Selective hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan over Ni-Ga intermetallic catalysts and its kinetic studies

5-Hydroxymethylfurfural (HMF) has been listed as the "TOP 14" most important biomass-derived platform molecules, which can be converted into 2,5-bis(hydroxymethyl)furan (BHF) via selective hydrogenation of the carbonyl group on HMF. BHF is a crucial monomer for various industrially important polymerization and etherification processes. Noble metal catalysts have been reported to be highly active and selective for hydrogenation, leading to high BHF yields (>90%) under mild reaction conditions. In contrast, it has been challenging for non-noble metal catalysts to balance the activity and selectivity for this reaction. Herein, we synthesized Ni-Ga intermetallic compounds with varied Ni/Ga ratios for the selective hydrogenation of HMF to BHF. An unprecedented BHF yield of 98.4% was obtained over the Ni1Ga1 intermetallic catalyst under relatively mild conditions, which is much higher than that observed on the referred Ni catalyst and previously reported non-noble metal catalysts. Moreover, Ni1Ga1 also showed higher activity and better hydrothermal stability than the referred Ni catalyst. Kinetic studies revealed an inhibitive effect from the strong adsorption of HMF on the referred Ni catalyst that caused the site blocking, which can be alleviated over the Ni-Ga intermetallic catalysts. Characterization results suggest that the addition of Ga disrupted the contiguous array of Ni sites that are necessary for the adsorption of bulky furan ring and thereby depressed the side reaction of furan ring hydrogenation.