Chemical kinetics of catalytic/non-catalytic pyrolysis and gasification of solid plastic wastes

In a circular economy perspective, solid plastic wastes (SPW) can become a valuable source of chemicals, energy vectors and fuels. Catalytic and non-catalytic pyrolysis, gasification, and partial oxidation technologies can be employed to produce hydrogen, syngas, chemicals, fuels, or energy, providing more efficient and environmentally sound options compared to landfill disposal. Product distribution optimization, experiment, reactor, and process design as well as pollutant formation control can largely benefit from accurate and predictive reactor models. Chemical kinetic models constitute a core part of reactive flow modeling approaches, together with heat and mass transfer models. Mechanistic models provide insights into the degradation process of polymers and into the chemical dynamics involved in the transformation of a polymer or a polymer mixture in valuable products. Kinetic analysis of the pyrolysis of plastics is pivotal for understanding the optimal conditions of the cracking process improving reactor design and providing a solid basis for scale-up. Beyond global models mostly aiming at representing the overall conversion of the polymer backbone, theory-based detailed and semi-detailed models allow to explore with good predictive capability a wide range of conditions also tracking the product distribution. This chapter provides an overview of state-of-the-art kinetic modeling approaches from the molecular scale understanding of the occurring chemistry in both thermal and thermo-catalytic conversion, to the design, assembly and validation of integrated semi-detailed kinetic models.