CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to US Provisional Application No. 62/750,565, dated October 25, 2019, which is incorporated herein in its entirety.

BACKGROUND

[0002] Aromatic acids, for example aromatic carboxylic acids, are important

intermediates for the preparation of linear polymers useful for films, fibers, or the like. Of particular importance are aromatic dicarboxylic acids such as purified terephthalic acid (PTA) and isophthalic acid (IPA), also known as 1,4- and l,3-benzenedicarboxylic acid, respectively, which are produced on large scale as key raw materials for various polymers, including thermoplastics like PET and PBT, and thermosetting polyester resins.

[0003] Most of the commercially applied processes for making aromatic carboxylic acids such as IPA use a soluble cobalt-manganese-bromine catalyst system to oxidize the starting xylene methyl groups. Acetic acid is generally used as solvent, and oxygen in compressed air is the oxidant, with reaction temperatures in the range of 140 to 2lO°C. The initial product obtained is commonly subjected to one or more further reaction, purification, or crystallization steps to obtain polymer grade aromatic carboxylic acids. The oxidation reaction is limited by catalyst degradation and byproduct contamination.

BRIEF DESCRIPTION

[0004] According to an aspect, a method for preparing an aromatic acid comprises contacting an alkyl aromatic compound, an oxidant, and a catalyst composition in a solvent under conditions effective to oxidize the alkyl aromatic compound and provide a reaction product comprising the aromatic acid, wherein the catalyst composition comprises, based on a total weight of the alkyl aromatic compound and the solvent, 400 to 1000 ppm by weight (ppm), preferably 500 to 800 ppm of cobalt; 200 to 500 ppm, preferably 300 to 400 ppm of manganese; 300 to 800 ppm, preferably 500 to 600 ppm of bromine; and 1 to 100 ppm, preferably 20 to 50 ppm of copper, and wherein the solvent comprises a carboxylic acid and water.

[0005] According to another aspect, a reaction mixture for the oxidation of an alkyl aromatic compound comprises the alkyl aromatic compound; an oxidant; and the catalyst composition. [0006] In another aspect, a reaction product is provided by oxidizing an alkyl aromatic compound with an oxidant in the presence of the catalyst composition, wherein the reaction product comprises an aromatic acid in an amount of greater than or equal to 90% by weight, based on the total weight of solids in the reaction product.

[0007] The above described and other features are exemplified by the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The figure is a bar graph of illustrating the experimental results from Examples 4 6

DETAILED DESCRIPTION

[0009] Described herein is a method for preparing an aromatic acid by oxidation of an alkyl aromatic compound. The method disclosed herein can lower production costs by minimizing raw material consumption, catalyst consumption, and processing equipment degradation.

[0010] The method for preparing the aromatic acid includes contacting an alkyl aromatic compound with an oxidant and a catalyst composition in a solvent under conditions effective to oxidize the alkyl aromatic compound and provide the aromatic compound. The method can include contacting the alkyl aromatic compound with an oxidant in the liquid phase in a reaction zone. The liquid phase comprises the solvent, dissolved reactants, and catalyst composition.

The applied reaction conditions, such as temperature and pressure, in the reaction zone are such that the liquid phase is maintained and that the desired reaction occurs to obtain a desired conversion. The temperature, pressure, and residence time can vary based on a variety of factors including, for example, the reactor configuration, size, and whether the process is batch, continuous, or semi-continuous.

[0011] At least a portion of the components provides a liquid phase, although dissolution of one or more of the mixture components may not be complete during the process. The liquid phase may be formed by mixing the components at ambient conditions. The liquid phase can be formed as the temperature of the mixture increases to the oxidation temperature. A mixture of the components may be formed prior to the oxidation step, in the same or different vessel as that used in the oxidation step, such as a feed mix drum. Optionally, a mixture of the components can be formed in an oxidation reactor, e.g. adding various streams of the components individually and/or in combination to a continuous or semi-continuous oxidation reactor. The combined components, and/or various streams of the components may be heated before they are mixed together.

[0012] The reaction zone can include one or more reactors. The reactor can generally be any reactor for carrying out a liquid phase oxidation of an alkyl aromatic compound. For example, the reactor can be a continuous or semi-continuous stirred tank reactor, a batch reactor, a tower reactor, a tubular reactor, or a multi-tubular reactor. Any of the aforementioned reactors can be employed in series or in parallel.

[0013] The contacting of an alkyl aromatic compound with an oxidant and a catalyst composition can be at any suitable temperature. For example, temperature can be in a range of 120 to 250°C, preferably 140 to 220°C, more preferably 160 to 2lO°C.

[0014] The contacting of an alkyl aromatic compound with an oxidant and a catalyst composition can be at any suitable pressure. For example, the pressure can be in a range of 0.15 to 3 megapascal (MPa), preferably 0.15 to 1.5 MPa, more preferably 0.15 to 0.9 MPa.

[0015] The contacting of an alkyl aromatic compound with an oxidant and a catalyst composition can be for any suitable amount of time. For example, the contacting time can be 30 to 120 minutes, preferably 50 to 90 minutes, more preferably 60 to 70 minutes.

[0016] The contacting can be for 30 to 120 minutes at a temperature of 120 to 250°C and at a pressure of 0.15 to 3 MPa, preferably for 50 to 90 minutes at a temperature of 140 to 220°C and at pressure of 0.15 to 1.5 MPa. Optionally, the contacting can be for 60 to 70 minutes at a temperature of 160 to 2lO°C and at a pressure of 0.15 to 0.9 MPa.

[0017] The catalyst composition comprises cobalt, manganese, bromine, and a metal cocatalyst. More specifically, the catalyst composition comprises 400 to 1000 ppm, preferably 500 to 800 ppm of cobalt; 200 to 500 ppm, preferably 300 to 400 ppm of manganese; 300 to 800 ppm, preferably 500 to 600 ppm of bromine; and 1 to 100 ppm, preferably 20 to 50 ppm of copper, each based on the total weight of the alkyl aromatic compound and the solvent.

[0018] The molar ratio of the cobalt to the manganese can be, for example, 1:1 to 5:1, preferably 1:1 to 4:1, more preferably 1:1 to 3:1. That is, the ratio of cobalt atoms to manganese atoms in the catalyst composition can be 1:1 to 5:1, preferably 1:1 to 4:1, more preferably 1:1 to 3:1.

[0019] The catalyst composition can include 400 to 1000 ppm of the cobalt, 200 to 500 ppm of the manganese, 300 to 800 ppm of the bromine, and 20 to 50 ppm, preferably 20 to 45 ppm, more preferably 25 to 40 ppm, of copper, wherein the molar ratio of the cobalt to the manganese is 1:1 to 5:1. [0020] Optionally, the catalyst composition includes 500 to 800 ppm of the cobalt, 300 to 400 ppm of the manganese, 500 to 600 ppm of the bromine, and 20 to 50 ppm, preferably 20 to 45 ppm, more preferably 25 to 40 ppm, of copper, wherein the molar ratio of the cobalt to the manganese is 1:1 to 3:1.

[0021] An atomic ratio of bromine to a total amount of cobalt and manganese is 0.2 to 0.8. As used herein,“total amount of cobalt, manganese, and metal of the metal cocatalyst” means the total number of cobalt atoms, manganese atoms, and metal atoms of the metal cocatalyst.

[0022] The cobalt can be introduced in the form of a cobalt compound such as an inorganic or organic salt. For example, the cobalt compound can be cobalt bromide, cobalt acetate, cobalt carbonate, cobalt oxide, or a combination comprising at least one of the foregoing. The cobalt compound can be cobalt acetate, cobalt bromide, or a combination comprising at least one of the foregoing.

[0023] The manganese can be introduced in the form of a manganese compound such as an inorganic or organic salt. For example, the manganese compound can be manganese bromide, manganese acetate, manganese carbonate, manganese oxide, or a combination comprising at least one of the foregoing. The manganese compound can be manganese bromide or manganese acetate.

[0024] The bromine can be introduced as any suitable bromine-containing compound, such as bromine (Br ₂ ), organic bromides, and bromide salts. Organic bromides include alkyl bromides and aryl bromides. Bromide salts include metal bromides, hydrobromic acid, ammonium bromide, and bromide-containing ionic liquids. The bromine compound can include bromine, hydrobromic acid, a metal bromide, an organic bromide, ammonium bromide, or a combination comprising at least one of the foregoing. For example, the bromine compound can be an organic bromide such as benzyl bromide, bromobenzene, bromoacetic acid, dibromoacetic acid, tetrabromomethane, bromoacetyl bromide, or a combination comprising at least one of the foregoing.

[0025] The bromine compound can be a bromide-containing ionic liquid, for example, an aryl or alkyl ionic liquid. Suitable aryl ionic liquids include l-benzyl-3-methylimidazolium bromide, benzyltributylphosphonium bromide, benzyltributylammonium bromide, l-phenyl-3- methylimidazolium bromide, phenyltributylphosphonium bromide, phenyltributylammonium bromide, l,3-dibenzylimidazolium bromide, or the like, or a combination comprising at least one of the foregoing. Suitable alkyl ionic liquids include 1 -butyl-3 -methylimidazolium bromide, l-ethyl-3-methylimidazolium bromide, tetrabutylphosphonium bromide, trihexyltetradecylphosphonium bromide, tetrabutylammonium bromide, (2- hydroxyethyl)trimethylammonium bromide (choline bromide), or the like, or a combination comprising at least one of the foregoing.

[0026] For example, the ionic liquid can be l-benzyl-3-methylimidazolium bromide, benzyltributylphosphonium bromide, benzyltributylammonium bromide, l-phenyl-3- methylimidazolium bromide, phenyltributylphosphonium bromide, phenyltributylammonium bromide, l,3-dibenzylimidazolium bromide, 1 -butyl-3 -methylimidazolium bromide, l-ethyl-3- methylimidazolium bromide, tetrabutylphosphonium bromide, trihexyltetradecylphosphonium bromide, tetrabutylammonium bromide, (2-hydroxyethyl)trimethylammonium bromide, l-butyl- 3 -methylimidazolium bromotrichloroaluminate, or a combination comprising at least one of the foregoing. In a preferred embodiment, the ionic liquid comprises l-ethyl-3-methylimidazolium bromide or 1 -butyl- 3 -methylimidazolium bromotrichloroaluminate.

[0027] The bromine compound can be metal bromide. For example, the metal bromide can be iron bromide, cobalt bromide, manganese bromide, copper bromide, zinc bromide, silver bromide, thallium bromide, potassium bromide, sodium bromide, cesium bromide, magnesium bromide, or a combination comprising at least one of the foregoing. Optionally, the bromine compound and the cobalt compound comprise cobalt bromide. The bromine compound and the manganese compound can comprise manganese bromide.

[0028] The metal cocatalyst can comprise copper, preferably the metal cocatalyst is copper. The metal or semi-metal in the metal cocatalyst can be neutral (i.e., an oxidation state of 0) or cationic (e.g., an oxidation state of +1, +2, +3, or +4). The metal or semi-metal compounds of the metal cocatalyst can be used in the form of an inorganic salt or an organic salt, preferably as an organic salt (e.g., having an organic anion), more preferably as a Ci _-3 carboxylic acid salt such as a metal acetate. The metal cocatalyst can be an inorganic salt (e.g., having an inorganic anion), wherein the anion(s) can be the same or different, and can be fluoride, chloride, bromide, iodide, carbonate, cyanide, hydroxide, oxide (O ² ), sulfide (S ² ), nitrate, phosphate, sulfate, chromate, dichromate, permanganate, or the like. The metal or semi metal compound can be a mixed salt comprising one or more organic anions and one or more inorganic anions. The individual metal or semi-metal compounds of the metal cocatalyst can include one or more metals or semi-metals, for example two different metals or a metal and a semi-metal.

[0029] The metal cocatalyst (e.g., copper) can be present in an amount of 20 to 50 ppm, for example 20 to 45 ppm, or 20 to 40 ppm, or 25 to 40 ppm. At higher concentrations, greater by-products are formed due to an increase in the temperature of the exothermic reaction. This also results in the use of a greater amount of the reactants, catalyst, and solvent. Hence, rendering the process less efficient. At lower amounts, the beneficial results of the cocatalyst are not realized.

[0030] The alkyl aromatic compound can be a benzene or naphthalene compound substituted with two or three alkyl or hydroxyalkyl groups having 1-6 carbon atoms.

Particularly suitable alkyl groups are methyl, ethyl, and isopropyl groups; suitable hydroxyalkyl groups are hydroxymethyl and hydroxyethyl groups. The two or three of such groups present on the aromatic nucleus of the compound can be the same or different. The alkyl aromatic compound can be a di(Ci- ₆ alkyl) aromatic compound, for example, a di(Ci- ₆ alkyl) C _6-i 2 aryl compound such as a xylene, 2,6-dimethylnaphthalene, 2,7-dimethylnaphthalene, 2,6- diisopropylnaphthalene, or a combination comprising at least one of the foregoing. Optionally, the alkyl aromatic compound is meta-xylene. Preferably, the alkyl aromatic compound is para- xylene. Other examples of compounds include derivatives of alkyl aromatic compounds that are partially oxidized to their corresponding carboxylic acids and esters thereof, for example, a toluic acid such as m-toluic acid, methyl m-toluate, and an aromatic carboxy-aldehyde such as 2- carboxybenzaldehyde, 3-carboxybenzaldehyde, 4-carboxybenzaldehyde, or a combination thereof.

[0031] The aromatic acid can comprise at least two carboxylic acid groups. For example, the aromatic acid can comprise 2, 3, 4, or 5 carboxylic acid groups. The aromatic acid can be an aromatic diacid such as a dicarboxylic acid or an aromatic triacid such as a

tricarboxylic acid. For example, the aromatic acid can be a phenyl dicarboxylic acid, a phenyl tricarboxylic acid such as benzene-l,3,5-tricarboxylic acid, a naphthyl dicarboxylic acid, a naphthyl tricarboxylic acid, or a combination comprising at least one of the foregoing.

Preferably, the aromatic acid is a diacid such as phthalic acid, terephthalic acid, isophthalic acid, or a combination comprising at least one of the foregoing. The aromatic acid can be isophthalic acid. The aromatic acid can be terephthalic acid.

[0032] The carboxylic acid solvent is a solvent for the starting substituted aromatic compound and is substantially unaffected under the oxidation reaction conditions. Exemplary carboxylic acid solvents include lower aliphatic monocarboxylic acids having 1-7 carbon atoms, and benzoic acid. For example, the carboxylic acid solvent can be acetic acid, propionic acid, n- butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caproic acid, benzoic acid, or a combination comprising at least one of the foregoing. More preferably, an aliphatic carboxylic acid solvent with 2-4 carbon atoms is used. Most preferably, acetic acid is used as the solvent. [0033] The carboxylic acid solvent can further comprise water, for example, 1 to 10 wt%, preferably 2 to 8 wt%, more preferably 3 to 7 wt% of water, based on the total weight of the carboxylic acid solvent.

[0034] The amount of carboxylic acid solvent that is used is not critical, and the weight ratio of solvent to alkyl aromatic compound can be in the range of 3: 1 to 15: 1, preferably 4: 1 to 15: 1, more preferably 5: 1 to 15: 1.

[0035] The oxidant can be any oxidant (i.e., oxidizing agent) capable of catalytically oxidizing the alkyl aromatic compound to the corresponding aromatic acid. For example, the oxidant can be hydrogen peroxide, air, dioxygen (0 ₂ ), ozone (0 ₃ ), an anthraquinone, a C2-32 alkyl peroxide (R-O-O-R’), a C2-32 alkyl hydroperoxide (R-O-O-H), a C2-32 ketone peroxide (HOO(R ¹ )(R ² )COOC(R ³ )(R ⁴ )OOH, e.g., cyclohexanone peroxide), a C2-32 diacyl peroxide (R ¹ C(=0)00C(=0)R ² ), a C3-22 diperoxy ketal (R ¹ R ² C(00) ₂ CR ³ R ⁴ ), a C2-32 peroxyester (R ¹ C(=0)OOR ² ), a C2-32 peroxydicarbonate (R ¹ 0C(=0)00C(=0)0R ² ), a C2-32 peroxy acid (R ¹ C(=0)OOH), a C ₆ -32 perbenzoic acid (ArC(=0)OOH), a periodinane, a periodate, or a combination comprising at least one of the foregoing, wherein R and R’ are each independently alkyl, and R ¹ to R ⁴ are each independently alkyl, aryl, or R ¹ and R ² together form a cycloalkyl, R ³ and R ⁴ together form a cycloalkyl, or a combination thereof. Preferably, the oxidant can be air or dioxygen; more preferably air. The oxidant can be a gas comprising oxygen, e.g., air, carbon dioxide, and molecular oxygen. As used herein,“air” means ambient air that includes approximately 78 volume percent (vol%) of nitrogen and 21 vol% dioxygen. The gas may be a mixture of gasses. The amount of oxidant used in the process is preferably in excess (e.g., greater than 1 equivalent) of the stoichiometric amount required for the desired oxidation process.

[0036] The oxidant can be a nitrogen oxide such as nitric acid, nitric oxide, nitrous oxide, nitrogen dioxide, a nitrite salt, peroxynitrite, hyponitrite, or the like.

[0037] The catalyst composition can further include an ionic liquid promoter. For example, the ionic liquid promoter can include l,2-dimethyl-3-propylimidazolium

tris(trifluoromethylsulfonyl)methide, 1 -ethyl-3 -methylimidazolium chloride, l-ethyl-3- methylimidazolium hexafluorophosphate, l-ethyl-3-methylimidazolium nitrate, l-ethyl-3- methyl imidazolium tetrafluoroborate, 1 -ethyl-3 -methyl imidazolium trifluoromethylsulfonate, l-ethyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide , l-ethyl-3- methylimidazoliumbis(pentafluoroethylsulfonyl)imide, l-ethyl-2,3-dimethylimidazolium chloride, 1 -butyl-3 -methylimidazolium chloride, l-ethyl-2,3-dimethylimidazolium tosylate, 1- butyl- 3 -methylimidazolium methylsulfate, 1 -butyl-3 -methylimidazolium hexafluorophosphate, 1 -butyl-3 -methylimidazolium diethyleneglycol monomethylether sulfate, N-propyl-3- methylpyridinium bis(trifluoromethylsulfonyl)imide, l-butyl-3- methylimidazolium tetrafluoroborate, 1 -butyl-3 -methylimidazolium diethyleneglycol monomethylether sulfate, l-butyl-3-methylimidazolium phosphate, l-butyl-3- methylimidazolium octylsulfate, l-butyl-2,3-dimethylimidazolium chloride, N-butyl-3- methylpyridinium bis(trifluoromethylsulfonyl)imide, l-hexyl-3-methylimidazoliumchloride, 1- hexyl-3-methylimidazolium hexafluorophosphate, l-hexyl-3- methylimidazolium tetrafluoroborate, l-hexyl-2,3-dimethylimidazolium chloride, l-octyl-3- methylimidazolium chloride, l-decyl-3-methylimidazolium chloride, l-methyl-3- octylimidazolium chloride, 1 -methyl- 3 -octylimidazolium diethyleneglycol monomethylether sulfate, l-methyl-3-octylimidazolium octylsulfate, l-methyl-3-octylimidazolium

tetrafluoroborate, l-octadecyl-3 -methylimidazolium chloride, l-butyl-4-methylpyridinium chloride, l-butyl-4-methylpyridinium hexafluorophosphate, l-butyl-4-methylpyridinium tetrafluoroborate, N-octylpyridinium tris(trifluoromethylsulfonyl)methide, N-hexylpyridinium tetrafluoroborate, 4-methyl-N-butyl-pyridinium chloride, N-hexylpyridinium

bis(trifluoromethylsulfonyl)imide, 1 -butyl- 1 -methyl -pyrrolidinium chloride, l,l-dimethyl- pyrrolidinium tris(pentafluoroethyl)trifluorophosphate, 1 -hexyl- 1 -methyl -pyrrolidinium dicyanamide, 1 -octyl- l-methyl-pyrrolidinium chloride, tetramethylammonium

bis(trifluoromethyl)imide, tetrabutylammonium bis(trifluoromethyl)imide, tetraethylammonium tris(pentafluoroethyl)trifluorophosphate, and tetrabutylphosphonium

tris (pentafluoroethyl) trifluoropho sphate .

[0038] A reaction product is produced by oxidizing an alkyl aromatic compound with an oxidant in the presence of the catalyst composition. The reaction product can comprise an aromatic acid in an amount of greater than or equal to 90% by weight, based on the total weight of solids in the reaction product. For example, the reaction product can include the aromatic acid in an amount of greater than 95 wt%, or 96 to 99.5 wt%, or 97 to 99.5 wt%, based on the total weight of solids in the reaction product.

[0039] The reaction product comprising the aromatic acid can include less than 0.5 weight percent, preferably less than 0.25 weight percent, more preferably less than 0.05 weight percent of an aromatic carboxy-aldehyde. The reaction product comprising the aromatic acid can include less than 0.2 weight percent, preferably less than 0.1 weight percent, more preferably less than 0.05 weight percent of a toluic acid. The reaction product comprising the aromatic acid can include less than 0.5 weight percent, preferably less than 0.25 weight percent, more preferably less than 0.05 weight percent of an aromatic carboxy-aldehyde; and less than 0.2 weight percent, preferably less than 0.1 weight percent, more preferably less than 0.05 weight percent of a toluic acid.

[0040] The method can further include additional steps to isolate and purify the aromatic acid, for example isophthalic acid, as obtained by the process as described above. Such processing steps are described, for example, in relevant chapters of Ullmann's Encyclopedia of Industrial Chemistry (e.g. as available via

http://www.mrw.interscience.wiley.com/ueic/articles/a26 l93/sect3-fs.html), and in above-cited patent publications, and literature references cited therein; especially for producing IPA. Such further processing steps may include isolation steps like filtration or centrifugation, washing steps, secondary reaction steps like hydrogenation or post-oxidation, and re-crystallization and drying steps. In an embodiment, the additional steps can include adding an aqueous solvent to the reaction product and crystallizing the aromatic acid. For example, the crystallizing can further remove the corresponding toluic acid from the aromatic acid.

[0041] This disclosure is further illustrated by the following examples, which are non limiting.

EXAMPLES

[0042] The following components listed in Table 1 were used in the examples. Unless specifically indicated otherwise, the amount of each component is in weight percent in the following examples, based on the total weight of the composition.

Example 1

[0043] The oxidation reaction can be performed in a continuous flow stirred-tank reactor. The catalyst composition can be provided in the reactor by combining appropriate amounts of cobalt bromide, manganese bromide, and an acetic acid and water (10 wt%) mixture. Optionally, hydrobromic acid or silver bromide can be added to the reactor to increase the concentration of bromide. An appropriate amount of a cocatalyst such as zinc acetate or zinc bromide can then be added to the reactor. The cocatalyst can further include an appropriate amount of one or more of a thallium salt, an iron salt, a palladium salt, a vanadium salt, and a cesium salt. Meta-xylene and air are subsequently introduced into the reactor, and the reaction mixture stirred at 300 rpm at 140 to 220°C under a pressure of 1 to 3 MPa for 30 to 90 minutes to afford a reaction product comprising isophthalic acid.

Example 2

[0044] The oxidation reaction can be performed in a continuous flow stirred-tank reactor. The catalyst composition can be provided in the reactor by combining appropriate amounts of cobalt bromide, manganese bromide, and an acetic acid and water (10 wt%) mixture. Optionally, hydrobromic acid or silver bromide can be added to the reactor to increase the concentration of bromide. An appropriate amount of l-butyl-3- methylimidazolium bromotrichloroaluminate and a cocatalyst such as zinc acetate or zinc bromide can then be added to the reactor. The cocatalyst can further include an appropriate amount of one or more of a thallium salt, an iron salt, a palladium salt, a vanadium salt, and a cesium salt. Meta-xylene and air are subsequently introduced into the reactor, and the reaction mixture stirred at 300 rpm at 140 to 220°C under a pressure of 1 to 3 MPa for 30 to 90 minutes to afford a reaction product comprising isophthalic acid.

Example 3

[0045] The oxidation reaction can be performed in a continuous flow stirred-tank reactor. The catalyst composition can be provided in the reactor by combining appropriate amounts of cobalt acetate, manganese acetate, hydrobromic acid, and an acetic acid and water (10 wt%) mixture. Optionally, silver bromide can be added to the reactor to increase the concentration of bromide. A cocatalyst such as zinc acetate or zinc bromide can then be added to the reactor. The cocatalyst can further include an appropriate amount of one or more of a thallium salt, an iron salt, a palladium salt, a vanadium salt, and a cesium salt. Meta-xylene and air are subsequently introduced into the reactor, and the reaction mixture stirred at 300 rpm at 140 to 220°C under a pressure of 1 to 3 MPa for 30 to 90 minutes to afford a reaction product comprising isophthalic acid.

Examples 4 - 6

[0046] In Examples 4-6, para-xylene was oxidized in the presence of different compositions of catalyst and co-catalyst in acetic acid to product terephthalic acid. The oxidation reactions were carried out in a semi continuous flow stirred-tank reactor in the presence of air. The catalyst composition was provided in the reactor by combining appropriate amounts of cobalt acetate, manganese bromide, and an acetic acid, water (10 wt%) mixture, optionally, hydrobromic acid to increase the concentration of bromide. The measured amount of cocatalyst was dissolved in acetic acid solvent separately, and then it was added to reaction mixture comprising the catalyst.

[0047] The reaction conditions are set forth in Table 3. The products and results are set forth in Table 4.

[0048] As can be seen from Table 4 and the Figure, Example 6 (Ex. 6), comprising the Cu cocatalyst, attained the lowest amounts of carbon dioxide and nearly the theoretical yield of terephthalic acid. Additionally, the selectivity with substantially improved, e.g., as compared to Ex. 4 (Zn cocatalyst) wherein the“others” was 11.41 mol%, while Ex. 6 (Cu cocatalyst) comprised 2.43 mol%. Comparing Ex. 6 to Ex. 4 (Ni cocatalyst), Ex. 5 had a significant increase in C0 ₂ . The system with the Cu cocatalyst exhibited reduced byproducts, reduced C0 ₂ production, reduced 4CBA production (compared to Ex. A, no cocatalyst), and improved selectivity and conversion.

[0049] This disclosure further encompasses the following Aspects.

[0050] Aspect 1. A method for preparing an aromatic acid, the method comprising: contacting an alkyl aromatic compound, an oxidant, and a catalyst composition in a solvent under conditions effective to oxidize the alkyl aromatic compound and provide a reaction product comprising the aromatic acid, wherein the catalyst composition comprises, based on a total weight of the alkyl aromatic compound and the solvent, 400 to 1000 ppm, preferably 500 to 800 ppm of cobalt; 200 to 500 ppm, preferably 300 to 400 ppm of manganese; 300 to 800 ppm, preferably 500 to 600 ppm of bromine; and 20 to 50 ppm, preferably 20 to 45 ppm, more preferably 25 to 40 ppm of a metal cocatalyst, wherein the metal cocatalyst comprises copper, and wherein the solvent comprises a carboxylic acid and water.

[0051] Aspect 2. The method of Aspect 1, wherein at least one of: the contacting is at a temperature in a range of 120 to 250°C, preferably 140 to 220°C, more preferably 160 to 2lO°C; the contacting is at a pressure in a range of 0.15 to 3 MPa, preferably 0.15 to 1.5 MPa, more preferably 0.15 to 0.9 MPa; or the contacting is for 30 to 120 minutes, preferably 50 to 90 minutes, more preferably 60 to 70 minutes.

[0052] Aspect 3. The method of any one or more of the preceding Aspects, wherein a molar ratio of the cobalt to the manganese is 1:1 to 5:1, preferably 1:1 to 4:1, more preferably 1:1 to 3:1.

[0053] Aspect 4. The method of any one or more of the preceding Aspects, wherein an atomic ratio of bromine to a total amount of cobalt and manganese is 0.2 to 0.8.

[0054] Aspect 5. The method of any one or more of the preceding Aspects, wherein the cobalt was introduced to the catalyst in the form of a cobalt compound comprises cobalt bromide, cobalt acetate, cobalt carbonate, cobalt oxide, or a combination comprising at least one of the foregoing; and wherein the manganese compound comprises manganese bromide, manganese acetate, manganese carbonate, manganese oxide, or a combination comprising at least one of the foregoing.

[0055] Aspect 6. The method of any one or more of the preceding Aspects, wherein the bromine compound comprises bromine, hydrobromic acid, a metal bromide, an organic bromide, ammonium bromide, or a combination comprising at least one of the foregoing; preferably wherein the bromine compound comprises hydrobromic acid, benzyl bromide, bromobenzene, bromoacetic acid, dibromoacetic acid, tetrabromomethane, bromoacetyl bromide, or a combination comprising at least one of the foregoing.

[0056] Aspect 7. The method of any one or more of the preceding Aspects, wherein the bromine compound is an ionic liquid; preferably wherein the ionic liquid comprises l-benzyl-3- methylimidazolium bromide, benzyltributylphosphonium bromide, benzyltributylammonium bromide, 1 -phenyl-3 -methylimidazolium bromide, phenyltributylphosphonium bromide, phenyltributylammonium bromide, l,3-dibenzylimidazolium bromide, l-butyl-3- methylimidazolium bromide, 1 -ethyl-3 -methylimidazolium bromide, tetrabutylphosphonium bromide, trihexyltetradecylphosphonium bromide, tetrabutylammonium bromide, (2- hydroxyethyl)trimethylammonium bromide, 1 -butyl-3 - methylimidazolium bromotrichloroaluminate, or a combination comprising at least one of the foregoing; more preferably wherein the ionic liquid comprises 1 -ethyl-3 -methylimidazolium bromide or 1 -butyl- 3 -methylimidazolium bromotrichloroaluminate.

[0057] Aspect 8. The method of any one or more of the preceding Aspects, wherein the bromine compound is metal bromide; preferably wherein the metal bromide comprises cobalt bromide, manganese bromide, copper bromide, or a combination comprising at least one of the foregoing. [0058] Aspect 9. The method of any one or more of the preceding Aspects, wherein the catalyst composition is free of cerium. In other words, the catalyst composition comprises no cerium.

[0059] Aspect 10. The method of any one or more of the preceding Aspects, wherein the alkyl aromatic compound is a di(Ci- ₆ alkyl) aromatic compound; preferably xylene, 2,6- dimethylnaphthalene, 2,7-dimethylnaphthalene, 2,6-diisopropylnaphthalene, or a combination comprising at least one of the foregoing; more preferably meta-xylene or para-xylene; and the aromatic acid is an aromatic diacid, preferably a phenyl dicarboxylic acid, more preferably isophthalic acid or terephthalic acid.

[0060] Aspect 11. The method of any one or more of the preceding Aspects, wherein the oxidant comprises hydrogen peroxide, air, dioxygen, ozone, an anthraquinone, a C2-32 alkyl peroxide, a C2-32 alkyl hydroperoxide, a C2-32 ketone peroxide, a C2-32 diacyl peroxide, a C3-22 diperoxy ketal, a C2-32 peroxyester, a C2-32 peroxydicarbonate, a C2-32 peroxy acid, a C ₆ -32 perbenzoic acid, a periodinane, a periodate, or a combination comprising at least one of the foregoing; preferably air or dioxygen; more preferably air.

[0061] Aspect 12. The method of any one or more of the preceding Aspects, wherein the carboxylic acid is a C 1-7 carboxylic acid; preferably acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caproic acid, benzoic acid, or a combination comprising at least one of the foregoing; preferably wherein the solvent comprises acetic acid and 1 to 10 weight percent of water.

[0062] Aspect 13. A reaction mixture for the oxidation of an alkyl aromatic compound, the reaction mixture comprising the alkyl aromatic compound; an oxidant; and the catalyst composition of Aspect 1.

[0063] Aspect 14. A reaction product provided by oxidizing an alkyl aromatic compound with an oxidant in the presence of the catalyst composition of Aspect 1, wherein the reaction product comprises an aromatic acid in an amount of greater than or equal to 90% by weight, based on the total weight of solids in the reaction product.

[0064] Aspect 15. The method of Aspect 14, wherein the aromatic acid comprises: less than 0.5 weight percent, preferably less than 0.25 weight percent, more preferably less than 0.05 weight percent of an aromatic carboxy-aldehyde; and less than 0.2 weight percent, preferably less than 0.1 weight percent, more preferably less than 0.05 weight percent of a toluic acid.

[0065] The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate materials, steps, or components herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any materials (or species), steps, or components, that are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles.

[0066] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of“up to 25 wt%, or, more specifically,

5 wt% to 20 wt%”, is inclusive of the endpoints and all intermediate values of the ranges of“5 wt% to 25 wt%,” etc.).“Combinations” is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms“a” and“an” and“the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means“and/or” unless clearly stated otherwise. Reference throughout the specification to“some embodiments”,“an embodiment”,“another embodiment”, and so forth, means that a particular element described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements in any embodiment may be combined in any suitable manner in the various embodiments.

[0067] Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

[0068] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this application belongs. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

[0069] Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash ("-") that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, -CHO is attached through carbon of the carbonyl group.

[0070] The term "alkyl" means a branched or straight chain, unsaturated aliphatic hydrocarbon group, e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, s- pentyl, and n- and s-hexyl.“Alkenyl” means a straight or branched chain, monovalent hydrocarbon group having at least one carbon-carbon double bond (e.g., ethenyl (-HC=CH ₂ )). “Alkoxy” means an alkyl group that is linked via an oxygen (i.e., alkyl-O-), for example methoxy, ethoxy, and sec-butyloxy groups. "Alkylene" means a straight or branched chain, saturated, divalent aliphatic hydrocarbon group (e.g., methylene (-CH ₂ -) or, propylene (-(CH ₂ ) ₃ - )).“Cycloalkylene” means a divalent cyclic alkylene group, -C _n H _2n-x , wherein x is the number of hydrogens replaced by cyclization(s). “Cycloalkenyl” means a monovalent group having one or more rings and one or more carbon-carbon double bonds in the ring, wherein all ring members are carbon (e.g., cyclopentyl and cyclohexyl). "Aryl" means an aromatic hydrocarbon group containing the specified number of carbon atoms, such as phenyl, tropone, indanyl, or naphthyl. “Arylene” means a divalent aryl group. “Alkylarylene” means an arylene group substituted with an alkyl group. “Arylalkylene” means an alkylene group substituted with an aryl group (e.g., benzyl). The prefix "halo" means a group or compound including one more of a fluoro, chloro, bromo, or iodo substituent. A combination of different halo groups (e.g., bromo and fluoro), or only chloro groups can be present. The prefix“hetero” means that the compound or group includes at least one ring member that is a heteroatom (e.g., 1, 2, or 3 heteroatom(s)), wherein the heteroatom(s) is each independently N, O, S, Si, or P.

[0071] Unless specifically indicated otherwise, each of the foregoing groups can be unsubstituted or substituted, provided that the substitution does not significantly adversely affect synthesis, stability, or use of the compound.“Substituted” means that the compound, group, or atom is substituted with at least one (e.g., 1, 2, 3, or 4) substituents instead of hydrogen, where each substituent is independently nitro (-N0 ₂ ), cyano (-CN), hydroxy (-OH), halogen, thiol (- SH), thiocyano (-SCN), Ci _-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, Ci _-6 haloalkyl, C1-9 alkoxy, Ci _-6 haloalkoxy, C _3-i2 cycloalkyl, C5-18 cycloalkenyl, C _6-i2 aryl, C7-13 arylalkylene (e.g., benzyl), C _7-i2 alkylarylene (e.g, toluyl), C _4-i2 heterocycloalkyl, C _3-i2 heteroaryl, Ci _-6 alkyl sulfonyl (-S(=0) ₂ - alkyl), C _6-i2 arylsulfonyl (-S(=0) ₂ -aryl), or tosyl (CH ₃ C ₆ H ₄ S0 ₂ -), provided that the substituted atom’s normal valence is not exceeded, and that the substitution does not significantly adversely affect the manufacture, stability, or desired property of the compound. When a compound is substituted, the indicated number of carbon atoms is the total number of carbon atoms in the compound or group, including those of any substituents.

[0072] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.