Method for producing 5-hmf via conversion of sugar in a non-aqueous solvent with water extraction during synthesis

Abstract

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

Description

[0001] Process for the production of 5-HMF by sugar conversion in a non-aqueous solvent with water extraction during synthesis

[0002] TECHNICAL FIELD

[0003] The present invention relates to the production of 5-HMF from a feedstock comprising a sugar, more particularly a hexose, by catalytic synthesis in an organic solvent.

[0004] PRIOR TECHNIQUE

[0005] 5-Hydroxymethylfurfural (5-HMF) is an interesting compound derived from biomass that can be used in many fields, including pharmaceuticals, agrochemistry, and specialty chemicals. The production of 5-HMF by dehydration of sugars has been known for many years and has been the subject of a large number of research projects. There are many dehydration conditions; the following methods are examples:

[0006] 5-HMF can be obtained in aqueous media, usually 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 seriously affects the yield.

[0007] 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 in a mixture with an ether or ester derivative of 5-HMF depending on the reaction medium used. The formation of these side products is due to the reaction of 5-HMF with the reaction solvent in an acidic medium.

[0008] Application WO 2007 / 104514 describes the synthesis of 5-HMF by dehydration of sugars using methanol or ethanol as 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 alcohol to give a mixture of 5-HMF and its methyl or ethyl ether form depending on the alcohol used as solvent.

[0009] 5-HMF can also be produced in a polar aprotic medium with or without an acid catalyst. Particularly noteworthy is the use of dimethyl sulfoxide (DMSO), which, with or without an acid catalyst, allows 5-HMF to be produced in very good yields, and without the undesirable reactions listed above. 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, no. 3, pp. 95-101).

[0010] 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.

[0011] However, the industrialization of 5-HMF production is pushing to reduce the dilution of sugars in DMSO to the strict minimum, which degrades the selectivity of sugar conversion. 5-HMF selectivity is defined as the ratio between the number of moles of 5-HMF produced and the number of converted moles of fructose contained in the feedstock introduced into the process. In a polar aprotic medium, the presence of water degrades the selectivity of sugar conversion, all the more significantly as the concentration of sugars in DMSO is high.

[0012] The object of the present application is to reduce the water content of the reaction medium by extraction of water during the synthesis (water resulting from the dehydration of the sugars and optionally the water from the syrup, if the feedstock is a syrup).

[0013] SUMMARY OF THE INVENTION

[0014] The present invention relates to a process for producing a 5-Hydroxymethylfurfural (5-HMF) solution comprising a step a) of bringing a feedstock comprising a hexose into contact with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature of between 30 and 200°C, preferably between 50 and 180°C, preferably between 70 and 150°C and very preferably between 90 and 130°C, and at a pressure of 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-HF and synthesis solvent.

[0015] 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 water during the synthesis has the following advantages: - Reducing the water content in the medium, the presence of which degrades the selectivity of the conversion;

[0016] - Continuously extract the water produced by the reaction which is a dehydration reaction and thus reduce its concentration throughout the synthesis of 5-HMF;

[0017] - Manage in a single step the extraction of any water present with the charge or synthesis solvent.

[0018] The clever management of the recycling of aqueous and organic streams within the process also makes it possible to obtain an economically optimized process for producing an aqueous solution of 5-HMF.

[0019] LIST OF FIGURES

[0020] Figure 1 represents the method according to a first embodiment.

[0021] Figure 2 represents the method according to a second embodiment in which step b) comprises 3 particular steps.

[0022] Figure 3 represents the method according to a third embodiment in which step b) comprises 5 particular steps.

[0023] DETAILED DESCRIPTION OF THE INVENTION

[0024] According to the present invention, the expression "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, such precision is provided by the present invention.

[0025] For the purposes of the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges may be used alone or in combination. For example, for the purposes of the present invention, a preferred pressure value range may be combined with a more preferred temperature value range.

[0026] In the remainder of the description, particular embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combinations when this is technically feasible.

[0027] Charge

[0028] The filler used in the method according to the invention comprises a hexose. By the filler which comprises a hexose is meant that the hexose can be in monomeric form (monosaccharide) or be a unit belonging to a disaccharide, oligosaccharide or polysaccharide. A saccharide is a compound also called 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 feedstock comprises free fructose, alone or in admixture with any saccharide species, or comprises any oligosaccharide or polysaccharide feedstock containing one or more fructosidic units capable of releasing fructose by one or more hydrolysis steps, optionally in admixture with other saccharide species. Preferably, the feedstock treated in the method is crystalline fructose, a syrup containing fructose and glucose, or crystalline sucrose or a sucrose syrup.

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

[0033] By filler containing free fructose taken in mixture with any saccharide species, we mean for example syrups of the High-Fructose-Corn-Syrup type 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 filler may comprise 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 fillers such as sucrose, kestose, fructans, oligofructans, inulin.

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

[0037] Preferably, the oligosaccharide has the following empirical formula: (C6mHiom+20sm+i) (CsnHs^C i) where m and n are integers whose sum is between 2 and 6. The monosaccharide units composing said oligosaccharide are identical or not, and preferably at least one unit of formula (C6mHiom+20sm+i) is fructose. By extension, preferably the polysaccharide has the following empirical formula (C6mHio m +205m+i) (Cs n H8n+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 in part after mixing it with the synthesis solvent. The synthesis solvent makes it possible to keep the sugar in a dilute medium and to substitute dilution with water for dilution with the synthesis solvent.

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

[0040] Advantageously, this step can be carried out by distillation and then 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 load, 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 feedstock is recycled and sent independently to one or more steps of the process requiring the supply of an aqueous stream, or sent to a global aqueous stream supplying said steps.

[0045] Step a) of dehydration of the load in 5-H MF and extraction of water

[0046] Dehydration of the 5-HMF charge

[0047] The process according to the invention comprises a step a) of bringing a feedstock comprising a hexose into contact with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature of between 30 and 200°C, preferably between 50 and 180°C, preferably between 70 and 150°C and very preferably between 90 and 130°C, and at a pressure of 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. The term “acid dehydration catalyst” means any Bronsted acid catalyst chosen from organic or inorganic, homogeneous or heterogeneous Bronsted acids capable of inducing the dehydration of the feedstock comprising a hexose to 5-HMF.

[0048] In one embodiment, the dehydration catalyst is in a homogeneous phase in the reaction medium.

[0049] Preferably, the acid dehydration catalyst is a Bransted acid having a pKa in the synthesis solvent of between 0 and 5.0, preferably between 0.5 and 4.0 and more preferably between 1.0 and 3.0. Said pKa are as defined in the article by F.G. Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0050] Preferably, the acid dehydration catalyst is selected from HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiWi204o, H3PW12O40, (NH4)6(Wi204o).xH20, H4SiMoi204o, H3PMO12O40, (NH4)6MO7O24.XH2O, H2MOO4, HReO4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HCIO4, HBF4, H sbF5, HPF6, H2FO3P, CISO3H, FSO3H, HN(SO2F)2, HIO3, BF3, AICI3, AI(OTf)3, FeCh, ZnCh, SnCh, CrCh, CeCh, ErCh, formic acid, acetic acid, trifluoroacetic acid, lactic acid, levulinic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, paratoluenesulfonic acid, 4-biphenylsulfonic acid, diphenylphosphate, and 1, 1-binaphthyl-2,2'-diyl hydrogen phosphate. Preferably, the acid dehydration catalyst is chosen from HCl, H2SO4, H3PO2, H3PO4, HNO3, AICI3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid alone or as a mixture.

[0051] Depending on the pressure and temperature conditions, the reaction medium is above or below the bubble point of the mixture. Bubble point refers to the pressure and temperature conditions under which the first gas bubbles appear for a liquid.

[0052] Preferably, the acid dehydration catalyst is introduced in a molar ratio of the catalyst relative to the feed comprising a hexose, expressed in 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%, preferably between 0.3 and 4 mol% and very preferably between 0.5 and 3 mol%.

[0053] 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, dimethylsulfoxide, propylene carbonate and g-valerolactone. Preferably, the synthesis solvent is selected from acetone, hexamethylphosphoramide, N,N-dimethylformamide, sulfolane, N-methylpyrrolidone, dimethylsulfoxide, propylene carbonate and g-valerolactone. Most preferably, the synthesis solvent is dimethyl sulfoxide (DMSO).

[0054] Dehydration can be carried out in different ways. Thus, it can advantageously be implemented discontinuously (called batch according to English terminology) or continuously. The addition of the charge can be progressive (called fed-batch according to English terminology) in the case of discontinuous implementation or staged in different CSTR reactors (Continuously Stirred Tank Reactor in English terminology) in series in a continuous implementation.

[0055] Extraction of water from the reaction medium

[0056] Step a) of the process according to the invention comprises a concomitant extraction of water from the reaction medium, to obtain a synthesis effluent comprising 5-HMF and synthesis solvent.

[0057] Advantageously, the reaction medium is above the bubble point of the mixture. Bubble point refers to the pressure and temperature conditions under 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.

[0058] Said water may come 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 feedstock, in the case where, for practical reasons, a feedstock in the form of syrup is used.

[0059] 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. 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.

[0060] Water extraction can be carried out by different methods such as: evaporation, adsorption (e.g. in a molecular sieve), membrane separation or osmosis.

[0061] Advantageously, this step can be carried out by distillation and requires that the synthesis solvent is less volatile than water. Distillation can then be carried out by a distillation column whose separation stages can be ensured by perforated trays, bulk packing or structured packing. Generally, this type of equipment has a reboiler to ensure the heat supply at the bottom of the column, a condenser to at least partially condense the overhead vapors and a reflux system.

[0062] In one embodiment, the water extracted from the reaction medium is recycled and sent independently to one or more stages of the process requiring the supply of an aqueous stream, or sent to a global aqueous stream supplying said stages.

[0063] 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.

[0064] 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, more preferably less than 30% by weight.

[0065] Advantageously, the extraction of water is carried out under conditions which allow at least 90% of the synthesis solvent used in the dehydration and extraction step to be recovered in the synthesis effluent, preferably at least 95% and even more preferably at least 99%.

[0066] In one embodiment, the synthesis effluent may further contain impurities, in particular humins. The term "humins" refers to all the undesirable polymeric compounds formed during the synthesis of 5-HMF. The humins advantageously represent less than 30% by weight of the feedstock, preferably less than 20% by weight. In one embodiment, the process according to the invention further comprises a step of neutralizing the synthesis effluent, preferably by bringing said synthesis effluent into contact with a basic compound, which follows step a).

[0067] Advantageously, the basic compound is chosen from NaOH, KOH, NH4OH, Na2CC>3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, Ba(OH)2.

[0068] The synthesis effluent contains the acid dehydration catalyst. The neutralization step advantageously reduces the reactivity of the medium and thus avoids the degradation mechanisms of 5-HMF, or even reduces the corrosion of equipment materials downstream of the dehydration step. Since the dehydration reaction can produce some organic acids, the quantity of neutralization agent can advantageously neutralize all the acids present in the synthesis effluent.

[0069] The neutralization step is advantageously carried out at a minimum at the stoichiometric ratio of the quantity of catalyst used. Since the dehydration reaction can produce some organic acids, the neutralization is generally carried out in slight over-stoichiometry compared to the catalyst used, preferably between 1 and 2 times the stoichiometric ratio, preferably between 1 and 1.5 times the stoichiometric ratio.

[0070] The optional neutralization step can be carried out:

[0071] - online on the synthesis effluents when they are transferred to step b) of substitution of the synthesis solvent by an aqueous solution;

[0072] - during step b) of substitution of the synthesis solvent by an aqueous solution;

[0073] - in the case of synthesis in batch or fed-batch mode in the synthesis tank at the end of the stage, at the pressure and temperature of the reaction medium.

[0074] Step b) substitution of the synthesis solvent

[0075] In one embodiment, the method 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.

[0076] Advantageously, the aqueous solution comprises between 5 and 60% by weight of water.

[0077] This step makes it possible to use in the process an organic synthesis solvent that is efficient in terms of selectivity and reaction productivity 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.In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution comprises the following steps: 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; 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; iii) separating the extraction solvent from the intermediate organic effluent and obtaining an aqueous solution of 5-HMF.

[0078] Step i) of bringing the synthesis effluent into contact with a liquid stream

[0079] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution comprises 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;

[0080] Advantageously, the 5-HMF represents more than 1% by weight of the synthesis 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, more preferably less than 30% by weight.

[0081] 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.

[0082] 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.

[0083] 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. In several embodiments, the liquid stream comprising at least 80% by weight of water may come from one or more streams of the process such as: the aqueous counter-extract from the backwashing step, the condensates produced during the extraction of water during the synthesis, the water produced in the step of regeneration of the synthesis solvent, or any other 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.

[0084] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further comprises a step of liquid-solid separation of the aqueous mixture obtained following step i) prior to step ii) of liquid / liquid extraction.

[0085] Some of the humins possibly initially 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, so as to obtain a liquid separated from suspended solid particles and a solid residue comprising humins and which is preferably removed from the process. Such a liquid-solid separation step thus makes it possible to remove the humins which have precipitated. 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 room 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, for example with a filter press, a belt filter, a drum filter, a candle filter, a clarifier, a decanter, a centrifuge or any combination of these techniques.Advantageously, the liquid-solid separation step is filtration, preferably carried out by a filter press.

[0086] Step ii) liquid / liquid extraction

[0087] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution comprises 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;

[0088] The liquid / liquid extraction carried out in step ii) advantageously corresponds to a washing of 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 filled with bulk or structured packing, in a pulsed column, or even in a stirred column.

[0089] 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).

[0090] 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.

[0091] In a non-limiting manner, the extraction solvent is preferably chosen from 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 between 1 and 10 carbon atoms (C1-C10), 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 as a mixture. Very preferably, the extraction solvent is methyl isobutyl ketone (MIBC or MIBK according to English terminology).

[0092] Advantageously, the extraction solvent is chosen so as to:

[0093] - have a very high difference in volatility with 5-HMF so as to facilitate its separation in step iii) of separation of the extraction solvent from the intermediate organic effluent and limit the degradation of 5-HMF, i.e. so as to present in step iii) a vaporization rate making it possible not to degrade 5-HMF and to minimize the quantity of residual extraction solvent,

[0094] - 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. The intermediate organic effluent may contain synthesis solvent.Preferably, said intermediate organic effluent preferably contains 5-HMF and synthesis solvent in a weight ratio, 5-HMF / (synthesis solvent+5-HMF), of between 50 / 50 and 99 / 01, preferably of between 50 / 50 and 95 / 05, preferably of between 55 / 45 and 90 / 10, more preferably of between 60 / 40 and 85 / 15 and more preferably of between 65 / 35 and 80 / 20.

[0095] In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further comprises a step of backwashing the intermediate organic effluent obtained in step ii), in the presence of an aqueous solvent, prior to step iii) of separation, to obtain at least one intermediate organic effluent depleted in synthesis solvent comprising 5-HMF, extraction solvent and having a content of synthesis solvent less than or equal to 20% by weight relative to the weight of 5-HMF, and an aqueous counter-extract comprising synthesis solvent.

[0096] In one embodiment, the aqueous counter-extract is advantageously sent in part or in whole to the contacting step i).

[0097] When the backwashing step is implemented, the extraction solvent introduced in step ii) is chosen from organic solvents immiscible with water, so as to form two liquid phases in the backwashing step. This property is highly dependent on the relative proportion of the flow rates of feedstock, aqueous back-extraction solvent and extraction solvent used in the process.

[0098] The introduction of the aqueous solvent is carried out in such a way that the quantity of aqueous solvent is as low as possible so as to reduce costs, but sufficient to guarantee a low weight content of synthesis solvent in the intermediate organic effluent and preferably less than or equal to 20.00% by weight relative to the weight of 5-HMF, preferably less than or equal to 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, very preferably between 0.01 and 10.00% by weight relative to the weight of 5-HMF.

[0099] 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 synthetic solvent and / or extraction solvent. The effectiveness of the backwash is higher the lower the amount of synthetic solvent present in the aqueous backwash solvent. Preferably, the aqueous solvent may comprise synthetic solvent, at most 1.0% by weight, and preferably at most 0.1% by weight.

[0100] According to several embodiments, the aqueous backwash solvent comes from one or more of the following process streams: the condensates produced in dehydration step b), the water extracted from the feed in step a), the water produced in the synthesis solvent regeneration step or any other aqueous stream containing a quantity of synthesis solvent preferably less than or equal to 1% by weight and preferably less than or equal to 0.1% by weight.

[0101] 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 with bulk or structured packing, in a pulsed column, or even in a stirred column.

[0102] 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).

[0103] The weight ratio (w / w) of aqueous backwash solvent to intermediate organic extract is preferably 0.04 to 5, preferably 0.07 to 3, preferably 0.1 to 1.

[0104] The backwashing step makes it possible to obtain an aqueous back-extract preferably comprising at least 60% by weight of water, preferably at least 80% by weight of water, and an intermediate organic effluent depleted in synthesis solvent. The intermediate organic effluent depleted in synthesis solvent obtained has a weight content of synthesis solvent 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.

[0105] In one embodiment, the aqueous counter-extract may be recycled similarly to the water extracted in step a).

[0106] Step iii) of separation of the extraction solvent In one embodiment, step b) of substitution of the synthesis solvent by an aqueous solution comprises a step iii) of separation of the extraction solvent from the intermediate organic effluent and obtaining an aqueous solution of 5-HMF.

[0107] If a backwash has been carried out beforehand, the intermediate organic effluent is the intermediate organic effluent depleted in synthesis solvent.

[0108] In one embodiment, the separated extraction solvent may advantageously be recycled to extraction step ii).

[0109] In one embodiment, separation step iii) is carried out by hydrodistillation.

[0110] 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.

[0111] In a particular embodiment of the invention, the aqueous stream is pure water, possibly external to the process, which makes it possible to further reduce the content of residual synthesis solvent in the aqueous solution of 5-HMF produced in step b).

[0112] In another particular embodiment of the invention, an aqueous stream isolated within the process can be used to feed the hydrodistillation step, thus making it possible 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.

[0113] 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.

[0114] The hydrodistillation step may be carried out at atmospheric pressure or under vacuum and in particular at a pressure of between 0.001 MPa and 0.1 MPa, preferably under vacuum at a pressure of between 0.005 MPa and 0.08 MPa. Advantageously, the hydrodistillation step is carried out under vacuum, in particular at a pressure of 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.

[0115] 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-H F.

[0116] 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.

[0117] 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.

[0118] The condensation of the vapors at the top of the distillation column generates two liquid phases: a phase rich in water which can be advantageously returned to the column as reflux, and a phase rich in extraction solvent which can be advantageously recycled to extraction step ii).

[0119] According to the invention, the aqueous solution of 5-HMF obtained at the end of step b) comprises a quantity 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 more preferably less than 80% by weight, the percentages being given by weight of 5-HMF relative to the weight of aqueous solution of 5-HMF obtained at the end of step b).

[0120] The process according to the invention thus makes it possible to produce an aqueous solution of 5-HMF very advantageously having a weight content of synthesis 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. In one embodiment, step b) of substituting the synthesis solvent with an aqueous solution further comprises 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 mainly extraction solvent.

[0121] Preferably, the stream comprising mainly extraction solvent is recycled, in whole or in part, to extraction step ii).

[0122] Preferably, the separation of a portion of the extraction solvent at this stage of concentration of the 5-HMF solution in the organic phase, prior to stage 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.

[0123] According to this preferred embodiment, the vaporization of the extraction solvent is advantageously carried out at atmospheric pressure or under vacuum, preferably at a pressure of between 0.01 MPa and 0.1 MPa, preferably under vacuum at a pressure of between 0.01 MPa and 0.09 MPa, so as to limit the temperature of the liquid and therefore the degradation of the 5-HMF. Preferably, the temperature of the liquid is kept less than or equal to 130°C, preferably kept less than or equal to 100°C, preferably kept less than or equal to 70°C. The level of vacuum to be applied to reach these temperatures is of course dependent on the synthesis solvent and more particularly on the extraction solvent used and the vaporization rate of the synthesis solvent.

[0124] The concentration step is carried out with a mass vaporization rate (or evaporation rate), corresponding to the mass of vaporized extraction solvent 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 as a function of the extraction solvent so as not to degrade the 5-HMF, but also in order to minimize the quantity 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 single-phase) when the concentrated intermediate organic effluent is brought into contact with an aqueous stream in step iii) when this is carried out by hydrodistillation.

[0125] 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 at most 95% by weight, preferably at most 90% by weight and 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 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 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.

[0126] Step c) regeneration of the synthesis solvent

[0127] In one embodiment, the method according to the invention further comprises a step c) of regeneration of the synthesis solvent substituted in step b).

[0128] “Regeneration” means obtaining a flow comprising mainly the desired solvent.

[0129] Advantageously, the regenerated synthesis solvent is recycled to step a).

[0130] The stream comprising the substituted synthesis solvent may contain a water fraction which may be separated and recycled to a global aqueous stream or 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 takes advantage of the extraction of water in step a) to maintain the selectivity of conversion of the sugar to 5-HMF.

[0131] During this step c), the synthesis solvent can be purified and purged at least in part of the co-products of the synthesis reaction. Among the co-products, we can notably find:

[0132] - unconverted sugars from the feedstock;

[0133] - saccharide oligomers produced during synthesis;

[0134] - 5-HMF;

[0135] - acids neutralized in the neutralization step;

[0136] - humins, for example not filtered in the precipitation and filtration step. In the embodiment in which step b) of substituting 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) which is used in step c) of regeneration of the synthesis solvent.

[0137] In this embodiment, the aqueous effluent may also comprise a small amount of extraction solvent which may itself be regenerated, optionally purged of co-products, and advantageously recycled to step ii).

[0138] The regeneration step can advantageously be carried out by a succession of gas / liquid separation in evaporation or distillation equipment. Generally, a first evaporation stage allows the majority of the extraction solvent to be recovered, at least 70%, preferably at least 80%, even more preferably 90%. A second stage allows the stream to be completely depleted of water; the stream then contains less than 10% by weight of water, preferably less than 5% by weight of water, even more preferably less than 1% by weight of water. The last stage consists of finalizing 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.

[0139] Preferably, the separation cascade is carried out with a maximum temperature imposed by the thermal stability of the products and the separation is pushed by successive reductions in pressure. This temperature is generally between 50 and 200°C, preferably between 80 and 150°C and even more preferably between 100 and 130°C.

[0140] Evaporation can advantageously be carried out in conventional tube and shell type exchangers followed by gas / liquid separation tanks or in single or multiple effect evaporators ensuring gas / liquid separation and the heat supply necessary for evaporation.

[0141] Preferably, the last evaporation steps 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 extract these humins whose viscosity can exceed 1000 cP at 100°C. DESCRIPTION OF THE FIGURES

[0142] Particular non-limiting examples of embodiments of the invention are described below with reference to the appended figures.

[0143] Figure 1: A feedstock 1 comprising a hexose is sent to a step a) in which it 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 of between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C, and very preferably between 80°C and 120°C, and at a pressure of between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, and the water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 comprising 5-HMF and synthesis solvent is obtained. The synthesis effluent 3 is sent to a step b) in which the synthesis solvent is substituted by an aqueous solution 21 which can 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 recycling the synthesis solvent 11, which is optionally purged of the synthesis co-products 20, and the synthesis solvent is recycled to step a). The losses in synthesis solvent are compensated by an addition of synthesis solvent 22.

[0144] Figure 2: A feedstock 1 comprising a hexose is sent to a step a) in which it 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 of between 50°C and 150°C, preferably between 60°C and 140°C, preferably between 70°C and 130°C and very preferably between 80°C and 120°C, and at a pressure of between 0.001 MPa and 1 MPa, preferably between 0.01 MPa and 0.1 MPa, and the water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 comprising 5-5-HMF and synthesis solvent is obtained. The synthesis effluent 3 is sent to step b) of 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, originating from a global aqueous stream 21 which can be supplied 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 extraction solvent is obtained.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, and a stream 17 of extraction solvent is obtained which can be recycled to step ii) (stream 9), and an aqueous solution of 5-HMF 16. The aqueous stream 11 is sent to a step c) of regeneration of the synthesis solvent in which said synthesis solvent is extracted from the stream 11 and is optionally purged of the synthesis co-products 20, and the synthesis solvent is recycled to step a). The losses of synthesis and extraction solvents are compensated by make-ups, respectively a synthesis solvent make-up 22 and an extraction solvent make-up 23.

[0145] Figure 3: A feedstock 1 comprising a hexose is sent to a step a) in which it 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 very 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 the water is extracted from the reaction medium 4 during the synthesis. A synthesis effluent 3 comprising 5-HMF and synthesis solvent is obtained. The synthesis effluent 3 is sent to step b) of 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, originating from a global aqueous stream 21 which can be supplied 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 flow 21, and an organic effluent depleted in synthesis solvent 13 is obtained, comprising 5-HMF, extraction solvent and having a content of synthesis solvent less than or equal to 20% by weight relative to the weight of 5-HF, and an aqueous counter-extract 14 comprising synthesis solvent which can be sent to step i). The organic effluent depleted in synthesis solvent 13 is sent to a step iii) in which the extraction solvent is separated from the organic effluent 13 using an aqueous solution 15 coming from a global aqueous flow 21, and a flow 17 of extraction solvent is obtained which can be recycled to step ii) contributing to the global flow of extraction solvent 9, and an aqueous solution of 5-HMF 16.The aqueous stream 11 is sent to a step c) of regeneration of the synthesis solvent in which said synthesis solvent is extracted from the stream 11 and is optionally purged of the synthesis co-products 20, and the synthesis solvent is recycled to step a), and optionally water 19 is extracted from the stream 11 which can be sent to the overall aqueous stream 21, and optionally extraction solvent 18 is extracted from the stream 11 which can be sent to the overall extraction solvent stream 9. The losses of synthesis and extraction solvents are compensated by make-ups, respectively a synthesis solvent make-up 22 and an extraction solvent make-up 23.

[0146] EXAMPLES

[0147] Example 1 - Synthesis of 5-HMF in a continuous stirred-tank reactor (CSTR) from crystalline fructose according to the prior art

[0148] Fructose is introduced in the form of a crystal with a purity greater than 99.5% by weight of sugar in DMSO, so that the fructose concentration is 35% by weight. The mixture is brought to a temperature of 120°C, and an acid catalyst, methanesulfonic acid, is added with a catalyst / sugar molar ratio of 1% mol.

[0149] The mixture is introduced into a reactor to carry out 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, therefore without a vapor phase to extract. The reaction medium is continuously withdrawn with 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 5 h for the feedstock.

[0150] 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, i.e. a molar yield of 5-HMF relative to fructose of 70%. Polymeric compounds (humins) soluble in the reaction medium were formed and represent, with the unconverted fructose, 9% by weight of the solution.

[0151] Example 2 - Synthesis of 5-HF in continuous mode CSTR of crystalline fructose according to the invention

[0152] Fructose is introduced in the form of a crystal with a purity greater than 99.5% by weight of sugar in DMSO, so that the fructose concentration is 35% by weight. The mixture is brought to a temperature of 120°C, and an acid catalyst, methanesulfonic acid, is added with a catalyst / sugar molar ratio of 1% mol.

[0153] The mixture is introduced into a reactor to carry out 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, therefore with a vapor phase to be extracted. The vapor phase is rectified in a packed column developing 8 theoretical stages, the reflux being adjusted so as to obtain a top product whose water / DMSO composition is respectively 99.5 / 0.5% by weight.

[0154] The liquid reaction medium is continuously withdrawn to produce the reaction effluents. The withdrawal flow rate is adjusted so that the liquid volume in the reactor ensures an average residence time of the feedstock of 5 hours.

[0155] 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, i.e. a molar yield of 5-HMF relative to fructose of 80%. Polymeric compounds (humins) soluble in the reaction medium were formed and represent, with the unconverted fructose, 6% by weight of the solution.

[0156] 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 very significantly improve its yield (80 mol% according to the invention and 70 mol% according to the prior art).

[0157] Example 3 - Production of an aqueous solution of 5-HMF by conversion of a syrup containing 70% by weight of fructose and 30% by weight of water according to the invention:

[0158] The exemplified process is consistent with that shown in Figure 3.

[0159] The process processes a syrup flow rate of 1 t / h or 700 kg / h of fructose. The syrup is mixed with streams containing recycled DSMO synthesis solvent from the synthesis 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 synthesis solvent leaving the regeneration step), 31.7% by weight of water and 43.3% by weight of DMSO.

[0160] The mixture thus obtained is injected into a packed column developing 8 theoretical stages whose bottom pressure 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% by weight.

[0161] Methanesulfonic acid (MSA) is introduced at the bottom of the column with a 1% MSA / fructose molar ratio. The dehydration reaction proceeds continuously with an average residence time of 5 h in the column bottom. Thanks to 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 part of the column. Under these conditions, the reaction medium, corresponding to the liquid phase in the column bottom, has a water content of 1% by weight. The withdrawal is carried out so as to maintain the liquid residence time in the column bottom. This withdrawal corresponds to the reaction effluents produced.

[0162] 1.8 t of synthesis effluent are 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 sugar and humins.

[0163] This synthesis effluent is mixed with the aqueous counter-extract from the backwashing step. The water collected during the regeneration steps of the synthesis and extraction solvents or during the distillation of the fructose / DMSO mixture is used to complete the mixture to produce a precipitation medium whose water / DMSO mass ratio is 0.91 (calculated taking into account the water and DMSO present in all the flows feeding the step). After 1 hour 30 minutes of maturation, the mixture is filtered on a filter press. At the end of the filtration sequence, the cake obtained is pressed. This step thus allows 29 kg / h of humins to be precipitated and filtered. The precipitation and filtration steps are carried out at 35 ° C and ambient pressure.

[0164] 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 through a pulsed column developing 9 theoretical stages, also operates at ambient temperature and pressure. The extraction solvent is IBK. The quantity of MIBK used is such that the mass ratio MIBK / feed at the liquid / liquid extraction stage is 1.5.

[0165] Under these conditions, the aqueous effluent obtained in the liquid / liquid extraction step comprises 3.5% of the HMF produced in the synthesis, i.e. a production loss of 3.5% of the HMF linked 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. 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:

[0166] - The first regeneration step is operated at 0.12 MPa. The steam is partially condensed. The condensed liquid is returned upstream of the first evaporation step. This arrangement makes it possible to produce, after partial condensation, an aqueous stream comprising 97.8% by weight of water directly sent to the process water tank and to recover by demixing the MIBK present in the aqueous effluent. The MIBK stream is returned to the extraction solvent collection tank. Under these conditions, 49% of the water contained in the aqueous effluent is extracted and does not require further treatment in the water / DM SO / fructose separation column.

[0167] - 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 which allows 92.9% of the mixture to be vaporized. The vapor is condensed then returned to the water / DMSO / fructose separation column and represents the largest contributor to the DMSO supply. Its composition is 34% by weight of water and 65% by weight of DMSO, its flow rate is 1.8 t / h. The effluent obtained has a residual DMSO content of 40% by weight, and only 1.2% by weight of water, the remainder being composed of unextracted 5-HMF, unconverted fructose, humins and salts present in the aqueous mixture.

[0168] - In a third step, the aqueous effluent from the third regeneration step is once again evaporated in a scraped film exchanger technology to exhaust as much of the heavy DMSO fraction as possible. The temperature is once again 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 liquid and viscous stream thus produced contains only 10% by weight of DMSO and makes it possible to limit losses of synthesis solvent and consequently the need for make-up.

[0169] 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% by weight of DMSO, or 5% of the DMSO used in the reaction, justifying the need to recover it by backwashing to limit losses of synthesis solvent. The backwashing step is carried out in a packed column developing 3 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 thus represent only 0.1% of the quantity of DMSO used in the reaction. The intermediate organic effluent depleted in synthesis solvent 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.

[0170] This intermediate organic effluent depleted in synthesis solvent is concentrated at a pressure of 0.0217 MPa and a temperature of 100°C, which makes it possible to achieve a vaporization mass rate of 84.2% and to produce an intermediate organic effluent concentrated at 50% by weight. The vapor fraction produced at this stage is condensed. The demixing makes it possible to separate 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 in the process water tank.

[0171] The intermediate organic effluent depleted in synthesis solvent and concentrated is sent to hydrodistillation and represents a flow rate of 753 kg / h. The stage is operated at 0.04 MPa in a distillation column equipped with packing developing 7 theoretical stages, with a process water reflux rate of 130 kg / h.

[0172] 560 kg / h of water are injected at the bottom of the column to dilute the 5-HMF and produce an aqueous 5-HMF solution. Reboiling is controlled to limit the MIBK content in the bottom product to 0.1% by weight. The aqueous 5-HMF solution thus produced has a 5-HMF concentration of 45% by weight 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. Demixing separates a liquid stream comprising 97.2% by weight of MIBK and an aqueous liquid stream comprising 98.7% by weight of water. The MIBK stream is recycled to the MIBK collection tank for recycling, the water stream is used to generate the column reflux and the excess is collected in the process water tank. The following table illustrates the flow rates of different process streams according to Example 3 in terms of total flow rate and flow rate by stream constituents:

[0173] Table 1

Claims

CLAIMS 1. A process for producing a 5-Hydroxymethylfurfural solution comprising a step a) of bringing a feedstock comprising a hexose into contact with a synthesis solvent and an acid dehydration catalyst, carried out at a temperature of between 30 and 200°C, preferably between 50 and 180°C, preferably between 70 and 150°C and very preferably between 90 and 130°C, and at a pressure of 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.

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

3. Process according to any one of the preceding claims, in which the acid dehydration catalyst is chosen from HCl, H2SO4, H3PO2, H3PO4, HNO3, AICI3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid alone or as a mixture.

4. Process according to any one of the preceding claims, in which the synthesis solvent is dimethyl sulfoxide.

5. Method according to any one of the preceding claims, further comprising a step of neutralizing the synthesis effluent, preferably by bringing said synthesis effluent into contact with a basic compound, which follows step a).

6. Method according to any one of the preceding claims, further comprising a step b) of substituting the synthesis solvent present in the synthesis effluent with an aqueous solution and obtaining an aqueous solution of 5-Hydroxymethylfurfural.

7. The method of claim 6, wherein step b) of substituting the synthesis solvent with an aqueous solution comprises the following steps: 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; 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.

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

9. A process according to any one of claims 7 or 8, wherein the separated extraction solvent can advantageously be recycled to extraction step ii).

10. Method according to any one of claims 7 to 9, further comprising a step of liquid-solid separation of the aqueous mixture obtained following step i) prior to step ii) of liquid / liquid extraction.

11. Process according to any one of claims 7 to 10, further comprising a step of backwashing the intermediate organic effluent obtained in step ii), in the presence of an aqueous solvent, prior to step iii) of separation, to obtain at least one intermediate organic effluent depleted in synthesis solvent comprising 5-Hydroxymethylfurfural, extraction solvent and having a content of synthesis solvent less than or equal to 20% by weight relative to the weight of 5-Hydroxymethylfurfural, and an aqueous counter extract comprising synthesis solvent.

12. Process according to any one of claims 7 to 11, in which step iii) of separation is carried out by hydrodistillation.

13. Method according to any one of the preceding claims, further comprising a step c) of regeneration of the synthesis solvent substituted in step b).

14. Method according to the preceding claim, in which the regenerated synthesis solvent is recycled to step a).

15. Process according to any one of the preceding claims, in which the water extracted from the reaction medium is recycled and sent independently to one or more stages of the process requiring the supply of an aqueous stream, or sent to a global aqueous stream supplying said stages.

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