(505c) Hydrothermal Liquefaction of Post-Consumer Recycled Linear Low-Density Polyethylene with Different Molar Mass in Supercritical Water

Hydrothermal liquefaction (HTL), which uses sub- and super-critical water as a reaction media, was used in this study to chemically recycle post-consumer recycled linear low-density polyethylene (PCR-LLDPE). In this study, it is hypothesized that PCR-LLDPE with lower molar mass can be hydrothermally depolymerized into oil with higher oil yield at the same reaction condition than those with higher molar mass. To examine this hypothesis, PCR-LLDPE with different molar mass ranges (7.20E+03-1.29E+05 g/mol) was converted into oil via HTL at 425°C with a reaction time of 2 h, a pre-determined reaction condition that can fully convert LLDPE into oil. The product yields validated our hypothesis—the lower the molar mass of PCR-LLDPE, the higher the oil yield. More specifically, when the molar mass is within the range of 7.20E+03-1.36E+04 (g/mol), a comparable oil yield (86-90 %) was obtained. However, when the molar mass increased from 1.06E+05 to 1.29E+05 (g/mol), a lower oil yield (73%) was realized. The chemical compositions of the oil converted from different molar mass ranges (7.20E+03-1.29E+05 g/mol) were also characterized, and found to mainly contain paraffin, olefins, cyclics, and aromatics. Additionally, it was found that PCR-LLDPE and the post-HTL solid residues contained metallic impurities such as Ca and Al that may participate in hydrothermal depolymerization of LLDPE, but more research is needed to elucidate the effect of these impurities on HTL of LLDPE.