Balzer Alex H, Hinton Zachary R, Vance Brandon C, Vlachos Dionisios G, Korley LaShanda T J, Epps Thomas H
Center for Plastics Innovation (CPI), University of Delaware, Newark, Delaware 19716, United States.
Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States.
ACS Cent Sci. 2024 Aug 21;10(9):1755-1764. doi: 10.1021/acscentsci.4c00951. eCollection 2024 Sep 25.
Catalytic deconstruction has emerged as a promising solution to valorize polyethylene (PE) waste into valuable products, such as oils, fuels, surfactants, and lubricants. Unfortunately, commercialization has been hampered by inadequate optimization of PE deconstruction due to an inability to either truly characterize the polymer transformations or adjust catalytic conditions to match the ever-evolving product distribution and associated property changes. To address these challenges, a detailed analysis of molar mass distributions and thermal characterization was developed herein and applied to low-density polyethylene (LDPE) deconstruction to enable more thorough identification of polymer chain characteristics within the solids (e.g., changes in molar mass or branching structure). For example, LDPE hydrocracking exhibited comparable rates of polymer chain isomerization and C-C bond scission, and the solids generated possessed a broadened molar mass distribution with a disappearance of a significant fraction of highly linear segments, indicating polymer-structure-dependent interactions with the catalyst. Solids analysis from pyrolysis yielded starkly different results, as the resulting solids were devoid of unreacted polymer chains and had a narrowed molar mass distribution even at short times (e.g., 0.2 h). By tracking the polymeric deconstruction behavior as a function of reaction type, time, and catalyst design, we mapped critical pathways toward PE valorization.
催化解构已成为一种将聚乙烯（PE）废料转化为有价值产品（如油、燃料、表面活性剂和润滑剂）的有前景的解决方案。不幸的是，由于无法真正表征聚合物转化过程或调整催化条件以匹配不断变化的产物分布及相关性能变化，PE解构的优化不足阻碍了其商业化。为应对这些挑战，本文开展了对摩尔质量分布和热表征的详细分析，并将其应用于低密度聚乙烯（LDPE）的解构，以更全面地识别固体中的聚合物链特征（例如摩尔质量或支化结构的变化）。例如，LDPE加氢裂化表现出相当的聚合物链异构化和C-C键断裂速率，生成的固体具有变宽的摩尔质量分布，且相当一部分高度线性链段消失，这表明聚合物与催化剂之间存在依赖于聚合物结构的相互作用。热解固体分析得出截然不同的结果，因为所得固体不含未反应的聚合物链，甚至在短时间（如0.2小时）时摩尔质量分布也变窄。通过追踪聚合物解构行为随反应类型、时间和催化剂设计的变化，我们绘制了PE增值的关键路径。
