Method for producing 5-hydroxymethylfurfural (5-HMF) aqueous solution

Abstract

The present invention relates to a process for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), comprising the following steps in succession: a) contacting a feed containing 5-HMF and dimethylsulfoxide (DMSO) with the intermediate aqueous back-extract from the backwash step c), b) liquid-liquid extraction with an organic solvent followed by a backwash step c) with an aqueous solvent; obtaining an organic raffinate rich in 5-HMF and solvent. The raffinate then undergoes a concentration step d) and then a steam distillation step e) to obtain an aqueous solution of 5-HMF.

Description

[Technical field]

[0001] The present invention relates to a method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF). [Background technology]

[0002] 5-HMF is an advantageous compound originating from biomass that can be utilized in many fields, especially in pharmaceutical, agricultural or specialty chemistry. The production of 5-HMF by dehydration of sugars has been known for many years and has formed the subject of many research studies. A huge number of dehydration conditions exist, and especially the following methods may be mentioned: - 5-HMF can be obtained in aqueous media, generally in the presence of acid catalysts, which make it possible to dehydrate C6 sugars (especially fructose) to give 5-HMF, but which also catalyze the rehydration of 5-HMF to give formic acid and levulinic acid, which is very detrimental to the yield. - 5-HMF can also be obtained in non-aqueous polar protic media, using solvents such as methanol, ethanol, or acetic acid and in the presence of acid catalysts. Under these conditions, 5-HMF is obtained as a mixture with ether or ester derivatives of 5-HMF, depending on the reaction medium used. The formation of these by-products results from the reaction of 5-HMF with the reaction solvent in acidic medium. - Patent document 1 describes the synthesis of 5-HMF by dehydration of sugars with methanol or ethanol as solvent in the presence of an acid catalyst, in which case the presence of said catalyst also catalyzes the etherification reaction of 5-HMF with alcohols to give a mixture of 5-HMF and its methyl or ethyl ether forms, depending on the alcohol used as solvent. 5-HMF can also be prepared in polar aprotic media with or without acid catalysis. More particular mention can be made of the use of dimethyl sulfoxide (DMSO). DMSO makes it possible to prepare 5-HMF with or without acid catalysis in very good yields and without the undesirable reactions listed above.

[0003] Furthermore, whatever the synthesis medium (water, methanol, DMSO, etc.), polymeric by-products called humins are formed during the production of 5-HMF (Non-Patent Document 1).

[0004] The synthesis of 5-HMF in a medium such as DMSO is particularly advantageous since it makes it possible to obtain 5-HMF in its alcohol form (rather than in its ether form) in very good yields. Nevertheless, the physicochemical properties of DMSO (or any other polar aprotic solvent) make its separation from 5-HMF by the usual methods known to those skilled in the art very difficult.

[0005] One known method for isolating 5-HMF from DMSO is liquid-liquid extraction followed by crystallization of the extract as described in US Pat. No. 5,399,663. The Applicant has already proposed an improvement to the method described in US Pat. No. 5,399,663, which was the subject of US Pat. No. 5,399,663. This improvement is based on modifying the extraction step, notably by adding a water backwash step and recycling the backwash water into the optional filtration step. This improvement makes it possible to increase the purity of 5-HMF without loss of yield of its intended product and to carry out the 5-HMF crystallization step under more favorable conditions.

[0006] Yet, despite the improvements provided by US Pat. No. 5,633,666, 5-HMF crystallization remains a costly operation. The high production costs of 5-HMF limit its use, and the development of cost-saving processes is needed.

[0007] The Applicant has discovered a process which makes it possible to recover 5-HMF in the form of an aqueous solution rather than in a crystallized form, opening up new possibilities for the utilization of 5-HMF in various applications or for further transformations which could not be carried out either in DMSO or in the extraction solvent. Moreover, the process according to the invention thus makes it possible to recover 5-HMF in an aqueous solution, while at the same time limiting the operating costs and the discharges and thus the environmental impact of said process. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2007 / 104514 [Patent Document 2] French Patent No. 2669635 [Patent Document 3] French Patent Invention No. 1758605 [Non-patent literature]

[0009] [Non-Patent Document 1] 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, pages 95-101 Summary of the Invention [Means for solving the problem]

[0010] (Summary of the invention) One subject of the present invention relates to a method for producing an aqueous solution of 5-HMF.

[0011] More particularly, the present invention relates to a method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), said method comprising the steps of: - step a): placing a feedstock comprising 5-HMF and dimethyl sulfoxide (DMSO) in contact with at least a portion of an intermediate aqueous back-extract, advantageously obtained from step c); obtaining at least one aqueous mixture, step b): liquid-liquid extraction in the presence of an extraction solvent of the aqueous mixture obtained at the end of step a), giving rise to an aqueous raffinate and an intermediate organic extract, followed by - step c): backwashing with an aqueous solvent: resulting in an intermediate aqueous back extract and an organic raffinate comprising 5-HMF and an organic solvent; - step d): concentrating the organic raffinate obtained from step c) by removing at least a portion of the organic solvent; obtaining a concentrated organic extract and a stream comprising the organic solvent, the concentrated organic extract comprising 5-HMF, preferably in a content of 40% by weight or more, and residual organic solvent, preferably in a content of 60% by weight or less, - steam distillation step e): carried out by distilling the concentrated organic extract obtained from step d) in the presence of water; giving rise to an aqueous solution of 5-HMF and a stream containing an organic solvent; - optional step f): treating the water-DMSO mixture produced in the process; making it possible to produce an aqueous effluent which may be used totally or partly in the backwash step c) and / or in step e). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Description of the embodiment) It is specified that throughout this description, the expression "between ... and ..." is to be understood as inclusive of the limits stated.

[0013] For the purposes of the present invention, the various embodiments presented may be used alone or in combination with each other without any limitations on said combinations.

[0014] For purposes of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination, e.g., for purposes of the present invention, a preferred range of pressure values ​​may be combined with a more preferred range of temperature values.

[0015] For a better understanding of the present invention, reference will be made below to the reference numerals appearing in the drawings to indicate the various elements of the method, but this is not to be considered as a limitation to the specific embodiment illustrated in FIGS. 1 and 2.

[0016] (Optional step of sugar dehydration to 5-HMF) Advantageously, the feedstock (1) comprising 5-HMF and dimethylsulfoxide (DMSO) introduced into step a) according to the invention can be obtained during a step of sugar dehydration to 5-HMF, very advantageously arranged upstream of step a) according to the invention, carried out by placing a sugar feedstock comprising one or more sugars in contact with DMSO and an acidic dehydration catalyst, resulting in an effluent comprising at least 5-HMF and DMSO, which advantageously corresponds to the feedstock (1) of the process according to the invention introduced into the mixing step a). The process according to the invention may thus optionally comprise a step of sugar dehydration to 5-HMF, which step is arranged upstream of step a).

[0017] The term "acidic dehydration catalyst" refers to any Bronsted acid catalyst selected from organic or inorganic, homogeneous or heterogeneous Bronsted acids, capable of inducing the dehydration of sugars to 5-HMF.

[0018] Preferably, the acidic dehydration catalyst is a Bronsted acid having a pKa in DMSO of 0 to 5.0, preferably 0.5 to 4.0, more preferably 1.0 to 3.0, as defined in the paper by FG ​​Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0019] Preferably, the acidic dehydration catalyst is HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiW 12 O 40 , H3PW 12 O 40 , (NH4)6(W 12 O 40 )·xH2O, H4SiMo 12 O 40 , H3PMo 12 O 40 , (NH4)6Mo7O 24 xH2O, H2MoO4, HReO4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HClO4, HBF4, HSbF5, HPF6, H2FO3P, ClSO3H, FSO3H, HN(SO2F)2, HIO3, BF3, AlCl3, 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 acidic dehydration catalyst is selected from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0020] The term "sugar" refers to sugars containing six carbon atoms (hexoses), but this does not exclude the presence in the feedstock of sugars containing five carbon atoms (pentoses) in the form of oligosaccharides and monosaccharides. In particular, the term "sugar" refers to glucose or fructose, sucrose, alone or in mixtures, and also oligosaccharides such as cellobiose, maltose, cellulose, or even inulin.

[0021] The sugar feedstock used may be sugar in solid form or an aqueous sugar solution. By way of example, sucrose is generally produced in solid form, while glucose or fructose, alone or in mixtures, are generally produced in the form of an aqueous solution (syrup), for example with 70% sugar by weight.

[0022] The optional dehydration step is carried out at a temperature between 50 and 150°C, preferably between 60 and 140°C, preferably between 70 and 130°C, more preferably between 80 and 120°C. Preferably, the optional dehydration step is carried out at a pressure between 1 and 0.001 MPa, preferably between 0.1 and 0.01 MPa. Depending on the pressure and temperature conditions, the reaction medium is above or below the bubble point of the mixture. The term "bubble point" indicates the pressure and temperature conditions at which the first gas bubbles are found in the liquid. When the reaction medium is above the bubble point of the mixture, the vapor phase can be removed from the reactor, optionally rectified and condensed to form a condensate, which can be sent to the optional step f) for treating the water-DMSO mixture.

[0023] Preferably, the acidic dehydration catalyst is introduced into the dehydration step in a molar ratio of catalyst relative to the sugar feedstock expressed as acid / sugar expressed as mole percent (mol%): 0.01-10 mol%, preferably 0.05-8 mol%, preferably 0.1-6 mol%, preferably 0.2-5 mol%, more preferably 0.3-4 mol%, highly preferably 0.5-3 mol%.

[0024] Advantageously, the effluent obtained at the end of the optional dehydration step comprises 5-HMF and DMSO, the latter generally representing from 30% to 95% by weight, preferably from 40% to 90% by weight, preferably from 50% to 90% by weight, more preferably from 55% to 85% by weight of the effluent obtained from the dehydration step and treated in step a) of the process according to the invention.

[0025] 5-HMF represents more than 1% by weight, preferably more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, preferably less than 40% by weight, more preferably less than 30% by weight, of the effluent obtained from the optional dewatering step and treated in step a) of the process according to the invention.

[0026] Moreover, the effluent from the optional dehydration step may contain water even before it is mixed with the intermediate aqueous back extract (9) in step a). The water may originate from the dehydration step: for example, water is formed during the dehydration reaction of sugar to 5-HMF (3 moles of water per mole of 5-HMF produced). This water may also have been introduced together with the sugar for practical reasons, in the case where sugar syrup is used, for example at about 70% by weight in water. Advantageously, during the optional dehydration step, a water-DMSO mixture may be recovered in the vapour phase. The water-DMSO mixture is advantageously sent to the optional step f). Thus, the effluent obtained from the optional dehydration step and introduced into step a) as feedstock (1) may contain water generally in a proportion of 0.1% to 30% by weight, preferably 0.1% to 15% by weight, more preferably 0.1% to 10% by weight.

[0027] The effluent obtained from the optional dewatering step and introduced into step a) as feedstock (1) may also contain impurities, in particular humins. The term "humins" refers to all undesirable polymeric compounds formed during the synthesis of 5-HMF. In particular, humins represent less than 30% by weight, preferably less than 20% by weight, of the converted sugar feedstock.

[0028] The optional dewatering step may be carried out according to various embodiments. This step may therefore advantageously be carried out in batch or continuous mode. The addition of the sugar feedstock may be gradual (fed-batch), in the case of a batch process, or staged in different CSTR reactors (Continuously Stirred Tank Reactors) in series, in the case of a continuous process. The process may be carried out in a closed reaction chamber or in a semi-open reactor.

[0029] (Mixing step a)) The process according to the invention comprises a step a) of placing (or mixing) the feedstock (1), optionally from a dewatering step, in contact with (or with) at least a portion of an intermediate aqueous back extract (9) to obtain at least one aqueous mixture (3). Advantageously, the intermediate aqueous back extract (9) is obtained from step c) of the process according to the invention.

[0030] Preferably, 5-HMF represents more than 1% by weight, preferably more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, preferably less than 40% by weight, more preferably less than 30% by weight, of the feedstock (1) introduced in step a) of the process according to the invention.

[0031] Preferably, DMSO represents from 30% to 95% by weight, preferably from 40% to 90% by weight, preferably from 50% to 90% by weight, more preferably from 55% to 85% by weight of the feedstock (1) introduced in step a).

[0032] The feed material (1) introduced in step a) may contain water in an amount of preferably 0.1% to 30% by weight, preferably 0.1% to 15% by weight, more preferably 0.1% to 10% by weight.

[0033] Feedstock (1) may also optionally contain humins, which in particular represent less than 30% by weight, preferably less than 20% by weight, of feedstock (1).

[0034] The intermediate aqueous back extract (9) or a portion of the intermediate aqueous back extract (9) is advantageously obtained from step c). It comprises water, DMSO and optionally 5-HMF. Advantageously, said intermediate aqueous back extract (9) contains more than 60% by weight of water, preferably more than 70% by weight of water and preferably more than 80% by weight of water.

[0035] Advantageously, the aqueous mixture (3) obtained at the end of step a) contains between 10% and 90% by weight of water, preferably between 20% and 80% by weight of water and more preferably between 40% and 75% by weight of water.

[0036] Preferably, step a) is carried out at a temperature between 0 and 60°C, preferably between 10 and 30°C, generally at room temperature, ie between 18 and 25°C.

[0037] Step a) may optionally feed an aqueous stream, for example a portion of the aqueous solvent used in the backwash step c).

[0038] By increasing the water content during step a), for example by introducing at least a portion of the intermediate aqueous back extract (9), some of the humins that may be present in the feedstock (1) can be precipitated out. The mixture resulting from the contact of said feedstock (1) with at least a portion of the intermediate aqueous back extract (9) can then advantageously be subjected to a liquid-solid separation step to obtain a liquid separated from the suspended solid particles and a solid residue comprising the humins, which is preferably excluded from the process. Such an optional liquid-solid separation step thus allows the elimination of the precipitated humins. At least a portion of the liquid obtained is then advantageously sent to a liquid-liquid extraction step b), advantageously said portion (or all) of the liquid sent to step b) corresponding to the aqueous mixture (3). If the amount of precipitated humins in the mixture is low (for example less than or equal to 1% by weight), the liquid-solid separation step is optional. This optional liquid-solid separation step is preferably carried out at a temperature between 0 and 60° C., preferably between 10 and 30° C., preferably between 15 and 25° C., and generally at room temperature (i.e. between 18 and 25° C.). The optional liquid-solid separation step is a simple solid-liquid separation and may be carried out via any method known to the skilled person, for example by a filter press, a belt filter, a clarifier, a decanter, or a centrifuge, for example a plate centrifuge. Preferably, the liquid-solid separation step is a filtration, preferably carried out by a filter press.

[0039] (Extraction step b)) The process according to the invention comprises a step b) of liquid-liquid extraction, in the presence of an extraction solvent (4), of the aqueous mixture (3) obtained at the end of step a), so as to give an aqueous raffinate (5) and an intermediate organic extract (6).

[0040] The liquid-liquid extraction carried out in step b) advantageously corresponds to washing the aqueous mixture with an organic extraction solvent. Preferably, the liquid-liquid extraction carried out in step b) is a countercurrent extraction of the aqueous mixture (3) obtained in step a) with an extraction solvent. This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a mixer-decanter array, in a column filled with random or structured packing, in a plug-flow column or else in a stirred column.

[0041] The liquid-liquid extraction step b) is advantageously carried out at a temperature between 0 and 60°C, preferably between 5 and 50°C, preferably between 10 and 40°C, more preferably between 15 and 30°C, and generally at room temperature (i.e. between 18 and 25°C).

[0042] The weight ratio (wt / wt) of the extraction solvent relative to the aqueous mixture (3) is preferably 0.2 to 5, preferably 1 to 3, more preferably 1.5 to 2.5.

[0043] The extraction solvent introduced in step b) is chosen from water-immiscible organic solvents so as to form two liquid phases in the backwash step c), the characteristics of which depend largely on the relative proportions of the feedstock, the back-extraction water and the flow rates of the extraction solvent used in the process.

[0044] In a non-limiting embodiment, the extraction solvent is preferably selected from chlorinated organic solvents, ethers, esters, ketones, and aromatic compounds. Preferably, the extraction solvent is a chlorinated solvent containing 1-10 carbon atoms, hereinafter referred to as C1-C10, a (C2-C10) ether containing 2-10 carbon atoms, a (C4-C10) ester containing 4-10 carbon atoms, a (C3-C10) ketone containing 3-10 carbon atoms, a (C1-C10) aldehyde containing 1-10 carbon atoms, or a C4-C10 aromatic compound. Preferably, the extraction solvent is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole, and toluene. Highly preferably, the extraction solvent is methyl isobutyl ketone.

[0045] Advantageously, the extraction solvent is chosen for: - having a very high volatility difference with 5-HMF to facilitate its removal in step d) and to limit the decomposition of 5-HMF, i.e. a vaporization rate in step d) which avoids the decomposition of 5-HMF and minimizes the amount of residual solvent to be removed in step e), while at the same time ensuring that no liquid phase separation occurs when the concentrated organic extract in step e) is placed in contact with water; - in step e) it is chosen to form a heterogeneous azeotrope with water, preferably one that is solvent-rich, i.e. has more than 50% by weight of solvent, preferably more than 60% by weight of solvent, more preferably more than 70% by weight of solvent. Advantageously, the boiling point of said azeotrope of the water / extraction solvent mixture is significantly lower than the boiling point of water, preferably at least 5°C lower than the boiling point of water, preferably at least 8°C lower than the boiling point of water, preferably at least 10°C lower than the boiling point of water.

[0046] Advantageously, the organic solvent streams arising in the subsequent steps may be recycled to extraction step b) as extraction solvent. These organic solvent streams may contain impurities that may have arisen during the implementation of the method. Advantageously, the organic solvent streams arising in the subsequent steps may be distilled, for example periodically, to avoid the accumulation of said impurities.

[0047] Step b) thus makes it possible to obtain, on the one hand, an aqueous stream depleted in 5-HMF and, on the other hand, an organic stream enriched in 5-HMF, said aqueous stream called aqueous raffinate (5) containing most of the DMSO originally contained in the feedstock, and said organic stream called intermediate organic extract (6) containing most of the 5-HMF originally contained in the feedstock (1) and the extraction solvent. This intermediate organic extract (6) may contain DMSO. Preferably, said intermediate organic extract contains 5-HMF and DMSO in a 5-HMF / DMSO weight ratio of 50 / 50 to 95 / 05, preferably 55 / 45 to 90 / 10, preferably 60 / 40 to 85 / 15, more preferably 65 / 35 to 80 / 20.

[0048] Advantageously, the intermediate organic extract (6) is sent directly to the backwash step c).

[0049] (backwashing process c)) The process according to the invention advantageously comprises a step c) of backwashing the intermediate organic extract (6) with an aqueous solvent (7), resulting in an intermediate aqueous back-extract (9) and an organic raffinate (8) comprising 5-HMF and an organic solvent. The intermediate aqueous back-extract (9) is advantageously sent partly or entirely to step a). The organic solvent in particular consists at least partly of the extraction solvent and may optionally comprise DMSO, preferably in small amounts.

[0050] The introduction of the aqueous solvent in step c) is carried out to carry out backwashing according to the general knowledge of the person skilled in the art. The introduction of the aqueous solvent is carried out so that the amount of the aqueous solvent is as small as possible to reduce costs, but sufficient to ensure a low DMSO weight content in the organic raffinate (8), the DMSO weight content: preferably less than 20.0% by weight relative to the weight of 5-HMF, preferentially less than 15.0% by weight relative to the weight of 5-HMF, preferably between 0.01% and 15.0% by weight relative to the weight of 5-HMF, highly preferably between 0.01% and 10.0% by weight relative to the weight of 5-HMF.

[0051] Advantageously, the aqueous backwash solvent introduced in step c) comprises more than 95% by weight of water, preferably more than 98% by weight of water (100% being the maximum). The aqueous solvent may optionally comprise DMSO. All backwash efficiencies are higher the lower the amount of DMSO present in the aqueous backwash solvent. Preferably, the aqueous solvent may comprise DMSO, preferably less than 1.0% by weight of DMSO, more preferably less than 0.1% by weight of DMSO. Advantageously, the aqueous backwash solvent originates from optional step f) of treating the water-DMSO mixture generated in the process. In a preferred embodiment of the invention, the aqueous raffinate (5) composed of water and DMSO generated in step b) is advantageously treated in optional step f), which comprises in particular distillation. The water-rich distillate thus obtained from this optional step f) is advantageously used as aqueous backwash solvent in step c); said water-rich distillate may contain a residual amount of DMSO, preferably less than 1% by weight, preferably less than 0.1% by weight of DMSO. The residual amount of DMSO in the distillate will be proportionately lower the more efficiently the distillation of optional step f) is carried out, especially with more than 10 distillation stages and suitable reboil and reflux rates.

[0052] The backwashing step c) is advantageously a liquid-liquid extraction of the organic stream obtained in step b), in particular the intermediate organic extract (6), in countercurrent to the aqueous solvent (7). This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a mixer-decanter array, in a column filled with random or structured packing, in a plug-flow column or else in a stirred column.

[0053] Step c) is preferably carried out at a temperature between 0 and 60° C., preferably between 5 and 50° C., preferably between 10 and 40° C., more preferably between 15 and 30° C., and generally at room temperature (i.e. between 18 and 25° C.).

[0054] The weight ratio (wt / wt) of the aqueous solvent relative to the intermediate organic extract (6) is preferably 0.04-5, preferably 0.07-3, more preferably 0.1-1.

[0055] Step c) gives rise to an aqueous stream, advantageously rich in DMSO, called intermediate aqueous back extract (9), which preferably contains at least 60% by weight of water, preferably at least 80% by weight of water, and the organic raffinate (8) is advantageously depleted in DMSO. Said intermediate aqueous back extract (9) is advantageously sent partially or preferably entirely to step a). The DMSO weight content of the obtained organic raffinate (8) is preferably at most 20.0% by weight relative to the weight of 5-HMF, preferably at most 15.0% by weight relative to the weight of 5-HMF, preferably at most 5.0% by weight relative to the weight of 5-HMF, preferably at most 4.0% by weight relative to the weight of 5-HMF, preferably at most 3.0% by weight relative to the weight of 5-HMF.

[0056] According to the invention, the organic raffinate (8) produced in step c) is sent to a concentration step d).

[0057] (concentration step d)) The process according to the invention comprises a step d) of concentrating the organic raffinate (8) obtained from step c) by removal of part of the organic solvent, resulting in a concentrated organic extract (10) containing 5-HMF and residual organic solvent, and a stream (11) comprising, and preferably consisting of, an organic solvent, advantageously constituted wholly or partly by the extraction solvent and optionally DMSO.

[0058] Preferably, the organic solvent-containing stream (11) is totally or partly recycled to the extraction step b).

[0059] Preferably, in step d), removal of a portion of the organic solvent is carried out by evaporation, for example in a distillation column at atmospheric pressure or under reduced pressure, in an evaporator, or via any method known to the skilled person.

[0060] According to this preferred embodiment, the evaporation of the organic solvent is advantageously carried out at atmospheric pressure or under reduced pressure, preferably at a pressure between 0.1 and 0.01 MPa, preferentially at a reduced pressure between 0.09 and 0.01 MPa, so as to limit the temperature of the liquor and thus the decomposition of 5-HMF. Preferably, the temperature of the liquor is kept below 130° C., preferably below 100° C., more preferably below 70° C. The level of reduced pressure to be applied to achieve these temperatures naturally depends on the organic solvent, more particularly on the extraction solvent used and on the rate of evaporation of the organic solvent.

[0061] In a preferred embodiment, the evaporation of the solvent is carried out by multiple effect evaporation or mechanical vapor recompression, or by any other method known to those skilled in the art, so as to reduce the operating costs associated with the solvent evaporation process while limiting the risk of decomposition of the intended product, i.e., 5-HMF. For example, in the case of a triple effect evaporation process, the liquid temperature is kept below 130° C. in the first effect, below 100° C. in the second effect, and below 70° C. in the third effect. Hence, the temperature of the liquid phase is progressively lowered as 5-HMF is concentrated in the organic solvent, limiting any risk of decomposition.

[0062] Step d) is carried out with a vaporization mass ratio (or evaporation rate): 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 more preferably at most 99%. The vaporization mass ratio corresponds to the mass of the organic solvent vaporized relative to the mass of the organic raffinate (8) from step c) (more particularly, the amount of the mass of stream (11) relative to the amount of the mass of the organic raffinate (8)). Advantageously, the vaporization rate is defined so as not to decompose the 5-HMF depending on the extraction solvent, but also to minimize the amount of residual solvent to be removed in step e), while at the same time ensuring that no liquid phase separation occurs when the concentrated organic extract (10) is placed in contact with water in step e) (i.e. ensuring that the liquid phase remains single-phase).

[0063] According to the invention, in particular by all combinations of the operating conditions of step d) and the preceding steps a), b) and c), the 5-HMF content of the concentrated organic extract (10) obtained at the end of step d) is very advantageously at least 40% by weight, preferably at least 50% by weight, preferably at least 60% by weight, relative to the weight of the concentrated organic extract, and preferably at most 95% by weight, preferably at most 90% by weight, preferably at most 85% by weight, relative to the weight of the concentrated organic extract. In other words, the residual organic solvent content of the concentrated organic extract (10) is preferably at least 5% by weight, preferably at least 10% by weight, relative to the weight of the concentrated organic extract, and preferably at most 60% by weight, preferably at most 50% by weight, more preferably at most 40% by weight, relative to the weight of the concentrated organic extract (10).

[0064] Advantageously, the organic solvent vaporized during step d) forms a stream (11) which comprises, preferably consists of, the organic solvent and which is preferably recycled to the extraction step b).

[0065] Advantageously, the concentrated organic extract (10) is subjected to a steam distillation step e).

[0066] (Steam distillation process e) The process according to the invention comprises a steam distillation step e) carried out by distilling the concentrated organic extract (10) from step d) in the presence of water to give an aqueous solution of 5-HMF (12) and a stream (13) comprising, preferably consisting of, an organic solvent.

[0067] The steam distillation step e) advantageously allows the residual organic solvent not removed during step d) to be at least partially removed. The residual organic solvent removed during step e), i.e. stream (13), may advantageously be recycled to the extraction step b), either alone or in a mixture with stream (11) comprising the organic solvent from step d).

[0068] Advantageously, the aqueous stream (14) is fed to a steam distillation step e). The aqueous stream (14) introduced in step e) preferably contains more than 95% by weight of water, more preferably more than 98% by weight of water.

[0069] In certain embodiments of the invention, the aqueous stream (14) is pure water, optionally external to the process, which even further minimizes the residual DMSO content in the aqueous 5-HMF solution (12) produced in step e).

[0070] In another particular embodiment of the invention, the water isolated in the process is used to feed step e), making it possible to limit the operational costs of the process and its environmental impact. Typically, if the process involves the preparation of a feedstock (1) and the sugar feedstock for the dehydration step is a sugar syrup at 70% by weight in water, then at the end of the dehydration step, about 1 ton of water (feedstock water and water generated during the dehydration reaction) is recovered per ton of 5-HMF produced. This water needs to be treated before being released into the environment. The process according to the invention advantageously makes it possible to use said water from the dehydration step to produce, at the end of step e), an aqueous solution of 5-HMF concentrated to preferably more than 30% by weight, preferentially more than 40% by weight, thus reducing the reworking costs of the process and its environmental impact.

[0071] Advantageously, the aqueous stream (14) introduced in step e) may correspond to at least a portion, possibly the entirety, of the distillate resulting in optional step f), said distillate possibly containing residual amounts of DMSO.

[0072] Advantageously, during step e), the extraction solvent used in the process forms a heterogeneous azeotrope with water, said azeotrope being preferably rich in the extraction solvent, preferably comprising more than 50% by weight of the extraction solvent, preferably more than 60% by weight of the extraction solvent, preferably more than 70% by weight of the extraction solvent. Advantageously, the boiling point of said water / extraction solvent azeotrope is significantly lower than the boiling point of water, preferably at least 5° C. lower than the boiling point of water, preferably at least 8° C. lower than the boiling point of water, preferably at least 10° C. lower than the boiling point of water.

[0073] Therefore, after placing the concentrated organic extract (10) in contact with the aqueous stream (14), the residual organic solvent contained in the concentrated organic extract (10) may be easily removed without decomposition of the 5-HMF.

[0074] The steam distillation step e) may be carried out at atmospheric pressure or under reduced pressure, in particular at a pressure between 0.1 MPa and 0.001 MPa, preferably at a reduced pressure between 0.08 and 0.005 MPa. Advantageously, the steam distillation step is carried out under reduced pressure, in particular at a pressure between 0.1 MPa and 0.001 MPa, preferably between 0.08 MPa and 0.005 MPa, so as to facilitate the removal of residual organic solvents without decomposition of 5-HMF.

[0075] Advantageously, the steam distillation step e) is carried out in a distillation column at a bottom temperature preferably below 140° C., preferably below 130° C., preferably below 120° C., preferably below 110° C., preferably below 100° C., so as to facilitate the removal of residual organic solvents without decomposition of 5-HMF.

[0076] In one particular embodiment, the concentrated organic extract (10) and the aqueous stream (14) are mixed prior to introduction into the distillation column, and the mixture is introduced at an intermediate point of the distillation column.

[0077] In another particular embodiment, the concentrated organic extract (10) is introduced into the upper portion of the distillation column, preferably into the upper half of the column, while the aqueous solvent is introduced into the lower portion of the distillation column, preferably into the lower half of the column, after which mixing of the concentrated organic extract and the aqueous stream is carried out in the distillation column.

[0078] Given the formation of a heterogeneous azeotrope between water and the extraction solvent, condensation of the overhead vapor of the distillation column generates two liquid phases: a water-rich phase which may advantageously be returned to the column as reflux and an organic solvent-rich phase which may advantageously be recycled to the extraction step b).

[0079] According to the invention, the amount of 5-HMF in the aqueous 5-HMF solution (12) obtained at the end of step e) is at least 30% by weight, preferably at least 40% by weight, and preferably less than 90% by weight, preferably less than 85% by weight, preferably less than 80% by weight, this percentage being given by the weight of 5-HMF relative to the weight of the aqueous 5-HMF solution obtained at the end of step e).

[0080] The process according to the invention thus makes it possible to produce an aqueous solution of 5-HMF, the DMSO weight content of which is very advantageously less than or equal to 10% by weight relative to the weight of 5-HMF, preferably less than or equal to 5% by weight relative to the weight of 5-HMF, preferably less than or equal to 3% by weight relative to the weight of 5-HMF.

[0081] (Optional step f) of treating the water-DMSO mixture) The process according to the invention may comprise an optional step f) of treating the water-DMSO mixture resulting from the steps of the process according to the invention, resulting in an aqueous effluent (also known as distillate) which may be used totally or partly in the backwash step c) and / or in step e), which may result in a DMSO-rich stream (16) and an impurities stream (17).

[0082] Residual amounts of DMSO in the aqueous effluents resulting upon termination of optional step f) are all lower since the distillation is carried out in an efficient manner according to the knowledge of the skilled person.

[0083] The water-DMSO mixture generated via the present process refers in particular to the aqueous raffinate (5) generated in step b) and, optionally, if the present process incorporates the optional step of dehydration of sugars to 5-HMF, to the water-DMSO mixture obtained as a result of such step.

[0084] Preferably, the optional step f) of treating the water-DMSO mixture comprises a section for evaporating the water-DMSO mixture to remove any impurities (stream (17)), in particular heavy impurities such as humins, followed by a distillation section.

[0085] The evaporation section is preferably operated at a temperature of 80-120° C., preferentially 100-110° C., and at a pressure of preferably 0.002-0.020 MPa, preferentially 0.005 MPa-0.010 MPa. Preferably, the evaporation section uses a Thin Film Evaporator (TFE).

[0086] The distillation section is advantageously a distillation column or some separation equipment. Preferably, the distillation section of optional step f) is advantageously operated in a distillation column, with a top temperature of preferably 25-60°C, preferentially 45-55°C, for example about 50°C, with a bottom temperature of preferably 80-120°C, preferentially 105-115°C, for example about 110°C, with a pressure of preferably 0.001-0.05 MPa, preferentially 0.005-0.02 MPa, more preferably 0.008-0.012 MPa, and with a corresponding reflux ratio of preferably 0.01-0.50, more preferably 0.05-0.10.

[0087] Thus, the aqueous raffinate (5) resulting from step b) and containing water and DMSO, and the water-DMSO mixture possibly recovered in the optional dehydration step, are evaporated and the gas phase is then recovered and distilled, preferably under reduced pressure, to give a DMSO-rich residue (16) on the one hand and a water-rich distillate (15) (corresponding to the aqueous effluent) on the other hand. The term "rich" here means more than 95% by weight, preferably more than 98% by weight. The water-rich distillate, or part or all of the aqueous effluent, may advantageously be recycled as aqueous solvent to step c) to carry out a backwash step and / or recycled as aqueous stream to the steam distillation step e). The water-rich distillate may be recycled in whole or in part as the water introduced into step a).

[0088] The DMSO-rich residue may advantageously be introduced into an optional dehydration step, either directly or after distillation, making it possible to remove any heavy products that may accumulate.

[0089] The following examples and accompanying drawings are illustrative of the present invention and are not intended to limit the scope of the invention.

[0090] (List of Drawings) Figure 1 illustrates a particular embodiment of the process according to the invention. The feedstock (1) containing 5-HMF, DMSO and humins is sent to step a) and placed in contact with the intermediate aqueous back extract (9) from step c), after which the precipitated humins (2) are removed from the mixture by liquid-solid filtration. The aqueous mixture (3) obtained at the end of step a) is sent to extraction step b) and placed in contact with the extraction solvent (4) recycled from steps d) and e), with which 5-HMF is extracted from the aqueous mixture, obtaining an aqueous raffinate (5) and an intermediate organic extract (6). The intermediate organic extract (6) is placed in contact with an aqueous solvent (7) in a backwash step c). The organic raffinate (8) obtained is concentrated in step d) by removing stream (11), which is recycled to step b). The concentrated organic extract (10) obtained at the end of step d) is subjected to a steam distillation step e) to remove the residual organic solvent (13), which is recycled to step b) to obtain an aqueous solution of 5-HMF (12).

[0091] FIG. 2 illustrates another particular embodiment of the process according to the invention, which differs from the embodiment of FIG. 1 in that it includes a step f) of treating the water-DMSO mixture generated in the process, and in particular the aqueous raffinate (5), giving rise to an aqueous effluent (15), a DMSO-rich residue (16) and an impurities stream (17), part of the aqueous effluent (15) being recycled to step c) as aqueous solvent (7) and part of the aqueous effluent (15) being recycled to the steam distillation step e) as aqueous stream (14).

[0092] (Example) Example 1: Preparation of organic extract (8) according to the present invention To demonstrate some of the advantages of the method according to the invention, the results of carrying out the method according to FIG. 1 are now presented.

[0093] The acid catalyst (methanesulfonic acid) is mixed with DMSO in a molar ratio (catalyst / sugar feedstock) of 1 mol % with the sugar feedstock and is brought to a temperature of 120° C. Fructose is introduced in the form of an aqueous solution (syrup) of 70% by weight of sugar, with a mass ratio of DMSO / fructose of 2.3. The pressure is maintained at 0.035 MPa. Under these conditions of pressure and temperature, the reaction medium is above the bubble point of the mixture, so that the vapour phase can be removed from the reactor, condensing and forming a condensate. The sugar dehydration step is carried out batchwise by gradual addition of the feedstock over a period of 2 hours. After the end of the addition, the reaction medium is maintained at the temperature and pressure indicated above for a further 2 hours.

[0094] The liquid effluent obtained from the dehydration step contains 74% by weight of DMSO, 21% by weight of 5-HMF and 3% by weight of water, giving a molar yield of 5-HMF relative to the fructose involved of 81%. Polymeric compounds soluble in the reaction medium (called humins) are formed in an amount of 5% by weight. During this dehydration step, a water-DMSO mixture is recovered in the vapor phase. The composition of said water-DMSO mixture is 32% by weight of DMSO and 68% by weight of water. This water-DMSO mixture is distilled under reduced pressure to give water containing only traces of DMSO.

[0095] The liquid effluent from the dehydration step corresponding to the feedstock (1) is subjected to a step a) of placing it in contact with a water-containing stream at room temperature to obtain a mixture containing a DMSO / water mass ratio equal to 1.

[0096] The mixture from step a) is subjected to a liquid-solid separation step on a Büchner filter equipped with a polypropylene gauze filter with a pore size of 10 μm. This liquid-solid separation step is carried out at room temperature. During the liquid-solid separation step, 7.5 g of "humic" solid residue per kg of filtered mixture weight are recovered together with a homogenous liquid phase corresponding to aqueous mixture (3). Aqueous mixture (3) is composed of 43% by weight DMSO, 12% by weight 5-HMF and 43% by weight water, and contains impurities (about 2% by weight humic).

[0097] The aqueous mixture (3) obtained from step a) is subjected to a countercurrent liquid-liquid extraction step b) in a stirred glass column (Keuhni or ECR type), which comprises 8 sections with a height of 225 mm and an internal diameter of 32 mm, including a lower decanter and an upper decanter. The effective height is about 1.8 m and the total column height is 2.60 m. The total volume is about 3 liters. The organic extraction solvent is methyl isobutyl ketone (MIBK). The aqueous mixture (3) is introduced at the top of the device and dispersed in the organic phase going upwards. The column inlet flow rates are set at 2.2 kg / h for the DMSO-aqueous phase and 4.1 kg / h for the organic extraction solvent. The proportion (w / w) of the MIBK solvent is 1.9 relative to the aqueous mixture (3) obtained from step a). In this step b), the temperature is 20° C. and the stirring speed is 300 rpm.

[0098] At the end of step b), a 5-HMF-depleted aqueous raffinate (5) and an intermediate organic extract (6) enriched in furan compounds are recovered. The 5-HMF-depleted aqueous raffinate (5) contains about 48% by weight of water, 48.5% by weight of DMSO, 0.4% by weight of 5-HMF, 1.8% by weight of MIBK, and humic impurities, and the intermediate organic extract (6) contains 2.8% by weight of DMSO, 5.9% by weight of 5-HMF (5-HMF / DMSO weight ratio: about 68 / 32), and 91.3% by weight of MIBK. The extraction yield is 97% for 5-HMF and 13% for DMSO.

[0099] The intermediate organic extract (6) obtained from the liquid-liquid extraction step b) is subjected to a backwash step c) in the same extraction device (Kuhni type stirred column or ECR). The organic extract is dispersed in a pure aqueous phase at 21.5° C. The column inlet flow rates are set at 5 kg / h for the organic extract and 1.5 kg / h for the aqueous phase. The proportion (w / w) of water introduced as aqueous backwash solvent relative to the intermediate organic extract is 0.3.

[0100] At the end of the backwash step c), a DMSO-enriched intermediate aqueous back extract (9) and an organic raffinate (8) are recovered, the DMSO-enriched intermediate aqueous back extract (9) containing 86% by weight of water, 7% by weight of DMSO, 5% by weight of 5-HMF and 2% by weight of MIBK, and the organic raffinate (8) containing 4.3% by weight of 5-HMF, 0.092% by weight of DMSO (i.e. 2.1% by weight of DMSO relative to the weight of 5-HMF) and 88% by weight of MIBK, giving a backwash yield of 27% by weight for 5-HMF and 95% by weight for DMSO.

[0101] Example 2: Implementation of steps d) and e) according to the present invention The organic raffinate (8) produced according to Example 1 is sent to the concentration step d). The solvent is distilled off under reduced pressure. The liquid temperature is set to 60° C. and the reduced pressure is set to 0.02 MPa.

[0102] Step d) is carried out with a vaporization mass ratio of 95%, which corresponds to the mass of vaporized organic solvent relative to the participating mass of organic raffinate from step c). The mass contents of the concentrated organic extract obtained at the end of step d) are 84% by weight of 5-HMF, 2% by weight of DMSO and 9% by weight of MIBK. The 5-HMF content of the concentrated organic extract (84% by weight) complies with the expected values ​​(minimum 40% by weight and not more than 95% by weight), just as the residual solvent content of the concentrated organic extract (sum of 9% MIBK + 2% DMSO) of 11% by weight complies with the expected values ​​(minimum 5% by weight and not more than 60% by weight). The concentrated organic extract obtained at the end of step d) also contains humic impurities (5% by weight). The recovered distillate essentially contains MIBK and water, which is removed in the form of an azeotrope with MIBK, which separates into two immiscible phases upon condensation.

[0103] The concentrated organic extract obtained from step d) is placed in contact with pure water in a water / concentrated extract mass ratio of 0.95 and then sent to a steam distillation step e) carried out by distillation. The steam distillation step e) is carried out at a bottom temperature of 35° C. and under a reduced pressure of 0.01 MPa, facilitating the removal of the residual MIBK organic solvent in the form of a water / MIBK azeotrope without decomposition of 5-HMF. The composition of the aqueous 5-HMF solution obtained at the end of step e) is 45% by weight 5-HMF, 53.3% by weight water, 1% by weight DMSO (i.e. 2.2% by weight DMSO relative to the weight of 5-HMF) and 0.7% by weight MIBK.

[0104] Example 3: Implementation of steps d) and e) according to the present invention The organic raffinate (8) produced according to Example 1 is sent to the concentration step d). The solvent is distilled off under reduced pressure. The liquid temperature is set to 60° C. and the reduced pressure is set to 0.02 MPa.

[0105] Step d) is carried out with a vaporization mass ratio of 93%, which corresponds to the mass of vaporized organic solvent relative to the participating mass of organic raffinate from step c). The mass contents of the concentrated organic extract obtained at the end of step d) are 59% by weight of 5-HMF, 1% by weight of DMSO and 34% by weight of MIBK. The content of 5-HMF (59% by weight) of the concentrated organic extract complies with the expected values ​​(minimum 40% by weight and not more than 95% by weight), just as the residual solvent content of 35% by weight (sum of 34% MIBK + 1% DMSO) complies with the expected values ​​(minimum 5% by weight and not more than 60% by weight). The concentrated organic extract obtained at the end of step d) also contains humic impurities (about 6% by weight). The recovered distillate essentially contains MIBK and water, which is removed in the form of an azeotrope with MIBK, which separates into two immiscible phases on condensation.

[0106] The concentrated organic extract obtained from step d) is placed in contact with pure water in a water / concentrated extract mass ratio of 0.83 and passes to a steam distillation step e), which is carried out by distillation. The steam distillation step e) is carried out at a bottom temperature of 49° C. and under a reduced pressure of 0.008 MPa, so as to facilitate the removal of the residual MIBK organic solvent in the form of a water / MIBK azeotrope without decomposition of 5-HMF. The composition of the aqueous 5-HMF solution obtained at the end of step e) is 42% by weight 5-HMF, 56.5% by weight water, 0.9% by weight DMSO (i.e. 2.1% by weight DMSO relative to the weight of 5-HMF) and 0.6% by weight MIBK.

[0107] (Example 4: Implementation of steps d) and e) The organic raffinate (8) from Example 1 is sent to the concentration step d). The solvent is distilled off under reduced pressure. The liquid temperature is set to 60° C. and the reduced pressure is set to 0.02 MPa.

[0108] Step d) is carried out with a vaporization mass ratio of 70%, which corresponds to the mass of vaporized organic solvent relative to the participating mass of organic raffinate from step c). The mass contents of the concentrated organic extract obtained at the end of step d) are 15% by weight of 5-HMF, 0.5% by weight of DMSO and 79% by weight of MIBK. The concentrated organic extract obtained at the end of step d) also contains humic impurities (5.5% by weight). The concentrated organic extract obtained at the end of step d) still contains 79.5% by weight of residual solvents (MIBK 79% + DMSO 0.5%). The recovered distillate essentially contains MIBK, and MIBK and water, which are removed in the form of an azeotrope, which separates into two immiscible phases during concentration.

[0109] The 5-HMF content of the concentrated organic extract, 15% by weight, is lower than expected (minimum 40% by weight and not more than 95% by weight). The residual solvent content of the concentrated organic extract, 79.5% by weight (sum of MIBK 79% + DMSO 0.5%), is therefore significantly above expected (minimum 5% by weight and not more than 60% by weight).

[0110] The concentrated organic extract obtained from step d) is placed in contact with pure water in a water / concentrated extract mass ratio of 0.45 and passes to a steam distillation step e) carried out by distillation, the steam distillation step e) being carried out at a bottom temperature of 49° C. and under a reduced pressure of 0.008 MPa, so as to facilitate the removal of the residual MIBK organic solvent in the form of a water / MIBK azeotrope without decomposition of 5-HMF.

[0111] However, placing in contact with the concentrated organic extract obtained at the end of concentration step d), which still contains 79.5 wt. % organic solvent (well above the targeted 60 wt. % limit), induces phase separation of the liquid phase into mutually immiscible aqueous and organic phases, making it impossible to carry out the steam distillation step e). [Brief description of the drawings]

[0112] [Figure 1] 1 illustrates a particular embodiment of the method according to the invention. [Diagram 2] 2 illustrates another particular embodiment of the method according to the invention.

Claims

1. 1. A method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), comprising the steps of: step a): placing a feedstock (1) containing 5-HMF and dimethyl sulfoxide (DMSO) in contact with an intermediate aqueous back extract (9), advantageously at least a portion of the intermediate aqueous back extract (9) obtained from step c); obtaining at least one aqueous mixture (3), step b): liquid-liquid extraction of the mixture (3) obtained at the end of step a) in the presence of an extraction solvent (4), giving an aqueous raffinate (5) and an intermediate organic extract (6), and then - step c) of backwashing with an aqueous solvent (7): to give an intermediate aqueous back extract (9) and an organic raffinate (8) comprising 5-HMF and an organic solvent, step d): concentrating the organic raffinate (8) obtained from step c) by removing at least a portion of the organic solvent, resulting in a concentrated organic extract (10) and a stream (11) comprising the organic solvent, the concentrated organic extract having a 5-HMF content preferably equal to or greater than 40% by weight and residual organic solvents preferably equal to or less than 60% by weight, steam distillation step e): carried out by distillation in the presence of water of the concentrated organic extract (10) obtained from step d); giving an aqueous solution of 5-HMF (12) and a stream (13) containing an organic solvent.

2. 2. The process according to claim 1, wherein the intermediate organic extract (6) from step b) is fed to a backwashing step c).

3. 3. The process according to claim 1 or 2, wherein the evaporation of the organic solvent in step d) is carried out at atmospheric pressure or under reduced pressure, preferably at a pressure of 0.1 to 0.01 MPa, preferentially under reduced pressure at a pressure of 0.09 to 0.01 MPa.

4. 2. The process of claim 1, wherein the temperature of the liquid in step d) is kept below 130°C, preferably below 100°C, more preferably below 70°C.

5. 2. The process according to claim 1, wherein the 5-HMF content of the concentrated organic extract (10) obtained at the end of step d) is at least 40% by weight, preferably at least 50% by weight, more preferably at least 60% by weight, relative to the weight of the concentrated organic extract, and preferably at most 95% by weight, preferably at most 90% by weight, more preferably at most 85% by weight, relative to the weight of the concentrated organic extract, and the residual organic solvent content is at least 5% by weight, preferably at least 10% by weight, relative to the weight of the concentrated organic extract, and preferably at most 60% by weight, preferably at most 50% by weight, more preferably at most 40% by weight, relative to the weight of the concentrated organic extract.

6. 2. The process according to claim 1, wherein the aqueous stream (14) is fed to a steam distillation step e).

7. 2. The process according to claim 1, wherein step e) is carried out at atmospheric pressure or under reduced pressure, in particular at a pressure of 0.1 MPa to 0.001 MPa, preferably under reduced pressure at a pressure of 0.08 to 0.005 MPa.

8. 2. The process according to claim 1, wherein step e) is carried out in a distillation column at a bottom temperature of preferably less than 140°C, preferably less than 130°C, preferably less than 120°C, preferably less than 110°C, preferably less than 100°C.

9. 2. The method according to claim 1, wherein the extraction solvent (4) is chosen from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene, highly preferably methyl isobutyl ketone.

10. 2. The process according to claim 1, wherein the weight ratio (wt / wt) of the aqueous solvent (7) relative to the intermediate organic extract (6) in the backwashing step c) is between 0.04 and 5, preferably between 0.07 and 3, more preferably between 0.1 and 1.

11. 2. The method of claim 1, comprising a step of dehydrating sugars to 5-HMF upstream of step a), preferably carried out by contacting a sugar feedstock comprising one or more sugars with DMSO and an acidic dehydration catalyst, preferably at a temperature of 50 to 150°C, preferably 60 to 140°C, preferably 70 to 130°C, more preferably 80 to 120°C, and preferably at a pressure of 1 to 0.001 MPa, more preferably 0.1 to 0.01 MPa.

12. 2. The process according to claim 1, comprising a step f) of treating the water-DMSO mixture produced in the process, allowing the production of an aqueous effluent, which may be used in whole or in part in the backwashing step c) and / or in step e).

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