Recent Advances in Hydrodeoxygenation of Lignin‐Derived Phenolics over Metal‐Zeolite Bifunctional Catalysts

Abstract The hydrodeoxygenation (HDO) reaction provides a promising catalytic strategy to remove oxygen in biomass‐derived bio‐oil to produce renewable transportation fuels and value‐added chemicals. The development of highly efficient and stable HDO catalysts plays an essential role in biomass valorization. Metal‐zeolite bifunctional catalysts have been well‐developed as the effective HDO catalysts in upgrading lignin‐derived phenolics due to their excellent activity, selectivity, and thermal and hydrothermal stability. However, clarifying the roles of the active sites and their synergistic effect, and establishing effective structure‐performance relationships in the HDO process still face challenges. In this review, we first survey the conventional catalysts applied in the HDO of bio‐oil, followed by thoroughly discussing the roles of metal centers, acid sites, supports, and their impacts on the HDO process of phenolic model compounds or bio‐oil. Finally, a discussion on the stability and deactivation of metal‐zeolite catalysts, especially in the aqueous‐phase HDO reaction, is provided. This critical review offers new insights into the development of state‐of‐the‐art metal‐zeolite bifunctional catalysts with well‐defined porosity and metal‐acid properties for viable biomass valorization.