Molybdenum-catalyzed oxidative depolymerization of alkali lignin: Selective production of Vanillin

Conversion of lignin raw material into aromatic commodity chemicals is a highly desirable target for biorefineries, and its depolymerization usually requires high temperatures and harsh conditions. Herein, we report the selective production of vanillin from oxidative depolymerization of alkali lignin in the presence of molybdenum pyrophosphate supported on CeO2 (MoPO/CeO2) catalyst under aerobic conditions. This catalyst showed excellent activity in terms of lignin conversion and obtained ethyl acetate soluble oil (EA soluble oil) in good yields under 5 bar oxygen in 2 M NaOH at 150 °C for 3 h. The EA soluble oil was further analyzed by GC-MS, GC-FID, 1H-13C HSQC, 1H, and 13C NMR. Under optimal reaction conditions, the highest 12.5 wt% monomers, including 9 wt% vanillin with 72% GC selectivity obtained. The catalyst before and after the reaction was characterized by XRD, XPS, Raman, BET, and TEM.