Oxygen vacancy modulated Ru/WO_X for hydrodeoxygenation of lignin-derived phenols to biofuels

Lignin is the most abundant renewable aromatic polymer source in the world, and its depolymerization coupled with hydrodeoxygenation (HDO) to value-added chemicals and fuels is a significantly important research topic. In this study, guaiacol was used as the model reactant in a Ru/WO_X-dodecane reaction system and conducted at 280 °C and 2 MPa H₂ for 3 h, yielding a 90% yield of cycloalkane/aromatic hydrocarbon products including 15.7% carbon-chain extended products toluene/methylcyclohexane. Reaction kinetics studies identified the main reaction pathway initialed at guaiacol demethylation (DME) to phenol, followed by phenol deoxygenation (DDO) to benzene and subsequent hydrogenation to cyclohexane; toluene/methylcyclohexane was obtained through HDO reaction coupled with a methyl transfer pathway. The Ru/WO_X catalyst exhibited advantages such as high oxygen vacancy concentration, large specific surface area, abundant acidic sites and strong metal-support interactions, which accelerated the migration of hydrogen radicals (H^*) to oxygen vacancies and the HDO rates of phenolic compounds. The catalytic system exhibited good cycling properties, and the reactants can be extended to diverse lignin-degraded phenolic compounds and phenolic-oil mixtures, achieving excellent HDO performance.