Tracking Chain\nPopulations and Branching Structure\nduring Polyethylene Deconstruction Processes

Catalytic deconstruction has emerged as a promising solution\nto\nvalorize polyethylene (PE) waste into valuable products, such as oils,\nfuels, surfactants, and lubricants. Unfortunately, commercialization\nhas been hampered by inadequate optimization of PE deconstruction\ndue to an inability to either truly characterize the polymer transformations\nor adjust catalytic conditions to match the ever-evolving product\ndistribution and associated property changes. To address these challenges,\na detailed analysis of molar mass distributions and thermal characterization\nwas developed herein and applied to low-density polyethylene (LDPE)\ndeconstruction to enable more thorough identification of polymer chain\ncharacteristics within the solids (e.g., changes in molar mass or\nbranching structure). For example, LDPE hydrocracking exhibited comparable\nrates of polymer chain isomerization and C–C bond scission,\nand the solids generated possessed a broadened molar mass distribution\nwith a disappearance of a significant fraction of highly linear segments,\nindicating polymer-structure-dependent interactions with the catalyst.\nSolids analysis from pyrolysis yielded starkly different results,\nas the resulting solids were devoid of unreacted polymer chains and\n had a narrowed molar mass distribution even at short times (e.g.,\n0.2 h). By tracking the polymeric deconstruction behavior as a function\nof reaction type, time, and catalyst design, we mapped critical pathways\ntoward PE valorization.