A Multitool for Circular Economy: Fast Ring‐Opening Polymerization and Chemical Recycling of (Bio)polyesters Using a Single Aliphatic Guanidine Carboxy Zinc Catalyst

• Published in: ChemSusChem Vol. 16; no. 12; pp. e202300192 - n/a
• Main Authors: Fuchs, Martin, Schäfer, Pascal M., Wagner, Wolf, Krumm, Ian, Walbeck, Marcel, Dietrich, Regina, Hoffmann, Alexander, Herres‐Pawlis, Sonja
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.06.2023
• Subjects: alcoholysis; Aliphatic compounds; Catalysts; Catalytic activity; chemical recycling; Circular economy; Industry standards; Lactates; Polyester resins; Polyethylene terephthalate; Polylactic acid; polylactide; Polymer blends; Polymerization; Recycling; Ring opening polymerization; Toluene; Zinc chloride; chemical recycling; alcoholysis; polylactide; polyethylene terephthalate; ring-opening polymerization
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300192

A new aliphatic hybrid guanidine N,O‐donor ligand (TMGeech) and its zinc chloride complex ([ZnCl2(TMGeech)]) are presented. This complex displays high catalytic activity for the ring‐opening polymerization (ROP) of lactide in toluene, exceeding the toxic industry standard tin octanoate by a factor of 10. The high catalytic activity of [ZnCl2(TMGeech)] is further demonstrated under industrially preferred melt conditions, reaching high lactide conversions within seconds. To bridge the gap towards a sustainable circular (bio)economy, the catalytic activity of [ZnCl2(TMGeech)] for the chemical recycling of polylactide (PLA) by alcoholysis in THF is investigated. Fast production of different value‐added lactates at mild temperatures is demonstrated. Selective PLA degradation from mixtures with polyethylene terephthalate (PET) and a polymer blend, catalyst recycling, and a detailed kinetic analysis are presented. For the first time, chemical recycling of post‐consumer PET producing different value‐added materials is demonstrated using a guanidine‐based zinc catalyst. Therefore, [ZnCl2(TMGeech)] is a promising, highly active multitool, not only to implement a circular (bio)plastics economy, but also to tackle today's ongoing plastics pollution. Complex as multitool: A new aliphatic N,O‐guanidine ligand and its ZnCl2 complex are presented. The complex shows high catalytic activity towards both ring‐opening polymerization of lactide in the monomer melt and methanolysis of polylactide, as well as other (bio)polyesters. It is therefore a highly attractive multitool for industry to implement a circular (bio)polyester economy.