Production of carbon-based precursor from non-recyclable waste poly(ethylene) terephthalate: effect of multilayer structure on carbonized product

In this paper, the carbonization of multilayer PET containing an oxygen barrier layer was investigated. The oxygen barrier layer was identified as MXD6 nylon, which is widely used in the beverage industry due to its excellent barrier properties but is difficult to be mechanically separated and unsuitable for recycling. Carbonization experiment was conducted using a 2.0-L batch reactor at 400–480 °C and residence time 2 h to investigate the effects of multilayer PET on carbonization product. Char, wax, and gas were obtained and evaluated in terms of calorific value, elemental analysis, surface analysis and compound identification. Data testify that char yield was approximately 20 wt% and char obtained from all runs had high carbon content with minimal effects from oxygen barrier layer. The results showed that oxygen barrier layer had no apparent effect in the char composition and characteristics, but produced more aromatic hydrocarbons such as biphenyl and fluorene in wax and more CO₂ in gaseous product.