Process for producing 5-HMF by converting sugar in a non-aqueous solvent with water extraction during synthesis

Abstract

The present invention relates to a process for producing a 5-Hydroxymethylfurfural (5-HMF) solution, comprising a step a) of contacting a feedstock comprising a hexose with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature between 30 and 200°C, preferably between 50 and 180°C, most preferably between 70 and 150°C, and most preferably between 90 and 130°C, and at a pressure between 0.001 MPa and 10 MPa, preferably between 0.001 MPa and 5 MPa, most preferably between 0.01 MPa and 1 MPa, obtaining a reaction medium and concomitantly extracting water from the reaction medium, to obtain a synthesis effluent comprising 5-HMF and the synthesis solvent. Figure 1 to be published

Description

Title of the invention: Process for producing 5-HMF by converting sugar in a non-aqueous solvent with water extraction during synthesis technical field

[0001] The present invention relates to the production of 5-HMF from a feed comprising a sugar, more particularly a hexose, by catalytic synthesis in an organic solvent. Previous technique

[0002] 5-Hydroxymethylfurfural (5-HMF) is a compound of interest derived from biomass that can be used in many fields, particularly in pharmaceuticals, agrochemicals, and specialty chemicals. The production of 5-HMF by sugar dehydration has been known for many years and has been the subject of extensive research. Numerous dehydration conditions exist; the following methods are examples:

[0003] 5-HMF can be obtained in aqueous media, generally in the presence of an acid catalyst. This acid catalyst allows the dehydration of C6 sugars (hexoses, and in particular fructose) into 5-HMF, but also catalyzes the rehydration of 5-HMF into formic acid and levulinic acid, which significantly reduces the yield.

[0004] 5-HMF can also be obtained in a non-aqueous, protic polar medium, with solvents such as methanol, ethanol, or acetic acid, and in the presence of an acid catalyst. Under these conditions, 5-HMF is obtained by mixing with an ether or ester derivative of 5-HMF, depending on the reaction medium used. The formation of these byproducts is due to the reaction of 5-HMF with the reaction solvent in an acidic medium.

[0005] Application WO 2007 / 104514 describes the synthesis of 5-HMF by dehydration of sugars using methanol or ethanol as a solvent in the presence of an acid catalyst. In this case, the presence of said catalyst also catalyzes the etherification reaction of 5-HMF by the alcohol to give a mixture of 5-HMF and its methyl or ethyl ether form, depending on the alcohol used as a solvent.

[0006] 5-HMF can also be produced in aprotic polar medium with or without an acid catalyst. Dimethyl sulfoxide (DMSO) is a particularly noteworthy example, as it allows the production of 5-HMF in very good yields, with or without an acid catalyst, and without the undesirable reactions listed above.

[0007] Furthermore, regardless of the synthesis medium (water, methanol, DMSO, etc.), polymeric by-products called humins are formed during the production of 5-HMF (van Dam, HE; ​​Kieboom, APG; van Bekkum, H. (1986) The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethylfurfural. In: Starch - Starke, vol. 38, n° 3, p. 95-101).

[0008] The synthesis of 5-HMF in a medium such as DMSO is particularly interesting, because it allows 5-HMF to be obtained in its alcohol form (and not ether) with very good yields.

[0009] However, the industrialization of 5-HMF production leads to reducing the dilution of sugars in DMSO to the bare minimum, which degrades the sugar conversion selectivity. 5-HMF selectivity is defined as the ratio between the number of moles of 5-HMF produced and the number of moles of fructose converted from the feedstock introduced into the process. In a polar aprotic environment, the presence of water degrades the sugar conversion selectivity more significantly as the sugar concentration in DMSO increases.

[0010] The object of this application is to reduce the water content of the reaction medium by extracting water during the synthesis (water from the dehydration of sugars and optionally water from the syrup, if the feedstock is a syrup). Summary of the invention

[0011] The present invention relates to a process for producing a solution of 5-Hydroxymethylfurfural (5-HMF) comprising a step a) of bringing into contact a feed comprising a hexose with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature between 30 and 200°C, preferably between 50 and 180°C, preferably between 70 and 150°C and most preferably between 90 and 130°C, and at a pressure between 0.001 MPa and 10 MPa, preferably between 0.001 MPa and 5 MPa, preferably between 0.01 MPa and 1 MPa, to form a reaction medium, and concomitant extraction of water from the reaction medium, to obtain a synthesis effluent comprising 5-HMF and synthesis solvent.

[0012] According to the invention, the water present during the synthesis is extracted in order to reduce its content and improve the selectivity of the reaction. Extracting the water during the synthesis has the following advantages:

[0013] - Reducing the water content in the medium, the presence of which degrades the selectivity of the conversion;

[0014] - Continuously extract the water produced by the reaction, which is a reaction of dehydration and thus reduce its concentration throughout the synthesis of 5-HMF;

[0015] - Manage in a single step the extraction of any water present with the charge or the synthesis solvent.

[0016] The clever management of the recycling of aqueous and organic streams within the process also makes it possible to obtain a production process of an aqueous solution of 5-HMF that is economically optimized. LIST OF FIGURES

[0017] [Fig.1]

[0018] Fig. 1 represents the process according to a first embodiment.

[0019] [Fig.2]

[0020] Figure [Fig.2] represents the process according to a second embodiment in which step b) comprises 3 particular steps.

[0021] [Fig.3]

[0022] Figure 3 represents the process according to a third embodiment in which step b) comprises 5 particular steps. DETAILED DESCRIPTION OF THE INVENTION

[0023] According to the present invention, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, this clarification is provided by the present invention.

[0024] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0025] In the following description, particular embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation of combinations where this is technically feasible.

[0026] Charge

[0027] The charge implemented in the process according to the invention comprises a hexose.

[0028] By a charge comprising a hexose, it is understood that the hexose may be in monomeric form (monosaccharide) or be a unit belonging to a disaccharide, oligosaccharide, or polysaccharide. A saccharide is a compound also called a sugar.

[0029] Preferably the hexose is fructose or a fructosidic unit.

[0030] The charge used can be in solid form, or in the form of an aqueous solution.

[0031] In one embodiment, the filler comprises free fructose, alone or in a mixture with any saccharide species, or comprises any oligosaccharide or polysaccharide filler containing one or more fructosidic units capable of releasing fructose by one or more hydrolysis steps, possibly in mixture with other saccharidic species. Preferably, the feedstock treated in the process is crystalline fructose, a syrup containing fructose and glucose, or crystalline sucrose or a sucrose syrup.

[0032] Advantageously, the load comprises fructose in monomeric, oligomeric or polymeric form.

[0033] By load containing free fructose taken in mixture with any saccharidic species, we mean for example High-Fructose-Com-Syrup type syrups containing fructose and glucose in different proportions (glucose / fructose in mass or molar ratios 58 / 42, 45 / 55, 10 / 90 for example).

[0034] Syrup is understood to mean a solution of sugars in water preferably having a concentration of at least 30% by weight, preferably at least 50% by weight, preferably at least 70% by weight.

[0035] The load may include a saccharide comprising one or more fructosidic units and one or more non-fructosidic units, fructose being able to be released by one or more hydrolysis steps, for example oligosaccharides and polysaccharides in which at least one monosaccharide unit is fructose, for example loads such as sucrose, kestose, fructans, oligofructans, rinulin.

[0036] Advantageously, the saccharidic fillers are capable of releasing monomeric fructose by glycoside hydrolysis, said fructose produced being able to be transformed into 5-HMF.

[0037] Preferably, the oligosaccharide has the molecular formula: (C6mH10m+2O5m+i)(C5nH8n+2O4n+i) where m and n are integers whose sum is between 2 and 6. The monosaccharide units composing said oligosaccharide may or may not be identical, and preferably at least one unit of formula (C6mH10m+2O5m+i) is fructose. By extension, preferably the polysaccharide has the molecular formula (C6mH10m+2O5m+i)(C5nH8n+2O4n+i) where m and n are integers whose sum is greater than or equal to 7.

[0038] In one embodiment, when the feed is in the form of a syrup, the water present in the feed can be extracted, at least partially, after mixing it with the synthesis solvent. The synthesis solvent allows the sugar to remain in a dilute medium and replaces dilution with water by dilution with the synthesis solvent.

[0039] Water extraction can be carried out by different methods such as: evaporation, adsorption (for example in a molecular sieve), membrane separation or osmosis.

[0040] Advantageously, this step can be carried out by distillation and therefore requires that the synthesis solvent be less volatile than water.

[0041] Advantageously the extracted water represents at least 50% by weight of the water present in the charge, preferably at least 80% by weight, even more preferably at least 90% by weight.

[0042] Advantageously, the extracted water comprises less than 10% by weight of the synthesis solvent, preferably less than 5% by weight of the synthesis solvent and even more preferably less than 1% by weight of the synthesis solvent.

[0043] In one embodiment, the extracted water represents between 90 and 99% by weight relative to the weight of water in the feed.

[0044] In one embodiment, the water extracted from the feed is recycled and sent independently to one or more process steps requiring the supply of an aqueous flow, or sent to an overall aqueous flow supplying said steps.

[0045] Step a) of dehydration of the 5-HMF load and extraction of water

[0046] Dehydration of the 5-HMF load

[0047] The process according to the invention includes a step a) of bringing a charge comprising a hexose into contact with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature between 30 and 200°C, preferably between 50 and 180°C, preferably between 70 and 150°C and most preferably between 90 and 130°C, and at a pressure between 0.001 MPa and 10 MPa, preferably between 0.001 MPa and 5 MPa, preferably between 0.01 MPa and 1 MPa, to form a reaction medium.

[0048] The term acid dehydration catalyst means any Brpnsted acid catalyst selected from among organic or inorganic, homogeneous or heterogeneous Brpnsted acids, capable of inducing the dehydration of the feed comprising a hexose in 5-HMF.

[0049] In one embodiment, the dehydration catalyst is in homogeneous phase in the reaction medium.

[0050] Preferably, the acid dehydration catalyst is a Brpnsted acid having a pKa in the synthesis solvent between 0 and 5.0, preferably between 0.5 and 4.0 and preferably between 1.0 and 3.0. Said pKa values ​​are as defined in the article by FG ​​Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0051] Preferably, the acid dehydration catalyst is selected from HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiW12O40, H3PW12O40, (NH4)6(Wi2O40).xH2O, H4SiMo12O40, H3PMo12O40, (NH4)6Mo7O24.xH2O, H2MoO4, HReO4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HC1O4, HBF4, HsbF5, HPF6, H2FO3P, C1SO3H, FSO3H, HN(SO2F)2, HIO3, BF3, Al(OTf)3, FeCl3, ZnCl2, SnCl2, CrCl3, CeCl3, ErCl3, formic acid, acetic acid, trifluoroacetic acid, lactic acid, levulinic acid, methanesulfinic acid, methanesulfonic acid, Trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, para-toluenesulfonic acid, 4-biphenylsulfonic acid, diphenyl phosphate, and 1,1'-Binaphthyl-2,2'-Diyl hydrogen phosphate. Preferably, the acid dehydration catalyst is selected from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, and trifluoromethanesulfonic acid, alone or in mixtures.

[0052] Depending on the pressure and temperature conditions, the reaction medium is above or below the bubble point of the mixture. The bubble point refers to the pressure and temperature conditions under which the first gas bubbles appear for a liquid.

[0053] Preferably, the acid dehydration catalyst is introduced in a molar ratio of the catalyst to the feed comprising a hexose, expressed as a molar percentage (%mol), of between 0.01 and 10 %mol, preferably between 0.05 and 8 %mol, preferably between 0.1 and 6 %mol, preferably between 0.2 and 5 %mol, most preferably between 0.3 and 4 %mol and most preferably between 0.5 and 3 %mol.

[0054] 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. The preferred solvent for synthesis is dimethyl sulfoxide (DMSO).

[0055] Dehydration can be carried out in various embodiments. For example, it can advantageously be implemented batchwise (called "batch" in English terminology) or continuously. The addition of the feedstock can be gradual (called "fed-batch" in English terminology) in the case of batch implementation or staged in different CSTRs (Continuously Stirred Tank Reactors) in series in a continuous implementation.

[0056] Extraction of water from the reaction medium

[0057] Step a) of the process according to the invention includes a concomitant extraction of water from the reaction medium, to obtain a synthesis effluent comprising 5-HMF and synthesis solvent.

[0058] Advantageously, the reaction medium is above the bubble point of the mixture. By bubble point, we mean the pressure and temperature conditions in at which the first gas bubbles appear for a liquid. When the reaction medium is above the bubble point of the mixture, the vapor phase can be withdrawn from the reactor, rectified and condensed to form water condensates which contain less than 10% by weight of the synthesis solvent, preferably less than 5% by weight of the synthesis solvent and even more preferably less than 1% by weight of the synthesis solvent.

[0059] Said water may originate from dehydration, for example, water is formed during the dehydration reaction of sugar to 5-HMF (3 moles of water generated per mole of 5-HMF produced). This water may also have been introduced with the feed, in the case where, for practical reasons, a feed in the form of syrup is used.

[0060] Advantageously at least 50% by weight of the water present in the reaction medium is extracted, preferably at least 80% by weight, even more preferably at least 90% by weight.

[0061] Advantageously the water extracted from the reaction medium represents at least 50% by weight of the water produced during dehydration, preferably at least 80% by weight, even more preferably at least 90% by weight.

[0062] Water extraction can be carried out by different methods such as, for example: evaporation, adsorption (for example in a molecular sieve), membrane separation or osmosis.

[0063] Advantageously, this step can be carried out by distillation, which requires that the synthesis solvent be less volatile than water. Distillation can then be performed using a distillation column whose separation stages can be provided by perforated trays, bulk packing, or structured packing. Generally, this type of equipment has a reboiler to provide heat at the bottom of the column, a condenser to at least partially condense the overhead vapors, and a reflux system.

[0064] In one embodiment, the water extracted from the reaction medium is recycled and sent independently to one or more process steps requiring the supply of an aqueous flow, or sent to an overall aqueous flow supplying said steps.

[0065] Advantageously, the synthesis effluent comprises synthesis solvent which represents 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.

[0066] Advantageously, the synthesis effluent comprises 5-HMF which represents more than 1% by weight of the synthesis effluent, 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.

[0067] Advantageously the water extraction is carried out under conditions which allow at least 90% of the synthesis solvent involved in the dehydration and extraction step to be recovered in the synthesis effluent, preferably at least 95% and even more preferably at least 99%.

[0068] In one embodiment, the synthesis effluent may further contain impurities, in particular humins. "Humins" refers to all undesirable polymeric compounds formed during the synthesis of 5-HMF. Advantageously, humins represent less than 30% by weight of the feedstock, preferably less than 20% by weight.

[0069] In one embodiment, the process according to the invention further includes a step of neutralizing the synthesis effluent, preferably by contacting said synthesis effluent with a basic compound, which follows step a).

[0070] Advantageously the basic compound is chosen from NaOH, KOH, NH4OH, Na2CO3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, Ba(OH)2.

[0071] The synthesis effluent contains the acid dehydration catalyst. The neutralization step advantageously reduces the reactivity of the medium and thus prevents the degradation mechanisms of 5-HMF, or reduces corrosion of the equipment materials downstream of the dehydration step. Since the dehydration reaction may produce some organic acids, the quantity of neutralizing agent can advantageously neutralize all the acids present in the synthesis effluents.

[0072] The neutralization step is advantageously carried out at a minimum stoichiometric ratio to the amount of catalyst used. Since the dehydration reaction may produce some organic acids, the neutralization is generally carried out at a slightly higher stoichiometric ratio than the amount of catalyst used, preferably between 1 and 2 times the stoichiometric ratio, preferably between 1 and 1.5 times the stoichiometric ratio.

[0073] The optional neutralization step can be performed:

[0074] - online on the synthesis effluents when transferred to step b) of substitution of the synthetic solvent by an aqueous solution;

[0075] - during step b) of substitution of the synthesis solvent by an aqueous solution;

[0076] - in the case of synthesis in batch or fed-batch mode in the synthesis tank at the end step, pressure and temperature of the reaction medium.

[0077] Step b) of substitution of the synthesis solvent

[0078] In one embodiment, the process according to the invention further comprises a step b) of substituting the synthesis solvent present in the synthesis effluent with an aqueous solution and obtaining an aqueous solution of 5-HMF.

[0079] Advantageously the aqueous solution comprises between 5 and 60% by weight of water.

[0080] This step makes it possible to use in the process a high-performance organic synthesis solvent in terms of the selectivity and productivity of the reaction and to produce 5-HMF for applications for which an aqueous solution is sufficient, for example in the case of resins for bonding as a substitute for phenol-formaldehyde resins.

[0081] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution comprises the following steps:

[0082] i) bringing the synthesis effluent into contact with a liquid stream comprising at least 80% by weight of water, preferably at least 90% by weight of water, even more preferably at least 95% by weight of water, and obtaining an aqueous mixture;

[0083] ii) 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 comprising synthesis solvent, and an intermediate organic effluent comprising 5-HMF and extraction solvent;

[0084] iii) separation of the extraction solvent from the intermediate organic effluent and obtaining an aqueous solution of 5-HMF.

[0085] Step i) of contacting the synthesis effluent with a liquid stream

[0086] In one embodiment, step b) of substitution of the synthesis solvent by an aqueous solution includes a step i) of bringing the synthesis effluent into contact with a liquid stream comprising at least 80% by weight of water, preferably at least 90% by weight of water, even more preferably at least 95% by weight of water, and obtaining an aqueous mixture;

[0087] Advantageously, 5-HMF represents more than 1% by weight of the synthetic effluent brought into contact in step i), 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.

[0088] Advantageously, the synthesis solvent represents between 30 and 95% by weight of the synthesis effluent brought into contact in step i), preferably between 40 and 90% by weight, preferably between 50 and 90% by weight, preferably between 55 and 85% by weight.

[0089] Advantageously, step i) is carried out at a temperature between 0 and 80°C, preferably between 10°C and 40°C and generally at room temperature, i.e. between 15°C and 35°C.

[0090] Advantageously, the aqueous mixture obtained at the end of step i) contains between 10% and 90% water by weight, preferably between 20% and 80% water by weight, preferably between 40% and 75% water by weight.

[0091] In several embodiments, the liquid stream comprising at least 80% by weight of water may originate from one or more process streams such as: the aqueous counter-extract from the backwashing step, the condensate produced during water extraction during the synthesis, the water produced at the regeneration stage of the synthesis solvent, or any other liquid stream comprising at least 80% water by weight, preferably at least 90% water by weight, even more preferably at least 95% water by weight.

[0092] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further includes a liquid-solid separation step of the aqueous mixture obtained as a result of step i) prior to step ii) of liquid / liquid extraction.

[0093] Some of the humins initially present in the synthesis effluent may precipitate. The aqueous mixture obtained in step i) can 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 removed from the process. Such a liquid-solid separation step thus makes it possible to remove the precipitated humins. This liquid-solid separation step is preferably carried out at a temperature between 0 and 60°C, preferably between 10°C and 40°C, and generally at ambient temperature (i.e., between 15°C and 35°C).The liquid-solid separation step can be carried out by any method known to those skilled in the art, for example with a filter press, belt filter, drum filter, candle filter, clarifier, decanter, centrifuge, or any combination of these techniques. Advantageously, the liquid-solid separation step is filtration, preferably carried out by a filter press.

[0094] Step ii) of liquid / liquid extraction

[0095] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution includes a step ii) 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 comprising synthesis solvent, and an intermediate organic effluent comprising 5-HMF and extraction solvent;

[0096] 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 an extraction solvent. The extraction can be carried out, for example, in a battery of mixer-settlers, in a column packed with bulk or structured material, in a pulsed column, or even in a stirred column.

[0097] Step ii) of liquid / liquid extraction is advantageously carried out at a temperature between 0 and 80°C, preferably between 5°C and 60°C, preferably between 10°C and 40°C and generally at room temperature (i.e. between 15°C and 35°C).

[0098] The weight proportion (weight / weight) of extraction solvent relative to the aqueous mixture is preferably from 0.2 to 5, preferably between 1 and 3, preferably between 1.5 and 2.5.

[0099] By way of non-limiting choice, the extraction solvent is preferably selected from among chlorinated organic solvents, ethers, esters, ketones, aldehydes, and aromatic compounds. Preferably, the extraction solvent is a chlorinated solvent having between 1 and 10 carbon atoms, hereinafter referred to as "C1-C10", an ether having between 2 and 10 carbon atoms (C2-C10), an ester having between 4 and 10 carbon atoms (C4-C10), a ketone having between 3 and 10 carbon atoms (C3-C10), an aldehyde having between 1 and 10 carbon atoms (C1-C10), or a C4-C10 aromatic compound. Preferably, the extraction solvent is chosen from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole, and toluene, alone or in mixtures. Most preferably, the extraction solvent is methyl isobutyl ketone (MIBC or MIBK).

[0100] Advantageously, the extraction solvent is chosen so as to:

[0101] - to have a very strong difference in volatility with 5-HMF so as to facilitate its separation at step iii) of the extraction solvent from the intermediate organic effluent and limit the degradation of 5-HMF, i.e. in such a way as to present at step iii) a vaporization rate which does not degrade the 5-HMF and to minimize the amount of residual extraction solvent,

[0102] - advantageously forming in step iii) a heterogeneous azeotrope with water, preferably rich in extraction solvent, i.e., more than 50% by weight of extraction solvent, preferably more than 60% by weight of extraction solvent, and preferably more than 70% by weight of extraction solvent. Advantageously, said azeotrope of the water / extraction solvent mixture has a boiling point significantly lower than that 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, and preferably at least 10°C lower than the boiling point of water.

[0103] The intermediate organic effluent may contain synthetic solvent. Preferably, said intermediate organic effluent contains 5-HMF and synthetic solvent in a weight ratio, 5-HMF / (synthetic solvent+5-HMF), of between 50 / 50 and 99 / 01, preferably between 50 / 50 and 95 / 05, preferably between 55 / 45 and 90 / 10, more preferably between 60 / 40 and 85 / 15 and preferably between 65 / 35 and 80 / 20.

[0104] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further includes a step of backwashing the effluent organic intermediate obtained in step ii), in the presence of an aqueous solvent, prior to step iii) of separation, to obtain at least one organic intermediate effluent depleted in synthetic solvent comprising 5-HMF, extraction solvent and having a synthetic solvent content less than or equal to 20% by weight relative to the weight of 5-HMF, and an aqueous counter-extract comprising synthetic solvent.

[0105] In one embodiment, the aqueous counter-extract is advantageously sent in part or in whole to the contacting step i).

[0106] When the backwashing step is implemented, the extraction solvent introduced in step ii) is chosen from among the organic solvents immiscible with water, so as to form two liquid phases in the backwashing step. This property is highly dependent on the relative proportions of the feed flow rates, aqueous back-extraction solvent, and extraction solvent used in the process.

[0107] The introduction of the aqueous solvent is carried out in such a way that the quantity of aqueous solvent is as low as possible in order to reduce costs, but sufficient to guarantee a low weight content of synthetic solvent in the intermediate organic effluent and preferably less than or equal to 20.00% weight relative to the weight of 5-HMF, preferably less than or equal to 15.00% weight relative to the weight of 5-HMF, preferably between 0.01 and 15.00% weight relative to the weight of 5-HMF, most preferably between 0.01 and 10.00% weight relative to the weight of 5-HMF.

[0108] 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 include a synthetic solvent and / or an extraction solvent. The backwash efficiency is higher when the amount of synthetic solvent present in the aqueous backwash solvent is lower. Preferably, the aqueous solvent may include a synthetic solvent of at most 1.0% by weight, and preferably at most 0.1% by weight.

[0109] According to several embodiments, the aqueous backwash solvent is derived from one or more of the following process streams: the condensates produced in the dehydration step b), the water extracted from the feed in the step a), the water produced in the regeneration step of the synthesis solvent or any other aqueous stream containing an amount of synthesis solvent preferably less than or equal to 1 wt% and preferably less than or equal to 0.1 wt%.

[0110] The backwashing step is advantageously a liquid-liquid extraction of an organic stream, in particular of the intermediate organic extract obtained in step ii), against the current of the aqueous backwashing solvent. This step can be carried out, for example, in a battery of mixer-settlers, in a column filled of bulk or structured packing, in a pulsed column, or even in an agitated column.

[0111] The backwashing step is preferably carried out at a temperature between 0 and 80°C, preferably between 5°C and 60°C, preferably between 10°C and 40°C and generally at room temperature (i.e. between 15 and 35°C).

[0112] The weight ratio (weight / weight) of aqueous backwash solvent relative to the intermediate organic extract is preferably from 0.04 to 5, preferably between 0.07 and 3, preferably between 0.1 and 1.

[0113] The backwashing step allows the production of an aqueous counter-extract comprising preferably at least 60% by weight of water, preferably at least 80% by weight of water, and an intermediate organic effluent depleted in synthetic solvent. The resulting intermediate organic effluent depleted in synthetic solvent has a synthetic solvent content preferably less than or equal to 20.0% by weight relative to the weight of 5-HMF, preferably less than or equal to 15.0% by weight relative to the weight of 5-HMF, preferably less than or equal to 5.0% by weight relative to the weight of 5-HMF, preferably less than or equal to 4.0% by weight relative to the weight of 5-HMF, preferably less than or equal to 3.0% by weight relative to the weight of 5-HMF.

[0114] In one embodiment, the aqueous counter-extract can be recycled in a similar way to the water extracted in step a).

[0115] Step iii) of separation of the extraction solvent

[0116] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution includes a step iii) of separating the extraction solvent from the intermediate organic effluent and obtaining an aqueous solution of 5-HMF.

[0117] If a backwash has been carried out previously, the intermediate organic effluent is the intermediate organic effluent depleted in synthetic solvent.

[0118] In one embodiment, the separated extraction solvent can advantageously be recycled in step ii) of extraction.

[0119] In one embodiment, separation step iii) is carried out by hydrodistillation.

[0120] An aqueous stream feeds the hydrodistillation step. The aqueous stream preferably comprises more than 95% by weight of water, preferably more than 98% by weight of water.

[0121] In a particular embodiment of the invention, the aqueous flow is pure water, possibly external to the process, which makes it possible to further reduce the residual synthetic solvent content in the aqueous solution of 5-HMF produced in step b).

[0122] In another particular embodiment of the invention, an isolated aqueous flow within the process can be used to feed the hydrodistillation step, allowing thus to limit the operating costs of the process and its environmental impact. Advantageously, the aqueous stream used can come from the condensates produced during the extraction of water during the synthesis, from the regeneration step of the synthesis solvent, or be any other aqueous stream containing less than 5% by weight of synthesis solvent, preferably less than 1% by weight of synthesis solvent, and preferably less than 0.1% by weight of synthesis solvent.

[0123] Advantageously, the extraction solvent used in the process forms a heterogeneous azeotrope with the aqueous stream, said azeotrope preferably being rich in extraction solvent, preferably comprising more than 50% by weight of extraction solvent, preferably more than 60% by weight of extraction solvent, and preferably more than 70% by weight of extraction solvent. Advantageously, said azeotrope has a boiling point significantly lower than that 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, and preferably at least 10°C lower than the boiling point of the aqueous stream.

[0124] The hydrodistillation step can be carried out at atmospheric pressure or under vacuum, and in particular at a pressure between 0.001 MPa and 0.1 MPa, preferably under vacuum at a pressure between 0.005 MPa and 0.08 MPa. Advantageously, the hydrodistillation step is carried out under vacuum, in particular at a pressure between 0.001 MPa and 0.1 MPa, preferably between 0.005 MPa and 0.08 MPa, so as to facilitate the separation of the extraction solvent without degrading the 5-HMF.

[0125] Advantageously, the hydrodistillation step is carried out in a distillation column, preferably at a column bottom temperature of less than or equal to 140°C, preferably less than or equal to 130°C, preferably less than or equal to 120°C, preferably less than or equal to 110°C and preferably less than or equal to 100°C, so as to facilitate the removal of the extraction solvent without degradation of the 5-HMF.

[0126] In a particular embodiment, the intermediate organic effluent and the aqueous stream are mixed before introduction into a distillation column and the mixture is introduced at an intermediate point of the distillation column.

[0127] 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. The mixing of the intermediate organic effluent and the aqueous stream is then carried out within the distillation column.

[0128] The condensation of vapors at the top of the distillation column generates two liquid phases: a water-rich phase which can advantageously be returned to the column as reflux, and an extraction solvent-rich phase which can advantageously be recycled in step ii) of extraction.

[0129] According to the invention, the aqueous solution of 5-HMF obtained at the end of step b) comprises an amount of 5-HMF of at least 30% by weight, preferably at least 40% by weight, and preferably less than 90% by weight, preferably less than 85% by weight and preferably less than 80% by weight, the percentages being given in weight of 5-HMF relative to the weight of aqueous solution of 5-HMF obtained at the end of step b).

[0130] The process according to the invention thus makes it possible to produce an aqueous solution of 5-HMF having very advantageously a weight content of synthetic solvent 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 and preferably less than or equal to 3% by weight relative to the weight of 5-HMF.

[0131] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further includes a step of concentrating the 5-HMF solution in the organic phase by separating a portion of the extraction solvent prior to step iii) of separating the extraction solvent from the intermediate organic effluent. This concentration step makes it possible to produce a concentrated intermediate organic effluent comprising 5-HMF and extraction solvent, and a stream comprising predominantly extraction solvent.

[0132] Preferably, the stream consisting mainly of extraction solvent is recycled, in whole or in part, to extraction step ii).

[0133] Preferably, the separation of part of the extraction solvent at this step of concentration of the 5-HMF solution in organic phase, prior to step iii), is carried out by vaporization, for example in a distillation column at atmospheric pressure or under vacuum, in an evaporator, or any method known to those skilled in the art.

[0134] According to this preferred method, the vaporization of the extraction solvent is advantageously carried out at atmospheric pressure or under vacuum, preferably at a pressure between 0.01 MPa and 0.1 MPa, preferably under vacuum at a pressure between 0.01 MPa and 0.09 MPa, so as to limit the temperature of the liquid and therefore the degradation of 5-HMF. Preferably, the temperature of the liquid is maintained at or below 130°C, preferably at or below 100°C, preferably at or below 70°C. The level of vacuum to be applied to reach these temperatures is, of course, dependent on the solvent. synthesis and more particularly of the extraction solvent used and the vaporization rate of the synthesis solvent.

[0135] The concentration step is implemented with a mass vaporization rate (or evaporation rate), corresponding to the mass of extraction solvent vaporized relative to the mass of the intermediate organic effluent 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 vaporization rate is defined according to the extraction solvent so as not to degrade the 5-HMF, but also in order to minimize the amount of residual extraction solvent to be separated in step iii) while ensuring the absence of liquid phase separation (i.e. while ensuring that the liquid phase remains monophasic) when the concentrated intermediate organic effluent is brought into contact with an aqueous stream in step iii) when this is carried out by hydrodistillation.

[0136] Advantageously, the concentrated intermediate organic effluent obtained at the end of the concentration step very advantageously has a 5-HMF content of at least 40% by weight relative to the weight of the concentrated intermediate organic effluent, preferably at least 50% by weight, preferably at least 60% by weight, and preferably up to 95% by weight, preferably up to 90% by weight, and preferably up to 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 extraction solvent content of at least 5% by weight relative to the weight of the concentrated intermediate organic effluent, preferably at least 10% by weight, and preferably up to 60% by weight, preferably up to 50% by weight, preferably up to 40% by weight, relative to the weight of the concentrated intermediate organic effluent.

[0137] Step c) of regeneration of the synthesis solvent

[0138] In one embodiment, the process according to the invention further comprises a step c) of regeneration of the synthetic solvent substituted in step b).

[0139] "Regeneration" means obtaining a stream comprising predominantly the desired solvent.

[0140] Advantageously the regenerated synthesis solvent is recycled to step a).

[0141] The stream comprising the substituted synthesis solvent may contain a fraction of water that can be separated and recycled to an 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, which benefits from the water extraction in step a) to maintain the selectivity of sugar conversion to 5-HMF.

[0142] During this step c), the synthesis solvent can be purified and purged, at least partially, of the co-products of the synthesis reaction. These co-products may include, in particular:

[0143] - unconverted sugars from the charge;

[0144] - saccharide oligomers produced during synthesis;

[0145] - of the 5-HMF;

[0146] - neutralized acids at the neutralization step;

[0147] - humines, for example unfiltered at the precipitation and filtration stage.

[0148] In the embodiment in which step b) of solvent substitution of synthesis by aqueous solution includes steps i), ii) and iii), it is the aqueous effluent comprising the synthesis solvent obtained in step ii) which is used in step c) of regeneration of the synthesis solvent.

[0149] In this embodiment, the aqueous effluent may also include a small amount of extraction solvent which can itself be regenerated, optionally purged of co-products, and advantageously recycled to step ii).

[0150] 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 recovers the majority of the extraction solvent, at least 70%, preferably at least 80%, and even more preferably, 90%. A second stage further depletes the stream of water, so that it contains less than 10% water by weight, preferably less than 5% water by weight, and even more preferably less than 1% water by weight. The final stage completes the evaporation of the synthesis solvent from the heavy co-products of the process. The loss of synthesis solvent in the heavy product purge is then less than 10% of the solvent used in synthesis, preferably less than 5% of the solvent used in synthesis, and even more preferably less than 1% of the solvent used in synthesis.

[0151] Preferably, the separation cascade is carried out with a maximum temperature imposed by the thermal stability of the products, and the separation is advanced by successive pressure reductions. This temperature is generally between 50 and 200 °C, preferably between 80 and 150 °C, and even more preferably between 100 and 130 °C.

[0152] Evaporations can advantageously be carried out in conventional shell and tube type exchangers followed by gas / liquid separation tanks or in so-called single or multiple effect evaporators ensuring gas / liquid separation and the supply of heat necessary for evaporation.

[0153] Preferably, the final evaporation stages are carried out in equipment with a short residence time, such as a scraped film evaporator, in order to limit the degradation of humins and the extraction of these humins whose viscosity can exceed 1000 cP at 100 °C. DESCRIPTION OF THE FIGURES

[0154] Specific, non-limiting examples of embodiments of the invention are described below with reference to the accompanying figures.

[0155] [Fig. 1]: A feed 1 comprising a hexose is sent to a step a) in which it is contacted with an acid dehydration catalyst and an organic synthesis solvent 2. The synthesis is initiated and carried out at a temperature between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and most preferably between 80°C and 120°C, and at a pressure between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, and water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 comprising 5-HMF and the synthesis solvent is obtained. The synthesis effluent 3 is sent to a step b) in which the synthesis solvent is replaced by an aqueous solution 21 which may come from the water stream extracted from the reaction medium 4, and an aqueous solution of 5-HMF 16 is obtained.The substituted synthesis solvent 11 is sent to a step c) of synthesis solvent recycling 11, which is optionally purged of synthesis co-products 20, and the synthesis solvent is recycled to step a). Losses of synthesis solvent are compensated by a replenishment of synthesis solvent 22.

[0156] [Fig.2]: A charge 1 comprising a hexose is sent to a step a) in which is brought into contact with an acid dehydration catalyst and an organic synthesis solvent 2. The synthesis begins and is carried out at a temperature between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and most preferably between 80°C and 120°C, and at a pressure between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa. Water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 is obtained, comprising 5-5-HMF and the synthesis solvent. The synthesis effluent 3 is sent to step b) for replacement of the synthesis solvent.This step begins with a step i) in which the synthesis effluent 3 is brought into contact with a liquid stream 5 comprising at least 80% by weight of water, preferably at least 90% by weight of water, even more preferably at least 95% by weight of water, from an overall aqueous stream 21 which can be fed by the water stream extracted from the reaction medium 4, and an aqueous mixture 6 is obtained. The aqueous mixture 6 is sent to a liquid / liquid extraction step ii) in which an aqueous stream 11 comprising synthesis solvent is extracted by an extraction solvent 9, and an intermediate organic effluent 10 comprising 5-HMF and solvent is obtained. extraction. The intermediate organic effluent 10 is sent to a step iii) in which the extraction solvent is separated from the organic effluent 10 using an aqueous solution 15 from the overall aqueous stream 21, yielding an extraction solvent stream 17 that can be recycled to step ii) (stream 9), and an aqueous solution of 5-HMF 16. The aqueous stream 11 is sent to a synthesis solvent regeneration step c) in which the synthesis solvent is extracted from stream 11 and is optionally purged of synthesis co-products 20, and the synthesis solvent is recycled to step a). Losses of synthesis and extraction solvents are compensated by replenishments, respectively a synthesis solvent replenishment 22 and an extraction solvent replenishment 23.

[0157] [Fig. 3]: A feed 1 comprising a hexose is sent to step a) in which it is contacted with an acid dehydration catalyst and an organic synthesis solvent 2. The synthesis is initiated and carried out at a temperature between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and most preferably between 80°C and 120°C, and at a pressure between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa. Water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 comprising 5-HMF and the synthesis solvent is obtained. The synthesis effluent 3 is sent to step b) for substitution of the synthesis solvent.This step begins with a step i) in which the synthesis effluent 3 is brought into contact with a liquid stream 5 comprising at least 80% by weight of water, preferably at least 90% by weight of water, even more preferably at least 95% by weight of water, from an overall aqueous stream 21 which can be fed by the water stream extracted from the reaction medium 4, and an aqueous mixture 6 is obtained. The aqueous mixture 6 is sent to a liquid-solid separation step iv) in which the impurities and in particular the humins are separated into a stream 8. The purified stream 7 is sent to a liquid / liquid extraction step ii) in which an aqueous stream 11 comprising synthesis solvent is extracted by an extraction solvent 9, and an intermediate organic effluent 10 comprising 5-HMF and extraction solvent is obtained.The intermediate organic effluent 10 is sent to a backwashing step v) in the presence of an aqueous solvent 12 from the overall aqueous stream 21, and a synthetic solvent-depleted organic effluent 13 is obtained, comprising 5-HMF, extraction solvent and having a synthetic solvent content less than or equal to 20% by weight relative to the weight of 5-HMF, and an aqueous counter-extract 14 comprising synthetic solvent which can be sent to step i). The synthetic solvent-depleted organic effluent 13 is sent to a step iii) in which the extraction solvent is separated from the organic effluent 13 using an aqueous solution 15 from an overall aqueous stream 21, and a stream 17 is obtained. of extraction solvent that can be recycled to step ii) contributing to the overall extraction solvent stream 9, and an aqueous solution of 5-HMF 16. The aqueous stream 11 is sent to a synthesis solvent regeneration step c) in which said synthesis solvent is extracted from stream 11 and is optionally purged of synthesis co-products 20, and the synthesis solvent is recycled to step a), and optionally water 19 is extracted from stream 11 which can be sent to the overall aqueous stream 21, and optionally extraction solvent 18 is extracted from stream 11 which can be sent to the overall extraction solvent stream 9. Losses of synthesis and extraction solvents are compensated by top-ups, respectively a synthesis solvent top-up 22 and an extraction solvent top-up 23. EXAMPLES

[0158] Example 1 - Synthesis of 5-HMF in continuous stirred-tank reactor (CSTR) mode from crystalline fructose according to the prior art

[0159] Fructose is introduced in the form of a crystal having a purity greater than 99.5% by weight of sugar into DMSO, so that the fructose concentration is 35% by weight. The mixture is heated to a temperature of 120°C, and an acid catalyst, methanesulfonic acid, is added with a catalyst / sugar molar ratio of 1 mol%.

[0160] The mixture is introduced into a reactor to perform the conversion in CSTR mode. The pressure is maintained at ambient temperature, i.e., 0.1013 MPa. Under these pressure and temperature conditions, the reaction medium is above the bubble point of the mixture, and therefore there is no vapor phase to extract. The reaction medium is continuously withdrawn at a mass flow rate equivalent to that of the mixture introduced into the reactor, so as to maintain a constant quantity and volume in the reactor. The volume is such that it ensures an average residence time of the feedstock of 5 h.

[0161] The synthesis effluent from the dehydration step contains 65% by weight of DMSO, 17% by weight of 5-HMF and 9% by weight of water, representing a molar yield of 5-HMF relative to fructose of 70%. Polymeric compounds (humins) soluble in the reaction medium were formed and, together with unconverted fructose, represent 9% by weight of the solution.

[0162] Example 2 - Continuous-mode synthesis of 5-HMF using crystalline fructose CSTR according to the invention

[0163] Fructose is introduced in the form of a crystal having a purity greater than 99.5% by weight of sugar into DMSO, so that the fructose concentration is 35% by weight. The mixture is heated to a temperature of 120°C, and an acid catalyst, methanesulfonic acid, is added with a catalyst / sugar molar ratio of 1 mol%.

[0164] The mixture is introduced into a reactor to perform the conversion 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 available for extraction. The vapor phase is rectified in a packed column with eight theoretical stages, the reflux being adjusted to obtain a head product with a water / DMSO composition of 99.5% / 0.5% by weight, respectively.

[0165] The liquid reaction medium is continuously withdrawn to produce the reaction effluents. The withdrawal rate is adjusted so that the liquid volume in the reactor ensures an average residence time of the feedstock of 5 h.

[0166] The synthesis effluent from the dehydration and extraction step contains 75% by weight of DMSO, 18% by weight of 5-HMF and 1% by weight of water, representing a molar yield of 5-HMF relative to fructose of 80%. Polymeric compounds (humins) soluble in the reaction medium were formed and, together with unconverted fructose, represent 6% by weight of the solution.

[0167] Thus, by carrying out a synthesis with the same temperature, quantity of catalyst and synthesis solvent and residence time, the invention makes it possible to treat a crystalline fructose and to improve its yield very significantly (80% molar according to the invention and 70% molar according to the prior art).

[0168] Example 3 - Production of an aqueous solution of 5-HMF by conversion of a syrup containing 70% wt. fructose and 30% wt. water according to the invention:

[0169] The exemplified process conforms to that shown in [Fig.3].

[0170] The process treats a syrup flow rate of 1 t / h, i.e., 700 kg / h of fructose. The syrup is mixed with streams containing recycled DSMO synthetic solvent from the synthetic solvent regeneration step and with the addition of 25.0 kg / h of DMSO required to compensate for process losses. The resulting mixture contains 24.3% by weight of fructose, 0.5% by weight of MIBK extraction solvent (from the recycled synthetic solvent exiting the regeneration step), 31.7% by weight of water, and 43.3% by weight of DMSO.

[0171] The mixture thus obtained is injected into a packed column developing 8 theoretical stages, the bottom pressure of which is maintained at 0.014 MPa, the reboiling and reflux being adjusted so as to obtain a bottom product whose temperature is 120 °C and whose DMSO composition of the water discharged at the top is 0.5 wt%.

[0172] Methanesulfonic acid (MSA) is introduced at the bottom of the column with an MSA / fructose molar ratio of 1%. The dehydration reaction proceeds continuously with an average residence time of 5 h at the bottom of the column. By reboiling, the reaction mixture is maintained at 120°C, i.e., below its bubble point. The vapor phase containing water and DMSO is therefore rectified in the packed section. The column. Under these conditions, the reaction medium, corresponding to the liquid phase at the bottom of the column, has a water content of 1% by weight. The withdrawal is carried out in such a way as to maintain the liquid residence time at the bottom of the column. This withdrawal corresponds to the reaction effluents produced.

[0173] 1.8 t of synthetic effluent is then recovered comprising 69.7% by weight of DMSO, 1.0% by weight of water, 22.1% by weight of 5-HMF and 7.2% by weight of unconverted sugars and humins.

[0174] This synthesis effluent is mixed with the aqueous counter-extract from the backwashing step. Water collected during the regeneration steps of the synthesis solvents and extraction, or during the distillation of the fructose / DMSO mixture, is used to supplement the mixture, producing a precipitation medium with a water / DMSO mass ratio of 0.91 (calculated taking into account the water and DMSO present in all the streams feeding the step). After 1.5 hours of maturation, the mixture is filtered using a filter press. At the end of the filtration sequence, the resulting cake is pressed. This step allows for the precipitation and filtration of 29 kg / h of humins. The precipitation and filtration steps are carried out at 35°C and ambient pressure.

[0175] The filtrate, mixed with the compaction filtrate, is sent to a liquid / liquid extraction stage and represents a continuous flow rate of 3.0 t / h. This stage, carried out using a pulsed column with 9 theoretical stages, also operates at ambient temperature and pressure. The extraction solvent is MIBK. The quantity of MIBK used is such that the MIBK / feed mass ratio in the liquid / liquid extraction stage is 1.5.

[0176] Under these conditions, the aqueous effluent obtained in the liquid / liquid extraction step contains 3.5% of the HMF produced in the synthesis, representing a 3.5% production loss of HMF related to this extraction step. The aqueous effluent has a composition of 46.0% by weight of DMSO, 44.9% by weight of water, 6.1% by weight of MIBK, 0.5% by weight of HMF, and 2.5% by weight of unconverted fructose and humins. Its flow rate is 2.7 t / h.

[0177] The aqueous effluent is treated in a synthesis solvent regeneration step which consists of 3 successive evaporations at increasingly lower pressures (0.120 MPa, 0.020 MPa, 0.0025 MPa) and a constant temperature of 120°C to limit the degradation of the species present:

[0178] - The first regeneration stage is carried out at 0.12 MPa. The steam is partially condensed. The condensed liquid is returned upstream of the first evaporation stage. This arrangement allows for the production, after partial condensation, of an aqueous stream comprising 97.8% by weight water, which is sent directly to the process water tank, and for the recovery, by separation, of the MIBK present in the aqueous effluent. The MIBK stream is returned to the extraction solvent collection flask. Under these conditions, 49% of the water contained in the aqueous effluent is extracted and does not require further treatment in the water / DMSO / fructose separation column.

[0179] - In a second step, the aqueous effluent from the first step of The regeneration process is again subjected to evaporation at 120°C, this time at a pressure of 0.02 MPa, which vaporizes 92.9% of the mixture. The vapor is condensed and then returned to the water / DMSO / fructose separation column, where it represents the largest contributor to the DMSO input. Its composition is 34% water by weight and 65% DMSO by weight, with a flow rate of 1.8 t / h. The resulting effluent has a residual DMSO content of 40% by weight and only 1.2% water by weight; the remainder consists of unextracted 5-HMF, unconverted fructose, humins, and salts present in the aqueous mixture.

[0180] - In a third step, the aqueous effluent from the third step of The regeneration process is once again evaporated using scraped film heat exchanger technology to maximize the removal of the heavy DMSO fraction. The temperature is again set at 120°C, while the pressure is reduced to 0.0025 MPa to vaporize 35% by weight of the product. The vapor is condensed and recycled to the water / DMSO / fructose separation column. The resulting viscous liquid stream contains only 10% DMSO by weight, thus minimizing losses of the synthesis solvent and consequently reducing the need for additional solvent.

[0181] 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 and it contains 1.5 wt% of DMSO, representing 5% of the DMSO involved in the reaction, thus justifying the need to recover it by backwashing to limit losses of the synthesis solvent. The backwashing step is carried out in a packed column with three theoretical stages, at ambient pressure and temperature, and with a solvent / load mass ratio of 0.1. This backwashing step reduces the losses of DMSO contained in the intermediate organic effluent. After backwashing, the losses of DMSO contained in the intermediate organic effluent represent only 0.1% of the quantity of DMSO involved in the reaction. The synthetic solvent-depleted intermediate organic effluent produced at this stage comprises 2.3% by weight of water, 89.1% by weight of MIBK, 8.0% by weight of 5-HMF and 0.6% by weight of humins.

[0182] This intermediate organic effluent, depleted in synthetic solvent, is concentrated at a pressure of 0.0217 MPa and a temperature of 100°C, resulting in a mass vaporization rate of 84.2% and producing an intermediate organic effluent concentrated to 50% by weight. The vapor fraction produced at this stage is condensed. Separation of the mixture results in a liquid stream comprising 97.6% by weight of MIBK and an aqueous liquid stream comprising 97.9% by weight of water. The MIBK stream is recycled to the MIBK collection tank for recycling, the water stream is collected to the process water tank.

[0183] The intermediate organic effluent, depleted in synthetic solvent and concentrated, is sent to hydrodistillation and represents a flow rate of 753 kg / h. The step is carried out at 0.04 MPa in a distillation column equipped with a packing developing 7 theoretical stages, with a process water reflux rate of 130 kg / h.

[0184] 560 kg / h of water are injected at the bottom of the column to dilute the 5-HMF and produce An aqueous solution of 5-HMF is prepared. 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 concentration of 45% by weight of 5-HMF and 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 vapors are condensed and cooled to 52°C. Separation separates a liquid stream comprising 97.2% by weight of MIBK from an aqueous liquid stream comprising 98.7% by weight of water. The MIBK stream is recycled to the MIBK collection vessel for recycling, the water stream is used to generate column reflux, and the excess is collected in the process water vessel.

[0185] The following table illustrates the flow rates of different process flows according to example 3 in terms of total flow rate and flow rate per component of the flow:

[0186] [Tables 1] Flow Rates (K g / h) Syrup Synthetic Effluent Charge Column Extraction HMF in Organic Solution Aqueous Effluent EL L Aqueous Solution 5-HMF Flow Rate (Figure 3) 1 3 7 13 11 16 Flow Rate Initial 1000 1785 3080 4751 2693 838 DMSO 0 1244 1312 1 1238 3 h2o 300 20 1189 108 1208 428 MIBK 0 0 25 4234 164 1 5-HMF 0 395 456 379 14 377 Fructose 700 12 12 0 12 0 Humines 0 114 86 29 57 29

Claims

Demands

1. A process for producing a 5-Hydroxymethylfurfural solution comprising the following steps: a) contacting a feed comprising a hexose with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature between 30 and 200°C, and at a pressure between 0.001 MPa and 10 MPa, to form a reaction medium, and concomitantly extracting water from the reaction medium, to obtain a synthesis effluent comprising 5-HMF and the synthesis solvent; b) substituting the synthesis solvent present in the synthesis effluent with an aqueous solution and obtaining an aqueous solution of 5-Hydroxymethylfurfural comprising the following steps.i) contacting the synthesis effluent with a liquid stream comprising at least 80% by weight of water and obtaining an aqueous mixture; ii) 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 comprising synthesis solvent, and an intermediate organic effluent comprising 5-Hydroxymethylfurfural and extraction solvent; iii) separation of the extraction solvent from the intermediate organic effluent and obtaining an aqueous solution of 5-Hydroxymethylfurfural.

2. A method according to claim 1, wherein the hexose is fructose or a fructosidic unit.

3. A process according to any one of the preceding claims, wherein the acid dehydration catalyst is selected from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid alone or in mixture.

4. A process according to any one of the preceding claims, wherein the synthesis solvent is dimethyl sulfoxide.

5. A method according to any one of the preceding claims, further comprising a step of neutralizing the effluent from synthesis by contacting said synthesis effluent with a basic compound, which follows step a).

6. A process according to any one of the preceding claims, wherein the extraction solvent is methylisobutyl ketone.

7. A process according to any one of the preceding claims, wherein the separated extraction solvent is recycled in step ii) of extraction.

8. A method according to any one of the preceding claims, further comprising a liquid-solid separation step of the aqueous mixture obtained as a result of step i) prior to step ii) of liquid / liquid extraction.

9. A process according to any one of the preceding claims, further comprising a backwashing step of the intermediate organic effluent obtained in step ii), in the presence of an aqueous solvent, prior to the separation step iii), to obtain at least one intermediate organic effluent depleted in synthetic solvent comprising 5-Hydroxymethylfurfural, extraction solvent and having a synthetic solvent content less than or equal to 20% by weight relative to the weight of 5-Hydroxymethylfurfural, and an aqueous counter-extract comprising synthetic solvent.

10. A process according to any one of the preceding claims, wherein the separation step iii) is carried out by hydrodistillation.

11. A process according to any one of the preceding claims, further comprising a step c) of regenerating the synthetic solvent substituted in step b).

12. A process according to claim 11, wherein the regenerated synthesis solvent is recycled to step a).

13. A process according to any one of the preceding claims, wherein the water extracted from the reaction medium is recycled and sent independently to one or more process steps requiring the supply of an aqueous flow, or sent to an overall aqueous flow supplying said steps.

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