**4. Conclusions**

In this study, we prepared a series of Ni-based catalysts for the in-situ HDO process of biomass-derived phenol to cyclohexane. The trimetallic 20Ni-5Co-5Cu/Al catalyst presented the highest activity compared to the other monometallic catalysts or bimetallic catalysts. The phenol conversion of 100% and the cyclohexane yield of 98.3% could be obtained in the in-situ HDO of phenol at 240 ◦C and 4 MPa initial N2 pressure. The high catalytic activity of the 20Ni-5Co-5Cu/Al catalyst could be attributed to the formation of Ni-Cu-Co alloy, which had the strong positive synergistic e ffects on the generation of hydrogen from the methanol aqueous-phase reforming and hydrodeoxygenation of phenol. The catalyst also showed excellent recyclability and exhibited good potential for upgrading the bio-oil to reduce the oxygen content by the in-situ hydrodeoxygenation.

**Author Contributions:** Conceptualization, H.X.; validation, H.X., X.G. and J.X.; writing—original draft preparation, H.X.; writing—review and editing, R.H.; funding acquisition, R.H.

**Funding:** Gratitude for the support from the National Natural Science Foundation of China (21276254, 21636006) and the Fundamental Research Funds for the Central Universities (GK201603051, GK201601005).

**Conflicts of Interest:** The authors declare no conflict of interest.
