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

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 residue at temperatures varying from 400-800 °C. To design a pyrolysis reactor that optimizes the chemistry for 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 milliseconds to 2.0 seconds for five temperatures (550, 575, 600, 625, and 650 °C) was characterized by measurement of the yield of chromatography-detectable compounds (