Ethylene oxide quietly underpins modern life, from the plastics in our homes to the disinfectants we rely on. But its production comes at a cost: millions of tons of carbon dioxide emissions and a reliance on toxic chlorine. Researchers have found a way to make this essential chemical cleaner and safer.
A research team led by Tufts University chemistry professor Charles Sykes has found a way to produce ethylene oxide, a widely used industrial chemical, while reducing carbon dioxide emissions and eliminating the need for toxic chlorine. This discovery could provide a more sustainable method for manufacturing ethylene oxide, which is essential for producing plastics, textiles, antifreeze, and disinfectants.
The findings, published in Science, describe how adding small amounts of nickel atoms to silver catalysts allows for the efficient production of ethylene oxide without chlorine, which is currently used in industrial processes to improve yield but poses environmental and safety risks. The ethylene oxide industry, valued at approximately $40 billion annually, is responsible for significant CO₂ emissions, and the new method could help mitigate its environmental impact.
Addressing an environmental and industrial challenge
The conventional process for producing ethylene oxide produces significant carbon dioxide emissions. Silver-based catalysts facilitate the reaction but produce two molecules of CO₂ for every ethylene oxide molecule generated. Introducing chlorine enhances efficiency, lowering emissions to about one molecule of CO₂ for every two molecules of ethylene oxide produced. However, chlorine presents hazards, as it is highly toxic and may lead to harmful byproducts.
Sykes and his longtime collaborator, Matthew Montemore, a chemical engineering professor at Tulane University, sought an alternative to maintain efficiency while reducing environmental risks. “The answer was nickel,” Sykes said on Tufts homepage, “which surprised us because we couldn’t find anything in the scientific or patent literature about nickel despite it being a common and inexpensive element used in many other catalytic processes. Could 70+ years of industrial R&D have missed it?”
Testing the hypothesis
The research team tested this approach using the single-atom alloy concept, which Sykes pioneered over a decade ago. This technique allows individual nickel atoms to be added to a silver catalyst, enabling precise control over the reaction. In experiments at Tufts, graduate students Elizabeth Happel and Laura Cramer examined the effectiveness of this approach, yielding promising results.
Seeking further validation, Sykes partnered with Phillip Christopher, a professor of chemical engineering at the University of California, Santa Barbara (UCSB), who led efforts to formulate a nickel-enhanced silver catalyst suitable for industrial conditions. “Selective oxidation is one of the more challenging reactions, and so I wouldn’t have been surprised if it hadn’t have worked,” Sykes said. “But it did.”
Christopher’s team at UCSB, including Ph.D. student Anika Jalil, encountered technical challenges in incorporating nickel into the catalyst in a reproducible manner. This difficulty may explain why the effect had not been reported in previous industrial research. “Incorporating nickel atoms into the silver catalyst by a reproducible protocol was a real technical hurdle that Anika Jalil, a Ph.D. student at UCSB, navigated impressively. The challenge in incorporating nickel could be why the effect we observed was never previously reported,” Christopher said.
Beyond demonstrating its feasibility, the researchers observed that the addition of nickel significantly improved the catalyst’s efficiency. “I have worked on ethylene oxide catalysts since my PhD and was so surprised and excited by the magnitude of the effect nickel addition had,” Christopher said.
Potential industrial applications
Given the potential environmental and economic benefits of this discovery, the research team has submitted a provisional patent (2022) and an international patent (2023) for the process. They are also discussing the feasibility of incorporating this new method into existing manufacturing facilities with a major commercial producer of ethylene oxide.
If implemented on an industrial scale, this approach could reduce the carbon footprint of ethylene oxide production while removing the need for chlorine, addressing both environmental and safety concerns. While further testing and commercialization efforts are needed, the research suggests a viable path toward more sustainable chemical manufacturing.
Dow also developed an ethylene oxide catalyst, METEOR EO-RETRO 2000 to reduce CO2 emissions, but the Tufts’ elimination of chlorine from the EO production process not only reduces CO₂ emissions but also enhances operational safety by removing a toxic and hazardous substance. This dual benefit addresses both environmental and health concerns
