CROSS-REFERENCE TO RELATED APPLICATION

The present application is an international filing which claims priority to U.S.

Provisional Serial No. 63/039,582, filed June 16, 2020, which is incorporated herein in its entirety.

BACKGROUND

[0001] Aromatic dicarboxylic acids (e.g., terephthalic acid) can be produced by oxidation of dimethyl aromatic compounds (e.g., para-xylene) in the presence of a catalyst.

[0002] U.S. Patent Number 5,453,538 discloses a process for the manufacture of aromatic dicarboxylic acids that uses bromine facilitated by the use of cerium along with the cobalt and manganese catalyst.

[0003] U.S. Patent Number 4,754,062 discloses a process for the manufacture of polycarboxylic acids, and where polycaxboxylic acids such as pseudocumene are converted to tiimeliitic acid which is used to manufacture plasticizers and polyamide-imide polymers used as molding compounds for replacement of metals.

SUMMARY

[0004] The present disclosure provides improved systems and methods for oxidizing dimethyl aromatic compounds (e.g., para-xylene) to produce aromatic dicarboxylic acids (e.g., terephthalic acid).

[0005] Provided is a method for oxidizing a dimethyl aromatic compound, including reacting the dimethyl aromatic compound and an oxidant in the presence of a catalyst system in a solvent to produce a reaction product including an aromatic dicarboxylic acid, such as terephthalic acid. The catalyst system includes a catalyst and a co-catalyst. The catalyst includes bromine, cobalt, and manganese. The co-catalyst includes iron. The iron is present in an amount of 10 to 100 parts per million by weight (ppm), such as 10 to 90 ppm, more particularly 10 to 50 ppm, based on the total weight of the dimethyl aromatic compound and the solvent. The bromine is present in an amount of 160 to 730 ppm, such as 200 to 400 ppm, more particularly 200 to 330 ppm, based on the total weight of the dimethyl aromatic compound and the solvent. The manganese is present in an amount of 100 to 450 ppm, such as 100 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent. The cobalt is present in an amount of 100 to 450 ppm, such as 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent. A total amount of cobalt and manganese in the catalyst can be greater than 300 to 900 ppm, such as greater than 300 to 800 ppm, more particularly greater than 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0006] A reaction mixture for the oxidation of a dimethyl aromatic compound by the method can include the dimethyl aromatic compound; the oxidant; the catalyst; the co-catalyst; water; and the solvent.

[0007] A reaction product can be produced by the method or using the reaction mixture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The following figures are exemplary embodiments wherein the like elements are numbered alike.

[0009] FIG. 1 is a process flow diagram of an embodiment of a process for oxidation of para-xylene to obtain terephthalic acid.

[0010] FIG. 2A is a graphical illustration of the mole percent of carbon monoxide and carbon dioxide (collectively “COx”) formed as over-oxidation products also referred to as by-products based on the total moles of reaction product, in Comparative Example A and Example 1 ; and the percent reduction in the moles of COx formed in Example 1 as compared to Comparative Example A.

[0011] FIG. 2B is a graphical illustration of the mole percent of COx formed as by products, based on the total moles of reaction product, in Comparative Example B and Example 2; and the percent reduction in the moles of COx formed in Example 2 as compared to Comparative Example B.

[0012] FIG. 2C is a graphical illustration of the mole percent of COx formed as by products, based on the total moles of reaction product, in Comparative Example C and Examples 3-4; and the percent reduction in the moles of COx formed in Examples 3-4 as compared to Comparative Example C.

[0013] FIG. 3A is a graphical illustration of the percent reduction in the weight of Cio+ hydrocarbons formed as by-products in Comparative Example A and Example 1 ; and the percent increase in the weight of terephthalic acid produced in Example 1 as compared to Comparative Example A; as used herein “Cio+ hydrocarbons” refers to hydrocarbons including 10 or more carbon atoms. [0014] FIG. 3B is a graphical illustration of the percent reduction in the weight of Cio+ hydrocarbons formed as by-products of Comparative Example B and Example 2; and the percent increase in the weight of terephthalic acid produced in Example 2 as compared to Comparative Example B.

[0015] FIG. 3C is a graphical illustration of the percent reduction in the weight of Cio+ hydrocarbons formed as by-products of Comparative Example C and Examples 3-4; and the percent increase in the weight of terephthalic acid produced in Examples 3-4 as compared to Comparative Example C.

[0016] FIG. 3D is a graphical illustration of the percent reduction in the weight of Cio+ hydrocarbons formed as by-products of Comparative Example C and Examples 3-4 as compared to Comparative Example A; and the percent increase in the weight of terephthalic acid produced in Comparative Example C and Examples 3-4 as compared to Comparative Example A.

[0017] The above described and other features are exemplified by the following detailed description, examples, and claims.

DETAILED DESCRIPTION

[0018] During production of aromatic dicarboxylic acids (e.g., terephthalic acid) by oxidation of dimethyl aromatic compounds (e.g., para-xylene) in the presence of a catalyst, by-products can be formed. As a result of by-product formation, consumption of the dimethyl aromatic compounds and solvent (e.g., acetic acid) can be undesirably high, e.g., due to oxidation of the aromatic dicarboxylic acids rather than oxidation of the dimethyl aromatic compounds and/or due to oxidation of solvent acetic acid.

[0019] Disclosed herein are methods for oxidizing dimethyl aromatic compounds to obtain aromatic dicarboxylic acids in the presence of a co-catalyst including iron. Desirably, the methods reduce side reactions that can consume the obtained aromatic dicarboxylic acids and solvent to form by-products. Previous methods for oxidizing dimethyl aromatic compounds suffered from side reactions, which can oxidize solvents or oxidize the aromatic dicarboxylic acids into by-products such as carbon monoxide, carbon dioxide, and/or Cio+ hydrocarbons.

[0020] The methods of the present disclosure use a catalyst system that includes a catalyst and a co-catalyst, the co-catalyst including iron. The methods for oxidizing dimethyl aromatic compounds to obtain aromatic dicarboxylic acids facilitate the reduction of the amount of carbon monoxide, carbon dioxide, and/or Cio+ hydrocarbons in the reaction product, and increase the purity of the aromatic dicarboxylic acids as compared to previous methods for oxidizing dimethyl aromatic compounds that did not utilize a co-catalyst including iron. For instance, the methods of the present disclosure can achieve a reduction in the total moles of COx produced equal to or greater than 5 mole %, such as equal to or greater than 10 mole %, more particularly at equal to or greater than 15 mole %, as compared to the total moles of COx produced in previous methods for oxidizing dimethyl aromatic compounds that did not utilize a co-catalyst including iron. Moreover, the methods of the present disclosure can achieve a reduction in the amount of Cio+ hydrocarbons produced equal to or greater than 10 weight percent (wt%), such as equal to or greater than 20 wt%, more particularly at equal to or greater than 30 wt%, as compared to the amount of Cio+ hydrocarbons produced in previous methods for oxidizing dimethyl aromatic compounds that did not utilize a co-catalyst including iron. Furthermore, the methods of the present disclosure can achieve an increase in the wt% of aromatic dicarboxylic acid produced equal to or greater than 0.5 wt%, such as equal to or greater than 1.0%, more particularly equal to or greater than 1.5 wt%, as compared to the moles of aromatic dicarboxylic acid produced in previous methods for oxidizing dimethyl aromatic compounds that did not utilize a co-catalyst including iron.

[0021] Moreover, it is observed that the amount of catalyst can be reduced as compared to previous methods. For instance, the present disclosure provides methods that allow for the inclusion of a lesser amount of manganese and/or bromine in the catalyst, while maintaining or improving the quality of aromatic dicarboxylic acid produced per milligram of catalyst. A reduction in the amount of manganese present can be equal to or greater than 25 wt%, such as equal to or greater than 50 wt%, more particularly equal to or greater than 75 wt%, as compared to the ppm of manganese present in previous methods for oxidizing dimethyl aromatic compounds. For example, manganese can be present in an amount in a range of 100 to 450 ppm, such as 100 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0022] Desirably, a reduction in the amount of bromine present can reduce, mitigate, or avoid corrosion of the equipment used for the oxidation or allow for use of different materials of construction for the equipment. A reduction in the amount of bromine present can be equal to or greater than 25 wt%, such as equal to or greater than 50 wt%, more particularly equal to or greater than 75 wt%, as compared to the ppm of bromine present in previous methods for oxidizing dimethyl aromatic compounds. For example, bromine can be present in the catalyst in an amount of 160 to 730 ppm, such as 200 to 400 ppm, more particularly 200 to 330 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0023] A method for oxidizing a dimethyl aromatic compound can include reacting the dimethyl aromatic compound and an oxidant in the presence of a catalyst system (e.g., a catalyst and a co-catalyst) in a solvent to produce a reaction product including an aromatic dicarboxylic acid.

[0024] The dimethyl aromatic compound can include at least one of xylene (e.g., least one of para-xylene, meta-xylene, or ortho-xylene), or 2,6-dimethylnaphthalene; such as para- xylene.

[0025] To catalyze the oxidation of the dimethyl aromatic compound, a catalyst is used. The catalyst includes bromine and manganese. For example, the catalyst can include bromine, cobalt, and manganese. Optionally, the catalyst can comprise no added titanium, chromium, vanadium, molybdenum, tin, cerium and zirconium. “No added” refers to the element being present in trace amounts as an impurity.

[0026] The catalyst can be unsupported and sources of the catalyst can be combined to form the catalyst as a catalyst mixture. Sources of the catalyst can include salts of cobalt (e.g., cobalt (II) acetate tetrahydrate) and manganese (e.g., manganese (II) acetate tetrahydrate). A bromine source can be at least one of hydrobromic acid, sodium bromide, ammonium bromide, or tetrabromoethane .

[0027] The total amount of catalyst (e.g., bromine, cobalt and manganese) can be present in an amount of greater than 460 to 1,630 ppm, such as 600 to 1,200 ppm, more particularly 600 to 1,130 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0028] The catalyst can include an amount of cobalt of 100 to 450 ppm, such as 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0029] The catalyst can include an amount of manganese of, for example, 100 to 450 ppm, such as 100 ppm to 400 ppm, based on a total weight of the dimethyl aromatic compound and the solvent.

[0030] A total amount of cobalt and manganese in the catalyst can be greater than 300 to 900 ppm, such as greater than 300 to 800 ppm, more particularly greater than 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0031] The catalyst can include cobalt, manganese, and bromine and a molar ratio of bromine to (cobalt and manganese) can be in a range of 0.3: 1 to 3: 1, such as 0.3: 1 to 2: 1, more particularly 0.3:1 to 1:1.

[0032] In addition to the catalyst, the method uses a co-catalyst. The co-catalyst can include iron in an amount of 10 to 100 ppm, such as 10 to 90 ppm, more particularly 10 to 50 ppm, based on the total weight of the dimethyl aromatic compound and the solvent. For instance, the catalyst can include cobalt and manganese and a weight ratio of iron to the total amount of cobalt and manganese can be in a range of 0.05: 1 to 0.25:1, such as 0.05: 1 to 0.20: 1, more particularly 0.05:1 to 0.15:1.

[0033] The co-catalyst can further include at least one of ruthenium, tantalum, tungsten, or nickel. Optionally, the co-catalyst comprises no added titanium, chromium, vanadium, molybdenum, tin, cerium, or zirconium.

[0034] To react the dimethyl aromatic compound and oxidant in solution, a solvent is used to at least partially dissolve the dimethyl aromatic compound, the catalyst, and the oxidant. The solvent can include a Ci-7 aliphatic carboxylic acid, such as acetic acid. The solvent can further include water (e.g., the solvent can be an aqueous solution). A weight ratio of solvent to dimethyl aromatic compound can be in a range of l5:l to 1:1, such as 10 : 1 to 1:1, more particularly 5 : 1 to 1:1.

[0035] To oxidize the dimethyl aromatic compound, the method uses an oxidant. The oxidant can include at least one of hydrogen peroxide, 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, a ketal, a C2-32 peroxyester, a C2-32 peroxydicarbonate, a C2-32 peroxy acid, a C6-32 perbenzoic acid, a C2-32 peracid, a periodinane, or a periodate, such as dioxygen (e.g., in air).

[0036] Desirably, the reacting of the dimethyl aromatic compound and the oxidant can be at a temperature in a range of 170 °C to 200 °C, such as 180 °C to 200 °C, more particularly 190 °C to 200 °C.

[0037] The reacting of the dimethyl aromatic compound and the oxidant can be at a pressure in a range of 1 to 1.8 MegaPascals (MPa), such as 1 to 1.7 MPa, more particularly 1 to 1.6 MPa.

[0038] A residence time in the reactor can be in a range of 20 minutes to 200 minutes, such as 40 minutes to 150 minutes, more particularly 60 minutes to 100 minutes.

[0039] The method can be carried out in a reactor such as a batch reactor, a continuous reactor, or semi-continuous reactor. The reactor can include an inlet for feeding at least one of the dimethyl aromatic compound, the solvent, the catalyst, or the co-catalyst continuously for a period of time and an outlet for removing the reaction product continuously for a period of time or at specific times. Desirably, the reacting of the dimethyl aromatic compound and the oxidant can be in a continuous stirred-tank reactor.

[0040] The aromatic dicarboxylic acid produced by the methods of the present disclosure can be at least one of terephthalic acid, isophthalic acid, ori/io-phthalic acid, or 2,6-naphthalenedicarboxylic acid. For example, the aromatic dicarboxylic acid can be terephthalic acid. Desirably, the aromatic dicarboxylic acid can be present in the reaction product in an amount equal to or greater than 90 wt%, such as equal to or greater than 92 wt%, more particularly equal to or greater than 94 wt%, based on the total weight of solids in the reaction product.

[0041] As noted above, the reaction product can include by-products such as carbon monoxide and carbon dioxide (collectively “COx”). A total amount of COx present in the reaction product can be reduced by equal to or greater than 5 mole %, such as equal to or greater than 10 mole %, more particularly equal to or greater than 15 mole %, as compared to a total amount of carbon monoxide and carbon dioxide present in a conventional reaction product of a method for oxidizing the dimethyl aromatic compound.

[0042] The reaction product can further include by-products such as Cio+ hydrocarbons. Cio+ hydrocarbons can be present in the reaction product in an amount greater than 0 and equal to or less than 1.5 wt%, such as equal to or less than 1.0 wt%, more particularly equal to or less than 0.5 wt%, based on the total weight of solids in the reaction product. For example, Cio+ hydrocarbons can be present in the reaction product in an amount of 0.1 to 1.5 wt%, such as 0.5 to 1.0 wt%, more particularly 1 to 0.5 wt%, based on the total weight of solids in the reaction product. As used herein “Cio+ hydrocarbon” refers to a hydrocarbon including 10 or more carbon atoms. Any number of Cio+ hydrocarbons can be present in a reaction product, such as at least five different Cio+ hydrocarbons, or at least fifteen different Cio+ hydrocarbons, or at least twenty different Cio+ hydrocarbons.

[0043] The method can further include separating the solvent, the catalyst, and the co-catalyst from the reaction product, and recycling the solvent, the catalyst, and the co-catalyst to the reactor. The catalyst and the co-catalyst can be in solution in the solvent and separation of the catalyst and the co-catalyst from the solvent can be performed via filtration or a solid-liquid separation method.

[0044] A reaction mixture for the oxidation of a dimethyl aromatic compound by the above-described methods can include the dimethyl aromatic compound, the oxidant, the catalyst, the co-catalyst, water, and the solvent.

[0045] A reaction product can be produced by the above-described methods, or using the above-described reaction mixture.

[0046] A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures (also referred to herein as “FIG.”) are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments. Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.

[0047] As illustrated in FIG. 1, a reaction mixture 6 including para-xylene, solvent, water, catalyst, and co-catalyst can be fed into reactor 10. An oxidant 8 also can be fed into reactor 10. Upon reaction of the para-xylene and the oxidant, reaction product 12 including terephthalic acid can be removed from reactor 10. Reaction product 12 can be fed into first crystallizer 20 to produce first crystallized stream 22. First crystallized stream 22 can be fed into second crystallizer 30 to produce second crystallized stream 32. Second crystallizer stream 32 can be fed into third crystallizer 40 to produce third crystallized stream 42 including crystallized terephthalic acid. In each of crystallizer 20, 30, and 40, Cio+ hydrocarbons can be reacted with the oxidant to obtain terephthalic acid. Solvent, catalyst, and co-catalyst stream 44 can be separated from third crystallized stream 42 and recycled to reaction mixture 6.

[0048] This disclosure is further illustrated by the following examples, which are non-limiting.

EXAMPLES

[0049] 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.

Table 1

Examples 1-4 and Comparative Examples A-C

[0050] In Examples 1-4 and Comparative Examples A-C, para-xylene was oxidized in the presence of different compositions of catalyst and co-catalyst in acetic acid (see Table 2 below).

[0051] The oxidation reactions were carried out in a semi-continuous stirred-tank batch reactor. The catalyst included cobalt, manganese, and bromine and the co-catalyst included iron. The catalyst and co-catalyst were prepared by dissolving cobalt acetate, manganese acetate, and iron acetate in 63 grams of water. Hydrobromic acid was then added to the catalyst/co-catalyst solution. The resulting homogeneous mixture was used as the catalyst and co-catalyst for oxidizing the para-xylene. The reactants were prepared by mixing 120 grams of p-xylene, 600 grams of acetic acid, and 8 wt% water (63 grams of water) to form a reactant mixture. The reaction mixture was mixed with catalyst and charged in the reactor.

[0052] After the reaction temperatures and pressures were reached under a nitrogen atmosphere, the oxidation was initiated by passing air as an oxidizing agent through the reactor continuously. A molar ratio of oxygen to para-xylene (“PX”) of 4: 1 was used during the oxidation reaction, while flow rate was varied throughout the reaction per process requirement.

[0053] In Examples 1-4, iron co-catalyst was used in an amount of 50 ppm, based on the total weight of the para-xylene, water, and the acetic acid. In Comparative Examples A-C, the iron co-catalyst was not present. As shown in Table 2 and for Example 2 and Comparative Example B, a lower reaction temperature of 180 °C was used. In the oxidation reactions of Examples 3 and 4 and Comparative Example C, a lesser amount of catalyst was used than in Examples 1-2 and Comparative Examples A-B. In Example 4, a different amount of bromine was used than in Example 3. The amounts of cobalt and manganese in ppm, the weight of iron relative to the weight of cobalt and manganese (Fe/[Co+Mn]), the moles of bromine relative to the moles of cobalt and manganese (Br/[Co+Mn]), the weight of acetic acid (“AcOH”) in grams, the weight of AcOH relative to the weight of para-xylene, and the temperature and pressure reaction conditions used in each of Examples 1-4 and Comparative Examples A-C are summarized in Table 2.

Table 2

[0054] As shown in FIGs. 2A-B, the reduction in total carbon monoxide and carbon dioxide (“COx”) formed was 9 mole % and 47.5 mole % for Example 1 and Example 2, respectively, as compared to Comparative Examples A and B, respectively.

[0055] In Example 2 the oxidation reaction at 180 °C produced, e.g., formed, 34.8 mole % less COx than in Example 1 at 190 °C.

[0056] Also, as shown in FIGs. 3A and 3B, a substantial reduction of Cio+ hydrocarbons occurred, with a reduction of 83 wt% and 40 wt% shown for Examples 2 and 1 as compared to Comparative Examples B and A, respectively. The decrease in Cio+ hydrocarbon formation was accompanied by a 0.8 wt% and 0.7 wt% increase in the terephthalic acid produced for Examples 2 and 1 as compared to Comparative Examples B and A, respectively.

[0057] As shown in FIG. 2C, Example 3 exhibited a reduction in COx formation of about 12 mole % as compared to Comparative Example C. In addition, Example 4, which included a greater amount of bromine as compared to Example 3, exhibited a greater reduction of COx formation as compared to Example 3, and as compared to Comparative Example C (24.2 mole %).

[0058] As shown in FIG. 3C, a reduction in the Cio+ hydrocarbons produced of 83.2 wt% and 81.4 wt% was observed for Examples 3 and 4, respectively as compared to Comparative Example C. As shown in FIG. 3D, a reduction in the Cio+ hydrocarbons produced of 90.5 wt%, and 89.5 wt% was observed for Examples 3-4, respectively, as compared to Comparative Example A. Examples 3 and 4 also has much higher reductions in the Cio+ hydrocarbons produced (90.5 wt%, and 89.5 wt%) as compared to Comparative Example C (43.5 wt%). The decrease in C10+ hydrocarbon formation was accompanied by a 2.0 and 1.8 wt% increase for the terephthalic acid produced for Examples 3 and 4 as compared to Comparative Example A.

[0059] From Examples 1-4, it was observed that the use of an iron co-catalyst (e.g., at 50 ppm Fe and based on the total weight of the dimethyl aromatic compound and the solvent) can reduce the side oxidation reactions of para-xylene and acetic acid, and COx formation can be reduced. The reduction in COx formation can be accompanied by an improvement in selective consumption of para-xylene and acetic acid. The presence of iron can also reduce the amount of Cio+ hydrocarbons produced. The reduction in formation of Cio+ hydrocarbons will lead to improved terephthalic acid yield. In addition, iron can allow for a reduction in the total metal content (e.g., cobalt and manganese) in the catalyst and improve product selectivity. The reduced total metal content can also reduce the bromine amount used, which helps to reduce corrosion in the production equipment.

Example 5 and Comparative Examples D-H

[0060] In Example 5 (Ex. 5) and Comparative Examples D-H (Ex. D-H in Table 3 below), para-xylene was oxidized in the presence of different compositions of catalyst and co catalyst (the co-catalyst was utilized in Example 5 only) in acetic acid.

[0061] The oxidation reactions were carried out in a semi -continuous stirred-tank batch reactor. The catalyst included cobalt, manganese, and bromine and the co-catalyst included iron (Example 5 only).

[0062] The catalyst and co-catalyst (if present) were prepared by dissolving cobalt acetate, manganese acetate, and iron acetate in 63 grams of water. Hydrobromic acid was then added to the catalyst/co-catalyst (if present) solution. The resulting homogeneous mixture was used as the catalyst and co-catalyst (if present) for oxidizing the para-xylene. The reactants were prepared by mixing 120 grams of p-xylene, 600 grams of acetic acid, and 8 wt% water (63 grams of water) to form a reactant mixture. The reaction mixture was mixed with catalyst and charged in the reactor.

[0063] After the reaction temperature (190 °C) and pressure (1.3 MPa) were reached under a nitrogen atmosphere for each reaction, the oxidation was initiated by passing air as an oxidizing agent through the reactor continuously. A molar ratio of oxygen to para-xylene ( PX ) of 4: 1 was used during each oxidation reaction, while flow rate stayed constant at 275 standard liters per hour. [0064] In Example 5 (Ex. 5), iron co-catalyst was used in an amount of 50 ppm, based on the total weight of the para-xylene, water, and the acetic acid. In Comparative Examples D- H, the iron co-catalyst was not present.

[0065] In Table 3, the amounts of cobalt, manganese and bromine are provided in ppm, and the moles of bromine relative to the moles of cobalt and manganese are provided as (Br/[Co+Mn]), and are summarized in Table 3.

[0066] Each weight ratio of cobalt to manganese is provided as Co/Mn. Each oxidation reaction time is provided as “Exp. Time” in minutes. The COx formation is provided in mole % (mol%), and the terephthalic acid yield is provided in weight percent (“TPA (wt%)”).

[0067] The formation of 4-carboxybenzaldehyde is provided in weight percent (“4-CBA (wt%)”), and the formation of Cio+ hydrocarbons is provided in weight percent (“Cio+ (wt%)”).

[0068] As used herein, “Cio+ hydrocarbons” refers to hydrocarbons including 10 or more carbon atoms.

[0069] As shown in Table 3, with Comparative Example D at a total content of cobalt and manganese of 200 ppm (100 ppm cobalt and 100 ppm manganese), the reaction was incomplete, due to the low total content of cobalt and manganese. This was observed by the low terephthalic acid yield of 85.04 wt%, and by the high formation of 4-carboxybenzaldehyde of 8.3 wt%.

[0070] With Comparative Example E having a total content of cobalt and manganese of 300 ppm (200 ppm cobalt and 100 ppm manganese), the formation of the Cio+ hydrocarbons (2.41 wt%) and the COx (0.1949 mol%) were higher than compared to Example 5. Example 5 had a total content of cobalt and manganese of 400 ppm (300 ppm cobalt and 100 ppm manganese), and had the formation of the Cio+ hydrocarbons at 0.21 wt% and the formation of the COx at 0.1333 mol%.

[0071] Also, with Comparative Example E having a total content of cobalt and manganese of 300 ppm (200 ppm cobalt and 100 ppm manganese), the formation of the Cio+ hydrocarbons (2.41 wt%) and the COx (0.1949 mol%) were higher than compared to Comparative Example F, which had a total content of cobalt and manganese of 400 ppm (300 ppm cobalt and 100 ppm manganese), and had the formation of the Cio+ hydrocarbons at 1.13 wt% and the formation of the COx at 0.1759 mol%.

[0072] It is also noted that with Comparative Example E having a total content of cobalt and manganese of 300 ppm (200 ppm cobalt and 100 ppm manganese), the formation of the Cio+ hydrocarbons (2.41 wt%) and the COx (0.1949 mol%) were higher than compared to Example 5, which had a total content of cobalt and manganese of 400 ppm (300 ppm cobalt and 100 ppm manganese), and had the formation of the Cio+ hydrocarbons at 0.21 wt% and the formation of the COx at 0.1333 mol%. [0073] With respect to Comparative Examples G and H, it is noted that the high total content of cobalt and manganese of 1200 ppm (100 ppm cobalt and 1,100 ppm manganese for Comparative Example G; and 1,100 ppm cobalt and 100 ppm manganese for Comparative Example H) also increased the bromine content (1,129 ppm for both), which is not favorable for the metallurgy of the reactor (e.g., an increase in metal corrosion of the reactor was observed). Moreover, the formation of undesired 4-carboxybenzaldehyde for Comparative Examples G and H (with the cobalt and manganese of 1,200 ppm, and with the bromine content of 1,129 ppm for both) were 2.32 and 2.15 wt%, which are higher than the formation of undesired 4- carboxybenzaldehyde for Example 5 (1.89 wt%), and where Example 5 had a total content of cobalt and manganese of 400 ppm (300 ppm cobalt and 100 ppm manganese), and a bromine content of 342 ppm. It is noted that an increase in 4-carboxybenzaldehyde formation can also negatively impact the metal corrosion of the reactor. Furthermore, the formation of undesired Cio+ hydrocarbons for Comparative Examples G and H were 1.32 and 0.5 wt%, which are higher than the formation of undesired Cio+ hydrocarbons for Example 5 (0.21 wt%).

[0074] In summary and with respect to reactions utilizing a total content of cobalt and manganese of 300 ppm or less (Comparative Examples D and E), these reactions were incomplete, and experienced low terephthalic acid yields and high formation of 4- carboxybenzaldehyde (Comparative Example D), and/or resulted in increased formation of the Cio+ hydrocarbons and the COx compared to reactions utilizing a total content of cobalt and manganese of greater than 300 ppm (e.g., Comparative Example E compared to Example 5).

[0075] Similarly and with respect to reactions utilizing a total content of cobalt of 200 ppm or less (Comparative Examples D and E), these reactions were incomplete, and experienced low terephthalic acid yields and high formation of 4-carboxybenzaldehyde (Comparative Example D), and/or resulted in increased formation of the Cio+ hydrocarbons and the COx compared to reactions utilizing a total content of cobalt of greater than 200 ppm (e.g., Comparative Example E compared to Example 5).

[0076] With respect to reactions utilizing a total content of cobalt and manganese of 1,200 ppm (Comparative Examples G and H), these reactions resulted in increased formation of undesired 4-carboxybenzaldehyde and undesired Cio+ hydrocarbons compared to reactions utilizing a total content of cobalt and manganese of less than 1,200 ppm (e.g., Comparative Examples G and H compared to Example 5).

[0077] Similarly and with respect to reactions utilizing a total content of manganese of 1,100 ppm (Comparative Example G), these reactions resulted in increased formation of undesired 4-carboxybenzaldehyde and undesired Cio+ hydrocarbons compared to reactions utilizing a total content of manganese of less than 1, 100 ppm (e.g., Comparative Example G compared to Example 5).

[0078] Likewise and with respect to reactions utilizing a total content of cobalt of 1,100 ppm (Comparative Example H), these reactions resulted in increased formation of undesired 4- carboxybenzaldehyde and undesired Cio+ hydrocarbons compared to reactions utilizing a total content of cobalt of less than 1,100 ppm (e.g., Comparative Example H compared to Example

5)·

[0079] With respect to reactions utilizing a total content of bromine of 1,129 ppm (Comparative Examples G and H), these reactions resulted in increased formation of undesired 4-carboxybenzaldehyde and undesired Cio+ hydrocarbons compared to reactions utilizing a total content of bromine of less than 1,129 ppm (e.g., Comparative Examples G and H compared to Example 5).

[0080] As is clear from Example 5 and Comparative Examples D-H, the use of a catalyst comprising: (i) bromine in an amount of 160 to 730 ppm (e.g., 342 ppm), (ii) manganese in an amount of 100 to 450 ppm (e.g., 100 ppm), and (iii) cobalt in an amount of 100 to 450 ppm (e.g., 300 ppm) and wherein the cobalt and manganese is present in an amount of greater than 300 to 900 ppm, along with a co-catalyst comprising iron (e.g., 50 ppm), this enables the production of aromatic dicarboxylic acids (e.g., terephthalic acid), while reducing the amount of the undesired 4-carboxybenzaldehyde, Cio+ hydrocarbons and COx, and while advantageously increasing the yield of the aromatic dicarboxylic acid. It is noted that an increase in 4-carboxybenzaldehyde formation can negatively impact the metal corrosion of the reactor. The reduction in formation of COx will lead to improved terephthalic acid yield. The iron co-catalyst can allow for a reduction in the total metal content (e.g., cobalt and manganese) in the catalyst system and improve product selectivity. The reduced total metal content can also reduce the bromine amount used, which facilitates reducing corrosion in the reactor.

[0081] This disclosure further encompasses the following aspects.

[0082] Aspect 1. A method for oxidizing a dimethyl aromatic compound, comprising: reacting the dimethyl aromatic compound and an oxidant in the presence of a catalyst system in a solvent to produce a reaction product comprising an aromatic dicarboxylic acid, such as terephthalic acid; wherein the catalyst system comprises a catalyst and a co-catalyst; wherein the catalyst comprises bromine, cobalt, and manganese; wherein the co-catalyst comprises iron; wherein the iron is present in an amount of 10 to 100 ppm, such as 10 to 90 ppm, more particularly 10 to 50 ppm, based on a total weight of the dimethyl aromatic compound and the solvent; wherein the bromine is present in an amount of 160 to 730 ppm, such as 200 to 400 ppm, more particularly 200 to 330 ppm, based on the total weight of the dimethyl aromatic compound and the solvent; wherein the manganese is present in an amount of 100 to 450 ppm, such as 100 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent; wherein the cobalt is present in an amount of 100 to 450 ppm, such as 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent; and wherein the cobalt and manganese are present in an amount of greater than 300 to 900 ppm, such as greater than 300 to 800 ppm, more particularly greater than 300 to 400 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0083] Aspect 2. The method of Aspect 1, wherein the dimethyl aromatic compound comprises at least one of para-xylene, meta-xylene, ortho-xylene, or 2,6-dimethylnaphthalene.

[0084] Aspect 3. The method of any one or more of the preceding aspects, wherein the aromatic dicarboxylic acid is present in the reaction product in an amount of equal to or greater than 90 wt%, such as equal to or greater than 92 wt%, more particularly equal to or greater than 94 wt%, based on a total weight of solids in the reaction product.

[0085] Aspect 4. The method of any one or more of the preceding aspects, wherein a total amount of carbon monoxide and carbon dioxide present in the reaction product is reduced by equal to or greater than 5 mole percent, such as equal to or greater than 10 mole percent, more particularly equal to or greater than 15 mole percent, as compared to a total amount of carbon monoxide and carbon dioxide present in a reaction product of a method for oxidizing a dimethyl aromatic compound outside the presence of the iron.

[0086] Aspect 5. The method of any one or more of the preceding aspects, wherein Cio+ hydrocarbons are present in the reaction product in an amount equal to or less than 1.5 wt%, such as equal to or less than 1.0 wt%, more particularly equal to or less than 0.5 wt%, based on a total weight of solids in the reaction product.

[0087] Aspect 6. The method of any one or more of the preceding aspects, wherein the catalyst is present in an amount of greater than 460 to 1,630 ppm, such as 600 to 1,200 ppm, more particularly 600 to 1,130 ppm, based on the total weight of the dimethyl aromatic compound and the solvent.

[0088] Aspect 7. The method of any one or more of the preceding aspects, wherein the co-catalyst further comprises at least one of ruthenium, tantalum, tungsten, or nickel.

[0089] Aspect 8. The method of any one or more of the preceding aspects, wherein the oxidant comprises at least one of hydrogen peroxide, 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, a ketal, a C2-32 peroxyester, a C2-32 peroxydicarbonate, a C2-32 peroxy acid, a C6-32 perbenzoic acid, a C2-32 peracid, a periodinane, or a periodate, such as dioxygen.

[0090] Aspect 9. The method of any one or more of the preceding aspects, wherein the solvent comprises a C1-7 aliphatic carboxylic acid, such as acetic acid.

[0091] Aspect 10. The method of any one or more of the preceding aspects, wherein the solvent further comprises water.

[0092] Aspect 11. The method of any one or more of the preceding aspects, wherein a weight ratio of solvent to dimethyl aromatic compound is in a range of 15: 1 to 1: 1, such as 10: 1 to 1: 1, more particularly 5 : 1 to 1: 1.

[0093] Aspect 12. The method of any one or more of the preceding aspects, wherein a molar ratio of bromine to cobalt and manganese is in a range of 0.3:1 to 3: 1, such as 0.3: 1 to 2: 1, more particularly 0.3 : 1 to 1: 1.

[0094] Aspect 13. The method of any one or more of the preceding aspects, wherein a weight ratio of iron to the total amount of cobalt and manganese is in a range of 0.05: 1 to 0.25: 1, such as 0.05: 1 to 0.20: 1, more particularly 0.05: 1 to 0.15: 1.

[0095] Aspect 14. The method of any one or more of the preceding aspects, wherein the reacting is at a temperature in a range of 170 °C to 200 °C, such as 180 °C to 200 °C, more particularly 190 °C to 200 °C.

[0096] Aspect 15. The method of any one or more of the preceding aspects, wherein the reacting is at a pressure in a range of 1 to 1.8 MegaPascals, such as 1 to 1.7 MegaPascals, more particularly 1 to 1.6 MegaPascals.

[0097] Aspect 16. The method of any one or more of the preceding aspects, further comprising separating the solvent, the catalyst, and the co-catalyst from the reaction product, and recycling the solvent, the catalyst, and the co-catalyst separated from the reaction product to a reactor in which the dimethyl aromatic compound and the oxidant are reacted to produce the reaction product.

[0098] Aspect 17. The method of any one or more of the preceding aspects, further comprising reacting the aromatic dicarboxylic acid and hydrogen in the presence of a hydrogenation catalyst.

[0099] Aspect 18. The method of any one or more of the preceding aspects, wherein the catalyst system comprises no added titanium, chromium, vanadium, molybdenum, tin and zirconium.

[0100] Aspect 19. The method of any one or more of the preceding aspects, wherein the catalyst system comprises no added cerium. [0101] The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate components or steps herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any steps, components, materials, ingredients, adjuvants, or species that are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles.

[0102] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. “Or” means “and/or” unless clearly indicated otherwise by context. The terms “first,” “second,” and the like, “primary,” “secondary,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

[0103] The endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of “less than or equal to 25 wt%, or 5 to 20 wt%,” is inclusive of the endpoints and all intermediate values of the ranges of “5 to 25 wt%,” etc.). Disclosure of a narrower range or more specific group in addition to a broader range is not a disclaimer of the broader range or larger group.

[0104] The suffix “(s)” is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorants). 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 disclosure belongs. A “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Unless specified to the contrary herein, a total weight of solids in the reaction product is 100 wt%.

[0105] 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.

[0106] 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 references are incorporated herein by reference in their entirety.

[0107] While typical embodiments have been set forth for the purpose of illustration, the foregoing descriptions should not be deemed to be a limitation on the scope herein.

Accordingly, various modifications, adaptations, and alternatives can occur to one skilled in the art without departing from the spirit and scope herein.