Efficient hydrodeoxygenation of phenolic compounds and lignin pyrolysis oil by core-shell Ru@SiO2-Al2O3 catalyst

Hydrodeoxygenation (HDO) is a common refinery process to convert oxygen-containing lignin pyrolysis oil into high-quality hydrocarbon liquid fuels. In this work, we prepared a core-shell Ru@SiO2-Al2O3 catalyst and employed it in the HDO of phenolic compounds and lignin pyrolysis oil. The unique core-shell structure of the catalyst reduces the size of Ru metal particles, which significantly improves the hydrogenation catalytic activity. The high surface area, large pore size, and large pore volume of the SiO2 shell provide a favorable environment for the substrate transfer during the reactions, meanwhile the doped Al2O3 introduces a substantial number of acid sites for the catalysis of deoxygenation. The synergistic effect between the metal sites and acid sites greatly promotes the HDO reaction efficiency. Under mild conditions of 220 °C and 1 MPa H2, Ru@SiO2-Al2O3 catalyst achieved a guaiacol conversion of 99.9 % and a cyclohexane selectivity of 99.9 %. This catalyst also demonstrates outstanding stability, with little loss of catalytic activity after 6 recycles. Furthermore, an efficient HDO performance was obtained in the upgrade of other phenolic compounds and lignin pyrolysis oil. At the temperature of 240 °C, the content of hydrocarbons in lignin pyrolysis oil increased from 11.0 % to 92.7 %. These results indicate that Ru@SiO2-Al2O3 holds significant potential for the efficient HDO refinery, providing a promising avenue for the future biofuel development.