Enhancement of hydrogenation activity by synergistically promoting Re booster in Ni/Al2O3 catalyst for selectively converting levulinic acid into γ-valerolactone

• Ni/Al 2 O 3 enhancing by Re booster exhibited the highest activity for GVL production from LA. • Re interacting with Ni species to form Ni–Re alloy with remaining the ReO x ( x > 3) on Al 2 O 3 . • Linear CO coordination on NiRe clarified adsorption model of C=O bond of LA. • Effects of temperature, time, H 2 pressure, and catalyst loading were evaluated with reusability. • Reaction route for LA hydrogenation occurred through a key intermediate of HPA. Heterogeneous catalytic hydrogenation offers a sustainable thermochemical approach to selectively convert levulinic acid (LA) to highly valuable γ-valerolactone (GVL). In this study, an enhanced Ni/Al 2 O 3 catalyst was designed by systematically varying the Re booster content to improve the catalytic activity for LA hydrogenation compared with those of Ni and Re benchmarks. Advanced in situ characterizations revealed the Re interacted with Ni species to form Ni–Re alloy with remaining the ReO x functioned as collaborative active sites for hydrogenation. The synergistic Re booster facilitated H 2 reduction and alleviated the H 2 adsorption and desorption of the Ni/Al 2 O 3 catalyst. Compared with the monometallic Ni reference catalyst, the designed Ni–Re catalyst comprised a moderate number of Lewis acidic sites, which improved the catalytic activity. Under the optimal conditions at 140 °C and 30 bar of H 2 for 2 h, the highest LA conversion and GVL yield were 100 % and 97.8 %, respectively. On the Ni–Re surface, the predominant linear CO coordination clarified the C=O bond adsorption model for LA hydrogenation. High kinetic constant and turnover frequency were obtained over Ni–Re catalyst, which are significantly higher than the values of Ni and Re catalysts owing to facilitation of rate determining step in hydroxypentanoic acid (HPA) dehydration. To elucidate the reaction mechanism, LA was hydrogenated to GVL via the key HPV intermediate. This extensive investigation provides valuable insights into the design of potential Ni–Re catalysts for application to bioresource hydrogenation at sustainable biorefineries.