On the intrinsic reaction kinetics of polypropylene pyrolysis

The growing global plastic waste challenge requires development of new plastic waste management strategies, such as pyrolysis, that will help to enable a circular plastic economy. Developing optimized, scalable pyrolysis reactors capable of maximizing the yield of desired products requires a fundamental understanding of plastic pyrolysis chemistry. Accordingly, the intrinsic reaction kinetics of polypropylene pyrolysis have been evaluated by the method of pulse-heated analysis of solid reactions (PHASR), which enables time-resolved measurement of pyrolysis kinetics at high temperature absent heat and mass transfer limitations on the millisecond scale. Polypropylene pyrolysis product evolution curves were generated at 525°C–625°C, and the overall reaction kinetics were described by a lumped first-order model with an activation energy of 242.0 ± 2.9 kJ mol⁻¹ and a pre-exponential factor of 35.5 ± 0.6 ln(s⁻¹). Additionally, the production of solid residues formed during polypropylene pyrolysis was investigated, revealing a secondary kinetic regime.