Simple Salt Serves as Catalyst to Convert Plastic Waste Into Fuel

SEATTLE (Scrap Monster): Researchers keep finding ingenious ways to manage plastic waste by converting it into new materials in a virtuous loop. While the technologies may work remarkably well, the intensive resources and costs involved make them a hard sell. Scientists at the US Department of Energy’s Oak Ridge National Laboratory (ONRL) have developed a method to convert waste polyethylene (PE) into gasoline- and diesel-like fuel using — and this is the salient part — cheap aluminum molten salts as a catalyst.

The researchers have applied for a patent and published the results of their work in the Journal of the American Chemical Society.

No metal catalysts, organic solvents, or external hydrogen needed

“We converted polymer waste to value-added fuels by using commercially available inorganic salts as the reaction media to provide the catalytic sites,” explained Zhenzhen Yang, an ORNL staff scientist and co-corresponding author of the paper published in the journal. “Unlike traditional techniques for converting polymer to fuel, the new process did not require noble-metal catalysts, organic solvents, or external hydrogen. This is the first time molten salts were used as media to produce high-value-added chemicals from waste without any catalytic initiator or solvent and at temperatures below 200°C.”

By comparison, converting PE to fuel using conventional pyrolysis requires temperatures as high as 500°C.

Experiment yields about 60% gasoline

The experiments produced a gasoline yield of about 60% under mild conditions, according to the researchers. If scaled beyond the laboratory, they believe the process could strengthen US energy security and industrial competitiveness.

The storied national lab founded in 1943 in Oak Ridge, TN, has pioneered molten salt research since the 1960s, when its Molten Salt Reactor Experiment showed that molten salt mixtures could serve as both fuel and coolant in a nuclear reactor. In the current experiment, Sheng Dai, ORNL Corporate Fellow and section head for separations and polymer chemistry, proposed using molten salts to turn polymer waste into fuel. Molten salts are inorganic compounds that remain stable under harsh reaction conditions.

Two fundamental issues solved

“The ORNL system solves two fundamental issues,” said Dai. “One, for a stable system, the process can be radically easier to scale up. Two, the previous system needed an initiator to kick off catalytic reactions. However, the ORNL system does not need one.”

"Although the . . . system is catalytically active and inexpensive, it is hygroscopic, meaning it absorbs water and loses stability," notes the article on the ORNL website. Next step for the researchers is to explore ways to confine molten salts, maybe with halogens or carbons, to improve separation and processing.

The current findings, however, do expand options for producing transportation and industrial fuels, according to the researchers. “Polymer source material is abundantly available from consumer waste, and our catalyst system — aluminum molten salts — is very cheap,” said Liqi Qiu, a postdoctoral researcher at the University of Tennessee, Knoxville, who performed most of the study’s experiments in the ORNL laboratory. “This advance may be promising for industry.”

For further information on the genesis of the research and the steps by which the experiment was brought to fruition, check out “Molten Salt Chemistry Converts Consumer Polymer Into Fuel” on the ORNL website.

Breaking new ground in circularity

The last couple of months alone have brought several other potentially groundbreaking developments in advancing circularity.

Researchers at the University of Bath report that they have developed a method for chemically recycling PMMA that requires lower temperatures than mechanical recycling and uses sustainable solvents. There is reportedly no loss in material quality, meaning the plastic can be recycled numerous times with minimal environmental impact.

Swiss specialty chemicals maker Clariant announced in March the completion of a pilot-scale project demonstrating its pyrolysis oil (pyoil) upgrading technology, marking a significant milestone in advancing circular economy solutions for the plastics industry.

In collaboration with materials supplier Borealis and SINTEF, one of Europe’s largest independent research organizations, the project focused on upgrading pyoil derived from plastic waste into steam cracker-compatible feedstock that meets stringent cracker-grade quality specifications. Using Clariant’s proprietary HDMax catalysts, pilot-scale testing at SINTEF’s research facility in Norway reportedly delivered exceptional results, transforming plastic waste-derived pyoil into feedstock suitable for virgin polyolefin production.

Also last month, PlasticsToday reported on research conducted at the Center for Marine Debris Research at Hawaiʻi Pacific University centered on turning waste fishing nets and residential plastic trash into asphalt roads. 

Presented at the American Chemical Society (ACS) Spring 2026 meeting, the study demonstrates that incorporating recycled plastic into asphalt is both technically feasible and environmentally safe, with minimal risk of microplastic shedding.

Courtesy: www.plasticstoday.com