Method for obtaining organic acids from an aqueous mother liquor

Abstract

The invention relates to a method for obtaining an aminobenzoic acid or an aliphatic saturated C4- 6-dicarboxylic acid from an aqueous solution, comprising: A) producing the organic acid, wherein a) the organic acid is crystallised from an aqueous medium, followed by a separation of the precipitated portions of the organic acid via a solid-liquid phase separation, leaving a first aqueous solution of the organic acid; B) treating the aqueous solution of the organic acid with am Mn2+, Fe2+ and / or Cu2+ metal salt, precipitating a metal compound of the organic acid, followed by a separation of the precipitated metal compound via a solid-liquid phase separation; C) carrying out a base treatment of the separated metal compound, precipitating metal hydroxide and separating precipitated metal hydroxide via a solid-liquid phase separation, leaving a basi`c aqueous solution containing anions of the organic acid; and D) crystallising organic acid from the basic aqueous solution obtained in C) by adding an inorganic acid.

Description

[0001] Process for the extraction of organic acids from an aqueous mother liquor

[0002] The invention underlying this application was financially supported by the German Federal Ministry of Food and Agriculture within the project "Bio-based production of intermediates for polyurethanes - Phase II (Bio4PURPro)" (grant number 22019918).

[0003] The present invention relates to a process for obtaining an organic acid from an aqueous solution of the organic acid, wherein the organic acid is selected from an optionally methyl-substituted aminobenzoic acid or an aliphatic saturated C4 to Cß-dicarboxylic acid, the process comprising:

[0004] A) Production of the organic acid by a biological process or a chemical reaction, wherein a) the organic acid is crystallized from an aqueous medium during or after production, followed by 1) separation of the portions of the organic acid precipitated in the crystallization by a solid-liquid phase separation to leave a first aqueous solution of the organic acid, and, optionally, 2) depletion of the portion of the organic acid dissolved in the first aqueous solution of the organic acid by extracting organic acid with an organic extractant or by adsorbing organic acid on an adsorbent, followed by separation of the organic extractant or adsorbent to obtain a second aqueous solution of the organic acid;

[0005] B) Treating the first or second aqueous solution of the organic acid with a metal salt whose metal ions Mn 2+, Fe 2+ and / or Cu 2+ comprising precipitating a metal compound of the organic acid, followed by separating the precipitated metal compound of the organic acid by a solid-liquid phase separation;

[0006] C) base treatment of the separated metal compound of the organic acid with an aqueous base solution to precipitate metal hydroxide and separation of precipitated metal hydroxide by a solid-liquid phase separation to leave a basic aqueous solution containing anions of the organic acid; and

[0007] D) Crystallizing organic acid from the basic aqueous solution obtained in C) containing anions of the organic acid by adding an inorganic acid.

[0008] The production of organic acids often includes crystallization steps from an aqueous medium to isolate and / or purify the organic acid, optionally from solutions containing the anion of the organic acid by lowering the pH (so-called reactive crystallization). After separation of the crystallized organic acid, an aqueous solution of the organic acid remains (= the mother liquor of the crystallization), which still contains a residual organic acid content corresponding to the solubility equilibrium, which can easily be in the range of several grams per liter.

[0009] One example of this is the production of anthranilic acid. Anthranilic acid is used, for example, in the production of dyes, fragrances, and pharmaceuticals. Per Wiklund's dissertation, "Synthesis of Heterocycles from Anthranilic Acid and Its Derivatives," deals with the production of heterocycles from anthranilic acid and its derivatives (Karolinska University Press 2004, ISBN 91-7349-913-7). In "Separation and Determination of Iron(II) and Iron(III) with Anthranilic Acid Using Solvent Extraction and Spectrophotometry," published in Anal. Chem. 1963, 35, 2077–2081, Donald L. Dinsel and Thomas R. Sweet describe the use of anthranilic acid as an extractant for iron salts. Alexander A. Kamnev and Ernö Kuzmann deal with the reduction of iron(III) by anthranilic acid in Mössbauer spectroscopic evidence for the reduction of iron(III) by anthranilic acid in aqueous solution, published in Polyhedron 1997, 16, 3353 - 3356.The redox chemistry and iron complexation of anthranilic acid and 3-hydroxyanthranilic acid is the subject of the work Iron chelation and redox chemistry of anthranilic acid and 3-hydroxyanthranilic acid: A comparison of two structurally related kynurenine pathway metabolites to obtain improved insights into their potential role in neurological disease development by V. Chobot, F. Hadacek, W. Weckwerth and L. Kubicova, published in J. Organomet. Chem. 2015, 782, 103 - 110.

[0010] Another example of an application for anthranilic acid is its use in the production of aniline by decarboxylation (as described, for example, in WO 2015 / 124687 A1). Aniline, in turn, is particularly important as an intermediate in the production of isocyanates. Anthranilic acid can be obtained, for example, by fermentation (see, for example, the aforementioned application WO 2015 / 124687 A1) or chemically (for example, by Hofmann rearrangement of phthalimide; see, for example, WO 2007 / 088346 A1). Regardless of the exact method of production, crystallization steps of the type mentioned above are regularly carried out. One example is the isolation of anthranilic acid from fermentation broths containing the anthranilic acid anion by reactive crystallization (see again WO 2015 / 124687 A1). Anthranilic acid is an example of an aminobenzoic acid.Other important representatives of this class of compounds are anthranilic acid derivatives, in which a hydrogen atom of the benzene ring is substituted by a methyl group. J.S. Decker and H. Frye discuss the complex formation properties of substituted aminobenzoic acids on the benzene ring in their article "Metal Ion Complexes of Aromatic Amino Acids - 1. Ring Substituted Amino Benzoic Acids," in Z. Naturforschg. 1966, 21 b, 522-526.

[0011] Another example is adipic acid. Adipic acid is an intermediate in the production of nylon. Adipic acid is also used as a precursor for the synthesis of polyester polyols for polyurethane products. Adipic acid can also be obtained by fermentation (see, for example, Peter CK Lau (Editor), Quality Living Through Chemurgy and Green Chemistry, Springer-Verlag GmbH Germany 2016, Chapter 3.3, pp. 47 to 54 and K. Raj, S. Partow et al., Biocatalytic production of adipic acid from glucose using engineered Saccharomyces cerevisiae in Metabolic Engineering Communications 2018, 6, 28-32) or chemically (for example, by hydrogenation of muconic acid, see, for example, WO 2015 / 086827 A1, or by oxidation of cyclohexane, see, for example, A. Castellan et al., Industrial production and use of adipic acid in Catal. Today 1991, 9, 237-254). Here, too, crystallization steps of the type mentioned above regularly occur.An example is the purification of the reaction product of muconic acid hydrogenation by crystallization (see WO 2015 / 086827 Al). Adipic acid is an example of an aliphatic saturated dicarboxylic acid. Another important representative of this class of compounds is succinic acid.

[0012] It is therefore important to reduce the residual content of organic acid in the mother liquor by suitable methods in order to avoid yield losses and to keep wastewater pollution as low as possible.

[0013] EP 0 502 384 A2 describes a process for the recovery of adipic acid from aqueous mother liquors containing nitric acid obtained during the industrial production of adipic acid by selective crystallization of the dissolved adipic acid, in which the mother liquor is mixed within the temperature range from 30 to 60 °C with such an amount of an aqueous adipic acid solution having an adipic acid content of 0.5 to 6% by weight that the nitric acid content of the mixture is reduced to 35 to 50% by weight, the mixture is then cooled by at least 5 °C within a period of 0.5 to 5 hours, the adipic acid which crystallizes out is isolated by filtration and the filtrate obtained is fed to the distillative glutaric acid processing.

[0014] WO 2015 / 085198 A1 describes a process for producing succinic acid and succinic esters from a succinic acid salt in a fermentation broth. In a first step, renewable carbon resources are used to produce succinic acid by biological fermentation. The succinic acid salt undergoes a double displacement reaction with a strong acid during the fermentation process, resulting in the release of succinic acid. Succinic acid is obtained by fractional crystallization integrated with SMB (simulated moving bed) chromatography to produce succinic acid and succinic esters. The international application WO 2015 / 124687 A1, already mentioned several times, discloses a preferred embodiment in which the mother liquor obtained during crystallization is processed to obtain further aminobenzoic acid. This occurs through a sequence of an adsorption and a desorption step.The resulting desorbate, enriched in aminobenzoic acid, is recycled to the crystallization process. This reduces yield losses. Adsorption occurs on zeolites or activated carbon, and desorption occurs with water at a pH in the range of 5 to 10 or, alternatively, with organic solvents, particularly 1-dodecanol. A variant of such a processing step, consisting of an adsorption and desorption step, is described in international application WO 2018 / 114841 A1. The process disclosed therein is characterized in particular by the fact that desorption is carried out in an acidic environment (pH -0.8 to 3.0).

[0015] The also previously mentioned international patent application WO 2007 / 088346 A1 describes a process for obtaining anthranilic acid from the mother liquor of a crystallization for the isolation of anthranilic acid obtained by a Hofmann rearrangement. The sodium carbonate-containing product of the Hofmann rearrangement is adjusted to a pH of 4.2 with sulfuric acid (a), and precipitated anthranilic acid is filtered off (b). The remaining mother liquor is extracted at a pH of 4.2 with an organic solvent, with acetic acid esters (especially ethyl or butyl acetate), ketones (especially 2-butanone), and aromatic hydrocarbons (especially toluene) being disclosed as suitable organic solvents. The organic extract obtained after phase separation (c) is then back-extracted with sodium hydroxide solution (d), whereby anthranilic acid passes as the anthranilate anion into the aqueous phase obtained after phase separation (e).This aqueous phase from the back extraction, enriched in anthranilic acid, is combined with the product of the Hofmann rearrangement and, together with it, fed to the crystallization process. The aqueous phase, depleted in anthranilic acid, resulting from the extraction is adjusted to pH 1.5 with sulfuric acid, mixed with additional organic solvent (f), and separated into an aqueous and organic phase (g). In this way, organic impurities enter the organic phase. This organic phase is combined with the organic phase from the back extraction and distilled. The distillate can be recycled into the process as a solvent. The distillation residue is incinerated. The aqueous phase from (g) is purified by a Fenton reaction and fed into the wastewater. A particular disadvantage of this process is the relatively high water solubility of the acetic acid esters and ketones.Although acetic acid esters and ketones dissolve anthranilic acid well, their comparatively high water solubility results in non-negligible amounts of the product entering the aqueous phase. This results in yield losses and increases the cost of wastewater treatment. Toluene, also disclosed as a suitable solvent in WO 2007 / 088346 A1, does not exhibit the disadvantages described, but dissolves anthranilic acid considerably less effectively, making it difficult to develop a practical, large-scale process using toluene as the extraction agent.

[0016] CN 102 190590 A describes a process for removing anthranilic acid from wastewater from anthranilic acid methyl ester production. In the described process, the wastewater from anthranilic acid methyl ester production is treated with acidic wastewater (in particular, sulfuric acid containing copper chloride) until a pH of 3.5 to 4.5 is established and copper anthranilate precipitates. The precipitated copper anthranilate is placed in a stirred tank together with calcium oxide, and an alkaline solution (pH 11 to 13) is added. The mixture is heated to 90 to 110 °C and boiled for 30 to 150 minutes. After filtration, the sodium anthranilate-containing filtrate is decolorized and adjusted to a pH of 3.5 to 4.0 with hydrochloric acid. Precipitated anthranilic acid is washed and dried.

[0017] None of the described prior art processes is free of disadvantages, so there is a need for further improvements in the field of recovering organic acids from aqueous solutions thereof (mother liquors). In particular, a process would be desirable in which, firstly, the organic acid can be selectively and almost completely removed from the aqueous mother liquor without other components, such as an organic solvent, passing into the aqueous phase. Secondly, a process would be desirable in which the separated organic acid can be converted back into an aqueous phase with high concentration and yield.

[0018] Taking this need into account, the present invention provides a process for obtaining an organic acid from an aqueous solution of the organic acid, wherein the organic acid is selected from

[0019] (i) an aminobenzoic acid of the formula (I), wherein R is CH3 or H, or

[0020] (ii) an aliphatic saturated dicarboxylic acid of the formula

[0021] (II), wherein n = 1 or - preferably - 2, the process comprising the steps:

[0022] A) Production of the organic acid by a biological process (preferably a fermentation) or a chemical reaction (i.e. in a non-biological process), wherein a) the organic acid is crystallized from an aqueous medium during or after production (in order to isolate it, optionally with protonation of the anion of the organic acid, or to purify already isolated organic acid by recrystallization), followed by

[0023] 1) Separating the organic acid fractions precipitated during crystallization (i.e. during crystallization of step a)) by a solid-liquid phase separation, leaving a first aqueous solution of the organic acid and

[0024] 2) optionally, depleting the proportion of organic acid dissolved in the first aqueous solution of organic acid by extracting organic acid with an organic extractant or by adsorbing organic acid on an adsorbent, followed by separating the (organic acid-laden) organic extractant or adsorbent to obtain a (organic acid-depleted) second aqueous solution of organic acid;

[0025] B) Treating the first aqueous solution of the organic acid or the second aqueous solution of the organic acid with a metal salt whose metal ions Mn 2+ , Fe 2+ and / or Cu 2+comprise (and are in particular selected from the group consisting of Mn 2+ , Fe 2+ and Cu 2+ ), with precipitation of a metal compound of the organic acid (sparingly soluble complex compound or sparingly soluble salt), followed by separation of the precipitated metal compound of the organic acid by a solid-liquid phase separation;

[0026] C) base treatment of the separated metal compound of the organic acid with an aqueous base solution to precipitate metal hydroxide and to separate precipitated metal hydroxide by a solid-liquid phase separation to leave a basic aqueous solution containing anions of the organic acid, wherein the base treatment is carried out in particular without the use of calcium oxide and in particular at a temperature of 20 °C to 85 °C, preferably 20 °C to 70 °C, particularly preferably 20 °C to 50 °C, in particular also at ambient temperature; and

[0027] D) Crystallizing organic acid from the basic aqueous solution obtained in C) containing anions of the organic acid by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.

[0028] Completely surprisingly, it was found that the combination of treatment with a metal salt of the type mentioned (step B)) and the base treatment (step C)) makes it possible to provide an aqueous solution of the organic acid (in anionic form) which is significantly more concentrated than the aqueous solution of the organic acid originating from A)a) and which can consequently be subjected to reactive crystallization (step D)) in order to isolate further organic acid.

[0029] In the context of the present invention, all pH values ​​refer to the temperature at which the corresponding step (e.g. step D)) is carried out and can be easily measured with a glass electrode.

[0030] In the context of the present invention, biological processes are understood to mean fermentative or enzymatic conversions of organic substances.

[0031] Accordingly, in the context of the present invention, the conversion of an organic substance is referred to as chemical (chemical conversion or chemical process) if it takes place without the use of fermentative or enzymatic processes (i.e., purely thermally or using non-biological catalysts). The attached figures show

[0032] FIG. 1 is a schematic representation of an embodiment of the method according to the invention; and

[0033] FIG. 2 shows a schematic representation of the multi-stage implementation of step C).

[0034] First, a brief summary of various possible embodiments of the invention follows:

[0035] In a first embodiment of the invention, which can be combined with all other embodiments, the base treatment in C) comprises n successive steps, where n is a natural number in the range from 2 to 10, preferably 3 to 9, particularly preferably 4 to 8, wherein in each of the n steps a portion of the separated metal compound of the organic acid is treated with an aqueous base solution to precipitate metal hydroxide, wherein after each step a separation of precipitated metal hydroxide is carried out by solid-liquid phase separation to leave a basic aqueous solution containing anions of the organic acid, wherein the aqueous base solution in the second to n-th step comprises the basic aqueous solution containing anions of the organic acid obtained in the respective preceding step (and optionally consists of this, i.e. comprises no further constituents);wherein the crystallization of the organic acid in D) is carried out with the basic aqueous solution containing anions of the organic acid obtained in the n-th step of C);

[0036] In a second embodiment of the invention, which can be combined with all other embodiments, provided that they do not provide for the separate implementation of the crystallization of the organic acid in D) and in A)a), the crystallization of organic acid in D) comprises the recycling of the basic aqueous solution containing anions of the organic acid obtained in C) (ie in the case of n-stage base treatment of the basic aqueous solution containing anions of the organic acid obtained in the n-th step of C)) to A)a).

[0037] In a third embodiment of the invention, which can be combined with all other embodiments, provided they do not provide for the joint crystallization of the organic acid in D) and in A)a), the crystallization of the organic acid in D) is carried out separately from A)a). In a fourth embodiment of the invention, which can be combined with all other embodiments, the metal hydroxide precipitated in C) is recycled to step B) and used there as a component of the metal salt.

[0038] In a fifth embodiment of the invention, which can be combined with all other embodiments, provided that they do not exclusively relate to aliphatic saturated dicarboxylic acid of the formula (II), the organic acid is an aminobenzoic acid of the formula (I), in particular 2-aminobenzoic acid (anthranilic acid) or 2-amino-5-methylbenzoic acid, preferably 2-aminobenzoic acid.

[0039] In a sixth embodiment of the invention, which is a particular embodiment of the fifth embodiment, in A)a) a pH in the range from 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6, is set by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, and in B) a pH in the same range is maintained (optionally by adding an acid or base, should the pH increase or decrease too much as a result of the addition of the metal salt).

[0040] In a seventh embodiment of the invention, which is a particular embodiment of the fifth and sixth embodiments, A) comprises a biological process, namely the fermentation of a raw material containing a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms.

[0041] In an eighth embodiment of the invention, which is a particular embodiment of the seventh embodiment,

[0042] (I) to carry out A)a), the fermentation is carried out at a pH in the range from 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6, so that the aminobenzoic acid of the formula (I) crystallizes during the fermentation; or

[0043] (II) the fermentation is carried out at a pH in the range of > 4.7 to 11 (in particular 6.0 to 11), preferably 4.8 to 9.0 (in particular 6.0 to 9.0), particularly preferably 5.0 to 8.0 (in particular 6.0 to 8.0), wherein for carrying out A)a) after the fermentation a pH in the range of 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6, is set.

[0044] In a ninth embodiment of the invention, which is a particular embodiment of the seventh and eighth embodiments, the microorganisms are selected from Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0045] In a tenth embodiment of the invention, which is a particular embodiment of the fifth and sixth embodiments, A) comprises a chemical reaction (ie a non-biological process).

[0046] In an eleventh embodiment of the invention, which is a particular embodiment of the tenth embodiment, A) comprises the reaction of optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalide (in particular sodium hypochlorite) in a basic medium, followed by the addition of an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, to carry out A)a).

[0047] In a twelfth embodiment of the invention, which can be combined with all other embodiments, provided that they do not exclusively relate to aminobenzoic acids of the formula (I), the organic acid is an aliphatic saturated dicarboxylic acid of the formula (II), in particular 1,6-hexane dicarboxylic acid (adipic acid).

[0048] In a thirteenth embodiment of the invention, which is a particular embodiment of the twelfth embodiment, in A)a) a pH in the range from 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5, is set by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, and in B) a pH in the range from > 4.0 to 7.0, preferably 4.7 to 5.8, particularly preferably 5.3 to 5.7, is set by adding a base.

[0049] In a fourteenth embodiment of the invention, which is a particular embodiment of the twelfth and thirteenth embodiments, A) comprises a biological process.

[0050] In a fifteenth embodiment of the invention, which is a particular embodiment of the fourteenth embodiment, the biological process comprises the fermentation of a raw material containing a fermentable carbon-containing compound in the presence of microorganisms.

[0051] In a sixteenth embodiment of the invention, which is a particular embodiment of the fifteenth embodiment,

[0052] (I) to carry out A)a), the fermentation is carried out at a pH in the range from 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5, so that the aliphatic saturated dicarboxylic acid of the formula (II) crystallizes already in the fermentation; or (II) the fermentation is carried out at a pH in the range from > 4.0 to 11 (in particular 6.0 to 11), preferably 5.0 to 9.0 (in particular 6.0 to 9.0), particularly preferably 5.0 to 8.0 (in particular 6.0 to 8.0), wherein to carry out A)a), a pH in the range from 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5, is set after the fermentation.

[0053] In a seventeenth embodiment of the invention, which is a particular embodiment of the fifteenth and sixteenth embodiments, the microorganisms are selected from Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Bacillus coagulans, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia polytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0054] In an eighteenth embodiment of the invention, which is a particular embodiment of the twelfth and thirteenth embodiments, A) comprises a chemical reaction (ie a non-biological process).

[0055] In a nineteenth embodiment of the invention, which is a particular embodiment of the eighteenth embodiment, n = 2 applies in particular (the organic acid is therefore in particular adipic acid), wherein A) comprises the hydrogenation of an aliphatic unsaturated dicarboxylic acid (such as in particular muconic acid) corresponding to the aliphatic saturated dicarboxylic acid of formula (II) (and A)a) is carried out in particular for the purification of the product obtained in the hydrogenation).

[0056] In a twentieth embodiment of the invention, which is a further particular embodiment of the eighteenth embodiment, the aliphatic saturated dicarboxylic acid of formula (II) is 1,6-hexanedicarboxylic acid (adipic acid), wherein A) comprises the oxidation of cyclohexane with oxygen or oxygen-containing gas mixtures (in particular air) to cyclohexanol and cyclohexanone and their subsequent oxidation with nitric acid.

[0057] In a twenty-first embodiment of the invention, which is a particular embodiment of the fourteenth and eighteenth embodiments, A) comprises an (enzymatic or chemical) cleavage of a polyester.

[0058] In a twenty-second embodiment of the invention, which can be combined with all other embodiments, in particular insofar as these relate to the production of an aliphatic saturated dicarboxylic acid of the formula (II) (preferably 1,6-hexane dicarboxylic acid, adipic acid), the metal ions of the metal salt used in B) comprise Fe 2+ and / or Cu 2+ and are in particular selected from the group consisting of Fe 2+ and Cu 2+ (particularly in the case of obtaining an aliphatic saturated dicarboxylic acid of the formula (II) Cu 2+is preferred). In a twenty-third embodiment of the invention, which can be combined with all other embodiments, in C) (in the case of n-stage base treatment in each of the n steps of the base treatment) a pH in the range from 9.0 to 14, preferably 10 to 14, particularly preferably 11 to 13, is set.

[0059] In a twenty-fourth embodiment of the invention, which can be combined with all other embodiments, in B) the metal ions are added in a maximum stoichiometric amount, based on the amount of organic acid.

[0060] In a twenty-fifth embodiment of the invention, which can be combined with all other embodiments, the metal salt comprises a sulfate, chloride and / or hydroxide.

[0061] In a twenty-sixth embodiment of the invention, which can be combined with all other embodiments, the solid-liquid phase separations in A), B) and / or C) are carried out by filtration, centrifugation or sedimentation, optionally assisted by a preceding flocculation.

[0062] In a twenty-seventh embodiment of the invention, which can be combined with all other embodiments, step 2) is carried out in A), wherein the organic extractant is selected from (i) an alcohol, in particular an alkanol, having 4 to 12 carbon atoms (in particular 1-decanol and / or 1-dodecanol), preferably 8 to 12 carbon atoms, particularly preferably 9 to 11 carbon atoms, (ii) a ketone (in particular methyl / iso-butyl ketone and / or cyclohexanone), (iii) an ether (in particular diethyl ether), (iv) an ester (in particular butyl acetate), (v) an aromatic, optionally halogen-substituted, hydrocarbon (in particular benzene, toluene, monochlorobenzene and / or dichlorobenzene) or (vi) a mixture of two or more of the aforementioned extractants, and the adsorbent is selected from (i) activated carbon, (ii) polymer-based adsorbents, (iii) graphite,(iv) a polar adsorbent such as, in particular, silica gel, limestone or an aluminum silicate or (v) a mixture of two or more of the aforementioned adsorbents.

[0063] In a twenty-eighth embodiment of the invention, which can be combined with all other embodiments, in B) after the precipitated metal compound of the organic acid has been separated off by solid-liquid phase separation, an aqueous phase remains which is adjusted to a pH in the range from 8.0 to 14, preferably 10 to 13, by addition of a base, whereby metal hydroxides precipitate, which are separated off by a further solid-liquid phase separation and subsequently used in B) as a component of the metal salt.

[0064] In a twenty-ninth embodiment of the invention, which is a particular embodiment of the twenty-eighth embodiment, the base used to adjust the pH comprises an alkali or alkaline earth metal hydroxide, an alkali or alkaline earth metal carbonate, an alkali or alkaline earth metal hydrogen carbonate, in particular sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution.

[0065] The embodiments briefly described above and other possible configurations of the invention are explained in more detail below. All of the embodiments described above and the other configurations of the invention described below can be combined with one another as desired, unless the context clearly indicates otherwise to a person skilled in the art or unless expressly stated otherwise.

[0066] PRODUCTION OF THE ORGANIC ACID

[0067] Step (A) of the process according to the invention, the preparation of the organic acid, naturally depends on the type of acid desired. The crystallization step A)a) takes place during or after the preparation.

[0068] Aminobenzoic acids of formula (I)

[0069] If the objective is to obtain aminobenzoic acid of formula (I), of which 2-aminobenzoic acid (= anthranilic acid) is preferred, it has proven advantageous to adjust a pH in the range of 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6, in step A)a) by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid. The exact manner of carrying out the crystallization according to step A)a) in turn depends on the manner in which step A) is carried out overall.

[0070] Biological processes

[0071] In one embodiment, step A) comprises a fermentation step. This is carried out by converting a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms to form the desired aminobenzoic acid or its anion. Such fermentations have already been described; see the literature cited below. Particularly suitable microorganisms for the fermentative production of an aminobenzoic acid of formula (I) are Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia polytica, Zygosaccharomyces bailii, or Saccharomyces cerevisiae.

[0072] The fermentation in step A) is preferably carried out such that the pH in the resulting fermentation broth is in the range from 3.0 to 11, preferably > 4.7 to 11 (= case (II); see below). If necessary, the pH can be regulated by adding aqueous or gaseous ammonia, aqueous potassium hydroxide or aqueous sodium hydroxide (in the case of excessively low pH values) or by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid (in the case of excessively high pH values). For different microorganisms, different pH ranges within the stated pH range of 3.0 to 11 can be particularly optimal. Furthermore, the pH in the fermentation influences step A)a).Depending on the specific pH value within the range of 3.0 to 11, the aminobenzoic acid in the fermentation broth is present as a readily water-soluble anion (HzNCeHsfRjCOO-) or in the relatively poorly water-soluble electroneutral form (H2NC6H3(R)COOH or H3N. + C6H3(R)COO-).

[0073] At pH values ​​in the range, in particular, of 4.7 or less, preferably of 3.7 or less, particularly preferably of 3.6 or less, the aminobenzoic acid is predominantly to completely in the electroneutral form and therefore crystallizes spontaneously during fermentation, so that a separate crystallization step is unnecessary and the crystallized aminobenzoic acid can be isolated directly from the fermentation broth (case (I)). Case (I) is particularly preferred, for example, if the described procedure results in advantages in the fermentation, such as, in particular, reduced toxicity for the microorganisms in the fermentation broth as a result of the precipitation of the aminobenzoic acid.

[0074] In case (I), the fermentation is preferably carried out at a pH in the range of 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6. Step A)a) is then part of the fermentation. Eukaryotes, in particular yeasts, are preferably used as microorganisms. In this regard, particular reference is made to international application WO 2017 / 102853 A1. Yeast cells capable of converting a fermentable carbon-containing compound into aminobenzoic acid in the presence of a suitable nitrogen source are preferably used, without the aminobenzoic acid thus formed being immediately consumed in intracellular biochemical processes, so that aminobenzoic acid accumulates in the cell and ultimately passes into the fermentation broth.Eukaryotes such as Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia polytica, Zygosaccharomyces bailii, and Saccharomyces cerevisiae preferentially cultivate in acidic environments and are therefore suitable for the case (I) described here. Step A)a) is part of the fermentation in case (I). The precipitated aminobenzoic acid is separated after the fermentation by a (first) solid-liquid phase separation, where it is obtained in a mixture with the microorganisms. To separate the two, one can proceed, for example, by selectively dissolving the aminobenzoic acid in the most concentrated form possible (e.g., with an aqueous base solution, an aqueous acid solution, or an organic solvent) and then, if necessary, re-precipitating it from this solution (by recrystallization or evaporation).It is also possible to proceed by taking up a first part of the solid mixture, in particular 50%, in as little aqueous base solution as possible (e.g. while maintaining a pH of the supernatant solution of 7.0) and a second part of the solid mixture, in particular 50%, in as little aqueous acid solution as possible (e.g. while maintaining a pH of the supernatant solution of 1.0) and, after separating off the undissolved portions, combining the remaining - comparatively highly concentrated - solutions so that a pH at or near the isoelectric point is established in the resulting mixture and the aminobenzoic acid precipitates again.The mother liquor remaining after separation of the precipitated aminobenzoic acid in a (second) solid-liquid phase separation has a significantly smaller volume than the mother liquor obtained after the first solid-liquid phase separation and, since it contains only comparatively little aminobenzoic acid, can be disposed of or advantageously combined with the mother liquor from the first solid-liquid phase separation.

[0075] The liquid phase obtained in the first solid-liquid phase separation or the combined liquid phases from the first and second solid-liquid phase separation represent / represent the "aqueous solution of the organic acid" in this embodiment. Solid-liquid phase separations are always carried out in the context of the present invention (regardless of the process step) preferably as filtration, centrifugation or sedimentation, optionally assisted by a preceding flocculation.

[0076] At pH values, in particular > 4.7, preferably 6.0 or more, particularly preferably 8.0 or more, the aminobenzoic acid is present predominantly to entirely as an anion, so that a separate crystallization step is carried out (case (II), which is preferred). In case (II), the fermentation is preferably carried out at a pH in the range of > 4.7 to 11 (in particular 6.0 to 11), preferably 4.8 to 9.0 (in particular 6.0 to 9.0), particularly preferably 5.0 to 8.0 (in particular 6.0 to 8.0). Prokaryotes, in particular bacteria, are preferably used as microorganisms.In this regard, particular reference is made to patent applications WO 2015 / 124686 A1 and WO 2015 / 124687 A1, which describe fermentation processes using bacteria (see, for example, WO 2015 / 124687 A1, (i) page 15, line 8 to page 16, line 30, (ii) Example 1 (page 29, lines 4 to 26), (iii) Example 3 (especially page 34, lines 10 to 18), (iv) Example 4 (especially page 55, lines 9 to 31)) and which provide the anion of aminobenzoic acid as a direct product of the fermentation, thus being suitable for case (II). In particular, bacteria are used which are able to convert a fermentable carbon-containing compound into aminobenzoic acid in the presence of a suitable nitrogen source, without the aminobenzoic acid thus formed being converted into cellular biochemical processes, so that aminobenzoic acid accumulates in the cell and eventually passes into the fermentation broth.Microorganisms such as Corynebacterium glutamicum, Pseudomonas putida, or Escherichia coli are preferably cultivated at "neutral to basic pH values" and are therefore suitable for the case (II) described here. Since in this case the aminobenzoic acid is obtained as an anion, it is crystallized in a step downstream of the fermentation by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, whereby a pH value in the range of 3.0 to 4.7, preferably 3.2 to 3.7, particularly preferably 3.4 to 3.6, is adjusted. In this case, step A)a) is therefore a step downstream of the fermentation.

[0077] Chemical processes

[0078] In another embodiment, step A) comprises a chemical reaction (i.e., a non-biological process). Particular mention should be made here of the reaction of optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalide (in particular sodium hypochlorite) in a basic medium. Such processes are known from the literature and are described, for example, in WO 2007 / 088346 A1. The desired aminobenzoic acid of formula (I) is obtained as an anion and is crystallized by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid (= step A)a)).

[0079] If the crystallization step A)a) is carried out separately from the actual production, such as in case (II) of fermentative production or in a crystallization used to purify a crude product, an additional technical apparatus suitable for crystallization, known in the art as a crystallizer, is used in addition to the reactor for producing the organic acid. Suitable crystallizers include, for example, stirred tanks or forced-circulation crystallizers such as those of the "Oslo type." In the crystallizer, the pH is adjusted, if necessary, to a suitable value; in the case of the aminobenzoic acid of formula (I), to a value in the range from 3.0 to 4.7, preferably 3.2 to 3.7, very particularly preferably 3.4 to 3.6. This is preferably done by adding an acid selected from hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid.Through this pH adjustment, the aminobenzoic acid anions (HzNCeHsfRjCOO-) are predominantly or completely converted into the electroneutral form (HzNCeHsfRjCOOH or HsN+CeFMRjCOO) and crystallize out. This type of crystallization is also called reoct / vcrystallization. The crystallized aminobenzoic acid is isolated by solid-liquid phase separation, leaving the "aqueous solution of the organic acid" behind.

[0080] Aliphatic saturated dicarboxylic acids of formula (II)

[0081] If the aim is to obtain aliphatic saturated dicarboxylic acid of formula (II), of which 1,6-hexane dicarboxylic acid (= adipic acid) is preferred, it has proven useful to adjust a pH in the range from 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5, in step A)a) by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid. The exact manner in which the crystallization is carried out in step A)a) in turn depends on the manner in which step A) is carried out overall. All possible embodiments of the invention described above in connection with the preparation of aminobenzoic acids of formula (I), which are not specific to these aminobenzoic acids, also apply accordingly to the case of the preparation of aliphatic saturated dicarboxylic acid of formula (II) described below. This concerns, for example, the design of a crystallizer.

[0082] Biological processes

[0083] In one embodiment, step A) comprises a biological process. In a first variant, this is carried out in particular by converting a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms to form the desired aliphatic saturated dicarboxylic acid or its anion. Such fermentations have already been described; see in particular the previously cited publications by Peter CK Lau (Editor), Quality Living Through Chemurgy and Green Chemistry, Springer-Verlag GmbH Germany 2016, Chapter 3.3, pp. 47 to 54, and K. Raj, S. Partow et al., Biocatalytic production of adipic acid from glucose using engineered Saccharomyces cerevisiae in Metabolic Engineering Communications 2018, 6, 28-32.

[0084] Particularly suitable microorganisms for the fermentative production of an aliphatic saturated dicarboxylic acid of formula (II) are Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Bacillus coagulans, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia Hpolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae. In analogy to the previously described preparation of the aminobenzoic acids of formula (I), there is also a pH dependence here: Depending on the pH value at which the fermentation is carried out, the aliphatic saturated dicarboxylic acid crystallizes out during the fermentation (case (I)) or the fermentation broth contains the aliphatic saturated dicarboxylic acid in the form of its anion, in which case a reactive crystallization follows the fermentation (case (II)).In case (I), the fermentation is preferably carried out at a pH in the range of 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5. To separate microorganisms and organic acid, one can proceed, for example, by selectively dissolving the saturated aliphatic dicarboxylic acid in the most concentrated form possible (e.g., with an aqueous base solution or an organic solvent) and then, if necessary, separating it from this solution again (by recrystallization or evaporation). Step A)a) is then part of the fermentation. In case (II), the fermentation is preferably carried out at a pH in the range of > 4.0 to 11 (in particular 6.0 to 11), preferably 5.0 to 9.0 (in particular 6.0 to 9.0), particularly preferably 5.0 to 8.0 (in particular 6.0 to 8.0).In this case, the aliphatic saturated dicarboxylic acid is obtained as an anion and is crystallized in a step downstream of the fermentation by adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, while adjusting the pH to a value in the range of 0 to 4.0, preferably 1.8 to 3.0, particularly preferably 2.0 to 2.5. In this case, step A)a) is therefore a step downstream of the fermentation.

[0085] In a second variant of the organic acid production using a biological process, enzymes are used to cleave polyesters. The enzymatic cleavage of polyesters using cutinases to release adipic acid was described, for example, in the following study: Perz, V., Bleymaier, K., Sinkel, C., Kueper, U., Bonnekessel, M., Ribitsch, D., & Guebitz, GM (2016), "Substrate specificities of cutinases on aliphatic-aromatic polyesters and on their model substrates," in "New biotechnology," 2016, 33(2), 295–304.

[0086] Chemical processes

[0087] In another embodiment, step A) comprises a chemical reaction (i.e., a non-biological process). Chemical processes for producing dicarboxylic acids of the type mentioned are known. For example, reference is made to the hydrogenation of the corresponding aliphatic unsaturated dicarboxylic acids. In the case of the most preferred adipic acid, the production can thus be carried out by hydrogenation of muconic acid, which is described, for example, in WO2015 / 086827A1. Step A)a) is carried out here in particular to purify the product obtained in the hydrogenation. An alternative possibility for producing adipic acid is the oxidation of cyclohexane with oxygen or oxygen-containing gas mixtures (especially air), already mentioned at the beginning and widely described in the literature, to cyclohexanol and cyclohexanone, followed by their subsequent oxidation with nitric acid (see A. Castellan et al. in Catal. Today 1991, 9, 237-254 for an overview).

[0088] In a chemical reaction, step A) can also involve the cleavage of polyesters, for example, by acidic or alkaline hydrolysis. Furthermore, step A) can involve the acidic or alkaline hydrolysis of a polyamide based on hexamethylenediamine and adipic acid, as described, for example, in US Pat. No. 3,223,731.

[0089] OPTIONAL STEP OF DEPLENISHING THE PROPORTION OF ORGANIC ACID DISSOLVED IN THE FIRST AQUEOUS ORGANIC ACID SOLUTION

[0090] The first aqueous solution of the organic acid obtained in one of the ways described above can be fed directly to step B). However, it is also possible to reduce the concentration of organic acid in this first aqueous solution of organic acid in another way before carrying out step B). Suitable methods for this are the extraction and

[0091] When using an extractive process, the first aqueous solution of the organic acid is extracted with an organic extractant, followed by a liquid-liquid phase separation to obtain an aqueous phase (= second aqueous solution of the organic acid depleted in organic acid) and an organic phase (= extractant loaded with organic acid). Within the scope of the present invention, liquid-liquid phase separations are always preferably carried out using separators, decanters, or centrifuges (regardless of the process step).

[0092] Suitable extractants are, for example, (i) alcohols, in particular alkanols, having 4 to 12 carbon atoms (in particular 1-decanol and / or 1-dodecanol), preferably 8 to 12 carbon atoms, particularly preferably 9 to 11 carbon atoms, (ii) ketones (in particular methyl / iso-butyl ketone and / or cyclohexanone), (iii) ethers (in particular diethyl ether), (iv) esters (in particular butyl acetate), (v) aromatic, optionally halogen-substituted, hydrocarbons (in particular benzene, toluene, monochlorobenzene and / or dichlorobenzene) and (vi) mixtures of two or more of the aforementioned extractants.

[0093] Suitable apparatus for carrying out an extraction are known in the art. Suitable examples are so-called mixer settlers or extraction columns with a theoretical number of plates of preferably 3 to 10, more preferably 3 to 7, and most preferably 4 to 6. The mass-based phase ratio of the organic to aqueous phases is preferably 0.20 to 1.0, more preferably 0.20 to 0.50, and most preferably 0.35 to 0.50. After separating the organic solvent phase and the aqueous phase, the aqueous solution of the organic acid is fed to step B). The extractant loaded with organic acid is preferably fed to a back extraction, in which the organic acid is converted into the anion by extraction with an aqueous base solution, and, after phase separation, an aqueous phase containing anions of the organic acid and an alcoholic phase are obtained.Since relatively polar impurities may arise during the production of the organic acid, and these relatively polar impurities, in particular, pass at least partially into the aqueous phase during this step, it is preferable to take measures to remove such impurities. The extraction can be carried out at temperatures of 20 °C to 90 °C, preferably 25 °C to 70 °C, particularly preferably 30 °C to 50 °C, and in particular also at ambient temperature.

[0094] The aqueous base solution used for the back-extraction is preferably an aqueous solution of an alkali or alkaline earth metal hydroxide (especially sodium hydroxide, potassium hydroxide, or calcium hydroxide), an alkali or alkaline earth metal bicarbonate (especially a sodium or potassium bicarbonate solution), an alkali or alkaline earth metal carbonate (especially a sodium or potassium carbonate solution), or a mixture of two or more of the aforementioned compounds. Sodium hydroxide and potassium hydroxide are particularly preferred. Regardless of the base used, it is preferable to maintain a molar ratio of hydroxide ions to organic acid group of 1.0 to 5.0, preferably 1.0 to 2.0, and particularly preferably 1.0 to 1.5.

[0095] The same apparatus as described for the extraction is suitable for the back extraction. The mass ratio of the organic to the aqueous phases is preferably 0.20 to 1.0, particularly preferably 0.20 to 0.50, and most preferably 0.20 to 0.40.

[0096] Instead of extraction, adsorption can also be used to deplete the first aqueous solution of organic acid. For this purpose, the first aqueous solution is passed through a bed of an adsorbent onto which the organic acid is adsorbed. Suitable adsorbents are typically non-polar adsorbents such as (i) activated carbon, (ii) graphite or (iii) adsorbent polymers, but also (typically) (iv) polar adsorbents such as silica gel, limestone or aluminum silicates and (v) mixtures of two or more of the aforementioned adsorbents. Adsorption is preferably carried out by flowing the aqueous solution over the adsorbent until the adsorption properties of the adsorbent decrease and regeneration of the adsorbent by desorption of the organic acid is required.Desorption is preferably carried out using aqueous solutions with a pH in the range of 5 to 10 (adjusting the pH, for example, with sodium hydroxide solution or hydrochloric acid) or, alternatively, with organic solvents, in particular 1-dodecanol. A variant of such a processing involving a sequence of adsorption and desorption steps is described in the international application WO 2018 / 114841 A1. The process disclosed therein is characterized in particular by the fact that desorption is carried out in an acidic environment (pH -0.8 to 3.0). In this embodiment, the liquid phase emerging from the adsorbent bed during desorption represents the second aqueous solution of organic acid and is fed to step B).

[0097] Suitable apparatus for adsorption are known in the art. Examples include columns, or on a laboratory scale, chromatography columns, into which the adsorbent is charged, particularly in the form of an adsorbent bed.

[0098] METAL SALT TREATMENT

[0099] In step B) of the process according to the invention, the first or second aqueous solution of the organic acid obtained in step A) is reacted with a metal salt whose metal ions Mn 2+ , Fe 2+ and / or Cu 2+ and are in particular selected from the group consisting of Mn 2+ , Fe 2+ and Cu 2+, with precipitation of a metal compound of the organic acid (sparingly soluble complex compound or sparingly soluble salt), followed by separation of the precipitated metal compound of the organic acid by solid-liquid phase separation. Of the metal ions usable according to the invention, Fe 2+ and Cu 2+ preferred (especially in the case of obtaining the aliphatic saturated dicarboxylic acids); particularly preferred is Cu 2+ (again especially in the case of the production of aliphatic saturated dicarboxylic acids).

[0100] The optimum pH in step B) depends on the type of organic acid to be obtained and is preferably 3.0 to 4.7, particularly preferably 3.2 to 3.7, very particularly preferably 3.4 to 3.6 in the case of the aminobenzoic acids of the formula (I), and preferably >4.0 to 7.0, particularly preferably 4.7 to 5.8, very particularly preferably 5.3 to 5.7 in the case of the aliphatic saturated dicarboxylic acids of the formula (II). Should the pH threaten to deviate from the desired ranges due to acidic or basic properties of the added metal salt, this can be easily compensated by adding acid (preferably hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid) or base (preferably sodium hydroxide solution, potassium hydroxide solution, or calcium hydroxide). The metal salt to be used in step B) is preferably a sulfate, chloride, and / or hydroxide.The use of a hydroxide enables a particularly economical embodiment of the process according to the invention, in which the precipitated metal hydroxide obtained in step e), described in more detail below, is recycled to step B) and used there as a component of the metal salt. Any excessive pH increase in step B) can be counteracted by adding acid.

[0101] Preferably, the metal ions of the metal salt are added in a maximum stoichiometric amount, based on the amount of organic acid.

[0102] The metal salt treatment is preferably carried out at 20°C to 50°C, particularly preferably at 20°C to 30°C, and in particular at ambient temperature. A suitable reaction apparatus, for example, is a stirred-tank reactor (or several stirred-tank reactors, particularly connected in series). The treatment can be carried out by initially introducing the metal salt (e.g., Cu(OH)z) into the reactor and adding the aqueous solution of the organic acid, if necessary with active pH adjustment (see the previous explanations on suitable pH values). After precipitation of the sparingly soluble metal compound of the organic acid, it is separated by solid-liquid phase separation. The remaining aqueous phase can be disposed of as wastewater.Since this aqueous phase still contains metal salts in proportions corresponding to their solubility at the prevailing (acidic, see above) pH, and these proportions can be undesirably high from an environmental perspective, one embodiment of the invention provides for increasing the pH of the aqueous liquid phase obtained in the solid-liquid phase separation to values ​​of 8.0 to 14, preferably 10 to 13, in order to precipitate dissolved metal ions as sparingly soluble hydroxides. These can then be separated in a second solid-liquid phase separation and recycled to step B). The aqueous liquid phase obtained in the second solid-liquid phase separation can then be easily disposed of, for example, in a biological wastewater treatment plant.Common bases such as alkali and alkaline earth metal hydroxides, alkali and alkaline earth metal carbonates, or alkali and alkaline earth metal hydrogen carbonates, especially sodium hydroxide, potassium hydroxide or calcium hydroxide, are suitable for increasing the pH value.

[0103] ALKALINE TREATMENT

[0104] In step e) of the process according to the invention, the metal compound of the organic acid obtained in step B) is treated with a base. The organic acid dissolves as an anion, and the metal ions used precipitate as hydroxides. It is preferred to carry out step e) in multiple stages, in n consecutive steps, where n is a natural number in the range from 2 to 10, preferably 3 to 9, particularly preferably 4 to 8.For this purpose, in each of the n steps, a portion of the separated metal compound of the organic acid is treated with an aqueous base solution to precipitate metal hydroxide, wherein after each step, a separation of precipitated metal hydroxide is carried out by solid-liquid phase separation to leave a basic aqueous solution containing anions of the organic acid, wherein the aqueous base solution in the second to n-th step comprises the basic aqueous solution containing anions of the organic acid obtained in the respective preceding step (and optionally consists of this, i.e., comprises no further constituents). The crystallization according to step D), described in more detail below, is carried out with the basic aqueous solution containing anions of the organic acid obtained in the n-th step of C).

[0105] In step C), a pH in the range from 9.0 to 14, preferably 10 to 14, particularly preferably 11 to 13, is preferably maintained, if necessary with subsequent addition of base solution. Suitable aqueous base solutions include all bases familiar to the person skilled in the art, such as, in particular, aqueous solutions of alkali or alkaline earth metal hydroxides (in particular sodium hydroxide solution, potassium hydroxide solution, or calcium hydroxide solution (aqueous solution of calcium hydroxide)), alkali or alkaline earth metal bicarbonates, alkali or alkaline earth metal carbonates (in particular a sodium or potassium bicarbonate solution or a sodium or potassium carbonate solution), or a mixture of two or more of the aforementioned base solutions. Sodium hydroxide and potassium hydroxide solution are particularly preferred. When step C) is carried out in several stages, the stated pH values ​​are maintained in each of the n steps.

[0106] Like step B), step C) is preferably carried out at ambient temperature. A stirred tank reactor (or several stirred tank reactors, especially connected in series) is also suitable here.

[0107] CRYSTALLISATION

[0108] In step D), the anions of the organic acid contained in the basic aqueous solution obtained in step C) are crystallized. This is achieved by lowering the pH through the addition of an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid. The simplest way to carry out step D) is to introduce the basic aqueous solution obtained in step C) into the crystallization according to A)a), where appropriate acidic conditions already exist. However, it is of course also possible to carry out step D) separately from A)a), for example in a separate crystallizer. The same types as described above are suitable for this, optionally in a smaller version (due to the smaller quantities). The pH values ​​should then be adjusted as described above for A)a).

[0109] The attached figures are intended to further deepen the understanding of the invention.

[0110] FIG. 1 shows a preferred embodiment of the process according to the invention, in which step Aa) is a step following the actual preparation of the organic acid and in which step D) is carried out by recycling the aqueous solution containing anions of the organic acid from step C) to the crystallization according to step Aa).

[0111] The reference symbols have the following meaning:

[0112] FIG. 2 shows the preferred embodiment of step C) in n stages (here, for example, with n = 7). Here, the metal compound of the organic acid (9) obtained in step B) is divided into seven portions (9.1, 9.2, ... 9.7), the first of which (9.1) is treated with an aqueous base solution (10). After solid-liquid phase separation, a first portion (12.1) of precipitated metal hydroxide (12) is obtained and separated (the steps of base treatment and solid-liquid phase separation are not shown separately here for the sake of simplicity). The remaining basic aqueous liquid phase is added to the second portion (9.2) of the metal compound, and a solid-liquid phase separation is carried out again, in which a second portion (12.2) of precipitated metal hydroxide (12) is separated.After these steps are carried out with five additional portions of the metal compound of the organic acid, the basic aqueous solution containing anions of the organic acid (13) is finally obtained. The resulting portions (12.1, 12.2, ... 12.7) of precipitated metal hydroxide are preferably combined and then subjected to the metal salt treatment according to step B), as shown in FIG. 1.

[0113] The following examples were based on organic acids that were not specifically prepared for the examples but were obtained from commercial sources. The aqueous solution of the organic acid obtained in step A) of the process according to the invention was therefore prepared artificially, which does not, however, detract from the validity of the experiments. Precipitation of 2-aminobenzoic acid in aqueous solution by addition of

[0114] CuSO4, FeSO or MnSO4

[0115] Chemicals:

[0116] 2-Aminobenzoic acid (anthranilic acid, ortho-aminobenzoic acid; CAS No.: 118-92-3) was purchased from Sigma-Aldrich with a purity of > 98%. 2-Aminobenzoic acid is abbreviated as "oAB" in the following, regardless of its form (electroneutral or anion). CuSO4, FeSO4 • 7 H2O, and MnSO4 • H2O were purchased from Sigma-Aldrich with a purity of > 99%. Ultrapure water (purified using a Millipore laboratory water purification system) was used. NaOH (pellets) and HCl ( aq ) (37%) were used by Acros. a) Providing the aqueous solution of the organic acid

[0117] By dissolving oAB in water, an aqueous oAB solution (oAB concentration 5 g / L) was prepared, and in this way, an aqueous solution of the organic acid obtained in a crystallization according to step A)a) (= mother liquor of the crystallization) was artificially prepared. b) Treating the aqueous solution of the organic acid with a metal salt (step B))

[0118] The aqueous oAB solution and a metal salt (CuSO4, FeSO4, or MnSO4) were mixed at room temperature for at least 30 minutes (molar ratio of metal salt to oAB = 1:2). The pH was adjusted to approximately 3.5 with a 1M NaOH solution (corresponding to the isoelectric point of oAB). A 30-minute wait was then made to allow complete settling of the formed solid (metal compound of the organic acid). A sample of the aqueous supernatant was analyzed for oAB concentration using HPLC (high-performance liquid chromatography) (sample A). The solid (Cu(oAB)2, Fe(oAB)2, or Mn(oAB)2, respectively) was separated from the liquid phase by centrifugation. c) Base treatment of the separated metal compound of the organic acid (step C))

[0119] In the case of the experiments with Fe and Cu, the separated solid was resuspended in water, and the pH was adjusted to pH = 12.0 to 12.5 with a 1M NaOH solution. The oAB metal compound dissolved, and metal hydroxide (CufOH or Fe(OH)z) precipitated as a solid. After 30 minutes of mixing and 30 minutes of settling time, a sample of the aqueous supernatant was analyzed for oAB by HPLC (sample B). The solid (precipitated metal hydroxide) was then separated from the liquid phase (basic aqueous solution containing anions of the organic acid). In the case of iron(II) hydroxide, the base treatment was repeated several times (see FIG. 2):

[0120] By repeated addition of Fe(oAB)z (a total of seven additions), the oAB concentration in the liquid phase was further increased. In each of the seven steps, Fe(OH)z precipitated as a solid, which was separated by centrifugation after each addition. d) Recirculation of precipitated metal hydroxide to the step of treating the aqueous solution of the organic acid with a metal salt.

[0121] Aqueous oAB solution (5 g / L) was mixed with the metal hydroxide solid at pH 3.5 for 30 minutes. The metal hydroxide dissolved, and Cu(oAB)z and Fe(oAB)z precipitated. A sample of the liquid phase was analyzed for oAB content by HPLC after the solid had settled (Sample C). ie:

[0122] An Agilent 1260 Infinity II LC with a diode array detector was used for the quantification of oAB. A C18 Zorbax Eclispe (4.6 x 150 mm) with a guard column served as the stationary phase. Water with 0.1% H3PO4 (A) and methanol (B) were used as the mobile phase with the following linear gradient:

[0123] • Min 0: 95% A / 5% B

[0124] • Min 4: 95% A / 5% B

[0125] • Min 15: 2% A / 98% B • Min 16 2% A / 98% B

[0126] • Min 16.5: 95% A / 5% B

[0127] • Min 21: 95% A / 5% B

[0128] The flow rate was set to 0.5 mL / min. 5 pL of sample was injected at each time. The column temperature was 35 °C. oAB was detected at wavelengths of 254 nm and 330 nm and compared with a calibration curve.

[0129] Results:

[0130] The aqueous supernatant after precipitation of the metal compound of the organic acid (sample A from b)) showed an oAB concentration below the detection limit of 0.05 g / L. This demonstrates that the oAB was successfully precipitated almost quantitatively (> 99%) in the form of an oAB metal compound as a solid.

[0131] The aqueous supernatant after the base-induced precipitation of metal hydroxide (sample B from c)) showed an oAB concentration of 14 g / L. In the case of iron, the seven-step base treatment increased the oAB concentration in the liquid phase to 301 g / L.

[0132] It was shown that the solid (precipitated metal hydroxide, Cu(OH) or Fe(OH)2) can be used to recomplex oAB from aqueous solution (see d)). Analogous to sample A from b), an oAB concentration below the detection limit of 0.05 g / L was measured in sample C after addition of both FefOH and Cu(OH)2.

[0133] Overall, it can be stated that the oAB present in the original "aqueous solution of the organic acid" (5 g / L) was significantly concentrated by the inventive sequence of treatment with a metal salt and base treatment (to at least 14 g / L, or to 301 g / L when the base treatment was carried out in seven steps). The significantly more concentrated solutions (of the oAB anion) thus obtained can be subjected to a crystallization step without any problems for the purpose of isolating the oAB (step D).

[0134] Example 2: Precipitation of adipic acid in aqueous solution by addition of CuSO

[0135] Chemicals:

[0136] Adipic acid (CAS No. 124-04-9) was purchased at a purity of 98%. CuSC was purchased from Sigma-Aldrich at a purity of >99%. Ultrapure water (purified using a Millipore laboratory water purification system) was used. NaOH (pellets) and HCl(aq) (37%) were supplied by Acros. a) Providing the aqueous solution of the organic acid

[0137] An aqueous adipic acid solution (12 g / L) was prepared by dissolving adipic acid in water, and in this way, an aqueous solution of the organic acid (= mother liquor of the crystallization) obtained in a crystallization according to step A)a) was artificially prepared. b) Treating the aqueous solution of the organic acid with a metal salt (step B))

[0138] The aqueous adipic acid solution and a metal salt (CuSC) were mixed at room temperature for at least 30 minutes (molar ratio of metal salt to adipic acid = 1:1). The pH was adjusted to approximately 5.5 with a 1M NaOH solution. A further 30 minutes were allowed to allow complete settling of the formed solid (metal compound of the organic acid). A sample of the aqueous supernatant was analyzed for adipic acid concentration by HPLC (high-performance liquid chromatography) (Sample A).

[0139] The solid (copper adipate) was separated from the liquid phase by centrifugation. c) Base treatment of the separated metal compound of the organic acid (step C))

[0140] The separated solid was resuspended in water, and the pH was adjusted to 12 to 12.5 with a 1M NaOH solution. The adipic acid metal compound dissolves, and metal hydroxide (Cu(OH)z) precipitates. After 30 minutes of mixing and 30 minutes of settling time, a sample of the aqueous supernatant was analyzed for adipic acid content by HPLC (Sample B).

[0141] The solid (precipitated metal hydroxide) was subsequently separated from the liquid phase (basic aqueous solution containing anions of the organic acid). d) Use of precipitated metal hydroxide in the step of treating the aqueous solution of the organic acid with a metal salt. Aqueous adipic acid solution (12 g / L) was mixed with the metal hydroxide (approximately stoichiometric) at pH 4.5 for 30 minutes. The metal hydroxide dissolved, and metal adipate precipitated. A sample of the liquid phase was analyzed for adipic acid content by HPLC after the solid had settled (Sample C). ie:

[0142] The samples were prepared in a 0.1 M aqueous phosphate buffer containing 0.1 wt% pimelic acid.

[0143] An Agilent 1260 Infinity II LC with a diode array detector was used for the quantification of adipic acid. A C18 Zorbax Eclispe (4.6 x 150 mm) with a precolumn (Poroshell 120 EC-C18 (4.6 x 5 mm)) was used as the stationary phase. Water with 0.1% H3PO4 (A) and acetonitrile (B) were used as the mobile phase with the following linear gradient:

[0144] • Min 0: 95% A / 5% B

[0145] • Min 0.5: 95% A / 5% B

[0146] • Min 4.5: 75% A / 25% B

[0147] • Min 6.5 75% A / 25% B

[0148] • Min 6.6.5: 95% A / 5% B

[0149] • Min 9.5: 95% A / 5% B

[0150] The flow rate was set to 1.5 mL / min. 1 pL of sample was injected at a time. The column temperature was 35 °C. Adipic acid was detected at a wavelength of 208.8 nm and compared with a calibration curve.

[0151] The aqueous supernatant after precipitation of the metal compound of the organic acid (sample A from b)) had an adipic acid concentration of 0.99 g / L. This indicates the low solubility of the salt.

[0152] The supernatant after the precipitation of :id (sample B from cj) showed an adipic acid concentration of 24 g / L.

[0153] It was demonstrated that the solid (precipitated Cu(OH)z) can be used to reprecipitate adipic acid from aqueous solution (see d)). The adipic acid concentration in sample C from d) was 3 g / L. Based on the available data, it is expected that this value can be further reduced by performing d) at pH = 5.5. Overall, it can be stated that the adipic acid present in the original "aqueous solution of the organic acid" (12 g / L) was significantly concentrated (to at least 24 g / L) by the inventive sequence of treatment with a metal salt and base treatment. The significantly more concentrated (adipate) solutions thus obtained can be easily subjected to a crystallization step for the purpose of isolating the adipic acid (step D)).

[0154] Precipitation of 2-amino-5-methylbenzoic acid in aqueous solution by addition of CuSO4

[0155] Chemicals:

[0156] 2-Amino-5-methylbenzoic acid (CAS No. 2941-78-8) was purchased from Sigma-Aldrich with a purity of 97%. CuSC was purchased from Sigma-Aldrich with a purity of >99%. Ultrapure water (purified using a Millipore laboratory water purification system) was used. NaOH (pellets) and HCl ( aq ) (37%) were used by Acros. a) Providing the aqueous solution of the organic acid

[0157] By dissolving 2-amino-5-methylbenzoic acid in water, an aqueous 2-amino-5-methylbenzoic acid solution (1 g / L) was prepared, and in this way an aqueous solution of the organic acid obtained in a crystallization according to step A)a) (= mother liquor of the crystallization) was artificially prepared. b) Treating the aqueous solution of the organic acid with a metal salt (step B))

[0158] The aqueous 2-amino-5-methylbenzoic acid solution and a metal salt (CuSC) were mixed at room temperature for at least 30 minutes (molar ratio of metal salt to 2-amino-5-methylbenzoic acid = 1:1). The pH was adjusted to 3.5 with NaOH. The mixture was then left for 30 minutes to allow complete settling of the formed solid (metal compound of the organic acid). A sample of the aqueous supernatant was analyzed by HPLC (high-performance liquid chromatography) for the 2-amino-5-methylbenzoic acid concentration (Sample A).

[0159] The solid (copper 2-amino-5-methylbenzoate) was separated from the liquid phase.

[0160] A centrifuge was used for improved solid-liquid separation. c) Base treatment of the separated metal compound of the organic acid

[0161] (Step C))

[0162] The separated solid was resuspended in water, and the pH was adjusted to 12.5 with a 1M NaOH solution. The 2-amino-5-methylbenzoate metal compound dissolves, and metal hydroxide (Cu(OH)z) precipitates. After 30 minutes of mixing and 30 minutes of settling, a sample of the aqueous supernatant was analyzed by HPLC for 2-amino-5-methylbenzoate content (Sample B). ie:

[0163] An Agilent 1260 Infinity II LC with a diode array detector was used for the quantification of 2-amino-5-methylbenzoic acid. A C18 Zorbax Eclispe (4.6 x 150 mm) with a guard column served as the stationary phase. Water with 0.1% H3PO4 (A) and methanol (B) were used as the mobile phase with the following linear gradient:

[0164] • Min 0: 95% A / 5% B

[0165] • Min 4: 95% A / 5% B

[0166] • Min 15: 2% A / 98% B

[0167] • Min 16 2% A / 98% B

[0168] • Min 16.5: 95% A / 5% B

[0169] • Min 21: 95% A / 5% B

[0170] The flow rate was set to 0.5 mL / min. 5 pL of sample was injected at each time. The column temperature was 35 °C. 2-Amino-5-methylbenzoic acid was detected at wavelengths of 254 nm and 330 nm and compared with a calibration curve.

[0171] Results:

[0172] The aqueous supernatant after precipitation of the metal compound of the organic acid (sample A from b)) showed a 2-amino-5-methylbenzoic acid concentration of less than 0.01 g / L. This demonstrates the low solubility of the metal compound.

[0173] The aqueous supernatant after base treatment-induced precipitation of metal hydroxide (sample B from cj) showed a 2-amino-5-methylbenzoic acid concentration of 0.72 g / L.

[0174] Overall, it can be stated that the 2-amino-5-methylbenzoic acid (Ig / L) present in the original "aqueous solution of the organic acid" was successfully separated from the aqueous solution by the inventive sequence of treatment with a metal salt and base treatment, and then redissolved in water. It is expected that a significant increase in the concentration of 2-amino-5-methylbenzoic acid (analogous to Example 1) can be achieved. Concentration was not performed in this example. The thus obtained (2-amino-5-methylbenzoic acid) solutions can be subjected to a crystallization step without any problems for the purpose of isolating the 2-amino-5-methylbenzoic acid (Step D).

Claims

A process for obtaining an organic acid from an aqueous solution of the organic acid, wherein the organic acid is selected from acids of the formula (I), wherein R is CH3 or H, or an aliphatic saturated dicarboxylic acid of the formula (II), wherein n = 1 or 2, the process comprising the steps: A) Production of the organic acid by a biological process or a chemical reaction, wherein a) the organic acid is crystallized from an aqueous medium during or after the production, followed by 1) Separating the organic acid fractions precipitated during crystallization by a solid-liquid phase separation, leaving a first aqueous solution of the organic acid, and 2) optionally, depleting the proportion of organic acid dissolved in the first aqueous solution of organic acid by extracting organic acid with an organic extractant or by adsorbing organic acid on an adsorbent, followed by separating the organic extractant or adsorbent to obtain a second aqueous solution of organic acid; B) Treating the first aqueous solution of the organic acid or the second aqueous solution of the organic acid with a metal Isa Iz whose metal ions Mn 2+ , Fe 2+ and / or Cu 2+ comprising precipitating a metal compound of the organic acid, followed by separating the precipitated metal compound of the organic acid by a solid-liquid phase separation; C) base treatment of the separated metal compound of the organic acid with an aqueous base solution to precipitate metal hydroxide and to separate the precipitated metal hydroxide by a solid-liquid phase separation, leaving a basic aqueous solution containing anions of the organic acid; and D) Crystallizing organic acid from the basic aqueous solution obtained in C) containing anions of the organic acid by adding an inorganic acid.A process according to claim 1, wherein the base treatment in C) comprises n successive steps, where n is a natural number in the range from 2 to 10, wherein in each of the n steps a portion of the separated metal compound of the organic acid is treated with an aqueous base solution to precipitate metal hydroxide, wherein after each step a separation of precipitated metal hydroxide is carried out by solid-liquid phase separation to leave a basic aqueous solution containing anions of the organic acid, wherein the aqueous base solution in the second to n-th step comprises the basic aqueous solution containing anions of the organic acid obtained in the respectively preceding step; wherein the crystallization of the organic acid in D) is carried out with the basic aqueous solution containing anions of the organic acid obtained in the n-th step of C).A process according to claim 1 or 2, wherein the crystallization of organic acid in D) comprises recycling the basic aqueous solution containing anions of the organic acid obtained in C) to A)a); or. in which the crystallization of organic acid in D) is carried out separately from A)a).

4. Process according to one of claims 1 to 3, in which the metal hydroxide precipitated in C) is recycled to step B) and used there as a component of the metal iso-Ize.

5. A process according to any one of claims 1 to 4, wherein the organic acid is an aminobenzoic acid of formula (I).

6. A process according to claim 5, wherein the aminobenzoic acid of formula (I) is 2-aminobenzoic acid or 2-amino-5-methylbenzoic acid.

7. Process according to claim 5 or 6, wherein in A)a) a pH value in the range of 3.0 to 4.7 is adjusted by adding an inorganic acid and in B) a pH value in the same range is maintained.

8. A process according to any one of claims 5 to 7, wherein A) comprises a biological process which comprises the fermentation of a raw material containing a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms.

9. A process according to any one of claims 5 to 7, wherein A) comprises a chemical reaction.

10. A process according to claim 9, wherein A) comprises reacting optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalide in a basic medium, followed by the addition of an inorganic acid to carry out A)a).

11. A process according to any one of claims 1 to 4, wherein the organic acid is an aliphatic saturated dicarboxylic acid of formula (II).

12. The process according to claim 11, wherein the aliphatic saturated dicarboxylic acid of formula (II) is 1,6-hexane dicarboxylic acid.

13. The process according to claim 11 or 12, wherein in A)a) a pH value in the range from 0 to 4.0 is adjusted by adding an inorganic acid and in B) a pH value in the range from > 4.0 to 7.0 is adjusted by adding a base.

14. A method according to any one of claims 11 to 13, wherein A) comprises a biological process.

15. The method according to claim 14, wherein the biological process comprises the fermentation of a raw material containing a fermentable carbon-containing compound in the presence of microorganisms. Process according to one of claims 11 to 13, in which A) comprises a chemical reaction. Process according to claim 16, in which A) comprises the hydrogenation of an aliphatic unsaturated dicarboxylic acid corresponding to the aliphatic saturated dicarboxylic acid of the formula (II); or in which the aliphatic saturated dicarboxylic acid of the formula (II) is 1,6-hexanedicarboxylic acid, where A) comprises the oxidation of cyclohexane with oxygen or oxygen-containing gas mixtures to cyclohexanol and cyclohexanone and their subsequent oxidation with nitric acid. Process according to claim 14 or 16, in which A) comprises a cleavage of a polyester. Process according to one of the preceding claims, in which the metal ions of the metal ions used in B) are Fe 2+ and / or Cu 2+comprise. Process according to one of the preceding claims, in which in C) a pH in the range of 9.0 to 14 is set. Process according to one of the preceding claims, in which in B) the metal ions are added in a maximum stoichiometric amount, based on the amount of organic acid. Process according to one of the preceding claims, in which the metal salt comprises a sulfate, chloride and / or hydroxide. Process according to one of the preceding claims, in which in B) after the precipitated metal compound of the organic acid has been separated off by solid-liquid phase separation, an aqueous phase remains which is adjusted to a pH in the range of 8.0 to 14 by adding a base, whereby metal hydroxides precipitate, which are separated off by a further solid-liquid phase separation and subsequently used in B) as a component of the metal salt.

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