Chemical Recycling: Glycolysis, Methanolysis, Hydrolysis
topic
Chemical recycling depolymerises PET to monomers for true circular recycling: (1) Glycolysis: EG at 190–220°C, Zn(OAc)₂ catalyst → BHET oligomers (repolymerisable); most commercially advanced. (2) Methanolysis: methanol + catalyst at 180–250°C, high pressure → DMT + EG (pure monomers); high quality but energy intensive. (3) Alkaline hydrolysis: NaOH at 100–200°C → disodium terephthalate + EG; acidification gives TPA. (4) Enzymatic hydrolysis (PETase, FAST-PETase) at mild temperatures — emerging biotechnology.
Role
Chemical recycling of polyester is the frontier of circular economy textile chemistry, enabling true monomer recovery and quality maintenance across cycles. Its academic importance lies in integrating polymer chemistry, reaction engineering, and sustainability science.