Abstract: The detailed molecular composition of pyrolysis oil derived from waste polyethylene (PE) plastic was systematically characterized using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF MS). The results show that the main components of the PE pyrolysis oil are n-alkanes (mass fraction 27.88%), α-olefins (mass fraction 31.54%), and linear dienes (mass fraction 5.07%). Concurrently, hydrocarbon compounds such as cyclic olefins, alkenylbenzenes, and polycyclic aromatic hydrocarbons were detected. Furthermore, non-hydrocarbon components including oxygenated compounds (e.g., benzoic acid), nitrogenous compounds (e.g., caprolactam), and trace chlorinated compounds were identified. These substances primarily originate from plastic additives or feedstock contamination. A comparative analysis of two PE pyrolysis oils from different sources revealed significant differences in their molecular composition, indicating that the pyrolysis process, catalysts, and feedstock type have a substantial impact on the product distribution. Consequently, this technique can provide crucial data support for the precise molecular characterization, product control, and subsequent processing and utilization of waste plastic pyrolysis oils.

Key words: waste plastic, polyethylene, pyrolysis oil, comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, n-paraffin, ɑ-olefins