Process for the production of 5-HMF, comprising resuspension of the filtered solid phase after filtration

Abstract

The present invention relates to a process for the production of 5-hydroxymethylfurfural (5-HMF) in the order: a) contacting a feedstock (1) containing 5-HMF and a polar aprotic synthesis solvent with an aqueous stream, b) liquid-solid separation, comprising two filtration steps separated by resuspension of the filter cake; c) liquid-liquid extraction using an organic extraction solvent, followed by a step d) of backwashing with an aqueous solvent, to obtain an organic raffinate enriched in 5-HMF and solvent. The optionally concentrated organic raffinate is then subjected to a purification step f), such as water distillation or crystallization, to obtain a 5-HMF stream, such as in the form of a 5-HMF aqueous solution or crystalline 5-HMF.

Description

Technical Field

[0001] This invention relates to a method for producing hydroxymethylfurfural (HMF) from a feedstock comprising HMF and a polar aprotic synthetic solvent, said feedstock typically obtained by dehydrating a feedstock containing sugars (e.g., fructose). More specifically, this invention relates to a method for producing HMF, preferably for producing an aqueous HMF solution, comprising a specific liquid-solid separation step upstream of a liquid-liquid extraction step, based on performing two filtration steps (with an intermediate step of resuspending the filtered solid phase (e.g., filter cake)). Existing technology

[0002] HMF, also known as 5-(hydroxymethyl)furfural or 5-HMF, is a biodegradable compound of interest with potential applications in various fields, particularly pharmaceuticals, agrochemicals, and specialty chemicals. 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 can be specifically mentioned as examples: 5-HMF can be obtained in aqueous media, typically in the presence of an acid catalyst. This acid catalyst enables the dehydration of C6 sugars (especially fructose) to produce 5-HMF, but it also catalyzes the rehydration of 5-HMF to formic acid and levulinic acid, which is very detrimental to the yield.

[0003] 5-HMF can also be obtained in non-aqueous polar protic media using solvents such as methanol, ethanol, or acetic acid, and in the presence of 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 attributed to the reaction of 5-HMF with the reaction solvent in an acidic medium.

[0004] Patent application WO 2007 / 104514 describes the synthesis of 5-HMF via 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 yield a mixture of 5-HMF and its methyl or ethyl ether forms, depending on the alcohol used as the solvent.

[0005] 5-HMF can also be produced in polar aprotic media, with or without an acid catalyst. More specifically, dimethyl sulfoxide (DMSO) can be mentioned, which produces 5-HMF in very good yields with or without an acid catalyst, and without the undesirable reactions listed above.

[0006] Furthermore, regardless of the synthesis medium (water, methanol, DMSO, etc.), a polymerization byproduct called humins is formed during the production of 5-HMF (van Dam, HE; ​​Kieboom, APG; van Bekkum, H. (1986), The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethylfurfural, in: Starch - Stärke, vol. 38, No. 3, pp. 95-101).

[0007] 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 alcohol form (rather than its ether form) in very good yields. However, the physicochemical properties of DMSO (or any other polar aprotic solvent) make it difficult to separate from 5-HMF using conventional methods known to those skilled in the art.

[0008] One known method for separating 5-HMF from DMSO is liquid-liquid extraction followed by crystallization of the extract, as described in patent FR2669635. 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 of the liquid-liquid extraction step, particularly by adding a backwashing step with 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 product of interest and allows the 5-HMF crystallization step to be carried out under more favorable conditions.

[0009] A liquid-liquid extraction method for separating 5-HMF from DMSO is also described in the applicant's patent FR3131313, but here it is as part of a method that allows the recovery of 5-HMF in the form of an aqueous solution rather than crystals, which may be advantageous given that crystallization of 5-HMF remains an expensive operation. To this end, the method described in FR3131313 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, and also involves a step of concentrating 5-HMF in the organic raffinate containing 5-HMF obtained in the backwashing step, and a step of hydrodistillation of the concentrated stream obtained from the concentration step to recover 5-HMF in the form of an aqueous solution. The disclosed method advantageously includes a liquid-solid separation step upstream of the liquid-liquid extraction, typically by filtration, to remove humin (solid particles) precipitated during the addition of water to the feed (the step of mixing the feed with the backwash water) before the feed is fed into the liquid-liquid extraction. This is because adding water to the 5-HMF feedstock fed into the liquid-liquid extraction process may cause humin present in the feedstock to precipitate, which may cause operational problems during the liquid-liquid extraction process, such as equipment blockage.

[0010] Therefore, the management of humic acid is crucial in this type of HMF production method.

[0011] In patent FR3131313, the liquid-solid separation step is typically carried out when the amount of humin precipitated in the mixture is greater than about 1% by weight, and can be carried out using various techniques such as filter press, belt filter, clarifier, decanter or centrifuge, such as plate centrifuge, preferably using a filter press.

[0012] Typically, a filter press is a device capable of separating a suspension under pressure to separate the liquid and solid phases. A filter press consists of plates (or frames) that allow filtration through a filter medium of a suspension formed from a mixture of water and a feed containing 5-HMF and a polar aprotic synthetic solvent (e.g., DMSO) containing humic acid, removing the humic acid as a filter cake. Therefore, the filter cake contains a solid fraction, but also a portion of the liquid fraction, which is retained, particularly due to limitations in the separation technique and the properties of the liquid and solid phases. Under filtration pressure, the liquid, called the filtrate, passes through a filter cloth that retains the solid particles. The filtrate is discharged throughout the process, while the filter cake formed between the plates is discharged only during a "disintegration" operation. Therefore, the equipment operates in batch cycles, each cycle comprising a series of steps, including filtration and disintegration steps, as well as a compaction step to increase the solid content of the filter cake.

[0013] In fact, in the sequence of filtration cycles, the step of washing the resulting filter cake after the filtration step or the compaction step enables the improvement of the liquid-solid separation step by using a filter press. Figure 1 and Figure 2 The diagram illustrates a filtration cycle performed by a filter press according to the prior art, which incorporates washing steps at different points in the filtration cycle sequence.

[0014] according to Figure 1 The feedstock 2 of the filter press (which is a suspension obtained by mixing HMF-DMSO feedstock 1 with water 21 in step a) is fed to the filtration step b1.1) to separate the solid phase (i.e., humin) from the liquid phase 3, which specifically contains HMF, DMSO, and water. At the end of step b1.1), the coarse filter cake 22 containing humin undergoes a washing step b1.2) with water 23 to produce a washed filter cake 25 and a washing filtrate 24 containing the products of interest extracted from the filter cake (e.g., 5-HMF and DMSO). The washed filter cake 25 then undergoes a compaction-purging step b1.3) to form a compacted / purged washed filter cake 27 and a compaction-purging filtrate 26. Finally, the compacted / purged washed filter cake 27 is broken up in a disintegration step b1.4) to form a compacted / purged washed disintegrated filter cake 28.

[0015] according to Figure 2 The described variant, the filter loop in... Figure 1 In the sequence shown, which is identical in order, an additional compaction / purge step b1.5 is included downstream of the filtration step b1.1) and upstream of the washing step b1.2). Then, in step b1.5), a primary compacted-purge filtrate 29 is produced (according to this sequence, filtrate 26 forms an additional compacted-purge filtrate), and a coarse compacted-purge filter cake 30 undergoes the washing step b1.2).

[0016] This is because such washing of the filter cake allows for the extraction of more of the product of interest remaining in the cake, primarily 5-HMF and polar aprotic synthesis solvents, in order to recover these products in the washing filtrate for recycling within the method. This is typically achieved by recycling the washing filtrate to a step upstream of the liquid-liquid extraction step where the HMF-DMSO feedstock is mixed with water, and particularly to obtain a better overall HMF yield for the method. However, for reliability, and especially to avoid excessive loss of HMF and DMSO from the filter cake, washing is performed at the cost of a relatively large amount of water. Summary of the Invention

[0017] The applicant has demonstrated that, compared to a liquid-solid separation step involving washing the filtered solid phase (e.g., filter cake) with water, a specific liquid-solid separation step based on implementing two filtration cycles (with an intermediate step (also referred to herein as a "re-slurrying" step) that resuspends the solid phase (e.g., filter cake) obtained at the end of the first filtration cycle) can increase the degree of extraction of products of interest (e.g., 5-HMF and polar aprotic synthesis solvents (e.g., DMSO)) from the filtered solid phase (e.g., filter cake) with the same amount of water. With the method according to the invention (which combines this original liquid-solid separation step with the reasonable recycling of the products of interest extracted from the filtered solid phase (e.g., filter cake) back into the method), HMF production is improved while limiting investment and operating costs due to the recycling of the polar aprotic synthesis solvent and water in the method.

[0018] One aspect of this invention relates to a method for producing 5-HMF, comprising the following steps: - Step a) Contact the raw material containing 5-HMF and a polar aprotic synthesis solvent with an aqueous stream to obtain at least one aqueous mixture containing solid particles; - Step b) involves liquid-solid separation of the aqueous mixture, including first and second filtration cycles (b1, b3) separated by an intermediate step b2), which resuspends the solid phase obtained at the end of the first filtration cycle b1) to produce at least a first aqueous filtrate, a second aqueous filtrate, and a final solid containing at least a portion of solid particles, the second aqueous filtrate being recycled to step a). -Step c), in the presence of the extraction solvent, the first aqueous filtrate obtained at the end of step b) is subjected to liquid-liquid extraction to produce an aqueous raffinate containing the polar aprotic synthesis solvent and an organic extract containing 5-HMF and the extraction solvent; and then - Step d) The organic extract is backwashed with an aqueous solvent to produce an aqueous back-extract and an organic raffinate containing 5-HMF and an organic solvent. -Optional step e), concentrating the organic raffinate obtained in step d) by removing at least a portion of the organic solvent, to produce a concentrated organic raffinate containing 5-HMF and residual organic solvent, and to produce a first stream containing organic solvent. - Step f) purify the organic raffinate or the concentrated organic raffinate to produce a 5-HMF stream.

[0019] According to one or more embodiments, the liquid-solid separation step b) is carried out using at least one piece of equipment selected from filter press, belt filter, centrifuge, candle filter, vacuum filter, belt filter press, decanter and drainer, preferably using at least one filter press.

[0020] According to one or more embodiments, the liquid-solid separation step b) is carried out in batches using at least one piece of equipment selected from filter press, candle filter, vacuum filter, belt filter press, decanter and drainer, preferably using at least one filter press.

[0021] According to one or more embodiments, the first and second filtration cycles are carried out in two separate equipment components, preferably two separate filter presses.

[0022] According to one or more embodiments, the intermediate step b2) of resuspending the solid phase obtained at the end of the first filtration cycle b1) is carried out at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C, and at atmospheric pressure, by contacting the solid phase with an aqueous solution at a mass ratio of 1 to 10 of the aqueous solution to the solid phase for a period of 1 minute to 4 hours, preferably in a tank separate from the equipment (pieces) used for the first and second filtration cycles.

[0023] According to one or more embodiments, the liquid-solid separation step b) is carried out using at least one filter press, and each of the first and second filtration cycles of the liquid-solid separation step b) comprises, in this order, the following sequence of sub-steps: - Sub-steps (b1.1, b3.1) for filtering the filter material to produce an aqueous filtrate and a coarse filter cake; - The filter cake is subjected to a compaction-purging sub-step (b1.3, b3.2) to produce a compaction-purging filtrate and a compaction-purging coarse filter cake; - Sub-steps (b1.4, b3.3) to break down the compacted-purge coarse filter cake to produce a broken-down filter cake; Furthermore, the broken-up filter cake obtained at the end of the breaking-up sub-step b1.4) of the first filtration cycle b1) is the solid phase that was resuspended by contact with an aqueous solution in step b2) to form the filter material for the filtration sub-step b3.1) of the second filtration cycle b3).

[0024] According to one or more embodiments, a first filtration cycle b1) includes a compaction-purge sub-step b1.3) to produce a first compaction-purge filtrate that is recycled to step c) in the method, and a second filtration cycle b3) includes a compaction-purge sub-step b3.2) to produce a second compaction-purge filtrate that is recycled to step a) in the method.

[0025] According to one or more embodiments, the filtration sub-steps (b1.1, b3.1) are carried out at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C, and at a pressure between 0.05 MPa and 1 MPa.

[0026] According to one or more embodiments, a filter aid, preferably diatomaceous earth, is added to the filter material in the filtration sub-step of the first filtration cycle b1) and / or the second filtration cycle b3), preferably in a content of 0.01% to 5% by mass relative to the filter material.

[0027] According to one or more embodiments, the compaction-purging sub-step (b1.3, B3.2) is carried out by injecting compressed air at a pressure between 1 MPa and 5 MPa and at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C.

[0028] According to one or more embodiments, the liquid-solid separation step b) does not include the step of washing the filtered solid phase generated during step b).

[0029] According to one or more embodiments, purification step f) is a water distillation step, which is carried out by distilling the organic raffinate obtained in step d) or the concentrated organic raffinate obtained in step e) in the presence of water to produce the 5-HMF stream (which is 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 of 0.001 MPa to 0.1 MPa, and preferably under vacuum at a pressure of 0.005 MPa to 0.08 MPa, and the bottom temperature of the column is less than or equal to 140°C, preferably less than or equal to 130°C, preferably less than or equal to 120°C, preferably less than or equal to 110°C, and preferably less than or equal to 100°C.

[0030] According to one or more embodiments, the method includes a step of dehydrating sugars to 5-HMF upstream of step a), preferably by contacting a sugar feedstock containing hexoses (preferably fructose or fructoside units) with the polar aprotic synthesis solvent and the dehydrating acid catalyst, preferably at a temperature between 30°C and 200°C and at a pressure between 0.001 MPa and 10 MPa.

[0031] According to one or more embodiments, in step a), the aqueous stream comprises all or part of the aqueous back-extraction solution obtained in step d).

[0032] 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, and is preferably methyl isobutyl ketone.

[0033] 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, alone or in mixtures, and preferably dimethyl sulfoxide.

[0034] Other subject matter and advantages of the invention will become apparent upon reading the description of particular exemplary embodiments of the invention, which are given by way of non-limiting example, with reference to the accompanying drawings below.

[0035] List of Attachments Figure 1 (As described above) An example of liquid-solid separation in a process for producing HMF according to the prior art is shown.

[0036] Figure 2 (As described above) shows another example of liquid-solid separation in a process for producing HMF according to the prior art.

[0037] Figure 3 An embodiment of the method according to the invention is shown, which incorporates a specific liquid-solid separation step b) upstream of the liquid-liquid extraction step.

[0038] Figure 4 This is a schematic diagram illustrating a specific liquid-solid separation step b) of the HMF production method according to the present invention.

[0039] In the accompanying drawings, the same reference numerals denote the same or similar elements.

[0040] Implementation Plan Description In the following detailed description, numerous specific details are disclosed to provide a deeper understanding of the method. However, those skilled in the art will understand that not all of these specific details are necessary for implementation. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0041] It should be noted that throughout this specification, unless otherwise stated, the phrase "between" should be understood to include the limits mentioned.

[0042] In this specification, the term "comprising" is synonymous with "including" and "containing" (meaning the same) and is inclusive or open-ended, not excluding other elements not mentioned. It should be understood that the term "comprising" includes both exclusive and closed terms such as "consisting of".

[0043] Furthermore, when used in this specification, the terms “substantially” or “about” related to a reference value correspond to an approximation of ±10%, preferably ±5%, very preferably ±2%, or even more preferably ±1% of that reference value, which may be temperature, pressure, distance, speed, flow rate, compound content, etc.

[0044] For the purposes of this invention, the various embodiments proposed can be implemented individually or in combination with each other, and there are no restrictions on the combination where technically feasible.

[0045] 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 pressure range can be combined with a more preferred temperature range.

[0046] Unless otherwise stated, pressure is expressed in absolute values ​​in this specification.

[0047] In this specification, aprotic solvent is understood to be 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 units, is greater than or equal to 2.00 when measured at 25°C.

[0049] Therefore, in this specification, a polar aprotic solvent is understood to be a molecule that acts as a solvent, in which all hydrogen atoms are carried by carbon atoms and whose dipole moment µ, expressed in Debye units, is greater than or equal to 2.00 when measured at 25°C.

[0050] In this specification, the term "filter cake" refers to the solid phase recovered from a filtration cycle, particularly the solid phase recovered by a filter press. It is a solid (which may be wet). This solidity can be characterized by its solids content, abbreviated as "SC". The solids content (SC) of such filter cake can be between 20% by mass and 90% by mass, preferably between 30% by mass and 90% by mass, more preferably between 35% by mass and 90% by mass, more preferably between 40% by mass and 85% by mass, relative to the total mass of the filter cake, and can vary depending on the type of operation performed during the filtration cycle from which the filter cake is derived. The solids content can be measured according to standard ASTM E1756-08 (2015). While the term "filter cake" is used in the singular, it also encompasses the plural, i.e., multiple filter cakes.

[0051] In this specification, the term "re-slurrying" refers to the operation of resuspending the solid phase recovered in a filtration cycle, particularly the solid phase recovered by a filter press, by contacting it with an aqueous solution. Further details are given below in conjunction with the description of the invention.

[0052] To better understand this invention, the following is mentioned: Figure 3 and Figure 4 The numerical notations appearing in these figures are used to represent various elements of the method, but this does not constitute a limitation of the invention to the specific embodiments shown in these figures.

[0053] Optional steps for dehydrating sugars to 5-HMF Advantageously, the feedstock 1 containing 5-HMF and a polar aprotic synthesis solvent introduced in step a) according to the invention can be obtained during the step of dehydrating the sugar to 5-HMF, which is very advantageously located upstream of step a) according to the invention, by contacting the sugar feedstock containing hexoses with the polar aprotic synthesis solvent and a dehydrating acid catalyst to produce a synthesis effluent containing at least 5-HMF and a polar aprotic synthesis solvent, and advantageously corresponding to the feedstock 1 introduced in step a) according to the method of the invention. Therefore, the method according to the invention may optionally include such a step of dehydrating the sugar feedstock to 5-HMF, which is located upstream of step a).

[0054] Sugar raw materials include hexoses, which can exist as monomers (monosaccharides) or as units belonging to disaccharides, oligosaccharides, or polysaccharides. Carbohydrates are compounds also known as sugars.

[0055] The hexose is preferably fructose or a fructose glycoside unit.

[0056] In one embodiment, the raw material comprises free fructose, alone or in mixture with any sugar species, or comprises any oligosaccharide or polysaccharide raw material 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 sugar raw material is crystalline fructose, a fructose-containing syrup, a syrup containing fructose and glucose, or crystalline sucrose or sucrose syrup.

[0057] Advantageously, the raw materials include fructose in monomeric, oligomeric, or polymeric forms.

[0058] The term "raw material containing free fructose mixed with any sugar species" refers, for example, to high-fructose corn syrup containing fructose and glucose in different proportions (e.g., glucose / fructose mass ratio or molar ratio of 58 / 42, 45 / 55, 10 / 90).

[0059] The term "syrup" refers to a solution of sugar (carbohydrates) in water having a concentration of at least 30% by weight, preferably at least 50% by weight, and more preferably at least 70% by weight.

[0060] The raw material may contain sugars comprising one or more fructoside units and one or more non-fructoside units, from which fructose may be released by one or more hydrolysis steps, for example, where at least one monosaccharide unit is an oligosaccharide or polysaccharide of fructose, such as raw materials such as sucrose, fructotriose, fructan, oligofructan and inulin.

[0061] Advantageously, the sugar raw material is suitable for releasing monomeric fructose through glycoside hydrolysis, and the fructose product can be converted into 5-HMF.

[0062] Oligosaccharides are preferably selected based on 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 whose sum is between 2 and 6. The monosaccharide units constituting the oligosaccharide are the same or different, and at least one of the formulas (C) is used. 6m H 10m+2 O 5m+1 The unit of polysaccharide is fructose. By extension, polysaccharides preferably have 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.

[0063] The polar aprotic synthesis solvent is advantageously selected from all polar aprotic solvents whose dipole moment, expressed as Debye (D), is greater than or equal to 2.00. 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.

[0064] 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.

[0065] Preferably, the polar aprotic solvent is advantageously selected from N,N-dimethylacetamide, NMP, DMSO and γ-valerolactone, alone or in mixtures.

[0066] Very preferably, the polar aprotic solvent is DMSO.

[0067] The term "dehydrating acid catalyst" is understood to refer to any Brønsted acid catalyst selected from organic or inorganic, homogeneous or heterogeneous Brønsted acids that can induce the dehydration of sugars to 5-HMF.

[0068] Preferably, the dehydrating acid 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 even more preferably between 1.0 and 3.0. The pKa value is as defined in the article by FGBordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0069] Preferably, the dehydration acid 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 dehydration acid catalyst is selected from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0070] The optional dehydration step is carried out at a temperature between 30 and 200°C, preferably between 50 and 180°C, more preferably between 70 and 150°C, and even more preferably between 90 and 130°C, for example, at 120°C. Preferably, the optional dehydration step is carried out at a pressure between 0.001 MPa and 10 MPa, more preferably between 0.001 MPa and 5 MPa, and even more preferably between 0.01 MPa and 1 MPa. Depending on the pressure and temperature conditions, the reaction medium is above or below the bubble point of the mixture. The term "bubble point" refers to the pressure and temperature conditions at which the first bubbles are observed 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 that can be sent to optional step g) (which is used to treat the water-polar aprotic synthesis solvent mixture).

[0071] Preferably, the dehydrating acid catalyst is introduced into the dehydration step at a molar ratio of catalyst to sugar feedstock (expressed as acid / sugar), which is expressed as a molar percentage (mol%) between 0.01 and 10 mol%, preferably between 0.05 and 8 mol%, preferably between 0.1 and 6 mol%, preferably between 0.2 and 5 mol%, preferably between 0.3 and 4 mol%, and most preferably between 0.5 and 3 mol%.

[0072] The optional dehydration step can be carried out according to various implementation schemes. Therefore, this step can advantageously be carried out in a batch or continuous manner. The addition of the sugar feedstock can be gradual (referred to as "feed-in batch"), in the case of batch implementation; or in a continuous implementation, it can be carried out in series in different CSTR (continuous stirred tank reactor) reactors in stages. This method can be carried out in a closed reaction chamber or in a semi-open reactor.

[0073] Advantageously, the synthesis effluent obtained at the end of the optional dehydration step comprises 5-HMF and a polar aprotic synthesis solvent, preferably DMSO. The polar aprotic synthesis solvent (typically DMSO) typically comprises between 30% and 95% by weight, preferably between 40% and 90% by weight, more preferably between 50% and 90% by weight, and more preferably between 55% and 85% by weight, of the synthesis effluent produced by the dehydration step and treated in step a) of the method according to the invention.

[0074] 5-HMF comprises at least 1% by weight, preferably at least 10% by weight, preferably at least 15% by weight, and preferably no more than 50% by weight, preferably no more than 40% by weight, and preferably no more than 30% by weight of the synthetic effluent obtained by the optional dehydration step and treated in step a).

[0075] Furthermore, the synthetic effluent obtained by the optional dehydration step may contain water even before being mixed with the aqueous stream 21 in step a). This water may be generated during the dehydration step itself: for example, water is formed during the reaction of sugar dehydrating to 5-HMF (3 moles of water are generated for every 1 mole of 5-HMF produced). This water may also be introduced along with the sugar, in the case of using, for example, about 70% by weight of syrup for practical reasons. Advantageously, during the optional dehydration step, the water / polar aprotic synthetic solvent mixture (e.g., DMSO) can be recovered in the gas phase. This water / polar aprotic synthetic solvent mixture (e.g., DMSO) can advantageously be fed to the optional step g). Therefore, the synthetic effluent obtained by the optional dehydration step and introduced as feedstock 1 in step a) may contain water in a proportion typically from 0.1% to 30% by weight, preferably from 0.1% to 15% by weight, more preferably from 0.1% to 10% by weight.

[0076] The synthesis effluent obtained by the optional dehydration step and introduced as feedstock 1 into step a) may also contain impurities, particularly humin. The term "humin" refers to all undesirable polymeric compounds formed during the synthesis of 5-HMF. In particular, humin constitutes less than 30% by weight of the converted sugar feedstock, preferably less than 20% by weight.

[0077] During the optional dehydration step, the degree of sugar (e.g., fructose) conversion is at least 80%, preferably at least 90%, and even more preferably at least 98%.

[0078] The term "degree of conversion" refers to the ratio of the sugar consumed during the reaction (the difference between the total sugar involved and the sugar remaining at the end of the reaction) to the total sugar involved in the reaction.

[0079] The selectivity of sugar to 5-HMF is defined as the molar ratio between the number of moles of 5-HMF produced by the reaction and the number of moles of sugar consumed in the reaction.

[0080] Finally, the molar yield of 5-HMF is defined as the molar ratio between the number of moles of 5-HMF produced in the reaction and the number of moles of sugar involved in the reaction. Therefore, the molar yield is the product of conversion and selectivity.

[0081] The molar yield of 5-HMF is at least 70%, preferably at least 80%.

[0082] An optional neutralization step can be performed on the synthetic effluent obtained from an optional dehydration step before introducing it as feedstock 1 into step a), the synthetic effluent containing a dehydrating acid catalyst. This allows for a reduction in the reactivity of the medium, thereby avoiding the mechanism of 5-HMF degradation, or reducing material corrosion in downstream equipment of the optional dehydration step. Since the dehydration reaction may produce some organic acids, the amount of neutralizing agent can advantageously be such that all acids present in the synthetic effluent obtained from the dehydration step can be neutralized. This neutralization step is advantageously carried out at a stoichiometric ratio of at least the amount of catalyst used, and generally 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, Ba(OH)2.

[0083] Mixing step a) The method according to the invention includes step a), contacting (or mixing) a raw material 1 (optionally obtained by a dehydration step) containing 5-HMF and a polar aprotic synthesis solvent with an aqueous stream 21 to obtain at least an aqueous mixture 2.

[0084] The aqueous stream 21 may consist of pure water outside the method or water recycled in the method. For example, the aqueous stream 21 may advantageously include all or some of the aqueous back-extraction solution 9 obtained from step c) and / or the water 15 generated in optional step g) of the treatment of the water-polar aprotic synthesis solvent mixture.

[0085] Preferably, 5-HMF accounts for at least 1% by weight of the raw material 1 introduced in step a) of the method according to the invention, preferably at least 10% by weight, preferably at least 15% by weight, and preferably no more than 50% by weight, preferably no more than 40% by weight, and preferably no more than 30% by weight.

[0086] Preferably, the polar aprotic synthesis solvent (e.g., DMSO) accounts for 30% to 95% by weight of the raw material 1 introduced in step a), more preferably 40% to 90% by weight, more preferably 50% to 90% by weight, and even more preferably 55% to 85% by weight.

[0087] The raw material 1 introduced in step a) may also contain water, preferably in a proportion between 0.1% by weight and 30% by weight, more preferably between 0.1% by weight and 15% by weight, and even more preferably between 0.1% by weight and 10% by weight.

[0088] Raw material 1 may optionally contain humin. Humin particularly constitutes less than 30% by weight of raw material 1, preferably less than 20% by weight.

[0089] Therefore, the aqueous stream 21 contains water and can be composed of water. When the aqueous stream 21 contains a portion of recycled process water, said portion can 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. The aqueous stream 21 can contain all or part of the aqueous back-extraction solution 9 obtained from step c). The aqueous back-extraction solution 9 contains water, a polar aprotic synthesis solvent (e.g., DMSO), and optionally 5-HMF. Advantageously, the aqueous back-extraction solution 9 contains more than 60% by weight of water, preferably more than 70% by weight, and more preferably more than 80% by weight of water.

[0090] Advantageously, the aqueous mixture 2 obtained at the end of step a) contains between 10% by weight and 90% by weight of water, preferably between 20% by weight and 80% by weight of water, and more preferably between 40% by weight and 75% by weight of water.

[0091] Preferably, step a) is carried out at a temperature between 0 and 60°C, more preferably between 5 and 40°C, and usually at ambient temperature, i.e., between 10 and 40°C.

[0092] By increasing the water content of raw material 1 during step a), some humic acid present in raw material 1 precipitates.

[0093] Therefore, the aqueous mixture 2 obtained from the contact of the raw material 1 with the aqueous stream 21 contains precipitated humin, forming solid particles, and thus undergoes a liquid-solid separation step b) to send only the liquid portion (separated from the suspended solid particles) to the liquid-liquid extraction step c).

[0094] Preferably, the raw material 1 is precipitated by adding water at a water / polar aprotic synthesis solvent (e.g., DMSO) ratio of 0.2 to 3, more preferably 1 to 2, for example 1.5. The water / polar aprotic synthesis solvent (e.g., DMSO) ratio in step a) is more specifically defined as the following mass ratio: (E AJ + E C1 ) / SS C1 E AJ Added water, E C1 : The water contained in raw material 1, SS C1 : The polar aprotic synthesis solvent contained in raw material 1.

[0095] For simplicity, this ratio does not take into account the polar aprotic synthesis solvent that may be present in the aqueous stream 21, which is the water added in the ratio definition.

[0096] Advantageously, the precipitation of raw material 1 lasts for a period of 30 seconds to 4 hours, preferably between 1 minute and 3 hours, more preferably between 30 minutes and 2 hours, for example 1.5 hours.

[0097] Step a) can be carried out continuously or in batches, and in any suitable equipment known to those skilled in the art for mixing raw material 1 and aqueous streams and precipitating humicin, such as tanks that may contain different types of agitators, mixers equipped with endless screws, etc.

[0098] Liquid-solid separation step b) The method according to the invention includes step b), performing a liquid-solid separation on the aqueous mixture 2 obtained from step a), to obtain a liquid separated from the suspended solid particles and a solid residue containing humin, wherein the solid residue is preferably removed from the method in the form of a solid stream. The liquid-solid separation step b) is carried out by filtration. Therefore, this step allows for the removal of "humin" that has precipitated in or upstream of the mixing step a). It is then advantageously that at least a portion of the resulting liquid is sent to a liquid-liquid extraction step c), wherein the portion or preferably all of the liquid sent to step c) corresponds to... Figure 3 and Figure 4 The aqueous filtrate 3 shown in the figure.

[0099] As a guideline, the amount of humin precipitated and present in the aqueous mixture 2 in step a) is, for example, greater than 1% of the total mass of the aqueous mixture 2.

[0100] According to one basic aspect of the invention, the liquid-solid separation step b) includes a first filtration cycle b1) and a second filtration cycle b3), which are separated by an intermediate step b2) that resuspends the solid phase obtained at the end of the first filtration cycle b1), also known as a reslurrying step.

[0101] Therefore, the term "re-slurrying" refers to the operation of contacting the solid phase obtained at the end of the filtration cycle (also known as the filter cake, typically the filter cake that has been broken up at the end of a filtration cycle via a filter press) with an aqueous solution 18 (preferably composed of water, also known as the re-slurrying solution or water) by suspending the solid phase in a solution.

[0102] Step b) produces at least a first aqueous filtrate 3, a second aqueous filtrate 20, and a final solid 19, which contains at least a portion, and preferably substantially all, of the solid particles, the final solid being the solid residue preferably removed from the method. The first aqueous filtrate 3 is produced from a first filtration cycle b1) and corresponds to the liquid portion sent to the liquid-liquid extraction step c), comprising water, 5-HMF, and a polar aprotic synthesis solvent (e.g., DMSO), and the second aqueous filtrate 20 is produced from a second filtration cycle b3) and recycled to step a) because it is an aqueous stream containing the compounds of interest extracted from the reslurryed solid phase, in this case 5-HMF and a polar aprotic synthesis solvent, which are therefore advantageously recycled in the method for producing 5-HMF. Thus, the production of this second aqueous filtrate 20 recycled to step a) enables an increase in the HMF yield of the method and saves on aprotic synthesis solvent, thereby limiting the operating costs of the method.

[0103] Advantageously, the liquid-solid separation step b) of the method according to the invention does not include a step of washing the filtered solid phase (filter cake) produced during said step b). The liquid-solid separation step b) of the method according to the invention incorporates a reslurry step between two filtration cycles, which, for the same amount of water, surprisingly enables the extraction of more residual products of interest remaining in the filter cake, including 5-HMF and polar aprotic solvents (e.g., DMSO), compared to filtration cycles that include a filter cake washing step. This gain in the extraction of 5-HMF and polar aprotic solvents advantageously allows for an increase in the overall yield of 5-HMF in the method (by specifically recycling the product extracted by filtration after reslurrying) and, to a lesser extent, savings in operating costs associated with the supply of polar aprotic solvents (e.g., DMSO).

[0104] The liquid-solid separation step b) uses one or more apparatuses configured to filter the suspension and produce at least one solid phase (typically a filter cake) at the end of each filtration cycle, and to reslurry the solid phase, for example, the filter cake (i.e., resuspend the solid phase by contacting it with an aqueous solution). Preferably, the liquid-solid separation step b) is carried out at a temperature between ambient temperature (i.e., between 10°C and 40°C) and 80°C, more preferably at ambient temperature, i.e., between 10°C and 40°C, preferably between 18°C ​​and 25°C.

[0105] Advantageously, for implementing the filtration cycle, the liquid-solid separation step b) includes the use of at least one device selected from pressing or draining apparatuses, such as filter presses, belt filters, centrifuges, candle filters, vacuum filters, belt filter presses, decanters, and drainers, preferably selected from filter presses, belt filters, centrifuges, and candle filters. In the case of centrifuges, the term "sediment" rather than filter cake is generally preferred to refer to the separated solid phase obtained at the end of centrifugation. Equipment such as centrifuges or belt filters allows for continuous operation.

[0106] The liquid-solid separation step b) is preferably carried out in batches, using at least one piece of equipment selected from filter press, candle filter, vacuum filter, belt filter press, decanter and drainer, preferably using at least one filter press.

[0107] Furthermore, in order to perform the repulping step b2), the liquid-solid separation step b) preferably includes a dedicated device, i.e. a device separate from the filtration equipment of the filtration cycles b1) and b3), such as a dedicated tank, which may include a suitable stirring system and is configured to receive the solid phase from the filtration equipment of the first filtration cycle b1) and send the repulped solid phase to the filtration equipment of the second filtration cycle b3).

[0108] In step b2), the reslurrying, which is carried out by contacting the solid phase obtained at the end of b1) with an aqueous solution, can be carried out continuously or in batches, in one or more operations / stages, by a mixer.

[0109] According to one or more embodiments, the first and second filtration cycles b1) and b3) are carried out in two separate equipment components, preferably in two separate filter presses.

[0110] According to one or more embodiments, the first and second filtration cycles b1) and b3) are carried out in one and the same common equipment, preferably in a common filter press.

[0111] Preferably, the liquid-solid separation step b) is performed in batches, resulting in the method being interrupted at the end of the first filtration cycle in step b) to re-slurry the solid phase extracted after the first filtration cycle, and then to perform a second filtration cycle of the re-slurryed solid phase, and possibly by using equipment that operates in batches during the filtration cycle.

[0112] Figure 4 The first and second filtration cycles and the intermediate repulping step b2 are shown in more detail, particularly according to one or more embodiments implementing filter press technology.

[0113] Liquid-solid separation via a filter press is a technique that allows the separation of a suspension under pressure to separate the liquid and solid phases. A filter press consists of plates (or frames) and filter media (typically filter cloth) through which an aqueous mixture 2 (including precipitated humic acid) is filtered, and the humic acid is removed as a solid filter cake. Under filtration pressure, the liquid, called filtrate, passes through the filter cloth that retains the solid particles. The filtrate is discharged throughout the process, while the filter cake formed between the plates is discharged only during the decomposition operation. Therefore, the technique operates in batch cycles, which include a series of steps including filtration and compaction (also known as compaction-purging, as compaction may optionally involve the injection of compressed air), which allows for increasing the solids content of the filter cake.

[0114] Filter presses typically consist of several vertical square frames forming sealed filter chambers. Each frame comprises two sides on which a filter cloth with a mesh size that is tight enough to allow the filter cake to settle. This configuration allows for a filtration surface area of ​​tens of square meters. The depth of the filter chambers (the space between the frames) enables the formation of a filter cake typically 10 mm to 50 mm thick, depending on the properties of the suspension being filtered, usually with a trade-off between circulation duration and filter cake weight.

[0115] Advantageously, the liquid-solid separation step b) is carried out using at least one filter press, and each of the first and second filtration cycles in the liquid-solid separation step b) comprises, in this order, the following sequence of sub-steps: - Sub-steps (b1.1, b3.1) for filtering the filter material to produce an aqueous filtrate (3, 20) and a coarse filter cake (22, 35); - Sub-steps (b1.3, b3.2) of compacting and purging the coarse filter cake to produce compacted-purged filtrate (31, 36) and compacted-purged coarse filter cake (32, 37); - Sub-steps (b1.4, b3.3) to break down the compacted-purge coarse filter cake to produce a broken-down filter cake (33, 19).

[0116] The shredded filter cake obtained at the end of the shredding sub-step b1.4) of the first filtration cycle b1) is a solid phase that is resuspended in the reslurrying step b2) by contact with the aqueous solution 18 to form the filter feed for the filtration sub-step b3.1) of the second filtration cycle b3).

[0117] First filtration cycle Preferably, the first filtration cycle is carried out using equipment selected from filter press, belt filter, centrifuge, candle filter, vacuum filter, belt filter press, decanter and drainer, and more preferably by filter press.

[0118] The first filtration cycle is preferably carried out at a temperature between ambient temperature and 80°C, preferably at ambient temperature, and at a pressure between 0.05 MPa (0.5 bar) and 5 MPa (50 bar), preferably between 0.1 MPa and 3 MPa.

[0119] The term "ambient temperature" refers to a temperature between 10°C and 40°C, preferably between 18°C ​​and 25°C.

[0120] Advantageously, the following sequence of sub-steps is performed: -b1.1) Filtration: An aqueous mixture 2, including solid particles (e.g., precipitated humin), is fed as the filter feed to filtration step b1.1) and to a filtration apparatus (preferably a filter press) to separate the solid particles in the form of a coarse filter cake 22 and a liquid phase containing 5-HMF and a polar aprotic synthetic solvent (e.g., DMSO) (forming an aqueous filtrate 3). Typically, the coarse filter cake 22 still contains a portion of the liquid phase that is retained due to the limitations of the solid / liquid separation apparatus and the nature of the aqueous mixture, which may contain precipitated humin. At this stage, the humin-containing filter cake is retained inside the filter. Preferably, filtration sub-step b1.1) is carried out at a temperature between ambient temperature and 80°C, preferably at ambient temperature, and at a pressure between 0.05 MPa (0.5 bar) and 1 MPa (10 bar), preferably between 0.1 MPa and 0.8 MPa, for example, 0.6 MPa. Preferably, a gradually increasing pressure ramp is applied.

[0121] A filter aid may be added to the aqueous mixture 2 sent to the filter sub-step b1.1), preferably diatomaceous earth, a polymer (e.g., polyethylene oxide) or an additive based on nuts, almonds or olives, more preferably diatomaceous earth, preferably in an amount of 0.01% to 5% by mass relative to the mass of the aqueous mixture 2.

[0122] In fact, in some cases, the suspension formed by aqueous mixture 2 may be difficult to filter, and the addition of such filter aids may be useful, especially to improve flow rate, filtration quality and filter cake porosity.

[0123] Diatomaceous earth is a well-known filter aid in the art, and its quality and content can be selected to facilitate filtration and the duration of filtration sub-steps. As an example, commercial diatomaceous earth, such as Clarcel® DIC3 diatomaceous earth, can be added at a content of 1% by mass relative to the mass of the raw material to be filtered.

[0124] Preferably, the filter aid is added in a stirring medium for a period of 1 minute to 4 hours, preferably 5 minutes to 1 hour, for example about 10 minutes, and preferably at ambient temperature before filtration begins.

[0125] A non-limiting practical example of implementing a filter press filtration sub-step is given: the filter is closed by actuating jacks that clamp the empty plates together. The closing pressure is self-regulating throughout the filtration process to maintain a seal at the plate joints. The feedstock (aqueous mixture 2) (optionally prepared as described above by adding filter aids) is then pumped into the filter chamber via a central or side feed port. This step is typically carried out under pressure, between 0.6 MPa and 0.8 MPa. The filtrate passes through the filter cloth and is collected in the channels of the plates to be discharged through holes located on the periphery of the plates. Solids gradually accumulate inside the filter chamber and between the plates until the desired filter cake thickness is formed. The filtration time varies depending on the properties of the suspension to be filtered and its filterability. When the final flow rate reaches 5 l / m³... 2 When the value of / h is reached, filtration is typically stopped. The feed pump is stopped, and the suspension and filtrate in the internal circuit are purged by injecting compressed air.

[0126] Preferably, the filter cloth is selected to be compatible with the raw material to be filtered, and practically compatible with polar aprotic synthesis solvents, preferably DMSO. Therefore, polypropylene filter cloth is preferred, which advantageously has a retention threshold of 10 µm.

[0127] -b1.3) Compaction-Purge: Preferably, the coarse filter cake 22 formed in the filtration sub-step b1.1) undergoes a compaction-purge operation, and a first compaction-purge filtrate 31 and a compaction-purge coarse filter cake 32 are formed.

[0128] This sub-step dehydrates the filter cake by pressurizing it, preferably by injecting compressed air into the filter cloth to compress the cake. Pressurizing the filter allows for an increase in the SC (solids content) of the filter cake, and the extraction of water and products of interest, primarily 5-HMF and polar aprotic synthesis solvents (e.g., DMSO).

[0129] Preferably, at the end of the compaction-purging sub-step, the compacted-purging coarse filter cake 32 has an SC of 20% to 90% by mass relative to the total mass of the filter cake, more preferably 50% to 90% by mass, and more preferably 65% ​​to 85% by mass.

[0130] Advantageously, compaction-purging is carried out by injecting compressed air.

[0131] Preferably, compaction / purging is carried out at a pressure between 1 MPa and 5 MPa, more preferably between 1 MPa and 3 MPa, more preferably between 1 MPa and 2 MPa, for example, 1.5 MPa.

[0132] The duration of compaction-purging is typically between 5 and 30 minutes, preferably between 10 and 20 minutes, such as 15 minutes.

[0133] For example, for the filtration sub-step b1.1), compaction-purging b1.3) is preferably carried out at an ambient temperature between 80°C, preferably between 10°C and 40°C, and preferably between 18°C ​​and 25°C.

[0134] Therefore, the first compacted-purge filtrate 31 (which may contain compounds of interest and has a composition similar to that of the first aqueous filtrate 3) is preferably recycled to the liquid-liquid extraction step c in this method.

[0135] -b1.4) Decomposition: Preferably, the compacted-purge coarse filter cake 32 is then decomposition to produce a decomposed filter cake 33.

[0136] The disintegration step b1.4) is preferably carried out at ambient temperature and atmospheric pressure.

[0137] The filtration equipment (typically a filter press) is opened to break up the filter cake. This mechanical action of opening the filter can be supplemented by suitable devices known to those skilled in the art (e.g., vibration or scraping operations) to aid in the breaking up of the filter cake.

[0138] The decomposition time is preferably between 15 minutes and 2 hours, more preferably between 15 minutes and 1.5 hours, and more preferably between 30 minutes and 1 hour, and generally depends on the number of plates equipped in the filter press.

[0139] Preferably, the broken-up filter cake is recovered in a tank to perform the intermediate repulping step b2).

[0140] Without limitation, defragmentation can actually be performed as follows: the moving head of the filter is moved back to open the filter chambers one by one via an automatic system. The resulting filter cake falls under its own weight. Defragmentation time is typically between 15 and 45 minutes, depending on the number of plates equipped in the filter press. Filter presses can include various devices that aid in defragmentation, such as plate vibrators, automatic scrapers, or manual defragmentation devices that can be used when the filter cake becomes sticky, or combinations of such devices. The filter cake falls directly into a tank placed below the filter, for example via a hopper, or into a tank further away from the filter via a conveyor belt or screw conveyor.

[0141] b2) Re-slurrying: intermediate re-suspension step The coarse filter cake 22 of filtration step b1.1) or preferably the disintegrated filter cake 33 obtained at the end of the disintegration sub-step b1.4) of the first filtration cycle b1) is the solid phase resuspended in the reslurry step b2).

[0142] Reslurrying involves resuspending the filtered solid phase (e.g., the broken-up filter cake 33) obtained at the end of the first filtration cycle by contacting it with an aqueous solution 18.

[0143] The repulping step is combined with a second filtration cycle (b3) which receives a suspension formed from the repulped solid phase 34 (repulped filter cake 34) as a filtration feedstock, in order to recover as much of the product of interest, such as 5-HMF and polar aprotic synthesis solvents (e.g., DMSO), as possible from the filtered solid phase at the end of the first filtration cycle during the liquid-solid separation step (b).

[0144] The repulping step b2) is preferably carried out in a dedicated device, typically a dedicated tank, which is separate from the filtration equipment of the filtration cycles b1) and b3).

[0145] The tank preferably includes a suitable stirring system and is configured to receive the shredded filter cake 33 as described above (placed below or further from the filter, with a conveying system) and to send the re-slurryed solid phase 34 to a second filtration cycle (b3) using a filtration device, such as a piping and pump system.

[0146] Re-pulping can be carried out continuously or in batches, in one or more operations / stages, using a mixer.

[0147] Preferably, the re-pulping step is carried out at an ambient temperature between 80°C and 10°C, more preferably between 40°C and 18°C, and even more preferably at atmospheric pressure.

[0148] The repulping time can be between 1 minute and 4 hours, preferably between 5 minutes and 3 hours, and more preferably between 30 minutes and 2 hours.

[0149] Aqueous solution 18 can be pure water, and may be used outside of this method.

[0150] The aqueous solution 18 may contain or consist of at least a portion of the aqueous effluent 15 produced in optional step g) of the treatment of the water-polar aprotic synthetic solvent mixture.

[0151] The mass ratio between the aqueous solution and the filter cake is preferably between 1 and 10, more preferably between 2 and 8, and even more preferably between 3 and 7.

[0152] Second filtration cycle Preferably, the second filtration cycle b3) is performed using equipment selected from filter presses, belt filters, centrifuges, candle filters, vacuum filters, belt filter presses, decanters, and drainers, and more preferably, a filter press. This can be equipment of the same or different natures, for example, a filter press used for the first filtration cycle and a belt filter used for the second filtration cycle, and preferably, to simplify the method, the equipment for both filtration cycles has the same nature.

[0153] Furthermore, the first and second filtration cycles can be performed in the same equipment, i.e., in a shared equipment.

[0154] Preferably, the first filtration cycle and the second filtration cycle are performed in separate devices.

[0155] The second filtration cycle is preferably carried out at a temperature between ambient temperature and 80°C, preferably at an ambient temperature (i.e., between 10°C and 40°C, more preferably between 18°C ​​and 25°C), and at a pressure between 0.05 MPa (0.5 bar) and 5 MPa (50 bar), preferably between 0.1 MPa and 3 MPa.

[0156] Advantageously, the following sequence of sub-steps is performed during the second filtering cycle b2): -b3.1) Filtration: The resuspended solid phase 34 (i.e., the reslurry filter cake) is fed as the filter feed to filtration step b3.1) and into a filtration apparatus (preferably a filter press) to separate the solid particles in the form of a reslurry coarse filter cake 35 (i.e., a coarse filter cake produced from the suspension obtained from reslurry B2) and a liquid phase 20 containing 5-HMF and a polar aprotic synthetic solvent (e.g., DMSO) (forming a reslurry filtrate 20, which is an aqueous filtrate). Typically, the reslurry coarse filter cake 35 still contains a portion of the liquid phase that is retained due to the limitations of the solid / liquid separation apparatus and possibly the characteristics of the feed 34. At this stage, the reslurry coarse filter cake is retained inside the filter. Preferably, filtration sub-step b3.1) is carried out at a temperature between ambient temperature and 80°C, preferably at ambient temperature, and at a pressure between 0.05 MPa (0.5 bar) and 1 MPa (10 bar), preferably between 0.1 MPa and 0.8 MPa, for example, 0.6 MPa. Preferably, a ramp with gradually increasing pressure is applied.

[0157] Filter aids may be added to the feed 34 fed to the filtration sub-step b3.1), preferably diatomaceous earth, polymers (e.g., polyethylene oxide), or nut, almond, or olive-based additives, more preferably diatomaceous earth, and preferably in an amount of 0.01% to 5% by mass relative to the mass of the feed 34. The purpose of such aids is to facilitate filtration, particularly to improve flow rate and / or filtration quality and / or filter cake porosity.

[0158] A non-limiting practical example of performing the filter press filtration sub-step is the same as that given in sub-step b1.1), and will not be repeated here.

[0159] Preferably, the filter cloth is selected to be compatible with the raw material to be filtered, and practically compatible with polar aprotic synthetic solvents, preferably DMSO. Therefore, polypropylene filter cloth is preferred, which advantageously has a retention threshold of 10 µm.

[0160] The second aqueous filtrate 20 is recycled to mixing step a as previously mentioned.

[0161] -b3.2) Compaction-Purge: Preferably, the re-slurry coarse filter cake 35 formed in the filtration sub-step b3.1) undergoes a compaction-purge operation, and a second compaction-purge filtrate 36 and a re-slurry compaction-purge coarse filter cake 37 are formed.

[0162] This sub-step b3.2) dewaters the filter cake by placing it under pressure (preferably by injecting compressed air into the filter cloth to press the filter cake). Pressurizing the filter allows for an increase in the solids content (SC) of the filter cake and the extraction of water and potentially interesting products, primarily 5-HMF and polar aprotic synthesis solvents (e.g., DMSO).

[0163] Preferably, at the end of the compaction-purging sub-step b3.2), the compaction-purging re-slurry coarse filter cake 37 has an SC of 20% to 90% by mass relative to the total mass of the filter cake, preferably 30% to 90% by mass, more preferably 35% to 80% by mass, and even more preferably 40% to 60% by mass.

[0164] Advantageously, compaction-purging is carried out by injecting compressed air.

[0165] Preferably, the compaction-purging (b3.2) is performed at a pressure between 1 MPa and 5 MPa, more preferably between 1 MPa and 3 MPa, more preferably between 1 MPa and 2 MPa, for example, 1.5 MPa.

[0166] The duration of compaction-purging (b3.2) is typically between 5 and 30 minutes, preferably between 10 and 20 minutes, for example, 15 minutes.

[0167] For example, for the filtration sub-step b1.1), compaction-purging b3.2) is carried out at a temperature between ambient temperature and 80°C, preferably at an ambient temperature (i.e., between 10°C and 40°C, preferably between 18°C ​​and 25°C).

[0168] Therefore, the second compacted-purge filtrate 36 (which may contain compounds of interest and, in particular, has a composition similar to that of the second aqueous filtrate 20) is preferably recycled to the mixing step a in this method.

[0169] -b3.3) Disintegration: Preferably, the second compacted-purge coarse filter cake 37 is then disintegrated to produce a disintegrated filter cake 19 forming the final solid, which is preferably removed from the method. Thus, the solid residue contains at least a portion, and preferably substantially all, of the solid particles of the aqueous mixture 2 fed to the liquid-solid separation step, and therefore contains the precipitated humic acid discharged from the method.

[0170] The disintegration step (b3.3) is preferably carried out at ambient temperature (i.e., between 10 and 40°C, preferably between 18 and 25°C) and atmospheric pressure.

[0171] The filtration equipment (usually a filter press) is opened to break up the filter cake. This mechanical action of opening the filter can be supplemented by vibration or scraping operations using suitable devices known to those skilled in the art to help break up the filter cake.

[0172] The decomposition time is preferably between 15 minutes and 2 hours, more preferably between 15 minutes and 1.5 hours, and more preferably between 30 minutes and 1 hour, and generally depends on the number of plates equipped in the filter press.

[0173] Without being restrictive, the disintegration can actually be carried out in the same manner as described in sub-step b1.4), and will not be repeated here.

[0174] Liquid-liquid extraction step c) The method according to the invention includes step c), performing liquid-liquid extraction on the aqueous mixture 3 obtained at the end of step b) in the presence of extraction solvent 4 to produce an aqueous raffinate 5 and an organic extract 6.

[0175] The liquid-liquid extraction performed in step c) advantageously corresponds to washing the aqueous mixture with an organic extraction solvent. Preferably, the liquid-liquid extraction performed in step c) is a countercurrent extraction of the aqueous mixture 3 obtained in step b) with extraction solvent 4. This technique is well known to those skilled in the art. It can be carried out, for example, in a mixer-clarifier array, in a column packed with bulk or structured packing, in a pulse column, or in a stirred column.

[0176] Liquid-liquid extraction may include implementing at least two theoretical separation stages. This is, for example, but not exclusively, when an additional liquid-solid separation step is performed on the intermediate liquid stream generated during liquid-liquid extraction step c), which returns to step c) after the solid particles have been removed. A first liquid-liquid separation stage can then be performed, producing the intermediate liquid stream sent to the additional liquid-solid separation step to form a particle-poor intermediate liquid stream, which is then sent to the second liquid-liquid extraction stage in step c).

[0177] Liquid-liquid extraction step c) is advantageously carried out at a temperature between 0 and 60°C, preferably between 5°C and 40°C, and is usually carried out at ambient temperature (i.e., between 10 and 40°C).

[0178] Typically, the extraction solvent content (defined as the mass ratio between the extraction solvent flow rate and the feed entering the extraction step) is determined by 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 entrained in the organic extract 9 and the amount of 5-HMF contained in the aqueous mixture 6 sent to extraction step d). 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%.

[0179] The extraction solvent 4 introduced in step c) is selected from an organic solvent that is immiscible with water, so as to form two liquid phases in steps c) and d). This property is highly dependent on the relative proportions of the feed, backwash water, and extraction solvent flow rates used in the method.

[0180] 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.

[0181] Advantageously, the extraction solvent is selected to have a very high volatility difference from 5-HMF, particularly to facilitate its removal in optional step e) and limit the degradation of 5-HMF, i.e., to ensure that 5-HMF is not degraded in step e) and to minimize the amount of residual solvent to be removed in water distillation step f), while simultaneously ensuring that there is no vaporization of liquid phase separation when the concentrated organic raffinate 10 is contacted with water in water distillation in step f).

[0182] The extraction solvent can also be selected to form a heterogeneous azeotrope with water during the water distillation in step f), preferably being solvent-rich, i.e., 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 significantly lower boiling point than water, preferably at least 5°C lower, more preferably at least 8°C lower, and more preferably at least 10°C lower.

[0183] Advantageously, the organic solvent streams generated in subsequent steps can be recycled as extraction solvents to extraction step c). These organic solvent streams may contain impurities that may be generated during the implementation of the method. Advantageously, the organic solvent streams generated in subsequent steps can be distilled, for example, periodically, to avoid the accumulation of said impurities.

[0184] Therefore, step c) enables the production of both a 5-HMF-deficient aqueous stream (referred to as aqueous raffinate 5), containing a large portion of the polar aprotic synthesis solvent (e.g., DMSO) initially present in feed 1, and a 5-HMF-rich organic stream (referred to as organic extract 6), containing a large portion of the 5-HMF initially present in feed 1 and extraction solvent 4. This organic extract 6 may also contain a polar aprotic synthesis solvent (e.g., DMSO). Preferably, the organic extract contains 5-HMF and a polar aprotic synthesis solvent (e.g., DMSO) in a weight ratio between 50 / 50 and 99 / 01, preferably between 50 / 50 and 95 / 05, preferably between 55 / 45 and 90 / 10, more preferably between 60 / 40 and 85 / 15, and most preferably between 65 / 35 and 80 / 20.

[0185] Advantageously, the organic extract 6 is sent directly to the backwashing step d).

[0186] Step c) may also contain some solid particles formed by the precipitation of humic acid. These may be humic acid that precipitated in the upstream mixing step a) and is still present in the aqueous mixture 3 sent to step c), or humic acid that precipitated in step c) or backwashing step d).

[0187] Backwashing step d) The method according to the invention includes step d), backwashing the organic extract 6 with an aqueous solvent 7 to produce an aqueous back-extract 9 and an organic raffinate 8 containing 5-HMF and an organic solvent. The aqueous back-extract 9 is advantageously fed, in part or in whole, into step a). 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 a small amount.

[0188] In step d), an aqueous solvent 7 is introduced to perform backwashing according to the general knowledge of those skilled in the art. The aqueous solvent 7 is introduced in such a low amount as possible to reduce costs, but sufficiently to ensure a low weight content of the polar aprotic synthesis solvent (e.g., DMSO) in the organic raffinate 8, preferably less than or equal to 20.0% by weight relative to 5-HMF, preferably less than or equal to 15.0% by weight relative to 5-HMF, preferably between 0.01% by weight and 15.0% by weight relative to 5-HMF, and most preferably between 0.01% by weight and 10.0% by weight relative to 5-HMF.

[0189] Advantageously, the aqueous backwash solvent 7 introduced in step d) 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). The lower the amount of polar aprotic synthesis solvent (e.g., DMSO) in the aqueous backwash solvent, the higher the effectiveness of the backwashing. The aqueous solvent may comprise no more than 1.0% by weight, and preferably no more than 0.1% by weight, of a polar aprotic synthesis solvent (e.g., DMSO). Advantageously, the aqueous backwash solvent 7 is obtained from step g) of treating the water-polar aprotic synthesis solvent mixture generated in this method, and thus comprises at least a portion of the recyclable effluent 15. In a preferred embodiment of the invention, the aqueous raffinate 5, consisting of water and a polar aprotic synthesis solvent (e.g., DMSO) produced in step c), is treated in step g), which advantageously includes distillation. The water-rich distillate obtained at the end of step g) (also known as the aqueous effluent 15 recyclable to the method) is advantageously used to form the aqueous backwash solvent 7 in step d), optionally as a mixture with makeup water, or to be used in step a) to form the aqueous stream 21, optionally together with at least one portion of the aqueous back-extraction solution 9 and / or makeup water. The recyclable effluent 15 (e.g., 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. The more efficient the distillation in step g), particularly with a distillation stage number greater than 5 and advantageously suitable reboiling rate and reflux ratio, the lower the residual amount of polar aprotic synthetic solvent (e.g., DMSO) in the aqueous effluent 15 (distillate).

[0190] Backwashing step d) is advantageously a countercurrent liquid-liquid extraction of the organic extract 6 obtained in the organic stream (particularly step c) with an aqueous solvent 7. This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a mixing and clarifier array, in a column packed with random or structured packing, in a pulse column, or in a stirred column.

[0191] Step d) 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).

[0192] The weight ratio (weight / weight) of the aqueous solvent 7 to the organic extract 6 is preferably between 0.04 and 5, more preferably between 0.07 and 3, and more preferably between 0.1 and 1.

[0193] Step d) enables the production of an aqueous stream (referred to as aqueous back-extraction solution 9) that is advantageously rich in a polar aprotic synthesis solvent (e.g., DMSO), preferably containing at least 60% by weight of water, more preferably at least 80% by weight of water, and an organic raffinate 8 that is advantageously depleted of a polar aprotic synthesis solvent (e.g., DMSO). The aqueous back-extraction solution 9 is advantageously partially or entirely fed into step a). The resulting organic raffinate 8 has a polar aprotic synthesis solvent content of preferably less than or equal to 20.0% by weight, preferably less than or equal to 15.0% by weight, more preferably less than or equal to 5.0% by weight, even more preferably less than or equal to 4.0% by weight, and more preferably less than or equal to 3.0% by weight relative to 5-HMF.

[0194] According to the present invention, the organic raffinate 8 produced in step d) is sent to an optional concentration step e) or directly to a water distillation step f).

[0195] Humin may still be present in the organic extract 6 sent to backwash step d). If they precipitate in this step, forming undesirable solid particles, they can be removed by sending part or all of the aqueous backwash 9 containing the precipitated humin to step c), where they can be removed during an additional liquid-solid separation step on the intermediate liquid stream generated in step c) and / or the aqueous raffinate 5 downstream of step d). If the aqueous backwash 9 is sent part or all to step a) to become part of or constitute the aqueous stream 21, the precipitated humin can also be separated during the liquid-solid separation in step b), as described above.

[0196] Optional concentration step e) The method according to the invention preferably includes step e), concentrating the organic raffinate 8 obtained in step d) by removing a portion of the organic solvent, to produce a concentrated organic raffinate 10 containing 5-HMF and residual organic solvent, and a first stream 11 containing and preferably composed of an organic solvent, which advantageously consists entirely or partially of an extraction solvent and an optional polar aprotic synthesis solvent (e.g., DMSO).

[0197] Preferably, the first stream 11 containing the organic solvent is recycled in whole or in part to the extraction step c), for example, to form at least a portion of the organic solvent stream 4.

[0198] Preferably, in step e), a portion of the organic solvent is removed by vaporization, for example in an atmospheric or vacuum distillation column, in an evaporator, or by any method known to those skilled in the art.

[0199] According to this preferred embodiment, the vaporization of the extraction solvent is advantageously carried out under atmospheric pressure or vacuum, preferably at a pressure of 0.01 MPa to 0.1 MPa, and more preferably under vacuum at a pressure of 0.01 MPa to 0.09 MPa, in order to limit the liquid temperature and thus limit the degradation of 5-HMF. Preferably, the liquid temperature is maintained at or below 130°C, more preferably at or below 100°C, and more preferably at or below 70°C. It should be noted that the pressure level, and in particular the vacuum level, required to achieve these temperatures depends on the organic solvent, and more specifically on the extraction solvent used and the degree of vaporization of the organic solvent.

[0200] In a preferred embodiment, the solvent is vaporized by multi-effect evaporation, vapor mechanical recompression, or any other method known to those skilled in the art, in order to reduce the operating costs associated with solvent evaporation while limiting the risk of degradation of the product of interest, 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 liquid phase temperature gradually decreases, limiting any risk of degradation.

[0201] Optionally, step e) is performed with a vaporization mass ratio (or evaporation ratio) corresponding to a vaporization mass ratio (or evaporation ratio) of at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 75%, preferably at least 80%, preferably at least 85%, preferably at least 90%, and more preferably at most 99%, relative to the mass of the organic raffinate 8 from step d). Advantageously, the degree of vaporization is defined as a function of the extraction solvent in order to prevent degradation of 5-HMF and to minimize the amount of residual solvent to be removed in the aqueous distillation step f), while ensuring that there is no liquid phase separation when the concentrated organic raffinate 10 is contacted with water during the aqueous distillation in step f) (i.e., ensuring that the liquid phase remains a single phase).

[0202] By utilizing a combination of all operating conditions in steps a), b), c), and d) and optional step e), the concentrated organic raffinate 10 obtained at the end of step e) advantageously has a 5-HMF content of at least 40% by weight, preferably at least 50% by weight, preferably at least 60% 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 10. In other words, the concentrated organic raffinate 10 preferably has a residual organic solvent content of at least 5% by weight, preferably at least 10% by weight, and preferably at most 60% by weight, preferably at most 50% by weight, and preferably at most 40% by weight, relative to the weight of the concentrated organic raffinate 10.

[0203] Advantageously, the organic solvent vaporized during optional step e) forms a first stream 11 comprising the organic solvent, preferably composed thereof, and is preferably recycled to extraction step c).

[0204] Advantageously, the concentrated organic raffinate 10 is sent to the water distillation step f).

[0205] Purification step f) The method according to the invention includes step f), purifying the organic raffinate 8 or the concentrated organic raffinate 10 to produce a 5-HMF stream.

[0206] According to one or more embodiments, purification step f) includes and may consist of a water distillation step, which is carried out by distilling the organic raffinate 8 obtained from step d) or the concentrated organic raffinate 10 obtained from optional step e) in the presence of water 14 to produce the 5-HMF stream (which is then a 5-HMF aqueous solution 12) and to produce a second stream 13 containing, and preferably consisting of, an organic solvent.

[0207] The water distillation step advantageously allows the removal of at least a portion of the residual organic solvent that was not removed during optional step e). The residual organic solvent removed during the water distillation step (i.e., the second stream 13 containing the organic solvent) can advantageously be recycled to the extraction step c, either alone or in combination with the first stream 11 obtained from optional step e).

[0208] Advantageously, the aqueous liquid 14 is fed into the water distillation step. The aqueous liquid 14 introduced into the water distillation step preferably contains more than 95% by weight of water, more preferably more than 98% by weight of water.

[0209] In a particular embodiment of the invention, the aqueous liquid 14 is pure water, possibly outside the method, which makes it possible to further reduce the content of residual polar aprotic synthesis solvent (e.g., DMSO) in the 5-HMF aqueous solution 12 produced in step f), which includes or is composed of water distillation.

[0210] In another specific embodiment of the invention, water separated within the method is used to supply the water distillation step, thereby limiting the operating costs and environmental impact of the method. Typically, if the sugar feedstock for the optional dehydration step is a syrup with a water concentration of 70% by weight, approximately one tonne of water (from the sugar feedstock and water generated during the dehydration reaction) can be obtained per tonne 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 said water from the sugar feedstock and / or the dehydration step to produce, at the end of the water distillation step, a 5-HMF aqueous solution preferably concentrated to 30% by weight or higher, preferably to 40% by weight or higher, thereby reducing the reprocessing costs and environmental impact of the method.

[0211] Advantageously, the aqueous liquid 14 introduced in the water distillation step may correspond to at least a portion, or possibly all, of the aqueous effluent 15 (distillate) produced in step h). The distillate may optionally contain a residual amount of a polar aprotic synthesis solvent (e.g., DMSO).

[0212] Advantageously, during the water distillation step, the extraction solvent used in this method forms a heterogeneous azeotrope with water, said azeotrope preferably being 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 significantly lower boiling point than water, preferably at least 5°C lower, more preferably at least 8°C lower, and more preferably at least 10°C lower.

[0213] Therefore, after contacting the concentrated organic raffinate 10 or the organic raffinate 8 with the aqueous liquid 14, the residual organic solvent can be easily removed without degrading 5-HMF.

[0214] The water distillation step can be carried out at atmospheric pressure or under vacuum, and particularly at pressures between 0.001 MPa and 0.1 MPa, and preferably under vacuum at pressures between 0.005 MPa and 0.08 MPa. Advantageously, the water distillation step is carried out under vacuum, particularly at pressures between 0.001 MPa and 0.1 MPa, preferably between 0.005 MPa and 0.08 MPa, in order to help remove residual organic solvents without degrading 5-HMF.

[0215] Advantageously, the water distillation step is carried out in a distillation column, preferably with 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, so as to help remove residual organic solvents without degrading 5-HMF.

[0216] In one particular embodiment, during the water distillation step, concentrated organic raffinate 10 or (if not) organic raffinate 8 and aqueous liquid 14 are mixed before being introduced into the distillation column, and the mixture is introduced into the middle point of the distillation column.

[0217] In another specific embodiment, during the water distillation step, concentrated organic raffinate 10 or organic raffinate 8 is introduced into the upper part of the distillation column, preferably the upper half of the distillation column, while the aqueous liquid is also introduced into the distillation column. Mixing with the aqueous liquid then takes place within the distillation column.

[0218] Considering the formation of a heterogeneous azeotrope between water and the 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 advantageously be returned to the column as reflux) and an organic solvent-rich phase 13 (which can advantageously be recycled to extraction step c).

[0219] The aqueous solution 12 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 in terms of the weight of 5-HMF relative to the aqueous solution of 5-HMF obtained at the end of the water distillation step.

[0220] The method according to the invention advantageously enables the production of an aqueous 5-HMF solution having a polar aprotic synthetic solvent (e.g., DMSO) content of less than or equal to 10% by weight relative to 5-HMF, preferably less than or equal to 5% by weight relative to 5-HMF, and preferably less than or equal to 3% by weight relative to 5-HMF.

[0221] According to one or more embodiments of the alternative water distillation, purification step f) includes the following and may consist of at least one step of crystallizing the 5-HMF contained in the organic raffinate 8 obtained by step d) or the concentrated organic raffinate 10 obtained by step e), followed by filtration to produce a 5-HMF stream containing solid 5-HMF (5-HMF crystals) and a filtrate rich in organic solvent.

[0222] 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 suitable for reducing the solubility of the 5-HMF to be crystallized from the organic raffinate.

[0223] The conditions are 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.

[0224] The filtrate, rich in organic solvent (essentially the extraction solvent), is advantageously partially or entirely (after optional purging) recycled to the liquid-liquid extraction step c) for a new 5-HMF extraction.

[0225] According to methods known to those skilled in the art, the crystallization-based purification step f) is performed in one or more passes, and the crystals are washed and dried.

[0226] Optional step g): Treatment of water / polar aprotic synthesis solvent mixture The method according to the invention may optionally include step g), treating the water / polar aprotic synthesis solvent (e.g., DMSO) mixture produced by the steps of the method according to the invention to produce an aqueous effluent 15 (also referred to as a distillate), which may be used in whole or in part in backwashing step d) and / or step a) and / or purification step f) by water distillation. This step may also produce a stream 16 rich in polar aprotic synthesis solvent (e.g., DMSO) and an impurity stream 17. Therefore, at least one water-polar aprotic synthesis solvent mixture produced in the method may be treated in step g). The mixture may be an aqueous raffinate obtained from step c).

[0227] Specifically, step g) allows the separation of water, polar aprotic synthesis solvent, and reaction products extracted from the raffinate, such as unconverted sugars, sugar oligomers, and residual 5-HMF, within the aqueous raffinate 5) of the at least one mixture (obtained from step c).

[0228] One or more other water-polar aprotic synthesis solvent mixtures generated within this method can be sent to step g).

[0229] According to those skilled in the art, the more efficient the distillation, the smaller the residual amount of polar aprotic synthesis solvent (e.g., DMSO) in the aqueous effluent 15 produced at the end of step g).

[0230] The water-polar aprotic synthesis solvent (e.g., DMSO) mixture produced by this method specifically refers to the aqueous raffinate 5 produced in step c) and optionally the water / polar aprotic synthesis solvent (e.g., DMSO) mixture produced from the optional step of dehydrating sugars to obtain 5-HMF (when the method incorporates such a step).

[0231] Step g) of treating the water-polar aprotic synthetic solvent (e.g., DMSO) mixture preferably employs a stage for evaporating the water-polar aprotic synthetic solvent (e.g., DMSO) mixture to remove any impurities, particularly heavy impurities such as humic acid or unconverted sugars, in the form of stream 17, followed by a distillation stage.

[0232] The evaporation section operates at a temperature preferably between 80°C and 130°C, more preferably between 100°C and 120°C, and preferably at a pressure 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 employs a scraped film evaporator (thin-film evaporator, TFE).

[0233] The distillation section, in itself, advantageously uses a distillation column or several separate equipment units. Preferably, the distillation section of step g) is advantageously carried out in a distillation column, with a column top temperature preferably between 25°C and 60°C, more preferably between 45°C and 55°C, for example about 50°C, a column bottom temperature preferably between 80°C and 140°C, more preferably between 100°C and 130°C, for example about 120°C, a pressure preferably between 0.001 MPa and 0.05 MPa, more preferably between 0.005 MPa and 0.02 MPa, and more preferably between 0.008 MPa and 0.012 MPa, and a reflux ratio preferably between 0.01 and 0.50, more preferably between 0.05 and 0.10.

[0234] Therefore, the aqueous raffinate 5 generated in step c) and containing water and a polar aprotic synthesis solvent (e.g., DMSO), along with the water / polar aprotic synthesis solvent (e.g., DMSO) mixture optionally recovered in an optional dehydration step, is evaporated, and then the gas phase is recovered and preferably distilled under vacuum to produce, on the one hand, a residue 16 rich in polar aprotic synthesis solvent (e.g., DMSO), and on the other hand, a water-rich distillate 15 (corresponding to the aqueous effluent), and finally a stream 17 containing heavy fractions (e.g., unfiltered humin and unconverted humin sugars). The term "rich" herein means at least 95% by weight, preferably at least 98% by weight. Some or all of the water-rich distillate or aqueous effluent can advantageously be recycled as an aqueous solvent to backwash step d) and / or as an aqueous stream to purification step e) by water distillation. The water-rich distillate can also be recycled, in whole or in part, as water introduced in step a).

[0235] Residues rich in polar aprotic synthetic solvents 16 (e.g., DMSO) can advantageously be dehydrated directly or after distillation, with an optional dehydration step introduced to remove any heavy products that may accumulate.

[0236] List of numerical labels used in the attached diagram: 1: Raw materials 2: Aqueous mixture 3: First aqueous filtrate 4: Extraction solvent 5: Aqueous raffinate 6: Organic extract 7: Aqueous solvents 8: Organic extract residue 9: Aqueous back-extraction solution 10: Concentrated organic raffinate 11: First stream containing organic solvents 12:5-HMF aqueous solution 13: Second stream containing organic solvents 14: Aqueous liquids 15: Watery effluent 16: Streams rich in polar aprotic synthesis solvents (or enriched "residues") 17: Impurity stream (or heavy fraction stream) 18: Aqueous solution 19: Final Solid 20: Second aqueous filtrate (re-slurry filtrate) 21: Water-based logistics 22: Coarse filter cake 23: Washing water 24: Washing filtrate 25: Washed filter cake 26: Compacting-Purge Filtrate 27: Compacting / Purge Washed Filter Cake 28: Compacted / purged filter cake after washing and breaking it up 29: Primary compaction-purging filtrate 30: Compacting and purging the coarse filter cake 31: First compaction-purge filtrate of the first filtration cycle 32: Compaction-purging of coarse filter cake in the first filtration cycle 33: Filter cake after being crushed 34: Re-pulping filter cake 35: Re-pulping coarse filter cake 36: Second compaction-purge filtrate of the second filtration cycle 37: Compacting-blowing and re-slurrying coarse filter cake. Example

[0237] The following embodiments are intended to demonstrate some advantages of the method according to the invention, particularly through comparison: According to an embodiment of the invention (Embodiment 2), this embodiment performs as follows Figure 4 The liquid-solid separation shown includes two filtration cycles b1) and b3) performed by a filter press, separated by an intermediate step b2) in which the filter cake obtained at the end of b1) is resuspended, and an embodiment of a method according to the prior art (Example 1) which includes a step of liquid-solid separation by a filter press, combined with... Figure 1 The filter cake washing step is performed by the method shown.

[0238] Example 1 (not in accordance with the present invention) According to Example 1, the washing of the filter cake is carried out directly in the separation apparatus (i.e., a filter press): the feed 2 of the filter press (which is a suspension obtained by mixing feed 1 containing 5-HMF and DMSO with water 21 in step a) is sent to the filtration step b1.1) to separate the solid phase (i.e., the precipitated humin) from the liquid phase 3, which specifically contains 5-HMF, DMSO, and water. At the end of step b1.1), the coarse filter cake 22 containing humin undergoes a washing step b1.2) with water 23, producing a washed filter cake 25 and a washing filtrate 24 containing 5-HMF and DMSO. The washed filter cake 25 then undergoes a compaction-purging step b1.3) to form a compacted / purged washed filter cake 27 and a compacted-purged filtrate 26. Finally, the compacted / purged washed filter cake 27 is broken up in a disintegration step b1.4) to form a compacted / purged washed and disintegrated filter cake 28.

[0239] In this embodiment, the feedstock 2 of the filter press consists of 11% 5-HMF and 35% DMSO. After filtration (b1.1), washing (b1.2), and compaction (b1.3), the degree of loss in the filter cake is defined as follows: the mass ratio of compound X of interest in the compacted / purged, washed, and broken-up filter cake 28 to the mass of said compound X in the filter feedstock 2: (M... X滤饼28 ) / (m X原料2 ).

[0240] The degree of loss of 5-HMF and DMSO as a function of the mass ratio of the input wash water 23 to the coarse filter cake 22 (unwashed) and as a function of the mass ratio of the input wash water 23 to the 22% filter material are given in Table 1 below.

[0241] Table 1 .

[0242] Operating by using washing directly integrated into the filter press filtration cycle requires washing the filter cake with a large flow of water to reduce the loss of the product of interest to less than 1%, whether it is 5-HMF or DMSO.

[0243] Example 2 (in accordance with the present invention) According to Example 2, liquid-solid separation is based on... Figure 4 The scheme shown is carried out according to the HMF production method according to the present invention.

[0244] There is no washing step during liquid-solid separation via a filter press.

[0245] The feedstock 2 (which is the same suspension as in Example 1) of the filter press is fed to the filtration step b1.1) to separate the solid phase (i.e., the precipitated humin) from the liquid phase 3, which specifically contains 5-HMF, DMSO and water. At the end of step b1.1), the coarse filter cake 22 is subjected to a compaction-purging operation b1.3) and forms a compacted-purging coarse filter cake 32, which is then broken up in sub-step b1.4).

[0246] According to the present invention, the crushed filter cake 33 is contacted with an aqueous solution 18 and resuspended in the reslurrying step b2), and the water / filter cake 33 ratio is shown in Table 2 below.

[0247] The resulting suspension is then fed to a second filtration cycle (b2), which includes the same sequence of sub-steps as the first filtration cycle (b1): filtration (b3.1), followed by compaction-purging (b3.2), and then decomposition (b3.3).

[0248] The final filter cake 19 is recovered at the end of the disintegration operation (b3.3).

[0249] Table 2 below shows the degree of loss of 5-HMF and DMSO as a function of the mass ratio of the added repulping water 18 to the crushed filter cake 33 (the raw material for the repulping step) and the mass ratio of the added repulping water 18 to the filter raw material 2.

[0250] Table 2 .

[0251] This embodiment of the invention demonstrates that the loss of 5-HMF and DMSO in the final filter cake 19 obtained after two filtration cycles and intermediate reslurrying is significantly lower than that of the filtration with cake washing in Example 1. With a water 18 / filter feed 2 ratio of 22%, the configuration of Example 2 reduces 5-HMF loss by 50% and DMSO loss by 20% compared to Example 1. Therefore, the specific liquid-solid separation b) according to the invention, combined with the reslurrying step, enables a reduction in the loss of 5-HMF and DMSO while simultaneously reducing the water / feed ratio. For the same water / feed ratio, significantly more 5-HMF and DMSO can be extracted from the filtered solid phase, allowing them to be recycled in the process of producing 5-HMF, thereby increasing HMF yield and achieving potential savings in DMSO.

Claims

1. A method for producing hydroxymethylfurfural, known as 5-HMF, comprising the following steps: - Step a) The raw material (1) containing 5-HMF and a polar aprotic synthesis solvent is contacted with an aqueous stream (21) to obtain at least one aqueous mixture (2) containing solid particles; - Step b) involves liquid-solid separation of the aqueous mixture (2) including first and second filtration cycles (b1, b3) separated by an intermediate step b2) that resuspends the solid phase obtained at the end of the first filtration cycle b1) to produce at least a first aqueous filtrate (3), a second aqueous filtrate (20), and a final solid (19) containing at least a portion of solid particles, wherein the second aqueous filtrate (20) is recycled to step a). - Step c), in the presence of extraction solvent (4), the first aqueous filtrate (3) obtained at the end of step b) is subjected to liquid-liquid extraction to produce an aqueous raffinate (5) containing the polar aprotic synthesis solvent and an organic extract (6) containing 5-HMF and the extraction solvent; and then - Step d) The organic extract (6) is backwashed with an aqueous solvent (7) to produce an aqueous back-extract (9) and an organic raffinate (8) containing 5-HMF and an organic solvent. -Optional step e), concentrating the organic raffinate (8) obtained in step d) by removing at least a portion of the organic solvent, to produce a concentrated organic raffinate (10) containing 5-HMF and residual organic solvent, and to produce a first stream (11) containing organic solvent. - Step f) purify the organic raffinate (8) or the concentrated organic raffinate (10) to produce a 5-HMF stream (12).

2. The method according to claim 1, wherein the liquid-solid separation step b) is carried out by at least one device selected from a filter press, belt filter, centrifuge, candle filter, vacuum filter, belt filter press, decanter and drainer, preferably by at least one filter press.

3. The method according to claim 2, wherein the liquid-solid separation step b) is performed in batches using at least one piece of equipment selected from filter press, candle filter, vacuum filter, belt filter press, decanter and drainer, preferably using at least one filter press.

4. The method according to any one of the preceding claims, wherein the first and second filtration cycles are carried out in two separate equipment components, preferably two separate filter presses.

5. The method according to any one of the preceding claims, wherein the intermediate step b2) of resuspending the solid phase obtained at the end of the first filtration cycle b1) is carried out at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C, and at atmospheric pressure, by contacting the solid phase with an aqueous solution (18) at a mass ratio between the aqueous solution (18) and the solid phase of 1 to 10 for a period of time between 1 minute and 4 hours, preferably in a tank separate from the equipment (pieces) used for the first and second filtration cycles.

6. The method according to any one of the preceding claims, wherein the liquid-solid separation step b) is performed using at least one filter press, and each of the first and second filtration cycles of the liquid-solid separation step b) comprises, in this order, the following sequence of sub-steps: - Sub-steps (b1.1, b3.1) for filtering the filter material to produce an aqueous filtrate (3, 20) and a coarse filter cake (22, 35); - Sub-steps (b1.3, b3.2) of compacting and purging the filter cake to produce compacted-purged filtrate (31, 36) and compacted-purged coarse filter cake (32, 37); - Sub-steps (b1.4, b3.3) to break down the compacted-purge coarse filter cake to produce a broken-down filter cake (33, 19); Furthermore, the shredded filter cake obtained at the end of the shredding sub-step b1.4) of the first filtration cycle b1) is the solid phase that was resuspended in step b2) by contact with the aqueous solution (18) to form the filter material of the filtration sub-step b3.1) of the second filtration cycle b3).

7. The method according to claim 6, wherein the first filtration cycle b1) includes a compaction-purge sub-step b1.3) to produce a first compaction-purge filtrate (31) that is recycled to step c) in the method, and the second filtration cycle b3) includes a compaction-purge sub-step b3.2) to produce a second compaction-purge filtrate (36) that is recycled to step a) in the method.

8. The method according to claim 6, wherein the filtration sub-steps (b1.1, b3.1) are carried out at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C, and at a pressure between 0.05 MPa and 1 MPa.

9. The method according to claim 6, wherein the compaction-purging sub-step (b1.3, B3.2) is carried out by injecting compressed air at a pressure between 1 MPa and 5 MPa and at a temperature between ambient temperature and 80°C, preferably between 10°C and 40°C.

10. The method according to any one of the preceding claims, wherein the liquid-solid separation step b) does not include the step of washing the filtered solid phase generated during step b).

11. The method according to any one of the preceding claims, wherein the purification step f) is a water distillation step, which is carried out by distilling the organic raffinate (8) obtained in step d) or the concentrated organic raffinate (10) obtained in step e) in the presence of water (14) to produce the 5-HMF stream and a second stream (13) containing an organic solvent, the 5-HMF stream being an aqueous 5-HMF solution (12), the water distillation preferably being 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 the bottom temperature of the column is 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.

12. The method according to any one of the preceding claims, comprising the step of dehydrating sugars to 5-HMF upstream of step a), preferably by contacting a sugar feedstock containing hexoses with the polar aprotic synthesis solvent and the dehydrating acid catalyst, preferably at a temperature between 30°C and 200°C and at a pressure between 0.001 MPa and 10 MPa, wherein the hexoses are preferably fructose or fructoside units.

13. The method according to any one of the preceding claims, wherein in step a), the aqueous stream (21) comprises all or part of the aqueous back-extraction solution (9) obtained in step d).

14. The method according to any one of the preceding claims, wherein the extraction solvent (4) is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene, and is preferably methyl isobutyl ketone.

15. The method according to any one 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.

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