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Intrinsic Millisecond Kinetics of Polyethylene Pyrolysis via Pulse-Heated Analysis of Solid Reactions

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posted on 2023-05-01, 10:43 authored by Isaac Mastalski, Nathan Sidhu, Ali Zolghadr, Saurabh Maduskar, Bryan Patel, Sundararajan Uppili, Tony Go, Ziwei Wang, Matthew Neurock, Paul J. Dauenhauer
Continued demand for polyolefins can be met by recycling plastic materials back to their constituent monomers, ethylene and propylene, via thermal cracking in a pyrolysis reactor. During pyrolysis, saturated polyolefin chains break carbon–carbon and carbon–hydrogen bonds, yielding a distribution of alkanes, alkenes, aromatic chemicals, light gases, and solid char residues at temperatures varying from 400 to 800 °C. To design a pyrolysis reactor that optimizes the chemistry for a maximum yield of light olefins, a detailed description of the chemical mechanisms and associated kinetics is required. To that end, the reaction kinetics of isothermal films of low-density polyethylene (LDPE) have been measured by the method of “pulse-heated analysis of solid reactions”, or PHASR, which allows for quantification of intrinsic kinetics via isothermal reaction-controlled experimental conditions. The evolution of LDPE films from 20 ms to 2.0 s for five temperatures (550, 575, 600, 625, and 650 °C) was characterized by measurement of the yield of chromatography-detectable compounds (–1, compared with existing kinetic models of polyethylene pyrolysis, and validated from first principles.

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