Support‐Governed Acid‐Redox Synergy in Molybdenum‐Catalyzed Reductive Depolymerization of Lignin
Ajibola T. Ogunbiyi, Wenzhi Li, Lida Wang, Gui Yunfan, Shengxin An, Kai HuangABSTRACT
Selective depolymerization of kraft lignin remains challenging because of its structural heterogeneity and the tendency of reactive fragments to undergo retrogressive condensation under N 2 without external H 2 . Here, Mo‐based catalysts supported on SiO 2 , activated carbon, Al 2 O 3 , and H‐Beta zeolite were evaluated for kraft lignin depolymerization in a 1,4‐dioxane/isopropanol/methanol donor‐solvent system at 290°C for 6 h under 0.5 MPa N 2 . Support identity strongly governed the balance between lignin fragmentation, intermediate stabilization, deoxygenation, and carbonaceous‐deposit formation. Mo/H‐Beta delivered the best overall performance, achieving 79.1% lignin conversion and 49.1% light‐fuel yield, while increasing the light‐fuelHHV from 25.45 to 36.01 MJ kg −1 . Although Mo/SiO 2 promoted the strongest molecular‐weight reduction, it was less effective in downstream stabilization, and deoxygenation, demonstrating that depolymerization severity alone does not determine product quality. Integrated catalyst and product analyses show that Mo/H‐Beta benefits from balanced acidity, dispersed redox‐active MoO x species, mixed‐valence Mo retention after reaction, and lower carbonaceous deposition. Overall, effective lignin valorization over supported Mo catalysts requires support‐enabled acid–redox balance rather than stronger cracking alone.