Promoted catalytic vapor phase transfer hydrogenation of levulinic acid to γ‐valerolactone by coordinated size effect and acid property of bimetallic Ni/ CeO 2 catalyst

A series of Ni/CeO2 catalysts with different Ni loadings was prepared by the impregnation method, and characterized by XRD, N2 adsorption/desorption isotherms, H2-TPR, H2-TPD, NH3-TPD, Pyridine probed FT-IR, TEM, XPS, EPR, and TG to study the crystalline phase, porosity, redox, dispersion of metal species, acid property, chemical state of surface and coke. The addition of Ni decreased efficiently the apparent activation energy by more than 14%. The correlation analysis revealed that the loading of NiO had profound influences on particle size and acidity which need to be well coordinated to get good catalytic performance. In the hydrogenation of levulinic acid using formic acid as the hydrogen source, the 5Ni/CeO2 catalyst with moderate Ni particle size of 6.9 nm and appropriate acidic strength distribution (Strong/Weak = ca. 2.8) demonstrated superior catalytic performance with a levulinic acid conversion of 73% and a γ-valerolactone selectivity of 90%. The 5Ni/CeO2 among the bimetallic catalysts showed the best coke resistance (0.32 gC/gcat.) despite the fact that coke deposition was still inevitable during the reaction.