2023-11-30 ノースウェスタン大学
◆これにより、環境浄化だけでなく、ナイロン-6廃棄物のアップサイクリングの初歩が可能になります。従来の処理方法では、有毒な排ガスを発生させたり、エネルギー効率の低い高温条件が必要だったりしましたが、この新しい触媒はそれらの問題を解決し、再生可能なモノマーを高収率で回収できます。これにより、再利用可能なプラスチック製品の生産に資する可能性があります。
＜関連情報＞
- https://news.northwestern.edu/stories/2023/11/durable-plastic-pollution-easily-cleanly-degrades-with-new-catalyst/
- https://www.cell.com/chem/fulltext/S2451-9294(23)00548-X
ナイロン6プラスチックの迅速、選択的、無溶媒解重合を可能にする金属-配位子設計触媒を開発 Catalyst metal-ligand design for rapid, selective, and solventless depolymerization of Nylon-6 plastics
Liwei Ye,Xiaoyang Liu,Kristen B. Beckett,Jacob O. Rothbaum,Clarissa Lincoln,Linda J. Broadbelt,Yosi Kratish,Tobin J. Marks
Chem Published:November 30, 2023
DOI:https://doi.org/10.1016/j.chempr.2023.10.022
Highlights
•Rapid and selective Nylon-6 depolymerization catalyzed by a new metallocene-based system
•Tunable catalytic structures enable effective and well-defined mechanisms
•Mild depolymerization conditions using reusable, earth-abundant catalysts
•Depolymerization of diverse end-of-life Nylons catalyzed by stable ansa-complex
Summary
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.
Graphical abstract
