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 Ni 1 -Zn 1 @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 H 2 and levulinic acid on Ni 0 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 Ni δ– Zn δ+ 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.
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