Process for obtaining organic acids from aqueous mother liquor

Abstract

The invention relates to a process for obtaining an aminobenzoic acid or an aliphatic saturated C4-6-dicarboxylic acid from an aqueous solution, comprising: A) preparing said organic acid, in which a) the organic acid is crystallized from an aqueous medium, followed by the separation of the precipitated organic acid fraction by solid-liquid phase separation, leaving a first aqueous solution of the organic acid; b) treating the aqueous solution of the organic acid with a Mn < 2 + >, Fe < 2 + > and / or Cu < 2 + > metal salt to precipitate a metal compound of the organic acid, and then separating the precipitated metal compound through solid-liquid phase separation; c) subjecting the separated metal compound to alkali treatment, precipitating metal hydroxide, and separating the precipitated metal hydroxide by solid-liquid phase separation, leaving an aqueous alkaline solution containing anions of the organic acid; and D) crystallizing the organic acid from the alkaline aqueous solution obtained in C) by adding an inorganic acid.

Description

[0001] The invention on which this application is based was financially supported by the German Federal Ministry of Food and Agriculture as part of the project “Biobasierte Herstellung von Intermediaten für Polyurethane-Phase II (Bio4PURPro)” [“Biogenic Preparation of Polyurethane Intermediates – Phase II (Bio4PURPro)”] (grant code 22019918).

[0002] The present invention relates to a method for obtaining an organic acid from an aqueous solution of an organic acid, wherein the organic acid is selected from aminobenzoic acid optionally substituted with methyl or an aliphatic saturated C4 to C6 dicarboxylic acid, the method comprising the following steps: A) preparing the organic acid by a biological method or a chemical reaction, wherein α) during or after the preparation, the organic acid is crystallized from an aqueous medium, followed by 1) removing the portion of the organic acid that has precipitated in the crystallization by solid-liquid phase separation, leaving a first aqueous solution of the organic acid, and optionally 2) reducing the portion of the organic acid dissolved in the first aqueous solution of the organic acid by extracting the organic acid with an organic extractant or by adsorbing the organic acid on an adsorbent, followed by removing the organic extractant or adsorbent to obtain a second aqueous solution of the organic acid; B) treating the first aqueous solution of the organic acid or the second aqueous solution of the organic acid with a metal salt to precipitate a metal compound of the organic acid, the metal ion of the metal salt comprising Mn 2+ , Fe 2+ and / or Cu 2+ , and then removing the precipitated metal compound of the organic acid by solid-liquid phase separation; C) treating the removed metal compound of the organic acid with an aqueous alkaline solution to precipitate a metal hydroxide, and removing the precipitated metal hydroxide by solid-liquid phase separation, leaving an alkaline aqueous solution containing anions of the organic acid; and D) crystallizing the organic acid from the alkaline aqueous solution containing anions of the organic acid obtained in C) by adding an inorganic acid.

[0003] A recurring feature in the preparation of organic acids is the step of crystallization from an aqueous medium, which serves to isolate and / or purify the organic acid, in some cases by crystallization from a solution containing the anion of the organic acid by lowering the pH (known as reactive crystallization). The crystallized organic acid is removed, leaving behind an aqueous solution of the organic acid (= mother liquor of crystallization), which still contains a residual content of organic acid corresponding to the solubility equilibrium, most likely in the range of a few grams per liter.

[0004] One example is the preparation of anthranilic acid. Anthranilic acid can be used, for example, to prepare dyes, flavor enhancers or drugs. The preparation of heterocyclic compounds from anthranilic acid and its derivatives is the subject of the paper Synthesis of Heterocycles from Anthranilic Acid and its Derivatives by Per Wiklund (Karolinska University Press 2004, ISBN 00006664).

[0005] 91-7349-913-7). Donald L. Dinsel and Thomas R. Sweet described the use of anthranilic acid as an extractant for iron salts 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. Alexander A.

[0006] Kamnev and Kuzmann Spectroscopic Evidence for the Reduction of Iron(III) by Anthranilic Acid in Aqueous Solution, published in Polyhedron 1997, 16, 3353-3356, explores the issue of the reduction of iron(III) by anthranilic acid. The redox chemistry of anthranilic acid and 3-hydroxyanthranilic acid and iron complexation are the subject of the paper 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).

[0007] Another example of the use of anthranilic acid is its use in the preparation of aniline by decarboxylation (described, for example, in WO 2015 / 124687 A1). Aniline is particularly important as an intermediate in the preparation of isocyanates. Anthranilic acid can be obtained, for example, by fermentation (see, for example, the already mentioned WO 2015 / 124687 A1) or chemical methods (for example, by Hofmann rearrangement of phthalimide; see, for example, WO 2007 / 088346 A1). Regardless of the exact preparation method, a crystallization step of the above type is regularly performed. By way of example, the separation of anthranilic acid by reactive crystallization from a fermentation broth containing an anthranilic acid anion is mentioned (again, see WO 2015 / 124687 A1). Anthranilic acid is an example of aminobenzoic acid. Other important representatives of this class of compounds are anthranilic acid derivatives in which the hydrogen atoms on the benzene ring are replaced by methyl groups. JS Decker and H. Frye in the article Metal Ion Complexes of Aromatic Amino Acids–I. Ring Substituted Amino Benzoic Acids (Z.

[0008] The complex-forming properties of aminobenzoic acid having substituents on the benzene ring were investigated in Naturforschg. 1966, 21b, 522-526.

[0009] Another example is adipic acid. Adipic acid is an intermediate for preparing nylon. Adipic acid is also used as a precursor for synthesizing polyester polyols for polyurethane products. Adipic acid can also be obtained by fermentation (e.g., see Peter CKLau (ed.), Quality Living Through Chemurgy and Green Chemistry, Springer-Verlag GmbHGermany 2016, Chapter 3.3, pages 47 to 54, and K.Raj, S.Partow et al., Biocatalytic production of adipic acid from glucose using engineered Saccharomycescerevisiae, Metabolic Engineering Communications, 2018, 6, 28-32), or chemical methods (e.g., by hydrogenating muconic acid; see, e.g., WO 2015 / 086827 A1, or by oxidation of cyclohexane; see, e.g., A.Castellan et al., Industrial production and use of adipic acid, Catal.Today 1991, 9, 237-254). Here too, a crystallization step of the type described above occurs regularly. Reference is made, for example, to the purification of the product of the hydrogenation of muconic acid by crystallization (cf. WO 2015 / 086827 A1). Adipic acid is an example of an aliphatic saturated dicarboxylic acid. Another important representative of this class of compounds is succinic acid.

[0010] Therefore, it is important to reduce the residual content of organic acids in the mother liquor by appropriate methods to avoid yield loss and minimize wastewater pollution.

[0011] EP 0 502 384 A2 describes a process for recovering adipic acid from nitric acid-containing aqueous mother liquors obtained in the industrial preparation of adipic acid by selective crystallization of dissolved adipic acid, wherein the mother liquor is mixed in a temperature range from 30 to 60° C. with an aqueous adipic acid solution having an adipic acid content of 0.5% to 6% by weight, in an amount such that the nitric acid content in the mixture is reduced to 35% to 50% by weight, the mixture is then cooled by at least 5° C. within 0.5 to 5 hours, the adipic acid crystallized therefrom is separated by filtration and the filtrate obtained is sent for work-up by distillation of glutaric acid.

[0012] WO 2015 / 085198 A1 describes a method for preparing succinic acid and succinates from succinate in a fermentation broth. In the first stage, succinic acid is prepared by biofermentation using renewable carbon resources. Succinate undergoes a double displacement reaction with a strong acid during the fermentation process, which results in the release of succinic acid. Succinic acid is obtained by fractional crystallization, combined with SMB (simulated moving bed) chromatography, to prepare succinic acid and succinates.

[0013] International application WO 2015 / 124687 A1, which has been mentioned several times, discloses a preferred embodiment in this regard, in which the mother liquor obtained in the crystallization is post-treated to further obtain aminobenzoic acid. This is accomplished by a sequence consisting of an adsorption step and a desorption step. The resulting desorbate rich in aminobenzoic acid is recycled to the crystallization step. In this way, yield losses are reduced. Adsorption is carried out on zeolite or activated carbon, and desorption is carried out with water in a pH range of 5 to 10, alternatively, with an organic solvent, in particular 1-dodecanol. A variant of this type of post-treatment carried out in a sequence of adsorption steps and desorption steps is described in international application WO 2018 / 114841A1. The method disclosed therein is particularly characterized in that the desorption is carried out in an acidic environment (pH-0.8 to 3.0).

[0014] International patent application WO 2007 / 088346 A1, which has likewise been mentioned, describes a method for recovering anthranilic acid from the mother liquor of crystallization (for isolating anthranilic acid obtained by Hofmann rearrangement). The sodium carbonate-containing product of the Hofmann rearrangement is adjusted to a pH of 4.2 with sulfuric acid (a), and the precipitated anthranilic acid is filtered off (b). The remaining mother liquor is extracted with an organic solvent at a pH of 4.2; suitable organic solvents disclosed are acetates (especially ethyl acetate or butyl acetate), ketones (especially 2-butanone) and aromatic hydrocarbons (especially toluene). The organic extract obtained after phase separation (c) is subsequently stripped with sodium hydroxide solution (d), and the anthranilic acid is transferred in the form of an anthranilate anion into the aqueous phase obtained after phase separation (e). The aqueous phase enriched in anthranilic acid from the stripping is combined with the product of the Hofmann rearrangement and crystallized together. The aqueous phase poor in anthranilic acid obtained by extraction is adjusted to pH 1.5 with sulfuric acid, an organic solvent (f) is added, and the mixture is separated into an aqueous phase and an organic phase (g). In this way, organic impurities are transferred to the organic phase. The organic phase is combined with the organic phase from the stripping and distilled. The distillate can be recycled into the method as a solvent. The distillation residue is incinerated. The aqueous phase from (g) is purified by the Fenton reaction and discharged into waste water. A particular disadvantage of this method is the relatively high water solubility of acetate and ketone. Acetate and ketone can effectively dissolve anthranilic acid, but they enter the aqueous phase in a non-negligible proportion due to their relatively high water solubility. This first leads to a loss in yield and secondly increases the complexity of wastewater purification. Toluene, which is also disclosed as a suitable solvent in WO 2007 / 088346 A1, does not have the disadvantages described, but it dissolves anthranilic acid quite inefficiently, which makes it difficult to develop a practical method using toluene as an extractant on an industrial scale.

[0015] CN 102 190 590A describes a method for removing anthranilic acid from wastewater produced from methyl anthranilate. In the method described, wastewater from the production of methyl anthranilate is mixed with acidic wastewater (especially sulfuric acid containing cupric chloride) until a pH of 3.5 to 4.5 is reached and copper anthranilate is precipitated. The precipitated copper anthranilate is added to a stirred tank together with calcium oxide and mixed with an alkaline solution (pH 11 to 13). The mixture is heated to 90 to 110° C. and kept at boiling for 30 to 150 minutes. After filtration, the filtrate containing sodium anthranilate is decolorized and adjusted to a pH of 3.5 to 4.0 with hydrochloric acid. The precipitated anthranilic acid is washed and dried.

[0016] The prior art methods described all have disadvantages, and therefore further improvements are needed in the field of recovering organic acids from their aqueous solutions (mother liquors). In particular, a desired method would be one in which, firstly, the organic acid can be selectively and almost completely removed from the aqueous mother liquor without transferring other components, such as organic solvents, to the aqueous phase. Secondly, a desired method would be one in which the removed organic acid can be transferred back to the aqueous phase at high concentrations and yields.

[0017] In view of this requirement, the present invention provides a method for obtaining an organic acid from an organic acid aqueous solution, wherein the organic acid is selected from

[0018] (i) aminobenzoic acid of the formula

[0019] Where R is CH3 or H,

[0020] or

[0021] (ii) an aliphatic saturated dicarboxylic acid of the formula

[0022] wherein n=1 or—preferably—2,

[0023] The method comprises the following steps:

[0024] A) preparing organic acids by biological methods (preferably fermentation) or chemical reactions (i.e. non-biological methods), wherein

[0025] a) crystallizing the organic acid from an aqueous medium during or after its preparation (optionally protonating the organic acid anion in order to isolate it, or purifying the isolated organic acid by recrystallization),

[0026] Afterwards

[0027] 1) removing the portion of the organic acid that has precipitated during crystallization (i.e., during the crystallization in step α)) by solid-liquid phase separation, leaving a first aqueous solution of the organic acid, and

[0028] 2) Optionally

[0029] by extracting the organic acid with an organic extractant, or

[0030] By adsorbing organic acids on adsorbents,

[0031] reducing the amount of organic acid dissolved in the first aqueous solution of organic acid,

[0032] Then, the organic extractant or adsorbent (enriched in organic acid) is removed to obtain a second aqueous solution of organic acid (depleted in organic acid);

[0033] B) treating the first aqueous solution of the organic acid or the second aqueous solution of the organic acid with a metal salt, the metal ions of which include Mn2+, Fe2+ and / or Cu2+ (and in particular selected from Mn2+, Fe2+ and Cu2+) to precipitate a metal compound (slightly soluble complex or low solubility salt) of the organic acid,

[0034] The precipitated metal compound of the organic acid is then removed by solid-liquid phase separation;

[0035] C) treating the removed metal compound of the organic acid with an aqueous alkaline solution to precipitate a metal hydroxide and removing the precipitated metal hydroxide by solid-liquid phase separation, leaving an alkaline aqueous solution containing the anions of the organic acid, wherein the alkaline 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., more preferably 20° C. to 50° C., in particular at ambient temperature;

[0036] as well as

[0037] D) Crystallizing the organic acid from the alkaline aqueous solution containing the anion of the organic acid obtained in C) by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.

[0038] Completely unexpectedly, it has been found that combining the treatment with a metal salt of the specified type (step B)) and the base treatment (step C)) can provide an aqueous solution of the organic acid (anionic form) whose concentration is much higher than the aqueous solution of the organic acid produced by A)α) and can therefore be sent to reactive crystallization (step D)) for further separation of the organic acid.

[0039] In the context of the present invention, all pH values ​​are related to the temperature at which the corresponding step (eg step (D)) is carried out and can be simply measured using a glass electrode.

[0040] In the context of the present invention, a biological process is the fermentation or enzymatic conversion of organic matter.

[0041] Thus, in the context of the present invention, the conversion of organic matter is referred to as chemical (chemical conversion or chemical process) if it is not carried out using fermentation or enzymatic methods (ie purely thermal methods or using non-biological catalysts).

[0042] The accompanying drawings show:

[0043] Figure 1 a schematic diagram of one embodiment of the method of the present invention; and

[0044] Figure 2 Schematic diagram of the multi-stage operation of step C).

[0045] First, various possible embodiments of the present invention are described. Overview as follows:

[0046] In a first embodiment of the present invention (which can be combined with all other embodiments), the alkali treatment in C) comprises n steps which are carried out in succession, wherein n is a natural number from 2 to 10, preferably from 3 to 9, more preferably from 4 to 8, wherein

[0047] In each of the n steps, a portion of the removed metal compound of the organic acid is treated with an aqueous alkaline solution to precipitate a metal hydroxide, wherein the precipitated metal hydroxide is removed by solid-liquid phase separation after each step to leave an alkaline aqueous solution containing anions of the organic acid, wherein the aqueous alkaline solution in the second step to the nth step comprises (and optionally consists of, i.e. does not contain any other components) the alkaline aqueous solution containing anions of the organic acid obtained in the respective previous step;

[0048] The crystallization of the organic acid in D) is carried out using the alkaline aqueous solution containing the anion of the organic acid obtained in the nth step of C).

[0049] In a second embodiment of the invention (which can be combined with all other embodiments, provided that these embodiments do not envisage separate performance of the crystallization of the organic acid in D) and in A)α), the crystallization of the organic acid in D) comprises recycling the alkaline aqueous solution containing the anion of the organic acid obtained in C) (i.e. in the case of an n-stage alkaline treatment, in the nth step of C)) to A)α).

[0050] In a third embodiment of the invention (which can be combined with all other embodiments, provided that these do not envisage separate crystallizations of the organic acid in D) and in A)α), the crystallization of the organic acid in D) is carried out separately from A)α).

[0051] In a fourth embodiment of the invention, which can be combined with all other embodiments, the metal hydroxide precipitated in C) is recycled into step B), where it is used as a component of the metal salt.

[0052] In a fifth embodiment of the invention (which can be combined with all other embodiments, provided that these embodiments do not exclusively relate to aliphatic saturated dicarboxylic acids of formula (II)), the organic acid is an aminobenzoic acid of formula (I), in particular 2-aminobenzoic acid (o-aminobenzoic acid) or 2-amino-5-methylbenzoic acid, preferably 2-aminobenzoic acid.

[0053] In a sixth embodiment of the invention, which is a special form of the fifth embodiment, the pH is set in A) α) to 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6 by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, and the pH is kept in the same range in B) (optionally by adding an acid or a base if the pH should increase or decrease too much due to the addition of a metal salt).

[0054] In a seventh embodiment of the invention, which is a special form of the fifth and sixth embodiments, step A) comprises a biological process, ie fermentation of the feedstock containing fermentable carbon-containing compounds and nitrogen-containing compounds in the presence of microorganisms.

[0055] In an eighth embodiment of the present invention, which is a specific form of the seventh embodiment,

[0056] (I) A) α) is carried out by fermenting at a pH of 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6, so that the aminobenzoic acid of formula (I) has crystallized during the fermentation;

[0057] or

[0058] (II) The fermentation is carried out at a pH of >4.7 to 11 (especially 6.0 to 11), preferably 4.8 to 9.0 (especially 6.0 to 9.0), more preferably 5.0 to 8.0 (especially 6.0 to 8.0), wherein A) α) is carried out by setting the pH after fermentation to 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6.

[0059] In a ninth embodiment of the invention, which is a special form of the seventh and eighth embodiments, the microorganism is selected from Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0060] In a tenth embodiment of the invention, which is a special form of the fifth and sixth embodiments, A) comprises a chemical conversion (ie a non-biological process).

[0061] In an eleventh embodiment of the invention, which is a special form of the tenth embodiment, A) comprises converting the optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalite, in particular sodium hypochlorite, in an alkaline medium and then adding an inorganic acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, to carry out A)α).

[0062] In a twelfth embodiment of the invention (which can be combined with all other embodiments, provided that these embodiments do not exclusively concern aminobenzoic acid of formula (I)), the organic acid is an aliphatic saturated dicarboxylic acid of formula (II), in particular hexane-1,6-dicarboxylic acid (adipic acid).

[0063] In a thirteenth embodiment of the invention, which is a special form of the twelfth embodiment, the pH is set in A) α) to 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5 by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, and the pH is set in B) to >4.0 to 7.0, preferably 4.7 to 5.8, more preferably 5.3 to 5.7 by adding a base.

[0064] In a fourteenth embodiment of the invention, which is a special form of the twelfth and thirteenth embodiments, step A) comprises a biological process.

[0065] In a fifteenth embodiment of the invention, which is a specific form of the fourteenth embodiment, the biological process comprises fermenting a feedstock containing a fermentable carbon-containing compound in the presence of a microorganism.

[0066] In a sixteenth embodiment of the present invention, which is a specific form of the fifteenth embodiment,

[0067] (I) A) α) is carried out by fermenting at a pH of 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5, so that the aliphatic saturated dicarboxylic acid of formula (I) has crystallized during the fermentation;

[0068] or

[0069] (II) The fermentation is carried out at a pH of >4.0 to 11 (especially 6.0 to 11), preferably 5.0 to 9.0 (especially 6.0 to 9.0), more preferably 5.0 to 8.0 (especially 6.0 to 8.0), wherein A) α) is carried out by setting the pH after fermentation to 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5.

[0070] In the seventeenth embodiment of the present invention, which is a specific form of the fifteenth and sixteenth embodiments, the microorganism is selected from Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Bacillus coagulans, Ashby's bacillus, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0071] In an eighteenth embodiment of the invention, which is a special form of the twelfth and thirteenth embodiments, A) comprises a chemical conversion (ie, a non-biological process).

[0072] In a nineteenth embodiment of the invention, which is a special form of the eighteenth embodiment, in particular in the case where n=2 (i.e. the organic acid is therefore in particular adipic acid), A) comprises the hydrogenation of an aliphatic unsaturated dicarboxylic acid corresponding to the aliphatic saturated dicarboxylic acid of formula (II), in particular muconic acid (and A)α) is carried out in particular for the purification of the product obtained in the hydrogenation).

[0073] In the twentieth embodiment of the present invention, which is another specific form of the eighteenth embodiment, the aliphatic saturated dicarboxylic acid of formula (II) is hexane-1,6-dicarboxylic acid (adipic acid), wherein A) comprises oxidizing cyclohexane using oxygen or an oxygen-containing gas mixture (especially air) to produce cyclohexanol and cyclohexanone, and subsequently oxidizing with nitric acid.

[0074] In a twenty-first embodiment of the invention, which is a special form of the fourteenth and eighteenth embodiments, A) comprises the (enzymatic or chemical) cleavage of the polyester.

[0075] In the twenty-second embodiment of the invention (which can be combined with all other embodiments, in particular to the extent that these embodiments are related to obtaining aliphatic saturated dicarboxylic acids of formula (II) (preferably hexane-1,6-dicarboxylic acid, adipic acid)), the metal ions of the metal salt used in B) include Fe2+ and / or Cu2+, in particular selected from Fe2+ and Cu2+ (wherein, in particular in the case of obtaining aliphatic dicarboxylic acids of formula (II), Cu2+ is preferred).

[0076] In a twenty-third embodiment of the present invention (which can be combined with all other embodiments), in C) (in the case of an n-stage alkali treatment, in each of the n steps of alkali treatment) the pH is set to 9.0 to 14, preferably 10 to 14, more preferably 11 to 13.

[0077] In a twenty-fourth embodiment of the invention, which can be combined with all other embodiments, the metal ions are added in B) in an amount not exceeding a stoichiometric amount, based on the amount of organic acid.

[0078] In a twenty-fifth embodiment of the invention, which can be combined with all other embodiments, the metal salt comprises a sulfate, a chloride and / or a hydroxide.

[0079] In a twenty-sixth embodiment of the invention, which can be combined with all other embodiments, the solid-liquid phase separation in A), B) and / or C) is performed by filtration, centrifugation or sedimentation, optionally assisted by previous flocculation.

[0080] In a twenty-seventh embodiment of the present invention (which can be combined with all other embodiments), step 2) is carried out in A), wherein

[0081] The organic extractant is selected from: (i) alcohols, in particular alkanols, containing 4 to 12 carbon atoms (in particular 1-decanol and / or 1-dodecanol), preferably 8 to 12 carbon atoms, more preferably 9 to 11 carbon atoms; (ii) ketones (in particular methyl isobutyl 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); or (vi) mixtures of two or more of the above extractants,

[0082] and

[0083] The adsorbent is selected from: (i) activated carbon; (ii) polymer-based adsorbent; (iii) graphite;

[0084] (iv) polar adsorbents, such as, in particular, silica gel, limestone or aluminium silicate; or (v) mixtures of two or more of the abovementioned adsorbents.

[0085] In a twenty-eighth embodiment of the invention (which can be combined with all other embodiments), the precipitated metal compound of the organic acid is removed by solid-liquid phase separation in B), leaving an aqueous phase, which is adjusted to a pH of 8.0 to 14, preferably 10 to 13, by adding a base, and a metal hydroxide is precipitated, which is removed by further solid-liquid phase separation and then used as a component of the metal salt in B).

[0086] In a twenty-ninth embodiment of the invention, which is a special form of the twenty-eighth embodiment, the base used to set the pH comprises an alkali metal or alkaline earth metal hydroxide, an alkali metal or alkaline earth metal carbonate, an alkali metal or alkaline earth metal bicarbonate, in particular sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution.

[0087] Below More detailsThe above briefly summarizes the embodiments and other possible forms of the invention. All the above embodiments and other forms of the invention described below can be combined with each other and collectively as desired, unless otherwise obvious to the skilled person from the context or explicitly stated otherwise.

[0088] Preparation of organic acids

[0089] Step (A) of the process according to the invention (preparation of the organic acid) depends, of course, on the type of acid desired. During or after the preparation, a crystallization step A) α) is carried out.

[0090] Aminobenzoic acid of formula (I)

[0091] If the goal is to obtain Aminobenzoic acid of formula (I) , wherein 2-aminobenzoic acid (= anthranilic acid) is preferred, it has been found useful to set the pH in step A) α) to 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6 by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid. The specific manner in which the crystallization is carried out in step A) α) in turn depends on the manner in which step A) is carried out overall.

[0092] Biological methods

[0093] In one embodiment, step A) comprises a fermentation step. This is carried out by converting fermentable carbon-containing compounds and nitrogen-containing compounds into the desired aminobenzoic acid or its anion in the presence of a microorganism. Such fermentation methods have been described; see the literature cited below. Microorganisms suitable for fermenting the aminobenzoic acid of formula (I) include in particular: Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbyella cotton, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0094] The fermentation in step A) is preferably carried out in such a way that the pH of the fermentation broth obtained is from 3.0 to 11, preferably from 4.7 to 11 (= case (II); see below). If necessary, the pH can be controlled by adding aqueous or gaseous ammonia, aqueous potassium hydroxide or sodium hydroxide solution (when the pH value is too low), or by adding mineral acids, in particular hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid (when the pH value is too high). Different pH ranges within the stated pH range of 3.0 to 11 may be particularly ideal for different microorganisms. The pH of the fermentation also influences step A) α). This is because, depending on the specific pH in the range of 3.0 to 11, the aminobenzoic acid in the fermentation broth is present in the well-water-soluble anionic form (H2NC6H3(R)COO-) or in the relatively sparingly water-soluble electrically neutral form (H2NC6H3(R)COOH or H3N+ C6H3(R)COO-) exists.

[0095] In the pH range of 4.7 or less, preferably 3.7 or less, particularly preferably 3.6 or less, aminobenzoic acid is mainly to completely in an electrically neutral form and thus crystallizes spontaneously during fermentation, so that a separate crystallization step is not necessary and the crystallized aminobenzoic acid can be separated directly from the fermentation broth (case (I)). Case (I) is particularly preferred, for example, when the step produces benefits in the fermentation, for example, in particular, a reduction in toxicity to microorganisms in the fermentation broth due to precipitation of aminobenzoic acid.

[0096] In case (I), fermentation is preferably carried out at a pH of 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6. Step A) α) is then part of the fermentation. In this case, eukaryotic organisms, in particular yeast, are preferably used as microorganisms. In this regard, particular reference is made to the international patent application WO 2017 / 102853A1. It is preferred to use yeast cells that are capable of converting fermentable carbon-containing compounds into aminobenzoic acid in the presence of a suitable nitrogen source, and the aminobenzoic acid thus formed is not immediately consumed in the intracellular biochemical process, with the result that aminobenzoic acid accumulates in the cell and is ultimately transferred to the fermentation broth. Eukaryotic organisms such as Ashbya cotton, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Baeyer's yeast or Saccharomyces cerevisiae are preferably cultured in an acidic medium and are therefore suitable for the case (I) described herein. In case (I), step A) α) is part of the fermentation. After the fermentation is finished, the precipitated aminobenzoic acid is separated by (first) solid-liquid phase separation and obtained in the form of a mixture with the microorganism. The step of separating the two can be such that, for example, the aminobenzoic acid is selectively dissolved at the maximum concentration (for example, with an aqueous alkaline solution, an aqueous acid solution or an organic solvent) and then separated from the solution if necessary (by another crystallization or concentration). The step can also be such that a first part of the solid mixture, in particular 50%, is dissolved in a minimum amount of aqueous alkaline solution (for example, to obtain a supernatant with a pH of 7.0), and a second part of the solid mixture, in particular 50%, is dissolved in a minimum amount of aqueous acid solution (for example, to obtain a supernatant with a pH of 1.0), and, after the undissolved components are separated, the relatively high concentration remaining solutions are combined so that the pH in the resulting mixture is set to be at or close to the isoelectric point and the aminobenzoic acid is precipitated again. After separation of the precipitated aminobenzoic acid, the volume of the mother liquor remaining in the (second) solid-liquid phase separation is significantly smaller than the volume of the mother liquor obtained after the first solid-liquid phase separation, and since it contains only a relatively small amount of aminobenzoic acid, it can be processed or advantageously combined with the mother liquor of the first solid-liquid phase separation.

[0097] In this embodiment, the liquid phase obtained in the first solid-liquid phase separation or the combined liquid phases of the first and second solid-liquid phase separations are both "aqueous solutions of organic acids". In the context of the present invention, solid-liquid phase separation is always (regardless of the process step) preferably carried out in the form of filtration, centrifugation or sedimentation, optionally assisted by a previous flocculation.

[0098] At pH values, in particular >4.7, preferably 6.0 or higher, more preferably 8.0 or higher, aminobenzoic acid is mainly to completely in anionic form and is therefore subjected to a separate crystallization step (case (II), which is preferred). In case (II), the fermentation is preferably carried out at a pH of >4.7 to 11 (in particular 6.0 to 11), preferably 4.8 to 9.0 (in particular 6.0 to 9.0), more preferably 5.0 to 8.0 (in particular 6.0 to 8.0). In this case, prokaryotes, in particular bacteria, are preferably used as microorganisms. In this respect, reference is made here in particular to patent application WO

[0099] 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 anions of aminobenzoic acid as direct fermentation process products, i.e. are suitable for case (II). In particular, the bacteria used are those which are capable of converting fermentable carbon-containing compounds into aminobenzoic acid in the presence of a suitable nitrogen source, without the aminobenzoic acid thus formed being immediately consumed in intracellular biochemical processes. Consumption, as a result, aminobenzoic acid is enriched in the cell and finally transferred to the fermentation liquid. Microorganisms such as Corynebacterium glutamicum, Pseudomonas putida or Escherichia coli are preferably cultivated under "neutral to alkaline pH value", and are therefore applicable to situation (II) described herein. Because aminobenzoic acid is obtained as anion in this case, therefore by adding mineral acid--particularly hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid--the pH is set to 3.0 to 4.7, preferably 3.2 to 3.7, more preferably 3.4 to 3.6, in the downstream step of fermentation, its crystallization. In this case, step A) α) is therefore the step after the fermentation.

[0100] Chemical methods

[0101] In another embodiment, step A) comprises a chemical conversion (i.e. a non-biological process). The reaction of optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalite (especially sodium hypochlorite) in an alkaline medium should be mentioned in particular here. Such processes are known in the literature and are described, for example, in WO 2007 / 088346 A1. In this case, the aminobenzoic acid of the desired formula (I) is obtained in anionic form and crystallized by adding a mineral acid (especially hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid) (= step A) α)).

[0102] If the crystallization step A) α) is carried out separately from the actual preparation process, such as in the case of fermentative preparation (II) or in the case of crystallization for purifying crude products, in addition to the reactor for organic acid preparation, an additional industrial device suitable for crystallization is used, which is called a crystallizer in the professional field. Suitable crystallizers are, for example, stirred tanks or forced circulation crystallizers, such as those of the "Oslo type". In the crystallizer, if necessary, the pH is adjusted to a suitable value, in the case of aminobenzoic acid of formula (I), to a value of 3.0 to 4.7, preferably 3.2 to 3.7, most preferably 3.4 to 3.6. This is preferably achieved by adding an acid selected from hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid. The adjustment of the pH leads to the formation of aminobenzoic acid anions (H2NC6H3(R)COO - ) is mainly or completely converted to the neutral form ((H2NC6H3(R)COOH or H3N + C6H3(R)COO - ) and crystallizes. This type of crystallization is also called reactive crystallization. The crystallized aminobenzoic acid is separated by solid-liquid phase separation, leaving behind an "aqueous solution of organic acid".

[0103] Aliphatic saturated dicarboxylic acid of formula (II)

[0104] If the goal is to obtain Aliphatic saturated dicarboxylic acid of formula (II) , wherein hexane-1,6-dicarboxylic acid (=adipic acid) is preferred, it has been found useful to set the pH in step A) α) to 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5 by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid. The specific manner in which the crystallization is carried out in step A) α) in turn depends on the overall manner in which step A) is carried out. All possible configurations of the invention described above in connection with the preparation of aminobenzoic acids of formula (I) (which are not specific to these aminobenzoic acids) accordingly also apply to the case of the preparation of aliphatic saturated dicarboxylic acids of formula (II) described below. This relates, for example, to the configuration of the crystallizer.

[0105] Biological methods

[0106] In one embodiment, step A) comprises a biological method. First variant In this, this is carried out in particular by converting fermentable carbon-containing compounds and nitrogen-containing compounds into the desired aliphatic saturated dicarboxylic acids or their anions in the presence of microorganisms. Such fermentations have been described; see in particular the already cited publications Peter CK Lau (ed.), Quality Living Through Chemurgy and Green Chemistry, Springer-Verlag GmbH Germany 2016, Chapter 3.3, pages 47 to 54, and K. Raj, S. Partow et al., Biocatalytic production of adipic acid from glucose using engineered Saccharomyces cerevisiae, Metabolic Engineering Communications 2018, 6, 28-32.

[0107] Suitable microorganisms for the fermentative preparation of aliphatic saturated dicarboxylic acids of the formula (II) include, in particular, Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Bacillus coagulans, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0108] Completely analogous to the preparation of aminobenzoic acid of formula (I) above, here too there is pH dependence: depending on the pH at which the fermentation is carried out, the aliphatic saturated dicarboxylic acid already crystallizes during the fermentation (case (I)), or the fermentation broth contains the aliphatic saturated dicarboxylic acid in anionic form, in which case the fermentation is followed by a reaction crystallization (case (II)). In case (I), the fermentation is preferably carried out at a pH of 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5. The separation step of the microorganism and the organic acid can be, for example, such that the saturated aliphatic dicarboxylic acid is selectively dissolved at maximum concentration (for example, with an aqueous alkaline solution or an organic solvent) and then, if necessary, separated from the solution (by another crystallization or concentration). Step A) α) is then part of the fermentation. In case (II), the fermentation is preferably carried out at a pH of >4.0 to 11 (especially 6.0 to 11), preferably 5.0 to 9.0 (especially 6.0 to 9.0), more preferably 5.0 to 8.0 (especially 6.0 to 8.0). In this case, the aliphatic saturated dicarboxylic acid is obtained in anionic form and crystallized in a step downstream of the fermentation by adding a mineral acid, in particular hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, to a pH of 0 to 4.0, preferably 1.8 to 3.0, more preferably 2.0 to 2.5. In this case, step A) α) is therefore a step after the fermentation.

[0109] In the use of biological methods to produce organic acids Second variant Enzymes are used to cleave polyesters. The enzymatic cleavage of polyesters to release adipic acid using cutinases has been described, for example, in the following paper: Perz, V., Bleymaier, K., Sinkel, C., Kueper, U., Bonnekessel, M., Ribitsch, D., and Guebitz, GM (2016), Substrate specificities of cutinases on aliphatic–aromatic polyesters and on their model substrates, New biotechnology, 2016, 33(2), 295-304.

[0110] Chemical methods

[0111] In another embodiment, step A) comprises a chemical conversion (i.e. a non-biological process). Chemical processes for preparing dicarboxylic acids of the specified type are known. For example, reference is made to the hydrogenation of the corresponding aliphatic unsaturated dicarboxylic acids. In the case of the most strongly preferred adipic acid, the preparation can therefore be carried out by hydrogenating muconic acid, which is described, for example, in WO 2015 / 086827 A1. Step A) α) is carried out here in particular for purifying the product obtained in the hydrogenation. An alternative method for preparing adipic acid is to oxidize cyclohexane with oxygen or an oxygen-containing gas mixture (in particular air) to cyclohexanol and cyclohexanone, and then oxidize them with nitric acid, which has already been mentioned at the beginning and is described many times in the literature (see the review by A. Castellan et al. in Catal. Today 1991, 9, 237-254).

[0112] In the case of chemical conversion, step A) may also comprise the cleavage of the polyester, for example by acidic or basic hydrolysis. Furthermore, step A) may comprise the acidic or basic hydrolysis of polyamides based on hexamethylenediamine and adipic acid, as described, for example, in US Pat. No. 3,223,731.

[0113] Optionally, a step of reducing the dissolved organic acid portion of the first aqueous solution of the organic acid

[0114] The first aqueous solution of an organic acid obtained by one of the above-described methods can be fed directly to step B). However, it is also possible to reduce the concentration of the organic acid in the first aqueous solution of an organic acid in another way before carrying out step B). Suitable methods for this purpose are known in the art. extraction Methods and Adsorption method.

[0115] In the case of an extraction process, the first aqueous solution of the organic acid is extracted with an organic extractant and subsequently subjected to 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 enriched in organic acid). In the context of the present invention, liquid-liquid phase separation is always preferably carried out (in whichever process step) by using a separator, decanter or centrifuge.

[0116] 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, more preferably 9 to 11 carbon atoms; (ii) ketones (in particular methyl isobutyl 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 abovementioned extractants.

[0117] Apparatuses suitable for carrying out the extraction are known in the professional field. Suitable examples include so-called mixer-settlers or extraction columns having a theoretical plate number of preferably 3 to 10, more preferably 3 to 7, most preferably 4 to 6. The mass-based ratio of the organic phase to the aqueous phase is preferably 0.20 to 1.0, more preferably 0.20 to 0.50, most preferably 0.35 to 0.50. After the organic solvent phase and the aqueous phase are separated, the aqueous solution of the organic acid is fed to step B). The extractant enriched in the organic acid is preferably sent to a stripping, wherein the organic acid is converted into anions by extraction with an aqueous alkaline solution, and after phase separation, an aqueous phase and an alcohol phase containing the organic acid anions are obtained. Since relatively polar impurities may be generated in the preparation of the organic acid, these relatively polar impurities can be at least partially transferred to the aqueous phase, especially in this step, so it is preferred to take measures to discharge such impurities. The extraction can be carried out at a temperature of 20°C to 90°C, preferably 25°C to 70°C, more preferably 30°C to 50°C, and in particular can also be carried out at ambient temperature.

[0118] The aqueous alkaline solution used for stripping is preferably an aqueous solution of an alkali metal or alkaline earth metal hydroxide (especially sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution), an aqueous solution of an alkali metal or alkaline earth metal bicarbonate (especially sodium bicarbonate solution or potassium bicarbonate solution), an aqueous solution of an alkali metal or alkaline earth metal carbonate (especially sodium carbonate solution or potassium carbonate solution) or a mixture of two or more of the above compounds. Sodium hydroxide solution and potassium hydroxide solution are particularly preferred. Regardless of the base used, the molar ratio of hydroxide ions to organic acid groups is preferably 1.0 to 5.0, preferably 1.0 to 2.0, more preferably 1.0 to 1.5.

[0119] Apparatus suitable for this stripping is the same as that used for the stripping described above. The mass-based ratio of the organic phase to the aqueous phase is preferably from 0.20 to 1.0, more preferably from 0.20 to 0.50, most preferably from 0.20 to 0.40.

[0120] In addition to extraction, adsorption can also be used to reduce the first aqueous solution of organic acid. For this purpose, the first aqueous solution is passed through an adsorbent bed, and the organic acid is adsorbed on it. Suitable adsorbents are generally non-polar adsorbents, such as (i) activated carbon, (ii) graphite, or (iii) adsorbent polymers, but also (usually) (iv) polar adsorbents, such as silica gel, limestone or aluminum silicate, and (v) mixtures of two or more of the above adsorbents. Adsorption is preferably achieved by passing an aqueous solution through the adsorbent until the adsorption performance of the adsorbent decreases, and it is necessary to regenerate the adsorbent by desorption of an inorganic acid. Desorption is preferably achieved with an aqueous solution having a pH of 5 to 10 (e.g., adjusting the pH with sodium hydroxide solution or hydrochloric acid), or alternatively with an organic solvent, particularly 1-dodecanol. This variant of post-treatment by the order of an adsorption step and a desorption step is described in international application WO 2018 / 114841 A1. The method disclosed therein is more particularly characterized in that desorption is carried out in an acidic environment (pH-0.8 to 3.0). In this embodiment, the liquid phase leaving the adsorbent bed during desorption is a second aqueous solution of an organic acid and is fed to step B).

[0121] Suitable apparatuses for carrying out the adsorption are known in the art. Suitable examples are columns and, on a laboratory scale, chromatography columns in which the adsorbent is packed, in particular in the form of an adsorption bed.

[0122] Metal salt treatment

[0123] In step B) of the method of the present invention, the first or second aqueous solution of the organic acid obtained in step A) is treated with a metal salt, the metal ion of the metal salt comprising Mn2 + ,Fe2 + and / or Cu2 + And in particular selected from Mn2 + ,Fe2 + and Cu2 + , to precipitate the metal compound of the organic acid (slightly soluble complex or slightly soluble salt), and then remove the precipitated metal compound of the organic acid by solid-liquid phase separation. Among the metal ions that can be used according to the present invention, Fe2 + and Cu2 + (especially in the case of obtaining aliphatic saturated dicarboxylic acids); Cu2 + (especially in the case of obtaining aliphatic saturated dicarboxylic acids).

[0124] The optimal pH in step B) depends on the type of organic acid to be obtained, in the case of aminobenzoic acid of formula (I), the pH is preferably 3.0 to 4.7, more preferably 3.2 to 3.7, most preferably 3.4 to 3.6; and in the case of aliphatic saturated dicarboxylic acids of formula (II), the pH is preferably >4.0 to 7.0, more preferably 4.7 to 5.8, most preferably 5.3 to 5.7. If there is a risk of the pH deviating from the target range due to the acidity or alkalinity of the added metal salt, this can be easily compensated by adding an acid (preferably hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid) or a base (preferably sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide).

[0125] The metal salt used in step B) is preferably a sulfate, chloride and / or hydroxide. The use of hydroxides makes the process version of the invention particularly economically feasible, wherein the precipitated metal hydroxide obtained in step C) described further below is returned to step B) and used as a component of the metal salt in step B). Any excessive increase in pH in step B) can be counteracted by adding acid.

[0126] The metal ions of the metal salt are preferably added in no more than a stoichiometric amount based on the amount of the organic acid.

[0127] The metal salt treatment is preferably carried out at 20°C to 50°C, more preferably at 20°C to 30°C, in particular also at ambient temperature. An example of a suitable reaction apparatus is a stirred tank reactor (or two or more stirred tank reactors, in particular connected in series). The treatment can be carried out in such a way that the metal salt (e.g. Cu(OH)2) is first charged into the reactor and mixed with an aqueous solution of an organic acid, and the pH can be actively adjusted if necessary (see above for details on suitable pH values). After the precipitation of the sparingly soluble metal compound of the organic acid, it is separated out by solid-liquid phase separation. The remaining aqueous phase can be treated as wastewater. Since the aqueous phase still contains metal salt portions corresponding to their solubility at the current (acidic; see above) pH, and these proportions may not be expected to be high from an environmental point of view, in a preferred embodiment of the present invention, the pH of the aqueous liquid phase obtained in the solid-liquid phase separation should be increased to a value of 8.0 to 14, preferably 10 to 13, in order to precipitate the dissolved metal ions as sparingly soluble hydroxides. These can then be separated out 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 processed without difficulty, for example in a biological treatment plant. Suitable bases for increasing the pH are standard bases, such as alkali metal and alkaline earth metal hydroxides, alkali metal and alkaline earth metal carbonates, or alkali metal and alkaline earth metal hydrogencarbonates, in particular sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution.

[0128] Alkali treatment

[0129] In step C) of the process according to the invention, the metal compound of the organic acid obtained in step B) is subjected to a base treatment. Here the organic acid enters the solution in the form of anions, while the metal ions used are precipitated out in the form of hydroxides.

[0130] Step C) is preferably carried out in multiple stages in n steps that are carried out continuously, wherein n is a natural number of 2 to 10, preferably 3 to 9, more preferably 4 to 8. For this purpose, in each of the n steps, a portion of the metal compound of the organic acid that has been removed is treated with an aqueous alkaline solution to precipitate a metal hydroxide, wherein after each step, the precipitated metal hydroxide is removed by solid-liquid phase separation, leaving an alkaline aqueous solution containing an organic acid anion, wherein the aqueous alkaline solution in the second to nth steps contains the alkaline aqueous solution containing an organic acid anion obtained in each previous step (and optionally consists of it, i.e., does not contain any other components). The crystallization according to step D) described in detail below is carried out using the alkaline aqueous solution containing an organic acid anion obtained in the nth step of C).

[0131] In step C), preferably a pH of 9.0 to 14, preferably 10 to 14, more preferably 11 to 13 is maintained, and if necessary, further alkaline solutions are metered in. Suitable aqueous alkaline solutions are all bases familiar to the person skilled in the art, for example, in particular aqueous solutions of alkali metal or alkaline earth metal hydroxides (in particular sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution (aqueous solution of calcium hydroxide)), alkali metal or alkaline earth metal hydrogen carbonates, alkali metal or alkaline earth metal carbonates (in particular sodium hydrogen carbonate solution or potassium hydrogen carbonate solution or sodium carbonate solution or potassium carbonate solution) or mixtures of two or more of the above alkaline solutions. Particularly preferred are sodium hydroxide solution and potassium hydroxide solution. In the case of multi-stage performance of step C), the pH values ​​mentioned are maintained in each of the n steps.

[0132] Like step B), step C) is preferably carried out at ambient temperature. Stirred tank reactors are also suitable here (or two or more stirred tank reactors, which are in particular connected in series).

[0133] crystallization

[0134] In step D), the organic acid anions present in the alkaline aqueous solution obtained in step C) are crystallized. This is achieved by adding a mineral acid to reduce the pH, and the mineral acid is particularly hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid. The simplest way to carry out step D) is to introduce the alkaline aqueous solution obtained in step C) into the crystallization of A) α), where corresponding acidic conditions already exist. However, it is certainly also possible to carry out step D) separately from step A) α), for example in a separate crystallizer. Suitable types for this purpose are those as described above, optionally (due to a smaller amount) with smaller specifications. The pH value should then be adjusted as described further above for A) α).

[0135] The accompanying drawings are intended to provide a deeper understanding of the invention.

[0136] Figure 1 A preferred embodiment of the process according to the invention is shown in which step Aα) is a step downstream of the actual preparation of the organic acid and in which step D) is carried out in which the aqueous solution containing the organic acid anion of step C) is returned to the crystallization of Aα).

[0137] The meanings of the reference numerals are as follows:

[0138]

[0139] Figure 2 A preferred configuration of step C) performed in n stages (here, for example, n=7) is shown. Here, the metal compound of an organic acid (9) obtained in step B) is divided into seven portions (9.1, 9.2, ... 9.7), the first portion (9.1) is treated with an aqueous alkaline solution (10), and after solid-liquid phase separation, a first portion (12.1) of a precipitated metal hydroxide (12) is obtained and removed (for the sake of simplicity, the steps of alkali treatment and solid-liquid phase separation are not described separately here). The remaining alkaline aqueous liquid phase is added to the second portion (9.2) of the metal compound, and then another solid-liquid phase separation is performed, wherein the second portion (12.2) of the precipitated metal hydroxide (12) is removed. After these steps are performed with another five portions of the metal compound of an organic acid, an alkaline aqueous solution (13) containing an organic acid anion is finally obtained. The obtained portions (12.1, 12.2, ... 12.7) of the precipitated metal hydroxide are preferably combined and then as Figure 1 As shown, it is fed to the metal salt treatment in step B). Example:

[0140] The following examples start with organic acids which were not prepared specifically for the examples but were obtained from commercial sources. Aqueous solution of organic acid It is artificially prepared, but this does not affect the significance of the experiment.

[0141] Embodiment 1: Precipitation of 2-aminobenzoic acid in aqueous solution by adding CuSO4, FeSO4 or MnSO4

[0142] Chemicals:

[0143] 2-Aminobenzoic acid (o-aminobenzoic acid, o-aminobenzoic acid; CAS number: 118-92-3) was obtained from Sigma-Aldrich with a purity of ≥98%. In the following, 2-aminobenzoic acid is abbreviated as "oAB" regardless of its form (neutral or as an anion). CuSO4, FeSO4·7H2O, and MnSO4·H2O were obtained from Sigma-Aldrich with a purity of ≥99%. Ultrapure water (prepared with a Millipore laboratory water treatment system) was used. NaOH (granules) and HCl from Acros were used. (aq) (37% concentration).

[0144] experiment:

[0145] a) Providing an aqueous solution of an organic acid

[0146] The aqueous solution of the organic acid obtained in the crystallization in step A) α) (= mother liquor of crystallization) was artificially prepared by dissolving oAB in water to prepare an oAB aqueous solution (oAB concentration 5 g / L).

[0147] b) treating the aqueous solution of the organic acid with a metal salt (step B))

[0148] The oAB aqueous solution was mixed with a metal salt (CuSO4, FeSO4 or MnSO4) at room temperature for at least 30 minutes (molar ratio of metal salt:oAB = 1:2). The pH was adjusted to about 3.5 (corresponding to the isoelectric point of oAB) with 1M NaOH solution. Then 30 minutes were waited to allow the formed solid (metal compound of organic acid) to completely settle. The concentration of oAB in the aqueous supernatant sample was analyzed by HPLC (High Performance Liquid Chromatography) (Sample A). The solid (Cu(oAB)2, Fe(oAB)2 and / or Mn(oAB)2) was separated from the liquid phase by centrifugation.

[0149] c) treating the removed metal compound of the organic acid with an alkali (step C))

[0150] In the case of the experiments with Fe and Cu, the removed solids were resuspended in water and the pH was adjusted to pH = 12.0 to 12.5 with 1 M NaOH solution. The oAB-metal compound went into solution and the metal hydroxide (Cu(OH)2 and / or Fe(OH)2) precipitated out as a solid. After 30 minutes of mixing and 30 minutes of settling, a sample of the aqueous supernatant was analyzed for oAB by HPLC (sample B). The solid (precipitated metal hydroxide) was subsequently separated from the liquid phase (alkaline aqueous solution containing the organic acid anion). In the case of iron(II) hydroxide, the alkaline treatment was repeated (see Figure 2 ):

[0151] The oAB concentration in the liquid phase was further increased by repeated additions of Fe(oAB)2 (seven additions in total). In each of the seven steps, Fe(OH)2 precipitated out as a solid and was removed by centrifugation after each addition.

[0152] d) recycling the precipitated metal hydroxide into the step of treating the aqueous solution of the organic acid with the metal salt

[0153] An oAB aqueous solution (5 g / L) was mixed with solid metal hydroxide at pH = 3.5 for 30 minutes. The metal hydroxide dissolved and Cu(oAB)2 and / or Fe(oAB)2 precipitated. After the solid precipitated, a sample of the liquid phase was analyzed for oAB content by HPLC analysis (Sample C).

[0154] HPLC:

[0155] Agilent 1260 Infinity II LC with diode array detector was used to quantify oAB. The stationary phase used was C18 Zorbax Eclipse (4.6×150 mm) with a precolumn. The mobile phases used were water (A) and methanol (B) containing 0.1% H3PO4, with the following linear gradients:

[0156] .0 minutes: 95% A / 5% B

[0157] 4 minutes: 95% A / 5% B

[0158] 15 minutes: 2% A / 98% B

[0159] 16 minutes: 2% A / 98% B

[0160] .16.5 minutes: 95% A / 5% B

[0161] .21 minutes: 95% A / 5% B

[0162] The volume flow rate was set at 0.5 mL / min. 5 μL was injected each time. The column temperature was 35 °C. oAB was detected at wavelengths of 254 nm and 330 nm and compared with the calibration curve.

[0163] result:

[0164] The oAB concentration of the aqueous supernatant after precipitation of the metal compound of the organic acid (sample A from b)) was less than 0.05 g oAB This indicates that oAB can be precipitated almost quantitatively (>99%) in the form of oAB-metal compounds in solid form.

[0165] The aqueous supernatant after the precipitation of the metal hydroxide initiated by the alkaline treatment (sample B from c)) showed an oAB concentration of 14 g / L. In the case of iron, the oAB concentration in the liquid phase could be increased to 301 g / L by carrying out the alkaline treatment in seven steps.

[0166] This indicates that the solid (precipitated metal hydroxide, Cu(OH)2 and / or Fe(OH)2) can be used again for the complexation of oAB in aqueous solution (see d)). Similar to sample A from b), in sample C after the addition of both Fe(OH)2 and Cu(OH)2, the measured oAB concentration was less than 0.05 g oAB The detection limit of .

[0167] In summary, it can be stated that by the sequence of metal salt treatment and base treatment according to the invention, the oAB (5 g / L) present in the original "aqueous solution of organic acid" can be significantly concentrated (to at least 14 g / L, up to 301 g / L in the case of seven-step base treatment). The significantly more concentrated (oAB anion) solution thus obtained can be subjected to the crystallization step for isolating oAB (step D) without any problems).

[0168] Embodiment 2: Precipitation of adipic acid in aqueous solution by addition of CuSO4

[0169] Chemicals:

[0170] Adipic acid (CAS No. 124-04-9) was obtained at a purity of 98%. CuSO4 was obtained from Sigma-Aldrich with a purity of ≥99%. Ultrapure water (prepared using a Millipore laboratory water treatment system) was used. NaOH (granules) and HCl from Acros were used. (aq) (37% concentration).

[0171] experiment:

[0172] a) Providing an aqueous solution of an organic acid

[0173] An aqueous solution of adipic acid (12 g / L) was prepared by dissolving adipic acid in water, in this way the aqueous solution of the organic acid obtained in the crystallization in step A) α) (= mother liquor of crystallization) was artificially prepared.

[0174] b) treating the aqueous solution of the organic acid with a metal salt (step B))

[0175] The aqueous solution of adipic acid was mixed with a metal salt (CuSO4) at room temperature for at least 30 minutes (molar ratio of metal salt: adipic acid = 1:1). The pH was adjusted to about 5.5 with 1M NaOH solution. Then 30 minutes were waited to allow the formed solid (metal compound of organic acid) to settle completely. The concentration of adipic acid in the aqueous supernatant sample was analyzed by HPLC (high performance liquid chromatography) (sample A).

[0176] The solid (copper adipate) was separated from the liquid phase by centrifugation.

[0177] c) treating the removed metal compound of the organic acid with an alkali (step C))

[0178] The removed solids were resuspended in water and the pH was adjusted to 12.0 to 12.5 with 1 M NaOH solution. The adipic acid-metal compound went into solution and the metal hydroxide (Cu(OH)2) precipitated out. After 30 minutes of mixing and 30 minutes of settling, the adipic acid content in the aqueous supernatant sample was analyzed by HPLC (Sample B).

[0179] The solid (precipitated metal hydroxide) is subsequently separated from the liquid phase (alkaline aqueous solution containing the organic acid anion).

[0180] d) using a precipitated metal hydroxide in the step of treating the aqueous solution of an organic acid with a metal salt

[0181] An aqueous solution of adipic acid (12 g / L) was mixed with a metal hydroxide (approximately stoichiometrically) at pH = 4.5 for 30 minutes. The metal hydroxide dissolved and the metal adipate precipitated. After the solid precipitated, a sample of the liquid phase was analyzed for adipic acid content using HPLC analysis (Sample C).

[0182] HPLC:

[0183] Samples were prepared in 0.1 M phosphate aqueous buffer containing 0.1 wt % pimelic acid.

[0184] Agilent 1260 Infinity II LC with diode array detector was used for adipic acid quantification. The stationary phase used was C18 Zorbax Eclipse (4.6×150 mm) with precolumn (Poroshell 120EC-C18 (4.6×5 mm)). The mobile phase used was water (A) and acetonitrile (B) containing 0.1% H3PO4, and the linear gradient was as follows:

[0185] 0 minutes: 95% A / 5% B

[0186] 0.5 minutes: 95% A / 5% B

[0187] 4.5 minutes: 75% A / 25% B

[0188] .6.5 minutes: 75% A / 25% B

[0189] .6.6.5 minutes: 95% A / 5% B

[0190] 9.5 minutes: 95% A / 5% B

[0191] The volume flow rate was set at 1.5 mL / min. 1 μL was injected each time. The column temperature was 35°C. Adipic acid was detected at a wavelength of 208.8 nm and compared with the calibration curve.

[0192] result:

[0193] Aqueous supernatant after precipitation of metal compounds of organic acids The adipic acid concentration of sample A) (from b) was 0.99 g / L. This indicates that the solubility of this salt is low.

[0194] Aqueous supernatant after precipitation of metal hydroxides induced by alkali treatment Sample B) (from c) showed an adipic acid concentration of 24 g / L.

[0195] This indicates that the solid (precipitated Cu(OH)2) can be used again to precipitate adipic acid from aqueous solution (see d)). The adipic acid concentration in sample C from d) is 3 g / L. Based on the current data, this value is expected to be still lower in the case of d) at pH = 5.5.

[0196] In summary, it can be stated that the sequence of metal salt treatment and base treatment according to the invention can significantly concentrate the adipic acid (12 g / L) present in the original "aqueous solution of organic acid" (to at least 24 g / L). The significantly more concentrated (adipate) solution thus obtained can be subjected to a crystallization step without any problems to isolate the adipic acid (step D)).

[0197] Example 3: Precipitation of 2-amino-5-methylbenzoic acid in aqueous solution by adding CuSO4

[0198] Chemicals:

[0199] 2-Amino-5-methylbenzoic acid (CAS No. 2941-78-8) was from Sigma-Aldrich with a purity of 97%. CuSO4 was from Sigma-Aldrich with a purity of ≥99%. Ultrapure water (prepared using a Millipore laboratory water treatment system) was used. NaOH (granules) and HCl from Acros were used. (aq) (37% concentration).

[0200] experiment:

[0201] a) Providing an aqueous solution of an organic acid

[0202] An aqueous solution of 2-amino-5-methylbenzoic acid (1 g / L) was prepared by dissolving 2-amino-5-methylbenzoic acid in water, in this way artificially preparing an aqueous solution of the organic acid obtained in the crystallization of step A) α) (= mother liquor of crystallization).

[0203] b) treating the aqueous solution of the organic acid with a metal salt (step B))

[0204] The aqueous solution of 2-amino-5-methylbenzoic acid was mixed with a metal salt (CuSO4) at room temperature for at least 30 minutes (mol ratio of metal salt: 2-amino-5-methylbenzoic acid = 1:1). The pH was set to 3.5 with NaOH. Then 30 minutes were waited to allow the formed solid (metal compound of organic acid) to settle completely. The 2-amino-5-methylbenzoic acid concentration in the aqueous supernatant sample was analyzed by HPLC (high performance liquid chromatography) (sample A).

[0205] The solid (copper 2-amino-5-methylbenzoate) is separated from the liquid phase. A centrifuge is used for better solid-liquid separation.

[0206] c) treating the removed metal compound of the organic acid with an alkali (step C))

[0207] The removed solids were resuspended in water and the pH was adjusted to 12.5 with 1 M NaOH solution. The 2-amino-5-methylbenzoic acid-metal compound went into solution and the metal hydroxide (Cu(OH)2) precipitated out. After 30 minutes of mixing and 30 minutes of settling, the 2-amino-5-methylbenzoic acid content in the aqueous supernatant sample was analyzed by HPLC (Sample B).

[0208] HPLC:

[0209] Agilent 1260 Infinity II LC with diode array detector was used for the quantification of 2-amino-5-methylbenzoic acid. The stationary phase used was C18 Zorbax Eclipse (4.6×150 mm) with a precolumn. The mobile phase used was water (A) and methanol (B) containing 0.1% H3PO4, and the linear gradient was as follows:

[0210] 0 minutes: 95% A / 5% B

[0211] .4 minutes: 95% A / 5% B

[0212] 15 minutes: 2% A / 98% B

[0213] 16 minutes: 2% A / 98% B

[0214] 16.5 minutes: 95% A / 5% B

[0215] 21 minutes: 95% A / 5% B

[0216] The volume flow rate was set at 0.5 mL / min. 5 μL was injected 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 the calibration curve.

[0217] result:

[0218] Aqueous supernatant after precipitation of metal compounds of organic acids The 2-amino-5-methylbenzoic acid concentration of sample A) (from b) was less than 0.01 g / L. This indicates that the solubility of the metal compound is low.

[0219] Aqueous supernatant after precipitation of metal hydroxides induced by alkali treatment Sample B) (from c) showed a 2-amino-5-methylbenzoic acid concentration of 0.72 g / L.

[0220] In summary, it can be shown that, by the sequence of the metal salt treatment and the alkali treatment according to the present invention, the 2-amino-5-methylbenzoic acid (1 g / L) present in the original "aqueous solution of organic acid" can be separated from the aqueous solution and then dissolved in water. It is expected that the concentration of 2-amino-5-methylbenzoic acid can be significantly concentrated (similar to Example 1). In this example, no concentration is performed. The (2-amino-5-methylbenzoic acid) solution thus obtained can be subjected to a crystallization step without any problems to separate 2-amino-5-methylbenzoic acid (step D)).

Claims

1. A method for obtaining an organic acid from an aqueous solution of an organic acid, wherein the organic acid is selected from (i) aminobenzoic acid of the formula Where R is CH3 or H, or (ii) an aliphatic saturated dicarboxylic acid of the formula Where n = 1 or 2, The method comprises the following steps: A) preparing organic acids by biological methods or chemical reactions, wherein α) crystallizing the organic acid from an aqueous medium during or after the preparation, Afterwards 1) removing the organic acid portion that has precipitated in the crystals by solid-liquid phase separation, leaving the first aqueous solution of the organic acid, and 2) Optionally, by extracting the organic acid with an organic extractant, or By adsorbing organic acids on adsorbents, reducing the amount of organic acid dissolved in the first aqueous solution of organic acid, The organic extractant or adsorbent is then removed to obtain a second aqueous solution of the organic acid. liquid; B) treating the first aqueous solution of the organic acid or the second aqueous solution of the organic acid with a metal salt to precipitate a metal compound of the organic acid, wherein the metal ion of the metal salt comprises Mn2 + ,Fe2 + and / or Cu2 + , subsequently removing the precipitated metal compound of the organic acid by solid-liquid phase separation; C) treating the removed metal compound of the organic acid with an aqueous alkaline solution to precipitate a metal hydroxide, and removing the precipitated metal hydroxide by solid-liquid phase separation to leave an alkaline aqueous solution containing anions of the organic acid; as well as D) Crystallizing the organic acid from the alkaline aqueous solution containing the anion of the organic acid obtained in C) by adding a mineral acid.

2. The method of claim 1, wherein the alkali treatment in C) comprises n steps performed continuously, wherein n is a natural number from 2 to 10, wherein In each of the n steps, a portion of the removed metal compound of the organic acid is treated with an aqueous alkaline solution to precipitate a metal hydroxide, wherein after each step, the precipitated metal hydroxide is removed by solid-liquid phase separation to leave an alkaline aqueous solution containing anions of the organic acid, wherein the aqueous alkaline solution in the second to nth steps includes the organic acid anion-containing aqueous solution obtained in the respective previous steps. Alkaline aqueous solution; The crystallization of the organic acid in D) is carried out using the alkaline aqueous solution containing the anion of the organic acid obtained in the nth step of C).

3. The method according to claim 1 or 2, wherein the crystallization of the organic acid in D) comprises recycling the alkaline aqueous solution containing the anion of the organic acid obtained in C) to A)α); or The crystallization of the organic acid in D) is carried out separately from A)α).

4. The process as claimed in claim 1, wherein the metal hydroxide precipitated in C) is recycled to step B) where it is used as a component of the metal salt.

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

6. The method of claim 5, wherein the aminobenzoic acid of formula (I) is 2-aminobenzoic acid or 2-amino-5-methylbenzoic acid.

7. The process as claimed in claim 5 or 6, wherein in A) α) the pH is set to 3.0 to 4.7 by adding a mineral acid and in B) the pH is maintained in the same range.

8. The process according to any one of claims 5 to 7, wherein A) comprises a biological process comprising fermenting a feedstock containing fermentable carbon-containing compounds and nitrogen-containing compounds in the presence of microorganisms.

9. The method of any one of claims 5 to 7, wherein A) comprises a chemical conversion.

10. The process as claimed in claim 9, wherein A) comprises the reaction of an optionally methyl-substituted phthalimide or phthalamide with an alkali metal hypohalite in a basic medium, followed by the addition of a mineral acid to carry out A) α).

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

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

13. The process as claimed in claim 11 or 12, wherein in A) α) the pH is set to 0 to 4.0 by adding a mineral acid; and in B) the pH is set to >4.0 to 7.0 by adding a base.

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

15. The method of claim 14, wherein the biological process comprises fermenting a feedstock containing fermentable carbon-containing compounds in the presence of a microorganism.

16. The method of any one of claims 11 to 13, wherein A) comprises a chemical conversion.

17. The method of claim 16, wherein A) comprises hydrogenating an aliphatic unsaturated dicarboxylic acid corresponding to an aliphatic saturated dicarboxylic acid of formula (II); or The aliphatic saturated dicarboxylic acid of the formula (II) is hexane-1,6-dicarboxylic acid and A) comprises the oxidation of cyclohexane with oxygen or an oxygen-containing gas mixture to cyclohexanol and cyclohexanone and their subsequent oxidation with nitric acid.

18. The process of claim 14 or 16, wherein A) comprises cleavage of the polyester.

19. A method as claimed in any one of the preceding claims, wherein the metal ion of the metal salt used in B) comprises Fe 2+ and / or Cu 2+ .

20. The process as claimed in any one of the preceding claims, wherein in C) the pH is set to between 9.0 and 14.

21. The process as claimed in any one of the preceding claims, wherein in B) the metal ions are added in no more than a stoichiometric amount, based on the amount of mineral acid.

22. The method of any one of the preceding claims, wherein the metal salt comprises a sulfate, a chloride and / or a hydroxide.

23. A process as claimed in any one of the preceding claims, wherein the precipitated metal compound of the organic acid is removed by solid-liquid phase separation in B), leaving an aqueous phase, which is adjusted to a pH of 8.0 to 14 by adding a base, precipitates a metal hydroxide, which is removed by further solid-liquid phase separation and then used as a component of the metal salt in B).

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