Hydrodeoxygenation of lignin phenolic derivatives to aromatics: A review of catalyst functionalization for targeted deoxygenation and active site modification strategies

The catalytic hydrodeoxygenation of lignin phenolic derivatives to produce aromatic hydrocarbons poses a significant challenge in achieving targeted cleavage of oxygen-containing functional groups (-OH and -OCH3) while maintaining the structural integrity of the aromatic ring. To achieve high selectivity of phenolic derivatives for aromatic hydrocarbons, a catalytic system with high stability and maintenance of targeted deoxygenation activity is required. The active site mechanism of action is reviewed, including the phenolic substrate adsorption-configuration under different metal sites and the synergistic effect of support and metal sites. In addition, modification strategies for the active sites on the catalyst surface are discussed, including metal dispersion and particle size on the support surface, surface active species, Brønsted acid sites, and oxygen vacancies. To ensure high catalytic activity of the catalysts for targeted deoxygenation, recommendations for the rational design of catalysts are proposed, which involve the functionalization of catalysts for targeted deoxygenation, strategies for active site modification and inhibition of catalyst deactivation. Finally, the challenges of hydrodeoxygenation of phenolic derivatives to aromatics are summarized and future developments in this field are presented.