Chemo-enzymatic depolymerization of industrial and assorted post-consumer poly(ethylene terephthalate) (PET) wastes using a eutectic-based catalyst

BACKGROUND Every minute, 1 million bottled drinks were purchased worldwide in 2017. Poly(ethylene terephthalate) (PET) bottles are highly recalcitrant wastes, taking at least 450 years to decompose naturally, and their accumulation in the environment triggers a series of environmental impacts. Recycling is an environmentally friendly alternative to PET waste management. A two-step PET depolymerization approach was studied in this work, comprising chemical glycolysis followed by enzymatic hydrolysis. RESULTS In the glycolysis reaction, 100% PET was depolymerized in the presence of a eutectic solvent-based catalyst and ethylene glycol, releasing bis(2-hydroxyethyl) terephthalate (BHET) as the main product (70% yield). The recovered BHET was then hydrolysed by the highly efficient Candida antarctica lipase B, releasing terephthalic acid (TPA), achieving 0.98 of mole fraction in the best result of the experimental design. The overall yield of chemo-enzymatic depolymerization of PET into TPA was 57%. CONCLUSION Using this integrated approach, a high overall yield of TPA from PET could be achieved within a short process timeframe (24 h). (c) 2021 Society of Chemical Industry (SCI).

Automated summary

This study investigated a two-step PET depolymerization approach involving chemical glycolysis and enzymatic hydrolysis, achieving a high overall yield of 57% TPA from PET. The integrated method proved to be effective in converting PET into TPA within a short processing timeframe.