Dual catalytic activity of antimony (III) oxide: The polymerization catalyst for synthesis of polyethylene terephthalate also catalyze depolymerization.

In this study polyethylene terephthalate (PET) waste from drinking water bottles was converted to bis(2-hydroxyethyl) terephthalate (BHET) in the presence of antimony (III) oxide (Sb 2 O 3) as the catalyst and excess ethylene glycol (EG). The yield of BHET, using 0.5 wt% of the catalyst, under 200°C and 2.1 bar was 97.5%, achieved in only 1 h. The crude of the reaction and the purified monomer was characterized by differential scanning calorimetry, infrared spectroscopy, high pressure liquid chromatography, thermogravimetric analysis, and nuclear magnetic resonance. The influences of reaction parameters, such as the catalyst loading, reaction time, EG:PET weight ratio, and reaction pressure on the yield of BHET was investigated. In addition, the activity of this catalyst was compared to zinc acetate, antimony (III) acetate, and antimony (V) oxide, demonstrating the highest catalytic activity of Sb 2 O 3 for PET glycolysis. Since Sb 2 O 3 is one of the catalysts for the industrial synthesis of PET, the results from this work can open up a venue for the synthesis of repolymerized PET from waste PET in the same glycolysis reactor. [Display omitted] [ABSTRACT FROM AUTHOR]