Research Revisited: Greener Path for Ethylene Oxide

Editor’s Note: Research Revisited looks back at articles previously published on ChemicalProcessing.com about university research. Here, we revisit “Ethylene Oxide: ‘Save A Lot of CO₂ And a Lot of Money'" published on Feb. 25, 2025. 

Louisiana is home to more than 150 petrochemical plants. The region produces a large volume of chemicals used in resins, rubber and plastics, including ethylene, propylene benzene and styrene. The corridor’s success has come at a cost, though. The region is a regulatory target due to hazardous air pollutants and elevated cancer rates that some attribute to industrial emissions, including ethylene oxide.

The U.S. Environmental Protection Agency and environmental justice advocates have called for limits on ethylene oxide emissions to minimize the impact on public health. Researchers in the heart of this chemical corridor at Tulane University, in collaboration with the University of California Santa Barbara and Tufts University, are looking at more environmentally friendly ways to produce ethylene oxide using nickel instead of chlorine.

Chlorine has been a primary additive in ethylene oxide production for decades. But it presents some safety and environmental concerns and must be separated from the product stream after the reaction, said Matthew Montemore, a Tulane engineering professor who co-led the study. 

The research team discovered that by applying tiny amounts of nickel to silver catalysts they could gain a performance comparable to alkyl chloride promoters. The researchers first reported on their success in a Science article published early last year. Since then, the university has signed a deal with a startup company specializing in catalyst commercialization.

Single-Atom Approach to Discovery

The study began in 2018 when Montemore and chemistry professor Charles Sykes were exploring selective oxidation reactions, according to a Tulane University article. 

“We were just trying to look at how we could improve silver for oxidation because silver can do multiple oxidation reactions, not just the one that we ended up focusing on—ethylene oxidation,” Montemore said. 

A key challenge was getting the oxygen molecules to dissociate, or split apart, more easily. Silver alone isn't very effective at breaking the bond between the two oxygen atoms in an oxygen molecule, Montemore explained.

The team decided to focus on ethylene oxidation because it’s a major industrial reaction that  already uses a silver-based catalyst. 

The researchers searched for promoters for silver-based ethylene oxide-producing catalysts. They did this using a single-atom alloy (SAA) approach developed by the team, which previously enabled them to identify new selective hydrogenation and dehydrogenation catalysts.

The researchers used density functional theory calculations to search for metals that could be added to silver surfaces in tiny amounts to form single, isolated atoms embedded in the surface. They were looking for two specific properties: the ability to easily break apart oxygen molecules but without holding onto the resulting oxygen atoms too tightly.

Among all the metals they tested, nickel stood out. The simulations predicted that nickel could break oxygen molecules apart easily while still maintaining a moderate grip on the oxygen atoms, according to the Science article.

Scalability in the Works

The catalyst has proven to be stable for short periods in the lab, but researchers will need to conduct further tests to ensure the catalyst can maintain the performance required to scale for industrial use, Montemore said. The research department signed a deal with a startup in fall 2025 to potentially move the nickel-silver promoter from the lab to commercialization. They’re using the industrial synthesis method to test the catalyst at a more industrial scale.

Meanwhile, research may prove that combining nickel with chlorine and some other promotors could be the best approach for maximizing efficiencies. 

“My collaborator will sometimes say a 1% improvement in selectivity beyond the current one saves $200 million in ethylene feed cost,” Montemore said. “And I did the calculation once, and that same 1% improvement could save as much CO₂ as a 100,000 cars. Those are big improvements even if we still have to use the chlorine.”