Effective Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran by an Acetal Protection Strategy

Abstract

An acetal protection strategy for 5-hydroxymethylfurfural (HMF) was used to obtain 2,5-diformyfuran (DFF) using concentrated HMF solutions and a γ-Al 2 O 3 -supported Ru catalyst (Ru/γ-Al 2 O 3 ). The HMF-acetal with 1,3-propanediol can be oxidized to DFFacetal with a yield of 84.0 % at an HMF conversion of 94.2 % from a 50 wt % solution. In contrast, aerobic oxidation of nonprotected HMF using a 10 wt % solution afforded DFF only in a moderate yield (52.3 %). Kinetic studies indicated that the six-membered ring acetal group not only prevents side reactions but also accelerates aerobic oxidation of the À CH 2 OH moiety to À CHO under retention of the acetal functionality. Organic deposits formed during the reaction explained the significant decrease in the activity of the Ru/γ-Al 2 O 3 catalyst, which could be recovered neither by washing in water or organic solvents, nor by a calcination-reduction treatment. Sonication of the used Ru/γ-Al 2 O 3 catalyst in an aqueous NaOH solution successfully removed the deposits and allowed reuse of the catalyst for at least four times without activity loss.

Covalent‐Bonding Oxidation Group and Titanium Cluster to Synthesize a Porous Crystalline Catalyst for Selective Photo‐Oxidation Biomass Valorization

“…[4] In this regard, it is particularly important to obtain FDCA through the highly selective oxidation of HMF and techniques including traditional thermal catalysis, electro-or photo-catalysis have been studied. [5] Compared with others, photo-catalysis driven by light and O 2 has attracted enormous attention in promoting photo-oxidation of HMF due to its advantages of cost-effectiveness and sustainability, consistent with the concept of sustainable development strategy. [6] However, the photo-oxidation products of HMF are diversified (including DFF, HMFCA or FFCA in addition to FDCA) and the relative mechanisms are complicated to be investigated, which makes it a giant challenge to achieve highly selective photo-oxidation of HMF-to-FDCA especially that conditions using visible light and molecular O 2 .…”

Computational survey of humin formation from 5-(hydroxymethyl)furfural under basic conditions

“…Although we did not consider the catalyst or molecular oxygen on the metal support in this study, the results shown in this paper suggest a deeper understanding of humin formation in various basic solutions and the effect of acetal protection on HMF. [36][37][38]…”

Scale-up preparation, column chromatography-free purification of protected carbonyl-containing biomass molecules and their derivatizations

“…15 In addition, a 50 wt% solution of PG-HMF (the solvent was N , N -dimethylformamide) could be oxidized to PG-DFF over Ru/g-Al 2 O 3 with a yield of 84.0% at 94.2% conversion. 16 In contrast, the aerobic oxidation of non-protected HMF as a 10 wt% solution only afforded a moderate yield of DFF (52.3%). A hydroxyapatite-supported Au catalyst was applied to selectively oxidize PG-HMF in a 10 wt% solution to PG-FFCA (5-formylfuran-2-carboxylic acid), obtaining a yield of 94% within 2 h at 373 K under 0.5 MPa O 2 .…”

“…18 Although the protection strategy has been applied to some preliminary works on biomass depolymerization and furanic compounds conversion, 6,7,[9][10][11][12][13][19][20][21][22] so far only limited reaction types have been investigated. [14][15][16][17][18]23 The effect of the protection strategy is most commonly investigated in an oxidative environment. In a reducing atmosphere, like H 2 , the influence of the protection strategy on hydrogenation or hydrodeoxygenation has not yet been systematically evaluated.…”