Hydrothermal liquefaction (HTL), which uses subcritical and supercritical water as reaction media, was used to chemically deconstruct post-consumer recycled linear low-density polyethylene (PCR-LLDPE) with different molar masses (from 7.20 × 10³ to 1.29 × 10⁵ g/mol) into oil at 425 °C for 2 h. When the molar mass was within the range of 7.20 × 10³–1.36 × 10⁴ (g/mol), a comparable oil yield (86–90%) was obtained. However, the oil yield was reduced to 66% when the molar mass increased to 1.20 × 10⁵ (g/mol). The chemical compositions of the oil converted from PCR-LLDPE with varying molar masses were mainly composed of paraffins, olefins, cyclics, and aromatics. Additionally, it was found that PCR-LLDPE and the post-HTL solid residues contained metallic impurities that may participate in HTL of LLDPE. The density functional theory was also used to elucidate the role of supercritical water under HTL in aiding deconstruction of LLDPE. The calculated electronic and thermodynamic parameters suggested that alkanes with smaller molar mass require lower energy to be deconstructed in HTL.

中文翻译：

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不同摩尔质量的消费后回收线性低密度聚乙烯在超临界水中的水热液化


水热液化 （HTL） 以亚临界和超临界水为反应介质，在 425 °C 下将具有不同摩尔质量 （从 7.20 × 10³ 到 1.29 × 10⁵ g/mol） 的消费后回收线性低密度聚乙烯 （PCR-LLDPE） 化学解构到油中 2 h。当摩尔质量在 7.20 × 10 3-1.36 × 10 ⁴ （g/mol） 范围内时，获得了相当的产率 （86-90%）。然而，当摩尔质量增加到 1.20 × 10⁵ （g/mol） 时，产油率降低到 66%。不同摩尔质量的 PCR-LLDPE 转化油的化学成分主要由石蜡、烯烃、环状和芳烃组成。此外，还发现 PCR-LLDPE 和 HTL 后固体残留物含有可能参与 LLDPE HTL 的金属杂质。密度泛函理论还用于阐明 HTL 下超临界水在帮助 LLDPE 解构中的作用。计算的电子和热力学参数表明，在 HTL 中解构摩尔质量较小的烷烃需要较低的能量。