Search

Ni phosphides and NiCo alloys are extensively explored for their remarkable efficiency in biomass alcohol oxidations, yet the underlying mechanisms remain inadequately understood. This study thoroughly elucidates the roles of Ni, Co, and P in improving the catalytic performance of Ni‐Co‐P catalysts for the electrochemical conversion of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), a promising biomass‐derived building block replacing terephthalic acid. Phosphorization of Ni results in the partial formation of Ni2P phase and significantly boosts the formation of the reactive NiOOH phase on the surface, which is the crucial catalytic phase for converting HMF into FDCA. The integration of Co into the heterojunction between Ni2P and NiOOH enhances the oxidation reactivity of 5‐formyl‐2‐furancarboxylic acid (FFCA), a pivotal intermediate influencing FDCA productivity, by selectively stabilizing aldehydes, thereby promoting further oxidation rather than surface desorption. in situ/operando spectroscopic analyses consistently highlight the equal significance of the rapid generation of NiOOH and the robust adsorption of reactant molecules at the surface in achieving high catalytic performance. These insights into elemental contributions set a new standard for designing multi‐component electrocatalysts for efficient biomass alcohol oxidation. [ABSTRACT FROM AUTHOR]

The key challenge for 5‐hydroxymethylfurfural oxidation reaction (HMFOR) lies in understanding the synergistic interactions between active sites and adsorption sites, but the uncertain spatial positions of these two sites largely limit their synergistic effect. Here, an embedded Pd/NiFe layered double hydroxide (LDH) with Pd nanoparticles (NPs) (3.6 nm) far larger than the interlayer spacing of LDH is reported, which results in the in situ generation of the defective structures at the interface of the NiFe laminate. The Pd/NiFe shows a lower onset potential of 1.34 V compared to NiFe (1.42 V). Experimental and theoretical calculations reveal that the Pd NPs exhibit a high level of orbital overlap with HMF, leading to a strong adsorption tendency and an increased local concentration of HMF near the Pd NPs. The Ni defects generated around Pd NPs result in the 3d‐orbitals of adjacent Ni sites approaching the Fermi level, reducing the oxidation barrier from Ni2+‐OH to Ni3+‐O active sites. Furthermore, this work provides crucial evidence for the hydration interactions between the aldehyde groups in HMF and the hydroxyl groups on the catalyst surface, demonstrating that the removal ability of the latter one can have an important influence on HMFOR activity. [ABSTRACT FROM AUTHOR]

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]

Maximizing the loadings of active centers without aggregation for a supported catalyst is a grand challenge but essential for achieving high gravimetric catalytic activity, especially toward multi‐step reactions. The oxidation of 5‐hydroxymethylfurfural (HMF), a key biomass‐derived platform molecule, into 2,5‐furandicarboxylic acid (FDCA), a promising alternative to polyester monomer, is such a multi‐step reaction that involves 6 proton and electron transfers. This process often demands strong alkaline environment but also suffers from the alkali‐driven polymerization side‐reaction. Meanwhile, neutral media ameliorates the polymerization, but lacks efficient catalyst toward deep oxidation. Herein, we devised a strategy of creating ultra‐dense supported Ru oxide clusters via directed ion exchange in a Co hydroxyanion (CoHA) support material. Pyrimidine ligands were first incorporated into the CoHA interlayers, and the subsequent evacuation of pyrimidines created porous channels for the directed ion exchange with the built‐in anions in CoHA, which allowed the dense and mono‐disperse functionalization of RuCl62− anions and their resulting Ru oxide clusters. These ultra‐dense Ru oxide clusters not only enable high HMF electrooxidation currents under neutral conditions but also create microscopic channels in‐between the clusters for the expedited re‐adsorption and oxidation of intermediates toward highly oxidized product, such as 5‐formyl‐2‐furoic acid (FFCA) and FDCA. A two‐stage HMF oxidation process, consisting of ambient conversion of HMF into FFCA and FFCA oxidation into FDCA under 60 °C, was eventually developed to first achieve a high FDCA yield of 92.1 % under neutral media with significantly reduced polymerization. [ABSTRACT FROM AUTHOR]

The oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) is a key reaction in valorizing biomass. DFF is hardly soluble in water, while HMF is often obtained from biorefineries in crude wet organic fractions. Thus, the reaction is challenging for both biocatalysis performed in aqueous media, and for chemocatalysis where the presence of water often results in catalyst poisoning. Galactose oxidase (GalOx) can selectively oxidize HMF to DFF and displays promising activity in aqueous‐organic media. In this study, GalOx was immobilized on ten carriers, assessing the immobilization yield, activity, and stability. Covalently immobilized GalOx catalyzed the oxidation of HMF to DFF in neat and water‐saturated EtOAc, and in biphasic systems of various water contents. At 50 % v/v H2O, the reaction was conducted at a semi‐preparative scale (50 mL) with no adverse effect on DFF yield. Some limitations arise, such as enzyme deactivation, and adsorption of DFF to the support, particularly in the aqueous fraction. Future options to upgrade the route may include designed stable enzymes under the presence of HMF/DFF, and the setup of microaqueous systems where DFF adsorption is minimized. The use of wet EtOAc media would be a promising approach in future biorefineries employing inexpensive crude wet organic fractions. [ABSTRACT FROM AUTHOR]

The design of an "H"‐shaped reactor has been studied to satisfy the possibility of using a triphasic medium to transform d‐glucose into 5‐hydroxymethylfurfural (HMF) by a hybrid catalytic process using an immobilized glucose isomerase, allowing the isomerization of D‐glucose to d‐fructose, and a heterogeneous chemical catalyst to catalyze the dehydration of d‐fructose to HMF. The various parameters influencing the transport of d‐fructose within the reactor were studied, namely the difference in pH between the two aqueous phases, the agitation and the quantity of 3,4‐DCPBA/Aliquat336® used to extract and transport continuously the d‐fructose. The pH discrepancy, which must be between 5.0 and 5.5, turns out to be the real driving force behind the extraction of D‐fructose. The D‐Fru/3,4‐DCPBA molar ratio of 1/0.25 allowed the transport of more than 80 % of the D‐fructose initially present and shows that the same molecule of 3,4‐DCPBA is involved at least twice in the transport of D‐fructose and that the 3,4‐DCPBA/Aliquat336® couple performs a turnover within the organic phase. Finally, a HMF production yield of 30.9 % and an isomerization yield of 79.1 % were obtained, illustrating the shift in the isomerization equilibrium made possible by a D‐fructose extraction yield of 96.8 %. [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.

Steam pretreatment is an effective approach to open up the intact lignocellulosic matrix for biofuels and animal feed production. However, crop residues especially corn stover contain certain amounts of water-soluble carbohydrates (WSC), which are easily degraded into toxic 5-hydroxymethylfurfural (HMF) at high temperature and bring negative effects on subsequent utilization of lignocellulose biomass. Few studies have focused on the WSC loss and proposed a corresponding solution to utilize them in steam pretreatment. This study introduced a solid-state fermentation prior to steam pretreatment of corn stover to convert WSC into lactic acid, which could catalyze the hydrolysis of hemicellulose and acetyl groups in pretreatment. Compared to the regular steam pretreatment at the same severity (180 °C for 5 min), the conversion yields of xylan and arabinan in the steam pretreatment were both increased from 9.6% and 37.2% to 28.8% and 69.6%, respectively. Cellulose conversion also increased from 48.1% to 50.7% in the subsequent enzymatic hydrolysis. On the other hand, the generation of the toxic HMF reduced by 42.1% due to the pre-conversion of WSC into the relatively thermal stable lactic acid. This study provided an effective approach to process corn stover with higher hydrolysis yield and lower inhibitor generation. [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.

Summary: 5‐Hydroxymethylfurfural (HMF) is a versatile biomass‐derived chemical from multifunctional compound. It is also a promising intermediate compound used in various chemical and fuel applications, including pharmaceuticals, solvents, biofuel, and other intermediates. The demand for innovative approaches to renewable energy resources has risen to diminish the dependency on petroleum‐based products and to seek economical and environmentally friendly processes for supplying energy to the world. Fructose, glucose, cellulose, and lignocellulosic materials are the most common feedstocks used to synthesize HMF. This study reviews previous studies on the development of high yield and selectivity of HMF from technical and economic perspectives. The article highlights a few significant parameters and focused on the solvent system used for the synthesis of HMF in the lab scale and through the development of process modeling using simulation software such as Aspen Plus to perform the techno‐economic analysis (TEA), which analyses the economic feasibility of the developed production process. The TEA can estimate the capital investment needed, including feedstock, catalyst, and equipment cost, and the final product's minimum selling price (MSP). HMF is cost‐efficient due to higher operational costs from the higher cost of fructose feedstock. By studying this analysis, the overall cost of HMF production can be minimized and more economically competitive with current commercial production. Besides, to make the production of HMF more cost‐effective, more research into alternative lignocellulosic feedstocks and the development of novel catalytic systems is needed. [ABSTRACT FROM AUTHOR]

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.

5‐hydroxymethylfurfural (HMF) is produced upon dehydration of C6 sugars in biorefineries. As the product, it remains either in aqueous solutions, or is in situ extracted to an organic medium (biphasic system). For the subsequent oxidation of HMF to 2,5‐furandicarboxylic acid (FDCA), 'media‐agnostic' catalysts that can be efficiently used in different conditions, from aqueous to biphasic, and to organic (microaqueous) media, are of interest. Here, the concept of a one‐pot biocatalytic cascade for production of FDCA from HMF was reported, using galactose oxidase (GalOx) for the formation of 2,5‐diformylfuran (DFF), followed by the lipase‐mediated peracid oxidation of DFF to FDCA. GalOx maintained its catalytic activity upon exposure to a range of organic solvents with only 1 % (v/v) of water. The oxidation of HMF to 2,5‐diformylfuran (DFF) was successfully established in ethyl acetate‐based biphasic or microaqueous systems. To validate the concept, the reaction was conducted at 5 % (v/v) water, and integrated in a cascade where DFF was subsequently oxidized to FDCA in a reaction catalyzed by Candida antarctica lipase B. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

5-Hydroxymethylfurfural (HMF) is synthesized by the thermal decomposition of the sugars. Numerous types of food products are having a significant amount of HMF. Besides the thermal processing, other food processing methods (drying and dehydration, roasting, baking and storage of the product) are important factors for the synthesis of the HMF. HMF possesses different health effects including positive and negative health effects. Only few regulatory bodies have issued the guidelines and limits related to HMF. The present review has been planned to explore the HMF in terms of synthesis, occurrence, the effect of food processing, health effects and the safety guidelines. [ABSTRACT FROM AUTHOR]

The development of enzymatic processes for the environmentally friendly production of 2,5-furandicarboxylic acid (FDCA), a renewable precursor for bioplastics, from 5-hydroxymethylfurfural (HMF) has gained increasing attention over the last years. Aryl-alcohol oxidases (AAOs) catalyze the oxidation of HMF to 5-formyl-2-furancarboxylic acid (FFCA) through 2,5-diformylfuran (DFF) and have thus been applied in enzymatic reaction cascades for the production of FDCA. AAOs are flavoproteins that oxidize a broad range of benzylic and aliphatic allylic primary alcohols to the corresponding aldehydes, and in some cases further to acids, while reducing molecular oxygen to hydrogen peroxide. These promising biocatalysts can also be used for the synthesis of flavors, fragrances, and chemical building blocks, but their industrial applicability suffers from low production yield in natural and heterologous hosts. Here we report on heterologous expression of a new aryl-alcohol oxidase, MaAAO, from Moesziomyces antarcticus at high yields in the methylotrophic yeast Pichia pastoris (recently reclassified as Komagataella phaffii). Fed-batch fermentation of recombinant P. pastoris yielded around 750 mg of active enzyme per liter of culture. Purified MaAAO was highly stable at pH 2–9 and exhibited high thermal stability with almost 95% residual activity after 48 h at 57.5 °C. MaAAO accepts a broad range of benzylic primary alcohols, aliphatic allylic alcohols, and furan derivatives like HMF as substrates and some oxidation products thereof like piperonal or perillaldehyde serve as building blocks for pharmaceuticals or show health-promoting effects. Besides this, MaAAO oxidized 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to FFCA, which has not been shown for any other AAO so far. Combining MaAAO with an unspecific peroxygenase oxidizing HMFCA to FFCA in one pot resulted in complete conversion of HMF to FDCA within 144 h. MaAAO is thus a promising biocatalyst for the production of precursors for bioplastics and bioactive compounds. Key points: • MaAAO from M. antarcticus was expressed in P. pastoris at 750 mg/l. • MaAAO oxidized 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). • Complete conversion of HMF to 2,5-furandicarboxylic acid by combining MaAAO and UPO. [ABSTRACT FROM AUTHOR]

In this work, a uniquely designed imidazolium-based dicationic ionic liquid (IL) was synthesized as a greener template and applied for the synthesis of ZSM-5 zeolite as a heterogeneous catalyst for the dehydration of fructose to 5-hydroxymethylfurfural (HMF). Characterization results confirmed that due to the presence of dicationic IL as template, effective interactions and structural alterations occurred during the construction of zeolitic framework wherein the vertices of ZSM-5 consisting of Al or Si and O elements were assumed to be bonded between the vertices of dicationic IL-assisted zeolite ZSM-5 catalyst. This resulted in superior structural advantages such as highly crystalline nature and stability as well as variation in mesopores when compared to commercial ZSM-5. Additionally, various reaction variables were investigated wherein synthesized dicationic IL-assisted ZSM-5 zeolite catalyst in the presence of [BMIm][Cl] as solvent demonstrated 95% conversion of fructose and 67.2% yield of HMF at 110°C within 90 min. The altered surface area and porous nature of synthesized ZSM-5 due to the presence of dicationic IL as template was responsible for the enhanced catalytic performance under mild reaction conditions. Most significantly, being a solid catalyst, the newly developed dicationic IL-assisted zeolite ZSM-5 catalyst showed recyclability for four recycles. [ABSTRACT FROM AUTHOR]

Hydroxymethylfurfural (HMF) has been considered as one of the most promising biomass derived precursors for producing bio-based materials. Lewis acids are usually used to facilitate the isomerization of glucose to fructose in order to improve the HMF yield. In this study, glucose was converted to HMF with p-toluenesulfonic acid (pTSA) and chlorides as Brønsted and Lewis acids catalysts in the DMSO medium at 120 °C under atmospheric pressure. Kinetic modeling of the process was investigated with consideration of glucose isomerization, dehydration of fructose, rehydration of HMF and formation of humin. NH4Cl was screened as the most efficient co-catalyst for glucose conversion with HMF yield of 47%. The developed model could be well used to simulate the process with satisfying goodness of fit. The activation energies for glucose isomerization, condensation, dehydration of fructose, and rehydration of HMF were determined to be 39.8, 18.1, 55.2, and 19.0 kJ/mol, respectively. However, because the fructose concentration was very low and the reaction rate of fructose dehydration was much higher than that of glucose isomerization, a pseudo-steady state assumption could be employed, by which the observed activation energy for a lumped reaction of glucose to HMF conversion (EHMF) was determined as 45.6 kJ/mol. The developed observed kinetic model could be well used to describe the kinetics of pTSA and chloride co-catalyzed conversion of HMF. Isomerization of glucose to fructose, condensation of glucose to form humin, dehydration of fructose to form HMF, and rehydration of HMF to LA were the major reactions in the system. To improve the HMF selectivity, efforts should be made to reduce the rate of glucose condensation to form humin [ABSTRACT FROM AUTHOR]

Alkanediols with five and six carbon atoms (1,2- & 1,5-pentanediols and 1,2- & 1,6-hexanediols, respectively) are an important class of industrial chemicals having wide application. Their production from lignocellulosic biomass-derived furfural and its derivatives using solid catalysts is a sustainable and attractive approach. Several bifunctional catalysts with metal (for hydrogenation/hydrogenolysis) and acid/base (for ring opening) functionalities have been reported. Effective and selective conversion of furfurals to a desired diol is still a challenge. This review discusses the recent advances in catalyst development for pentane- and hexanediols. The reaction pathways, active sites, and possible reaction mechanisms over the solid catalysts are discussed. A comparative catalytic activity data of the known catalysts are reported. [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]

Niobic acid (Nb2O5·nH2O) was immobilized on regenerated cellulose (Re-Cellulose) to afford a heterogeneous catalyst, termed Nb2O5·nH2O@Re-Cellulose, that was characterized by powder X-ray diffraction, microscopy (SEM and TEM) and spectroscopic (Raman and FTIR) techniques. The surface acidity of the catalyst was determined using FTIR spectroscopy employing pyridine as a molecular probe. The Nb2O5·nH2O@Re-Cellulose catalyst was investigated in the conversion of glucose into 5-hydroxymethylfurfural (HMF) in aqueous media. The catalyst can be reused several times without undergoing a significant loss in activity. [ABSTRACT FROM AUTHOR]

Calcium fluoride (CaF 2) quantum dots have many applications in various fields. But there is no report on fluorescent characteristics of CaF 2 quantum dots (CaF 2 QDs). Here, a synthesis of multiple-color emission CaF 2 QDs by changing the temperature, time and raw ratio is reported, by which the CaF 2 QDs with purple, blue, green, and yellow emission can be obtained, respectively. They were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). On this basis, a novel molecular imprinting ratiometric fluorescence sensor (MIR sensor) had been constructed based on the prepared CaF 2 QDs and CdTe QDs, in which the yellow emission CaF 2 QDs was used as a responsive signal material and the red emission CdTe QDs was served as a reference signal material. And the β-CD and methylacrylic acid (MAA) as bifunctional monomers were used for constructing the specific molecularly imprinted polymers (MIPs) in MIR sensor. This MIR sensor was applied for highly selective and excellent sensitive detection of 5-hydroxymethylfurfural (HMF). Under optimum conditions, it exhibited an excellent linear relationship between the fluorescence intensity ratio (I 599 /I 625) and the concentration of HMF in the range of 0.1–6.0 μg/mL with a detection limit of 0.043 μg/mL. Finally, the established HMF-MIR sensor was successfully utilized to detect HMF in honey with satisfactory results. This work provided a reference for the application of the CaF 2 QDs and the detection of the furfural substances. Image 1 • The multiple color emission CaF 2 QDs had been synthesized for the first time. • A novel MIR sensor based on CaF 2 QDs was used for the visual detection of HMF in honey. • A specific HMF-MIR sensor had been constructed by using β-CD and MAA as functional monomers. [ABSTRACT FROM AUTHOR]

The genes involved in the aerobic bacterial metabolism of furfural and 5-hydroxymethylfurfural (HMF) have been characterized in two species, Pseudomonas putida Fu1 and Cupriavidus basilensis HMF14. A third furan-metabolizing strain, Pseudomonas putida ALS1267, was recently identified that grows robustly on both furfural and HMF as sole carbon sources, with a growth rate of 0.250 h−1 on furfural and 0.311 h−1 on HMF, and we have characterized the genes involved in furfural and HMF metabolism in this bacterium. Unlike C. basilensis HMF14, which contains separate furfural and HMF operons, P. putida ALS1267 contains one contiguous 18.1-kb operon, which harbors all of the furfural- and HMF-metabolizing genes except for one, the hmfH gene that encodes HMF/furfural oxidoreductase and has both HMF acid oxidase and furfural/HMF dehydrogenase activity. The 18.1-kb operon was cloned into P. putida KT2440, which cannot metabolize furans, enabling growth on furfural as the sole carbon source with a growth rate of 0.340 h−1. The clone did not allow P. putida KT2440 to metabolize HMF, most likely due to the lack of the hmfH gene. No hmfH homolog was identified in P. putida ALS1267, suggesting that another gene in the ALS1267 genome provides this function. [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]

2,5-Furandicarboxylic acid (FDCA) and 5-hydroxymethylfurfural (HMF) are top biomass-based platform chemicals with promising potential and an essential part of the future of green chemistry. HMF can be obtained mainly from fructose or glucose. Lignocellulosic glucose has a high production potential from not edible biomass. In the present paper life cycle assessment (LCA) was performed aiming at a better understanding of the environmental performance of the production of FDCA and HMF from lignocellulosic feedstock. Two case studies from the literature were modeled to obtain the life cycle inventory data. The production routes to FDCA comprise seven different process sections: hydrolysis, HMF synthesis, HMF recovery, FDCA synthesis, FDCA flash separation, FDCA purification and HMF boiler. By means of the LCA methodology, solvents such as dimethyl sulfoxide (DMSO) and dichloromethane (DCM), together with the energy demand, were found to be clear critical points in the process. Two scenarios were in focus: Scenario 1 considered the purification of FDCA through crystallization, whereas in Scenario 2 purification was performed through distillation. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: 5‐Hydroxymethylfurfural (HMF) is regarded as a thermal process contaminant in foods. Six flavan‐3‐ol fractions were isolated or semisynthesized from sorghum, cranberry and grape seed. Their unit compositions, interflavan linkages and degree of polymerization were characterized. The aim of this study was to investigate the effect of flavan‐3‐ols on the formation of HMF in chemical reaction models and fried potato chips. RESULTS: Results showed that all flavan‐3‐ols significantly mitigated the HMF formation at concentrations of 50, 100 and 200 µg mL−1 in the chemical model system, and the inhibition was positively related to dose. Using the food model, HMF content was reduced by about 50% when potato chips were soaked in an optimal concentration of 0.1 mg mL−1 flavan‐3‐ol solutions before frying. Based on the same mass concentration, B‐type flavan‐3‐ols mitigated more HMF than A‐type, and oligomeric proanthocyanidins had stronger inhibitory activity than polymers. At suitable addition levels (0.01–0.1 mg mL−1), the browning of auto‐oxidized flavan‐3‐ols under high temperature compensated the anti‐browning effect along with the supression of the Maillard reaction; therefore, the color of fried potato chips was not affected. CONCLUSION: This study demonstrates that flavan‐3‐ols could be effective additives for reducing HMF levels in fried potato chips without changing sensory properties. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Investigated sustainable route for HMF and EMF synthesis from waste mushroom. • Studied catalytic effectiveness of –SO 3 H functionalized Brønsted acidic ionic liquids (BAILs). • Correlated BAILs activity with DFT calculated deprotonation energy (DPE). • BAILs with lower DPE exhibited higher catalytic performance. Abstract This paper reports the synthesis of sulfonic acid functionalized Brønsted acidic ionic liquids (BAILs) using N,N- dimethyl acetamide [DMA]+, N -methylpyrrolidone [NMP]+ and 1-butyl-3-(4-sulfobutyl)imidazole [BBIM-BuSO 3 H]+ as cation, and methanesulfonyl [CH 3 SO 3 ]− or (OTh−), trifluoromethanesulfonate [CF 3 SO 3 ]− or (OTf−), and bis((trifluromethyl)sulfonyl)amide [(CF 3 SO 3) 2 N]− or (NTf 2 −) as anion source. The ionic liquids (ILs) demonstrated excellent catalytic performance in the valorization of waste streams of biomass to 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF), a high-value platform chemical and a promising biofuel additive. Catalytic screening indicated that BAILs containing NTf 2 anion exhibits superior performance, giving highest HMF yield. Strong electron withdrawing properties of the trifluoromethyl functionality of [NTf 2 ]− anion is proposed for this high activity of these BAILs. Detailed studies using NMR reveal the reaction proceeds through the (i) depolymerization of cellulose into glucose, followed by (ii) glucose isomerization to fructose and then the product HMF is formed by (iii) triple dehydration of fructose to HMF. Direct conversion of mushroom to EMF is also observed in one-pot with high yield when ethanol is used as a solvent in access amount. DFT calculations elucidated that the catalytic performance of the ILs followed the order of their deprotonation energies (DPE) which can be correlated directly to the residual charge on the Brønsted acidic proton. This study of valorization of waste mushroom coupled with DFT calculations, revealing DPE as an important descriptor, is likely the first report of this kind. [ABSTRACT FROM AUTHOR]

The first principle calculations with on-site Coulomb repulsion U terms were carried out to investigate the 5-hydroxymethylfurfural (HMF) adsorption on the CuO(1 1 1) and Co 3 O 4 (1 1 0) surfaces, two widely used oxidation catalysts. The adsorption of HMF molecule is energetically favoured in both cases, and HMF is more inclined to bridge adsorption via hydroxyl and formyl groups binding with surface O and metal sites. Moreover, the adsorption energy relies on both the coordination type of surface lattice oxygen to which the H atom binds and the formation of H-bond involving hydroxyl and formyl groups on the adsorbed HMF. Also, the hydroxyl O H bond breaking is very easy and is likely to be the first step in HMF oxidation, and then the OH insertion reaction to produce 2,5-furandicarboxylic acid (FDCA). The corresponding experimental results also show that the CuO and Co 3 O 4 surfaces are promising candidate catalysts. [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.

This study investigated acrylamide and 5-hydroxymethylfurfural (HMF) formation during biscuit baking. Four types of wheat flour with different molar ratios of total fructose and glucose to asparagine were investigated. Nevertheless, the molar ratio in all four biscuit doughs exceeded one after proofing due to enzyme action. Data obtained after baking were used to develop a mechanistic model, based on the asparagine-related pathway, for acrylamide and HMF formation in the four baked biscuit types. Asparagine reacted with fructose to form a Schiff base before decarboxylation to produce acrylamide without Amadori rearrangement product and sugar fragmentation. Fructose contributed considerably to acrylamide formation and to HMF formation via caramelization in all four biscuit types. No clear correlation was found between acrylamide and HMF in baked biscuits, nor between asparagine and the sum of glucose and fructose concentrations in the wheat flour. [ABSTRACT FROM AUTHOR]

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]

In this study, a new method was developed for the oxidation of 5-hydroxymethylfurfural (HMF) into 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) over heterogeneous Ru catalyst. Cs-substituted tungstophosphate (CsPW) was prepared by the exchange of H + in H 3 PW 12 O 40 with Cs + , which was then used to immobilize Ru nanoparticles to give the Ru/CsPW catalyst. The Ru/CsPW catalyst was well characterized by TEM, XRD, XPS and FT-IR technologies. The physical characterizations clearly indicated that the spherica Ru nanoparticles with an average size of 2.4 nm were homogeneously dispersed on the surface of the CsPW support. The as-prepared catalyst was studied for the oxidation of HMF, and some important parameters were investigated. The reaction solvent showed a great effect on both HMF conversion and the products selectivity. Aromatic solvents were found to be the best reaction medium for the oxidation of HMF into HMFCA. Increasing the reaction temperature and the amount of the Ru/CsPW catalyst accelerated the HMF conversion and HMFCA yield. High HMF conversion of 97.2% and HMFCA yield of 72.9% were obtained after 12 h at 130 °C with oxygen flow rate of 20 ml/min. Unfortunately, the Ru/CsPW catalyst was not very stable during the reaction, and a slight loss of its catalytic activity was observed during the recycling experiments. [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.