The discovery, based on a single electrochemical process, could help reduce emissions from industries that are the most difficult to decarbonize, such as steel and cement.
In an effort to curb greenhouse gas emissions around the world, scientists are Massachusetts Institute of Technology focuses on carbon capture technologies to decarbonize the most challenging industrial emissions sources.
Industries such as steel, cement, and chemical manufacturing are particularly difficult to decarbonize because their processes inherently use carbon and fossil fuels. Developing technology to capture carbon dioxide emissions and reuse them within production processes could lead to significant reductions in emissions from these ‘hard-to-reduce’ sectors.
However, current experimental techniques for capturing and converting carbon dioxide do it as two separate processes, which themselves require enormous amounts of energy to run. The MIT team is looking to combine the two processes into one integrated, much more energy-efficient system. The system could potentially run on renewable energy and capture and convert carbon dioxide from concentrated industrial sources.
Recent research findings on carbon capture and conversion
In a study published in the journal Sept. 5, ACS catalysis, researchers uncovered the hidden features of how carbon dioxide is captured and transformed through a single electrochemical process. The process involves using electrodes to attract carbon dioxide released from an adsorbent and convert it into a reduced, reusable form.
Similar demonstrations have been reported elsewhere, but the mechanism that causes the electrochemical reaction remains unclear. The MIT team conducted extensive experiments to determine the contributing factor, and found that it ultimately came down to the partial pressure of carbon dioxide. In other words, the more pure the carbon dioxide that comes into contact with the electrode, the more efficiently the electrode can capture and convert molecules.
Knowledge of this main driving force, i.e. “active” seed” will help scientists tune and optimize similar electrochemical systems to efficiently capture and convert carbon dioxide in integrated processes.
The results of this study indicate that these electrochemical systems probably do not work in very dilute environments (e.g., directly capturing and converting carbon emissions from the air), but do work in highly concentrated emissions produced by industrial processes. suggests that it is suitable. This is especially true for those for which there are no clear renewable alternatives.
“We can and should switch our electricity production to renewable energy. But thoroughly decarbonizing industries such as cement and steel production will be difficult and take longer. “It’s going to take a long time,” said study author Betar Gallant, associate professor of career development at the Massachusetts Institute of Technology, Class of 1922. “Even if we retire all power plants, we need solutions to address emissions from other industries in the short term before fully decarbonizing them. We think there’s a sweet spot where something like a system might fit.”
The study’s MIT co-authors are first author and postdoctoral researcher Graham Leverrick and graduate student Elizabeth Bernhardt, as well as Aisyah Illyani Ismail, Jun Hui Law, Arif Arifutzzaman, and Mohamed Kheireddine Aroua of Sunway University in Malaysia. .
Understanding the carbon capture process
Carbon capture technology is designed to capture emissions, or “tail gases,” from the stacks of power plants and manufacturing facilities. It primarily concentrates the effluent into a chamber filled with a “capture” solution, which is a mixture of amine or ammonia-based compounds that chemically combine with carbon dioxide to produce a stable form that can be separated from the rest of the material. Extensive renovations will be made to make it easier. of exhaust gas.
High temperatures, usually in the form of fossil fuel-produced steam, are then applied to free the trapped carbon dioxide from the amine bonds. In its pure form, the gas is pumped into storage tanks or underground where it is mineralized and further converted into chemicals and fuels.
“Carbon capture is a mature technology in that the chemical reaction has been known for about 100 years, but it requires very large equipment and is very expensive and energy-intensive to run. ,” Gallant points out. “What we want is a technology that is more modular, flexible, and adaptable to a more diverse range of carbon dioxide sources. Electrochemical systems can help address that issue.”
Her group at MIT is developing electrochemical systems that capture captured carbon dioxide and convert it into reduced, usable products. Such an integrated system, rather than an isolated system, could potentially be powered entirely by renewable electricity rather than fossil fuel-derived steam, she says.
Their concept centers around electrodes that fit into existing chambers of carbon capture solutions. When a voltage is applied to the electrodes, electrons flow onto the reactive form of carbon dioxide, converting it into a product using protons provided by water. This allows the adsorbent to bind more carbon dioxide instead of using steam.
Dr. Gallant has previously demonstrated that this electrochemical process works to capture carbon dioxide and convert it to carbon dioxide. solid carbonate form.
“We showed that this electrochemical process is feasible in a very early concept,” she says. “Since then, other research has focused on attempts to use this process to produce useful chemicals and fuels. But how these reactions work under the hood is unclear. There have been inconsistent explanations for this.
Role of “Solo CO2”
In the new study, the MIT team used a magnifying glass under the hood to uncover the specific reactions that cause the electrochemical process. In the lab, they produced an amine solution similar to industrial capture solutions used to extract carbon dioxide from flue gases. They systematically changed various properties of each solution, such as pH, concentration, and type of amine, and passed each solution through an electrode made of silver. Silver is a metal that is widely used in electrolysis research and is known to efficiently convert carbon dioxide to carbon. monoxide. We then measure the concentration of carbon monoxide converted at the end of the reaction and compare this number with those of all other solutions tested to determine which parameter most influences the amount of carbon monoxide produced. I have confirmed.
In the end, it turned out that what mattered most was not, as many had suspected, the type of amine used to capture the carbon dioxide in the first place. Instead, it was a concentration of a single, floating carbon dioxide molecule, which avoided combining with the amine but was still present in solution. This “single CO2” determines the concentration of carbon monoxide that is ultimately produced.
“We found that this ‘alone’ CO2 was more reactive compared to CO2 captured by amines,” says Leverick. “This shows future researchers that this process is feasible in industrial flows and that high concentrations of carbon dioxide could be efficiently captured and converted into useful chemicals and fuels. It shows.”
“This is not a removal technique, and it’s important to state that,” Gallant emphasizes. “The value it brings is that while maintaining existing industrial processes, we can recycle carbon dioxide several times and reduce associated emissions. Ultimately, my dream is to use electrochemical systems to This is a long-term vision. And a lot of the science that we’re starting to understand is going to help engineer those processes. This is the first step.”
reference: “Revealing active species in amine-mediated carbon dioxide2 “Ag CO2 Reduction” by Graham Leverrick, Elizabeth M. Bernhardt, Aisyah Ilyani Ismail, Jun Hui Law, A. Arifutzzaman, Mohamed Kheireddine Aroua, Betar M. Gallant*, September 5, 2023. ACS catalysis.
DOI: 10.1021/acscatal.3c02500
This research is supported by Sunway University, Malaysia.