Process for producing aniline or an aniline derivative

Description

[0001] 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).

[0002] The present invention relates to a process for the preparation of aniline or an aniline derivative, comprising the steps of (I) providing aminobenzoic acid, (II) decarboxylating the aminobenzoic acid to aniline in the presence of an inorganic heterogeneous metal oxide catalyst containing a mass fraction of Al 2 O 3 of 40.0% to 100%, preferably 50.0% to 100%, particularly preferably 60.0% to 100%, based on the total mass of the metal oxides, wherein the mass fraction of Al 2 O 3 based on the total mass of the inorganic heterogeneous metal oxide catalyst is 25% to 100%, and (III) optionally converting the aniline to an aniline derivative.

[0003] The production of aniline by decarboxylation of aminobenzoic acid is generally known in the prior art. For example, see international patent applications WO 2015 / 124686 A1 and WO 2015 / 124687 A1 and the literature cited therein. The starting compound, aminobenzoic acid, can be obtained chemically or, preferably, by fermentation.

[0004] The chemical The production of aminobenzoic acid is well known. One suitable synthesis route is the reaction of phthalimide with sodium hypochlorite. Phthalimide, in turn, can be obtained from phthalic anhydride and ammonia.

[0005] The fermentative The production of aminobenzoic acid is also known and described in the literature; see, for example, the aforementioned applications WO 2015 / 124686 A1 and WO 2015 / 124687 A1 and the literature cited therein.

[0006] WO 2015 / 124686 A1 describes the decarboxylation of fermentatively or chemically produced anthranilic acid by extraction of aniline formed during the decarboxylation with a non-system organic solvent (an alcohol, phenol, amide, ether, or aromatic hydrocarbon; 1-dodecanol is particularly highlighted as a suitable solvent). Acidic catalysts such as zeolites or basic catalysts such as Mg-Al hydrotalcite (Mg 6 Al 2 (CO 3 )(OH) 16 4H 2 O, corresponding to a calculated mass fraction of "Al 2 O 3 " of 16.88%) are described as catalysts for the decarboxylation.

[0007] WO 2015 / 124687 A1 describes the decarboxylation of fermentatively produced anthranilic acid, among other things, in water or in a non-system organic solvent, in particular 1-dodecanol, optionally in a mixture with aniline (see page 18, lines 28 and 29). Furthermore, this document also describes the possibility of carrying out the decarboxylation in aniline (without 1-dodecanol; see Figures 35 and 37 to 38 and the corresponding text), optionally in the presence of 10 mass% water (see Figure 36 and the corresponding text).

[0008] WO 2018 / 002088 A1 describes a process in which aminobenzoic acid is decarboxylated in a mixture with crude aniline. The crude aniline originates from the process itself, as a portion of the product stream is not fed to the purification but is recycled into the process. CatalystsFor carrying out the decarboxylation, aqueous acids such as sulfuric acid, nitric acid, and hydrochloric acid; solid acids such as zeolites and Si-Ti molecular sieves, solid bases such as hydroxyapatites and hydrotalcites; and polymeric acids such as ion exchange resins (especially Amberlyst) are described.

[0009] WO 2020 / 020919 A1 describes the decarboxylation of aminobenzoic acid using only the product aniline as a catalyst. External catalysts are deliberately avoided.

[0010] None of the previously described processes is economical, especially with regard to the yield of aniline (reduction of the by-product 2-aminobenzanilide, which not only reduces the proportion educated Aniline, but also its quantitative insulationThis is entirely satisfactory, particularly as regards the purification of aniline by distillation (which is facilitated as a result of reduced aniline losses due to the necessary removal of high-boiling components from the bottoms). Further improvements in the production of aniline or aniline derivatives by decarboxylation of aminobenzoic acid, particularly that obtained by fermentation, would therefore be desirable.

[0011] Taking the above into account, the invention provides: A process for the preparation of aniline or an aniline derivative, comprising the steps of: (I) Providing aminobenzoic acid (in particular ortho-aminobenzoic acid); (II) Decarboxylating the aminobenzoic acid to aniline in the presence of an inorganic heterogeneous metal oxide catalyst (hereinafter also referred to as catalyst(referred to as) containing a mass fraction of Al 2 O 3 of 40.0% to 100%, preferably 50.0% to 100%, particularly preferably 60.0% to 100%, based on the total mass of the metal oxides, wherein the mass fraction of Al 2 O 3 based on the total mass of the inorganic heterogeneous metal oxide catalyst is 25% to 100%; and (III) optionally, converting the aniline to an aniline secondary product.

[0012] In the terminology of the present invention, a Metal oxide catalyst a catalyst which contains at least one metal oxide or which can be represented by formula as containing at least one metal oxide. Total mass of metal oxides refers to the maximum number of metal oxides that can be represented by a formula. For example, if the composition of a catalyst can be represented by a formula as a "mixture" of aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), and water (H 2 O) (approximately " m Al2O3 · n MgO · o H2O" - first formula ), It is usually also possible to use the same catalyst in a second formula to be described as a "mixture" of aluminum hydroxide (Al(OH) 3 ) or aluminum oxide hydroxide (AlO(OH)) and magnesium hydroxide (Mg(OH) 2 ), where neither formula is necessarily a correct representation of the actual structure. To determine the mass fraction of Al 2 O 3 for the purposes of the present invention The formula containing the maximum number of metal oxides is used, regardless of whether the formula thus established adequately reflects the actual structure of the catalyst. The mass fraction of Al 2 O 3 within the meaning of the present invention can therefore be a calculated value. In the selected example, the first formula is therefore decisive. The same applies to the mass fractions of any other metal oxides.

[0013] First, there follows a Short summary various possible Embodiments of the invention, The list of embodiments is not to be regarded as exhaustive: In a first embodiment of the invention, which can be combined with all other embodiments, the inorganic heterogeneous metal oxide catalyst contains MgO in a mass fraction of 1.0% to 60.0%, preferably 2.0% to 50.0%, particularly preferably 5.0% to 35.0%, based on the total mass of the metal oxides.

[0014] In one second embodiment of the invention, which can be combined with all other embodiments, the inorganic heterogeneous metal oxide catalyst contains SiO 2 in a mass fraction of 1.0% to 30.0%, preferably 2.0% to 20.0%, particularly preferably 2.0% to 10.0%, based on its total mass.

[0015] In one third embodiment of the invention, which can be combined with all other embodiments, the Al 2 O 3 comprises γ-Al 2 O 3 or η-Al 2 O 3 , wherein the catalyst preferably does not comprise any further metal oxides.

[0016] In one fourth embodimentof the invention, which can be combined with all other embodiments, the decarboxylation of the aminobenzoic acid is carried out at a temperature of 150 °C to 300 °C, preferably 160 °C to 280 °C, most preferably 180 °C to 240 °C.

[0017] In one fifth embodiment of the invention, which can be combined with all other embodiments, the decarboxylation of the aminobenzoic acid is carried out at an absolute pressure of 0.05 bar to 300 bar, preferably 1.0 bar to 100 bar, particularly preferably 1.0 bar to 60 bar.

[0018] In one sixth embodiment of the invention, which can be combined with all other embodiments, the decarboxylation of the aminobenzoic acid is carried out in the presence of aniline.

[0019] In one seventh embodimentof the invention, which is a particular embodiment of the sixth embodiment and can otherwise be combined with all other embodiments, provided that these do not provide for continuous decarboxylation, the decarboxylation of the aminobenzoic acid is carried out discontinuously, wherein before the start of the decarboxylation a mass fraction of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90%, preferably 1.0% to 70%, particularly preferably 5.0% to 50% is set.

[0020] In one eighth embodimentof the invention, which is a further particular embodiment of the sixth embodiment and which can otherwise be combined with all other embodiments, provided that these do not provide for a discontinuous implementation of the decarboxylation, the decarboxylation of the aminobenzoic acid is carried out continuously, wherein during the decarboxylation a mass fraction of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90%, preferably 1.0% to 70%, particularly preferably 5.0% to 50% is always set.

[0021] In one ninth embodiment of the invention, which can be combined with all other embodiments, the decarboxylation of the aminobenzoic acid in the liquid or gas phase in a reactor (in particular in a tubular reactor) with an integrated fixed bed of the inorganic heterogeneous metal oxide catalyst (comprising a bed of the catalyst as a shaped body (extrudates) or a configuration of the catalyst as a monolithic structure), in the liquid or - preferably - gas phase in a fluidized bed reactor or in the liquid phase in a stirred tank with a suspension contained therein ( Slurry ) of the inorganic heterogeneous metal oxide catalyst.

[0022] In one tenth embodimentof the invention, which is a particular embodiment of the ninth embodiment, the decarboxylation of the aminobenzoic acid is carried out in the liquid or gas phase in a reactor (in particular in a tubular reactor) with an integrated fixed bed of the inorganic heterogeneous metal oxide catalyst comprising a bed of the catalyst as a shaped body (extrudate) or an embodiment of the catalyst as a monolithic structure, wherein the inorganic heterogeneous metal oxide catalyst is regenerated and reused after decarboxylation.

[0023] In one eleventh embodiment of the invention, which can be combined with all other embodiments, step (I) comprises fermenting a raw material containing a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms.

[0024] In one twelfth embodimentof the invention, which is a particular embodiment of the eleventh embodiment, the fermentable carbon-containing compound comprises starch hydrolysate, sugar cane juice, sugar beet juice, hydrolysates from lignocellulose-containing raw materials or a mixture of two or more of the above, wherein the nitrogen-containing compound comprises ammonia gas, ammonia water, ammonium salts, urea or a mixture of two or more of the above.

[0025] In one thirteenth embodiment of the invention, which is a particular embodiment of the eleventh and twelfth embodiments, the microorganisms comprise Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

[0026] In one fourteenth embodiment of the invention, which can be combined with all other embodiments, step (III) is carried out and comprises one of the following reactions: (1) Acid-catalyzed reaction of aniline with formaldehyde to form di- and polyamines of the diphenylmethane series; (2) Acid-catalyzed reaction of aniline with formaldehyde to form di- and polyamines of the diphenylmethane series, followed by their reaction with phosgene to form di- and polyisocyanates of the diphenylmethane series; or (3) Conversion of aniline to an azo compound.

[0027] In one fifteenth embodiment of the invention, which can be combined with all other embodiments, the aminobenzoic acid provided in step (A) comprises ortho-aminobenzoic acid (anthranilic acid) and is in particular ortho- Aminobenzoic acid (i.e. does not include other isomers of aminobenzoic acid).

[0028] The previously briefly described embodiments and further possible embodiments of the invention are described below explained in more detail. All embodiments and further developments of the invention can be combined with one another as desired, unless the context clearly indicates the opposite to a person skilled in the art or something else is explicitly stated.

[0029] The Step (I) The aminobenzoic acid to be provided can in principle be obtained by any method known in the art. One possibility is the production of aminobenzoic acid by chemical means. Preferred processes are those that selectively yield the ortho-isomer of aminobenzoic acid. One suitable chemical method is the reaction of phthalimide with sodium hypochlorite. Phthalimide, in turn, can be obtained from phthalic anhydride and ammonia.

[0030] The chemical production of para-aminobenzoic acid can be achieved by nitration of toluene with nitric acid, subsequent oxidation of the resulting para-nitrotoluene with oxygen to para-nitrobenzoic acid and finally reduction to para-aminobenzoic acid with hydrazine.

[0031] For example, meta-aminobenzoic acid can be produced starting from methyl benzoate: Nitration of methyl benzoate with nitric acid yields methyl meta-nitrobenzoate. This methyl ester is then saponified with sodium hydroxide solution. Neutralization with hydrochloric acid yields meta-nitrobenzoic acid, which is finally reduced with hydrazine to meta-aminobenzoic acid.

[0032] However, according to the invention, it is preferred to prepare the aminobenzoic acid required for carrying out step (I) by a fermentative processIn this embodiment of the invention, the provision of aminobenzoic acid comprises the fermentation of a raw material comprising at least one fermentable carbon-containing compound and one nitrogen-containing compound using microorganisms to obtain an aminobenzoate and / or aminobenzoic acid-containing Fermentation broth. This step can be carried out by any fermentation process known in the art and suitable for the production of aminobenzoic acid.

[0033] Under a fermentable carbon-containing compoundFor the purposes of this embodiment of the present invention, any organic compound or mixture of organic compounds is understood that can be used by the recombinant cells of the microorganism used to produce aminobenzoic acid. The production of aminobenzoic acid can take place in the presence or absence of oxygen. Preference is given to those fermentable carbon-containing compounds that can additionally serve as an energy and carbon source for the growth of the recombinant cells of the microorganism used. Particularly suitable are starch hydrolysate, sugar cane juice, sugar beet juice and hydrolysates from lignocellulose-containing raw materials as well as mixtures thereof (i.e. mixtures of two or more of the aforementioned compounds). Also suitable are glycerol and C1 compounds, in particular carbon monoxide. Suitable for step (I)(1) Nitrogen-containing compoundsParticularly suitable are ammonia gas, ammonia water, ammonium salts (in particular inorganic ammonium salts such as ammonium chloride and / or ammonium sulfate, preferably ammonium sulfate), urea or mixtures thereof (ie mixtures of two or more of the aforementioned compounds).

[0034] Preferred microorganisms for carrying out the fermentation are bacteria or Mushrooms, in particular Yeasts. Particularly preferred are microorganisms such as Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Kluyveromyces marxianus, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae, whereby the sole use of Corynebacterium glutamicum, in particular Corynebacterium glutamicum ATCC 13032, is particularly preferred. The pH value to be maintained during fermentation depends on the microorganism used. Microorganisms such as Corynebacterium glutamicum, Pseudomonas putida or Escherichia coli are preferably cultivated at neutral pH values (i.e., at a pH value in the range of 6.0 to 8.0). Microorganisms such as Saccharomyces cerevisiaeare preferably cultivated in acidic environments (i.e. at a pH value in the range of 3.0 to 6.0).

[0035] In any case, the microorganism of the fermentation is preferably selected so that the ortho-isomer of aminobenzoic acid is formed in the fermentation.

[0036] In a preferred embodiment of the invention, Bacteria as microorganismsused. In this connection, particular reference is made to the patent applications WO 2015 / 124686 A1 and WO 2015 / 124687 A1, in which a fermentation using bacteria which can be used according to the invention is described (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). 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 immediately consumed again in cellular biochemical processes, so that aminobenzoic acid accumulates in the cell and is finally converted into the fermentation broth.

[0037] In another preferred embodiment of the invention, Yeasts as microorganismsused. Particular reference is made to the international application WO 2017 / 102853 A1. In particular, yeast cells are used that are capable of converting a fermentable carbon-containing compound into aminobenzoic acid in the presence of a suitable nitrogen source without the resulting aminobenzoic acid being immediately consumed in intracellular biochemical processes, so that aminobenzoic acid accumulates in the cell and ultimately passes into the fermentation broth.

[0038] Suitable bacteria or yeast cells can be identified, for example, by screening for mutants that release aminobenzoic acid into the surrounding medium. However, targeted modification of key enzymes using genetic engineering is preferred. Using conventional genetic engineering methods, gene expression and enzyme activity can be enhanced, reduced, or even completely suppressed at will. This results in recombinant strains.

[0039] In the majority of cases, the fermentation broth present at the end of fermentation is basic to neutral or at most slightly acidic (pH > 4.7), and the aminobenzoic acid is therefore present in dissolved form in the form of its anion, aminobenzoate. In these cases, it is preferable to treat the fermentation broth with acid, in particular with hydrochloric acid, sulfuric acid and / or phosphoric acid, in order to convert the anion into the electroneutral form. The acid is added in particular until the pH of the resulting mixture is in the range of 3.0 to 4.7, preferably in the range of 3.2 to 3.7 (especially for meta- and para-aminobenzoic acid), particularly preferably in the range of 3.4 to 3.6 (especially for ortho-aminobenzoic acid).Aminobenzoic acid is then predominantly or entirely in the electroneutral form and, due to its low water solubility, precipitates, except for a small portion due to a certain residual solubility, and can be easily separated from the supernatant fermentation broth, particularly by filtration or centrifugation. Filtration can be carried out at reduced pressure, ambient pressure, or elevated pressure. Centrifugation can be performed using commercially available centrifuges. It is also possible to allow the suspension obtained from the acid treatment to rest until the precipitated crystals of aminobenzoic acid settle, and then to decant or suction off the supernatant mother liquor.

[0040] However, if the fermentation broth is highly acidic (pH < 3.0), a pH within the aforementioned range is ensured by adding a base (preferably caustic soda, lime). However, if the pH of the fermentation broth is in the range of 3.0 to 4.0, as may be the case when yeasts are used as microorganisms, in a preferred embodiment, neither acid nor base is added; instead, the fermentation broth is processed directly without further pH adjustment. In this case, it is to be expected that crystals of aminobenzoic acid will precipitate spontaneously and can be separated directly. Regarding the methods applicable for this, the above statements regarding acid treatment apply accordingly.

[0041] If necessary, separation of solid aminobenzoic acid present in aqueous solution from solid microorganisms is best achieved by centrifugation. This applies to all embodiments of the present invention in which such a separation is required.

[0042] The aminobenzoic acid obtained in one of the ways described above can be further processed before carrying out the decarboxylation. Washing with aqueous washing media, especially water, is preferred. To avoid yield losses, the pH of the aqueous washing medium can be adjusted to the same value as after the acid addition (or, in the case of yeasts, the base addition) has ended; thus, in this embodiment, washing is carried out with a dilute acid instead of water. Suitable acids for this purpose are those mentioned above in connection with the acid treatment.

[0043] The aminobenzoic acid thus provided chemically or fermentatively is Step (II) to Aniline is decarboxylated. The catalyst used for this purpose is characterized according to the invention by a high aluminum oxide mass fraction (at least 40%, determined as described above). The aluminum oxide is preferably γ-Al 2 O 3 or η-Al 2 O 3 , in particular when no other metal oxides are present besides aluminum oxide. In principle, other metal oxides can also be present besides aluminum oxide, in particular magnesium oxide (MgO) in a mass fraction based on the total mass of the metal oxides of 1.0% to 60.0%, preferably 2.0% to 50.0%, particularly preferably 5.0% to 35.0%. Furthermore, the catalyst to be used according to the invention can contain SiO 2 in a mass fraction based on its total mass of 1.0% to 30.0%, preferably 2.0% to 20.0%, particularly preferably 2.0% to 10.0%.

[0044] As for the reaction conditions, the decarboxylation can be carried out over a wide range of temperature and pressure. A suitable reaction temperature is preferably in the range of 150°C to 300°C, more preferably 160°C to 280°C, and most preferably 180°C to 240°C. The (absolute) reaction pressure can be 0.05 bar to 300 bar, preferably 1.0 bar to 100 bar, and most preferably 1.0 bar to 60 bar.

[0045] In one embodiment of the invention, the decarboxylation is carried out in the presence of aniline, ie the aminobenzoic acid is dissolved in aniline. When the reaction is carried out batchwise, before the startthe decarboxylation, a mass fraction of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90%, preferably 1.0% to 70%, particularly preferably 5.0% to 50% is set. If the reaction is carried out continuously, during the decarboxylation always a mass fraction of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90%, preferably 1.0% to 70%, particularly preferably 5.0% to 50%.

[0046] In addition to aniline, other solvents or diluents can of course also be used, especially water. Furthermore, organic, polar, or protic solvents are preferably suitable, such as halogenated aliphatic or aromatic hydrocarbons, linear or cyclic ethers, linear or cyclic esters, linear or cyclic amides, alcohols, ketones, nitriles, phenol derivatives, benzanilides, sulfonamides, or sulfolane, which preferably have a boiling point that, under the selected conditions, is higher than the selected reaction temperature and, at this temperature, preferably forms a homogeneous reaction mixture with the reaction components.

[0047] As far as the reaction procedure is concerned, both gas phase and liquid phase are suitable. The reaction can be carried out continuously (preferred) or discontinuously.

[0048] Preferred procedures include carrying out the decarboxylation of the aminobenzoic acid in the liquid or gas phase in a reactor, in particular in a tubular reactor, with an integrated fixed bed of the catalyst (including a bed of the catalyst as a shaped body (extrudates) or a configuration of the catalyst as a monolithic structure), in the liquid or - preferably - gas phase in a fluidized bed reactor or in the liquid phase in a stirred tank with a suspension contained therein (slurry) of the catalyst.

[0049] In the context of the present invention, a Tubular reactor A tubular reactor is understood as a tubular reactor through which the reacting reaction mixture flows during operation in continuous reaction mode (which is preferred). Tubular reactors with small length-to-diameter ratios are also called Tower reactorsThese are also covered by the inventive understanding of the term tubular reactor.

[0050] The use of catalyst moldings (extrudates) or monolithic catalyst structures allows easy reuse of the catalyst after decarboxylation. "After decarboxylation" In the case of a batch process, this means after the maximum conversion of a batch of aminobenzoic acid to be converted has been reached. In the case of a continuous process, this means "after decarboxylation"the point in time at which the conversion drops significantly below the initial conversion (the conversion at the start of a new reaction cycle with new or regenerated catalyst) (in particular to a value of 97.0% or less of the initial conversion) and the reaction is therefore not continued. All methods known in the art for monitoring continuously carried out reactions are suitable for determining the conversion, in particular high-performance liquid chromatography (HPLC) or gas chromatography (GC). The common methods generally produce consistent results within the limits of measurement accuracy. If, contrary to expectations, different methods produce significantly different results for the conversion at a specific point in time, the conversion determination using high-performance liquid chromatography (HPLC) is decisive for the purposes of the present invention.

[0051] The catalyst remaining after decarboxylation is regenerated before reuse. This can be done by washing the catalyst with organic solvents or aqueous solutions and / or burning it out at elevated temperatures in the presence of O2 to remove organic deposits.

[0052] The aniline formed can be isolated and purified using standard techniques, particularly distillation.

[0053] The aniline obtained in this way can be used in Step (III) diverse subsequent applications under the formation of a Aniline derivative The following implementations are examples: (1) Acid-catalyzed reaction of aniline with formaldehyde to form di- and polyamines of the diphenylmethane series; (2) Acid-catalyzed reaction of aniline with formaldehyde to form di- and polyamines of the diphenylmethane series, followed by their reaction with phosgene to form di- and polyisocyanates of the diphenylmethane series; or (3) Conversion of aniline to an azo compound.

[0054] The further reaction of aniline with formaldehyde to Di- and polyamines of the diphenylmethane series (III)(1) is known per se and can be carried out by any prior art process. The continuous or partially discontinuous preparation of di- and polyamines of the diphenylmethane series from aniline and formaldehyde is disclosed, for example, in EP 1 616 890 A1, US-A-5286760, EP-A-451442, and WO-A-99 / 40059. The reaction takes place under acid catalysis. Hydrochloric acid is preferably suitable as the acid catalyst.

[0055] The further reaction of the resulting di- and polyamines of the diphenylmethane series with phosgene to Di- and polyisocyanates of the diphenylmethane series (III)(2) is also known per se and can be carried out using any prior art method. Suitable methods are described, for example, in EP 2 077 150 B1, EP 1 616 857 A1, EP 1 873 142 A1, and EP 0 314 985 B1.

[0056] The conversion of the aniline obtained according to the invention to Azo compounds, in particular azo dyes (III)(3) can also be carried out using any known method. Examples include the known production of aniline yellow (para-aminoazobenzene; CAS 493-5-7) or indigo (2,2'-bis(2,3-dihydro-3-oxomethylidene); CAS 482-89-3).

[0057] The invention is explained in more detail with reference to the following examples. Examples: Connections used: Educts:

[0058] Anthranilic acid (AS, petrochemical): C 7 H 7 NO 2 , purity ≥ 98%, Acros Organics Anthranilic acid (AS, biogenic): C 7 H 7 NO 2 , purity: 98%, Covestro Deutschland AG Aniline (ANL): C 6 H 7 N, purity ≥ 99.5%, Sigma-Aldrich 2-Aminobenzanilide (AMD): C 13 H 12 N 2 O, purity 95%, abcr GmbH Demineralized water: deionized Catalysts:TiO 2 (Anatas, ST61120), SAINT-GOBAIN SiO 2 (SS61138), SAINT-GOBAIN Mesostrukturiertes SiO 2 (MCM-41, - 1000 m 2< / g BET-SA, Sigma-Aldrich) ZrO 2 (tetragonal, SZ61152), SAINT-GOBAIN W-dotiertes ZrO 2 (SZ61143), SAINT-GOBAIN ZnO (≥ 99%), Sigma-Aldrich Pural Zn44 (44 % Zn in Al 2 O 3 ), Sasol MgO (Reinheit - 98 %), Acros Organics Pural MG5 (Mischoxid, Massenverhältnis MgO : Al 2 O 3 5 : 95), Sasol Pural MG20 (Massenverhältnis MgO : Al 2 O 3 20 : 80), Sasol Pural MG30 (spinellartige Struktur, Massenverhältnis MgO : Al 2 O 3 30 : 70), Sasol Al 2 O 3 (Al 4126 E), BASF γ-Al 2 O 3 (SA6175), SAINT-GOBAIN Silylated γ-Al 2 O 3 (SA6175), SAINT-GOBAIN Pural TH100-AlO(OH), Sasol η-Al 2 O 3 (Eta-Alox V1900) Siralox 5 (Massenverhältnis SiO 2 : Al 2 O 3 5 : 95), Sasol Siralox10 (Massenverhältnis SiO 2 :Al 2 O 3 10 : 90), Sasol Siralox30 (Massenverhältnis SiO 2 : Al 2 O 3 30 : 70), Sasol Zeolite CBV600 (Na 2 O · Al 2 O 3 · SiO 2 , Massenverhältnis SiO 2 / Al 2 O 3 = 5,2;contains 0.2 mass% Na 2 O), Zeolyst International. Puralox SCFa-160 / Ce20, 160 m 2< / g BET-SA, Sasol Puralox SCFa-190 / Zr20, 190 m 2< / g BET-SA, Sasol Puralox TH100-150 / Ti10, 150 m 2< / g BET-SA, Sasol Puralox TH100 / 150 / L4, 150 m 2< / g BET-SA, Sasol; Catalyst preparation:

[0059] All catalysts for reactions under slurry conditions were sieved (45-90 µm) before use and dried for 3 h at 10 mbar and 200 °C. The catalysts were then stored under an Ar atmosphere until use. Method description:

[0060] HPLC:For HPLC analysis, an Agilent setup with UV detection (DAD, measured at 254 nm) was used. An Agilent column (Eclipse XDB-C18; 5 µm; 4.6 x 150 mm) was used for separation. A mixture of MeOH and buffer was used as the eluent (volume ratio MeOH:buffer = 40:60, buffer: 0.7 mL of 85% pA H3PO4 was diluted to a final volume of 1 L with HPLC water, whereby the pH value was adjusted to 3.0 with sodium hydroxide solution before final filling). The flow rate was 0.7 mL / min. The column oven was heated to 40 °C. The injection volume was 1 µL. The retention times of the individual components aniline (ANL), anthranilic acid (AA), and 2-aminobenzanilide (ABD) were: ANL = 3.2 min; AA = 5.2 min; amide = 15.7 min.

[0061] The peak areas are converted to area percent (A%). The quantification of the individual components in mass percent (wt%), based on the reaction mixture, was made possible by a previously performed calibration with pure substances. In addition to the mass composition, the conversion of anthranilic acid, the yield of aniline formed, the selectivity of aniline formation, and the selectivity for the formation of 2-aminobenzanilide are determined based on these values. General Procedure 1: Decarboxylation of anthranilic acid (slurry; examples 1 to 62)

[0062] The decarboxylation of anthranilic acid is carried out in a steel reactor filled with 1.6 g of anthranilic acid, aniline (optional, for quantity see Table 1), powdered catalyst (optional, for quantity see Table 2) and deionized water (optional, for quantity see Table 1). The steel reactor is then sealed and flushed with Ar. The reaction mixture is then stirred for a defined reaction time at a defined temperature and 360 rpm. During this time, pressure builds up due to the release of CO2. The reaction mixture is then cooled in an ice bath, the pressure is released and the mixture is diluted with 4.0 g of methanol. The diluted mixture is filtered and characterized by HPLC analysis. General Procedure 2: Decarboxylation of anthranilic acid (extrudates; Examples 63 to 74)

[0063] For the decarboxylation of anthranilic acid with extrudates, Al 2 O 3 extrudates (BASF; Al 4126 E) in cylindrical form (cross-sectional diameter ≈ 3 mm, length ≈ 4.5 mm) were used, and their recyclability was investigated over 6 catalyst recycling cycles. For this purpose, 1.6 g of anthranilic acid were placed in an autoclave with a stainless steel cage containing 0.2 g of Al 2 O 3 extrudates. Subsequently, 0.25 g of distilled water (13.5 wt%) was added. After reducing the pressure to 100 mbar and purging the reactor with Ar gas, the reaction mixture was heated to 225 °C and stirred for 1 h (360 rpm). During this time, pressure gradually built up due to the release of CO 2. The reaction mixture is then cooled in an ice bath, the pressure is released, and the mixture is diluted with approximately 4.0 g of methanol. The diluted mixture is characterized by HPLC analysis. The used extrudates are then used for the next reaction cycle.

[0064] The experiments are summarized in the following tables. The following abbreviations are used: V = Comparative example Cat. = Catalyst ANL = Aniline AS = Anthranilic acid AMD = 2-Aminobenzanilide Table 1: Metal oxide compositions of the tested catalysts catalyst Al2O3 MgO SiO2 TiO2 ZnO ZrO2 CeO2 La2O3 Nr. Designation Mass fraction in %, based on the total mass of all metal oxides present in the material K1 TiO 2 (anatase) 0 0 0 100 0 0 0 0 K2 SiO2 0 0 100 0 0 0 0 0 K3 MCM41 / SiO2 0 0 100 0 0 0 0 0 K4 ZrO2 0 0 0 0 0 100 0 0 K5 W-doped ZrO 2 0 0 0 0 0 ≥90 0 0 K6 ZnO 0 0 0 0 100 0 0 0 K7 MgO 0 100 0 0 0 0 0 0 K8 Zeolite CBV 600 24,6 0 75,4 0 0 0 0 0 K9 η-Al 2 O 3 100 0 0 0 0 0 0 0 K10 γ-Al 2 O 3 100 0 0 0 0 0 0 0 K11 γ-Al 2 O 3 ;silylated 100 0 0 0 0 0 0 0 K12 Al 2 O 3 (BASF, Al 4126 E) 100 0 0 0 0 0 0 0 K13 TH100-AlO(OH) (boehmite) 100 0 0 0 0 0 0 0 K14 Pural ®< ZN44 56 0 0 0 44 0 0 0 K15 Pural ®< MG5 95 5 0 0 0 0 0 0 K16 Pural ®< MG20 80 20 0 0 0 0 0 0 K17 Pural ®< MG30 70 30 0 0 0 0 0 0 K19 Siralox ®< 5 95 0 5 0 0 0 0 0 K20 Siralox ®< 10 90 0 10 0 0 0 0 0 K21 Siralox ®< 30 70 0 30 0 0 0 0 0 K22 Puralox ®< SCFa-160 / Ce20 79,7 0 0 0 0 0 20,3 0 K23 Puralox ®< SCFa-190 / Zr20 79,6 0 0 0 0 20,4 0 0 K24 Puralox ®< TH100-150 / Ti10 89,6 0 0 10,4 0 0 0 0 K25 Puralox ®< TH100 / 150 / L4 96,0 0 0 0 0 0 0 4,0 Table 2 Changing catalysts. Decarboxylation of anthranilic acid to aniline. Reaction temperature T = 185 °C; reaction time t R = 20 min. e.g. Cat.[a] AS t=t0 [b] ANL t = t0 [b] H 2 O [b] ANL t = t R [c] AS t=tR [c] AMD t=tR [c] A ANL [d] X AS [e] S ANL [f] S AMD [f] 1 (V) - 0 50,0 50,0 0 57,5 41,7 0,8 17,1 19,0 90,0 5,0 2 (V) K1 5,9 50,0 50,0 0 58,1 41,0 0,9 18,2 20,4 89,4 5,3 3 (V) K2 5,9 50,0 50,0 0 59,4 39,6 1,0 21,3 23,7 89,7 5,1 4 (V) K3 5,9 50,0 50,0 0 61,4 37,5 1,1 25,3 28,0 90,4 4,8 5 (V) K4 5,9 50,0 50,0 0 59,8 39,3 0,8 21,8 23,9 91,4 4,3 6 (V) K5 5,9 50,0 50,0 0 65,1 34,1 0,8 32,9 34,9 94,1 3,0 7 (V) K6 5,9 50,0 50,0 0 67,2 32,3 0,4 38,1 39,2 97,2 1,4 8 (V) K7 5,9 50,0 50,0 0 70,3 29,2 0,6 44,4 45,8 97,1 1,5 9(V) K8 5,9 50,0 50,0 0 71,2 28,1 0,7 46,2 47,8 96,6 1,7 10 K9 5,9 50,0 50,0 0 94,7 5,0 0,3 90,8 91,5 99,2 0,4 11 K10 5,9 50,0 50,0 0 94,3 5,2 0,5 90,0 91,1 98,8 0,6 12 K11 5,9 50,0 50,0 0 95,5 4,1 0,4 92,1 93,0 99,1 0,5 13 K12 5,9 50,0 50,0 0 88,4 11,1 0,5 79,5 80,5 98,6 0,7 13a K12 5,9 50,0 [g] 50,0 0 92,5 7,2 0,3 86,8 87,5 99,2 0,4 14 K13 5,9 50,0 50,0 0 89,0 10,4 0,6 80,5 81,9 98,3 0,9 15 K14 5,9 50,0 50,0 0 73,7 25,8 0,6 51,2 52,6 97,4 1,3 16 K15 5,9 50,0 50,0 0 95,6 4,2 0,1 92,5 92,8 99,7 0,2 17 K16 5,9 50,0 50,0 0 96,8 3,1 0,1 94,6 95,0 99,8 0,1 18 K17 5,9 50,0 50,0 0 96,5 3,4 0,1 94,0 94,2 99,7 0,1 18a K17 5,9 50,0 [g] 50,0 0 97,0 2,9 0,1 94,9 95,1 99,8 0,1 20 K19 5,9 50,0 50,0 0 95,7 4,0 0,3 92,5 93,1 99,4 0,3 21 K20 5,9 50,0 50,0 0 95,4 4,3 0,3 92,0 92,7 99,3 0,4 22 K21 5,9 50,0 50,0 0 77,8 21,4 0,9 59,3 61,3 96,8 1,6 23 K22 5,9 50,0 50,0 0 82,6 16,9 0,6 68,7 70,0 98,1 1,0 24 K23 5,9 50,0 50,0 0 74,0 25,3 0,7 51,6 53,3 96,8 1,6 25 K24 5,9 50,0 50,0 0 76,2 23,2 0,6 56,4 57,9 97,5 1,3 26 K25 5,9 50,0 50,0 0 74,5 24,9 0,6 52,9 54,3 97,4 1,3 Table 3: Changing reactant mixture compositions. Decarboxylation of anthranilic acid to aniline. Reaction temperature T = 185 °C. e.g. Cat. [a] AS t=t0 [b] ANL t=t0 [b] H 2 O [b] t R / min ANL t = tR [c] AS t=tR [c] AMD t=tR [c] A ANL [d] X AS [e] S ANL [f] S AMD [f] 27 - 0 50,0 50,0 0 60 75,2 22,8 1,9 53,9 58,5 92,2 3,9 28 K17 5,9 50,0 50,0 0 60 98,4 1,5 0,1 97,2 97,4 99,7 0,1 29 (V) - 0 60,0 40,0 0 60 75,0 23,0 2,2 61,8 66,0 94,0 3,1 30 K17 6,9 60,0 40,0 0 60 98,2 1,7 0,1 97,5 97,7 99,7 0,1 31 (V) - 0 72,0 28,0 0 60 72,8 24,7 2,5 67,7 71,4 94,8 2,6 32 K17 8,3 72,0 28,0 0 60 97,1 2,7 0,2 96,9 97,1 99,7 0,1 33 (V) - 0 88,0 12,0 0 60 70,4 26,9 2,7 72,9 76,0 95,9 2,1 34 K17 10 88,0 12,0 0 60 91,0 8,6 0,4 92,5 92,9 99,5 0,2 35 (V) - 0 100 0 0 60 70,0 27,1 3,0 77,0 80,0 96,4 1,8 36 K17 11 100 0 0 60 85,2 14,0 0,8 89,3 90,0 99,2 0,4 37 K12 20 100 0 0 180 98,1 1,0 0,9 98,5 99,3 99,2 0,4 38 K12 5,9 100 0 0 180 97,2 0,6 2,2 97,6 99,6 98,0 1,0 Table 4: Varying water contents. Decarboxylation of anthranilic acid to aniline. Reaction temperature T = 185 °C. Reaction time t R = 20 min. e.g. Cat. [a] AS t=t0 [b] ANL t=t 0 [b] H 2 O [b] ANL t = t R [c] AS t=tR [c] AMD t=tR [c] A ANL [d] X AS [e] S ANL [f] S AMD [f] 39 (V) - 0 48,0 48,0 5,0 58,6 40,7 0,7 18,9 20,7 91,2 4,4 40 (V) - 0 45,0 45,0 10,0 61,1 38,3 0,6 25,1 26,5 94,6 2,7 41 (V) - 0 43,0 43,0 13,0 63,4 36,2 0,4 30,1 31,1 96,6 1,7 42 K12 5,6 48,0 48,0 5,0 94,5 5,3 0,2 90,5 90,9 99,5 0,2 43 K12 5,4 45,0 45,0 10,0 94,0 5,9 0,1 89,5 89,8 99,6 0,2 44 K12 5,2 43,0 43,0 13,0 94,8 5,1 0,1 90,9 91,2 99,7 0,1 45 K10 5,6 48,0 48,0 5,0 94,5 5,4 0,1 90,4 90,7 99,7 0,2 46 K10 5,4 45,0 45,0 10,0 95,3 4,7 0,1 91,8 92,0 99,8 0,1 47 K10 5,2 43,0 43,0 13,0 95,6 4,3 0,1 92,5 92,7 99,8 0,1 48 K17 5,6 48,0 48,0 5,0 96,7 3,2 0,05 94,4 94,6 99,9 0,06 49 K17 5,4 45,0 45,0 10,0 96,0 4,0 0,04 93,1 93,2 99,9 0,05 50 K17 5,2 43 43 13 93,6 6,4 0,02 89,0 89,1 99,9 0,03 Table 5: Varying water contents, reaction temperatures and durations, as well as different anthranilic acid sources with K17 or K12. Decarboxylation of anthranilic acid to aniline. e.g. Cat. [a] AS t=t0 [b] AN L t=t 0 [b] H 2 O [b] T / °C t R / min ANL t=t R [c] A St=t R [c] AMD t=t R [c] A ANL [d] X AS [e] S ANL [f] S AMD [f] 51 K17 5,9 50 50 0 185 60 98,9 1,0 0,1 98,1 98,3 99,8 0,1 52 K17 5,6 48 48 5,0 185 60 98,9 1,1 0,04 98,1 98,2 99,9 0,05 53 K17 5,9 50 50 0 200 20 98,7 1,2 0,1 97,8 97,9 99,8 0,1 54 K17 5,9 50 50 0 200 60 99,1 0,8 0,1 98,4 98,7 99,8 0,1 55 K17 5,6 48 48 5,0 200 60 99,3 0,6 0,1 98,8 98,9 99,9 0,06 56 K17 5,9 50 50 0 225 20 98,7 1,2 0,1 97,8 98,0 99,8 0,1 57 K17 5,9 50 50 0 225 60 99,2 0,7 0,1 98,6 98,9 99,7 0,1 57a K17 5,9 50 [g] 50 0 225 60 97,9 1,9 0,2 96,4 96,8 99,6 0,2 58 K17 5,6 48 48 5,0 225 60 99,2 0,7 0,1 98,6 98,8 99,8 0,1 59 K17 5,9 50 50 0 230 20 98,8 1,1 0,1 98,0 98,2 99,8 0,1 60 K17 5,9 50 50 0 230 60 99,2 0,7 0,1 98,6 98,9 99,7 0,1 61 K17 5,6 48 48 5,0 230 60 99,0 0,9 0,1 98,4 98,5 99,8 0,1 62 K12 9,7 86,5 0 13,5 225 60 99,5 0,2 0,3 99,6 99,9 99,7 0,1 62a K12 9,7 86,5 [g] 0 13,5 225 60 98,9 0,6 0,5 99,2 99,6 99,5 0,2 Table 6: Use of the catalyst as an extrudate and recycling it. Decarboxylation of anthranilic acid to aniline without dilution with ANL. e.g. Cat. [h] AS t=t0 [b] ANL t=t0 [b] H 2 O [b] T / °C t R / min ANL t=tR [c] AS t=tR [c] AMD t=tR [c] A ANL [d] X AS [e] S ANL [f] S AMD [f] 63 K12 9,7 86,5 0 13,5 225 60 98,3 0,5 1,2 98,6 99,6 98,9 0,5 64 K12 9,7 86,5 0 13,5 225 60 98,2 0,7 1,1 98,6 99,5 99,0 0,5 65 K12 9,7 86,5 0 13,5 225 60 98,8 0,1 1,1 98,9 99,9 99,1 0,5 66 K12 9,7 86,5 0 13,5 225 60 98,7 0,4 0,9 98,9 99,7 99,2 0,4 67 K12 9,7 86,5 0 13,5 225 60 98,7 0,4 0,9 98,9 99,7 99,2 0,4 68 K12 9,7 86,5 0 13,5 225 60 99,0 0,2 0,7 99,2 99,8 99,4 0,3 69 K12 9,7 86,5 0 13,5 225 60 99,0 0,1 0,9 99,1 99,9 99,2 0,4 70 K12 9,7 86,5 0 13,5 225 60 98,8 0,3 0,9 99,0 99,8 99,2 0,4 71 K12 9,7 86,5 0 13,5 225 60 98,7 0,5 0,9 98,9 99,7 99,2 0,4 72 K12 9,7 86,5 0 13,5 225 60 98,9 0,3 0,8 99,1 99,8 99,3 0,3 73 K12 9,7 86,5 0 13,5 225 60 98,6 0,4 1,0 98,9 99,7 99,1 0,4 74 K12 9,7 86,5 0 13,5 225 60 99,1 0,3 0,6 99,2 99,8 99,5 0,3 Explanations of the tables:

[0065] [a] Mass fraction in % based on the sum of AS, ANL, H2O and cat.; catalyst is used as a powder (slurry); [b] Mass fraction in % in the reactant mixture, based on the total mass of AS, ANL and H2O; [c] Mass fraction in % in the product mixture, based on the total mass of AS, ANL and 2-aminobenzanilide; [d] Chemical yield of aniline in %; [e] Chemical conversion of anthranilic acid in % [f] Selectivity to aniline or 2-aminobenzanilide in %; [g] Anthranilic acid produced by fermentation; [h] Mass fraction in % based on the sum of AS, ANL, H2O and cat.; catalyst is used as an extrudate. In Examples 63 to 74, the catalyst from the previous example was reused. Example 74 therefore represents the twelfth usage cycle in the sense of catalyst recycling over several experiments.

[0066] As the examples demonstrate, the process according to the invention enables the conversion of aminobenzoic acid with high conversions and low by-product formation, leading to a high yield of aniline. The catalysts according to the invention enable the formation of aniline in very high yields with variable composition of the ANL / AA substrate mixture, the water content, and a variable process window with respect to reaction time and temperature. The technical effect of the catalysts according to the invention in terms of increased aniline yield compared to the prior art was demonstrated. The catalyst can be used as a slurry or extruded solid. Long-term stability of the catalyst was demonstrated over 12 cycles without a noticeable decrease in aniline yield. The catalysts according to the invention are suitable for the decarboxylation of petrochemically produced anthranilic acid as well as biogenically derived anthranilic acid.

Claims

1. Process for preparing aniline or an aniline conversion product, comprising the steps of: (I) providing aminobenzoic acid; (II) decarboxylating the aminobenzoic acid to aniline in the presence of an inorganic heterogeneous metal oxide catalyst containing a proportion by mass of Al2O3 based on the total mass of the metal oxides of 40.0% to 100%, the proportion by mass of Al2O3 based on the total mass of the inorganic heterogeneous metal oxide catalyst being 25% to 100%; and (III) optionally converting the aniline to an aniline conversion product.

2. Process according to Claim 1, in which the inorganic heterogeneous metal oxide catalyst contains MgO in a proportion by mass based on the total mass of the metal oxides of 1.0% to 60.0%.

3. Process according to Claim 1 or 2, in which the inorganic heterogeneous metal oxide catalyst contains SiO2 in a proportion by mass based on its total mass of 1.0% to 30.0%.

4. Process according to any of the preceding claims, in which the Al2O3 comprises γ-Al2O3 or η-Al2O3.

5. Process according to any of the preceding claims, in which the decarboxylation of the aminobenzoic acid is performed at a temperature of 150°C to 300°C.

6. Process according to Claim 5, in which the decarboxylation of the aminobenzoic acid is performed at an absolute pressure of 0.05 bar to 300 bar.

7. Process according to any of the preceding claims, in which the decarboxylation of the aminobenzoic acid is performed in the presence of aniline.

8. Process according to Claim 7, in which the decarboxylation of the aminobenzoic acid is performed batchwise and a proportion by mass of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90% is established before the start of the decarboxylation.

9. Process according to Claim 7, in which the decarboxylation of the aminobenzoic acid is performed continuously and a proportion by mass of aniline, based on the total mass of aniline and aminobenzoic acid, of 0.1% to 90% is always established during the decarboxylation.

10. Process according to any of the preceding claims, in which the decarboxylation of the aminobenzoic acid is performed • in the liquid or gas phase in a reactor with an integrated fixed bed of the inorganic heterogeneous metal oxide catalyst, • in the liquid or gas phase in a fluidized bed reactor or • in the liquid phase in a stirred tank with a suspension of the inorganic heterogeneous metal oxide catalyst contained therein.

11. Process according to Claim 10, in which the decarboxylation of the aminobenzoic acid is performed in the liquid or gas phase in a reactor with an integrated fixed bed of the inorganic heterogeneous metal oxide catalyst containing a bed of the catalyst as shaped bodies or a configuration of the catalyst as a monolithic structure, the inorganic heterogeneous metal oxide catalyst being regenerated and reused on completion of decarboxylation.

12. Process according to any of the preceding claims, in which step (I) comprises the fermentation of a raw material containing a fermentable carbon-containing compound and a nitrogen-containing compound in the presence of microorganisms.

13. Process according to Claim 12, in which the microorganisms comprise Escherichia coli, Pseudomonas putida, Corynebacterium glutamicum, Ashbya gossypii, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, Zygosaccharomyces bailii or Saccharomyces cerevisiae.

14. Process according to any of the preceding claims, in which step (III) is performed and comprises one of the following conversions: (1) acid-catalyzed reaction of the aniline with formaldehyde to form di- and polyamines of the diphenylmethane series; (2) acid-catalyzed reaction of the aniline with formaldehyde to form di- and polyamines of the diphenylmethane series, followed by reaction thereof with phosgene to form di- and polyisocyanates of the diphenylmethane series; or (3) conversion of the aniline to an azo compound.

15. Process according to any of the preceding claims, in which the aminobenzoic acid provided in step (A) comprises ortho-aminobenzoic acid.