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A mixture of hexafluoroisopropanol (HFIP) and water was used as a new and unknown monophasic reaction solvent for fructose dehydration in order to produce HMF. HFIP is a low-boiling fluorous alcohol (b.p. 58 °C). Hence, HFIP can be recovered cost efficiently by distillation. Different ion-exchange resins were screened for the HFIP/water system in batch experiments. The best results were obtained for acidic macroporous ion-exchange resins, and high HMF yields up to 70% were achieved. The effects of various reaction conditions like initial fructose concentration, catalyst concentration, water content in HFIP, temperature and influence of the catalyst particle size were evaluated. Up to 76% HMF yield was attained at optimized reaction conditions for high initial fructose concentration of 0.5 M (90 g/L). The ion-exchange resin can simply be recovered by filtration and reused several times. This reaction system with HFIP/water as solvent and the ion-exchange resin Lewatit K2420 as catalyst shows excellent performance for HMF synthesis.

5-Hydroxymethylfurfural (HMF) is a very promising component for bio-based plastics. Efficient synthesis of HMF from biomass is still challenging because of fast degradation of HMF to by-products under formation conditions. Therefore, different studies, conducted mainly in monophasic and biphasic batch systems with and without water addition have been published and are still under investigation. However, to produce HMF at a large scale, a continuous process is preferable. Until now, only a few studies have been published in this context. In this work, it is shown that fluorous alcohol hexafluoroisopropanol (HFIP) can act as superior reaction solvent for HMF synthesis from fructose in a fixed bed reactor. Very high yields of 76% HMF can be achieved in this system under optimized conditions, whilst the catalyst is very stable over several days. Such high yields are only described elsewhere with high boiling reaction solvents like dimethylsulfoxide (DMSO), whereas HFIP with a boiling point of 58 °C is very easy to separate from HMF.

Chlorogenic acid (CGA) is a phenolic acid that ubiquitously exists in fruits. This work aims to investigate whether and how CGA influences HMF formation during heating fructose alone, or with an amino acid. The results showed that that CGA increased 5-hydroxymethylfurfural (HMF) formation. At pH 5.5 and 7.0, the addition of 5.0 μmol/ml CGA increased HMF formation by 49.4% and 25.2%, respectively when heating fructose alone, and by 9.0% and 16.7%, respectively when heating fructose with aspartic acid. CGA significantly increased HMF formation by promoting 3-deoxosone formation, and its conversion to HMF by inhibiting HMF elimination, especially in the Maillard reaction system. A comparison of the catalytic capacity of CGA with its six analogous compounds showed that both its di-hydroxyphenyl and carboxyl groups function in increasing HMF formation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Chemistry development of renewable resources is a real challenge. Carbohydrates from biomass are complex and their use as substitutes for fossil materials remains difficult (European involvement on the incorporation of 20% raw material of plant origin in 2020). Most of the time, the transformation of these polyhydroxylated structures are carried out in acidic conditions. Recent reviews on this subject describe homogeneous catalytic transformations of pentoses, specifically toward furfural, and also the transformation of biomass-derived sugars in heterogeneous conditions. To complete these informations, the objective of this review is to give an overview of the structural variety described during the treatment of two monosaccharides (D-Fructose and D-xylose) in acidic conditions in homogeneous phases. The reaction mechanisms being not always determined with certainty, we will also provide a brief state of the art regarding this., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Here, a series of nitrogen‐doped carbon (NC) supported transition metal oxide catalysts were prepared by pyrolysis of chitosan‐metal salt mixtures for the efficient synthesis 2,5‐diformylfuran (DFF) from 5‐hydroxymethylfurfural (HMF) and fructose. Among them, supported molybdenum‐based species on nitrogen‐doped carbon (Mo/NC) exhibited excellent activity and selectivity for selective oxidation of HMF to DFF. The presence of nitrogen species reduces the electron cloud density around the Mo species, thereby improving the catalytic activity. Moreover, the interaction between active MoO2 species on the catalyst surface and NC ensured the stability of the catalyst, resulting in no significant loss of activity after four catalytic cycles. 99.5 % and 55.1 % yields of DFF with full conversion were obtained from HMF and fructose respectively over Mo/NC‐chitosan‐600 in DMSO under ambient air. In order to enhance DFF yield from fructose, sulfonate groups were introduced into Mo/NC‐chitosan‐600 catalyst, leading to the highest DFF yield of 70.2 %. In addition, this catalyst also allowed 10.0%, 22.9% and 33.3% DFF yields from glucose, sucrose and inulin, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solvent polarity and basicity effect on fructose selective conversion was discussed. • High polarity-low basicity solvent was favorable for furfural formation. • High polarity-high basicity solvent promoted the HMF formation. • Solvents around fructose preferential arrangement caused the selective conversion. • High yields of furfural (76.2%, GBL-H 2 O) and HMF (90.5%, DMSO-H 2 O) were obtained. Selective transformation of biomass-based feedstocks into value-added energy chemical is one of the most critical steps in biorefinery process. Herein, we gave insight into solvent effect on selective production of furfural or 5-hydroxymethylfurfural (HMF) from fructose with the combination of experiments, nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulation. It was found that the selective formation of furfural and HMF was mainly dominated by solvent polarity and basicity, and solvent properties could change the reaction pathway of fructose. High polarity-high basicity solvent promoted HMF formation, while high polarity-low basicity solvent was conductive to furfural formation. The preferential arrangement of solvents around fructose tautomers, especially on different C-OH, consequently led to the different products. High yields of furfural (76.2%) and HMF (90.5%) were obtained in the solvents of γ-butyrolactone (GBL)–H 2 O and dimethyl sulfoxide (DMSO)–H 2 O. [ABSTRACT FROM AUTHOR]

Honey is an excellent alternative to be used in different applications by the food, pharmaceutical, and cosmetics industries. However, the use of honey in its liquid form can present several disadvantages due to its high viscosity and density. In addition, honey can naturally crystallize during storage time, limiting its application in new products by industries. Thus, an alternative to using liquid honey in industry is the powder form. The objective of this study was to obtain honey powder by spray drying using a plant-based protein as a carrier. The honey used as raw material showed acceptable physicochemical parameters by the legislation of honey quality control, such as pH of (4.0 ± 0.1), the water content of (20.70 ± 0.3) g/100 g, ash of (0.48 ± 0.02) g/100 g, the fructose content of (35.42 ± 0.14) g/100 g, (43.05 ± 0.46) g/100 g for glucose, (0.56 ± 0.02) g/100 g for sucrose, and 5-hydroxymethylfurfural (HMF) value of (37.47 ± 1.04) mg/kg of honey, leading to the production of the honey powder. The mixture of fresh honey and plant-based protein was made with dispersions of 15, 16 and 18 g/100 g of honey using isolated rice protein as a carrier (total solid at 30 g/100 g d.b.). Finally, the honey powder produced was physicochemically characterized. The dispersion with 16 g/100 g of honey achieved an intermediary sugar/honey recovery of 35.93 ± 0.82% and 68.54 ± 2.16% of total protein recovery, and the spray drying yield was satisfactory > 50%. The overall results suggested that this dispersion is the ideal formulation when commercialization of the honey powder as an ingredient is intended. [ABSTRACT FROM AUTHOR]

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In this work, a deep eutectic solvent (DES) composed of choline chloride (ChCl) and ethylene glycol (EG) was prepared and applied for the conversion of fructose to 5-hydroxymethylfurfural (HMF), catalyzed by HCl in both laboratory batch reactors and continuous flow microreactors. The effects of reaction temperature, batch time, catalyst loading and molar ratio of ChCl to EG on the fructose conversion and HMF yield were first investigated in the monophasic batch system of ChCl/EG DES. To inhibit HMF-involved side reactions (e.g., its polymerization to humins), methyl isobutyl ketone (MIBK) was used as the extraction agent to form a biphasic system with DES in batch reactors. As a result, the maximum HMF yield could be enhanced at an MIBK to DES volume ratio of 3:1, e.g., increased from 48% in the monophasic DES (with a molar ratio ChCl to EG at 1:3) to 63% in the biphasic system at 80°C and 5 mol% of HCl loading. Based on the optimized results in batch reactors, biphasic experiments were conducted in capillary microreactors under slug flow operation, where a maximum HMF yield of ca. 61% could be obtained in 13 min, which is similar to that in batch under otherwise the same conditions. The slight mass transfer limitation in microreactors was confirmed by performing experiments with microreactors of varying length, and comparing the characteristic mass transfer time and reaction time, indicating further room for improvement. Highlights: • The efficient fructose conversion to HMF in deep eutectic solvents was achieved in batch reactors and microreactors. • An HMF yield over 60% could be obtained at a fructose conversion above 90% in both reactors at 80°C within 14 min. • The HMF yield was enhanced from 48% in the monophasic ChCl/EG system to 63% in the DES-MBIK biphasic system in batch. • A slight mass transfer limitation was found in the biphasic slug flow microreactor. [ABSTRACT FROM AUTHOR]

The production of polymers from lignocellulosic biomass is currently one of the challenges to minimizing dependence on fossil fuels such as oil. The cellulosic fraction of this feedstock can be transformed into simple sugars such as glucose or fructose. These sugars can be further converted into 2,5-furandicarboxylic acid (FDCA), a precursor of polyethylene furanoate (PEF). The dehydration of sugars to 5-hydroxymethylfurfural (HMF), a platform molecule to obtain products of interest, has been extensively studied. In addition, the oxidation of this platform molecule to FDCA has been widely investigated. However, a study of the direct or one-step production of FDCA from sugars is needed. This review provides a general overview of the recent research on the catalytic systems for the direct production of FDCA from sugars. Ideally, a single-stage system should be employed. The investigations carried out in a one-step process are first detailed. Different strategies have been tested, such as the physical separation of two phases, where dehydration and oxidation took place separately. In this case, an efficient transfer of HMF is needed. To avoid HMF transfer limitations, other authors focused on the investigation of the one-pot transformation of HMF without physical separation. The major requirement of these processes is to achieve catalytic systems functional for both dehydration and oxidation reactions. Therefore, other investigations focused on the study of two-step integrated systems are also analyzed in this review. [ABSTRACT FROM AUTHOR]

5-hydroxymethylfurfural (HMF) is formed by reducing sugars in honey in acidic environments by the Maillard reaction and is known as a carcinogenic, mutagenic and genotoxic compound. The aim of this study is to investigate the toxic HMF content of unbranded flower honey samples sold under the sun under inappropriate conditions and unsupervised on the highway sides and to make an evaluation in terms of food safety. The quality of the analysis results was guaranteed by participating in an international proficiency test. Analysis was performed on a High-Performance Liquid Chromatography (HPLC) device with Diode Array Detector (DAD) and Refractive Index (RI) detectors- The HMF levels of 5 honey samples were determined to exceed the legal limit (40 mg kg-1). It is revealed by the current study that the honey sold on the roadside is not safe in terms of toxic HMF. In addition, 5 samples were not found to comply with the regulation in terms of glucose + fructose content and 2 samples in terms of fructose/glucose ratio. Thus, it has also been determined that these honeys are not reliable in terms of purity. [ABSTRACT FROM AUTHOR]

The aim of the study is to determine the mineral content and some quality parameters of Thrace region floral and honeydew honeys. Quality parameters such as soluble solid, pH, electrical conductivity, free acidity, sugar content and mineral content (Ca, Fe, K, Mg, Na, Zn, P, Se) were determined and evaluated in 25 honey samples including 16 sunflower, 2 gorse, 3 canola, 3 oak and 1 linden honey locally produced in Trace Region, Turkey. Mineral contents of the samples were determined by Inductivelly Coupled Plasma Optical Emission Spectrometer (ICP-OES). The most abundant minerals were potassium, phosphorus and calcium, ranging between 18.91–1018.74, 244.40–429.98 and 8.50–140.82mg/kg, respectively. The mean values were determined as pH 4.42 (3.86-6.54), soluble dry matter 81.4°Bx (79.3-83.0), free acidity 15.66 mEq/kg (9.00-28, 00), HMF 13.00 mg/kg (0.16-33.45), electrical conductivity 595 μS/cm (207-1376), glucose 33.66% (25.51- 38.58), fructose 38% .17 (33.32-47.91) and sucrose 0.17% (0.01-0.67). [ABSTRACT FROM AUTHOR]

A diverse suite of Zn-SAPO-34 catalysts was synthesized employing three distinct methodologies for the incorporation of zinc species: thermal ion exchange, wet impregnation, and physical mixing. The catalysts were characterized using various analytical techniques including XRD, FT-IR, BET, SEM, XRF, XPS, NH 3 -TPD, and Py-IR, to elucidate the crystal structure, morphology, surface acidity, and the presence of zinc species within the catalysts. The study showed that the method of zinc introduction markedly impacts the physicochemical properties of the catalysts. Different approaches to introducing zinc species significantly influence the acid strength and type on the catalyst surface, with variations in the existing states of zinc across the catalysts. Specifically, zinc species introduced via thermal ion exchange coexist as ZnOH+ and ZnO within the catalyst, whereas those from wet impregnation and physical mixing are individually present as either ZnOH+ or ZnO. Furthermore, the study examined the catalytic performance of these Zn-SAPO-34 catalysts in the dehydration of fructose to produce 5-hydroxymethylfurfural (HMF). Catalysts prepared via thermal ion exchange exhinited superior performance, achieving an remarkable HMF yield of 94.6 %. Additionally, in situ infrared technology was used to investigate the effect of zinc species introduction on the fructose dehydration process, indicating suggesting that the introduction of zinc species enhances the transformation of fructose molecules. • The preparation method directly influences the state of Zn species on the catalysts. • The states of Zn species on various catalysts encompass ZnO and ZnOH+. • The catalyst prepared via thermionic exchange exhibits the highest yield of HMF. • The introduction of zinc species enhances the transformation of fructose molecules. [ABSTRACT FROM AUTHOR]

Levoglucosan (LGA), as the main primary anhydrosugar of cellulose pyrolysis, is of great significance for future value-added chemicals production. In this study, effective conversion of LGA to 5-hydroxymethylfurfural (HMF) was investigated in a NaCl–H 2 O/acetone biphasic system over sulfonated resin and AlCl 3. The results show that the biphasic system could efficiently inhibit the overreaction of HMF compared with pure water, leading to a significant enhancement of HMF production. HMF was obtained with the highest yield of 68.5 % at 96.5 % of LGA conversion at the optimized conditions. The use of cellobiose as substrate produced 61 % of HMF while LGA-rich bio-oil led to a sharp decease of HMF yield to 33 %. Through the respective experiments using LGA, glucose and fructose as the substrates, the reaction network was constructed for kinetic analysis, and satisfactory fitting results are observed in agreement with the experimental results, providing the best conditions for producing glucose and HMF, respectively. In addition, the mechanism of LGA conversion to HMF was calculated by DFT, which needs to overcome the highest free energy barrier of 121 kJ/mol. [Display omitted] • LGA conversion to HMF is employed in a NaCl–H 2 O/acetone biphasic system. • The reaction pathway is clarified by the synergistic effect of sulfonated resin and AlCl 3. • HMF was obtained with the highest yield of 68.5 % at 96.5 % of LGA conversion. • Results predicted by the kinetics are well consistent with the experimental results. • LGA conversion to HMF has an energy barrier of 121 kJ/mol by DFT calculations. [ABSTRACT FROM AUTHOR]

5‐hydroxymethylfurfural (HMF) is the object of extensive research in recent times. The challenge in the industrial production of HMF is the choice of cheap, hexose feedstock. This study compares continuous HMF synthesis from hexoses—fructose and glucose, and biomass—Miscanthus × giganteus and chicory roots. The experiments were conducted in technical‐scale biorefinery (TRL 6/7). In the first stage, optimal conditions for the production of HMF from hexoses were selected using sulfuric acid as a catalyst in an aqueous medium. The following conditions were chosen for fructose: temperature of 200°C, the reaction time of 18 min, and pH = 2, and for glucose: 210°C, 18 min, and pH = 3. Under these conditions, the HMF yield was 56.5 mol% (39.6 wt.%) from fructose and 18.1 mol% (12.6 wt.%) from glucose. From the biomass, the HMF yields were 36.7 and 16.2 wt.% for miscanthus and chicory roots, respectively. Some results from the conversion of biomass solutions are unexpected and show a need for further investigations. This work has demonstrated the capacity to produce HMF from biomass as part of an environmentally friendly process in a biorefinery. Further research in this field and process optimization will be a step forward in the sustainable production of bioplastics. [ABSTRACT FROM AUTHOR]

The conversion of glucose and fructose to 5-hydroxymethylfurfural (HMF) was investigated using a series of functionalized SBA-15 catalysts in a glass tube reactor. The synthesized SBA-15 as a support was grafted with various organosilanes in order to acquire the acid-modified SBA-15 (SBA-A), acid- and hydrophobicity-modified SBA-15 (SBA-AC), and base-modified SBA-15 (SBA-N) catalysts. Effects of the reaction temperature and time, reactant concentration, and catalyst loading level on the catalyst performances in this reaction, in terms of the hexose conversion level, product yield, and selectivity, were evaluated. The prepared catalysts were extensively characterized by X-ray diffractometry, nitrogen adsorption–desorption, Fourier transform infrared spectrometry, CHN/S elemental analysis, solid-state nuclear magnetic resonance spectroscopy, contact angle measurement, and acid–base titration. The hexose-to-HMF reaction was greatly enhanced by increasing the reaction temperature, whereas the other factors had only a minor effect. In the case of the glucose-to-HMF production, the SBA-N catalyst exhibited reasonably high levels of glucose conversion and HMF yield, but its catalytic activity was pretty low for the fructose-to-HMF reaction. Herein, fructose was identified as an intermediate substance for further dehydration to HMF. The different catalyst types provided different functions, where isomerization required a basic property, whereas dehydration was optimal over an acidic one. Suppression of the levulinic acid formation was obtained via an increased hydrophobicity of the SBA-AC catalyst. [ABSTRACT FROM AUTHOR]

Metal organic framework UiO‐66 is studied as an adaptable heterogeneous catalyst for glucose conversion. UiO‐66 was modified by; i) partial linker substitution, ii) particle size modulation and iii) linker defects. We studied the effect of crystallinity and functional groups on the glucose conversion and product yields. The main products are: i) fructose from the isomerisation of glucose, ii) mannose from the epimerisation of glucose and iii) 5‐hydroxymethyl furfural from the dehydration of fructose. We found that defective and nano crystalline UiO‐66 catalyst performs best for isomerisation. When 50 % of the linkers of UiO‐66 are replaced by a sulfonate‐containing linker, the catalyst shows higher isomerisation activity than other UiO‐66 catalysts. Naphthalene‐dicarboxylate linkers were introduced to induce hydrophobicity and this catalyst further increased isomerisation activity showing 31 % fructose selectivity. Finally, the promising catalysts were tested in a flow reactor and a bifunctional mixed linker catalyst possessing both hydrophobic and acidic functional groups is shown to be stable in a time‐on‐stream study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Niobia-based magnetic nanoparticles (MNP) coated with Nb 2 O 5 or Nb 2 O 5 -SiO 2 shells were prepared. • Prepared catalysts may produce HMF selectively by glucose dehydration. • High selectivity to HMF was correlated to pseudohexagonal niobium oxide (TT-Nb2O5) phase. • High catalytic activity was correlated to the small nanoparticles size. Niobia-based magnetic nanocomposites were prepared by covering magnetite nanoparticle cores (Fe 3 O 4 , MNP) with either Nb 2 O 5 or Nb 2 O 5 -SiO 2 shells using a two-step procedure. In the first step magnetite nanoparticles were prepared by the coprecipitation method. The second step involved their coverage with either Nb 2 O 5 shells, through a precipitation method, or with Nb 2 O 5 -SiO 2 shells, through a sol-gel protocol followed by precipitation in the presence of the CTAB surfactant. The obtained materials were exhaustively characterised by X-ray diffraction, Mössbauer spectroscopy, magnetic measurements, ICP-OES, DRIFT and Raman spectroscopy, and CO 2 - and NH 3 -TPD measurements, and investigated for glucose dehydration to HMF. The catalytic performances were directly correlated to the nature of the supported niobia phases, which, in turn, has been dictated by the niobia content and the preparation route. The high selectivity to HMF was correlated with to the large pseudohexagonal niobium oxide (TT-Nb 2 O 5) phase while the catalytic activity was directly correlated to the small nanoparticles size. A proper combination of these features led to an optimum catalytic system for the selective production of HMF through glucose dehydration. A third important feature making the developed catalyst promising is its magnetic property, ensured by the magnetite nanoparticles core. This allowed its easy separation from the reaction products. [ABSTRACT FROM AUTHOR]

The sulfonated H‐β zeolite was successfully prepared and used for the synthesis of levulinic acid (LA) from D‐fructose. The catalyst was characterized by powder X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, N2 physisorption, NH3‐temperature programmed desorption and carbon–hydrogen–nitrogen–sulfur analysis. The total acid amount is increased with increase in sulfur loading, confirmed that the sulfonic acid group (SO3‐H) is successfully grafted onto zeolite structure. The various parameters such as different amount of sulfur loading, reaction temperature, time, catalyst loading was studied for selective production of LA. The catalytic activity of sulfonated H‐β (S‐β) zeolite was found to be efficient for synthesis of LA from D‐fructose in aqueous media. Maximum LA yield of 43.5 mol%, low HMF yield (<1%) with 98.15% fructose conversion was obtained with 3% S‐β catalyst at 160°C for 7 hr. The catalyst was reusable for minimum three times by H2O2 regeneration. This study provides the new zeolitic catalyst for the efficient production of LA at shorter reaction time (7 hr) and low catalyst to substrate ratio (0.7:1). [ABSTRACT FROM AUTHOR]

Honey is a complex foodstuff found in nature which is used without any processing. Honey has been in use in medicine as well as raw food since ancient times. Essentially, it is a blend of sugars especially fructose and glucose. The objectives of the study were to determine major sugar composition as well as pesticides contamination in honey samples. Further, Hydroxy-methyl-furfuraldehyde (HMF) level was also determined to ascertain the freshness of honey samples. A total of 14 samples were collected from local market and tested for fructose, glucose, sucrose, HMF and organochlorine pesticides using HPLC and GC–MS techniques respectively. The total sugars in the 14 honey samples were found ranging between 50.26 and 74.74 g/100 g of honey. The chromatographic results showed the presence of the sugars like fructose and glucose in all honey samples. The honey sample SH–11 was found to contain the highest amount of fructose (40.63%). On the other hand, the lowest amount of fructose with 29.08% was observed in SH–7. The HPLC analysis also revealed the presence of sucrose in two samples but under the permissible limit. The average ratio of fructose to glucose in these honey samples was 1.3. None of the sample has ratio below 1.0 indicating lesser chances for honey to crystallize on storage. Out of 14 honey samples, 13 samples were found negative for the presence of any of the 63 pesticides tested. Only sample No. 13, was found to contain 15.95 ppb hexachlorobenzene per kilogram of honey. The HMF was not detected in four samples but in remaining samples it was well below the maximum permissible limit. No pesticide and sugar adulteration was observed in any of the honey samples. The honeys collected from Saudi Arabian markets were found to confirm the standards set by the regional and international standardization organization, the GSO and Codex Alimentarius Commission respectively. [ABSTRACT FROM AUTHOR]

This study was aimed to determine some quality parameters of honeys produced in Çorum province. Quality parameters such as pH, soluble solid, HMF, moisture content, electrical conductivity, ash, free acidity, diastase and sugar were evaluated for 47 honey samples. The mean values were determined as pH 3.83 (3.55-4.20), soluble solid 81.5°Bx (76.8-83.8), moisture 16.9% (14.5-21.7), free acidity 32.2 meq/kg (21.1-47.8), HMF 3.5 mg/kg (0.3-36.5), ash 0.18% (0.02-1.58), electrical conductivity 350 µS/cm (205-674), diastase activity 16.4 (0.1-32.2), glucose 30.4% (26.0-34.3), fructose 35.3% (31.5-39.1), sucrose 0.34% (<0.05-4.64), sum of glucose and fructose 65.8% (57.5-73.4) and the ratio of fructose to glucose 1.16 (1.03-1.24). The results generally show that honey samples were acceptable for legal limits according to Turkish Food Codex. However, one sample was not comply with the legislation in terms of moisture content and sum of glucose and fructose, and also three samples were not comply in terms of diastase number. [ABSTRACT FROM AUTHOR]

The oxidation of 5-(Hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is of high interest for the production of renewable monomers. To achieve a cost-efficient, sustainable process for the large-scale production of FDCA, it is important to use the as-synthesized crude HMF-solution without extensive purification steps. In this work, we present the direct oxidation of crude HMF-solution produced from fructose syrup with an AuPd/C catalyst. The catalyst shows good tolerance against various remaining impurities from the HMF-preparation. A 95% FDCA yield with a productivity of 75.5 mol FDCA mol AuPd −1 h−1 could be achieved under increased temperature (140 °C) and pressure (40 bar) with only 2 eq. Na 2 CO 3. We further improved the process' efficiency by using a two-step oxidation with a split addition of the base in the same reactor. First, a mild oxidation (1 eq. Na 2 CO 3 , 100 °C, 1.5 h) of HMF afforded the intermediates HFCA and FFCA, which were then further oxidized under harsher conditions (3.3 eq. NaOH, 140 °C, 4 h) to FDCA. Due to the higher efficiency, this process enabled increasing the HMF concentration up to 0.3 M for crude solution and 0.6 M for purified solution while minimizing the degradation of HMF, leading to a more cost-efficient oxidation of crude HMF-solution, and facilitating the industrial implementation of renewable FDCA. [Display omitted] • Direct use of crude fructose-based HMF eliminates purification and reduces costs. • AuPd/C catalyst yields 95% FDCA, tolerating impurities inherent to the bio-source. • 75.5 mol FDCA mol AuPd −1 h−1 productivity at optimized conditions. • Enhanced efficiency by "one-pot two-step" process allowing higher HMF-concentration. • Up-scaling potential through decreasing the volume and minimizing purification. [ABSTRACT FROM AUTHOR]

We employ in-line FTIR monitoring, in-situ 13C NMR, and HPLC-MS techniques to investigate the formation mechanism and pathway of 5-hydroxymethylfurfural (HMF) from fructose dehydration. Additionally, the rationality of the cyclic formation mechanism is theoretically verified using DFT. [Display omitted] • The dehydration of fructose to produce 5-hydroxymethylfurfural (HMF) is initial ring formation followed by dehydration. • The initial stable intermediate is a furan-type fructose. • The key intermediates in the cyclic mechanism exhibit greater electronegativity differences at the reaction sites. The formation mechanism and pathway of HMF from fructose dehydration were investigated using in-line FTIR monitoring and in-situ 13C NMR in this study. The results of the infrared absorption spectrum obtained at different time intervals during the reaction process showed significant inconsistencies with the acyclic pathway. However, the in-situ NMR analysis revealed the direct observation of two intermediates, fructose furan and (4R-5R)-4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-formaldehyde, providing direct evidence to support the cyclic carbocation pathway. This study also included theoretical analysis of the intermediates involved in the key steps of various reaction pathways using density functional theory (DFT) calculations. The key steps in the cyclic pathway were found to have lower activation energy compared to the acyclic pathway, while exhibiting significant differences in electronegativity at the reaction sites. The computational results not only reveal but also provide support for the rationality of the cyclic formation mechanism. The response surface methodology (RSM) was utilized to optimize the preparation process of HMF through fructose dehydration. It enabled determination of the significance order for each factor (reaction temperature > reaction time > mass percentage of water in the solvent) and identification of the optimal process conditions (reaction time of 3.5 h, reaction temperature of 143.5 °C, mass percentage of water in the solvent of 5.0 %, and maximum yield of 5-HMF reaching 82.4 %). [ABSTRACT FROM AUTHOR]

Zeolite-metal organic framework nanocomposite catalyst is developed for the synthesis of 2-((5-(hydroxymethyl)furan-2-yl)methylene)malononitrile from sucrose/fructose/glucose via one-pot cascade protocol. To accomplish this objective, zeolite Beta and Zr based metal- organic frameworks such as UiO-66 and UiO-66-NH 2 are investigated for the independent steps, i.e. the conversion of sucrose to HMF and the Knoevenagel condensation of HMF and malononitrile. Beta zeolite exhibits the best activity in the sucrose to HMF conversion, whereas UiO-66-NH 2 exhibits the best activity in the Knoevenagel condensation. Therefore, zeolite Beta and UiO-66-NH 2 are integrated to develop a highly sustainable and efficient multi-functional catalyst for the conversion of sucrose to 2-((5-(hydroxymethyl)furan-2-yl)methylene)malononitrile via one-pot cascade reaction. The composite catalyst contains the optimum acidity and basicity for the cascade reaction. The presence of both the frameworks in the composite material is confirmed by using various physico-chemical characterization techniques. Further, the integration of both the active frameworks enhances the chemical stability and recyclability of the composite catalyst in the cascade reaction. This study demonstrates a unique approach to develop a synthesis strategy for the integration of inorganic zeolite and MOFs to achieve the desired activity, selectivity, and stability of the developed catalyst. [ABSTRACT FROM AUTHOR]

The extraction of fructan and sugars from chicory roots is promising with regard to the production of 5-hydroxymethylfurfural. In this study, the extraction of chicory roots after the salad production was investigated for the first time in order to determine the extraction kinetics. Chicory roots were cut into different shapes (juliennes, slices, and cubes) and were extracted at different temperatures (T = 65 °C; T = 80 °C; T = 90 °C) and with different solid-to-liquid ratios (1:5; 1:10; 1:20) in batch experiments. Maximum extraction yields (90.15% of extracted sugars) were achieved for T = 80 °C and chicory roots that were cut into julienne shape. A solid-to-liquid ratio of 1:10 should be maintained in order to keep the process economical. Regarding the subsequent use of the extract for 5-hydroxymethylfurfural production, 89.5% of initial fructose and 89.8% of initial fructan were extracted at 80 °C. According to this, the sugar-containing extracts could be used in the future in decentralized biorefineries to produce 5-hydroxymethylfurfural directly from chicory roots as an agricultural residue. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to understand the detailed reaction mechanism of aluminum alkoxy‐catalyzed conversion of glucose to 5‐hydroxymethylfurfural (HMF) using Al(OMe)3 as catalyst. Potential energy surfaces were studied for aggregates formed between the organic compounds and Al(OMe)3 and effects of the medium were considered via continuum solvent models. The reaction takes place via two stages: isomerization from glucose to fructose (stage I) and transformation of fructose to HMF (stage II). Stage II includes three successive dehydrations, which begins with a 1,2‐elimination to form an enolate (i.e., B), continues with the formation of the acrolein moiety (i.e., D), and ends with the formation of the furan ring (i.e., HMF). All of these steps are facilitated by aluminum alkoxy catalysis. The highest barriers for stage I and stage II are 23.9 and 31.2 kcal/mol, respectively, and the overall catalytic reaction is highly exothermic. The energetic and geometric results indicate that the catalyzed reaction path has feasible kinetics and thermodynamics and is consistent with the experimental process under high temperature (i.e., 120 °C). Remarkably, the released water molecules in stage II act as the product, reactant, proton shuttle, as well as stabilizer in the conversion of fructose to HMF. The metal–ligand functionality of the Al(OMe)3 catalyst, which combines cooperative Lewis acid and Lewis base properties and thereby enables proton shuttling, plays a crucial role in the overall catalysis and is responsible for the high reactivity. © 2019 Wiley Periodicals, Inc. The metal–ligand functionality of the Al(OMe)3 catalyst, which combines cooperative Lewis acid and Lewis base properties and thereby enables proton shuttling, plays a crucial role in the overall catalysis of glucose‐to‐HMF conversion and is thus responsible for the high reactivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Valorisation with in-situ CO/H2 Highlights • Methoxycarbonylation of 1-hexene to methyl hepatanoate using HMF as CO surrogate with Pd-complex is studied in methanol. • Methyl levulinate and GVL are found to be other major ester products when changing the concentration of acid additive. • The influence of phosphine ligand and Pd source on the yield of ester products is investigated. • The direct conversion of sugars, such as glucose and fructose to ester products is studied in methanol with Pd-complex. Abstract A cascade reaction involving decarbonylation of 5-hydroxymethylfurfural (HMF) followed by methoxycarbonylation of 1-hexene produces methyl heptanoate (MH) using a catalytic system composed of a Pd-phosphine complex and methanesulfonic acid (MSA) co-catalyst at moderate reaction temperature. Concomitant hydration of HMF followed by hydrogenation of methyl levulinate (ML) to γ-valerolactone (GVL) occurs with the catalytic system under the same reaction conditions using HMF and methanol as the source of CO and H 2 , respectively. Under optimized reaction conditions, about 50% of MH along with 12% ML and 35% GVL is obtained from HMF using Pd-(1,2-bis(di-tert-butylphosphinomethyl)benzene) (DTBPMB), MSA and 1-hexene in methanol at 120 °C. Interestingly, sugars, such as glucose, fructose and xylose, are able to be converted to MH, ML and GVL as well. Isotopic labeling studies with 13C 1 -fructose in methanol-d 4 and 13C-methanol-d 4 confirm that H 2 originates from methanol, while CO generates predominantly from the formyl group of the HMF formed by fructose dehydration. [ABSTRACT FROM AUTHOR]

Abstract A mesoporous SBA-15 supported sulfonic acid catalyst (SBA-15-SO 3 H) was successfully prepared and used for the selective conversion of fructose to 5-hydroxymethylfurfural (HMF). Up to 96% of HMF selectivity with 100% fructose conversion was obtained under mild conditions (120 °C, 60 min, DMSO as solvent). Solvent effect, reaction time, reaction temperature and fructose-to-catalysts mass ratio have been investigated. The SBA-15-SO 3 H solid acid catalyst can be separated from the reaction mixture after reaction and reused by simple centrifugalization, and 100% fructose conversion with 95% HMF yield could be retained. Further, reaction activation energy of 56.4 kJ/mol has been fitted with kinetic analysis, which means that the dehydration of fructose into HMF is relative easier over SBA-15-SO 3 H catalyst in this work. Besides, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) measurements reveal that the –SO 3 H grafting on the SBA-15 surface have no obvious influence on its mesoporous structure even after five catalytic cycles, and acid site measurements demonstrate that there was no significant loss of acid site concentration, indicating high catalytic stability. This fruit give a useful reference to chemical engineering and materials, besides future energy and smart city. Highlights • An efficient mesoporous SBA-15 supported sulfonic acid catalyst (SBA-15-SO 3 H). • Up to 96% HMF yield with 100% fructose conversion could be achieved. • Fructose solubility and solvent polar play work together on SBA-15-SO 3 H activity. • The reaction activation energy for fructose is 56.4 kJ/mol which is lower than previous reports. [ABSTRACT FROM AUTHOR]

An extractive-reaction process for the synthesis of HMF from fructose was implemented in microreactor. Experimental conditions were 10 wt.% fructose in water, MIBK as extracting solvent and HCl as catalyst in a temperature window of 120-160 °C, a MIBK/H2O ratio 1 to 9 and an HCl concentration of 0.25-2 M. The dehydration of fructose to HMF is achieved in less than 40s with a total HMF yield higher than 90% at 150 °C. Aqueous and organic phase spontaneously separate at the outlet of the reactor and HMF is obtained in MIBK with a yield of 80% and a purity of 92%.ᅟ [ABSTRACT FROM AUTHOR]

Hydroxymethylfurfural (HMF) has an outstanding position among bio-based platform chemicals, because high-value polymer precursors and fuel additives can be derived from HMF. Unfortunately, the large-scale industrial production of HMF is not yet realized. An open research question is the choice of hexose feedstock material. In this study, we used the highly available disaccharide sucrose for HMF synthesis. The conversion of sucrose was catalyzed by sulfuric acid in water media. Experiments were conducted at temperatures of 180, 200, and 220 °C with reaction times of 2-24 min. A carbon balance showed that the yield of unwanted side products rose strongly with temperature. We also developed a kinetic model for the conversion of sucrose, involving nine first-order reactions, to uncover the kinetics of the main reaction pathways. Within this model, HMF is produced exclusively via the dehydration of fructose. Glucose isomerizes slowly to fructose. Side products arise simultaneously from glucose, fructose, and HMF. A pathway from hexoses to xylose via reverse aldol reaction was also included in the model. We believe that sucrose is the ideal feedstock for large-scale production of HMF because it is more abundant than fructose, and easier to process than sugars obtained from lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Four Fe-containing ionic liquids (ILs) were synthesized by coupling of conventional imidazole ionic liquids [Cmim]Cl ( x = 4, 8, 12, 16) with FeCl and were characterized by FT-IR, Raman, ESI-MS and TG. All of the Fe-containing ILs were applied to the conversion of fructose into 5-hydroxymethylfurfural (HMF) in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) subsequently and the result showed that [Cmim]FeCl exhibited excellent catalytic performance. Then the different reaction parameters with [Cmim]FeCl as catalyst were studied in detail. A 92.8% yield of HMF was obtained with 0.03 g [Cmim]FeCl and 0.1 g fructose in 1.0050 g [Bmim]Cl at 80 °C for 40 min in fructose/[Bmim]Cl solution. [ABSTRACT FROM AUTHOR]

The dehydration of fructose in aqueous and biphasic system was studied using heteropolyacids, immobilized in silica, as catalyst. The catalysts were characterized by ICP-AES, nitrogen sorption, NH 3 -TPD, TEM, FT-IR, XRD, and TGA. The effect of different parameters, such as reaction temperature, reaction time, catalyst loading and volume ratio of water with methyl isobutyl ketone (MIBK) was studied. Silica included tungstosilisic acid (HSiW) was found to function as an efficient catalyst for the transformation of fructose into 5-hydroxymethylfurfural in aqueous phase. Addition of MIBK into the reaction system can increase both of fructose conversion and HMF selectivity. Besides, MIBK showed a positive effect in increasing the stability of the catalyst by suppressing the formation and deposition of humins over catalyst surface. After the third catalysis cycles, a stabilization of the catalytic activity was observed. [ABSTRACT FROM AUTHOR]

Well-ordered KIT-6 mesoporous silica was synthesized via a sol–gel process and functionalized with sulfonic acid groups. The catalyst was characterized using XRD, BET, TGA, SEM, TEM and pyridine FTIR spectroscopy techniques. The prepared catalyst was used to catalyze the conversion of fructose to 5-hydroxymethylfurfural (HMF) in DMSO. Various reaction parameters such as effect of reaction temperature, reaction time, catalyst loading, and solvent on HMF yield were investigated. A fructose conversion of 100% and 84.1% yield of HMF was obtained at 165 °C after 30 min in DMSO. The reaction is quite selective toward HMF. The catalyst was used several times without significantly losing its catalytic effect. [ABSTRACT FROM AUTHOR]

A carbon-based solid acid catalyst was prepared via hydrothermal method using glucose as carbon precursors and aqueous solution of H 2 SO 4 as sulfonation agent. The as-synthesized solid acid catalyst was attempted in the catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF). The effects of acid site density, reaction time, solvents, catalyst amount, temperature and mole ratio of catalyst to substrate were investigated. Under the optimum reaction conditions, the HMF yield of 90% was achieved in dimethylsulfoxide (DMSO) solvent at 160 °C after 1.5 h reaction time duration. The solid acid catalyst can be separated from the reaction mixture after reaction and reused without substantial loss in catalytic activity. [ABSTRACT FROM AUTHOR]

Metal dispersion is key for designing highly active and well-defined catalytic systems. Herein, to shed light on the effects of Nb dispersion on the conversion of fructose into HMF, highly porous silica glasses grafted with niobium oxide were prepared. Preliminary catalytic screening was done for the microwave-assisted conversion of fructose into 5-hydroxymethylfurfural (HMF) in a biphasic system. The highly porous silica glasses impregnated with niobium oxide presented HMF productivities about 10- to 20 times higher than the mesoporous NbOPO 4 reference material. Intriguingly, humin formation correlates with HMF yield regardless of the catalyst employed, although metal dispersion influences the acidity profile. [Display omitted] • Highly porous silica glasses allow for high surface dispersion of niobium oxide. • Niobium-containing mesoporous glass catalyzes the dehydration of fructose to HMF. • Fast and efficient conversion of fructose is obtained by microwave irradiation. • Low loading of Nb on the glass matrix allows tailoring Lewis and Brønsted acid sites. [ABSTRACT FROM AUTHOR]

We conduct a combined experimental and computational study to reveal the kinetics of tandem glucose isomerization and fructose dehydration to 5-hydroxymethylfurfural (HMF) over a bifunctional zeolite H-BEA-25 in water. The model accounts for multicomponent adsorption, homogeneous Brønsted acid catalyzed chemistry of fructose, intrinsic heterogeneous Lewis acid catalyzed isomerization, Brønsted acid catalyzed fructose dehydration, HMF rehydration, and humin formation chemistry. The octahedrally coordinated extra-framework Al sites catalyze glucose to fructose isomerization effectively. The activation energy for the isomerization in H-BEA-25 is between those reported for Ti-BEA and Sn-BEA. We reveal that tandem reactions exhibit multiple kinetic regimes. When a bifunctional catalyst with a fixed total number of acid sites is used (e.g., aluminosilicate zeolites), the HMF formation rate exhibits a volcano type curve vs. the Lewis to Brønsted acid site ratio. On the other hand, when the two types of sites are varied independently (e.g., in Sn-BEA and HCl), the HMF formation rate increases and then approaches a plateau with increasing Brønsted acid site density. These appear to be generic features of tandem reactions catalyzed by multiple or multifunctional catalysts. We show that materials with stronger sugar adsorption would produce HMF in significantly higher yields and higher rate than H-BEA. When HMF degradation reactions are suppressed, a ratio of Lewis to Brønsted acid sites of ∼0.3 maximizes the HMF rate produced from glucose and the HMF yield (which is predicted to be ∼60% at 130 °C). These predictions provide a framework for understanding and improving tandem reactions catalyzed by heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Liquid-liquid extraction of fructose, 5-hydroxymethylfurfural (HMF), and HMF rehydration products, levulinic acid (LA) and formic acid (FA), from aqueous solutions to C4 to C7 linear and branched alcohols was studied. The alcohol-water partition coefficients for these compounds were measured at 30 °C and 1 atm. The COSMO-SAC method was used to predict these partition coefficients and the water/alcohol and HMF/water/alcohol liquid-liquid equilibria. The predictions are in good agreement with experiments, and both show that the partition coefficients decrease with increasing the number of carbon atoms in the alcohols. Furthermore, with the same alcohol, the partition coefficient of HMF is higher than that of fructose and the HMF rehydration products. The agreement between the results of experiments and calculations indicates that the COSMO-SAC method is reasonable for the prediction of such thermodynamic data, and can be used to provide insights into the separations of these systems that is generally lacking in biomass processing. This is an important step towards screening organic solvents for liquid-liquid extraction that may preferentially extract HMF from an aqueous phase into an organic phase, thereby preventing HMF rehydration. [ABSTRACT FROM AUTHOR]

A novel CoAl-hydrotalcite catalyst with different Co2+/Al3+ratios was facilely synthesized using a modified coprecipitation method. Different techniques such as X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) were used to characterize the resultant CoAl-hydrotalcite. It was indicated that high crystallinity and a single-phase, layered structure with good composition was successfully fabricated. The resultant CoAl-hydrotalcite catalysts and two comparative hydrotalcites (ZnAl-HT and NiAl-HT) were employed for the selective dehydration of D-fructose into platform chemical 5-hydroxymethylfurfural (HMF), which is a versatile intermediate for the production of biofuels and value-added chemicals. It was shown that the metal variation in Co2+/Al3+ratios and reaction temperature display clear influence on the catalytic activities. Furthermore, the spent CoAl-hydrotalcite catalysts were easily recycled and show high catalytic stability over three consecutive runs. [Supplementary materials are available for this article. Go to the publisher's online edition ofChemical Engineering Communicationsfor the following free supplemental resources: Table S1 and Figure S1.] [ABSTRACT FROM PUBLISHER]

Highlights: [•] Moderate dissolution of zeolites occurs during aqueous fructose dehydration. [•] Dissolution occurs for many zeolite frameworks and Si/Al ratios. [•] The dissolved species catalyze fructose and HMF side reactions, but not fructose isomerization. [•] The dissolved species are likely small fragments of the zeolite frameworks. [ABSTRACT FROM AUTHOR]

Abstract: Polymer-supported NHC–metal catalysts were prepared from chloromethyl polystyrene resin via two-step reaction. Metals were loaded into 1.6 – 16mol% of total imidazolium and the remaining imidazolium chloride salt provided ionic liquid moiety. The formation of metal complex with the polymer-supported NHC ligand was analyzed by ATR FT-IR, XRD, and XPS. The synthesized polymer-supported NHC–metal catalysts were applied to the dehydration of fructose into HMF. The environmentally benign and inexpensive polymer-supported NHC–FeIII catalyst showed good catalytic activity and yielded HMF at 73% (with a conversion of 97%). It could also be reused without significant loss of catalytic activity. [Copyright &y& Elsevier]

The analysis was carried out of 5-hydroxymethyl-2-furfural (HMF) formation during the baking of shortbreads. The investigation was done on three types of shortbread in which sucrose, glucose, or fructose were used as sweeteners. In all the samples the concentration of sugar was 20% (w/w). The cookies were baked in a laboratory oven at temperatures of 200, 215, 230, and 245°C. The samples for the HMF determination were taken at intervals from 5 to 18 min depending on the baking temperature. It was found that HMF formation can be described by exponential equation. The HMF formation was correlated with the colour changes of the cakes determined according to CIELab system. Different parameters of colour were investigated, however, only in the case of brightness difference may the correlation be treated as statistically important. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we report that phase separation of water/acetonitrile solution to a biphasic system can be induced by the presence of an acidic ionic liquid, i.e., 1-methyl-3-(butyl-4-chlorosulfonyl) imidazolium chlorosulfate ([MBCIm]SO3Cl), which allows to produce pseudo ternary phase of the/water/actonitrile/[MBCIm]SO3Cl system at room temperature. Based on this finding, an efficient and recyclable aqueous acetonitrile biphasic system is established for catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF) in the presence of [MBCIm]SO3Cl at low temperature in a shorter period of time. The ionic liquids remaining in the organic phase can be efficiently removed by simple treatment with alumina. This leaves only HMF, with a yield of up to 88.7%, in the acetonitrile phase, which could be easily removable. [Copyright &y& Elsevier]

Abstract: Furanic compounds such as 5-hydroxymethylfurfural (HMF) can be obtained from sugars and have the potential to serve as substitutes of petroleum derived building blocks in the production of fuels and chemicals. In this work, we propose a process for the production of HMF from fructose based on extractive-reaction and formulate an optimization problem in order to find the operating conditions that minimize its cost of production. [Copyright &y& Elsevier]

Abstract: In the fructose dehydration to 5-hydroxymethylfurfural (HMF) in dimethyl sulfoxide, the catalytic function of 1,3-dialkylimidazolium-based ionic liquids with different counter-anions was investigated. It was found that the effects of alkyl chain length and additional alkyl group in Cl-containing ionic liquids were negligible whereas the activity of 1-butyl-3-methylimidazolium-based ionic liquids was considerably changed by varying the anion (particularly, halide ions). The latter finding was confirmed by the control experiment result that the addition of KBr or Ca(CH3COO)2 dramatically tuned the catalytic activity of 1-butyl-3-methylimidazolium chloride. From these results and the proposed reaction pathway, it was consequently believed that 1,3-dialkylimidazolium halide contained the dual catalytic function to act as both Brönsted acid and nucleophile for the fructose dehydration to HMF. [Copyright &y& Elsevier]

Fructose is a significant component in unprocessed food and has become one of the most commonly sweeteners used in food manufacturing. Fructose is also a useful pharmaceutical excipient and derivatives of fructose are exploited as renewable chemical building blocks. Fructose based polysaccharides have extensive pharmaceutical and dietary functions. We discuss here the chemistry and physical behaviours of this saccharide and how these factors affect the utility and health implications of fructose. [ABSTRACT FROM AUTHOR]