JP2000128824A - Production of aromatic carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aromatic carboxylic acid, capable of increasing an oxygen absorption efficiency and an oxygen utilization and reducing a feed rate of an oxygen-containing gas to increase an effective power efficiency, capable of increasing a reaction efficiency to depress impurity formation and solvent consumption, and consequently capable of efficiently producing the carboxylic acid of a high purity. SOLUTION: This method for producing an aromatic carboxylic acid comprises subjecting an alkyl substituted aromatic compound to liquid phase oxidation reaction with an oxygen-containing gas in the presence of an oxidation catalyst in an aliphatic carboxylic acid-containing reaction solvent in a reactor 1. Therein, the oxidation reaction is carried out by introducing the oxygen- containing gas 7 into a lower part of the reactor 1 to ascend upward, and separately feeding the raw material 6(a), 6(b) into two or more positions which are arranged so that each position has a different radial distance from the peripheral wall of the reactor 1 or has a different height, while stirring with a stirrer 3 having a vertical rotating shaft 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an aromatic carboxylic acid by subjecting an alkyl aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent to liquid phase oxidation with an oxygen-containing gas.

[0002]

2. Description of the Related Art Aromatic carboxylic acids are important as basic chemicals, and aromatic dicarboxylic acids are particularly useful as raw materials for fibers, resins and the like. For example, the demand for terephthalic acid as a polyester raw material has been increasing in recent years.

[0003] As a method for producing an aromatic carboxylic acid, generally, in an oxidation reactor, a heavy metal compound and a bromine compound are used as catalysts, and an alkyl-substituted aromatic compound is converted into a molecule in a reaction solvent containing a lower aliphatic carboxylic acid such as acetic acid. A method of contacting with a gaseous oxygen-containing gas to perform liquid phase oxidation is employed. In such a production method, an alkyl-substituted aromatic compound such as para-xylene as a raw material, a mixture of acetic acid and a catalyst as a raw material, and an oxygen-containing gas such as air are introduced into the reactor, and an oxidation reaction is performed by stirring with a stirrer. And aromatic carboxylic acids such as terephthalic acid.

FIG. 4 is a system diagram showing a conventional method for producing an aromatic carboxylic acid disclosed in JP-A-63-83046. In FIG. 4, reference numeral 1 denotes a reactor, which is formed in a vertical cylindrical shape, has a baffle plate 2 on the inner peripheral wall, and a stirrer 3 at the center. The stirrer 3 has a rotating shaft 4 and multi-stage stirring blades 5. The alkyl aromatic compound, the catalyst and the solvent are introduced into the reactor 1 through the raw material supply path 6 and the oxygen-containing gas is introduced into the reactor 1 through the oxygen-containing gas introduction path 7, and an aromatic carboxylic acid is generated by the oxidation reaction. In this case, the generated crude aromatic carboxylic acid slurry is taken out through the slurry take-out passage 8.

[0005] A reaction gas outlet 9 is provided at the top of the reactor 1, and a heat exchanger 10 is provided for removing condensable components from the reaction gas. A distillation column (not shown) may be provided instead of the heat exchanger 10 or together with the heat exchanger 10. The reaction gas in the reactor 1 enters the heat exchanger 10 through the reaction gas outlet 9 and is cooled. The condensable component condensed by cooling is received by the separation drum 11 as a condensate, and a part of the condensate is returned to the reactor 1 from the circulation path 12 by the pump 13, and a part is condensed liquid discharge path 14 as necessary. And the solvent is recovered by a subsequent distillation column. Exhaust gas obtained by removing condensable components in the separation drum 11 is partially discharged out of the system through an exhaust gas passage 15. The slurry taken out from the slurry take-out passage 8 is subjected to a purification treatment such as an oxidation treatment and a reduction treatment in a subsequent purification step, and then recrystallized in a crystallization tank to obtain a purified aromatic carboxylic acid crystal.

In such a method for producing an aromatic carboxylic acid, the raw material supply path 6 communicates with the vertical intermediate portion of the reactor 1, and the raw material is supplied to the first and second stages of the stirring blades 5. The aromatic carboxylic acid is generated by being oxidized by the oxygen-containing gas supplied to the intermediate position and introduced from the oxygen-containing gas introduction passage 7 communicating with the lower portion. In this case, the raw material supplied from the raw material supply path 6 is agitated by the stirring blade 5 and the rising gas, but basically flows downward as a downward flow, and comes into contact with the rising oxygen-containing gas in gas flow. It is believed that the oxidation reaction takes place.

For this reason, the reaction zone is defined as a region extending from the first-stage stirring blade 5 to the bottom of the tower, and a raw material supply path 6 communicates with a position near the upper end thereof. Therefore, when a plurality of raw material supply paths 6 are provided to dispense raw materials in order to enlarge the reactor 1 and increase the throughput, a plurality of raw material supply passages 6 are provided on circumferential walls of the same height which are substantially equally spaced in the circumferential direction. The raw material is supplied to the peripheral wall portion having the same height to conduct the reaction.

In such a method for producing an aromatic carboxylic acid, if the absorption efficiency of oxygen is low, it is necessary to supply a large amount of an oxygen-containing gas, so that the efficiency is lowered and the oxidation conditions become severe. There is a problem that 4-CBA (4-carboxybenzaldehyde) or a coloring component as an impurity is generated, and a lower fatty acid such as acetic acid as a solvent is wasted.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to increase oxygen absorption efficiency and oxygen utilization rate, reduce the supply of oxygen-containing gas to increase efficiency, and increase reaction efficiency to increase impurity efficiency. It is an object of the present invention to provide a method for producing an aromatic carboxylic acid capable of efficiently producing a high-purity aromatic carboxylic acid by suppressing the production of a carboxylic acid and the consumption of a solvent.

[0010]

The present invention relates to the following method for producing an aromatic carboxylic acid. (1) A method for producing an aromatic carboxylic acid by subjecting an alkyl aromatic compound as a raw material to liquid-phase oxidation with an oxygen-containing gas in a reaction solvent containing an aliphatic carboxylic acid in a reactor in the presence of an oxidation catalyst, Introduce the oxygen-containing gas into the lower part of the reactor and raise it, and while stirring with a stirrer having a rotating shaft in the vertical direction, feed the raw material to a plurality of positions with different distances from the peripheral wall of the reactor to the center or different heights. A method for producing an aromatic carboxylic acid, wherein the oxidation reaction is performed by dispensing. (2) The method for producing an aromatic carboxylic acid according to (1), wherein the stirrer has a plurality of stirring blades at different heights. (3) The method for producing an aromatic carboxylic acid according to the above (1) or (2), wherein the raw material is dispensed below the first stage stirring blade. (4) The method for producing an aromatic carboxylic acid according to any one of the above (1) to (3), wherein when dispensing the raw materials at different positions in the height, the raw materials are dispensed at different positions in the circumferential direction. (5) The method for producing an aromatic carboxylic acid according to any one of the above (1) to (4), wherein an oxygen-containing gas is introduced into a central portion of a lower portion of the reactor.

As a raw material for producing an aromatic carboxylic acid in the method of the present invention, an aromatic compound having an alkyl substituent or a partially oxidized alkyl substituent (hereinafter sometimes simply referred to as an oxidizing raw material) is used. it can. Such an aromatic compound may be monocyclic or polycyclic. Examples of the alkyl substituent include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Examples of the partially oxidized alkyl group include an aldehyde group, an acyl group, a carboxyl group, and a hydroxyalkyl group.

Specific examples of the aromatic compound having an alkyl substituent, that is, the alkyl-substituted aromatic hydrocarbon include, for example, m-diisopropylbenzene, p-diisopropylbenzene, m-cymene, p-cymene, m-xylene, An alkyl group having 1 to 4 carbon atoms such as p-xylene, trimethylbenzenes and tetramethylbenzenes is
Di or polyalkyl benzenes having from 2 to 4 di or polyalkyl naphthalenes having from 2 to 4 alkyl groups having 1 to 4 carbon atoms, such as dimethyl naphthalenes, diethyl naphthalenes and diisopropyl naphthalenes;
And polyalkylbiphenyls having 2 to 4 alkyl groups having 1 to 4 carbon atoms, such as dimethylbiphenyls.

The aromatic compound having a partially oxidized alkyl substituent is a compound in which the alkyl group in the above compound is partially oxidized and oxidized to the aldehyde group, acyl group, carboxyl group or hydroxyalkyl group. It is. Specific examples include, for example, 3-methylbenzaldehyde, 4-methylbenzaldehyde, m-
Toluic acid, p-toluic acid, 3-formylbenzoic acid,
Examples include 4-formylbenzoic acid and 2-methyl-6-formylnaphthalenes. These are used alone or as a mixture of two or more.

In the method of the present invention, a heavy metal compound and a bromine compound are used as catalysts. Examples of such compounds are as follows. That is,
As the heavy metal in the heavy metal compound, for example, cobalt, manganese, nickel, chromium, zirconium, copper,
Lead, hafnium, cerium and the like can be mentioned. These can be used alone or in combination, but it is particularly preferable to use a combination of cobalt and manganese. Such heavy metal compounds include, for example, acetate, nitrate, acetylacetonate, naphthenate, stearate, bromide, etc., with acetate being particularly preferred.

As the bromine compound, for example, molecular bromine,
Inorganic bromine compounds such as hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide and manganese bromide; methyl bromide, methylene bromide, bromoform, benzyl bromide, bromomethyltoluene, dibromoethane, tribromoethane and Organic bromine compounds such as tetrabromoethane can be mentioned. These bromine compounds are also used alone or as a mixture of two or more.

In the present invention, the catalyst comprising the combination of the heavy metal compound and the bromine compound is used in an amount of 0.05 to 10 mol, preferably 0.1 mol, of bromine atom per 1 mol of heavy metal atom.
Those having a range of 2 to 2 mol are desirable. Such a catalyst is usually used as a heavy metal concentration in a reaction solvent of 10 to 100.
It is used in the range of 00 ppm, preferably 100 to 5000 ppm.

In the method of the present invention, in an oxidation reactor, in the presence of the catalyst, an aromatic compound as an oxidation raw material is oxidized in a liquid phase with a molecular oxygen-containing gas in a reaction solvent containing a lower aliphatic carboxylic acid. Thereby, crystals of the aromatic carboxylic acid are precipitated to form a slurry.

The molecular oxygen-containing gas includes, for example, oxygen and air, but practically, air is preferably used. The molecular oxygen-containing gas is supplied in excess of the amount required to oxidize the aromatic compound serving as the oxidation raw material to the aromatic carboxylic acid. When air is used as the molecular oxygen-containing gas, aromatic compound 1 serving as an oxidation raw material
2 to 20 Nm ³ , preferably 2.5 to 15 kg / kg
It is desirable to supply Nm ^{3 to} the reaction system at a ratio of Nm ³ .

Specific examples of the lower aliphatic carboxylic acid used as the reaction solvent include acetic acid, propionic acid and butyric acid. The lower aliphatic carboxylic acid can be used alone as a reaction solvent, or can be mixed with water and used as a reaction solvent in the form of a mixture. Specific examples of the reaction solvent include, for example, acetic acid, propionic acid, butyric acid and mixtures thereof,
Alternatively, a mixture of these lower aliphatic carboxylic acids and water can be used. Among these, a mixture of acetic acid and water is preferable, and a mixture of 1 to 20 parts by weight of water, preferably 5 to 15 parts by weight of water is particularly desirable with respect to 100 parts by weight of acetic acid.

The temperature of the oxidation reaction is usually 100 to 250 ° C.,
Preferably, the range of 150 to 220 ° C is desirable. Also,
The reaction pressure may be any pressure as long as the reaction system can be maintained in a liquid phase.

By reacting in this manner, an aromatic carboxylic acid corresponding to the aromatic compound serving as an oxidation raw material is obtained. Specific examples of the aromatic carboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid; and aromatic dicarboxylic acids such as trimellitic acid and trimesic acid. Aromatic tricarboxylic acids such as pyromellitic acid; and the like.

The method of the present invention is preferably applied to the production of an aromatic dicarboxylic acid or an aromatic carboxylic acid insoluble or hardly soluble in a reaction solvent, particularly preferably to the production of terephthalic acid.

In the present invention, an aromatic carboxylic acid is produced by subjecting an alkyl aromatic compound as a raw material to liquid phase oxidation with an oxygen-containing gas in a reaction solvent containing an aliphatic carboxylic acid in a reaction solvent in the presence of an oxidation catalyst. At the time, the oxygen-containing gas is introduced into the lower portion of the reactor and raised, while stirring with a stirrer having a rotating shaft in the vertical direction, the distance from the peripheral wall of the reactor to the center,
Alternatively, the oxidation reaction is performed by dispensing the raw materials to a plurality of positions having different heights, thereby increasing the oxygen absorption efficiency and the oxygen utilization rate, and efficiently performing the oxidation reaction.

In performing the above oxidation reaction, as a result of observing the flow of the liquid in the reactor, when the oxygen-containing gas is introduced into the inside of the stirring chamber at the center of the lower part of the reactor while stirring with the stirrer, the gas becomes It was found that the reaction liquid rises in the center of the reactor, and as a result, the reaction liquid rises as a swirling upward flow along the stirring axis in the center and descends as a swirl flow along the peripheral wall.

For this reason, even when the raw material is dispersed and dispensed at a plurality of positions, if the raw material is dispersed and dispensed in the circumferential direction at the same height, the raw material is injected in an extremely narrow region of the flow of the reaction solution. And there is substantially no difference from the case of injecting from one place. Therefore, when dispensing in the circumferential direction at the same height on the peripheral wall of the reactor and dispensing, the raw material descends while rotating the peripheral wall, rises from the bottom with the gas together with the gas, and is oxidized. Circulates down the part.

Oxygen absorption occurs continuously while the oxygen-containing gas and the reaction solution are in contact with each other. If a raw material is present in the reaction solution during that time, the raw material is oxidized. If not present, the lower fatty acid as a solvent is oxidized. However, when the raw material is intensively injected at almost one point as in the conventional method, a portion where the raw material concentration is higher or lower than the oxygen absorption amount occurs in the process of flowing the reaction solution, and a uniform oxidation reaction can be performed. Disappears.

For this reason, in the present invention, the raw material is dispensed along the flow of the reaction solution by dispensing the raw material to a plurality of positions having different distances or heights from the peripheral wall of the reactor to the center. As a result, the raw material concentration in the process of flowing the reaction solution can be made more uniform, and the oxygen absorption efficiency, oxygen utilization rate, and oxidation reaction efficiency can be increased.

In the present invention, an oxygen-containing gas introduction path is connected to the lower part of the reactor, and a stirrer having a rotating shaft in the vertical direction is provided. The reactor is provided at a plurality of positions having different distances or heights from the peripheral wall to the center of the reactor. The reactor connected to the raw material supply path is used.

The distance from the peripheral wall to the center of the reactor is a radial distance. Since a downward flow is formed at the peripheral wall of the reactor and an upward flow is formed at the center, the pipette is dispensed at different distances from the peripheral wall to the center, so that the raw material flows in different areas of the reaction liquid flow. Can be dispensed. Also, when dispensing to different portions of the reactor, the raw materials can be dispensed to different portions of the flow of the reaction solution.

The above-mentioned flow of the reaction solution is a large flow combined with rising of the bubble and stirring by rotation of the stirrer. In addition to such a large flow, a fine flow caused by individual stirring blades or bubbles is also caused. Since it is formed, by dispensing at different positions of a large flow, the material concentration in each region can be homogenized even when there are few dispensing points.

Since oxygen absorption occurs continuously while the reaction solution and the oxygen-containing gas are in contact with each other, by homogenizing the concentration of the raw material in each region of the reaction solution, the absorbed oxygen can be immediately used for the oxidation reaction of the raw material. Utilization can be used to increase the oxygen utilization rate, make the reaction more efficient, and prevent oxidation of the solvent.

When the concentration of the raw material in each region in the flow direction of the reaction liquid is homogenized in this manner, the oxygen absorbed in each region is used as it is for oxidation of the raw material, so that the oxidation reaction efficiency is increased. Since the absorbed oxygen is used for oxidizing the raw material, wasteful consumption due to oxidation of the solvent is also prevented. In addition, since the reaction efficiency is increased, the supply amount of oxygen can be reduced, the energy efficiency can be reduced, and the oxidation of the solvent can be reduced under mild conditions of the oxidation reaction.

[0033]

As described above, according to the present invention, the oxidation reaction is performed by dispensing the raw materials to a plurality of positions having different distances or heights from the peripheral wall to the center of the reactor, so that the oxygen A high-purity aromatic carboxylic acid with high absorption efficiency and high oxygen utilization and low supply of oxygen-containing gas to increase efficacy efficiency, and high reaction efficiency to suppress generation of impurities and consumption of solvent Can be manufactured efficiently.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are sectional views showing a reactor of another embodiment, FIG. 3 is a sectional view showing a reactor of a reference example, and the same reference numerals as in FIG. 4 indicate the same or corresponding parts.

1 to 3, a reactor 1 is formed in a vertical cylindrical shape, has a baffle plate 2 on an inner peripheral wall, and has a stirrer 3 in a central portion. In the stirrer 3, first to third stages of stirring blades 5 a to 5 c are provided in the reaction liquid 16 from above the rotating shaft 4 arranged in the vertical direction. An oxygen-containing gas introduction passage 7 is opened inside the stirring blades 5a to 5c at the center of the lower part of the reactor 1, and a slurry discharge passage 8 communicates with the outside of the stirring blades 5a to 5c at the lower part of the reactor 1. A reaction gas outlet 9 communicates with the upper part of the reactor 1, and the circulation gas 1 flows through the reaction solution 16 on the side wall.
Two are in contact.

The above structure is common to FIGS. 1 to 3 and is substantially the same as that of FIG. The first raw material supply path 6a has the same configuration, and the first raw material supply path
The second raw material supply path 6b is connected to a different position while the second raw material supply path 6b is connected between the second stage stirring blades 5a and 5b. That is, they are the same height in FIG. 1 and have different distances from the peripheral wall of the reactor 1 to the center, that is, they communicate with the inside of the stirring blades 5a and 5b, and in FIG. In addition, it is in contact with a position that keeps a distance in the circumferential direction. In FIG. 3, they are located at the same height and at a distance in the circumferential direction.

When the stirrer 3 is rotated in each of the reactors 1 shown in FIGS. 1 to 3, the swirling flow in the horizontal radial direction is generated by the rotation of the stirring blades 5a to 5c as shown by solid arrows a and b. In this state, when the oxygen-containing gas is introduced from the oxygen-containing gas introduction passage 7 into the lower central portion of the reactor 1, a part of the gas also flows in the directions of the arrows a and b, but most of the gas flows in broken arrows c and d. As shown in the figure, the reaction liquid rises inside the stirring blades 5a to 5c, whereby the rising reaction liquid descends along the peripheral wall, and a vertical swirling flow is generated. For this reason, these two streams combine, and the reaction solution follows the rising bubbles.
There is a flow that rises while turning around the center and descends while turning around the periphery.

In such a flow of the reaction solution, oxygen absorption occurs during gas-liquid contact, and the higher the oxygen partial pressure, the greater the amount of absorption. , Absorption occurs in almost all regions.

In this state, when the aromatic compound, the catalyst and the solvent as the raw materials are introduced from the raw material supply passages 6a and 6b having the same height on the peripheral wall as shown in FIG. 3, they are introduced from the raw material supply passages 6a and 6b. Since the raw materials at the same height are dispensed at almost the same position, they are partially oxidized while descending the peripheral wall, and then oxidized by oxygen that is absorbed abundantly while ascending from the lower central part. An aromatic carboxylic acid is formed.

When the raw materials are introduced from the raw material supply passages 6a and 6b dispersed at the same height of the peripheral wall as described above, the raw materials are injected from substantially the same position, and therefore, the same as in the case of the single injection in FIG. Then, the oxidized region of the raw material is concentrated in a specific region.
Therefore, it is necessary to introduce a large amount of oxygen to complete the oxidation in that region, and excess oxygen results in oxidation of the lower aliphatic carboxylic acid as a solvent.

On the other hand, when the raw materials are dispensed from the raw material supply passages 6a and 6b having different distances from the peripheral wall to the center as shown in FIG. 1, the raw material introduced from the first raw material supply passage 6a descends along the peripheral wall portion. Then, the raw material introduced from the second raw material supply passage 6b rises in the center, and is also stirred by the stirring by the stirring blades 5a to 5c, so that the concentration of the raw material in each region is homogenized, and in each region, The oxygen is efficiently oxidized by the absorbed oxygen, and the oxygen utilization rate and the oxidation efficiency are increased. For this reason, the supply amount of oxygen can be reduced, and the oxidation of the solvent is also reduced.

In FIG. 2, raw material supply paths 6a, 6
In order to dispense the raw material from b, homogenization is performed in substantially the same manner, and since each raw material is oxidized before both raw materials merge,
Similarly, the oxidation efficiency is increased, the oxygen supply amount may be small, and wasteful consumption due to oxidation of the solvent is reduced.

[0043]

EXAMPLES Examples of the present invention and comparative examples will be described below.

Examples 1 and 2, Reference Example 1 Using the reactor shown in FIG. 1 as Example 1, FIG. 2 as Example 2, and the reactor shown in FIG. 3 as Reference Example 1, para-xylene, catalyst and A mixture of acetic acid solvents was dispensed, and air having an oxygen concentration of 21% by volume was supplied from the oxygen-containing gas supply path 7 to perform an oxidation reaction at 180 ° C. and 1 MPa. The supply amount of air was determined such that the oxygen concentration in the exhaust gas was 3%. 4-CBA concentration of the obtained terephthalic acid, light transmittance, molecular oxygen gas supply amount, oxygen concentration in exhaust gas, CO
Table 1 shows the x generation amount.

[0045]

[Table 1]

From the results shown in Table 1, it can be seen that Examples 1 and 2 have lower 4-CBA concentration of terephthalic acid, higher light transmittance and higher purity than Reference Example 1. In addition, it can be seen that the oxygen supply amount is small, the oxygen concentration of the exhaust gas is low and the oxygen utilization rate is high, and the small amount of COx generated indicates that the consumption of the acetic acid solvent by combustion is small.

[Brief description of the drawings]

FIG. 1 is a sectional view of a reactor according to an embodiment.

FIG. 2 is a cross-sectional view of a reactor according to another embodiment.

FIG. 3 is a sectional view of a reactor according to an embodiment of the reference example.

FIG. 4 is a system diagram showing a conventional method for producing an aromatic carboxylic acid.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reactor 2 baffle plate 3 stirrer 4 rotating shaft 5, 5 a to 5 c stirring blade 6, 6 a, 6 b material supply path 7 oxygen-containing gas introduction path 8 slurry extraction path 9 reaction gas extraction path 10 heat exchanger 11 separation drum 12 circulation Path 13 Pump 14 Condensate drainage path 15 Exhaust gas path 16 Reaction liquid

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4H006 AA02 AC12 AC46 AD15 BA05 BA10 BA11 BA14 BA16 BA20 BA21 BA30 BA32 BA34 BA37 BB17 BB31 BC10 BC11 BD80 BE30

Claims (5)

[Claims] 1. A method for producing an aromatic carboxylic acid by subjecting an alkyl aromatic compound as a raw material to liquid phase oxidation with an oxygen-containing gas in a reaction solvent containing an aliphatic carboxylic acid in a reactor in the presence of an oxidation catalyst. In the reactor, an oxygen-containing gas is introduced into the lower part of the reactor and raised, and while being stirred by a stirrer having a rotating shaft in a vertical direction, at a distance from the peripheral wall of the reactor to the center or at a plurality of positions having different heights. A method for producing an aromatic carboxylic acid, wherein an oxidation reaction is performed by dispensing raw materials. 2. The method for producing an aromatic carboxylic acid according to claim 1, wherein the stirrer has a plurality of stirring blades at different positions. 3. The method for producing an aromatic carboxylic acid according to claim 1, wherein the raw material is dispensed below the first-stage stirring blade. 4. The method according to claim 1, wherein when dispensing the raw materials at different heights, the raw materials are dispensed at different circumferential positions.
The method for producing an aromatic carboxylic acid according to any one of the above. 5. The method for producing an aromatic carboxylic acid according to claim 1, wherein an oxygen-containing gas is introduced into a central portion of a lower portion of the reactor.