Bimetallic Ni-Zn@OMC catalyst for selective hydrogenation of levulinic acid to -valerolactone in water

Hydrogenation of levulinic acid to gamma-valerolactone is one of the important reactions for conversion of biomass into renewable fuels and chemicals. Ni-Zn non-noble bimetallic catalysts supported on ordered mesoporous carbon (Ni-Zn@OMC) were prepared by one-pot solvent evaporation induced self-assembly (EISA) method and used for hydrogenation of levulinic acid to gamma-valerolactone (GVL) in water. A GVL yield of 93% was obtained over bimetallic Ni-1-Zn-1@OMC catalyst at 180 degrees C in 90 min reaction time, with a turnover frequency (TOF) of 686.4 h(-1). Compared with Ni@OMC, the incorporation of Zn metal leads to the formation of Ni-Zn alloy and high dispersion of Ni particle on the catalyst surface. Ni-O sites on the catalysts lowered competitive adsorption between H-2 and levulinic acid on Ni0 sites, as well as the Ni-Zn alloy is beneficial to the activation of carbonyl group in levulinic acid, and they synergistically promote the hydrogenation of levulinic acid to 4-hydroxyvaleric acid (4-HVA). Zn content in the catalyst influences both the activity of Lewis acid sites and the ratio of Lewis acid to Bronsted acid sites, and the active sites of Ni delta-Zn delta+ can facilitates the weakening and cleavage of C-O in 4-HVA, both of them are beneficial to the dehydration of 4-HVA to GVL.