HMF Yield Research Articles

High-efficient microwave-assisted conversion of fructose to 5-hydroxymethylfurfural over rice straw-derived sulfonated porous carbonaceous catalyst

5-Hydroxymethylfurfural (HMF) has emerged as a pivotal platform chemical derived from biomass, attracting considerable attention for its renewable applications. In this study, sulfonated rice straw biochar (RSBC-SA) catalysts were developed and employed for microwave-assisted catalytic conversion of fructose to HMF. The RSBC-SA catalysts, synthesized by pyrolyzing rice straw biomass at different temperatures and subsequent functionalization with sulfonic acid groups, were characterized using X-ray photoelectron spectroscopy (XPS), elemental analysis, temperature programmed desorption (TPD) and Fourier-transform infrared spectroscopy (FT-IR). A comparative analysis of catalytic performance between microwave irradiation and conventional oil bath heating revealed a substantial enhancement in efficiency with the former. Notably, the 700 ℃ pyrolyzed RSBC-SA catalyst demonstrated the highest HMF yield of 92.6 % within just 5 min of reaction time under a microwavehydrothermal condition, surpassing the conventional oil bath heating method. In addition, moderate to high yields of HMF were achieved from different carbohydrates in our developed microwave reaction system, demonstrating significant catalytic activity. This superior catalytic effect under microwave irradiation can be attributed to the responsive dipole polarization of sulfonic acid groups, selective heating of the RSBC carrier via microwave absorption, and synergistic interactions among these factors. Overall, this study highlights the innovative use of agricultural waste and introduces a new method for creating microwave-responsive catalysts with biochar. This strategy enables efficient fructose conversion to HMF, promotes sustainable biomass transformation, and offers value-added uses for agricultural residues in chemical production.

Catalytic Dehydration of Biomass-Derived Feedstocks to Obtain 5-Hydroxymethylfurfural and Furfural

Biomass-produced furanics, furfural and 5-hydroxymethylfurfural (5-HMF), are considered as vital platform chemicals used in the production of active pharmaceutical ingredients (APIs), commodity goods, and fuels. The primary challenge associated with their production pertains to the high cost involved in scaling up to industrial levels. Consequently, it is essential to explore more cost-effective options that yield efficient end products. In this study, the use of Lewis and Brønsted acids such as HCl and AlCl3 enhances the isomerization of glucose through catalytic dehydration into 5-HMF. It was observed that employing moderate reaction conditions increased the yield of 5-HMF to 44.94 % and 50.60 % respectively, with changes in HCl concentration and AlCl3 mass loading. The suitable conditions to achieve the highest yield of 5-HMF were 100 μL of HCl, 0.75 g of AlCl3, reaction temperature 150 °C, and reaction time 4 h. In the second experiment, corncob was converted into furfural in the presence of 20 % H2SO4, in combination with NaCl as a promoter. The optimal conditions under which a yield of 44.77 % was achieved were as follows: 50 mL of 20 % H2SO4, reaction temperature 140 °C, 0.5 g of NaCl, 5 g of corncob, and reaction time 160 min. Furthermore, a proposed reaction mechanism was outlined to elucidate the pathway for the production of the aforementioned platform chemicals.

Agro-waste derived sulfonated biochar material as a sustainable heterogeneous catalyst for conversion of fructose to 5-hydroxymethylfurfural

BackgroundDevelopment of biomass derived solid acid catalysts has the advantage to conform the green chemistry protocol for production of 5-hydroxymethylfurfural (HMF) by dehydration of fructose. MethodWe have reported waste cashew nut shell produced char as a biochar to prepare sulfonated biochar (SBC) catalyst by incorporating –SO3H group through treatment of concentrated sulfuric acid. Significant findingsDifferent methods of characterization including XRD, FT-IR, XPS, FESEM-EDS, TEM, TPD and BET analysis, were used to study the structure, morphology, chemical compositions, acidity and porosity of the produced SBC catalysts. The mesoporous nature of the material was confirmed by the powder X-ray diffraction patterns (PXRD), type IV isotherm (BET), and flakes-like structure was observed in TEM analysis. The catalyst showed high yield of HMF (92%) under optimum conditions of 120 °C in 60 min under biphasic solvent mixture of water and toluene (1:2). High yield could be explained by high acid strength of catalyst as observed by NH3-TPD analysis. Leaching test by Sheldon's method and recyclability experiment proved the need and heterogeneity of the present catalyst.

Fabrication of Keggin heteropolyacid modified macroporous covalent triazine frameworks with cyano group-rich defects for high-value utilization of carbohydrates

Designing an efficient, stable and recyclable solid acid for catalytic conversion of biomass and its derived compounds to synthesize high value-added organic chemicals could effectively alleviate the environmental problems caused by the energy crisis and carbon dioxide emissions. We prepared a Keggin heteropolyacid modified macroporous covalent triazine frameworks (PW12-MCTF) catalyst using a simple template method and post-impregnation technology for efficient conversion of carbohydrates to produce 5-hydroxymethylfurfural (HMF). Abundant structural defects of MCTF can be constructed in situ through incomplete polymerization, which can firmly bind H3PW12O40 through physical confinement effect and bonding interactions. Under optimized conditions, PW12-MCTF exhibited high HMF yield (79.4 % or 44.4 %) and the highest turnover frequency (4.39 min−1 or 1.86 min−1) in microwave-assisted catalytic conversion of fructose or inulin, respectively. Its catalytic activity surpassed that of bulk PW12-CTF and commercial acid zeolite and resin catalysts, due to its appropriate acid properties, well-dispersed nature in DMSO, inter-connected pore structure and outstanding nucleophilic effect of N-rich units. Density Functional Theory (DFT) study provides a plausible mechanism in PW12-CTF-catalyzed fructose dehydration. The catalytic performance of PW12-MCTF remained unchanged after three cycles due to strong bonding interaction between the Keggin units and framework of MCTF. This study will provide a new strategy for the fabrication of heteropolyacid modified covalent organic frameworks with structural defects to achieve the high-value utilization of carbohydrates.

Reduction-Assisted Calcination Enhances the Photocatalytic Activity of ZnO and WO3 Nanoparticles in Biomass Conversion.

Rising energy needs and environmental issues have prompted the creation of effective and affordable photocatalysts for converting biomass. Utilizing abundant biomass, oxidation of 5-hydroxymethylfurfural (HMF) emerges as a method for generating high-value chemicals from biomass, offering an alternative to fossil fuels. We synthesized defect-engineered metal oxides (ZnO and WO3) by calcination with NaBH4 as a reducing agent. Atomic-level analyses identified oxygen vacancy defects induced by the reduction of metal ions within the metal oxide nanoparticles. Further analysis showed an unchanged band gap but an up to 4-fold increase in current density. This enhancement is attributed to the trapping of electrons in defect sites created during the calcination process. The formation of new electron donor states hindered photogenerated electron-hole recombination, enhancing the photocatalytic efficiency of the metal oxide. The photocatalytic degradation yield of HMF was over 95%, and the selective organic products 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA) were obtained without byproducts. Kinetic studies demonstrated that the photocatalytic conversion reaction rates were accelerated by up to 3.5-fold. Improved photocatalytic activity for HMF oxidation was achieved by introducing oxygen vacancy defects upon the reduction of metal ions within the metal oxides. Our results provide a promising approach for designing efficient photocatalysts.

Interfacial nanoarchitectonics for enhanced photo-assisted thermo-catalytic conversion of glucose to 5-hydroxymethylfurfural

Photo-assisted thermo-catalytic conversion of glucose to 5-hydroxymethylfurfural (HMF) is one of the most promising ways for channeling solar energy. Photo-assisted thermo-catalytic conversion of glucose and HMF yield were improved with SnO2/Cr-MOFs/Cr(OH)3 catalysts under visible light irradiation at 135 ℃-165 ℃ nitrogen atmosphere. SnO2/Cr-MOFs/Cr(OH)3 afforded relatively high Lewis acidity and Brønsted acidity, which was beneficial for thermo-catalytic conversion of glucose. The light and the interface between SnO2 and Cr-MOFs/Cr(OH)3 assistantly promoted the HMF formation. The photo-generated holes (h+) under light irradiation was the driving force for the formation of “free” protons from water and carboxylic acid in Cr-MOFs, which acted as Brønsted acid sites to promote HMF formation. With 576 mg glucose as the substrate and DMSO as the solvent, 92 % glucose conversion with 43.2 % HMF yield was achieved at 150 ℃ for 2 h under nitrogen atmosphere and 500 W Xe lamp irradiation. The results demonstrate the promise of photo-assisted thermo-catalytic conversion of glucose in the future.

Alcohol formaldehyde resin solid acid catalytic conversion of biomass into furan compounds

The conversion of waste lignocellulosic biomass into biomass platform chemicals is very promising. In this work, a novel resin-based solid acid catalyst was obtained by condensation of furfuryl alcohol with furfural, and mild calcination and sulfonation process. Then it was used to convert sugars and biomass to obtain furan compounds. Results showed that the solid acid with a furfural to furfuryl alcohol molar ratio of 3:1 is an irregular mesoporous material, with a specific surface area of 134.18 m2/g and an acid content of 2.723 mmol/g, which is extremely stable below 200 °C. 82.2 % (from fructose), 15.8 % (from glucose), 10.0 % (from cellobiose) yields of 5-HMF and 35.5 % (from xylose) yield of furfural could be obtained at 160 °C for 2 h. It can be reused more than 5 times and can restore the best catalytic effect after re-sulfonation. Notably, in the catalytic conversion of rice husk, rice straw, camphor tree branch and leaves under typical reaction conditions, 5-HMF and furfural was in yields of 9.4–24.5 % and 20.3–47.9 %, respectively. Moreover, a 10 % water dropwise to solvent can effectively promote the catalytic conversion of biomass, while there is a significant inhibitory effect after it exceeds 20 %.

A binary catalytic system of sulfonated metal–organic frameworks and deep eutectic solvents towards highly efficient synthesis of 5-hydroxymethylfurfural from fructose

The green synthesis of 5-hydroxymethylfurfural (HMF) from biomass feedstocks is a crucial step for the development of sustainable fuels, resins and plastics. Here, a novel binary catalytic system was developed with metal–organic frameworks (MOFs) and deep eutectic solvents (DESs), which synergically exhibited a superior fructose dehydration efficiency with a HMF yield of 98.5% within 40 min. The replacement from terephthalic acid to 2,5-furandicarboxylic acid as the organic ligand in MOFs catalysts altered the coordination microenvironment of metal nodes, resulting in remarkably enhanced fructose conversion rates. The formation of hierarchical porous structures and moderated Brønsted acid sites in sulfonated MOFs further promoted the HMF production. Notably, HMF could be readily separated from the MOFs-DESs system and the MOF catalyst maintained stable performance after six recycles. Theoretical calculations clarified a positive correlation between the hydrogen bond interaction (between fructose and DESs components) energy and reaction efficiency. This study provided a new strategy to couple hierarchical solid acid catalysts with functional solvents binary towards effective and sustainable upgrading of biomass-derived molecules.

Unveiling kinetics post rate-determining step in Brønsted acid-catalyzed reactions of fructose: A strategy for 5-hydroxymethylfurfural production from concentrated feedstock

The development of high-yielding catalytic systems is pivotal in biomass upgrading. However, the investigation of kinetics in these complex reaction systems is often highly challenging, especially when reactions leading to byproduct formation are obscured by a preceding, slow rate-determining step. In this work, we introduce a unique approach to kinetic analysis that enables the investigation of reactions occurring post rate-determining step. The technique was applied to the conversion of sugars to 5-hydroxymethylfurfural (HMF), an important platform molecule for sustainable chemical production. First, screening experiments were carried out to identify a catalytic solvent system that achieves a balance between solvent stability, HMF yield, and cost-effectiveness. Our kinetic analysis on the identified system reveals that the fructose reactant undergoes a rate-determining dehydration step to form an unstable reactive intermediate. This intermediate further reacts competitively with other reactive species, such as the hexose reactants or the HMF product, ultimately lowering the HMF selectivity. The calculated relative activation energies of these reactions post rate-determining step provide intuitive insights into the effects of temperature, co-existing reactive species, as well as the previously unexplained effect of feed concentration on HMF selectivity. Additionally, we propose a novel reaction strategy that significantly enhances HMF yield when compared to a traditional batch synthesis. Notably, a high HMF yield of 74 % was achieved with an extreme 55 wt% fructose loading on an aqueous basis (20 wt% loading on a total weight basis) in a low-boiling 80 wt% dioxane/water mixture using an HCl catalyst at 393 K.

Ultra-thin layer HTaMoO6 catalyst for the upgrading of carbohydrates into 5-hydroxymethylfurfural

The conversion of carbohydrates into 5-hydroxymethylfurfural (HMF), a vital and valuable platform chemical, is sought after in industrial applications but poses significant challenges. In this research, we engineered an ultra-thin layer HTaMoO6 catalyst using ball-milling/liquid-exfoliation technique, demonstrating its efficiency in catalyzing the transformation of carbohydrates to HMF. In contrast to the conventional method utilizing tetra(n-butylammonium) hydroxide as the intercalation agent, the ball-milling/liquid-exfoliation technique not only reduces catalyst preparation time (within 12 h) but also enhances the efficient intercalation, leading to the formation of an ultra-thin layer structure. The resulting catalyst exhibits high total acidity, a favorable Brønsted/Lewis acid ratio, and improved accessibility of active sites due to the thin layer structure post-exfoliation. Compared with bulk LiTaMoO6, the ultrathin layer HTaMoO6 catalyst enables complete fructose dehydration with an HMF yield reaching 89.1 % under moderate reaction conditions (120 °C, 1 h) and 47.2 % yield of HMF is obtained from sucrose at 130 °C. This work provides a new method to fabricate the solid acid for the transformation of carbohydrates.

Boosting transformation of glucose and fructose to 5-hydroxymethylfurfural by a strategy of dual catalyst in biphasic solvent system with salt

5-Hydroxymethylfurfural (HMF) derived from biomass can be converted to a variety of high-value chemicals. Transformation of glucose and fructose to HMF is the typical reactions involved in transformation of raw biomass to HMF. However, poor stability of heterogeneous solid acid and the side reactions of HMF consumption still is a challenge for the entitled reaction. In the present work, a strategy of catalyst with dual acid of Lewis acid and Brønsted acid combined with the biphasic solvent system of organic-aqueous salt is employed to design the effective catalytic system for the transformation of glucose and fructose to HMF. An SiO2-Zr-P heterogeneous solid acid with the dual acid sites was prepared by grafting of zirconium dioxide on silica followed by its phosphation. The surface grafted zirconium dioxide was transformed to the zirconium phosphate with the formula of Zr(HPO4)2·H2O. Both the Lewis acid and Brønsted acid of the SiO2-Zr-P are enhanced and their influences for the entitled reaction was investigated. The prepared catalyst was employed to catalyse the entitled reaction in the biphasic solvent of tetrahydrofuran-aqueous NaCl solvent, giving 99.9% yield of HMF for fructose and 75.2% yield of HMF for glucose. The catalyst showed good stability and can be applied for the catalytic transformation of various sugars to corresponding HMF and fufural with satisfied yield.

Catalytic conversion of mannose to 5-hydroxymethylfurfural promoted by hydrophobic halloysite-based catalyst in biphasic system

A novel halloysite (Hal) based acidic catalyst was synthesized by anchoring functional alkyl group and Cr site and catalyzed the selective conversion of mannose to 5-hydroxymethylfurfural (HMF) in NaCl-H2O/dimethyl sulfoxide/methyl isobutyl ketone (MIBK) biphasic system. Herein, adjusting the hydrophilicity/hydrophobicity of catalyst by modifying the octyl group can facilitate the HMF yield. The density functional theory (DFT) calculation and in-situ FT-IR results revealed that increasing the hydrophobicity of catalyst surface weakened the interaction between HMF, water molecule and acid sites and inhibited the rehydration of HMF. Moreover, the synergistic effect between Cr and sulfonic group active sites remarkedly promoted the isomerization of mannose to fructose and the dehydration of fructose to HMF, and the 48.1% yield of HMF was obtained. This study provides references for the high value conversion of hemicellulose with the high efficiency reaction system.

Stepwise processing strategy for efficient and comprehensive utilization of sugarcane bagasse via enzymatic hydrolysis and catalytic conversion to produce 5-hydroxymethylfurfural

To achieve the goal of “no waste” in circular bioeconomy on the basis of waste-to-energy conversion, the development of efficient technology for sustainable treatment and utilization of lignocellulosic biomass is significant yet challenging. In this study, a stepwise processing strategy based on enzymatic hydrolysis and catalytic conversion was proposed for comprehensive utilization of sugarcane bagasse (SCB) to produce value-added products. Mechanical activation (MA) pretreatment was adopted to disrupt the recalcitrant structure of SCB for improving enzymatic hydrolysis of polysaccharides to produce reducing sugars, obtaining a high yield (392 mg/g SCB) of target sugars (TS; i.e., cellobiose and glucose). The enzymolysis residue and Al(NO3)3·9 H2O were treated by MA and then calcinated to construct the biochar (BC)-based catalyst (denoted as MA-Al/BC) with Brønsted–Lewis dual-acidic sites, which effectively catalyzed the conversion of TS to produce 5-hydroxymethylfurfural (5-HMF). A TS conversion of 94.5% and a 5-HMF yield of 77.6% were achieved at 190 °C for 4 h in the biphasic system. MA-Al/BC exhibited excellent universality for efficient catalytic conversion of various carbohydrates. This study offers a promising approach for value-added exploitation of agricultural wastes within circular bioeconomy principles.

H-Beta Zeolite as Catalyst for the Conversion of Carbohydrates into 5-Hydroxymethylfurfural: The Role of Calcination Temperature

H-Beta zeolite is a solid acid catalyst commonly utilized in the catalytic conversion of biomass resources. In this study, H-Beta zeolite was calcined at different temperatures (350, 550, 750, and 1000 °C) to explore the effects of high temperature-induced dealumination on its physicochemical properties and its catalytic ability to convert glucose into 5-hydroxymethylfurfural (HMF). It was shown that as the calcination temperature increased, the Si-O-Al bond of H-Beta zeolite was broken and its dealumination effect was enhanced. Dealumination led to the collapse of the framework of H-Beta zeolite and a reduction in the number of acid sites, which in turn reduced its catalytic performance and the efficiency of HMF formation from glucose. Furthermore, H-Beta zeolite exhibited an extraordinary catalytic ability for the production of HMF from carbohydrates. Using glucose and cellulose as substrates, superior HMF yields of 91% and 46%, respectively, were achieved under optimal reaction conditions. Further, calcination removes carbon deposits in the recovered H-Beta zeolite, but it affects the cycling stability of the catalyst. Meanwhile, the by-products formed during the synthesis of HMF from glucose catalyzed by H-Beta zeolite catalyst were also clearly detected.

Cellulose conversion to 5-hydroxymethylfurfural via a simple and efficient phosphate-doped hafnium oxide catalyst

The efficient catalytic conversion of cellulose to 5-hydroxymethylfurfural (HMF) can provide a valuable reference for the high-value utilization of biomass. In this work, a series of simple phosphate-doped hafnium oxide catalysts (x-P-HfO2) were prepared, and their physicochemical properties were analyzed by ICP-OES, XRD, XPS, FTIR, SEM-EDX, N2 adsorption-desorption isotherms, NH3-TPD and Py-FTIR characterizes. Detailed evaluation of the reaction conditions demonstrated the ideal catalytic performance of the x-P-HfO2 catalysts, and the HMF yield from cellulose reached a satisfactory 61% in the water(NaCl)/tetrahydrofuran biphasic reaction system. Based on the captured intermediates and detected by-products, possible catalytic pathways are summarized. Meanwhile, the hydrothermal stability of the catalyst was also investigated, and the reason for its performance degradation after five cycles was determined to be the loss of useful Brønsted active sites. In addition, the effects of the phosphating and sulfating modification approaches on the catalyst activity were also compared, verifying that the introduction of phosphate is more conducive to the catalyst expressing high activity for the formation of HMF from cellulose.

Sn-modified SBA-15 with tailored acid properties for efficient 5-hydroxymethylfurfural production from glucose

Interest in production and utilization of 5-hydroxymethylfurfural (5-HMF) has risen greatly as 5-HMF is considered as an extremely important platform compound. It remains a huge challenge to develop efficient and low-cost solid catalysts with suitable acid properties for sustainable production of 5-HMF from glucose. Herein, a bifunctional Sn-modified SBA-15 (Sn–OH/SBA-15) catalyst containing both Lewis and Brønsted acid sites was fabricated. Dimethyldichlorostannane was grafted onto mesoporous SBA-15, and the methyl groups were then converted to hydroxyl groups by calcination. The synergistic effects of Lewis and Brønsted acid significantly boosted the synthesis of 5-HMF from glucose adopting the one-pot method. By optimizing the reaction conditions, the Sn–OH/SBA-15 sample was able to achieve a glucose conversion of 96.9% with a 5-HMF yield of 70.6% (180 °C, 5 h). Moreover, the catalyst demonstrated superior recyclability and reusability. This work would enlighten the exploitation and preparation of highly efficient catalysts for the transformation of carbohydrates into value-added chemicals.

The Impact of the Ratio Between Stronger and Weaker Acid Sites on the Production of 5‐Hydroxymethylfurfural and Furfural from Monosaccharides

AbstractSulfonated carbons and commercial Amberlyst 15 and 45 served as model catalysts to explore the impact of the ratio between stronger and weaker acid sites (NS/NW) on 5‐hydroxymethylfurfural (HMF) and furfural production from fructose and xylose. Catalysts with varying structural and surface properties, and consequently different NS/NW ratios, were prepared from diverse templated mesoporous carbons and distinct sulfonation methods. HMF or furfural yields exhibited an exponential correlation with the NS/NW ratio. However, the catalytic activity per site (TON) displayed a volcano‐like plot, reaching a maximum between NS/NW=2–4. Consequently, our findings suggest the involvement of both strong (sulfonic acid) and weak acid (surface carboxylic acid, alcohol, and phenol groups) sites in monosaccharide dehydration mechanisms. These insights may guide the development of novel catalysts.

Investigation on the preparation of 5-Hydroxymethylfurfural through fructose dehydration using in-line FTIR and in-situ 13C NMR

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

Efficient catalytic conversion of cellulose into 5-hydroxymethylfurfural by modified cerium zirconium phosphates in a biphasic system

Numerous metal phosphates have shown activity in the conversion of cellulose into 5-hydroxymethylfurfural (HMF). However, challenges persist due to low HMF yields and unclear structure-reactivity relationships. Herein, a series of zirconium-cerium phosphate-based catalysts were prepared by the co-precipitation method. These catalysts were sulfonated and loaded with tungsten to introduce Brønsted acidity. The effects of catalyst types and operating conditions on the production of HMF from cellulose using a biphasic system of tetrahydrofuran (THF) and water were systematically investigated in an autoclave reactor. The structure-reactivity relationship of these catalysts was subsequently elucidated using various catalyst characterization techniques. For an understanding of the reaction mechanism, in-situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) was employed to monitor the reaction process. Experimental results revealed that the optimal HMF yield of 41.5% could be obtained using the 2W/CeZr2P + AC–SO3H–2 catalyst at 180 °C with a reaction time of 4 h. Compared to monometallic phosphate pairs of zirconium and cerium, this represents an enhancement in HMF yield by approximately 8%–20%. The enhancement could be attributed to the adequate acid amount and the balanced Brønsted/Lewis acid site ratio of this catalyst. These findings provide valuable guidance for future design and optimization of bimetallic phosphate catalysts.

A Closed-Loop Biorefinery Approach for the Valorization of Winery Waste: The Production of Iron-Sulfonated Magnetic Biochar Catalysts and 5-Hydroxymethyl Furfural from Grape Pomace and Stalks

In this work, a closed-loop strategy for the management and valorization of winery waste was proposed. The exhausted pomace and grape stalks that are typically obtained from white wine industries were used as a source of simple sugars, namely, glucose and fructose, and of lignocellulosic feedstock for the preparation of selective catalysts for the 5-hydroxymethylfurfural (5-HMF) production from fructose. A novel synthetic procedure was developed for the synthesis of iron-sulfonated magnetic biochar catalysts (Fe-SMBCs). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), BET surface area, porous structure analysis and determination of total amount of acid sites were performed in order to characterize the physico-chemical properties of the synthesized systems. Then, these heterogeneous catalysts were successfully tested via the dehydration of simple sugars into 5-HMF by using methyl isobutyl ketone (MIBK) and gamma valerolactone (GVL) as co-solvents. The optimum 5-HMF yield of 40.9 ± 1.1%mol with a selectivity of 59.8 ± 2.6%mol was achieved by adopting the following optimized conditions: 0.1 g of catalyst, volume ratio of GVL to H2O = 2 to 1, 403 K, 6 h. In addition, the catalyst was easily recycled using an external magnetic field and used for at least five reaction cycles without significant loss of catalytic activity.