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

Abstract

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.

Synergistic Catalysis for Promoting Ring-Opening Hydrogenation of Biomass-Derived Cyclic Oxygenates

“…The synergistic effect between the metallic and basic sites was also observed in the MgAlO-supported metal (Cu, Co) catalysts on the ring-opening hydrogenation of furfuryl alcohol and 5-hydroxymethylfurfural (Figure a), − where the basic sites played a critical role in the ring-opening reaction. In the conversion of 5-hydroxymethylfurfural to 1,2-hexanediol catalyzed by CuMgAl catalyst, the increase of basic sites concentration increased from 269 to 543 μmol g –1 and afforded the improvement of 1,2-hexanediol yield from 20 to 34%, suggesting a close relationship between the reaction rate and basic site concentration (Figure b) .…”

“…112 Furthermore, the appropriate size of the Cu particles was also beneficial to the high ring-opening hydrogenation rate due to its relationship with hydrogenation activity. 111,112 Hence, the synergistic catalysis between basic and metallic sites played a significant role in synthesizing the desired diols from biomass-derived furans.…”

“…(b) Relation between reaction rate and basic site concentration over CuMgAl. Adapted from refs and . Copyright 2022 and 2021 American Chemical Society.…”

“…The synergistic effect between the metallic and basic sites was also observed in the MgAlO-supported metal (Cu, Co) catalysts on the ring-opening hydrogenation of furfuryl alcohol and 5-hydroxymethylfurfural (Figure a), − where the basic sites played a critical role in the ring-opening reaction. In the conversion of 5-hydroxymethylfurfural to 1,2-hexanediol catalyzed by CuMgAl catalyst, the increase of basic sites concentration increased from 269 to 543 μmol g –1 and afforded the improvement of 1,2-hexanediol yield from 20 to 34%, suggesting a close relationship between the reaction rate and basic site concentration (Figure b) . Furthermore, the appropriate size of the Cu particles was also beneficial to the high ring-opening hydrogenation rate due to its relationship with hydrogenation activity. , Hence, the synergistic catalysis between basic and metallic sites played a significant role in synthesizing the desired diols from biomass-derived furans.…”

Tuning of Catalytic Dimethyl Adipate Hydrogenation by Changing Composition of Cu–ZnO–TiO2 Catalysts

“…The catalysts were prepared with reference to the previous literature. 28 Briefly, Cu(NO 3 ) 2 •3H 2 O and Zn(NO 3 ) 3 •6H 2 O were weighted with a stoichiometric ratio. A mixture of NaOH and Na 2 CO 3 precipitant was used to maintain the pH of the preparation solution at 10.0 ± 0.2.…”