Recycling PET with PEF traces by a eutectic solvent-assisted depolymerization: Experimental and DFT Insights

The global reliance on plastics has driven significant economic growth, with production surpassing 400 million tons in 2022 [1]. Yet, only around 15% of plastic waste is currently recycled [2] and among polyesters, poly(ethylene terephthalate) (PET) is the most widely recycled. However, the imminent commercialization of poly(ethylene 2,5-furandicarboxylate) (PEF), a bio-based PET alternative, raises concerns about its impact on existing PET recycling streams due to structural similarities and potential co-occurrence.

In this study, we present a greener chemical recycling strategy for PET containing residual amounts of PEF (2%, 5%, and 10%) using a eutectic solvent (ES) system composed of urea and zinc acetate as a catalyst. This work reports, for the first time, the structural and thermal characterization of the resulting copolymers (rPET-co-PEF). The recycled materials exhibited structural and thermal properties comparable to virgin PET, suggesting negligible interference from PEF residues in PET’s recycling.

Additionally, the depolymerization mechanism was investigated through density functional theory (DFT) calculations by using Gaussian software. The results indicate that hydrogen bonding interactions between urea alongside zinc coordination with ester groups, significantly reduce the activation energy of the reaction. These findings confirm the catalytic efficiency of the urea-based ES and support its wider application as a sustainable solution for mixed polyester waste recycling.

REFERENCES

1. Plastics Europe. Plastics - the fast facts. 2023.
2. Timmy Thiounn, Rhett C. Smith, Journal of Polymer Science. 2020, 58, 1347-1364.