A focused review on recycling and hydrolysis techniques of polyethylene terephthalate

• Published in: Polymer engineering and science Vol. 63; no. 9; pp. 2651 - 2674
• Main Author: Abedsoltan, Hossein
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.09.2023; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Ammonolysis; catalysis; Chemical properties; Copolymers; degradation; Depolymerization; Energy minerals; Fossil fuels; Glycolysis; green chemistry; Hydrolysis; Monomers; Observations; Packaging; plastics; polyesters; Polyethylene terephthalate; Pyrolysis; Recycling; Recycling (Waste, etc.); Solvents; sustainability; Terephthalic acid; Waste management; Wastes; United States
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.26406

Polyethylene terephthalate (PET) is used in textile and packaging industries. The main source of PET production is fossil fuels with limited capacity. Also, PET products are single use that transform into high volumes of wastes, causing ecosystem problems. Recycling is proposed to confront this challenge. The four major PET recycling techniques are mechanical, chemical, pyrolysis, and enzymatic. Mechanical, pyrolysis, and enzymatic techniques have constrained capabilities to manage PET waste. Chemical recycling is the potential path to expanding recycling PET waste with possibility of upcycling and addressing dirty waste streams. Several chemical methods are introduced and discussed in literature. The five major chemical recycling techniques are glycolysis, alcoholysis, aminolysis, ammonolysis, and hydrolysis. This review describes PET depolymerization via these techniques and introduces hydrolysis as the one that can depolymerize PET in an organic‐free solvent environment. Hydrolysis tolerates PET mixed wastes streams including copolymers. It helps avoid challenges attributed to using organic solvents in reaction systems. Moreover, hydrolysis produces terephthalic acid, PET monomer, which has recently gained attention as the initiative monomer for PET production. The review focuses on three forms of hydrolysis—alkaline, neutral, and acid, by presenting background studies, issued patents, and recent trends on application of hydrolysis. Synthesis paths and applications of polyethylene terephthalate are presented. Recycling strategies of polyethylene terephthalate are discussed. Chemical techniques for recycling of polyethylene terephthalate are described. Hydrolysis technique is delineated for recycling of polyethylene terephthalate.