologies by effectively reducing the industry’s overall CO2 emissions. “It’s a net negative,” he said. “For every 1 tonne of ethylene produced, you take 6 tonnes of CO2 from point sources that would otherwise be released into the atmosphere.”

Previous attempts to convert carbon dioxide to ethylene have been based on reactors that produce ethylene in the carbon dioxide emission source stream. In these cases only 10% CO2 emissions are usually converted to ethylene. The ethylene must later be separated from the carbon dioxide in an energy-intensive process that often uses fossil fuels.

In the UIC approach, an electrical 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 pulls charged hydrogen atoms from the water molecules to 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.

Of the chemicals produced worldwide, ethylene ranks third for carbon emissions, after ammonia and cement. Ethylene is not only used to make plastic products for the packaging, agriculture and automotive industries, but also to produce chemicals used in antifreeze, medical sterilizers and vinyl siding for homes.

Ethylene is usually made in a process called steam cracking, which requires enormous amounts of heat. Cracking generates approximately 1.5 tons of carbon emissions per ton of ethylene produced. On average, manufacturers produce about 160 million tons of ethylene annually, resulting in more than 260 million tons of CO2 emissions worldwide.

In addition to ethylene, the UIC scientists were able to produce other carbon-rich products useful to industry with their electrolysis approach. They also achieved a very high solar conversion efficiency, with 10% of the energy from the solar panels being converted directly into the output of carbon products. This is well above the state-of-the-art standard of 2%. For all the ethylene they produced, the conversion efficiency of solar energy was about 4%, about the same rate as photosynthesis.

Conversion process converts carbon dioxide into cash

More information:
Aditya Prajapati et al, CO2-free high-purity ethylene from CO2 electroreduction with 4% solar-to-ethylene and 10% solar-to-carbon efficiency, Cell reports Physical Science (2022). DOI: 10.116/j.xcrp.2022.101053

Provided by the University of Illinois at Chicago

Quote: A Groundbreaking Discovery in Carbon Capture Conversion for Ethylene Production (2022, September 9,), retrieved September 10, 2022 from https://phys.org/news/2022-09-breakthrough-discovery-carbon-capture-conversion .html

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