Hydrogenolysis of Lignin with Endogenous Hydrogen from Aqueous Phase Reforming of Methanol

Catalytic hydrogenolysis of the renewable aromatic polymer of lignin to value-added fine chemicals without external molecular hydrogen is of great significance. In this work, catalytic conversion of lignin with in situ H2 produced from the aqueous phase reforming (APR) of methanol is studied in the presence of ZnO-modified Pd/ AC (Pd-Zn/AC). 259.8 mg g-1 yield of monophenols is obtained when the lignin depolymerization is catalyzed by Pd-Zn/AC-10 in a methanol aqueous solution (VCH3OH/VH2O=9/1) at 250 degrees C for 4 h. Extensive analysis showed that this effective process should be attributed to the synergistic effect between Pd-Zn alloy and the metallic Pd, which promote the H2 production from the APR of methanol and the hydrogenolysis of lignin, respectively. Moreover, a plausible pathway for selective hydrogenolysis of lignin is proposed based on the comparative characterization of the raw lignin, residual lignin, and the transformation behavior of lignin model compounds.