HMF Selectivity Research Articles

Synthesis of 5-hydroxymethylfurfural (HMF) by acid catalyzed dehydration of glucose–fructose mixtures

Synthesis of 5-hydroxymethylfurfural (HMF) from hexoses has been studied extensively in the scientific literature. However, a process has yet to be implemented at industrial scale. In this paper the simultaneous dehydration of glucose and fructose was investigated, in order to develop a process allowing the use of the cheapest available source of fructose: high fructose corn syrup. The dehydration was catalyzed by hydrochloric acid and conducted in acetone–water mixtures, which ensured good selectivity towards HMF and eliminated precipitation of polymer by-products (insoluble humins). Through a detailed experimental investigation a reaction network was proposed, and subsequently the corresponding kinetic model was fitted to experimental data in order to obtain estimates of the reaction kinetic parameters. The kinetic model is capable of predicting the formation of HMF along with the important by-products: soluble humins, glucose dimers, anhydroglucose, and formic acid. The reaction conditions in four different reactor configurations were optimized and compared using the kinetic model. It was found that a recirculating reactor setup is preferable, where the equilibrium controlled by-products (anhydroglucose and glucose dimers) are recirculated to the dehydration reactor. The model predicts an HMF selectivity of close to 70% in a recirculating reactor at conditions where HMF degradation is avoided.

Acid-Catalyzed Dehydration of Fructose to 5-(Hydroxymethyl)furfural

AbstractHydroxymethylfurfural (abbreviated as HMF), also 5-(hydroxymethyl)furfural, is an organic compound derived from dehydration of certain sugars. HMF is primarily considered as a starting material for liquid transportation fuels and polyester building block chemicals. The most convenient synthetic method of HMF is based on acidcatalyzed triple dehydration of fructose. Although there are many studies about fructose dehydration to 5-HMF since this field started to be investigated, it is necessary to provide a new review about fructose dehydration to 5-HMF. In the following, we will make a summary (in detail) of catalytic systems of fructose dehydration to HMF achieved by different acid catalysts, including mineral and organic acids, metal complexes, heteropoly acid-based materials, Ionic Liquids, ion-exchange resins, zeolites, functionalized carbonaceous materials and mesoporous silica materials. It has been demonstrated that nearly full conversion of fructose and 100% HMF selectivity could be obtained with some acidic catalytic systems up to now.

Effect of carboxylic acid of periodic mesoporous organosilicas on the fructose-to-5-hydroxymethylfurfural conversion in dimethylsulfoxide systems

This manuscript presents the preparation and catalytic application of highly ordered benzene bridged periodic mesoporous organosilicas (PMOs) functionalized with carboxylic acid (–COOH) group at varied density. The COOH-functionalized PMOs were synthesized by one-step condensation of 1,4-bis (triethoxysilyl) benzene and carboxylic group containing organosilane carboxyethylsilanetriol sodium salt using Brij-76 as the template. The obtained materials were characterized by a mean of methods including powder X-ray diffraction, nitrogen adsorption-desorption, scanning- and transmission electron microscopy, and 13C solid-state nuclear magnetic resonance measurements. The potentials of the obtained PMO materials with ordered mesopores were examined as solid catalysts for the chemical conversion of fructose to 5-hydroxymethylfurfural (HMF) in an organic solvent. The results showed that COOH-functionalized PMO with 10% COOH loading exhibited best results for the fructose to HMF conversion and selectivity. The high surface area, the adequate density acid functional group, and the strength of the PMO materials contributing to a promising catalytic ability were observed.

고정화 산성 이온성 액체 촉매와 금속염화물 촉매를 이용한 셀룰로우스의 5-HMF로의 직접 전환 연구

Various metal chlorides and acid catalysts in ionic liquid solvent were investigated to directly convert cellulose into 5-hydroxymethylfurfural (5-HMF). Metal chlorides containing Sn(II), Zn(II), Al(III), Fe(III), Cu(II), and Cr(III) were used and acidic ionic liquid immobilized on silica gel as an acid catalyst and commercial acid catalysts (sulfuric acid, chloric acid, Am- berlyst-15,DOWEX50x8) were used for comparison studies. The acid strength and amount of acid catalysts were probed with Hammett indicator. The selectivity and yield of 5-HMF were determined with reaction temperature, reaction time and catalyst ratio. A catalyst containing CrCl3-6H2O and SiO2-(ASBI)HSO4 showed the highest selectivity and it was found that this catalyst had higher activity than commercial solid acid catalysts such as Amberlyst-15 and DOWEX50x8. The selectivity of 5-HMF appeared to be mainly dependent on the acid strength and catalyst ratio, it was found that levulinic acid was produced from 5-HMF by rehydration.

Catalytic conversion of glucose in dimethylsulfoxide/water binary mix with chromium trichloride: Role of water on the product distribution

The production of 5-Hydroxymethylfurfural (HMF) from hexoses is a stoichiometric dehydration process. Water content in a solvent is expected to play an important role in HMF formation by affecting the equilibrium and the reaction kinetics. In this work, the impact of water content on the catalytic conversion of glucose was investigated in detail in different dimethylsulfoxide (DMSO)/H2O mixtures (vw = 0–1) with chromium trichloride hexahydrate (CrCl36H2O) as the catalyst at 110–130 C. Water content in the binary mix was found to dominantly affect the product distribution. Anhydrous DMSO system is favored for HMF formation from glucose but caused a number of side reactions, especially the undesired dehydration of glucose into cellobiose. Adding an appropriate amount of water in DMSO (vw = 0.17–0.50) was found to significantly suppress the undesired dehydration side reactions while preserving high HMF yield over the CrCl36H2O catalyst, therefore remarkably improving the total selectivity of HMF and fructose from glucose conversion. While CrCl36H2O was essential in isomerizing glucose into fructose, hydrochloric acid (HCl) from CrCl36H2O hydrolysis in DMSO/H2O mixed system catalyzed the dehydration of in situ formed fructose to HMF. Although effective water removal was pronounced toward improving HMF yield from hexose dehydration in previous work, the results of this work indicate that a controlled amount of water in the non-aqueous system is favorable to drive the thermodynamic equilibrium for high HMF yield and desired product selectivity, providing reference information on designing a one-pot process for HMF synthesis from cellulosic materials.

Dehydration of fructose into furans over zeolite catalyst using carbon black as adsorbent

Formation of 5-hydroxymethylfurfural (HMF) from the dehydration of fructose over zeolite catalysts in aqueous phase was studied in a reactive adsorption system using carbon black (BP2000) as an adsorbent. The dehydration of fructose over zeolite beta catalyst in water revealed that selectivity to HMF is largely influenced by the formation of levulinic acid and formic acid from the rehydration of produced HMF as well as subsequent condensation reactions. In order to increase selectivity to HMF, reactive adsorption with carbon adsorbents was used to prevent the further reactions of the produced HMF. It was found that BP2000 carbon black exhibited high selectivity and capacity for the adsorption of HMF and furfural from the aqueous phase. The unique adsorption performance of BP2000 is likely due to the large surface area, hydrophobic nature and micropore structure. With using the carbon adsorbent, furan selectivity (selectivity of HMF and furfural) over zeolite beta was improved from 27% to 44% with a furan yield of 41%. The furan selectivity and yield obtained in the presence of the carbon adsorbent were similar to those obtained from the aqueous/organic reaction system using methyl isobutyl ketone (MIBK) as an extraction phase.

ChemInform Abstract: Advances in 5‐Hydroxymethylfurfural Production from Biomass in Biphasic Solvents

AbstractReview: 85 refs.

Dehydration of glucose into 5-hydroxymethylfurfural in SO3H-functionalized ionic liquids

Abstract The continuous dehydration of d -glucose into 5-hydroxymethylfurfural (HMF) was carried out under mild conditions, using SO 3 H-functionalized acidic ionic liquids as catalysts and H 2 O-4-methyl-2-pentanone (MIBK) biphasic system as solvent. High glucose conversion of 97.4% with HMF yield of 75.1% was obtained at 120 °C for 360 min, also, small amounts of levulinic acid (LA) and formic acid were generated. Generally, the dosage of catalyst and the initial content of glucose influenced the reaction significantly; the HMF selectivity decreased with the excessive elevation of temperature and prolonging of time; and water content in the system had a negative effect on the reaction. The ionic liquid catalyst could be recycled and exhibited constant activity for five successful runs. This paper provided a new strategy for HMF production from glucose.

Advances in 5-hydroxymethylfurfural production from biomass in biphasic solvents

Biomass derived 5-hydroxymethylfurfural (HMF) has emerged as an important platform chemical for the production of value added chemicals and liquid fuels that are currently obtained from petroleum. Although a significant amount of research has been performed over the past decade, the high production cost of HMF is still a bottleneck for its sustainable utilization for making other value added chemicals and fuels on a commercial scale. Among several factors, low product selectivity and high purification cost are major constraints. To address these drawbacks, HMF production methodology in recent years has been directed towards utilization of biphasic media for concurrent extraction of HMF into an organic phase immediately after its formation in the reactive phase. As a result, several dozens of journal and patent articles have appeared, demonstrating the benefit of biphasic media for effective HMF extraction. This review article summarizes the findings of the most recent research articles with critical discussion on the factors that enhance the performance of biphasic media. Particular emphasis has been given to the development of more effective extracting solvents and their beneficial effect in enhancing HMF yield and selectivity, improvement of partition coefficient, mechanistic role of the bi-functional acid catalysts and factors that control high HMF selectivity for solid catalysts.

Kinetics of Homogeneous Brønsted Acid Catalyzed Fructose Dehydration and 5-Hydroxymethyl Furfural Rehydration: A Combined Experimental and Computational Study

We perform the first extensive experimental kinetic studies of fructose dehydration and 5-hydroxymethyl furfural (HMF) rehydration at low temperatures over a wide range of conditions (T ∼ 70–150 °C; pH values 0.7–1.6 and initial concentrations of fructose (5–20%w/v) and HMF (2.5–10%w/v)). Guided from insights from our first-principles calculations, we perform kinetic isotope effect (KIE) experiments of labeled fructose to validate the rate-limiting step. Subsequently, we develop the first skeleton model for fructose dehydration and HMF rehydration that integrates the fundamental kinetic experiments and accounts for the KIE, as well as the distribution of fructose tautomers, which changes significantly with temperature, and a direct path of fructose conversion to formic acid. It is shown that the skeleton mechanism of two steps consisting of fast protonation and dehydration followed by intramolecular hydride transfer as the rate-limiting step can capture the experimental kinetics and KIE experiments well. Fructose dehydration is found to result in stoichiometric excess of formic acid relative to levulinic acid, produced directly from fructose. All reactions are shown to be pseudo-first order in both catalyst and substrate. These insights are incorporated in a continuous flow reactor model; higher temperatures improve the optimum yield of HMF, while HMF selectivity at low conversions is less sensitive to temperature.

Stability and catalytic properties of porous acidic (organo)silica materials for conversion of carbohydrates

Sulfonic acid-modified mesoporous SBA-15-type silica and hybrid organosilica catalysts were prepared using the co-condensation and grafting functionalization methods. The catalytic activity of these materials for fructose dehydration to 5-hydroxymethylfurfural was studied in aqueous medium and in DMSO. The prepared materials were characterized by XRD, SEM, elemental analysis, nitrogen physisorption and 29Si CP MAS NMR. Special focus was on evaluating the influence of the structural modification of the mesoporous catalysts on their stability under the conditions of catalytic conversion of carbohydrates. In aqueous medium all catalysts show very low activity and HMF selectivity. However, when the reaction is carried out in DMSO, HMF yields of up to 88% can be achieved with a minimum amount of sulfonic acid-modified catalyst. Among the materials tested, the hybrid organosilica-based catalyst shows the highest dehydration rate. It is demonstrated that pure silica-based catalysts degrade strongly under the catalytic conditions. The hydrothermal stability of the mesoporous catalysts is improved in the presence of organic moieties in their structure. The co-condensed organic–inorganic catalysts retain much better the mesoporosity and are less susceptible to the loss of catalytic functional groups anchored to their surface compared to their pure silica counterparts. The methodology for the introduction of functional groups has also a profound impact on the catalyst stability. Species incorporated into the catalysts via the direct co-condensation method show much higher stability than those introduced via a post-synthetic grafting procedure.

Elucidating structure–properties relations for the design of highly selective carbon-based HMF sorbents

5-Hydroxymethyl furfural (HMF) production from fructose dehydration in DMSO with various catalytic systems has shown superior selectivity and high yields. Yet, the subsequent need for energy-intensive separation of HMF from HMF/fructose/DMSO mixtures challenges the practical feasibility of this process. Microporous carbon materials have shown promise as substrates for alternative adsorption-based separations, but the origin of HMF selectivity and adsorption capacity, and thereby structure–properties relations enabling rational design of enhanced sorbents, has remained elusive. Through systematic quantification of the functionality and texture of various commercial (BP2000, Norit1240) and synthetic carbons (three-dimensionally ordered macroporous carbons; mesoporous carbons), we link, for the first time, adsorption capacity and HMF adsorption selectivity to two tunable materials properties of the carbon sorbents: microporosity and oxygenate functionality (i.e., carbon polarity). In the process, we exploit these newly elucidated structure–properties relations for realizing a class of synthetic carbons with sub-micron particulate morphology that achieve more than 60% higher selectivity and more than 20% higher capacity for HMF over fructose as compared to the best performing commercial product, BP2000.

Dehydration of fructose to 5-hydroxymethyl furfural over ordered AlSBA-15 catalysts

5-Hydroxymethyl furfural is an important platform chemical. It is successfully synthesized from renewable carbohydrates using mesoporous AlSBA-15 catalysts under biphasic conditions. Fine tuning of the catalyst acidity is important to drive the reaction to give good yields of furan compound. Al-SBA-15 catalysts with different Si/Al ratios were prepared and characterized by XRD, 27Al MASNMR, SEM, TEM, N2 sorption, ICP-OES and TPD of ammonia. Results show that part of aluminium is substituted into tetrahedral positions. The catalyst with lower acid site density but medium to strong acidstrength favours selective formation of HMF. Under the optimized conditions, HMF selectivity was as high as 88% at 59 mol% conversion of fructose. Leaching of part of aluminium occurs under hydrothermal conditions, if solvent mixtures containing water are used, while activity can be retained if DMSO is used as solvent.

The effect of hydrochloric acid on the conversion of glucose to 5-hydroxymethylfurfural in AlCl3–H2O/THF biphasic medium

The effect of hydrochloric acid (HCl) on the conversion of glucose to 5-hydroxymethylfurfural (HMF) in AlCl3–H2O/THF biphasic system was investigated. The route via isomerization to fructose followed by tandem dehydration to HMF is the dominant pathway. Lewis acid sites of Al3+ aqua/hydroxo complexes play the leading role for the dehydration step. The introduction of a suitable amount to HCl increases the amount of Brønsted acid sites and improves the selectivity for HMF. The maximum HMF yield from glucose is enhanced from 51% to 62% in the presence of 0.1M HCl. The introduction of HCl lowers the reaction rate of glucose-to-fructose isomerization but enhances the reaction rate of fructose dehydration. Higher loading of HCl (1.0M) leads to increased direct dehydration of glucose to humins and results in lower selectivity to HMF.

Sustainable Solvent Systems for Use in Tandem Carbohydrate Dehydration Hydrogenation

Monophasic separation-friendly solvent systems were investigated for the sustainable acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF). The HMF selectivity depends on both fructose conversion, temperature, and the amount of cosolvent present in the aqueous solvent mixture. Use of HMF-derived 2,5-(dihydroxymethyl)tetrahydrofuran (DHMTHF) or low-boiling tetrahydrofuran (THF) as co-solvents results in increased selectivity (>70%) to HMF at fructose conversions of ca. 80%. Analysis of the fructose tautomer distribution in each solvent system by 13C NMR revealed higher furanose fractions in the presence of these and other protic (tetrahydrofurfuryl alcohol) and polar aprotic co-solvents (DMSO) relative to water alone. Formation of fructosides and/or difructose anhydrides in the presence of the co-solvents causes lower selectivity at early reaction times, but reversion to fructose and dehydration to HMF at longer reaction times results in increasing HMF selectivity with fructose conversion...

An efficient and heterogeneous recyclable silicotungstic acid with modified acid sites as a catalyst for conversion of fructose and sucrose into 5-hydroxymethylfurfural in superheated water

Acidity modified silver exchanged silicotungstic acid (AgSTA) catalyst was prepared and characterized by X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, FT-IR pyridine adsorption, SEM imaging, EDX mapping, and antimicrobial activity was also tested. The catalytic activity was evaluated for the dehydration of fructose and sucrose in superheated water. As a result, 98% conversion of fructose with 85.7% HMF yield and 87.4% HMF selectivity in 120min reaction time at 120°C reaction temperature using 10wt.% of AgSTA catalyst was achieved. While, 92% sucrose conversion with 62.5% of HMF yield was obtained from sucrose at uniform condition in 160min. The effect of reaction parameters, such as reaction temperature, time, catalyst dosage, and effect acidity on HMF yield was also investigated. The AgSTA catalyst was separated from the reaction mixture by filtration process at end of the reaction and reused eight times without loss of catalytic activity.

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.

Acid-Functionalized SBA-15-Type Periodic Mesoporous Organosilicas and Their Use in the Continuous Production of 5-Hydroxymethylfurfural

The activity, selectivity, and stability of several supported acid catalysts were evaluated in tubular reactors designed to produce 5-hydroxymethylfurfural (HMF) continuously from fructose dissolved in a single-phase solution of THF and H2O (4:1 w/w). The reactors, packed with the solid catalysts, were operated at 403 K for extended periods, up to 190 h. The behaviors of three propylsulfonic acid-functionalized, ordered porous silicas (one inorganic SBA-15-type silica, and two ethane-bridged SBA-15-type organosilicas) were compared with that of a propylsulfonic acid-modified, nonordered, porous silica. The HMF selectivity of the catalysts with ordered pore structures ranged from 60 to 75%, whereas the selectivity of the nonordered catalyst under the same reaction conditions peaked at 20%. The latter was also the least stable, deactivating with a first-order rate constant of 0.152 h–1. The organosilicas are more hydrothermally stable and maintained a steady catalytic activity longer than the inorganic SBA-...

On the Mechanism of Lewis Acid Catalyzed Glucose Transformations in Ionic Liquids

AbstractA complementary computational and experimental study of the reactivity of Lewis acidic CrCl2, CuCl2 and FeCl2 catalysts towards glucose activation in dialkylimidazolium chloride ionic liquids is performed. The selective dehydration of glucose to 5‐hydroxymethylfurfural (HMF) proceeds through the intermediate formation of fructose. Although chromium(II) and copper(II) chlorides are able to dehydrate fructose with high HMF selectivity, reasonable HMF yields from glucose are only obtained with CrCl2 as the catalyst. Glucose conversion by CuCl2 is not selective, while FeCl2 catalyst does not activate sugar molecules. These differences in reactivity are rationalized on the basis of in situ X‐ray absorption spectroscopy measurements and the results of density functional theory calculations. The reactivity in glucose dehydration and HMF selectivity are determined by the behavior of the ionic liquid‐mediated Lewis acid catalysts towards the initial activation of the sugar molecules. The formation of a coordination complex between the Lewis acidic Cr2+ center and glucose directs glucose transformation into fructose. For Cu2+ the direct coordination of sugar to the copper(II) chloride complex is unfavorable. Glucose deprotonation by a mobile Cl− ligand in the CuCl42− complex initiates the nonselective conversion. In the course of the reaction the Cu2+ ions are reduced to Cu+. Both paths are prohibited for the FeCl2 catalyst.

Selective adsorption of HMF on porous carbons from fructose/DMSO mixtures

5-Hydroxymethylfurfural (HMF) is an important intermediate chemical for producing valuable chemicals from biomass and can be synthesized with high yield from the dehydration of fructose in dimethyl sulfoxide (DMSO). Here, we investigate the room temperature separation of HMF from DMSO for a cost effective recovery of the product from the reaction mixture that contains unreacted fructose. BP2000, Norit1240, BP1300, BP880 and XC72 were tested as sorbents. BP2000 and Norit1240 exhibit selectivity and capacity for HMF. Depending on relative concentrations, HMF/fructose separation factors up to 45 for BP2000 and 13 for Norit1240 were obtained. Under certain conditions, by increasing the concentration of fructose in the solution, HMF adsorption increased significantly.