This review elucidates structure-activity relationships in Ru-supported catalysts for hydrodeoxygenation of lignin-derived phenolics to cyclohexane-based products. It highlights the synergy between Ru nanoparticle size, dispersion, and electronic state with tailored support acidity and defects, enabling efficient hydrogenation–deoxygenation. Insights into metal–support interactions guide catalyst design for selective, sustainable biomass valorization under optimized HDO conditions.

Abstract

Lignin, being an underutilized component of cellulosic biomass has the potential to be converted into value-added chemicals and fuels. However, the recalcitrant nature of lignin to degradation has been a major hurdle in the valorization of lignin. The depolymerization (catalytic and pyrolytic) of lignin results in the formation of lignin-derived bio-oil comprising low-molecular-weight phenolic compounds (monomers, dimers, and oligomers) with much higher oxygen content than that required for the fuels. The catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds is one of the alluring opportunities for converting biomass materials to chemicals and fuels. The current article systematically reviews the advancement in the production of cyclohexane-based compounds from five primary lignin-derived monomers, phenol (PHE), guaiacol (GUA), cerulignol (CER), eugenol (EUG), and vanillin (VAN) using supported ruthenium (Ru) catalysts. The carbon-based zeolites and TiO₂-based materials with distinguished properties are explored as the support for Ru nanoparticles. Understanding the characteristics of metal and its supports, along with the catalytic mechanisms and structure-activity relationships is crucial in developing HDO catalysts to produce selective products from lignin-derived phenolic monomers for practical applications. This review particularly highlights the significance of the synergistic interactions between ruthenium and the support materials during HDO reactions.