Low-temperature demethoxylation pathways and solvent-driven hydrodeoxygenation for guaiacol upgrading catalyzed by anaerobically synthesized Ru/Al2O3

The valorization and toxicity reduction of phenolic substances are critical challenges for achieving green and sustainable development in the petroleum, coal, and biomass industries. This study investigated the phenolic model compound guaiacol hydrodeoxygenation over Ru/Al 2 O 3 catalysts, demonstrating that synthesis within an anaerobic glovebox significantly enhances catalytic activity compared to ambient synthesis. Four solvents (ethanol, methanol, tetrahydrofuran, and n-dodecane) were evaluated for their impact on guaiacol conversion and product distribution. Experimental results demonstrated that non-polar n-dodecane achieved 100 % guaiacol conversion and 92.8 % cyclohexane selectivity, attributed to weak catalyst-solvent interactions verified by first-principles calculations. Reaction optimization enabled > 90 % yields of 2-methoxycyclohexanol, cyclohexanol, and cyclohexane. Crucially, a novel low-temperature demethoxylation pathway via the intermediate 2-methoxy-1-cyclohexen-1-ol was identified through quantum chemistry calculations, offering a strategy to enhance cyclohexanol production. Kinetic analysis revealed apparent activation energies of 55 kJ/mol (demethoxylation) and 72 kJ/mol (dehydroxylation). The catalyst maintained stable performance over five cycles. These findings underscore the critical importance of catalyst synthesis, solvent environment, and reaction control in achieving efficient and selective guaiacol hydrodeoxygenation, offering strategies for green valorization and toxicity reduction of phenols.