Method for producing 5-HMF via sugar inversion in non-aqueous solvents with aqueous extraction during synthesis

Abstract

The present invention relates to a method for producing a 5-hydroxymethylfurfural (5-HMF) solution, the method comprising: step a) contacting a raw material containing hexose with a synthesis solvent and a dehydration acid catalyst at a temperature of 30 to 200°C, preferably 50 to 180°C, more preferably 70 to 150°C, and very preferably 90 to 130°C, and at a pressure of 0.001 MPa to 10 MPa, preferably 0.001 MPa to 5 MPa, and more preferably 0.01 MPa to 1 MPa, to obtain a reaction medium; and simultaneously extracting water from the reaction medium to obtain a synthesis effluent containing 5-HMF and the synthesis solvent.

Description

[Technical Field]

[0001] The present invention relates to the production of 5-HMF by catalytic synthesis in organic solvents from feedstocks containing sugars, more particularly hexoses. [Background technology]

[0002] 5-Hydroxymethylfurfural (5-HMF) is an interesting compound obtained from biomass and can be upgraded in many fields, especially in pharmaceuticals, agricultural chemistry or specialty chemistry. The production of 5-HMF by dehydration of sugars has been known for many years and has been the subject of numerous research studies. Many dehydration conditions exist, and particular mention may be made of the following methods, by way of example:

[0003] 5-HMF can be obtained in aqueous media, generally in the presence of an acid catalyst, which allows the dehydration of C6 sugars (hexoses, especially fructose) to give 5-HMF, but which also catalyzes the rehydration of 5-HMF to give formic acid and levulinic acid, which is very detrimental to the yield.

[0004] 5-HMF can also be obtained in a non-aqueous polar protic medium using a solvent such as methanol, ethanol, or acetic acid in the presence of an acid catalyst. Under these conditions, 5-HMF is obtained as a mixture with ether or ester derivatives of 5-HMF, depending on the reaction medium used. The formation of these by-products results from the reaction of 5-HMF with the reaction solvent in an acidic medium.

[0005] Patent document 1 describes the synthesis of 5-HMF by dehydration of sugars using methanol or ethanol as a solvent in the presence of an acid catalyst, which in this case also catalyzes the etherification reaction of 5-HMF with alcohols, giving a mixture of 5-HMF and its methyl or ethyl ether forms, depending on the alcohol used as the solvent.

[0006] 5-HMF can also be produced in polar aprotic media, with or without acid catalysis. Particular mention may be made of the use of dimethyl sulfoxide (DMSO), which allows 5-HMF to be produced, with or without acid catalysis, in very good yields and without the undesired reactions listed above.

[0007] Furthermore, whatever the synthesis medium (water, methanol, DMSO, etc.), polymeric by-products called humins are formed during the production of 5-HMF (Non-Patent Document 1).

[0008] The synthesis of 5-HMF in a medium such as DMSO is particularly advantageous because it makes it possible to obtain 5-HMF in its alcohol form (rather than in its ether form) in very good yields.

[0009] However, industrialization of 5-HMF production requires reducing the dilution of sugars in DMSO to the minimum necessary, which reduces the selectivity of sugar inversion. 5-HMF selectivity is understood to mean the ratio of the number of moles of 5-HMF produced to the number of moles of converted fructose contained in the feedstock introduced into the process. In polar aprotic media, the presence of water reduces the selectivity of sugar inversion, and this reduction becomes more pronounced the higher the concentration of sugars in DMSO.

[0010] The object of the present application is to reduce the water content of the reaction medium during synthesis by extracting water (water resulting from the dehydration of sugars and, optionally, water of the syrup, if the feedstock is a syrup). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2007 / 104514 [Non-patent literature]

[0012] [Non-Patent Document 1] van Dam, HE;Kieboom, APG;van Bekkum, H., The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethylfurfural, in: Starch - Starke, 1986, Vol. 38, No. 3, p.95-101 Summary of the Invention [Means for solving the problem]

[0013] (Summary of the Invention) The present invention relates to a method for producing a solution of 5-hydroxymethylfurfural (5-HMF), comprising step a) contacting a hexose-containing feedstock with a synthesis solvent and an acid dehydration catalyst to form a reaction medium, wherein the step is carried out at a temperature of 30°C to 200°C, preferably 50°C to 180°C, preferably 70°C to 150°C, and highly preferably 90°C to 130°C, and at a pressure of 0.001 MPa to 10 MPa, preferably 0.001 MPa to 5 MPa, and preferably 0.01 MPa to 1 MPa, while extracting water from the reaction medium and obtaining a synthesis effluent containing 5-HMF and the synthesis solvent.

[0014] According to the present invention, the water present during the synthesis is extracted to reduce its content and improve the selectivity of the reaction. Extracting water during the synthesis has the following advantages: - reducing the water content in the medium; the presence of moisture reduces the selectivity of the conversion; - Continuous extraction of the water produced by the reaction; this reaction is a dehydration reaction, thus reducing its concentration throughout the synthesis of 5-HMF; - Controlled extraction of any water present with the feedstock or synthesis solvent in a single step.

[0015] The judicious management of the recycling of the aqueous and organic streams within the process also makes it possible to obtain an economically optimized process for producing aqueous 5-HMF solutions. DETAILED DESCRIPTION OF THE INVENTION

[0016] (List of drawings) FIG. 1 represents a method according to a first embodiment.

[0017] FIG. 2 represents a method according to a second embodiment, in which step b) comprises three specific steps.

[0018] FIG. 3 represents a method according to a third embodiment, in which step b) comprises five specific steps.

[0019] (Detailed Description of the Invention) According to the present invention, the expressions "of between ... and ..." and "between A and B, A to B (between ... and ...)" are equivalent and mean that both the upper and lower limits of the interval are included in the range of values ​​stated. If this is not the case and both limits are not included in the range stated, such clarification is provided by the present invention.

[0020] For purposes of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination. For example, for purposes of the present invention, a range of preferred pressure values ​​may be combined with a range of more preferred temperature values.

[0021] In the remainder of this description, specific embodiments of the present invention are described, which may be implemented separately or in combination with each other, without limitation in combination, where technically feasible.

[0022] (Feed material) The feedstock used in the process according to the invention contains hexoses.

[0023] A hexose-containing feedstock is understood to mean that the hexose may be in the form of a monomer (monosaccharide) or else a unit forming part of a disaccharide, oligosaccharide or polysaccharide. Saccharides are compounds also called sugars.

[0024] The hexose is preferably a fructose or fructoside unit.

[0025] The feedstock used may be sugar in solid form or in the form of an aqueous solution.

[0026] In one embodiment, the feedstock contains free fructose, alone or in admixture with any sugar species, or any oligosaccharide or polysaccharide feedstock containing one or more fructoside units that can release fructose through one or more hydrolysis steps, optionally in admixture with other sugar species. The feedstock treated in this method is preferentially crystalline fructose, syrup containing fructose and glucose, or crystalline sucrose or sucrose syrup.

[0027] The feedstock advantageously comprises fructose in monomeric, oligomeric or polymeric form.

[0028] Feedstocks containing free fructose in admixture with any sugar species refer, for example, to high fructose corn syrup-type syrups containing fructose and glucose in various proportions (glucose / fructose weight or molar ratios, e.g., 58 / 42, 45 / 55, 10 / 90).

[0029] Syrup is understood as meaning a solution of sugar in water, the concentration of which is preferably at least 30% by weight, preferably at least 50% by weight, preferably at least 70% by weight.

[0030] The feedstock may include sugars containing one or more fructosidic units and one or more non-fructosidic units from which fructose may be released through one or more hydrolysis steps, for example, oligosaccharides and polysaccharides in which at least one monosaccharide unit is fructose, such as feedstocks such as sucrose, kestose, fructans, oligofructans and inulin.

[0031] The sugar feedstock may advantageously be subjected to glycosidic hydrolysis to release monomeric fructose, which may then be converted to 5-HMF.

[0032] The oligosaccharide preferably has the empirical formula: 6m H 10m+2 O 5m+1 )(C 5n H 8n+2 O 4n+1 ), wherein m and n are integers and the sum of these is 2 to 6. The monosaccharide units constituting the oligosaccharide may be the same or different, and preferably have the formula (C 6m H 10m+2 O 5m+1 ) is fructose. By extension, the polysaccharide preferably has the empirical formula (C 6m H 10m+2 O 5m+1 )(C 5n H 8n+2 O 4n+1 ), wherein m and n are integers and their sum is 7 or greater.

[0033] In one embodiment, when the feedstock is in the form of a syrup, the water present in the feedstock can be at least partially extracted after mixing the feedstock with a synthesis solvent, which makes it possible to keep the sugars in a diluent medium and to replace dilution with water by dilution with the synthesis solvent.

[0034] Extraction of the water can be carried out by various methods, such as evaporation, adsorption (eg adsorption on molecular sieves), membrane separation or permeation.

[0035] Advantageously, this step can be carried out by distillation, in which case the synthesis solvent must be less volatile than water.

[0036] Advantageously, the extracted water accounts for at least 50% by weight of the water present in the feedstock, preferentially at least 80% by weight, and even more preferentially at least 90% by weight.

[0037] Advantageously, the extracted water contains less than 10% by weight of synthetic solvents, preferentially less than 5% by weight of synthetic solvents, and even more preferentially less than 1% by weight of synthetic solvents.

[0038] In one embodiment, the extracted water comprises 90% to 99% by weight relative to the weight of water in the feedstock.

[0039] In one embodiment, the water extracted from the feedstock is recycled and sent separately to one or more steps of the process requiring the supply of an aqueous stream, or sent to the overall aqueous stream feeding said steps.

[0040] (Step a) Dehydration of Feedstock and Extraction of Water to Give 5-HMF) (Dehydration of Feedstock to Give 5-HMF) The process according to the invention comprises step a) of contacting a hexose-containing feedstock with a synthesis solvent and an acidic dehydration catalyst to form a reaction medium, said step being carried out at a temperature of 30°C to 200°C, preferably 50°C to 180°C, preferably 70°C to 150°C, and highly preferably 90°C to 130°C, and at a pressure of 0.001 MPa to 10 MPa, preferably 0.001 MPa to 5 MPa, and preferably 0.01 MPa to 1 MPa.

[0041] Acidic dehydration catalyst is understood to mean any Brönsted acid catalyst selected from organic or inorganic homogeneous or heterogeneous Brönsted acids capable of inducing the dehydration of a hexose-containing feedstock to give 5-HMF.

[0042] In one embodiment, the dehydration catalyst is present in a homogeneous phase in the reaction medium.

[0043] Preferably, the acidic dehydration catalyst is a Brønsted acid having a pKa in the synthesis solvent of 0 to 5.0, preferably 0.5 to 4.0, more preferably 1.0 to 3.0, as defined in the paper by F. G. Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0044] Preferably, the acidic dehydration catalyst is HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiW 12 O 40 , H3PW 12 O 40 , (NH4)6(W 12 O 40 )·xH2O, H4SiMo 12 O 40 , H3PMo 12 O 40 , (NH4)6Mo7O 24 ·xH2O, H2MoO4, HReO4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HClO4, HBF4, H SThe acidic dehydration catalyst is preferably selected from bF, HPF, HFO, ClSO, FSO, HN(SOF), HIO, BF, AlCl, Al(OTf), FeCl, ZnCl, SnCl, CrCl, CeCl, ErCl, formic acid, acetic acid, trifluoroacetic acid, lactic acid, levulinic acid, methanesulfonic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, paratoluenesulfonic acid, 4-biphenylsulfonic acid, diphenyl phosphate, and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate. Preferably, the acidic dehydration catalyst is selected from HCl, HSO, HPO, HPO, HNO, AlCl, acetic acid, trifluoroacetic acid, methanesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid, either alone or in mixtures.

[0045] Depending on the pressure and temperature conditions, the reaction medium may be above or below the bubble point of the mixture. The term "bubble point" refers to the pressure and temperature conditions at which the first gas bubbles appear in the liquid.

[0046] Preferably, the acidic dehydration catalyst is introduced in a molar ratio of catalyst relative to the hexose-containing feedstock, expressed as a molar percentage (mol%), of 0.01 to 10 mol%, preferably 0.05 to 8 mol%, preferably 0.1 to 6 mol%, preferably 0.2 to 5 mol%, preferably 0.3 to 4 mol%, highly preferably 0.5 to 3 mol%.

[0047] In one embodiment, the synthesis solvent is an organic solvent, advantageously selected from butan-2-one, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methyl ethyl ketone, propionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, and γ-valerolactone. Preferably, the synthesis solvent is selected from acetone, hexamethylphosphoramide, N,N-dimethylformamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, and γ-valerolactone. Highly preferably, the synthesis solvent is dimethyl sulfoxide (DMSO).

[0048] The dehydration can be carried out according to various embodiments. It can therefore advantageously be carried out batchwise or continuously. The addition of the feedstock can be staged (fed-batch) in the case of a batch process, or staged in various CSTR (continuously stirred tank reactor) reactors in series in the case of a continuous process.

[0049] (Extraction of water from the reaction medium) Step a) of the process according to the invention comprises the simultaneous extraction of water from the reaction medium to obtain a synthesis effluent containing 5-HMF and the synthesis solvent.

[0050] Advantageously, the reaction medium is above the bubble point of the mixture. The term "bubble point" refers to the pressure and temperature conditions at which the first gas bubbles appear in the liquid. When the reaction medium is above the bubble point of the mixture, the vapor phase may be withdrawn from the reactor, rectified and condensed to form condensed water, which contains less than 10% by weight of synthetic solvent, preferentially less than 5% by weight of synthetic solvent, and even more preferentially less than 1% by weight of synthetic solvent.

[0051] The water may be obtained from dehydration, for example, water formed during the dehydration reaction of sugars to give 5-HMF (3 moles of water are generated per mole of 5-HMF produced), which may for practical reasons have been introduced with the feedstock in cases where the feedstock is in the form of a syrup.

[0052] Advantageously, at least 50% by weight, preferentially at least 80% by weight and even more preferentially at least 90% by weight of the water present in the reaction medium is extracted.

[0053] Advantageously, the water extracted from the reaction medium accounts for at least 50% by weight, preferentially at least 80% by weight and even more preferentially at least 90% by weight of the water produced during dehydration.

[0054] Extraction of water can be carried out by various methods, such as evaporation, adsorption (eg, adsorption on molecular sieves), membrane separation or permeation.

[0055] Advantageously, this step can be carried out by distillation, in which case the synthesis solvent must have a lower volatility than water. The distillation can be carried out by a distillation column, the separation stages of which can be provided by perforated plates, random packing or structured packing. Generally, this type of installation has a reboiler providing heat input at the bottom of the column, a condenser for at least partially condensing the overhead vapor, and a reflux system.

[0056] In one embodiment, the water extracted from the reaction medium is recycled and sent independently to one or several steps of the process requiring the supply of an aqueous stream, or sent to the entire aqueous stream feeding said steps.

[0057] Advantageously, the synthesis effluent comprises synthesis solvents that make up between 30% and 95% by weight of the synthesis effluent, preferably between 40% and 90% by weight, preferably between 50% and 90% by weight, preferably between 55% and 85% by weight.

[0058] Advantageously, the synthesis effluent comprises 5-HMF in an amount of more than 1% by weight, preferably more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, preferably less than 40% by weight, preferably less than 30% by weight of the synthesis effluent.

[0059] Advantageously, the extraction of water is carried out under conditions that allow at least 90%, preferentially at least 95%, and even more preferentially at least 99% of the synthesis solvent used in the dehydration and extraction steps to be recovered in the synthesis effluent.

[0060] In one embodiment, the synthesis effluent may contain impurities, particularly humins. The term "humins" refers to all of the undesired polymeric compounds formed during the synthesis of 5-HMF. Humins advantageously account for less than 30% by weight of the feedstock, preferably less than 20% by weight.

[0061] In one embodiment, the process according to the invention further comprises a step of neutralizing the synthesis effluent, preferably carried out by contacting said synthesis effluent with a basic compound, following step a).

[0062] Advantageously, the basic compound is chosen from NaOH, KOH, NH4OH, Na2CO3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, Ba(OH)2.

[0063] The synthesis effluent contains an acidic dehydration catalyst. The neutralization step advantageously reduces the reactivity of the medium, thus avoiding the mechanism of decomposition of 5-HMF or reducing the corrosion of materials in the equipment downstream of the dehydration step. Since the dehydration reaction may produce a small number of organic acids, the amount of neutralizing agent advantageously allows all of the acids present in the synthesis effluent to be neutralized.

[0064] The neutralization step is advantageously carried out in a minimal stoichiometric ratio to the amount of catalyst used. Since the dehydration reaction may produce a small amount of organic acid, the neutralization is generally carried out in a slight stoichiometric excess relative to the catalyst used, preferentially 1 to 2 times the stoichiometric ratio, preferentially 1 to 1.5 times the stoichiometric ratio.

[0065] The optional neutralization step may be carried out as follows: - inline with the synthesis effluent when it is transferred to step b) of replacing the synthesis solvent with an aqueous solution; - during step b) of replacing the synthesis solvent with an aqueous solution; - In the case of synthesis at the pressure and temperature of the reaction medium in batch or fed-batch mode in synthesis tanks at the end of the process.

[0066] (Step b) Replacing the synthesis solvent) In one embodiment, the process according to the invention further comprises a step b) of replacing the synthesis solvent present in the synthesis effluent with an aqueous solution to obtain an aqueous 5-HMF solution.

[0067] Advantageously, the aqueous solution contains between 5% and 60% by weight of water.

[0068] This step allows the use of organic synthesis solvents in the process that perform well in terms of reaction selectivity and productivity, and allows the production of 5-HMF in aqueous solution for satisfactory applications, for example, in the case of adhesive resins as a replacement for phenol-formaldehyde resins.

[0069] In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution comprises the following steps: i) contacting the synthesis effluent with a liquid stream containing at least 80% by weight of water, preferentially at least 90% by weight of water, even more preferentially at least 95% by weight of water, to obtain an aqueous mixture; ii) a step of liquid-liquid extraction of the aqueous mixture obtained in step i), carried out in the presence of an extraction solvent, to obtain at least one aqueous effluent containing the synthesis solvent and an intermediate organic effluent containing 5-HMF and the extraction solvent; iii) Separating the extraction solvent from the intermediate organic effluent to obtain an aqueous 5-HMF solution.

[0070] (Step i) Contacting the synthesis effluent with a liquid stream) In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution comprises step i) of contacting the synthesis effluent with a liquid stream comprising at least 80% by weight of water, preferentially at least 90% by weight of water, even more preferentially at least 95% by weight of water, to obtain an aqueous mixture.

[0071] Advantageously, 5-HMF represents more than 1 wt.%, preferably more than 10 wt.%, preferably more than 15 wt.%, and preferably less than 50 wt.%, preferably less than 40 wt.%, preferably less than 30 wt.%, of the synthesis effluent contacted in step i).

[0072] Advantageously, the synthesis solvent represents from 30% to 95% by weight, preferably from 40% to 90% by weight, preferably from 50% to 90% by weight, preferably from 55% to 85% by weight of the synthesis effluent contacted in step i).

[0073] Advantageously, step i) is carried out at a temperature between 0°C and 80°C, preferably between 10°C and 40°C, generally at ambient temperature, ie between 15°C and 35°C.

[0074] Advantageously, the aqueous mixture obtained at the end of step i) contains between 10% and 90% by weight of water, preferably between 20% and 80% by weight of water, preferably between 40% and 75% by weight of water.

[0075] In some embodiments, the liquid stream containing at least 80% by weight of water can be obtained from one or more process streams, such as: the aqueous back extract of a backwashing step, the condensate produced during the extraction of water during synthesis, the water produced in the step of regenerating the synthesis solvent, or any other liquid stream containing at least 80% by weight of water, preferentially at least 90% by weight of water, even more preferentially at least 95% by weight of water.

[0076] In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution further comprises a step of liquid-solid separation of the aqueous mixture obtained after step i) prior to the liquid-liquid extraction step ii).

[0077] Some of the humins that may initially be present in the synthesis effluent may precipitate. The aqueous mixture obtained in step i) may then advantageously be subjected to a liquid-solid separation step to obtain a liquid separated from suspended solid particles and a solid residue containing humins, which is preferably excluded from the process. Such a liquid-solid separation step therefore makes it possible to remove the precipitated humins. The temperature at which this liquid-solid separation step is preferably carried out is preferably between 0°C and 60°C, preferably between 10°C and 40°C, generally at ambient temperature (i.e., between 15°C and 35°C). The liquid-solid separation step may be carried out by any method known to those skilled in the art, such as a filter press, a belt filter, a drum filter, a candle filter, a clarifier, a settler, a centrifuge, or any combination of these techniques. Advantageously, the liquid-solid separation step is a filtration, preferably carried out by a filter press.

[0078] (Step ii) Liquid-liquid extraction) In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution comprises step ii) of liquid-liquid extraction of the aqueous mixture obtained in step i), which is carried out in the presence of an extraction solvent, to obtain at least one aqueous effluent comprising the synthesis solvent and an intermediate organic effluent comprising 5-HMF and the extraction solvent.

[0079] The liquid-liquid extraction carried out in step ii) advantageously corresponds to washing the aqueous mixture obtained in step i) with an organic extraction solvent. Preferably, the liquid-liquid extraction carried out in step ii) is a countercurrent extraction of the aqueous mixture obtained in step i) with the extraction solvent. The extraction may be carried out, for example, in a mixer-settler array, in a column filled with random or structured packing, in a pulsed column or even in a stirred column.

[0080] The liquid-liquid extraction step ii) is advantageously carried out at a temperature between 0°C and 80°C, preferably between 5°C and 60°C, preferably between 10°C and 40°C, generally at ambient temperature (i.e. between 15°C and 35°C).

[0081] The weight ratio (wt / wt) of the extraction solvent relative to the aqueous mixture is preferably 0.2-5, preferably 1-3, preferably 1.5-2.5.

[0082] In a non-limiting manner, the extraction solvent is preferably selected from chlorinated organic solvents, ethers, esters, ketones, aldehydes, and aromatic compounds. Preferably, the extraction solvent is a chlorinated solvent containing 1 to 10 carbon atoms (hereinafter referred to as C1 to C10), an ether containing 2 to 10 carbon atoms (C2 to C10), an ester containing 4 to 10 carbon atoms (C4 to C10), a ketone containing 3 to 10 carbon atoms (C3 to C10), an aldehyde containing 1 to 10 carbon atoms (C1 to C10), or a C4 to C10 aromatic compound. Preferably, the extraction solvent is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole, and toluene, either alone or in mixture. Most preferably, the extraction solvent is methyl isobutyl ketone (MIBK).

[0083] Advantageously, the extraction solvent is - have a very large difference in volatility with 5-HMF, in order to facilitate its separation in step iii) of the extraction solvent from the intermediate organic effluent, and to limit the decomposition of 5-HMF, i.e. have an evaporation rate which avoids the decomposition of 5-HMF in step iii) and which minimizes the amount of residual extraction solvent, in step iii), so as to advantageously form a heterogeneous azeotrope with water, The azeotrope is preferably rich in the extractant, i.e., has more than 50% by weight of the extractant, preferably more than 60% by weight of the extractant, preferably more than 70% by weight of the extractant. Advantageously, the boiling point of said azeotrope of water / extractant mixture is significantly lower than the boiling point of water, preferably at least 5° C. lower than the boiling point of water, preferably at least 8° C. lower than the boiling point of water, preferably at least 10° C. lower than the boiling point of water.

[0084] The intermediate organic effluent may contain a synthetic solvent. Preferably, said intermediate organic effluent contains 5-HMF and a synthetic solvent in a 5-HMF / (synthetic solvent+5-HMF) weight ratio of 50 / 50 to 99 / 01, preferably 50 / 50 to 95 / 05, preferably 55 / 45 to 90 / 10, more preferentially 60 / 40 to 85 / 15, preferably 65 / 35 to 80 / 20.

[0085] In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution further comprises backwashing the intermediate organic effluent obtained in step ii) in the presence of an aqueous solvent prior to separation step iii) to obtain at least one intermediate organic effluent and an aqueous back-extract comprising the synthesis solvent, the intermediate organic effluent being depleted of the synthesis solvent and comprising 5-HMF and the extraction solvent, with the synthesis solvent having a content of 20% by weight or less relative to the weight of 5-HMF.

[0086] In one embodiment, the aqueous back extract is advantageously passed, in part or in whole, to the contacting step i).

[0087] If a backwash step is performed, the extraction solvent introduced in step ii) is selected from water-immiscible organic solvents so as to form two liquid phases in the backwash step, a characteristic that is highly dependent on the relative proportions of the feedstock, the back-extraction aqueous solvent and the extraction solvent flow rates used in the process.

[0088] The aqueous solvent is introduced in such a way that the amount of aqueous solvent is as small as possible to reduce costs, but in a quantity sufficient to ensure a low weight content of synthetic solvent in the intermediate organic effluent, i.e. preferably not more than 20.00% by weight relative to the weight of 5-HMF, preferentially not more than 15.00% by weight relative to the weight of 5-HMF, preferably between 0.01% and 15.00% by weight relative to the weight of 5-HMF, and highly preferably between 0.01% and 10.00% by weight relative to the weight of 5-HMF.

[0089] Advantageously, the aqueous backwash solvent comprises at least 95% by weight of water, preferably at least 98% by weight of water (100% being the maximum). The aqueous solvent may optionally comprise a synthetic solvent and / or an extractant. The lower the amount of synthetic solvent present in the aqueous backwash solvent, the higher the backwashing effectiveness. Preferably, the aqueous solvent may comprise at most 1.0% by weight of synthetic solvent, preferably at most 0.1% by weight.

[0090] According to some embodiments, the aqueous backwash solvent is obtained from one or more of the following process streams: condensate produced in the dehydration step b), water extracted from the feedstock in step a), water produced in the step of regenerating the synthesis solvent or any other aqueous stream containing synthesis solvent in an amount preferably not greater than 1 wt. %, preferably not greater than 0.1 wt. %.

[0091] The backwashing step is advantageously a liquid-liquid extraction of the organic stream obtained in step ii), in particular the intermediate organic extract, countercurrent to the aqueous backwashing solvent, and can be carried out, for example, in a mixer-settler array, in a column packed with random or structured packing, in a plug flow column, or even in a stirred column.

[0092] The temperature at which the backwashing step is preferably carried out is 0°C to 80°C, preferably 5°C to 60°C, preferably 10°C to 40°C, and generally room temperature (ie, 15°C to 35°C).

[0093] The weight ratio (wt / wt) of the aqueous backwash solvent relative to the intermediate organic extract is preferably 0.04-5, preferably 0.07-3, preferably 0.1-1.

[0094] The backwashing step makes it possible to obtain an aqueous back extract and a synthetic solvent-depleted intermediate organic effluent, the aqueous back extract preferably containing at least 60% by weight of water, preferably at least 80% by weight of water. The weight content of synthetic solvent in the obtained synthetic solvent-depleted intermediate organic effluent is preferably not more than 20.0% by weight relative to the weight of 5-HMF, preferably not more than 15.0% by weight relative to the weight of 5-HMF, preferably not more than 5.0% by weight relative to the weight of 5-HMF, preferably not more than 4.0% by weight relative to the weight of 5-HMF, preferably not more than 3.0% by weight relative to the weight of 5-HMF.

[0095] In one embodiment, the aqueous back extract may be recycled in a similar manner as the water extracted in step a).

[0096] (Step iii) Separating the extraction solvent) In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution comprises step iii) of separating the extraction solvent from the intermediate organic effluent to obtain an aqueous 5-HMF solution.

[0097] If backwashing has been performed beforehand, the intermediate organic effluent is a synthetic solvent-depleted intermediate organic effluent.

[0098] In one embodiment, the separated extraction solvent may advantageously be recycled to extraction step ii).

[0099] In one embodiment, the separation step iii) is carried out by steam distillation.

[0100] The aqueous stream is fed to a steam distillation step. The aqueous stream preferably comprises more than 95% water by weight, preferably more than 98% water by weight.

[0101] In certain embodiments of the invention, the aqueous stream may be pure water and external to the process, which may further reduce the content of residual synthesis solvents remaining in the aqueous 5-HMF solution produced in step b).

[0102] In another particular embodiment of the invention, the aqueous stream isolated within the process can be used to feed a steam distillation step, thus making it possible to limit the operational costs of the process and its environmental impact. Advantageously, the aqueous stream used may be from the condensate produced during the extraction of water during the synthesis, from the step of regenerating the synthesis solvent, or any other aqueous stream containing less than 5% by weight of the synthesis solvent, preferentially less than 1% by weight of the synthesis solvent, preferentially less than 0.1% by weight of the synthesis solvent.

[0103] Advantageously, the extraction solvent used in the process forms a heterogeneous azeotrope with the aqueous stream, said azeotrope being preferably rich in the extraction solvent, preferably comprising more than 50% by weight of the extraction solvent, preferably more than 60% by weight of the extraction solvent, preferably more than 70% by weight of the extraction solvent. Advantageously, the boiling point of said azeotrope is significantly lower than the boiling point of the aqueous stream, preferably at least 5°C lower than the boiling point of the aqueous stream, preferably at least 8°C lower than the boiling point of the aqueous stream, preferably at least 10°C lower than the boiling point of the aqueous stream.

[0104] The steam distillation step may be carried out at atmospheric pressure or under vacuum, in particular at a pressure of 0.001 MPa to 0.1 MPa, preferably under vacuum at a pressure of 0.005 MPa to 0.08 MPa. Advantageously, the steam distillation step is carried out under vacuum, in particular at a pressure of 0.001 MPa to 0.1 MPa, preferably at a pressure of 0.005 MPa to 0.08 MPa, to separate the extraction solvent without decomposing 5-HMF.

[0105] Advantageously, the steam distillation step is carried out in a distillation column, preferably with a temperature at the bottom of the column of not more than 140°C, preferably not more than 130°C, preferably not more than 120°C, preferably not more than 110°C, preferably not more than 100°C, to facilitate removal of the extractant without decomposition of 5-HMF.

[0106] In one particular embodiment, the intermediate organic effluent and the aqueous stream are mixed prior to being introduced into the distillation column, and the mixture is introduced at an intermediate point in the distillation column.

[0107] In another particular embodiment, the intermediate organic effluent is introduced into the upper part of the distillation column, preferably into the upper half of the distillation column, while the aqueous stream is introduced into the lower part of the distillation column, preferably into the lower half of the distillation column. Mixing of the intermediate organic effluent and the aqueous stream is then carried out within the distillation column.

[0108] Condensation of the overhead vapors of the distillation column generates two liquid phases: one is a water-rich phase which may advantageously be returned to the column as reflux, and the other is an extractant-rich phase which may advantageously be recycled to the extraction step ii).

[0109] According to the invention, the amount of 5-HMF in the aqueous 5-HMF solution obtained at the end of step b) is at least 30% by weight, preferably at least 40% by weight, and preferably less than 90% by weight, preferably less than 85% by weight, preferably 80% by weight, the percentages being given by weight of 5-HMF relative to the weight of the aqueous 5-HMF solution obtained at the end of step b).

[0110] The process according to the invention thus makes it very advantageously possible to produce aqueous 5-HMF solutions, which very advantageously have a synthesis solvent content of less than or equal to 10% by weight relative to the weight of 5-HMF, preferably less than or equal to 5% by weight relative to the weight of 5-HMF, preferably less than or equal to 3% by weight relative to the weight of 5-HMF.

[0111] In one embodiment, step b) of replacing the synthesis solvent with an aqueous solution further comprises, prior to step iii) of separating the extraction solvent from the intermediate organic effluent, concentrating the 5-HMF solution in the organic phase by separating a portion of the extraction solvent, which concentration step makes it possible to produce a concentrated intermediate organic effluent containing 5-HMF and the extraction solvent, and a stream containing mainly the extraction solvent.

[0112] Preferably, the stream containing mainly the extraction solvent is totally or partly recycled to extraction step ii).

[0113] Preferably, the separation of a portion of the extraction solvent in this step of concentrating the 5-HMF solution in the organic phase is carried out by evaporation, for example in an atmospheric or vacuum distillation column, in an evaporator, or via any method known to those skilled in the art, prior to step iii).

[0114] According to this preferred embodiment, evaporation of the extraction solvent is advantageously carried out under reduced pressure, preferably at atmospheric pressure or under vacuum, at a pressure between 0.01 MPa and 0.1 MPa, and preferentially between 0.01 MPa and 0.09 MPa, to limit the temperature of the liquid and hence the decomposition of 5-HMF. Preferably, the temperature of the liquid is kept below 130°C, preferably below 100°C, and preferably below 70°C. The level of vacuum to be applied to reach these temperatures naturally depends on the synthesis solvent, more particularly on the extraction solvent used and the evaporation rate of the synthesis solvent.

[0115] The concentration step is carried out at a mass evaporation rate (or evaporation rate), corresponding to the mass of the evaporated extraction solvent relative to the mass of the intermediate organic effluent obtained from step ii), of at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 75%, preferably at least 80%, preferably at least 85%, preferably at least 90%, and preferably at most 99%. Advantageously, the evaporation rate is defined relative to the extraction solvent so as not to decompose 5-HMF, but also to minimize the amount of residual extraction solvent to be separated in step iii), while at the same time preventing liquid phase separation (i.e., ensuring that the liquid phase remains single) when the concentrated intermediate organic effluent is contacted with an aqueous stream in step iii), if step iii) is carried out by steam distillation.

[0116] Advantageously, the concentrated intermediate organic effluent obtained at the end of the concentration step highly advantageously has a 5-HMF content of at least 40% by weight, preferably at least 50% by weight, preferably at least 60% by weight, relative to the weight of the concentrated intermediate organic effluent, and preferably at most 95% by weight, preferably at most 90% by weight, preferably at most 85% by weight, relative to the weight of the concentrated intermediate organic effluent. In other words, the concentrated intermediate organic effluent preferably has a residual extractant content of at least 5% by weight, preferably at least 10% by weight, relative to the weight of the concentrated intermediate organic effluent, and preferably at most 60% by weight, preferably at most 50% by weight, preferably at most 40% by weight, relative to the weight of the concentrated intermediate organic effluent.

[0117] (Step c) Regenerating the synthesis solvent) In one embodiment, the method according to the invention further comprises a step c) of regenerating the synthesis solvent displaced in step b).

[0118] The term "regeneration" is understood to mean the production of a stream containing mainly the desired solvent.

[0119] Advantageously, the regenerated synthesis solvent is recycled to step a).

[0120] The stream containing the displaced synthesis solvent may contain a water fraction, which may be separated and recycled to the overall aqueous stream or to one of the steps requiring the presence of an aqueous solution. The presence of water in this stream is not detrimental to the process of step a) utilizing water extraction to maintain selectivity in the conversion of sugars to 5-HMF.

[0121] During this step c), the synthesis solvent can be purified and at least partially purged from the by-products of the synthesis reaction, which may include, in particular: - raw uninverted sugar; - sugar oligomers formed during synthesis; - 5-HMF; - neutralized acid in the neutralization step; Humins, for example humins that were not filtered out during the precipitation and filtration process.

[0122] In embodiments in which step b) of replacing the synthesis solvent with an aqueous solution comprises steps i), ii) and iii), it is the aqueous effluent comprising the synthesis solvent obtained in step ii) that is used in step c) of regenerating the synthesis solvent.

[0123] In this embodiment, the aqueous effluent may also contain small amounts of extraction solvent, which may itself be regenerated, optionally purged from by-products, and advantageously recycled to step ii).

[0124] The regeneration step can advantageously be carried out by a series of gas / liquid separations in evaporation or distillation equipment. Generally, a first evaporation stage allows for the recovery of the majority of the extraction solvent, at least 70%, preferentially at least 80%, and more preferentially at least 90%. A second step allows for the complete depletion of the water stream, which then contains less than 10% by weight of water, preferentially less than 5% by weight, and more preferentially less than 1% by weight. The final step consists of completing the evaporation of the synthesis solvent from the heavy by-products of the process. The loss of synthesis solvent in the purge of the heavy products is then less than 10% of the solvent used in the synthesis, preferentially less than 5% by weight, and more preferentially less than 1% by weight.

[0125] Preferentially, the separation cascade is carried out at a maximum temperature imposed by the thermal stability of the products, the separation being driven by successive reductions in pressure, which is generally between 50°C and 200°C, preferentially between 80°C and 150°C, and even more preferentially between 100°C and 130°C.

[0126] The evaporation can advantageously be carried out in a conventional shell-and-tube heat exchanger followed by a gas / liquid separation vessel, or in a single- or multiple-effect evaporator ensuring the supply of the heat necessary for the gas / liquid separation and evaporation.

[0127] Preferentially, the final evaporation step is carried out in equipment with a short residence time, such as a wiped film evaporator, to limit the degradation of humins and to extract these humins, the viscosity of which can exceed 1000 cP at 100°C.

[0128] DESCRIPTION OF THE DRAWINGS Specific exemplary embodiments of the present invention are described below, without limitation, with reference to the accompanying drawings, in which: FIG.

[0129] Figure 1: A hexose-containing feedstock (1) is sent to step a), where it is contacted with an acidic dehydration catalyst and an organic synthesis solvent (2). The synthesis is initiated and carried out at temperatures between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and highly preferably between 80°C and 120°C, and at pressures between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, during which water is extracted from the reaction medium (4). A synthesis effluent (3) is obtained, which contains 5-HMF and the synthesis solvent. The synthesis effluent (3) is sent to step b), where the synthesis solvent is replaced with an aqueous solution (21), which can be derived from the water stream extracted from the reaction medium (4), to obtain an aqueous 5-HMF solution (16). The displaced synthesis solvent (11) is sent to step c) for recycling the synthesis solvent (11), the synthesis solvent is optionally purged from the synthesis by-products (20), and the synthesis solvent is recycled to step a). The loss of synthesis solvent is compensated for by the replenishment of synthesis solvent (22).

[0130] Figure 2: A hexose-containing feedstock (1) is sent to step a), where it is contacted with an acidic dehydration catalyst and an organic synthesis solvent (2). The synthesis is initiated and carried out at temperatures between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and highly preferably between 80°C and 120°C, and at pressures between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, during which water is extracted from the reaction medium (4). A synthesis effluent (3) containing 5-HMF and the synthesis solvent is obtained. The synthesis effluent (3) is sent to step b), where the synthesis solvent is replaced. This process begins with step i), in which the synthesis effluent (3) is contacted with a liquid stream (5) to obtain an aqueous mixture (6). The liquid stream (5) contains at least 80% by weight of water, preferentially at least 90% by weight, and even more preferentially at least 95% by weight of water originating entirely from the aqueous stream (21) and can be fed by the water stream extracted from the reaction medium (4). The aqueous mixture (6) is sent to a liquid-liquid extraction step (ii), in which an aqueous stream (11) containing the synthesis solvent is extracted with an extraction solvent (9), to obtain an intermediate organic effluent (10) containing 5-HMF and the extraction solvent. The intermediate organic effluent (10) is sent to step (iii), in which the extraction solvent is separated from the organic effluent (10) using an aqueous solution (15) originating entirely from the aqueous stream (21), to obtain an extraction solvent stream (17) and an aqueous 5-HMF solution (16). The extraction solvent stream (17) can be recycled to step ii) (stream (9)). The aqueous stream (11) is sent to step c) for regenerating the synthesis solvent, where said synthesis solvent is extracted from stream (11), optionally purged from the synthesis by-products (20), and the synthesis solvent is recycled to step a). Losses of synthesis solvent and extraction solvent are compensated for by replenishment of synthesis solvent replenishment (22) and extraction solvent replenishment (23), respectively.

[0131] Figure 3: A hexose-containing feedstock (1) is sent to step a), where it is contacted with an acidic dehydration catalyst and an organic synthesis solvent (2). The synthesis is initiated and carried out at temperatures between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and highly preferably between 80°C and 120°C, and at pressures between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, during which water is extracted from the reaction medium (4). A synthesis effluent (3) is obtained, which contains 5-HMF and the synthesis solvent. The synthesis effluent (3) is sent to step b), where the synthesis solvent is replaced. The process begins with step i), in which the synthesis effluent (3) is contacted with a liquid stream (5) containing at least 80% by weight of water, preferentially at least 90% by weight of water, and even more preferentially at least 95% by weight of water, originating entirely from an aqueous stream (21), which can be fed by the water stream extracted from the reaction medium (4), to obtain an aqueous mixture (6). The aqueous mixture (6) is sent to a liquid-solid separation step iv), in which impurities, in particular humins, are separated into stream (8). The purified stream (7) is sent to a liquid-liquid extraction step ii), in which an aqueous stream (11) containing the synthesis solvent is extracted with an extraction solvent (9), to obtain an intermediate organic effluent (10) containing 5-HMF and the extraction solvent. The intermediate organic effluent (10) is sent to step v) for backwashing in the presence of aqueous solvent (12) obtained from the entire aqueous stream (21), to obtain a synthetic solvent-depleted organic effluent (13) and an aqueous back extract (14) containing the synthetic solvent. The synthetic solvent-depleted organic effluent (13) contains 5-HMF and the extractant, with the synthetic solvent having a content of 20% by weight or less relative to the weight of 5-HMF, and the aqueous back extract (14) can be sent to step i). The synthetic solvent-depleted organic effluent (13) is sent to step iii), where the extractant is separated from the organic effluent (13) using an aqueous solution (15) originating from the entire aqueous stream (21), to obtain a stream of extractant (17) and an aqueous 5-HMF solution (16), stream (17) can be recycled to step ii) contributing to the overall stream of extractant (9).The aqueous stream (11) is sent to a synthesis solvent regeneration step c), where the synthesis solvent is extracted from stream (11), optionally purged from synthesis by-products (20), the synthesis solvent is recycled to step a), optionally water (19) is extracted from stream (11) and sent to the overall aqueous stream (21), and optionally extraction solvent (18) is extracted from stream (11) and sent to the overall extraction solvent (9) stream. Losses of synthesis solvent and extraction solvent are compensated for by the replenishment of synthesis solvent replenishment (22) and extraction solvent replenishment (23), respectively.

[0132] (Example) Example 1: Synthesis of 5-HMF from crystalline fructose in a continuous stirred tank reactor (CSTR) mode according to the prior art Fructose is introduced in crystalline form. The purity is greater than 99.5% by weight of sugar in DMSO, resulting in a fructose concentration of 35% by weight. The mixture is brought to a temperature of 120°C and the acid catalyst methanesulfonic acid is added in a catalyst / sugar molar ratio of 1% by mole.

[0133] The mixture is introduced into the reactor and the conversion is carried out in CSTR mode. The pressure is maintained at ambient pressure, i.e., 0.1013 MPa. Under these pressure and temperature conditions, the reaction medium is above the mixture's bubble point, so there is no vapor phase to be extracted. The reaction medium is continuously withdrawn at a mass flow rate equal to the mass flow rate of the mixture introduced into the reactor, maintaining the volume of the reactor constant. This volume is set to ensure an average residence time of the feedstock of 5 hours.

[0134] The synthetic effluent resulting from the dehydration step contained 65% by weight of DMSO, 17% by weight of 5-HMF, and 9% by weight of water. This means that the molar yield of 5-HMF relative to fructose is 70%. Polymeric compounds (humins) soluble in the reaction medium were formed, which, together with unconverted fructose, accounted for 9% by weight of the solution.

[0135] Example 2: Synthesis of 5-HMF from crystalline fructose in a continuous CSTR mode in accordance with the present invention Fructose is introduced in crystalline form, with a purity of more than 99.5% by weight of sugar in DMSO, resulting in a fructose concentration of 35% by weight. The mixture is brought to a temperature of 120°C and an acid catalyst, methanesulfonic acid, is added in a catalyst / sugar molar ratio of 1% by mole.

[0136] The mixture is introduced into a reactor and converted in CSTR mode. The pressure is maintained at 0.01 MPa. Under these pressure and temperature conditions, the reaction medium is above the bubble point of the mixture, and therefore a vapor phase is present to be extracted. The vapor phase is rectified in a packed column with 8 theoretical plates, and the reflux is adjusted to obtain an overhead product with a water / DMSO composition of 99.5% by weight / 0.5% by weight, respectively.

[0137] The liquid reaction medium is continuously withdrawn to form a reaction effluent, the withdrawal flow rate and the liquid volume in the reactor being adjusted to ensure an average residence time of the feedstock of 5 hours.

[0138] The synthetic effluent resulting from the dehydration and extraction steps contained 75% by weight of DMSO, 18% by weight of 5-HMF, and 1% by weight of water. This means that the molar yield of 5-HMF relative to fructose is 80%. Polymeric compounds (humins) soluble in the reaction medium were formed, which, together with unconverted fructose, accounted for 6% by weight of the solution.

[0139] Therefore, by carrying out the synthesis at the same temperature, with the same amount of catalyst and synthesis solvent and with the same residence time, the present invention makes it possible to process crystalline fructose and improve its yield very significantly (80 mol % according to the present invention, 70 mol % according to the prior art).

[0140] Example 3: Conversion of a syrup containing 70% by weight fructose and 30% by weight water to produce an aqueous 5-HMF solution in accordance with the present invention The illustrated method follows that shown in FIG.

[0141] The process processes syrup at a flow rate of 1 t / h, i.e., 700 kg / h of fructose. The syrup is mixed with a stream containing recycled DSMO synthesis solvent from the synthesis solvent regeneration step and a make-up of 25.0 kg / h of DMSO required to compensate for losses from the process. The resulting mixture contains 24.3 wt.% fructose, 0.5 wt.% MIBK extraction solvent (from the recycled synthesis solvent leaving the regeneration step), 31.7 wt.% water, and 43.3 wt.% DMSO.

[0142] The mixture thus obtained is poured into a packed column realizing 8 theoretical plates, the bottom pressure of which is maintained at 0.014 MPa, and reboiling and reflux are adjusted to obtain a bottom product with a temperature of 120°C, and the DMSO composition of the water discharged at the top is 0.5% by weight.

[0143] Methanesulfonic acid (MSA) is introduced at the bottom of the column in an MSA / fructose molar ratio of 1%. The dehydration reaction is carried out continuously in the bottom of the column with an average residence time of 5 hours. The reaction mixture is maintained at 120°C, i.e., below its bubble point, by reboiling. The vapor phase containing water and DMSO is thus rectified in the packed section of the column. Under these conditions, the water content of the reaction medium, which corresponds to the liquid phase at the bottom of the column, is 1% by weight. A withdrawal is carried out so as to maintain the liquid residence time at the bottom of the column. This withdrawal corresponds to the reaction effluent produced.

[0144] 1.8 t of synthetic effluent is then collected, which contains 69.7 wt% DMSO, 1.0 wt% water, 22.1 wt% 5-HMF and 7.2 wt% uninverted sugars and humins.

[0145] This synthesis effluent is mixed with the aqueous back extract from the backwashing step. Water collected during the synthesis solvent regeneration and extraction step or during the distillation of the fructose / DMSO mixture is used to supplement the mixture for generating the precipitation medium, the water / DMSO weight ratio of which is 0.91 (calculated taking into account the water and DMSO present in all streams feeding this step). After aging for 1 hour and 30 minutes, the mixture is filtered through a filter press. At the end of the filtration sequence, the resulting cake is pressed. This step thus makes it possible to precipitate and filter off 29 kg / h of humin. The precipitation and filtration steps are carried out at 35 °C and ambient pressure.

[0146] The filtrate is mixed with the compressed filtrate and sent to a liquid-liquid extraction step, representing a continuous flow rate of 3.0 t / h. This step is carried out through a pulsed column realizing 9 theoretical plates, also operated at ambient temperature and pressure. The extraction solvent is MIBK. The amount of MIBK used is such that the weight ratio of MIBK / feedstock in the liquid-liquid extraction step is 1.5.

[0147] Under these conditions, the aqueous effluent obtained in the liquid-liquid extraction process contains 3.5% of the HMF produced in the synthesis. That is, the production loss is 3.5% of the HMF involved in this extraction process. The composition of the aqueous effluent is 46.0% by weight DMSO, 44.9% by weight water, 6.1% by weight MIBK, 0.5% by weight HMF, and 2.5% by weight unconverted fructose and humins. The flow rate is 2.7 t / h.

[0148] The aqueous effluent is treated in a synthetic solvent regeneration step, which consists of three successive evaporations at a constant temperature of 120°C and at progressively lower pressures (0.120 MPa, 0.020 MPa, 0.0025 MPa) to limit the decomposition of the species present: - The first regeneration step is carried out at 0.12 MPa. The vapor is partially condensed. The condensed liquid is returned upstream of the first evaporation step. This arrangement results in an aqueous stream containing 97.8% by weight of water after partial condensation, which can be sent directly to the water vessel of the process and the MIBK present in the aqueous effluent can be recovered by demixing. The MIBK stream is returned to the extraction solvent collection vessel. Under these conditions, 49% of the water contained in the aqueous effluent is extracted, without requiring further treatment in the water / DMSO / fructose separation column. - In a second step, the aqueous effluent from the first regeneration step is again subjected to evaporation at 120 °C, this time at a pressure of 0.02 MPa, allowing 92.9% of the mixture to evaporate. The vapor is condensed and then returned to the water / DMSO / fructose separation column, where it contributes most to the DMSO feed. Its composition is 34% by weight of water and 65% by weight of DMSO, with a flow rate of 1.8 t / h. The residual DMSO content of the resulting effluent is 40% by weight, with only 1.2% by weight of water, the remainder consisting of unextracted 5-HMF, unconverted fructose, humins and salts present in the aqueous mixture. - In the third step, the aqueous effluent from the third regeneration step is evaporated again using wiped film exchanger technology to remove as much of the heavy DMSO fraction as possible. The temperature is once again brought to 120°C, while the pressure is reduced to 0.0025 MPa in order to vaporize 35% by weight of the product. The vapor is condensed and recycled to the water / DMSO / fructose separation column. The resulting liquid and viscous stream contains less than 10% by weight of DMSO, limiting losses of synthesis solvent and, therefore, replenishment requirements.

[0149] The intermediate organic effluent obtained in the liquid-liquid extraction step is sent to a backwashing step. Its flow rate is 3.4 t / h. It contains 1.5 wt. % DMSO, i.e., 5% of the DMSO used in the reaction, justifying the need to recover it by backwashing to limit losses of the synthetic solvent. The backwashing step is carried out at ambient pressure and temperature in a packed column with three theoretical plates and a solvent / feedstock weight ratio of 0.1. This backwashing step allows for a reduction in the loss of DMSO contained in the intermediate organic effluent. After backwashing, the loss of DMSO contained in the intermediate organic effluent therefore accounts for only 0.1% of the amount of DMSO used in the reaction. The synthetic solvent-depleted intermediate organic effluent obtained in this step contains 2.3 wt. % water, 89.1 wt. % MIBK, 8.0 wt. % 5-HMF, and 0.6 wt. % humins.

[0150] This intermediate organic effluent, depleted of synthesis solvent, is concentrated at a pressure of 0.0217 MPa and a temperature of 100°C, which makes it possible to achieve a mass vaporization rate of 84.2% and produce an intermediate organic effluent concentrated to a quantity of 50% by weight. The vapor fraction produced in this step is condensed. Demixing makes it possible to separate a liquid stream containing 97.6% by weight of MIBK from an aqueous liquid stream containing 97.9% by weight of water. The MIBK stream is recycled to a container for collecting MIBK for recycling, and the water stream is collected in a process water container.

[0151] The intermediate organic effluent, depleted and enriched in synthesis solvent, is sent to steam distillation, which effluent has a flow rate of 753 kg / h. This step is carried out in a distillation column equipped with packing realizing 7 theoretical plates at 0.04 MPa, with a process water reflux ratio of 130 kg / h.

[0152] 560 kg / h of water is injected into the bottom of the column to dilute the 5-HMF, producing an aqueous 5-HMF solution. The reboiling is controlled to limit the MIBK content in the bottom product to 0.1% by weight. The resulting aqueous 5-HMF solution has a 5-HMF concentration of 45% by weight, 0.4% by weight of DMSO, 51.1% by weight of water, 0.1% by weight of MIBK, and 3.4% by weight of humins. The overhead vapor is condensed and cooled to 52°C. Demixing allows for the separation of a liquid stream containing 97.2% by weight of MIBK from an aqueous liquid stream containing 98.7% by weight of water. The MIBK stream is recycled to a vessel for collecting MIBK for recycling, and the water stream is used to generate reflux for the column, with the excess being collected in a process water vessel.

[0153] The table below shows the flow rates of the various streams of the process according to Example 3, in terms of total flow rate and flow rate per component of the stream.

[0154] [Table 1] [Brief explanation of the drawings]

[0155] [Figure 1] 1 illustrates a method according to a first embodiment. [Figure 2] 1 illustrates a method according to a second embodiment, in which step b) comprises three specific steps. [Figure 3] 1 illustrates a method according to a third embodiment, in which step b) includes five specific steps.

Claims

1. 1. A process for producing a solution of 5-hydroxymethylfurfural, comprising step a) contacting a hexose-containing feedstock with a synthesis solvent and an acidic dehydration catalyst to form a reaction medium, said process being carried out at a temperature of from 30°C to 200°C, preferably from 50°C to 180°C, preferably from 70°C to 150°C, and highly preferably from 90°C to 130°C, and at a pressure of from 0.001 MPa to 10 MPa, preferably from 0.001 MPa to 5 MPa, preferably from 0.01 MPa to 1 MPa, with simultaneous extraction of water from the reaction medium to obtain a synthesis effluent comprising 5-HMF and the synthesis solvent.

2. 2. The method of claim 1, wherein the hexose is a fructose or fructoside unit.

3. The acidic dehydration catalyst is selected from the group consisting of HCl, H ２ SO ４ , H ３ P.O. ２ , H ３ P.O. ４ , HNO ３ , AlCl ３ 3. The process according to claim 1 or 2, wherein the acid is selected from the group consisting of acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid and trifluoromethanesulfonic acid, either alone or in mixtures.

4. The method according to any one of claims 1 to 3, wherein the synthesis solvent is dimethyl sulfoxide.

5. 5. The method according to claim 1, further comprising a step of neutralizing the synthesis effluent, preferably carried out after step a) by contacting said synthesis effluent with a basic compound.

6. 6. The process according to any one of claims 1 to 5, further comprising a step b) of replacing the synthesis solvent present in the synthesis effluent with an aqueous solution to obtain an aqueous solution of 5-hydroxymethylfurfural.

7. 7. The method of claim 6, wherein step b) of replacing the synthesis solvent with an aqueous solution comprises: i) contacting the synthesis effluent with a liquid stream containing at least 80% by weight of water, preferentially at least 90% by weight of water, even more preferentially at least 95% by weight of water, to obtain an aqueous mixture; ii) a step of liquid-liquid extraction of the aqueous mixture obtained in step i) in the presence of an extraction solvent, obtaining at least one aqueous effluent containing the synthesis solvent and an intermediate organic effluent containing 5-hydroxymethylfurfural and the extraction solvent; iii) Separating the extraction solvent from the intermediate organic effluent to obtain an aqueous solution of 5-hydroxymethylfurfural.

8. 8. The method of claim 7, wherein the extraction solvent is methyl isobutyl ketone.

9. 9. The method according to claim 7 or 8, wherein the separated extraction solvent can advantageously be recycled to extraction step ii).

10. 10. The method according to any one of claims 7 to 9, further comprising a step of liquid-solid separation of the aqueous mixture obtained after step i) and before the liquid-liquid extraction step ii).

11. 11. The method according to claim 7, further comprising, prior to separation step iii), a step of backwashing the intermediate organic effluent obtained in step ii) in the presence of an aqueous solvent, to obtain at least one intermediate organic effluent and an aqueous back-extract comprising a synthetic solvent, said intermediate organic effluent being depleted of synthetic solvent and comprising 5-hydroxymethylfurfural and an extractant, said intermediate organic effluent having a content of synthetic solvent of not more than 20% by weight relative to the weight of 5-hydroxymethylfurfural.

12. 12. The method according to any one of claims 7 to 11, wherein the separation step iii) is carried out by steam distillation.

13. 13. The method according to any one of claims 1 to 12, further comprising a step c) of regenerating the synthesis solvent displaced in step b).

14. 14. The method according to claim 13, wherein the regenerated synthesis solvent is recycled to step a).

15. 15. The process according to any one of claims 1 to 14, wherein the water extracted from the reaction medium is recycled and fed either independently to one or more steps of the process requiring the supply of an aqueous stream, or to the overall aqueous stream feeding said steps.

Images