In-situ metal (Fe/Cu) doping for catalytic hydrothermal liquefaction of Tetra Pak waste for bio-oil production

The rapid accumulation of Tetra Pak waste (TPW), a complex multilayered packaging material, presents a significant environmental challenge due to its non-biodegradable nature and low recyclability. This study introduces a novel catalytic approach to hydrothermal liquefaction, enabling the simultaneous valorization of TPW into high-yield bio-oil and metallic carbon nanocomposites (MCN) using Fe and Cu metal effluents as liquefaction media. The influence of key process parameters such as temperature (280–340 °C), residence time (10–40 min), and metal effluent concentration (0.05–0.3 wt%) on the catalytic liquefaction of TPW was extensively investigated. Optimal total bio-oil yields of 53.20 wt% and 55.85 wt% were achieved with Fe and Cu effluents, respectively, at 320 °C, 30 min, and 0.2 wt% metal effluent concentration. In addition to the operating parameters, the improved performance is attributed to the in situ carbothermal reduction of metal ions (Fe⁺³/Fe⁺² and Cu⁺²/Cu⁺¹) to their zero-valent states, as confirmed by XRD analysis, which facilitated feedstock depolymerization and suppressed repolymerization. GC-MS and NMR characterization of oil fractions revealed a diverse array of compounds, including alcohols, ethers, phenols, ketones, furans, and hydrocarbons, indicating enhanced fuel quality. This integrated catalytic hydrothermal liquefaction-based valorization approach offers a sustainable pathway for managing post-consumer TPW while simultaneously generating energy-rich biofuels and value-added materials.