Hydrothermal Liquefaction of Polyethylene and Polypropylene: Recent Advances and Future Perspectives
Daniel Lachos‐Perez, Taofeng Lu, Wan‐Ting Chen
Abstract
The global plastic market is at an all-time high and plays a major role in many sectors of daily life. Plastics, especially polyethylene (PE) and polypropylene (PP), are versatile and stable, but their durability results in a slow degradation rate, causing environmental issues. Moreover, PE and PP are commonly mixed together. Any solution to this plastic waste problem must therefore be able to handle mixed plastic streams, address impurities, and be cost-effective. Hydrothermal liquefaction (HTL) technologies have emerged as a potential solution for achieving plastic circularity at lower temperatures than traditional thermochemical conversion methods and have therefore garnered attention recently. This chapter highlights the current state-of-the-art of HTL of PE and PP into monomers, chemicals, or fuels. Discussion of non-catalytic HTL, benefits, limitations, and new techniques involving organic solvents are also included. To improve the energy efficiency of HTL, perspectives on catalytical HTL of PE and PP are presented, while new research gaps are identified.