Maximum HMF Yield Research Articles

A novel experimental approach for the catalytic conversion of lignocellulosic Bambusa bambos to bioethanol

Bambusa bambos (B.B) biomass is cellulose rich lignocellulosic material, containing 47.49% cellulose, 17.49% hemicellulose, 23.56% lignin was used as a potential substrate for bioethanol production. The research paper investigates the use of B.B biomass as a substrate for bio-ethanol production through a two-phase catalytic conversion process. Four water-regulated regimes were identified to optimize the conversion of lignocellulosic biomass to biofuel precursors. The catalytic hydrolysis of B.B using CuCl2 was conducted for 10 hours at 110˚C, in aprotic ionic liquid (1-Butyl-3-methylimidazolium chloride) medium. The concentrations of glucose and 5-hydroxymethylfurfural (5-HMF) were measured while varying the amount of water addition. Water played a crucial role in the conversion of cellulose to glucose and 5-HMF by influencing product yields through the interplay of transport properties like heat conduction and viscosity. The highest glucose yield was achieved at 60.82% when operating at a water inclusion rate of 115.72 µL water/h for a duration of 6 hours at 110˚C. On the other hand, the maximum HMF yield was observed as 5.84% at water inclusion rate of 77.15 µL water/h for 5 hours at 110˚C. Yeast mediated glucose fermentation resulted in a bioethanol concentration of 5.5 mg/mL utilizing 15 mg/mL of catalytically produced glucose at a temperature of 30°C. After catalytic hydrolysis, the ionic liquid was also efficiently recycled for a sustainable economy.

Sulfonated ionic liquid immobilized SBA-16 as an active solid acid catalyst for the synthesis of biofuel precursor 5-hydroxymethylfurfural from fructose

The catalytic conversion of biomass-derived chemicals to 5-hydroxymethylfurfural (HMF) is of high current interest. In this work, an efficient solid acid catalyst was synthesized by anchoring sulfonic imidazolium-based ionic liquid (IL) over the surface of mercaptopropyl-modified SBA-16 via thiol-ene click reaction. Various characterization techniques exhibited that the mesostructure of SBA-16 was preserved after the immobilization of acidic IL on its surface. The catalytic activity of the synthesized catalyst was evaluated for the dehydration of fructose to HMF. The influence of different reaction parameters on the catalyst efficiency was examined and optimized. A maximum HMF yield of 98% was attained after 30 min of reaction at 120 °C in dimethyl sulfoxide (DMSO) with a catalyst load of 15 mg. Importantly, the catalyst was simply recoverable and can be reused for five successive runs.

Niobium oxide-phosphorylated carbon xerogel composites as solid acid catalysts for cascade conversion of glucose to 5-hydroxymethylfurfural (HMF) in pure water

The cascade conversion of glucose to a key platform commodity, 5-hydroxymethylfurfural (HMF), was studied as a sustainable method for producing platform molecules from biomass. Bifunctional catalysts were prepared by the deposition/precipitation of Nb2O5 (containing NbO4 Lewis and Nb-OH Brønsted acid sites) onto the surface of phosphorylated carbon xerogels (CX_P) with Brønsted acid sites (BA) in the form of oxygen and phosphorus functionalities. The number of Lewis acid (LA) sites in the composites was tuned by varying the Nb loading (0–60%), and Brønsted acidity was modified by thermal (post)treatments. Catalytic tests carried out in pure water revealed that the LA sites played an important role in selective glucose conversion, enhancing the isomerization of glucose to fructose, whereas BA sites, in the absence of LA sites, catalyzed the degradation of glucose to humin. For bifunctional catalysts, the glucose conversion was proportional to the total Brønsted acidity of the catalysts. Moreover, the glucose conversion to fructose increased with higher Nb loadings, while the selectivity to HMF decreased, resulting in similar HMF yields obtained on the composites. The drop in selectivity to HMF was attributed to the degradation of HMF to humin catalyzed by high concentrations of BA sites. After the removal of strong BA sites originating from Nb2O5, the selectivity to HMF significantly increased, leading to the maximum HMF yield of 31% obtained by a composite containing 60% Nb2O5 and treated at 300 °C in air. Thus, a catalyst with poor Brønsted acidity of Nb2O5 origin (Nb-OH) was shown to be preferable to achieve moderate HMF yield without humin formation in an environmentally friendly and cost-effective process. It was also shown that the type and amount of BA sites from the carbon component affected the yield of HMF. BA in the form of oxygen functionalities increased the selectivity to HMF, whereas larger concentrations of P-OH showed the opposite effect.

5-Hydroxymethylfurfural synthesis from fructose over deep eutectic solvents in batch reactors and continuous flow microreactors

In this work, a deep eutectic solvent (DES) composed of choline chloride (ChCl) and ethylene glycol (EG) was prepared and applied for the conversion of fructose to 5-hydroxymethylfurfural (HMF), catalyzed by HCl in both laboratory batch reactors and continuous flow microreactors. The effects of reaction temperature, batch time, catalyst loading and molar ratio of ChCl to EG on the fructose conversion and HMF yield were first investigated in the monophasic batch system of ChCl/EG DES. To inhibit HMF-involved side reactions (e.g., its polymerization to humins), methyl isobutyl ketone (MIBK) was used as the extraction agent to form a biphasic system with DES in batch reactors. As a result, the maximum HMF yield could be enhanced at an MIBK to DES volume ratio of 3:1, e.g., increased from 48% in the monophasic DES (with a molar ratio ChCl to EG at 1:3) to 63% in the biphasic system at 80°C and 5 mol% of HCl loading. Based on the optimized results in batch reactors, biphasic experiments were conducted in capillary microreactors under slug flow operation, where a maximum HMF yield of ca. 61% could be obtained in 13 min, which is similar to that in batch under otherwise the same conditions. The slight mass transfer limitation in microreactors was confirmed by performing experiments with microreactors of varying length, and comparing the characteristic mass transfer time and reaction time, indicating further room for improvement.Highlights• The efficient fructose conversion to HMF in deep eutectic solvents was achieved in batch reactors and microreactors.• An HMF yield over 60% could be obtained at a fructose conversion above 90% in both reactors at 80°C within 14 min.• The HMF yield was enhanced from 48% in the monophasic ChCl/EG system to 63% in the DES-MBIK biphasic system in batch.• A slight mass transfer limitation was found in the biphasic slug flow microreactor.Graphical

CATALYTIC CONVERSION OF FRUCTOSE INTO 5-HYDROXYMETHYLFURFURAL BY USING Cr-MODIFIED KUNIPIA-F CLAY

Catalytic conversion of fructose into 5-hydroxymethylfurfural (HMF) is investigated in detail using chromium-exchanged Kunipia-F clay (K550-Cr-calcined at 550°C) using dimethylsulfoxide (DMSO) as the solvent. The as-synthesized catalyst is characterized using XRD, ICE-AES, BET, SEM, FTIR, and EDX. The clay catalysts are initially screened for fructose conversion and HMF yield and then K550-Cr, which shows the superior activity amongst the catalysts understudy, is chosen for further experiments. Various reaction parameters like reaction temperature and time, catalyst dosage, initial substrate concentration, and catalyst reusability are studied in detail. The maximum HMF yield obtained is about 89% at milder reaction conditions (130°C for 3 h). The most interesting result is that the catalyst can be recovered easily without any loss and reused four times without loss in activity (HMF yield after five cycles is 88%).

Microporous and mesoporous structure catalysts for the production of 5‐hydroxymethylfurfural (5‐HMF)

In recent years, researchers have gained attention in finding new strategies for alternative renewable energy resources in reducing the dependency on fossil fuel in providing energy to the world. 5-Hydroxymethylfurfural (HMF) is one of the most promising chemicals as it is a multi-functional compound and an intermediate compound that is beneficial in numerous chemical and fuel applications. This study provides recent progress on developing high yield and selectivity of HMF using hydrothermal reaction, emphasizing the catalytic performance efficiency of the developing structured catalysts from a technical perspective. We highlighted a few critical factors and parameters in maximizing the synthesis of HMF by selectively optimizing the desired kinetic reactions, which are hydrolysis, isomerization, and dehydration of sugars, and limiting the undesired side reactions, including HMF rehydration and depolymerization. The use of different types of microporous and mesoporous catalysts provides different HMF conversion results, and by applying few parameters, including catalyst: substrate ratio, Lewis: Brønsted acid ratio, reaction temperature, and duration of reaction, can be tunable in achieving maximum HMF yield and selectivity.

Catalytic conversion of whey permeate into 5-hydroxymethylfurfural: Optimization and kinetic modeling approach

This work presents an efficient catalytic system for the valorization of whey permeate into 5-hydroxymethylfurfural (HMF). Lactose was studied as the model carbohydrate. The side products formed during the reaction were levulinic acid (LA), formic acid (FA), and humins. It was found that 0.25 mol/L of acetic acid and 0.21 mol/L of AlCl3·6H2O showed a synergistic effect on the HMF yield in γ-valerolactone and water as the binary solvent system. Three independent reaction parameters (reaction temperature, time, and AlCl3·6H2O concentration) were investigated to understand their effects on the formation of HMF, LA, and FA. The maximum HMF yield (59 mol%) for lactose was obtained at the optimum conditions (135 °C, 100 min, and 0.21 mol/L AlCl3·6H2O). The developed catalytic system was applied on different concentrations of whey permeates namely, whey permeate, ultrafiltered whey permeate, combined reverse osmosis-nanofiltered whey permeate after 30% evaporation, and whey permeate powder. Amongst all, the application of the developed catalytic system on whey permeate powder showed promising results, where 74 mol% HMF yield was obtained in a shorter reaction time (40 min) than lactose. The kinetic study demonstrated all the possible reaction pathways occurring during HMF formation for lactose and whey permeate powder. Key findingThe reaction kinetics for whey permeate powder discloses various possible reaction pathways for lactose to HMF conversion.

High-efficiency synthesis of 5-hydroxymethylfurfural and 2,5-diformylfuran from fructose over magnetic separable catalysts

In this work, a sulfonic acid-functionalized magnetic separable solid acid (Fe3O4@SiO2-SO3H) was synthesized, characterized, and tested for fructose conversion to 5-hydroxymethylfurfural (HMF). Results indicated that the prepared catalyst had a good efficacy for fructose dehydration to HMF due to its larger specific surface area, appropriate acid amount and homogeneous acid distribution. The maximum HMF yield of this work was 96.1 mol%. It was obtained at 120 °C for 1.5 h with 100 mol% fructose conversion. More importantly, the produced HMF could be further in-situ oxidized into 2,5-diformylfuran (DFF) after the replacing of the Fe3O4@SiO2-SO3H with a ZnFeRuO4 catalyst, and the highest DFF yield of 90.2 mol% (based on initial fructose) was obtained after reaction another 8.5 h. The production of DFF from fructose through the above two consecutive steps avoids the intermediate HMF separation, which saves time and energy. In addition, both Fe3O4@SiO2-SO3H and ZnFeRuO4 catalysts exhibited satisfied stability in the recycling experiments, which can be reused at least for five times with the HMF and DFF yield loss<5.3% and 3.3%, respectively. Finally, the plausible reaction mechanisms for fructose conversion to HMF or DFF over Fe3O4@SiO2-SO3H or/and ZnFeRuO4 catalysts were also proposed in this work.

Improved conversion of levoglucosenone into 5-hydroxymethylfurfural in a biphasic system

Levoglucosenone (LGO), derived from catalytic pyrolysis of cellulose, has shown its potential as a bio-renewable platform for the production of fine and commodity chemical. In this study, we report a biphasic system for conversion of LGO to 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) with a substantial yield. The hydrolysis parameters, including single-biphasic phase, catalyst, temperature, and reaction time, were investigated on LGO conversion, respectively. The results showed that NaCl/H2O-MIBK biphasic system led to a profoundly increase of HMF selectivity by 37% compared to aqueous phase. An increase of acid site significantly enhanced LGO conversion and meanwhile promoted overreaction of HMF to LA and humins. Thus, HMF yield was observed firstly increased and then decreased with a maximum yield of 53.6% by using oxalic acid as a catalyst. The biphasic system effectively suppressed the humins formation and resulted in a maximum total HMF and LA yield of 86.7%.

Efficient microwave-assisted production of furanics and hydrochar from bamboo (Phyllostachys nigra “Boryana”) in a biphasic reaction system: effect of inorganic salts

In this study, a microwave-assisted process was developed for the production of 5-hydroxymethylfurfural (HMF), furfural, and hydrochar from bamboo (Phyllostachys nigra “Boryana”) in a biphasic reaction system. The system consisted of an acidified aqueous phase and methyl isobutyl ketone (MIBK) as the organic phase and enabled the instantaneous extraction of HMF and furfural in the organic phase. In this way, unwanted side and rehydration reactions are avoided. The aim of the study was to maximize HMF and furfural yields from bamboo in short reaction times. Building on previous studies, an HCl concentration of 0.13 M was used to ensure the simultaneous conversion of cellulose and xylan to HMF and furfural, respectively. To shorten the reaction time considerably, higher reaction temperatures were applied in this study (200–240°C). The use of microwave irradiation allowed very short reaction rates for maximum HMF and furfural production. Yields of 21 wt% HMF, 13 wt% furfural, and 39.5 wt% hydrochar were achieved using bamboo culm particles and by applying 0.13 M HCl (10 wt% NaCl) and 220°C with a reaction time of 2 min. The results show that the required reaction time to reach a maximum HMF and furfural yield was not significantly influenced by the particle size (< 200μm–2 mm). The effect of NaCl in the production of HMF and furfural was assessed. It was clear that the addition of NaCl increased the maximum HMF yield but also enhanced the unwanted rehydration reaction to levulinic acid. Results indicated that NaCl could be absorbed on the surface of the hydrochar.

Selective fructose dehydration to 5-hydroxymethylfurfural from a fructose-glucose mixture over a sulfuric acid catalyst in a biphasic system: Experimental study and kinetic modelling

A two-step process combining the (equilibrium) glucose isomerization to fructose with selective dehydration of fructose in the obtained sugar mixture to 5-hydroxymethylfurfural (HMF), where glucose is largely unconverted and recycled, represents an attractive concept to increase the overall efficiency for HMF synthesis. This work presents experimental and modelling studies on the conversion of such fructose-glucose mixture to HMF using the sulfuric acid catalyst in a water-methyl isobutyl ketone biphasic system under a wide range of conditions (e.g., temperature, catalyst and sugar concentrations). Through detailed product analyses and ESI-MS spectroscopy, the excess formation of formic acid (together with humins) by the direct sugar/HMF degradation was confirmed and included in the reaction network (neglected in most literatures). The kinetic modelling based on batch experiments in monophasic water well describes the measurements thereof, whereas distinct deviations were found in the prediction of typical literature kinetic models. The incorporation of HMF equilibrium extraction into the developed kinetic model, with consideration of phase volume change as a function of temperature and partial phase miscibility, enables to predict reaction results in the biphasic system in batch. This kinetic model allows to optimize conditions for HMF synthesis that are favored in continuous reactors with minimized back mixing. Based on the model implications, the biphasic system was optimized with slug flow microreactors to better address process intensification and scale-up aspects. Using a simulated fructose-glucose mixture feedstock to represent commercially available high fructose corn syrups, a maximum HMF yield of 81% was obtained at 155 °C over 0.05 M H2SO4 at a residence time of 16 min in the microreactor, with 96% fructose conversion and over 95% of glucose remaining unconverted.

Production of 5-Hydroxymethylfurfural from Direct Conversion of Cellulose Using Heteropolyacid/Nb2O5 as Catalyst

This study aimed to select the best reaction conditions to produce 5-hydroxymethylfurfural (HMF) from cellulose using heterogeneous catalyst based on a heteropolyacid (H3PW12O40—HPW) and Nb2O5. Initially, the influence of the temperature (160 or 200 °C), acetone:water ratio (50:50 or 75:25 v/v), cellulose load (5% or 10% w/v) and catalyst concentration (1% or 5% w/v) on HMF production from cellulose was evaluated through a Taguchi’s L16 screening experimental design. Afterwards, the main variables affecting this process, namely the temperature (160–240 °C) and acetone:water ratio (60:40–90:10 v/v), were optimized using a central composite rotatable design. Next, a kinetic study on HMF production from cellulose was carried out. Finally, HMF production from cellulose obtained from different biomass sources was evaluated. It was found that the reaction conditions able to result in maximum HMF yield, i.e., around 20%, were 200 °C, acetone:water ratio of 75:25 (v/v), 10% w/v of cellulose, and 5% w/v of catalyst concentration. The kinetic study revealed that the Langmuir–Hinshelwood–Hougen–Watson approach fit to the experimental data. Under the optimized conditions, the catalyst HPW/Nb2O5 was also effective in converting different sources of cellulose into HMF.

Catalytic production of 5-hydroxymethylfurfural from sucrose and molasses by aluminum chloride in green aqueous γ-valerolactone system

5-Hydroxymethylfurfural (HMF) is a promising platform chemical for production of value-added chemicals and fuels. Conversion of abundantly available and cheap sucrose for HMF synthesis was systematically investigated in the present study. Results showed that Lewis acid AlCl3 is effective in catalytic transformation of sucrose. Combining AlCl3 with different Bronsted acids, no matter whether they were inorganic acids (HCl, H2SO4, and H3PO4) or organic acids (malic acid, succinic acid, and oxalic acid), or variation of ratio of Lewis acid/Bronsted acid represented by AlCl3/HCl, did not change the obtained maximum HMF yields compared with AlCl3 alone, but shortened the time required to reach the maximum HMF yield. Sucrose conversion in a green reaction media of aqueous γ-valerolactone (GVL) solvent resulted into comparable HMF yields with dimethyl sulfoxide (DSMO)-water system. Addition of monovalent salt NaCl and divalent salt Na2SO4 produced opposite effect with Cl− promoting while SO42− inhibiting HMF production. Furthermore, HMF synthesis from constituent monosaccharides of sucrose and molasses, a by-product from sugar manufacturing process, was also carried out and it was found that an equivmole mixture of glucose and fructose gave rise to almost identical HMF yield to the same mole of sucrose. Molasses, even after chemical pretreatment for removal of certain amount of inorganic salts and color substances, was significantly inferior to synthetic molasses in terms of HMF formation, indicating the complexity and difficulty in chemical valorization of molasses for production of platform molecules.

Simultaneous production of 5-hydroxymethylfurfural and furfural from bamboo (Phyllostachys nigra “Boryana”) in a biphasic reaction system

In this study, the microwave-assisted hydrolysis of bamboo (Phyllostachys nigra “Boryana”) to 5-hydroxymethylfurfural (HMF) and furfural in a dilute acid (H2O) / methyl isobutyl ketone (MIBK) biphasic system is investigated. Building on previous studies using model components cellulose and xylan, main emphasis in this study is given to the effect of particle size on the reaction rates that are involved in the conversion of bamboo particles by incorporating solid-liquid interactions into the reaction kinetics. Conversion yields of 37% HMF and 35% furfural from bamboo culm and 35% HMF and 34% furfural from bamboo leaves (based on cellulose and xylan content) were achieved, applying 0.13 M HCl and 177 °C under microwave (MW) heating. The results showed that the required reaction time to reach a maximum HMF and furfural yield increased significantly with increasing particle size. For particles having a diameter <2.5 mm, the reaction rates follow first-order homogeneous kinetics, whereas for particles ≥2.5 mm, the reaction kinetics follow the shrinking core model. The chemical reaction (i.e., hydrolysis) at the surface of the unreacted particle core was shown to be the rate limiting step. The reaction rate constants for the hydrolysis of cellulose and xylose decreased with increasing particle size. Moreover, for bamboo culm particles with a particle size of 5 mm, the hydrolysis reaction rate constant decreased by a factor 10 compared to 1–1.5 mm particles.

Catalytic Low-Temperature Dehydration of Fructose to 5-Hydroxymethylfurfural Using Acidic Deep Eutectic Solvents and Polyoxometalate Catalysts.

HMF synthesis typically requires high temperature and is carried out in aqueous solutions. In this work, the low-temperature dehydration of fructose to HMF in different deep eutectic solvents (DES) was investigated. We found a very active and selective reaction system consisting of the DES tetraethyl ammonium chloride as hydrogen bond acceptor (HBA) and levulinic acid as hydrogen bond donor (HBD) in a molar ratio of 1:2 leading to a maximum HMF yield of 68% after 120 h at 323 K. The DES still contained a low amount of water at the initial reaction, and water was also produced during the reaction. Considering the DES properties, neither the molar ratio in the DES nor the reaction temperature had a significant influence on the overall performance of the reaction system. However, the nature of the HBA as well as the acidity of the HBD play an important role for the maximum achievable HMF yield. This was validated by measured yields in a DES with different combinations of HBD (levulinic acid and lactic acid) and HBA (choline chloride and tetra-n-alkyl ammonium chlorides). Moreover, addition of vanadium containing catalysts, especially the polyoxometalate HPA-5 (H8PV5Mo7O40) leads to drastically increased reaction kinetics. Using HPA-5 and the DES tetraethyl ammonium chloride—levulinic acid we could reach a maximum HMF yield of 57% after only 5 h reaction time without decreasing the very high product selectivity.

Conversion of fructose into furfural or 5-hydroxymethylfurfural over HY zeolites selectively in γ-butyrolactone

Furfural is one of the most valuable biomass platform compounds which is typically prepared from hemicellulose. Conversion of cellulose and its derived hexoses, which are the most abundant resource in nature, to furfural, is a big challenge. The amount of the reactive form (fructofuranose) which was beneficial to the formation of furfural and HMF, was increased when the solvent transformed from water to γ-butyrolactone (GBL)-water. The GBL promoted the adsorption of fructose on HY. The transfer of fructose from the solution to the channels of HY was enhanced with the introducing of GBL in solvent. The HY zeolite with apertures of 7.4 Å was found to promote the formation of acyclic fructose from cyclic fructose (8.6 Å) in the synergy with GBL. The Brønsted acid sites in the channels of HY favored the selective cleavage of the CC bond in acyclic fructose to xylose, and promoted the following dehydration of xylose to furfural, simultaneously. The furfural yield was increased while the 5-hydroxymethylfurfural (HMF) yield was decreased with the decrease of the Brønsted acid sites density. The maximum furfural yield was 37.8% over HY-3, while the maximum HMF yield was 69.2% over HY-1 in the conversion of fructose in GBL-water solvent. In addition, the etherification of HMF was the main factor for the low HMF yield and carbon balance in fructose conversion in GBL-water solvent.

A microwave-assisted process for the in-situ production of 5-hydroxymethylfurfural and furfural from lignocellulosic polysaccharides in a biphasic reaction system

In this study, a biphasic reaction system was developed for the microwave-assisted production of 5-hydroxymethylfurfural (HMF) and furfural. The proposed biphasic reaction system is a possible solution in the transition of current industrially state-of-the-art technologies which use C6 carbohydrates to an industrial process where lignocellulosic biomass can be processed, thus being a true sustainable process. In this respect, cellulose and xylan were chosen as model compounds since they are considered as the major building blocks of lignocellulosic polysaccharides. The reaction system consisted of an acidified aqueous phase and methyl isobutyl ketone (MIBK) as the organic phase. Upon the formation of HMF and furfural in the water phase, an instantaneous extraction into MIBK took place. The proposed biphasic reaction system offers many advantages over a monophasic reaction system, including (i) upon formation, furfural and HMF are continuously extracted into the MIBK layer, leading to the suppression of unwanted rehydration reactions, (ii) no unwanted solid particles are formed, and (iii) HMF and furfural can more easily be recovered from the reaction mixture. The goal of this study was to develop the microwave-assisted process in such a way that both cellulose and xylan were simultaneously converted. To this end, optimum process parameters in terms of HCl concentration (cHCl), temperature (T) and reaction time (t) were determined. A maximum HMF yield of 33.65 ± 0.46 w% (or 43.27 mol%) and a maximal furfural yield of 33.30 ± 1.30 w% (or 45.79 mol%) were achieved. To validate the proposed biphasic system, bamboo (Phyllostachys aureosulcata) was applied as a lignocellulosic feedstock, which resulted in a HMF yield of 42.44 mol% and a furfural yield of 48.90 mol%, based upon the cellulose and hemicellulose fraction of the bamboo particles. Since similar yields are observed compared to the model compounds, it is concluded that the lignocellulosic structure does not influence the reaction pathway. This means that the proposed biphasic system can be generalized for a wide variety of lignocellulosic feedstocks.

Sulfonated biochar as acid catalyst for sugar hydrolysis and dehydration

This study investigated the use of 30 w/v% H2SO4 sulfonated wood waste-derived biochar as catalysts for production of value-added chemicals from carbohydrates in water as an environmentally benign solvent. Physicochemical characteristics of the sulfonated biochar were revealed by Fourier transform infrared spectroscopy (FTIR), acid-base neutralization titration, gas adsorption analysis, thermogravimetric analysis (TGA), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Using the sulfonated biochar as catalysts, hydrolysis of maltose at 140–160 °C resulted in the maximum glucose yield of 85.4% and selectivity of 88.2%, whereas dehydration of fructose at 160–180 °C produced the maximum HMF yield of 42.3% and selectivity of 60.4%. A higher range of reaction temperature was required for fructose dehydration due to the higher energy barrier compared to maltose hydrolysis. While increasing the temperature accelerated the catalytic reactions, the maximum product selectivity remained unchanged in the sulfonated biochar-catalyzed systems. The products were stable despite the increase in reaction time, because rehydration and adsorption of products was found to be minor although polymerization of intermediates led to unavoidable carbon loss. This study highlights the efficacy of engineered biochars in biorefinery as an emerging application.

Experimental and Kinetic Modeling Studies on the Conversion of Sucrose to Levulinic Acid and 5-Hydroxymethylfurfural Using Sulfuric Acid in Water.

We here report experimental and kinetic modeling studies on the conversion of sucrose to levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) in water using sulfuric acid as the catalyst. Both compounds are versatile building blocks for the synthesis of various biobased (bulk) chemicals. A total of 24 experiments were performed in a temperature window of 80–180 °C, a sulfuric acid concentration between 0.005 and 0.5 M, and an initial sucrose concentration between 0.05 and 0.5 M. Glucose, fructose, and HMF were detected as the intermediate products. The maximum LA yield was 61 mol %, obtained at 160 °C, an initial sucrose concentration of 0.05 M, and an acid concentration of 0.2 M. The maximum HMF yield (22 mol %) was found for an acid concentration of 0.05 M, an initial sucrose concentration of 0.05 M, and a temperature of 140 °C. The experimental data were modeled using a number of possible reaction networks. The best model was obtained when using a first order approach in substrates (except for the reversion of glucose) and agreement between experiment and model was satisfactorily. The implication of the model regarding batch optimization is also discussed.

Dehydration of Glucose to 5-Hydroxymethylfurfural Using Combined Catalysts in Ionic Liquid by Microwave Heating

The dehydration of glucose into 5-hydroxymethylfurfural (HMF) was catalyzed by NKC-9 (a macroporous sulfonated polystyrene ion-exchange resin) combined with metal oxides (TiO2, ZrO2, Al2O3 calcined at different temperatures). In the combined catalytic system, Al2O3 calcined at 550°C exhibited excellent catalytic activity, when the dosage of NKC-9 was kept constant. Four parameters (catalyst dosage, reaction temperature, reaction time, and initial glucose amount) were optimized by employing response surface methodology (RSM), with HMF yield as the response parameter. The maximum HMF yield of 62.09% was obtained at catalyst 0.07 g, temperature 140°C, time 20 min, and glucose 0.01 g. The catalytic activity of the binary catalyst (NKC-9 and Al2O3) for the conversion of glucose into HMF did not show significant decrease after five-times uses at 140°C for 20 min.