New process gives CO2 conversion more “bang for the buck”

A new chemical process is giving carbon capture and conversion (CCC) “more bang for the buck” by more efficiently converting captured CO2 into multi-carbon products like ethylene, which are used in a wide range of everyday products from pharmaceuticals to plastics.

Researchers at the University of Sydney and the University of Toronto have devised a new acid-based electrochemical process for the conversion of CO2 captured from emission sources or directly from the air.

CCC is gaining momentum worldwide, with the Australian Academy of Science recently publishing a report urging the necessity of coupling carbon capture with a reduction in emissions to cap global heating at 1.5°C.

The new paper, published in Nature Synthesis, differs from previous CO2 conversion methods in that it uses an acidic – not alkaline or neutral – reactive chemical, with the experimental study rendering a twofold improvement in energy efficiency compared to the team’s previous benchmark work, when converting CO2 to multicarbon products such as ethylene and ethanol.

Most commonly derived from oil extraction, multicarbon products are widely used chemicals and raw materials in industry. Ethylene is the precursor of polyethylene – a plastic used in everyday products from packaging to pharmaceuticals.

The catalyst works by applying an acidic electrolyte, with more carbon being utilised for conversion in the process compared with alkaline-based solutions. When being treated with electricity, the catalyst catalyses the CO2 into multicarbon products.

Dr Fengwang Li, from the School of Chemical and Biomolecular Engineering, added, “Until now, converting CO2 into multicarbon products in acidic media has been challenging. Using an adlayer system, the catalyst acquires a reactive environment that is favourable for multicarbon formation at an energy-efficient operating condition. Our catalyst system allows for more multicarbon products to be converted from CO2, essentially giving carbon capture more “bang for the buck” by creating a secondary market of materials.”

While carbon capture is the aim of many CCUS programs, this one has the added benefit of extracting a usable product in the form of ethylene. Dr Yong Zhao, the study’s lead author, said: “Governments and industry are becoming increasingly aware of the necessity of carbon capture, but conversion is not just ‘nice to have’. By converting CO2, rather than simply capturing and burying it, we can create fully circular carbon economies, potentially reducing the reliance of oil extraction to create ethylene.”

The process has the potential of creating large-scale carbon capture and conversion systems that turn carbon capture into a value-added industry, thereby increasing its financial viability and creating a more solid commercial basis for carbon removals.

Dr Li added: “While the overall goal worldwide should be to slash emissions by transitioning to renewables and moving away from the burning of fossil fuels, the transition for heavy industry will take time, making the capturing of CO2 at the emissions site an important interim step.”

The researchers will next look to again double the energy efficiency of the process. Dr Li explained: “If we want our process to be deployed at scale and used by industry, we need to double efficiency again and improve stability. That will be our key focus moving forward.”

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