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

Hydrogenation of levulinic acid to γ-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 γ-valerolactone (GVL) in water. A GVL yield of 93% was obtained over bimetallic Ni1-Zn1@OMC catalyst at 180 °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. NiO sites on the catalysts lowered competitive adsorption between H2 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 Brønsted acid sites, and the active sites of Niδ–Znδ+ 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.