From Greenhouse Gases to Plastics
Using Copper to Convert CO2 to Ethylene
Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms (CO2
). It is present in the Earth's atmosphere at a low concentration and acts as a greenhouse gas. The vast majority of anthropogenic carbon dioxide emissions (i.e., emissions produced by human activities) come from combustion of fossil fuels, principally coal, oil, and natural gas. It has been estimated that if greenhouse gas emissions continue at their present rate, Earth's surface temperature could exceed historical values as early as 2047, with potentially harmful effects on ecosystems, biodiversity and the livelihoods of people all over the world (source: Wikipedia).
Scientists worldwide have been looking for ways to reduce the greenhouse effect, e.g. by taking CO2 , that most notorious of greenhouse gases, and convert it into something useful, for example plastic. The positive effects could be significant, both diverting CO2 from the atmosphere and reducing the need for fossil fuels to make products.
A group of researchers, led by the University of Toronto Ted Sargent group, just published results that bring this possibility a lot closer. Working together with the Canadian Light Source (CLS), center of synchrotron-based research, and using a new technique exclusive to the facility, they were able to pinpoint the conditions that convert CO2 to ethylene most efficiently. Ethylene, in turn, is used to make polyethylene − the most common plastic used today − whose annual global production is around 80 million tonnes.
At the heart of this work is the carbon dioxide reduction reaction, wherein CO2 is converted into other chemicals through the use of an electrical current and a chemical reaction, aided by a catalyst. Many metals can serve as catalysts in this type of reaction: gold, silver and zinc can make carbon monoxide, while tin and paladium can make formate. Only copper can produce ethylene, the core component of polyethylene plastic.
“Copper is a bit of a magic metal. It's magic because it can make many different chemicals, like methane, ethylene, and ethanol, but controlling what it makes is difficult,” says University of Toronto PhD student Phil De Luna, the lead researcher on this project. The team was able to design a catalyst and pinpoint the ideal conditions to maximize ethylene production, while minimizing the methane output to nearly nothing. Paired with carbon capture technology, this could lead to a green production mechanism for everyday plastics, meanwhile sequestering harmful greenhouse gases.
A unique piece of equipment developed by CLS senior scientist Tom Regier made it possible for the researchers to study both the morphology, or shape, and the chemical environment of their copper catalyst throughout the CO2 reduction reaction, in real time. “This has never been done before,” says PhD student Rafael Quintero-Bermudez, the paper’s other first co-author. “This unique measurement allowed us to explore a lot of research questions about how the process takes place and how it can be engineered to improve.” By identifying the precise conditions that maximize ethylene production during the reaction, it is possible to engineer a catalyst to meet those conditions.