Inhibition of Ni oxidation in a Ni-based catalyst to enhance the catalytic activity for lignin upgrading: Sacrificing Co to protect Ni

Hydrodeoxygenation (HDO) is a promising technology for high-value utilization of lignin. However, the oxidative deactivation of active metals is still an insurmountable obstacle in the development of catalysts. NiCo/USY was prepared by Co sacrificial protection method and used for the HDO of lignin. A series of characterization and experimental results confirmed that the electron transfer from Co to Ni inhibited the oxidation of Ni and activated the intrinsic catalytic activity of Ni. Lignin was subjected to catalytic HDO over NiCo/USY in n-hexane under 2 MPa of initial hydrogen pressure at 220 °C for 4 h. The result shows that NiCo/USY exhibits excellent HDO activity of lignin with the yield of cyclanes is 56.1 %. In NiCo/USY, nickel nanoparticles with electron transferred from Co and mesoporous USY with abundant acidic centers play an important role in hydrogenating aromatic rings and removing oxygen atom, respectively. benzyloxybenzene and (oxybis(methylene))dibenzene were used as the lignin-related model compounds to investigate the mechanism for the HDO of lignin. [Display omitted] •NiCo/USY is active for the hydrodeoxygenation of lignin with 56.1 % cyclanes yield.•Electron transfer improves the ability of Ni to activate H2.•The introduction of Co inhibits the oxidation of Ni.