WO2016207365A1 - Method for continuously producing 5-hydroxymethylfurfural (hmf) in a reactor arrangement - Google Patents

Abstract

The invention relates to a method for continuously producing 5-hydroxymethylfurfural (referred to as HMF below, a compound of the formula (I)) in a reactor arrangement, having the following steps: - setting reaction conditions in a mixture G comprising - one, two, or more reactant compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, - one, two, or more organic salts with a melting point < 180 °C and a boiling point > 200 °C at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation, - water, - 5-hydroxymethylfurfural (HMF) in a concentration ranging from 15 wt.% to 35 wt.%, based on the total mass of the mixture G, and - optionally additional substances such that in the set reaction conditions, a quantity of the one reactant compound or at least one of the two or more reactant compounds is converted into 5-hydroxymethylfurfural (HMF).

Description

 Process for the continuous production of 5-hydroxymethyl furfural (HMF) in a reactor arrangement

The present invention relates to a process for the continuous production of 5-hydroxymethylfurfural (hereinafter referred to as HMF, compound of formula (I))

(i) in a reactor arrangement, with the following step:

Adjusting reaction conditions in a mixture G comprising one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation,

Water, 5-hydroxymethylfurfural (HMF) at a concentration in the range of 15

Wt .-% to 35 wt .-%, based on the total mass of the mixture G, optionally further substances, so that at the set reaction conditions, an amount of a reactant compound or at least one of the two or more educt compounds to 5-hydroxymethylfurfural (HMF) implements.

Numerous methods of producing HMF from hexoses, oligosaccharides and polysaccharides are known. HMF is usually prepared by acid-catalyzed dehydration of hexoses such as glucose or fructose. Typical product mixtures are pH-acidic solutions, which in addition to HMF usually contain unreacted starting materials and / or by-products. The use of ionic liquids (hereinafter also referred to only as "IL") (an ionic liquid in the context of the present invention is one or two organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013, 25 hPa) as solvent in the HMF synthesis is particularly advantageous, since high yields of HMF are usually obtained in these solvents Since the dehydration of fructose is usually catalysed by Brönsted acids, it is advantageous to ensure that the Anion of the acid used and the anion of the IL to agree to an additional (and undesirable) to change the composition of the product mixture (by entry of the anion of the acid used) to avoid, especially if the acid (s) used a Have boiling point, which is at least a pressure value in the range of 0, 1 to 500 mbar lower than the boiling point of the 5-Hyd roxymethylfurfurals at the same pressure value.

The separation of HMF from a product mixture which, in addition to HMF, also contains starting materials and / or by-products of the HMF synthesis, is generally complicated and hinders the production of pure HMF. The separation of HMF from pro- Duktgemischen comprising ionic liquids as a solvent is further complicated because of the interactions of the HMF with the solvent.

Our own investigations have shown that a comparatively high concentration of HMF (during or after the preparation) in a product mixture frequently favors the formation of undesired dimers, oligomers and / or polymers of the HMF. The product mixtures disclosed in the relevant prior art therefore have a comparatively low concentration of HMF. For example, the scientific article "Entrainer-intensified vacuum reactive distillation process for the separation of 5-hydroxylmethylfurfural from the dehydration of carbohydrates catalyzed by a metal salt ionic liquid", Green Chemistry, 2012, 14, 1220-1226, generally discloses on page 1223 , left column, first full paragraph excerpt: "[...] and the fraction of 5-HMF in [OMIM] CI is always less than 10% in the dehydration of carbohydrate [...]".

The dehydration of fructose in ionic liquids (IL) is well described in the literature and high yields of HMF are obtained in these solvents (see "Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources", Chemical Reviews 2013, 1 13, pages 1499 to 1597. However, ionic liquids are typically expensive, so it is desirable to achieve a relatively high mass ratio of fructose (or other reactant compounds) used to IL without lowering HMF selectivity to an undesirable level In addition, it is important for economic process design to use ionic liquids which are long-term stable at temperatures up to 220 ° C. and in combination with aqueous carbohydrate mixtures (educt mixtures) .Furthermore, it is important that both the HMF prepared and the ILs subsequently largely non-destructive as value products from each other It can be separated, for example, to be able to return the ILs in the manufacturing process.

Further methods known from the prior art:

EP 2 813 494 A1 discloses "a process for the preparation of 5-hydroxymethylfurfural (HMF)" (title), preferably an embodiment of a corresponding process "in which the intermediate mixture or parts to be transferred to the second reactor (fraction) thereof or upon entry into the second reactor are subjected to the conditions of distillation [...] whereby HMF is separated "(see section [0061]). It was a primary object of the present invention to provide an improved process for the continuous production of 5-hydroxymethylfurfural in a reactor assembly which largely satisfies the above-mentioned claims.

The object is achieved by an inventive method for the continuous production of 5-hydroxymethylfurfural (HMF) in a reactor arrangement, with the following step:

Setting reaction conditions in a mixture G comprising one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa selected from the group of organic salts with an imidazolium or phosphonium cation, - water,

5-hydroxymethylfurfural (HMF) in a concentration in the range of 15 wt .-% to 35 wt .-%, based on the total mass of the mixture G, optionally further substances, so that at the set reaction conditions, an amount of a

Reactive or at least one of the two or more reactant compounds to 5-hydroxymethylfurfural (HMF).

In this case, the concentration of the HMF in the reaction mixture (ie a mixture G or a mixture resulting therefrom) is preferably increased at least temporarily (but preferably throughout the reaction period), ie the reaction for forming the HMF predominates at least temporarily (but preferably throughout the entire reaction) Reaction time) in comparison with optionally competing reactions of the HMF to secondary products. A "reactor arrangement" in the context of the present invention collectively designates a single reactor or a number of reactors arranged in parallel and / or in series Particularly preferred is a method according to the invention (as described above, preferably as defined above as preferred), wherein the reactor arrangement consists of a In some cases, a preferred reactor arrangement is a combination of (i) a stirred tank reactor and a tubular reactor, or (ii) a tubular reactor and a reactor, and / or a plurality of reactors Stirred tank reactor, which are each arranged one after the other (serial arrangement).

The term "reaction conditions in a mixture G" comprises in particular the reaction parameters (a) reaction temperature, (b) pressure, (c) concentration and quantitative ratios of the substances / compounds present (starting materials, products, catalysts, solvents), in each case based on the mixture G. A "process for the continuous production of 5-hydroxymethylfurfural (HMF)" in the context of the present invention is when a continuous or semi-continuous process is carried out in its entirety so that continuously (ie, for example, regardless of the discontinuous design individual steps of a semi-continuous process) HMF is formed. For the purposes of the present invention, there is then a "continuous" production of 5-hydroxymethylfurfural (HMF) when the period of preparation of HMF (ie, the time period under which conditions are set in the mixture G) the conversion to HMF takes place) is at least twice as large as the average residence time of the said organic salts with a melting point <180 ° C. and a boiling point> 200 ° C. at 1013.25 hPa in the reactor arrangement. as described above), the period of preparation of HMF is at least 10 times the average residence time of said organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa in the reactor arrangement in a process according to the invention for the continuous preparation of 5-hydroxymethylfurfural (HMF) (as described above, preferably as previously defined as preferred) in a reactor assembly for an uninterrupted period of at least 8 hours, preferably at least 24 hours, producing HMF in the reactor assembly. The process according to the invention defines that an amount of one educt compound or at least one of the two or more educt compounds converts to 5-hydroxymethylfurfural (HMF) in the mixture G, the mixture G 5-hydroxymethylfurfural (HMF) already having a concentration in the range of 15% by weight to 35% by weight, based on the total mass of the mixture G. It has surprisingly been found in our own investigations that, even in the presence of such HMF concentrations, a (further) conversion of reactant compounds to HMF takes place without that the selectivity of the conversion to HMF decreases to unacceptable levels. Preferably, the selectivity is at least 50%, more preferably at least 70%. The process according to the invention offers various advantages, since it allows recycling of the ionic liquids together with residual amounts of HMF in the production process. Our own investigations have shown that the conversion to HMF at already present comparatively high HMF concentrations (at least 15% by weight, based on a corresponding total mixture) is only possible in combination with the specific ILs mentioned above in the text. Only these ILs stabilize the comparatively high amount of HMF in such a way that degradation and side reactions can be largely avoided. This has the consequence that the mixture that results after the conversion to HMF, not nearly all HMF must be removed by means of separation operations. A common way of separation is a distillation. However, our own investigations have shown that distillation usually always leads to thermal loading of the HMF. This thermal load regularly favors the formation of undesired by-products. The longer this thermal load persists or the more intense this thermal load is, the higher the risk of the formation of undesired by-products, in particular if a largely quantitative separation of the HMF is to be achieved. Our own investigations have shown that this risk can be significantly reduced if relatively mild and only short-lasting distillation conditions are present. Although this has the consequence of not quantitatively separating HMF, this disadvantage can be neglected in many cases because unseparated HMF is returned to the process along with some or all of the ILs.

Preferably, the process according to the invention (as described above, preferably as defined above as preferred) before the step of adjusting the reaction conditions in the mixture G comprises the additional step:

- Add in the mixture G - One or more acids (as a catalyst (s) for the reaction of the reactant compound or at least one of the two or more reactant compounds to 5-hydroxymethylfurfural (HMF)) selected from the group consisting of homogeneous acids and heterogeneous acids, preferably the Anion or the anions of the one or more acids is identical or are each identical to the anion of or one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, - preferably added to the mixture G of one or more acids (as catalysts) for the reaction of the one educt compound or at least one of the two or more educt compounds to 5-hydroxymethylfurfural (HMF)) selected from the group consisting of sulfuric acid, phosphoric acid , Methanesulfonic acid and p-toluenesulfonic acid, preferably the one or at least one of the plurality of acids is methanesulfonic acid, preferably the anion or the anions of the one or more acids are identical or in each case identical with the anion of the one or two or more organic salts having a melting point <180 ° C. and a boiling point> 200 ° C. at 1013, 25 hPa. Alternatively, the mixture G comprises as further substance one or more acids selected from the group consisting of homogeneous acids and heterogeneous acids, wherein preferably the anion or the anions of the one or more acids is identical or in each case identical with the anion of or one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa.

Preferably, the mixture G comprises one or more acids selected from the group consisting of sulfuric acid, phosphoric acid, methanesulfonic acid and p-toluenesulfonic acid, more preferably, the one or at least one of the plurality of acids is methanesulfonic acid. In any case, it is preferable that preferably the anion or the anions of the one or more acids are identical or are each identical to the anion of the or the one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa.

In our own investigations, particularly high yields of HMF were achieved if in the mixture G the methanesulfonic acid and / or an acid (preferably one of the above-mentioned individual acids) was present, whose anion is identical to the anion of the organic used Salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa. Such embodiments are therefore preferred.

Particularly preferred is a method according to the invention (as described above, preferably as defined above as preferred), wherein the mixture G is a solids-free mixture, which preferably comprises a single liquid phase.

Preferably, the total amount of (i) is water and (ii) compounds having a boiling temperature which is at least a pressure in the range of 0, 1 to 500 mbar lower than the boiling point of 5-hydroxymethylfurfural at the same pressure value in the mixture G. at most 10% by weight, based on the total mass of the mixture G. Our own investigations have shown that a total amount of (i) and (ii) of (significantly) greater than 10% by weight regularly leads to an undesired precipitation of water-insoluble impurities ( eg water-insoluble humins), in particular if the water content in the total amount of (i) and (ii) is at least 50% by weight, based on the total amount of (i) and (ii). Particularly preferably, the total amount of (i) and (ii) is at most 5% by weight, based on the total mass of the mixture G.

Particularly preferred is a method according to the invention (as described above, preferably as defined above as preferred), wherein the one, two or more educt compounds comprise one, two or more than two compounds selected from the group consisting of fructose, glucose, oligosaccharides comprising fructose units, oligosaccharides comprising glucose units, polysaccharides comprising fructose units and polysaccharides comprising glucose units, preferably one, two or more than two compounds selected from the group consisting of fructose, oligosaccharides comprising fructose units and polysaccharides comprising fructose units. In many cases, a process according to the invention is preferred (as described above, preferably as defined above as preferred) wherein the mixture G is directly preparable by (i) respectively preparing or providing (a) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa selected from the group of organic salts with an imidazolium or phosphonium cation and (b) one, two or more educt compounds selected from the group consisting of hexoses, Oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (c) water and (d) 5-hydroxymethylfurfural (HMF) in a concentration in the range of 15% by weight to 35% by weight, based on the Total mass of the mixture G and (ii) mixing the components (a), (b), (c) and (d).

More preferably, the mixture G is preparable by (i) respectively preparing or providing (a) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa selected from the group the organic salts having an imidazolium or phosphonium cation and (b) one, two or more reactant compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (ii) reacting an amount of the one Reactant compound or at least one of the two or more starting compounds to 5-hydroxymethylfurfural (HMF), so that the mixture G results, comprising one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose Units, one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa selected from the group of organic salts with an imidazolium or phosphonium cation,

Water,

5-hydroxymethylfurfural (HMF) in a concentration in the range from 15% by weight to 35% by weight, based on the total mass of the mixture G, optionally further substances.

Particularly preferred is a preparation of the mixture G described above, wherein the total amount of the educt compounds (component (b)) consists of a syrup, preferably from a fructose syrup. Typically, such syrups include water. Particularly preferred syrups are fructose syrups whose fructose content is at least 85% by weight, preferably at least 90% by weight, more preferably at least 94% by weight, based in each case on the total mass of the anhydrous syrup. Typical other ingredients of such syrups are comparatively small amounts of other monosaccharides (e.g., glucose, mannose, idose, galactose), hexose oligosaccharides (e.g., maltose), hexose polysaccharides, inorganic salts.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as preferred), wherein in mixture G the mass fraction of fructose predominates, based on the total mass of all carbohydrates in mixture G, preferably the mass fraction of fructose is greater than 80 wt. %, based on the total mass of all carbohydrates in the mixture G.

Those skilled in the art are aware of methods for determining the total mass of all carbohydrates in the mixture G (e.g., by HPLC or ion chromatography).

The mixture G defined according to the process according to the invention comprises water. This water comes, inter alia, from the dehydration of the educt compounds. In addition, additional water can be introduced into the mixture G by the educt compounds used (see what was said about syrups above).

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein the one or at least one of two or more of said organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa is selected from the group of organic salts having an imidazolium or phosphonium cation and an anion selected from the group consisting of methylsulfonate and tosylate. is preferably selected from the group of organic salts having a dialkylimidazolium cation or tetraalkylphosphonium cation, more preferably selected from the group of organic salts with a dialkylimidazolium cation or tetraalkylphosphonium cation and an anion selected from the group consisting of methylsulfonate and tosylate.

The anion "methylsulfonate" (methylsulfonate is also referred to as methanesulfonate and mesylate) is a compound of formula (II)

O

I i

H _Q CSO

(II).

The anion "tosylate" is a compound of the formula (III)

(III).

Preferred organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa are thus combinations of:

(i) imidazolium cation and methyl sulfonate anion,

(ii) imidazolium cation and tosylate anion,

(iii) phosphonium cation and methylsulfonate anion,

(iv) Phosphonium cation and tosylate anion. Particularly preferred organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa are thus combinations of:

(v) dialkylimidazolium cation and methyl sulfonate anion,

(vi) dialkylimidazolium cation and tosylate anion, (vii) tetraalkylphosphonium cation and methylsulfonate anion,

(viii) tetraalkylphosphonium cation and tosylate anion.

Preferred dialkylimidazolium cations are selected from the group consisting of 1, 3-dimethylimidazolium, 1, 3-diethylimidazolium, 1, 3-di (1-propyl) -imidazolium, 1, 3-di (2-propyl) -imidazolium, 1 , 3-di (1-allyl) -imidazolium, 1, 3-di (1-butyl) -imidazolium, 1, 3-di (1-octyl) -imidazolium, 1, 3-di (1-dodecyl) -imidazolium , 1,3-di (1-tetradecyl) -imidazolium, 1,3-di (1-hexadecyl) -imidazolium, 1-ethyl-3-methylimidazolium, 1- (1-butyl) -3-methylimidazolium, 1- ( 1-butyl) -3-ethylimidazolium, 1- (1-hexyl) -3-methylimidazolium, 1- (1-hexyl) -3-ethylimidazolium, 1- (1-hexyl) -3-butylimidazolium , 1- (1-octyl) -3-methylimidazolium, 1- (1-octyl) -3-ethylimidazolium, 1- (1-octyl) -3-butylimidazolium, 1- (1-dodecyl) -3-methylimidazolium, 1 - (1-dodecyl) -3-ethylimidazolium, 1- (1-dodecyl) -3-butylimidazolium, 1- (1-dodecyl) -3-octylimidazolium, 1- (1-tetradecyl) -3-methylimidazolium, 1- (1-Tetradecyl) -3-ethylimidazolium, 1- (1-tetradecyl) -3-butylimidazolium, 1- (1-tetradecyl) -3-octylimidazolium, 1- (1-hexadecyl) -3-m ethylimidazolium, 1- (1-hexadecyl) -3-ethylimidazolium, 1- (1-hexadecyl) -3-butylimidazolium, 1- (1-hexadecyl) -3-octylimidazolium, 1,2-dimethylimidazolium.

Particularly preferred dialkylimidazolium cations are selected from the group consisting of 1, 3-dimethylimidazolium, 1, 3-diethylimidazolium, 1-ethyl-3-methylimidazolium and 1- (1-butyl) -3-methylimidazolium.

Preferred tetraalkylphosphonium cations are selected from the group consisting of tetraalkylphosphonium cations of the formula (II)

(Ii) wherein R1, R2, R3 and R4 are each independently selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, n-hexyl, n-octyl, Dodecyl, tetradecyl, hexadecyl and allyl.

Particularly preferred tetraalkylphosphonium cations are selected from the group consisting of trihexyl (tetradecyl) phosphoniunr), tributyl (octyl) phosphoniunr), tributyl (tetradecyl) phosphoniunr), tetrabutylphosphonium, tributyl (ethyl) phosphoniunr), triisobutyl (methyl) phosphoniunr) and tributyl (methyl) phosphoniunr).

In some cases, mixtures of the aforementioned preferred tetraalkylphosphonium cations are preferred.

A particularly preferred ionic liquid (organic salt) is Ν, Ν'- ethylmethylimidazolium methyl sulfonate (or 1-ethyl-3-methylimidazolium methyl sulfonate called - EMIM OMs).

Our own investigations have shown (and confirmed) that this particularly preferred IL has a largely excellent thermal stability up to at least 200 ° C. In addition, no decomposition was regularly observed in aqueous solutions. In addition, this particularly preferred IL usually does not react with the educt compounds, in particular with fructose (cf., for example, Clough et al., Lonic Liquids: Not Always Innocent Solvents for Cellulose, Green Chemistry, 17, 231 (2015)).

Our own investigations have also shown that the choice of anion has a significant impact on the implementation of HMF. The anions of typical strong acids are preferred here (for example, hydrogen sulfate, chloride, bromide, methanesulfonate, tosylate). However, not every one of these anions is particularly preferred or suitable for the process according to the invention. In particular, chloride ions regularly lead to certain process disadvantages, even if in some cases high yields of HMF are obtained, In a large number of cases, it has been observed in our own investigations that chloride ions lead to increased corrosivity on metal surfaces and therefore expensive corrosion-resistant apparatus must be used. Our own investigations have also shown that in the presence of an acid, the presence of chloride ions in some cases leads to the formation of undesired and corrosive hydrogen chloride, which can potentially volatilize gaseous. Hydrogen chloride also often has a negative effect on the stability of the ILs and in many cases favors their decomposition.

Preference is therefore given to a process according to the invention (as described above, preferably as defined above as preferred), where the mixture G contains one, two or more organic salts with a melting point <180 ° C. and a boiling point> 200 ° C. at 1013.25 hPa, selected from the group of organic salts having an imidazolium or phosphonium cation, wherein the total amount of chloride ions in the mixture G is less than 0.1% by weight, more preferably the mixture G comprises no chloride ions.

Our own investigations have also shown that the choice of cation has a significant influence on the thermal stability of an organic salt. It has been found that ammonium-based alkylated cations (eg, choline as an ammonium-based specific cation), piperidinium, and pyridinium are often dealkylated at temperatures in the range of 140 to 150 ° C, whereas alkylated cations are based on of imidazolium and phosphonium remain regularly stable (and are therefore preferred). It is therefore preferred that the mixture G comprises an amount of at most 0, 1 wt .-%, preferably no alkylated cations of such organic salts, which are fully alkylated at a temperature of 25 ° C, but with a heat treatment of 24 Hours and a temperature of 200 ° C, especially in the presence of

(i) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, (ii) HMF,

(iii) water and (iv) optionally other substances tend to dealkylate ("tend to dealkylate" means that more than 1 mol% of the cations have lost at least one alkyl radical.) Those skilled in the art can identify corresponding cations or organic salts (eg using gas chromatography and mass spectrometry analyzes).

Also preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein the mixture G comprises no organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, which are selected from the group of organic salts with an ammonium, piperidinium or pyridinium cation.

Preferably, the mixture G comprises no choline chloride, more preferably no choline cation.

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein the reaction temperature is in the range of 100 to 160 ° C, preferably in the range of 120 to 140 ° C at the set reaction conditions. The abovementioned reaction temperatures relate to the abovementioned reaction conditions in the process according to the invention, in which an amount of one educt compound or at least one of the two or more educt compounds reacts to give 5-hydroxymethylfurfural (HMF). In some cases, a method according to the invention is preferred (as described above, preferably as defined above as preferred), wherein when adjusting the reaction conditions, a reaction pressure in the range of 20 to 500 mbar is set, preferably a reaction pressure in the range of 50 to 300 mbar, respectively particularly preferably in a stirred tank reactor of a reactor arrangement comprising the method according to the invention. The abovementioned reaction pressures relate to the abovementioned reaction conditions in the process according to the invention, in which an amount of one educt compound or at least one of the two or more educt compounds reacts to give 5-hydroxymethylfurfural (HMF). Particularly preferably, the abovementioned reaction temperatures are present in combination with the reaction pressures mentioned. At the above-mentioned preferred reaction temperatures and preferred reaction pressures, the total amount of water in the mixture G is already reduced by evaporation, preferably it is Total water content in a range of 0, 1 to 5.0 wt .-%, based on the total mass of the mixture G.

In other cases, particularly preferably in a tubular reactor in a reactor arrangement comprising the process according to the invention, a process according to the invention is preferred (as described above, preferably as defined above as preferred), wherein (depending on the operating mode) the reaction conditions are adjusted

- A reaction pressure in the range of 20 to 500 mbar, preferably a reaction pressure in the range of 50 to 300 mbar is set or - a reaction pressure in the range of 1 to 10 bar, preferably a reaction pressure in the range of 1 to 5 bar is set.

Particularly preferred is a method according to the invention (as described above, preferably as defined above as preferred), wherein in the mixture G, the concentration of 5-hydroxymethylfurfural (HMF) in the range of 18 wt .-% to 35 wt .-% (preferably to 31 wt .-%), based on the total mass of the mixture G, preferably in the range of 20 wt .-% to 35 wt .-% (preferably to 30 wt .-%).

Our own investigations have shown that the formation of (further) HMF in a mixture which already contains a comparatively high concentration of HMF is often hindered to a considerable extent. Instead, dimers of HMF and (mostly mixture-soluble) humins are formed in many cases. Humins in the context of the present invention are oligomers and polymers of the HMF and their blends with other oligomers and polymers. The formation of such humins is favored, since there is already a comparatively high concentration of HMF. The risk of the formation of humins can be reduced by selecting suitable ILs, so that when using the ILs defined according to the method according to the invention, an acceptable conversion to HMF also takes place even at an HMF concentration of up to and including 35% by weight. Although under these conditions, formation of unwanted humins is observed, the extent of humin formation is still acceptable in most cases. Therefore, it is preferable in some cases to design the method according to the invention such that the mixture G has lower HMF maximum concentrations than 35% by weight. includes. According to their own investigations, this regularly leads to the formation of less humins.

Our own investigations have also shown that at an HMF concentration greater than 35 wt .-%, based on the total mass of a mixture (eg greater than 36 wt .-% or greater 37 wt .-%.) The extent of formation of humins regularly is no longer acceptable. The reactant compounds reacted under such conditions increasingly lead to undesirable humins and no longer primarily to the desired value product HMF. It is then preferable to design the process according to the invention in such a way that no (or at least temporarily no) reaction of the educt compounds takes place, preferably by at least temporarily interrupting the feed of further educt compounds.

Particular preference is therefore given to a process according to the invention (as described above, preferably as defined above as preferred), the process being carried out such that no reaction of educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose Units in a mixture comprising more than 37% by weight of 5-hydroxymethylfurfural (HMF), preferably more than 33% by weight, more preferably more than 32% by weight.

The process according to the invention (as described above, preferably as defined above as preferred) is a process for the continuous preparation of 5-hydroxymethylfurfural (HMF) in a reactor arrangement. The result is an HMF-containing mixture as the final product or intermediate. The valuable product HMF must usually be separated by one or more separation steps from other constituents in the resulting HMF-containing mixture. Preferably, the process according to the invention after the step of adjusting the reaction conditions in the mixture G comprises one or more than one further step, preferably one, more than one or all steps selected from the group of steps consisting of partial neutralization with a Bronsted Base, water separation, separation of volatile compounds and HMF separation. Highly volatile compounds are compounds having a boiling temperature which is lower than the boiling point of 5-hydroxymethylfurfuraldehyde (HMF) at the same pressure value at at least one pressure value in the range from 0.1 to 500 mbar. Typical volatile compounds having a boiling temperature which are at least at a pressure in the range of 0, 1 to 500 mbar lower. ger than the boiling point of 5-hydroxymethylfurfural at the same pressure value are furfural, levulinic acid, formic acid, Alkyllävulinate, alkyl formates, formaldehyde.

Particular preference is therefore given to a process according to the invention (as described above, preferably as defined above as preferred), wherein 5-hydroxymethylfurfural (HMF) prepared in the process is removed by distillation, preferably by short-path distillation. Preferably, the short path distillation is carried out at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C. Preferably, the (preferred) short path distillation is fed with a mixture comprising water in an amount of not more than 0.5% by weight. The total water content before the short path distillation is preferably reduced to not more than 0.5% by weight by further distillation at a pressure in the range from 1 to 200 mbar and a temperature in the range from 80 to 180 ° C.

As already stated above, it is advantageous for an economic process design of the process according to the invention that no reaction of starting material compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units in a mixture occurs, which comprises more than 37% by weight of 5-hydroxymethylfurfural (HMF), preferably more than 33% by weight, more preferably more than 32% by weight. It is thus particularly advantageous to control or regulate the process according to the invention accordingly.

Therefore, a method according to the invention (as described above, preferably as defined above as preferred) is particularly preferred, wherein

(A) the amount of one, two or more educt compounds introduced into the reactor per unit time selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and / or

(B) the average residence time of said organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa in the reactor arrangement and or

(C) the reaction conditions in the mixture G are controlled or regulated depending on the concentration of one or more substances selected from the group consisting of (i) educt compounds, (ii) 5-hydroxymethylfurfural (HMF) and (iii) humins in one place within the reactor, preferably in the mixture G and / or at the reactor outlet.

The amount of one, two or more reactant compounds introduced into the reactor per unit time selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units is preferably determined by means of flow measurement and / or scale-controlled metering. The person skilled in this conventional measuring devices are known. With regard to the control of the composition of starting mixtures comprising one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, we refer to the statements below.

The above applies to the amount of one, two or more organic salts introduced into the reactor per unit time with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa selected from the group of organic salts with a Imidazolium or phosphonium cation accordingly.

Ways of determining the average residence time in the reactor arrangement are also known to the person skilled in the art. The skilled person is usually familiar with the volume of the reactor or reactors used (preferably reactors selected from the group consisting of tubular reactors and stirred tank reactors). The average residence time can thus be controlled or regulated via the feeds (for example, in a tubular reactor). In a typical stirred tank reactor, the mean residence time is preferably controlled by a level-dependent discharge pump. If the discharge is increased, the volume of the liquid phase in the reactor and thus also the residence time decreases. If the discharge is reduced, the volume of the liquid phase in the reactor and thus also the residence time increases. The reaction conditions in the mixture G can be determined by the skilled person by means of conventional measuring devices, largely even determined continuously. Typical parameters are the reaction temperature in the mixture G, the pressure above the liquid phase of the mixture G and the pH in the mixture G (or alternatively the acid number in mg KOH per g mixture G). In some cases, it is preferable to compare continuously or at intervals recorded chromatograms / spectra of different analytical measuring methods, preferably HPLC, NMR, IR and / or Raman spectra. Such analyzes allow statements about the concentration or quantitative ratios of present compounds / substances and / or classes of compounds (eg starting material (s), intermediate (s), product (s), catalyst (s), solvent).

As mentioned above in the text, a method according to the invention is preferred, wherein the reactor arrangement consists of one or more reactors, wherein the or at least one of the plurality of reactors is selected from the group consisting of tubular reactors and stirred tank reactors.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as being preferred), wherein a starting mixture S is fed to the reactor arrangement at its inlet

(a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and

(B) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation, wherein the mass ratio of respective total amounts of (a) and (b) in the starting mixture S is in a range of 0.4 to 1.7, preferably in a range of 0.4 to 1.1, and wherein (i) in the reactor arrangement said mixture G is formed from the starting mixture S or (ii) the starting mixture S is introduced into a mixture to form the mixture G.

In some cases, a process according to the invention (as described above, preferably as defined above as preferred) is particularly preferred, wherein the reactor arrangement comprises a tubular reactor, wherein at the entrance of the tubular reactor, a starting mixture S is used, from which said mixture G is formed by reaction of educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, wherein the starting mixture S preferably comprises less than 10 wt .-% 5-hydroxymethylfurfural (HMF), based on the total mass of Starting mixture S, preferably less than 5% by weight 5-hydroxymethylfurfural (HMF).

Our own investigations have shown that when the reactor arrangement in the process according to the invention (as described above, preferably as defined above as preferred) comprises a tubular reactor, in many cases no back-mixing occurs. As a result, comparatively accurate concentration profiles can be established in a tubular reactor depending on the reactor length. Particularly preferred is a reactor arrangement comprising a tubular reactor in which the reaction temperature within the tubular reactor is controlled by means of a temperature gradient.

The starting mixture S preferably comprises (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (b) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation. The above in the text to preferred Eduktverbindungen said applies to the starting mixture S accordingly.

Particular preference is given to a process according to the invention (as defined above as being preferred), in which starting mixture S the mass ratio of the respective total amounts of (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (b) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa, selected from the group of organic salts having an imidazolium or phosphonium cation, in a range from 0.4 to 1.7, preferably in a range from 0.4 to 1.1.

Our own investigations have shown that the process according to the invention (as described above, preferably as defined above as being preferred) can be controlled or regulated particularly advantageously via the starting mixture S. A corresponding control or regulation (or a correspondingly controlled or regulated method according to the invention) is thus preferred. In some cases, it is preferred that the amount introduced per time of the starting mixture S be increased or decreased (i.e., adjusted) (feed rate), for example, by increasing or decreasing the flow rate in a corresponding flow meter. It is particularly preferred that the mass ratio of the respective total amounts of (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (b) one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation, in the starting mixture S is changed, so that the inventive method (as described above, preferably as defined above as preferred) is controlled or regulated. In this case, preferably the total amount of said one, two or more reactant compounds in the starter mixture S is increased or decreased while the total amount of the said one, two or more organic salts remains the same. This results in a correspondingly changed mass ratio in the starting mixture S. Such a control or regulation is particularly preferred in the case of a continuous feeding of the starting mixture S into the reactor arrangement, preferably into a tubular reactor or into a stirred tank reactor. The amount of HMF forming in the mixture G is thereby particularly preferably controlled or regulated.

In some cases, a process according to the invention (as described above, preferably as defined above as preferred) is particularly preferred, wherein the reactor arrangement comprises a stirred tank reactor in which the mixture G is present.

Our own investigations have shown that when the reactor arrangement in the process according to the invention (as described above, preferably as defined above as preferred) comprises a stirred tank (also referred to as stirred tank reactor), in many cases a complete backmixing occurs. Particularly preferred a reaction vessel comprising a reactor arrangement, wherein the water contained in the mixture G in the stirred tank is already largely separated by means of vacuum.

Particular preference is given in some cases to a process according to the invention (as defined above as preferred), wherein the mass ratio of the respective total amounts of (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and Polysaccharides comprising hexose units and (b) one, two or more organic salts having a melting point <180 ° C. and a boiling point> 200 ° C. at 1013.25 hPa, selected from the group of organic salts with an imidazolium or phosphonium Cation in which mixture G is in a range of 0.4 to 1.7, preferably in a range of 0.4 to 1, 1.

Preferably, the reactor assembly, preferably comprising a stirred tank reactor, in which the mixture G is present, also the starting mixture S is fed.

Particular preference is given to a mass ratio in the starting mixture S (both for process configurations according to the invention comprising a tubular reactor and for process configurations according to the invention comprising a stirred tank reactor) in the range of 0.4 kg (a) one, two or more educt compounds selected from the group consisting of hexoses, Oligosaccharides comprising hexose units, and polysaccharides comprising hexose units per 1 kg (b) one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa, selected from Group of organic salts with an imidazolium or phosphonium cation to 1, 5 kg (a) per 1 kg (b) presented. Particularly preferred is a mass ratio in the starting mixture S in the range of 0.4 kg fructose per 1 kg (b) to 1, 5 kg of fructose per 1 kg (b) presented, preferably a mass ratio in the range of 0.4 kg fructose per 1 kg (b) to 1, 2 kg of fructose per 1 kg (b).

The above for the control or regulation of the Stargem S Said applies here accordingly.

The invention will be explained in more detail by way of examples. Examples:

Example 1: Continuous production of 5-hydroxymethylfurfural (HMR by means of

 Dehydration of fructose in the ionic liquid EMIM OMs (semi- batch process):

The dehydration was carried out in a 2L jacketed glass reactor with disc stirrer, flow breakers and thermostat, and a distillate transfer with snake cooler and connection for a vacuum pump. The starting compound used was fructose syrup which was fed via a pump to the reactor at a constant metering rate.

The ionic liquid used was a salt of the formula (III) (EMIM OMs).

(III)

In a first partial step, the ionic liquid EMIM OMs (Basionics ST 35) was initially charged in the reactor and then a catalytic amount of methanesulfonic acid (1 mol%, based on the total amount of fructose used) was added to the ionic liquid. It resulted in a first sub-mixture. Subsequently, this first part mixture was heated to 150 ° C. at 100 mbar. In a second partial step, an aqueous fructose solution (about 67% in water) was continuously fed to the reactor at a constant metering rate of about 9 g / min via a pump, with the introduced water evaporating. The temperature in the liquid phase dropped to about 130 ° C, which was held by an additional heat input by means of the thermostat at an average of 130 ° C. After the end of the addition of the fructose syrup stirring was continued for a further 60 minutes at 130 ° C. and the resulting product mixture was analyzed by means of HPLC. The continuous production of HMF described above was repeated several times, so that a total of nine individual experiments were carried out (1-1 to 1-IX, wherein individual experiment 1-1 is a comparative experiment, ie a non-inventive individual experiment). A summary of the various experimental parameters and the results of the individual experiments is shown in the following table, where:

- conversion fructose [%] = (1 minus (molar amount of fructose in the product mixture / amount of fructose used)) * 100 and

- Yield HMF [%] = (molar amount of HMF in the product mixture / molar amount of fructose used) * 100.

Single test

 1-1 1-11 1-111 1-IV 1-V 1-VI 1-VII 1-VI 11 1-IX Amount used

Fructose [mol] 1, 67 2.48 3.59 4.55 5.56 6.73 6.89 7.63 8.71 amount used

EMIM OMs [g] 1200 1200 1200 1200 1200 1200 1020 920 850

Fructose Conc.

[% By weight] 20 27 35 40 45 50 55 60 65

Molar ratio

Fructose to IL

[mol / mol] 0.29 0.43 0.62 0.76 0.94 1, 15 1, 41 1, 72 2, 13

mass ratio

Fructose to IL [kg / kg] 0.25 0.37 0.54 0.67 0.83 1, 00 1, 22 1, 50 1, 86

Dye Pro1883.3 Duktmischung [g] 1445 1544.5 1684 1861, 4 1962 2121, 5 1910.8 2 1934.8

HMF in the product mixture [weight%] 12.6 17.1 22.1 25.0 27.9 30.3 30.8 30.2 28.9

Di-HMF in the product mixture 0.06 0.1 0.2 0, 18 0.5 1, 1 2.3 4 6.5 [% by weight]

Sales Fructose [%] 97.6 98.3 96.9 95.7 98.6 99.0 100.0 100.0 100.0

Yield HMF [%] 86.5 84.4 82.2 81, 1 78.1 75.7 67.7 59.1 50.9

Ratio IL / HMF

[mol / mol] 4.05 2.79 1, 98 1, 63 1, 36 1, 16 1, 06 0.99 0.93

Ratio IL / HMF

[kg / kg] 6,62 4,56 3,23 2,66 2,22 1, 89 1, 73 1, 62 1, 52 Weight percentages in the above table refer to the total mass of the product mixture. Di-HMF (CAS Number: 7389-38-0) is the name for the dimer of HMF and is a compound of formula (IV) shown below:

(IV)

In all individual experiments 1-11 to 1 -IX there was initially no HMF. HMF was formed by reaction. In each case, by exceeding the concentration threshold for HMF of 15% by weight, a mixture G (as defined in the claims) was formed.

Example 2: Continuous production of 5-hydroxymethylfurfural (HMF) by means of

 Dehydration of fructose in various ionic liquids (semi-batch process):

For the individual experiments according to Example 2, the following ionic liquids were used (hereinafter the individual tests have the same designations as the ionic liquids used for this purpose and hereinafter referred to as lower-case letters):

(a) 1-Ethyl-3-methylimidazolium mesylate (EMIM OMs)

 (b) 1-Ethyl-3-methylimidazolium tosylate (EMIM OTs)

 (c) 1-Ethyl-3-methylimidazolium hydrogen sulfate (EMIM HS04)

(d) 1-ethyl-3-methylimidazolium chloride (EMIM Cl)

 (e) 1- (1-Butyl) -3-methylimidazolium mesylate (BMIM OMs)

In the context of Example 2, a total of five individual experiments (2 (a) to 2 (e)) were carried out. Each individual test was carried out in a 250 mL double-jacket glass reactor with disk stirrer, flow breakers and thermostat, as well as a distillate transition with a snake cooler and connection for a vacuum pump. In a preparatory step, the ionic liquids (a) and (b) and (d) and (e) were added with a Brönsted acid whose anion is identical to the anion of the respective ionic liquid. In each case, only enough of the corresponding acid was added so that the acid number of the respectively resulting partial mixtures was 6 ± 0.5 mg KOH / g of ionic liquid. No Bronsted acid was added to the ionic liquid (c); nevertheless, it will hereinafter be referred to as a partial mixture, as is the case for (a) and (b) and (d) and (e) after addition of the corresponding Bronsted acid.

The acid number was determined using a Metrohm 848 Titrino Plus Titrometer. For this purpose, 0, 1 to 0.2 g of a corresponding sample against

Titrated tetrabutylammonium hydroxide ([n-Bu ₄ N] [OH]) 0, 1 mol / L in ethanol). The instrument returns by internal conversion as the result a standard acid number, which is expressed in the unit milligrams [mg KOH] (potassium hydroxide) per gram [g] sample. In a first substep, 150 g of the corresponding sub-mixture were initially charged in the reactor for each individual test (see the following table) and then heated to 150 ° C. at 100 mbar.

In a second sub-step, 143 g of an aqueous fructose solution (70% in water) at a constant metering rate of about 1.7 g / min were fed continuously to the reactor via a pump for each individual test, whereby the introduced water evaporated. The temperature in the liquid phase dropped to about 130 ° C, which was maintained by an additional heat input by means of the thermostat at an average of 130 ° C. In all individual experiments, the duration of the experiment (dosing time and post-reaction) was 150 min; This resulted in the respective product mixtures of the individual experiments 2 (a) to 2 (e). Subsequently, these product mixtures were analyzed by HPLC. The results are summarized in the table below. Single test

 2 (a) 2 (b) 2 (c) 2 (d) 2 (e)

HMF in the Pro 25,6 16, 1 15.5 23, 1 24, 1 product mixture

 [Wt.%]

 Di-HMF in the 0.7 5.2 0.09 0.2 1, 2

 product mix

 [Wt.%]

 Conversion fructose 99 99 99 99 99

 [%]

 Yield HMF [%] 82 51 44 81 75

Weight percentages in the above table refer to the total mass of the product mixture. For "conversion of fructose [%]" and "yield HMF [%]" in the table above, the statements made in relation to example 1 apply accordingly.

In all individual experiments 2 (a) to 2 (e) initially no HMF was present. HMF was formed by reaction. In each case, by exceeding the concentration threshold for HMF of 15% by weight, a mixture G (as defined in the claims) was formed.

Example 3: Continuous production of 5-hydroxymethylfurfural (HMF) by means of

 Dehydration of fructose in the ionic liquid EMIM OM (stirred tank):

The continuous production of HMF in a stirred tank was carried out in a continuously operated thermostated glass reactor with disk stirrers and flow breakers, wherein the stirred tank with (i) two separate feeds (for the streams to be supplied), (ii) a reflux condenser with vacuum port for distilling off Water and (iii) an overflow for a discharge of the liquid phase (product mixture) is equipped. The weight of the liquid phase (Mixture G) in the reactor was 187 g; It is thus possible to calculate the residence time of the liquid phase in the reactor (and thus also the one, two or more organic salts used). The reaction temperature corresponds to the temperature of the liquid phase in the stirred tank reactor. Experimental parameters were first determined and recorded after a steady state condition was reached. By means of a scale-controlled mass balancing of the feeds (aqueous fructose syrup and ionic liquid) and discharges (liquid phase and distillate) and the extraction and HPLC analysis of representative samples of the liquid phase and of the distillate, the conversion and yield of the reaction were determined. The "conversion of fructose [%]" was 93% and the "yield HMF [%]" in the liquid phase was 75.8%, whereby for "conversion fructose [%]" and "yield HMF [%]" to Example 1 Said accordingly applies.

The stirred tank was also operated during steady state with the following parameters:

Internal temperature of the reactor: 130 ° C,

 - pressure reactor: l OO mbar,

 Residence time of the liquid phase: 2 h,

 Feed 1: aqueous fructose syrup (about 67% in water) with a feed rate of 53.4 g / h,

 Feed 2: EMIM OMs (Basionics ST 35) with additionally 0.35% by weight of methanesulfonic acid (based on the total amount of EMIM OMs and methanesulfonic acid in feed 2 (ie based on the total amount of feed 2) with a feed rate of 56, 1 g / h,

 - Discharge of distillate, discharge rate: 18.1 g / h:

 0.2% by weight of HMF,

 -> 99 wt .-% water

 - discharge liquid phase, discharge rate: 90.63 g / h:

 about 3% by weight of saccharides,

 20.8% by weight of HMF,

0.2% by weight of di-HMF. Continuous production of 5-hydroxymethylfurfural (HMR by dehydration of fructose in the ionic liquid EMIM OMs (tubular reactor):

The continuous production of HMF in a tubular reactor was carried out in a glass ring-filled continuous jacketed tubular reactor (12 mm diameter, 140 cm long filled with 5 mm diameter glass rings as a bed to reduce the volume) with external thermostat. Via a scale-controlled feed metering, a starting mixture S was fed via the inlet (bottom-up mode) of the tubular reactor at the bottom of the tubular reactor. In the tube reactor, a mixture G is present. At the top of the tube reactor, the product HMF-containing mixture G was expanded and collected via a 3.5 bar transfer valve into a cooled receiver. The mass of the liquid phase in the reactor was 1 10 g; Thus, it is possible to calculate the residence time of the liquid phase (and thus also of the one, two or more organic salts used) in the reactor. The measurement of the temperature took place within the tube at two measuring points, in each case at a distance of 5 cm to the tube inlet and to the tube outlet. The temperature of the external thermostat was chosen to reach the following "internal reactor temperature" (liquid phase temperature at the outlet of the reactor) of 130 ° C. The temperature at the inlet of the reactor was 125 ° C.

Experimental parameters were first determined and recorded after a steady state condition was reached. Via a scale-controlled mass balancing of the feed and the discharge as well as the extraction and HPLC analysis of representative samples of the liquid phase, the conversion and the yield of the reaction were determined. The "conversion of fructose [%]" was 97% and the "yield HMF [%]" in the liquid phase was 71.4%, whereby for "conversion fructose [%]" and "yield HMF [%]" to Example 1 Said accordingly applies.

The tubular reactor was also operated during steady state with the following parameters:

Internal temperature of the reactor: 130 ° C, Pressure reactor: 3.5 bar,

 Residence time of the liquid phase: 2 h,

 Containing feed: 36.9% by weight of fructose, 3% by weight of water, 59.9% by weight of EMIM OMs (Basionics ST 35), 0.18% by weight of methanesulfonic acid (percent by weight refers to the total amount of the inflow)

Feed rate: 55 g / h,

 Discharge comprising: about 1.5% by weight of saccharides, 18.4% by weight of HMF, 0.2% by weight of di-HMF, 0.08% by weight of furfural,> 3% by weight water

 - Output rate: 55, 1 g / h.

Example 5: Preparation of 5-hydroxymethylfurfural (HMF) by means of acid-catalvized

 Dehydration of fructose (catalyst: p-TsOH: in supplementary experiments: MsOH) in various ionic liquids

For the individual experiments according to Example 5, the following ionic liquids were used (hereinafter, the individual tests have the same designations as the ionic liquids used for this purpose and hereinafter referred to as lower-case letters):

(a) 1-Ethyl-3-methylimidazolium chloride (EMIM Cl) and

(b) 1-Ethyl-3-methylimidazolium tosylate (EMIM OTs).

In the context of example 5, a total of two individual experiments (5 (a) and 5 (b)) were carried out.

Each individual experiment was performed in a 20 ml tube of a Radley carousel.

In a preparatory step, in each case 4 g of the ionic liquids ((a) and (b)) were admixed with 10 mg of p-toluenesulfonic acid (as Brönsted acid, 50% by weight in H ₂ O), so that a part mixture (a) or (a) was added a partial mixture (b) resulted. In a first step, the corresponding sub-mixtures were placed in the respective 20 ml tube for each individual experiment, added 1 g of fructose and then heated to 120 ° C.

In all individual experiments, the test duration was 120 min; This resulted in the respective product mixtures (a) and (b).

Subsequently, these product mixtures were analyzed by HPLC. The results are summarized in Table A below.

For "conversion of fructose [%]" and "yield HMF [%]" in the table above, the statements made in relation to example 1 apply accordingly.

In all individual experiments 5 (a) to 5 (b) initially no HMF was present. HMF was formed by reaction.

A comparison of the "yields HMF" of the individual experiments 5 (a) and 5 (b) in Table A shows that the yield of HMF can be determined by a suitable selection of the counterion of the organic salt (ie "ionic liquid", in short: IL) is additionally increased (without adversely affecting the conversion of fructose), if the counterion of the organic salt (tosylate) corresponds to the anion of the acid used.

In further complementary experiments, the compound methanesulfonic acid was used instead of toluenesulfonic acid and instead of EMIM OTs EMIM OMs was used. Also in these experiments, the yield of HMF was high.

Claims

claims: A process for the continuous production of 5-hydroxymethylfurfural (HMF) in a reactor arrangement, comprising the following step: Setting reaction conditions in a mixture G comprising one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa selected from the group of organic salts with an imidazolium or phosphonium cation, Water, 5-hydroxymethylfurfural (HMF) in a concentration in the range of 15 wt .-% to 35 wt .-%, based on the total mass of the mixture G, optionally further substances, so that at the set reaction conditions, an amount of a reactant compound or at least one of the two or more reactant compounds to 5-hydroxymethylfurfural (HMF). 2. The method according to any one of the preceding claims, wherein the one, two or more Eduktverbindungen comprise one, two or more than two compounds selected from the group consisting of fructose, glucose, oligosaccharides comprising fructose units, oligosaccharides comprising glucose Units, polysaccharides comprising fructose units and polysaccharides comprising glucose units, preferably one, two or more than two compounds selected from the group consisting of fructose, oligosaccharides comprising fructose units and polysaccharides comprising fructose units. Process according to one of the preceding claims, wherein the one or at least one of two or more of said organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa is selected from the group of organic salts with an imidazolium or phosphonium cation and an anion from the group consisting of methylsulfonate, tosylate, preferably methylsulfonate, preferably selected from the group of organic salts with a dialkylimidazolium cation or tetraalkylphosphonium cation, very particularly preferably selected from the group of organic salts having a dialkylimidazolium cation or tetraalkylphosphonium cation and an anion selected from the group consisting of methylsulfonate and tosylate. Method according to one of the preceding claims, wherein at the set reaction conditions, the reaction temperature in the range of 100 to 160 ° C, preferably in the range of 120 to 140 ° C. Method according to one of the preceding claims, wherein in the mixture G, the concentration of 5-hydroxymethylfurfural (HMF) in the range of 18 wt .-% to 31 wt .-%, based on the total mass of the mixture G, preferably in the range of 20 Wt .-% to 30 wt .-%. Method according to one of the preceding claims, wherein the method is carried out so that no reaction of educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units in a mixture which more than 37 wt. % 5-hydroxymethylfurfural (HMF), preferably more than 33% by weight, more preferably more than 32% by weight. Method according to one of the preceding claims, wherein produced in the process 5-hydroxymethylfurfural (HMF) is separated by distillation, preferably by short path distillation. Method according to one of the preceding claims, wherein the mixture comprises G as further substance: - One or more acids selected from the group consisting of homogeneous acids and heterogeneous acids, wherein the one or at least one of the plurality of acids is preferably selected from the group consisting of sulfuric acid, phosphoric acid, methanesulfonic acid and p-toluenesulfonic acid. 9. The method of claim 8, wherein the one or at least one of the plurality of acids is methanesulfonic acid and / or wherein the anion or the anions of the one or more acids are identical or are identical to the anion of the one, two or more organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa. 10. The method according to any one of the preceding claims, wherein (A) the amount of one, two or more educt compounds introduced into the reactor per unit time selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and / or (b) the average residence time of the said organic salts with a melting point <180 ° C and a boiling point> 200 ° C at 1013.25 hPa in the reactor arrangement and / or (c) the reaction conditions in the mixture G are controlled or regulated as a function of the concentration of one or more substances selected from the group consisting of (i) Educt compounds, (ii) 5-hydroxymethylfurfural (HMF) and (iii) humins at a location within the reactor, preferably in mixture G and / or at the reactor outlet. 1 1. The method according to any one of the preceding claims, wherein the reactor arrangement comprises a tubular reactor, wherein at the entrance of the tubular reactor, a starting mixture S is used, from which said mixture G is formed by reacting Eduktverbindungen selected from the group consisting of hexoses, comprising oligosaccharides Hexose units, and polysaccharides comprising hexose units, wherein the starting mixture S preferably comprises less than 10 wt .-% 5-hydroxymethylfurfural (HMF), based on the total mass of the starting mixture S, preferably less than 5 wt .-% 5-hydroxymethylfurfural (HMF). 12. The method of claim 1 1, wherein in said starting mixture S, the mass ratio of the respective total amounts of (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and ( b) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa, selected from the group of organic salts with an imidazolium or phosphonium cation, in a range of 0 , 4 to 1, 7, preferably in a range of 0.4 to 1, 1. 13. The method according to any one of the preceding claims, wherein the reactor arrangement comprises a stirred tank reactor in which the mixture G is present. 14. The method of claim 13, wherein the mass ratio of the respective total amounts of (a) one, two or more educt compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units and (b) one, two or more organic salts having a melting point <180 ° C and a boiling point> 200 ° C at 1013,25 hPa selected from the group consisting of organic salts with an imidazolium or phosphonium cation, in which mixture G is in a range of 0, 4 to 1, 7, preferably in a range of 0.4 to 1, 1.