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The copper–cobalt metal oxide composite magnesium oxide catalyst loaded with Ru has achieved the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to the bio-based polyester monomer 2,5-furandicarboxylic acid (FDCA) under base-free conditions. Several Ru/Cu-Co-O·MgO catalysts were prepared, with Cu-Co-O being a combination of CuO and Co3O4 . The catalyst’s activity was boosted by the synergistic interaction between copper and cobalt, as well as an optimal copper-to-cobalt molar ratio. Optimal catalytic activity was observed in the Ru4/Cu1-Co1-O·MgO catalyst, loaded with 4 wt% Ru when copper-to-cobalt molar ratio of 1:1 and magnesium oxide compounding amount of 6 mmol were employed. The inclusion of MgO and the load of Ru not only expanded the specific surface area of the catalyst but also heightened its basicity. Additionally, the presence of loaded Ru improved the catalyst’s reducibility at low temperatures. In aqueous solution under oxygen pressure, the conversion rate of HMF achieved 100%, and the yield of FDCA was 86.1%. After five reaction cycles, examining the catalyst and solution revealed that Ru nanoparticles resisted leaching or oxidation, and MgO exhibited only slight dissolution. The green separation of the product was achieved using semi-preparative liquid chromatography, selectively collecting the FDCAcontaining solution by exploiting variations in interactions between solutes and the stationary/mobile phases. The subsequent steps involved rotary evaporation and drying, resulting in FDCA powder with a purity exceeding 99%. Notably, this approach eliminated the need to introduce concentrated hydrochloric acid into the system for FDCA separation, providing a novel method for synthesising powdered FDCA. [ABSTRACT FROM AUTHOR]

The presence of toxic compounds in lignocellulosic hydrolysates (LCH) is among the main barriers affecting the efficiency of lignocellulose-based fermentation processes, in particular, to produce biofuels, hindering the production of intracellular lipids by oleaginous yeasts. These microbial oils are promising sustainable alternatives to vegetable oils for biodiesel production. In this study, we explored adaptive laboratory evolution (ALE), under methanol- and high glycerol concentration-induced selective pressures, to improve the robustness of a Rhodotorula toruloides strain, previously selected to produce lipids from sugar beet hydrolysates by completely using the major C (carbon) sources present. An evolved strain, multi-tolerant not only to methanol but to four major inhibitors present in LCH (acetic acid, formic acid, hydroxymethylfurfural, and furfural) was isolated and the mechanisms underlying such multi-tolerance were examined, at the cellular envelope level. Results indicate that the evolved multi-tolerant strain has a cell wall that is less susceptible to zymolyase and a decreased permeability, based on the propidium iodide fluorescent probe, in the absence or presence of those inhibitors. The improved performance of this multi-tolerant strain for lipid production from a synthetic lignocellulosic hydrolysate medium, supplemented with those inhibitors, was confirmed. [ABSTRACT FROM AUTHOR]

Furandicarboxylic acid (FDCA) is recognized as a valuable product of hydroxymethylfurfural (HMF) derived from cellulosic materials as an abundant renewable source. It could find future bioplastic application if a feasible separation process is developed. To find a commercially available solvent, FDCA should be selectively separated from HMF and the downstream process be supported by pyrolysis-gas chromatography-mass spectrometry experiments in line with density functional theory (DFT). Evaluation of the sigma potential and sigma surface analysis demonstrated that benzene and ethyl acetate enjoyed better extraction and HMF selectivity, whereas FDCA exhibited ideal behavior in the presence of DMF and DMSO solvents. It was proved that the hydrophobicity could be changed by improving the hydrogen-bonding interaction between them. Moreover, the up-down selection of classes of solvents based on the experimental data found by GC-MS revealed that polar molecular solvents (ethanol-water) were more compatible with carboxylic acids and alcohol compounds, while n-hexane was a desirable solvent for phenolic compounds. It was found that levoglucosan retained a significant fraction of water compared to other solvents, which need to be considered for further economic and environmental analysis under the multifaceted framework of biomass-derived products.

The production of 2,5-furandicarboxylic acid (FDCA) as a biobased commodity chemical has gained great importance over the last years. The possibility of replacing conventional polyethylene terephthalate (PET)-based plastics by polyethylene furanoate (PEF) is accelerating applied research in the direction of novel and highly productive synthesis routes to FDCA. This paper explores the patent activities related to FDCA production, with particular emphasis on the potential role that enzymatic catalytic methods may have. An increasing number of patent applications (and granted ones) have been disclosed over the last decade. The innovation is set on the development of multi-step catalytic processes, involving multi-enzymatic and chemoenzymatic cascades, or using whole-cells, either as resting (non-growing) biocatalysts or as living organisms in fermentative processes. Moreover, other innovative paths use substrates different from fructose and 5-hydroxymethylfurfural (HMF), such as gluconic acid, or furfural. Overall, opportunities for innovation exist, albeit current production metrics in biotechnological methods remain mostly at the proof-of-concept level. Large development efforts to reach industrial targets are needed, which may be stimulated by the less severe processing conditions expected for biotechnology, leading to energy savings, less by-product formation, and to the valorization of crude effluents.

The presence of toxic compounds in lignocellulosic hydrolysates (LCH) is among the main barriers affecting the efficiency of lignocellulose-based fermentation processes, in particular, to produce biofuels, hindering the production of intracellular lipids by oleaginous yeasts. These microbial oils are promising sustainable alternatives to vegetable oils for biodiesel production. In this study, we explored adaptive laboratory evolution (ALE), under methanol- and high glycerol concentration-induced selective pressures, to improve the robustness of a Rhodotorula toruloides strain, previously selected to produce lipids from sugar beet hydrolysates by completely using the major C (carbon) sources present. An evolved strain, multi-tolerant not only to methanol but to four major inhibitors present in LCH (acetic acid, formic acid, hydroxymethylfurfural, and furfural) was isolated and the mechanisms underlying such multi-tolerance were examined, at the cellular envelope level. Results indicate that the evolved multi-tolerant strain has a cell wall that is less susceptible to zymolyase and a decreased permeability, based on the propidium iodide fluorescent probe, in the absence or presence of those inhibitors. The improved performance of this multi-tolerant strain for lipid production from a synthetic lignocellulosic hydrolysate medium, supplemented with those inhibitors, was confirmed.

There is a demand for renewable resources, such as biomass, to produce compounds considered as platform molecules. This study deals with dehydration of fructose for the formation of 5-hydroxymethylfurfural (HMF), a feedstock molecule. Different catalysts (aluminosilicates, niobic acid, 12-tungstophosphoric acid—HPW, and supported HPW/Niobia) were studied for this reaction in an aqueous medium. The catalysts were characterized by XRD, FT-IR, N2 sorption at −196 °C and pyridine adsorption. It was evident that the nature of the sites (Brønsted and Lewis), strength, quantity and accessibility to the acidic sites are critical to the conversion and yield results. A synergic effect of acidity and mesoporous area are key factors affecting the activity and selectivity of the solid acids. Niobic acid (Nb2O5·nH2O) revealed the best efficiency (highest TON, yield, selectivity and conversion). It was determined that the optimum acidity strength of catalysts should be between 80 to 100 kJ mol−1, with about 0.20 to 0.30 mmol g−1 of acid sites, density about 1 site nm−2 and mesoporous area about 100 m2 g−1. These values fit well within the general order of the observed selectivity (i.e., Nb2O5 > HZSM-5 > 20%HPW/Nb2O5 > SiO2-Al2O3 > HY > HBEA).

The copper-cobalt metal oxide composite magnesium oxide catalyst loaded with Ru has achieved the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to the bio-based polyester monomer 2,5-furandicarboxylic acid (FDCA) under base-free conditions. Several Ru/Cu-Co-O·MgO catalysts were prepared, with Cu-Co-O being a combination of CuO and Co 3 O 4 . The catalyst's activity was boosted by the synergistic interaction between copper and cobalt, as well as an optimal copper-to-cobalt molar ratio. Optimal catalytic activity was observed in the Ru 4 /Cu1-Co1-O·MgO catalyst, loaded with 4 wt% Ru when copper-to-cobalt molar ratio of 1:1 and magnesium oxide compounding amount of 6 mmol were employed. The inclusion of MgO and the load of Ru not only expanded the specific surface area of the catalyst but also heightened its basicity. Additionally, the presence of loaded Ru improved the catalyst's reducibility at low temperatures. In aqueous solution under oxygen pressure, the conversion rate of HMF achieved 100%, and the yield of FDCA was 86.1%. After five reaction cycles, examining the catalyst and solution revealed that Ru nanoparticles resisted leaching or oxidation, and MgO exhibited only slight dissolution. The green separation of the product was achieved using semi-preparative liquid chromatography, selectively collecting the FDCA-containing solution by exploiting variations in interactions between solutes and the stationary/mobile phases. The subsequent steps involved rotary evaporation and drying, resulting in FDCA powder with a purity exceeding 99%. Notably, this approach eliminated the need to introduce concentrated hydrochloric acid into the system for FDCA separation, providing a novel method for synthesising powdered FDCA.

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Fructose was converted to 5-hydroxymethylfurfural (HMF), an important biomass-derived platform chemical, under mild conditions (100–130 °C) with several organic acids including p-toluene sulfonic (pTSA), oxalic, maleic, malonic and succinic acids as the catalysts. The process kinetics was compared considering fructose dehydration to HMF as the objective reaction and condensation of fructose and HMF to humin and rehydration of HMF as the main side reactions. DMSO was found to be the most effective solvent reaction medium to obtain high fructose conversion and HMF yield. Observed kinetic modeling illustrated that the rehydration and condensation of HMF in DMSO actually could be neglected, especially for the oxalic acid catalyzed system. The determined observed activation energy for fructose conversion to HMF and humin in DMSO medium was 33.75 and 24.94 kJ/mol for pTSA catalyzed system, and 96.51 and 78.39 kJ/mol for oxalic acid-catalyzed system, respectively. HMF yields of 90.2% and 84.1% were obtained for pTSA and oxalic acid catalyzed systems, respectively.

There is a demand for renewable resources, such as biomass, to produce compounds considered as platform molecules. This study deals with dehydration of fructose for the formation of 5-hydroxymethylfurfural (HMF), a feedstock molecule. Different catalysts (aluminosilicates, niobic acid, 12-tungstophosphoric acid—HPW, and supported HPW/Niobia) were studied for this reaction in an aqueous medium. The catalysts were characterized by XRD, FT-IR, N2 sorption at −196 ◦C and pyridine adsorption. It was evident that the nature of the sites (Brønsted and Lewis), strength, quantity and accessibility to the acidic sites are critical to the conversion and yield results. A synergic effect of acidity and mesoporous area are key factors affecting the activity and selectivity of the solid acids. Niobic acid (Nb2O5 ·nH2O) revealed the best efficiency (highest TON, yield, selectivity and conversion). It was determined that the optimum acidity strength of catalysts should be between 80 to 100 kJ mol−1, with about 0.20 to 0.30 mmol g−1 of acid sites, density about 1 site nm−2 and mesoporous area about 100 m² g −1 . These values fit well within the general order of the observed selectivity (i.e., Nb2O5 > HZSM-5 > 20%HPW/Nb2O5 > SiO2 -Al2O3 > HY > HBEA). [ABSTRACT FROM AUTHOR]

Fructose was converted to 5-hydroxymethylfurfural (HMF), an important biomass-derived platform chemical, under mild conditions (100–130 °C) with several organic acids including p -toluene sulfonic (p TSA), oxalic, maleic, malonic and succinic acids as the catalysts. The process kinetics was compared considering fructose dehydration to HMF as the objective reaction and condensation of fructose and HMF to humin and rehydration of HMF as the main side reactions. DMSO was found to be the most effective solvent reaction medium to obtain high fructose conversion and HMF yield. Observed kinetic modeling illustrated that the rehydration and condensation of HMF in DMSO actually could be neglected, especially for the oxalic acid catalyzed system. The determined observed activation energy for fructose conversion to HMF and humin in DMSO medium was 33.75 and 24.94 kJ/mol for p TSA catalyzed system, and 96.51 and 78.39 kJ/mol for oxalic acid-catalyzed system, respectively. HMF yields of 90.2% and 84.1% were obtained for p TSA and oxalic acid catalyzed systems, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydrogenolysis of HMF to DMF reaction catalyzed by various catalytic systems was reviewed. • Pathways to produce DMF were determined by different catalysts and reaction conditions. • Some noble metal-based catalysts showed good catalytic performance, but needed strict reaction conditions. • Highly active and good recyclable catalysts are needed for DMF production from HMF hydrogenolysis. Abstract 2, 5-dimethylfuran (DMF), which is synthesized through catalytic hydrogenolysis of 5-hydroxymethylfurfural (HMF), is one of the most promising liquid biofuels for transportation because of its high energy density, high boiling point, and water insolubility. In recent years, studies of the hydrogenolysis of HMF to DMF have attracted increasing attention, with numerous novel catalytic systems and significant research achievements being reported as a result. Thus, in this review, we focus on hydrogenolysis of HMF into DMF through various catalytic systems, and systemically summarize the latest advances and progress on this reaction from the perspective of catalysts, including noble and non-noble metal-based catalysts. Moreover, the reaction mechanisms for different catalysts, the limitations and problems in current research, and potential research trends are discussed in this review. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ir supported on SiO 2 was investigated for 5-hydroxymethylfurfural (HMF) conversion. • Hydrogenation route from HMF to 2,5- bis -(hydroxymethyl)furan (BHMF) was preferred. • Ir dispersion combined with acid sites and H 2 SO 4 promoted 2,5-dimethylfuran formation. • High activity to value-added products was achieved over Ir supported on SiO 2. Abstract Catalytic performance of iridium supported on SiO 2 was investigated for 5-hydroxymethylfurfural (HMF) transformation. Ir/SiO 2 catalysts exhibiting different metal loading (1, 3, and 5 wt.%) were tested in the preliminary experiments in the hydrogenation of two probe molecules, e.g. ethyl pyruvate (EP) and ketopantolactone (KP) to evaluate the Ir dispersion on the catalyst activity in C O hydrogenation. In the transformation of HMF the influence of metal dispersion, iridium precursor and addition of H 2 SO 4 were studied revealing that 2,5- bis -(hydroxymethyl)furan (BHMF) was the main product with 83% selectivity at 70% conversion of HMF over chlorine free Ir/SiO 2 together with H 2 SO 4 at 333 K in THF under 10 bar H 2 pressure. On the other hand, one-pot synthesis of HMF to 2,5-dimethylfuran (DMF) was promoted in the presence of chlorine containing 1%Ir/SiO 2 (Cl) and H 2 SO 4. Both of these products are considered high value-added chemicals from biomass-derived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF. [ABSTRACT FROM AUTHOR]

Abstract In this survey, ultrasonic irradiation was used as a source of energy and a mild method for producing 5-hydroxymethylfurfural (5-HMF) from fructose in the presence of SBA-15 grafted with different amount of alumina at room temperature. Effect of different parameters such as the power of ultrasonic irradiation, alumina loading on SBA-15, catalyst amount, reaction time, and solvent was investigated. Catalysts were characterized using different techniques such as FT-IR, XRD, BET, SEM, TEM, EDX, elemental mapping and ICP analysis. While dehydration reaction at room temperature gave <5% 5-HMF after 48 h, after 150 min sonication under the power of 300 W the HMF yield reached to 47% at room temperature. The effect of various solvents such as DMSO, NMP, DMF and sulfolane was investigated and DMSO was selected as suitable solvent for dehydration of fructose. Finally, the reusability of catalyst was examined and it was found that the recovered catalyst showed high activity in repeated experiments. [ABSTRACT FROM AUTHOR]

Background: Hydroxymethylfurfural (HMF) is a common Maillard reaction product directly formed from dehydration of sugars under acidic conditions during heating and storage in carbohydrate rich foods. The aim of the present study was to detect and quantify the amount of HMF in date syrup by HPLC method. In addition, the amount of HMF in date syrup produced by traditional and industrial methods were compared. Methods: A HPLC method for determination of HMF in date syrup was developed and validated. The amount of HMF in date syrup products produced by the traditional and industrial methods was compared. In addition, to determine whether HMF was produced during storage in date syrup, its amount was measured in fresh and old samples. Results: The HMF content of fresh traditional products varied between 1000 to 2675 mg⁄kg and in the old products varied between 2580 to 6450 mg⁄kg. The HMF concentration of the fresh industrial products varied between 12 to 456 mg⁄kg and 611 to 943 mg⁄kg in the old ones. The HMF concentration of the traditionally produced products was significantly higher than industrial products (P

The process of dehydration of glucose to 5-hydroxymethylfurfural (HMF), using caprolactam-lithium chloride (CPL/LiCl) as a solvent, was investigated. Dual-wavelength ultraviolet spectrophotometry provides a new approach for the determination of glucose conversion rate and yield of HMF. Experiments were performed to demonstrate the accuracy and precision of this method. Various reaction parameters, such as the ratio of ionic liquid, reaction temperature, reaction time, catalyst dosage, and solid absorbent, were investigated in detail for the dehydration of glucose. The optimal conditions were explored. Finally, a possible mechanism for the dehydration of fructose to HMF was proposed.

Notably available from the cellulose contained in lignocellulosic biomass, glucose is a highly attractive substrate for eco-efficient processes towards high-value chemicals. A recent strategy for biomass valorization consists on combining biocatalysis and chemocatalysis to realise the so-called chemo-enzymatic or hybrid catalysis. Optimisation of the glucose conversion to 5-hydroxymethylfurfural (HMF) is the object of many research efforts. HMF can be produced by chemo-catalyzed fructose dehydration, while fructose can be selectively obtained from enzymatic glucose isomerization. Despite recent advances in HMF production, a fully integrated efficient process remains to be demonstrated. Our innovative approach consists on a continuous process involving enzymatic glucose isomerization, selective arylboronic-acid mediated fructose complexation/transportation, and chemical fructose dehydration to HMF. We designed a novel reactor based on two aqueous phases dynamically connected via an organic liquid membrane, which enabled substantial enhancement of glucose conversion (70%) while avoiding intermediate separation steps. Furthermore, in the as-combined steps, the use of an immobilized glucose isomerase and an acidic resin facilitates catalyst recycling. [ABSTRACT FROM AUTHOR]

One-pot synthesis of 5-hydroxymethylfurfural (HMF) from cellulose or glucose through employing a concentrated solution of LiBr as solvent together with a combined metal (II) and surfactant catalyst was studied. First, cellulose was dissolved in the solvent, and then it was hydrolyzed with hydrogen bromide (HBr) under moderate conditions before the solution was neutralized. The next step toward HMF synthesis was performed at 140 °C for 3 h with the addition of the abovementioned catalyst at a 10 mol% level of the substrate. Metal (II) chlorides that could serve as a Lewis acid (i.e., catalysts), or combined metal (II) and surfactant catalysts, were adopted for converting glucose to HMF. The yield of HMF reached 30.5% from glucose, and 33.8% from cellulose when tin (II) dodecylsulfate was used as a Lewis acid catalyst. The catalyst containing tin (II) yielded better results than those that contained zinc (II) or copper (II). [ABSTRACT FROM AUTHOR]

Bio-ethanol plant derived crude lignin was utilized in the synthesis of carbon catalysts for the conversion of xylose in acid pretreatment liquid (APL, another by-product of bio-ethanol plant) into furfural. Also, xylose dehydration to furfural by carbon catalysts carried out in water-MIBK biphasic system showed a maximum yield of 60% furfural. In addition, a carbon catalyst modified with 1 N H 2 SO 4 was found to be highly active as concentrated acids reported earlier in the open literature. Only a small part of the total crude lignin from the bio-ethanol plant was utilized in this manner. Further research is necessary on the valorization of remaining crude lignin waste. [ABSTRACT FROM AUTHOR]

Solvent nitromethane along with a variety of metal chloride and mineral acids as catalyst were studied for the synthesis of 5-Hydroxymethylfurfural (HMF), a key precursor in the formation of alternative fuel 2,5-dimethylfuran (DMF) and other value added chemicals. Reaction time, temperature and catalyst concentration were also systematically studied to achieve highest HMF formation. Among the carbohydrates studied for HMF synthesis, D-fructose and inulin were found particularly most productive yielding >70% and with 100% selectivity using ZrCl4 in nitromethane at 100 oC during 3h. Readily available reagents, solvents, and simple reaction conditions could mark this process promising for HMF formation from biomass.

Background: Furfural and 5-hydroxymethylfurfural (HMF) are the two major furan aldehyde inhibitors generated from lignocellulose dilute acid pretreatment which significantly inhibit subsequent microbial cell growth and ethanol fermentation. Zymomonas mobilis is an important strain for cellulosic ethanol fermentation but can be severely inhibited by furfural and (or) HMF. Previous study showed that Z. mobilis contains its native oxidoreductases to catalyze the conversion of furfural and HMF, but the corresponding genes have not been identified. Results: This study identified a NADPH-dependent alcohol dehydrogenase gene ZMO1771 from Z. mobilis ZM4, which is responsible for the efficient reduction of furfural and HMF. Over-expression of ZMO1771 in Z. mobilis significantly increased the conversion rate to both furfural and HMF and resulted in an accelerated cell growth and improved ethanol productivity in corn stover hydrolysate. Further, the ethanol fermentation performance was enhanced again by co-expression of the transhydrogenase gene udhA with ZMO1771 by elevating the NADPH availability. Conclusions: A genetically modified Z. mobilis by co-expressing alcohol dehydrogenase gene ZMO1771 with transhydrogenase gene udhA showed enhanced conversion rate of furfural and HMF and accelerated ethanol fermentability from lignocellulosic hydrolysate. The results presented in this study provide an important method on constructing robust strains for efficient ethanol fermentation from lignocellulose feedstock. [ABSTRACT FROM AUTHOR]

An efficient production of 5-hydroxymethylfurfural (HMF) from raw lignocellulosic biomass is achieved through combinational treatments of diluted acid/base-assisted pretreatment and catalytic conversion. Remarkably, an HMF yield of around 79 mol% could be achieved when the raw lignocellulosic biomass (wood chips) was pre-treated in diluted NaOH solution (3 wt%) and then catalyzed in the system using CrCl 3 ·6H 2 O as the catalyst and 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) as the solvent at 120 °C for 2 h. In addition, the activation energy for producing HMF was calcuted to be around 74 kJ/mol in our system. The combinational treatments proposed in this study demonstrate an effective transformation of raw lignocellulosic biomass into HMF with a high yield. [ABSTRACT FROM AUTHOR]

Notably available from the cellulose contained in lignocellulosic biomass, glucose is a highly attractive substrate for eco-efficient processes towards high-value chemicals. A recent strategy for biomass valorization consists on combining biocatalysis and chemocatalysis to realise the so-called chemo-enzymatic or hybrid catalysis. Optimisation of the glucose conversion to 5-hydroxymethylfurfural (HMF) is the object of many research efforts. HMF can be produced by chemo-catalyzed fructose dehydration, while fructose can be selectively obtained from enzymatic glucose isomerization. Despite recent advances in HMF production, a fully integrated efficient process remains to be demonstrated. Our innovative approach consists on a continuous process involving enzymatic glucose isomerization, selective arylboronic-acid mediated fructose complexation/transportation, and chemical fructose dehydration to HMF. We designed a novel reactor based on two aqueous phases dynamically connected via an organic liquid membrane, which enabled substantial enhancement of glucose conversion (70%) while avoiding intermediate separation steps. Furthermore, in the as-combined steps, the use of an immobilized glucose isomerase and an acidic resin facilitates catalyst recycling.

The lively acidic properties in water of niobium phosphate (NBP) catalyst and NBP modified samples by acidic treatments in HCl solutions at 0.1, 1.0, and 10 M concentration (NBP01, NBP1, and NBP10, respectively) have been exploited for the direct conversion reaction of cellobiose to hydroxymethylfurfural (HMF) at temperature of 80–130 °C. Acidity of the samples was determined by liquid-solid titrations working in a modified HPLC line with basic solutions of phenylethylamine (PEA), used as a base probe. As solvents, an apolar-aprotic one, cyclohexane, was used for determining the intrinsic acidity and water for the effective acidity. In addition, pyridine/water co-adsorption FT-IR experiments complemented the acidity study, and the results obtained confirmed the presence of both water-tolerant Lewis acid sites (LAS) and some residual Brønsted acid sites (BAS) on all the NBP samples. On NBP, the LAS to BAS ratio was 1.69, measured in cyclohexane, and only slightly decreased to 1.30, when measured in water. Catalytic activity was studied in a liquid-solid reaction line with fixed bed flow reactor working in complete recirculation. The reaction of HMF formation from cellobiose consists of three distinct catalytic actions: hydrolysis of the β-1,4-glycosidic bonds of cellobiose, isomerization of the formed glucose monomers to fructose, and cyclo-dehydration of fructose to HMF. Comparative catalytic results obtained with a sulfonic acid resin (Amberlite IR 120) showed that it was not able to form any HMF from cellobiose in the range of temperature studied, only cellobiose hydrolysis to glucose can be successfully achieved on the protonic acid resin. [ABSTRACT FROM AUTHOR]

Pt nanoparticles (NPs, 0.5 wt.%) encapsulated in a zirconium-based metal–organic framework (UiO-67 MOF) were synthesized via a linker design method. Thermal behavior of Pt in UiO-67 composite materials was compared with UiO-67 using thermogravimetric and differential thermal analysis (TG-DTA). The results showed that Pt insertion can impair the thermal stability of bulk UiO-67, resulting in a ca. 14% drop in the critical temperature of the thermal decomposition. Temperature-programmed oxidation of materials showed that calcination at 450 K was essential to provide a clean framework. Temperature-programmed reduction of materials revealed that the chemisorption of H 2 on UiO-67 (at 323 K) was evidently enhanced owing to the incorporation of Pt NPs, thus making PtNP@UiO-67 suitable for hydrogenation reactions and hydrogen storage. PtNP@UiO-67 catalyst was evaluated by the oxidation and hydrogenation of 5-hydroxymethylfurfural in aqueous solutions at 363 K, showing improved activity and selectivity in hydrogenation reactions. [ABSTRACT FROM AUTHOR]

The process of dehydration of glucose to 5-hydroxymethylfurfural (HMF), using caprolactam-lithium chloride (CPL/LiCl) as a solvent, was investigated. Dual-wavelength ultraviolet spectrophotometry provides a new approach for the determination of glucose conversion rate and yield of HMF. Experiments were performed to demonstrate the accuracy and precision of this method. Various reaction parameters, such as the ratio of ionic liquid, reaction temperature, reaction time, catalyst dosage, and solid absorbent, were investigated in detail for the dehydration of glucose. The optimal conditions were explored. Finally, a possible mechanism for the dehydration of fructose to HMF was proposed. [ABSTRACT FROM AUTHOR]

Background: Current large-scale pretreatment processes for lignocellulosic biomass are generally accompanied by the formation of toxic degradation products, such as 5-hydroxymethylfurfural (HMF), which inhibit cellulolytic enzymes and fermentation by ethanol-producing yeast. Overcoming these toxic effects is a key technical barrier in the biochemical conversion of plant biomass to biofuels. Pleurotus ostreatus, a white-rot fungus, can efficiently degrade lignocellulose. In this study, we analyzed the ability of P. ostreatus to tolerate and metabolize HMF and investigated relevant molecular pathways associated with these processes. Results: P. ostreatus was capable to metabolize and detoxify HMF 30 mM within 48 h, converting it into 2,5-bis-hydroxymethylfuran (HMF alcohol) and 2,5-furandicarboxylic acid (FDCA), which subsequently allowed the normal yeast growth in amended media. We show that two enzymes groups, which belong to the ligninolytic system, aryl-alcohol oxidases and a dehydrogenase, are involved in this process. HMF induced the transcription and production of these enzymes and was accompanied by an increase in activity levels. We also demonstrate that following the induction of these enzymes, HMF could be metabolized in vitro. Conclusions: Aryl-alcohol oxidase and dehydrogenase gene family members are part of the transcriptional and subsequent translational response to HMF exposure in P. ostreatus and are involved in HMF transformation. Based on our data, we propose that these enzymatic capacities of P. ostreatus either be integrated in biomass pretreatment or the genes encoding these enzymesmay function to detoxify HMF via heterologous expression in fermentation organisms, such as Saccharomyces cerevisiae. [ABSTRACT FROM AUTHOR]

Three zeolitic imidazolate frameworks (ZIF-8, ZIF-90 and ZIF-93) were investigated for adsorption of 5-hydroxymethylfurfural (HMF) from aqueous solution. The equilibrium uptake of HMF decreased following the order of ZIF-8 (465 mg g −1 )>ZIF-90 (307 mg g −1 )>ZIF-93 (279 mg g −1 ), in accordance with the hydrophobicity of the frameworks. The adsorption equilibrium data were found to follow Langmuir adsorption model. The sorption kinetics could be well described by the pseudo-second-order kinetic equation. The HMF-loaded ZIFs could be fully regenerated with ethanol as the desorption solvent. Selective adsorption of HMF from HMF/fructose/water mixtures was also carried out. The uptake of HMF remained unchanged, with no observable adsorption of fructose. In liquid phase breakthrough experiments, the uptake of HMF on ZIF-8 in column was consistent with the batch study. Furthermore, the ZIF-8 packed column could be regenerated effectively and recycled with no discernible loss of adsorption capacity. These findings confirm that ZIF-8 can be employed as an effective and reusable adsorbent for HMF recovery from aqueous solution. [ABSTRACT FROM AUTHOR]

In our present paper, the effect of water activity and processing conditions in reconstituted potato chips was considered as a model to investigate the changes of acrylamide (AA) and 5-hydroxymethylfurfural (HMF). The results suggested that the formation of AA and HMF was highly correlated with frying temperature and time. Water activity could also influence the formation of AA and HMF. Meanwhile, the formation of HMF has significant correlation with the formation of AA in reconstituted potato chips. A typical exponential growth curve was observed by plotting AA levels vs HMF content which were all determined under different heating condition: $$ AA=0.002\exp \left( {\frac{HMF }{10.850 }} \right)+0.143\,\left( {{R^2}=0.850} \right) $$. The model could be used as a tool for estimating the formation of AA when the content of HMF was known. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enhancing anaerobic biodegradability of sugarcane bagasse using pretreatments. [•] Delignification for improving biochemical methane potential of sugarcane bagasse. [•] Production of renewable energy via anaerobic digestion of sugarcane bagasse. [•] Sugarcane bagasse pretreatment optimisation by using response surface methodology. [ABSTRACT FROM AUTHOR]

Highlights: [•] Unsymmetrical dicationic imidazolium based ILs were synthesized. [•] Imidazolium, pyridinium, and triethyl ammonium cations were used. [•] Prepared ILs showed efficient catalytic activity in fructose dehydration. [•] 100% fructose conversion and 92.3% HMF yield was obtained. [•] 70°C temperature and 40min reaction time gave the good results. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that the physical and chemical properties of ionic liquids are dependent on their structure. Understanding the types and strengths of interactions is necessary for a knowledge-based design of ionic liquid structures. In the first section, we introduce some of our recent physico-chemical and spectroscopic investigations on binary ionic liquid+solute mixtures (with water, an organic solute or a second ionic liquid), showing that hydrogen bonding plays a vital role for the arrangement of the ions in mixtures, and preferential interactions can lead to subtle changes resulting in deviation from ideal mixing behavior. The second section shows examples of how specific interactions with solutes affect reactions and other processes, regarding e.g. the rate of reaction, yields, extraction efficiencies, dissolution capacities of biofeeds, and selectivity in crystal framework formation. The third section is dedicated to some examples regarding the development of ionic liquids as materials. [Copyright &y& Elsevier]

Abstract: Low melting systems consisting of ammonium salts and highly concentrated fructose were used for the conversion of fructose into 5-hydroxymethylfurfural (HMF). Not only acting as solvents, at sufficiently high temperatures, the ammonium salts themselves could also catalyse the dehydration of fructose to HMF. Among those salts, tetraethyl ammonium chloride (TEAC) was found to be the most efficient solvent-catalyst, demonstrated by its ability to achieve 81.3% HMF yield with 33.3wt% fructose concentration at 120°C. 79.2% HMF yield was obtained with 50wt% fructose concentration in the TEAC/fructose system using 5mol% NaHSO4·H2O as a co-catalyst. A semi continuous biphasic system of TEAC/fructose/NaHSO4·H2O melt using tetrahydrofuran (THF) to recover HMF was proposed and demonstrated in a laboratory scale process operating at 120°C. The impurities in the HMF recovered, involving TEAC and NaHSO4·H2O, were determined using 1H NMR, elemental analysis and ICP-OES. [Copyright &y& Elsevier]

The juice extracted from Primus mume (Mei-Gin) is in the form of a highly concentrated dark black syrup. It is a common health supplement in Asia. The active component, 5-hydroxymethylfurfural (HMF), manifested a concentration-dependent effect on the inhibition of β-hexosaminidase degranulation upon antigen-sensitized RBL-2H3 cells. In order to investigate HMF (1) of P. mume extract, HMF was isolated and the HPLC profiles of 23 commercial Mei-Gin products (6 types) were qualitatively and quantitatively analyzed for HMF content. The samples included 10 Taiwanese Mei-Gin products, 3 Japanese Mei-Gin products, 5 specific-processing Mei-Gin products, 2 commercial plum drinks, 1 fresh mature plum extract, and 2 heat-processed samples. The HPLC profiles showed that the commercial products contained various amounts of HMF. Among them, the water extract of P. mume showed better yield of HMF. The yields from such products may differ due to different Mei-Gin original materials and different extraction and manufacturing procedures. [ABSTRACT FROM AUTHOR]

• HMF can inhibit the production of hydrogen and change the community structure of microorganisms. • Low concentrations of HMF could be utilized to increase methane production. • HMF can interfere with the normal physiological functions of microorganisms. • The strategies of reducing the effects of HMF on fermentation were summarized. Anaerobic fermentation is a clean production process for recycling of many agricultural and industrial wastes. During anaerobic fermentation, the existence of various inhibitors often leads to low efficiency or even failure of anaerobic digesters. 5-hydroxymethylfurfural (HMF) is such an inhibitor which can be produced in the pretreatment of biomass for subsequent anaerobic digestion. This paper provides a review of various production methods of HMF and its effects on hydrogen production, methane production and ethanol production through fermentation. The conversion and removal of HMF were summarized from the aspects of biomass pretreatment, non-biological treatment and biological treatment. This article aims to provide new ideas and methods for reducing the inhibition effect of HMF on anaerobic fermentation of biomass and restoring the performance of the anaerobic fermentation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Humins by-product was employed as carrier to prepare NbO x -based solid catalysts. • The preparation methodology induces structural modifications of the humins carrier. • NbO x is merely homogeneously distributed on the humins-derived carrier. • A high yield to HMF requires a catalyst with an optimum base/acid sites ratio. • In biphasic TBP/water system the yield to HMF reached 96 %, at 180 °C and after 8 h. Highly dispersed supported NbOx species were prepared via a deposition precipitation-carbonization (DPC)-like method. As precursors for niobium species and carrier ammonium niobate(V) oxalate hydrate and humins were used. Characterization of the resulted catalysts indicated bi-functional acid-base niobium species anchored onto a highly hydrophobic graphite-like carbon structure. These catalysts were investigated in the one-pot conversion of glucose to 5-hydroxymethylfurfural (HMF) in a biphasic system consisting of a mixture of a 20 wt% NaCl aqueous solution phase and an organic extracting phase (methyl-isobutyl-ketone (MIBK), 2-tert-butylphenol (TBP) or 2-sec-butylphenol (SBP)). The optimization conditions afforded the highest yield to HMF (96 %) for the GHNb1.2 catalyst (with 2.5 wt%Nb), the base/acid sites ratio of 1.76, in biphasic TBP/water system, at 180 °C after 8 h. [ABSTRACT FROM AUTHOR]

• Multifunctional nanocomposites with non-precious metals and magnetic core. • Catalysts combine Nb-MCM-41 and Mn, Co and Fe oxides as a shell. • Selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. • The new developed catalysts do not require the presence of a base. • Catalysts combine unique oxidation properties with practical separation advantages. The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has been investigated on multi-functional magnetic nano-composite catalysts (10M@xNb@MNP, where M = CoO x , MnO x or FeO x , "10" - 10wt% and x = Si/Nb ratio of 50 and 22) combining Nb-MCM-41 and Mn, Co and Fe oxides as a shell of a magnetic nanoparticles core. These catalysts were exhaustively characterized by several techniques such as XRD, adsorption-desorption of liquid nitrogen at 77K, CO 2 - and NH 3 -TPD, DRIFT, XPS, SEM-EDX, ICP-OES and ToF-SIMS. The new composite catalysts produced FDCA with a selectivity of 96.5 % for a X HMF = 96.9 % (10Co@22Nb@MNP). A synergetic effect between MO x and Nb species in the activation of t -BuOOH and oxidation of HMF has been identified. The new developed catalysts do not require the presence of a base in the homogeneous phase and combine unique oxidation properties with practical separation advantages. [ABSTRACT FROM AUTHOR]