Method of making furan-based bis-hydroxymethyl compounds from mixtures comprising hydroxymethylfurfural, and respective mixtures for use as intermediates

Abstract

Described herein is a method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural, in particular from mixtures comprising hydroxymethylfurfural, and a reaction mixture comprising hydroxymethylfurfural as obtainable by said method, as well as a use of said reaction mixture in a hydrogenation method for making 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran.

Description

[0001] Method of making furan-based bis-hydroxymethyl compounds from mixtures comprising hydroxymethylfurfural, and respective mixtures for use as intermediates

[0002] The present invention relates to a method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural, in particular from mixtures comprising hydroxy methylfurfural, and to a reaction mixture comprising hydroxymethylfurfural as obtainable by the method according to the invention, as well as to a use of said reaction mixture in a hydro- genation method for making 2,5-bis(hydroxymethyl)furan and / or 2, 5-bis(hydroxymethyl)tet- rahydrofuran.

[0003] Aldehydes from renewable sources, like hydroxymethylfurfural (“HMF”) or furfural, are important intermediates for the synthesis of mono- and di-functionalized alcohols, carboxylic acids, amines and other derivatives. Facilitated access to such aldehydes is therefore of particular interest for the chemical industry. Unfortunately, in particular HMF and furfural are thermodynamically and chemically unstable and very sensitive compounds. Due to the tendency of said compounds for forming humins, their isolation is often difficult and associated with high losses of material and low yields.

[0004] For example, 2,5-bis(hydroxymethyl)furan and 2,5-bis(hydroxymethyl)tetrahydrofuran are attractive starting compounds for the production of a broad range of polymers, such as BASF SE 230849 polyesters, polyester polyols, alcohol alkoxylates and other valuable polymeric structures. Said polymeric structures have the advantage of being derived from renewable raw materials and will usually be biodegradable, which makes them extremely valuable for sustainable future products or applications.

[0005] In the existing literature, several publications are dealing with methods for producing furan- based bis-hydroxymethyl compounds:

[0006] In document CN 103804329 A, a method is discussed which uses a catalyst to directly synthesize 2,5-bis(hydroxymethyl)furan or 2,5-bis(hydroxymethyl)tetrahydrofuran from hexoses.

[0007] Document WO 2014 / 033289 deals with the production of hydroxymethylfurfural from fructose.

[0008] S. Fulignati et al. report in Applied Catalysis A, General, 578 (2019) 122-133, of the hydrogenation of 2-hydoxymethylfurfural to furan diols, using Ru / C as catalyst.

[0009] P.P. Upare et al. in Green Chemistry 17 / 6 (2015) 3310-3313 discuss an integrated process for the production of 2,5-dihydroxymethylfuran from fructose.

[0010] P.P. Upare et al. in Green Chemistry 20 / 4 (2018) 879-885 report of an integrated process for the production of 2,5-dihydroxymethylfuran and its polymer from fructose.

[0011] Document KR 2017 0031269 A deals with a process for selective hydrogenation of hydroxymethyl furfural using a ruthenium nanoparticle supported catalyst.

[0012] Document DE 21 32 547 A1 pertains to a process for hydrogenating aromatic compounds to the respective cycloaliphatic compounds, involving a catalyst comprising ruthenium oxide hydroxide.

[0013] In the light of the prior art, there is, however, still a need for a simple, robust and efficient method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural, in particular 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran. BASF SE 230849

[0014] Correspondingly, it was a primary object of the present invention to provide a method of making furan-based bis-hydroxymethyl compounds, in particular 2, 5-bis(hydroxymethyl)fu- ran and / or 2, 5-bis(hydroxymethyl)tetrahydrofuran, in high yields, while said method of making said compounds should be particularly simple and robust.

[0015] It was another object of the present invention to provide a mixture comprising an intermediate or starting compound, where said intermediate or starting compound could be directly used in a hydrogenation method for making furan-based bis-hydroxymethyl compounds, in particular 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran, with the least possible effort required of purifying or isolating said intermediate or starting compound from said mixture.

[0016] It has now been found that the primary object and other objects of the present invention can be accomplished by a method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural, comprising the following steps:

[0017] 51 ) reacting a hexose sugar in a reaction mixture, the reaction mixture further comprising an acid, water and an organic solvent, at a temperature in the range of from 50 to 200 °C, and removing water from the reaction mixture, so that hydroxymethylfurfural is formed,

[0018] 52) preferably essentially neutralizing the reaction mixture from step S1) or essentially neutralizing the acid components present in the reaction mixture from step S1), preferably by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, to obtain an essentially neutralized reaction mixture comprising hydroxy methylfurfural, and

[0019] 53) subjecting BASF SE 230849 the reaction mixture comprising hydroxy-methylfurfural from step S1) or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1), or

[0020] (in case step S2) has been performed or in case the present method comprises step S2)) the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethyl- furfural from step S2), to hydrogenation in the presence of a catalyst comprising ruthenium (preferably selected from the group consisting of ruthenium on aluminium oxide; ruthenium on carbon and ruthenium oxide hydroxide, preferably ruthenium-lll-oxide hydroxide as is further defined below), comprising a temperature in the range of from 50 to 150 °C and a hydrogen pressure in the range of from 5 to 20 MPa, so that 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran is formed.

[0021] The invention as well as preferred variants and preferred combinations of parameters, properties and elements thereof are defined in the appended claims. Preferred aspects, details, modifications and advantages of the present invention are also defined and explained in the following description and in the examples stated below.

[0022] It has now been found that the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention as outlined here above is a simple, robust and efficient method of making furan-based bis-hydroxymethyl compounds, in particular 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetra- hydrofuran. It has further been found that the intermediate compound, hydroxymethylfurfu- BASF SE 230849 ral, as well as the products of the method of the invention, i.e. in particular 2,5-bis(hy- droxymethyl)furan and 2,5-bis(hydroxymethyl)tetrahydrofuran can be obtained in high purity and high yields, where the yields of the desired products, 2,5-bis(hydroxymethyl)furan or 2,5-bis(hydroxymethyl)tetrahydrofuran, or the specificity of the reaction, can be controlled by the choice of reagents used and / or by the choice of the reaction conditions applied.

[0023] In the method according to the present invention as outlined herein, the reaction mixture comprises at least the hexose sugar and further, in addition to the hexose sugar: water, an organic solvent and an acid, as is further explained in more detail below.

[0024] In the context of the present invention, “hydroxymethylfurfural” means the compound also known as 5-(hydroxymethyl)furan-2-carbaldehyde (preferred IUPAC name), which has the CAS RN 67-47-0, according to formula I shown here below:

[0025] In the context of the present invention, “2,5-bis(hydroxymethyl)furan” means the compound also known as (furan-2,5-diyl)dimethanol (preferred IUPAC name), which has the CAS RN 1883-75-6, according to formula II shown here below:

[0026] In the context of the present invention, “2,5-bis(hydroxymethyl)tetrahydrofuran” means the compound also known as “tetrahydrofuran-2,5-dimethanol”, in the form of both of its isomers (“cis” and “trans”, unless otherwise stated herein), according to formula III shown here below:

[0027] The “cis” form of 2,5-bis(hydroxymethyl)tetrahydrofuran has the CAS RN 2144-40-3 and the “trans” form of 2,5-bis(hydroxymethyl)tetrahydrofuran has the CAS RN 104-80-3. BASF SE 230849

[0028] It has been found that a catalyst comprising ruthenium as used in step S3) is particularly suited for use in the present method of making furan-based bis- hydroxymethyl compounds from hydroxymethylfurfural, e.g. because a catalyst comprising ruthenium has proven to be catalytically active even under robust reaction conditions, e.g. in the presence of nitrogencontaining compounds (e.g. nitrogen-containing compounds which may be used as organic solvents in the present method, like N-methyl-2-pyrrolidone) or in the presence of sulfur- containing compounds, i.e. under conditions under which the catalytic activity of other noble metal catalysts used in hydrogenation reactions is often impaired, reduced or completely lost.

[0029] Preferred is a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein in step S1):

[0030] - the hexose sugar is selected from the group consisting of D-glucose, D-fructose, D- saccharose and mixtures thereof, wherein preferably the hexose sugar comprises or is D-fructose; and / or

[0031] - the organic solvent is selected from the group consisting of N-alkyl-2-pyrrolidones, preferably selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyr- rolidone; 2-pyrrolidone; N-methyl succinimide; 1 ,3-dimethyl-2-imidazolidinone; dimethylformamide; dimethylsulfoxide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein preferably the organic solvent is selected from the group consisting of N-me- thyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein more preferably the organic solvent comprises or is N-methyl-2-pyrrolidone; and / or the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, methanesulfonic acid, benzenesulfonic acid, para-toluenesulfonic acid, naphthalenesulfonic acid, camphorsulfonic acid and mixtures thereof, BASF SE 230849 wherein preferably the acid comprises or is sulfuric acid.

[0032] In one more specific variant of the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention as defined herein (or of a respective method according to the invention as described above or below as being preferred), a method is preferred, comprising the following steps:

[0033] S1 ) reacting a hexose sugar in a reaction mixture, the reaction mixture further comprising an acid, selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, methanesulfonic acid, benzenesulfonic acid, para-toluenesul- fonic acid, naphthalenesulfonic acid, camphorsulfonic acid and mixtures thereof; wherein preferably the acid comprises or is sulfuric acid water and an organic solvent, selected from the group consisting of N-alkyl-2-pyrrolidones, preferably selected from the group consisting of N-methyl-2-pyrrolidone and N- ethyl-2-pyrrolidone; 2-pyrrolidone; N-methyl succinimide, 1 ,3-dimethyl-2-imidaz- olidinone; dimethylformamide; dimethylsulfoxide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein preferably the organic solvent is selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein more preferably the organic solvent comprises or is N-methyl-2-pyrroli- done; at a temperature in the range of from 50 to 200 °C, and removing water from the reaction mixture, so that hydroxymethylfurfural is formed, BASF SE 230849

[0034] 52) essentially neutralizing the reaction mixture from step S1) or essentially neutralizing the acid components present in the reaction mixture from step S1) by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, to obtain an essentially neutralized reaction mixture comprising hydroxy methylfurfural, and

[0035] 53) subjecting the reaction mixture comprising hydroxymethylfurfural from step S1) or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1), or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethyl- furfural from step S2), to hydrogenation in the presence of a catalyst comprising ruthenium, comprising a temperature in the range of from 50 to 150 °C and a hydrogen pressure in the range of from 5 to 20 MPa, so that 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran is formed.

[0036] In step S1) of the method according to the present invention as described above, the hexose sugar is preferably D-fructose or comprises D-fructose. A hexose sugar comprising D- fructose which is particularly suited for use in step S1) of the method according to the present invention is a mixture comprising D-glucose and D-fructose, preferably a mixture comprising D-glucose and D-fructose which is known as “high fructose corn syrup” (“HFCS”). BASF SE 230849

[0037] High fructose corn syrup is an industrial product (usually as an aqueous syrup, i.e. a syrup containing water) and available commercially with different D-fructose contents, e.g. with D-fructose contents of 42 wt.-%, 55 wt.-% or 90 wt.-%, relative to the total dry weight of the HFCS. All of said HFCS types are suited for use as hexose in step S1) of the method according to the present invention as described above and below, with the HFCS-types with a higher D-fructose content being preferred. D-fructose of higher purity is preferred as hexose sugar for use in step S1) over hexose sugars comprising D-fructose in varying amounts, e.g. as part of a mixture with other substances, e.g. other hexose sugars. In step S1), the hexose sugar is preferably used in the form of an aqueous solution, where preferably the aqueous solution has a strength of from 25 to 85 % (w / v) hexose sugar, preferably of from 35 to 75 % (w / v).

[0038] As regards the organic solvent for use in step S1) of the method according to the present invention, it was found in own experiments that dipolar, e.g. dipolar-aprotic solvents are preferred. Particularly preferred as organic solvent in step S1) is N-methyl-2-pyrrolidone (“NMP”). Without wishing to be bound by theory, it is assumed that the dipole moment of NMP has a beneficial impact on the reaction taking place in step S1).

[0039] It has further been found in own experiments that strong acids like the acids specified above as being preferred for use in step S1) of the method according to the present invention have a beneficial effect on conversion rate, desired selectivity of the reaction and yield. Most preferred in this regard is sulfuric acid. When sulfuric acid is used as acid in step S1) of the method according to the present invention, it is preferred to use concentrated sulfuric acid in a total amount in the range of from 1 : 50 to 1 : 150 molar equivalents, preferably of from 1 : 75 to 1 : 125 molar equivalents, relative to the molar amount of hexose sugar used in step S1) (i.e. 1 molar equivalent of sulfuric acid : 50 molar equivalents of hexose sugar, etc.).

[0040] Preferably, the total amount of the water present at the start of step S1) of the method according to the present invention is in the range of from 8 to 30 mass-%, preferably of from 10 to 25 mass-% and more preferably of from 12 to 20 mass-%, relative to the total mass of organic solvent, preferably to the total mass of N-methyl-2-pyrrolidone, present at the start of said step S1).

[0041] In the method according to the present invention as described herein, the mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1) orfrom the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), respectively, preferably is or comprises: BASF SE 230849

[0042] (i) a part of the reaction mixture comprising hydroxymethylfurfural from step S1) or a part of the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), respectively; or

[0043] (ii) a reaction mixture comprising hydroxymethylfurfural from step S1) whose volume has been reduced (preferably by removing or evaporating at least a part of the solvent previously present), or an essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) whose volume has been reduced (preferably by removing or evaporating at least a part of the solvent previously present), respectively; or

[0044] (iii) a reaction mixture comprising hydroxymethylfurfural from step S1) whose volume has been increased (preferably by adding solvent) or an essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) whose volume has been increased (preferably by adding solvent), respectively.

[0045] Usually, the reaction mixture comprising hydroxymethylfurfural from step S1) or the mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1) and / or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) or the mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), comprise typical side products from the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural as described herein, in particular side products selected from the group consisting of unreacted starting compounds, acetic acid, formic acid, levulinic acid, acetoxymethylfurfural, methoxymethylfurfural and humins (including dimers of hydroxymethylfurfural, which are commonly known to be humin precursors in the early phase of humin formation). BASF SE 230849

[0046] It has been found in own experiments that the present method of making furan-based bishydroxymethyl compounds from hydroxymethylfurfural is particularly simple and robust, in that the reaction mixture comprising hydroxymethylfurfural from step S1) or the mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1) and / or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) or the mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) can be used in the hydrogenation method of step S3) without the need of further purification or work-up, while nonetheless yielding the desired product or products in good yields and purity.

[0047] Also preferred is a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein in step S1):

[0048] - the removing of water from the reaction mixture comprises distilling off water from the reaction mixture (preferably continuously distilling off water from the reaction mixture); and / or

[0049] - the reacting is performed for a period of time in the range of from 3 to 8 hours, preferably of from 4 to 7 hours; and / or the temperature comprises a temperature (or the temperature is) in the range of from 60 to 190 °C, preferably of from 80 to 180 °C, more preferably of from 120 to 180 °C and even more preferably of from 140 to 180 °C (at least for a part of the total period BASF SE 230849 of time during which reacting in step S1) is performed, preferably forthe total period of time during which reacting in step S1) is performed).

[0050] Preferably, the period of time specified above for the “reacting” in step S1) comprises (i) the time required for metering (dosing) the hexose sugar (preferably the aqueous hexose sugar syrup) to a receiving mixture comprising organic solvent and acid, and (ii) the time allowed for reaction of the reactants when the addition of the hexose sugar was completed.

[0051] It is further preferred in the method according to the present invention to bring the mixture received after step S1) to a temperature in the range between 15 and 60 °C, preferably of from 15 to 35 °C, before starting step S2) of the method.

[0052] Preferred is then a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein the method comprises step S2) and wherein preferably in step S2):

[0053] - the reaction mixture from step S1) is essentially neutralized or the acid components present in the reaction mixture from step S1) are essentially neutralized, by adding 0.8 to 1 .2 molar equivalents of a base, relative to the molar amount of acid (as defined above) present in the reaction mixture at the start of step S1), wherein preferably the base is selected from the group consisting of alkali metal hydroxides, preferably aqueous alkali metal hydroxides; alkaline earth metal hydroxides, preferably aqueous alkaline earth metal hydroxides; and mixtures thereof, wherein more preferably the base is selected from the group consisting of sodium hydroxide, preferably aqueous sodium hydroxide; potassium hydroxide, preferably aqueous potassium hydroxide; and mixtures thereof; and / or the reaction mixture from step S1) is essentially neutralized by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, preferably of from 6.5 to 7.5, preferably by adding a base to the reaction mixture from step S1), BASF SE 230849 wherein preferably the base comprises or is selected from the group consisting of alkali metal hydroxides, preferably aqueous alkali metal hydroxides; alkaline earth metal hydroxides, preferably aqueous alkaline earth metal hydroxides; and mixtures thereof, wherein more preferably the base is selected from the group consisting of sodium hydroxide, preferably aqueous sodium hydroxide; potassium hydroxide, preferably aqueous potassium hydroxide; and mixtures thereof.

[0054] Where in the method according to the present invention as defined herein (or in a method according to the invention as described above or below as being preferred), the reaction mixture from step S1) is essentially neutralized or the acid components present in the reaction mixture from step S1) are essentially neutralized in step S2) by adding 0.8 to 1.2 molar equivalents of a base, relative to the molar amount of acid present in the reaction mixture at the start of step S1), preferably said molar amount of acid present in the reaction mixture at the start of step S1) is equivalent to or is the molar amount of acid that is (or has been) added when the reaction mixture for use in step S1) is (or was) prepared.

[0055] In own experiments it has been found that the method according to the present invention as defined herein which comprises step S2) is particularly advantageous: Hydroxymethylfurfural was found to be stable and not subject to decomposition or undesired further reactions for longer time periods in an essentially neutralized reaction mixture comprising hydroxymethylfurfural as received from step S2), than it was found in e.g. a reaction mixture comprising hydroxymethylfurfural as received from step S1). A method according to the present invention as defined herein which comprises step S2) therefore results in an essentially neutralized reaction mixture comprising hydroxymethylfurfural, wherein the hydroxymethylfurfural is particularly stable and thus may be stored for extended time periods. A method according to the present invention as defined herein which comprises step S2) usually also contributes to higher overall yields of furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural, when compared with a method according to the present invention as defined herein which does not comprise step S2). Without wishing to be bound by theory, it is assumed that an essentially neutralized reaction mixture from step S1) contributes to stabilizing the hydroxymethylfurfural which has formed in step S1) and that it contributes to reducing, inhibiting or avoiding decomposition thereof, or to reducing, inhibiting or avoiding the undesired side reaction of hydroxymethylfurfural to form humins.

[0056] Where in step S2) the reaction mixture from step S1) is essentially neutralized by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, preferably of from 6.5 to 7.5, the pH is preferably determined by measuring with a glass electrode. BASF SE 230849

[0057] Moreover is preferred a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein in step S3) the temperature comprises a temperature (or the temperature is) in the range of from 60 to 150 °C, preferably of from 60 to 140 °C, more preferably of from 70 to 130 °C.

[0058] A particular advantage of the method according to the present invention is the possibility of controlling the yields of the desired products, 2,5-bis(hydroxymethyl)furan or 2,5-bis(hy- droxymethyl)tetrahydrofuran, respectively, or the specificity of the reaction, by the choice of reagents used and / or by the choice of the reaction conditions applied, as is further explained below.

[0059] In a first variant of the method according to the present invention, a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred) is preferred, wherein in step S3) the catalyst comprising ruthenium comprises or is ruthenium on carbon (also referred to as “ruthenium on carbon black, “Ru / C”). As used herein, “ruthenium on carbon” includes ruthenium on carbon comprising a binder (preferably comprising ruthenium on carbon comprising polytetrafluoroethylene, “Ru / C-PTFE”, wherein preferably the catalyst comprising ruthenium on carbon comprising polytetrafluoroethylene is a catalyst made according to the methods disclosed in document WO 2020 / 069972 A1), preferably comprising a total amount of ruthenium in the range of 2 to 10 wt.-%, more preferably of from 3 to 8 wt.-%, relative to the total weight of the “ruthenium on carbon” catalyst.

[0060] It has been found in own experiments that it is preferred to use ruthenium on carbon (preferably including ruthenium on carbon comprising a binder, see above) as the catalyst comprising ruthenium in step S3), in particular when it is desired to predominantly produce 2,5- bis(hydroxymethyl)tetrahydrofuran and / or to increase the yield of 2,5-bis(hydroxymethyl)- tetrahydrofuran in the method according to the present invention as described herein.

[0061] Preferred is furthermore a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred, in particular a method according to the first variant of the present invention as defined above), wherein in step S3) the hydrogenation is performed for a time period in the range of from 5 to 30 hours, preferably of from 5 to 28 hours and more preferably of from 5 to 26 hours; BASF SE 230849 and / or

[0062] - the hydrogen pressure comprises or is a pressure in the range of from 6 to 18 MPa, preferably of from 6 to 16 MPa and more preferably of from 6 to 10 MPa (at least for a part of the total period of time during which hydrogenation in step S3) is performed, preferably for the total period of time during which hydrogenation in step S3) is performed); and / or

[0063] - the concentration of hydroxymethylfurfural in the reaction mixture comprising hydroxymethylfurfural from step S1) is > 5 wt.-%, preferably > 10 wt.-%, relative to the total weight of the reaction mixture comprising hydroxymethylfurfural from step S1), or the concentration of hydroxymethylfurfural in the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) is > 5 wt.-%, preferably > 10 wt.-%, relative to the total weight of the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2); and / or

[0064] - the concentration of hydroxymethylfurfural in the reaction mixture comprising hydroxymethylfurfural from step S1) is in the range of from > 5 to < 25 wt-%, more preferably of from > 5 to < 20 wt-% and even more preferably of from > 10 to < 20 wt-%, relative to the total weight of the reaction mixture comprising hydroxymethylfurfural from step S1); or the concentration of hydroxymethylfurfural in the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) is in the range of from > 5 to < 25 wt-%, more preferably of from > 5 to < 20 wt-% and even more preferably of from > 10 to < 20 wt-%, relative to the total weight of the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2); and / or the temperature comprises a temperature (or the temperature is) in the range of from 60 to 140 °C, preferably of from 70 to 130 °C and more preferably of from 70 to 90 °C BASF SE 230849

[0065] (at least for a part of the total period of time during which hydrogenation in step S3) is performed, preferably for the total period of time during which hydrogenation in step S3) is performed).

[0066] While the above defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation may be applied to all variants of the method according to the present invention, each of said above defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation individually, when applied in the first variant of the present method (i.e. when the catalyst comprising ruthenium comprises or is ruthenium on carbon), furthers the predominant production of 2,5-bis(hydroxymethyl)tetrahydro- furan or the increase in yield of 2,5-bis(hydroxymethyl)tetrahydrofuran relative to the yield of 2,5-bis(hydroxymethyl)furan. When two or all three of the above-defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation are combined in the first variant of the method according to the present invention, the effect of a predominant production of 2,5-bis(hydroxymethyl)tetrahydrofuran is even more pronounced.

[0067] In a second variant of the method according to the present invention, a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred) is preferred, wherein in step S3) the catalyst comprising ruthenium comprises or is ruthenium oxide hydroxide, preferably ruthenium-lll- oxide hydroxide. Preferably, a ruthenium oxide hydroxide catalyst is used in this second variant of the method according to the present invention which is synthesized according to the preparation instructions of example 1 (“Beispiel 1 ”) of German Offenlegungsschrift (published patent application) No. 21 32 547 (i.e. “DE-OS 21 32 547“) .

[0068] It has been found in own experiments that it is preferred to use said ruthenium oxide hydroxide (preferably ruthenium-lll-oxide hydroxide) as the catalyst comprising ruthenium in step S3), when it is desired to predominantly produce 2,5-bis(hydroxymethyl)furan and / or to increase the yield of 2,5-bis(hydroxymethyl)furan in the method according to the present invention as described herein.

[0069] A method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfu- ral according to the second variant of the method according to the present invention (or of a respective method according to the present invention as described above or below as being preferred) is particularly preferred, comprising the following steps: BASF SE 230849

[0070] 51 ) reacting a hexose sugar in a reaction mixture, the reaction mixture further comprising an acid, water and an organic solvent, at a temperature in the range of from 50 to 200 °C, and removing water from the reaction mixture, so that hydroxymethylfurfural is formed,

[0071] 52) essentially neutralizing the reaction mixture from step S1) or essentially neutralizing the acid components present in the reaction mixture from step S1) by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, to obtain an essentially neutralized reaction mixture comprising hydroxy methylfurfural, and

[0072] 53) subjecting the reaction mixture comprising hydroxymethylfurfural from step S1) or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1), or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethyl- furfural from step S2), to hydrogenation in the presence of a catalyst comprising ruthenium, wherein the catalyst comprising ruthenium comprises or is ruthenium oxide hydroxide, preferably comprises or is ruthenium-lll-oxide hydroxide, BASF SE 230849 comprising a temperature in the range of from 50 to 150 °C and a hydrogen pressure in the range of from 5 to 20 MPa, so that 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran is formed.

[0073] Preferred is furthermore a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred, in particular a method according to the second variant of the present invention as defined above), wherein in step S3)

[0074] - the hydrogenation is performed for a time period in the range of from 8 to 24 hours, preferably of from 8 to 18 hours and more preferably of from 10 to 14 hours; and / or

[0075] - the hydrogen pressure comprises or is a pressure in the range of from 8 to 18 MPa, preferably of from 10 to 18 MPa and more preferably of from 12 to 16 MPa (at least for a part of the total period of time during which hydrogenation in step S3) is performed, preferably for the total period of time during which hydrogenation in step S3) is performed); and / or

[0076] - the temperature comprises a temperature (or the temperature is) in the range of from 70 to 140 °C, preferably of from 80 to 120 °C and more preferably of from 90 to 110 °C (at least for a part of the total period of time during which hydrogenation in step S3) is performed, preferably for the total period of time during which hydrogenation in step S3) is performed).

[0077] While the above defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation may be applied to all variants of the method according to the present invention, each of said above defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation individually, when applied in the second variant of the present method (i.e. when the catalyst comprising ruthenium comprises or is ruthenium oxide hydroxide as defined above), furthers the predominant production of 2,5- bis(hydroxymethyl)furan or the increase in yield of 2,5-bis(hydroxymethyl)furan relative to BASF SE 230849 the yield of 2,5-bis(hydroxymethyl)tetrahydrofuran. When two or all three of the above-defined reaction conditions of temperature, hydrogen pressure and time period of the hydrogenation are combined in the second variant of the method according to the present invention, the effect of a predominant production of 2,5-bis(hydroxymethyl)furan is even more pronounced.

[0078] When ruthenium oxide hydroxide (synthesized as described in example 1 of DE-OS 21 32 547, see above) was used as catalyst comprising ruthenium in step S3) of the above-described second variant of the method according to the present invention, the present inventors have made the following unexpected finding: It was found that not the core of the starting compound (here: hydroxymethylfurfural) was hydrogenated - as could have been expected in view of the findings published in DE-OS 21 32 547 - but instead the side chain of the hydroxymethylfurfural was hydrogenated with high selectivity, in particular when N- methyl-2-pyrrolidone was used as organic solvent in step S1) of the method according to the present invention.

[0079] It is then also preferred a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein the method comprises the further step:

[0080] S4) isolating 2,5-bis(hydroxymethyl)furan and / or 2, 5-bis(hydroxymethyl)tetrahydrofuran, preferably from the reaction mixture received after step S3).

[0081] A further advantage of the method according to the present invention as described herein is the relative ease with which the furan-based bis-hydroxymethyl compounds produced and obtained in step S3) of the method can be isolated and purified and the relatively gentle conditions which can be applied therefor, thus resulting in high yields of the desired furan- based bis-hydroxymethyl compounds which can be obtained in high purity.

[0082] Preferred is therefore a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), in particular such method which comprises the further step S4) (as defined above), wherein isolating 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofu- ran comprises isolating by distillation or evaporation, preferably comprising a step of fractionated distillation or fractionated evaporation, BASF SE 230849 where preferably isolating by evaporation or isolating by fractionated evaporation comprises thin film evaporation.

[0083] Where isolating 2,5-bis(hydroxymethyl)furan and / or 2, 5-bis(hydroxymethyl)tetrahydrofuran comprises (a step of) thin film evaporation, such thin film evaporation can preferably be performed in two or more stages (“runs”), e.g. in two, three or four stages, where preferably in the first stages (e.g. in the first, second and / or third stage) the organic solvent, in particular N-methyl-2-pyrrolidone, water and other light volatiles are separated or partially separated “overhead”, and in the final stage (e.g. in the second, third or fourth stage) 2,5-bis(hy- droxymethyl)furan or 2,5-bis(hydroxymethyl)tetrahydrofuran, respectively, is isolated. Performing (the step of) thin film evaporation in two or more stages (“runs”), e.g. in two, three or four stages, can often further increase purity of the desired product, e.g. of 2,5-bis(hy- droxymethyl)furan or 2,5-bis(hydroxymethyl)tetrahydrofuran.

[0084] An additional advantage of the method of the invention as described herein, in particular an advantage associated with step S4) of said method, is therefore the possibility of isolating and recycling the organic solvent used in the method (at least in part, ideally to a very high extent), which further contributes to the method’s sustainability.

[0085] In accordance with the first variant of the method according to the present invention, there is preferred a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein such method comprises the further step S4) and the catalyst used in step S3) comprises or is ruthenium on carbon, and wherein in step S4) 2,5-bis(hydroxymethyl)tetrahydrofuran is isolated or is predominantly isolated.

[0086] In accordance with the second variant of the method according to the present invention, there is preferred a method according to the present invention as defined herein (or a method according to the invention as described above or below as being preferred), wherein such method comprises the further step S4) and the catalyst used in step S3) comprises or is ruthenium oxide hydroxide, preferably ruthenium-lll-oxide hydroxide, and step S3), and wherein in step S4) 2,5-bis(hydroxymethyl)furan is isolated.

[0087] The present invention also pertains to an essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method of making furan-based bishydroxymethyl compounds from hydroxymethylfurfural according to the present invention BASF SE 230849 as defined herein, preferably as obtained in or as obtainable by or after step S1) of the method according to the present invention as defined herein.

[0088] Generally, all aspects of the present invention discussed herein in the context of the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention as defined herein, apply mutatis mutandis to the essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein, and vice versa.

[0089] Preferably, said essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein therefore has a pH in the range of from 6 to 8, more preferably of from 6.5 to 7.5.

[0090] Preferred is an essentially neutralized reaction mixture comprising hydroxymethylfurfural according to the present invention as described herein (or an essentially neutralized reaction mixture comprising hydroxymethylfurfural according to the present invention as described herein as being preferred), wherein in the method of making furan-based bis-hy- droxymethyl compounds from hydroxymethylfurfural according to the present invention as described herein (or in the respective method according to the present invention as described herein as being preferred) the reaction mixture in step S1 ) further comprises as the organic solvent an organic solvent selected from the group consisting of N-alkyl-2-pyrrol- idones, preferably selected from the group consisting of N-methyl-2-pyrrolidone and N- ethyl-2-pyrrolidone; 2-pyrrolidone; N-methyl succinimide, 1 ,3-dimethyl-2-imidazolidinone; dimethylformamide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein more preferably the organic solvent is selected from the group consisting of N- methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein even more preferably the organic solvent comprises or is N-methyl-2-pyrrolidone.

[0091] Preferably, said essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein is characterized by typically comprising as side products (and apart from hydroxy methylfurfural) one or more members of the group consisting of furfural, formic acid, acetic acid, levulinic acid, acetoxymethylfurfural, methoxymethylfurfural and humins (including dimers of hydroxymethylfurfural, which are commonly known to be humin precursors in the early phase of humin formation), where said humins are not further specified. BASF SE 230849

[0092] Humins, which are typically produced as side products of the method of making furan- based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention, are also known to occur e.g. during the (naturally occurring or industrial chemical) conversion of lignocellulosic biomass to smaller, higher value organic compounds like hydroxymethylfurfural. These humins can be in the form of either viscous liquids or solids, depending on the process conditions involved. Both, the structure of humins and the mechanism by which they are synthesized, are at present not well understood, as the formation and chemical properties of humins usually change depending on the environmental or process conditions. Typical intermediates in the early phase of humin formation, which may also occur as side products in the course of the method according to the present invention, are hydroxymethylfurfural dimers. Generally, humins have a polymeric furanic-type structure, with hydroxyl, aldehyde and ketone functionalities. However, the structure is dependent on feedstock type (e.g. fructose, xylose or glucose) or concentration, reaction time, temperature, catalysts and many other parameters involved in the process.

[0093] The present invention then further pertains to the use of said essentially neutralized reaction mixture comprising hydroxymethylfurfural as defined here above, or as obtained in or as obtainable by a method according to the present invention as defined herein, preferably as obtained in or as obtainable by or after step S1) of the method according to the present invention as defined herein, in a hydrogenation method for making 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hy- droxymethyl)tetrahydrofuran.

[0094] Generally, all aspects of the present invention discussed herein in the context of the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention as defined herein and / or to the essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein, apply mutatis mutandis to the use of the essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein, and vice versa.

[0095] Moreover, the present invention pertains to the use of ruthenium oxide hydroxide, preferably of ruthenium-lll-oxide hydroxide, as hydrogenation catalyst in a method of hydrogenating hydroxymethylfurfural. BASF SE 230849

[0096] Generally, all aspects of the present invention discussed herein in the context of the method of making furan-based bis-hydroxymethyl compounds from hydroxymethylfurfural according to the present invention as defined herein and / or to the essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention and / or to the use of the essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to the present invention as defined herein, apply mutatis mutandis to the use of ruthenium oxide hydroxide, preferably of ruthenium-lll-oxide hydroxide, as hydrogenation catalyst in a method of hydrogenating hydroxymethylfurfural.

[0097] Preferred is a use of ruthenium oxide hydroxide, preferably of ruthenium-lll-oxide hydroxide, as hydrogenation catalyst in a method of hydrogenating hydroxymethylfurfural as defined herein, wherein the ruthenium oxide hydroxide comprises or is a ruthenium oxide hydroxide (catalyst) which is synthesized according to the preparation instructions of example 1 of DE-OS 21 32 547.

[0098] Examples

[0099] The following examples are meant to further explain and illustrate the present invention without limiting its scope.

[0100] Unless indicated otherwise, in the examples below, the following terms have the indicated meanings:

[0101] Room temperature / RT: ca. 23 °C,

[0102] Normal pressure: ca. 1013 hPa,

[0103] GC: gas chromatography

[0104] HPLC high-performance liquid chromatography

[0105] BHM-Furan: 2,5-bis(hydroxymethyl)furan

[0106] BHM-THF: 2,5-bis(hydroxymethyl)tetrahydrofuran BASF SE 230849

[0107] Example 1 : Preparation of hydroxymethylfurfural according to step S1) and optionally to step S2) of the method described herein

[0108] Example 1.1 :

[0109] Sulfuric acid (95-98 % strength, 3.8 g) was added to N-methyl-2-pyrrolidone (2005 g) at room temperature in an HWS glass vessel (a technical glass vessel provided by HWS La- bortechnik, Mainz, Germany) under stirring (700 U / min) and the resulting mixture was warmed up to 150 °C. Subsequently, aqueous fructose syrup (1000 g; 67 % w / v) was metered continuously to the mixture over the course of 135 min., while water (446 g in total at the end of the reaction) was constantly distilled off.

[0110] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 140-150 °C at normal pressure for 1 h, then cooled below 60 °C yielding hydroxymethylfurfural in the resulting mixture (2550 g in total, pH 3.0, yield: 79 % hydroxymethylfurfural, determined by HPLC).

[0111] About 5 days after completion of the reaction of Example 1.1 , it was observed that the hydroxymethylfurfural in the reaction mixture obtained, gradually began to decompose and / or to react further to form undesired side products.

[0112] Example 1 .2:

[0113] Sulfuric acid (95-98 % strength, 3.8 g) was added to N-methyl-2-pyrrolidone (2010 g) at RT in an HWS glass vessel under stirring (800 U / min) and the resulting mixture was warmed up to 150 °C. Subsequently, aqueous fructose syrup (1000 g; 67 % w / v) was metered continuously to the mixture over the course of 6 hrs, while water (474 g in total at the end of the reaction) was constantly distilled off.

[0114] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 150-155 °C at normal pressure for 1 h, then cooled below 60 °C and neutralized (pH 7.1) with aqueous sodium hydroxide (30 g, 10 % w / v) yielding hydroxymethylfurfural in the resulting mixture (2575 g in total, yield: 82 % hydroxymethylfurfural, determined by HPLC).

[0115] It was observed that hydroxymethylfurfural in the essentially neutralized reaction mixture obtained was stable for a period of > 5 days after completion of the reaction of Example BASF SE 230849

[0116] 1.2 and no significant decomposition or further reaction to undesired side products was observed during said period.

[0117] Example 1 .3:

[0118] Sulfuric acid (95-98 % strength, 0.4 g) was added to N-methyl-2-pyrrolidone (202 g) at RT in a 500 mL round-bottom flask under stirring (700 U / min) and the resulting mixture was warmed up to 155 °C. Subsequently, aqueous fructose syrup (112 g; 67 % w / v) was metered continuously to the mixture over the course of 90 min. under reflux conditions (no water distilled off), whereby the temperature dropped to 120 °C.

[0119] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 120 °C at normal pressure for 5 hrs, then cooled to RT and neutralized (pH 7.0) with aqueous sodium hydroxide (3 g, 10 % w / v) yielding hydroxymethylfurfural in the resulting mixture (313 g in total, yield: 34 % hydroxymethylfurfural, determined by HPLC).

[0120] Example 1 .4 :

[0121] 2,5-Furandicarboxylic acid (5.9 g) was added to N-methyl-2-pyrrolidone (2001 g) at RT in an HWS glass vessel under stirring (800 U / min) and the reaction mixture was warmed up to 160 °C. Subsequently, aqueous fructose syrup (1001 g; 67 % w / v) was metered continuously to the mixture over the course of 3.5 h, while water (457 g in total at the end of the reaction) was constantly distilled off.

[0122] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 160-170 °C at normal pressure for 1 h, then cooled below 60 °C yielding hydroxymethylfurfural in the resulting mixture (2536 g in total, pH 4.9, yield: 53 % hydroxymethylfurfural, determined by HPLC).

[0123] Example 1 .5:

[0124] Sodium dithionite (> 85% purity, 2.1 g) was added to N-methyl-2-pyrrolidone (2000 g) at RT in an HWS glass vessel under stirring (800 U / min) and the reaction mixture was warmed up to 160 °C. Subsequently, aqueous fructose syrup (1000 g; 67 % w / v) was metered continuously to the mixture over the course of 4 hrs, while water (453 g in total at the end of the reaction) was constantly distilled off. BASF SE 230849

[0125] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 160-170 °C at normal pressure for 1 h, then cooled below 60 °C yielding hydroxymethylfurfural in the resulting mixture (2515 g in total, pH 7.0, yield: 9 % hydroxymethylfurfural, determined by HPLC).

[0126] Example 1 .6:

[0127] Sulfuric acid (95-98 % strength, 0.4 g) was added to N-methyl succinimide (200 g) at 70 °C in a 500 mL round-bottom flask under stirring (800 U / min) and the reaction mixture was warmed up to 160 °C. Subsequently, aqueous fructose syrup (100 g; 67 % w / v) was metered continuously (8 mL / min) to the mixture over the course of 3 hrs, while water (50 g) was constantly distilled off.

[0128] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 160-170 °C at normal pressure for 1 h, then cooled below 75 °C and neutralized with aqueous sodium hydroxide (3 g, 10 % w / v) yielding hydroxymethylfurfural in the resulting mixture (232 g in total, yield: 79 % hydroxymethylfurfural, determined by HPLC).

[0129] Example 1 .7:

[0130] Sulfuric acid (95-98 % strength, 0.4 g) was added to toluene (200 g) at RT in an HWS glass vessel under stirring (800 U / min) and the reaction mixture was warmed up to 100 °C. Subsequently, aqueous fructose syrup (95 g; 67 % w / v) was metered continuously to the reaction mixture over the course of 2 hrs, while water (474 g in total at the end of the reaction) was constantly distilled off.

[0131] After complete addition of the fructose syrup, the reaction mixture was stirred at a temperature of 100-1 10 °C at normal pressure for 1 h, then cooled to RT. The organic phase was washed once with saturated aqueous sodium bicarbonate, yielding hydroxymethylfurfural in the resulting mixture (132 g in total, yield: 0.1 % hydroxymethylfurfural, determined by HPLC).

[0132] Examples 1 .8-1.11 were performed analogously to Example 1 .2 as shown above, but with the deviations noted in table 1 below.

[0133] Example 1.12 was performed analogously to Example 1 .6 as shown above, but with the deviations noted in table 1 below. BASF SE 230849

[0134] Table 1 : Further preparation examples of hydroxymethylfurfural according to steps S1) and S2)

[0135] From the above examples it can be seen that removing water from the reaction mixture results in an increased yield of hydroxymethylfurfural (for comparison see Example 1.3), that sulfuric acid is a preferred acid to be used in step S1) (for confirmation see Examples 1.1-1 .2, 1.6, and 1.9-1.1 1) and that N-methyl-2-pyrrolidone and N-methyl succinimide are particularly preferred organic solvents to be used in step S1) (for comparison see Example 1.7).

[0136] Furthermore, the following typical by-products were identified in the crude mixtures received after steps S2) or S3), respectively (given in “wt.-%“ of the total weight of the crude mixture received):

[0137] Dimers of hydroxymethylfurfural: 0 to < 2.5

[0138] Formic acid: 0.03 to < 0.5

[0139] Acetic acid: < 0.01 to < 1 .2

[0140] Levulinic acid: 0 to < 0.6

[0141] Example 2: Preparation of 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tet- rahydrofuran according to step S3) of the method described herein

[0142] Example 2.1 :

[0143] Ruthenium on carbon I PTFE (5 wt-%, 1 .0 g) was added to 100 g of a crude mixture comprising N-methyl-2-pyrrolidone and hydroxymethylfurfural (14 wt.-% hydroxymethylfurfural BASF SE 230849 relative to the total mass of the crude mixture, determined by HPLC), as was received from the preparation of hydroxymethylfurfural by a method as described in Example 1 .2 above.

[0144] The resulting mixture was placed in an autoclave and the autoclave was subsequently purged with nitrogen gas (twice at 500 kPa) and thereafter with hydrogen gas (twice at 500 kPa). The reaction mixture was stirred (700 U / min) at an initial hydrogen gas pressure of 5 MPa, then the reaction mixture was warmed up to 120 °C and the hydrogen pressure was increased to 15 MPa and maintained at 15 MPa.

[0145] The reaction mixture was stirred under these conditions for 6 hrs, then cooled to RT and purged with nitrogen gas (twice at 2 MPa). Afterwards, the heterogeneous ruthenium catalyst was filtered off, yielding 2,5-bis(hydroxymethyl)tetrahydrofuran in the crude mixture (10.7 wt.-% in 100 g crude mixture, yield: 73 % 2,5-bis(hydroxymethyl)tetrahydrofuran, relative to the amount of hydroxymethylfurfural present in the crude starting mixture comprising N-methyl-2-pyrrolidone and hydroxymethylfurfural stated above, determined by HPLC).

[0146] Examples 2.2 - 2.3 were performed analogously to Example 2.1 as shown above, but with the deviations noted in table 2 below.

[0147] Example 2.4:

[0148] Ruthenium on aluminium oxide (0.5 wt-%, 5.0 g) was added to 100 g of a crude mixture comprising N-methyl-2-pyrrolidone and hydroxymethylfurfural (14.5 wt.-% hydroxy methylfurfural relative to the total mass of the crude mixture, determined by HPLC), as was received from the preparation of hydroxymethylfurfural by a method as described in Example 1 .2 above.

[0149] The resulting mixture was placed in an autoclave and the autoclave was subsequently purged with nitrogen gas (twice at 500 kPa) and thereafter with hydrogen gas (twice at 500 kPa). The reaction mixture was stirred (700 U / min) at an initial hydrogen gas pressure of 5 MPa, then the reaction mixture was warmed up to 100 °C and the hydrogen pressure increased to 15 MPa and maintained at 15 MPa.

[0150] The reaction mixture was stirred under these conditions for 24 hrs, then cooled to RT and purged with nitrogen gas (twice at 2 MPa). Afterwards, the heterogenous ruthenium catalyst was filtered off, yielding 2,5-bis(hydroxymethyl)furan in the crude mixture (10.0 wt.-% in 100 g crude mixture, yield: 68 % 2,5-bis(hydroxymethyl)furan, relative to the amount of | BASF SE | 230849 hydroxymethylfurfural present in the crude mixture comprising N-methyl-2-pyrrolidone and hydroxymethylfurfural stated above, determined by GC).

[0151] Example 2.5 was performed analogously to Example 2.4 as shown above, but with the deviations noted in table 2 below. Table 2: Overview of preparation examples of 2,5-bis(hydroxymethyl)furan and / or 2,5- bis(hydroxymethyl)tetrahydrofuran according to step S3)

[0152] 1: Ruthenium on carbon comprising as binder polytetrafluoroethylene - catalyst synthesized according to the preparation instructions of WO 2020 / 069972 A1 (with the devia- tion that the catalyst used in the present experiments comprises ruthenium instead of the palladium used in the examples of WO 2020 / 069972 A1).

[0153] 2: RU2O3, ruthenium oxide hydroxide catalyst synthesized according to the preparation instructions of example 1 of DE-OS 21 32 547.

[0154] Example 3: Isolation of 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetra- hydrofuran according to step S4) of the method described herein

[0155] 841 g of a crude solution of 2,5-bis(hydroxymethyl)tetrahydrofuran (10.3 wt.-%, determined by GC) in N-methyl-2-pyrrolidone as was received from several preparations by a method corresponding to the method as described in Example 2.3 above (further comprising minor | BASF SE | 230849 | 230849WQ01 ~ amounts of 2,5-bis(hydroxymethyl)furan, sodium sulfate, humins and water) was distilled over four runs with a thin film evaporator under the following conditions:

[0156] 1strun: 70 - 80 °C; 0.9 - 1.4 hPa;

[0157] 2ndrun: 100 °C; 0.21-0.24 hPa 3rdrun: 100 °C; 0.21-0.24 hPa

[0158] 4thrun: 125 - 130 °C; 0.22 hPa

[0159] Collected fractions were analyzed by GC and NMR for structure confirmation.

[0160] The distillation yielded a colourless sample of 2,5-bis(hydroxymethyl)tetrahydrofuran (84 wt.-%, 72 g, yield: 70%) which only contained residual N-methyl-2-pyrrolidone (ca. 16 wt.-%). Byproducts from the previous reactions (such as humins from the acidic cyclization or from the hydrogenation), water and salts from neutralization were completely removed.

Claims

BASF SE230849Claims:1 . Method of making furan-based bis-hydroxymethyl compounds from hydroxymethyl- furfural, comprising the following steps:51) reacting a hexose sugar in a reaction mixture, the reaction mixture further comprising an acid, water and an organic solvent, at a temperature in the range of from 50 to 200 °C, and removing water from the reaction mixture, so that hydroxymethylfurfural is formed,52) preferably essentially neutralizing the reaction mixture from step S1 ) or essentially neutralizing the acid components present in the reaction mixture from step S1), to obtain an essentially neutralized reaction mixture comprising hydroxymethylfurfural, and53) subjecting the reaction mixture comprising hydroxy-methylfurfural from step S1) or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1), or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2),BASF SE230849or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), to hydrogenation in the presence of a catalyst comprising ruthenium, comprising a temperature in the range of from 50 to 150 °C and a hydrogen pressure in the range of from 5 to 20 MPa, so that 2,5-bis(hydroxymethyl)furan and / or 2, 5-bis(hydroxymethyl)tetrahydro- furan is formed.

2. Method according to claim 1 , wherein in step S1)- the hexose sugar is selected from the group consisting of D-glucose, D-fructose, D-saccharose and mixtures thereof, wherein preferably the hexose sugar comprises or is D-fructose; and / or- the organic solvent is selected from the group consisting of N-alkyl-2-pyrrol- idones, preferably selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone; 2-pyrrolidone; N-methyl succinimide, 1 ,3-dimethyl-2- imidazolidinone; dimethylformamide; dimethylsulfoxide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein preferably the organic solvent is selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein more preferably the organic solvent comprises or is N-methyl-2-pyrroli- done; and / orBASF SE230849- the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, methanesulfonic acid, benzenesulfonic acid, para-toluenesul- fonic acid, naphthalenesulfonic acid, camphorsulfonic acid and mixtures thereof, wherein preferably the acid comprises or is sulfuric acid.

3. Method according to any of the preceding claims, comprising the following steps:S1) reacting a hexose sugar in a reaction mixture, the reaction mixture further comprising an acid, selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, methanesulfonic acid, benzenesulfonic acid, para-toluenesulfonic acid, naphthalenesulfonic acid, camphorsulfonic acid and mixtures thereof; wherein preferably the acid comprises or is sulfuric acid water and an organic solvent, selected from the group consisting of N-alkyl-2-pyrrol- idones, preferably selected from the group consisting of N-methyl-2-pyr- rolidone and N-ethyl-2-pyrrolidone; 2-pyrrolidone; N-methyl succinimide, 1 ,3-dimethyl-2-imidazolidinone; dimethylformamide; dimethylsulfoxide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein preferably the organic solvent is selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein more preferably the organic solvent comprises or is N-methyl-2- pyrrolidone; at a temperature in the range of from 50 to 200 °C, and removing water from the reaction mixture,BASF SE230849so that hydroxymethylfurfural is formed,52) essentially neutralizing the reaction mixture from step S1) or essentially neutralizing the acid components present in the reaction mixture from step S1) by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, to obtain an essentially neutralized reaction mixture comprising hydroxymethylfurfural, and53) subjecting the reaction mixture comprising hydroxymethylfurfural from step S1) or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the reaction mixture comprising hydroxymethylfurfural from step S1), or the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), or a mixture comprising hydroxymethylfurfural, which is derived or resulting from the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2), to hydrogenation in the presence of a catalyst comprising ruthenium, comprising a temperature in the range of from 50 to 150 °C and a hydrogen pressure in the range of from 5 to 20 MPa, so that 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran is formed.

4. Method according to any of the preceding claims, wherein in step S1)BASF SE230849- the removing of water from the reaction mixture comprises distilling off water from the reaction mixture; and / or- the reacting is performed for a period of time in the range of from 3 to 8 hours, preferably of from 4 to 7 hours; and / or- the temperature comprises a temperature in the range of from 60 to 190 °C, preferably of from 80 to 180 °C, more preferably of from 120 to 180 °C and even more preferably of from 140 to 180 °C.

5. Method according to any of the preceding claims, wherein the method comprises step S2) and wherein preferably in step S2)- the reaction mixture from step S1) is essentially neutralized or the acid components present in the reaction mixture from step S1) are essentially neutralized, by adding 0.8 to 1 .2 molar equivalents of a base, relative to the molar amount of acid present in the reaction mixture at the start of step S1), wherein preferably the base is selected from the group consisting of alkali metal hydroxides, preferably aqueous alkali metal hydroxides; alkaline earth metal hydroxides, preferably aqueous alkaline earth metal hydroxides; and mixtures thereof, wherein more preferably the base is selected from the group consisting of sodium hydroxide, preferably aqueous sodium hydroxide; potassium hydroxide, preferably aqueous potassium hydroxide; and mixtures thereof; and / or- the reaction mixture from step S1) is essentially neutralized by adjusting the pH of the reaction mixture from step S1) to a value in the range of from 6 to 8, preferably of from 6.5 to 7.5, preferably by adding a base to the reaction mixture from step S1),BASF SE230849wherein preferably the base comprises or is selected from the group consisting of alkali metal hydroxides, preferably aqueous alkali metal hydroxides; alkaline earth metal hydroxides, preferably aqueous alkaline earth metal hydroxides; and mixtures thereof, wherein more preferably the base is selected from the group consisting of sodium hydroxide, preferably aqueous sodium hydroxide; potassium hydroxide, preferably aqueous potassium hydroxide; and mixtures thereof.

6. Method according to any of the preceding claims, wherein in step S3) the temperature comprises a temperature in the range of from 60 to 150 °C, preferably of from 60 to 140 °C, more preferably of from 70 to 130 °C.

7. Method according to any of the preceding claims, wherein in step S3) the catalyst comprising ruthenium comprises or is ruthenium on carbon.

8. Method according to claim 7, wherein in step S3)- the hydrogenation is performed for a time period in the range of from 5 to 30 hours, preferably of from 5 to 28 hours and more preferably of from 5 to 26 hours; and / or- the hydrogen pressure comprises or is a pressure in the range of from 6 to 18 MPa, preferably of from 6 to 16 MPa and more preferably of from 6 to 10 MPa; and / or- the concentration of hydroxymethylfurfural in the reaction mixture comprising hydroxymethylfurfural from step S1) is > 5 wt.-%, preferably > 10 wt.-%, relative to the total weight of the reaction mixture comprising hydroxymethylfurfural from step S1), or the concentration of hydroxymethylfurfural in the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) is > 5 wt.-%, preferably > 10 wt.-%, relative to the total weight of the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2);BASF SE230849and / or- the concentration of hydroxymethylfurfural in the reaction mixture comprising hydroxymethylfurfural from step S1) is in the range of from > 5 to < 25 wt-%, more preferably of from > 5 to < 20 wt-% and even more preferably of from > 10 to < 20 wt-%, relative to the total weight of the reaction mixture comprising hydroxymethylfurfural from step S1); or the concentration of hydroxymethylfurfural in the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2) is in the range of from > 5 to < 25 wt-%, more preferably of from > 5 to < 20 wt-% and even more preferably of from > 10 to < 20 wt-%, relative to the total weight of the essentially neutralized reaction mixture comprising hydroxymethylfurfural from step S2); and / or- the temperature comprises a temperature in the range of from 60 to 140 °C, preferably of from 70 to 130 °C and more preferably of from 70 to 90 °C.

9. Method according to any of claims 1 to 6, wherein in step S3) the catalyst comprising ruthenium comprises or is ruthenium oxide hydroxide, preferably ruthenium-lll-oxide hydroxide.

10. Method according claim 9, wherein in step S3)- the hydrogenation is performed for a time period in the range of from 8 to 24 hours, preferably of from 8 to 18 hours and more preferably of from 10 to 14 hours; and / or the hydrogen pressure comprises a pressure in the range of from 8 to 18 MPa, preferably of from 10 to 18 MPa and more preferably of from 12 to 16 MPa; and / orBASF SE230849- the temperature comprises a temperature in the range of from 70 to 140 °C, preferably of from 80 to 120 °C and more preferably of from 90 to 110 °C.11 . Method according to any of the preceding claims, wherein the method comprises the further step:S4) isolating 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahy- drofuran, preferably from the reaction mixture received after step S3).

12. Method according to claim 11 , wherein isolating 2,5-bis(hydroxymethyl)furan and / or 2,5-bis(hydroxymethyl)tetrahydrofuran comprises isolating by distillation or evaporation, preferably comprising a step of fractionated distillation or fractionated evaporation, where preferably isolating by evaporation or isolating by fractionated evaporation comprises thin film evaporation.

13. Method according to any of claims 11 to 12, wherein the catalyst used in step S3)- comprises or is ruthenium on carbon and step S3) is performed as defined in claim 8, wherein in step S4) 2,5-bis(hydroxymethyl)tetrahydrofuran is isolated; or- comprises or is ruthenium oxide hydroxide, preferably ruthenium-lll-oxide hydroxide, and step S3) is performed as defined in claim 10, wherein in step S4) 2,5-bis(hydroxymethyl)furan is isolated.

14. Essentially neutralized reaction mixture comprising hydroxymethylfurfural, obtained or obtainable by a method according to any of claims 1 to 5, preferably as obtained in or as obtainable by or after step S1) of the method according to any of claims 1 to 5, wherein preferably the reaction mixture has a pH in the range of from 6 to 8.BASF SE23084915. Essentially neutralized reaction mixture according to claim 14, wherein in the method according to any of claims 1 to 5 the reaction mixture in step S1) further comprises as the organic solvent an organic solvent selected from the group consisting of N- alkyl-2-pyrrolidones, preferably selected from the group consisting of N-methyl-2- pyrrolidone and N-ethyl-2-pyrrolidone; 2-pyrrolidone; N-methyl succinimide, 1 ,3-di- methyl-2-imidazolidinone; dimethylformamide; N,N-dimethyllactamide; dimethylpropyleneurea and mixtures thereof, wherein more preferably the organic solvent is selected from the group consisting of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl succinimide and mixtures thereof, wherein even more preferably the organic solvent comprises or is N-methyl-2-pyrrol- idone.

16. Use of an essentially neutralized reaction mixture comprising hydroxymethylfurfural, according to any of claims 14 or 15, or as obtained in or as obtainable by a method according to any of claims 1 to 5, in a hydrogenation method for making 2,5-bis(hydroxymethyl)furan and / or 2,5- bis(hydroxymethyl)tetrahydrofuran.

17. Use of ruthenium oxide hydroxide, preferably of ruthenium-lll-oxide hydroxide, as hydrogenation catalyst in a method of hydrogenating hydroxymethylfurfural.

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