Producing epoxides — used to manufacture numerous everyday products — requires extreme temperatures and pressures, and generates carbon dioxide emissions. So, researchers at the Massachusetts Institute of Technology (MIT), Cambridge, have created a more-sustainable approach using electricity. Their process takes place at room temperature and atmospheric pressure, eliminates carbon dioxide as a byproduct, and promises lower-cost production.
The team uses electricity to split water into oxygen, protons and electrons, and then attaches the oxygen atom to an olefin, a precursor to epoxides.
Olefins and water react only when an electric voltage is applied. So, the MIT team designed a reactor with an anode that breaks water down into oxygen, hydrogen ions (protons) and electrons. Manganese oxide nanoparticles act as a catalyst for this reaction, and for incorporating the oxygen into an olefin to make an epoxide. Protons and electrons flow to the cathode, where they are converted into hydrogen gas. An article in the Journal of the American Chemical Society highlights the process and its results.
Thermodynamically, this reaction only uses about 1 volt of electricity and doesn’t generate any carbon dioxide. Using renewable sources to make the electricity to power the epoxide conversion could further reduce the carbon footprint, believe the researchers.
The researchers have used the process to create an epoxide called cyclooctene oxide; they now are working on adapting it to other epoxides.
“We select targets based on the carbon footprint and energy footprint of chemicals. This means that key targets in addition to epoxides include ammonia and olefins. We are developing, for instance, a room temperature and ambient pressure route by which renewable electricity can be used to convert nitrogen into ammonia fertilizers,” says Karthish Manthiram, an assistant professor of chemical engineering at MIT, who lead the project.
Presently, about 30% of the electrical current goes into the conversion reaction, but the researchers hope to double that to make it more efficient.
“Our preliminary technoeconomic analysis indicates that doubling the Faradaic Efficiency is necessary to make the process competitive,” notes Manthiram. This will require developing anodic catalysts which facilitate selective transfer of oxygen-atoms from water to olefins to generate an epoxide.
“Achieving higher energy efficiency will necessitate creating more efficient catalysts for the cathode, which conducts hydrogen evolution, and developing cell architectures which minimize the distances for ion transport,” he adds.
The researchers plan to continue developing the technology in hopes of eventually commercializing it for industrial use; the team is in early-stage discussions with companies interested in the process.
If scaled up, the researchers estimate the process could produce ethylene oxide at a cost of $900/ton, compared to $1,500/ton using current methods. That cost could be lowered further as the process becomes more efficient. In addition, its hydrogen byproduct can be used to power fuel cells, further enhancing the process’ economic viability.
The system is relatively robust to perturbations and conducive to ramping up and down rapidly because the process runs at ambient conditions, says Manthiram. “This means the reactor can be dynamically operated to follow renewable electricity generation, to operate when the sun shines and the wind blows,” he explains.
However, Manthiram points out that key challenges for successful scaleup are developing energy efficient reactor architectures, and selective and robust catalysts tolerant to impurities. “This is the focus of our ongoing efforts in our lab. This is still early-stage research, but translating this to understand the scale-up constraints is essential for continued development,” he notes.
