A tandem strategy of mild preoxidation-hydrogenolysis for efficient depolymerization of lignin

A tandem strategy of “mild preoxidation-hydrogenolysis” was proposed for the efficient depolymerization of lignin. Firstly, a mild oxidation system was constructed with H2O2 as the green oxidant and NaOH/Fe2(SO4)3/CuO as the catalyst to pretreat lignin; then NiMoS catalyst was used for the further hydrogenolysis of the pretreated lignin. The reaction results showed that the strategy could achieve efficient lignin depolymerization. Under optimal conditions, the lignin liquefaction degree reached 91.1 wt.% and the monomer yield reached 20.6 wt.%. The structural analysis of the recovered lignin showed that the mild oxidation pretreatment could initially break the linkage bonds within the lignin molecule and get some large fragment molecules. Meanwhile, it also made the hydroxyl group in the Cα position of the β-O-4 bond oxidized to carbonyl group, thus reducing the dissociation energy of the β-O-4 bond.