Kinetics, Product Evolution, and Mechanism for the Pyrolysis of Typical Plastic Waste

This research investigates the kinetic, product evolution, mechanism of polyethylene (PE), polypropylene (PP), and a simulated mixture of plastic waste (SMP) via TGA/DSC–MS and Py-GC–MS. The pyrolysis reactions were predominantly endothermic, and the main degradation stage of PE, PP, and SMP ranged from 389.85 to 502.17 °C, from 374.91 to 495.15 °C, and from 368.30 to 496.29 °C, respectively. The kinetic results showed that polyolefin pyrolysis was identified to be the geometrical contraction models with apparent activation energies of 224.31–235.32 kJ mol–1 for PE and 199.00–207.66 kJ mol–1 for PP, respectively. The SMP pyrolysis follows the first-order reaction models, and its apparent activation energy was 185.29–199.54 kJ mol–1. Polyolefin pyrolysis products only contain C4–C35 paraffin with linear alkenes for PE and branch or cyclic alkenes for PP. The large amounts of benzene radicals in the pyrolysis of SMP tended to form aromatics. The pyrolysis behavior and product formation mechanism of the plastic waste could make available practical implications for the reactor design and parameter optimization.