Researchers have discovered how carbon dioxide can be captured and converted using a unique electrochemical process in which an electrode, like the one shown in the bubble-covered image, is used to attract carbon dioxide released by an absorbent material. and convert it to carbon neutral. products. Credit: John Frieda/MIT MechE
These results, which are based on a single electrochemical process, could help reduce emissions from industries that are difficult to decarbonize, such as steel and cement.
As part of efforts to reduce global greenhouse gas emissions around the world, scientists at the Massachusetts Institute of Technology are focusing on carbon capture technologies to decarbonize the most difficult industrial emissions.
Industries such as steel, cement, and chemical manufacturing are particularly difficult to decarbonize due to the inherent use of carbon and fossil fuels in their processes. If technologies can be developed to capture carbon emissions and reuse them in the production process, this could lead to a significant reduction in emissions from these “hard to mitigate” sectors.
However, current experimental technologies that capture and convert carbon dioxide do so through two different processes, which in turn require an enormous amount of energy to operate. The MIT team seeks to combine the two processes into a single, more energy-efficient integrated system that can run on renewable energy to capture and convert carbon dioxide from concentrated industrial sources.
Recent discoveries on carbon capture and conversion
In a study published September 5 in the journal Catalyze SCAResearchers reveal the hidden function of how carbon dioxide is captured and converted through a single electrochemical process. The process involves using an electrode to capture the carbon dioxide released from the absorbent material and convert it into a reusable diluted form.
Others have reported similar demonstrations, but the mechanisms behind the electrochemical reaction remain unclear. The MIT team conducted extensive experiments to determine this increase and eventually discovered that it was due to the partial pressure of carbon dioxide. In other words, the purer the CO2 that comes into contact with the electrode, the more efficiently it captures and converts the molecule.
Find out what this prime or “active” driver is. Class,” could help scientists refine and optimize similar electrochemical systems to efficiently capture and convert carbon dioxide in an integrated process.
The study results indicate that although these electrochemical systems are not suitable for highly dilute environments (for example, to capture and convert carbon emissions directly from the air), they would be very suitable for highly concentrated emissions generated by industrial processes. Especially those who do not have a clear alternative to renewable energy.
“We can and should turn to renewable energy sources to produce electricity,” says study author Petar Galant, associate professor of professional development at MIT, Class of 1922. “Deep decarbonizing industries, such as cement or steel production , are challenging and will take time. » “Even if we phase out all our power plants, we need solutions to manage emissions from other industries in the short term, before we can fully decarbonize them. This is where we see a sweet spot, where something like this system could work.
Co-authors of the MIT study are lead author and postdoctoral researcher Graham Leverick and graduate student Elizabeth Bernhardt, along with Aisha Iliani Ismail, Jun Hui Lo, Arif Arifuzzaman and Mohd Khairuddin Arua of Sunway University Malaysia.
Understand the carbon capture process
Carbon capture technologies are designed to capture emissions or “flue gases” from the smokestacks of power plants and manufacturing facilities. This is done primarily by using large renovations to direct emissions into chambers filled with a “capture” solution: a mixture of amines or ammonia-based compounds, which chemically bond with carbon dioxide, creating a stable form. that can be separated from the rest. . Combustion gases.
High temperatures, usually in the form of fossil fuel vapor, are then applied to release the carbon dioxide captured by the amine bond. In its pure form, the gas can then be pumped into storage or underground tanks, mineralized, or processed into chemicals or fuel.
“Carbon capture is a mature technology, because its chemistry has been known for about 100 years, but it requires very large facilities and its operation is very expensive and consumes a lot of energy,” Gallant emphasizes. “What we want are more flexible and flexible technologies, which can adapt to more diverse sources of carbon dioxide. Electrochemical systems can help solve this problem. »
His group at MIT is developing an electrochemical system that takes captured carbon dioxide and transforms it into a reduced, usable product. An integrated, rather than separate, system could run entirely on renewable electricity rather than steam derived from fossil fuels, he says.
Its concept revolves around an electrode that can be installed in existing chambers for carbon capture solutions. When a voltage is applied to the electrode, electrons flow over the reactive form of carbon dioxide and convert it into a product using protons supplied by the water. This makes the absorbent available to bind more carbon dioxide, rather than using steam to do the same.
Gallant has already shown that this electrochemical process can capture carbon dioxide and transform it into a gas. Solid carbonate form.
“We have shown that this electrochemical process was possible from the first concepts,” he says. “Since then, more studies have been done on using this process to try to produce useful chemicals and fuels. But there have been inconsistent explanations for how these reactions work, in secret. »
Role of CO2 alone
In the new study, the MIT team used a magnifying glass to uncover the specific reactions that drive the electrochemical process. In the laboratory, they produced amine solutions that resemble industrial capture solutions used to extract carbon dioxide from flue gases. They systematically varied the different properties of each solution, such as pH, concentration, and type of amine, then passed each solution through an electrode made of silver, a metal widely used in electrolysis studies and known for its ability to efficiently convert carbon dioxide into carbon. . . Monoxide. They then measured the concentration of carbon monoxide converted at the end of the reaction and compared this figure to all the other solutions tested, to see which parameter had the greatest effect on the amount of carbon monoxide produced.
In the end, they discovered that what mattered most was not the type of amine initially used to trap carbon dioxide, as many expected. Instead, it was the concentration of individual, free CO2 molecules that prevented binding to amines but were nonetheless present in the solution. The “single carbon dioxide” determines the concentration of carbon monoxide that is ultimately produced.
“We found that it was easier to react with a single carbon dioxide than with the carbon dioxide captured by the amine,” Leverick says. “This indicates to future researchers that this process could be feasible for industrial streams, because high concentrations of carbon dioxide can be efficiently captured and converted into useful chemicals and fuels. »
“This is not an elimination technique and it is important to mention that,” Gallant emphasizes. “The value that this brings is that it allows us to recycle CO2 several times while maintaining existing industrial processes, to reduce associated emissions. Ultimately, my dream is that electrochemical systems can be used to facilitate the mineralization and permanent storage of CO2, a true elimination technology. » This is a long-term vision and much of the science we are beginning to understand is a first step towards designing these processes.
Reference: “Detection of active species in carbon dioxide mediated by amines2 “CO2 reduction in agriculture” by Graham Leverick, Elizabeth M. Bernhardt, Aisha Iliani Ismail, Jun Hui Lu, A. Arif Al-Zaman, Muhammad Khairuddin Arwa and Petar M. Gallant*, September 5, 2023, Catalyze SCA.
doi:10.1021/acscatal.3c02500
This research is supported by Sunway University Malaysia.
