Dehydration Of Saccharides Research Articles

One-pot aqueous-phase conversion of biomass into furfural catalyzed by supported heteropolyacids with the addition of LiBr

Catalytic conversion of waste biomass to furfural (FF) is an important valorization of lignocellulose. Heteropolyacid catalysts were designed for efficient aqueous-phase dehydration of saccharides by supporting phosphotungstic acid (H3PW12O40, abbreviated as PW12) on H-ZSM-5 zeolite at different loadings (xPW12/ZSM-5, x = 10%, 20%, 30%, 40%, 50%). The PW12/ZSM-5 was used in the one-pot conversion of biomass (xylose, xylan, and corn stover) to FF in LiBr aqueous solution. The low PW12 loading catalyst (10%PW12/ZSM-5) could efficiently convert biomass to FF with the yields of 73.3% (xylose) and 75.1% (xylan) at moderate temperature (130 °C), respectively. The PW12 loading and acid sites distribution were crucial to the catalytic performance. Moreover, LiBr enhanced the yield of FF because of its Lewis acidity. The PW12/ZSM-5 based solid polyacid was a promising catalyst for the efficient FF production from biomass with high yield and easy separation.

Challenges of Green Production of 2,5-Furandicarboxylic Acid from Bio-Derived 5-Hydroxymethylfurfural: Overcoming Deactivation by Concomitant Amino Acids.

The oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) is highly attractive as FDCA is considered as substitute for the petrochemically derived terephthalic acid. There are only few reports on the direct use of unrefined HMF solutions from biomass resources and the influence of remaining constituents on the catalytic processes. In this work, the oxidation of HMF in a solution as obtained from hydrolysis and dehydration of saccharides in chicory roots was investigated without intermediate purification steps. The amount of base added to the solution was critical to increase the FDCA yield. Catalyst deactivation occurred and was attributed to poisoning by amino acids from the bio‐source. A strong influence of amino acids on the catalytic activity was found for all supported Au, Pt, Pd, and Ru catalysts. A supported AuPd(2 : 1)/C alloy catalyst exhibited both superior catalytic activity and higher stability against deactivation by the critical amino acids.

Selective conversion of lignocellulosic biomass and its components into value-added furans over Al-based bimetals: Analytical Py-GC × GC/MS

Furans is a versatile chemical family, developing environmental-friendly methods to prepare furans and enhance the selectivity of high-value furans are of great significance. In present study, bio-based activated carbon supported Al-containing bimetals were devised to serve as solid acid catalysts for selective transformation lignocellulosic biomass and its components into valuable furans. Among the bimetallic catalysts, 2Al-4Zr/AC increased both the content of furans and the selectivity of 5-methylfurfural (5-MFF) , and the highest peak area% of furans and selectivity of 5-MFFwere 88.6% and 44.5%, which were derived from the catalytic pyrolysis of glucose, and the counterparts from the catalytic pyrolysis of pine wood were 56.3% and 30.7%, respectively. In addition to 5-MFF, 2-methylfuran (2-MF), furfural (FF) and 2,5-dimethylfuran (DMF) were also included into major furans. In the catalytic pyrolysis process of lignocellulosic biomass, C6-based sugars were conducive to the production of 5-MFF, and C5-based sugars favored the formation of 2-MF and FF. Characterization with NH3-TPD, Pyridine-IR, N2 adsorption-desorption, XRD and XPS indicated that 2Al-4Zr/AC, with mild Lewis acidity and combined Brønsted acid sites, high surface area and micro-mesoporous structure, promoted both the dehydration of saccharides and the dehydrogenation of cyclopentanones to increase the content of furans. In the catalyst, the synergistic effect between Al species (including Al2O3, AlO(OH) and Al(OH)3) and Zr species (mainly ZrO2) played an important role in its catalytic activity, and Al species were the major contributor to its activity.

Dehydration of saccharides to anhydro-sugars in dioxane: effect of reactants, acidic strength and water removal in situ

The dehydration of cellulose in polar aprotic solvents produces high-value anhydro-sugars, opening up a new avenue for the utilization of cellulose. However, there are still some problems that need to be solved. Herein, we selected some carbohydrates (e.g. cellulose, starch, cellobiose, maltose, methyl-β-D-glucopyranoside and methyl-α-D-glucopyranoside) to examine the influence of different glycosidic bonds and substituents on the preparation of levoglucosan (LGA). The results of LGA yields, reaction rate constants and activation energies from different saccharides show that β-glycosidic bond is more vulnerable to break, forming LGA more easily. The activation energies of the latter 4 carbohydrates are 89.9, 104.2, 93.3, 113.6 kJ/mol, respectively. The strength of acid affects the dehydration process of cellulose greatly. These acids whose pKa values are between − 3 and − 2, including p-toluenesulfonic acid, methanesulfonic acid, and sulfuric acid, can achieve the best yields of LGA and levoglucosenone (LGO). Accordingly, those acids with higher pKa value have no catalytic activity, whereas the rate of cellulose degradation using lower pKa valued acids as catalyst is too fast to be efficiently monitored and carbonization is severe. The side reaction of cellulose hydrolysis and the formation of byproducts including 5-hydroxymethylfurfural (HMF) and furfural (FF) could be suppressed effectively through the addition of phosphorus pentoxide as water absorbent into the reaction system. The molar concentration ratio of LGO and (HMF + FF + Glucose) reached 12.04, which is 105% higher than those without water absorbent. This ratio can reach 21.38 in LGA dehydration into LGO process when phosphorus pentoxide was added.

Selective conversion of lignocellulosic biomass into furan compounds using bimetal-modified bio-based activated carbon: Analytical Py-GC×GC/MS

Bio-based activated carbon supported Cu, Al, Sn and their bimetals were devised to serve as solid acid catalysts for the pyrolysis of xylan to generate furan compounds, and their catalytic activity was evaluated by Py-GC × GC/MS. The Cu–Al/C catalysts with diverse Cu to Al ratios exhibited better performance in enhancing the content of furans and the selectivity of 2-MF compared with other catalysts. Among the series of Cu–Al/C catalysts, 4Cu–2Al/C achieved a content of furan compounds as high as 80.6%, and 2-MF, FF and furan were the major furan products with selectivity values of 44.0%, 30.0% and 15.8%, respectively. Furthermore, the catalyst also worked well in promoting the pyrolysis of xylose, glucose, cellulose and pine to produce furans, and the highest and lowest contents of furans were obtained from glucose (87.8%) and pine (70.1%), respectively. These results suggest the 4Cu–2Al/C obviously promotes the formation of furans, which is comparable to those of recently reported solid acid catalysts. Characterization with XRD, XPS, NH3-TPD, N2 adsorption-desorption, and SEM, demonstrated that the effective interactions between Cu species and Al species facilitated the dehydration of saccharides and the dehydrogenation of cyclopentanones to increase furan compounds. Al species, mainly Al2O3 were the major contributor to the Lewis acid sites, and Cu specie played an essential role in regulating the acidity and enhancing the selectivity of 2-MF. In addition to furans, 4Cu–2Al/C was found to have positive effects on hindering the formation of acids in the pyrolysis products.

Interactions in saccharide/cation/water systems: Insights from density functional theory

Interactions between saccharides and ions in aqueous solutions are of great importance in many fields (chemistry, physico-chemistry, biology, food industries). Thus, this work proposes to develop a methodology dealing with the characterization and the understanding of interactions between saccharides and cations in presence of water molecules, by a quantum mechanics approach. In the first part, the saccharide hydration properties (xylose, glucose, sucrose) in pure water are determined. Results show that the saccharide coordination numbers, as well as the saccharides hydration enthalpy, increase with the saccharide hydrophilic group number. In the second part, the influence of cations on saccharides hydration properties, and inversely, is evaluated. In saccharide/cation/water systems, the decrease in hydration enthalpy of cations and saccharides shows that both species are dehydrated and that saccharide dehydration depends on the nature of the cation. The dehydration sequence of saccharides was explained from the study of saccharide/cation interactions.

Mechanistic aspects of saccharide dehydration to furan derivatives for reaction media design.

The conversion of abundant hexoses (e.g. glucose, mannose and galactose) and pentoses (e.g. xylose and arabinose) to 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F) is subject to intensive research in the hope of achieving competitive production of diverse materials from renewable resources. However, the abundance of literature on this topic as well as the limited number of studies systematically comparing numerous monosaccharides hinder progress tracking. Herein, we compare and rationalize reactivities of different ketoses and aldoses. Dehydration mechanisms of both monosaccharide types are reviewed regarding the existing experimental evidence. Ketose transformation to furan derivatives likely proceeds through cyclic intermediates and is hindered by side-reactions such as isomerization, retro-aldol reactions and polymerization. Different strategies can improve furan derivative synthesis from ketoses: limiting the presence of water, improving the dehydration rate, protecting 5-HMF and 2-F reactive moieties with derivatization or solvent interactions and extracting 5-HMF and 2-F from the reaction medium. In contrast to ketoses, aldose conversion to furan derivatives is not favored compared to polymerization reactions because it involves their isomerization or a ring contraction. Enhancing aldose isomerization is possible with metal catalysts (e.g. CrCl3) promoting a hydride shift mechanism or with boric/boronic acids promoting an enediol mechanism. This catalysis is however far more challenging than ketose dehydration because catalyst activity depends on numerous factors: Brønsted acidity of the medium, catalyst ligands, catalyst affinity for monosaccharides and their accessibility to several chemical species simultaneously. Those aspects are methodically addressed to support the design of new monosaccharide dehydration systems.

Content of 5-hydroxymethyl-2-furfural in biscuits for kids.

5-hydroxymethyl-2-furfural (5-HMF) is a thermal decomposition product of saccharides. There are two main ways for the formation of 5-HMF. First, 5-HMF is forming during Maillard reaction and second, during thermic dehydration of saccharides under acid conditions. Significant parameters of 5-HMF formation are temperature, time, pH, water activity, type of saccharide and amino acids. It is suspected that 5-HMF has genotoxic, mutagenic and carcinogenic potential. This chemical can be found in many food sources, e.g. honey, dried fruits, fruit juice and concentrates, alcoholic beverages, bakery products, roasted nuts and seeds, brown sugar, and milk. The present study aimed to determine the amount of 5-HMF in children´s biscuits. The examined samples were divided into three groups. The first group of biscuits claimed availability for children older than six months, the second for children older than one year. The third group did not give a determined age range.For the assessment of 5-HMF, a HPLC method with UV/VIS detection was used. In the first group of samples, the amount of 5-HMF ranged from 0.34±0.04 to 1.73±0.03 mg/kg, in the second group from 0.57±0.09 to 1.78±0.07 mg/kg, and in the third group the amounts of 5-HMF were from 1.80±0.05 to 34.99±0.22 mg/kg.In conclusion, the results showed that the content of 5-HMF in biscuits without age group determination was significantly higher than in biscuits with declared availability for children older than six months or one year. Since the acceptable daily intake is 2 mg/kg bw, the established amount of 5-HMF in all samples cannot be regarded as dangerous in a normal dose of biscuits.

First Detection of Unprotected 1,2-Anhydro Aldopyranoses

The unprotected 1,2-anhydro aldopyranoses have been detected for the first time using low-temperature NMR spectroscopy. The formation of these unstable chemical species was successfully achieved through an intramolecular dehydration of saccharides in aqueous media under extremely mild and essentially neutral conditions.

Role of the triple solute/ion/water interactions on the saccharide hydration: A volumetric approach

The aim of this study is to further the understanding of the mechanisms that govern the hydration behavior of neutral solutes, with respect to the ions' properties that are present in a solution. For that, a systematic volumetric study of saccharides (xylose, glucose and sucrose), in the presence of various electrolytes (LiCl, NaCl, KCl, Na2SO4, K2SO4, CaCl2, MgCl2, MgSO4) has been carried out with density measurements at 298.15 K. From this data, the standard transfer molar volume of the saccharide ΔVϕ,S0, which characterizes the hydration state of the solute, has been determined.Positive and increasing values of ΔVϕ,S0 with increasing electrolyte concentrations were obtained. This indicated the dehydration of the saccharide in the presence of the electrolyte, due to the predominance of saccharide/cation interactions.Concerning the influence of the cation, it was shown that saccharides are more dehydrated in the presence of divalent cations than in the presence of monovalent ones. This is because the interactions are stronger between saccharides and divalent cations, in comparison to those with monovalent cations. For a specific cation valence and molality, regardless of the anion, saccharide dehydration increases according to the following sequences: Li+< Na+< K+ and Mg2+< Ca2+. These saccharide dehydration sequences have been explained by the Gibbs free energy of hydration of the cations, reflecting the cation/water interactions. For a specific cation valence, it was concluded that decreasing cation/water interactions induce the increase of saccharide dehydration.Concerning the influence of the anion, it was also observed that saccharides are more dehydrated in the presence of divalent anions than in the presence of monovalent ones. It was stated that saccharide/cation interactions are modulated by the nature of the anion. The anion impact was again attributed to its capacity to interact with water molecules. It was pointed out that anions with increasing values of Gibbs free energy of hydration cause an increase in saccharide/cation interactions or a decrease in saccharide/anion interactions. Therefore, saccharide dehydration increases.

How do ions enhance the transfer during nanofiltration of saccharides? Experimental assessment of the dehydration assumption

AbstractThe aim of the work was to improve the understanding of the role of ion hydration on the transfer during nanofiltration of saccharides. More precisely, it consisted in evaluating the physical relevance of the dehydration assumption to explain the increased transfer of saccharides in presence of electrolytes. Experiments were carried out using saccharides (xylose, glucose) and electrolytes containing ions of different hydration levels (NaCl, Na2SO4). The Filmtec NF membrane (previously referred to as NF45) was used. Unlike saccharide/NaCl solutions, Na2SO4 had a weak influence on the saccharide transfer. This means that the impact of the electrolyte on the transfer of saccharide was strongly affected by the ions retention. Indeed, SO42‐ ions were much more often retained than Cl‐. Thus, an enhanced saccharide transfer was expected as the electrolyte concentration in the permeate was high. The physical relevance of the assumed dehydration was evaluated. The decrease of the saccharide radius was determined from the mass transfer modelling. It was shown that the decrease was physically relevant with the dehydration phenomenon since this decrease corresponded to a fraction of the water molecule (2–3 %). Next, the increased transfer was compared with the variation of the apparent molar volume, characterizing the hydration state of solutes, to better understand the mechanisms involved. For a given electrolyte, the transfer increased continuously with saccharide dehydration. This result could confirm that the increase of the transfer could be attributed to the saccharide dehydration caused by the electrolyte.

Phosphoric acid doped polybenzimidazole as an heterogeneous catalyst for selective and efficient dehydration of saccharides to 5-hydroxymethylfurfural

PA–PBI was used as an heterogeneous catalyst for the dehydration of high fructose concentration to produce HMF with high selectivity.

Demineralization of glucose solutions by electrodialysis: Influence of the ionic composition on the mass transfer and process performances

AbstractThe aim of the present work was to investigate the influence of the ionic composition on the demineralization of a saccharide solution containing glucose. Experiments were carried out in order to evaluate the influence of the ionic composition on the solvent and solutes fluxes (glucose and electrolytes) through the membrane under different conditions (ionic compositions: NaCl, Na2SO4 and CaCl2; with or without current). From diffusion experiments (without current), it was shown that the glucose diffusion flux decreases for increasing ion hydration. These results are in agreement with those obtained in a previous work showing that the transfer modification reflects changes in the membrane properties associated with the hydration of its counter‐ion which is likely linked to swelling mechanisms at a microscopic scale.From the experiments carried out in normal ED conditions (with current) an additional convective contribution was pointed out. This kind of result is rather scarce in the literature. The glucose flux was then the sum of two contributions: diffusion and convection, due to the electro‐osmotic flux which is proportional to the electrical current. The contribution of the glucose convection flux on the overall glucose transfer was ranged between 70 and 90 % according to the electrolyte nature (NaCl, Na2SO4 and CaCl2) and the electric current (150 or 300 A m−2). The variation of the convective flux has been further correlated to the hydration of the ions. Indeed increasing convection fluxes were obtained for decreasing anion (or cation) hydration. It was shown that the saccharide transfer increases in presence of salts and that this increase was correlated to the saccharide dehydration in presence of electrolyte. Finally, the solvent, ions and glucose fluxes were used to calculate the glucose loss factor versus the demineralization factor to evaluate the influence of the electrolyte nature on the demineralization process performances. It was observed that, for a fixed demineralization factor, the glucose loss factor (comprised between 4 and 5 % for a demineralization factor of 90 %) increased with the ion hydration due to the higher contribution of the glucose convection flux.

ChemInform Abstract: Toward a Rational Control of Solid Acid Catalysis for Green Synthesis and Biomass Conversion

AbstractReview: 144 refs.

Calorimetric and Theoretical Study of the Interaction between Some Saccharides and Sodium Halide in Water

Dilution enthalpies and mixing enthalpies of sodium halide and some saccharides (glucose, galactose, xylose, arabinose, fructose, and sucrose) in aqueous solution were determined by calorimetric measurements at 298.15 K. The values were used to determine enthalpic pair interaction parameters. Combined with Gibbs energy pair parameters, entropic pair interaction parameters were also obtained. Theoretical calculations at the B3LYP/6-311++G(d,p) level were carried out to provide the information of structures and thermodynamic functions. The information reveals the thermodynamic essence of the interactions between sodium halide and saccharides in aqueous solutions. The experimental results and theoretical calculations show that the sign of enthalpic pair interaction parameter 2υh(ES) is determined by the direct interaction between saccharides and ions, whereas the difference in value of 2υh(ES) for different saccharides or electrolytes depends on the partial dehydration of saccharides or anions in aqueous solution. The difference in value of entropic pair interaction parameters depends partly on the different dominant interactions in the process of partial dehydration of saccharides or ions. An enthalpy-entropy compensation relationship was observed for the sodium bromide-aldopyranose-water systems. Remarkably, it can be conjectured that the hydration entropy of glucose is lower than for other monosaccharides. Perhaps it is one of the reasons why glucose plays an important role in living organisms rather than other monosaccharides.

Hydrophobic precipitation of carbonaceous spheres from fructose by a hydrothermal process

We report a new mechanism of hydrophobic ripening for the formation of carbonaceous spheres by the dehydration of saccharides in a hydrothermal aqueous environment using fructose as a model precursor material. We investigated the formation of carbonaceous spheres from fructose in aqueous solutions under hydrothermal conditions. The spheres were found to contain 65.7wt.% C, 4.3wt.% H and 30.0wt.% O, implying incomplete dehydration of the fructose. The spheres, typically ranging between 400nm and 10μm in diameter, are found to be constructed entirely of primary particles of ∼5nm. The chemical structure of the carbonaceous spheres and the chemical compositions of residual solutions were analysed using solid state and solution 13C nuclear magnetic resonance and Fourier transform infrared spectroscopy. Based on these results, a four-step mechanism for the formation and growth of carbonaceous spheres has been proposed.

Toward a rational control of solid acid catalysis for green synthesis and biomass conversion

Design of solid acid catalysts is one of the key technologies to establish environmental friendly catalytic processes. Featuring cation-exchanged clay and metal salts of heteropolyacids as model solid acid catalysts, a strategy for design of active catalysts for green chemical and biomass conversion processes is discussed. The important role of solid Lewis acids was suggested in acetylation of alcohols with acetic anhydride by cation-exchanged clay, Friedel–Crafts acylation and alkylation of aromatic compounds with metal salts of heteropolyacids, and hydrolysis of cellulose into saccharides. The significant influence of reactor design and reaction conditions on dehydration of saccharides into 5-hydroxymethylfurfural (HMF) is also discussed.

Tantalum compounds as heterogeneous catalysts for saccharide dehydration to 5-hydroxymethylfurfural

A new solid acid, based on tantalum hydroxide, was used to catalyze saccharide dehydration into 5-hydroxymethylfurfural (HMF) with high catalytic activity and excellent stability in a water-2-butanol biphasic system. Furthermore, good results were also obtained from Jerusalem artichoke juice with the catalyst under the same conditions.

Kinetics of levulinic acid formation from carbohydrates at moderate temperatures

The kinetic curves of levulinic acid accumulation in the process of saccharide dehydration at 80-98oC are compared. The structural features of the substrates and 5-hydroxymethylfurfural, which is the intermediate of the process, explain the observed difference in the rates of fructose and glucose conversion. Sulfuric acid can be effectively used under moderate conditions to synthesize levulinic acid with yields exceeding 35 mol % for glucose and 50% for sucrose at 98oC.

Highly Efficient Catalytic Activity of Lanthanide(III) Ions for Conversion of Saccharides to 5-Hydroxymethyl-2-furfural in Organic Solvents

Abstract All lanthanide(III) ions were found to catalyze dehydration of saccharides to 5-hydroxymethyl-2-furfural (HMF) in DMSO at 100 - 120 °C. Particularly, d-fructose was almost quantitatively converted to HMF without generating any byproducts. The results of the reaction with di- and trisaccharides indicated that the d-fructose moiety in the substrates was selectively converted to HMF.