Effect of Ce in Ni10Cex/γ-Al2O3 for the in situ hydrodeoxidation of Tetra Pak bio-oil during hydrothermal liquefaction

Abstract

Ni10Cex/γ-Al2O3 catalysts with different Ce loading were prepared by co-impregnation method. The effects of catalysts on the hydrothermal liquefaction of Tetra Pak at 360 °C, 20 MPa and 30 min were systematically investigated. The results showed that the main crystal planes of the catalysts were mainly NiO and CeO2. The interactions between Ni and Ce facilitate the dispersion of NiO and CeO2, and the highest proportion of oxygen vacancies was found with 5 wt% Ce loading, which acted as active sites for activation the C–O bonds in oxygenated group. However, the crystal particles began to agglomerate when the Ce loading was 7 wt%. The maximum bio-oil yield of 35.53 wt% was obtained with Ni10Ce5/γ-Al2O3. In addition, the O content decreased from 22.04% without catalyst to 4.31% with Ni10Ce5/γ-Al2O3 catalyst. The order of the catalytic activity was Ni10Ce5/γ-Al2O3 > Ni10Ce7/γ-Al2O3 > Ni10Ce3/γ-Al2O3 > Ni10Ce1/γ-Al2O3, which was consistent with that of the concentration of oxygen vacancies in catalysts. The main components of bio-oil were hydrocarbons, ketones and esters. Hydrocarbons dramatically increased while ketones gradually decreased with the increasing Ce doping, which was mainly because of the promoted decarbonylation, cracking and aromatization reactions. The possible catalytic mechanism of Ni10Cex/γ-Al2O3 on Tetra Pak hydrothermal liquefaction was proposed.