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Sandia research targets more sustainable jet fuel

Cycloalkanes feasible frontrunners for reducing aviation emissions, Livermore scientists say
Sandia National Laboratories recently published research data demonstrating how cycloalkanes, when used in jet fuel, may reduce condensation trail formation and soot emissions as compared to current fuels.

New data developed by scientists in Livermore could hold the promise of reducing greenhouse effect and providing sustainable aviation fuel, according to Sandia National Laboratories. 

Sandia has collaborated with researchers at Los Alamos National Laboratory exploring the physical properties of cycloalkanes, which are molecules composed of hydrogen and carbon atoms arranged in a ring structure using single bonds. Using cycloalkanes as part of jet fuel may reduce condensation trail formation and soot emissions as compared to current fuels, according to Sandia researcher and chemist Alexander Landera.

"Unlike other forms of travel, such as cars and trucks, there is currently no foreseeable path to electrify the aviation sector," Landera said last week. "Therefore, mitigation efforts are necessary to decarbonize the aviation industry."

The newly discovered data on the potential impacts of cycloalkanes is still in the research phase, so it could take a few years before moving to the next level.

"Nothing has been tested yet. It's really difficult to replace all the aromatics, but some of the aromatics can be replaced by cycloalkanes," Landera said. "Literature does show that you can generate a jet fuel that has this kind of combination of cycloalkanes and aromatics, and it does actually perform really good."

The research team's key objectives has been to minimize the aromatic content of aviation fuel and replace it with cycloalkanes. Aromatics are substances derived from refining crude oil and are used as a source of octane, which increases the engine's power and fuel efficiency, according to Sandia.  

Aromatics are beneficial in fuel because they cause the O-rings in the engine to swell, an important function in maintaining engine seals and preventing fuel leaks. But the problem is the soot produced during combustion contributing to climate change, Sandia officials said. 

The primary goal of the research was to understand different behavioral changes in renewably sourced molecules when used as jet fuels. Cycloalkanes are a broad class of hydrocarbon molecules, like molecules found in petroleum which contain thousands of different kinds of hydrocarbons, but can be produced biologically from renewable resources, according to Sandia. 

Researchers say that this isn't a technology, but a method to understand fuel properties. Sandia officials believe their research data and insights will be beneficial to the aviation industry as they make decisions about which new fuels to produce.

"There is a strong market pull for sustainable aviation fuels right now and the research data published by Sandia will contribute to innovative solutions being explored," Sandia officials said. 

Previous scientific research had already discovered that some cycloalkanes could reduce soot, but no systematic study had been done of these molecules more broadly. 

The Sandia research showed which of these molecules would be suitable for use in jet fuels and which were not. They also developed some relationships to be able to predict their performance, according to the lab. 

Cycloalkanes can also be produced from feedstock or renewable biological material, potentially making their production more carbon sustainable. Landera hopes that by building a database of these properties, their research will help clear the way for cycloalkane's inclusion in future aviation fuels.

"We've looked at various families of cycloalkanes to identify which ones have the strongest fuel properties, and which have higher energy content," Landera said.

Sandia officials said the lab is engaged in work to decrease the cost, increase the sustainability and expand the production and use of sustainable aviation fuels.

"As we develop these, we've looked at the different trends and see which ones are good, which ones might not be so good and hopefully that informs the community in terms of what types of cycloalkanes (are feasible)," Landera said. 

Funded by the Department of Energy's Bioenergy Technologies Office, the research is part of Sandia's overall mission to address the national and global security threats associated with the climate crisis, said Anthe George, senior manager of the labs' applied biosciences and engineering group.