Experimental study on the gasification characteristics of polyethylene terephthalate (PET) microplastics in supercritical H₂O/CO₂ environment

Plastic waste can be seen everywhere in our life, while the increasing emission of CO₂ is causing concern. The use of supercritical fluids to treat plastic waste is highly efficient and provides a new idea for the green treatment of plastic waste. Green treatment of plastics can be achieved, and the possibility of CO₂ consumption can be explored in supercritical fluids. Still, its mechanism has not been clearly explained yet, so it is essential to study its laws carefully. This paper carried out the gasification experiment of polyethylene terephthalate (PET) in supercritical H₂O/CO₂. The effects of temperature, residence time, initial CO₂ volume and seawater on the gasification reaction are discussed. The results showed that: increasing the gasification temperature, extending the reaction residence time, and increasing the amount of carbon dioxide can improve the gasification efficiency, and the metal salts contained in seawater can promote the pyrolytic gasification of plastics. And the temperature change significantly influences the interface of PET plastics. The carbon conversion efficiency of PET plastics reached 40.5% with a certain amount of raw material and water for 20 min at 700 °C in supercritical carbon dioxide and water. At 500 °C, PET plastic has the best thermochemical reduction of CO₂. This work provides new ideas for future green treatment of plastic waste and contributes to carbon reduction efforts.