Water-mediated catalytic hydrodeoxygenation of biomass

Hydrodeoxygenation (HDO) is a critical step in upgrading biomass-derived feedstocks to renewable fuels and valuable chemicals. Water plays the role of solvent, reactant, or byproduct in biomass HDO reactions catalyzed by synthetic heterogeneous catalysts. And the unique property of water contributes to the regulation of the reaction rates, selectivity, and rates of mass transfer during the process of biomass HDO. The article introduces the latest development of biomass HDO in aqueous phase and summarizes the effects of water in the HDO process. The effects include regulating the mass transfer, stabilizing the transition states, promoting the ringopening, and direct participating in the catalytic reaction, as well as occupying active site and changing catalyst structure. Furthermore, the different mechanistic features of biomass catalytic HDO reactions influenced by water are discussed, in order to help understand the reaction process in aqueous phase. Finally, some inspirational strategies of utilizing the synergistic effects of water and metallic catalysts were proposed to develop novel catalytic systems for the synthesis of renewable chemicals from biomass.