Chlorinated solvent-mediated catalytic depolymerization of polypropylene under mild thermal conditions

Waste polymer-based materials such as polyolefins realize low-carbon treatment through thermochemical recovery, which is of great significance to environmental protection and the development of the circular economy. The high dissociation energy associated with C-C bonds in these materials presents challenges for their depolymerization at low to medium temperatures. This study proposes a strategy that leverages the solvent effect to enhance the ductility of C-C bonds and reduce the energy required for bond cleavage. Concurrently, the solvent aids in the uniform dispersion of hydrogen radicals and small molecular fragments produced during polymer degradation, which mitigates the propensity for re-polymerization. The findings indicate that the incorporation of dichloromethane reduced the reaction temperature from 380°C to 330°C, facilitated the conversion of a greater quantity of lighter components, and increased gas yield. Following pyrolysis with the solvent, elevated levels of light alkanes in the C8-C14 range were detected, with aliphatic compounds predominating. By optimizing the thermochemical recovery process of polyolefins through the solvent introduction, intermolecular interaction forces were diminished, allowing for easier cracking of C16+ components. The heat released during this process provided additional energy for the further depolymerization of plastics into smaller molecules, resulting in a 90% improvement in the liquefaction rate of plastics at 330°C. This research holds significant implications for the recycling of waste polymer materials and the promotion of a circular economy, as well as for environmental protection efforts.