A research team led by Professor Aditya Bhan at the University of Minnesota Twin Cities, in collaboration with scientists at the SLAC National Accelerator Laboratory, has demonstrated a new method for selectively combusting contaminants in hydrocarbon mixtures. Their work focuses on removing trace acetylene from ethylene-rich gas streams, a long-standing challenge in polymer production. The group developed a catalytic process using bismuth oxide that provides a more efficient and targeted way to oxidize unwanted molecules without affecting the desired feedstock.
Jacob, M., Nguyen, H., Raj, R., Garcia-Barriocanal, J., Hong, J., Perez-Aguilar, J. E., Hoffman, A. S., Mkhoyan, K. A., Bare, S. R., Neurock, M., & Bhan, A. (2025). Selective chemical looping combustion of acetylene in ethylene-rich streams. Science, 387(6735), 744–749. https://doi.org/10.1126/science.ads3181
The process relies on chemical looping, a mode of operation where the catalyst itself supplies oxygen atoms from its own lattice. During the reaction, the bismuth oxide catalyst donates oxygen to oxidize acetylene into carbon dioxide and water, leaving the bulk ethylene untouched. The catalyst is then reoxidized by air and reused, completing a redox cycle. This differs from conventional combustion approaches that typically expose the entire mixture to oxygen and heat, risking unwanted side reactions or flammability hazards.
Aditya Bhan at the University of Minnesota Twin Cities stated,
“No one else has shown that you could combust one hydrocarbon present in low concentrations, in mixtures with others.”
Experimental results showed that acetylene could be removed from ethylene streams to concentrations well below the two parts per million threshold necessary for preventing downstream catalyst poisoning. Current industrial practice often uses semi-hydrogenation to convert acetylene into ethylene, but that process requires hydrogen, high pressure, and considerable energy input. By contrast, selective chemical looping avoids co-feeding oxygen or hydrogen while maintaining precision in targeting only the undesired molecule.
The researchers found that the catalyst was highly selective, with the rate of acetylene oxidation several thousand times faster than the rate of ethylene oxidation under the same conditions. Spectroscopic studies at SLAC confirmed that the structural environment of the bismuth remained stable across multiple redox cycles, suggesting good long-term durability. This stability is particularly important because repeated reduction and reoxidation steps can sometimes cause structural changes or degradation in catalysts.
The implications for the plastics industry are immediate. Even very small amounts of acetylene can deactivate the catalysts used to produce polyethylene, one of the most widely manufactured polymers in the world. Removing acetylene efficiently and without wasting energy could reduce costs, minimize downtime, and improve overall process reliability. For industries that operate at massive scales, such incremental improvements can translate into significant economic and environmental benefits.
There are, however, hurdles to overcome before the method can be applied at scale. Ensuring that the catalyst does not over-reduce, managing structural stability over extended use, and designing reactors that can handle the solid material efficiently are all engineering challenges that must be addressed. The research team has indicated interest in testing other oxide systems that might offer even greater selectivity or robustness. Extending the concept to more complex hydrocarbon streams will also be a focus of future work.
This development highlights the broader value of understanding catalytic reactions at a molecular level. By designing materials that can discriminate between molecules as similar as acetylene and ethylene, researchers open the door to new strategies for cleaning industrial streams, reducing waste, and improving safety. Selective combustion through chemical looping is not about burning everything in sight, but about selectively targeting what needs to be removed. It is a subtle but potentially transformative tool in the ongoing effort to make chemical production cleaner and more efficient.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
