Study on the Pyrolysis Characteristics, Synergistic Effect, and Kinetics of Waste Polypropylene and Waste Tires

Pyrolysis technology provides an important way to achieve high-value utilization of organic solid waste. This paper focuses on the pyrolysis characteristics, synergistic effects and pyrolysis kinetics of single-component waste polypropylene (WPp), waste tires (WTs) and mixed components (WPp/WTs), aiming to promote the resource recycling of WPp and WTs. The results show that the pyrolysis temperature ranges of WPp, WTs and WPp/WTs are 356.9–479.1, 236.0–484.1, and 237.9–475.9°C, respectively, and WPp/WTs have a significant synergistic effect in the pyrolysis process. The apparent activation energies of WPp, WTs and WPp/WTs calculated by the model-free method are 212.17–230.66, 164.97–240.43, and 195.39–282.39 kJ/mol, respectively. The pyrolysis of WPp was found to follow the pyrolysis mechanism function model of chemical reaction RO(2), while the pyrolysis of WTs followed both the pyrolysis mechanism function model of chemical reaction RO(2) and the D3 diffusion pyrolysis mechanism function model, according to the Malek model fitting method; and the pyrolysis of the WPp/WTs mixed system follows the 3D diffusion pyrolysis mechanism function model and the A3/2 random nucleation followed by growth pyrolysis mechanism function model. The above research results deepen the understanding of the pyrolysis process of single-component WPp, WTs and mixed-component WPp/WTs, and enrich the theoretical basis of their pyrolysis.