Production of 5-HMF in non-aqueous solvents using pre-liquid-liquid extraction concentration of 5-HMF

Abstract

The present invention relates to a process for the production of 5-hydroxymethylfurfural (5-HMF) comprising, in order: a) contacting a sugar feedstock with a polar aprotic synthesis solvent and an acidic dehydration catalyst at a temperature of 30-200 DEG C and a pressure of 0.001-10 MPa to produce a synthesis effluent comprising 5-HMF; b) concentrating the 5-HMF in the synthetic effluent; c) contacting the concentrated synthetic effluent with an aqueous stream; d) liquid-liquid extraction with an organic extraction solvent, followed by step e) backwashing with an aqueous solvent to obtain an organic raffinate rich in 5-HMF and solvent. The optionally concentrated organic raffinate is then subjected to a purification step g), for example water distillation or crystallization, to obtain a 5-HMF stream, for example in the form of an aqueous 5-HMF solution or crystalline 5-HMF.

Description

Technical Field

[0001] This invention relates to a method for producing hydroxymethylfurfural (HMF) from a feedstock containing sugars, particularly at least one hexose, and preferably fructose, in the presence of at least one polar aprotic solvent. More particularly, this invention relates to a method for producing HMF, such as an aqueous solution of HMF, the method comprising a liquid-liquid extraction step prior to a step of concentrating the HMF in the synthesis effluent fed to the liquid-liquid extraction. Existing technology

[0002] HMF, also known as 5-(hydroxymethyl)furfural or 5-HMF, is a target compound derived from biomass that can be upgraded in many fields, especially in pharmaceuticals, agricultural chemistry, or specialty chemistry.

[0003] The production of 5-HMF via sugar dehydration has been known for many years and has been the subject of extensive research. Numerous dehydration conditions exist, and the following methods are particularly noteworthy: - 5-HMF can be obtained in an aqueous medium, typically in the presence of an acid catalyst. This acid catalyst can dehydrate C6 sugars (hexoses, and especially fructose) to 5-HMF, but it also catalyzes the rehydration of 5-HMF to formic acid and levulinic acid, which greatly reduces the yield; - 5-HMF can also be obtained in a non-aqueous polar protic medium using solvents such as methanol, ethanol, or acetic acid in the presence of an acid catalyst. Under these conditions, 5-HMF is obtained as a mixture with ether or ester derivatives of 5-HMF, depending on the reaction medium used. The formation of these byproducts is due to the reaction of 5-HMF with the reaction solvent in an acidic medium. For example, patent application WO 2007 / 104 514 describes the synthesis of 5-HMF by sugar dehydration using methanol or ethanol as a solvent in the presence of an acid catalyst. In this case, the presence of the catalyst also catalyzes the etherification reaction of 5-HMF with an alcohol to produce a mixture of 5-HMF and its methyl or ethyl ether forms, depending on the alcohol used as the solvent.

[0004] - 5-HMF can also be produced in a polar aprotic medium with or without an acid catalyst. More particularly noteworthy is the use of dimethyl sulfoxide (DMSO), which enables the production of 5-HMF in very good yields with or without an acid catalyst, and without the undesirable reactions listed above.

[0005] The synthesis of 5-HMF in a medium such as DMSO is particularly advantageous because it allows for the acquisition of 5-HMF in its alcoholic form (rather than its etheric form) in very good yields. However, the physicochemical properties of DMSO (or any other polar aprotic solvent) make it very difficult to separate it from 5-HMF using conventional methods known to those skilled in the art.

[0006] One known method for separating 5-HMF from DMSO is liquid-liquid extraction followed by crystallization of the extract, as described in patent FR2669635.

[0007] The applicant has proposed an improvement to the method described in patent FR2669635, which is the subject of patent FR3071172. This improvement is based on a modification to the liquid-liquid extraction step, particularly by adding a backwashing step using water and recycling the backwash water upstream of the liquid-liquid extraction to mix it with the 5-HMF / DMSO feedstock, the mixture of which is optionally filtered prior to the liquid-liquid extraction. This improvement allows for increased purity of 5-HMF without loss of the yield of the target product and enables the 5-HMF crystallization step to be carried out under more favorable conditions.

[0008] A liquid-liquid extraction method for separating 5-HMF from DMSO is also described in patent application FR3131313, but here it is as part of a method to recover 5-HMF in aqueous solution rather than in crystalline form, which may be advantageous since crystallization of 5-HMF remains an expensive operation. To this end, the method described in FR 3131313 involves a liquid-liquid extraction step combined with a water backwashing step of the organic extract containing 5-HMF obtained from the liquid-liquid extraction, a step of concentrating the 5-HMF in the organic raffinate containing 5-HMF obtained from the backwashing step, and a step of water distillation to obtain the concentrated stream from said steps, thereby recovering 5-HMF in the form of an aqueous solution.

[0009] In the process of synthesizing 5-HMF by dehydration of sugar feedstock using synthetic solvents such as DMSO, those skilled in the art know that diluting the sugar feedstock in DMSO improves the selectivity of the reaction and thereby improves the molar yield of 5-HMF relative to the sugar feedstock used, as described in patent WO 19 / 137810.

[0010] However, this dilution of the sugar feedstock in DMSO proves disadvantageous for liquid-liquid extraction as described in patents FR3071172 and FR3131313, especially due to the amount of extraction solvent (e.g., methyl isobutyl ketone or MIBK) and water involved, which are related to the amount of DMSO used for synthesis.

[0011] Typically, the extraction solvent is a water-immiscible organic solvent, which is preferably recycled back into the process after being separated from 5-HMF downstream of the liquid-liquid extraction step. This allows for minimizing the amount of extraction solvent used in the liquid-liquid extraction, thereby simplifying and reducing the cost of the extraction solvent recovery and recycling steps.

[0012] Similarly, water is necessary for liquid-liquid extraction, and for backwashing organic extracts from liquid extraction by water if optional.

[0013] The amount of water used in liquid-liquid extraction depends on the amount of DMSO introduced into the feedstock. Specifically, water is necessary to enable the extraction of 5-HMF by the extraction solvent because it allows the formation of a homogeneous liquid phase with the highly polar DMSO, preventing the DMSO from dissolving in the extraction solvent (e.g., MIBK). The extraction solvent, in turn, has a greater affinity for 5-HMF, allowing it to dissolve and form a 5-HMF-rich organic phase that is immiscible with the aqueous phase containing DMSO. These two liquid phases can then be separated, for example, by simple decantation under suitable temperature and pressure conditions.

[0014] Furthermore, the amount of water used in the water backwashing step depends on the amount of extraction solvent used in the liquid-liquid extraction, which in turn depends on the amount of DMSO in the feedstock entering the liquid-liquid extraction step.

[0015] This method is advantageous for reducing the amount of water used in the process, both because of its cost and complexity in recycling water and for environmental reasons.

[0016] In practice, a trade-off is typically struck between the amount of DMSO required to achieve a good 5-HMF yield during synthesis and the operational and capital expenditures (OPEX / CAPEX) and complexity of the liquid-liquid extraction step, which involves the amount of extraction solvent and water used: the amount of synthesis solvent (e.g., DMSO) is chosen such that a satisfactory (though not optimal) 5-HMF yield can be achieved in order to keep the cost and complexity of the liquid-liquid extraction step within acceptable limits.

[0017] Overcoming such limitations would constitute a significant improvement to the implementation of 5-HMF production processes based on this type of synthesis and liquid-liquid extraction. Summary of the Invention

[0018] The overall objective of this invention is to provide a method for producing 5-HMF from sugar feedstock in good yield and with good selectivity under mild operating conditions (moderate temperature and pressure).

[0019] In the foregoing context, the object of the present invention is to at least partially overcome the problems of the prior art, and particularly to provide a method for producing 5-HMF in which two steps are decoupled (the two steps being the synthesis of 5-HMF by dehydrating fructose using a polar aprotic solvent and the liquid-liquid extraction step that enables the recovery of 5-HMF), thereby maximizing the molar yield of 5-HMF and / or simplifying the liquid-liquid extraction step.

[0020] With the present invention, the current trade-off between 5-HMF yield and liquid-liquid extraction cost associated with the amount of synthetic solvent used in the synthesis process can be avoided or at least made with fewer limitations.

[0021] Therefore, one object of the present invention is to provide a method for producing 5-HMF from sugar feedstock using a polar aprotic solvent and possibly an acid catalyst, which, compared with prior art methods, has an improved 5-HMF yield and / or simplifies the liquid-liquid extraction step, and in particular, with respect to liquid-liquid extraction, reduces the number of extraction stages and / or reduces the amount of extraction solvent and water used for liquid-liquid extraction.

[0022] According to one aspect, the method according to the invention is capable of producing crystalline 5-HMF as a final product.

[0023] According to another aspect, the method according to the invention enables the production of an aqueous solution of 5-HMF as the final product, eliminating the need for an additional crystallization step, thereby limiting operating costs and providing new possibilities for upgrading 5-HMF in various applications or for further conversions that cannot be carried out in synthesis or extraction solvents.

[0024] Therefore, in particular to achieve at least one of the above objectives, the present invention proposes a method for producing 5-HMF, the method comprising the following steps: - Step a) Contact a sugar feedstock comprising hexose with at least one polar aprotic synthesis solvent and at least one acidic dehydration catalyst to produce a synthesis effluent containing 5-HMF and the polar aprotic synthesis solvent, the contact being carried out at a temperature between 30°C and 200°C and a pressure between 0.001 MPa and 10 MPa. - Step b) Concentrate the 5-HMF in the synthesis effluent to obtain a concentrated synthesis effluent; - Step c) Contact the concentrated synthetic effluent with an aqueous stream to obtain at least one aqueous mixture; - Step d) Perform liquid-liquid extraction on the aqueous mixture obtained at the end of step c) in the presence of the extraction solvent to produce an aqueous raffinate containing the polar aprotic synthesis solvent and an organic extract containing 5-HMF and the extraction solvent; and subsequently - Step e) Backwash the organic extract with an aqueous solvent to produce an intermediate aqueous back extract and an organic raffinate containing 5-HMF and an organic solvent; - Optionally, step f) concentrates the organic raffinate obtained from step e) by removing at least a portion of the organic solvent, producing a concentrated organic raffinate containing 5-HMF and residual organic solvent, and producing a first stream containing organic solvent. - Step g) Purify the organic raffinate or the concentrated organic raffinate to produce a 5-HMF stream.

[0025] According to one or more embodiments, the method further includes a step of neutralizing the synthetic effluent from step a) prior to step b), preferably by contacting the synthetic effluent with an alkaline compound.

[0026] According to one or more embodiments, the mass concentration factor (corresponding to the mass ratio of synthetic effluent to concentrated synthetic effluent) in step b) is between 1.2 and 20, preferably between 1.5 and 20, more preferably between 1.5 and 15, and even more preferably between 2 and 10.

[0027] According to one or more embodiments, the synthesis effluent obtained from step a) contains a 5-HMF / polar aprotic synthesis solvent ratio between 5 / 95 and 40 / 60, and the concentrated synthesis effluent obtained from step b) contains a 5-HMF / polar synthesis solvent ratio between 30 / 70 and 70 / 30.

[0028] According to one or more embodiments, step b) includes evaporation or distillation to vaporize a portion of the polar aprotic synthesis solvent, at a temperature of 200°C or less, preferably 150°C or less, and more preferably 130°C or less, and at atmospheric pressure or vacuum, preferably at a pressure between 0.0001 MPa and 0.1000 MPa, and more preferably at a pressure between 0.0001 MPa and 0.0500 MPa under vacuum.

[0029] According to one or more embodiments, purification step g) is a water distillation step performed by distilling the organic raffinate obtained from step e) or the concentrated organic raffinate obtained from step f) in the presence of water to produce a 5-HMF stream as an aqueous solution of 5-HMF and a second stream containing an organic solvent. The water distillation is preferably carried out in a distillation column at atmospheric pressure or under vacuum, preferably at a pressure between 0.001 MPa and 0.1 MPa, and preferably under vacuum at a pressure between 0.005 MPa and 0.08 MPa, and at a 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, preferably less than or equal to 100°C.

[0030] According to one or more embodiments, purification step g) includes at least one step of crystallizing 5-HMF contained in the organic raffinate obtained from step e) or the concentrated organic raffinate obtained from step f), followed by filtration to produce a 5-HMF stream containing solid 5-HMF and a filtrate rich in organic solvent.

[0031] According to one or more embodiments, the method further includes step h) treating at least one water-polar aprotic synthesis solvent mixture generated in the method to produce at least one aqueous effluent that can be recycled in the method, the mixture comprising the aqueous raffinate obtained from step d).

[0032] According to one or more embodiments, the method further includes a liquid-solid separation step, preferably filtering the aqueous mixture generated in step c) or the intermediate liquid stream generated during the liquid-liquid extraction step d) or even the aqueous raffinate obtained from step d).

[0033] According to one or more embodiments, step f) of concentrating the organic raffinate obtained in step e) includes vaporizing the organic solvent at atmospheric pressure or under vacuum, preferably at a pressure between 0.01 MPa and 0.10 MPa and at a liquid temperature of less than or equal to 130°C, wherein the concentrated organic raffinate contains 30% or more of 5-HMF by weight and less than or equal to 60% by weight of residual organic solvent.

[0034] According to one or more embodiments, the hexose in the sugar raw material is fructose or a fructose glycoside unit.

[0035] According to one or more embodiments, the polar aprotic synthesis solvent is selected from pyridine, butanone, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methyl ethyl ketone, propionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, and γ-valerolactone, used alone or as a mixture, and preferably dimethyl sulfoxide.

[0036] According to one or more embodiments, the extraction solvent is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole, and toluene, with methyl isobutyl ketone being preferred.

[0037] According to one or more embodiments, in step c), the aqueous stream comprises all or part of the intermediate aqueous back-extract obtained from step e).

[0038] According to one or more embodiments, all or part of the aqueous effluent generated in step h) is used in step c) and / or step e) and / or step g).

[0039] Other objects and advantages of the invention will become apparent after reading the following description of specific embodiments thereof, which is given with reference to the accompanying drawings described below without any implied limitation.

[0040] Attached Figure Figure 1 An embodiment of the method according to the present invention is shown. Invention Details In the detailed description below, many specific details are disclosed to provide a deeper understanding of the method. However, it will be apparent to those skilled in the art that the method can be implemented without all of these specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0042] It should be noted that throughout this specification, the phrase "...to..." should be understood to include the boundary mentioned, unless otherwise stated.

[0043] In this specification, the term "comprising" is synonymous with "including" and "containing" (meaning the same as), and is inclusive or open-ended, not excluding other elements not specified. It should be understood that the verb "comprising" includes the exclusive and closed term "consisting of".

[0044] Furthermore, when used in this specification, the terms “basically”, “substantially”, or “approximately” for reference values ​​correspond to ±10%, preferably ±5%, very preferably ±2%, or even more preferably ±1% of the reference value, which may be temperature, pressure, distance, speed, flow rate, compound content, etc.

[0045] For the purposes of this invention, the various embodiments presented can be implemented individually or in combination with each other, and there are no restrictions on the combination where technically feasible.

[0046] For the purposes of this invention, various parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used individually or in combination. For example, for the purposes of this invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0047] In this specification, the term "aprotic solvent" refers to a molecule that acts as a solvent and in which all hydrogen atoms are carried by carbon atoms.

[0048] In this specification, the term "polar solvent" refers to a molecule that acts as a solvent and whose dipole moment µ, expressed in Debye form, has a value greater than or equal to 2.00 as measured at 25°C.

[0049] In this specification, the term "polar aprotic solvent" refers to a molecule that acts as a solvent, wherein all hydrogen atoms are carried by carbon atoms, and its dipole moment µ, expressed in Debye form, has a value greater than or equal to 2.00 as measured at 25 °C.

[0050] To better understand this invention, the following is mentioned: Figure 1 The reference numerals appearing in the accompanying drawings are used to indicate different elements of the method, but this does not constitute a limitation on the specific embodiments described below.

[0051] Step a) Dehydrate the sugar to 5-HMF The method according to the invention includes the step of dehydrating a sugar feedstock containing a hexose to 5-HMF by contacting it with a polar aprotic synthesis solvent and an acidic dehydration catalyst, so as to produce a synthesis effluent containing at least 5-HMF and a polar aprotic synthesis solvent.

[0052] The sugar raw material used in the method according to the invention comprises hexose.

[0053] The term "raw material containing hexoses" refers to the fact that hexoses can be in monomeric form (monosaccharides) or can be units belonging to disaccharides, oligosaccharides, or polysaccharides. Carbohydrates are compounds also known as sugars.

[0054] Preferably, the hexose is fructose or a fructose glycoside unit.

[0055] In one embodiment, the raw material comprises free fructose, alone or in mixture with any sugar species, or comprises any oligosaccharide or polysaccharide containing one or more fructoside units capable of releasing fructose via one or more hydrolysis steps, optionally in mixture with other sugar species. Preferably, the raw material processed in the method is crystalline fructose, a fructose-containing syrup, a syrup containing fructose and glucose, or crystalline sucrose or sucrose syrup.

[0056] Advantageously, the raw material contains fructose in monomeric, oligomeric, or polymeric form.

[0057] The term "raw material containing free fructose mixed with any sugar" refers to, for example, high-fructose corn syrup containing different proportions of fructose and glucose (e.g., glucose / fructose in mass or molar ratios of 58 / 42, 45 / 55, or 10 / 90).

[0058] The term "syrup" refers to a solution of sugar (especially sugars) in water with a concentration of at least 30% by weight, preferably at least 50% by weight, and more preferably at least 70% by weight.

[0059] The raw material may contain sugars containing one or more fructoside units and one or more non-fructoside units, wherein the fructose can be released via one or more hydrolysis steps, such as oligosaccharides and polysaccharides in which at least one monosaccharide unit is fructose, such as raw materials such as sucrose, fructotriose, fructan, oligofructose and inulin.

[0060] Advantageously, the sugar raw material is suitable for releasing monomeric fructose through glycoside hydrolysis, and the fructose product can be converted into 5-HMF.

[0061] Preferably, the oligosaccharide has the empirical formula: (C 6m H 10m+2 O 5m+1 ) (C 5n H 8n+2 O 4n+1 ), where m and n are integers, and their sum is between 2 and 6. The monosaccharide components of the oligosaccharide may be the same or different, and formula (C) 6m H 10m+2 O 5m+1 At least one unit of the polysaccharide is fructose. Further, the polysaccharide preferably has the empirical formula (C... 6m H 10m+2 O 5m+1 (C) 5n H 8n+2 O 4n+1 ), where m and n are integers, and their sum is greater than or equal to 7.

[0062] The polar aprotic synthesis solvent is advantageously selected from all polar aprotic solvents with a dipole moment greater than or equal to 2.00, denoted by Debye (D). Preferably, the polar aprotic solvent is selected from pyridine (2.37), butanone (5.22), acetone (2.86), acetic anhydride (2.82), N,N,N',N'-tetramethylurea (3.48), benzonitrile (4.05), acetonitrile (3.45), methyl ethyl ketone (2.76), propionitrile (3.57), hexamethylphosphoramide (5.55), nitrobenzene (4.02), nitromethane (3.57), N,N-dimethylformamide (3.87), N,N-dimethylacetamide (3.72), sulfolane (4.80), N-methylpyrrolidone (4.09) (denoted as NMP), dimethyl sulfoxide (3.90) (denoted as DMSO), propylene carbonate (4.94), and γ-valerol (4.71), alone or as a mixture.

[0063] Preferably, the polar aprotic solvent is advantageously selected from acetone, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, NMP, DMSO, propylene carbonate and γ-valerolactone, alone or in mixtures.

[0064] Preferably, the polar aprotic solvent is advantageously selected from N,N-dimethylacetamide, NMP, DMSO and γ-valerolactone, alone or in mixtures.

[0065] Very preferably, the polar aprotic solvent is DMSO.

[0066] The term "acidic dehydration catalyst" refers to any Brønsted acid catalyst selected from organic or inorganic, homogeneous or heterogeneous Brønsted acids that can induce sugar dehydration to 5-HMF.

[0067] Preferably, the acidic dehydration catalyst is a Brønsted acid in a polar aprotic synthesis solvent, preferably in DMSO, with a pKa between 0 and 5.0, more preferably between 0.5 and 4.0, and more preferably between 1.0 and 3.0. The pKa value is as defined in the article by FG ​​Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0068] Preferably, the acidic dehydration catalyst is selected from HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, and 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, acetopropionic acid, methanesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, p-toluenesulfonic acid, 4-biphenylsulfonic acid, diphenyl phosphate and 1,1'-binaphthyl-2,2'-dimethylhydrogen phosphate. Preferably, the acidic dehydration catalyst is selected from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0069] The dehydration step is carried out at a temperature between 30°C and 200°C, preferably between 50°C and 180°C, more preferably between 70°C and 150°C, and more preferably between 90°C and 130°C, for example, at 120°C. The dehydration step is carried out at a pressure 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. Depending on the pressure and temperature conditions, the reaction medium may be above or below the bubble point of the mixture. The term "bubble point" refers to the pressure and temperature conditions at which the first bubble appears in the liquid. When the reaction medium is above the bubble point of the mixture, the gas phase can be removed from the reactor, optionally distilled, and condensed to form a condensate, which can be sent to step h) of processing the water-polar aprotic synthetic solvent mixture.

[0070] Preferably, the acidic dehydration catalyst is introduced into the dehydration step at a molar ratio (expressed as acid / sugar, in molar percentages (mol%)) of 0.01 to 10 mol%, more preferably 0.05 to 8 mol%, more preferably 0.1 to 6 mol%, more preferably 0.2 to 5 mol%, more preferably 0.3 to 4 mol%, and very preferably 0.5 to 3 mol% relative to the sugar feedstock.

[0071] The dehydration step can be carried out according to different implementation schemes. Therefore, it can advantageously be carried out in a batch mode or continuously. The addition of sugar feedstock can be gradual (batch feeding) in the batch process, or staged in different CSTR reactors (continuous stirred tank reactors) in series in the continuous process. The method can be carried out in a closed reaction chamber or in a semi-open reactor.

[0072] Preferably, the sugar feed and aprotic synthesis solvent are introduced in step a) at a total mass ratio of feed to aprotic synthesis solvent (e.g., MDSO) between 5 / 95 and 40 / 60, preferably between 10 / 90 and 30 / 70 (e.g., including all streams fed to step a).

[0073] The synthetic effluent 2 obtained at the end of the optional dehydration step contains 5-HMF and a polar aprotic synthetic solvent, preferably DMSO.

[0074] The polar aprotic synthesis solvent, typically DMSO, comprises approximately 30% to 95% by weight, preferably 40% to 90% by weight, more preferably 50% to 90% by weight, and most preferably 55% to 85% by weight, of the synthesis effluent 2 from the dehydration step and fed to step b) of the method according to the invention.

[0075] 5-HMF comprises at least 1% by weight of the synthetic effluent 2 from the dehydration step a) and fed to step b) of the method according to the invention, preferably at least 10% by weight of the synthetic effluent 2 from the dehydration step a), preferably at least 15% by weight and preferably no more than 50% by weight, preferably no more than 40% by weight, preferably no more than 30% by weight.

[0076] Furthermore, even before mixing with the aqueous stream 5 in step c), the synthetic effluent 2 obtained from the dehydration step may contain water. This water may originate from the dehydration step: for example, water is formed during the sugar dehydration reaction to 5-HMF (3 moles of water are generated for every mole of 5-HMF produced). Water may also be introduced along with the sugar if a syrup (e.g., approximately 70% by weight in water) is used for practical reasons. Advantageously, during the dehydration step, the water-polar aprotic synthesis solvent (e.g., DMSO) mixture can be recovered in the gas phase. The water-polar aprotic synthesis solvent (e.g., DMSO) mixture can advantageously be sent to step h) for processing the water-polar aprotic synthesis solvent mixture. Thus, the synthetic effluent 2 obtained from dehydration step a) and introduced into step b) for concentrating 5-HMF may contain water, typically in a proportion between 0.1% by weight and 30% by weight, preferably between 0.1% by weight and 15% by weight, and more preferably between 0.1% by weight and 10% by weight.

[0077] During the dehydration step, it is advantageous to simultaneously extract water from the reaction medium to reduce its content and thereby improve the selectivity of the reaction. The term "selectivity for 5-HMF" refers to the ratio between the number of moles of 5-HMF produced and the number of moles of fructose converted in the sugar feedstock introduced into the method. In polar aprotic media, the presence of water reduces the selectivity of sugar conversion, and this is more pronounced the higher the sugar concentration in DMSO. Such continuous water extraction in the synthesis of 5-HMF is therefore advantageous in this respect and also allows for management in a single step of extracting water that may be present in the sugar feedstock (if it is in syrup form). In such water extraction from the reaction medium, the reaction medium is above the bubble point of the mixture. The vapor phase can be removed from the reactor, distilled, and condensed to form a water condensate containing less than 10% by weight, preferably less than 5% by weight, or even less than 1% by weight of the polar aprotic synthesis solvent. The extracted water may originate from dehydration and / or, in the case of using a syrup feedstock for practical reasons, may have already been introduced with the sugar feedstock. Advantageously, at least 50% by weight, preferably at least 80% by weight, or even 90% by weight, of the water present in the reaction medium is extracted. The water extracted from the reaction medium may account for at least 50% by weight, preferably at least 80% by weight, or even 90% by weight of the water produced during the dehydration process. Water extraction can be carried out by various methods, such as evaporation, adsorption (e.g., in molecular sieves), membrane separation, or permeation, and is advantageously carried out by distillation, requiring that the polar aprotic synthetic solvent is less volatile than water. Advantageously, water extraction is carried out under conditions that allow at least 90% by weight, preferably at least 95% by weight, or even 99% by weight of the polar aprotic synthetic solvent used in the dehydration step to be recovered from the synthetic effluent 2 obtained at the end of the dehydration step. The water thus extracted can be recycled to one or more steps of the method that require the supply of an aqueous stream, as in the case of the aqueous effluent 20 obtained from step h) of the water-polar aprotic synthesis solvent mixture, or mixed with the recyclable aqueous effluent 20, or sent to step h) for treatment and removal of any polar aprotic synthesis solvent that it may still contain, in order to produce, in particular, the recyclable aqueous effluent 20.

[0078] When the sugar raw material is in syrup form, it is advantageous to reduce the water content upstream of the sugar raw material dehydration step, optionally by extracting water from the dehydration reaction during the dehydration step, as described above and not repeated here. Thus, the water in the syrup form of the sugar raw material can be extracted and replaced with a polar aprotic synthetic solvent (e.g., DMSO) to produce a mixture sent to the dehydration step. Water from the syrup can be at least partially extracted after mixing the syrup with the polar aprotic synthetic solvent. The solvent allows the sugar to be held in a dilution medium, and dilution with the synthetic solvent is used instead of dilution with water. Water extraction can be carried out by various methods, such as evaporation, adsorption (e.g., in a molecular sieve), or membrane separation, and advantageously by distillation, requiring the polar aprotic synthetic solvent to be less volatile than water. Advantageously, the extracted water accounts for at least 50% by weight of the water present in the syrup, preferably at least 80% by weight or even at least 90% by weight. The extracted water can account for 90% to 99% by weight of the water in the syrup. Advantageously, the extracted water contains less than 10% by weight, preferably less than 5% by weight, or even less than 1% by weight of synthetic solvent. The water thus extracted can be recycled to one or more steps of the method that require the supply of an aqueous stream, as in the case of the aqueous effluent 20 obtained from step h) of treating the water-polar aprotic synthetic solvent mixture, or mixed with the recyclable aqueous effluent 20, or sent to step h) for treatment and removal of any polar aprotic synthetic solvent that it may still contain, in order to produce, in particular, the recyclable aqueous effluent 20.

[0079] The synthesis effluent 2 from the dehydration step and introduced into step b)1 may also contain impurities, particularly black matter. The term "black matter" refers to all undesirable polymeric compounds formed during the synthesis of 5-HMF. In particular, black matter accounts for less than 30% by weight of the converted sugar feedstock, preferably less than 20% by weight.

[0080] During the dehydration step a), the conversion rate of sugar (e.g., fructose) is at least 80%, preferably at least 90%, and even more preferably at least 98%.

[0081] The term "conversion rate" refers to the ratio between the sugar consumed during the reaction (the difference between the total sugar used and the residual sugar at the end of the reaction) and the total sugar used in the reaction.

[0082] The selectivity of sugar to 5-HMF is defined as the molar ratio of the number of moles of 5-HMF produced to the number of moles of sugar consumed in the reaction.

[0083] Finally, the molar yield of 5-HMF is defined as the molar ratio of the number of moles of 5-HMF produced by the reaction to the number of moles of sugar used in the reaction. The molar yield is thus the product of conversion and selectivity.

[0084] The molar yield of 5-HMF is at least 70%, preferably at least 80%.

[0085] An optional neutralization step can be performed upstream of step b) of the 5-HMF concentration step on the synthetic effluent 2 from the dehydration step a), said synthetic effluent 2 containing an acidic dehydration catalyst. This allows for a reduction in the reactivity of the medium, thereby preventing 5-HMF degradation mechanisms or reducing corrosion of equipment materials downstream of the dehydration step. Since the dehydration reaction can produce certain organic acids, the amount of neutralizing agent can advantageously be such that all acids present in the synthetic effluent 2 from the dehydration step can be neutralized. Such a neutralization step is advantageously carried out at a minimum stoichiometric ratio to the amount of catalyst used, and typically at a slightly overstoichiometric ratio relative to the amount of catalyst used, preferably between 1 and 2 times the stoichiometric ratio, more preferably between 1 and 1.5 times the stoichiometric ratio. The neutralizing agent can be a basic compound selected from NaOH, KOH, NH4OH, Na2CO3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, and Ba(OH)2.

[0086] Step b) 5-HMF Concentration According to one basic aspect, the method of the present invention includes step b) concentrating 5-HMF from the synthetic effluent 2 from step a), wherein the synthetic effluent 2 is optionally neutralized by contacting it with the aforementioned basic compound to obtain concentrated synthetic effluent 3.

[0087] Step b) Concentration is performed on the synthetic effluent 2 obtained at the end of step a) to achieve the maximum sugar conversion rate, preferably at least 80%, preferably at least 90%, and even more preferably at least 98% of the sugar (e.g., fructose) conversion rate.

[0088] Advantageously, step b) 5-HMF concentration includes an evaporation or distillation step, which allows for the evaporation of a portion of the synthetic solvent, thereby taking advantage of the fact that 5-HMF has a high boiling point (>280°C).

[0089] Due to the thermal stability of 5-HMF and its associated residual sugars and 5-HMF byproducts, the temperature during the evaporation or distillation process must be limited in this concentration step b). Therefore, step b) of 5-HMF concentration (which involves removing a portion of the synthesis solvent, such as DMSO, by vaporization) is carried out at a temperature less than or equal to 200°C, preferably less than or equal to 150°C, and more preferably less than or equal to 130°C. The thermal stability of the polar aprotic synthesis solvent also limits the temperature of this step. Preferably, when DMSO is used as the polar aprotic synthesis solvent, the temperature is less than or equal to 150°C and preferably less than or equal to 130°C. Advantageously, the operating temperature in step b) is greater than or equal to 70°C.

[0090] The operating pressure depends on the properties of the substances (5-HMF and the polar aprotic synthesis solvent). The pressure level, especially the vacuum level, applied to achieve these temperature values ​​depends, of course, on the synthesis solvent and the degree of vaporization of the synthesis solvent.

[0091] Step b) is advantageously carried out at atmospheric pressure or under vacuum to limit the temperature of the liquid and thereby limit the degradation of 5-HMF and the polar aprotic synthesis solvent, preferably at a pressure between 0.0001 MPa and 0.1000 MPa (absolute pressure), preferably under vacuum at a pressure between 0.0001 MPa and 0.0500 MPa (absolute pressure), more preferably between 0.0001 MPa and 0.0200 MPa (absolute pressure), even more preferably between 0.0001 MPa and 0.0100 MPa (absolute pressure), and even more preferably between 0.0001 MPa and 0.0050 MPa (absolute pressure).

[0092] The concentrated synthesis effluent 3 has a higher 5-HMF content than the synthesis effluent 3 from step a), and thus includes less polar aprotic synthesis solvent than the synthesis effluent from step a). Advantageously, the concentrated synthesis effluent 3 produced in step b) contains no more than 70% by weight of polar aprotic synthesis solvent, preferably no more than 60% by weight and even more preferably no more than 50% by weight, and preferably at least 10% by weight and more preferably at least 20% by weight of polar aprotic synthesis solvent.

[0093] Advantageously, the concentration of the synthesis solvent at the end of step b) is determined to prevent 5-HMF from degrading at the selected operating temperature. Specifically, it is known that 5-HMF becomes increasingly thermally unstable the more concentrated it is and the longer its residence time under high-temperature conditions.

[0094] Preferably, in step b), the concentration of 5-HMF from the synthetic effluent 2 from step a) is achieved by removing a portion of the synthetic solvent (e.g., DMSO), said removal being carried out by vaporization (e.g., in a distillation column at atmospheric pressure or under vacuum, in an evaporator) or by any method known to those skilled in the art.

[0095] Step b) can be performed using a simple evaporator or distillation column, which allows for the distillation of the gas phase and improves the separation between the synthesis solvent and 5-HMF.

[0096] Given the temperature sensitivity of the products, it may be necessary to use evaporation or distillation techniques with short residence times, such as wiped-film evaporators or short-path distillation.

[0097] Depending on the target concentration factor, step b) can be carried out in several consecutive steps: several consecutive vaporization operations of the polar aprotic synthesis solvent can be performed under the conditions given above and using one or more of the devices mentioned.

[0098] In a preferred embodiment, solvent vaporization is performed by multi-effect evaporation, mechanical vapor recompression, or any other method known to those skilled in the art to reduce operating costs associated with solvent evaporation while limiting the risk of degradation of the target product (i.e., 5-HMF). For example, in the case of a triple-effect evaporator, the liquid temperature is maintained below 200°C in the first effect, below 150°C in the second effect, and below 130°C in the third effect. Thus, as 5-HMF is concentrated in the solvent, the temperature of the liquid phase decreases, limiting any risk of degradation.

[0099] The mass concentration factor in step b) corresponds to the ratio between the amount (by mass) of synthetic effluent 2 entering the concentration step b) and the amount (by mass) of the concentrated synthetic effluent 3 generated at the end of step b) and sent to step c), i.e., the ratio between the mass of effluent 2 from step a) and the mass of stream 3. This factor depends largely on the dilution selected in the dehydration step a) and the target concentration of 5-HMF in step b).

[0100] Preferably, the concentration factor is between 1.2 and 20, more preferably between 1.5 and 20, more preferably between 1.5 and 15, and even more preferably between 2 and 10.

[0101] Advantageously, the synthesis effluent 2 from step a), after possible neutralization and sent to step b), contains a 5-HMF / polar aprotic synthesis solvent ratio between 5 / 95 and 40 / 60, and the concentrated synthesis effluent 3 from step b) contains a 5-HMF / polar synthesis solvent ratio between 30 / 70 and 70 / 30.

[0102] Step b) also produces a stream 3' containing the synthetic solvent, as well as optionally water and a small amount of 5-HMF. The stream 3' containing the organic solvent can advantageously be recycled in liquid form to step h) for treating the water / synthetic solvent mixture, or, if the synthetic solvent is more volatile than water, directly to the dehydration step a) (recycling to step a) is not shown). Figure 1 middle).

[0103] Step b) of concentrating 5-HMF in the synthetic effluent allows for the decoupling of two steps: step a) sugar dehydration to 5-HMF and step d) liquid-liquid extraction, and in particular decoupling from the constraints associated with obtaining a good yield of 5-HMF in step a) the amount of synthetic solvent used (significant dilution of the sugar feedstock in the synthetic solvent is necessary), but the amount of synthetic solvent conflicts with the liquid extraction process in step d), particularly regarding the amount of extraction solvent used, the water involved in backwashing associated with liquid-liquid extraction, the size of the equipment used for liquid-liquid extraction, downstream steps for removing the extraction solvent, etc.

[0104] Specifically, particularly by means of step b) integrated into the method according to the invention, it is possible to: - For example, an improved 5-HMF yield can be obtained through potentially higher dilution in the synthesis solvent during step a), such dilution favoring 5-HMF selectivity during the dehydration process in step a), especially for kinetic reasons, and / or - Simplify liquid-liquid extraction steps, for example: - Reducing the number of extraction stages by using the same amount of extraction solvent means lower investment costs for liquid-liquid extraction columns, and / or - By reducing the amount of extraction solvent for a given amount of 5-HMF to be extracted, it is possible to reduce the energy and investment costs and operating costs required for regenerating the extraction solvent, thereby reducing process costs.

[0105] Step c) Mixing The method according to the invention includes step c), which involves contacting (or mixing) a concentrated synthetic effluent 3 from step b), comprising 5-HMF and a polar aprotic synthetic solvent (e.g., DMSO), with an aqueous stream 5 to obtain at least one aqueous mixture 6.

[0106] The aqueous stream 5 may consist of pure water from outside the method and / or recycled process water; for example, the aqueous stream 5 may advantageously include all or part of the intermediate aqueous back-extractant 11 from step e) and / or the water 20 generated in the water-polar aprotic synthesis solvent mixture in step h).

[0107] Preferably, 5-HMF accounts for at least 20% by weight, more preferably at least 30% by weight, more preferably at least 40% by weight and more preferably no more than 80% by weight, more preferably no more than 60% by weight, and more preferably no more than 50% by weight of the concentrated synthetic effluent 3 introduced in step c) of the method according to the invention.

[0108] Preferably, the polar aprotic synthesis solvent (e.g., DMSO) accounts for 10% to 70% by weight, more preferably 10% to 60% by weight, more preferably 10% to 50% by weight, and more preferably 20% to 50% by weight of the concentrated synthesis effluent 3 introduced in step c).

[0109] Aqueous stream 5 contains water and may consist of water. When aqueous stream 5 contains a recycled process water component, the component may contain at least 60% by weight of water, preferably at least 70% by weight, more preferably at least 80% by weight, and even more preferably at least 95% by weight or even 98% by weight of water. Aqueous stream 5 may contain all or part of the intermediate aqueous back-extract 11 obtained from step e). The intermediate aqueous back-extract 11 contains water, a polar aprotic synthesis solvent (e.g., DMSO), and optionally 5-HMF. Advantageously, the intermediate aqueous back-extract 11 contains more than 60% by weight of water, preferably more than 70% by weight, and more preferably more than 80% by weight.

[0110] Advantageously, the aqueous mixture 6 obtained at the end of step c) contains between 10% and 90% by weight of water, preferably between 20% and 70% by weight, and more preferably between 30% and 50% by weight of water.

[0111] Preferably, step c) is carried out at a temperature between 0°C and 60°C, more preferably between 5°C and 40°C, and usually at ambient temperature, i.e., between 10°C and 40°C.

[0112] By increasing the water content of the concentrated synthetic effluent 3 during step c), a portion of the black matter present in the concentrated synthetic effluent 3 can precipitate. The mixture resulting from the contact of the concentrated synthetic effluent 3 with the aqueous stream 5 can thus advantageously undergo a liquid-solid separation step before being fed to step d) of liquid-liquid extraction to obtain a liquid separated from suspended solid particles and a solid residue containing the black matter, which is preferably removed from the method in the form of solid stream 4. Such an optional liquid-solid separation step thus makes it possible to remove the "black matter" that has already precipitated in step c) or upstream. Subsequently, at least a portion of the obtained liquid is advantageously fed to the liquid-liquid extraction step d), and the portion or preferably all of the liquid fed to step d) corresponds to the aqueous mixture 6. Such a liquid-solid separation step in step c) can be advantageously performed when the amount of black matter precipitated in the mixture formed by the concentrated synthetic effluent 3 and the aqueous stream 5 in step c) is, for example, greater than 1% by weight.

[0113] The precipitate can be quantified in various ways known to those skilled in the art, such as by size exclusion chromatography. Optional liquid-solid separation operations, such as filtration, can remove the precipitated precipitate.

[0114] The optional liquid-solid separation step is preferably carried out at a temperature between 0°C and 60°C, more preferably between 5°C and 40°C, and typically at room temperature (i.e., between 10°C and 40°C). The optional liquid-solid separation step preceding step d) is a simple solid-liquid separation and can be carried out by any method known to those skilled in the art, such as using a filter press, belt filter, clarifier, decanter, or centrifuge, e.g., a disc centrifuge, said techniques used alone or in any combination in any order. Preferably, the liquid-solid separation step is filtration, preferably carried out using a filter press.

[0115] Step d) Liquid-liquid extraction The method according to the invention includes step d) liquid-liquid extraction in the presence of extraction solvent 7 of the aqueous mixture 6 obtained at the end of step c) to produce an aqueous raffinate 8 and an organic extract 9.

[0116] The liquid-liquid extraction performed in step d) advantageously corresponds to washing the aqueous mixture 6 with the organic extraction solvent 7. Preferably, the liquid-liquid extraction performed in step d) is a countercurrent extraction of the aqueous mixture 6 obtained in step c) with the extraction solvent 7. This technique is well known to those skilled in the art. It can be carried out, for example, in an array of mixers and settlers, in a column filled with random or structured packing, in a pulse column, or in a stirred column.

[0117] Liquid-liquid extraction may involve the use of at least two theoretical separation stages. This is, for example, but not exclusively, when a liquid-solid separation step is performed on the intermediate liquid stream produced during liquid-liquid extraction step d), which can be returned to step d) once the solid particles are removed. A first liquid-liquid separation stage can then be performed, producing the intermediate liquid stream sent to the liquid-solid separation step to remove any precipitated black matter present during the liquid-liquid extraction, and forming a particle-poor intermediate liquid stream sent to the second liquid-liquid extraction stage of step d).

[0118] The liquid-liquid extraction step d) is advantageously carried out at a temperature between 0°C and 60°C, preferably between 5°C and 40°C, and usually at room temperature (i.e., between 10°C and 40°C).

[0119] Typically, the extraction solvent content (defined as the mass ratio between the extraction solvent flow rate and the feed entering the extraction step) comes from the number of separation stages involved, the selection of the extraction solvent, and the 5-HMF recovery target (defined as the ratio between the amount of 5-HMF carried in the organic extract 9 and the amount of 5-HMF contained in the aqueous mixture 6 sent to extraction step d).

[0120] The target recovery rate is preferably between 80% and 100%, more preferably between 90% and 99.9%, and even more preferably between 95% and 99.9%.

[0121] The extraction solvent 7 introduced in step d) is selected from an organic solvent that is immiscible with water, so as to form two liquid phases in step d) and in the backwashing step e). This property is highly dependent on the relative flow rates of the feedstock, back-extraction water, and extraction solvent used in the method.

[0122] In a non-limiting manner, 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 to 10 carbon atoms (hereinafter referred to as C1-C10), an ether containing 2 to 10 carbon atoms (C2-C10), an ester containing 4 to 10 carbon atoms (C4-C10), a ketone containing 3 to 10 carbon atoms (C3-C10), an aldehyde containing 1 to 10 carbon atoms (C1-C10), 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. Very preferably, the extraction solvent is methyl isobutyl ketone.

[0123] Advantageously, the extraction solvent is selected to have a very high volatility difference with 5-HMF, in particular to promote its removal in optional step f) and limit the degradation of 5-HMF, i.e., to have a degree of vaporization in step f) that does not degrade 5-HMF and minimizes the amount of residual solvent to be removed in step g), while ensuring that no liquid phase separation occurs in the case of purification step g) which includes water distillation when the organic raffinate 12 or concentrated organic raffinate 13 is contacted with water in step g).

[0124] If step g) includes water distillation, an extraction solvent may be selected to form a heterogeneous azeotrope with water in step g), preferably rich in solvent, i.e., containing more than 50% by weight, more than 60% by weight, and more than 70% by weight. Advantageously, the azeotrope of the water / extraction solvent mixture has a boiling temperature significantly lower than that of water, preferably at least 5°C lower, more preferably at least 8°C lower, and more preferably at least 10°C lower.

[0125] Advantageously, the organic solvent stream (extraction solvent) generated in subsequent steps can be recycled as an extraction solvent to extraction step d). These extraction solvent streams may contain impurities that may be generated during the implementation of the method. Advantageously, the extraction solvent streams generated in subsequent steps can be distilled, for example, periodically, to prevent the accumulation of said impurities.

[0126] Step d) thus produces, on the one hand, a 5-HMF-depleted aqueous stream, referred to as aqueous raffinate 8, containing a majority of the polar aprotic synthesis solvent (e.g., DMSO) initially contained in the concentrated synthesis effluent 3, and on the other hand, a 5-HMF-rich organic stream, referred to as organic extract 9, containing a majority of the 5-HMF initially contained in the concentrated synthesis effluent 3 and extraction solvent 7. Organic extract 9 may also contain a polar aprotic synthesis solvent (e.g., DMSO). Preferably, organic extract 9 contains 5-HMF and polar aprotic synthesis solvent (e.g., DMSO) at a weight ratio of 5-HMF to polar aprotic synthesis solvent (e.g., DMSO) between 50 / 50 and 99 / 01, more preferably between 50 / 50 and 95 / 05, more preferably between 55 / 45 and 90 / 10, more preferably between 60 / 40 and 85 / 15, and more preferably between 65 / 35 and 85 / 15.

[0127] Advantageously, the organic extract 9 is sent directly to the backwashing step e).

[0128] Some of the solid particles formed by the precipitated putrefactive matter may also be present in step d). These may be putrefactive matter precipitated in the upstream mixing step c), still present in the aqueous mixture 6 sent to step d), or putrefactive matter precipitated in step d) or in the backwashing step e).

[0129] Backwashing step e) The method according to the invention includes step e) backwashing the organic extract 9 with an aqueous solvent 10 to produce an intermediate aqueous backextract 11 and an organic raffinate 12 comprising 5-HMF and an organic solvent. The intermediate aqueous backextract 11 is advantageously sent, in whole or in part, to step c). The organic solvent is particularly composed at least in part of the extraction solvent and may optionally contain a polar aprotic synthesis solvent (e.g., DMSO), preferably in small amounts.

[0130] The introduction of aqueous solvent 10 in step e) for backwashing is performed in accordance with the general knowledge of those skilled in the art. The introduction of aqueous solvent 10 is made to ensure that the amount of aqueous solvent is as low as possible to reduce costs, but sufficient to ensure a low weight content of the polar aprotic synthesis solvent (e.g., DMSO) in the organic raffinate 12, preferably less than or equal to 20.0% by weight relative to 5-HMF, preferably less than or equal to 10.0% by weight relative to 5-HMF, preferably less than or equal to 2.0% by weight relative to 5-HMF, and very preferably less than or equal to 1.0% by weight relative to 5-HMF.

[0131] Advantageously, the aqueous backwash solvent 10 introduced in step e) comprises at least 95% by weight water, preferably at least 98% by weight water (100% is the maximum). The aqueous solvent may optionally comprise a polar aprotic synthesis solvent (e.g., DMSO). Higher backwash efficiency is achieved when the amount of polar aprotic synthesis solvent (e.g., DMSO) present in the aqueous backwash solvent is low. The aqueous solvent may comprise no more than 1.0% by weight, and preferably no more than 0.1% by weight of polar aprotic synthesis solvent (e.g., DMSO). Advantageously, the aqueous backwash solvent 10 is obtained from the water-polar aprotic synthesis solvent mixture generated in the method during step h), and thereby comprises at least a portion of the recyclable effluent 20. In a preferred embodiment of the invention, the aqueous raffinate 8, consisting of water and a polar aprotic synthesis solvent (e.g., DMSO), generated in step d) is treated in step h), which advantageously includes distillation. The water-rich distillate (also known as aqueous effluent 20) thus obtained at the end of step h) can be recycled in the method and advantageously used to form the aqueous backwash solvent 10 in step e), possibly in the form of a mixture with supplemental water, or possibly together with at least one intermediate aqueous back-extractant portion 11 and / or supplemental water in mixing step c) to form the aqueous stream 5. The recyclable effluent 20, such as the water-rich distillate, may also contain a residual amount of a polar aprotic synthetic solvent (e.g., DMSO), preferably less than or equal to 1% by weight and preferably less than or equal to 0.1% by weight. When distillation in step h) is carried out efficiently, the residual amount of polar aprotic synthetic solvent (e.g., DMSO) in the aqueous effluent 20 (distillate) is reduced proportionally, particularly at distillation stages exceeding 5 and advantageously at suitable reboiling and reflux ratios.

[0132] Backwashing step e) is advantageously a liquid-liquid extraction of the organic stream flowing countercurrently with aqueous solvent 10, particularly the organic extract 9 obtained in step d). 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 packed with random or structured packing, in a pulse column, or in a stirred column.

[0133] Step e) is preferably carried out at a temperature between 0°C and 60°C, more preferably between 5°C and 40°C, and usually at room temperature (i.e., between 10°C and 40°C).

[0134] The weight ratio (weight / weight) of the aqueous solvent 10 to the organic extract 9 is preferably between 0.04 and 5, more preferably between 0.07 and 3, and more preferably between 0.1 and 1.

[0135] Step e) produces an aqueous stream advantageously rich in a polar aprotic synthesis solvent (e.g., DMSO), referred to as intermediate aqueous back-extract 11, which preferably contains at least 60% by weight of water, more preferably at least 80% by weight of water, and organic raffinate 12 (advantageously depleted of the polar aprotic synthesis solvent (e.g., DMSO)). The intermediate aqueous back-extract 11 is advantageously sent partially or preferably entirely to step c).

[0136] According to the present invention, the organic raffinate 12 generated in step e) is sent to an optional concentration step f) or directly to a purification step g).

[0137] Black matter may still be present in the organic extract 9 sent to backwash step e). If the black matter precipitates in this step to form undesirable solid particles, these can be removed in the liquid-solid separation step by sending all or part of the intermediate aqueous back-extract 11, including the precipitated black matter, to step d). The intermediate aqueous back-extract 11 can be sent to the liquid-solid separation step along with the intermediate liquid stream generated in step d) and / or downstream of step d) with the aqueous raffinate 8. If the intermediate aqueous back-extract 11 is sent partially or entirely to step c) to enter the composition or constitute the aqueous stream 5, the precipitated black matter can also be separated in the optional liquid-solid separation process of step c).

[0138] Optional step f) Concentration after liquid-liquid extraction The method according to the invention preferably includes step f) concentrating the organic raffinate 12 obtained from step e) by removing a portion of the organic solvent, producing a concentrated organic raffinate 13 containing 5-HMF and residual organic solvent, and a first stream 14 containing organic solvent, preferably composed of organic solvent, which advantageously consists entirely or partially of an extraction solvent and an optional polar aprotic synthesis solvent (e.g., DMSO).

[0139] Preferably, all or part of the first stream 14 containing the organic solvent is recycled to the extraction step d), for example, to form at least a portion of the organic solvent stream 7.

[0140] Preferably, in step f), a portion of the organic solvent is removed by vaporization (e.g., in a distillation column at atmospheric pressure or under vacuum, in an evaporator) or by any method known to those skilled in the art.

[0141] According to this preferred embodiment, the vaporization of the organic solvent is advantageously carried out at atmospheric pressure or under vacuum, preferably at a pressure between 0.01 MPa and 0.1 MPa, and more preferably under vacuum at a pressure between 0.01 MPa and 0.09 MPa, to limit the temperature of the liquid and thereby prevent 5-HMF degradation. Preferably, the temperature of the liquid is maintained below or equal to 130°C, more preferably below or equal to 100°C, and more preferably below or equal to 70°C. The pressure level, especially the vacuum level, applied to achieve these temperatures depends, of course, on the organic solvent, and more particularly on the extraction solvent used and the degree of vaporization of the organic solvent.

[0142] In a preferred embodiment, solvent vaporization is performed via multi-effect evaporation, mechanical vapor recompression, or any other method known to those skilled in the art to reduce operating costs associated with solvent evaporation while limiting the risk of degradation of the target product (i.e., 5-HMF). For example, in the case of a triple-effect evaporator, the liquid temperature is maintained below 130°C in the first effect, below 100°C in the second effect, and below 70°C in the third effect. Thus, as 5-HMF is concentrated in the organic solvent, the temperature of the liquid phase gradually decreases, limiting any risk of degradation.

[0143] Optionally, step f) is performed with a mass vaporization degree (or evaporation degree) of at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 75%, preferably at least 80%, and preferably up to 99%, which corresponds to the mass of the vaporized organic solvent relative to the mass of the organic raffinate 12 obtained from step e) (more particularly, the mass of the stream 14 relative to the mass of the organic raffinate 12). Advantageously, the vaporization degree is defined as a function of the extraction solvent, thereby preventing the degradation of 5-HMF and minimizing the amount of residual solvent to be removed in step g), while ensuring that no liquid phase separation occurs if water distillation is performed in step g) (i.e., while ensuring that the liquid phase remains a single phase).

[0144] Due to the combination of all operating conditions in steps a), b), c), d), e), and optional step f), the concentrated organic raffinate 13 obtained at the end of step f) advantageously has a 5-HMF content of at least 30% by weight, preferably at least 40% by weight, preferably at least 50% by weight, and preferably no more than 95% by weight, preferably no more than 90% by weight, and preferably no more than 85% by weight, relative to the weight of the concentrated organic raffinate. In other words, the concentrated organic raffinate 13 preferably has a residual organic solvent content of at least 5% by weight, preferably at least 10% by weight, and preferably no more than 60% by weight, preferably no more than 50% by weight, and preferably no more than 40% by weight, relative to the weight of the concentrated organic raffinate 13.

[0145] Advantageously, in optional step f), the vaporized organic solvent forms a first stream 14 containing organic solvent, preferably composed of organic solvent, and is preferably recycled to extraction step d).

[0146] Advantageously, the concentrated organic raffinate 13 is sent to the purification step g).

[0147] Purification step g) The method according to the invention includes step g) purifying organic raffinate 12 or concentrated organic raffinate 13 to produce a 5-HMF stream.

[0148] According to one or more embodiments, purification step g) includes and may consist of a water distillation step, which is carried out by distilling the organic raffinate 12 obtained from step e) or the concentrated organic raffinate 13 obtained from optional step f) in the presence of water 17 to produce the 5-HMF stream, which is thereby an aqueous solution 15 of 5-HMF and generates a second stream 16 containing an organic solvent and preferably composed of an organic solvent.

[0149] The water distillation step advantageously allows for the removal of at least a portion of the residual organic solvent that was not removed in optional step f). The residual organic solvent removed in the water distillation step, i.e., the second stream 16 containing the organic solvent, can advantageously be recycled to the extraction step d, either alone or in combination with the first stream 14 obtained from optional step f).

[0150] Advantageously, the aqueous liquid 17 is fed into the water distillation step. The aqueous liquid 17 introduced into the water distillation step preferably contains more than 95% by weight of water, more preferably more than 98% by weight of water.

[0151] In a particular embodiment of the invention, the aqueous liquid 17 is pure water, possibly outside the method, which makes it possible to further reduce the residual content of polar aprotic synthesis solvents (e.g., DMSO) in the aqueous solution 15 of 5-HMF produced in step g) which includes water distillation or is composed of water distillation.

[0152] In another specific embodiment of the invention, the water separated in the process is used as feed to the water distillation step, thereby limiting the operating costs of the method and its environmental impact. Typically, if the sugar feedstock for the dehydration step is a syrup with a water concentration of 70% by weight, approximately 1 ton of water (water from the sugar feedstock and water generated during the dehydration reaction) is obtained per ton of 5-HMF produced at the end of the dehydration step. This advantageously recovered water requires treatment before being discharged into the environment. The method according to the invention can then advantageously utilize the water from the sugar feedstock and / or the dehydration step to produce, at the end of the water distillation step, an aqueous solution of 5-HMF preferably concentrated to 30% by weight or higher, preferably concentrated to 40% by weight or higher, thereby reducing the reprocessing costs of the method and its environmental impact.

[0153] Advantageously, the aqueous liquid 17 introduced in the water distillation step may correspond to at least a portion, or possibly all, of the aqueous effluent 20 (distillate) produced in step h). The distillate may optionally contain a residual amount of a polar aprotic synthesis solvent (e.g., DMSO).

[0154] Advantageously, during the water distillation step, the extraction solvent used in the method forms a heterogeneous azeotrope with water. This azeotrope is preferably rich in the extraction solvent, preferably containing more than 50% by weight, more than 60% by weight, and more than 70% by weight. Advantageously, the water / extraction solvent azeotrope has a boiling temperature significantly lower than that of water, preferably at least 5°C lower, more preferably at least 8°C lower, and more preferably at least 10°C lower.

[0155] Therefore, after contacting the concentrated organic raffinate 13 or organic raffinate 12 with the aqueous liquid 17, the residual organic solvent can be easily removed without degrading 5-HMF.

[0156] The water distillation step can be carried out at atmospheric pressure or under vacuum, particularly at a pressure between 0.001 MPa and 0.1 MPa, preferably under vacuum at a pressure between 0.005 MPa and 0.08 MPa. Advantageously, the water distillation step is carried out under vacuum, particularly at a pressure between 0.001 MPa and 0.1 MPa, preferably between 0.005 MPa and 0.08 MPa, in order to remove residual organic solvents without degrading 5-HMF.

[0157] Advantageously, the water distillation step is carried out in a distillation column, preferably at a bottom temperature of less than or equal to 140°C, more preferably less than or equal to 130°C, more preferably less than or equal to 120°C, more preferably less than or equal to 110°C, and more preferably less than or equal to 100°C, in order to facilitate the removal of residual organic solvents without degrading 5-HMF.

[0158] In one particular embodiment, during the water distillation step, the concentrated organic raffinate 13 or, if not, the organic raffinate 12, is mixed with an aqueous liquid 17 before being introduced into the distillation column, and the mixture is introduced at the midpoint of the distillation column.

[0159] In another specific embodiment, during the water distillation step, concentrated organic raffinate 13 or organic raffinate 12 is introduced into the upper part of the distillation column, preferably into the upper half of the distillation column, while the aqueous liquid is also introduced into the distillation column. Subsequently, mixing with the aqueous liquid takes place in the distillation column.

[0160] Considering the formation of a heterogeneous azeotrope between water and extraction solvent during the water distillation step, the condensation of vapor from the top of the distillation column produces two liquid phases: a water-rich phase, which can be advantageously returned to the column as reflux, and an organic solvent-rich phase 16, which can be advantageously recycled to the extraction step d).

[0161] According to the invention, the aqueous solution 15 of 5-HMF obtained at the end of the water distillation step has an amount of at least 30% by weight, preferably at least 40% by weight, and preferably less than 90% by weight, preferably less than 85% by weight, and preferably less than 80% by weight of 5-HMF, the percentages being given by the weight of 5-HMF relative to the weight of the aqueous solution of 5-HMF obtained at the end of the water distillation step.

[0162] The method according to the invention advantageously enables the production of an aqueous solution of 5-HMF, which very advantageously has a weight content of less than or equal to 10% by weight of 5-HMF, preferably less than or equal to 5% by weight of 5-HMF, and preferably less than or equal to 3% by weight of a polar aprotic synthetic solvent (e.g., DMSO) by weight of 5-HMF.

[0163] According to one or more embodiments of the alternative water distillation, purification step g) includes at least one of the following steps and may consist of at least one of the following steps: crystallizing the 5-HMF contained in the organic raffinate 12 obtained from step e) or the concentrated organic raffinate 13 obtained from step f), followed by filtration to produce a 5-HMF stream containing solid 5-HMF (5-HMF crystals) and a filtrate rich in organic solvents.

[0164] Crystallization can be carried out in any manner known to those skilled in the art, such as by lowering the temperature, increasing the concentration of the 5-HMF to be crystallized, increasing the concentration of the 5-HMF to be crystallized while lowering the temperature, or by adding a third compound as a poor solvent for the 5-HMF to be crystallized.

[0165] The conditions are those known to those skilled in the art. The temperature is preferably less than or equal to 30°C, and is generally between -100°C and 0°C, preferably between -50°C and 0°C, and even more preferably between -40°C and -10°C.

[0166] The filtrate, rich in organic solvent (essentially the extraction solvent), is advantageously partially or entirely (after optional purification) recycled to step d) of liquid-liquid extraction for a new 5-HMF extraction.

[0167] According to methods known to those skilled in the art, the crystallization-based purification step g) is performed in one or more passes, and the crystals are washed and dried.

[0168] Optional step h) Treatment of the water-polar aprotic synthesis solvent mixture The method according to the invention may optionally include step h) treating the water-polar aprotic synthesis solvent (e.g., DMSO) mixture generated by the steps of the method according to the invention to produce an aqueous effluent (also referred to as a distillate), which may be used wholly or partially for backwashing steps e) and / or c) and / or g). This step may also produce a stream 18 rich in polar aprotic synthesis solvent (e.g., DMSO) and an impurity stream 19. Thus, at least one water-polar aprotic synthesis solvent mixture generated in the method is treated in step h). The mixture may be an aqueous raffinate 8 obtained from step d).

[0169] This step enables the separation of water, polar aprotic synthesis solvent, and reaction products extracted from the raffinate (8) of the at least one mixture (obtained from step d) from the aqueous raffinate, such as unconverted sugars, sugar oligomers, and residual 5-HMF.

[0170] One or more other mixtures of water and polar aprotic synthesis solvent produced in the method may be sent to step h).

[0171] If the method integrates (i) extracting water from the reaction medium simultaneously during step a) or (ii) separating water contained in the sugar raw material upstream of step a), wherein the raw material is initially in syrup form, including extracting and replacing water from the syrup with a polar aprotic synthetic solvent, then in both (i) and (ii) cases, the synthetic solvent-rich stream 16 can remove water while extracting it.

[0172] When distillation is performed effectively according to the knowledge of those skilled in the art, the residual amount of polar aprotic synthesis solvent (e.g., DMSO) in the aqueous effluent produced at the end of step h) is reduced.

[0173] The water-polar aprotic synthesis solvent (e.g., DMSO) mixture generated by the method specifically refers to the aqueous raffinate 8 obtained from step d), and possibly the water-polar aprotic synthesis solvent (e.g., DMSO) mixture obtained from sugar dehydration to 5-HMF.

[0174] Step h) of treating a water-polar aprotic synthetic solvent (e.g., DMSO) mixture preferably uses an evaporation section for the water-polar aprotic synthetic solvent (e.g., DMSO) mixture to remove any impurities, especially heavy impurities such as rotten matter or unconverted sugars, in the form of stream 19, followed by a distillation section.

[0175] The evaporation section operates at a temperature preferably between 80°C and 130°C, more preferably between 100°C and 120°C, and at a pressure preferably between 0.0001 MPa and 0.0200 MPa, more preferably between 0.0002 MPa and 0.0100 MPa, and more preferably between 0.0005 MPa and 0.0050 MPa. Preferably, the evaporation section uses a thin-film evaporator (TFE).

[0176] The distillation section advantageously uses a distillation column or several separate units. Preferably, the distillation section of step h) is advantageously carried out in a distillation column at a top temperature preferably between 25°C and 60°C, preferably between 45°C and 55°C, for example about 50°C, preferably between 80°C and 140°C, preferably between 100°C and 130°C, for example about 120°C, preferably at a pressure between 0.001 MPa and 0.05 MPa, preferably between 0.005 MPa and 0.02 MPa, and preferably between 0.008 MPa and 0.012 MPa, and preferably with a reflux ratio between 0.01 and 0.50, preferably between 0.05 and 0.10.

[0177] Thus, the aqueous raffinate 8, generated in step d) and comprising water and a polar aprotic synthetic solvent (e.g., DMSO) and an optional water-polar aprotic synthetic solvent (e.g., DMSO) mixture recovered in the dehydration step, is subsequently recovered and distilled under vacuum, thereby producing, on the one hand, a residue 18) rich in polar aprotic synthetic solvent (e.g., DMSO), and on the other hand, a water-rich distillate 20 (corresponding to the aqueous effluent), and a final stream 19 containing heavy fractions (e.g., unfiltered scurvy and unconverted scurvy sugars). The term "rich" here means at least 95% by weight, preferably at least 98% by weight. A portion or all of the water-rich distillate or aqueous effluent can advantageously be recycled as an aqueous solvent in step e) for a backwashing step and / or as an aqueous stream in the water distillation step of step g). The water-rich distillate can also be recycled, in whole or in part, as water introduced in step c).

[0178] Residues rich in polar aprotic synthetic solvents (e.g., DMSO) can advantageously be introduced directly or at the dehydration step after distillation to remove any accumulative heavy products.

[0179] The embodiments and accompanying drawings described in detail below illustrate the present invention, but do not limit its scope.

[0180] Figure 1A specific embodiment of the method according to the invention is shown. In step a), sugar feedstock 1 is contacted with a polar aprotic synthesis solvent (e.g., DMSO) and an acidic dehydration catalyst at a temperature between 30°C and 200°C and a pressure between 0.001 MPa and 10 MPa to produce a synthesis effluent 2 containing 5-HMF and the polar aprotic synthesis solvent. The synthesis effluent 2, optionally neutralized with a basic compound, is sent to a concentration step b) to concentrate the 5-HMF in the synthesis effluent, thereby producing a concentrated synthesis effluent 3 and a stream 3' containing the synthesis solvent. The concentrated synthesis effluent 3, containing 5-HMF, the polar aprotic synthesis solvent (e.g., DMSO), and the sulphurant, is sent to step c) and contacted with an aqueous stream 5. The aqueous mixture 6 obtained at the end of step c) is sent to an extraction step d) and contacted with an extraction solvent 7 to extract 5-HMF from the aqueous mixture using the extraction solvent to obtain an aqueous raffinate 8 and an organic extract 9. Organic extract 9 is contacted with aqueous solvent 10 in backwashing step e). Organic raffinate 12 obtained at the end of step e) can be concentrated in an optional liquid-liquid extraction post-concentration step f) by removing stream 14, which can be recycled to step d). Organic raffinate 12 obtained at the end of step e), or concentrated organic raffinate 13 obtained at the end of step f) (if performed), is treated in purification step g) including a water distillation column to remove residual organic solvent 16 and obtain an aqueous solution 15 of 5-HMF.

[0181] The aqueous raffinate 9 obtained from the liquid-liquid extraction step d) is sent to step h) for processing the water-polar aprotic synthesis solvent mixture. Step h) produces an aqueous effluent 20, an enriched polar aprotic synthesis solvent stream 18, and a heavy component stream 19 containing unfiltered scavenging material and unconverted sugars (the scavenging material and sugars are in liquid form, although they are very viscous at the processing temperature of the mixture).

[0182] In the illustrated embodiment, the mixture 6 formed in step c) may be subjected to a liquid-solid separation step to separate the precipitated black matter (solid particles) from the remainder of the mixture in step c) to produce a solid stream 4.

[0183] The aqueous stream 5 used in mixing step c) may contain recycled water from the method. In particular, the aqueous stream 5 contains backwash extract 11 and may be a portion of the aqueous effluent 20 generated in step h) of treating the water-polar aprotic synthesis solvent mixture.

[0184] The aqueous solvent 10 used in backwash step e) may comprise a portion of the aqueous effluent 20 generated in step h) of the water-polar aprotic synthesis solvent mixture and makeup water (i.e., water outside the method, in other words, water neither generated in the method nor obtained from recycling within the method). Alternatively, the aqueous solvent 10 used in backwash step e) may be formed from a portion of the aqueous effluent 20 generated in step g) without makeup water. In this case, makeup water may be sent to step c) to form an aqueous stream 5 comprising a portion of the aqueous effluent 20 generated in step h). Despite water recycling, providing makeup water to the method may be necessary.

[0185] The aqueous stream 17 used for water distillation in step g) may consist of a portion of the aqueous stream 20 generated in step h) of the treatment of the water-polar aprotic synthetic solvent mixture.

[0186] The extraction solvent 7 used in extraction step d) may consist of solvent streams generated in steps f) and g). In other words, the organic solvent streams 14 and 16 generated in steps f) and g) respectively are recycled in step d) and specifically form part of the composition of extraction solvent 7.

[0187] The illustrated embodiment may thus include recycling the aqueous effluent 20 obtained from step h) for treating the water-polar aprotic synthesis solvent mixture in steps c), e), and g), and recycling the organic solvent streams 14 and 16 in step d) of liquid-liquid extraction. This enables optimal water management in the method by integrating water treatment and avoiding excessive addition of makeup water, and also minimizes the consumption of extraction solvents, all of which ultimately have a beneficial impact on the operating cost and environmental impact of the method.

[0188] Products obtained and methods for their analysis The product obtained by the method according to the invention is 5-hydroxymethylfurfural (5-HMF).

[0189] The contents of 5-HMF, organic acids, and residual sugars can be determined by high-performance liquid chromatography (HPLC) at the end of synthesis step a) or at the end of 5-HMF concentration step b). Humic acids do not elute on this analytical system. However, their concentrations are estimated during the synthesis phase by performing molar carbon balance. The difference in the balance is attributed to humic substances.

[0190] List of reference numerals used in the figure: 1: Sugar raw materials 2: Synthetic effluent 3: Concentrated synthetic effluent 3': Synthetic solvent stream 4: Solid Logistics 5: Water-based logistics 6: Aqueous mixtures 7: Extraction solvent 8: Aqueous raffinate 9: Organic extracts 10: Aqueous solvents 11: Intermediate aqueous back-extractants 12: Organic raffinate 13: Concentrated organic raffinate 14: First stream containing organic solvents 15:5-HMF aqueous solution 16: Second stream containing organic solvents 17: Aqueous liquids 18: Streams rich in polar aprotic synthesis solvents (or "enriched residues") 19: Impurity stream (or heavy component stream) 20: Recyclable aqueous effluent Example

[0191] The following embodiments are intended to illustrate some advantages of the method according to the invention. Figure 1 The implementation shown in the figure was run and produced an aqueous solution of 5-HMF. Table 1 below summarizes the results of the five examples presented below.

[0192] Table 1 .

[0193] Example 1 - 5-HMF was synthesized according to existing technology without a post-synthetic and pre-liquid-extraction concentration step, and the fructose / DMSO ratio was 25 / 75. Example 1 is an embodiment of a method according to the prior art, without step b) of concentrating the reaction effluent before the liquid-liquid extraction step. The method according to this embodiment includes steps a), c), d), e), f), g), and h) similar to those described in the method of the present invention. Example 1 is used as a reference to illustrate some advantages provided by the present invention.

[0194] Step a) of dehydrating sugar to 5-HMF was carried out in a stirred tank in batch mode. The tank was prepared by adding crystalline fructose, DMSO, and methanesulfonic acid (MSA) as catalysts. The average flow rate of fructose was 1 t / h. The mass ratio of sugar to DMSO was 25 / 75. The molar ratio of catalyst to sugar was 2.5 mol% MSA / fructose. The reaction was carried out at ambient pressure (0.1013 MPa) and 120°C for 2 hours. At the end, the medium was neutralized with sodium hydroxide (MSA / NaOH molar ratio = 1) and cooled to room temperature.

[0195] Under these conditions, 99% of the fructose was converted to 5-HMF with an 80% carbon molar yield, 19% to byproducts, and 1% to fructose.

[0196] In mixing step c), the synthesis effluent from step a) is contacted with an aqueous stream in a stirred tank at room temperature and ambient pressure. Water is added such that the water-to-DMSO mass ratio in the mixture is 1.4. No liquid-solid separation occurs in this embodiment. The mixture is then transferred to liquid-liquid extraction step d).

[0197] Liquid-liquid extraction step d) was carried out in a pulse column comprising nine theoretical stages. The extraction solvent was methyl isobutyl ketone (MIBK), and extraction was conducted at ambient pressure and room temperature at a solvent-to-feed (aqueous mixture 6) mass ratio of 1.9 wt / wt. Under these conditions, the extraction yield of 5-HMF was 98.0%.

[0198] Backwashing step e) is carried out in a structured packed column comprising two theoretical stages. It is conducted at ambient pressure and room temperature. The backwash solvent is as described above in step e) and... Figure 1 The water (aqueous effluent 20) recycled by the method is shown in the figure. The amount used is such that the mass ratio of the aqueous backwash solvent to the organic extract 9 of the feedstock (obtained from step d) is 0.1 wt / wt.

[0199] The post-extraction liquid-liquid concentration step f) is an evaporation at 90°C and 0.015 MPa absolute pressure (150 mbar), which produces an enriched organic raffinate with a 50% by weight content of 5-HMF.

[0200] Purification step g) involves water distillation in a distillation column comprising seven theoretical stages and operating at a top pressure of 0.04 MPa absolute (400 mbar). The reflux ratio and reboiler power are adjusted to produce an aqueous 5-HMF solution containing 75 wt% 5-HMF and 0.1 wt% MIBK. The temperature at the top of the column (where the vapor phase exits the column and enters its condenser) is 70°C, and the temperature at the reboiler outlet is 88°C.

[0201] Step h) for treating the water-polar aprotic synthesis solvent mixture consists of a series of three evaporation systems (cascaded heat exchangers / separators) operating at 120°C. The pressure is sequentially reduced to 0.09 MPa absolute pressure / 0.015 MPa absolute pressure / 0.0005 MPa absolute pressure (900 mbar / 150 mbar / 5 mbar), which allows for a residual DMSO value of approximately 15% by weight in stream 19.

[0202] The vapors from these three steps are condensed to form three distillates, which are then fed into a nine-plate distillation column operating at a reflux ratio of 15% by weight (the mass ratio of reflux to feed). The top pressure is 0.01 MPa absolute (100 mbar). The bottom product is DMSO containing 0.1% by weight water, which is recycled to step a). At the top of the column, the water produced is used in steps c) and e).

[0203] Under these conditions, the synthesis in step a) was thus carried out with a DMSO dilution of 75 wt%, and the flow rate at the inlet of the liquid / liquid extraction step d) was 8957 kg / h. The 5-HMF synthesis yield was 80 mol%, the 5-HMF extraction yield was 98.1%, and the yield of the sugar to 5-HMF from the synthetic method was 78.5 mol%. The energy consumption, by summing up all the energy supplied by the method, was 14.9 MW / t. 5-HMF (MW / ton 5-HMF), supplied here by steam.

[0204] Example 2 - Synthesis of 5-HMF according to the present invention, including a concentration step b) after synthesis and before liquid-liquid extraction, and the synthesized fructose / DMSO ratio is 25 / 75. In Example 2, the method was carried out under the same conditions as in Example 1 (pressure, temperature, solvent content, sugar feedstock, synthesis catalyst, solvent properties). According to the invention, the method according to Example 2 includes a step b) of 5-HMF concentration. In step b), evaporation is carried out at an absolute pressure of 0.005 MPa (50 mbar) and 120°C. The effluent from step a) of the synthesis is thus neutralized but not cooled. Under these conditions, the DMSO concentration is reduced from 75% by weight at the end of the synthesis to 45% by weight at the end of the concentration step b), and then fed to the mixing step c).

[0205] Steps c), d), and e) are performed at the same water and solvent ratio as in Example 1.

[0206] Compared to Example 1, the concentration step b) resulted in a decrease in the flow rate at the inlet of the liquid-liquid extraction step d) to 2453 kg / h (for a similar amount of 5-HMF). This increase in the 5-HMF concentration in step b) significantly improved the liquid-liquid extraction performance, from 98.1% (Example 1) to 99.8% (Example 2), enabling a total molar yield of fructose to 5-HMF of 79.8%, an increase of 1.3 moles relative to the reference Example 1.

[0207] Similarly, the reduction in the solvent flow rate processed in steps f) and h) results in significant energy savings: the requirement in Example 2 is 5.3 MW / t. 5-HMF This represents a 65% energy saving compared to Example 1.

[0208] Example 2 thus demonstrates the contribution of the concentration step to the improvement in energy consumption and 5-HMF yield due to the improved liquid-liquid extraction performance.

[0209] Example 3 - Synthesis of 5-HMF according to the present invention, including a concentration step b) after synthesis and before liquid-liquid extraction, and the synthesized fructose / DMSO ratio is 10 / 90. Example 3 specifically illustrates the advantages of step b) in concentrating 5-HMF in terms of the 5-HMF yield during step a) of sugar dehydration to 5-HMF.

[0210] Example 3 is identical to Example 1 in all respects, except that it includes a concentration step b), and the mass ratio of sugar (crystalline fructose) to DMSO is 10 / 90 instead of 25 / 75 in Example 1. Under these conditions, the carbon molar yield of 5-HMF is 85%, representing a 5% gain relative to Example 1.

[0211] Concentration step b) was carried out at 120°C and 0.0106 MPa absolute pressure (106 mbar) to maintain a flow rate Q of approximately 8960 kg / h at the inlet of liquid-liquid extraction step d), which is comparable to the flow rate in Example 1.

[0212] Mixing step c) is carried out in a similar manner to Example 1 and with the same water and solvent ratio (water / DMSO mixture equals 1.4) as in Example 1.

[0213] Compared to Example 1, the performance of the liquid / liquid extraction in step d) was unaffected, where the 5-HMF extraction yield in Example 3 was 98.1%, as in Example 1. Throughout the method according to Example 3, the 5-HMF yield subsequently reached 83.4 mol%, representing an increase of 4.9 mol% relative to Example 1.

[0214] The operating conditions for steps d), e), f), g), and h) are the same as those presented in Example 1. This implementation results in excessive energy consumption of the method related to the concentration step, reaching 17.3 MW / t. 5-HMF This represents a 16% improvement compared to Example 1.

[0215] According to the implementation of the method described in Example 3, the method provides a significant gain (+4.9 mol%) in 5-HMF yield, even at the cost of an increase in energy demand (+16%), which may be acceptable if the 5-HMF yield is given priority.

[0216] Example 4 - Synthesis of 5-HMF according to the present invention, including a concentration step b) after synthesis and before liquid-liquid extraction, and the synthesized fructose / DMSO ratio is 10 / 90. In Example 4, the method was carried out in the same manner as in Example 3, except that the concentration step b) was performed at a different pressure, at 0.0099 MPa (99 mbar) compared to the 0.0106 MPa (106 mbar) absolute pressure in Example 3. This slight reduction in pressure in step b) allowed for a slightly greater concentration of 5-HMF during step b), resulting in a lower flow rate Q of 7350 kg / h at the inlet of the liquid-liquid extraction step d), compared to 8964 kg / h in Example 3. The reduced flow rate improved the 5-HMF extraction yield in step d), increasing it to 98.5%. The overall 5-HMF yield of the method was 83.7 mol%, an improvement of 5.3 mol% compared to the reference of Example 1.

[0217] The reduced flow rate at the inlet of liquid-liquid extraction step d) compensates for the energy requirement of concentration step b). This results in a power consumption of 17.4 MW / t. (5-HMF) The consumption is similar to the reference case shown in Example 1.

[0218] According to this embodiment, the method thus does not provide any gain in terms of energy consumption, but enables a significant improvement in the fructose to 5-HMF yield of the entire method.

[0219] Example 5 - The synthesis of 5-HMF according to the present invention includes a concentration step after synthesis and before liquid-liquid extraction, and the synthesized fructose / DMSO ratio is 10 / 90. Example 5 illustrates the contribution of the present invention to the 5-HMF yield and total energy consumption of the method during the synthesis process.

[0220] The implementation methods and operating conditions are identical to those in Examples 3 and 4, except for the concentration step b), which is carried out at an absolute pressure of 0.0036 MPa (36 mbar). Under these conditions, although the reaction medium in step a) has a high dilution (fructose / DMSO mass ratio of 10 / 90) as in Examples 3 and 4, and thus the synthetic effluent also has a high dilution, the concentrated synthetic effluent obtained from step b) contains 45% by weight DMSO, i.e., the "dilution" of 5-HMF in the concentrated effluent is the same as that used in the method implemented in Example 2. The flow rate and extraction performance at the start of the liquid-liquid extraction step d) are thus comparable to those in Examples 2 (2462 kg / h at the start of step d), and the 5-HMF extraction yield in step d) is 99.8%.

[0221] Compared to Example 1, the total 5-HMF yield of the method increased from 78.5 mol% to 84.8 mol%, of which 5% was attributable to step a), via the fructose / DMSO mass ratio of the reaction (a high “dilution” of 5-HMF in DMSO), and 1.4% was related to the gain in 5-HMF recovery in liquid-liquid extraction step d), which was carried out in both cases with the same extraction solvent / feed (aqueous mixture 6) ratio.

[0222] The total energy consumption of the method is 7.5 MW / t. 5-HMF Compared to Example 1, it saves 50%.

[0223] Compared to Example 1, Example 5 enables the demonstration of the set of benefits provided by the present invention, as shown in Examples 2 to 4: - The yield of 5-HMF may be increased in the synthesis step by increasing the dilution with a polar aprotic synthesis solvent (e.g., DMSO). - By pre-concentrating the feedstock before liquid-liquid extraction in step b), the yield of 5-HMF extraction in liquid-liquid extraction step d) is increased. - Despite the presence of an additional step (concentration step b) downstream of step a) in dehydrating sugar to 5-HMF, this method is energy-efficient.

Claims

1. A method for producing hydroxymethylfurfural (5-HMF), the method comprising the following steps: - Step a) Contact a sugar feedstock (1) comprising hexose with at least one polar aprotic synthesis solvent and at least one acidic dehydration catalyst to produce a synthesis effluent (2) containing 5-HMF and the polar aprotic synthesis solvent, the contact being carried out at a temperature between 30°C and 200°C and a pressure between 0.001 MPa and 10 MPa. - Step b) Concentrate the 5-HMF of the synthetic effluent (2) to obtain concentrated synthetic effluent (3); - Step c) Contact the concentrated synthetic effluent (3) with an aqueous stream (5) to obtain at least one aqueous mixture (6); - Step d) The aqueous mixture (6) obtained at the end of step c) is subjected to liquid-liquid extraction in the presence of the extraction solvent (7) to produce an aqueous raffinate (8) containing the polar aprotic synthesis solvent and an organic extract (9) containing 5-HMF and the extraction solvent; and subsequently - Step e) Backwash the organic extract (9) with an aqueous solvent (10) to produce an intermediate aqueous back extract (11) and an organic raffinate (12) containing 5-HMF and an organic solvent; - Optionally, step f) concentrates the organic raffinate (12) obtained from step e) by removing at least a portion of the organic solvent, to produce a concentrated organic raffinate (13) containing 5-HMF and residual organic solvent, and to produce a first stream (14) containing organic solvent. - Step g) Purify the organic raffinate (12) or the concentrated organic raffinate (13) to produce a 5-HMF stream (15).

2. The method claimed in claim 1 further includes a step of neutralizing the synthetic effluent (2) from step a) prior to step b), preferably by contacting the synthetic effluent (2) with an alkaline compound.

3. The method claimed in claim 1 or claim 2, wherein the mass concentration factor in step b) corresponds to the mass ratio of the synthetic effluent (2) to the concentrated synthetic effluent (3), and is between 1.2 and 20, preferably between 1.5 and 20, more preferably between 1.5 and 15, and more preferably between 2 and 10.

4. The method claimed in any of the preceding claims, wherein the synthetic effluent (2) obtained from step a) contains a 5-HMF / polar aprotic synthetic solvent ratio between 5 / 95 and 40 / 60, and the concentrated synthetic effluent (3) obtained from step b) contains a 5-HMF / polar synthetic solvent ratio between 30 / 70 and 70 / 30.

5. The method claimed in any of the preceding claims, wherein step b) comprises evaporation or distillation to vaporize a portion of the polar aprotic synthesis solvent, at a temperature of 200°C or less, preferably 150°C or less, and more preferably 130°C or less, and at atmospheric pressure or vacuum, preferably at a pressure between 0.0001 MPa and 0.1000 MPa, and more preferably at a pressure between 0.0001 MPa and 0.0500 MPa under vacuum.

6. The method claimed in any of the preceding claims, wherein the purification step g) is a water distillation step performed by distilling the organic raffinate (12) obtained from step e) or the concentrated organic raffinate (13) obtained from step f) in the presence of water (17) to produce the 5-HMF stream (15) as an aqueous solution of 5-HMF and a second stream (16) containing an organic solvent, wherein the water distillation is preferably carried out in a distillation column at atmospheric pressure or under vacuum, preferably at a pressure between 0.001 MPa and 0.1 MPa, and preferably under vacuum at a pressure between 0.005 MPa and 0.08 MPa, and at a 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, preferably less than or equal to 100°C.

7. The method claimed in any one of claims 1 to 5, wherein the purification step g) comprises at least one step of crystallizing 5-HMF contained in the organic raffinate (12) obtained from step e) or the concentrated organic raffinate (13) obtained from step f), and then filtering to produce the 5-HMF stream containing solid 5-HMF and a filtrate rich in organic solvent.

8. The method claimed in any of the preceding claims further includes step h) treating at least one water-polar aprotic synthesis solvent mixture generated in the method to produce at least one aqueous effluent (20) that can be recycled in the method, the mixture comprising the aqueous raffinate (8) obtained from step d).

9. The method claimed in any of the preceding claims further includes a liquid-solid separation step, preferably filtering the aqueous mixture generated in step c) or the intermediate liquid stream generated during the liquid-liquid extraction step d) or the aqueous raffinate obtained from step d) (8).

10. The method claimed in any of the preceding claims, comprising step f) concentrating the organic raffinate (12) obtained from step e), said step f) comprising vaporizing an organic solvent at atmospheric pressure or under vacuum, preferably at a pressure between 0.01 MPa and 0.10 MPa and at a liquid temperature of less than or equal to 130°C, said concentrated organic raffinate (13) comprising 30% by weight of 5-HMF and 60% by weight of residual organic solvent.

11. The method claimed in any of the preceding claims, wherein the hexose is fructose or a fructoside unit.

12. The method claimed in any of the preceding claims, wherein the polar aprotic synthesis solvent is selected from pyridine, butanone, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methyl ethyl ketone, propionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, and γ-valerolactone, used alone or in mixtures, and preferably dimethyl sulfoxide.

13. The method claimed in any of the preceding claims, wherein the extraction solvent (7) is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene, and preferably methyl isobutyl ketone.

14. The method claimed in any of the preceding claims, wherein, In step c), the aqueous stream (5) comprises all or part of the intermediate aqueous back-extract (11) obtained from step e).

15. The method claimed in any one of claims 8 to 14, wherein the aqueous effluent (20) generated in step h) is used in whole or in part for steps c) and / or e) and / or g).

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