Optimization of Poly(ethylene terephthalate) Fiber Degradation by Response Surface Methodology Using an Amino Acid Ionic Liquid Catalyst

Abstract

With large quantities of poly­(ethylene terephthalate) (PET) fibers being used and discarded each year, the chemical recycling of PET fibers is of far-reaching importance. The metal-based catalysts currently used in chemical recycling often lead to metal residues and product coloration, which limits the industrialization of PET recycling. In this work, environmentally friendly amino acid ionic liquids were synthesized, which can replace the conventional zinc acetate catalyst for the glycolysis of PET fibers, enabling 100% PET fiber conversion and 84.5% bis­(2-hydroxyethyl) terephthalate (BHET) yields. Meanwhile, the effects of different factors on the process were explored by response surface methodology (RSM), and the optimal conditions (125 min, 193.5 °C, 8 wt % catalyst dosage, and 15.7 g of ethylene glycol (EG)) were predicted, which were further verified experimentally. The error between the model prediction and the experimental value was only 3.49%, which proved the reliability of the model. This method breaks the limitation of a single-factor study and allows exploring the relationship between multiple factors simultaneously to find the optimal solution.

Lactate anion catalyzes aminolysis of polyesters with anilines

“…Lactate-based ILs catalyzed reductive amination/cyclization of keto acids under mild conditions (29). Recently, ILs have been reported to be capable of catalyzing the decomposition of polyethylene terephthalate (30)(31)(32). Because of their unique structures and properties, task-specific ILs provide opportunity to develop green strategies for degradation of spent polymers.…”

Depolymerization within a Circular Plastics System

“…A relatively large catalyst loading of 5 wt % was needed. This need for high catalyst-loading has been documented elsewhere. − Other systems include 1,5-diazabicyclo[4.3.0]­non-5-ene (DBN) phenols (Figure ), which have been reported as reusable up to 8 times, although the DBN-phenol was not separated from the EG between each run. ILs have also been incorporated into heterogeneous catalysts by grafting onto a graphene support …”

Green Catalytic Ionic Liquids Containing Organophosphorus for Efficient Glycolysis of Waste PET Bottle Flakes

“…The well-established paradigm of metal-catalyzed PET degradation involves metal–ligand interactions activating chemical bonds for reaction with ethylene glycol (EG), ultimately resulting in chain breaks. , Analogously, the mechanism of ionic liquid catalysis relies on cationic ion interactions with PET and EG to form hydrogen bonds, thereby activating the reaction sites between EG and PET and accelerating the depolymerization of PET. − Consequently, enhancing the positive characteristics of cations in ionic liquids and promoting their interaction with carbonyl groups on PET structural units holds the potential to significantly expedite the catalytic depolymerization process of PET. , …”