An efficient NixZryO catalyst for hydrogenation of bio-derived methyl levulinate to γ-valerolactone in water under low hydrogen pressure

γ-Valerolactone (GVL) has been identified as a key intermediate for the sustainable production of fuels and value-added chemicals. In this work, an efficient NixZryO catalyst was prepared by co-precipitation and used in the low pressure hydrogenation to prepare GVL from bio-derived methyl levulinate (ML) in aqueous solution. Several catalysts that differed in their Ni/Zr molar ratio were prepared and characterized by BET, XRD, H2-TPR, NH3-TPD and XPS, and they exhibited different catalytic activities in the catalytic hydrogenation reaction of ML. The best catalytic activity was realized with Ni1Zr1O, which gave a 96.9% yield of GVL by low hydrogen pressure at 0.3 MPa in the aqueous solution at 150 °C. By comparison with NiO and Raney Ni, it was found that introducing zirconium into nickel oxide remarkably enhanced the performance of the NixZryO catalysts. According to the XRD, H2-TPR and XPS results, when a certain amount of zirconium was introduced (e.g., Ni/Zr = 1), part of the nickel either coordinated with zirconium or formed NimZrnO quasi solid solution and was not readily reduced by H2. Theoretical calculations showed that the formed Ni − O − Zr species was superior to pure nickel or zirconium oxides for the adsorption of ML. The synergy between metallic nickel, which activated H2, and the Ni − O − Zr species, which activated ML, was believed to expedite the production of γ-valerolactone. Moreover, Ni1Zr1O showed good catalytic stability and retained the catalytic performance even after five reaction cycles of the ML hydrogenation.