The Catalytic Valorization of Lignin from Biomass for the Production of Liquid Fuels

With the overuse of fossil fuels, people are looking for alternatives. This is an area where biofuels have received a lot of attention. Studies have also shown that a large variety of liquid fuels of commercial interest can be obtained via lignin valorization. Lignin is rich in aromatic ring structures and can be used as a sustainable raw material to produce high-value energy. Therefore, progress in the preparation of liquid fuels from lignin by pyrolysis, hydro-processing, and oxidation is analyzed in this review. Nevertheless, due to the three-dimension network structure of lignin, there are many barriers that need to be surmounted before utilizing it, such as its complex connection with cellulose and hemicellulose, which makes its separation difficult. In this paper, different pretreatment methods are summarized for separating lignin from other two components. Finally, the challenges in future trends of lignin valorization are summarized and outlined. It is clear that the construction of efficient separation and catalytic systems will be the focus of future research in this field.