Co‐Al Hydrotalcites: Highly Active Catalysts for the One‐Pot Conversion of Fructose to 2,5‐Diformylfuran

Abstract

In this work, a series of Co−Al hydrotalcites were synthesized in the molar ratio of 1:1(cat‐3), 2:1(cat‐4), 3:1(cat‐5). These synthesized Co−Al hydrotalcites were characterized by different characterization techniques such as XRD, XPS, FT‐IR, SEM, EDX, TGA, and N2 physical adsorption. The catalytic properties of the prepared Co−Al hydrotalcites in different molar ratio were investigated for the dehydration of fructose to 5‐hydroxymethylfurfural (HMF), and selective oxidation of the HMF into 2,5‐diformylfuran (DFF). The complete conversion of HMF led to 95% yield of DFF at 120 °C under 3 bar oxygen pressure in dimethyl sulfoxide (DMSO) for 6 h. DFF in the yield of 87% with 100% conversion of fructose could be achieved in a one pot and two‐step reaction using Co−Al calacite in ratio of 2:1(cat‐4). A 77% yield of DFF was obtained in one‐pot and one‐step reaction using the same hydrotalcite catalyst. A DFF yield of 59% was achieved in a one pot and one‐step reaction using air as oxidant. After completion of the reaction, the catalyst can be separate very easily and can be reused up to four times without any significant loss in its catalytic activity.

One-Pot Synthesis of 2,5-Diformylfuran from Fructose by Bifunctional Polyaniline-Supported Heteropolyacid Hybrid Catalysts

“…This bifunctional hybrid catalyst produced higher or considerable DFF yields to the Cs3HPMo11VO40 [23], graphene oxide [24], f-Ce9Mo1Oδ [26], sulfonated MoO3-ZrO2 [28], and Ru/H-beta [33] catalysts, especially by shortening the reaction time to 7 h ( Table 3). Although the catalytic performance of our hybrid catalyst was relatively lower than those of the V2O5@MOR(+HCl) [29], Au-Ru/rGO [34], and Co/Al hydrotalcites [35] catalysts, the use of liquid acid catalyst and/or the switching of the reaction atmosphere have been avoided in our work. Significantly, this inorganic-organic hybrid catalyst showed higher activity for DFF formation when compared with our previously reported Cs0.5H2.5PMo12O40 catalyst because of the strengthening of the Notably, over the bifunctional 40-PMo 12 /F 3 -PAN catalyst, the DFF yields in the "one-pot" and "one-step" fructose-to-DFF transformation could be increased to 76.7 mol% by prolonging the reaction time to 7 h ( Figure 5b).…”

“…The reported bifunctional catalysts included the cesium salts of Mo-or Mo−V-containing Keggin heteropolyacids [22,23], graphene oxide [24], sulfonated amine-functionalized carbonaceous catalyst (CC-SO 3 H-NH 2 ) [25], Mo-or V-containing composite catalysts (e.g., f-Ce 9 Mo 1 O δ [26], Mo-HNC [27], sulfonated MoO 3 -ZrO 2 [28], V 2 O 5 @MOR [29], and V-g-C 3 N 4 (H + ) [30]), and magnetic acid catalysts (e.g., Fe 3 O 4 @C-SO 3 H [31] and WO 3 HO-VO(salten)-SiO 2 @Fe 3 O 4 [32]). Relatively higher DFF yields (70~86%) have been obtained by conducting the fructose dehydration under a nitrogen atmosphere while subsequent oxidation under oxygen atmosphere [24][25][26][32][33][34][35], wherein the fructose oxidation could be reduced while a long reaction time of 11~24 h was required. In addition to the larger energy input, such a long reaction time also resulted in further oxidation of DFF to 5-formyl-2-furancarboxylic (FFCA) and/or 2,5-furandicarboxylic acid (FDCA) (Scheme 1), which undoubtedly increases the separation energy of the target product DFF.…”

Efficient Selective Oxidation of 5-Hydroxymethylfurfural with Oxygen over a ZnCrAl Mixed Oxide Catalyst Derived from Hydrotalcite-like Precursor

“…In recent years, mixed metal oxide catalysts, generally with a uniform metal ion dispersion, large surface area, basic surface property, and high stability, prepared with roasting hydrotalcite-structured precursors have been used as efficient catalysts in transesterification and oxidation reactions. − However, only a limited number of works focused on the selective oxidation of 5-HMF. Nea̧u et al used a manganese–copper mixed oxide catalyst prepared from layered double hydroxide in HMF selective oxidation and obtained a 90% HMF conversion and an 87% DFF selectivity under 8.0 MPa oxygen pressure in 24 h. Raut and Bhanage reported a cobalt–aluminum hydrotalcite-derived mixed metal oxide catalyst and applied the catalyst in the one-pot and two-step DFF synthesis from fructose. A 77.0% DFF yield was obtained at 120 °C for 8 h under 3.0 MPa O 2 .…”

Highly efficient and tunable visible-light-catalytic synthesis of 2,5-diformylfuran using HBr and molecular oxygen

“…Some efficient catalytic protocols using molecular oxygen as an oxidant, which are summarized in Table 1, have been developed to directly synthesize DFF from fructose by one-pot, two-steps [28][29][30][31][32][33][34][35][36] or one-step, [37][38][39][40][41][42][43] affording medium to high DFF yields of 49-87%. However, these synthesis protocols usually employ relatively complex catalysts and high reaction temperatures above 110 C. The two-step synthesis protocol usually requires the stepwise addition of acidic and oxidative catalysts in order to improve the DFF yield.…”