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

Abstract

The present invention relates to a method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), comprising the following steps: - step a): contacting a feed containing 5-HMF and dimethyl sulfoxide (DMSO) with the intermediate aqueous back-extract from step c); obtaining an aqueous mixture; - step b): liquid-liquid extraction of the aqueous mixture with a stream of extraction solvent; yielding an aqueous raffinate and an intermediate organic extract; - step c): back-washing of the intermediate organic extract with an aqueous solvent; yielding an intermediate aqueous back-extract and an organic raffinate; and - step d): liquid-liquid back-extraction of the organic raffinate obtained at the end of step c) with an aqueous stream; yielding an organic effluent and an aqueous back-extract.

Description

[Technical field]

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

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

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

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

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

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

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

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

[0009] [Non-Patent Document 1] van Dam, HE; ​​Kieboom, APG; van Bekkum, H. (1986), The Conversion of Fructose and Glucose in Acidic Media: Formation of Hydroxymethylfurfural, In: Starch - Starke, vol. 38, No. 3, pages 95-101 Summary of the Invention [Means for solving the problem]

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

[0011] More particularly, the present invention relates to a method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), said method comprising the steps of: - step a): placing a feedstock containing 5-HMF and dimethyl sulfoxide (DMSO) in contact with at least a portion of the intermediate aqueous back-extract advantageously obtained from step c); obtaining at least one aqueous mixture, - step b): liquid-liquid extraction of the aqueous mixture obtained at the end of step a) in the presence of a stream of extraction solvent; giving rise to an aqueous raffinate and an intermediate organic extract; - step c): backwashing the intermediate organic extract with an aqueous solvent: resulting in an intermediate aqueous back extract and an organic raffinate (8) comprising 5-HMF and an organic solvent; - step d): the organic raffinate obtained at the end of step c) is subjected to liquid-liquid back extraction with an aqueous stream; an organic effluent and an aqueous back extract are produced.

[0012] The process for preparing an aqueous solution of 5-HMF may optionally include a step e) of concentrating the aqueous back-extract obtained from step d) by removal of the aqueous effluent, resulting in a concentrated aqueous solution containing 5-HMF. Optionally, it also includes a step f) of treating the water-DMSO mixture generated in the process, resulting in a treated aqueous effluent, which may be used in whole or in part in the backwash step c) and / or in the back-extraction step d). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Description of the embodiment) It is specified that throughout this description, the expression "between ... and ..." is to be understood as inclusive of the limits stated.

[0014] For the purposes of the present invention, the various embodiments presented may be used alone or in combination with each other, without any limitations on said combinations.

[0015] For purposes of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination, e.g., for purposes of the present invention, a preferred range of pressure values ​​may be combined with a more preferred range of temperature values.

[0016] For a better understanding of the present invention, reference will be made below to the reference numerals that appear in the accompanying drawings to indicate various elements of the method, but this does not constitute a limitation to the present invention or to the specific embodiment illustrated in FIG. 1 and described in more detail below.

[0017] (Optional step of sugar dehydration) Advantageously, the feedstock (1) comprising 5-HMF and dimethylsulfoxide (DMSO) introduced in step a) according to the invention can be obtained during a step of sugar dehydration to 5-HMF, very advantageously arranged upstream of step a) according to the invention, carried out by placing a sugar feedstock comprising one or more sugars in contact with DMSO and an acidic dehydration catalyst, resulting in an effluent comprising at least 5-HMF and DMSO, which advantageously corresponds to the feedstock (1) of the process according to the invention introduced in the mixing step a). The process according to the invention may thus optionally comprise a step of sugar dehydration to 5-HMF, which step is arranged upstream of step a).

[0018] The term "acidic dehydration catalyst" refers to any Bronsted acid catalyst selected from organic or inorganic, homogeneous or heterogeneous Bronsted acids, capable of inducing the dehydration of sugars to 5-HMF.

[0019] Preferably, the acidic dehydration catalyst is a Bronsted acid having a pKa in DMSO of 0 to 5.0, preferably 0.5 to 4.0, more preferably 1.0 to 3.0, as defined in the paper by FG ​​Bordwell et al. (J. Am. Chem. Soc., 1991, 113, 8398-8401).

[0020] Preferably, the acidic dehydration catalyst is HF, HCl, HBr, HI, H 2 SO 3 , H 2 SO 4 , H 3 PO 2 , H 3 PO 4 , HNO2 、HNO 3 、H 2 WO 4 、H 4 SiW 12 O 40 、H 3 PW 12 O 40 、(NH 4 ) 6 (W 12 O 40 )·xH 2 O、H 4 SiMo 12 O 40 、H 3 PMo 12 O 40 、(NH 4 ) 6 Mo 7 O 24 ·xH 2 O、H 2 MoO 4 、HReO 4 、H 2 CrO 4 、H 2 SnO 3 、H 4 SiO 4 、H 3 BO 3 、HClO 4 、HBF 4 、HSbF 5 、HPF 6 、H 2 FO 3 P、ClSO 3 H、FSO 3 H、HN(SO 2 F) 2 、HIO 3 、BF 3 、AlCl 3 、Al(OTf) 3 、FeCl 3 、ZnCl 2 、SnCl 2 、CrCl 3 、CeCl 3 、ErCl 3, formic acid, acetic acid, trifluoroacetic acid, lactic acid, levulinic acid, methanesulfinic acid, methanesulfonic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)amine, benzoic acid, para-toluenesulfonic acid, 4-biphenylsulfonic acid, diphenyl phosphate, and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate. Preferably, the acidic dehydration catalyst is selected from HCl, H 2 SO 4 , H 3 PO 2 , H 3 PO 4 , HNO 3 , AlCl 3 , acetic acid, trifluoroacetic acid, methanesulfinic acid, methanesulfonic acid and trifluoromethanesulfonic acid.

[0021] The term "sugar" refers to sugars containing six carbon atoms (hexoses), but this does not exclude the presence in the feedstock of sugars containing five carbon atoms (pentoses) in the form of oligosaccharides and monosaccharides. In particular, the term "sugar" refers to glucose or fructose, sucrose, alone or in mixtures, and also oligosaccharides such as cellobiose, maltose, cellulose or even inulin.

[0022] The sugar feedstock used may be sugar in solid form or an aqueous sugar solution. By way of example, sucrose is generally produced in solid form, while glucose or fructose, alone or in mixtures, are generally produced in the form of an aqueous solution (syrup), for example with 70% sugar by weight.

[0023] The optional dehydration step is carried out at a temperature between 50 and 150°C, preferably between 60 and 140°C, preferably between 70 and 130°C, more preferably between 80 and 120°C. Preferably, the optional dehydration step is carried out at a pressure between 1 and 0.001 MPa, preferably between 0.1 and 0.01 MPa. Depending on the pressure and temperature conditions, the reaction medium is above or below the bubble point of the mixture. The term "bubble point" indicates the pressure and temperature conditions at which the first gas bubbles are found in the liquid. When the reaction medium is above the bubble point of the mixture, the vapor phase can be removed from the reactor, optionally rectified and condensed to form a condensate, which can be sent to the optional step f) for treating the water-DMSO mixture.

[0024] Preferably, the acidic dehydration catalyst is introduced into the dehydration step in a molar ratio of catalyst relative to the sugar feedstock expressed as acid / sugar expressed as mole percent (mol%): 0.01-10 mol%, preferably 0.05-8 mol%, preferably 0.1-6 mol%, preferably 0.2-5 mol%, more preferably 0.3-4 mol%, highly preferably 0.5-3 mol%.

[0025] Advantageously, the effluent obtained at the end of the optional dehydration step comprises 5-HMF and DMSO, the latter generally representing from 30% to 95% by weight, preferably from 40% to 90% by weight, preferably from 50% to 90% by weight, more preferably from 55% to 85% by weight of the effluent obtained from the dehydration step and treated in step a) of the process according to the invention.

[0026] 5-HMF represents more than 1% by weight, preferably more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, preferably less than 40% by weight, more preferably less than 30% by weight, of the effluent obtained from the optional dewatering step and treated in step a) of the process according to the invention.

[0027] Moreover, the effluent from the optional dehydration step may contain water even before it is mixed with the intermediate aqueous back extract (9) in step a). The water may originate from the dehydration step: for example, water is formed during the dehydration reaction of sugar to 5-HMF (3 moles of water per mole of 5-HMF produced). This water may also have been introduced together with the sugar for practical reasons, in the case where sugar syrup is used, for example at about 70% by weight in water. Advantageously, during the optional dehydration step, a water-DMSO mixture may be recovered in the vapour phase. The water-DMSO mixture is advantageously sent to the optional step f). Thus, the effluent obtained from the optional dehydration step and introduced in step a) as feedstock (1) may generally contain water in a proportion of 0.1% to 30% by weight, preferably 0.1% to 15% by weight, more preferably 0.1% to 10% by weight.

[0028] The effluent obtained from the optional dewatering step and introduced in step a) as feedstock (1) may also contain impurities, in particular humins. The term "humins" refers to all undesirable polymeric compounds formed during the synthesis of 5-HMF. In particular, humins represent less than 30% by weight, preferably less than 20% by weight, of the converted sugar feedstock.

[0029] The optional dewatering step may be carried out according to various embodiments. This step may therefore advantageously be carried out in batch or continuous mode. The addition of the sugar feedstock may be gradual (fed-batch), in case of a batch process, or staged in different CSTR reactors (Continuously Stirred Tank Reactors) in series, in case of a continuous process. The process can be carried out in a closed reaction chamber or in a semi-open reactor.

[0030] (Mixing step a)) The process according to the invention optionally comprises a step a) of placing the feedstock (1) from the dewatering step in contact with at least a portion of an intermediate aqueous back extract (9) to obtain an aqueous mixture (3). Advantageously, the intermediate aqueous back extract (9) is obtained from step c) of the process according to the invention.

[0031] Preferably, 5-HMF represents more than 1% by weight, preferably more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, preferably less than 40% by weight, more preferably less than 30% by weight, of the feedstock (1) introduced in step a) of the process according to the invention.

[0032] Preferably, DMSO represents from 30% to 95% by weight, preferably from 40% to 90% by weight, preferably from 50% to 90% by weight, more preferably from 55% to 85% by weight of the feedstock (1) introduced in step a).

[0033] The feedstock (1) introduced in step a) may contain water in an amount of preferably 0.1% to 30% by weight, preferably 0.1% to 15% by weight, more preferably 0.1% to 10% by weight.

[0034] Feedstock (1) may also optionally contain humins, which in particular represent less than 30% by weight, preferably less than 20% by weight, of feedstock (1).

[0035] The intermediate aqueous back extract (9) or a portion of the intermediate aqueous back extract (9) is advantageously obtained from step c). It comprises water, DMSO and optionally 5-HMF. Advantageously, said intermediate aqueous back extract (9) contains more than 60% by weight of water, preferably more than 70% by weight of water, preferably more than 80% by weight of water.

[0036] Advantageously, the aqueous mixture (3) obtained at the end of step a) contains between 10% and 90% by weight of water, preferably between 20% and 80% by weight of water and more preferably between 40% and 75% by weight of water.

[0037] Preferably, step a) is carried out at a temperature between 0 and 60°C, preferably between 10 and 30°C, generally at room temperature, ie between 18 and 25°C.

[0038] Step a) may optionally feed an aqueous stream, for example a portion of the aqueous solvent used in the backwash step c).

[0039] By increasing the water content during step a), for example by introducing at least a portion of the intermediate aqueous back extract (9), some of the humins that may be present in the feedstock (1) can be precipitated out. The mixture obtained from the contact of said feedstock (1) with at least a portion of the intermediate aqueous back extract (9) can thus advantageously be subjected to a liquid-solid separation step to obtain a liquid separated from the suspended solid particles and a solid residue comprising the humins, which is preferably excluded from the process. Such an optional liquid-solid separation step thus allows the elimination of the precipitated humins. At least a portion of the liquid obtained is then advantageously sent to a liquid-liquid extraction step b), said portion (or all) of the liquid advantageously sent to step b) corresponding to the aqueous mixture (3). This optional liquid-solid separation step is preferably carried out at a temperature between 0 and 60°C, preferably between 10 and 30°C, preferably between 15 and 25°C, and generally at room temperature (i.e. between 18 and 25°C). The optional liquid-solid separation step is a simple solid-liquid separation and may be carried out via any method known to the person skilled in the art, for example by a filter press, a belt filter, a clarifier, a decanter or a centrifuge, for example a plate centrifuge. Preferably, the liquid-solid separation step is a filtration, preferably carried out by a filter press.

[0040] (Extraction step b)) The process according to the invention comprises a step b) of liquid-liquid extraction, in the presence of a stream of extraction solvent (4), of the aqueous mixture (3) obtained at the end of step a), so as to give an aqueous raffinate (5) and an intermediate organic extract (6).

[0041] The liquid-liquid extraction carried out in step b) advantageously corresponds to washing the aqueous mixture with an organic extraction solvent. Preferably, the liquid-liquid extraction carried out in step b) is a countercurrent extraction of the aqueous mixture (3) obtained in step a) with a flow of the extraction solvent. This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a mixer-decanter array, in a column filled with random or structured packing, in a plug-flow column or else in a stirred column.

[0042] The extraction step b) is advantageously carried out at a temperature between 0 and 60°C, preferably between 5 and 50°C, preferably between 10 and 40°C, more preferably between 15 and 30°C, and generally at room temperature (i.e. between 18 and 25°C).

[0043] The ratio (wt / wt) of the extraction solvent stream relative to the aqueous mixture (3) is preferably 0.2-5, preferably 1-3, more preferably 1.5-2.5.

[0044] The extraction solvent introduced in step b) is chosen from water-immiscible organic solvents, in particular to form two liquid phases in the backwash step c) and in the back-extraction step d), the characteristics of which depend largely on the relative proportions of the flow rates of the feedstock, the back-extraction water and the extraction solvent used in the process.

[0045] In a non-limiting embodiment, the extraction solvent is preferably selected from the family of chlorinated organic solvents, ethers, esters, ketones and aromatic compounds. Preferably, the extraction solvent is a chlorinated solvent containing 1-10 carbon atoms, hereinafter denoted C1-C10, a (C2-C10) ether containing 2-10 carbon atoms, a (C4-C10) ester containing 4-10 carbon atoms, a (C3-C10) ketone containing 3-10 carbon atoms, a (C1-C10) aldehyde containing 1-10 carbon atoms or a C4-C10 aromatic compound. Preferably, the extraction solvent is selected from dichloromethane, diethyl ether, diisopropyl ether, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, thiophene, anisole and toluene. Highly preferably, the extraction solvent is methyl isobutyl ketone.

[0046] Advantageously, the organic solvent streams arising in the subsequent steps may be advantageously recycled to the extraction step b). These organic solvent streams may contain impurities arising in the process. Advantageously, the organic solvents may be periodically distilled to avoid the accumulation of said impurities.

[0047] According to a preferred embodiment of the invention, the extraction solvent stream comprises, preferably consists of, a stream obtained from one of the steps of the process according to the invention. According to this preferred embodiment, the extraction solvent stream comprises, preferably consists of, at least a part, preferably the whole, of the organic effluent, advantageously obtained from stripping step d) and recycled to extraction step b), which part or all of the organic effluent, advantageously obtained from stripping step d), can optionally be mixed with fresh extraction solvent, i.e. extraction solvent external to the process, to constitute the extraction solvent stream introduced in step b).

[0048] The extraction step b) thus makes it possible to obtain, on the one hand, an aqueous stream depleted in 5-HMF and, on the other hand, an organic stream enriched in 5-HMF, said aqueous stream called aqueous raffinate (5) containing most of the DMSO originally contained in the feedstock, and said organic stream called intermediate organic extract (6) containing most of the 5-HMF originally contained in the feedstock (1) and the extraction solvent. This intermediate organic extract (6) may contain DMSO. Preferably, said extract contains 5-HMF and DMSO in a 5-HMF / DMSO weight ratio of 50 / 50 to 95 / 05, preferably 55 / 45 to 90 / 10, preferably 60 / 40 to 85 / 15, more preferably 65 / 35 to 80 / 20.

[0049] Advantageously, the intermediate organic extract (6) is sent to a backwashing step c).

[0050] (backwashing process c)) The process according to the invention advantageously comprises a step c) of backwashing the intermediate organic extract (6) with an aqueous solvent (7), resulting in an intermediate aqueous back-extract (9) and an organic raffinate (8) comprising 5-HMF and an organic solvent. The organic solvent in particular consists at least partly of the extraction solvent and may optionally comprise DMSO, preferably in small amounts. Advantageously, the intermediate aqueous back-extract (9) is sent partly or entirely to step a).

[0051] The introduction of the aqueous solvent in step c) is carried out in accordance with the general knowledge of the person skilled in the art to carry out the backwash. The introduction of the aqueous solvent is carried out in such a way that the amount of the aqueous solvent is as small as possible to reduce costs, but sufficient to ensure a low DMSO weight content in the organic raffinate (8): preferably less than 20.0% by weight relative to the weight of 5-HMF, preferentially less than 15.0% by weight relative to the weight of 5-HMF, preferably between 0.01% and 15.0% by weight relative to the weight of 5-HMF, preferably between 0.01% and 10.0% by weight relative to the weight of 5-HMF.

[0052] Advantageously, the aqueous backwash solvent introduced in step c) comprises more than 95% by weight of water, preferably more than 98% by weight of water (100% being the maximum). The aqueous solvent may optionally comprise DMSO. All backwash efficiencies are higher the lower the amount of DMSO present in the aqueous backwash solvent. Preferably, the aqueous solvent may comprise DMSO, preferably less than 1.0% by weight of DMSO, more preferably less than 0.1% by weight of DMSO. Advantageously, the aqueous backwash solvent originates from optional step f) of treating the water-DMSO mixture generated in the process and / or from optional concentration step e). In a preferred embodiment of the invention, the aqueous raffinate (5) composed of water and DMSO generated in step b) is advantageously treated in optional step f), which comprises in particular distillation. The water-rich distillate (7) obtained from this optional step f) is advantageously used as aqueous backwash solvent in step c); said water-rich distillate may contain a residual amount of DMSO, preferably less than 1% by weight, preferably less than 0.1% by weight. The residual amount of DMSO in the distillate is proportionally lower the more efficiently the distillation of optional step f) is carried out, in particular by more than 10 distillation stages and suitable reboil and reflux rates.

[0053] The backwashing step c) is advantageously a liquid-liquid extraction of the intermediate organic extract (6) obtained in step b) in countercurrent to the aqueous solvent (7) introduced. This technique is well known to those skilled in the art. The extraction can be carried out, for example, in a mixer-decanter array, in a column filled with random or structured packing, in a plug-flow column or else in a stirred column.

[0054] Step c) is generally carried out at a temperature between 0 and 60° C., preferably between 5 and 50° C., preferably between 10 and 40° C., more preferably between 15 and 30° C., and generally at room temperature (i.e. between 18 and 25° C.).

[0055] The mass ratio (wt / wt) of the aqueous solvent relative to the intermediate organic extract (6) is preferably 0.04-5, preferably 0.07-3, more preferably 0.1-1.

[0056] Step c) gives rise to an aqueous stream and an organic raffinate (8), which is rich in DMSO and is called intermediate aqueous back extract (9) and which preferably contains at least 60% by weight of water, preferably at least 80% by weight of water, said organic raffinate (8) being advantageously depleted in DMSO. Said intermediate aqueous back extract (9) is advantageously partially or preferably totally sent to the mixing step a). The DMSO weight content of the obtained organic raffinate (8) is preferably at most 20.0% by weight relative to the weight of 5-HMF, preferably at most 15.0% by weight relative to the weight of 5-HMF, preferably at most 5.0% by weight relative to the weight of 5-HMF, preferably at most 4.0% by weight relative to the weight of 5-HMF, preferably at most 3.0% by weight relative to the weight of 5-HMF.

[0057] According to the invention, the organic raffinate (8) produced in step c) is sent to a back-extraction step d).

[0058] (Reverse extraction process d)) The process according to the invention comprises a step d) of back-extraction of the organic raffinate (8) with an aqueous stream (10), resulting in an aqueous back-extract (11) comprising 5-HMF and an organic effluent comprising the extraction solvent.

[0059] The aqueous back extract (11) preferably contains 5-HMF in a content of at least 40% by weight, preferably at least 50% by weight, relative to the total of the organic compounds, i.e. relative to the total of 5-HMF, DMSO and the extraction solvent.

[0060] Advantageously, the method according to the invention results in an aqueous back extract of 5-HMF of very high purity, containing very small amounts of humins, more particularly trace amounts (i.e. amounts that are not quantifiable or even detectable by HPLC liquid chromatography) or even no humins.

[0061] An aqueous stream (10) is introduced in step d) to carry out the back extraction according to the general knowledge of the person skilled in the art. The amount of aqueous stream (10) introduced is adjusted to be as low as possible to reduce costs, but sufficient to ensure efficient back extraction of 5-HMF. Advantageously, at least 90% by weight, preferably at least 95% by weight, highly preferably at least 98% by weight of the 5-HMF contained in the organic raffinate (8) fed to step d) is back extracted and is therefore advantageously present in the aqueous back extract (11).

[0062] The back-extraction carried out in step d) is preferably a countercurrent extraction with an aqueous stream (10) of the organic raffinate (8) obtained at the end of step c). This technique is well known to those skilled in the art. The extraction may be carried out, for example, in a series of mixer-settlers, in columns filled with bulk or structured packing, in pulse columns or in stirred columns.

[0063] The back-extraction step d) is preferably carried out at a temperature between 0 and 60°C, preferably between 5 and 50°C, preferably between 10 and 40°C, preferably between 15 and 30°C, and more particularly at room temperature (i.e. between 18 and 25°C).

[0064] The ratio (w / w) of the aqueous stream (10) relative to the organic raffinate (8) is preferably 0.5 to 5, preferably 1.0 to 3.0, preferably 1.5 to 2.5. The amount of water in the aqueous stream added in the back-extraction step d) is preferably greater than the amount of water in the aqueous solvent added in the backwash step c).

[0065] Advantageously, the aqueous stream (10) introduced in the back-extraction step d) comprises at least 95% by weight of water, preferably at least 98% by weight of water (100% being a maximum). The aqueous stream may optionally comprise DMSO. Suitably, the aqueous stream comprises less than 1.0% by weight of DMSO, preferably less than 0.1% by weight of DMSO. Advantageously, the aqueous back-extraction solvent originates at least in part from the optional step f) and / or the optional concentration step e) of the treatment of the water-DMSO mixture generated in the process. In one particular embodiment of the invention, the aqueous raffinate (5) formed in step b) and composed of water and DMSO is advantageously treated in an optional step f) comprising in particular a distillation, the water-rich distillate obtained at the conclusion of this optional step f) being advantageously used, at least in part, as aqueous back-extraction stream in step d); this water-rich distillate obtained at the conclusion of this optional step f) may contain residual amounts of DMSO, preferably less than 1% by weight, suitably less than 0.1% by weight of DMSO.

[0066] At the end of the back-extraction step d), an aqueous solution containing 5-HMF, corresponding to the aqueous back extract (11), and an organic effluent containing the extraction solvent are obtained. The process according to the invention thus produces an aqueous solution of 5-HMF of high purity, i.e. containing very small traces of humins or even free of humins.

[0067] The aqueous back extract (11) resulting from step d) may advantageously be sent, in whole or in part, to an optional concentration step e). The organic effluent may then be recycled, in whole or in part, to the extraction step b) and form at least a portion of the extraction solvent stream (4).

[0068] (Optional back-extraction concentration step e)) Advantageously, the aqueous back extract (11) may be concentrated to a concentrated aqueous solution of 5-HMF (12) by removal of the aqueous effluent (13).

[0069] Advantageously, the concentration of the aqueous solution, i.e. the removal of the aqueous effluent (13), is carried out by any method known to those skilled in the art, such as evaporation or distillation or else reverse osmosis.

[0070] Advantageously, the concentrated aqueous solution of 5-HMF (12) obtained at the end of optional step e) comprises 5-HMF and water in a content of at least 30% by weight, preferably at least 40% by weight, and preferably at least 50% by weight. Preferably, the aqueous solution of 5-HMF (12) obtained at the end of optional step e) comprises at most 90% by weight of 5-HMF, preferably at most 85% by weight of 5-HMF, and preferably at most 80% by weight of 5-HMF, the remainder up to 100% being very advantageously essentially water. The aqueous solution of 5-HMF (12) obtained at the end of optional step e) therefore highly preferably comprises at least 10% by weight of water, preferably at least 15% by weight of water, preferably at least 20% by weight of water, and highly preferably at most 70% by weight of water, more particularly at most 50% by weight of water, in particular at most 30% by weight of water. Preferably, the DMSO content of the concentrated aqueous solution (12) is very low, preferably less than 0.1% by weight, more preferably less than 500 ppm by weight, preferably less than 100 ppm by weight, relative to the weight of 5-HMF.

[0071] The aqueous effluent (13) obtained at the end of the optional concentration step e) preferably consists essentially of water and preferably contains more than 95% by weight of water, preferably more than 98% by weight of water (100% being the maximum). The aqueous effluent (13) may advantageously be recycled to the backwash step c) and / or to the back extraction step d).

[0072] (Optional step f) of treating the water-DMSO mixture) The process according to the invention may comprise an optional step f) of treating the water-DMSO mixture generated by the steps of the process according to the invention, resulting in a treated aqueous effluent (also known as distillate) which may be used totally or partially in the backwash step c) and / or in the back extraction step d), which may also result in a DMSO-rich stream and an impurities stream.

[0073] Any residual amount of DMSO in the treated aqueous effluent resulting upon termination of optional step f) will be less since the distillation is carried out in an efficient manner according to the knowledge of the skilled person.

[0074] The water-DMSO mixture generated by the present process refers in particular to the aqueous raffinate (5) generated in step b) and, if the present process incorporates the optional step of dehydration of sugars to 5-HMF, the water-DMSO mixture resulting from such step.

[0075] The water-DMSO mixture generated by the present process refers in particular to the aqueous raffinate (5) generated in step b) and, optionally, if the present process incorporates the optional step of dehydration of sugars to 5-HMF, the water-DMSO mixture resulting from such step.

[0076] Preferably, the optional step f) of treating the water-DMSO mixture comprises a section for evaporating the water-DMSO mixture to remove any impurities, in particular heavy impurities such as humins, followed by a distillation section.

[0077] The evaporation section is preferably operated at a temperature of 80-120° C., preferentially 100-110° C., and at a pressure of preferably 0.002-0.020 MPa, preferentially 0.005 MPa-0.010 MPa. Preferably, the evaporation section uses a Thin Film Evaporator (TFE).

[0078] The distillation section is advantageously a distillation column or some separation equipment. Preferably, the distillation section of optional step f) is advantageously operated in a distillation column, with a top temperature of preferably 25-60°C, preferentially 45-55°C, for example about 50°C, with a bottom temperature of preferably 80-120°C, preferentially 105-115°C, for example about 110°C, with a pressure of preferably 0.001-0.05MPa, preferentially 0.005-0.02MPa, more preferably 0.008-0.012MPa, and with a reflux ratio of preferably 0.01-0.50, more preferably 0.05-0.10.

[0079] Thus, the aqueous raffinate (5) resulting in step b) and containing water and DMSO, and the water-DMSO mixture possibly recovered in the optional dehydration step, are evaporated and the gas phase is then recovered and distilled, preferably under reduced pressure, to give a DMSO-rich residue on the one hand and a water-rich distillate (corresponding to the treated aqueous effluent) on the other hand. The term "rich" here means more than 95% by weight, preferably more than 98% by weight. The water-rich distillate, or part or all of the treated aqueous effluent, may advantageously be recycled as aqueous solvent to step c) to carry out the backwash step and / or recycled as aqueous stream to the back extraction step d). The water-rich distillate may be recycled in whole or in part as the water introduced into step a).

[0080] The DMSO-rich residue may advantageously be introduced into an optional dehydration step, either directly or after distillation, making it possible to remove any heavy products that may accumulate.

[0081] The following examples and accompanying figures illustrate the invention but do not limit its scope.

[0082] (List of Drawings) FIG. 1 illustrates an embodiment of the method according to the invention. The feedstock (1) containing 5-HMF, DMSO and humins is sent to a mixing step a) and placed in contact with an intermediate aqueous back extract (9) from step c), after which the precipitated humins (2) are removed from the mixture by liquid-solid filtration. The aqueous mixture (3) obtained at the end of step a) is sent to an extraction step b) and placed in contact with the extraction solvent (4) recycled from step d), with which 5-HMF is extracted from the aqueous mixture, obtaining an aqueous raffinate (5) and an intermediate organic extract (6). The intermediate organic extract (6) is placed in contact with an aqueous solvent (7) in a backwash step c). The organic raffinate (8) obtained is sent to a back extraction step d) and placed in contact with an aqueous stream (10) to extract 5-HMF from the water, forming an aqueous stream (11). The aqueous stream (11) is then advantageously concentrated in step e) to obtain an aqueous solution of 5-HMF (12) and an aqueous effluent (13).

[0083] (Example) Example 1: Methods in Accordance with the Invention Example 1 presents the method and results obtained by the exemplary method according to the embodiment of the invention in FIG.

[0084] The acid catalyst (methanesulfonic acid) is mixed with DMSO in a molar ratio (catalyst / sugar feedstock) of 1 mol % with the sugar feedstock and is brought to a temperature of 120° C. Fructose is introduced in the form of an aqueous solution (syrup) of 70% by weight of sugar, with a mass ratio of DMSO / fructose of 2.3. The pressure is maintained at 0.035 MPa. Under these conditions of pressure and temperature, the reaction medium is above the bubble point of the mixture, so that the vapour phase can be removed from the reactor, condensing and forming a condensate. The sugar dehydration step is carried out batchwise by gradual addition of the feedstock over a period of 2 hours. After the end of the addition, the reaction medium is maintained at the temperature and pressure indicated above for a further 2 hours.

[0085] The effluent obtained from the dehydration step contains 74% by weight of DMSO, 21% by weight of 5-HMF and 3% by weight of water, giving a molar yield of 5-HMF relative to the fructose involved of 81%. Polymeric compounds soluble in the reaction medium (called humins) are formed in an amount of 5% by weight. During this dehydration step, a water-DMSO mixture is recovered in the vapor phase. The composition of said water-DMSO mixture is 32% by weight of DMSO and 68% by weight of water. This water-DMSO mixture is distilled under reduced pressure to give water containing only traces of DMSO.

[0086] The liquid effluent from the dehydration step corresponding to the feedstock (1) is subjected to a step a) of placing it in contact with water at room temperature to obtain a mixture, the DMSO / water mass ratio of which is equal to 1.

[0087] The mixture from step a) is subjected to a liquid-solid separation step on a Büchner filter equipped with a polypropylene gauze filter with a pore size of 10 μm. This liquid-solid separation step is carried out at room temperature. During the liquid-solid separation step, 7.5 g of "humic" solid residue per kg of filtered mixture weight are recovered together with a homogenous liquid phase corresponding to aqueous mixture (3). Aqueous mixture (3) is composed of 43% by weight DMSO, 12% by weight 5-HMF, 43% by weight water, and contains impurities (about 2% by weight humic).

[0088] The aqueous mixture (3) obtained from step a) is subjected to a countercurrent liquid-liquid extraction step b) in a stirred glass column (ECR or Keuhni type), which contains 8 sections with a height of 225 mm and an internal diameter of 32 mm, including a lower decanter and an upper decanter. The effective height is about 1.8 m and the total column height is 2.60 m. The total volume is about 3 liters. The organic extraction solvent is methyl isobutyl ketone (MIBK). The aqueous mixture (3) is introduced at the top of the device and dispersed in the organic phase going upwards. The column inlet flow rates are set at 2.2 kg / h for the DMSO-aqueous phase and 4.1 kg / h for the organic extraction solvent. The proportion (w / w) of the MIBK solvent is 1.9 relative to the aqueous mixture (3) obtained from step b). The temperature is 20° C. and the stirring speed is 300 rpm.

[0089] At the end of step b), a 5-HMF-depleted aqueous raffinate (5) and an intermediate organic extract (6) enriched in furan compounds are recovered. The 5-HMF-depleted aqueous raffinate (5) contains about 48% by weight of water, 48.5% by weight of DMSO, 0.4% by weight of 5-HMF, 1.8% by weight of MIBK, and humic impurities, and the intermediate organic extract (6) contains 2.8% by weight of DMSO, 5.9% by weight of 5-HMF (5-HMF / DMSO weight ratio: about 68 / 32) and 91.3% by weight of MIBK. The extraction yield is 97% for 5-HMF and 13% for DMSO.

[0090] The intermediate organic extract (6) obtained from the liquid-liquid extraction step b) is subjected to a backwash step c) in the same type of extraction device (a stirred column of the ECR or Kuehni type). The organic extract is dispersed in the descending pure aqueous phase at 21.5° C. The column inlet flow rates are set at 5 kg / h for the organic extract and 1.5 kg / h for the aqueous phase. The proportion (w / w) of water introduced as aqueous backwash solvent relative to the intermediate organic extract is 0.3.

[0091] At the end of the backwash step c), a DMSO-enriched intermediate aqueous back extract (9) and an organic raffinate (8) are recovered, the DMSO-enriched intermediate aqueous back extract (9) containing 86% by weight of water, 7% by weight of DMSO, 5% by weight of 5-HMF and 2% by weight of MIBK, and the organic raffinate (8) containing 0.092% by weight of DMSO, 4.3% by weight of 5-HMF (i.e. 2.1% by weight of DMSO relative to the weight of 5-HMF) and 88% by weight of MIBK, giving a backwash yield of 27% by weight for 5-HMF and 95% by weight for DMSO.

[0092] The organic raffinate (8) obtained from the backwash step c) is subjected to a liquid-liquid back-extraction step d) in the same type of extraction device (ECR or Kuehni type stirred column). The organic raffinate (8) is dispersed in a descending pure aqueous phase at 21.5° C. and 300 rpm. The column inlet flow rates are set at 2.2 kg / h for the organic raffinate and 4.4 kg / h for the aqueous phase. The ratio (w / w) of the water introduced in step d) relative to the organic raffinate (8) is 2.

[0093] At the end of the back-extraction step d), the following are recovered: an organic raffinate depleted of 5-HMF and an aqueous solution rich in 5-HMF (11); the organic raffinate contains 0% by weight of DMSO, 0.15% by weight of 5-HMF and 96% by weight of MIBK, and the aqueous solution (11) contains 0.045% by weight of DMSO, 2.0% by weight of 5-HMF, 1.6% by weight of MIBK and approximately 96.4% by weight of water. The extraction yield is 97% for 5-HMF. The aqueous solution (11) does not contain humics or contains them only in trace form (not detectable by liquid chromatography or HPLC).

[0094] The aqueous solution (11) is then concentrated by distillation to give a concentrated aqueous solution (12) containing 78% by weight 5-HMF, and an aqueous effluent (13). [Brief description of the drawings]

[0095] [Figure 1] 1 illustrates an embodiment of a method according to the present invention;

Claims

1. 1. A method for producing an aqueous solution of 5-hydroxymethylfurfural (5-HMF), comprising the steps of: step a): placing a feedstock (1) containing 5-HMF and dimethyl sulfoxide (DMSO) in contact with an intermediate aqueous back extract (9), advantageously at least a portion of the intermediate aqueous back extract (9) obtained from step c); obtaining at least one aqueous mixture (3), step b): liquid-liquid extraction of the aqueous mixture (3) obtained at the end of step a) in the presence of a stream of extraction solvent (4); giving an aqueous raffinate (5) and an intermediate organic extract (6), - step c): backwashing of the intermediate organic extract (6) with an aqueous solvent (7) to give an intermediate aqueous back-extract (9) and an organic raffinate (8) comprising 5-HMF and an organic solvent, Step d): liquid-liquid back-extraction with an aqueous stream (10) of the organic raffinate (8) obtained at the end of step c); giving an organic effluent and an aqueous back-extract (11).

2. 2. The process according to claim 1, wherein the back-extraction carried out in step d) is a countercurrent extraction with an aqueous stream (10) of the organic raffinate (8) obtained at the end of step c).

3. 3. The method according to claim 1 or 2, wherein step d) is carried out at a temperature of 0 to 60°C, preferably 15 to 30°C.

4. 2. The process according to claim 1, wherein in step d) the weight ratio of the aqueous stream (10) relative to the organic raffinate (8) is between 0.5 and 5, preferably between 1.0 and 3.0, preferably between 1.5 and 2.

5.

5. 2. The method of claim 1, wherein the amount of water in the aqueous stream (10) added in back-extraction step d) is greater than the amount of water in the aqueous solvent (7) added in backwash step c).

6. 2. The process according to claim 1, wherein the aqueous stream (10) introduced in the back-extraction step d) comprises at least 95% by weight of water, preferably at least 98% by weight of water.

7. 2. The process of claim 1, further comprising a step e) of concentrating the aqueous back extract (11) obtained from step d) by removing an aqueous effluent (13) to produce a concentrated aqueous solution (12) comprising 5-HMF.

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

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

10. 2. The process of claim 1, comprising an optional step of dehydrating sugars to 5-HMF upstream of step a), preferably carried out by placing a sugar feedstock comprising one or more sugars in contact with DMSO and an acidic dehydration catalyst, preferably at a temperature of from 50 to 150°C, and preferably at a pressure of from 1 to 0.001 MPa.

11. 2. The method of claim 1, comprising an optional step f) of treating the water-DMSO mixture produced within the method to produce a treated aqueous effluent, which may be used in whole or in part in the backwashing step c) and / or in step e).

Images