New method removes pollutants from industrial processes

This new method from the University of Minnesota Twin Cities could help in the removal of pollutants and improve efficiency for industrial processes ranging from the production of fuels and medications to fertilisers and plastics. The research is published in Science.

By using a bismuth oxide catalyst the researchers can selectively burn one molecule in a mixture of combustibles. The researchers showed that it is possible to effectively combust small amounts of acetylene in mixtures with ethylene. Removing acetylene is a crucial process to prevent poisoning of polymerisation catalysts, which is vital to produce polyethylene plastics.

“No one else has shown that you could combust one hydrocarbon present in low concentrations, in mixtures with others,” said Aditya Bhan, a Distinguished McKnight University Professor in the Department of Chemical Engineering and Materials Science and lead investigator on the paper. 

Conventionally, combustion processes are used to burn hydrocarbon fuel mixtures at high temperatures to produce heat. The use of a catalyst allowed the researchers to tackle the challenge of burning one molecule but not the others. The bismuth oxide catalyst is claimed to be unique as it provides its own oxygen during combustion, rather than using oxygen from an outside source, in a process called chemical looping.

“We were able to take oxygen out of the catalyst and put it back in multiple times, where the catalyst changes slightly, but its reactivity is not impacted. Operating in this chemical looping mode avoids flammability concerns,” said first author Matthew Jacob, a University of Minnesota chemical engineering PhD candidate.

Traditionally, eliminating small concentrations of contaminants is very challenging and energy-intensive, but this new method could provide a more energy-efficient alternative.

“You want to do this process selectively. Removing acetylene and other trace hydrocarbon contaminants in this manner could be more energy efficient,” said senior co-author Matthew Neurock, a professor in Department of Chemical Engineering and Materials Science. “You just want to be able to go into a gas mixture to remove some molecules without touching the rest of the molecules.”

The researchers said the long-term impact could be significant given the range of catalysts used in industrial processes. Understanding how molecules combust – and do not combust - on catalyst surfaces is valuable for making fuels and plastics production more efficient.

“If we can understand how a catalyst works, at a molecular atomic level, we can adapt it to any particular reaction,” said co-author Simon Bare, a Distinguished Scientist at the SLAC National Accelerator Laboratory at Stanford University. “This can help us understand how catalysts, that produce fuels and chemicals needed in modern living, react to their environment.”