Converting Poly(ethylene terephthalate) Waste into Carbon Microspheres in a Supercritical CO₂ System

Well-shaped carbon spheres in micrometer dimensions were prepared by pyrolyzing postconsumer poly(ethylene terephthalate) (PET) in supercritical carbon dioxide at 500-650 °C for 3 h. It was also found that the yield of carbon microspheres increased as the reaction temperature increased and the reaction time was prolonged. Carbon microspheres were obtained in 47.5% yield as the reaction occurred at 650 °C for 9 h. A high-pressure carbonization mechanism of aromatic hydrocarbons decomposed from PET waste was proposed according to gas chromatography combined with mass spectrometry analysis. One possible application of the carbon microspheres as a negative electrode material for lithium ion batteries was evaluated.