Efficient chemical depolymerization of polyethylene terephthalate via transesterification with ethanol using CaO catalyst

The depolymerization of polyethylene terephthalate (PET) waste has become increasingly important to address environmental concerns. As the production and consumption of PET continue to rise, development of efficient recycle PET methods is essential. This study investigates the depolymerization of PET waste flakes obtained from drinking water bottles through transesterification with ethanol in the presence of a CaO catalyst. The study explores the effects of reaction temperature, time course, catalyst loading, PET to ethanol molar ratio, and water content in ethanol. The results demonstrate that PET flakes can be completely depolymerized within 3 h at 200 °C (2 wt% CaO catalyst and an ethanol to PET molar ratio of 65). Moreover, CaO also showed efficient catalytic activity for the transesterification with other short-chain alcohols such as methanol, ethylene glycol, and 1-butanol. The recrystallized monomer products were characterized using HPLC, GC-MSTOF, and 1 H-, 13 C-NMR spectra, confirming the structure of the recrystallized monomers with high purity. This simple procedure has the promising potential for further scale-up in the recycled PET and value-added chemicals industries.