Study on the Pyrolysis Characteristics and Kinetics of Plastic Solid Waste

Solid waste management, particularly the treatment of plastic waste, is a global challenge. This study investigates the pyrolysis characteristics of polypropylene (PP), polyethylene (PE), polystyrene (PS), and their mixture (MP). Thermogravimetric analysis (TG/DTG), differential thermal analysis (DTA), and gas chromatography–mass spectrometry (GC–MS) with a single quadrupole mass spectrometer were employed to analyze the driving factors, pathways, phenomena, mechanisms, and products of the pyrolysis process for these four plastics. The kinetic parameters of the pyrolysis and co-pyrolysis processes were calculated using the Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Starink, and Vyazovkin non-modeling methods, and the Fraser–Suzuki deconvolution method was applied to analyze the pyrolytic characteristics of the components in mixed plastics (MP). Based on the activation energy analysis results, the Master-plots method was used to obtain the pyrolysis mechanism functions for the four plastics. The analysis revealed that MP exhibited synergistic effects during co-pyrolysis. Heating rate experiments conducted under different pressures demonstrated that higher pressures promote secondary reactions such as the polymerization and condensation of olefins in the products. These findings indicate that MP has the potential for higher pyrolysis efficiency. The findings are expected to provide valuable insights for optimizing recycling technologies and enhancing the sustainability of plastic waste management.