A critical review of recent advances in the production of furfural and 5-hydroxymethylfurfural from lignocellulosic biomass through homogeneous catalytic hydrothermal conversion

Furan energy platform compounds including furfural and 5-hydroxymethylfurfural (HMF), can be produced by hydrothermal conversion of biomass. After hydrodeoxygenation, these furans can be converted into value-added chemicals and liquid fuels. This will help achieve efficient utilization of biomass and alleviate the environment issues caused by the overuse of fossil fuels. This review introduces the recent progress in the production of furfural and HMF from biomass and its derived sugars in homogeneous catalytic systems. The topics mainly include catalytic mechanisms, catalytic systems, and conversion processes. The synergistical catalytic effect of Lewis acid and Brunsted acid is crucial in furan production. Therefore, the development of metal salts and ionic liquids, which exhibit both kinds of acidity, has been the focus of recent attention. The type and composition of catalyst also play key roles in producing furan products. Thus, the design and improvement of the catalyst based on mechanism research will be helpful to the highly selective hydrothermal conversion of biomass. Reasonable selection of solvent system can improve the conversion efficiency significantly and avoid the occurrence of various side reactions. Especially, the online extraction of the biphasic solvent system can prevent some certain products from being consumed by the secondary reaction. Till now, the lab-scale homogeneous conversion process has been fully developed. Future research will focus on the magnification and commercialization of laboratory process. The key technical problems in the commercialization process is how to increase the recyclability, economy and eco-friendly property of the reaction system under the premise of satisfying product yield.

Automated summary

Furan energy platform compounds can be produced from biomass through hydrothermal conversion, which can be further converted into value-added chemicals and liquid fuels after hydrodeoxygenation. The crucial role of catalytic systems and design in achieving efficient biomass utilization and mitigating environmental issues is emphasized.