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 C_Ar–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 C_Ar–OCH₃ bonds occurs preferentially over aromatic ring hydrogenation on the 1.5 nm Ru particles, minimizing side reactions and enhancing cyclohexanol selectivity.