A process for the production of 5-HMF comprising filtration with resuspension of a filtered solid phase

Abstract

The invention relates to a process for producing 5-hydroxymethylfurfural (5-HMF) comprising successively a) contacting a feed (1) containing 5-HMF and an aprotic polar synthesis solvent with an aqueous stream, b) a liquid-solid separation comprising two filtration steps separated by resuspension of a filter cake, c) a liquid-liquid extraction with an organic extraction solvent followed by a backwashing step d) with an aqueous solvent to obtain an organic raffinate rich in 5-HMF and solvent. The organic raffinate, optionally concentrated, is then subjected to a purification step f), for example hydrodistillation or crystallization, to obtain a stream of 5-HMF, for example in the form of an aqueous solution of 5-HMF or crystallized 5-HMF. Figure 3 to be published

Description

Title of the invention: Process for the production of 5-HMF comprising filtration with resuspension of a filtered solid phase. Technical field

[0001] The invention relates to a process for producing hydroxymethylfurfural (HMF) from a feed comprising HMF and a polar aprotic synthesis solvent, typically obtained by dehydrating a feed containing sugars such as fructose. More particularly, the invention relates to a process for producing HMF, preferably the production of an aqueous solution of HMF, comprising a specific liquid-solid separation step upstream of a liquid-liquid extraction, based on the implementation of two filtration steps with an intermediate step of resuspending a filtered solid phase, e.g., a filter cake. Prior art

[0002] HMF, also called 5-(hydroxymethyl)furfural or 5-HMF, is a compound of interest derived from biomass that can be used in many fields, particularly in pharmaceuticals, agrochemicals, and specialty chemicals. The production of 5-HMF by sugar dehydration has been known for many years and has been the subject of extensive research. There are numerous dehydration conditions; the following methods are examples: - 5-HMF can be obtained in an aqueous medium, generally in the presence of an acid catalyst. This acid catalyst dehydrates the C6 sugar (especially fructose) into 5-HMF, but also catalyzes the rehydration of 5-HMF into formic acid and levulinic acid, which significantly reduces the yield. 5-HMF can also be obtained in a non-aqueous, protic polar medium, using solvents such as methanol, ethanol, or acetic acid, and in the presence of an acid catalyst. Under these conditions, 5-HMF is obtained by mixing with an ether or ester derivative of 5-HMF, depending on the reaction medium used. The formation of these byproducts results from the reaction of 5-HMF with the reaction solvent in an acidic medium. - Application WO 2007 / 104514 describes the synthesis of 5-HMF by sugar dehydration using methanol or ethanol as a solvent in the presence of an acid catalyst. In this case, the presence of said catalyst also catalyzes the etherification reaction of 5-HMF by the alcohol to give a mixture of 5-HMF and its methyl or ethyl ether form, depending on the alcohol used as a solvent. - 5-HMF can also be produced in aprotic polar media with or without an acid catalyst. The use of dimethyl sulfoxide is a particularly noteworthy example. (DMSO) which, with or without an acid catalyst, allows the production of 5-HMF with very good yields, and without the undesirable reactions listed above.

[0003] Moreover, regardless of the synthesis medium (water, methanol, DMSO, etc.), polymeric secondary products called humines are formed during the production of 5-HMF (van Dam, HE; ​​Kieboom, APG; van Bekkum, H. (1986) The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethyl-furfural. In: Starch - Stârke, vol. 38, no. 3, p. 95-101).

[0004] The synthesis of 5-HMF in a medium such as DMSO is particularly interesting because it allows 5-HMF to be obtained in its alcohol (and not ether) form with very good yields. However, the physicochemical properties of DMSO (or any other aprotic polar solvent) make it very difficult to separate from 5-HMF using the usual methods known to those skilled in the art.

[0005] A known method for isolating 5-HMF from DMSO is liquid-liquid extraction, followed by crystallization of the extract, as described in patent FR2669635. The applicant has already proposed an improvement to the process described in patent FR2669635, which was the subject of patent FR3071172. This improvement is based on modifying the liquid-liquid extraction step, in particular by adding a water backwash step and recycling the backwash water upstream of the liquid-liquid extraction to mix it with the 5-HMF / DMSO feedstock, said mixture optionally being filtered before the liquid-liquid extraction. This improvement makes it possible to increase the purity of the 5-HMF without loss of yield of the product of interest, and to carry out the 5-HMF crystallization step under more favorable conditions.

[0006] A liquid-liquid extraction method for isolating 5-HMF from DMSO is also described in the Applicant's patent FR3131313, but this time within the framework of a process for recovering 5-HMF not in crystalline form but in aqueous solution, which can be advantageous since the crystallization of 5-HMF remains a costly operation. To this end, the process described in FR3131313 implements a liquid-liquid extraction step combined with a water backwashing step of the organic extract containing the 5-HMF obtained from the liquid-liquid extraction, as well as a 5-HMF concentration step of the organic raffinate containing the 5-HMF obtained in the backwashing step, and a hydrodistillation step of the concentrated stream from said concentration step, in order to recover the 5-HMF in the form of an aqueous 5-HMF solution.The disclosed process advantageously includes a liquid-solid separation step, typically by filtration, upstream of the liquid-liquid extraction to remove precipitated humins (solid particles) when water is added to the feed (feed mixing step with backwash waters) before it is sent to extraction. liquid-liquid. Indeed, adding water to the 5-HMF feed sent to liquid-liquid extraction can cause the precipitation of humins present in the feed, which can generate operational problems during liquid-liquid extraction, for example clogging equipment.

[0007] Humine management is therefore critical in such a process of HMF production.

[0008] In patent FR3131313, the liquid-solid separation step is typically put implemented when the amount of humins precipitated in the mixture is greater than about 1% by weight, and can be carried out with different technologies such as a filter press, a belt filter, a clarifier, a decanter, a centrifuge, for example a plate centrifuge, implementation by filter press being preferred.

[0009] Conventionally, a filter press is a piece of equipment used for the pressure separation of suspensions to separate the liquid and solid phases. The filter press consists of trays (or frames) that filter the suspension formed by the mixture of water and a feedstock comprising 5-HMF and a polar aprotic synthetic solvent (e.g., DMSO) containing humins, through a filter medium, removing the humins in the form of a cake. The cake therefore contains the solid fraction, but also a portion of the liquid fraction that remains trapped, primarily due to limitations in the separation technology and the characteristics of the liquid and solid phases. Under filtration pressure, the liquid, called the filtrate, passes through the filter cloths, which retain the solid particles.The filtrates are removed throughout the process, while the cakes formed between the trays are only removed during a so-called debatching operation. The equipment thus operates discontinuously, in cycles ("batch" according to English terminology), each cycle comprising a sequence of steps, including the filtration step and the debatching step, but also a compaction step which increases the dry matter content of the cake.

[0010] In practice, during the filtration cycle sequence, a washing step of the cake obtained after the filtration step or after a compaction step improves the liquid-solid separation step by filter press. Figures 1 and 2 illustrate a filter press filtration cycle according to the prior art incorporating a washing step at different points in the filtration cycle sequence.

[0011] According to [Fig. 1], the filter press feed 2, which is a suspension resulting from a mixing step a) of an HMF-DMSO feed 1 with water 21, is sent to a filtration step b1.1) to separate the solid phase, i.e., the humins, from the liquid phase 3 comprising, in particular, HMF, DMSO, and water. Following step b1.1), the raw cake 22 containing the humins undergoes a washing step b1.2) with water 23, producing a washed cake 25 and a washing filtrate 24 containing products of interest extracted from the cake, such as 5-HMF and DMSO. The washed cake 25 undergoes then a compaction-blow step b 1.3) forming a compacted / blown washed cake 27 and a compaction-blow filtrate 26. Finally, the compacted / blown washed cake 27 is debatched in the debatching step b 1.4) to form a compacted / blown washed debatched cake 28.

[0012] According to a variant illustrated in [Fig. 2], the filtration cycle includes an additional compaction / blowing step b 1.5) downstream of the filtration step bl.1) and upstream of the washing step b 1.2) in the same order as the sequence illustrated in [Fig. 1]. A primary compaction-blowing filtrate 29 is then produced in step bl.5) (the filtrate 26 forming an additional compaction-blowing filtrate according to this sequence), as well as a raw compaction-blowing cake 30 subjected to the washing step bl.2).

[0013] Such cake washing makes it possible to extract more of the remaining products of interest from the cake, primarily 5-HMF and the aprotic polar synthesis solvent, in order to recover said products in a washing filtrate for recycling in the process, typically by recycling the washing filtrate at the stage of mixing the HMF-DMSO feed with water upstream of the liquid-liquid extraction step, and in particular to obtain a better overall HMF yield from the process. However, to be reliable, and in particular to avoid excessive loss of HMF and MDSO in the cake, the washing is carried out at the cost of a relatively large quantity of water. Summary of the invention

[0014] The applicant has demonstrated that a particular liquid-solid separation step, based on the implementation of two filtration cycles with an intermediate step of resuspending a solid phase obtained at the end of the first filtration cycle, e.g. a filter cake, also referred to as the "repulping" step in this description, makes it possible to increase the extraction rate of products of interest such as 5-HMF and the aprotic polar synthesis solvent (e.g. DMSO) from the filtered solid phase (e.g. filter cake) at the same amount of water, compared to a liquid-solid separation step incorporating a water washing step of the filtered solid phase (e.g. cake). Thanks to the process according to the invention, which incorporates such an original liquid-solid separation step, as well as judicious recycling in the process of the products of interest extracted from the filtered solid phase (e.g.(filtration cake), HMF production is improved, while limiting investment and operating costs due to the recycling of aprotic polar synthesis solvent and water in the process.

[0015] An object of the present invention relates to a process for the production of 5-HMF, comprising the following steps: - a step a) of bringing into contact a charge comprising 5-HMF and a solvent of aprotic polar synthesis with an aqueous flow, so as to obtain at least an aqueous mixture containing solid particles; - a liquid-solid separation step b) of said aqueous mixture comprising a first and a second filtration cycle (bl, b3) separated by an intermediate step b2) of resuspension of a solid phase obtained at the end of the first filtration cycle bl), to produce at least a first aqueous filtrate, a second aqueous filtrate, and a final solid comprising at least a fraction of the solid particles, said second aqueous filtrate being recycled in step a); - a step c) of liquid-liquid extraction of the first aqueous filtrate obtained at the end of step b) in the presence of an extraction solvent, so as to produce an aqueous raffinate comprising said aprotic polar synthesis solvent, and an organic extract comprising 5-HMF and extraction solvent; then - a step d) of counter-washing the organic extract with an aqueous solvent, so as to produce an aqueous counter-extract and an organic raffinate comprising 5-HMF and an organic solvent; - an optional step e) of concentration of said organic raffinate from step d) by removal of at least part of the organic solvent, producing a concentrated organic raffinate comprising 5-HMF, and residual organic solvent, and producing a first stream comprising organic solvent; - a step f) of purification of said organic raffinate or of said concentrated organic raffinate to produce a stream of 5-HMF.

[0016] According to one or more embodiments, the liquid-solid separation step b) is carried out by at least one piece of equipment selected from a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a spin dryer, and preferably by at least one filter press.

[0017] According to one or more embodiments, the liquid-solid separation step b) is carried out discontinuously, by at least one piece of equipment selected from a filter press, a candle filter, a vacuum filter, a belt press, a decanter, a centrifuge, and preferably by at least one filter press.

[0018] According to one or more implementations, the first and second filtration cycles are carried out in two separate pieces of equipment, preferably two separate filter presses.

[0019] According to one or more embodiments, the intermediate step b2) of resuspending the solid phase obtained at the end of the first filtration cycle bl) is carried out at a temperature between ambient temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at atmospheric pressure, by contacting said solid phase with an aqueous solution in a mass ratio between said aqueous solution and said solid phase of between 1 and 10, for a period of between 1 minute and 4 hours, preferably in a separate tank from the equipment used for the first and second filtration cycles.

[0020] According to one or more embodiments, the liquid-solid separation step b) is operated by at least one filter press, and each of the first and second filtration cycles of the liquid-solid separation step b) comprises the following sequence of substeps, in this order: - a filtration substep (bl.l, b3.1) of a filtration feed to produce an aqueous filtrate and a raw cake; - a compaction-blowing substep (b 1.3, b3.2) of said cake to produce a compaction-blowing filtrate and a raw compaction-blowing cake; - a sub-step of unbatching (b 1.4, b3.3) said compacted-blown raw cake to produce an unbatched cake; and in which the unbattered cake obtained at the end of the unbattering substep b 1.4) of the first filtration cycle bl) is the solid phase resuspended in step b2) by contacting an aqueous solution, to form the filtration charge of the filtration substep b3.1) of the second filtration cycle b3).

[0021] According to one or more implementations, the first filtration cycle bl) includes the substep of compaction-blowing b 1.3) producing a first compaction-blowing filtrate recycled in the process in step c), and the second filtration cycle b3) includes the substep of compaction-blowing b3.2) producing a second compaction-blowing filtrate recycled in the process in step a).

[0022] According to one or more implementations, the filtration sub-steps (bl.l, b3.1) are operated at a temperature between ambient temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at a pressure between 0.05 MPa and 1 MPa.

[0023] According to one or more embodiments, a filtration facilitating agent, preferably diatomaceous earth, is added to the filtration charge of the filtration substage of the first filtration cycle bl) and / or the second filtration cycle b3), preferably in a content of between 0.01% and 5% by mass relative to the mass of said filtration charge.

[0024] According to one or more implementations, the compaction-blowing sub-steps (b 1.3, b3.2) are 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.

[0025] According to one or more embodiments, step b) of liquid-solid separation does not include a step of washing a filtered solid phase produced during said step b).

[0026] According to one or more embodiments, the purification step f) is a hydrodistillation step carried out by distillation in the presence of water of said organic raffinate from step d) or of said concentrated organic raffinate from step e), to produce said 5-HMF stream being an aqueous solution of 5-HMF and a second stream comprising organic solvent, preferably said hydrodistillation 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 at a column bottom temperature 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.

[0027] According to one or more embodiments, the process includes a step of dehydrating sugars into 5-HMF upstream of step a), preferably by contacting a sugar feed comprising a hexose, preferably said hexose being fructose or a fructosidic unit, with said aprotic polar synthesis solvent and an acid dehydration catalyst, preferably at a temperature between 30°C and 200°C and at a pressure between 0.001 MPa and 10 MPa.

[0028] According to one or more implementations, in step a) said aqueous stream comprises all or a fraction of said aqueous counter-extract from step d).

[0029] According to one or more embodiments, the extraction solvent is chosen from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene, and preferably is methyl isobutyl ketone.

[0030] According to one or more embodiments, the aprotic polar synthesis solvent is chosen from pyridine, butan-2-one, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methylethyl ketone, propionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate and γ-valerolactone, taken alone or in mixture, and is preferably dimethyl sulfoxide.

[0031] Other objects and advantages of the invention will become apparent from the following description, particular examples of embodiments of the invention, given by way of non-limiting examples, the description being made with reference to the attached figures described below. LIST OF FIGURES

[0032] Fig. 1, already described above, illustrates an example of liquid-solid separation in a prior art HMF production process.

[0033] Fig. 2, already described above, illustrates another example of liquid-solid separation in a prior art HMF production process.

[0034] Figure 3 illustrates an embodiment of the process according to the invention incorporating the particular liquid-solid separation step b) upstream of the liquid-liquid extraction step.

[0035] The [Fig.4] is a schematic diagram detailing the particular liquid-solid separation step b) of the HMF production process according to the invention.

[0036] In the figures, the same references designate identical or analogous elements. Description of the implementation methods

[0037] In the following detailed description, many specific details are set out to provide a more thorough understanding of the process. However, it will be apparent to those skilled in the art that the process can be carried out without necessarily including all of these specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0038] It is specified that, throughout this description, the expression "between ... and ..." should be understood as including the limits mentioned, unless otherwise specified.

[0039] In this description, the term "include" is synonymous with (means the same as) "comprise", "include", and "contain", and is inclusive or open and does not exclude other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist".

[0040] Furthermore, when used in this description, the terms "essentially" or "substantially" or "approximately" in relation to a reference value correspond to an approximation of ± 10%, preferably ± 5%, most preferably ± 2%, or even more preferably ± 1% of that reference value, which may be a temperature, a pressure, a distance, a speed, a flow rate, a content of compound(s), etc.

[0041] In the sense of the present invention, the different embodiments presented can be implemented separately or in combination with each other, without limitation of combinations when this is technically feasible.

[0042] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0043] In this description, pressures are expressed in absolute values, except specified otherwise.

[0044] In the present description, an aprotic solvent is understood to be a molecule acting as a solvent and in which all of the hydrogen atoms are carried by carbon atoms.

[0045] In the present description, a polar solvent is understood to be a molecule acting as a solvent whose dipole moment p, expressed in Debye, has a numerical value greater than or equal to 2.00 measured at 25°C.

[0046] In the present description, the term aprotic polar solvent means a molecule acting as a solvent in which all of the hydrogen atoms are carried by carbon atoms and whose dipole moment p expressed in Debye has a numerical value greater than or equal to 2.00 measured at 25 °C.

[0047] In this description, the term "cake" refers to the solid phase recovered from a filtration cycle, particularly by filter press. This solid may be moist. It can be characterized by its dry matter content, abbreviated as "DM". The dry matter (DM) content of such a cake can be between 20% and 90% by mass, preferably between 30% and 90% by mass, more preferably between 35% and 90% by mass, and more preferably between 40% and 85% by mass, relative to the total mass of the cake, and can vary depending on the types of operations performed during the filtration cycle from which the cake originates. The dry matter content can be measured according to ASTM E1756-08(2015). The term "cake", although used in the singular, also covers the plural, i.e., a plurality of cakes.

[0048] In this description, "repulping" means an operation of resuspending the solid phase recovered from a filtration cycle, particularly by filter press, by contacting it with an aqueous solution. Further details are given below in the description of the invention.

[0049] For a better understanding of the invention, reference is made below to numerical numbers appearing in figures 3 and 4 to designate different elements of the process, without this constituting a limitation of the invention to the particular embodiments illustrated in these figures.

[0050] Optional step of sugar dehydration into 5-HMF

[0051] Advantageously, the feed 1 comprising 5-HMF and an aprotic polar synthesis solvent introduced in step a) according to the invention can be obtained during a sugar dehydration step to 5-HMF, very advantageously located upstream of step a) according to the invention, by contacting a sugar feed comprising a hexose with an aprotic polar synthesis solvent and an acid dehydration catalyst so as to produce a synthesis effluent containing at least 5-HMF and aprotic polar synthesis solvent, and advantageously corresponding to the feed 1 of the process according to the invention introduced in the mixing step a). The process according to the invention can therefore optionally include such a step of dehydrating a sugar load into 5-HMF, located upstream of step a).

[0052] The sugar charge comprises a hexose, said hexose being in monomeric form (monosaccharide) or being a unit belonging to a disaccharide, oligosaccharide or polysaccharide. A saccharide is a compound also called a sugar.

[0053] Preferably the hexose is fructose or a fructosidic unit.

[0054] In one embodiment, the filler comprises either free fructose, alone or in a mixture with any saccharide species, or any oligosaccharide or polysaccharide filler containing one or more fructosidic units capable of releasing fructose through one or more hydrolysis steps, optionally in a mixture with other saccharide species. Preferably, the sugar filler is crystalline fructose, a fructose-containing syrup, a fructose- and glucose-containing syrup, or crystalline sucrose or a sucrose syrup.

[0055] Advantageously, the charge comprises fructose in monomeric, oligomeric or polymeric form.

[0056] By load containing free fructose taken in mixture with any saccharidic species, we mean for example high-fructose corn syrup type syrups (“High-Fructose-Com-Syrup” according to Anglo-Saxon terminology) containing fructose and glucose in different proportions (glucose / fructose in mass or molar ratios 58 / 42, 45 / 55, 10 / 90 for example).

[0057] Syrup is understood to mean a solution of sugars (saccharides) in water having a concentration of at least 30% by weight, preferably at least 50% by weight, preferably at least 70% by weight.

[0058] The load may include a saccharide comprising one or more fructosidic units and one or more non-fructosidic units, fructose being able to be released by one or more hydrolysis steps, for example oligosaccharides and polysaccharides in which at least one monosaccharide unit is fructose, for example loads such as sucrose, kestose, fructans, oligofructans, rinulin.

[0059] Advantageously, the saccharidic fillers are capable of releasing monomeric fructose by glycosidic hydrolysis, said fructose produced being able to be transformed into 5-HMF.

[0060] Preferably, the oligosaccharide has the molecular formula: (C6mH10m+2O5m+i)(C5nH8n+2O4n+i) where m and n are integers whose sum is between 2 and 6. The monosaccharide units composing said oligosaccharide may or may not be identical, and at least one unit with the formula (C6mH10m+2O5m+i) is fructose. By extension, preferably the polysaccharide has the molecular formula (C6mH10m+2O5m+i)(C5nH8n+2O4n+i) where m and n are integers whose sum is greater than or equal to 7.

[0061] The aprotic polar synthesis solvent is advantageously chosen from among all aprotic polar solvents whose dipole moment expressed in Debye (D) is greater than or equal to 2.00. Preferably, the aprotic polar solvents are chosen from pyridine (2.37), butan-2-one (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 NMP, dimethyl sulfoxide (3.90) denoted DMSO, the propylene carbonate (4.94) and y-valerolactone (4.71), alone or in mixture.

[0062] Preferably, the aprotic polar solvent is advantageously chosen from acetone, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, NMP, DMSO, propylene carbonate and γ-valerolactone, alone or in mixture.

[0063] Preferably, the aprotic polar solvent is advantageously chosen from N,N-dimethylacetamide, NMP, DMSO, and γ-valerolactone, alone or in mixture.

[0064] Preferably, the aprotic polar solvent is DMSO.

[0065] The term acid dehydration catalyst means any Brønsted acid catalyst selected from organic or inorganic, homogeneous or heterogeneous Brønsted acids capable of inducing the dehydration of sugars into 5-HMF.

[0066] Preferably, the acid dehydration catalyst is a Brpnsted acid having a pKa in the aprotic polar synthesis solvent, preferably in DMSO, between 0 and 5.0, preferably between 0.5 and 4.0 and preferably between 1.0 and 3.0. Said pKa values ​​are as defined in the article by FG ​​Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0067] Preferably, the acid dehydration catalyst is chosen from HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiW12O40, H3PW12O40, (NH4)6(W12O40).xH2O, H4SiMo12O40, H3PMo12O40, (NH4)6Mo7O24.xH2O, H2MoO4, HreO4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HClO4, HBF4, HSbF5, HPF6, H2FO3P, C1SO3H, FSO3H, HN(SO2F)2, HIO3, BF3, Al(Otf)3, FeCl3, ZnCl2, SnCl2, CrCl3, CeCl3, ErCl3, formic acid, acetic acid, trifluoroacetic acid, lactic acid, levulinic acid, methanesulfinic acid, methanesulfonic acid, tri-fluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, para-toluenesulfonic acid, 4-biphenylsulfonic acid, diphenyl phosphate, and l,l'-binaphthyl-2,2'-diyl hydrogen phosphate.Preferably, the acid dehydration catalyst is chosen from HCl, H2SO4, H3PO2, H3PO4, HNO3, AlCl3, acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid.

[0068] The optional dehydration step is carried out at a temperature between 30°C and 200°C, preferably between 50°C and 180°C, preferably between 70°C and 150°C, and preferably between 90°C and 130°C, for example, a temperature of 120°C. Preferably, the optional dehydration step is carried out at a pressure between 0.001 MPa and 10 MPa, preferably between 0.001 MPa and 5 MPa, and 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 bubble point refers to the pressure and temperature conditions at which the first gas bubbles appear for a liquid.When the reaction medium is above the bubble point of the mixture, the vapor phase can be withdrawn from the reactor, optionally rectified, and condensed to form condensates which can be sent to an optional step g) of processing of the aprotic polar synthesis water-solvent mixtures.

[0069] Preferably, the acid dehydration catalyst is introduced at the dehydration step in a molar ratio of catalyst to sugar charge, denoted Acid / Sugar, expressed in molar percentage (%mol), of between 0.01 and 10 %mol, preferably between 0.05 and 8 %mol, preferably between 0.1 and 6 %mol, preferably between 0.2 and 5 %mol, most preferably between 0.3 and 4 %mol and most preferably between 0.5 and 3 %mol.

[0070] The optional dehydration step can be carried out in various embodiments. For example, the step can advantageously be implemented batch or continuously (batch being referred to as "batch" in English terminology). The addition of the sugar feed can be gradual (referred to as "fed-batch" in English terminology) in the case of batch implementation or staged in several continuously stirred tank reactors (CSTRs) in series in continuous implementation. The process can be carried out in a closed reaction vessel or in a semi-open reactor.

[0071] Advantageously, the synthesis effluent obtained at the end of the optional dehydration step comprises 5-HMF and an aprotic polar synthesis solvent, preferably DMSO. The aprotic polar synthesis solvent, typically DMSO, generally represents between 30 and 95% by weight of the synthesis effluent from the dehydration step and treated in step a) of the process according to the invention, preferably between 40 and 90% by weight, preferably between 50 and 90% by weight, and preferably between 55 and 85% by weight.

[0072] The 5-HMF represents at least 1% by weight of the synthetic effluent from the optional dewatering step and treated in step a), preferably at least 10% by weight, preferably at least 15% by weight and preferably at most 50% by weight, preferably at most 40% by weight, preferably at most 30% by weight.

[0073] Furthermore, said synthesis effluent from the optional dehydration step may contain water even before its mixing in step a) with the aqueous stream 21. Said water may originate from the dehydration step, for example, water is formed during the dehydration reaction of sugar to 5-HMF (3 moles of water generated per mole of 5-HMF produced). This water may also have been introduced with the sugar, in the case where, for practical reasons, a sugar syrup, for example at about 70 wt% in water, is used. Advantageously, during the optional dehydration step, a water-solvent mixture of a polar aprotic synthesis (e.g., DMSO) may be recovered in the vapor phase. Said water-solvent mixture of a polar aprotic synthesis (e.g., DMSO) may advantageously be sent to the optional step g).Thus, the synthetic effluent from the optional dewatering step and introduced in step a) as feed 1 may contain water, in a proportion generally between 0.1 and 30% by weight, preferably between 0.1 and 15% by weight, preferably between 0.1 and 10% by weight.

[0074] The synthesis effluent from the optional dehydration step and introduced in step a) as feed 1 may also contain impurities, in particular humins. Humins are defined as all undesirable polymeric compounds formed during the synthesis of 5-HMF. Humins represent, in particular, less than 30% by weight of the converted sugar feed, preferably less than 20% by weight.

[0075] During the optional dehydration step, the sugar conversion rate, e.g. fructose, is at least 80%, preferably at least 90% and even more preferably at least 98%.

[0076] By conversion rate, we mean the ratio between the sugar consumed during the reaction (difference between the total sugar involved and the residual sugar at the end of the reaction) relative to the total sugar involved in the reaction.

[0077] The selectivity of conversion of sugar into 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 by the reaction.

[0078] Finally, the molar yield of 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 involved in the reaction. The molar yield is therefore the product of the conversion and the selectivity.

[0079] The molar yield in 5-HMF is at least 70%, preferably at least 80%.

[0080] An optional neutralization step can be carried out on the synthesis effluent from the optional dehydration step before its introduction into step a) as feed 1, said synthesis effluent containing the acid dehydration catalyst. This reduces the reactivity of the medium and thus avoids dehydration mechanisms The gradation of 5-HMF, or even the reduction of corrosion of equipment materials downstream of the optional dehydration step, can be achieved. Since the dehydration reaction may produce some organic acids, the amount of neutralizing agent can advantageously neutralize all the acids present in the synthesis effluent from the dehydration step. Such a neutralization step is advantageously carried out at a minimum stoichiometric ratio to the amount of catalyst used, and generally carried out at a slightly higher stoichiometric ratio than the catalyst used, preferably between 1 and 2 times the stoichiometric ratio, preferably between 1 and 1.5 times the stoichiometric ratio. The neutralizing agent can be a basic compound chosen from among NaOH, KOH, NH4OH, Na2CO3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, and Ba(OH)2. Step a) of mixing

[0081] The process according to the invention includes a step a) of contacting (or mixing) the charge 1 comprising 5-HMF and an aprotic polar synthesis solvent, possibly from the dehydration step, with an aqueous stream 21 so as to obtain at least one aqueous mixture 2.

[0082] The aqueous stream 21 can be composed of pure water, external to the process, or of recycled water from the process, for example the aqueous stream 21 can advantageously comprise all or part of the aqueous counter-extract 9 from step c) and / or the water 15 produced in the optional step g) of treatment of the aprotic polar synthetic water-solvent mixtures.

[0083] Preferably, the 5-HMF represents at least 1% by weight of the charge 1 introduced in step a) of the process according to the invention, preferably at least 10% by weight, preferably at least 15% by weight and preferably at most 50% by weight, preferably at most 40% by weight, preferably at most 30% by weight.

[0084] Preferably, the aprotic polar synthesis solvent (e.g. DMSO) represents between 30 and 95% by weight of the charge 1 introduced in step a), preferably between 40 and 90% by weight, preferably between 50 and 90% by weight, preferably between 55 and 85% by weight.

[0085] The charge 1 introduced in step a) may also contain water, preferably in a proportion of between 0.1 and 30% by weight, preferably between 0.1 and 15% by weight and more preferably between 0.1 and 10% by weight.

[0086] Optionally, charge 1 may also contain humins. The humins represent, in particular, less than 30% of the weight of charge 1, preferably less than 20% of the weight.

[0087] The aqueous stream 21 therefore comprises, and may consist of, water. When the aqueous stream 21 comprises a fraction of recycled process water, said fraction may comprise at least 60% by weight of water, preferably at least 70% by weight, more preferably advantageously at least 80% by weight, more preferably at least 95% by weight or even 98% by weight of water. The aqueous stream 21 may comprise all or part of the aqueous counter-extract 9 obtained in step c). Said aqueous counter-extract 9 comprises water, a polar aprotic synthesis solvent (e.g., DMSO), and optionally 5-HMF. Advantageously, said aqueous counter-extract 9 contains more than 60% by weight of water, preferably more than 70% by weight of water, and preferably more than 80% by weight of water.

[0088] Advantageously, the aqueous mixture 2 obtained at the end of step a) contains between 10% and 90% water by weight, preferably between 20% and 80% water by weight, preferably between 40% and 75% water by weight.

[0089] Preferably, step a) is carried out at a temperature between 0 and 60°C, preferably between 5°C and 40°C, and is generally carried out at room temperature, i.e. at a temperature between 10°C and 40°C.

[0090] By increasing the water content of the feed 1 during step a), some of the humins present in the feed 1 precipitate.

[0091] The aqueous mixture 2 resulting from the contact of said charge 1 with aqueous flow 21 therefore contains precipitated humins, forming solid particles, and is thus subjected to a liquid-solid separation step b) in order to send only the liquid part, separated from the suspended solid particles to the liquid-liquid extraction step c).

[0092] Preferably, the charge 1 is precipitated by the addition of water in a water / polar aprotic synthesis solvent (e.g., DMSO) ratio of between 0.2 and 3, more preferably between 1 and 2, for example 1.5. The water / polar aprotic synthesis solvent (e.g., DMSO) ratio at this step a) is more precisely defined as the following mass ratio: (EAj + Eci) / SSci with EAj: added water, ECi: water contained in charge 1, SSCi: aprotic polar synthesis solvent contained in charge 1.

[0093] For the sake of simplification, this ratio does not take into account the possible presence of aprotic polar synthesis solvent in the aqueous stream 21, which is the water added in the definition of the ratio.

[0094] Advantageously, the charge 1 is precipitated for a period of between 30 seconds and 4 hours, preferably between 1 minute and 3 hours, more preferably between 30 minutes and 2 hours, for example for 1.5 hours.

[0095] Step a) can be implemented continuously or discontinuously, and in any suitable equipment known to those skilled in the art for mixing the charge 1 and the aqueous stream and precipitating the humins, such as a tank that may include different types of agitators, a mixer equipped with a screw conveyor, etc. Step b) of liquid-solid separation

[0096] The process according to the invention comprises a step b) of liquid-solid separation of the aqueous mixture 2 from step a) is separated to obtain a liquid free of suspended solid particles and a solid residue containing humins, which is preferably removed from the process as a solid stream. Liquid-solid separation step b) is carried out by filtration. This step removes the humins that precipitated in mixing step a) or upstream. At least a portion of the resulting liquid is then advantageously sent to liquid-liquid extraction step c), this portion, or preferably all of the liquid, being sent to step c) corresponding to the aqueous filtrate 3 illustrated in Figures 3 and 4.

[0097] By way of example, the quantity of humins precipitated in step a) and present in aqueous mixture 2 is, for instance, greater than 1% by mass relative to the total mass of aqueous mixture 2.

[0098] According to an essential aspect of the invention, the liquid-solid separation step b) comprises a first filtration cycle b 1) and a second filtration cycle b3) separated by an intermediate step b2) of resuspension of a solid phase obtained at the end of the first filtration cycle bl), also called the pulping step.

[0099] The term "repulping" refers to the operation of bringing the solid phase obtained at the end of a filtration cycle, also called cake, typically a cake broken up at the end of a filter press filtration cycle, into contact with an aqueous solution 18, preferably made up of water, also called repulping solution or water, by suspending said solid phase in the solution.

[0100] Step b) produces at least a first aqueous filtrate 3, a second aqueous filtrate 20, and a final solid 19, comprising at least a fraction of the solid particles, and preferably substantially all of the solid particles, which is the preferably removed solid residue from the process. The first aqueous filtrate 3 is obtained from the first filtration cycle bl) and corresponds to the liquid fraction, comprising water, 5-HMF and the aprotic polar synthesis solvent (e.g. DMSO), sent to the liquid-liquid extraction step c), and the second aqueous filtrate 20 is obtained from the second filtration cycle b3), and is recycled to step a) because it is an aqueous stream containing compounds of interest extracted from the repelled solid phase, in this case 5-HMF and the aprotic polar synthesis solvent, which are thus advantageously recirculated in the 5-HMF production process.The production of this second recycled aqueous filtrate 20 in step a) thus makes it possible to increase the production of HMF from the process, and to save aprotic synthesis solvent, consequently limiting the operating costs of the process.

[0101] Advantageously, the liquid-solid separation step b) of the process according to the invention does not include a washing step of a filtered solid phase (cake) produced during said step b). The liquid-solid separation step b) of the process according to the invention incorporates a pulping step between two filtration cycles Surprisingly, this method allows for the extraction of more residual products of interest remaining in the cake, including 5-HMF and the aprotic polar solvent (e.g., DMSO), compared to a filtration cycle with a cake washing step, for the same amount of water used. This gain in extracted 5-HMF and aprotic polar solvent advantageously increases the overall 5-HMG yield of the process through specific recycling of the extracted products by filtration after pulping, and to a lesser extent, reduces operating costs related to the supply of aprotic polar solvent (e.g., DMSO).

[0102] Step b) of liquid-solid separation employs one or more pieces of equipment configured to filter a suspension and produce at least one solid phase at the end of each filtration cycle, typically a cake, and to perform the repulping of said solid phase, e.g., the cake, i.e., the resuspension of said 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.

[0103] Advantageously, the liquid-solid separation step b) comprises, for carrying out a filtration cycle, the use of at least one piece of equipment selected from a pressing or dewatering device such as a filter press, belt filter, centrifuge, candle filter, vacuum filter, belt press, decanter, or centrifuge, preferably selected from a filter press, belt filter, centrifuge, or candle filter. In the case of a centrifuge, the term "sediment" is generally preferred to the term "cake" to designate the separated solid phase obtained after centrifugation. Devices such as a centrifuge or a belt filter allow for continuous operation.

[0104] The liquid-solid separation step b) is preferably carried out discontinuously, by at least one piece of equipment selected from a filter press, a candle filter, a vacuum filter, a belt press, a decanter, a centrifuge, and preferably by at least a filter press.

[0105] In addition, the liquid-solid separation step b) preferably includes, for carrying out step b2) of repulping, a dedicated device, i.e. separate from the filtration equipment of the filtration cycles bl) and b3), for example a dedicated tank which may include a suitable stirring system, and configured to receive the solid phase from the filtration equipment of the 1st filtration cycle bl) and to send the repulped solid phase to the filtration equipment of the 2nd filtration cycle b3).

[0106] In step b2), the repulping of the solid phase obtained at the end of bl) in contact with the aqueous solution can be carried out by a mixer continuously or discontinuously, in a or several operations / stages.

[0107] According to one or more embodiments, the first and second filtration cycles bl) and b3) are carried out in two separate pieces of equipment, preferably in two separate filter presses.

[0108] According to one or more embodiments, the first and second filtration cycles bl) and b3) are carried out in the same equipment which is common, preferably in a common filter press.

[0109] Preferably, the liquid-solid separation step b) is carried out in a discontinuous manner (also called "batch" according to Anglo-Saxon terminology), resulting in an interruption of the process at step b) at the end of the 1st filtration cycle in order to proceed with the repulping of the solid phase extracted at the end of the 1st filtration cycle, and then proceed with the 2nd filtration cycle of the repulped solid phase, as well as by a possible implementation of devices operating discontinuously during the filtration cycles.

[0110] Figure 4 illustrates in more detail the first and second filtration cycles and the intermediate pulping step b2), in particular according to one or more embodiments implementing filter press technology.

[0111] Liquid-solid separation by filter press is a technique for separating suspensions under pressure to separate the liquid and solid phases. The filter press consists of trays (or frames) and a filter medium, typically filter cloths, through which the aqueous mixture 2, containing precipitated humins, is filtered and the humins removed as a solid cake. Under filtration pressure, the liquid, called the filtrate, passes through the filter cloths, which retain the solid particles. The filtrate is discharged throughout the process, while the cake formed between the trays is only discharged during the cake removal operation.This technology thus operates in a discontinuous cycle, the cycle comprising a sequence of steps, including filtration, and compaction, also called compaction-blowing because the compaction can optionally involve an injection of compressed air, which increases the dry matter content of the cake.

[0112] The filter press typically comprises several vertical square frames forming sealed filtration chambers. Each frame consists of two faces on which are placed the filter cloths with a fairly tight mesh, allowing the filter cake to settle. This configuration provides a filtering surface area of ​​several tens of square meters. The depth of a filtration chamber (the space between the frames) allows for the formation of filter cakes with a thickness typically ranging from 10 mm to 50 mm, depending on the nature of the suspension to be filtered, with a compromise generally reached between the cycle time and the weight of the filter cake.

[0113] Advantageously, the liquid-solid separation step b) is carried out by at least one filter press, and each of the first and second filtration cycles of the liquid-solid separation step b) comprises the following sequence of substeps, in this order - a filtration substep (bl.l, b3.1) of a filtration charge to produce an aqueous filtrate (3, 20) and a raw cake (22, 35); - a compaction-blowing substep (b 1.3, b3.2) of said raw cake to produce a compaction-blowing filtrate (31, 36) and a compacted-blown raw cake (32, 37); - a sub-step of unbatching (b 1.4, b3.3) said compacted-blown raw cake to produce an unbatched cake (33, 19).

[0114] The debatched cake obtained at the end of the debatching substep bl.4) of the 1st filtration cycle bi) is the solid phase resuspended at the repulping step b2) by contacting the aqueous solution 18, to form the filtration charge of the filtration substep b3.1) of the 2nd filtration cycle b3). bl) 1st filtration cycle

[0115] Preferably, the first filtration cycle is carried out using equipment chosen from a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a spin dryer, and more preferably is carried out by a filter press.

[0116] 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.

[0117] Ambient temperature means a temperature between 10°C and 40°C, preferably between 18°C ​​and 25°C.

[0118] Advantageously, the following sequence of substeps is carried out: - bl.l) Filtration: The aqueous mixture 2 containing solid particles, e.g., precipitated humins, is sent as a filter feed to the filtration step bl.l), in the filtration tool, preferably a filter press, to separate the solid particles in the form of a raw cake 22 and the liquid phase containing 5-HMF and the aprotic polar synthesis solvent (e.g., DMSO) forming the aqueous filtrate 3. Generally, the raw cake 22 still contains some of the liquid phase trapped due to the limitations of the solid / liquid separation tool and possibly the characteristics of the aqueous mixture containing the precipitated humins. At this stage, the cake containing the humins is trapped inside the filter. Preferably, the filtration substep bl.l) 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 at 0.6 MPa. Preferably, a gradual pressure ramp is applied.

[0119] A filtration facilitating agent, preferably diatomaceous earth, polymers such as poly(ethylene oxide) or additives based on nuts, almonds, olives, more preferably diatomaceous earth, can be added to the aqueous mixture 2 sent to the filtration substep b 1.1), preferably in a content of between 0.01% and 5% mass relative to the mass of the aqueous mixture 2. Indeed, in some cases, the suspension formed by the aqueous mixture 2 can be difficult to filter, and the addition of such a filtration aid agent can be useful, particularly to improve the flow rate, filtration quality and cake porosity. Diatomaceous earth is a well-known filtration aid, and its quality and concentration can be selected to facilitate filtration and reduce the duration of the filtration substage. For example, a commercial diatomaceous earth such as Clarcel® DIC3 can be used at a concentration of 1% by mass relative to the mass of the material to be filtered.

[0120] Preferably, the addition of the filtration facilitating agent is carried out in agitated medium, for a duration of between 1 minute and 4 hours, preferably between 5 minutes and 1 hour, for example about 10 minutes, and preferably at room temperature before starting the filtration.

[0121] A non-limiting practical example of implementing the filter press filtration substep is given: the filter is closed by actuating a cylinder that clamps the empty trays together. The closing pressure is self-regulated throughout the filtration process so as to maintain the seal at the tray joints. The feed (aqueous mixture 2), optionally prepared with the addition of a filtration facilitating agent as described above, is then pumped into the filtration chambers via central or lateral feed ports. This step is typically carried out under pressure, at a pressure between 0.6 MPa and 0.8 MPa. The filter filtrate passes through the filter cloths and is collected in the grooves of the trays for discharge through ports positioned around the periphery of the trays.The solid gradually accumulates inside the filtration chambers, between the trays, until the desired cake thickness is formed. The filtration time varies depending on the nature of the suspension to be filtered and its filterability. Filtration is often stopped when the final flow rate reaches a value of 5 l / m² / h. The feed pump is stopped and the internal circuits are emptied of the suspension and filtrate by injecting compressed air.

[0122] Preferably, the filter cloths are chosen so as to be compatible with the load to be filtered, in practice the aprotic polar synthetic solvent, preferably the DMSO. Thus, polypropylene filter cloths are preferably used, with an advantageous cut-off threshold of 10 µm.

[0123] - bl.3) compaction-blowing: preferably, the raw cake 22 formed in the sub-step (filtration bl.l) undergoes a compaction-blowing operation, and a first compaction-blowing filtrate 31 and a compaction-blowing raw cake 32 are formed.

[0124] This substep allows the cake to be dehydrated by pressurization, preferably by injecting compressed air into the filter cloths to press the cake. Pressurizing the filter increases the dry matter content of the cake and extracts water and products of interest, i.e., primarily 5-HMF and the aprotic polar synthesis solvent (e.g., DMSO). Preferably, at the end of the compaction-blowing substep, the raw compaction-blowing cake 32 has a dry matter content of between 20% and 90% by mass, preferably between 50% and 90% by mass, more preferably between 65% and 85% by mass, relative to the total mass of the cake.

[0125] Advantageously, the compaction-blowing is carried out by injection of compressed air.

[0126] Preferably, the compaction-blowing is carried out at a pressure between 1 MPa and 5 MPa, preferably between 1 MPa and 3 MPa, more preferably between 1 MPa and 2 MPa, for example 1.5 MPa.

[0127] The duration of the compaction-blowing is classically between 5 minutes and 30 minutes, preferably between 10 minutes and 20 minutes, for example 15 minutes.

[0128] As for the filtration substep bl.l), the compaction-blowing bl.3) is preferably carried out at a temperature between ambient temperature and 80°C, preferably at an ambient temperature between 10°C and 40°C, preferably between 18°C ​​and 25°C.

[0129] The first compaction-blowing filtrate 31, which may include compounds of interest with a composition approaching that of the first aqueous filtrate 3, is thus preferably recycled in the process at step c) of liquid-liquid extraction.

[0130] - bl.4) De-cake removal: preferably, the raw compacted-blown cake 32 is then debating to produce a debating cake 33.

[0131] This substep of deconstruction bl.4) is preferably carried out at ambient temperature and atmospheric pressure.

[0132] The filtration equipment, typically the filter press, is opened to break up the filter cake. This mechanical action of opening the filter can be supplemented by a vibration or scraping operation using suitable devices known to those skilled in the art, to assist in breaking up the filter cake.

[0133] The debating time is preferably between 15 minutes and 2 hours, preferably between 15 minutes and 1.5 hours, more preferably between 30 minutes and 1 hour, and generally depends on the number of trays that equip the filter press.

[0134] The deconstructed cake is preferably recovered in a tank, for the purpose of carrying out the intermediate pulping step b2).

[0135] Without being limiting, cake removal can, in practice, be carried out as follows: the movable head of the filter is retracted to open the filter chambers one after the other by an automatic system. The formed cake falls by its own weight. The cake removal time is generally between 15 and 45 minutes depending on the number of trays in the filter press. The filter press may include various devices to facilitate cake removal, such as a tray vibration device, an automatic scraping device, or a manual cake removal device that can be used when the cakes are sticky, or a combination of such devices. The cakes fall directly into a tank, for example, one placed under the filter via a hopper, or into a tank further from the filter via a conveyor belt or screw conveyor.

[0136] b2) Pulping: intermediate step of resuspension

[0137] The raw cake 22 (filtration step b 1.1) or preferably the debatched cake 33 obtained at the end of the debatching substep bl.4) of the 1st filtration cycle bl) is the solid phase resuspended at the pulping step b2).

[0138] Repulping consists of resuspending the filtered solid phase obtained at the end of the 1st filtration cycle, e.g. the debattened cake 33, by contact with an aqueous solution 18.

[0139] This repulping step, combined with the second filtration cycle b3) which receives as a filtration charge the suspension formed by the repulped solid phase 34 (repulped cake 34), allows the recovery of as much as possible of products of interest such as 5-HMF and the aprotic polar synthesis solvent, e.g. DMSO, which remained in the filtered solid phase at the end of the 1st filtration cycle during the liquid-solid separation step b).

[0140] Step b2) of pulping is preferably carried out in a dedicated device, typically a dedicated tank, i.e. separate from the filtering equipment of the filtration cycles bl) and b3).

[0141] Said tank preferably includes a suitable agitation system, and is configured to receive the debattened cake 33 as already described above (tank placed under the filter or further away with a conveying system, and to send the repelled solid phase 34 to the filtration equipment of the 2nd filtration cycle b3), for example with a system of conduits and pump.

[0142] Pulping can be carried out by a mixer continuously or discontinuously, in one or more operations / stages.

[0143] Preferably, the pulping step is carried out at a temperature between ambient temperature and 80°C, preferably at ambient temperature between 10°C and 40°C, preferably between 18°C ​​and 25°C, and preferably at atmospheric pressure.

[0144] The pulping time can be between 1 minute and 4 hours, preferably between 5 minutes and 3 hours, more preferably between 30 minutes and 2 hours.

[0145] The aqueous solution 18 may be pure water, possibly external to the process.

[0146] The aqueous solution 18 may comprise, or be constituted by, at least a fraction of the aqueous effluent 15 produced in the optional step g) of processing the aprotic polar synthetic water-solvent mixtures.

[0147] The mass ratio between the aqueous solution and the cake is preferably between 1 and 10, preferably between 2 and 8, more preferably between 3 and 7. b3) 2nd filtration cycle

[0148] Preferably, the 2nd filtration cycle b3) is carried out using equipment selected from a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a spin dryer, and more preferably by a filter press. This can be equipment of the same or different nature, for example a filter press for the 1st filtration cycle and a belt filter for the 2nd filtration cycle, and preferably the equipment of the two filtration cycles is of the same nature through process simplification. Furthermore, the 1st and 2nd filtration cycles can be carried out in the same equipment, i.e. in a common piece of equipment.

[0149] Preferably, the 1st and 2nd filtration cycles are carried out in separate equipment.

[0150] The 2nd filtration cycle is preferably operated at a temperature between ambient temperature and 80°C, preferably at ambient temperature (i.e. temperature between 10°C and 40°C, 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.

[0151] Advantageously, the following substep sequence is carried out during the 2nd filtration cycle b2): - b3.1) Filtration: The resuspended solid phase 34, i.e., the repulped cake, is sent as a filter feed to filtration step b3.1), in the filtration tool, preferably a filter press, in order to separate the solid particles into a raw repulped cake 35, i.e., a raw cake resulting from the feed consisting of the suspension from repulping b2), and the liquid phase 20 containing 5-HMF and the aprotic polar synthesis solvent (e.g., DMSO) forming the filtrate of Pulping 20, which is an aqueous filtrate. Generally, the repulped raw cake 35 still contains some of the liquid phase trapped due to limitations of the solid / liquid separation tool and possibly the characteristics of the feed 34. At this stage, the repulped raw cake is trapped inside the filter. Preferably, the filtration substep 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 at 0.6 MPa. Preferably, a gradual pressure ramp is applied.

[0152] A filtration facilitating agent, preferably diatomaceous earth, polymers such as poly(ethylene oxide) or additives based on nuts, almonds, olives, more preferably diatomaceous earth, can be added to the feed 34 sent to the filtration sub-step b3.1), preferably in a content of between 0.01% and 5% mass relative to the mass of the feed 34. Such an agent is intended to facilitate filtration, in particular to improve the flow rate and / or the filtration quality and / or the porosity of the cake.

[0153] A non-limiting practical example of implementation of the filter press filtration substep is identical to that given in substep bl.l) and is not repeated here.

[0154] Preferably, the filter cloths are chosen so as to be compatible with the load to be filtered, in practice the aprotic polar synthetic solvent, preferably DMSO. Thus, polypropylene filter cloths are preferably used, advantageously with a cut-off threshold of 10 µm.

[0155] The second aqueous filtrate 20 is recycled in step a) of mixing, as already mentioned above.

[0156] - b3.2) compaction-blowing: preferably, the repulped raw cake 35 formed at the sub-filtration step b3.1) undergoes a compaction-blowing operation, and a second compaction-blowing filtrate 36 and a compaction-blowing repulped raw cake 37 are formed.

[0157] This substep b3.2) allows the cake to be dehydrated by pressurization, preferably by injecting compressed air into the filter cloths to press the cake. Pressurizing the filter increases the dry matter (“DM”) of the cake and extracts water and possibly products of interest, i.e., mainly 5-HMF and the aprotic polar synthesis solvent (e.g., DMSO). Preferably, at the end of the compacting-blowing substep b3.2), the compacted-blown repulped raw cake 37 has a dry matter content of between 20% and 90% by mass, preferably between 30% and 90% by mass, more preferably between 35% and 80% by mass, and even more preferably between 40% and 60% by mass, relative to the total mass of the cake.

[0158] Advantageously, the compaction-blowing is carried out by injecting compressed air.

[0159] Preferably, the compaction-blowing b3.2) is at a pressure between 1 MPa and 5 MPa, preferably between 1 MPa and 3 MPa, more preferably between 1 MPa and 2 MPa, for example 1.5 MPa.

[0160] The duration of the compaction-blowing b3.2) is classically between 5 minutes and 30 minutes, preferably between 10 minutes and 20 minutes, for example 15 minutes.

[0161] As for the filtration substep bl. 1), the compaction-blowing b3.2) is carried out at a temperature between ambient temperature and 80°C, preferably at ambient temperature (i.e. between 10°C and 40°C, preferably between 18°C ​​and 25°C).

[0162] The second compaction-blowing filtrate 36, which may include compounds of interest, and in particular have a composition approaching that of the second aqueous filtrate 20, is thus preferably recycled in the process at step a) of mixing.

[0163] - b3.3) De-cake: preferably, the second raw compacted-blown cake 37 is then debatched to produce a debatched cake 19 forming the final solid preferably removed from the process. This solid residue therefore contains at least a fraction of the solid particles of the aqueous mixture 2 sent to the liquid-solid separation step, and preferably essentially all of the solid particles, and consequently of the precipitated humins, removed from the process.

[0164] This deconstruction substep b3.3) is preferably carried out at ambient temperature (i.e. between 10 and 40°C, preferably between 18 and 25°C) and at atmospheric pressure.

[0165] The filtration equipment, typically the filter press, is opened to break up the filter cake. This mechanical action of opening the filter can be supplemented by a vibration or scraping operation using suitable devices known to those skilled in the art, to assist in breaking up the filter cake.

[0166] The debating time is preferably between 15 minutes and 2 hours, preferably between 15 minutes and 1.5 hours, more preferably between 30 minutes and 1 hour, and generally depends on the number of trays that equip the filter press.

[0167] Without being limiting, the deconstruction can, in practice, be carried out in the same way as described for substep b 1.4) and is not repeated here. Step c) Liquid-liquid extraction

[0168] The process according to the invention includes a step c) of liquid-liquid extraction of the aqueous mixture 3 obtained at the end of step b) in the presence of an extraction solvent 4, so as to produce an aqueous raffinate 5 and an organic extract 6.

[0169] The liquid-liquid extraction carried out in step c) advantageously corresponds to a The aqueous mixture is washed with an organic extraction solvent. Preferably, the liquid-liquid extraction carried out in step c) is a countercurrent extraction of the aqueous mixture 3 obtained in step b) with an extraction solvent 4. This technique is well known to those skilled in the art. It can be carried out, for example, in a battery of mixer-settlers, in a column packed with bulk or structured material, in a pulsed column, or in a stirred column.

[0170] Liquid-liquid extraction may include the implementation of at least two theoretical separation stages. This is the case, for example, but not exclusively, when an additional liquid-solid separation stage is carried out on an intermediate liquid stream produced during liquid-liquid extraction step c), which returns to step c) once it has been cleared of solid particles. A first liquid-liquid separation stage may then be carried out, producing said intermediate liquid stream which is sent to the additional liquid-solid separation stage to form a particle-depleted intermediate liquid stream which is sent to the second liquid-liquid extraction stage of step c).

[0171] Step c) of liquid-liquid extraction is advantageously carried out at a temperature between 0 and 60°C, preferably between 5°C and 40°C, and generally at room temperature (i.e. between 10 and 40°C).

[0172] Generally, the extraction solvent rate, defined as the mass ratio between the extraction solvent flow rate and the feed entering the extraction stage, results from the number of separation stages involved, the choice of the extraction solvent and the 5-HMF recovery target defined as the ratio between the quantity of 5-HMF carried in the organic extract 9 and the quantity of 5-HMF contained in the aqueous mixture 6 sent to the extraction step d). The target recovery rate is preferably between 80 and 100%, preferably between 90% and 99.9% and even more preferably between 95 and 99.9%.

[0173] The extraction solvent 4 introduced in step c) is chosen from among organic solvents immiscible with water, so as to form two liquid phases in step c) and in the backwashing step d). This property is highly dependent on the relative proportions of the feed flow rates, backwash water, and extraction solvent used in the process.

[0174] By way of non-limiting choice, the extraction solvent is preferably selected from chlorinated organic solvents, ethers, esters, ketones, and aromatic compounds. Preferably, the extraction solvent is a chlorinated solvent having between 1 and 10 carbon atoms, hereinafter denoted as C1-C10, an ether having between 2 and 10 carbon atoms (C2-C10), an ester having between 4 and 10 carbon atoms (C4-C10), a ketone having between 3 and 10 carbon atoms (C3-C10), an aldehyde having between 1 and 10 carbon atoms (C1-C10), or a C4-C10 aromatic compound. Preferably, the The extraction solvent is chosen from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole, and toluene. Methyl isobutyl ketone is the preferred extraction solvent.

[0175] Advantageously, the extraction solvent is chosen so as to have a very high volatility difference with 5-HMF, in particular so as to facilitate its removal in the optional step e) and limit the degradation of 5-HMF, i.e. so as to present in step e) a rate of vaporization which does not degrade the 5-HMF and minimizes the amount of residual solvent to be removed by hydrodistillation in step f) while ensuring the absence of liquid phase separation when the concentrated organic raffinate 10 is brought into contact with water in hydrodistillation in step f). The extraction solvent can also be chosen so as to form, upon hydrodistillation in step f), a heterogeneous azeotrope with water, preferably rich in solvent, i.e., with more than 50 wt% solvent, preferably with more than 60 wt% solvent, and preferably with more than 70 wt% solvent. Advantageously, said azeotrope of the water / extraction solvent mixture has a boiling point significantly lower than that of water, preferably at least 5°C lower than the boiling point of water, preferably at least 8°C lower than the boiling point of water, and preferably at least 10°C lower than the boiling point of water.

[0176] Advantageously, the organic solvent streams produced in subsequent steps can be recycled to step c) of extraction, as an extraction solvent. These organic solvent streams may contain impurities generated during the implementation of the process. Advantageously, the organic solvent streams produced in subsequent steps can be distilled, for example periodically, to prevent the accumulation of said impurities.

[0177] Step c) thus makes it possible to obtain, on the one hand, an aqueous stream depleted in 5-HMF, called aqueous raffinate 5, which contains a large part of the polar aprotic synthesis solvent (e.g. DMSO) initially contained in the feed 1, and on the other hand an organic stream enriched in 5-HMF, called organic extract 6, which contains a large part of the 5-HMF, initially contained in the feed 1, and the extraction solvent 4. This organic extract 6 may also contain polar aprotic synthesis solvent (e.g. DMSO). Preferably, said organic extract contains 5-HMF and aprotic polar synthesis solvent (e.g., DMSO) in a weight ratio of 5-HMF / aprotic polar synthesis solvent (e.g., DMSO) of between 50 / 50 and 99 / 1, preferably between 50 / 50 and 95 / 5, preferably between 55 / 45 and 90 / 10, more preferably between 60 / 40 and 85 / 15, and preferably between 65 / 35 and 80 / 20.

[0178] Advantageously, the organic extract 6 is sent directly to the backwashing step d).

[0179] A fraction of solid particles, formed by precipitated humins, may also be present in step c). This may consist of humins precipitated in the upstream mixing step a), still present in the aqueous mixture 3 sent to step c), or of humins precipitated in step c) or even in the backwashing step d). Backwashing step d

[0180] The process according to the invention includes a step d) of backwashing the organic extract 6 with an aqueous solvent 7, so as to produce an aqueous counter-extract 9 and an organic raffinate 8 comprising 5-HMF and an organic solvent. The aqueous counter-extract 9 is advantageously sent in part or in whole to step a). The organic solvent is in particular composed at least in part of an extraction solvent and may optionally include a polar aprotic synthesis solvent (e.g., DMSO), preferably in small amounts.

[0181] The introduction of an aqueous solvent 7 in step d) is carried out in such a way as to implement a backwash, according to the general knowledge of a person skilled in the art. The introduction of the aqueous solvent 7 is carried out in such a way that the quantity of aqueous solvent is as small as possible in order to reduce costs, but sufficient to guarantee a low weight content of polar aprotic synthetic solvent (e.g. DMSO) in the organic raffinate 8 and preferably less than or equal to 20.0 wt% relative to the weight of 5-HMF, preferably less than or equal to 15.0 wt% relative to the weight of 5-HMF, preferably between 0.01 and 15.0 wt% relative to the weight of 5-HMF, most preferably between 0.01 and 10.0 wt% relative to the weight of 5-HMF.

[0182] Advantageously, the aqueous backwash solvent 7 introduced in step d) comprises at least 95 wt% water, preferably at least 98 wt% water (100% being the maximum). The aqueous solvent may optionally include a polar aprotic synthetic solvent (e.g., DMSO). The backwash efficiency is higher when the amount of polar aprotic synthetic solvent (e.g., DMSO) present in the aqueous backwash solvent is lower. The aqueous solvent may comprise at most 1.0 wt%, and preferably at most 0.1 wt%, of a polar aprotic synthetic solvent (e.g., DMSO). Advantageously, the aqueous backwash solvent 7 is obtained from step g) of the treatment of water-aprotic polar synthetic solvent mixtures produced within the process, and thus comprises at least a fraction of the recyclable effluent 15. In a preferred embodiment of the invention, the aqueous raffinate 5, composed of water and aprotic polar synthetic solvent (e.g.DMSO), produced in step c) is dealt with in step g) which advantageously includes . a distillation. The water-rich distillate thus obtained at the end of this step (g), also called the recyclable aqueous effluent 15 in the process, is advantageously used to form the aqueous backwash solvent 7 in step (d), optionally mixed with additional water, or is used in the mixing step (a) to form the aqueous stream 21, optionally with at least one aqueous back-extract fraction 9 and / or additional water. This recyclable effluent 15, e.g., the water-rich distillate, may also contain a residual amount of aprotic polar synthetic solvent (e.g., DMSO), preferably less than or equal to 1 wt% and preferably less than or equal to 0.1 wt%. The residual amount of aprotic polar synthetic solvent (e.g., DMSO) isDMSO) in the aqueous effluent 15 (the distillate) is lower the more efficiently the distillation of step g) is carried out, in particular with a number of distillation stages greater than 5, and advantageously with suitable reboiling and reflux ratios.

[0183] The backwashing step (d) is advantageously a liquid-liquid extraction of an organic stream, in particular of the organic extract 6 obtained in step (c) against the aqueous solvent 7. This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a battery of mixer-settlers, in a column packed with bulk or structured material, in a pulsed column, or even in a stirred column.

[0184] Step d) is preferably carried out at a temperature between 0 and 60°C, preferably between 5°C and 40°C and generally at room temperature (i.e. between 10°C and 40°C).

[0185] The weight ratio (weight / weight) of aqueous solvent 7 relative to organic extract 6 is preferably between 0.04 and 5, preferably between 0.07 and 3, preferably between 0.1 and 1.

[0186] Step d) enables the obtaining of an aqueous stream advantageously enriched in aprotic polar synthesis solvent (e.g., DMSO), called aqueous counter-extract 9, preferably containing at least 60 wt% water, preferably at least 80 wt% water, and an organic raffinate 8, advantageously depleted in aprotic polar synthesis solvent (e.g., DMSO). Said aqueous counter-extract 9 is advantageously sent, in part or preferably in whole, to step a). The organic raffinate 8 obtained has a weight content of polar aprotic synthesis solvent preferably less than or equal to 20.0 wt% relative to the weight of 5-HMF, preferably less than or equal to 15.0 wt% more preferably less than or equal to 5.0 wt%, even more preferably less than or equal to 4.0 wt%, and most preferably less than or equal to 3.0 wt% relative to the weight of 5-HMF.

[0187] According to the invention, the organic raffinate 8 produced in step d) is sent to the optional concentration step e) or directly to hydrodistillation in step f).

[0188] Humins may still be present in the organic extract 6 sent to the backwashing step d). If they precipitate at this step, forming undesirable solid particles, these could be removed by sending the aqueous counter-extract 9, in whole or in part, to step c), which would contain the precipitated humins. These humins could then be removed during an additional liquid-solid separation step on an intermediate liquid stream produced in step c) and / or on the aqueous raffinate 5 downstream of step d). If the aqueous counter-extract 9 is sent in whole or in part to step a) to form part of the composition or to constitute the aqueous stream 21, the precipitated humins could also be separated during the liquid-solid separation in step b), as already described above. Optional step e) of concentration

[0189] The process according to the invention preferably comprises a step e) of concentration of the organic raffinate 8 from step d), by removal of part of the organic solvent, producing a concentrated organic raffinate 10, comprising 5-HMF and residual organic solvent, and a first stream 11 comprising, preferably made up of, organic solvent, said organic solvent advantageously being composed in whole or in part of the extraction solvent and optionally of aprotic polar synthesis solvent (e.g. DMSO).

[0190] Preferably, the first stream 11 comprising organic solvent is recycled, in whole or in part, to step c) of extraction, for example forming at least part of the organic solvent stream 4.

[0191] Preferably, in step e), the removal of part of the organic solvent is carried out by vaporization, for example in a distillation column at atmospheric pressure or under vacuum, in an evaporator, or any method known to those skilled in the art.

[0192] According to this preferred method, the vaporization of the organic solvent is advantageously carried out at atmospheric pressure or under vacuum, preferably at a pressure between 0.01 MPa and 0.1 MPa, preferably under vacuum at a pressure between 0.01 MPa and 0.09 MPa, so as to limit the temperature of the liquid and therefore the degradation of 5-HMF. Preferably, the temperature of the liquid is maintained at or below 130°C, preferably at or below 100°C, preferably at or below 70°C. The pressure level, particularly the vacuum level, to be applied to reach these temperatures is of course dependent on the organic solvent and more particularly on the extraction solvent used and the vaporization rate of the organic solvent.

[0193] In a preferred mode, the vaporization of the solvent is carried out by multi-effect evaporation or with mechanical recompression of the vapors, or any other methods These methods are 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, i.e., 5-HMF. For example, in the case of a triple-effect evaporator, the liquid temperature is maintained below 130°C in the first effect, below 100°C in the second effect, and below 70°C in the third effect. Thus, the temperature of the liquid phase is reduced as the 5-HMF is concentrated in the organic solvent, limiting any risk of degradation.

[0194] The optional step e) is implemented with a mass vaporization rate (or evaporation rate), corresponding to the mass of organic solvent vaporized relative to the mass of the organic raffinate 8 from step d) (more particularly the mass quantity of the stream 11 relative to the mass quantity of the organic raffinate 8), of at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 75%, preferably at least 80%, preferably at least 85%, preferably at least 90%, and preferably at most 99%.Advantageously, the vaporization rate is defined as a function of the extraction solvent so as not to degrade the 5-HMF, but also in order to minimize the amount of residual solvent to be removed by hydrodistillation in step f) while ensuring the absence of liquid phase separation (i.e. while ensuring that the liquid phase remains monophasic) when the concentrated organic raffinate 10 is brought into contact with water by hydrodistillation in step f).

[0195] Thanks to the combination of all the operating conditions of the preceding steps a), b), c), and d), and the optional step e), the concentrated organic raffinate 10 obtained at the end of step e) most advantageously has a 5-HMF content of at least 40 wt% relative to the weight of the concentrated organic raffinate, preferably at least 50 wt%, preferably at least 60 wt%, and preferably at most 95 wt%, preferably at most 90 wt%, and preferably at most 85 wt% 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 wt% relative to the weight of the concentrated organic raffinate, preferably at least 10 wt%, and preferably at most 60 wt%, preferably of at most 50% by weight, preferably at most 40% by weight, relative to the weight of the concentrated organic raffinate 10.

[0196] Advantageously, the organic solvent vaporized during the optional step e) forms a first stream 11 comprising, preferably consisting of, organic solvent and is preferably recycled to the extraction step c).

[0197] Advantageously, the concentrated organic raffinate 10 is sent to hydrodistillation in step f). Step f) of purification

[0198] The process according to the invention includes a step f) of purifying the organic raffinate 8 or the concentrated organic raffinate 10 to produce a stream of 5-HMF.

[0199] According to one or more embodiments, the purification step f) comprises, and may consist of, a hydrodistillation step carried out by distillation in the presence of water 14 of the organic raffinate 8 from step d) or of the concentrated organic raffinate 10 from the optional step e), to produce said 5-HMF stream which is then an aqueous solution of 5-HMF 12 and generating a second stream 13 comprising, and preferably consisting of, organic solvent.

[0200] The hydrodistillation step advantageously allows the removal, at least in part, of the residual organic solvent not removed during the optional step e). The residual organic solvent removed during the hydrodistillation step, i.e. the second stream 13 comprising organic solvent, can advantageously be recycled in the extraction step c), alone or mixed with the first stream 11 from the optional step e).

[0201] Advantageously, an aqueous liquid 14 feeds the hydrodistillation step. The aqueous liquid 14 introduced into the hydrodistillation step preferably contains more than 95% by weight of water, preferably more than 98% by weight of water.

[0202] In a particular embodiment of the invention, the aqueous liquid 14 is pure water, possibly external to the process, which makes it possible to further minimize the residual content of aprotic polar synthesis solvent (e.g. DMSO) in the aqueous solution 12 of 5-HMF produced in step f) comprising or consisting of hydrodistillation.

[0203] In another particular embodiment of the invention, isolated water within the process is used to feed the hydrodistillation step, thereby limiting the operating costs of the process and its environmental impact. Typically, if the sugar feed for the optional dehydration step is a sugar syrup at 70% wt% in water, approximately 1 tonne of water is available at the end of the dehydration step (the water from the sugar feed and the water produced during the dehydration reaction) per tonne of 5-HMF produced. This water, which is advantageously recovered, requires treatment before being discharged into the environment.The process according to the invention can then advantageously use said water from the sugar feed and / or the dehydration step to produce, at the end of the hydrodistillation step, an aqueous solution of 5-HMF concentrated preferably at 30% wt or more, preferably at 40% wt or more, and thus reduce the reprocessing costs and its environmental impact.

[0204] Advantageously, the aqueous liquid 14 introduced in the hydrodistillation step may correspond to at least a fraction, possibly all, of the aqueous effluent 15 (distillate) produced in step h). Said distillate may optionally contain a residual quantity of aprotic polar synthesis solvent (e.g. DMSO).

[0205] Advantageously, during the hydrodistillation step, the extraction solvent used in the process forms a heterogeneous azeotrope with water, said azeotrope preferably being rich in extraction solvent, preferably comprising more than 50% by weight of extraction solvent, preferably more than 60% by weight of extraction solvent, and preferably more than 70% by weight of extraction solvent. Advantageously, said water / extraction solvent azeotrope has a boiling point significantly lower than that of water, preferably at least 5°C lower than the boiling point of water, preferably at least 8°C lower than the boiling point of water, and preferably at least 10°C lower than the boiling point of water.

[0206] Thus, 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 degradation of the 5-HMF.

[0207] The hydrodistillation step can be carried out at atmospheric pressure or under vacuum, and in particular at a pressure between 0.00 MPa and 0.1 MPa, preferably under vacuum at a pressure between 0.005 MPa and 0.08 MPa. Advantageously, the hydrodistillation step is carried out under vacuum, in particular at a pressure between 0.001 MPa and 0.1 MPa, preferably between 0.005 MPa and 0.08 MPa, so as to facilitate the removal of the residual organic solvent without degradation of the 5-HMF.

[0208] Advantageously, the hydrodistillation step is carried out in a distillation column, preferably at a column bottom temperature of less than or equal to 140°C, preferably less than or equal to 130°C, preferably less than or equal to 120°C, preferably less than or equal to 110°C and preferably less than or equal to 100°C, so as to facilitate the removal of the residual organic solvent without degradation of the 5-HMF.

[0209] In a particular embodiment, during the hydrodistillation step, the concentrated organic raffinate 10 or failing that the organic raffinate 8 and the aqueous liquid 14 are mixed before introduction into a distillation column and the mixture is introduced at an intermediate point of the distillation column.

[0210] In another particular embodiment, during the hydrodistillation step, the concentrated organic raffinate 10 or the organic raffinate 8 is introduced into the upper part of the distillation column, preferably into the upper half of the distillation column, while the aqueous liquid is also introduced into the distillation column. The mixing with the aqueous liquid is then carried out within the distillation column.

[0211] Given the formation of a heterogeneous azeotrope between water and the extraction solvent during the hydrodistillation step, the condensation of the overhead vapors of the distillation column generates 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 in step c) of extraction.

[0212] The aqueous solution 12 of 5-HMF obtained at the end of the hydrodistillation step, has an amount of 5-HMF of at least 30% by weight, preferably at least 40% by weight, and preferably less than 90% by weight, preferably less than 85% by weight and preferably less than 80% by weight, the percentages being given by weight of 5-HMF relative to the weight of aqueous solution of 5-HMF obtained at the end of the hydrodistillation step.

[0213] The process according to the invention advantageously makes it possible to produce an aqueous solution of 5-HMF having very advantageously a weight content of polar aprotic synthesis solvent (e.g. DMSO) less than or equal to 10% weight relative to the weight of 5-HMF, preferably less than or equal to 5% weight relative to the weight of 5-HMF and preferably less than or equal to 3% weight relative to the weight of 5-HMF.

[0214] According to one or more alternative embodiments to hydrodistillation, the purification step f) comprises, and may consist of, at least one step of crystallizing the 5-HMF contained in the organic raffinate 8 from step d) or said concentrated organic raffinate 10 from step e, followed by filtration, to produce a 5-HMF stream comprising solid 5-HMF (5-HMF crystals) and an organic solvent-rich filtrate.

[0215] Crystallization can be achieved by all methods known to those skilled in the art, for example by lowering the temperature, increasing the concentration of 5-HMF to be crystallized, increasing the concentration of 5-HMF to be crystallized with lowering the temperature, or by adding a third compound suitable for reducing the solubility of the 5-HMF to be crystallized in the organic raffinate.

[0216] The conditions are those known to a person skilled in the art. The temperature is preferably less than or equal to 30°C, and generally between -100°C and 0°C, preferably between -50°C and 0°C, and even more preferably between -40°C and -10°C.

[0217] The filtrate rich in organic solvent, essentially extraction solvent, is advantageously recycled, in part or in whole (after possible purging) to step c) of liquid-liquid extraction to carry out a new extraction of 5-HMF.

[0218] According to methods known to the person skilled in the art, step f) of purification based on crystallization is carried out in one or more passes, and the crystals are washed and dried.

[0219] Optional step g) of treatment of aprotic polar synthetic water-solvent mixtures

[0220] The process according to the invention may include an optional step (g) of treating water-aprotic polar synthetic solvent mixtures (e.g., DMSO) generated by the steps of the process according to the invention, to produce an aqueous effluent 15 (also called distillate), which may be used in whole or in part in the backwashing step (d) and / or in the hydrodistillation purification step (a) and / or in the hydrodistillation purification step (f). This step may also produce a stream 16 rich in aprotic polar synthetic solvent (e.g., DMSO) and an impurity stream 17. At least one water-aprotic polar synthetic solvent mixture produced in the process may therefore be treated in step (g). Said mixture may be the aqueous raffinate from step (c).

[0221] This step g) makes it possible to separate within said at least one mixture (aqueous raffinate 5 from step c)), water, the aprotic polar synthesis solvent and reaction products extracted in the raffinate such as unconverted sugars, sugar oligomers, residual 5-HMF.

[0222] One or more other aprotic polar synthetic water-solvent mixtures produced within the process may be sent to step g).

[0223] The residual quantity of aprotic polar synthesis solvent (e.g. DMSO) in the aqueous effluent 15 produced at the end of step g) is lower the more efficiently the distillation is carried out according to the knowledge of a person skilled in the art.

[0224] The water-solvent mixtures of polar aprotic synthesis (e.g. DMSO) generated by the process refer in particular to the aqueous raffinate 5 produced in step c), and possibly the water-solvent mixture of polar aprotic synthesis (e.g. DMSO) from the optional step of sugar dehydration to 5-HMF when the process incorporates such a step.

[0225] Step g) of treatment of water-solvent mixtures of polar aprotic synthesis (e.g. DMSO) preferably implements an evaporation section of a water-solvent mixture of polar aprotic synthesis (e.g. DMSO), to remove any impurities in the form of stream 17 in particular heavy impurities such as humins or unconverted sugars, followed by a distillation section.

[0226] The evaporation section is operated at a temperature preferably between 80 and 130°C, preferably between 100 and 120°C, and preferably at a pressure between 0.0001 MPa and 0.0200 MPa, preferably between 0.0002 MPa and 0.0100 MPa, preferably between 0.0005 MPa and 0.0050 MPa. Preferably, the evaporation section is implemented by a thin film evaporator (TFE).

[0227] The distillation section advantageously employs a distillation column or several separate pieces of equipment. Preferably, the distillation section of step g) is advantageously implemented in a distillation column, at a column head temperature preferably between 25 °C and 60 °C, preferably preferably between 45°C and 55°C, for example about 50°C, preferably at a bottom-of-column temperature between 80°C and 140°C, preferably between 100°C and 130°C, for example about 120°C, preferably at a pressure between 0.001 MPa and 0.05 MPa, preferably between 0.005 MPa and 0.02 MPa and preferably between 0.008 MPa and 0.012 MPa, and preferably with a reflux ratio between 0.01 and 0.50, preferably between 0.05 and 0.10.

[0228] Thus, the aqueous raffinate 5 produced in step c) and comprising water and aprotic polar synthesis solvent (e.g., DMSO), and optionally the water-aprotic polar synthesis solvent (e.g., DMSO) mixture recovered in the optional dehydration step, are evaporated, and then the gaseous phase is recovered and distilled, preferably under vacuum, so as to produce a residue 16 rich in aprotic polar synthesis solvent (e.g., DMSO) on the one hand, a distillate 15 rich in water (corresponding to the aqueous effluent) on the other hand, and, finally, a stream 17 containing the heavy fractions such as unfiltered humins and unconverted humin sugars. By rich, we mean here at least 95 wt., preferably at least 98 wt. Part or all of the water-rich distillate, or aqueous effluent, can advantageously be recycled in step d) of backwashing as an aqueous solvent and / or in step e) of hydrodistillation purification as an aqueous stream.The said water-rich distillate can also be, in whole or in part, recycled as water introduced in step a).

[0229] The residue rich in aprotic polar synthesis solvent 16 (e.g. DMSO) can advantageously be introduced at the optional dehydration step, either directly or after distillation allowing the removal of heavy products that could accumulate.

[0230] List of numerical references used in the figures: 1: charge 2: aqueous mixture 3: first aqueous filtrate 4: Extraction solvent 5: aqueous refiner 6: organic extract 7: aqueous solvent 8: organic refiner 9: aqueous counter-extract 10: Concentrated organic raffinate 11: first stream including organic solvent 12: aqueous solution of 5-HMF 13: second stream including organic solvent. 14: aqueous liquid 15: aqueous effluent 16: solvent-rich flux of aprotic polar synthesis (or rich "residue"...) 17: Impurity flux (or heavy fraction flux) 18: aqueous solution 19: Solid finish 20: second aqueous filtrate (repulping filtrate) 21: Water flow 22: raw cake 23: wash water 24: washing filtrate 25: washed cake 26: compaction-blowing filtrate 27: washed, compacted / puffed cake 28: Washed, compacted / puffed cake 29: Primary compaction-blowing filtrate 30: Raw, compacted-puffed cake 31: first compaction-blowing filtrate of the 1st filtration cycle 32: Raw compacted-blown cake from the 1st filtration cycle 33: cake debating 34: Plumped-up cake 35: Raw cake with added volume 36: Second compaction-blowing filtrate of the 2nd filtration cycle 37: Raw cake, re-plumped, compacted-puffed Examples

[0231] The examples below are intended to show some of the advantages of the process according to the invention, in particular by comparison of an example according to the invention (example 2) operating a liquid-solid separation as shown in [Fig.4] implementing 2 filtration cycles bl) and b3) by filter press separated by an intermediate step b2) of resuspension of the cake obtained at the end of bl), with an example of a process according to the prior art (example 1) comprising a liquid-solid separation step by filter press incorporating a cake washing step as operated according to the method shown in [Fig. 1]. Example 1 (not in accordance with the invention)

[0232] According to this example 1, a washing of the cake is carried out directly in the separation tool which is a filter press: the charge of the filter press 2, which is a suspension from a mixing step a) of a charge 1 comprising 5-HMF and DMSO with water 21, is sent to the filtration step b 1.1) to separate the solid phase, i.e. the precipitated humins, from the liquid phase 3 comprising in particular 5-HMF, DMSO and water. Following step bl.l), the raw cake 22 containing the humins undergoes a washing step b 1.2) with water 23, producing a washed cake 25 and a washing filtrate 24 containing 5-HMF and DMSO. The washed cake 25 then undergoes a compaction-blow step b 1.3) forming a compacted / blown washed cake 27 and a compaction-blow filtrate 26. Finally, the compacted / blown washed cake 27 is debatched in the debatching step bi,4) to form a compacted / blown washed debatched cake 28.

[0233] In this example, the filter press charge 2 is composed of 11% of 5-HMF and 35% of DMSO. After filtration bl.1), washing bl.2), and compaction bl.3), the loss rate in the cake is defined as follows: mass ratio of a compound of interest X in the washed compacted / blown cake 28 and of said compound X in the filtration charge 2: (mXcake28) / (mXcharge2).

[0234] Table 1 below shows the loss rate of 5-HMF and DMSO as a function of the mass ratio of wash water used 23 to the raw cake 22 (unwashed) and as a function of the mass ratio of wash water used 23 to the filtration load of 22%.

[0235] [Tables 1] Example 1: Wash water ratio 23 / filter load 2: 50% 22% Wash water ratio 23 / raw filter cake 22 (unwashed): 58% 9% 5-HMF loss rate: 0.39% 1.92% DMSO loss rate: 0.13% 1.48%

[0236] When operating with a wash directly integrated into the filter press filtration cycle, it is necessary to wash the cake with a significant flow of water to reduce losses of products of interest below 1%, whether for 5-HMF or DMSO. Example 2 (according to the invention)

[0237] According to this example 2, the liquid-solid separation is carried out according to the scheme illustrated in [Fig.4] in accordance with the HMF production process according to the invention.

[0238] There is no washing step during the liquid-solid separation by filter press.

[0239] The filter press feed 2, which is the same suspension as in Example 1, is sent to the filtration step bl.1) to separate the solid phase, i.e. the precipitated humins, from the liquid phase 3, which includes 5-HMF, DMSO, and water. At the end of step bl.1), the raw cake 22 undergoes a compaction-blow operation bl.3), and a compaction-blow raw cake 32 is formed and is then debatched in substep b 1.4).

[0240] According to the invention, the debattened cake 33 is resuspended at the repulping step b2), in contact with the aqueous solution 18, according to water / cake 33 ratios indicated in Table 2 below.

[0241] The suspension thus formed is sent to the 2nd filtration cycle b2) comprising the same sub-step sequence as the first filtration cycle bl): filtration b3.1), then compaction-blowing b3.2), then debating b3.3).

[0242] A final cake 19 is recovered at the end of the debating b3.3).

[0243] Table 2 below shows the loss rate of 5-HMF and DMSO as a function of the mass ratio of engaged pulping water 18 to the debattened cake 33 (pulping stage load) and as a function of the mass ratio of engaged pulping water 18 to the filtration load 2.

[0244] [Tables2] Example 2: Pulping Ratio of pulping water 18 / filtration load 2 2.6% 13% 22% Ratio of pulping water 18 / defatted cake 33 1% 4.9% 8.3% Loss rate of 5-HMF 1.41% 1.27% 0.94% Loss rate of DMSO 0.38% 0.41% 0.30%

[0245] This example according to the invention shows that the loss rates of 5-HMF and DMSO in the final cake 19 obtained after the two filtration cycles and the intermediate pulping are much lower than in Example 1 of a filtration with cake washing. For a water 18 / filtration charge 2 ratio of 22%, the configuration according to Example 2 reduces losses by 50% for 5-HMF and 20% for DMSO compared to Example 1. The specific liquid-solid separation b) according to the invention, incorporating a pulping step, thus reduces the water / charge ratio while also reducing the loss rates of 5-HMF and DMSO. For the same water / load ratio, much more 5-HMF and DMSO can be extracted from the filtered solid phase, thus allowing their recycling in the 5-HMF production process for improved HMF yield and potential DMSO savings.

Claims

Demands

1. A process for the production of hydroxymethylfurfural, referred to as 5-HMF, comprising the following steps: - a step a) of contacting a feed (1) comprising 5-HMF and a polar aprotic synthesis solvent with an aqueous stream (21), so as to obtain at least one aqueous mixture comprising solid particles (2); - a step b) of liquid-solid separation of said aqueous mixture (2) comprising a first and a second filtration cycle (bl, b3) separated by an intermediate step b2) of resuspension of a solid phase obtained at the end of the first filtration cycle bl), to produce at least one first aqueous filtrate (3), a second aqueous filtrate (20), and a final solid (19) comprising at least a fraction of the solid particles, said second aqueous filtrate (20) being recycled to step a);- a step c) of liquid-liquid extraction of the first aqueous filtrate (3) obtained at the end of step b) in the presence of an extraction solvent (4), so as to produce an aqueous raffinate (5) comprising said aprotic polar synthesis solvent, and an organic extract (6) comprising 5-HMF and extraction solvent; then - a step d) of backwashing the organic extract (6) with an aqueous solvent (7), so as to produce an aqueous counter-extract (9) and an organic raffinate (8) comprising 5-HMF and an organic solvent; - an optional step e) of concentrating said organic raffinate (8) from step d) by removing at least part of the organic solvent, producing a concentrated organic raffinate (10) comprising 5-HMF, and residual organic solvent, and producing a first stream (11) comprising organic solvent;- a step f) of purifying said organic raffinate (8) or said concentrated organic raffinate (10) to produce a stream of 5-HMF (12).;

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

3. A method according to claim 2, wherein the liquid-solid separation step b) is carried out discontinuously, by at least one piece of equipment chosen from among a filter press, a candle filter, a vacuum filter, a belt press, a decanter, a centrifuge, and preferably by at least one filter press.

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

5. A 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 bl) is carried out at a temperature between ambient temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at atmospheric pressure, by contacting said solid phase with an aqueous solution (18) in a mass ratio between said aqueous solution (18) and said solid phase of between 1 and 10, for a period of between 1 minute and 4 hours, preferably in a tank separate from the equipment used for the first and second filtration cycles.

6. A method according to any one of the preceding claims, wherein the liquid-solid separation step b) is carried out by at least one filter press, and each of the first and second filtration cycles of the liquid-solid separation step b) comprises the following sequence of substeps, in this order: - a filtration substep (bl.1, b3.1) of a filter charge to produce an aqueous filtrate (3, 20) and a raw cake (22, 35); - a compaction-blow substep (b 1.3, b3.2) of said cake to produce a compaction-blow filtrate (31, 36) and a compaction-blow raw cake (32, 37); - a debating substep (b 1.4, b3.3) of said compaction-blow raw cake to produce a debating cake (33, 19); and in which unbaked cake obtained at the end of the unbaking sub-step b 1.4) of the first filtration cycle bl) is the solid phase resuspended in step b2) by contacting an aqueous solution (18), to form the filtration charge of the filtration substep b3.1) of the second filtration cycle b3).

7. A process according to claim 6, wherein the first filtration cycle bl) comprises the compaction-blowing substep bl.3) producing a first compaction-blowing filtrate (31) recycled in the process in step c), and the second filtration cycle b3) comprises the sub-step of compaction-blowing b3.2) producing a second compaction-blowing filtrate (36) recycled in the process in step a).

8. A method according to claim 6, wherein the filtration substeps (bl.l, b3.1) are operated at a temperature between ambient temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at a pressure between 0.05 MPa and 1 MPa.

9. A method according to claim 6, wherein the compaction-blowing substeps (b 1.3, b3.2) are 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. A method according to any one of the preceding claims, wherein the liquid-solid separation step b) does not include a washing step of a filtered solid phase produced during said step b).

11. A process according to any one of the preceding claims, wherein the purification step (f) is a hydrodistillation step carried out by distillation in the presence of water (14) of said organic raffinate (8) from step (d) or of said concentrated organic raffinate (10) from step (e), to produce said 5-HMF stream being an aqueous solution of 5-HMF (12) and a second stream (13) comprising organic solvent, preferably said hydrodistillation 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 at a column bottom temperature 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 at 110°C, preferably less than or equal to 100°C.

12. A process according to any one of the preceding claims, comprising a step of dehydrating sugars into 5-HMF upstream of step a), preferably by contacting a sugar feed comprising a hexose, preferably said hexose being fructose or a fructosidic unit, with said aprotic polar synthesis solvent and an acid dehydration catalyst, preferably at a temperature between 30°C and 200°C and at a pressure between 0.001 MPa and 10 MPa.

13. A method according to any one of the preceding claims, wherein at step a) said aqueous stream (21) comprises all or a fraction of said aqueous counter-extract (9) from step d).

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

15. A process according to any one of the preceding claims, wherein said aprotic polar synthesis solvent is selected from pyridine, butan-2-one, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methyl ethyl ketone, propionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate and γ-valerolactone, taken alone or in mixtures, and is preferably dimethyl sulfoxide.

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