Catalytic hydrothermal liquefaction of tetra Pak waste over Ni – Cu /

Abstract

Hydrothermal liquefaction (HTL) is a promising route for converting multilayer composite packaging waste into liquid fuels, although efficient upgrading of oxygen‐rich intermediates remains challenging. In this work, Ni ₁₀ Cu _x /Al ₂ O ₃ catalysts with tunable Ni:Cu ratios were developed for the catalytic HTL of Tetra Pak waste at 350°C and 25 MPa for 30 min. XRD and XPS analyses confirmed the formation of Ni–Cu alloy structures and composition‐dependent electronic interactions between Ni and Cu. Among the catalysts, Ni ₁₀ Cu ₅ /Al ₂ O ₃ showed the best performance, achieving the highest bio‐oil yield (41%) and a higher heating value of 41.14 MJ kg ⁻¹ . Compared with Ni ₁₀ /Al ₂ O ₃ , the O/C ratio of the bio‐oil decreased markedly from 0.33 to 0.07. The enhanced catalytic performance was attributed to Ni–Cu synergistic effects that promoted hydrogenation/deoxygenation and suppressed secondary condensation reactions responsible for solid formation. Excessive Cu addition, however, weakened the benefit due to over‐dilution of active Ni ensembles. The catalyst also exhibited good hydrothermal stability during cumulative durability testing up to 100 h, with negligible Ni ²⁺ and Cu ²⁺ leaching (<0.02 mg L ⁻¹ ). This work demonstrates an effective catalytic strategy for converting composite packaging waste into energy‐dense bio‐oil.