Enhanced hydrodeoxygenation of lignin-derived phenolic compounds by regulating support composition of Ni/Al2O3-C catalyst

Hydrodeoxygenation (HDO) is an effective method for upgrading lignin-derived phenolic compounds into high-quality liquid fuels, and the support rational design of HDO catalysts is critical for boosting reaction efficiency. In this study, a series of Ni/Al 2 O 3 -C catalysts with different ratio of Al 2 O 3 and carbon components were proposed for the HDO of lignin-derived phenolic compounds. Ni/Al 2 O 3 -C-0.25 catalyst is screened for a superior HDO efficacy compared to the other catalysts, in which guaiacol can be completely converted at 220 °C, with 99.9 % cyclohexane selectivity produced at 4 h. Various characterizations for the catalysts were carried out, including BET, XRD, TEM, XPS and NH 3 -TPD. According to the characterization results, Ni/Al 2 O 3 -C-0.25 catalyst presents little dense Al 2 O 3 fiber structure, which favors the Ni metal dispersion and possesses the smallest Ni metal particle size (10.9 nm). This leads to the outstanding catalytic hydrogenation activity. Moreover, the specific interaction between Al 2 O 3 and carbon in Ni/Al 2 O 3 -C-0.25 catalyst results in the moderate acid property, which promotes the deoxygenation process of the intermediate products, as evidenced by the effective cleavage of C-O bond and the enhanced selectivity of cyclohexane products. The adaptation of Ni/Al 2 O 3 -C-0.25 catalyst to lignin-oil upgrade was also investigated, with a rise of hydrocarbon content from 6.1% to 47.5%. These results indicate that the catalysts with this composite support had the potential to upgrade lignin-derived phenolic compounds to superior grade hydrocarbon liquid fuels.