Hydrothermal decomposition of polyethylene waste to hydrocarbons rich oil

In the present study the supercritical water (SCW) degradation of polyethylene (PE) plastics (virgin LDPE, PE waste) has been investigated in a batch reactor at 380–450 °C and reaction time of 15–240 min. The experiments (virgin LDPE) were also performed with the addition of acetic acid. During the SCW decomposition of PE plastics oil or wax, aqueous, gas and solid (only in PE waste) phases were formed. The obtained oil phase was composed of alkanes, alkenes, cycloalkanes, aromatics, and alcohols, while the gas phase manly contained light hydrocarbons (C1–C6). By performing reaction at high temperatures (425–450 °C) and reaction times from 30 to 240 min the concentrations of long-chain hydrocarbons (>C20) and C9–C20 (diesel) fraction in oil phase decreased, while concentration of C6–C8 hydrocarbons (gasoline fraction) increased. Finally, the influence of acetic acid on the PE degradation has been discussed and the potential degradation mechanism of PE waste in SCW is proposed.