The electrochemical oxidation of the biorefinery product 5‐(hydroxymethyl)furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), an important platform chemical for the polymer industry, is receiving ...increasing interest. FDCA‐based polymers such as polyethylene 2,5‐furandicarboxylate (PEF) are sustainable candidates for replacing polyethylene terephthalate (PET). Herein, we report the highly efficient electrocatalytic oxidation of HMF to FDCA, using Ni foam modified with high‐surface‐area nickel boride (NixB) as the electrode. Constant potential electrolysis in combination with HPLC revealed a high faradaic efficiency of close to 100 % towards the production of FDCA with a yield of 98.5 %. Operando electrochemistry coupled to ATR‐IR spectroscopy indicated that HMF is oxidized preferentially via 5‐hydroxymethyl‐2‐furancarboxylic acid rather than via 2,5‐diformylfuran, which is in agreement with HPLC results. This study not only reports a low‐cost active electrocatalyst material for the electrochemical oxidation of HMF to FDCA, but additionally provides insight into the reaction pathway.
Adding value through electrocatalysis: The electrocatalytic oxidation of the biorefinery product 5‐(hydroxymethyl)furfural (HMF) to the prospective platform chemical 2,5‐furandicarboxylic acid (FDCA) over nickel boride (NixB) modified nickel foam in an electrochemical flow reactor proceeds with a very high FDCA yield of 98.5 % at a faradaic efficiency of 100 %. NixB appears to be a very promising catalyst for electrochemical HMF oxidation.
With the aim of developing an efficient and inexpensive catalyst for the production of HMF from glucose, a solid Lewis acid catalyst γ-AlOOH, a common industrial catalyst with easy preparation and ...low price, was used as the sole catalyst to directly synthesize 5-hydroxymethylfurfural (HMF) from glucose in dimethyl sulfoxide. Various reaction parameters, such as catalyst loading, temperature, reaction duration, and solvent, were investigated. An impressive HMF yield of 61.2% was obtained at the reaction conditions of 130 °C for 3 h. Furthermore, HMF yields from other carbohydrates such as fructose (44.8%), cellulose (50.3%), maltose (53.6%) and sucrose (62.2%) could be achieved using γ-AlOOH as a catalyst. More importantly, the catalyst γ-AlOOH could be reused several times without the loss of its catalytic activities. After five reaction runs, an HMF yield of 57.2% was obtained.
The effects of the 22-year variation of solar magnetic fields in the galactic cosmic ray (GCR) intensity were first observed and interpreted as manifestations of inversion of the high-latitude solar ...magnetic field in properties of heliospheric magnetic fields by the Lebedev Physical Institute team in 1973. Since then, these effects have been studied already for 50 years.
The situation with the heliospheric magnetic field is clear for periods of medium and low sunspot activity — the heliosphere consists of two unipolar “hemispheres” separated by a wavy global heliospheric current sheet and characterized by a general polarity A (unit quantity with the sign of the radial component of the heliospheric magnetic field in the northern hemisphere). Yet there is no consensus on what the inversion of the heliospheric magnetic field is and which effects in the GCR intensity are connected with this phenomenon.
In this article, we briefly formulate general concepts of the 22-year variation in characteristics of the Sun, heliosphere, and GCR intensity and discuss the observed effects in the GCR intensity, which we attribute to the heliospheric magnetic field reversal. Models for this phenomenon and the results of GCR intensity calculations with these models will be discussed in the next article.
Here we conduct an experimental study of fructose dehydration to 5-hydroxymethyl furfural (HMF) in a biphasic microreactor as a function of residence time, temperature, and sugar loading using methyl ...butyl iso-ketone (MIBK) and 2-pentanol as extracting solvents. We demonstrate stable operation with maximum HMF yields of 93% and 87% in the two solvents, respectively, at 200 °C and a residence time of 2 s for a 5 wt% fructose aqueous feed. We report the highest optimal HMF space–time yield of 60 kg/L-hr at 200 °C (10 – 2,500-fold higher than published reports). Unexpectedly, an optimum organic-to-water ratio exists that depends on the solvent. Notably, we observe experimentally an increased fructose rate and HMF yield well above the extraction thermodynamic limit and hypothesize that the solvent plays a dual role, that of an extractant to protect HMF from degradation and a modifier of the fundamental chemistry. We expose mass transfer limitations of microreactors at longer residence times and higher temperatures and provide reactivity maps for their design. We show that batch reactors are unfit for high throughput and distributed manufacturing where small, farm-based systems are necessary.
•The Pt/ZIS/MnO2 (PMZIS) heterojunctions with photothermal effect was constructed.•The PMZIS showed high photocatalytic activity both for HMF oxidation to DFF or FDCA.•The spatial charge separation ...structure inhibit the charge recombination of PMZIS.•The photothermal effect could adjust the photocatalytic oxidation production of HMF.
The selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-dicarbofuran (DFF), and 2,5-furanedicarboxylic acid (FDCA) is essential to its practical application. Herein, a novel Pt/ZIS/MnO2 (PMZIS) photocatalysts with photothermal effect were well designed for selective and controlled oxidation of HMF toward DFF or FDCA. The product distribution of HMF photo-oxidation on PMZIS can be regulated by the photothermal effect. At a low temperature (10 °C) with PMZIS, DFF is the primary oxidation product with the yield of 54.6% and selectivity of 85.4%. At a high temperature (60–70 °C) induced by photothermal effect, the FDCA can be obtained with the yield of 61.5 % and selectivity of 82.9%. Moreover, the Z-scheme transfer pathway and Pt cocatalysts realize the spatial charge separation structure of PMZIS heterojunctions. This unique structure greatly inhibits charge recombination and maximizes the activation ability of molecular oxygen to efficiently generate of the reactive oxygen species (e.g., 1O2 and O2–), thus significantly improving the photocatalytic performance. This work would provide valuable insight in the product regulation through photothermal effect for the photocatalytic specific selective oxidation of organic molecules.
In biorefining, Green electrochemistry offers an intelligent approach to produce valuable chemicals that are not derived from fossil fuels. In this study, we demonstrate the electrochemical reduction ...of 5-hydroxymethylfurfural (HMF), a biomass-derived compound, into 2,5-bis-hydroxymethylfuran (BHMF), which serves as a fundamental component in the polymer industry. This reaction was performed using Cu and Ag electrodes, but a better performance was obtained by combining the properties of the two metals in Ag decorated Cu foils. Additionally, by means of Impedance Spectroscopy IS we could uncover that the incorporation of Ag onto Cu electrodes not only increases the active area of the electrodes but also improves both the HMF adsorption on Cu and the catalytic properties of Ag. This synergistic effect leads to a more efficient reduction of HMF. Nonetheless, the diffusion of reactive species imposes a constraint on the increase in current. Finally, the observed inverted hysteresis in the cyclic voltammetry is attributed to variations in the amount of HMF adsorbed on the electrode surface during the forward and reverse directions of the cyclic voltammetry. Unlike other systems such as solar cells, where this effect is linked to the presence of a low frequency inductive behavior which, in this case, plays a negligible role.
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•HMF is a quality marker in food.•It is formed in the Maillard reaction and caramelization process.•HMF indicates food non-conformities and processing efficiency.•Novel spectrometric, ...chromatographic, and electroanalytical methods for HMF determination are critically discussed.
The thermal processing, storage, and transportation of foodstuffs (e.g., fruit juices, coffee, honey, and vinegar) generate 5-hydroxymethylfurfural (HMF). The food industry uses this compound as a quality marker, thus increasing the demand for fast and reliable analytical methods for its determination. This review focuses on the formation of HMF in food, its desirable and toxic effects, and recent advances in analytical methods for its determination in foodstuffs. The advantages and limitations of these analytical approaches are discussed relative to the main analytical features.
The use of non-edible raw materials from agriculture as a form of biomass to obtain carbon-based compounds is the most viable solution to replace fossil resources. Within this, 5-hydroxymethyl ...furfural (HMF) is a platform monomer from which other high value-added monomers are obtained, such as 2,5-furandicarboxylic acid (FDCA), a compound that can be obtained from 5-methoxymethyl furfural (MMF), and which can be used as a fuel, fuel additive or polymer precursor. Several catalysts (mostly zeolites) have been tested to produce MMF. Specifically, with a ZSM-5 zeolite a yield towards this compound of 97 % has been achieved, carrying out the reaction in a batch reactor for 5 h. Through the characterization of the catalysts, a strong correlation has been observed between the acidity of these catalysts and their effectiveness in the reaction of HMF through MMF.
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•MMF is one of the starting substrates for the industrial production of FDCA.•HZSM-5_11.5 and HZSM-5_40 catalysts showed the best performance in HMF etherification.•HZSM-5_11.5 catalyst provided a MMF yield of 97 % and a HMF conversion of 98 % at 5 h.•Strong BAS presence and high BAS/LAS ratio are key factors for MMF production.•Metal load onto HZSM-5_11.5 support did not improve the catalytic activity of the support.
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•An biomimetic catalyst CeCu(OH)6Mo6O18 was employed in reaction of HMF to DFF.•The yield of DFF could reach 99% under quite mild conditions.•The Mo5+ and Ce4+ species play very ...important roles in the oxidation process.•Ce4+ species was employed as ETMs and CuMo6 anion was used as the electron-donor.
2,5-diformylfuran (DFF) is a key near-market platform chemical that has been widely used to synthesize various useful compounds. In this study, a unique biomimetic system was developed by splitting the oxidation process into multi-step redox circulations, which can increase markedly the activity and selectivity for the aerobic oxidation 5-hydroxymethylfurfural (HMF) to DFF. An Anderson-type catalyst CeCu(OH)6Mo6O18, with similar properties to oxygenase enzymes, was prepared by the ion exchange method, in which the cation Ce4+ species was employed as electron transfer mediators (ETMs) as well as the anion Cu(OH)6Mo6O184− was used as the electron-donor. The Mo5+ and Ce4+ species on the surface of the catalyst play very important roles in the oxidation process of HMF to DFF. The aerobic oxidation of HMF over the CeCu(OH)6Mo6O18 catalyst could bring out DFF with a yield of 99% in p-chlorotoluene. It provides a promising and highly environmentally friendly approach for the aerobic oxidation HMF to DFF.
With the growing shortage of fossil energy and the increasing of concerns over global climate changes and environmental problems have driven the development of alternative energy sources. Recently, ...great interest has been oriented towards the development of sustainable resources, especially the utilization of lignocellulosic biomass, a renewable and the most abundant source of biomass originating from plant photosynthesis in nature. Catalytic conversion of renewable cellulosic biomass can produce a series of compounds such as 5-hydroxymethylfurfural (HMF) and 2,5-dimethylfuran (DMF) which are important platform compounds and ideal renewable alternative to fossil fuels. To obtain the renowned bio-based platform molecules, various catalysts and reaction systems have been used in the past decade years. To fully understand current biomass to HMF and DMF development, it is necessary to have an overview and comparison of different homogeneous and heterogeneous catalysts. The reaction systems also exhibit a remarkable impact on the yield and distribution of products with different catalysts. General trends and future research directions of using biomass for HMF, DMF production are also discussed systematically.
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•Shifting from fossil resources to sustainable biomass for chemicals production is important in both academic and our society.•A comprehensive review about the catalytic conversion of biomass into HMF and DMF have been presented.•Catalysts, and reaction systems for the production of HMF and DMF developed in the last few years are discussed.•The scale-up conversion of biomass and the process economy analysis of HMF and DMF production are also discussed.
