More than a support: the unique role of Nb2O5 in supported metal catalysts for lignin hydrodeoxygenation

Abstract

Nb₂O₅-supported metal materials are a vital class of green catalysts with excellent lignin hydrodeoxygenation activity and reusability in an aqueous catalytic system, in which the Nb₂O₅ support plays a pivotal role because of its nontoxic nature, strong acidity and remarkable stability in water. This review summarizes the recent advances in Nb₂O₅-supported metal catalysts for lignin hydrodeoxygenation, especially the special role of Nb₂O₅. In particular, the review first presents an overview of the structure, acid and redox properties of Nb₂O₅. It then focuses on the unique contribution of Nb₂O₅ in hydrodeoxygenation of lignin model compounds based on comparison with other common supports, including its promotion of C–O cleavage and enhancement of suitability and reusability in the aqueous phase. Strategies for the modification of Nb₂O₅ and the conversion of real lignin or its oil to aromatics over Nb₂O₅-supported metal catalysts are further summarized. Finally, the article attempts to highlight the remaining challenges and provide some outlooks for the future development of Nb₂O₅-supported metal catalysts. This review will provide valuable insights for developing advanced green catalysts for lignin valorization and other challenging environmental catalytic processes.