posted on 2023-05-01, 10:43authored byIsaac 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.