Catalytic conversion of lignocellulosic biomass into chemicals and fuels

In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future, lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock. This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels. Following a brief introduction on the structure, major resources and pretreatment methods of lignocellulosic biomass, the catalytic conversion of three main components, i.e., cellulose, hemicellulose and lignin, into various compounds are comprehensively discussed. Either in separate steps or in one-pot, cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF, furfural, polyols, and organic acids, or even nitrogen-containing chemicals such as amino acids. On the other hand, lignin is first depolymerized into phenols, catechols, guaiacols, aldehydes and ketones, and then further transformed into hydrocarbon fuels, bioplastic precursors and bioactive compounds. The review then introduces the transformations of whole biomass via catalytic gasification, catalytic pyrolysis, as well as emerging strategies. Finally, opportunities, challenges and prospective of woody biomass valorization are highlighted.