Researchers have been exploring the possibility of converting carbon dioxide to ethylene for several years, but the UIC team’s approach is said to be the first to achieve nearly 100 per cent utilisation of carbon dioxide to produce hydrocarbons. Their system uses electrolysis to transform captured carbon dioxide gas into high purity ethylene, with other carbon-based fuels and oxygen as by products. Their findings are published in Cell Reports Physical Science.
According to UIC, the process can convert up to six metric tons of carbon dioxide into one metric ton of ethylene, recycling almost all carbon dioxide captured. Furthermore, the system runs on electricity and the use of renewable energy can make the process carbon negative.
According to research leader Meenesh Singh, the team’s approach surpasses the net-zero carbon goal of other carbon capture and conversion technologies by reducing the total carbon dioxide output from industry.
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“It’s a net negative,” he said. “For every one ton of ethylene produced, you’re taking six tons of CO2 from point sources that otherwise would be released to the atmosphere.”
Previous attempts at converting carbon dioxide into ethylene have relied on reactors that produce ethylene within the source carbon dioxide emission stream. In these cases, as little as 10 per cent of CO2 emissions typically converts to ethylene. The ethylene must later be separated from the carbon dioxide in an energy-intensive process often involving fossil fuels.
In UIC’s 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 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 manufacture of ethylene – an organic compound used to create plastic products and chemicals - ranks third globally for carbon emissions after ammonia and cement.
Ethylene is usually made via steam cracking, a process that requires large amounts of heat. Cracking generates about 1.5 metric tons of carbon emissions per ton of ethylene created. On average, manufacturers produce around 160 million tons of ethylene each year, which results in more than 260 million tons of carbon dioxide 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 are also said to have achieved a very high solar energy conversion efficiency, converting 10 per cent of energy from the solar panels directly to carbon product output, which is above the state-of-the-art standard of two per cent. For all the ethylene they produced, the solar energy conversion efficiency was around four per cent, approximately the same rate as photosynthesis.
Does this research represent a breakthrough for low-carbon ethylene production? Let us know in Comments below.
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