Enhanced energy recovery from polyethylene terephthalate via pyrolysis in CO₂ atmosphere while suppressing acidic chemical species

Highlights: • CO₂ is used as a pyrolysis medium for treating polyethylene terephthalate (PET) waste. • The generation of CO for pyrolysis of PET waste is enhanced in CO₂ condition. • CO₂ reduces production of acidic byproducts like benzoic acid for pyrolysis of PET. - Abstract: Herein, CO₂ is employed as a pyrolysis medium for thermal treatment (i.e., pyrolysis) of polyethylene terephthalate (PET) waste in an environmentally benign way. The CO₂-assited pyrolysis provides a novel way to not only enhance energy recovery from the PET waste but also reduce acidic byproducts such as benzoic acid. The generation of carbon monoxide (CO) for pyrolysis of the PET waste in CO₂ is ∼5 times more than that in N₂. In addition to the enhancement of CO generation, the compositions of benzene derivatives, PAHs, and acidic compounds are lower in pyrolytic products in CO₂ than that in N₂. This study suggests that the employment of CO₂ in pyrolysis of PET waste would be a more environmentally friendly waste treatment process with enhancing energy recovery.