(532w) Pulse-Heated Analysis of Solid Reactions (PHASR) to Promote a Plastic Circular Economy: Intrinsic Kinetics of Polyethylene Pyrolysis

Plastic use has grown exponentially over the past several decades, yet the current linear economy model is insufficient for meeting demand and effectively remediating waste. Advanced recycling techniques are thus required to address these needs and enable a plastic circular economy, whereby used plastics are recycled through a closed-loop process to regenerate monomers and, in turn, produce new plastics. To this end, the technique of pyrolysis has recently shown significant promise. Pyrolysis, or thermal degradation under an inert atmosphere, has many advantages over traditional mechanical recycling techniques. However, little agreement exists in the plastic pyrolysis literature as to the kinetics and mechanisms underlying the process, which has been caused by various systematic limitations that only allow measurement of apparent kinetics. This complicates lab-scale analyses and hinders development of scalable systems, since large-scale reactor and catalyst design is much more effective with intrinsic reaction kinetics.

In order to rectify these discrepancies, we have applied the Pulse-Heated Analysis of Solid Reactions (PHASR) system to polyethylene pyrolysis in order to measure intrinsic reaction kinetics for the first time. First, the PHASR system was extensively redesigned for use with plastics, since polyolefin pyrolysis requires much harsher conditions than that of cellulose, the material for which PHASR was originally developed about a decade ago. [1] In this work, we have fully established that PHASR is uniquely capable of operating in the isothermal, reaction-controlled regime required for elucidating intrinsic reaction kinetics. [2] These intrinsic lumped kinetics are described for polyethylene pyrolysis, as well as attempts to characterize post-pyrolysis residues. [2] Finally, comparisons are made between the intrinsic kinetics reported here and the apparent kinetics reported in the literature, and the application of PHASR data to industrial catalysis and reactor design is discussed. [2]

References:

[1] ChemSusChem, 2021, 14 (19), 4214-4227.

[2] In preparation, 2022.