Interactions of the Main Components in Paper-Plastic-Aluminum Complex Packaging Wastes during the Hydrothermal Liquefaction Process

Hydrothermal liquefaction was applied to treat paper-plastic-aluminum (Al-PE-Pa) complex packaging waste for bio-oil production. The interactive effects between the main components of paper fiber, low-density polyethylene (LDPE), and aluminum foil in such complex material were studied. The co-liquefaction of paper fiber and LDPE had a significant synergistic effect. The addition of hydrogen-rich LDPE effectively promoted the removal of oxygen-containing groups. Aluminum foil had only a slight impact on the liquefaction of paper fiber, but it can significantly decrease the oxygen content of the bio-oil, increase the high heating value of the bio-oil, and significantly reduce the ester and phenol contents in the bio-oil. The co-liquefaction of paper fiber/LPDE/aluminum foil exhibited superimposed effects of paper-plastic synergy and in-situ hydrogenation of Al-H₂O reaction. A new pathway for the energy utilization of Al-PE-Pa complex packaging waste is provided.