Process for producing 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 feedstock (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 backwash 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 5-HMF stream, 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 feedstock comprising HMF and an aprotic polar synthesis solvent, typically obtained by dehydration of a feedstock 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 step, based on the implementation of two filtration steps with an intermediate step of resuspension of 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 pharmacy, agrochemistry or specialty chemistry. The production of 5-HMF by dehydration of sugars has been known for many years and has been the subject of a large number of research studies. The dehydration conditions are numerous; the following methods can be cited as examples: - 5-HMF can be obtained in an aqueous medium, generally in the presence of an acid catalyst. This acid catalyst makes it possible to dehydrate the C6 sugar (in particular fructose) into 5-HMF, but also catalyzes the rehydration of 5-HMF into formic acid and levulinic acid, which seriously affects the yield. - 5-HMF can also be obtained in a non-aqueous protic polar medium, with solvents such as methanol, ethanol or acetic acid, and in the presence of an acid catalyst. Under these conditions, 5-HMF is obtained in a mixture with an ether or ester derivative of 5-HMF depending on the reaction medium used. The formation of these side products is due to the reaction of 5-HMF with the reaction solvent in an acid medium. - Application WO 2007 / 104514 describes the synthesis of 5-HMF by dehydration of sugar using methanol or ethanol as solvent in the presence of an acid catalyst. In this case, the presence of said catalyst also catalyzes the etherification reaction of 5-HMF by alcohol to give a mixture of 5-HMF and its methyl or ethyl ether form depending on the alcohol used as solvent. - 5-HMF can also be produced in a polar aprotic medium with or without an acid catalyst. Particularly noteworthy is the use of dimethyl sulfoxide. (DMSO) which, with or without an acid catalyst, allows the production of 5-HMF with very good yields, and without the undesirable reactions listed above.

[0003] Furthermore, whatever the synthesis medium (water, methanol, DMSO, etc.), polymeric secondary products called humins are formed during the production of 5-HMF (van Dam, HE; ​​Kieboom, APG; van Bekkum, H. (1986) The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethyl-furfural. In: Starch - Stârke, vol. 38, n° 3, p. 95-101).

[0004] The synthesis of 5-HMF in a medium such as DMSO is particularly interesting, because it makes it possible to obtain 5-HMF in its alcohol form (and not ether) with very good yields. However, the physicochemical properties of DMSO (or any other polar aprotic solvent) make it very difficult to separate from 5-HMF by 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 the modification of the liquid-liquid extraction step, in particular by adding a backwashing step with water, and by recycling the backwashing 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 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 making it possible to recover 5-HMF not in crystallized form but in aqueous solution, which can be advantageous because the crystallization of 5-HMF remains a costly operation. To this end, the process described in FR3131313 implements a liquid-liquid extraction step associated with a backwashing step with water of the organic extract comprising the 5HMF resulting from the liquid-liquid extraction, as well as a 5-HMF concentration step of the organic raffinate comprising the 5-HMF obtained in the backwashing step, and a hydrodistillation step of the concentrated stream resulting from said concentration step, in order to recover the 5-HMF in the form of an aqueous solution of 5-HMF.The disclosed method advantageously comprises a liquid-solid separation step, typically by filtration, upstream of the liquid-liquid extraction to remove the precipitated humins (solid particles) when adding water to the feed (step of mixing the feed with the backwash water) before sending it to extraction. liquid-liquid. Indeed, the addition of 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 the equipment.

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

[0008] In patent FR3131313, the liquid-solid separation step is typically implemented implemented when the quantity of precipitated humins in the mixture is greater than approximately 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, the filter press is a piece of equipment allowing the separation under pressure of suspensions to separate the liquid and solid phases. The filter press is composed of trays (or frames) which allow the suspension formed by the mixture of water and the feed comprising 5-HMF and an aprotic polar synthesis solvent (eg DMSO) containing humins to be filtered through a filter medium, and the humins to be eliminated in the form of a cake. The cake therefore contains the solid fraction, but also a part of the liquid fraction which remains trapped, in particular due to the limitations of the separation technology and the characteristics of the liquid and solid phases. Under the filtration pressure, the liquid called 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 de-batching operation. The equipment thus operates discontinuously, in cycles ("batch" in English terminology), each cycle comprising a sequence of steps, including the filtration step and the de-batching step, but also a compaction step which increases the dry matter content of the cake.

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

[0011] According to [Fig.l], the feedstock of the filter press 2, which is a suspension resulting from a mixing step a) of an HMF-DMSO feedstock 1 with water 21, is sent to a filtration step b1.l) to separate the solid phase, i.e. the humins, from the liquid phase 3 comprising in particular HMF, DMSO and water. At the end of step b1.l), 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 comprising products of interest extracted from the cake such as 5-HMF and DMSO. The washed cake 25 undergoes then a compacting-blowing step b 1.3) forming a compacted / blown washed cake 27 and a compacting-blowing filtrate 26. Finally, the compacted / blown washed cake 27 is deconstructed in the deconstructing step b 1.4) to form a compacted / blown washed deconstructed cake 28.

[0012] According to a variant illustrated in [Fig. 2], the filtration cycle comprises an additional compacting / blowing step b 1.5) downstream of the filtration step b 1.1) and upstream of the washing step b 1.2) in the same order of the sequence illustrated in [Fig. 1]. A primary compacting-blowing filtrate 29 is then produced in step b 1.5) (the filtrate 26 forming an additional compacting-blowing filtrate according to this sequence), as well as a compacted-blown raw cake 30 subjected to the washing step b 1.2).

[0013] Such washing of the cake in fact makes it possible to extract more products of interest remaining in the cake, essentially 5-HMF and the aprotic polar synthesis solvent, in order to recover said products in a washing filtrate, to recycle them in the process, typically by recycling the washing filtrate to the step of mixing the HMF-DMSO feedstock with water upstream of the liquid-liquid extraction step, and in particular to obtain a better overall yield of the process in HMF. However, to be reliable, and in particular not to have too much 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 resuspension of a solid phase obtained at the end of the first filtration cycle, e.g. a filter cake, also called a “repulping” step in the present description, makes it possible to increase the extraction rate of the 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 quantity of water, compared to a liquid-solid separation step integrating a step of washing the filtered solid phase (e.g. cake) with water. Thanks to the method according to the invention integrating such an original liquid-solid separation step, as well as a judicious recycling in the process of the products of interest extracted from the filtered solid phase (e.g.filter cake), HMF production is improved, while limiting investment and operating costs due to the recycling of polar aprotic synthesis solvent and water in the process.

[0015] An object of the present invention relates to a method for producing 5-HMF, comprising the following steps: - a step a) of bringing into contact a charge comprising 5-HMF and a solvent of polar aprotic synthesis with an aqueous stream, so as to obtain at least one aqueous mixture comprising solid particles; - a step b) of liquid-solid separation of said aqueous mixture comprising a first and a second filtration cycle (b1, b3) separated by an intermediate step b2) of resuspension of a solid phase obtained at the end of the first filtration cycle b1), to produce at least a first aqueous filtrate, a second aqueous filtrate, and a final solid comprising at least a fraction of the solid particles, said second aqueous filtrate being recycled to 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 the extraction solvent; then - a step d) of backwashing the organic extract with an aqueous solvent, so as to produce an aqueous back-extract and an organic raffinate comprising 5-HMF and an organic solvent; - an optional step e) of concentrating said organic raffinate from step d) by removing 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 purifying said organic raffinate or said concentrated organic raffinate to produce a 5-HMF stream.

[0016] According to one or more implementations, the liquid-solid separation step b) is carried out by at least one piece of 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 preferably by at least one filter press.

[0017] According to one or more implementations, the liquid-solid separation step b) is carried out discontinuously, by at least one piece of equipment chosen from a filter press, a candle filter, a vacuum filter, a belt press, a decanter, a spin dryer, 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 implementations, the intermediate step b2) of resuspension of the solid phase obtained at the end of the first filtration cycle b1) is carried out at a temperature between room temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at atmospheric pressure, by bringing said solid phase into contact with an aqueous solution according to 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 tank separate from the equipment(s) used for the first and second filtration cycles.

[0020] According to one or more implementations, 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 sub-steps, in this order: - a filtration sub-step (bl.l, b3.1) of a filtration feedstock to produce an aqueous filtrate and a crude cake; - a compacting-blowing sub-step (b 1.3, b3.2) of said cake to produce a compacting-blowing filtrate and a compacted-blowed raw cake; - a sub-step of deconstructing (b 1.4, b3.3) said compacted-blown raw cake to produce a deconstructed cake; and in which the deconstructed cake obtained at the end of the deconstructing sub-step b 1.4) of the first filtration cycle b1) is the solid phase resuspended in step b2) by contacting with an aqueous solution, to form the filtration load of the filtration sub-step b3.1) of the second filtration cycle b3).

[0021] According to one or more implementations, the first filtration cycle b1) comprises the compacting-blowing sub-step b1.3) producing a first compacting-blowing filtrate recycled in the process in step c), and the second filtration cycle b3) comprises the compacting-blowing sub-step b3.2) producing a second compacting-blowing filtrate recycled in the process in step a).

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

[0023] According to one or more implementations, a filtration facilitating agent, preferably diatomaceous earth, is added to the filtration load of the filtration sub-step of the first filtration cycle b1) and / or of the second filtration cycle b3), preferably in a content of between 0.01% and 5% by mass relative to the mass of said filtration load.

[0024] According to one or more implementations, the compacting-blowing sub-steps (b 1.3, b3.2) are carried out by injecting compressed air at a pressure of between 1 MPa and 5 MPa, and at a temperature of between room temperature and 80°C, preferably of between 10°C and 40°C.

[0025] According to one or more implementations, 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 implementations, the purification step f) is a hydrodistillation step carried out by distillation in the presence of water of said organic raffinate resulting from step d) or of said concentrated organic raffinate resulting 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 of between 0.001 MPa and 0.1 MPa, and preferably under vacuum at a pressure of between 0.005 MPa and 0.08 MPa, and 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, preferably less than or equal to 100°C.

[0027] According to one or more implementations, the method comprises a step of dehydrating the sugars into 5-HMF upstream of step a), preferably by bringing a sugar feedstock comprising a hexose, preferably said hexose being fructose or a fructosidic unit, into contact with said aprotic polar synthesis solvent and an acid dehydration catalyst, preferably at a temperature of between 30°C and 200°C and at a pressure of 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 implementations, the extraction solvent is chosen from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methylisopropyl ketone, methylisobutyl ketone, thiophene, anisole and toluene, and preferably is methylisobutyl ketone.

[0030] According to one or more embodiments, the aprotic polar synthesis solvent is selected from pyridine, butan-2-one, acetone, acetic anhydride, N,N,N',N'-tetramethylurea, benzonitrile, acetonitrile, methyl ethyl ketone, pro-pionitrile, hexamethylphosphoramide, nitrobenzene, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate and y-valerolactone, taken alone or as a mixture, and is preferably dimethyl sulfoxide.

[0031] Other objects and advantages of the invention will appear on reading the following description of particular embodiments of the invention, given as non-limiting examples, the description being made with reference to the appended figures described below. LIST OF FIGURES

[0032] [Fig.l], already described above, illustrates an example of liquid-solid separation in a process for producing HMF according to the prior art.

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

[0034] [Fig. 3] illustrates an embodiment of the method according to the invention integrating the particular liquid-solid separation step b) upstream of the liquid-liquid extraction step.

[0035] [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 similar elements. Description of the embodiments

[0037] In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the method. However, it will be apparent to those skilled in the art that the method may be practiced without necessarily all of these specific details. In other instances, 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 ..." must be understood as including the limits cited, unless otherwise specified.

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

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

[0041] Within the meaning of the present invention, the various 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 may be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​may be combined with a more preferred range of temperature values.

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

[0044] In the present description, the term aprotic solvent means a molecule acting as a solvent and all of whose hydrogen atoms are carried by carbon atoms.

[0045] In the present description, the term polar solvent means 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” is therefore understood to mean a molecule acting as a solvent in which all the hydrogen atoms are carried by carbon atoms and in which the dipole moment p expressed in Debye has a numerical value greater than or equal to 2.00 measured at 25°C.

[0047] In the present description, the term “cake” means the solid phase recovered from a filtration cycle, in particular by filter press. It is a solid that may be wet. This solid may be characterized by its dry matter content, the acronym of which is “DM”. The dry matter content (DM) of such a cake may be between 20% and 90% by mass, preferably between 30% and 90% by mass, more preferably between 35% and 90% by mass, more preferably between 40% and 85% by mass, relative to the total mass of the cake, and may vary depending on the types of operations carried out during the filtration cycle from which the cake originates. The dry matter content may be measured according to the ASTM E1756-08(2015) standard. The term cake, although used in the singular, also covers the plural, i.e. a plurality of cakes.

[0048] In the present description, the term "repulping" means an operation of resuspension of the solid phase recovered from a filtration cycle, in particular by filter press, by contacting with an aqueous solution. More details are given below with the description of the invention.

[0049] For a better understanding of the invention, reference numerals appearing in Figures 3 and 4 are mentioned below to designate different elements of the method, without this constituting a limitation of the invention to the particular embodiments illustrated in these figures.

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

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

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

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

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

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

[0056] By filler containing free fructose taken in mixture with any saccharide species, we mean for example syrups of the high fructose corn syrup type ("High-Fructose-Com-Syrup" according to the 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 filler may comprise a saccharide comprising one or more fructosidic units and one or more non-fructosidic units, fructose being able to be released by one or more hydrolysis steps, for example oligosaccharides and polysaccharides in which at least one monosaccharide unit is fructose, for example fillers such as sucrose, kestose, fructans, oligofructans, rinulin.

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

[0060] Preferably, the oligosaccharide has the following empirical formula: (C6mHi0m+2O5m+i) (C5nH8n+2O4n+i) where m and n are integers whose sum is between 2 and 6. The monosaccharide units composing said oligosaccharide are identical or not, and at least one unit of formula (C6mHiom+205m+i) is fructose. By extension, preferably the polysaccharide has the following empirical formula: (C6mHiom+205m+i) (C5nH8n+2O4n+i) where m and n are integers whose sum is greater than or equal to 7.

[0061] The polar aprotic synthesis solvent is advantageously chosen from all polar aprotic 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) noted NMP, dimethyl sulfoxide (3.90) noted DMSO, propylene carbonate (4.94) and γ-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 as a mixture.

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

[0064] Very preferably, the aprotic polar solvent is DMSO.

[0065] The term “acid dehydration catalyst” means any Brônsted acid catalyst chosen from organic or inorganic, homogeneous or heterogeneous Brônsted 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 polar aprotic synthesis solvent, preferably in DMSO, of between 0 and 5.0, preferably between 0.5 and 4.0 and most preferably between 1.0 and 3.0. Said pKa are as defined in the article by F.G. Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0067] Preferably, the acid dehydration catalyst is selected from HF, HCl, HBr, HI, H2SO3, H2SO4, H3PO2, H3PO4, HNO2, HNO3, H2WO4, H4SiW12O40, H3PW12O40, (NH4)6(W12O40).xH2O, H4SiMo12O40, H3PMo12O40, (NH4)6Mo7O24.xH2O, H2MoO4, HreO 4, H2CrO4, H2SnO3, H4SiO4, H3BO3, HclO4, HBF4, HSbF5, HPF6, H2FO3P, C1SO3H, FSO3H, HN(SO2F)2, HIO3, BF3, A1C13, 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, paratoluenesulfonic acid, 4-biphenylsulfonic acid, diphenylphosphate, and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate.Preferably, the acid dehydration catalyst is chosen from HCl, H2SO4, H3PO2, H3PO4, HNO3, A1C13, 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 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, 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. Bubble point refers to the pressure and temperature conditions under which the first gas bubbles appear for a liquid.When the reaction medium is above the bubble point of the mixture, the vapor phase can be withdrawn from the reactor, optionally rectified, and condensed to form the condensates which can be sent to an optional step g) of treatment of water-solvent mixtures of polar aprotic synthesis.

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

[0070] The optional dehydration step can be carried out according to different embodiments. Thus, the step can advantageously be implemented discontinuously or continuously (the discontinuous mode being called "batch" according to English terminology). The addition of the sugar feedstock can be gradual (called "fed-batch" according to English terminology) in the case of discontinuous implementation or staged in different CSTR reactors (Continuously Stirred Tank Reactor in English terminology) in series in a continuous implementation. It can be carried out in a closed reaction chamber or in a semi-open reactor.

[0071] Advantageously, the synthesis effluent obtained at the end of the optional dehydration step comprises 5-HMF and 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 resulting 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, preferably between 55 and 85% by weight.

[0072] 5-HMF represents at least 1% by weight of the synthesis effluent from the optional dehydration 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, more 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 come from the dehydration step, for example water is formed during the dehydration reaction of the sugar into 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 approximately 70% by weight in water, is used. Advantageously, during the optional dehydration step, a water-aprotic polar synthesis solvent mixture (e.g. DMSO) may be recovered in the vapor phase. Said water-aprotic polar synthesis solvent mixture (e.g. DMSO) may advantageously be sent to optional step g).Thus, the synthesis effluent from the optional dehydration 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 into step a) as feedstock 1 may also contain impurities, in particular humins. The term "humins" refers to all the undesirable polymeric compounds formed during the synthesis of 5-HMF. The humins represent, in particular, less than 30% by weight of the converted sugar feedstock, preferably less than 20% by weight.

[0075] During the optional dehydration step, the conversion rate of the sugar, 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 used and the residual sugar at the end of the reaction) to the total sugar used in the reaction.

[0077] The selectivity of conversion of sugar to 5-HMF is defined as the molar ratio between the number of moles of 5-HMF produced by the reaction and the number of moles of sugar consumed 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 of 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 makes it possible to reduce the reactivity of the medium and thus to avoid the dehydration mechanisms. gradation of 5-HMF, or even reduce the corrosion of equipment materials downstream of the optional dehydration step. Since the dehydration reaction can 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 least at the stoichiometric ratio of the amount of catalyst used, and generally carried out in slight over-stoichiometry compared to the catalyst used, preferably between 1 and 2 times the stoichiometric ratio, preferably between 1 and 1.5 the stoichiometric ratio. The neutralizing agent can be a basic compound chosen from NaOH, KOH, NH4OH, Na2CO3, K2CO3, NaHCO3, KHCO3, Mg(OH)2, Ca(OH)2, Ba(OH)2. Step a) mixing

[0081] The process according to the invention comprises a step a) of bringing into contact (or mixing) the feedstock 1 comprising 5-HMF and an aprotic polar synthesis solvent, optionally resulting from the dehydration step, with an aqueous stream 21 so as to obtain at least one aqueous mixture 2.

[0082] The aqueous stream 21 may be composed of pure water, external to the process, or of water recycled from the process, for example the aqueous stream 21 may 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 water-solvent mixtures of aprotic polar synthesis.

[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, more preferably at most 30% by weight.

[0084] Preferably, the polar aprotic synthesis solvent (eg 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 filler 1 introduced in step a) may also contain water, in a proportion preferably 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, the filler 1 may further contain humins. The humins represent, in particular, less than 30% by weight of the filler 1, preferably less than 20% by 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 potentially at least 80% by weight, even more preferably at least 95% by weight or even 98% by weight of water. The aqueous stream 21 may comprise all or a fraction of the aqueous counter-extract 9 from step c). Said aqueous counter-extract 9 comprises water, aprotic polar 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 more 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% by weight of water, preferably between 20 and 80% by weight of water, preferably between 40 and 75% by weight of water.

[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 feed 1 during step a), some of the humins present in 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 step b) of liquid-solid separation, in order to send only the liquid part, separated from the solid particles in suspension to step c) of liquid-liquid extraction.

[0092] Preferably, charge 1 is precipitated by adding water according to a water / aprotic polar synthesis solvent (eg DMSO) ratio of between 0.2 and 3, more preferably between 1 and 2, for example 1.5. The water / aprotic polar synthesis solvent (eg DMSO) ratio at this step a) is more precisely defined as being the following mass ratio: (EAj + Eci) / SSci with EAj: added water, ECi: water contained in charge 1, SSCi: polar aprotic 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 carried out continuously or discontinuously, and in any suitable equipment known to those skilled in the art for mixing feedstock 1 and the aqueous flow and precipitating the humins, such as a tank which can include different types of agitators, a mixer equipped with an endless screw, etc. Step b) liquid-solid separation

[0096] The method according to the invention comprises a step b) of liquid-solid separation of the aqueous mixture 2 from step a), so as to obtain a liquid separated from suspended solid particles and a solid residue comprising humins and which is preferably removed from the process in the form of a solid stream. Step b) of liquid-solid separation is carried out by filtration. This step thus makes it possible to remove the “humins” which have precipitated in the mixing step a) or upstream. At least part of the liquid obtained is then advantageously sent to step c) of liquid-liquid extraction, said part or preferably all of the liquid advantageously sent to step c) corresponding to the aqueous filtrate 3 illustrated in Figures 3 and 4.

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

[0098] According to an essential aspect of the invention, step b) of liquid-solid separation comprises a first filtration cycle b1) 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 b1), also called the repulping step.

[0099] “Repulping” is thus understood to mean the operation consisting of bringing into contact the solid phase obtained at the end of a filtration cycle, also called cake, typically a cake removed at the end of a filtration cycle by filter press, with an aqueous solution 18, preferably consisting 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 essentially all of the solid particles, which is the solid residue preferably removed from the process. The first aqueous filtrate 3 comes from the first filtration cycle b1) 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 comes from the second filtration cycle b3), and is recycled to step a) because it is an aqueous stream comprising compounds of interest extracted from the repulped 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 aqueous filtrate 20 recycled to step a) thus makes it possible to increase the production of HMF in 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 step of washing a filtered solid phase (cake) produced during said step b). The liquid-solid separation step b) of the process according to the invention includes a repulping step between two filtration cycles surprisingly, allows more residual products of interest remaining in the cake to be extracted, including 5-HMF and the aprotic polar solvent (e.g. DMSO), compared to a filtration cycle including a cake washing step, for the same quantity of water used. This gain in extracted 5-HMF and aprotic polar solvent advantageously increases the overall 5-HMG yield of the process, by specific recycling in the process of the products extracted by filtration after repulping, and to a lesser extent saves operating costs related to the supply of aprotic polar solvent (e.g. DMSO).

[0102] The liquid-solid separation step b) uses 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 carry out the repulping of said solid phase, e.g. of the cake, i.e. the resuspension of said solid phase by contacting with an aqueous solution. Preferably, the liquid-solid separation step b) is carried out at a temperature between room temperature (i.e. between 10°C and 40°C) and 80°C, more preferably at room temperature, i.e. at a temperature 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 implementation of at least one piece of equipment chosen from a pressing or draining device such as a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a spin dryer, preferably chosen from a filter press, a belt filter, a centrifuge, a 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 at the end of the centrifugation. Devices such as a centrifuge or a belt filter allow continuous operation.

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

[0105] In addition, the liquid-solid separation step b) preferably comprises, to carry out the repulping step b2), a dedicated device, i.e. separate from the filtering equipment of the filtration cycles b1) and b3), for example a dedicated tank which may comprise a suitable stirring system, and configured to receive the solid phase from the filtration equipment of the 1st filtration cycle b1) 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 b1) in contact with the aqueous solution can be carried out by a mixer continuously or discontinuously, in one or several operations / stages.

[0107] According to one or more embodiments, the first and second filtration cycles b1) 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 b1) 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 discontinuously (also called "batch" according to English terminology), resulting in an interruption of the process at step b) at the end of the 1st filtration cycle in order to repulp the solid phase extracted at the end of the 1st filtration cycle, and then carry out 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] [Fig.4] illustrates in more detail the first and second filtration cycles and the intermediate repulping step b2), in particular according to one or more embodiments implementing filter press technology.

[0111] Liquid-solid separation by filter press is a technique allowing the separation under pressure of suspensions to separate the liquid and solid phases. The filter press is composed of trays (or frames) and a filter medium, typically filter cloths, through which the aqueous mixture 2, comprising the precipitated humins, is filtered and the humins removed in the form of a solid cake. Under the filtration pressure, the liquid called filtrate passes through the filter cloths which retain the solid particles. The filtrate is evacuated throughout the process while the cake formed between the trays is evacuated only during the de-sludge operation.This technology thus operates in a discontinuous cycle, said cycle comprising a sequence of stages, including filtration, and compaction, also called compaction-blowing because the compaction can optionally involve an injection of compressed air, which makes it possible to increase the dry matter content of the cake.

[0112] The filter press conventionally comprises several vertical square frames forming sealed filtration chambers. Each frame is composed of two faces on which are placed the filtration cloths of fairly tight mesh allowing the cake to settle. This configuration makes it possible to obtain a filtering surface of several tens of square meters. The depth of a filtration chamber (space between the frames) makes it possible to form 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 made between the cycle duration and the weight of the 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 sub-steps, in this order - a filtration sub-step (bl.l, b3.1) of a filtration feedstock to produce an aqueous filtrate (3, 20) and a crude cake (22, 35); - a compacting-blowing sub-step (b 1.3, b3.2) of said raw cake to produce a compacting-blowing filtrate (31, 36) and a compacted-blown raw cake (32, 37); - a sub-step of deconstructing (b 1.4, b3.3) said compacted-blown raw cake to produce a deconstructed cake (33, 19).

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

[0115] Preferably, the 1st 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 wringer, and more preferably is carried out by a filter press.

[0116] The 1st filtration cycle is preferably carried out at a temperature between room temperature and 80°C, preferably at room 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 sub-steps is carried out: - bl.l) filtration: the aqueous mixture 2 comprising solid particles, e.g. precipitated humins, is sent as filtration feed to the filtration step bl.l), in the filtration tool, preferably a filter press, in order to separate the solid particles in the form of a crude 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 crude cake 22 still contains a part of the liquid phase which has remained 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 sub-step bl.l) is carried out at a temperature between room temperature and 80°C, preferably at room temperature, and at a pressure between 0.05 MPa (0.5 bar) and 1 MPa (10 bar), preferably between 0.1 MPa and 0.8 MPa, for example 0.6 MPa. Preferably, a gradual pressure increase 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, may be added to the aqueous mixture 2 sent to the filtration sub-step b 1.1), preferably in a content of between 0.01% and 5% by mass relative to the mass of the aqueous mixture 2. Indeed, in certain cases, the suspension formed by the aqueous mixture 2 may be difficult to filter, and the addition of such an agent aiding filtration may be useful, in particular in order to improve the flow rate, the filtration quality and the porosity of the cake. Diatomaceous earth is a filtration facilitator well known to those skilled in the art, and its quality and content can be chosen to facilitate filtration and the duration of the filtration sub-step. For example, a commercial diatomaceous earth such as Clarcel® DIC3 diatomaceous earth added at a content of 1% by mass relative to the mass of the load to be filtered can be used.

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

[0121] A non-limiting practical example of carrying out the filtration sub-step by filter press is given: the filter is closed by actuation of a jack which 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), possibly prepared with the addition of a filtration facilitating agent as described above, is then pumped into the filtration chambers, via central or lateral feed orifices. This step is typically carried out under pressure, at a pressure of between 0.6 MPa and 0.8 MPa. The filtration filtrate passes through the filter cloths and is collected in the grooves of the trays to be evacuated by means of orifices positioned at the periphery of the trays.The solid gradually accumulates inside the filtration chambers, between the plates, 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 filtration cloths are chosen so as to be compatible with the load to be filtered, in practice the aprotic polar synthesis solvent, preferably the DMSO. Thus, polypropylene filter cloths are preferably used, advantageously with a cut-off threshold of 10 pm.

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

[0124] This sub-step allows the dehydration of the cake by pressurizing, preferably by injecting compressed air into the filter cloths to press the cake. Pressurizing the filter makes it possible to increase the MS (dry matter) of the cake, and to extract the water and the products of interest, i.e. mainly 5-HMF and the polar aprotic synthesis solvent (eg DMSO). Preferably, at the end of the compacting-blowing sub-step, the compacted-blown raw cake 32 has a MS 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 compacting-blowing is carried out by injecting compressed air.

[0126] Preferably, the compacting-blowing is carried out at a pressure of 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 compacting-blowing is conventionally between 5 minutes and 30 minutes, preferably between 10 minutes and 20 minutes, for example 15 minutes.

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

[0129] The first compacting-blowing filtrate 31, which may comprise 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) deconstructing: preferably, the compacted-blown raw cake 32 is then deconstructed to produce a deconstructed cake 33.

[0131] This stripping sub-step bl.4) is preferably carried out at room temperature and atmospheric pressure.

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

[0133] The de-constructing 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 plates which equip the filter press.

[0134] The deconstructed cake is preferably recovered in a tank, with a view to implementing the intermediate repulping step b2).

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

[0136] b2) Repulping: intermediate resuspension step

[0137] The raw cake 22 from the filtration step b 1.1) or preferably the deconstructed cake 33 obtained at the end of the deconstructing sub-step b1.4) of the 1st filtration cycle b1) is the solid phase resuspended from the repulping step b2).

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

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

[0140] The repulping step b2) is preferably carried out in a dedicated device, typically a dedicated tank, i.e. separate from the filtering equipment of the filtration cycles b1) and b3).

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

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

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

[0144] The plumping time may 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 treatment of the water-solvent mixtures of aprotic polar synthesis.

[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 chosen from a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a wringer, and more preferably by a filter press. It 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 by a simplification of process. In addition, the 1st cycle and the 2nd filtration cycle can be carried out in the same equipment, i.e. in common equipment.

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

[0150] The 2nd filtration cycle is preferably carried out at a temperature between room temperature and 80°C, preferably at room 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 sequence of sub-steps 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 filtration feed to the filtration step b3.1), in the filtration tool, preferably a filter press, in order to separate the solid particles in the form of a repulped raw cake 35, i.e. a raw cake resulting from the feed consisting of the suspension resulting from repulping b2), and the liquid phase 20 containing 5-HMF and aprotic polar synthesis solvent (e.g. DMSO) forming the filtrate of repulping 20 which is an aqueous filtrate. Generally the repulped raw cake 35 still contains a portion of the liquid phase remaining trapped due to the limitations of the solid / liquid separation tool and possibly the characteristics of the feedstock 34. At this stage, the repulped raw cake is trapped inside the filter. Preferably, the filtration sub-step b3.1) is carried out at a temperature between room temperature and 80°C, preferably at room 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 increase 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, may be added to the feed 34 sent to the filtration sub-step b3.1), preferably in a content of between 0.01% and 5% by mass relative to the mass of the feed 34. The purpose of such an agent is 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 carrying out the filtration sub-step by filter press is identical to that given in sub-step b1.l) and is not repeated here.

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

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

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

[0157] This sub-step b3.2) allows the dehydration of the cake by pressurizing, preferably by injecting compressed air into the filter cloths to press the cake. Pressurizing the filter makes it possible to increase the dry matter ("DM") of the cake, and to extract the water and possibly the products of interest, i.e. mainly 5-HMF and the aprotic polar synthesis solvent (eg DMSO). Preferably, at the end of the compacting-blowing sub-step b3.2), the compacted-blowed repulped raw cake 37 has a MS 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 compacting-blowing is carried out by injecting compressed air.

[0159] Preferably, the compacting-blowing b3.2) is at a pressure of 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 compacting-blowing b3.2) is conventionally between 5 minutes and 30 minutes, preferably between 10 minutes and 20 minutes, for example 15 minutes.

[0161] As for the filtration sub-step b1. 1), the compacting-blowing b3.2) is carried out at a temperature between room temperature and 80°C, preferably at room temperature (i.e. between 10°C and 40°C, preferably between 18°C ​​and 25°C).

[0162] The second filtrate of compacting-blowing filtrate 36, which may comprise 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) deconstructing: preferably, the second compacted-blown raw cake 37 is then deconstructed to produce a deconstructed cake 19 forming the final solid preferably removed from the process. This solid residue therefore comprising 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 the precipitated humins, removed from the process.

[0164] This de-construction sub-step b3.3) is preferably carried out at room 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 remove cake. This mechanical action of opening the filter may be supplemented by a vibration or scraping operation using suitable devices known to those skilled in the art, to assist in removing the cake.

[0166] The de-constructing 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 plates which equip the filter press.

[0167] Without being limiting, the clearing can, in practice, be carried out in an identical manner to that described for sub-step b 1.4) and is not repeated here. Step c) Liquid-liquid extraction

[0168] The process according to the invention comprises 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 washing the aqueous mixture 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-decanters, in a column filled with bulk or structured packing, in a pulsed column, or even in a stirred column.

[0170] The liquid-liquid extraction may comprise the implementation of at least two theoretical separation stages. This is for example the case, but not exclusively, when an additional liquid-solid separation step is carried out on the intermediate liquid stream produced during the liquid-liquid extraction step c), which returns to step c) once freed from solid particles. A first liquid-liquid separation stage may then be carried out, producing said intermediate liquid stream sent to the additional liquid-solid separation step to form an intermediate liquid stream depleted in particles 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 speaking, the extraction solvent rate, defined as the mass ratio between the extraction solvent flow rate and the feed entering the extraction step, results from the number of separation stages involved, the choice of extraction solvent and the 5-HMF recovery target defined as the ratio between the amount of 5-HMF entrained in the organic extract 9 and the amount of 5-HMF contained in the aqueous mixture 6 sent to the extraction step d). The targeted 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 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 proportion of the flow rates of feedstock, back-extraction water and extraction solvent used in the process.

[0174] In a non-limiting manner, the extraction solvent is preferably chosen 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 referred to as C1-C10, an ether having between 2 and 10 carbon atoms (C2-C10), an ester having between 4 and 10 carbon atoms (C4-C10), a ketone having between 3 and 10 carbon atoms (C3-C10), an aldehyde between 1 and 10 carbon atoms (C1-C10), a C4-C10 aromatic compound. Preferably, the extraction solvent is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene. Most preferably, the extraction solvent is methyl isobutyl ketone.

[0175] Advantageously, the extraction solvent is chosen so as to have a very high difference in volatility with the 5-HMF, in particular so as to facilitate its elimination in the optional step e) and limit the degradation of the 5-HMF, that is to say so as to present in step e) a vaporization rate making it possible not to degrade the 5-HMF and to minimize the quantity of residual solvent to be eliminated in a hydrodistillation in step f) while guaranteeing the absence of liquid phase separation when the concentrated organic raffinate 10 is brought into contact with water in a hydrodistillation in step f). The extraction solvent may also be chosen so as to form, upon hydrodistillation in step f), a heterogeneous azeotrope with water, preferably rich in solvent, i.e. more than 50% by weight of solvent, preferably more than 60% by weight of solvent and preferably more than 70% by weight of 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 the subsequent steps can be recycled to the extraction step c), as extraction solvent. These organic solvent streams can contain impurities possibly generated during the implementation of the process. Advantageously, the organic solvent streams produced in the subsequent steps can be distilled, for example periodically, to avoid 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 aprotic polar synthesis solvent (e.g. DMSO) initially contained in 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 feed 1, and the extraction solvent 4. This organic extract 6 may also contain aprotic polar synthesis solvent (e.g. DMSO). Preferably, said organic extract preferably contains 5-HMF and polar aprotic synthesis solvent (eg DMSO) in a weight ratio, 5-HMF / polar aprotic synthesis solvent (eg DMSO), of between 50 / 50 and 99 / 01, preferably of between 50 / 50 and 95 / 05, preferably of between 55 / 45 and 90 / 10, more preferably of between 60 / 40 and 85 / 15 and 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). These may be humins precipitated in the upstream mixing step a), still present in the aqueous mixture 3 sent to step c), or humins precipitated in step c) or in step d) of backwashing. Backwashing step d

[0180] The method according to the invention comprises 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 full to step a). The organic solvent is in particular composed at least in part of extraction solvent and may optionally comprise aprotic polar synthesis solvent (e.g. DMSO), preferably in small quantities.

[0181] The introduction of an aqueous solvent 7 in step d) is carried out so 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 so that the quantity of aqueous solvent is as low as possible so as to reduce costs, but sufficient to guarantee a weight content of aprotic polar synthesis solvent (e.g. DMSO) in the organic raffinate 8 which is low and preferably less than or equal to 20.0% by weight relative to the weight of the 5-HMF, preferably less than or equal to 15.0% by weight relative to the weight of the 5-HMF, preferably between 0.01 and 15.0% by weight relative to the weight of the 5-HMF, very preferably between 0.01 and 10.0% by weight relative to the weight of the 5-HMF.

[0182] Advantageously, the aqueous backwash solvent 7 introduced in step d) comprises at least 95% by weight of water, preferably at least 98% by weight of water (100% being the maximum). The aqueous solvent may optionally comprise aprotic polar synthesis solvent (e.g. DMSO). The effectiveness of the backwash is higher the lower the amount of aprotic polar synthesis solvent (e.g. DMSO) present in the aqueous backwash solvent. The aqueous solvent may comprise at most 1.0% by weight, and preferably at most 0.1% by weight of aprotic polar synthesis solvent (e.g. DMSO). Advantageously, the aqueous backwash solvent 7 comes from step g) of treatment of water-aprotic polar synthesis 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 synthesis solvent (egDMSO), produced in step c) is treated in step g) which advantageously comprises. a distillation. The water-rich distillate thus obtained at the end of this step g), also called aqueous effluent 15 recyclable in the process, and is advantageously used to form the aqueous backwash solvent 7 in step d), optionally mixed with a water make-up, or is used in step a) of mixing to form the aqueous stream 21, optionally with at least one aqueous counter-extract fraction 9 and / or a water make-up. Said recyclable effluent 15, e.g. water-rich distillate, may also contain a residual quantity of aprotic polar synthesis solvent (e.g. DMSO), preferably less than or equal to 1% by weight and preferably less than or equal to 0.1% by weight. The residual quantity of aprotic polar synthesis solvent (e.g.DMSO) in the aqueous effluent 15 (the distillate) is all the 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 suitable reboiling and reflux rates.

[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 current of 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-decanters, in a column filled with bulk or structured packing, 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) makes it possible to obtain an aqueous stream advantageously enriched in aprotic polar synthesis solvent (e.g. DMSO), called aqueous counter-extract 9, preferably containing at least 60% by weight of water, preferably at least 80% by weight of 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 full, to step a). The organic raffinate 8 obtained has a weight content of aprotic polar synthesis solvent preferably less than or equal to 20.0% by weight relative to the weight of 5-HMF, preferably less than or equal to 15.0% by weight, more preferably less than or equal to 5.0% by weight, even more preferably less than or equal to 4.0% by weight, and more preferably less than or equal to 3.0% by weight relative to 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). In the case where they precipitate at this step, thus forming undesirable solid particles, the latter could be eliminated by sending to step c) the aqueous counter-extract 9, in part or in full, which would comprise the precipitated humins, and which could be eliminated 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). In the case where the aqueous counter-extract 9 is sent in part or in full to step a) to enter into the composition or constitute the aqueous stream 21, the precipitated humins could also be separated during the liquid-solid separation of 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 resulting from step d), by elimination of a 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 consisting of, organic solvent, said organic solvent being advantageously composed in whole or in part of the extraction solvent and optionally of aprotic polar synthesis solvent (eg DMSO).

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

[0191] Preferably, in step e), the elimination of a portion 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 embodiment, the vaporization of the organic solvent is advantageously carried out at atmospheric pressure or under vacuum, preferably at a pressure of between 0.01 MPa and 0.1 MPa, preferably under vacuum at a pressure of between 0.01 MPa and 0.09 MPa, so as to limit the temperature of the liquid and therefore the degradation of the 5-HMF. Preferably, the temperature of the liquid is kept less than or equal to 130°C, preferably kept less than or equal to 100°C, preferably kept less than or equal to 70°C. The pressure level, in particular vacuum, 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 embodiment, the vaporization of the solvent is carried out by multi-effect evaporation or with mechanical recompression of the vapors, or any other methods. known to those skilled in the art, so as to reduce the operating costs associated with the evaporation of the solvent while limiting the risks of degradation of the product of interest, i.e. 5-HMF. For example, in the case of a triple-effect evaporator, the temperature of the liquid is kept 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] Optional step e) is implemented with a vaporization mass rate (or evaporation rate), corresponding to the mass of vaporized organic solvent 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 quantity of residual solvent to be removed at a hydrodistillation in step f) while guaranteeing the absence of liquid phase separation (i.e. while guaranteeing that the liquid phase remains single-phase) when the concentrated organic raffinate 10 is brought into contact with water at a hydrodistillation in step f).

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

[0198] The process according to the invention comprises a step f) of purification of 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 be constituted by, a hydrodistillation step carried out by distillation in the presence of water 14 of the organic raffinate 8 resulting from step d) or of the concentrated organic raffinate 10 resulting from the optional step e), to produce said stream of 5-HMF 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 makes it possible to eliminate, at least in part, the residual organic solvent not eliminated during the optional step e). The residual organic solvent eliminated during the hydrodistillation step, i.e. the second stream 13 comprising organic solvent, can advantageously be recycled to the extraction step c), alone or in a mixture with the first stream 11 resulting 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 (eg 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, water isolated within the process is used to feed the hydrodistillation step, making it possible to limit the operating costs of the process and its environmental impact. Typically, if the sugar feedstock of the optional dehydration step is a sugar syrup at 70% by weight in water, approximately 1 tonne of water is available at the end of the dehydration step (the water from the sugar feedstock and the water produced during the dehydration reaction) per tonne of 5-HMF produced. This water, which is advantageously recovered, needs to be treated before being released into the environment.The process according to the invention can then advantageously use said water from the sugar feed and / or from the dehydration step to produce, at the end of the hydrodistillation step, an aqueous solution of 5-HMF concentrated preferably at 30% by weight or more, preferably at 40% by weight or more, and thus reduce the reprocessing costs of the process and its environmental impact.

[0204] Advantageously, the aqueous liquid 14 introduced into 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 possibly contain a residual quantity of polar aprotic synthesis solvent (eg 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 may be carried out at atmospheric pressure or under vacuum and in particular at a pressure of between 0.00 IMPa and 0.1 MPa, preferably under vacuum at a pressure of between 0.005 MPa and 0.08 MPa. Advantageously, the hydrodistillation step is carried out under vacuum, in particular at a pressure of between 0.001 MPa and 0.1 MPa, preferably between 0.005 MP 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. 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 phase rich in water which can advantageously be returned to the column as reflux, and a phase rich in organic solvent 13 which can advantageously be recycled to extraction step c).

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

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

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

[0215] The crystallization can be carried out by any method 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 even 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 those 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 a possible purge) to step c) of liquid-liquid extraction to carry out a new extraction of 5-HMF.

[0218] According to methods known to those 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 water-solvent mixtures of aprotic polar synthesis

[0220] The process according to the invention may comprise an optional step g) of treatment of water-aprotic polar synthesis 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 step d) of backwashing and / or in step a) and / or in step f) of purification by hydrodistillation. This step may also produce a stream 16 rich in aprotic polar synthesis solvent (e.g. DMSO) and a stream of impurities 17. At least one water-aprotic polar synthesis solvent mixture produced in the process may therefore be treated in step g). Said mixture may be the aqueous raffinate resulting from step c).

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

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

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

[0224] The water-aprotic polar synthesis solvent mixtures (eg DMSO) generated by the process designate in particular the aqueous raffinate 5 produced in step c), and possibly the water-aprotic polar synthesis solvent mixture (eg DMSO) resulting from the optional step of dehydration of sugars into 5-HMF when the process integrates such a step.

[0225] Step g) of treatment of water-solvent mixtures of aprotic polar synthesis (eg DMSO) preferably uses a section of evaporation of a water-solvent mixture of aprotic polar synthesis (eg DMSO), to eliminate possible 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 operated by a scraped film evaporator (Thin film Evaporator or TFE according to English terminology).

[0227] The distillation section advantageously uses a distillation column or several separate pieces of equipment. Preferably, the distillation section of step g) is advantageously used in a distillation column, at a temperature at the top of the column preferably between 25°C and 60°C, preferably entially between 45°C and 55°C, for example about 50°C, preferably at a column bottom temperature of between 80°C and 140°C, preferably between 100°C and 130°C, for example about 120°C, preferably at a pressure of 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 of 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, then the gas 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 is meant here at least 95% by weight, preferably at least 98% by weight. Some or all of the water-rich distillate, or aqueous effluent, may advantageously be recycled to backwash step d) as aqueous solvent and / or to hydrodistillation purification step e) as aqueous stream.Said water-rich distillate may also be, in whole or in part, recycled as water introduced in step a).

[0229] The residue rich in aprotic polar synthesis solvent 16 (eg DMSO) can advantageously be introduced into the optional dehydration step, directly or after distillation, allowing the removal of heavy products which 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 raffinate 6: organic extract 7: aqueous solvent 8: organic raffinate 9: aqueous counter-extract 10: concentrated organic raffinate 11: first stream comprising organic solvent 12: aqueous solution of 5-HMF 13: second stream comprising organic solvent. 14: aqueous liquid 15: aqueous effluent 16: stream rich in aprotic polar synthesis solvent (or rich “residue”) 17: impurity flow (or heavy fraction flow) 18: aqueous solution 19: final solid 20: second aqueous filtrate (plumping filtrate) 21: aqueous flow 22: raw cake 23: wash water 24: washing filtrate 25: washed cake 26: compaction-blowing filtrate 27: compacted / puffed washed cake 28: washed, compacted / puffed cake 29: primary compaction-blowing filtrate 30: compacted-puffed raw cake 31: first compacting-blowing filtrate of the 1st filtration cycle 32: compacted-puffed raw cake from the 1st filtration cycle 33: unbuilt cake 34: plumped cake 35: plumped raw cake 36: second compacting-blowing filtrate of the 2nd filtration cycle 37: raw, plumped, compacted-puffed cake Examples

[0231] The examples below aim to show some of the advantages of the process according to the invention, in particular by comparing an example according to the invention (example 2) carrying out a liquid-solid separation as shown in [Fig. 4] implementing 2 filtration cycles b1) and b3) by filter press separated by an intermediate step b2) of resuspension of the cake obtained at the end of b1), with an example of a process according to the prior art (example 1) comprising a step of liquid-solid separation by filter press integrating a step of washing the cake as carried out 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 resulting 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. At the end of step b1.l), the crude cake 22 containing the humins undergoes a washing step b1.2) with water 23, producing a washed cake 25 and a washing filtrate 24 comprising 5-HMF and DMSO. The washed cake 25 then undergoes a compacting-blowing step b1.3) forming a compacted / blown washed cake 27 and a compacting-blowing filtrate 26. Finally, the compacted / blown washed cake 27 is deconstructed in the deconstructing step b1.4) to form a compacted / blown washed deconstructed cake 28.

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

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

[0235] [Tables 1] Example 1 Wash water ratio 23 / filtration load 2 50% 22% Wash water ratio 23 / raw 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 (in accordance with 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 feed of the filter press 2, which is the same suspension as in example 1, is sent to the filtration step b1.l) to separate the solid phase, i.e. the precipitated humins, from the liquid phase 3 comprising in particular 5-HMF, DMSO and water. At the end of step b1.l), the raw cake 22 undergoes a compacting-blowing operation b1.3)), and a compacted-blown raw cake 32 is formed and is then deconstructed in sub-step b1.4).

[0240] In accordance with the invention, the deconstructed cake 33 is resuspended in 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 in the first filtration cycle bl): filtration b3.1), then compacting-blowing b3.2), then clearing b3.3).

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

[0243] Table 2 below shows the rate of losses in 5-HMF and DMSO as a function of the mass ratio of repulping water used 18 compared to the deconstructed cake 33 (repulping stage charge) and as a function of the mass ratio of repulping water used 18 compared to the filtration charge 2.

[0244] [Tables2] Example 2: Repulping Ratio of repulping water 18 / filtration charge 2 2.6% 13% 22% Ratio of repulping water 18 / deconstructed cake 33 1% 4.9% 8.3% Rate of loss in 5-HMF 1.41% 1.27% 0.94% Rate of loss in 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 2 filtration cycles and the intermediate repulping are much lower than in example 1 of a filtration with washing of the cake. For a water 18 / filtration load 2 ratio equal to 22%, the configuration according to example 2 makes it possible to reduce the losses by 50% for 5-HMF and 20% for DMSO in comparison with example 1. The specific liquid-solid separation b) according to the invention integrating a repulping step thus makes it possible to reduce the water / load ratio while reducing the loss rate of 5-HMF and DMSO. For the same water / feed ratio, much more 5-HMF and DMSO can be extracted from the filtered solid phase, thus allowing their recycling into the 5-HMF production process for improved HMF yield and potential DMSO savings.

Claims

Claims

1. A process for producing hydroxymethylfurfural, called 5-HMF, comprising the following steps: - a step a) of bringing a feedstock (1) comprising 5-HMF and an aprotic polar synthesis solvent into contact 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 (b1, b3) separated by an intermediate step b2) of resuspension of a solid phase obtained at the end of the first filtration cycle b1), to produce at least a first aqueous filtrate (3), a second aqueous filtrate (20), and a final solid (19) 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) resulting from step d) by removing at least a portion 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 5-HMF stream (12).;

2. Method according to claim 1, in which the liquid-solid separation step b) is carried out by at least one piece of equipment chosen from a filter press, a belt filter, a centrifuge, a candle filter, a vacuum filter, a belt press, a decanter, a wringer, and preferably by at least one filter press.

3. Method according to claim 2, in which 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 wringer, and preferably by at least one filter press.

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

5. Method according to any one of the preceding claims, in which the intermediate step b2) of resuspension of the solid phase obtained at the end of the first filtration cycle b1) is carried out at a temperature between room temperature and 80°C, preferably at a temperature between 10°C and 40°C, and at atmospheric pressure, by bringing said solid phase into contact with an aqueous solution (18) according to 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(s) 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 sub-steps, in this order: - a filtration sub-step (b1.1, b3.1) of a filtration feedstock to produce an aqueous filtrate (3, 20) and a raw cake (22, 35); - a compacting-blowing sub-step (b1.3, b3.2) of said cake to produce a compacting-blowing filtrate (31, 36) and a compacted-blown raw cake (32, 37); - a de-bagging sub-step (b1.4, b3.3) of said compacted-blown raw cake to produce a de-bagged cake (33, 19); and in which the deconstructed cake obtained at the end of the deconstructing sub-step b 1.4) of the first filtration cycle bl) is the solid phase resuspended in step b2) by contacting with an aqueous solution (18), to form the filtration load of the filtration sub-step b3.1) of the second filtration cycle b3).

7. A method according to claim 6, wherein the first filtration cycle b1) comprises the compacting-blowing sub-step b1.3) producing a first compacting-blowing filtrate (31) recycled into the method in step c), and the second filtration cycle b3) comprises the compacting-blowing sub-step b3.2) producing a second compacting-blowing filtrate (36) recycled into the process in step a).

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

9. Method according to claim 6, in which the compacting-blowing sub-steps (b 1.3, b3.2) are carried out by injecting compressed air at a pressure of between 1 MPa and 5 MPa, and at a temperature of between room temperature and 80°C, preferably of between 10°C and 40°C.

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

11. A method 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 said concentrated organic raffinate (10) from step e), to produce said 5-HMF stream being an aqueous 5-HMF solution (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 of between 0.001 MPa and 0.1 MPa, and preferably under vacuum at a pressure of between 0.005 MPa and 0.08 MPa, and 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, preferably less than or equal to 100°C.

12. Process according to one of the preceding claims, comprising a step of dehydrating the sugars into 5-HMF upstream of step a), preferably by bringing into contact a sugar feedstock 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 of between 30°C and 200°C and at a pressure of between 0.001 MPa and 10 MPa.

13. Method according to one of the preceding claims, in which step a) said aqueous stream (21) comprises all or a fraction of said aqueous counter-extract (9) from step d).

14. A method according to any preceding claim, wherein the extraction solvent (4) is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methylisopropyl ketone, methylisobutyl ketone, thiophene, anisole and toluene, and preferably is methylisobutyl ketone.

15. A method according to any preceding claim, wherein said polar aprotic 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 y-valerolactone, taken alone or as a mixture, and is preferably dimethyl sulfoxide.

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