A review for lignin valorization: Challenges and perspectives in catalytic hydrogenolysis

Lignin is one of the renewable natural aromatic polymers, the use of lignin as a raw material for the preparation of high value-added chemicals and fuels is regarded as a promising strategy for lignin valorization, and hydrogenolysis is one of the more common and effective way for lignin depolymerization. Hence, this paper reviews the present status, advantages and disadvantages of catalytic hydrogenolysis of lignin from two aspects of the solvent system and catalyst system. Solvents have been found to have a huge impact on the hydrogenolysis process and product distribution of lignin, the repolymerization of active intermediates is the main reason for char formation. It is proposed that the influence of different lignin structures should be fully considered in the catalyst design process, and the mechanism study of the hydrogenolysis process should focus on real lignin rather than model compounds. Finally, the challenges and prospects in this field are proposed.