Optimized Ru catalysts for the selective cleavage of CAr–OCH3 bonds in guaiacol under mild conditions

The one-pot hydrodeoxygenation of lignin-derived (alkyl)-guaiacols to (alkyl)-cyclohexanols with high selectivity is an attractive process for biomass conversion. However, designing catalysts that preferentially cleave etheric CAr–O(R) bonds over hydrogenating aromatic rings under mild conditions remains a significant challenge. In this study, we explore the structure sensitivity of supported Ru catalysts with varying particle sizes (0.6–7.5 nm) and identify the optimal catalyst for selective hydrodeoxygenation. Using a catalyst with 1.5 nm Ru particles, we achieve a ∼95% yield of cyclohexanol from guaiacol under relatively mild conditions (190 °C, 5 bar H2). In situ DRIFTS analysis reveals that the cleavage of CAr–OCH3 bonds occurs preferentially over aromatic ring hydrogenation on the 1.5 nm Ru particles, minimizing side reactions and enhancing cyclohexanol selectivity.