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Plastic pyrolysis is a promising technology for converting plastic waste into valuable fuels and chemicals; however, insufficient understanding of reaction mechanisms and kinetics limits reactor design and industrial application. In this study, the pyrolysis of polyethylene (PE) was systematically investigated through a combination of experiments with ReaxFF molecular dynamics (ReaxFF-MD) simulations and density functional theory (DFT) calculations. Experimental results for C 6 -C 29 products show that PE pyrolysis at 500 °C mainly yields wax (79.76 %) and oil (<C23, 20.26 %). ReaxFF-MD simulations reveal that PE conversion increases from 20 % at 2073 K to nearly complete decomposition at 2473 K within 200 ps, while ethylene (C 2 H 4 ) is the most abundant gaseous product. DFT calculations indicate that C–C bond cleavage (365.17–372.25 kJ/mol) is energetically more favorable than C–H bond cleavage (397.32–410.72 kJ/mol) during the initial pyrolysis stage. Subsequent β-scission reactions of macromolecular radicals exhibit energy barriers ranging from 127.98 to 163.69 kJ/mol, with the ethylene-forming pathway showing the lowest barrier (1127.98 kJ/mol). In addition, radical-assisted hydrogen abstraction reactions present much lower energy barriers (30.37–67.63 kJ/mol), significantly accelerating PE decomposition. The corresponding reaction rate constants and Arrhenius parameters for major reaction pathways were determined over a temperature range of 500–1000 K. These results provide quantitative mechanistic and kinetic insights into PE pyrolysis, offering theoretical guidance for optimizing product distribution and reactor design.
Liu et al. (Wed,) studied this question.