WO2016207025A1

WO2016207025A1 - Method for synthesizing and separating hmf

Info

Publication number: WO2016207025A1
Application number: PCT/EP2016/063613
Authority: WO
Inventors: Benoit BLANK; Johannes David HOECKER; Holger WERHAN; Ortmund Lang; Sunghee Son; Markus Piepenbrink; René BACKES; Alois Kindler
Original assignee: Basf Se
Priority date: 2015-06-24
Filing date: 2016-06-14
Publication date: 2016-12-29

Abstract

Described is a method that involves synthesizing a mixture containing 5-hydroxmethylfurfural (HMF, compound of formula (I)), and separating 5-hydroxymethylfurfural from the obtained mixture. The disclosed method involves step (A), synthesizing the mixture comprising one or more ionic liquids and 5 to 50 wt% 5-hydroxymethylfurfural, and step (B), separating 5-hydroxymethylfurfural from the mixture obtained in step (A) using short-path evaporation.

Description

Method of making and separating HMF

The present invention relates to a process comprising preparing a mixture comprising 5-hydroxymethylfurfural (HMF, compound of formula (I)) and separating 5-hydroxymethylfurfural from the prepared mixture.

(0

The process of the invention comprises the steps of (A) preparing the mixture comprising one or more ionic liquids and 5-hydroxymethylfurfural in an amount of 5 to 50% by weight and (B) separating 5-hydroxymethylfurfural from that prepared in step (A) Mixture by short path evaporation.

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

Opportunities (IL) as a solvent in the HMF synthesis is particularly advantageous because in these solvents usually high yields of HMF are obtained. However, the separation of the HMF from the product mixture, which besides HMF also contains starting materials and / or by-products of the HMF synthesis, is generally particularly complicated and hampers the production of pure HMF. The separation of HMF from product mixtures comprising ionic liquids as solvent is additionally complicated because of the interactions of the HMF with the solvent.

The scientific article entitled "Hydroxymethylfurfural, A Versatile Platform Chemical Made from Enabling Resources", Chemical Reviews 2013, 1 13, 1499 to 1597, disclosed on page 1500, right column, lines 5 to 7: "In this review, the authors focus on one particular route, namely, the dehydration of hexoses to obtain furan-type platform chemicals, HMF in particular. " It is then further stated on page 1548, left column, first complete paragraph, in excerpts: "[...] the ionic liquids apparently stabilize the formed HMF,". It is further stated in the second complete paragraph: "This apparent stabilizing effect therefore has a disadvantage, it is difficult to separate the HMF from the ionic liquid, requiring large amounts of extracting solvent. Since ionic liquids have essentially no vapor pressure and HMF is the most sensitive, solvent evaporation and HMF distillation, the extraction method is the only method for HMF purification. "The scientific article entitled" 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 discloses in the abstract:" In this paper, for the first time, we have entrained a process called EIVRD (entrainer-intensified vacuum reactive distillation) to separate 5-HMF from the dehydration Solutions of carbohydrates catalyzed by a metal chloride / 1-methyl-3-octyl imidazolium chloride ([OMIMjCI) ionic liquid, in which high vacuity and entrainers were used to intensify the distillation of 5-HMF as well as the dehydration of fructose or glucose. " According to page 1221, left column, penultimate sentence, the "entrainer" (entrainer) is "nitrogen and other organic vapors [...] to increase the evaporation efficiency".

Also, on page 1222, right column, first full paragraph, states: "[...] 5-HMF is quite thermally unstable at 120 ° C in [OMIMjCI when no metal salt is added, with only 68% recovery after heating for 3 hours. In contrast, it is 7 mol% of lrCI ₃ or CrCl ₃ , in which only 1-3% degradation is found. " In summary, according to Green Chemistry (see above), in a distillation of HMF from an ionic liquid, it is generally not possible to dispense with the additional presence of an entraining agent and stabilizing salts.

CN 102399203 A entitled "Method for preparing 5-hydroxymethylfurfural by degradation of carbohydrates by ionic liquid" discloses in paragraph [0007]: "The present invention provides a method for preparing 5-hydoxy methy Ifu rf u ral (5-HMF) by the degradation of carbohydrate by an ionic liquid: a method which combines the degradation of carbohydrate, and moreover, a high yield of 5-hydroxymethylfurfural product The product is difficult to separate. " According to CN 102399203 A, an entrainer can not be dispensed with in order to separate HMF from an ionic liquid (see the table in paragraph [0050] in CN 102399203 A.) Finally, paragraph [0052] states: [...] the present invention, the high-vacuum distillation process and the introduction of the high-vacuum distillation process in the process of producing the water and 5-HMF Production of 5-HMF and product Separation, and effectively solving the problem of 5-HMF being difficult to separate. "

US 2,994,645 A relates to a "PURIFICATION OF HYDROXYMETHYL FURFURAL". It says in column 1, first paragraph: "This invention relates to the purification of crude hydroxymethyl furfural (HMF), and has for its object the provision of an improved distillation process for distilling the crude HMF in good yield."

US Pat. No. 3,201,331 also relates to a "PURIFICATION OF HYDROXYMETHYL FURFURAL". It says in column 1, first paragraph: "This invention relates to the recovery of hydroxymethyl furfural from mixtures and more particularly to an improved process for the purification of crude hydroxymethyl furfural by vacuum distillation."

Neither US 2,994,645 A nor US 3,201,331 A disclose the use of ionic liquids.

EP 2 813 494 A1 discloses a "process for the preparation of 5-hydroxymethylfurfural (HMF)" (title). WO 2013/087614 A1 describes the preparation of 5-hydroxypropyl fluoride (HMF) from saccharide solutions in the presence of a solvent having a boiling point greater than 60 ° C. and less than 200 ° C. (at normal pressure, in short term low-boiling components) "( Description).

WO 2012/175584 A1 describes a "method for dehydrating a carbohydrate-containing composition" (abstract).

WO 2008/019219 A1 describes a "method for conversion of carbohydrates in ionic liquids to hydroxymethylfurfural" (Title).

In the production of HMF from saccharides in ionic liquids, there is still an urgent need to separate the produced HMF from the ionic liquids by suitable and in particular gentle separation processes. It is particularly desirable that in such separation operations, the desired product be separated as much as possible and, as far as possible, no degradation products or by-products of HMF (e.g., dimers, oligomers, and polymers of HMF) are formed, i. the separation takes place as gently as possible. Gentle separation also has the advantage that the ionic liquids freed from HMF can be reused without the need for expensive additional purification of the ionic liquids.

First own investigations have confirmed the already published findings that a standard distillation of HMF from ionic liquids very often leads to degradation products or by-products of HMF. This is especially the case when HMF is to be quantitatively separated. These degradation products reduce the yield of HMF and additionally contaminate the ionic liquids, making it difficult or impossible to recycle the ionic liquids. It is assumed that the high thermal load in such (quantitative) standard distillations leads to the decomposition products or by-products. The limited thermal stability of the HMF can be improved for example by adding certain salts (see the reference to 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 "in the text above).

It is the object of the present invention to provide a process for the production of HMF and for gentle separation of HMF, which largely overcomes the above-mentioned problems and in particular enables a nearly quantitative separation of the HMF. The process should also be simple, economical and ecological. The above-mentioned problems are solved by a method according to the invention comprising preparing a mixture comprising 5-hydroxymethylfurfural and separating 5-hydroxymethylfurfural from the prepared mixture, comprising the following steps:

(A) preparing the mixture comprising:

(a) one or more ionic liquids,

(b) 5-hydroxymethylfurfural (HMF) in an amount of 5 to 50% by weight,

(c) 5,5 '- [oxybis (methylene)] bis-2-furancarboxaldehyde (Di-HMF) in an amount of not more than 7% by weight,

(d) water in an amount of not more than 0.5% by weight,

(e) other substances, wherein the ratio of the total mass of ionic liquids and other salts to the mass of 5-hydroxymethylfurfural in the mixture is in the range of 19: 1 to 1: 1, preferably from 10: 1 to 1: 1, especially preferably from 6: 1 to 1: 1 and very particularly preferably from 4: 1 to 1: 1, the acid number of the mixture is in the range from 0.1 to 15 mg KOH / g, percentages by weight being based on the total mass of the mixture,

(B) separating 5-hydroxymethylfurfural from the mixture prepared in step (A) by short path evaporation at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C.

An ionic liquid (as mentioned above and below, ie for the purposes of the present invention) is a salt having an organic cation and a melting point of less than 180 ° C and a boiling point greater than 200 ° C, each at a pressure of 1013.25 hPa ionic liquid may comprise an organic or inorganic anion. The compound 5.5 '- [oxybis (methylene)] bis-2-furancarboxaldehyde mentioned under (c) is a dimer of HMF (CAS number: 7389-38-0, compound of formula (II)).

(ii) For the determination of the acid number, see the comments below in the text.

It has been shown in our own investigations that the mixture produced according to step (A) with water in an amount of not more than 0.5% by weight leads to excellent to largely acceptable results in short path evaporation. If a value of 0.5% by weight (significantly) is exceeded, no satisfactory release effect is regularly achieved. Preferably, the mixture comprises water in an amount of not more than 0.4% by weight, more preferably in an amount of not more than 0.3% by weight, more preferably in an amount of not more than 0.2% by weight. %, more preferably in an amount of not more than 0.1% by weight, and particularly preferably in an amount of not more than 0.08% by weight. The "short path evaporation" employed in the process of the present invention includes evaporation and subsequent condensation of appropriate compounds. "Short path evaporation", for purposes of the present invention, is a thermal separation operation utilizing a short path evaporator.

For the purposes of the present invention, a short-path evaporator is an evaporator in which "the condenser is integrated into the evaporation body, so that the vaporized components only travel a very short distance in the vapor phase [...]", see "Fluidverfahrenstechnik: Fundamentals, Methodology, Technology, Practice ", Ralf Goedecke, Publisher: John Wiley & Sons: 201 1; Page 643, point 7.3.2.7.

The term "short path evaporation" for the purposes of the present invention also includes the so-called short path distillation (short path distillation).

The short-path evaporation is preferably carried out at the pressure to be used according to the invention in the range of 1 to 0.001 mbar and the temperature in the range of 50 to 250 ° C. carried out in a corresponding short-path evaporator with internally arranged capacitor with continuous mixing of the substance film aufzutrennenden on the evaporator surface.

The principle of the short-path evaporation is based on the fact that a mixture of substances supplied to the evaporator is heated at an evaporator surface and the constituents of the substance mixture that evaporate condense on a condenser surface opposite the evaporator surface. In order to minimize pressure losses, the distance between the evaporator surface and the capacitor surface is chosen to be very small. The distance from the evaporator surface to the condenser (or condenser surface) is preferably a few centimeters.

A common and for the purposes of the present invention preferred short path evaporator (short path evaporator) comprises a cylindrical body with an externally disposed heating jacket and an internally arranged wiper system, so that the evaporation can be carried out with continuous mixing of the substance film to be separated. Short path evaporators suitable for the purposes of the present invention are commercially available, e.g. from UIC GmbH or Buss-SMS-Canzler GmbH.

The short-path evaporator used in the method according to the invention usually comprises an evaporator surface and a condenser surface. In the context of the present invention, the surface of the evaporator means the evaporator surface of the short-path evaporator used and the condenser surface means the condenser surface of the short-path evaporator used.

The above-mentioned temperature in the range of 50 to 250 ° C is the average temperature of the heating medium, with which the Verdampferoberfiäche is heated in short path evaporator. This also applies to the preferred temperatures mentioned below in the text. The mean temperature of the heating medium is understood as the arithmetic mean of the inlet and outlet temperature of the heating medium.

When carrying out the process according to the invention, the evaporator surface and the condenser surface of the short-path evaporator are preferably directly opposite each other. In this case, the evaporator surface and the condenser surface of the short-path evaporator are particularly preferably arranged in a cylindrical manner, two cylinders being interlocked in the cylindrical arrangement. During the evaporation, the pressure within the pressure range defined above in the text is preferably lowered so far that the mean free path of the vaporized particles in the vapor is greater than the distance between the evaporator surface and the condenser surface (molecular distillation). The mean free path can be determined by known methods. The pressure required therefore depends, inter alia, on the dimensions of the apparatus and on the vapor pressure of the substance to be distilled at the selected temperature (see Kirk Othmer, Encyclopedia of Chemical Technology, 4th Ed., Wiley, Volume 8, page 349). Suitable arrangements are described, for example, in: HJL Burgess (ed), Molecular Stills, Chapman and Hall, 1963. An apparatus arrangement comprising the evaporator surface and the condenser surface can be designed in almost any geometric shape as long as short path evaporation is possible. It is preferred that the two surfaces are directly opposite each other, so that the molecules can pass unhindered from the evaporator surface to the condenser surface. Considering, for example, a plane-parallel arrangement of the two surfaces or a cylindrical arrangement in which two cylinders are set into each other and the directly opposite surfaces of the two cylinders form the evaporator and the condenser surface. The evaporator surface is suitably heated, generally by means of backside devices, and also the condenser surface is suitably cooled, also generally by means of backside devices.

A feature of a short path evaporator in the context of the present invention is both the evaporation of volatile compounds (compounds having a lower boiling temperature than HMF, for a more precise definition, see below), and (in the context of the present invention) the evaporation of the HMF from a Product movie out. Preferably, the mechanical influence of the product film by so-called wiper systems. The mixture to be distilled is fed at the top of the apparatus and distributed evenly on the inner circumference of the evaporator by the rotating wiper system. The product flows as a film due to gravity at the externally heated evaporator surface down. To ensure a uniform wetting of the evaporator surface, to produce an intensive mixing and a high turbulence in the product film and thus to increase the evaporation performance, the known and common wiper systems can be used. It has now surprisingly been found that in the separation of HMF by short-path evaporation, especially when carrying out a preferred short-path evaporation and when using preferably designed short-path evaporator little or no degradation products or by-products of HMF arise and that in a corresponding inventive method HMF with high purity and very good performance properties is obtained. In addition, the ionic liquid can be recycled.

In the process according to the invention, HMF (as a desired product) is separated from the mixture prepared in step (A) and withdrawn as distillate from the condenser surface. The ionic liquid (s) remain or remain on the evaporator surface. Suitable devices are e.g. such that the ionic liquid (s) drain from the evaporator surface and are collected; Accordingly, the HMF flows off the condenser surface and is obtained as a distillate. The distance between the evaporator surface and the condenser surface is also dependent on the size of the short-path evaporator due to constructive boundary conditions.

In a preferred embodiment of the method according to the invention, a short-path evaporator is used, in which the evaporator surface and the condenser surface are arranged in a cylindrical manner, and in which the distance between the evaporator surface and condenser surface preferably in the range of 1/10 to 1/3, particularly preferably 1 / 8 to 1/4 of the inner diameter of the housing shell lies.

According to another preferred embodiment, the distance between evaporator surface and condenser surface is in the range of 1 cm to 100 cm. The evaporator surface and the condenser surface can be the same size or different sizes. Preferably, a short path evaporator is used in which the ratio of the evaporator surface to the condenser surface is in the range of 10: 1 to 1:10.

Preferably, the condensation takes place at the condenser surface at a temperature in the range of 0 ° C to 200 ° C, more preferably 10 ° C to 150 ° C and most preferably 20 ° C to 100 ° C, said information to the middle Temperature of the cooling medium, with which the condenser surface is cooled, are related. The mean temperature of the cooling medium is the arithmetic mean of the inlet and outlet temperature of the cooling medium.

The average residence time of the residue (ie, essentially the total amount of ionic liquids) on the evaporator surface is preferably in the range of 1 second to 10 minutes, more preferably in the range of 1 second to 5 minutes, and most preferably in the range of 1 second to 2 minutes. The mean residence time is the time which the distillation residue requires on average to flow over the evaporator surface. The effective residence times of individual particles may be different, e.g. due to flow effects and / or turbulence. To determine the average residence time, tracer compounds, e.g. Dyes or radiolabelled compounds, preferably dyes, are used.

In a preferred embodiment, a splash guard is used between the evaporator surface and the condenser surface in order to prevent an undesired transfer of the two products of value (HMF; ionic liquid (s)) into the respective other product of value, i. e.g. from the evaporator surface to the condenser surface, for example by entrainment or spraying, to reduce or largely completely avoided.

As a splash protection predominantly blinds are used, which usually comprise vertically arranged slats made of metal or plastic. The horizontal spacing of the lamellae is chosen such that a transfer of liquid droplets from the evaporator surface to the condenser surface is reduced or completely prevented. The spray protection used preferably has a pressure drop of less than 0.1 mbar, more preferably less than 0.01 mbar, very particularly preferably less than 0.001 mbar. The attachment of the splash guard can be done both on a wiper system and on an inner capacitor. Design, material and method of attachment of the splash guard are insignificant for the present invention so far as long as the passage of liquid droplets largely prevented or reduced and only a slight pressure loss (preferably as described above) is maintained. The acid value of the mixture described above (and below) in the text (see step (A)) was determined in the context of the present invention using a Metrohm 848 Titrino Plus Titrometer. For this purpose, 0.1 to 0.2 g of a corresponding sample were titrated against tetrabutylammonium hydroxide ([n-Bu ₄ N] [OH]) 0.1 mol / L in ethanol). The By internal conversion, the instrument delivers as a result a standard acid number, which is expressed in units of milligrams [mg KOH] (potassium hydroxide) per gram [g] of sample. Our own investigations have shown that the ionic liquids used for the mixture often already contain acids of different strengths, so that when tirring a sample of a mixture according to step (A) regularly several points of change are observed. In this case, the acid number refers to the sum of all determined individual acid numbers. The acid number of the mixture according to step (A) has the unit milligrams [mg KOH] (mg potassium hydroxide) per gram [g] (mixture according to step (A)). For the qualitative and quantitative determination of the cations of the ionic liquids and the HMF and Di-HMF, methods suitable for the person skilled in the art are known, in particular comparative HPLC analyzes based on reference samples.

For the quantitative determination of HMF, Di-HMF and imidazolium-based ionic liquids (for example the quantitative determination of the ethyl-methylimidazolium cation (EMIM)), such an HPLC analysis is preferably used. Using reference samples with known concentrations (EMIM from EMIM Octanoate, HMF, Di- HMF), separate calibration runs are first carried out for the respective analytes. This allows for quantitation in samples where the quantitative composition is unknown. The HPLC analysis was carried out in own investigations as follows:

Separation column: Primesep 200 (250 * 3.2mm), 2 columns in a row,

Temperature: 25 ° C,

Injection volume 6 μΙ,

Detection: UV, 210 nm,

Eluent: 60 vol% H ₂ O + 40 vol% acetonitrile + 0.03 vol% 85% H ₃ P0 ₄ ,

Flow: 0.5 ml / min.

Running time: 30 min

Our own investigations have also shown that in a (to be set according to the invention in step (B)) in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C regularly excellent to satisfactory separation results are achieved. If the pressure exceeds (significantly) 1 mbar, higher temperatures are required to maintain the separation efficiency. However, this leads to a increased thermal load and thus to a much higher risk that unwanted degradation or by-products arise. This applies equally to temperatures (significantly) greater than 250 ° C.

If the pressure falls below (clearly) 0.001 mbar, the process can no longer be carried out in a simple and economical manner, and additional apparatus requirements are imposed on the plant in order to maintain the vacuum. In addition, the condensation of the vaporized HMF on the condenser surface deteriorates, resulting in a loss of HMF in the distillate and thus unnecessary losses of HMF.

Our own investigations have shown that when (clearly) falling below a temperature of 50 ° C, the inventive method is regularly no longer efficiently feasible. In these cases, a comparatively much longer residence time is required in the short path evaporator (or, alternatively, additional passes through the short path evaporator are required) to maintain separation efficiency and to avoid inefficient separation. Step (B) of the process according to the invention (as described above, preferably as defined above as preferred) is preferably carried out continuously, more preferably the steps (A) and (B) are carried out continuously. In some cases, the process according to the invention (as described above, preferably as defined above as being preferred) is preferably carried out semi-continuously.

Particular preference is given to a process according to the invention (as described above), wherein the mixture prepared in step (A) comprises as constituent of the other substances one, more than one or all substances selected from the group consisting of: (e1) Bronsted acids ( can be used one or more Brönsted acids),

(e2) salts with inorganic cation (it is possible to use one or more such salts),

(e3) sugar (saccharide) (it is possible to use one or more such sugars),

(e4) Humins, (e5) Furfural and

(e6) levulinic acid,

The sugars of the substance (e3) are preferably one, several or all of the compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, preferably (e3) comprises fructose and / or glucose.

The short-path evaporation to be carried out in the process according to the invention also regularly leads to good separation results in the presence of the abovementioned compounds / substances. A separation e.g. the Humine before performing the short-path evaporation is regularly not required. The total amount of the other substances in the mixture prepared according to step (A) is preferably less than 20% by weight, more preferably less than 15% by weight, particularly preferably less than 10% by weight, based on the total mass of the mixture. Our own investigations on commercially available ionic liquids have shown that in some cases they comprise residues of one or more Brönsted acids from the production process of the ionic liquids. These residues cause such commercial ionic liquids to have an acid number typically in the range of 0.2 to 15 mg KOH / g. Our own investigations have also shown that some of these Brönsted acids can not be separated from the commercially available ionic liquids by distillation regularly, or not completely, in particular those Brönsted acids whose boiling point is 300 ° C or more, at a pressure of 1013.25 hPa , is.

For salts preferably not contained in the mixture and their amounts, see below in the text.

The removal of HMF according to step (B) of the process according to the invention is carried out from the mixture prepared in step (A) by short path evaporation at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C. The preparation of the mixture according to step (A) usually comprises one or more than one step ((A1), (A2), etc., see below in the text). In some cases, the mixture is preferably prepared by mixing the compounds comprising the mixture. fertilized, so that a mixture according to step (A) defined results. In other cases it is preferred to convert one or more starting compounds into a reaction medium by reaction in product compounds, so that according to step (A) of the process according to the invention, a (product) mixture results and is produced.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as being preferred), wherein the preparation of the mixture according to step (A) comprises the following steps:

(A1) by Bronsted acid or otherwise catalyzed dehydration of one, two or more starting compounds selected from the group consisting of hexoses. Oligosaccharides comprising hexose units, and polysaccharides comprising hexose units. preferably fructose and / or glucose, in a reaction mixture comprising said one or more ionic liquids as solvent to give a product mixture comprising 5-hydroxymethylfurfural, (A2) optionally partially neutralizing the product mixture obtained according to step (A1) or mixture obtained therefrom in further steps, and

(A3) optionally separating (preferably distillative separation) of water and / or 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 from that according to step (A1) obtained product mixture or a mixture obtained therefrom in further steps or - from the partially neutralized product mixture obtained according to step (A2) or from a mixture obtained therefrom in further steps.

Preferably, the partially neutralized product mixture or mixture obtained after step (A2) has an acid number of less than 10 mg KOH / g, preferably less than 7 mg KOH / g and more preferably less than 5 mg KOH / g and most preferably less than 4 mg KOH / g, however, in each of these preferred cases the acid number of the partially neutralized product mixture is preferably at least 0.2 mg KOH / g, more preferably at least 0.3 mg KOH / g: preferably the acid number is in the range of 0.2 (preferably 0.3) to 1 mg KOH / g (or even lower), preferably in a range of 0.2 (preferably 0.3) to 0.6 mg KOH / g, the acid value after the partial neutralization smaller than before partial neutralizing.

Typical compounds having a boiling temperature which is at least at a pressure in the range of 0.1 to 500 mbar lower than the boiling point of 5-hydroxymethylfurfural at the same pressure value are furfural, levulinic acid, alkyl levulinates, formic acid, alkyl formates and formaldehyde.

In some cases, a method according to the invention is preferred (as described above, preferably as defined above as preferred), wherein the optional step (A3) comprises one, two, three or more than three steps. Preferably, from the mixture resulting after step (A1) or (A1) and (A2), both water and compounds having a boiling temperature which is at least at a pressure in the range of 0.1 to 500 mbar lower than the boiling point of 5-hydroxymethylfurfural at the same pressure value, separated. The separation of these compounds is preferably carried out in two, three or more than three substeps, the following preferably applying to the substeps: the pressure in a substep N + 1 immediately following a substep N is lower compared to the pressure in substep N and / or the temperature in the immediately following substep N + 1 is higher compared to the temperature in substep N. Preferably, the resulting mixture is subsequently fed to the cake in accordance with step (B). Step (A) of the process according to the invention (as described above, preferably as defined above as preferred) in some cases preferably comprises further steps, for example storage. The number and type of steps required for the preparation of a mixture according to step (A) is irrelevant: it should be noted that (i) a mixture results as defined in step (A) of the process according to the invention and (ii) from this mixture prepared in step (A) according to step (B) by short path evaporation at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C HMF is separated.

The preparation of HMF from hexoses or hexose-containing educts is known to the person skilled in the art (cf Hydroxymethylfurfural, A Versatile Platform Chemical Made from Enabling Resources, Chemical Reviews, 2013, 1 13, 1499 to 1597). Step (A2) concerns an optional partial neutralization. This means, for example, that the total amount of acidic groups in the mixture is reduced (partially neutralized) by neutralization reaction by adding a suitable amount of a Brönsted base. The result is a partially neutralized product mixture with a reduced acid number compared to the product mixture before the partial neutralization. Preferably, the partial neutralization comprises the addition of a Bronsted base. Partial neutralization is always preferred when (i) the total amount of acidic groups favors the formation of by-products and degradation products of the HMF in the mixture beyond acceptable levels and / or (ii) the acid-reactive groups become one or more compounds that would be separated during the short path evaporation along with the HMF (and correspondingly in the distillate would promote the formation of by-products and degradation products of the HMF).

In preferred embodiments of the process according to the invention (as described above, preferably as defined above as preferred), the amount of Bronsted base is chosen so that the acid number of the resulting partially neutralized product mixture is less than 10 mg KOH / g, preferably less than 7 mg KOH / g and more preferably less than 5 mg KOH / g and most preferably less than 4 mg KOH / g, however, in each of these preferred cases the acid number of the partially neutralized product mixture is preferably at least 0.2 mg KOH / g, more preferably at least 0 , 3 mg KOH / g. Preferred Bronsted bases for neutralization are hydroxides of the organic cations which (the cations) are also constituents of the ionic liquids), particularly preferred are EMIM hydroxide, EMIM methyl carbonate and mixtures thereof. In some cases, inorganic bases are preferred, preferably NaOH, KOH, Mg (OH) ₂ and mixtures thereof. However, inorganic bases have the disadvantage that, unlike EMIM hydroxide and EMIM methyl carbonate, the salts of inorganic bases usually accumulate in the IL. In other cases, the use of polymer-based ion exchange resins with weakly basic groups (eg Amberlite IRA67) is preferred.

In some cases, a process according to the invention is preferred (as described above, preferably as defined above as preferred), with no partial neutralization being carried out if the product mixture comprising 5-hydroxymethylfurfural obtained in step (A1) comprises those Brönstedt acids which are described in US Pat Step (B) during the short-path evaporation only to a very small extent together with the HMF into the distillate and there lead only to a negligible decomposition of the desired product HMF; especially in the presence of small amounts of conditions of methanesulfonic acid, it is preferable in some cases to dispense with carrying out a partial neutralization according to step (A2).

Our own investigations have shown that the process according to the invention leads to HMF which is largely free from impurities. Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein the total amount of HMF in the distillate is greater than 90 wt .-%, preferably greater than 95 wt .-%, particularly preferably greater than 96 wt .-% , based on the total mass of the distillate.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as preferred), wherein after step (B) and optionally after separation of further constituents of the mixture, the one or more ionic liquids are used as solvents for saccharides, preferably fructose and / or glucose, be used

preferably in a dehydration of one, two or more starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, in a reaction mixture according to step (A1), catalyzed by Brönsted acid or otherwise.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as preferred), after step (B) and optionally after separation of further mixture constituents, the one or more ionic liquids as solvent in a reaction mixture according to step (A1). in a Bronsted acid catalyzed dehydration of one, two or more starter compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units.

Particularly preferred is a process of the invention (as described above, preferably as defined above as preferred), wherein the mixture prepared in step (A) no HMF at a temperature of 120 ° C in the mixture stabilizing amount of lrCI ₃ and / or CrCl ₃ preferably comprises no IrCl ₃ and no CrCl ₃ , preferably no iridium halide and no chromium halide, more preferably no HMF at a temperature of 120 ° C in the mixture stabilizing amount of iridium and / or chromium ions, most preferably no iridium - And no chromium ions covers. In some cases, a process according to the invention (as described above, preferably as defined above as preferred) is preferred, wherein the mixture prepared in step (A) comprises chloride ions in a total amount less than 100 ppm, based on the total amount in step (A) prepared mixture; Preferably, the mixture prepared in step (A) does not comprise chloride ions. Our own investigations have shown that in selected cases the presence of chloride ions and water in the mixture produced in step (A) leads to an undesirable formation of corrosive hydrogen chloride, or the chloride ions themselves lead to severe corrosion on metal surfaces. Our own investigations have surprisingly shown that when carrying out the process according to the invention (ie by means of short-path evaporation) it is possible to dispense regularly with the addition of the stabilizing total amount of iridium chloride and chromium chloride known from the prior art. On the one hand, this simplifies the process design and, on the other hand, leads to a more economical process, since iridium salts are very costly. In addition, chromium compounds are potential environmental toxins. A waiver of chromium salts thus leads in addition to a more ecological process.

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein in step (B) no additional entraining agent is used. Conventional entrainers known from the prior art (also regularly referred to as stripping agents) are compounds which are present in gaseous form under distillation conditions. Commonly preferred entrainers are low or non-reactive gases (inert gases) (preferably nitrogen, carbon dioxide), alkanes of one to eight carbon atoms (preferably hexane), ketones (preferably acetone, isobutyl ketones (preferably methyl isobutyl ketone (MIBK)) and water. According to a particularly preferred embodiment of the process according to the invention, no additional compound (as entrainer) is used in step (B) selected from the group consisting of nitrogen, carbon dioxide, hexane, acetone, isobutyl ketones and water, preferably no compounds selected from the group consisting of

- protective gases,

Alkanes of one to eight carbon atoms,

- ketones and - Water.

Dispensing with a gaseous entrainment agent is always preferred when the process of the invention (as described above, preferably as defined above as preferred) in a simple and economical manner at the most preferred pressures within the range of 0.001 to 1 mbar and in combination at a temperature in the range of 50 to 250 ° C (for the most preferred pressures see below in the text). The additional presence of a gaseous entrainment agent regularly adversely affects the vacuum in a short path evaporator. Particular preference is given to a process according to the invention (as described above, preferably as defined above as preferred), wherein step (B) is carried out at least until at least 80% of the 5-hydroxypropyl is optionally removed from the A) are prepared, preferably until at least 85% of the 5-hydroxymethylfurfural are separated from the mixture prepared in step (A), preferably at least 90% and particularly preferably at least 95%.

Particular preference is given to a process according to the invention (as described above, preferably as defined above as being preferred), the mixture prepared in step (A) comprising:

(b) 5-hydroxymethylfurfural in an amount of 10% by weight or more than 10% by weight, preferably more than 15% by weight, and preferably less than 50% by weight, more preferably less than 40% by weight. -%.

The abovementioned percentages by weight relate to the total mass of the mixture prepared in step (A) (and optionally obtained by further treatment).

Our own investigations have surprisingly shown that when carrying out the process according to the invention (ie by means of short-path evaporation), a comparatively small formation of dimers and / or oligomers of the HMF is regularly observed. This is a surprise given that with increasing total amount of HMF in the Step (A) vorgesteilten mixture, especially in the presence of significant amounts of Bronsted acids (the acid number of the mixture is according to the invention in the range of 0.1 to 15 mg KOH / g) both the risk of dimer and / or oligomer formation increases, as well as the risk increased degradation reactions. On the other hand, the short residence times which are usual in short-path evaporation - and thus gentle evaporation conditions - have a surprisingly favorable effect on the risks mentioned above, so that the otherwise known and customary amount of HMF in a corresponding mixture in many cases becomes apparent without disadvantages may be exceeded. Thus, the above-mentioned scientific article in Green Chemistry on page 1223, left column, first excerpt paragraph extracts: "[...] and the fraction of 5-HMF in [OMIMJCI is always less than 10% in the dehydration of carbohydrates [...] ".

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein the mixture produced in step (A) 5-hydroxymethylfurfural in an amount of 15 wt .-% or more, preferably 20 wt .-% or more, based on the total mass of the mixture produced in step (A) (and optionally obtained by further treatment).

Preferably, the mixture to be separated according to step (B) is fed to the evaporator surface of the short-path evaporator in a predetermined amount per hour and per square meter of the evaporator surface (the so-called surface load). By surface loading is meant the mass of the mixture to be separated according to step (B), which is supplied to the evaporator surface of the short path evaporator in one hour, based on one square meter of the evaporator surface.

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), wherein in step (B) the surface loading in the range of 2 to 500 kg in step (A) prepared mixture per m ² evaporator surface per hour, preferably in the range of 50 to 400 kg in step (A) prepared mixture) per m ^{2 of} evaporator surface per hour, more preferably in the range of 80 to 350 kg in step (A) prepared mixture per m ^{2 of} evaporator surface per hour. The unit of surface loading is given below as kg / h / m ² .

Our own investigations have shown that when (significantly) exceeding the value of 500 kg / h / m ^2, the residence time of the mixture on the evaporator surface is often too low. In some cases, this means that the HMF is not completely or sufficiently isolated (due to excessive surface loading). Particularly preferred is a method according to the invention (as described above, preferably as defined above as preferred), wherein in step (B) the short-path evaporation in a

Pressure in the range of 0.01 to 0.9 mbar, preferably 0.05 to 0.85 mbar and / or one

Temperature in the range of 80 to 245 ° C, preferably 100 to 240 ° C, more preferably 140 to 240 ° C, in particular preferably 160 to 220 ° C is performed.

More preferably, the combination of pressure and temperature is selected so that at a given pressure a temperature prevails during the short path evaporation which (i) exerts only a small thermal load but at the same time (ii) produces a largely acceptable separation performance. Particularly preferred combinations of pressure and temperature are:

Temperatures in the range of 160 to 250 ° C, preferably 175 to 230 ° C, more preferably 190-230 ° C and

Pressures in the range of 0.05 to 0.9 mbar, preferably 0.05 to 0.6 mbar, particularly preferably from 0.05 to 0.4 mbar.

Preferably, one of the immediately above mentioned, differently preferred temperature ranges is combined with one of the directly above mentioned, differently preferred pressure ranges. The person skilled in the art can determine particularly preferred and suitable combinations by means of simple experiments.

Particularly preferred is a method of the invention (as described above, preferably as defined above as preferred), wherein the one or at least one of the plurality of ionic liquids comprises an organic cation selected from the group consisting of unsubstituted imidazolium ions, substituted imidazolium ions, unsubstituted phosphonium ions and substituted phosphonium ions. Particularly preferred imidazolium ions are selected from the group consisting of 1-methylimidazolium, 1-ethylimidazolium, 1- (1-propyl) -imidazolium, 1- (2-propyl) -imidazolium, 1- (1-allyl) -imidazolium, 1 - (1-butyl) -imidazolium, 1- (1-octyl) -imidazolium, 1- (1-dodecyl) -imidazolium, 1- (1-tetradecyl) -imidazolium, 1- (1-hexadecyl) -imidazolium, 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-methylimidazolium, 1- (1-hexadecyl) -3-ethylimidazolium, 1- (1-hexadecyl) -3-butylimidazolium, 1- (1-hexadecyl ) -3-octylimidazolium, 1, 2-dimethylimidazolium, 1, 2,3-trimethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1- (1-butyl) -2,3-dimethylimidazolium, 1- (1-Hexy !) - 2,3-dimethyl-imidazolium, 1- (1-octyl) -2,3-dimethylimidazolium, 1,4-dimethylimidazolium, 1,3,4-trimethylimidazolium, 1, 4-dimethyl-3-ethylimidazolium, 3-methylimidazolium, 3-ethylimidazolium, 3-n-propylimidazolium, 3-n-butylimidazolium, 1, 4-dimethyl-3-octylimidazolium, 1,4,5-trimethylimidazolium, 1,3,4,5-tetramethylimidazolium, 1, 4,5-trimethyl-3-ethylimidazolium, 1, 4,5-trimethyl-3-butylimidazolium, 1, 4,5-trimethyl-3-octylimidazolium, 1-prop-1-en-3-yl-3-methylimidazolium and 1- prop-1-en-3-yl-3-butylimidazolium. Particularly preferred imidazolium ions are selected from the group consisting of 1, 3-dimethylimidazolium, 1, 3-diethylimidazolium, 1-ethyl-3-methylimidazolium and 1- (1-butyl) -3-methylimidazolium. In some cases, mixtures of the aforementioned preferred imidazolium ions are preferred. Preferred phosphonium ions are tetraalkylphosphonium ions, preferably selected from the group consisting of tetraalkylphosphonium ions of the formula (II) R1

R4 ^ \

R2

R3

(II) wherein 1, R2, R3 and R4 are each independently selected from the group consisting of methyl, ethyl, n -propyl, iso -propyl, n -butyl, iso -butyl, n -hexyl, n -octyl, Dodecyl, tetradecyl, hexadecyl and allyl.

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

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

Particularly preferred is a process according to the invention (as described above, preferably as defined above as preferred), comprising preparing a mixture comprising 5-hydroxymethylfurfurai and separating 5-hydroxymethylfurfural from the prepared mixture, comprising the following steps:

(A) preparing the mixture comprising:

(a) one or more ionic liquids,

(b) 5-hydroxymethylfurfural (HMF) in an amount of 5 to 50% by weight, preferably more than 10% by weight,

(c) 5,5 '- [oxybis (methylene)] bis-2-furancarboxaldehyde in an amount of not more than 7% by weight

(d) water in an amount of not more than 0.5% by weight,

(e) other substances, wherein the ratio of the total mass of ionic liquids and other salts to the mass of 5-hydroxymethylfurfural in the mixture is in the range of 19: 1 to 1: 1, preferably from 10: 1 to 1: 1, more preferably from 6: 1 to 1: 1 and most preferably from 4: 1 to 1: 1. and the acid number of the mixture is in the range of 0.1 to 15 mg KOH / g, wherein percentages by weight are based on the total mass of the mixture, wherein the mixture produced in step (A) as part of the other substances one, more than one or all Substances comprises, selected from the group consisting of:

(e1) Bronsted acids (one or more Bronsted acids can be used),

(e2) salts with inorganic cation (one or more of such salts may be used), (e3) sugars (saccharide) (one or more of such sugars may be used), (e4) humins, (f5) furfural and

(e6) levulinic acid, wherein the preparation of the mixture comprises the following steps:

(A1) by Brönsted acid or otherwise catalyzed dehydration of one, two or more starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, preferably fructose and / or glucose, in a reaction mixture comprising said one or more ionic liquids as solvent to give a product mixture comprising 5-hydroxymethylfurfural,

(A2) optionally partially neutralizing the product mixture obtained according to step (A1) or a mixture obtained therefrom in further steps, and

(A3) optionally separating water and / or 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 from the obtained according to step (A1) product mixture or a mixture obtained therefrom in further steps or from the partially neutralized product mixture obtained according to step (A2) or from a mixture obtained therefrom in further steps,

(B) separating 5-hydroxymethylfurfural from the mixture prepared in step (A) by short path evaporation at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C, to at least 85% of 5-hydroxymethylfurfural the mixture prepared in step (A) are separated, wherein after step (B) and optionally after separation of further mixture constituents, the one or more ionic liquids are used as solvent in a dehydration of one, two or more catalyzed by said Brönsted acid dehydration Starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, in a reaction mixture according to step (A1).

The comments made above in the text on preferred embodiments preferably also apply to the particularly preferred (above) embodiment of the method according to the invention.

The invention will be explained in more detail by way of examples. Preparation of a mixture (step (A)):

Dehydration of saccharides to HMF in an ionic liquid (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 (II) (EMIM OMs).

(I I I)

In a first substep, 1200 g of the ionic liquid EMIM OM (Basionics ST35) together with 4.6 g (about 47.9 mmol) of methanesulfonic acid (MsOH) as catalyst were introduced into the 2L double-walled glass reactor. Subsequently, this first part mixture was heated to 150 ° C. at 100 mbar. In a second sub-step 1200 g of fructose syrup (as a 67% solution in water) were continuously added within 1 10 min. The temperature of the liquid phase was maintained at an average of 130 ° C by an additional heat input by means of the (external) thermostat. After completion of the addition of the fructose syrup was stirred for a further 30 minutes at 130 ° C. This resulted in a product mixture. Subsequently, the product mixture was allowed to cool to room temperature.

The cooled product mixture had the following composition as shown in Table 1: Table 1 :

The conversion was 95% and the yield of HMF was 78%, based on the total amount of fructose used (from the fructose syrup).

Partial neutralization:

103.2 g (about 45.5 mmol) of an EMIM hydroxide solution (EMIM OH, 5.65% in water) were added with stirring to the cooled product mixture obtained according to step 1, in order to prepare the catalyst used in step 1 as catalyst for the dehydration To neutralize the amount of methanesulfonic acid (MsOH) added as far as possible (about 95%). This resulted in a cooled and partially neutralized product mixture. During partial neutralization, the conductivity of the cooled product mixture increased from 1521 pS / cm to 4.70 mS / cm and the pH from 2.54 to 4.22.

The cooled and partially neutralized product mixture had the following composition as shown in Table 2:

Table 2:

(Di-HMF)

ionic liquid (EMIM OMs) 64 ± 2.5

Water 7.5 ± 1.5

Methanesulfonic acid (MsOH) <0, 1

Other 5 ± 1 .5

Water separation:

The cooled and partially neutralized product mixture obtained according to step 2 was transferred in step 3 for the most complete removal of the water in a continuously operated glass thin-layer evaporator (surface: 920 cm ² ) and at a temperature of 160 ° C and a pressure of 60 mbar treated. Subsequently, the amount of water was less than 0.3 wt .-%, based on the total mass of the heat-treated product mixture. The result was a low-water, partially neutralized product mixture.

The low-water, partially-neutralized product mixture had the following composition as shown in Table 3:

Table 3:

Example 2: Separation of HMF by means of Kurzweaverdampfuna (step (B)):

The low-water, partially neutralized product mixture resulting at the end of Example 1 was then subjected to short-path evaporation to separate the HMF from the ionic liquid into a glass short-path evaporator of the type VKL 70-4-SKR from VTA GmbH.

The apparatus for short path evaporation included the following modules: a heated storage tank, a variable gear pump for dosing the original, an evaporator with internal rotor, equipped with a comb wiper from Grafitteflon, a controllable via an HT thermostat wall heater, an intensive cooler, designed as a cold finger and filled with a cooling medium, a heated sump outlet, controllable via a gear pump, a cooled distillate outlet, a low boiler outlet with cold trap (in particular for compounds having a boiling temperature which is at least a pressure value in the range of 0, 1 to 500 mbar lower than the boiling temperature of the 5-hydroxymethylfurfural at the same pressure value) and a two-stage oil rotary vane pump with switchable diffusion pump and vacuum throttling via a needle valve for vacuum generation.

The evaporator surface was 465 cm ² . The internal rotor was operated at a speed of 400 revolutions per minute. The temperature in the storage tank was 50 ° C. The temperature in the condenser was 35 ° C.

Short path evaporation was performed at various evaporation conditions (runs). A summary of the evaporation conditions and the resulting results is shown in Table 4.

Table 4:

2 180 0.08 385 2.02 0.82 97.21

3 185 0.12 399 2.10 0.83 96.92

4 190 0.42 1 152 5.69 1, 05 96.00

5 185 0.1 1 452 2.41 0.59 96.46

6 185 0.45 464 2.48 0.62 96.98

7 190 0.09 1 165 5.84 1, 03 95.43

8 190 0.1 1 2426 1 1.99 4.74 82.56

Example 2 according to the invention shows that an efficient separation of HMF from an ionic liquid without entrainer and without the addition of stabilizing amounts of inorganic salts is achieved.

Example 3: Separation of HMF from a mixture without partial neutralization:

Step 1: Dehydration of saccharides to HMF in an ionic liquid

(Semi-batch procedure):

The dehydration was carried out as described above in Example 1, Step 1, with the differences that (i) instead of the 4.6 g methanesulfonic acid (MsOH) 20 g poly (styrenesulfonic acid) (a non-volatile acid, CAS) Number: 28210-41-5) were used and (ii) after completion of the addition of the fructose syrup for a further 90 minutes (instead of 30 minutes) was stirred.

The resulting product mixture had the following composition (Table 5):

Table 5:

Water 2 ± 0.5

Polysulfonic acid 1, 1 ± 0,2 other 6 ± 1, 5

The conversion was> 95% and the yield of HMF was about 76%, based on the total amount of fructose used (from fructose syrup).

A partial neutralization was then not carried out, but the resulting product mixture was immediately for the most complete removal of the water in a thin film evaporator at 1 10 ° C, a pressure of 60 mbar and at 400 revolutions per minute (mass flow or feed rate: 600 g / h) dewatered with 16 liters of nitrogen per hour in countercurrent. This resulted in a water-poor product mixture with a water content of 0.41% by weight and an HMF

Content of 22.84 wt .-%, each based on the total mass of the low-water product mixture.

Step 2: C u rt ve ction:

The low-water product mixture (comprising polysulfonic acid) obtained after step 1 is then treated by short path evaporation to separate the HMF from the ionic liquid. The short-path evaporation is carried out in a plant, as described above in the text under Example 2. The following evaporation conditions or evaporation parameters were present: The temperature in the storage tank was 50 ° C. The temperature in the condenser was 35 ° C. The bottom temperature was 70 ° C. A total of 1743.4 g of the low-water product mixture were used in the short-path evaporation. The total mass of the distillate was 381.0 g, with the proportion of HMF in the distillate being 97.52% by weight. The removal rate of the HMF by short path evaporation was 93.3% in total.

Further parameters and the results are shown in Table 6: Table 6:

Claims

claims:

1 . A process comprising preparing a mixture comprising 5-hydroxymethylfurfural and separating 5-hydroxymethylfurfural from the prepared mixture, comprising the steps of:

(A) preparing the mixture comprising:

(a) one or more ionic liquids,

(b) 5-hydroxymethylfurfural (HMF) in an amount of 5 to 50% by weight,

(d) water in an amount of not more than 0.5% by weight,

(e) other substances, wherein the ratio of the total mass of ionic liquids and other salts to the mass of 5-hydroxymethylfurfural in the mixture is in the range of 19: 1 to 1: 1, preferably from 10: 1 to 1: 1, especially preferably from 6: 1 to 1: 1 and most preferably from 4: 1 to 1: 1. the acid number of the mixture is in the range from 0.1 to 15 mg KOH / g, weight percentages being based on the total mass of the mixture,

2. The method of claim 1, wherein the mixture prepared in step (A) as part of the other substances comprises one, more than one or all substances selected from the group consisting of: (e1) Bronsted acids,

(e2) salts with inorganic cation,

(e3) Sugars, (e4) Humines, (e5) Furfural and

(e6) levulinic acid.

3. The method according to any one of the preceding claims, wherein the preparation of the mixture according to step (A) comprises the following steps:

(A3) optionally separating water and / or compounds having a boiling temperature which is at least a pressure value in the range of 0.1 to 500 mbar lower than the boiling point of 5-hydroxymethylfurfural at the same pressure value from the product mixture obtained according to step (A1) or a mixture obtained therefrom in further steps or from the partially neutralized product mixture obtained according to step (A2) or from a mixture obtained therefrom in further steps.

4. The method according to any one of the preceding claims, wherein after step (B) and optionally after separation of further mixture constituents, the one or more ionic liquids are used as solvents for saccharides, preferably fructose and / or glucose,

in a dehydration of one, two or more starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, in a reaction mixture according to step (A1 ).

5. The method according to any one of the preceding claims, wherein after step (B) and optionally after separation of further mixture constituents, the one or more ionic liquids as solvent in a reaction mixture according to step (A1) in a Brönsted acid catalyzed dehydration of one, two or more starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units are used.

6. The method according to any one of the preceding claims, wherein the mixture prepared in step (A) comprises no HMF at a temperature of 120 ° C in the mixture stabilizing amount of lrCI ₃ and / or CrCI ₃ , preferably no lrCI ₃ and no CrCl ₃ preferably comprises no iridium halide and no chromium halide, more preferably no HMF comprises at a temperature of 120 ° C in the mixture stabilizing amount of iridium and / or chromium ions, most preferably comprises no iridium and no chromium ions.

7. The method according to any one of the preceding claims, wherein in step (B) no additional entraining agent is used.

8. The method according to any one of the preceding claims, wherein step (B) is carried out at least until at least 80% of the 5-hydroxymethylfurfural are separated from the mixture prepared in step (A), preferably at least 85% of the 5-H yd roxymethy If u rf u ra I are separated from the mixture prepared in step (A), preferably at least 90% and particularly preferably at least 95%.

A process according to any one of the preceding claims, wherein the mixture prepared in step (A) comprises:

(b) 5-hydroxymethylfurfural in an amount of

10 wt .-% or more than 10 wt .-%, preferably more than 15 wt .-%, and preferably less than 50 wt .-%, more preferably less than 40 wt .-%.

10. The method according to any one of the preceding claims, wherein in step (B) the surface loading in the range of 2 to 500 kg in step (A) prepared mixture per m ² evaporator surface per hour, preferably in the range of 50 to 400 kg in step ( A) prepared mixture) per m ^{2 of} evaporator surface per hour, more preferably in the range of 80 to 350 kg in step (A) prepared mixture per m ^{2 of} evaporator surface per hour.

1 1. The method according to any one of the preceding claims, wherein in step (B) the short-path evaporation at a pressure in the range of 0.01 to 0.9 mbar, preferably 0.05 to 0.85 mbar and / or a

Temperature in the range of 80 to 245 ° C, preferably 100 to 240 ° C, more preferably 140 to 240 ° C. in particular preferably 160 to 220 ° C is performed.

12. A process according to any one of the preceding claims, wherein the one or at least one of the plurality of ionic liquids comprises an organic cation selected from the group consisting of unsubstituted imidazolium ions, substituted imidazolium ions, unsubstituted phosphonium ions and substituted phosphonium ions.

13. A method according to any one of the preceding claims comprising preparing a mixture comprising 5-hydroxymethylfurfural and separating 5-hydroxymethylfurfural from the prepared mixture, comprising the steps of:

(A) preparing the mixture comprising:

(a) one or more ionic liquids,

(d) water in an amount of not more than 0.5% by weight,

(e) other substances, wherein the ratio of the total mass of ionic liquids and other salts to the mass of 5-hydroxymethylfurfural in the mixture is in the range of 19: 1 to 1: 1, preferably from 10: 1 to 1: 1, especially preferably from 6: 1 to 1: 1 and most preferably from 4: 1 to 1: 1, and the acid number of the mixture in the range of 0.1 to 15 mg KOH / g, wherein weight percentages are based on the total mass of the mixture in which the mixture produced in step (A) comprises as constituent of the other substances one, more than one or all substances selected from the group consisting of:

(e1) Bronsted acids,

Salts with inorganic cation, (e3) sugar,

(e4) Humins,

(e5) furfural and (e6) levulinic acid, wherein the preparation of the mixture comprises the steps of:

(A1) by Bronsted acid or otherwise catalyzed dehydration of one, two or more starting compounds selected from the group consisting of hexoses, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, preferably fructose and / or glucose. in a reaction mixture comprising said one or more ionic liquids as solvent to give a product mixture comprising 5-hydroxymethylfurfural,

(A3) optionally separating water and / or compounds having a boiling temperature which is at least a pressure value in the range of 0.1 to 500 mbar lower than the boiling point of the 5-hydroxymethylfurfural at the same pressure value from the obtained according to step (A1) product mixture or a mixture obtained therefrom in further steps or from the partially neutralized product mixture obtained according to step (A2) or from a mixture obtained therefrom in further steps,

(B) separating 5-hydroxymethylfurfural from the mixture prepared in step (A) by short path evaporation at a pressure in the range of 0.001 to 1 mbar and a temperature in the range of 50 to 250 ° C until at least 85% of the 5-hydroxy methyl furfural are separated from the mixture prepared in step (A), wherein after step (B) and optionally after separation of further mixture constituents the one or more ionic Liquids are used as solvents in a catalyzed by said Brönsted acid dehydration of one, two or more starting compounds selected from the group consisting of hexoses sen, oligosaccharides comprising hexose units, and polysaccharides comprising hexose units, in a reaction mixture according to step (A1).