Bimetallic NiCu Alloy Catalysts for Hydrogenation of Levulinic Acid

Abstract

Upgrading of the biomass-derived levulinic acid (LA) with the activation of carbonyl functional groups is a pivotal reaction in converting biomass into high-value-added products. Herein, we reported a modified strategy to synthesize highly dispersed noble-metal-free bimetallic NiCu alloy nanoparticles (NPs) from metal–organic frameworks for the selective hydrogenation of LA, in which the ligand effect between Ni and Cu plays a crucial role under relatively mild conditions. Among the tested catalysts, the catalyst with a Ni/Cu ratio of 1:2 presented the best catalytic performance in comparison with the homometallic Ni/Cu and bimetallic catalysts with different ratios; an outstanding yield of 93.9% was obtained for γ-valerolactone (GVL). Both experimental studies and characterization analyses verified that the ligand effect is responsible for the excellent catalytic performance. A possible reaction pathway for the samples in the LA hydrogenation process is proposed; after dissociation of adsorbed H2 on the NiCu alloy surface, reactant LA is adsorbed and activated by NPs with the formation of intermediate, and through a self-condensation reaction to form products. The straightforward synthesis, superior performance, and high stability make these noble-metal-free bimetallic NiCu nanoparticles very attractive for the transformation of various biomass-derived sources into valuable products.