Chemical recycling of post-consumer polyester wastes using a tertiary amine organocatalyst

Recycling diverse waste plastics poses challenges due to complex sorting and processing, resulting in high costs and inefficiency. To tackle this, we present a metal-free catalytic sorting method for targeted deconstruction of polyester from post-consumer plastic waste, encompassing textiles, plastic mixtures, and multilayer packaging materials. This method employs N-methylpiperidine, a tertiary amine catalyst in methanol, to depolymerize polyethylene terephthalate (PET). Operating under these conditions (160°C, 1 h), we achieve 100% yields of dimethyl terephthalate and ethylene glycol. This technique also effectively breaks down other polyesters, including polylactic acid, polycarbonate, and polybutylene terephthalate, yielding high-yield monomers at relatively low temperatures. Through comprehensive nuclear magnetic resonance (NMR) analysis, we propose that N-methylpiperidine’s role is in enhancing methanol nucleophilicity and activating PET’s ester bond. Our insights advance the chemical recycling of post-consumer plastic waste, offering a potentially simple and efficient path to closing the polyester production loop.. Authors: Xie, Shaoqu [Washington State Univ., Pullman, WA (United States)]; Wang, Caiqi [Washington State Univ., Pullman, WA (United States)] (ORCID:0000000198849990); Hu, Wenda [Washington State Univ., Pullman, WA (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Institute for Integrated Catalysis]; Hu, Jian Zhi [Washington State Univ., Pullman, WA (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Institute for Integrated Catalysis]; Wang, Yong [Washington State Univ., Pullman, WA (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Institute for Integrated Catalysis]. DOE Contract: AC05-76RL01830. Subjects: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; NMR; PET; circular economy; organocatalyst; plastic recycling; polyester; sustainability; tertiary amine