Enhancing carbon fiber production with low-cost oil residues

Advanced carbon fiber materials could be used in applications from wind turbine blades to biomedical implants following the development of a low-cost carbon fiber feedstock.

The carbon fibers were spun from synergistic blends of the low-value heavy oils left over from crude oil refining by members of KAUST’s Clean Energy Research Platform. The work could not only facilitate broader carbon fiber uptake but also create sustainable new uses for residual oils as the world transitions to alternative energy systems.

“Crude oil is a resource with immense potential beyond fuels,” says Edwin Guevara Romero, a researcher in the labs of Mani Sarathy, who led the work. “Using oil residues as feedstocks for carbon materials is an innovative, high-value application of oil-derived resources, paving the way for economic diversification,” he says.

Carbon fiber is in increasing demand across many industries due to its exceptional properties, including high mechanical strength and durability, low weight, thermal stability, and electrical conductivity. One limiting factor is its high cost, which can largely be attributed to the expensive carbon precursor, polyacrylonitrile (PAN), used to make it.

PAN’s high cost has prompted a search for alternative feedstocks. “Oil residues could offer a cost-effective and abundant alternative,” Guevara says. For their research, the team targeted the heaviest, most complex—and traditionally, hardest to process—components of residual oil, called asphaltenes and resins.

Previously, asphaltenes have been trialed as carbon fiber feedstocks. However, efforts to spin these materials into fibers were limited by their tendency to break, and the carbon fiber yield from the final carbonization heat treatment step was relatively low.

“Previous studies of oil residues have suggested that resins stabilize asphaltene molecules, highlighting their strong molecular affinity,” Guevara says. “This led us to hypothesize that blending asphaltenes with resins could create a synergistic feedstock for carbon fiber production.”

Published in Fuel, the team showed that the blend offered several advantages over asphaltenes alone as carbon fiber feedstocks. It had better flow characteristics and could be spun at a lower temperature, reducing energy consumption. The team also observed fewer strand breakages during spinning and attained a higher yield after the carbonization step.

“This improves the viability of the process by maximizing the conversion of the precursor material into the final carbon fiber product,” Guevara says.

The resulting carbon fibers were also of high quality. “The properties of our fibers are comparable to those of ‘isotropic carbon fibers,” which are commonly used in applications requiring moderate-to-high mechanical performance,” Guevara says.

“Traditionally, oil residues have been used in very low-value applications such as road surfacing. By extracting the heaviest asphaltenes and resins for high-value carbon fiber manufacturing, the remaining residual oils can also be more easily processed to produce cleaner fuels or valuable small molecules, further improving the economics of the process,” Sarathy adds.

The researchers are now fine-tuning the residual oil blend to maximize the chemical interaction between the components to improve the fibers’ physical attributes further. They are also collaborating with Saudi Aramco to scale up the process.

“Our primary objective is to generate high-performance carbon fibers and then scale towards an industrial process,” Sarathy says. “This will give Saudi Arabia a unique, economically competitive product that can be marketed globally.”