Boosted Hydrodeoxygenation of Lignin-Derived Phenolics to Cycloalkanes with a Complex Copper Acid Catalyst

A complex copper acid catalyst (SA-Cu/CuMgAlOx) was developed with boosted catalytic activity for the hydrodeoxygenation (HDO) of lignin-derived phenolics. Remarkably, the yields of total monomers and cyclohexanes from the HDO of lignin pyrolysis bio-oil were significantly improved after the catalyst modification with salicylic acid, which increased by 17 and 40%, respectively, at 300 °C for 8 h. The catalyst characterizations revealed that acidic oxygen-containing functional groups (−OH and −COOH) were introduced onto the catalyst surface without corrosion to the metallic framework. The acidic groups contributed to the formation of surface Brønsted acid sites, which participated in the hydrogenolysis and dehydroxylation reactions of the phenolics in bio-oil. The catalyst was deactivated after four cycles of bio-oil HDO and could be recovered after the removal of carbon deposits and the reactivation of Cu species. The results offered appealing opportunities for tailoring more efficient copper-containing catalysts for the HDO of lignin-based phenolics.