Cu-Based Nanoparticles as Catalysts for Selective Hydrogenation of Biomass-Derived 5-Hydroxymethylfurfural to 1,2-Hexanediol

1,2-Hexanediol (1,2-HDO) has essential applications in manufacturing cosmetics and pharmaceuticals, but its selective production from 5-hydroxymethylfurfural (HMF) over non-noble metal catalysts is challenging, due to the multiple parallel reaction routes for the conversion of HMF. In this study, Cu-based nanocatalysts with Cu nanoparticles derived from Mg–Al layered double hydroxides were reported to catalyze the conversion of HMF to 1,2-HDO. The results showed that the introduction of Mg species into the CuAl catalyst facilitated the formation of Cu nanoparticles with a smaller size, mesoporous structures, abundant basic sites, and also more surface area of metallic Cu sites. CuMgAl catalysts exhibited superior catalytic behavior and reusability for the conversion of HMF to 1,2-HDO with 5-methyl furfuryl alcohol (5-MFA) as the reaction intermediate by suppressing the sintering of Cu. The ring opening of 5-MFA controlled the formation rate of 1,2-HDO. The abundant basic sites with medium strength in CuMgAl facilitated the adsorption and subsequent ring opening of 5-MFA over metallic Cu sites to form 1,2-HDO. The critical side reaction from HMF to 1,2-HDO was the polymerization of HMF and reaction intermediates, which could be suppressed via an alcohol reaction medium like isopropanol.