Metal-free recycling of waste polyethylene terephthalate mediated by TBD protic ionic salts: the crucial role of anionic ligands

Abstract

The structure–activity relationships of TBD based protic ionic salts for PET glycolysis by EG were comprehensively investigated through theoretical prediction and experimental verification.

Overcoming the Limitations of Organocatalyzed Glycolysis of Poly(ethylene terephthalate) to Facilitate the Recycling of Complex Waste Under Mild Conditions

“…Among these methods, glycolysis is currently the most studied, as BHET is a common monomer for PET production, and the reaction only requires a catalyst and ethylene glycol, which is one of the monomers of PET. − To date, numerous reports describe the glycolysis of PET under various conditions with different catalytic systems. − Among the available catalysts utilized in the open literature, nitrogen-based organocatalysts, such as 1,5,7-triazabicyclo[4.4.0]­dec-5-ene (TBD), 1,8-diazabicyclo 5.4.0 undec-7-ene (DBU), or 4-dimethylaminopyridine (DMAP), have been widely studied. , With TBD as the catalyst, full degradation of the polymer can be obtained in minutes using ethylene glycol in excess at 190 °C under a nitrogen atmosphere. More recent reports, including publications from our group, have explored the use of thermally resistant acid/base complexes − while other organocatalytic routes, mainly using metal-free ionic liquids, have also been explored. − However, these methodologies usually require high temperatures, over 180 °C, to reach complete depolymerization on an acceptable time scale.…”