Northwestern University chemists have developed a new catalyst that quickly, cleanly and completely breaks down Nylon-6 in a matter of minutes — without generating harmful byproducts. Even better: The process does not require toxic solvents, expensive materials or extreme conditions, making it practical for everyday applications.
Not only could this new catalyst play an important role in environmental remediation, it also could perform the first step in upcycling Nylon-6 wastes into higher-value products.
The research was published in the journal Chem.
Marks is the Charles E. and Emma H. Morrison Professor of Chemistry and Vladimir N. Ipatieff Professor of Catalytic Chemistry at Northwestern’s Weinberg College of Arts and Sciences and a professor of materials science and engineering at Northwestern’s McCormick School of Engineering. He also is a faculty affiliate at the Paula M. Trienens Institute for Sustainability and Energy. Northwestern co-authors include Linda J. Broadbelt, the Sarah Rebecca Roland Professor of Chemical and Biological Engineering and senior associate dean of McCormick, and Yosi Kratish, a research assistant professor in Marks’ group.
Recovering building blocks for upcycling
To bypass these issues, the researchers looked to a novel catalyst already developed in Marks’ laboratory. The catalyst harnesses yttrium (an inexpensive Earth-abundant metal) and lanthanide ions. When the team heated Nylon-6 samples to melting temperatures and applied the catalyst without a solvent, the plastic fell apart — reverting to its original building blocks without leaving byproducts behind.
In experiments, Marks and his team were able to recover 99% of plastics’ original monomers. In principle, those monomers then could be upcycled into higher-value products, which are currently in high demand for their strength and durability.
“Recycled nylon is actually worth more money than regular nylon,” Marks said. “Many high-end fashion brands use recycled nylon in clothes.”
Efficiently targeting Nylon-6
In addition to recovering a high yield of monomers, the catalyst is highly selective — acting only on the Nylon-6 polymers without disrupting surrounding materials. This means industry could apply the catalyst to large volumes of unsorted waste and selectively target Nylon-6.
“If you don’t have a catalyst that’s selective, then how do you separate the nylon from the rest of waste?” Marks said. “You would need to hire humans to sort through all the waste to remove the nylon. That’s enormously expensive and inefficient. But if the catalyst only degrades the nylon and leaves everything else behind, that’s incredibly efficient.”
Recycling these monomers also avoids the need to produce more plastics from scratch.
“These monomers are produced from crude oil, so they have a huge carbon footprint,” Ye said. “That’s just not sustainable.”
After filing a patent for the new process, Marks and his team have already received interest from potential industrial partners. They hope others can use their catalysts on a large scale to help solve the global plastic problem.