Hydrodeoxygenation of lignin biophenolics to cyclohexanes over sub-nanometric Ru multifunctional catalyst

Hydrodeoxygenation of lignin-derived phenolics into cyclohexanes is recognized as an attractive philosophy for producing high energy density fuels in a sustainable manner. Here, we report a catalyst made of low-loading, sub-nanoscaled Ru species and multifarious acidic centers on amorphous-silica-alumina, which shows excellent activity, selectivity, and stability in hydrodeoxygenation of 4-propylguaiacol to propylcyclohexane. Catalytic performance exhibits a linear relationship to the total acidities of this family catalysts, demonstrating a synergistic interaction between the metallic and acidic components. The superior performance of this catalyst allows the conversion of various lignin-derived monophenols, dimers, more significantly, a biophenolic stream from miscanthus lignin into cyclohexanes with high efficiency and yield. This work highlights the importance of the sub-nanometric size of Ru species in the advancement of efficient and affordable approaches towards lignin-based fuel production.