회수 가능한 고분자전해질 촉매를 이용한 폴리에틸렌테레프탈레이트의 해중합

Depolymerization of Poly(Ethylene Terephthalate) using Polyelectrolytes as an Efficient and Recoverable Catalyst

Glycolysis has been considered one of the most promising pathways for converting poly(ethylene terephthalate) into monomeric feedstock- bis(2-hydroxyethyl) terephthalate (BHET}-which can be used as a starting material to produce virgin PET. In this process, metal-salts, such as zinc acetate, are generally used as a catalyst for the glycolysis of PET. However, these metal-based salt catalysts often suffer from low thermal stability at elevated temperature for the glycolysis reaction. Moreover, traces of metal salts can be included in the final products, critically reducing the quality of the chemically recycled PET. To address tills, many of previous studies have used organic salts including ionic liquids as an efficient catalyst for the glycolysis. Here, we present a new organic catalyst based on polyelectrolytes which offer excellent thermal stability and ease of separation and reusability. Among various types of polyelectrolytes, polyanions such as poly(sodium styrene sulfonate)(PSSNa), sodium polyacrylate(PANa), poly[l-ethyl-3-methyl imidazolium (3-sulfopropyl) acrylate](PES) shows high depolymerization yields of PET, comparable to that of metal-based catalysts while polycations shows significantly lower efficiency. We speculate that for the glycolysis of PET, cations play a crucial role in initiating the glycolysis process while the covalently bounded cations in polycation electrolytes appear to impede this initiation step.