Production of 5-hydroxymethylfurfural in a eutectic mixture of citric acid and choline chloride and its extractive recovery

Biphasic Production of 5-hydroxymethylfurfural (HMF) in a Recyclable Deep Eutectic Solvent-based System Catalyzed by H4SiW12O40

The reaction with in situ extraction to yield 5-hydroxymethylfurfural (HMF) from d-fructose (Fru) was investigated using a biphasic system based on a self-consuming deep eutectic solvent (DES) as reaction phase. The significance of choline chloride (ChCl), a cost-effective and safe quaternary ammonium salt, was evident in enhancing HMF yield through fructose dehydration and concurrently suppressing side reactions. The DES system demonstrated fast reactions with high selecivities and recyclability across five cycles. The observed decline in H4SiW12O40 activity, primarily due to proton leaching, was successfully restored with the addition of HCl. Furthermore, ChCl exhibited ease of recrystallization in the presence of acetonitrile. This research proposes an environmentally friendlier approach for HMF production through a reusable-biphasic process. The presented reaction system suppresses completely the formation of levulinic and formic acid leading to HMF yields of up to 84 % of selectivities of up to 88 % after 30 minutes at 80 °C. The system was recycled over 16 runs and after an initial slight loss of activity the system in the run 0-5, run 6-15 has shown a constant HMF output as in the first recycling run.

Synthesis of 5-hydroxymethylfurfural from glucose, fructose, cellulose and agricultural wastes over sulfur-doped peanut shell catalysts in ionic liquid

In this study, waste peanut shells were sulfur-impregnated and used as acid catalysts in the presence of an ionic liquid for the conversion of fructose, glucose, and cellulose into 5-hydroxymethylfurfural, a useful chemical intermediate for biofuel production. Effects of sulfur-doping duration (1 h and 5 h), solvent type and proportion, reaction temperature (130 °C, 140 °C, and 150 °C), time (30-240 min), catalyst-to-substrate ratio (1-2.5 m/m), and agricultural residue (peanut shell, Canada wheat straw, water hyacinth, stalk, and reed) on HMF yields were investigated. Monophasic and biphasic ionic liquids such as [amim]Cl, [bmim]HSO₄, and [emim]Cl were employed in combination with choline chloride and dimethyl sulfoxide to improve HMF yields. Results show that peanut shells subjected to prolonged sulfur impregnation produced higher HMF yields. At 130 °C and 2 h, HMF yields from fructose and glucose reached 94.6% and 55.1%, respectively. Higher reaction temperatures improved HMF yields and accelerated conversion rates for the sugar substrates. Moreover, HMF production from waste biomass namely, peanut shells, peanut stalk, Canadian wheat straw, reed, and water hyacinth were examined in separate one-pot catalytic reactions. Overall, the study showed the effectiveness of sulfur-doped peanut shells as solid acid catalysts for the synthesis of HMF from various sources and the results may be used in designing large-scale production of furanic biofuel precursors from agricultural wastes.

Controlling the Reaction Networks for Efficient Conversion of Glucose into 5-Hydroxymethylfurfural

Biomass-derived hexose constitutes the main component of lignocellulosic biomass for producing value-added chemicals and biofuels. However, the reaction network of hexose is complicated, which makes the highly selective synthesis of one particular product challenging in biorefinery. This Review focuses on the selective production of 5-hydroxymethylfurfural (HMF) from glucose on account of its potential significance as an important platform molecule. The complex reaction network involved in glucose-to-HMF transformations is briefly summarized. Special emphasis is placed on analyzing the complexities of feedstocks, intermediates, (side-) products, catalysts, solvents, and their impacts on the reaction network. The strategies and representative examples for adjusting the reaction pathway toward HMF by developing multifunctional catalysts and promoters, taking advantage of solvent effects and process intensification, and synergizing all measures are comprehensively discussed. An outlook is provided to highlight the challenges and opportunities faced in this promising field. It is expected to provide guidance to design practical catalytic processes for advancing HMF biorefinery.

One-Pot Synthesis of 5-Hydroxymethylfurfural from Glucose by Brønsted Acid-Free Bifunctional Porous Coordination Polymers in Water

Efficient synthesis of 5-hydroxymethylfurfural (HMF) using glucose (Glc) as a starting material represents an important process in biomass transformation. In this study, novel bifunctional porous coordination polymer (PCP) catalysts [PCP(Cr)-NH2-x (CH3) x ; x = 0, 1, or 2] containing Lewis acidic and Lewis basic sites have been synthesized and utilized as solid-phase catalysts for HMF synthesis starting from a Glc-in-water system. PCP(Cr)-NH2 was found as the optimal catalyst, with an HMF yield of 65.9% and Glc conversion of 99.9% in a water/tetrahydrofuran (THF) system. Compared with PCP(Cr), amino groups in PCP(Cr)-NH2 catalysts play a vital role in Glc isomerization and subsequent dehydration-cyclization process to obtain the highly selective and effective fructose-to-HMF conversion. High yield and chemoselectivity are ascribed to concurrent extraction of HMF into the THF layer just upon its formation in water. The mechanism of Lewis acid-base synergistic catalysis was deduced by means of infrared spectroscopy, and catalysts could be reused after simple washing procedure with high reproducibility.

Development of Betaine-Based Sustainable Catalysts for Green Conversion of Carbohydrates and Biomass into 5-Hydroxymethylfurfural

Renewable and sustainable betaine-based catalysts (BX) derived from the betaine sugar industry or ChCl were developed for the production of 5-hydroxymethylfurfural (HMF) from various carbohydrates. The HMF yields in the BX-based media reached up to 88 %, 66 %, 37 % and 53 %, for the conversion of fructose, glucose, cellulose, and lignocellulosic biomass, respectively. In addition, choline-O-sulfate was synthesized and demonstrated to be an efficient catalyst for the conversion of fructose to HMF. From the perspective of green and sustainable chemistry, this work demonstrates benefits not only in the preparation of sustainable catalysts but also the green production of HMF from biomass.

Green Processing of Lignocellulosic Biomass and Its Derivatives in Deep Eutectic Solvents

The scientific community has been seeking cost-competitive and green solvents with good dissolving capacity for the valorization of lignocellulosic biomass. At this point, deep eutectic solvents (DESs) are currently emerging as a new class of promising solvents that are generally liquid eutectic mixtures formed by self-association (or hydrogen-bonding interaction) of two or three components. DESs are attractive solvents for the fractionation (or pretreatment) of lignocellulose and the valorization of lignin, owing to the high solubility of lignin in DESs. DESs are also employed as effective media for the modification of cellulose to afford functionalized cellulosic materials, such as cellulose nanocrystals. More interestingly, biomassderived carbohydrates, such as fructose, can be used as one of the constituents of DESs and then dehydrated to 5-hydroxymethylfurfural in high yield. In this review, a comprehensive summary of recent contribution of DESs to the processing of lignocellulosic biomass and its derivatives is provided. Moreover, further discussion about the challenges of the application of DESs in biomass processing is presented.

Decomposition Kinetics of Glucose and Fructose in Subcritical Water Containing Sodium Chloride

The kinetics of the decomposition and isomerization of glucose and fructose in pure water and water containing sodium chloride (1-20 % w/w) under subcritical conditions at 180-220 °C was investigated. The addition of sodium chloride in subcritical water accelerated the decrease of glucose, and the rate was expressed by the Weibull equation. Although the isomerization of glucose to fructose was observed in parallel with decomposition, the yield of fructose was lower at higher sodium chloride concentrations. Mannose was also formed from glucose with very low yield. It was seen that fructose decomposed much faster than glucose, in pure and salty subcritical water. The decomposition of fructose obeyed first-order kinetics in the initial stages of the reaction and could be expressed by the autocatalytic model in the later stages. The formation of glucose and mannose from fructose was not observed under any of the conditions investigated.

Efficient conversion of glucose to 5-hydroxymethylfurfural using bifunctional partially hydroxylated AlF3

Mesoporous AlF₃ material bearing both Lewis and Brønsted acid sites exhibits high catalytic performance in glucose-to-fructose isomerization and subsequent dehydration to HMF (57.3% yield).