Synergy of Ni Nanoparticles and MoO x Species for Selective Hydrodeoxygenation of Lignin into Cycloalkanes

The selective hydrodeoxygenation of lignin as a substitute for fossil resources into aviation fuel-range cycloalkanes faces significant challenges due to its complex structure and diverse reaction pathways. Herein, we introduced MoOx species onto Ni nanoparticles-loaded Beta zeolite (Ni-0.2MoOx/Beta), which catalyzed the complete hydrodeoxygenation of lignin dimers and lignin-derived phenols into the corresponding cycloalkanes under mild conditions (200 °C, 2 MPa H2). Ni-0.2MoOx/Beta also enabled the hydrodeoxygenation of real lignin, achieving a cycloalkanes selectivity of over 83%. Mechanistic studies indicated that the synergistic effect between Ni nanoparticles and MoOx species was key to enhancing the hydrodeoxygenation performance. Ni nanoparticles enabled the adsorption and dissociation of H2, and horizontally adsorbed benzene ring in the oxygen-containing substrate, while adjacent MoOx species with abundant oxygen vacancies facilitated the vertical adsorption of oxygen-containing groups in the ring-saturated intermediates and the activation of C–O bonds. Simultaneously, the strong hydrogen spillover on Ni-0.2MoOx/Beta ensured the benzene ring hydrogenation and the cleavage of C–O bonds. This work provides an approach for designing non-noble metal catalysts for lignin hydrodeoxygenation, holding significant value for advancing the application of lignin-based aviation fuels.