Effective catalysts derived from waste ostrich eggshells for glycolysis of post-consumer PET bottles

Abstract

Herein, we report an effective chemical recycling of poly(ethylene terephthalate) (PET) using sustainable sources of catalysts, calcium oxide (CaO) derived from ostrich eggshells. The active catalysts were demonstrated in the chemical depolymerization of post-consumer PET bottles. Beverage bottles were proceeded with 1 wt% catalyst derived from ostrich eggshells in the presence of ethylene glycol at 192 °C under atmospheric pressure to give the major product as bis(2-hydroxyethyl terephthalate) (BHET) which was confirmed by melting point, IR spectroscopy, 1H-, 13C-NMR spectroscopy and mass spectrum. The catalyst could fully depolymerize PET within 2 h, producing a good yield of highly pure BHET monomer. The catalysts were successfully characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy analysis (FE-SEM), and thermo-gravimetric analysis (TGA). Furthermore, catalysts derived from chicken eggshells, geloina, mussel, and oyster shells were run to compare the catalytic activities. For better understanding of catalytic parameters, effects of calcination temperatures of catalyst, weight ratio of catalyst, ratio of weight of solvent, and time of depolymerization for the ostrich eggshells catalyst were also investigated.