Editor’s Note: This project is sponsored by the Department of the Navy, Office of Naval Research under ONR Award Number N000142512239.
What if the exhaust from a jet plane was not just pollution, but rather a source of its next tank of fuel? While it may sound like science fiction, converting carbon dioxide (CO₂) into fuel is already possible, and a team of UT San Antonio researchers is working to fine-tune the process.
The researchers are developing catalysts that transform CO₂, ultimately producing functional, military-grade jet fuel of a higher quality than has previously been possible. If successful, the technology could provide a sustainable source of aviation fuel with multiple benefits.
“The potential impact is the production of liquid military fuels with improved characteristics that are derived from recycled carbon obtained from captured CO₂ from the atmosphere or seawater,” said Gary Jacobs, PhD, associate professor of chemical engineering in the Department of Biomedical Engineering and Chemical Engineering in Klesse College. “This is a way to produce hydrocarbon fuel with high volumetric energy density, while at the same time decreasing our dependency on fossil fuels and enhancing our energy security.”
Fuel for the future
One benefit to this technology is that it may offer a better alternative to existing conversion methods using dihydrogen (H₂).
“H₂ can be produced sustainably by solar, wind and nuclear-powered electrolysis, but it is a gas and therefore has low volumetric energy density,” said Jacobs, who is also the principal investigator. “That’s why we aim to recycle carbon, essentially to utilize it as a chemical carrier of hydrogen. The benefit is that liquid hydrocarbon fuels have high volumetric energy density, which is critical for long-distance travel,” he added.
To make this energy-dense fuel, the team will convert CO₂ into carbon monoxide (CO) through a process called reverse water-gas shift, a process Jacobs has been refining since 2021 with Southwest Research Institute (SwRI). The team will then use a process called Fischer-Tropsch synthesis (FTS) to bind the carbon monoxide with hydrogen and transform it into the longer chains of carbon and hydrogen atoms that make up fuel.
The team plans to improve the catalysts used in the FTS stage to bend these hydrocarbon chains into the ring-shaped molecules, or aromatic molecules, that military jets require.
Inter-institutional collaboration
Jacobs will work in his lab at UT San Antonio with his doctoral student Nadia ALHirbawi, Southwest Research Institute (SwRI) researchers led by Chan Meza and University of Kentucky Center for Applied Energy (CAER) researchers led by Michela Martinelli.
“UT San Antonio will be preparing modified Fischer-Tropsch synthesis and methanol synthesis catalysts with the aim of boosting the aromatic content of synthetic kerosene fuels,” Jacobs said.
“SWRI will be testing the catalysts in a fixed bed reactor configuration, whereas UK-CAER will be testing them in a slurry phase reactor configuration,” he added.
The team will build on the discoveries of other chemical engineers in this growing field. In addition to aviation fuel, scientists have found ways to transform CO₂, along with hydrogen (H₂), into diesel, gasoline, methanol and formate, a solid fuel that can be used to heat homes.
Facing headwinds
While this emerging technology is promising, there are still several hurdles to clear before it becomes mainstream. Jacobs noted several persistent challenges, including:
- Lack of infrastructure for CO₂ capture
- High costs associated with capturing and concentrating CO₂
- Costs associated with converting CO₂ to CO
- The need to improve efficiencies at every step, and
- The development of active and selective catalysts that are stable for long-term use
The research is backed by over $600,000 in funding from the Office of Naval Research – Science and Technology for a three-year period. After that time, Jacobs hopes to continue refining the technology and incorporating the progress of his peers in the field.
“Breakthroughs are happening all the time, and if these advancements continue, we certainly hope to see CO₂-derived fuels playing a greater role in the future,” he said.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Office of Naval Research.
