Abstract
Developing effective catalysis to address end-of-life Nylon pollution is urgent yet remains underdeveloped. Nylon-6 is a resilient synthetic plastic and a major contributor to ocean pollution. Here, we report a metallocene catalytic system based on earth-abundant early transition and lanthanide metals that mediates Nylon-6 depolymerization at unprecedented rates up to 810 (ε-caprolactam)·mol(Cat.)−1·h−1 at 240°C in ≥99% yield. This solventless process operates with catalyst loadings as low as 0.04 mol % at temperatures as low as 220°C—the mildest Nylon-6 depolymerization conditions reported to date. This metallocene catalysis can be carried out in a simulated continuous process, and the resulting ε-caprolactam can be re-polymerized to higher-quality Nylon-6. Experimental and DFT analyses identify effective depolymerization pathways involving catalytic intra-Nylon-chain “unzipping” assisted by π-ligand effects and inter-chain “hopping.” A robust chelating ansa-yttrocene is particularly effective in depolymerizing diverse commodity end-of-life articles, such as fishing nets, carpets, clothing, and plastic mixtures.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 172-189 |
| Number of pages | 18 |
| Journal | Chem |
| Volume | 10 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 11 2024 |
Funding
The support of RePLACE (Redesigning Polymers to Leverage A Circular Economy), funded by the Office of Science of the U.S. Department of Energy via award no. DE-SC0022290 (T.J.M. L.Y. K.B. L.J.B. and X.L.), is gratefully acknowledged. Y.K. acknowledges support from the Office of Basic Energy Sciences, US Department of Energy (DE-FG02-03ER15457) to the Institute for Catalysis in Energy Processes (ICEP) at Northwestern U. J.O.R. acknowledges support from NSF CAT Program grant CHE-1856619. This work made use of the IMSERC NMR facility at Northwestern U. supported by NSF (CHE-1048773). This work used Expanse at San Diego Supercomputer Center through allocation CTS120055 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by NSF grants # OAC-2138259, # OAC-2138286, # OAC-2138307, # OAC-2137603, and # OAC-2138296. This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under contract no. DE-AC36-08GO28308. Funding is provided by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, the Advanced Materials & Manufacturing Technologies Office (AMMTO), and the Bioenergy Technologies Office (BETO). This work was performed as part of the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium and was supported by AMMTO and BETO under contract no. DE-AC36-08GO28308 with the National Renewable Energy Laboratory (NREL), operated by Alliance for Sustainable Energy, LLC. The views expressed in the article do not necessarily represent the views of the DOE or the US Government. The US Government retains and the publisher, by accepting the article for publication, acknowledges that the US Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for US Government purposes. Conceptualization, L.Y. Y.K. and T.J.M.; material synthesis, L.Y. K.B. J.O.R. and Y.K.; experimental analysis, L.Y. K.B. and C.L.; DFT calculations, X.L. L.J.B. and Y.K.; writing – original draft, L.Y. X.L. and Y.K.; writing – review & editing, L.J.B. Y.K. and T.J.M.; funding acquisition, L.J.B. and T.J.M. The authors declare no competing interests. The support of RePLACE (Redesigning Polymers to Leverage A Circular Economy), funded by the Office of Science of the U.S. Department of Energy via award no. DE-SC0022290 (T.J.M., L.Y., K.B., L.J.B., and X.L.), is gratefully acknowledged. Y.K. acknowledges support from the Office of Basic Energy Sciences, US Department of Energy ( DE-FG02-03ER15457 ) to the Institute for Catalysis in Energy Processes (ICEP) at Northwestern U. J.O.R. acknowledges support from NSF CAT Program grant CHE-1856619 . This work made use of the IMSERC NMR facility at Northwestern U., supported by NSF ( CHE-1048773 ). This work used Expanse at San Diego Supercomputer Center through allocation CTS120055 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by NSF grants # OAC-2138259 , # OAC-2138286 , # OAC-2138307 , # OAC-2137603 , and # OAC-2138296 . This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under contract no. DE-AC36-08GO28308 . Funding is provided by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, the Advanced Materials & Manufacturing Technologies Office (AMMTO), and the Bioenergy Technologies Office (BETO). This work was performed as part of the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium and was supported by AMMTO and BETO under contract no. DE-AC36-08GO28308 with the National Renewable Energy Laboratory (NREL), operated by Alliance for Sustainable Energy, LLC. The views expressed in the article do not necessarily represent the views of the DOE or the US Government. The US Government retains and the publisher, by accepting the article for publication, acknowledges that the US Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for US Government purposes.
Keywords
- Nylon
- SDG11: Sustainable cities and communities
- SDG9: Industry, innovation, and infrastructure
- catalysis
- depolymerization
- end-of-life plastic
- fishing net recycling
- ligand design
- metallocene catalysts
- ocean plastics
- plastic circularity
- plastic recycling
ASJC Scopus subject areas
- General Chemistry
- Biochemistry
- Environmental Chemistry
- General Chemical Engineering
- Biochemistry, medical
- Materials Chemistry
