Tuning Ni/Al2O3 catalyst via Cu incorporation for selective deoxygenation and (de)methylation of guaiacol

Summary Hydrodeoxygenation (HDO) of lignin-derived phenolics is a key strategy for producing renewable fuels and value-added chemicals. Conventional Ni/Al₂O₃ catalysts lead to the formation of undesired saturated oxygenates, due to their high tendency toward aromatic-ring hydrogenation. Here, we report that Cu incorporation into Ni/Al₂O₃ selectively tunes reaction pathways in guaiacol and anisole HDO. The resulting Ni-Cu/Al₂O₃ catalysts suppress hydrogenation and (de)methylation to different extents. While anisole conversion shows minor selectivity changes, guaiacol exhibits a pronounced shift toward deoxygenation and methylation, due to stronger inhibition of hydrogenation. Kinetic modeling reveals unequal suppression of competing pathways and corresponding changes in rate-determining steps. Notably, the shift away from hydrogenated oxygenates toward deoxygenated and methylated products persists at elevated hydrogen pressures. At 270°C and 40 bar H₂, 5% Ni-5% Cu/Al₂O₃ achieves >70% guaiacol conversion, and this produces cyclohexane and methylated naphthenics and phenolics as primary products.