Ce-Modified CuNiAl Hydrotalcite Catalysts for Catalytic Transfer Hydrogenolysis of Enzymatic Hydrolysis Lignin

Lignin, a promising sustainable biopolymer, exhibits immense potential as a renewable feedstock for aromatic chemicals and advanced materials, offering a green alternative to fossil resources. However, its complex aromatic structure and recalcitrant β-O-4 ether bond pose significant challenges for efficient depolymerization. In this study, a series of Ce-modified Cu-Ni-Al layered double hydroxide (LDH) catalysts (CuNiAlCe x ) were designed for the catalytic transfer hydrogenolysis (CTH) of enzymatic hydrolysis lignin (EHL) using ethanol as a hydrogen donor, aiming to produce low-molecular-weight lignin oil (LO) enriched with phenolic hydroxyl groups. Structural and surface analyses revealed that Ce modification enhanced oxygen vacancy concentration through dynamic Ce 3+ /Ce 4+ redox cycling and optimized acid site distribution, synergistically facilitating C-O bond cleavage. The highest LO yield of 71.8% was attained under optimized reaction parameters, accompanied by a marked reduction in molecular weight and concurrent increases in phenolic hydroxyl and carboxyl groups. GC-MS analysis identified diverse aromatic monomers (total yield: 21.34%), predominantly guaiacyl derivatives. This study reveals the synergistic interaction between oxygen vacancies and acid sites in CuNiAlCe x catalysts, providing a green strategy for the selective valorization of lignin into aromatic compounds, thereby advancing sustainable biorefinery technology. Graphical