Hydrodeoxygenation of lignin-derived phenolics to cycloalkanes over Ni–Co alloy coupled with oxophilic NbO

• The Ni–Co alloy and oxophilic species co-catalyzed deoxygenation by hydrogenolysis. • A high selectivity of cycloalkanes (98.9%) was obtained in the HDO of guaiacol. • The 5Ni–5Co/NbO x catalyst also showed high stability and applicability. Hydrodeoxygenation (HDO) of lignin-derived bio-oil is a promising route to produce advanced biofuels. However, the removal of oxygen-containing functional groups with high bond strength in bio-oil challenges the development of efficient, stable, and inexpensive catalysts. In this study, a series of bifunctional catalysts were synthesized by coupling Ni–Co alloy with an oxophilic NbO x support, which was used for the HDO of lignin-derived phenolics to produce cycloalkanes. The Ni–Co alloy formed on the bimetallic catalysts during calcination and reduction was verified by TEM, XPS, and H 2 -TPR measurements, which showed excellent hydrogenolysis activity. The composition of the Ni–Co alloy was the most uniform with a Ni/Co molar ratio of 1, and the catalyst achieved the highest catalytic activity. The oxygen vacancies provided by the NbO x support also enhanced the adsorption of phenolics and promoted the removal of oxygen-containing functional groups by forming a specific configuration. The synergistic catalysis of Ni–Co alloy and oxygen vacancies achieved complete conversion of guaiacol with a high cycloalkane selectivity of 98.9 % under optimal conditions (300 °C, 3 MPa H 2 , and 2 h). More importantly, only marginal deactivation occurred on the 5Ni–5Co/NbO x catalyst after 5 cycles and it was also successfully applied to the efficient conversion of other complex lignin-derived phenolics. Therefore, an efficient and economical strategy of coupling the Ni–Co alloy with an oxophilic NbO x support to catalyze the HDO of lignin-derived phenolics to produce cycloalkanes was prospective.