Acid-catalyzed Dehydration Of Fructose Research Articles

Direct Conversion of Cellulose into 5-HMF by Transition-Metal Doped Montmorillonite Catalyst in Water

AbstractCatalysts are very important in the use of cellulose, the main component of biomass, as a raw material for the large-scale production of liquid fuels and chemicals. 5-Hydroxymethylfurfural (HMF) is an extremely important intermediate in the fine chemical industry. HMF can be synthesized by acid-catalyzed dehydration of fructose, glucose, cellulose, or sucrose. The conversion of cellulose to HMF is challenging due to its chemical structure. The objective of the present study was to devise a more facile synthesis method using transition metal-doped montmorillonite catalysts (10Cr-Mnt, 10Cu-Mnt, 10Fe-Mnt, and 10Zn-Mnt) by wet impregnation. Samples were characterized by X-ray powder diffraction, specific surface area, and NH3-TPD analyses. The synthesized catalysts were used for the conversion of cellulose to 5-HMF in an aqueous medium. Among the metals studied, Cr showed the greatest catalytic activity. With the use of this catalyst, efficient conversion of cellulose to 5-HMF was achieved, affording a conversion yield of 93.47% and 5-HMF yield of 9.07% within 6 h at 200°C. The study described here could be useful for the efficient conversion of cellulose into 5-HMF, as well as into other biomass-derived chemicals.

Preparation of SAPO-34-Based Catalyst for Conversion of Fructose to 5-Hydroxymethylfurfural

Solid acid-catalyzed dehydration of fructose to produce 5-hydroxymethylfurfural (5-HMF) has been a hotspot in biomass conversion research in recent years. In this study, a novel SAPO‑34‑based catalyst was prepared by consecutive steps of titanium doping, sulfuric acid impregnation, and sulfonic acid functionalization. Characterization of the catalyst with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), inductively coupled plasma optical emission spectrometer (ICP-OES), and acid-base titration revealed different pore structures and more acid content compared to SAPO‑34. The catalyst was applied to the preparation of 5-HMF by dehydration of fructose, and the maximum yield (74.0%) of 5-HMF was obtained by reacting in dimethyl sulfoxide (DMSO) at 170 °C for 50 min. In addition, the applicability of the catalytic system to other substrates and the stability of the catalyst after five cycles were investigated, which are valuable for further probing on the concerned aspects.

Preparation of Hydrophobic Acidic Metal–Organic Frameworks and Their Application for 5-Hydroxymethylfurfural Synthesis

The production of 5-hydroxymethylfurfural (HMF) by the acid-catalyzed dehydration of fructose is of great significance for the comprehensive utilization of biomass resources. However, the water generated in situ not only leads to the deactivation of the active sites but also triggers the rehydration side reaction of HMF, resulting in an unsatisfactory catalytic activity and selectivity. Herein, for the first time, metal–organic frameworks (MOFs) with strong Brønsted acidity and hydrophobicity were prepared by grafting arenesulfonic acid by a diazo method. These functionalized MOFs have a large specific surface area of 1700–2600 m2/g, a high acid density of over 1.2 mmol/g, and a strong hydrophobicity with an H2O contact angle of greater than 125°. Compared with the MOF directly functionalized with sulfonic acid, the arenesulfonic acid-functionalized MOFs, which have a stronger hydrophobicity, exhibit higher activity and selectivity (up to 98.3% yield) in the transformation of fructose to HMF. Meanwhile, these arenesulfonic acid-functionalized MOFs also exhibit an excellent HMF yield for glucose and inulin reactions via the cooperative catalysis of Lewis and Brønsted acids. Furthermore, the good activity and stability of the functionalized MOFs can be maintained after recycling for five runs. The successful preparation of hydrophobic acidic MOFs provides not only an efficient catalytic system for the synthesis of HMF but also a novel, efficient route for MOF functionalization.

Technological aspects of fructose conversion to high-purity 5-hydroxymethylfurfural, a versatile platform chemical

Two improved methods for the synthesis of 5-hydroxymethylfurfural by acid-catalyzed dehydration of fructose have been developed. The first one is the synthesis in ionic liquids with continuous removal of water under reduced pressure, and the second is the synthesis in the two-phase system consisting of aqueous NaHSO4 and methyl isobutyl ketone under atmospheric pressure. Both methods ensure isolation of crystalline 5-hydroxymethylfurfural with high purity and multiple recycling of the catalytic system. The synthesis in ionic liquid is convenient on a laboratory scale. Despite relatively low yield, the two-phase synthesis is preferred for industrial scale-up due to simple isolation and purification procedures combined with efficient regeneration of extractant and the catalytic system.

The influence of hydrophobic/hydrophilic balance of the mesoporous solid acid catalysts in the selective dehydration of fructose into HMF

The application of a number of mesoporous sulfonic acids including MCM-41–PrSO3H (1a), MCM-41–Ph–PrSO3H (1b), SBA-15–PrSO3H (2a), SBA-15–Ph–PrSO3H (2b), SBA-15–EtPhSO3H (3a), and SBA-15–Ph–EtPhSO3H (3b) with different surface hydrophobicity in acid-catalyzed dehydration of fructose into 5-hydroxymethylfurfural (HMF) in a water–nitromethane solvent mixture was investigated. Among the studied mesoporous solid acids, the catalysts with lower surface hydrophobicity and relative acidity were found to be more selective and efficient catalytic system for HMF production. Our studies showed that the hydrophilic surface of the employed solid acids might indeed provide a means of faster departure of HMF from the system mesopores as soon as it forms, thus retarding the rehydration of HMF to unwanted by-products and improving the HMF selectivity. HMF selectivity of 75% was reached in 93% fructose conversion in a water–NM system at 140 °C within 30 min in the presence of catalyst 2a, which is comparable or even superior to other systems which employ MIBK–2-butanol or other organic co-solvents.

Atomic Layer Deposition for Improved Stability of Catalysts for the Conversion of Biomass to Chemicals and Fuels

ABSTRACTAtomic layer deposition (ALD) has been used to coat SBA-15 and functionalized SBA-15 with various metal oxides. Use of SBA-15 coated with 4-10 ALD cycles of titania, alumina, niobia, or zirconia in the acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF) resulted in 24-57% conversion, with 0-22% selectivity, at 130 °C with 2 wt % fructose in 4:1 THF:H2O. Propylsulfonic acid functionalized SBA-15 (SBA-15-PrSO3H) had a 25% conversion and 48% selectivity for HMF under the same conditions. SBA-15-PrSO3H was also coated with 2 ALD cycles of titania followed by 8 ALD cycles silica. The deactivation rate constant for SBA-15-PrSO3H was 2.7 x 10-2 h-1 for the dehydration of fructose to HMF in a flow reactor at 130 °C with a feed of 2 wt % fructose in 4:1 THF:H2O. In comparison, the deactivation rate constant for the ALD coated SBA-15-PrSO3H-ALD was 7.9 x 10-3 h-1.

Acid‐Catalyzed Dehydration of Fructose and Inulin with Glycerol or Glycerol Carbonate as Renewably Sourced Co‐Solvent

Ionic liquids (ILs) can be partially substituted by glycerol or glycerol carbonate as cheap, safe, and renewably sourced co-solvents in the acid-catalyzed dehydration of fructose and inulin to 5-hydroxymethylfurfural (HMF). In the particular case of glycerol, we found that HMF can be conveniently extracted from the IL/glycerol (65:35) mixture with methylisobutylketone, limiting the reactivity of glycerol with HMF and allowing the recovery of HMF with a high purity (95 %). Influences of the fructose content, temperature, and the nature of the ionic liquid are also discussed. The possible use of industrial-grade glycerin is also investigated. We demonstrate that by using glycerol carbonate, up to 90 wt % of the IL can be successfully substituted, decreasing the environmental costs of traditional IL-based processes.

Dehydration of fructose and sucrose into 5-hydroxymethylfurfural in the presence of 1-H-3-methyl imidazolium chloride acting both as solvent and catalyst

The acid-catalyzed dehydration of fructose was performed in a microbatch reactor at 90 °C using 1-H-3-methyl imidazolium chloride, HMIM +Cl −, acting both as solvent and catalyst. A yield in 5-hydroxymethylfurfural (HMF) as high as 92% is achieved within 15–45 min. A productivity of 0.02 mmol of HMF, per min and per mmol of ionic liquid, can then be obtained. A remarkable feature, as compared with other catalytic systems, is the absence of decomposition of 5-hydroxymethylfurfural which can then be separately or continuously extracted in a simple manner with diethyl ether, thus allowing easier recycling of the ionic liquid after water removal. The absence of decomposition of 5-hydroxymethylfurfural is due to the lower free energy of activation calculated in the presence of the ionic liquid compared to other homogeneous or heterogeneous catalysts, which then makes, in a consecutive reaction network, the formation of the 5-hydroxymethylfurfural intermediate nearly quantitative. Under similar operating conditions, sucrose is nearly quantitatively transformed into HMF and unreacted glucose.

Dehydration of fructose into 5-hydroxymethylfurfural in the presence of ionic liquids

The acid-catalyzed dehydration of fructose was performed in a microbatch reactor at 80 °C using two commercially available ionic liquids, a hydrophilic one, 1-butyl 3-methyl imidazolium tetrafluoroborate (BMIM +BF 4 −), and a hydrophobic one, 1-butyl 3-methyl imidazolium hexafluorophosphate (BMIM +PF 6 −). When the reaction is carried out in 1-butyl 3-methyl imidazolium tetrafluoroborate as solvent and Amberlyst-15 as catalyst, a yield up to 50% in 5-hydroxymethylfurfural (HMF) is obtained within around 3 h. When the reaction is carried out now in 1-butyl 3-methyl imidazolium tetrafluoroborate and in 1-butyl 3-methyl imidazolium hexafluorophosphate as solvents and Amberlyst-15 as catalyst, DMSO is used as a co-solvent, in order, in particular, to solubilize fructose in the hydrophobic ionic liquid. Under these conditions, both ionic liquids allow the reaction to work more rapidly than in DMSO alone and with yields in HMF close to 80% within 24 h.