Catalytic hydrothermal liquefaction of Tetra Pak with Ni-xCe/CNTs

A series of Ni-xCe/CNTs were synthesized by incipient wetness impregnation method and characterized by XRD, XPS, and H₂-TPR. Their catalytic performances were systematically evaluated in hydrothermal liquefaction of Tetra Pak. The effects of Ni:Ce ratio (10:0–10:7) in the bio-oil yield, boiling point, elemental composition, higher heating value (HHV) and chemical components of the bio-oil were investigated, and the solid residue and the used catalysts were also analyzed by TG, FT-IR and XRD, SEM, respectively. Maximum bio-oil yield of 20.75 wt% was obtained at Ni:Ce of 10:5. The minimum crystallite size of CeO₂ and the highest Ce³⁺ concentration, respecting the highest oxygen vacancies was obtained for Ni–5Ce/CNTs by XRD, and the lowest reduction temperature was also found for Ni–5Ce/CNTs in H₂-TPR analysis, indicating the good reducibility. The CeO₂ became to accumulate and form bigger clusters when the Ce loading increased to 7 wt%. GC-MS results showed that the hydrocarbons and esters in bio-oils increased with Ce loading, while those of ketones and aldehydes decreased. The possible catalytic reaction pathway was accordingly proposed.