Northwestern scientists develop nickel-based catalyst to transform plastic recycling

The research, published in Nature Chemistry, introduces a novel upcycling process that selectively breaks down polyolefin plastics—polyethylenes and polypropylenes that make up nearly two-thirds of global plastic consumption—into oils, waxes and fuels.

"One of the biggest hurdles in plastic recycling has always been the necessity of meticulously sorting plastic waste by type," said Professor Tobin Marks, senior author of the study. "Our new catalyst could bypass this costly and labor-intensive step for common polyolefin plastics, making recycling more efficient, practical and economically viable than current strategies."

The new method is designed to transform low-value solid waste into higher-value products. Importantly, the catalyst also works on plastics contaminated with polyvinyl chloride (PVC), a polymer that typically disrupts recycling processes. Remarkably, PVC even accelerated the catalyst’s activity.

"Adding PVC to a recycling mixture has always been forbidden," explained Dr. Yosi Kratish, co-corresponding author of the paper. "But apparently, it makes our process even better. That is crazy. It's definitely not something anybody expected."

Addressing a global challenge

Polyolefins are the most widely used plastics in the world, found in food packaging, bottles, disposable utensils and household items. Industry produces more than 220 million tons annually, yet recycling rates remain as low as 1–10% worldwide. Their chemical structure, based on strong carbon-carbon bonds, has made them notoriously difficult to recycle.

"When people think of plastic, they likely are thinking about polyolefins," said Kratish. "Basically, almost everything in your refrigerator is polyolefin-based. If we don’t have an efficient way to recycle them, then they end up in landfills and in the environment, where they linger for decades before degrading into harmful microplastics."

To address this, the Northwestern team turned to hydrogenolysis, which uses hydrogen gas and a catalyst to break down plastics into hydrocarbons. Unlike existing approaches that require high temperatures and costly noble metals such as platinum, the new process employs an Earth-abundant nickel compound in a single-site molecular catalyst. This structure allows the catalyst to act with surgical precision in breaking carbon-carbon bonds.

"Compared to other nickel-based catalysts, our process uses a single-site catalyst that operates at a temperature 100 degrees lower and at half the hydrogen gas pressure," Kratish noted. "We also use 10 times less catalyst loading, and our activity is 10 times greater. So, we are winning across all categories."

Stability and industrial potential

The nickel catalyst proved exceptionally stable, maintaining activity even in mixtures with up to 25% PVC contamination. It can also be regenerated over multiple cycles through a simple and inexpensive treatment. This offers a scalable solution for industries struggling with unsorted plastic waste.

"The polyolefin production scale is huge, but the global noble metal reserves are very limited," said Qingheng Lai, the study’s first author. "That’s why we are interested in Earth-abundant metals. Even if we used all noble metals, there still would not be enough to address the plastic problem."

By combining affordability, efficiency and resilience, Northwestern’s nickel-based catalyst could provide a transformative pathway to address one of the world’s most urgent environmental challenges—plastic waste.

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