Production of HMF catalyzed by a mixture of salt and acid

Abstract

The present invention relates to a process for producing 5-hydroxymethylfurfural (HMF) by converting a fructose-containing component at a temperature of 90 to 200° C. using a catalyst system comprising a solution of a salt and acid mixture and obtaining an HMF-containing product mixture, wherein a high HMF selectivity is advantageously achieved and the formation of by-products is significantly reduced.

Description

Technical Field

[0001] The present invention relates to a process for producing 5-hydroxymethylfurfural (HMF) by converting a fructose-containing component at 90-200° C. using a catalytic system comprising a solution of a salt and acid mixture to obtain an HMF-containing product mixture, wherein a high HMF selectivity is advantageously achieved while the formation of by-products is significantly reduced. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is a multifunctional molecule with an aromatic five-ring system, an aldehyde group and an alcohol group. The many functional groups of the molecule make it a platform chemical that lends itself to many different applications and can serve as the basis for many other compounds. Compounds that can be produced based on HMF include, first of all, chemicals such as caprolactam or adipic acid, which can already be produced in large quantities via petrochemical methods, but also 2,5-furandicarboxylic acid (FDCA), which has a wide range of uses and for which there is currently no technological method for its production.

[0003] Despite the great potential of HMF and FDCA, there is still a lack of economical, technically mature methods for the production of these compounds. The versatility of HMF, one of the greatest advantages of the molecule, has also proven to be a major disadvantage in terms of the synthesis of secondary chemical processes that may subsequently occur due to this versatility. In particular, in aqueous systems, HMF is unstable under the reaction conditions required for the synthesis (acidic pH, high temperature), and firstly, HMF reacts with itself and / or the starting materials and intermediates during the polymerization to form so-called humins, which are soluble or insoluble depending on the chain length and cause the reaction solution to be brown to black. Another undesirable side reaction is the acid-catalyzed rehydration of HMF to form levulinic acid and formic acid, wherein in particular levulinic acid can react with HMF to form further undesirable by-products. Therefore, in order to produce HMF most economically, it is absolutely necessary to avoid this side reaction as much as possible, as well as the side reactions of HMF and levulinic acid.

[0004] In principle, among the numerous different synthetic routes for producing HMF that have been described in the prior art, a distinction can be made between single-phase and two-phase reaction systems. Both approaches can use homogeneous and heterogeneous catalysts. In single-phase systems, HMF synthesis can be carried out not only in purely aqueous systems, but also in organic solvents (such as DMSO, DMF and sulfolane) or in ionic liquids. In terms of chemical reactions, avoiding the use of aqueous systems will result in better HMF selectivity, but in order to remove the solvent, high temperatures are usually required, at which HMF undergoes thermal decomposition, thereby greatly reducing the purity and yield of HMF. In addition, when anhydrous systems are used, the cost of solvents as well as safety and environmental aspects play a major role. This has proven to be disadvantageous, as the hexoses used for HMF synthesis, in particular fructose and / or glucose, are poorly soluble in many common organic solvents.

[0005] In a two-phase reaction system, the reaction from hexoses to form HMF is carried out in the aqueous phase and the resulting HMF is continuously extracted with an organic solvent. The solvent must not be miscible with water and must have a sufficiently high HMF partition coefficient between the aqueous phase and the organic phase to ensure efficient extraction of HMF. Since the dispersion coefficients of most solvents in particular are not very high, very large amounts of solvent must usually be used in such systems. The most commonly used organic solvent in a two-phase reaction system is methyl isobutyl ketone (MIBK), optionally in combination with a phase modifier such as 2-butanol. As has already been shown for a single-phase anhydrous reaction system, the subsequent removal of the used solvent has proven to be problematic due to the high boiling point of a suitable solvent.

[0006] EP 0230250 B1 discloses a method for producing 5-hydroxymethylfurfural containing a crystalline product using only water as a solvent. In the batch method described, sugars are decomposed into a mixture of hexoses and HMF using an acidic catalyst in an aqueous solution at a temperature of more than 100°C, and the formed HMF is subsequently separated from the by-products by an ion exchange column at a temperature of 35-85°C, so that in addition to the HMF portion, a sugar portion that can be used for another HMF synthesis can also be obtained according to the above method. The batch conversion disclosed in this document requires a high fructose conversion rate and directly leads to a high HMF concentration in the reaction solution, which, under the current conditions, leads to an increase in the formation of by-products and degradation products, thereby reducing the HMF yield relative to the conversion amount of fructose.

[0007] WO 2013 / 106136 A1 relates to a method for producing HMF and HMF derivatives from sugars, including the recovery of unreacted sugars suitable for direct use in ethanol fermentation. A hexose-containing solution in an aqueous phase is converted into HMF by an acid-catalyzed dehydration reaction, and the unreacted sugars contained in the product mixture are subsequently separated from the product mixture by adsorption and / or solvent extraction, and finally these sugars are used in an aerobic or anaerobic fermentation process to produce ethanol. It is taught that the acid-catalyzed dehydration reaction is carried out at a temperature of 175-205°C.

[0008] WO 2015 / 113060 A2 discloses the conversion of a fructose-containing starting material into a HMF-containing product. By the above method, fructose, water, an acid catalyst, and at least one other solvent are mixed in a reaction zone and reacted for about 1–60 min by selecting appropriate reaction parameters so that the HMF yield does not exceed 80%. When the specified conversion rate is achieved, the reaction components should be immediately cooled to minimize the formation of unwanted by-products.

[0009] WO 2014 / 158554 discloses a method for producing HMF or its derivatives from a solution containing glucose and / or fructose, wherein an acid-catalyzed dehydration reaction is carried out under oxygen-reducing conditions. This will increase the stability of HMF and prevent possible degradation reactions, thereby reducing the formation of undesirable by-products. Optionally, an antioxidant can be added to prevent auto-oxidation of HMF.

[0010] Li et al. (RSCAdv., 2017, 7, 14330–14336) described the conversion of glucose into HMF without isomerization to fructose using a mixture of hydrochloric acid and sodium chloride in a water / γ-valerolactone system at a temperature of 140°C and a reaction time of 60 min. However, as mentioned above, since the decomposition of HMF already occurs from 170°C, the final removal of the solvent is also problematic here due to the high boiling point of 205°C.

[0011] In order to ensure a cost-effective and efficient process for the production of HMF, it is essential that, during the conversion of the fructose-containing starting solution into HMF, the formation of undesirable by-products and the decomposition of the HMF formed by the dehydration reaction are avoided as far as possible by selecting suitable reaction conditions and process steps. Furthermore, it makes economic sense if the unconverted fructose is separated from the disruptive by-products formed during the dehydration reaction and is thus available in the purest possible form for recirculation to the continuous production process.

[0012] To date, there is no corresponding method in the prior art for producing HMF cost-effectively and efficiently, preferably in a continuous process. Summary of the invention

[0013] Therefore, the object of the present invention is to overcome the disadvantages and limitations of the above-mentioned prior art disclosed processes and in particular to provide a process for converting fructose into HMF in a highly selective manner, in particular minimizing the formation of by-products and in a cost-effective and efficient manner.

[0014] The object of the present invention is achieved by the technical teaching of the claims.

[0015] In particular, the present invention relates to a process for producing 5-hydroxymethylfurfural (HMF), comprising the following steps:

[0016] a) providing a catalyst system comprising a component comprising fructose and a solution comprising a salt and an acid mixture,

[0017] b) mixing the fructose-containing component with the catalyst system to obtain a reaction solution,

[0018] c) converting fructose present in the reaction solution into HMF at a temperature of 90° C. to 200° C. to obtain a liquid HMF-containing product mixture; and

[0019] d) obtaining a liquid HMF-containing product mixture.

[0020] Thus, according to the present invention, a process is provided for producing 5-hydroxymethylfurfural (HMF) by selectively, preferably highly selectively, converting fructose in a fructose-containing component. According to the present invention, a catalyst system comprising a solution, in particular an aqueous solution, of a salt and acid mixture is used for converting fructose. Thus, the present invention advantageously provides mixing a fructose-containing component with a solution, in particular an aqueous solution, of a salt and acid mixture and subsequently converting the fructose present in the reaction solution into HMF. Compared to conventional HMF production processes using sulfuric acid as a catalyst, the use of a salt and acid mixture for converting fructose present in a fructose-containing component into HMF has the advantage that the selectivity of HMF is significantly increased, while the formation of by-products is significantly reduced, and fructose is converted at a comparable rate. In an advantageous preferred embodiment, a fructose conversion of ≥30% is possible, and an acceptable selectivity of more than 80% is possible. In addition, the use of a salt and acid mixture also enables a higher carbohydrate concentration in the reaction solution, i.e. in an advantageous preferred embodiment, a carbohydrate concentration of up to 40%, calculated on carbohydrate dry matter. According to the invention, in an advantageous preferred embodiment, the use of a catalyst system comprising a solution of a salt and acid mixture results in a very high HMF selectivity without the use of other catalysts in homogeneous or heterogeneous form. In addition, the use of the catalyst system according to the invention leads to a significant reduction in the formation of humic substances, in particular insoluble humic substances, which in conventional processes cause technical problems due to agglomeration and scaling. Thus, in particular, the use of a catalyst system of a salt and acid mixture according to the invention results in a significantly increased fructose conversion with an economically reasonable HMF selectivity.

[0021] In a particularly preferred embodiment, the process according to the invention, in particular the implementation of process steps a) to d), results in a significantly increased HMF selectivity, wherein the formation of by-products is reduced, in particular the rehydration of HMF to levulinic acid and formic acid is reduced, and the fructose conversion is reduced compared to the prior art.

[0022] In a particularly preferred embodiment, in the process according to the invention, in particular in process steps a) to d), the selectivity for levulinic acid is ≤6%, preferably ≤5%, preferably ≤4%, particularly preferably ≤3% (based on the converted fructose content).

[0023] The catalyst system according to the invention comprises a solution of a mixture of salt and acid, wherein the acid is preferably an inorganic acid and / or an organic acid, and the salt is preferably a salt of an inorganic acid and / or a salt of an organic acid.

[0024] In a particularly preferred embodiment, the catalyst system according to the invention comprises a solution of a salt and an acid mixture, wherein the acid is preferably an inorganic acid, an organic acid or a mixture of an inorganic acid and an organic acid.

[0025] In a particularly preferred embodiment, the catalyst system according to the invention comprises a solution of a salt and an acid mixture, wherein the salt is preferably a salt of an inorganic acid, a salt of an organic acid or a mixture of a salt of an inorganic acid and a salt of an organic acid.

[0026] The inorganic acid is particularly preferably selected from hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; the organic acid is selected from acetic acid, citric acid, tartaric acid, oxalic acid, glycolic acid and gluconic acid. The salt of the inorganic acid is particularly preferably selected from alkali metal halides, alkali metal halides, alkali metal nitrates, alkaline earth metal nitrates, alkali metal sulfates, alkaline earth metal sulfates, alkali metal phosphates, alkaline earth metal phosphates and mixtures thereof; the salt of the organic acid is selected from acetates, citrates, tartrates, oxalates, glycolates, gluconates and mixtures thereof.

[0027] In a preferred embodiment, the acid contained in the catalyst system according to the present invention is an inorganic acid. The inorganic acid is particularly preferably selected from hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. The inorganic acid is particularly preferably hydrochloric acid or nitric acid. In another preferred embodiment, the acid contained in the catalyst system is an organic acid. The organic acid is particularly preferably selected from acetic acid, citric acid, tartaric acid, oxalic acid, glycolic acid and gluconic acid.

[0028] In a preferred embodiment, the salt contained in the catalyst system according to the present invention is a salt of an inorganic acid. The salt is particularly preferably selected from alkali metal halides, alkaline earth metal halides, alkali metal nitrates, alkaline earth metal nitrates, alkali metal sulfates, alkaline earth metal sulfates, alkali metal phosphates, alkaline earth metal phosphates and mixtures thereof. Particularly preferred are sodium chloride, sodium nitrate, calcium chloride, magnesium chloride or mixtures thereof. In another preferred embodiment, the salt contained in the catalyst system is a salt of an organic acid. The salt is particularly preferably selected from acetate, citrate, tartrate, oxalate, glycolate, gluconate and mixtures thereof.

[0029] In a particularly preferred embodiment, the solution of the salt and acid mixture is an aqueous solution. According to the invention, preferably a one-phase process is provided. Preferably a two-phase process is excluded. Preferably, no phase separation is provided, in particular no induced phase separation is provided. The catalyst system according to the invention comprises, in particular consists of, an aqueous solution of a salt and acid mixture, wherein the acid is an inorganic acid, preferably selected from hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; the salt is a salt of an inorganic acid, preferably selected from sodium chloride, sodium nitrate, calcium chloride and magnesium chloride.

[0030] In a particularly preferred embodiment, the catalyst system according to the invention comprises sodium chloride as salt and hydrochloric acid as mineral acid.

[0031] In a further preferred embodiment, the catalyst system according to the invention comprises sodium nitrate as salt and nitric acid as mineral acid.

[0032] In a further preferred embodiment of the present invention, the catalyst system according to the invention comprises hydrochloric acid as mineral acid and calcium chloride as salt.

[0033] In a further preferred embodiment of the present invention, the catalyst system according to the invention comprises hydrochloric acid as mineral acid and magnesium chloride as salt.

[0034] In another preferred embodiment, the salt is an alkali metal salt or an alkaline earth metal salt, in particular an alkali metal salt, in particular an alkaline earth metal salt.

[0035] Surprisingly, although nitrates were previously considered to be unsuitable catalysts for the formation of HMF, in the process of the present invention, good results in terms of HMF selectivity were achieved using a mixture of nitric acid and sodium nitrate as the catalyst system (see Examples 4 and 6; Tao et al., Journal of Molecular Catalysis A: Chemical, 357, 2012, 11-18; Tyrlik et al., Starch / Strength, 47(5), 1995, 171-174).

[0036] In another embodiment, the catalyst system comprises, in particular consists of, an aqueous solution of a salt and an acid mixture, wherein the acid is an organic acid, preferably selected from acetic acid, citric acid, tartaric acid, oxalic acid, glycolic acid and gluconic acid, and the salt is a salt of an organic acid, preferably selected from acetate, citrate, tartrate, oxalate, glycolate and gluconate.

[0037] In the process according to the invention, the concentration of the mixture of salt and acid, i.e. the catalyst system, is preferably 0.01 to 2.00% by weight, preferably 0.05 to 1.75% by weight, preferably 0.1 to 1.5% by weight, preferably 0.2 to 1.4% by weight, preferably 0.3 to 1.3% by weight, preferably 0.4 to 1.2% by weight, preferably 0.5 to 1.1% by weight, preferably 0.6 to 1.0% by weight, preferably 0.75 to 0.9% by weight (in each case based on the total weight of the reaction solution obtained in process step b)). The catalyst system is used in a concentration of preferably at most 2.0% by weight, preferably at most 1.75% by weight, preferably at most 1.5% by weight, preferably at most 1.3% by weight, preferably at most 1.0% by weight, preferably at most 0.75% by weight, preferably at most 0.5% by weight (in each case based on the total weight of the reaction solution obtained in process step b)). These concentrations are much lower than those used in the prior art. Surprisingly, however, it is precisely due to these low concentrations of salt and acid mixtures that a particularly high HMF selectivity and a low by-product formation occur.

[0038] In a preferred embodiment, the salt concentration of the reaction solution in step b) of the process according to the invention is 1×10 -5 to 0.45 mol / L, preferably 5×10 -5 to 0.4 mol / L, preferably 1×10 -4 to 0.35 mol / L, preferably 1×10 -3 The concentration of iodine is preferably 0.1 to 0.25 mol / L, and the concentration of iodine is preferably 0.01 to 0.25 mol / L.

[0039] In a preferred embodiment, the acid concentration of the reaction solution in step b) of the method of the present invention is 1×10 -6 to 0.35 mol / L, preferably 8×10 -6 to 0.3 mol / L, preferably 1×10 -5 to 0.25 mol / L, preferably 1×10 -4 to 0.2 mol / L, particularly preferably 1×10 -3 To 0.15mol / L.

[0040] In the catalyst system according to the invention, the ratio of salt to free acid in the reaction solution obtained in process step b) is from 0.8 to 10, preferably from 1 to 9, preferably from 1.2 to 8, preferably from 1.5 to 7, preferably from 2 to 6, preferably from 2.3 to 5, preferably from 2.5 to 4 (in each case mol / mol).

[0041] The ratio of anions of the salt and acid mixture to cations of the salt of the salt and acid mixture in the reaction solution obtained in process step b) is particularly preferably from 0.55 to 4, preferably from 1.0 to 3.5, preferably from 1.1 to 2.0, preferably from 1.5 to 3, preferably from 1.75 to 2.75, preferably from 2 to 2.5 (in each case mol / mol).

[0042] According to the present invention, the anion concentration of the catalyst system in the reaction solution obtained in process step b) is 1×10 -5 to 0.6 mol / L, preferably 8×10 -5 to 0.55 mol / L, preferably 1×10 -4 to 0.53 mol / L, preferably 1×10 -3 To 0.45 mol / L, preferably 0.01 to 0.35 mol / L, preferably 0.05 to 0.5 mol / L, preferably 0.1 to 0.4 mol / L, preferably 0.2 to 0.3 mol / L.

[0043] According to the invention, the cation concentration of the catalyst system in the reaction solution obtained in process step b) is 1×10 -5 to 0.45 mol / L, preferably 5×10 -5 to 0.4 mol / L, preferably 1×10 -4 to 0.35 mol / L, preferably 1×10 -3 The concentration of iodine is preferably 0.1 to 0.25 mol / L, and the concentration of iodine is preferably 0.01 to 0.25 mol / L.

[0044] At the above-mentioned preferred concentrations, the use of the catalyst system according to the invention preferably results in a pH of the reaction solution obtained in process step b) of 1.2 to 4.5, preferably 1.3 to 4, preferably 1.4 to 3.5, preferably 1.5 to 3, preferably 1.7 to 2.5, preferably 2 to 2.2. Due to the use of salts in the catalyst system according to the invention, the pH of the reaction solution obtained in step b) is mostly higher than in purely acid-catalyzed processes, but as a result, unexpectedly higher HMF selectivities are achieved (see Examples).

[0045] In the process according to the invention, in particular in process steps a) to d), in particular a) to c), preferably no further catalytically active components are used besides the salt and acid mixture.

[0046] In a particularly preferred embodiment, in the process according to the invention, in particular in process steps a) to d), in particular a) to c), no organic solvents are used. In particular, in process steps a) to d), in particular a) to c), no water-miscible or water-immiscible organic solvents are used.

[0047] In particular, process steps a) to d) are carried out in aqueous solution.

[0048] In addition to the salt and acid mixture, a fructose-containing component is provided in step a) of the method according to the invention. It is preferably a solid fructose-containing component, in particular fructose; or a liquid fructose-containing component, in particular a fructose syrup, a fructose / glucose syrup or a fructose solution, in particular an aqueous fructose solution. Therefore, the fructose-containing component is also referred to as a fructose-containing starting solution here. According to the invention, the fructose-containing component can also be obtained from sucrose or starch, or the glucose obtained from biomass can be isomerized to fructose. The fructose-containing component preferably has a dry matter (DM) content of fructose of 40-100% by weight, preferably 50-90% by weight, preferably 60-85% by weight.

[0049] In a preferred embodiment of the present invention, the components provided in step a) are mixed in step b) to obtain a reaction solution having a carbohydrate content of 5% to 50% by weight (dry matter, also referred to below as DM, carbohydrates relative to the total weight of the reaction solution) and the conversion is carried out according to process step c). The carbohydrate content in the reaction solution in step b) is particularly preferably from 10% to 45% by weight, preferably from 15% to 40% by weight, preferably from 25% to 35% by weight, preferably 20%, 30% or 40% by weight (in each case carbohydrates DM relative to the total weight of the reaction solution).

[0050] In a preferred embodiment of the process, the fructose content in the reaction solution obtained in process step b) is from 40 to 100% by weight, preferably from 70 to 100% by weight, preferably from 80 to 100% by weight, preferably from 90 to 100% by weight, preferably from 95 to 100% by weight, preferably from 40 to 99% by weight, preferably from 45 to 99% by weight, preferably from 50 to 95% by weight, preferably from 45 to 90% by weight, preferably from 55 to 85% by weight (in each case fructose DM relative to the dry matter of the carbohydrate content, i.e. all carbohydrates present in the reaction solution).

[0051] In a particularly preferred embodiment of the present invention, the components provided in step a) are mixed in step b) to obtain a reaction solution having a carbohydrate content of 5 to 50% by weight, preferably 10 to 45% by weight, preferably 15 to 40% by weight, preferably 25 to 35% by weight, preferably 20, 30 or 40% by weight (in each case, carbohydrates DM relative to the total weight of the reaction solution) and a fructose content of 40 to 100% by weight, preferably 70 to 100% by weight, preferably 80 to 100% by weight, preferably 90 to 100% by weight, preferably 95 to 100% by weight, preferably 40 to 99% by weight, preferably 45 to 99% by weight, preferably 50 to 95% by weight, preferably 45 to 90% by weight, preferably 55 to 85% by weight (in each case, fructose DM relative to the dry matter of the carbohydrate content, i.e. all carbohydrates present in the reaction solution) and converted according to process step c).

[0052] In a particularly preferred embodiment, the mixing of the components for preparing the reaction solution, i.e., in particular the fructose-containing component and the catalyst system, i.e., step b) of the process according to the invention, takes place in a mixing device and / or a conduit. The mixing device or conduit and the reactor system in which the conversion takes place (i.e., step c) of the process) can be represented as spatially separated structural units which are connected to one another by at least one conduit; they can also represent independent and inseparable components of the device. The reaction solution is preferably introduced into the reactor system by means of a pump, in particular a high-pressure pump.

[0053] In a preferred embodiment of the present invention, the fructose-containing component, the catalyst system or both provided in step a) are set to a temperature of 90° C. to 200° C. prior to step b). Thus, preferably at least one component provided in step a), preferably all components, i.e. the fructose-containing component and the catalyst system, are individually preheated to a temperature of 90° C. to 200° C., preferably 100° C. to 175° C., preferably 150° C. to 175° C., prior to step b). In a preferred embodiment of the present invention, at least one component provided in step a), preferably all components are preheated to a temperature of 120° C. to 180° C., preferably 130° C. to 180° C., preferably 140° C. to 180° C., prior to step b). In particular, at least one component provided in step a), preferably all components are individually preheated to 160° C., 165° C., 170° C. or 175° C. prior to step b).

[0054] In an alternative preferred embodiment of the present invention, the reaction solution obtained in step b) is set to a temperature of 90° C. to 200° C. Thus, preferably after step b) and before step c), the reaction solution obtained in step b) by mixing the components provided in step a) is preferably set to a temperature of 90° C. to 200° C., preferably 100° C. to 175° C., preferably 150° C. to 175° C. Preferably after step b) and before step c), the reaction solution obtained in step b) is heated to a temperature of 120° C. to 180° C., preferably 130° C. to 180° C., preferably 140° C. to 180° C. In particular, the reaction solution obtained in step b) is heated to 160° C., 165° C., 170° C. or 175° C.

[0055] In a particularly preferred embodiment, the subsequent step c) of the process, i.e. the conversion of the fructose present in the reaction solution into HMF, is carried out at a temperature of 90 to 200°C, in particular 120 to 195°C, in particular 140 to 190°C, in particular 150 to 180°C, in particular 160 to 175°C, in particular 165 to 170°C, in particular 165 to 175°C, in particular 170 to 175°C, in particular 160 to 165°C, in particular 165°C, in particular 170°C, in particular 175°C.

[0056] According to the invention, in a preferred embodiment, the temperature for carrying out the process according to the invention is at most 200° C., preferably at most 175° C., in particular at most 165° C. at any point in time.

[0057] In a preferred embodiment of the present invention, in step c), the fructose contained in the reaction solution is converted into HMF within the following time period: 0.1-20 min, in particular 0.1-15 min, in particular 8-13 min, in particular 4-10 min, in particular 8-10 min, preferably 0.1-8 min, preferably 0.2-7 min, preferably 0.5-5 min, preferably 1-4 min, preferably 5-6 min. In step c), fructose is preferably converted into HMF within the following time period: at most 10 min, preferably at most 9 min, preferably at most 8 min, preferably at most 7 min, preferably at most 6 min, preferably at most 5 min, preferably at most 4 min.

[0058] In a preferred embodiment, the invention provides that the conversion of fructose in step c) is from 1 mol% to 50 mol%. In a preferred embodiment, fructose is converted into HMF in step c) with a conversion of fructose of from 1 mol% to 50 mol%, preferably from 5 mol% to 40 mol%, preferably from 10 mol% to 30 mol%, preferably from 15 mol% to 25 mol%, preferably from 20 mol% to 25 mol%. Preferably, fructose is converted into HMF in step c) with a conversion of fructose of at most 50 mol%, preferably at most 40 mol%, preferably at most 30 mol%, preferably at most 25 mol%, preferably at most 20 mol%. According to the invention, this takes place at a temperature of from 90°C to 200°C.

[0059] For the purposes of the present invention, "setting the fructose conversion" means selecting the reaction parameters for converting fructose into HMF, in particular the reaction temperature and reaction time in the reactor, so as to have a limited fructose conversion of a maximum of 50 mol%, thereby achieving a high HMF selectivity while also reducing the formation of by-products.

[0060] Thus, preferably a specifically defined fructose conversion can be provided within the framework of given parameters, in particular by using the reaction temperature preferred according to the invention in step c), optionally also the reaction time in a preferred embodiment. The HMF selectivity preferred according to the invention can also be set based on these parameters. In a preferred manner according to the invention, the desired fructose conversion and optionally the HMF selectivity can be set by taking samples during the process, analyzing the samples, and then calculating the parameters to be maintained or set in order to achieve the desired fructose conversion value and optionally the desired HMF selectivity.

[0061] In a particularly preferred embodiment, the fructose contained in the fructose-containing component is converted in step c) at 90-200° C., preferably 150-190° C., in particular 160° C., 165° C., 170° C. or 175° C., for 4-7 min, preferably 5-6 min, in particular 5.6 min. This preferably results in a fructose conversion of 1-50 mol%.

[0062] In a preferred embodiment of the invention, the process is set such that the HMF selectivity in step c) is from 60 mol % to 100 mol %, preferably from 65 mol % to 100 mol %, preferably from 70 mol % to 100 mol %, preferably from 75 mol % to 100 mol %, preferably from 80 mol % to 100 mol %, preferably from 85 mol % to 100 mol %, preferably from 90 mol % to 100 mol %. The HMF selectivity in step c) is preferably at least 60 mol %, preferably at least 65 mol %, preferably at least 70 mol %, preferably at least 75 mol %, preferably at least 80 mol %, preferably at least 85 mol %, preferably at least 90 mol %, preferably at least 95 mol %.

[0063] In a preferred embodiment of the invention, the process is set such that in step c) the HMF selectivity is from 60 mol % to 100 mol %, preferably from 65 mol % to 100 mol %, preferably from 70 mol % to 100 mol %, preferably from 75 mol % to 100 mol %, preferably from 80 mol % to 100 mol %, preferably from 85 mol % to 100 mol %, preferably from 90 mol % to 100 mol %, preferably at least 60 mol %, preferably at least 65 mol %, preferably at least 70 mol %, preferably at least 75 mol %, preferably at least 80 mol %, preferably at least 85 mol %, preferably at least 90 mol %, preferably at least 95 mol % and the fructose conversion is from 1 mol % to 50 mol %, preferably from 5 mol % to 40 mol %, preferably from 10 mol % to 30 mol %, preferably from 15 mol % to 25 mol %, preferably from 20 mol % to 25 mol %, preferably at most 50 mol %, preferably at most 40 mol %, preferably at most 30 mol %, preferably at most 25 mol %, preferably at most 20 mol %.

[0064] In a particularly preferred embodiment of the invention, the process is arranged such that in step c) the HMF selectivity is from 60 mol % to 100 mol %, preferably from 65 mol % to 100 mol %, preferably from 70 mol % to 100 mol %, preferably from 75 mol % to 100 mol %, preferably from 80 mol % to 100 mol %, preferably from 85 mol % to 100 mol %, preferably from 90 mol % to 100 mol %, preferably at least 60 mol %, preferably at least 65 mol %, preferably at least 70 mol %, preferably at least 75 mol %, preferably at least 80 mol %, preferably at least 85 mol %, preferably at least 90 mol %, preferably at least 95 mol %, and the fructose conversion is from 1 mol % to 50 mol %, preferably from 5 mol % to 40 mol %, preferably from 10 mol % to 30 mol %, preferably from 15 mol % to 25 mol %, preferably from 2 0 mol % to 25 mol %, preferably up to 50 mol %, preferably up to 40 mol %, preferably up to 30 mol %, preferably up to 25 mol %, preferably up to 20 mol %, wherein this is achieved by using a temperature of 90–200 ° C, in particular 140–190 ° C, in particular 150–180 ° C, in particular 160–175 ° C, in particular 165–170 ° C, in particular 165–175 ° C, in particular 170–175 ° C, in particular 160–165 ° C, in particular 165 ° C, in particular 170 ° C, in particular 175 ° C, and a duration of 0.1–20 min, in particular 0.1–15 min, in particular 8–13 min, in particular 4–10 min, in particular 8–10 min, preferably 0.1–8 min, preferably 0.2–7 min, preferably 0.5–5 min, preferably 1–4 min, preferably 5–6 min.

[0065] For the purposes of the present invention, HMF selectivity is related to the amount of converted fructose, without taking into account the amount of other carbohydrates, in particular glucose.

[0066] In a preferred embodiment of the present invention, the HMF yield is 3-50 mol %, preferably 5-45 mol %, preferably 10-40 mol %, preferably 15-35 mol %, particularly preferably 20-30 mol %.

[0067] In a preferred embodiment of the present invention, in step c), the pressure for converting the fructose present in the reaction solution into HMF is set so as to avoid boiling of the reaction solution and thus avoid the occurrence of vapor bubbles. In the reactor system, the pressure for converting the fructose present in the reaction solution into HMF is preferably 0.1-2 MPa, preferably 0.2-1.5 MPa, particularly preferably 1 MPa.

[0068] According to the invention, it is provided that in step c), by setting various parameters, such as temperature, reaction time, pH, catalyst concentration, acid / salt ratio and / or pressure, the fructose present in the reaction solution is converted into HMF, and in step d), a liquid HMF-containing product mixture is obtained. Thus, the process is preferably carried out in such a way that by setting the temperature and preferably also the reaction time, a targeted limited conversion of fructose (1 mol% to 50 mol%) occurs, so that the HMF selectivity is surprisingly high, preferably 60 mol% to 100 mol% can be achieved.

[0069] In a particularly preferred embodiment, the process for converting the fructose present in the reaction solution into HMF and obtaining HMF according to method steps c) and d) is a one-step process. In particular, according to the present invention, the process according to method steps c) and d) is preferably not a two-stage process.

[0070] In a preferred embodiment, the method further comprises the following steps:

[0071] e) cooling the liquid HMF-containing product mixture obtained in step d) to 20 to 80° C., preferably 25 to 70° C., preferably 30 to 60° C., preferably 30 to 55° C., preferably 30 to 50° C., preferably 30 to 45° C., preferably 30 to 40° C., preferably 80° C., preferably 70° C., preferably 60° C., preferably 55° C., preferably 50° C., preferably 45° C., preferably 40° C., preferably 35° C., preferably 30° C. The liquid HMF-containing product mixture in step e) is preferably heated to a temperature of not more than 75° C., preferably not more than 70° C., preferably not more than 60° C., preferably not more than 55° C., preferably not more than 50° C., preferably not more than 45° C., preferably not more than 40° C., preferably not more than 35° C. According to the invention, this can be done in one or two stages.

[0072] In a preferred embodiment of the present invention, the temperature of the liquid HMF-containing product mixture in step e) is set or cooled within the following time period: 0.1-10 min, preferably 0.1-9 min, preferably 0.1-8 min, preferably 0.2-7 min, preferably 0.2-6 min, preferably 0.5-5 min, preferably 0.5-4 min, preferably 0.5-3 min. Preferably, the temperature of the product mixture in step e) is set or cooled within the following time period: at most 10 min, preferably at most 9 min, preferably at most 8 min, preferably at most 7 min, preferably at most 6 min, preferably at most 5 min, preferably at most 4 min, preferably at most 3 min, preferably at most 2 min, preferably at most 1 min, preferably at most 0.5 min.

[0073] Therefore, after reaching a limited fructose conversion of maximum 50 mol % in step e), the HMF-containing product mixture obtained in step d) is cooled to a temperature of 20 to 80° C. This advantageously largely prevents the formation of undesired by-products and the decomposition of the HMF formed.

[0074] The process according to the invention for producing HMF is preferably carried out in a suitable reactor system. According to the invention, this is preferably a continuous reactor system.

[0075] In a particularly preferred embodiment, the continuous reactor system used is designed as a tubular reactor system. Such continuous reactor systems are reactor systems known to the person skilled in the art. In a particularly preferred embodiment, continuous reactor systems, in particular continuous systems, which have virtually no backmixing can also be used. In a particularly preferred embodiment, a plug-flow reactor (PFR) can be used as the continuous reactor system. In a preferred embodiment, the continuous reactor system can also be designed as a flow tube, a stirred tank or a stirred tank cascade. For the purposes of the present invention, a plug-flow reactor (PFR) is understood to mean a so-called ideal flow tube [German: “ideales IR"], i.e. a tubular reactor in which there is a plug flow. This type of reactor is also characterized in particular in that no mixing, reflux or turbulence of the reaction solution takes place, but rather a uniform flow takes place in parallel with the material conversion. The plug flow reactor ensures in particular that each substance fed into the plug flow reactor, in particular each component of the feed, is continuously converted under the same conditions, i.e. all components undergo a conversion process of the same time.

[0076] In a preferred embodiment, the method optionally further comprises the following steps:

[0077] f) Filtration, decolorization and / or purification of the liquid HMF-containing product mixture.

[0078] This means that, in another preferred embodiment, the HMF product mixture is preferably filtered using a suitable filter or a suitable filter system, and the product mixture is decolorized and / or purified, preferably using activated carbon for decolorization and / or purification. Preferably, after step e), the product mixture is filtered using a suitable filter or a suitable filter system, and the product mixture is decolorized and / or purified using, for example, activated carbon. Preferably, before step g) or h), the product mixture is filtered using a suitable filter or a suitable filter system, and the product mixture is decolorized and / or purified using, for example, activated carbon. In a particularly preferred embodiment, after method step e) and / or method step g), the product mixture can be preferably filtered using a suitable filter or a suitable filter system, and decolorized and / or purified in any order, in particular using activated carbon, optionally after step g), using a suitable filter or a suitable filter system for another filtration. In a particularly preferred embodiment, after step e) and / or method step g), first filter using a suitable filter or a suitable filter system, then decolorize and / or purify, in particular using activated carbon, optionally after step g), then filter using a suitable filter or a suitable filter system in this order. According to the invention, filtration is preferably carried out using a sintered metal filter.

[0079] Undesirable by-products, in particular soluble and insoluble humic substances, are preferably removed from the product mixture by filtering the product mixture on a suitable filter or a suitable filter system and decolorizing and / or purifying it, for example on activated carbon.

[0080] In a preferred embodiment of the present invention, the dry matter content of the product mixture obtained in step e) or optionally step f) is 5-50% by weight, preferably 10-40% by weight, preferably at least 5% by weight, preferably at least 10% by weight, preferably at most 40% by weight, preferably at most 60% by weight.

[0081] If the dry matter content of the product mixture obtained in step e) or optionally f) is too low, the invention can provide that the process optionally further comprises the following steps:

[0082] g) The dry matter content of the liquid HMF-containing product mixture is set to 20-70% by weight, preferably 25-50% by weight, preferably 25-45% by weight, preferably 30-45% by weight, preferably 30-40% by weight.

[0083] In another preferred embodiment, the dry matter content of the product mixture obtained in step e) or optionally f) is reduced to 20-70 wt.-%, preferably at least 20 wt.-%, preferably at least 30 wt.-%, preferably at least 40 wt.-%, preferably at least 50 wt.-%, preferably at most 70 wt.-%, preferably at most 60 wt.-%, preferably at most 50 wt.-%.

[0084] In a preferred embodiment, the method further comprises the following steps:

[0085] h) purifying the liquid HMF-containing product mixture by chromatography, ultrafiltration and / or nanofiltration, extraction with a suitable extractant, adsorption on a suitable material with subsequent directed desorption, and / or electrodialysis to separate at least one HMF fraction, and

[0086] i) obtaining at least one HMF fraction.

[0087] That is, preferably at least one HMF fraction is separated from the liquid HMF-containing product mixture by using at least one of the above-mentioned purification methods, so that only other components contained in the product mixture, such as unreacted fructose, glucose or by-products such as organic acids and humic substances, remain. According to the invention, a combination of at least two or more of the above-mentioned purification methods can also be used for separating at least one HMF fraction and / or other fractions optionally comprising one or more other components of the product mixture.

[0088] In an alternative preferred embodiment, the method further comprises the following steps:

[0089] h) purifying the liquid HMF-containing product mixture by chromatography, ultrafiltration and / or nanofiltration, extraction with a suitable extractant, adsorption on a suitable material with subsequent directed desorption, and / or electrodialysis to separate at least one fraction selected from the group consisting of an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction, and

[0090] i) obtaining at least one fraction selected from the group consisting of an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction.

[0091] It can further be provided that at least one of the fractions obtained in step i) is further treated using a purification method selected from chromatography, ultrafiltration and / or nanofiltration, extraction with a suitable extractant, adsorption on a suitable material and subsequent directed desorption, and / or electrodialysis.

[0092] One of the purification methods provided by the method of the present invention is ultrafiltration and / or nanofiltration. Suitable membranes can be used first to concentrate the HMF-containing product mixture of the liquid, and secondly to remove soluble and / or insoluble humic substances, or in the case of nanofiltration, to separate HMF and / or organic acids from the product mixture. Preferably, the concentrated product mixture, the product mixture without soluble and / or insoluble humic substances, the HMF portion and the product mixture without HMF, the HMF portion and / or the organic acid portion and the product mixture without HMF and / or organic acids, or the glucose and / or fructose portion and the product mixture without humic substances and / or glucose and / or fructose, can be obtained by ultrafiltration and / or nanofiltration.

[0093] Another purification method provided by the method according to the present invention is extraction with a suitable extraction agent. In order to extract HMF from the HMF product mixture, it is preferred to use a solvent that is immiscible or almost immiscible with water and has a sufficiently high affinity for HMF. Ideally, the boiling point of the organic solvent is preferably relatively low, and the density difference between water and the solvent is sufficiently high, thereby phase separation can be achieved. Suitable solvents are preferably methyl isobutyl ketone, ethyl acetate, methyl ethyl ketone, butanol, diethyl ether, methyl butyl ether, isopentanol, methyltetrahydrofuran, etc. After the extraction step, an aqueous product mixture containing unreacted fructose and glucose is retained, and an organic phase containing HMF and possible organic acids is obtained.

[0094] Another purification method provided in the method according to the present invention is adsorption onto a suitable material and then desorbing. In principle, HMF can be adsorbed on any material that preferentially adsorbs HMF from a hexose-containing solution. Preferred materials are polymer-based resins (e.g., divinylbenzene-styrene copolymers), adsorbent resins, activated carbon, zeolites, aluminum oxides, non-functionalized resins, or cation exchange resins. Preferably, the product mixture obtained in step e), f) or g) is contacted continuously with the HMF-adsorbent material, but at most until the material is exhausted. The adsorbed HMF is then desorbed with a suitable desorbent such as water or a polar organic solvent such as alcohol, ethyl acetate, THF, etc. HMF can then be obtained from an organic solvent by a suitable method.

[0095] Another purification method provided by the method according to the invention is electrodialysis. This is an electrochemically driven membrane process in which an ion exchange membrane is used in combination with an electric potential difference to separate ionic species from uncharged species or impurities in solution. In the case of the present method, electrodialysis is used to separate a product mixture from inorganic and / or organic cations and anions, for example, to separate a salt and acid mixture from a salt, with levulinic acid and formic acid as byproducts.

[0096] Another purification method provided by the method according to the invention is chromatography. This will be described in more detail below.

[0097] All of the above-mentioned purification methods can be used alone or in combination with one another.

[0098] In step h), the HMF present in the product mixture is particularly preferably separated from other components of the product mixture by chromatography, in particular chromatography on ion exchange resins, in particular cation exchange resins, in particular single-stage or multistage chromatography on ion exchange resins, in particular cation exchange resins.

[0099] In a particularly preferred embodiment of the present invention, the chromatography, in particular chromatography on an ion exchange resin, in particular chromatography on a cation exchange resin, is ion exchange chromatography, in particular cation exchange chromatography.

[0100] In a preferred embodiment of the present invention, the liquid HMF-containing product mixture is separated into at least four fractions, including an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction, by chromatography in step h), and at least one HMF fraction, glucose fraction, fructose fraction and organic acid fraction is obtained in step i).

[0101] According to step h), the product mixture obtained in step e), optionally f) or optionally g) is particularly preferably purified by continuous chromatography. Continuous chromatography is preferably also understood to mean simulated chromatography by countercurrent, for example simulated moving bed chromatography (SMB).

[0102] Continuous chromatography is well known to those skilled in the art. For example, US 2011 / 0137084 A1 shows how the SMB method works. Other suitable chromatography methods are disclosed in A. Rajendran et al.; J. Chromatogr. A 1216 (2009), pp. 709-738.

[0103] A simulated moving bed (SMB) system or further developments of an SMB system, such as sequential SMB (SSMB), intermittent / improved SMB (ISMB) or new MCI (NMCI), advantageously allows separation and recovery of the four fractions described in a continuous operation.

[0104] In a preferred embodiment of the present invention, the chromatography in step h), in particular the chromatography on an ion exchange resin, is a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process or an intermittent simulated moving bed process (ISMB). Preferably, the chromatography in step h), in particular the chromatography on an ion exchange resin, is a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) or a new MCI process (NMCI). Advantageously, by using a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) or a new MCI process (NMCI) in step h), the product mixture obtained in step e), f) or g) can be advantageously purified to continuously separate the HMF fraction, the glucose fraction, the fructose fraction and the organic acid fraction.

[0105] In a preferred embodiment of the present invention, the chromatography in step h), in particular the chromatography on an ion exchange resin, in particular the chromatography on a cation exchange resin, is a one-step process. The chromatography in step h), in particular the chromatography on an ion exchange resin, in particular the chromatography on a cation exchange resin, is preferably a multistage process, preferably a two-stage process.

[0106] The chromatography in step h), in particular chromatography on an ion exchange resin, in particular chromatography on a cation exchange resin, preferably comprises a plurality of stages, preferably at least two stages, preferably at least three stages, preferably two stages, preferably three stages.

[0107] In a preferred embodiment of the present invention, in step h), in a first stage of chromatography, at least one fraction, preferably exactly one fraction, in particular the HMF fraction or the glucose fraction, preferably at least two fractions, preferably exactly two fractions, preferably exactly three fractions are separated.

[0108] In another preferred embodiment of the present invention, in step h), in the second stage of chromatography, at least one fraction, preferably exactly one fraction, preferably at least two fractions, preferably exactly two fractions, preferably exactly three fractions, in particular a glucose fraction, a fructose fraction and an organic acid fraction, or a HMF fraction, a fructose fraction and an organic acid fraction, are separated.

[0109] In a preferred embodiment of the present invention, the first stage of chromatography in step h) is a chromatography process selected from the group consisting of a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) and a new MCI process (NMCI).

[0110] The first stage of chromatography in step h) is preferably an improved simulated moving bed process (ISMB). Preferably, in step h) the first stage, the separation of at least one fraction, preferably exactly one fraction, in particular the HMF fraction or the organic acid fraction, is carried out by a chromatography selected from the group consisting of a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) and a new MCI process (NMCI), preferably by a simulated moving bed process (ISMB).

[0111] In a preferred embodiment of the present invention, the second stage of chromatography in step h) is a chromatography process selected from the group consisting of a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) and a new MCI process (NMCI).

[0112] The first stage of chromatography in step h) is preferably a new MCI process (NMCI). Preferably, in the second stage of step h), at least one fraction, preferably exactly one fraction, preferably at least two fractions, preferably exactly two fractions, preferably at least three fractions, preferably exactly three fractions, in particular a glucose fraction, a fructose fraction and an organic acid fraction, or a HMF fraction, a fructose fraction and an organic acid fraction, are separated by a chromatography selected from a simulated moving bed process (SMB), a sequential simulated moving bed process (SSMB), an improved simulated moving bed process (ISMB) and a new MCI process (NMCI), preferably by a new MCI process (NMCI).

[0113] In particular, at least two-stage chromatographic separations are preferred, wherein the separation of the HMF fraction is carried out in the first stage. Alternatively, in the first stage, the separation of the glucose fraction may occur. Preferably, the first stage of the at least two-stage chromatographic separation is a moving bed process (ISMB). Preferably, the second stage of the at least two-stage chromatographic separation is a new MCI process (NMCI).

[0114] Particularly preferred is a two-stage chromatographic separation, wherein the separation of the HMF fraction occurs in the first stage. Alternatively, the separation of the glucose fraction occurs in the first stage. Preferably, the first stage of the two-stage chromatographic separation is a moving bed process (ISMB). Preferably, the second stage of the two-stage chromatographic separation is a new MCI process (NMCI). Preferably, the organic acid fraction, the fructose fraction and the glucose fraction are separated from each other in the second stage of the two-stage chromatographic separation. Alternatively, in the second stage of the two-stage chromatographic separation, the organic acid fraction, the fructose fraction and the HMF fraction are separated from each other.

[0115] In a preferred embodiment of the present invention, in step h), the chromatography, in particular the chromatography on an ion exchange resin is a chromatography on a cation exchange resin.

[0116] In a preferred embodiment of the present invention, in step h), chromatography, in particular chromatography on an ion exchange resin, is carried out using H + The reaction was carried out in the form of cation exchange resin.

[0117] In a preferred embodiment, in step h), the chromatography, in particular chromatography on an ion exchange resin, is carried out at a temperature of 40 to 80°C, preferably 40 to 70°C, preferably 40 to 60°C, preferably 50 to 80°C, preferably 50 to 70°C, preferably 50 to 60°C, preferably 60 to 80°C, preferably 60 to 70°C.

[0118] The fructose fraction optionally obtained in step i) is preferably recycled continuously to process step a). Advantageously, the fructose fraction optionally obtained in step i) is largely, preferably completely, free of levulinic acid formed. In another preferred embodiment, advantageously, the fructose fraction obtained in step i) is largely, preferably completely, free of levulinic acid and formic acid formed.

[0119] In a particularly preferred embodiment, the fructose fraction optionally obtained in step i), optionally after concentration, is continuously and preferably completely recycled to step a). In another preferred embodiment, the fructose fraction obtained in step i), continuously, optionally after concentration, is at least partly recycled in step a), in particular at least 70%, preferably at least 80%, preferably at least 90%, preferably at least 95%, preferably at least 98%, preferably at least 99% (in each case the weight percentage of the recycled fructose fraction relative to the fructose fraction obtained in step i)).

[0120] According to the invention, "recycled fructose fraction" is understood to mean the aqueous fraction of unconverted fructose obtainable after purification according to the process according to the invention, i.e. step h), which is substantially, preferably completely free of by-products formed during the conversion of fructose, in particular levulinic acid, formic acid and humic substances. The resulting aqueous fraction of unreacted fructose is so pure that, in a preferred embodiment, optionally after concentration, it is directly recycled to process step a), which means that no further purification is required, and after mixing the fructose-containing component and the catalyst system, i.e. step b), it can be used for further conversion into HMF in step c). Therefore, step a) of the process according to the invention particularly preferably provides a fructose-containing component, a salt and acid mixture and a recycled fructose fraction, which are mixed in step b) to obtain a reaction solution. When starting the process according to the invention, since there is initially no recycled fructose fraction in this preferred embodiment, in this case, it is preferred to use a correspondingly larger amount of a fructose-containing component instead.

[0121] In step i) of the process according to the invention, i.e. after the purification is carried out, in addition to the HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction are optionally obtained, in particular in separated form. Advantageously, the individual fractions obtained by the purification process used have such a high purity that they can be used directly in various subsequent processes, optionally after concentration, which means that no further purification is required.

[0122] According to the invention, the optionally obtained fructose fraction is preferably substantially free, in particular completely free, of levulinic acid formed. According to the invention, the fructose fraction is preferably substantially free, in particular completely free, of organic acids formed, in particular levulinic acid and formic acid.

[0123] Disadvantageously, during the HMF synthesis process, levulinic acid is conducive to the formation of humus. Therefore, according to a preferred embodiment, the increase in the levulinic acid content in the reaction solution caused by the recycled fructose part will lead to an increase in humus formed by HMF and carbohydrates, thus significantly reducing the economic efficiency of the method. However, the fructose part optionally obtained in step i) in the method of the present invention is advantageously of such high purity, in particular free of levulinic acid formed, particularly preferably free of levulinic acid and formic acid, that in a preferred embodiment it can be directly recycled to the method, in particular step a) for further conversion, optionally after concentration, in particular without the need for a purification step. In particular, by the limited conversion of fructose provided by the method according to the present invention and the reduction of the formation of related by-products and degradation products, in particular levulinic acid and formic acid and humus, and in a preferred embodiment, the part separated from the product mixture of unconverted fructose is recovered, high HMF selectivity and high HMF yield can be obtained.

[0124] In a particularly preferred embodiment, the process according to the invention consists of process steps a), b), c) and d), in particular no further process steps being carried out between these process steps.

[0125] In a particularly preferred embodiment of the present invention, the process according to the invention comprises process steps a), b), c) and d), wherein no further process steps are carried out between process steps a), b), c) and d), but further process steps are optionally carried out after process step d).

[0126] According to the invention, the process comprises steps a) to d), preferably a) to e), preferably a) to f), preferably a) to g), preferably a) to h), in particular a) to i). According to the invention, the process particularly preferably comprises steps a), b), c), d), e), f), g), h) and i). However, it is also possible that the process comprises steps a), b), c), d), e), h) and i), or a), b), c), d), e), f), h) and i), or a), b), c), d), e), g), h) and i). In a particularly preferred embodiment, the process consists of process steps a) to d), preferably a) to e), preferably a) to f), preferably a) to g), preferably a) to h), in particular a) to i). In a particularly preferred embodiment, the process consists of the process steps a), b), c), d), e), h) and i), or a), b), c), d), e), f), h) and i), or a), b), c), d), e), g), h) and i). In a preferred embodiment, the process is carried out in the order of the process steps a), b), c), d), e), f), g), h) and i). However, it is also possible to carry out the process in the order of the process steps a), b), c), d), e), h) and i), or a), b), c), d), e), f), h) and i), or a), b), c), d), e), g), h) and i).

[0127] According to the invention, in the process for the production of 5-hydroxymethylfurfural according to steps a) to i), the conversion of fructose present in the reaction mixture into HMF and the subsequent purification of the product mixture obtained are carried out continuously in a continuous reactor system with separation into at least four fractions, which means a continuous supply of raw materials and removal of products.

[0128] A continuous process according to the invention is preferably understood to mean a process in which not only the reactor system but also the process for the purification of the product mixture is continuous.

[0129] The present invention enables to provide a process for the production of HMF and / or formic acid and / or levulinic acid, in particular for the co-production from a raw material, ie a fructose-containing component and an optionally recycled fructose fraction.

[0130] Therefore, in a preferred embodiment, the process for producing HMF according to the invention is also a process for producing HMF and formic acid and levulinic acid, comprising steps a) to i) for the targeted production of three products of interest.

[0131] Therefore, in a preferred embodiment, the process according to the invention for producing HMF is also a process for producing HMF and formic acid, which comprises steps a) to i) and is used for producing two valuable substances of interest.

[0132] Therefore, in a preferred embodiment, the process for producing HMF according to the invention is also a process for producing HMF and levulinic acid, comprising steps a) to i) and for producing two valuable substances of interest.

[0133] According to the invention, the glucose fraction obtained in step i) comprises at least 20% by weight of the glucose contained in the product mixture (DM in each case based on the product mixture).

[0134] In another preferred embodiment of the present invention, the glucose fraction optionally obtained in step i) has a sufficiently high purity, in particular is free of fermentation inhibitors, so that it can be used directly, optionally after concentration, as a raw material (feed material) for fermentation processes, in particular for the production of ethanol, in particular the fermentation of glucose to ethanol, and as a raw material for chemical processes, in particular the oxidation of glucose to gluconic acid.

[0135] In another preferred embodiment, part of the glucose optionally obtained in step i) is used for ethanol production, in particular for the fermentation of glucose to form ethanol, in particular for bioethanol production and / or for the production of gluconic acid.

[0136] The present invention therefore also provides a process for producing a feed for a fermentation process, in particular for the production of ethanol, in particular the fermentation of glucose to ethanol, or for producing a starting material, i.e. an educt, in a chemical process, in particular for the production of gluconic acid, in which case the process according to the invention is carried out with process steps a) to i), while obtaining a glucose fraction which can be used as feed or educt.

[0137] In a particularly preferred embodiment, a method for producing ethanol, in particular a method for fermenting glucose to ethanol, is provided, in which case the method according to the invention, in particular method steps a) to i), is carried out, in particular to obtain a glucose fraction, wherein the glucose fraction obtained is used for producing ethanol, in particular for fermenting glucose to ethanol, in particular for producing bioethanol.

[0138] In a further preferred embodiment, the glucose fraction optionally obtained in step i) is used for obtaining gluconic acid, optionally after concentration.

[0139] In a particularly preferred embodiment, a process for producing gluconic acid is provided, which comprises the process according to the invention, in particular process steps a) to i), in particular a process for obtaining a glucose moiety for obtaining glucose and subsequently oxidizing the glucose to gluconic acid.

[0140] In a preferred embodiment of the present invention, the organic acid fraction optionally obtained in step i) is used to separate levulinic acid and formic acid. In another preferred embodiment, the organic acid fraction obtained in step i) is used to separate levulinic acid. In another preferred embodiment, the organic acid fraction obtained in step i) is used to separate formic acid.

[0141] Therefore, the present invention also relates to a process for producing levulinic acid, formic acid or levulinic acid and formic acid, wherein a process comprising steps a) to i) of the present invention is carried out and levulinic acid, formic acid or levulinic acid and formic acid are obtained in one step i).

[0142] In another preferred embodiment of the present invention, the HMF obtained in step i) is partly oxidized in a further step directly to 2,5-furandicarboxylic acid (FDCA), optionally after concentration, which means that no labor-intensive further purification is necessary.

[0143] The present invention therefore also relates to a process for producing FDCA comprising steps a) to i) according to the invention, wherein the HMF obtained in step i) is preferably partially oxidized directly to FDCA, optionally after concentration, and without laborious further purification.

[0144] According to the invention, the optionally obtained glucose fraction comprises 0.8 to 100 wt.-% glucose; 0 to 99.2 wt.-% fructose; up to 2 wt.-%, preferably up to 1 wt.-%, preferably up to 0.5 wt.-%, preferably up to 0.1 wt.-% levulinic acid and formic acid; and up to 10 wt.-%, preferably up to 5 wt.-%, preferably up to 2 wt.-%, more preferably up to 1 wt.-%, preferably up to 0.5 wt.-%, preferably up to 0.1 wt.-% HMF (DM in each case based on the sum of the analyzed components (glucose, fructose, levulinic acid, formic acid, HMF, difructose anhydride (DFA))). According to the invention, the glucose fraction preferably comprises up to 10 wt.-%, more preferably up to 5 wt.-% HMF.

[0145] The fructose fraction optionally obtained in step i) according to the invention comprises at least 70% by weight, preferably at least 80% by weight (in each case DM, based on the product mixture) of the fructose contained in the product mixture.

[0146] According to the invention, the optionally obtained fructose fraction comprises 0 to 60 wt.-% glucose; 40 to 100 wt.-% fructose; at most 2 wt.-%, preferably at most 1 wt.-%, preferably at most 0.5 wt.-%, preferably at most 0.1 wt.-% levulinic acid; at most 2 wt.-%, preferably at most 1.5 wt.-%, preferably at most 1 wt.-%, preferably at most 0.5 wt.-%, preferably at most 0.25 wt.-%, preferably at most 0.1 wt.-% formic acid; and at most 2 wt.-%, preferably at most 1.5 wt.-%, preferably at most 1 wt.-%, preferably at most 0.8 wt.-%, preferably at most 0.6 wt.-%, preferably at most 0.4 wt.-%, preferably at most 0.2 wt.-%, preferably at most 0.1 wt.-% HMF (DM is in each case based on the sum of the analyzed components (glucose, fructose, levulinic acid, formic acid, HMF, difructose anhydride (DFA))). According to the invention, the fructose fraction preferably comprises at most 2 wt.-% HMF. According to the invention, the fructose fraction preferably comprises at most 2 wt.-% levulinic acid. In a particularly preferred embodiment, the ratio of fructose to glucose in the fructose fraction is not less than the ratio in the fructose-containing component provided in step a).

[0147] According to the invention, the organic acid fraction optionally obtained in step i) comprises at least 60% by weight, preferably at least 65% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight, preferably at least 98% by weight, preferably at least 99% by weight, preferably at least 99.5% by weight, preferably at least 99.8% by weight, preferably 100% by weight of the levulinic acid and formic acid contained in the product mixture (DM in each case based on the product mixture).

[0148] According to the present invention, the optionally obtained organic acid fraction comprises levulinic acid and formic acid in an amount of 50% to 100% by weight, preferably 60% to 100% by weight, more preferably 65% ​​to 100% by weight, preferably 70% to 100% by weight, preferably 80% to 100% by weight, preferably 90% to 100% by weight, preferably 95% to 100% by weight, preferably 98% to 100% by weight, preferably 99% to 100% by weight, preferably 99.5% to 100% by weight, preferably 99.7% to 100% by weight (DM in each case based on the sum of the analyzed components (glucose, fructose, levulinic acid, formic acid, HMF, difructose anhydride (DFA)). According to the present invention, the organic acid portion preferably comprises at least 50% by weight of levulinic acid, more preferably at least 60% by weight of levulinic acid, more preferably at least 70% by weight of levulinic acid.

[0149] According to the invention, the HMF fraction obtained in step i) comprises at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, preferably at least 98% by weight, preferably at least 99% by weight, preferably at least 99.5% by weight, preferably at least 99.8% by weight, preferably 100% by weight of the HMF contained in the product mixture (in each case DM, based on the product mixture).

[0150] According to the invention, the HMF fraction comprises an amount of HMF of 80 to 100 wt. %, preferably of 85 to 100 wt. %, preferably of 90 to 100 wt. %, preferably of 95 to 100 wt. %, preferably of 98 to 100 wt. %, preferably of 99 to 100 wt. %, preferably of 99.5 to 100 wt. %, preferably of 99.7 to 100 wt. %; and an amount of levulinic acid and propionic acid of at most 16 wt. %, preferably of at most 14 wt. %, preferably of at most 12 wt. %, preferably of at most 10 wt. %, preferably of at most 8 wt. %, preferably of at most 6 wt. %, preferably of at most 4 wt. %, preferably of at most %; comprises a content of glucose of at most 2 wt.-%, preferably at most 1 wt.-%, preferably at most 0.8 wt.-%, preferably at most 0.6 wt.-%, preferably at most 0.4 wt.-%, preferably at most 0.2 wt.-%, preferably at most 0.1 wt.-%; and a content of fructose of at most 2 wt.-%, preferably at most 1 wt.-%, preferably at most 0.8 wt.-%, preferably at most 0.6 wt.-%, preferably at most 0.4 wt.-%, preferably at most 0.2 wt.-%, preferably at most 0.1 wt.-% (DM is in each case based on the sum of the analyzed components (glucose, fructose, levulinic acid, formic acid, HMF, difructose anhydride (DFA))).

[0151] In a preferred embodiment, in the process according to the invention, in particular in steps a) to g), optionally a) to i), no organic solvents, in particular no ionic liquids, are used.

[0152] In a preferred embodiment, the process according to the invention, in particular steps a) to i), is not carried out under oxygen-reducing conditions.

[0153] With regard to the present invention, the term "and / or" should be understood to mean that all elements of the group connected by the term "and / or" are disclosed as substitutes for each other and as additions to each other in any combination. For the expression "A, B and / or C", this means that the following disclosure should be understood according to this expression: A or B or C or (A and B) or (A and C) or (B and C) or (A, B and C).

[0154] In conjunction with the present invention, the term "comprehensive" should be understood to mean that in addition to the elements explicitly covered by the term, other elements that are not explicitly mentioned can also be added. In conjunction with the present invention, these terms should also be understood to mean that only the elements explicitly mentioned are included, and there are no other elements. In this particular embodiment, the meaning of the term "comprising" is synonymous with the term "consisting of..." In addition, the term "comprehensive" also includes such an entity that, in addition to the explicitly named elements, the entity also contains other unnamed elements that are subordinate in function and quality. In this embodiment, the term "comprising" is synonymous with the term "consisting essentially of..."

[0155] Further preferred embodiments are found in particular in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0156] The invention is explained in more detail with reference to the following exemplary embodiments and the related drawings.

[0157] The attached pictures are as follows:

[0158] Figure 1 is a schematic diagram of a reactor system used in accordance with the present invention.

[0159] Figure 2 is a schematic diagram of the process according to the invention, wherein the components provided in step a) are first mixed in step b), the reaction solution obtained is subsequently heated and the HMF fraction is obtained after a purification step h) (step i)).

[0160] Figure 3 is similar to Figure 2 Schematic diagram of the method according to the invention, wherein in step h) a column chromatography separation is carried out and an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction are obtained (step i)).

[0161] Figure 4 is a schematic diagram of a process according to the invention, wherein the components provided in step a) are heated separately from one another and only subsequently mixed in step b) to obtain a reaction solution, and wherein after a purification step h) an HMF fraction is obtained (step i)).

[0162] Figure 5 is similar to Figure 4 Schematic diagram of the method according to the invention, wherein in step h) a column chromatography separation is carried out and an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction are obtained (step i)).

[0163] Figure 6Results are shown for the synthesis of HMF using 20% ​​DM KH (85% fructose purity) and 0.08 wt% HCl at 145-152°C without added salt. Results are presented in terms of fructose conversion, selectivity for HMF, levulinic acid and formic acid, and balance.

[0164] Figure 7 Results are shown for the synthesis of HMF using 20% ​​DM KH (85% fructose purity) and 0.18 wt% HNO3 at 145-152°C without added salt. Results are presented in terms of fructose conversion, selectivity for HMF, levulinic acid and formic acid, and equilibrium.

[0165] Figure 8 Shown are the reaction temperature required for -18% fructose conversion as a function of sodium content at a constant chloride content, as well as the selectivity for HMF, levulinic acid, and formic acid and the degree of equilibrium at that point.

[0166] Fig. 9 The reaction temperature required for a fructose conversion of -20% as a function of sodium content at a constant nitrate content is shown, as well as the selectivity for HMF, levulinic acid, and formic acid and the degree of equilibrium at that point.

[0167] Fig.10 Shown are the reaction temperatures required for -20% fructose conversion as a function of the concentration of the salt and acid mixture with a constant chloride / sodium ratio, as well as the selectivities for HMF, levulinic acid, and formic acid and the degree of equilibrium at that point.

[0168] Fig.11 Shown are the reaction temperatures required for -27% fructose conversion as a function of the concentration of the salt and acid mixture with a constant nitrate / sodium ratio, as well as the selectivities for HMF, levulinic acid, and formic acid and the degree of equilibrium at that point.

[0169] Fig.12 Results are shown for the synthesis of HMF using 20% ​​DM KH (85% fructose purity) and 0.12 wt% HCl / CaCl2 at temperatures of 165-169°C. Results are presented in terms of fructose conversion, HMF, levulinic acid and formic acid selectivity, and equilibrium.

[0170] Fig.13 Results are shown for the synthesis of HMF using 20% ​​DM KH (85% fructose purity) and 0.12 wt% HCl / MgCl2 at temperatures of 162-169°C. Results are presented in terms of fructose conversion, HMF, levulinic acid and formic acid selectivity, and equilibrium. DETAILED DESCRIPTION

[0171] Example

[0172] In the method according to the present invention, a fructose-containing component with a variable ratio of fructose to glucose and an aqueous solution of a salt and acid mixture are used as starting materials. The fructose-containing component is mixed with an aqueous solution of a salt and acid mixture to obtain a reaction solution with a dry matter content of ≥20% DM. The reaction solution obtained in this way is pumped into a heated tubular reactor (8 mm in outer diameter, 6 mm in inner diameter, 630 mm in length) by means of a high performance liquid chromatography pump. The tubular reactor is designed as a countercurrent double-tube heat exchanger, and the temperature is controlled by the heat-conducting oil in the outer tube of the heat exchanger, and the temperature of the heat-conducting oil is controlled by a thermostat. After the so-called heating zone of the tubular reactor, a direct transition to the cooling zone is made. This is also designed as a countercurrent double-tube heat exchanger (inner tube size carrying the product: 8 mm in outer diameter, 6 mm in inner diameter, 125 mm in length). In the cooling zone, the reaction solution is cooled to room temperature and conversion is stopped. The product mixture is then filtered through a metal sintered filter (pore size 7 m) to remove any insoluble humus that may be formed. The pressure in the reactor system was set by means of a pressure-maintaining valve in order to avoid boiling of the reaction solution and thus the occurrence of steam bubbles (about 1 MPa at 180° C.).

[0173] The following examples illustrate the implementation of the method of the present invention at different salts and acids, different acid or salt concentrations and different temperatures. In addition, comparative experiments were performed without adding salt.

[0174] In all experiments, samples were collected during the test and analyzed by high performance liquid chromatography (BIORAD Aminex 87-H, 5 mmol / L sulfuric acid, 50°C). Subsequently, the fructose conversion rate, HMF selectivity and equilibrium (equilibrium = (total amount of unconverted sugar, HMF and formic acid (in moles) * 100 / sugar used (in moles))) were calculated based on the analysis results. Levulinic acid is not taken into account in the equilibrium because one molecule of formic acid and one molecule of levulinic acid are obtained from one molecule of HMF.

[0175] Example 1: HMF synthesis with 0.08 wt% hydrochloric acid (comparative experiment without adding salt)

[0176] Fructose syrup with a fructose purity of 85% and a DM content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with hydrochloric acid so that the dry matter content of the resulting solution was 20% DM and the hydrochloric acid content was 0.08 wt% (equivalent to 0.025 mol / L) based on the total solution. The pH of the reaction solution was 1.52. The reaction solution was then reacted in a heating zone of 145°C–152°C (thermal oil temperature) with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state. The results of fructose conversion, HMF selectivity, levulinic acid selectivity, formic acid selectivity and equilibrium are shown in Figure 2. Figure 6 And as shown in Table 1.

[0177]

[0178] Table 1: Fructose conversion, HMF selectivity, levulinic acid selectivity, and formic acid selectivity as well as equilibrium as a function of reaction temperature when 0.08 wt% HCl is used.

[0179] Example 2: HMF Synthesis with 0.18 wt% Nitric Acid (Comparative Experiment without Addition of Salt)

[0180] Fructose syrup with a fructose purity of 85% and a DM content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with nitric acid so that the dry matter content of the resulting solution was 20% DM and the nitric acid content was 0.18 wt% (equivalent to 0.03 mol / L) based on the total solution. The pH of the reaction solution was 1.44. The reaction solution was then reacted in a heating zone of 145°C–150°C (thermal oil temperature) with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state. The results of fructose conversion, HMF selectivity, levulinic acid selectivity, formic acid selectivity and equilibrium are shown in Figure 2. Figure 7 And as shown in Table 2.

[0181]

[0182]

[0183] Table 2: Fructose conversion, HMF selectivity, levulinic acid selectivity, and formic acid selectivity as well as equilibrium as a function of reaction temperature when 0.18 wt% nitric acid is used.

[0184] Example 3: HMF Synthesis Using Sodium Chloride / Hydrochloric Acid Mixtures - Effect of the Sodium Chloride / Hydrochloric Acid Ratio

[0185] Fructose syrup with a fructose purity of 85% and a DM content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with hydrochloric acid and sodium chloride in the desired proportions so that the dry matter content of the resulting solution was 20% DM and the chloride content was 0.09 wt. % (equivalent to 0.03 mol / L) based on the total solution. The chloride / sodium ratio, the salt / acid ratio and the resulting pH value are shown in Table 3.

[0186]

[0187] Table 3: Chlorine content, chlorine / sodium ratio, salt / acid ratio and pH value in the reaction solution used in Example 3 and reaction temperature.

[0188] These reaction solutions were then converted in the heating zone with a residence time of 5.6 min at the reaction temperature (thermal oil temperature) shown in Table 3. After each temperature increase, the system was given 2 h to reach a steady state.

[0189] Figure 8 Table 4 shows the reaction temperature required for a fructose conversion of 18% and the selectivity and equilibrium of HMF, levulinic acid and formic acid obtained.

[0190]

[0191]

[0192] Table 4: Selectivities of HMF, levulinic acid and formic acid and the degree of equilibrium, depending on the sodium content (chlorine concentration constant), at the reaction temperature required for 18% fructose conversion.

[0193] Applicants have found that with increasing sodium content and thus pH, higher temperatures are required to achieve the same conversion (see Figure 6 ), but at the same time, the HMF selectivity increased from 85% in the absence of sodium to 94% at a sodium content of 500 mg / L.

[0194] Example 4: HMF Synthesis Using Sodium Nitrate / Nitric Acid Mixtures - Effect of Sodium Nitrate / Nitric Acid Ratio

[0195] Fructose syrup with a fructose purity of 85% and a dry matter content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with nitric acid and sodium nitrate in the desired proportions so that the resulting solution had a dry matter content of 20% DM and a nitrate content of 0.19 wt. % (equivalent to 0.03 mol / L) based on the total solution. The nitrate / sodium ratio, the salt / acid ratio and the resulting pH value are shown in Table 5.

[0196]

[0197] Table 5: Nitrate content, nitrate / sodium ratio, salt / acid ratio and pH value in the reaction solution used in Example 4 and reaction temperature.

[0198] These reaction solutions were then converted in the heating zone with a residence time of 5.6 min at the reaction temperature (thermal oil temperature) shown in Table 5. After each temperature increase, the system was given 2 h to reach a steady state.

[0199] Fig. 9 Table 6 shows the reaction temperature required for a fructose conversion of 20% and the selectivity and equilibrium of HMF, levulinic acid and formic acid obtained.

[0200] Here it can also be seen that with increasing sodium content and thus pH, higher temperatures are required to achieve the same conversion, but at the same time the selectivity of HMF increases significantly from 86.3% (at 19.7% conversion) in the absence of sodium to 93.1% (at 17.6% conversion) at a sodium content of 600 mg / L. If the same conversion is compared, the selectivity of the by-products levulinic acid and formic acid is also lower in the presence of sodium.

[0201]

[0202]

[0203] Table 6: Selectivities for HMF, levulinic acid and formic acid and carbon balance as a function of the sodium content (nitrate concentration constant) at the reaction temperature required for 18% fructose conversion.

[0204] Example 5: HMF Synthesis Using Hydrochloric Acid / Sodium Chloride Mixtures - Effect of Acid / Salt Mixture Concentration

[0205] Fructose syrup with a fructose purity of 85% and a dry matter content of 75% was used as starting material. The fructose syrup was diluted with deionized water and mixed with a mixture of hydrochloric acid and sodium chloride with a chloride / sodium ratio of 1.3. Different reaction solutions were prepared, all with a dry matter content of 20% DM and a concentration of the acid / salt mixture variable between 0.01–0.75 wt. % based on the total solution.

[0206] These reaction solutions were then reacted in the heating zone at the reaction temperature (thermal oil temperature) shown in Table 7 with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state.

[0207]

[0208] Table 7: Concentration of the hydrochloric acid / sodium chloride mixture of the reaction solution used in Example 5, pH value and reaction temperature.

[0209] exist Fig.10 In Table 8, the necessary reaction temperature and the resulting selectivities and equilibrium of HMF, levulinic acid and formic acid for a fructose conversion of 20% are shown.

[0210]

[0211]

[0212] Table 8: Selectivities of HMF, levulinic acid and formic acid at different reaction temperatures and the degree of equilibrium, depending on the concentration of the acid / salt mixture with a constant chloride / sodium ratio.

[0213] As the salt concentration increases, the temperature needs to be significantly reduced to achieve the same conversion. It can also be seen that even at higher fructose conversions >30%, a high HMF selectivity of -90% can still be achieved.

[0214] Example 6: HMF Synthesis Using Nitric Acid / Sodium Nitrate Mixtures - Effect of Acid / Salt Mixture Concentration

[0215] Fructose syrup with a fructose purity of 85% and a dry matter content of 75% was used as starting material. The fructose syrup was diluted with deionized water and mixed with a mixture of nitric acid and sodium nitrate, with a nitrate / sodium ratio of 1.2. Different reaction solutions were prepared, all with a dry matter content of 20% DM and a concentration of the acid / salt mixture variable between 0.01–1.5 wt. % based on the total solution. These reaction solutions were then reacted in a heating zone at the reaction temperature (thermal oil temperature) shown in Table 9 with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state.

[0216]

[0217] Table 9: Concentration of nitric acid / sodium nitrate mixture of the reaction solution used in Example 5, pH value and reaction temperature.

[0218] exist Fig.11 In Table 10, the necessary reaction temperature and the resulting selectivities and equilibrium of HMF, levulinic acid and formic acid for a fructose conversion of 27% are shown.

[0219]

[0220]

[0221] Table 10: Selectivities of HMF, levulinic acid and formic acid at different reaction temperatures and the degree of equilibrium, depending on the concentration of the acid / salt mixture with a constant nitrate / sodium ratio.

[0222] As the salt concentration increases, the temperature needs to be significantly reduced to achieve the same conversion. It can also be seen that even with higher fructose conversions >37%, a high HMF selectivity of ∼90% can still be achieved. Even with a fructose conversion of ∼47%, a HMF selectivity of ∼89% was achieved.

[0223] Example 7: HMF Synthesis Using 0.11 wt% Hydrochloric Acid / Calcium Chloride Mixture

[0224] Fructose syrup with a fructose purity of 85% and a dry matter content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with a mixture of hydrochloric acid and calcium chloride to obtain the same amount of free acid as in Example 5 with 0.12% by weight HCl / NaCl (i.e., Table 7, Test 2). The pH of the reaction solution was 2.08. The reaction solution was then reacted in a heating zone at a temperature of 165°C–169°C (thermal oil temperature) with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state. Fig.12 Table 11 and Table 12 show the results of fructose conversion, HMF selectivity, levulinic acid selectivity, formic acid selectivity, and equilibrium degree.

[0225]

[0226] Table 11: Fructose conversion, HMF selectivity, levulinic acid selectivity, and formic acid selectivity as well as carbon balance as a function of reaction temperature when 0.12 wt% HCl / CaCl2 is used.

[0227] Example 8: HMF Synthesis Using 0.12 wt% Hydrochloric Acid / Magnesium Chloride Mixture

[0228] Fructose syrup with a fructose purity of 85% and a dry matter content of 75% was used as the starting material. The fructose syrup was diluted with deionized water and mixed with a mixture of hydrochloric acid and magnesium chloride to obtain the same content of free acid as in Example 5 using 0.12 wt. % HCl / NaCl (Table 7, Test 2). The pH of the reaction solution was 2.09. The reaction solution was then converted in a heating zone at 162°C–169°C (thermal oil temperature) with a residence time of 5.6 min. After each temperature increase, the system was given 2 h to reach a steady state. Fig.13 Table 12 and Table 12 show the results of fructose conversion, HMF selectivity, levulinic acid selectivity, formic acid selectivity, and equilibrium degree.

[0229]

[0230]

[0231] Table 12: Fructose conversion, HMF selectivity, levulinic acid selectivity, and formic acid selectivity as a function of reaction temperature and the degree of equilibrium when 0.12 wt% HCl / MgCl2 is used.

[0232] Examples 7 and 8 show that positive effects with regard to high HMF selectivity are also achieved when other cations are used, here calcium and magnesium.

Claims

1. A method for producing 5-hydroxymethylfurfural HMF, comprising the following steps: a) providing a catalyst system comprising a component comprising fructose and a solution comprising a salt and an acid mixture, b) mixing the fructose-containing component with the catalyst system to obtain a reaction solution, c) converting fructose present in the reaction solution into HMF at a temperature of 90° C. to 200° C. to obtain a liquid HMF-containing product mixture; and d) obtaining a liquid HMF-containing product mixture; wherein no organic solvent is used in steps a) to d) and the salt is an alkali metal salt or an alkaline earth metal salt, The acid is an inorganic acid selected from hydrochloric acid, sulfuric acid and nitric acid; The salt is a salt of an inorganic acid selected from the group consisting of alkali metal halides, alkaline earth metal halides, alkali metal nitrates, alkaline earth metal nitrates, alkali metal sulfates, alkaline earth metal sulfates, alkali metal phosphates, alkaline earth metal phosphates, and mixtures thereof; The HMF selectivity in step c) is 60 to 100 mol %.

2. The method according to claim 1, wherein: The concentration of the salt and acid mixture is from 0.01 to 2.00% by weight, based on the total weight of the reaction solution obtained in process step b).

3. The method according to any one of claims 1 to 2, wherein: The pH of the reaction solution obtained in process step b) is from 1.2 to 4.

5.

4. The method according to claim 3, wherein: The pH of the reaction solution obtained in process step b) is from 1.5 to 3.

5. The method according to claim 1, wherein: The reaction solution obtained in process step b) and used in process step c) has a carbohydrate content of 5 to 50% by weight, carbohydrate dry matter, relative to the total weight of the reaction solution.

6. The method according to claim 5, wherein: The fructose content of the reaction solution obtained in process step b) and used in process step c) is from 40 to 100% by weight, fructose dry matter relative to carbohydrate dry matter.

7. The method according to claim 1, wherein: The fructose-containing component is a solid fructose-containing component or a liquid fructose-containing component.

8. The method according to claim 7, wherein: The solid fructose-containing component is fructose.

9. The method according to claim 7, wherein: The liquid fructose-containing component is fructose syrup or fructose solution.

10. The method according to claim 1, wherein: The ratio of salt to free acid in the reaction solution obtained in process step b) is from 0.8 to 10 mol / mol.

11. The method according to claim 1, wherein: In the reaction solution obtained in process step b), the ratio of anions in the mixture of salt and acid to cations in the salt of the mixture of salt and acid is from 0.5 to 4 mol / mol.

12. The method according to claim 1, wherein: The concentration of the anions of the catalyst system in the reaction solution obtained in process step b) is 1×10 -5 To 0.6mol / L.

13. The method according to claim 1, wherein: Prior to process step b), the temperature of the fructose-containing component provided in process step a), the catalyst system or both is set to 90° C. to 200° C., or wherein, The temperature of the reaction solution obtained in process step b) is set at 90°C to 200°C.

14. The method according to claim 11, wherein: The process is carried out such that a fructose conversion of 1 to 50 mol % is achieved in process step c).

15. The method according to claim 1, wherein: Apart from the catalyst system, no further catalytically active components are used in the process.

16. The method according to claim 1, comprising the steps of: e) cooling the liquid HMF-containing product mixture to a temperature between 20°C and 80°C.

17. The method according to claim 1, comprising the steps of: f) filtering, decolorizing and / or purifying the liquid HMF-containing product mixture.

18. The method according to claim 1, comprising the steps of: g) The liquid, HMF-containing product mixture is adjusted to a dry matter content of 20 to 70% by weight.

19. The method according to claim 1, comprising the steps of: h) purifying the liquid HMF-containing product mixture using chromatography, ultrafiltration and / or nanofiltration, extraction with a suitable extractant, adsorption on a suitable material with subsequent directed desorption, and / or electrodialysis to separate at least one HMF fraction, and i) obtaining at least one HMF fraction.

20. The method according to claim 19, wherein: In step h), the liquid HMF-containing product mixture is separated into at least four fractions, including an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction, using chromatography, and in step i), at least an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction are obtained.

21. The method according to claim 20, wherein: The fructose fraction obtained in process step i) is recycled into step a).

22. The method according to claim 20, wherein: The glucose obtained in process step i) is partly used for the production of ethanol.

23. The method according to claim 20, wherein: The organic acid fraction obtained in process step i) is used to separate levulinic acid and formic acid.

24. The method according to any one of claims 20 to 23, wherein: The HMF obtained in process step i) is partially oxidized directly and in a further step to 2,5-furandicarboxylic acid without further purification.

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