Catalytic Chemical Recycling of Post-Consumer Polyethylene

• Published in: Journal of the American Chemical Society Vol. 144; no. 51; pp. 23280 - 23285
• Main Authors: Arroyave, Alejandra, Cui, Shilin, Lopez, Jaqueline C., Kocen, Andrew L., LaPointe, Anne M., Delferro, Massimiliano, Coates, Geoffrey W.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.12.2022; American Chemical Society (ACS)
• Subjects: Catalysis; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Plastics; Polyethylene; Polymers; Waste Products
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c11949

Among commercial plastics, polyolefins are the most widely produced worldwide but have limited recyclability. Here, we report a chemical recycling route for the conversion of post-consumer high-density polyethylene (HDPE) into telechelic macromonomers suitable for circular reprocessing. Unsaturation was introduced into HDPE by catalytic dehydrogenation using an Ir-POCOP catalyst without an alkene acceptor. Cross-metathesis with 2-hydroxyethyl acrylate followed by hydrogenation transformed the partially unsaturated HDPE into telechelic macromonomers. The direct repolymerization of the macromonomers gave a brittle material due to the low overall weight-average molecular weight. Aminolysis of telechelic macromonomers with a small amount of diethanolamine increased the overall functionality. The resulting macromonomers were repolymerized through transesterification to generate a polymer with comparable mechanical properties to the starting post-consumer HDPE waste. Depolymerization of the repolymerized material catalyzed by an organic base regenerated the telechelic macromonomers, thereby allowing waste polyethylene materials to enter a chemical recycling pathway.