Selective Vanillin Hydrodeoxygenation over Pt/CoOx Catalysts: The Mediation of Product Distribution

Vanillin (VAL) is an important lignin-derived platform compound whose multifunctional structure enables selective hydrodeoxygenation (HDO) to products with different degrees of deoxygenation. Herein, Pt/CoOx catalysts with reduction-dependent metal and oxide states were developed to regulate product distribution. Pt/CoOx-240 afforded 2-methoxy-4-methylphenol (MMP) in 95.0% yield at 90 °C after 8 h and 4-methylcyclohexanol (MCYL) in 90.4% yield at 150 °C after 8 h. Methanol and methane were quantified together with the principal liquid products to describe the detected one-carbon (C1) stream; at 210 °C, their measured yields were approximately 13.6 and 90.0%, respectively, and their nominal sum is treated as an apparent methoxy-associated C1 recovery rather than a closed carbon balance. Model-compound controls support an association between methoxy substituents and C1-product formation, although isotope labeling was not performed. Beyond model-compound conversion, Pt/CoOx-240 directly converted isolated enzymolysis lignin without a separately prepared lignin-oil intermediate, affording independently quantified unsubstituted cyclohexanol at a carbon yield of 15.7%. Characterization and catalytic comparisons are consistent with a reduction-dependent cooperative state that involves reduced Pt- and Co-containing species together with residual CoOx environments and contributes to product-distribution control. Reaction-stage process mass intensity (PMI) values were approximately 121 and 154 g g−1 for the MMP- and MCYL-forming routes, respectively, with isopropanol accounting for most of the quantified material input. The present system therefore combines switchable product selectivity, direct isolated-lignin conversion, and explicit C1-product reporting, while solvent demand remains the principal current limitation.