JP2014019676A - Method for manufacturing aromatic carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an aromatic carboxylic acid except a terephthalic acid, having a catalyst collection process using a pyridine ring containing chelating resin and capable of immediately simply analyzing concentration variation of a collected catalyst solution and stabilizing a liquid phase oxidation reaction by reducing variation in concentration of a catalyst component and water in a catalyst preparation tank for returning the collected catalyst solution to obtain an aromatic carboxylic acid having stable quality.SOLUTION: A method for manufacturing an aromatic carboxylic acid includes analyzing each concentration of a cobalt ion, water, a manganese ion and a bromide ion in the collected catalyst solution by an infrared analyzer and a full automatic titration device online-connected to a predetermined place in the periphery of a collected catalyst solution tank.

Description

  The present invention relates to terephthalic acid by liquid phase oxidation of an alkyl group-containing aromatic hydrocarbon using a molecular oxygen-containing gas in the presence of a catalyst comprising a heavy metal compound and a bromine compound in a solvent containing a lower aliphatic carboxylic acid. The present invention relates to a method for producing an aromatic carboxylic acid having a stable quality by reducing fluctuations in catalyst components in a liquid phase oxidation reaction system.

Aromatic carboxylic acids are produced by the liquid phase oxidation reaction of alkyl group-containing aromatic hydrocarbons. Usually, in the presence of acetic acid solvent, heavy metal compounds such as cobalt and manganese, or further promoters such as bromine compounds and acetaldehyde are added. Catalyst is used.
An oxidation reaction slurry containing an aromatic carboxylic acid obtained by such a liquid phase oxidation reaction is usually made into a low-pressure, low-temperature slurry by a crystallization operation and subjected to a solid-liquid separation operation at a pressure close to normal pressure. Group carboxylic acid crystals are isolated.

On the other hand, the oxidation reaction mother liquor obtained by solid-liquid separation contains useful catalyst components such as heavy metal ions and bromide ions derived from the catalyst. When industrially implemented, these catalyst components are recycled. By doing so, it is necessary to reduce the manufacturing cost.
The simplest circulation method of the catalyst component is to return the oxidation reaction mother liquor as it is to the reaction system and reuse it, which is widely performed in a commercial scale aromatic carboxylic acid production process.
However, in the oxidation reaction mother liquor, various organic impurities by-produced in the liquid phase oxidation reaction and inorganic impurities derived from corrosion of the apparatus are mixed, and when the oxidation reaction mother liquor is reused in the reaction system as it is. The concentration of these impurities in the reaction system gradually increases, and if it exceeds a certain concentration, the liquid phase oxidation reaction is adversely affected.

  Therefore, a part of the oxidation reaction mother liquor needs to be discharged out of the system as a purge mother liquor. This purge mother liquor contains the solvent, catalyst component, by-product, etc. used in the liquid phase oxidation reaction, and the solvent is recovered by distillation, but the catalyst component is recovered by using a pyridine ring-containing chelate resin Is known (see, for example, Patent Document 1).

  In Patent Document 1, heavy metal ions and bromide ions derived from a catalyst are continuously adsorbed on a pyridine ring-containing chelate resin, and then the adsorbed heavy metal ions and bromide ions are eluted using hydrous acetic acid having a water concentration of 20% by mass or more. To obtain a recovered catalyst solution. This process is a batch process in which the adsorption and elution steps are repeated, and the catalyst component is recovered while switching a plurality of pyridine ring-containing chelate resins.

  Since the catalyst component once adsorbed to the pyridine ring-containing chelate resin elutes and elutes from the chelate resin, the concentration of the recovered catalyst solution fluctuates during the cycle of the adsorption step and the elution step. This is the same phenomenon as the component adsorbed on the ion exchange resin or the synthetic adsorbent shows an elution pattern having a concentration peak at the time of elution.

  When the recovered catalyst solution whose concentration has been varied in this manner is returned directly to the liquid phase oxidation reaction system, more specifically, to the catalyst preparation tank, even if the recovered catalyst solution is continuously fed at a constant flow rate, Since the amount of the catalyst component contained varies, the catalyst concentration in the catalyst preparation tank varies.

  Changes in the catalyst concentration in the liquid phase oxidation reaction are known to affect the reaction activity and destabilize the quality of the aromatic carboxylic acid crystals that are produced. A new method for supplying a considerable amount of acetic acid linked to the catalyst to the oxidation reaction tank has been proposed, but the catalyst concentration is adjusted by feedforward control, which requires a complicated control system ( For example, see Patent Document 2).

  In Patent Document 3, in a method for producing terephthalic acid by reacting para-xylene with molecular oxygen in the presence of a catalyst containing manganese, cobalt, and bromine in an acetic acid solvent, an on-line system is provided between the raw material liquid adjusting tank and the reactor. The automatic analysis of manganese ions by the automatic titrator of No. 1 is performed, the replenishment of the catalyst solution is controlled, and the coefficient of variation of the manganese ion concentration is suppressed. However, in Patent Document 3, only the manganese ion concentration is analyzed, and when the ratio of cobalt ion, manganese ion, and bromide ion is deviated, there is a defect that only the manganese ion can be controlled to an appropriate concentration. .

  Patent Document 4 discloses a method for producing an aromatic dicarboxylic acid by liquid phase oxidation of a dialkyl aromatic hydrocarbon with a molecular oxygen-containing gas in an acetic acid solvent in the presence of a catalyst comprising cobalt, manganese and bromine. The catalyst concentration of cobalt, manganese and bromine in the mother liquor varies, and water is generated by the oxidation reaction, so that the moisture concentration also varies in the treatment step after the oxidation reaction. It is disclosed that fluctuations in the catalyst concentration and the water concentration as a reaction inhibitor are involved in the adjustment of the reaction solvent, complicate influencing factors on the oxidation reaction, and destabilize the oxidation reaction. And the method of measuring the catalyst density | concentration fluctuation | variation which is one of the factors which fluctuate | oxidize an oxidation reaction previously with the online analyzer by a fluorescent X ray analysis, and replenishing a required quantity according to a density | concentration is disclosed. Cobalt, manganese, and bromine can be analyzed at once by fluorescent X-ray analysis, and the analysis result can be obtained instantly. However, the apparatus is relatively expensive, and there is a disadvantage in that an X-ray working chief must be appointed depending on the apparatus.

In Patent Document 5, in a method for producing acetic acid by carbonylating methanol with carbon monoxide in a liquid reaction composition containing metal carbonyl, methyl iodide, methyl acetate, acetic acid, water, etc., catalyst rhodium, iridium Ruthenium metal carbonyls exist in equilibrium composition as several catalytically active species as metal carbonyls with different activities in solution. It is disclosed that concentration ratios can be optimized by measuring the ratio of concentrations by infrared spectroscopy in which the active species having different activities are connected on-line, and adding carbon monoxide and adding lithium iodide.
However, the metal carbonyl to be measured is suitable for the determination of metal carbonyl because it is highly sensitive to infrared spectroscopic analysis, but it is difficult to apply to other catalytic species universally, so infrared spectroscopy Application to analysis of catalyst concentration by analysis is limited.

Unlike infrared analysis based on molecular vibration in ordinary organic substances, Patent Document 6 measures the concentration of an inorganic electrolyte mixture such as HCl, H ₂ O ₂ or NH ₄ OH that does not absorb based on molecular vibration. An example is seen.

International Publication No. 2008/075752 JP 2007-70254 A Japanese Patent Laid-Open No. 5-229988 Patent No. 4812220 Special table 2009-530358 Japanese Patent No. 3290982

In the method for producing an aromatic carboxylic acid excluding terephthalic acid having a catalyst recovery process using a pyridine ring-containing chelate resin, the concentration fluctuation occurs in the cycle of the adsorption-elution step of the catalyst as described in the above paragraph 0005. As a result, the oxidation reaction fluctuates due to fluctuations in the catalyst concentration and moisture in the recovered catalyst solution, and further, the oxidation reaction fluctuates, affecting the quality of the aromatic carboxylic acid obtained.
The object of the present invention is to stabilize the liquid phase oxidation reaction by analyzing the concentration fluctuation of the recovered catalyst solution immediately and efficiently, and reducing the fluctuation of the concentration and moisture of the catalyst component in the catalyst preparation tank to which the recovered catalyst solution is returned. And providing a simple method for obtaining an aromatic carboxylic acid having a stable quality.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have installed it at a specific location in the process,
(I) Infrared analysis known as an analytical method for measuring the concentration of alkali and acid in an aqueous hydrogen peroxide solution for semiconductor processing described in Patent Document 6 is a catalyst for producing aromatic carboxylic acids excluding terephthalic acid Found to be applicable to the measurement of cobalt ion concentration and water concentration in the recovered catalyst solution in the recovery process,
(II) By measuring the manganese ion concentration and bromide ion concentration with a fully automatic titrator connected online,
Each concentration can be analyzed immediately, catalyst and moisture management becomes easy, and by adding a catalyst as necessary in the catalyst preparation tank, fluctuations in the concentration of catalyst components at the time of elution from the chelate resin tower can be mitigated. And found that the concentration fluctuation at the outlet of the catalyst preparation tank can be kept small, the catalyst concentration in the liquid phase oxidation reaction system is stable, and high-quality aromatic carboxylic acid can be easily obtained, and the present invention has been achieved. . That is, the present invention provides the following method for producing an aromatic carboxylic acid.
(1)
Fragrance excluding terephthalic acid by liquid-phase oxidation of an alkyl group-containing aromatic hydrocarbon using a molecular oxygen-containing gas in the presence of a catalyst containing a heavy metal compound and a bromine compound in a hydrous acetic acid solvent having a moisture content of 1 to 15% by mass. In the method for producing an aromatic carboxylic acid, an oxidation reaction slurry obtained by liquid phase oxidation is cooled and separated into an aromatic carboxylic acid crystal and an oxidation reaction mother liquor, and 25 to 95% of the oxidation reaction mother liquor is used as a recycle mother liquor. When the catalyst component is recovered from the purge mother liquor by purging the remaining oxidation reaction mother liquor out of the system as a purge mother liquor through circulation in the liquid phase oxidation reaction system,
(I) an adsorption step of contacting the purge mother liquor with a pyridine ring-containing chelate resin to adsorb heavy metal ions and bromide ions derived from the catalyst;
(II) An elution step in which a recovered catalyst solution (A) is obtained by bringing the hydrated acetic acid or water into contact with the pyridine ring-containing chelate resin adsorbing the catalyst component in step (I) to elute the heavy metal ions and bromide ions. Switch by formula,
(III) The recovered catalyst solution (A) is retained in the recovered catalyst solution tank for 1.5 to 6 hours, and the recovered catalyst solution (B) from the recovered catalyst solution tank is mixed with the recycle mother liquor in the catalyst preparation tank, Having a step of circulating to the liquid phase oxidation reaction system,
Measure the cobalt ion concentration and water concentration, manganese ion and bromide ion concentration of the recovered catalyst solution (B) with an infrared analyzer and a fully automatic titrator connected online at the following (i) or (ii) A process for producing an aromatic carboxylic acid characterized by comprising:

(i) A part of the closed pipe that is pulled out from the pipe connected to the lower part of the recovered catalyst tank and returned to the catalyst recovery tank
(ii) Part of piping connected from the recovered catalyst tank to the catalyst preparation tank

(2)
The recovered catalyst solution (A) from step (II) and a part or all of the recycled mother liquor are previously mixed in the recovered catalyst solution tank, and the catalyst mixture solution (C) obtained by mixing is mixed for 1.5 to 6 hours. Fully automatic titrator with on-line connection of manganese ion and bromide ion concentration by analyzing the concentration of cobalt ion in the catalyst mixture (C) with an infrared analyzer connected online to the catalyst solution tank The method for producing an aromatic carboxylic acid according to (1), wherein the concentration is analyzed by and introduced into the catalyst preparation tank.
(3)
Concentration of cobalt ion, manganese ion and bromide ion A catalyst solution containing cobalt ion or manganese ion and / or bromide ion in a known catalyst recovery solution (B) or catalyst mixture (C) The method for producing aromatic carboxylic acid according to (1) or (2), comprising a step of replenishing accordingly (4)
When the recovered catalyst solution (B) from step (III) is returned to the catalyst preparation tank, the coefficient of variation of each concentration of cobalt ion, manganese ion and bromide ion at the catalyst preparation tank outlet is 5% or less (1 )-(3) The manufacturing method of aromatic carboxylic acid in any one of.
(5)
Aromatic carboxylic acids are benzoic acid, phthalic acid, isophthalic acid, metatoluic acid, trimesic acid, 3,5-dimethylbenzoic acid, trimellitic acid, pyromellitic acid, 1,5-naphthalenedicarboxylic acid and 2,6-naphthalene The method for producing an aromatic carboxylic acid according to any one of (1) to (4), which is at least one selected from dicarboxylic acids.
(6)
The method for producing an aromatic carboxylic acid according to any one of (1) to (4), wherein the aromatic carboxylic acid is isophthalic acid or 2,6-naphthalenedicarboxylic acid.

In the present invention, a recovered catalyst liquid tank is provided for receiving the recovered catalyst liquid eluted from the pyridine ring-containing chelate resin tower, a certain amount of recovered catalyst liquid is stored in the recovered catalyst liquid tank, and the retained recovered catalyst liquid is continuously added. When returning to the catalyst preparation tank, sufficient residence time in the recovered catalyst tank is taken, and by further measuring the catalyst concentration and moisture concentration in the recovered catalyst tank in advance, The concentration variation of the catalyst component due to the batch process is mitigated, the concentration variation at the catalyst preparation tank outlet is kept small, and it does not affect the liquid phase oxidation reaction. An acid can be obtained.
Therefore, according to the present invention, it is possible to efficiently produce an aromatic carboxylic acid excluding terephthalic acid having a stable quality by a simple operation without using an analyzer that requires labor and maintenance.

In the present invention, terephthalic acid is obtained by liquid phase oxidation of an alkyl group-containing aromatic hydrocarbon using a molecular oxygen-containing gas in the presence of a catalyst comprising a heavy metal compound and a bromine compound in a solvent containing a lower aliphatic carboxylic acid. The present invention relates to a method for producing an aromatic carboxylic acid.
The alkyl group-containing aromatic hydrocarbon may be a compound in which at least one alkyl group is substituted with an aromatic ring, and the aromatic ring is either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. Also good. Examples of the alkyl group include a methyl group, an ethyl group, an isopropyl group, and a hydroxymethyl group, and a methyl group is preferable. In addition to the alkyl group, a formyl group can also be used.
Specific examples of the alkyl group-containing aromatic hydrocarbon include toluene, orthoxylene, metaxylene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,4,5-tetra Examples thereof include methylbenzene, 2,4-dimethylbenzaldehyde, 3,4-dimethylbenzaldehyde, 2,4,5-trimethylbenzaldehyde, 1,5-dimethylnaphthalene, 2,6-dimethylnaphthalene and the like.

  Specific examples of the aromatic carboxylic acid obtained by liquid phase oxidation of the alkyl group-containing aromatic hydrocarbon include benzoic acid, phthalic acid, isophthalic acid, metatoluic acid, trimesic acid, and 3,5-dimethylbenzoic acid. , Trimellitic acid, pyromellitic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and the like. Isophthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferable.

As a solvent containing a lower aliphatic carboxylic acid used as a solvent for liquid phase oxidation, water-containing acetic acid having a water content of 1 to 15% by mass is preferable, and water-containing acetic acid having a water content of 3 to 13% by mass is more preferable.
In the liquid phase oxidation reaction, a heavy metal compound and a bromine compound are used as catalysts. The heavy metal compound includes at least one of a cobalt compound and a manganese compound, and further includes a nickel compound, a cerium compound, a zirconium compound, and the like as necessary. Examples of these cobalt compounds, manganese compounds and other heavy metal compounds include organic acid salts, hydroxides, halides, carbonates, etc., and acetates and bromides are particularly preferably used.

  The bromine compound for the liquid phase oxidation catalyst may be any bromine compound that dissolves in the reaction system and generates bromide ions, such as inorganic bromine compounds such as hydrogen bromide, sodium bromide, cobalt bromide, and bromoacetic acid. An organic bromine compound such as tetrabromoethane is exemplified, and hydrogen bromide (including hydrobromic acid), cobalt bromide or manganese bromide is particularly preferably used.

The catalyst preparation tank is a tank for mixing a lower aliphatic carboxylic acid as a solvent, an alkyl group-containing aromatic hydrocarbon as a liquid phase oxidation raw material, a heavy metal compound and a bromine compound as a catalyst, and an internal liquid in the catalyst preparation tank. It is preferable to provide a stirrer that mixes the internal liquid in order to achieve uniformization. Here, the uniformly mixed liquid (referred to as a feed mix) is continuously sent to the liquid phase oxidation reactor, and the liquid phase oxidation reaction is carried out by contact with the molecular oxygen-containing gas used as the oxidizing agent. Is called.
It is preferable to use a recycled mother liquor as the solvent and catalyst supplied to the catalyst preparation tank. Solvents and catalysts that are insufficient in terms of material balance are replenished as new supplies.

The temperature of the liquid phase oxidation is 160 to 230 ° C, preferably 180 to 210 ° C. By setting the reaction temperature to 160 ° C. or higher, a large amount of the reaction intermediate does not remain in the produced slurry, and by setting it to 230 ° C. or lower, the combustion loss of the lower aliphatic carboxylic acid as the solvent is reduced.
The pressure of the oxidation reactor in the liquid phase oxidation is not particularly limited as long as the reaction system can maintain the liquid phase at the reaction temperature, and is usually 0.8 to 3.2 MPaG, preferably 1.0 to 1.9 MPaG.
Examples of the molecular oxygen-containing gas used as an oxidant in liquid phase oxidation include air, oxygen diluted with an inert gas, or oxygen-enriched air. However, in terms of equipment and cost, air is usually used. preferable.

  The oxidation reaction slurry containing the crude aromatic carboxylic acid crystals produced in the oxidation reactor is preferably sent to the next oxidation reactor connected in series, and after finishing with an oxygen-containing gas, and after undergoing an oxidation reaction, If necessary, the pressure is lowered and cooled through two or more crystallization tanks connected in series, and continuous multi-stage crystallization is performed, and the resultant is sent to the next solid-liquid separation step. The number of stages of the crystallization tank is preferably 2 to 3 stages.

  For example, when isophthalic acid is produced by a commercial scale apparatus, liquid phase oxidation of metaxylene in hydrous acetic acid in the presence of cobalt acetate, manganese acetate and hydrobromic acid at a reaction temperature of 200 ° C. and a reaction pressure of 1.6 MPa. Thus, a crude isophthalic acid slurry (isophthalic acid concentration 33% by mass, water concentration of hydrous acetic acid as dispersion medium 14% by mass) was obtained, led to a crystallization tank connected in series, and gradually dropped and cooled. It is sent to the liquid separation process.

  In the solid-liquid separation process in which the oxidation reaction slurry is cooled to separate the aromatic carboxylic acid crystals, the crude aromatic carboxylic acid slurry generated by the oxidation reaction is separated into the crude aromatic carboxylic acid crystals and the oxidation reaction mother liquor by a solid-liquid separator. Is done. This solid-liquid separation is usually performed under atmospheric pressure, but may be under pressure. Although there is no special restriction | limiting in separation temperature, Usually, it is performed in the temperature lower than the boiling point of the solvent under atmospheric pressure, for example, the range of 50-115 degreeC. Under pressure, the upper limit of the separation temperature is 150 ° C. Examples of the solid-liquid separator include a centrifuge, a centrifugal filter, and a vacuum filter.

The oxidation reaction mother liquor after separating the crude aromatic carboxylic acid crystals contains useful catalyst components such as catalyst-derived heavy metal ions and bromide ions, and is 25 to 95%, preferably 30 to 30% of the oxidation reaction mother liquor. 90% is recycled to the liquid phase oxidation reaction system as a recycled mother liquor, but the remaining oxidation reaction mother liquor (purge mother liquor) avoids the concentration of reaction by-products that affect the liquid phase oxidation reaction and corrosion metals from the equipment. Therefore, it is discharged out of the system. Since the purge mother liquor contains acetic acid as a solvent, it is usually sent to a step of recovering acetic acid.
However, the purge mother liquor also contains a useful catalyst component, and in the present invention, in step (I), it is brought into contact with a pyridine ring-containing chelate resin to adsorb heavy metal ions and bromide ions derived from the catalyst, The catalyst component is recovered.

  Here, the pyridine ring-containing chelate resin used in the present invention is an anion exchange type chelate resin having a pyridine ring, which is obtained by polymerization using 4-vinylpyridine and divinylbenzene as main raw materials. Chelate resins generally have a ligand that coordinates to metal ions to form a complex, are insoluble in water, and have a function of selectively adsorbing and separating specific metal ions. In particular, the inclusion of a pyridine ring has the advantage of efficiently adsorbing heavy metal ions. Such a pyridine ring-containing chelate resin may be a commercially available product. Examples of commercially available products include “REILLEX (registered trademark) 425 Polymer” (trade name, manufactured by Vertellus), “Sumichelate (registered trademark)”. CR-2 "(trade name, manufactured by Sumitomo Chemtex Co., Ltd.) and the like.

This method using a chelate resin mainly comprises an adsorption step and an elution step. The adsorption step is a step in which the purge mother liquor is brought into contact with a pyridine ring-containing chelate resin to adsorb heavy metal ions such as cobalt ions and manganese ions and bromide ions, and the elution step contains the catalyst components adsorbed on the chelate resin. Elution with acetic acid or water. By repeating this adsorption step and elution step, the catalyst component in the purge mother liquor can be recovered.
The contact between the liquid and the resin in the adsorption process and the elution process is a batch system in which the liquid and the chelate resin are placed in a container at the same time to perform the adsorption operation and the elution operation, or continuous circulation in which the chelate resin is packed in the tower and the liquid is supplied. Done in a manner. However, since the purge mother liquor purged out of the system is continuously discharged from the liquid phase oxidation reaction step, the contact between the purge mother liquor and the chelate resin is preferably a continuous flow system.

The continuous flow system is a method of using a plurality of pyridine ring-containing chelate resin towers and recovering catalyst components while switching between the adsorption process and the elution process. For example, in the case of 2 towers (referred to as A tower and B tower), When Tower A is in the adsorption step, Tower B is in the elution step, and when the catalyst component is sufficiently adsorbed in Tower A (before the breakthrough exceeds the adsorption capacity), the Tower A is switched and the Tower A is eluted. The tower becomes the adsorption process.
The elution of the adsorbing component is relatively simple with the pyridine ring-containing chelate resin, and the relationship between the adsorption and the time required for the elution is expressed by equation (1).

Adsorption process time ≥ Elution process time (1)

Therefore, the adsorption treatment of the purge mother liquid can be performed continuously while switching between the A tower and the B tower.
The supply rate of the purge mother liquid at the time of adsorption is preferably 1.0 to 10.0 [1 / hr] in space velocity (SV). The adsorption process time may be before the pyridine ring-containing chelate resin breaks through, and is preferably 1.0 to 6.0 [hr]. In addition, the supply rate of the eluent during elution is preferably 1.0 to 10.0 [1 / hr] in space velocity (SV), and the elution step time satisfies 0.5 to 6 while satisfying the formula (1). 0.0 [hr] is preferable.

  When the catalyst component (cobalt ion, manganese ion, bromide ion, etc.) contained in the purge mother liquor is brought into contact with the pyridine ring-containing chelate resin and the purge mother liquor, the bromine ratio of the purge mother liquor (in the purge mother liquor) It is preferable to adjust the amount of bromide ions of the total amount of cobalt ions and manganese ions in the purge mother liquor). This is because the higher the bromide ratio, the higher the adsorption rate of cobalt ions and manganese ions, and the lower the adsorption rate of carboxylic acids as reaction by-products. The bromine ratio is preferably 0.7 to 3.5, more preferably 0.9 to 3.0. In particular, by increasing the bromine ratio of the purge mother liquor in the adsorption step, it is possible to efficiently separate the carboxylic acids as reaction by-products from the catalyst components composed of cobalt ions, manganese ions, and bromide ions. Examples of the method for adjusting the bromide ratio include a method in which an aqueous solution of the bromine compound such as hydrobromic acid is added as a bromide source to the purge mother liquor.

  In the elution step of the catalyst recovery method using a chelate resin, the effluent from the chelate resin tower supplying the eluent is recovered, but the effluent does not always have a catalyst component that elutes from the resin. It is necessary to send only the portion containing the catalyst component to the recovered catalyst solution tank as the recovered catalyst solution. This is because water derived from the eluent having a high water concentration is not collected as much as possible, and water is not brought into the oxidation reaction system. Moreover, the elution of the catalyst component from the resin has a pattern with a peak, and the concentration of the catalyst component during the elution is constantly changing, and it is important to recover an effective catalyst component.

In the present invention, step (I) corresponds to an adsorption step, and the remainder of the oxidation reaction mother liquor is brought into contact with a pyridine ring-containing chelate resin to adsorb heavy metal ions and bromide ions derived from the catalyst. Step (II) corresponds to the elution step described above, and hydrous acetic acid or water is used as the eluent.
Moreover, in the catalyst recovery method using such a chelate resin tower, it is preferable to provide a recovery step of recovering byproduct carboxylic acid after the adsorption step.
That is, hydrated acetic acid having a water concentration of 1 to 15% by weight, preferably 1 to 14% by weight, more preferably 1 to 9% by weight, is brought into contact with the pyridine ring-containing chelate resin after the adsorption step. It is preferable that after a recovery step of selectively eluting the by-product carboxylic acid mixture, an elution step of recovering heavy metal ions and bromide ions derived from the catalyst by contacting with hydrous acetic acid or water is preferable. By having a recovery step before the elution step of step (II), other organic impurities and metal impurities are hardly adsorbed on the pyridine ring-containing chelate resin, so hydrous acetic acid having a water concentration of 20% by mass or more as an eluent. The heavy metal ions and bromides that can be reused in the liquid phase oxidation reaction by contacting hydrous acetic acid having a water concentration of 20 to 70% by mass, more preferably 25 to 50% by mass with a pyridine ring-containing chelate resin. Hydrous acetic acid containing ions or the like, that is, “recovered catalyst solution (A)” is obtained.

Moreover, from the viewpoint of the adsorption efficiency of the catalyst component, the pyridine ring-containing chelate resin that has undergone the elution step is provided with a substitution step, and has a moisture concentration of 1 to 15% by mass, preferably a moisture concentration of 1 to 14% by mass, more preferably moisture. It is preferable to regenerate the pyridine ring-containing chelate resin by contacting hydrous acetic acid having a concentration of 1 to 9% by mass as a replacement liquid. The regenerated pyridine ring-containing chelate resin can be reused in the adsorption step.
By such a substitution step, the water concentration of the hydrous acetic acid present around the chelate resin is lowered to the moisture concentration of the substitution solution, and the heavy metal ions and bromide ions are quickly adsorbed in the next adsorption step. On the other hand, when the replacement step is not provided, immediately after the elution step, the periphery of the chelate resin layer is covered with hydrous acetic acid having a high water concentration, so that the adsorption efficiency of the catalyst component at the initial contact with the mother liquor in the adsorption step Becomes worse, the recovery rate of the catalyst component is lowered, which is economically disadvantageous.
Furthermore, in order to make it easy to adsorb heavy metal ions and bromide ions to the pyridine ring-containing chelate resin, it is more preferable to use hydrous acetic acid having a water concentration of 1 to 15% by mass and containing bromide ions of 1 to 1000 mass ppm as the replacement liquid. preferable.
In addition, the recovered acetic acid (moisture concentration of 4 to 4) obtained from the bottom of the distillation tower when water is distilled off from the mother liquor residual liquid obtained in the adsorption process, the recovered liquid obtained in the recovery process, and the replacement liquid used in the above replacement process. 12 mass%, bromide ion concentration 1-50 mass ppm) can also be used as a replacement liquid.

In the step (III) of the present invention, in order to reduce the concentration fluctuation of the catalyst component, the recovered catalyst liquid (A) flowing out from the resin tower is temporarily stored in the recovered catalyst liquid tank, and after maintaining a certain residence time, the catalyst preparation is performed. It returns to the liquid phase oxidation reaction system through the tank.
When the effective volume of the recovered catalyst solution tank is V [m ³ ] and the flow rate of the recovered catalyst solution (A) is Q [m ³ / hr], the residence time T [hr] in the recovered catalyst solution tank is expressed by the equation (2). Is defined as

Residence time: T = V / Q (2)

The residence time of the recovered catalyst solution in the recovered catalyst solution tank in the present invention is 1.5 to 6 hours, preferably 1.5 to 4 hours. By setting the residence time to 1.5 hours or more, the concentration fluctuation of the catalyst component can be reduced, and the concentration fluctuation at the catalyst preparation tank outlet can be suppressed to a small level.

The effluent from the chelate resin tower in the elution step is sent to the recovered catalyst solution tank when the catalyst component is eluted, but when the catalyst component is not eluted in the recovery step or the replacement step. The effluent is sent to a separately installed purge solution tank, and the solvent and by-product carboxylic acid are recovered as necessary. Further, since the concentration of the catalyst component is also eluted, the concentration variation is mitigated by installing a recovered catalyst solution tank and setting a certain residence time according to the present invention.
The recovered catalyst solution (B) sent from the recovered catalyst solution tank to the catalyst preparation tank for liquid phase oxidation is continuously supplied in a constant amount to the liquid phase oxidation system in order to stabilize the catalyst components in the liquid phase oxidation. It is necessary. In order to lengthen the residence time, it is necessary to increase the effective volume of the recovered catalyst liquid tank, which is limited because it leads to an increase in the amount of capital investment. In order to reduce the concentration fluctuation of the recovered catalyst liquid (B), it is necessary to take a certain residence time. Taking these into consideration, the residence time of the recovered catalyst liquid tank is 1.5 to 6 hours. A range is preferred.

  The recovered catalyst solution (A) flowing out from the chelate resin tower in the elution step is sent to the recovered catalyst solution tank, and after a predetermined residence time, the recovered catalyst solution (B) with reduced concentration fluctuations is subjected to liquid phase oxidation. Recycled to catalyst preparation tank. The residence time is adjusted by raising and lowering the liquid level of the recovered catalyst tank. In order to make the catalyst composition uniform in the recovered catalyst liquid tank, it is preferable to have a stirrer that mixes the internal liquid.

  The recovered catalyst solution (B) is usually recycled directly to the catalyst preparation tank, but it can also be mixed with the recycle mother liquor in advance and recycled to the catalyst preparation tank. Premixing with the recycled mother liquor means adding the recovered catalyst solution (B) to the pipe through which the recycled mother liquor is circulated, which may be added as it is or using a mixer such as a static mixer. . By mixing the recovered catalyst solution (B) with the recycle mother liquor, the fluctuation range of the concentration fluctuation of the catalyst component is reduced, and the concentration fluctuation in the vicinity of the return port when returned to the catalyst preparation tank can be suppressed.

Conventionally, analysis by infrared spectroscopy is a method for observing absorption spectra derived from molecular vibrations, that is, an effective analysis method for functional groups of organic molecules, and is applicable to inorganic ions without molecular absorption spectra. It was considered an analytical method that could not be done. However, inorganic ions exist as hydrated clusters in aqueous solutions, and the coordinated water molecules have a slightly different vibration pattern and change in the absorption spectrum compared to free water. An infrared analyzer that reads the slight difference in the absorption spectrum and simultaneously measures the inorganic ion concentration and the water concentration is commercially available. The infrared analyzer is an aromatic carboxylate that contains manganese ions. Cobalt ions can also be analyzed in the recovered catalyst solution system in the acid recovery catalyst recovery process. Therefore, for the analysis of cobalt ion and moisture concentration, analysis by infrared spectroscopy that can be simultaneously measured and is less susceptible to interference with other coexisting ions is preferably used.
Regarding the water concentration, the water concentration at the catalyst preparation tank outlet is preferably 15% by mass or less.

  The analysis of manganese ions and bromide ions in the present invention can be performed by an on-line automatic titrator. As a titration method for manganese ions, a known method may be applied, and it is preferably performed by a formaldoxime absorptiometric method that is relatively insensitive to cobalt ions. Titration of bromide ions can be performed by a known method, and it is preferable to analyze by potentiometric titration with silver nitrate.

The infrared analyzer and the automatic titration apparatus are preferably connected on-line to a part of a closed pipe drawn out from a pipe connected to the lower part of the recovery catalyst tank and returned to the catalyst recovery tank. Further, there is a possibility of being connected to a part of the pipe connected from the recovered catalyst tank to the catalyst preparation tank. However, in this case, after passing through a predetermined residence time in the recovered catalyst tank, it may be analyzed with an infrared analyzer and an automatic titrator connected online when the liquid is fed to the catalyst preparation tank.
On the other hand, a recycled mother liquor separated into solid and liquid after crystallization is directly injected into the catalyst preparation tank, and the recycled mother liquor dissolves organic impurities at a high concentration, and a slurry solution in which organic impurities are precipitated due to a decrease in temperature. Therefore, the red pipe is pulled out from the pipe connected to the lower part of the catalyst preparation tank and part of the closed pipe returned to the catalyst preparation tank or the part of the pipe connected to the reactor from the catalyst preparation tank. When the external analyzer and the automatic titration apparatus are connected online, crystals of organic impurities are precipitated in the analysis cell, which is not preferable from the viewpoint of maintenance and management of the analysis apparatus.

  The catalyst recovery liquid which has been retained in the catalyst recovery tank for 1.5 to 6 hours and analyzed for concentration is returned to the catalyst adjustment tank, and 25 to 95% of the recycled mother liquor directly recovered from the oxidation reaction mother liquid after solid-liquid separation It is mixed in the catalyst preparation tank. What is necessary is just to replenish a catalyst as needed in a catalyst adjustment tank. When it is not necessary to replenish, it is not necessary to replenish the catalyst.

In order to suppress the state fluctuation of the liquid phase oxidation reaction caused by the concentration fluctuation of the recovered catalyst liquid, it is necessary to manage the concentration fluctuation width. As a management point, a recovered catalyst solution tank or a catalyst preparation tank is suitable. A catalyst preparation tank is important in that it directly affects the liquid phase oxidation reaction. The catalyst components actually managed here are heavy metal ions and / or bromide ions. Specifically, for the cobalt ion concentration, manganese ion concentration, and bromide ion concentration, the catalyst components are managed by the variation coefficient of their concentration fluctuations. Become.
Here, the coefficient of variation is defined as in equation (3).

Coefficient of variation = (standard deviation / average value) x 100 [%] (3)

The cobalt ion concentration, manganese ion concentration, and bromide ion concentration are preferably measured 3 times / day or more in the recovered catalyst solution tank or catalyst preparation tank, and the coefficient of variation is preferably managed with 15 or more measurements.
The coefficient of variation of each concentration of cobalt ion, manganese ion, and bromide ion at the catalyst preparation tank outlet is preferably 5.0% or less, and more preferably 3.0% or less.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further in detail, this invention is not limited at all by these examples. The analysis methods used in the examples are described below.

  In the following examples, pretreatment of pyridine ring-containing chelate resin, measurement of catalyst ion concentration by infrared analysis and automatic titration device connected online to the recovery catalyst tank, and measurement of catalyst ion concentration other than the recovery catalyst tank It went as follows.

<Pretreatment of pyridine ring-containing chelate resin>
An aqueous solution of hydrobromic acid having a HBr content of 1.2% by mass is passed through a pyridine ring-containing chelate resin ["REILLEX (registered trademark) 425 Polymer": trade name, manufactured by Vertellus] to pass the chelate resin in an aqueous solvent. (Br ^- form), and then the water content is passed through the acetic acid solvent is 7.0% by weight the chelate resin acetic acid solvent ^- was (Br shape).

<Measurement by online connection infrared analysis and automatic titrator>
An infrared analyzer and an automatic titrator are connected online to a part of the closed pipe that is returned to the catalyst recovery tank via a pump from the pipe connected to the lower part of the recovery catalyst tank, and the concentration of the catalyst in the catalyst recovery tank is measured. did. The infrared spectrometer used a Waterlyzer explosion-proof liquid component concentration meter RD-701B, manufactured by Kurabo Industries, to measure cobalt ions and water concentration. The automatic titration apparatus measured the manganese ion and bromide ion concentration using RTR-700-76 process titrator manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of heavy metal ion concentration>
When analyzing manually sampled, the concentration of heavy metal ions was measured using an atomic absorption spectrometer with the following specifications.
Model: Polarized Zeeman atomic absorption photometer Z-2300 (manufactured by Hitachi High-Technologies Corporation)
Wavelength: Cobalt ion 240.7nm, Manganese ion 279.6nm
Frame: Acetylene-air Measuring method: Weigh the sample in a 100 ml glass container with an electronic balance, put an appropriate amount, add about 2 ml of 20 mass% hydrochloric acid (constant boiling point, iron-free hydrochloric acid) for precision analysis, and add pure water to measure The diluted sample is weighed and diluted with an electronic balance so that the concentration of heavy metal ions is about 1 ppm. A calibration curve is prepared using standard samples of 0 ppm, 1 ppm, and 2 ppm, and the concentration of the diluted sample is measured. Multiply the concentration of the diluted sample by the dilution factor to determine the concentration of heavy metal ions.

<Measurement of bromide ion concentration>
When analyzing manually sampled, the bromide ion concentration was measured under the following conditions.
Titrator: automatic potentiometric titrator AT-510 (manufactured by Kyoto Electronics Industry Co., Ltd.)
Titration solution: 1/250 normal silver nitrate aqueous solution Detection electrode: Composite glass electrode C-172
Silver electrode M-214
Temperature compensation electrode T-111
Measuring method: Put a Teflon (registered trademark) stirrer in a 200 ml beaker and put an appropriate amount of sample (weigh the sample with a balance). Pure water is added to make the liquid in the beaker about 150 ml, and about 2 ml of 60% by mass nitric acid is added. Precipitation titration is performed with the above automatic titrator to determine bromide ion concentration.

<Measurement of moisture>
When manually sampling and analyzing, moisture was measured by the Karl Fischer method using a trace moisture measuring device CA-100 manufactured by Mitsubishi Chemical Corporation.

<Example 1>
Liquid phase oxidation (reaction temperature 200 ° C., reaction pressure 1.6 MPaG) in air continuously in two stages with air in the presence of cobalt ion 650 ppm, manganese ion 420 ppm and bromide ion 700 ppm in hydrous acetic acid with a water concentration of 9% by mass. ) To obtain a crude isophthalic acid slurry (isophthalic acid concentration of 33% by mass, water concentration of hydrous acetic acid as dispersion medium of 14% by mass), which is led to a series of two crystallization tanks connected in series and gradually reduced in pressure. Thus, a crude isophthalic acid slurry under atmospheric pressure was obtained. This slurry was subjected to solid-liquid separation to obtain a crude isophthalic acid cake and an oxidation reaction mother liquor. In addition, a sufficient amount of an oxidation reaction mother liquor was prepared for the next liquid phase oxidation using the catalyst recovery process and the recovered catalyst liquid (B). The catalyst composition of the oxidation reaction mother liquor is shown in Table-1.

    70% of the oxidation reaction mother liquor is recycled to the reaction system as a recycled mother liquor, and 30% purge mother liquor that is not recycled is cross-flow filtered using a ceramic filter to remove fine crystals containing isophthalic acid as the main component and the filtrate. Got. In order to improve the recovery rate of the catalyst component in the catalyst recovery step, an aqueous hydrobromic acid solution was added to the filtrate. Table 2 shows the composition of the catalyst component of this bromine-added purge mother liquor.

By circulating 80 ° C. hot water through the jacket of the pyridine ring-containing chelate resin tower in which the pretreated pyridine ring-containing chelate resin 50 [L] is packed in a glass double tube, the pyridine ring-containing chelate resin is obtained. Was kept at 80 ° C.
The bromine-added purge mother liquor was passed from the top of the pyridine ring-containing chelate resin tower downward for 120 minutes at a flow rate of 125 [L / hr] [adsorption step].
Thereafter, hydrous acetic acid having a water concentration of 7.0% by mass was passed from the top of the tower downward for 10 minutes at a flow rate of 100 [L / hr] [recovery step].
After the recovery step, hydrous acetic acid having a water concentration of 35.0% by mass was passed from the top of the tower downward for 100 minutes at a flow rate of 90 [L / hr] [elution step].
When the elution step was completed, a substitution solution (hydrous acetic acid having a water concentration of 7.0% by mass) was passed from the top of the column downward for 10 minutes at a flow rate of 100 [L / hr] [substitution step].
This cycle of adsorption process → recovery process → elution process → replacement process → (adsorption process) was repeated at 240 minutes / cycle.
In addition, the effluent from the chelate resin tower has an effluent from the chelate resin tower because the catalyst component eluting in the elution step is collected for 110 minutes in the recovery catalyst liquid tank, and there is almost no elution of the catalyst component. Was sent to the purge solution tank for 130 minutes.

  The recovered catalyst solution (A) obtained in the elution step was sent to a recovered catalyst solution tank equipped with a stirrer. The average flow rate of the recovered catalyst solution (A) fed was 90 [L / hr], and the average liquid level of the recovered catalyst solution tank was 50% (average effective volume at this time 180 [L]). The residence time is 2 [hr]. Table 3 shows the concentration fluctuation range of the catalyst component of the recovered catalyst solution (A). The measurement of the catalyst component, etc. was performed 48 times in 2 hours, and the concentration fluctuation range of 48 points was shown.

回収触媒液槽に２時間滞留させた後の回収触媒液(B)を予めリサイクル母液と共に混合して触媒調合槽へ送液し、液相酸化を行い、イソフタル酸を製造した。回収触媒液(B)の流量は回収触媒液(A)の平均流量と同じ９０[Ｌ／ｈｒ]とした。この回収触媒液(B)を回収触媒槽にオンライン接続された赤外分光計と自動滴定装置により、触媒組成及び水分濃度を分析した。オンラインでの分析により、サンプリングを行わなくても速やかに分析結果が得られた。触媒組成の平均値を表−４に示す。触媒成分などの測定は触媒調合槽への送液を行っている間、２時間で４８回行い、４８点の濃度変動幅を示したものである。

The recovered catalyst solution (B) that had been retained in the recovered catalyst solution tank for 2 hours was mixed with the recycle mother liquor in advance and sent to the catalyst preparation tank, and liquid phase oxidation was performed to produce isophthalic acid. The flow rate of the recovered catalyst solution (B) was 90 [L / hr], which is the same as the average flow rate of the recovered catalyst solution (A). The recovered catalyst solution (B) was analyzed for catalyst composition and water concentration using an infrared spectrometer and an automatic titrator connected online to the recovered catalyst tank. The analysis results were obtained promptly without online sampling. The average value of the catalyst composition is shown in Table-4. The measurement of the catalyst component and the like was performed 48 times in 2 hours while the solution was being fed to the catalyst preparation tank, and the concentration fluctuation range of 48 points was shown.

The catalyst mixture (C) mixed with the recycled mother liquor at the catalyst preparation tank outlet is in the form of a slurry and cannot be analyzed online. However, since it was in the state immediately before the oxidation reaction, analysis was performed by manually sampling in order to confirm the fluctuation range of the catalyst composition in the present application.
The catalyst mixed solution (C) was sampled 48 times in 2 hours at the catalyst preparation tank outlet, and the concentration fluctuation range at 48 points was analyzed. Samples were analyzed for cobalt ions and manganese ions using an atomic absorption spectrometer, and bromide ions were analyzed by titration with silver nitrate. Table 5 shows the standard deviation and coefficient of variation of the catalyst composition and the quality of the resulting crude isophthalic acid crystals. The quality referred to here includes absorbance at a wavelength of 340 nm (hue value, referred to as OD ₃₄₀ ) of a solution in which isophthalic acid is dissolved in an alkali, and 3-carboxybenzaldehyde (abbreviated as 3-CBA) as an oxidation reaction intermediate. Amount.

<Example 2>
The operation was performed in the same manner as in Example 1 except that the average effective volume of the recovered catalyst solution tank was 360 [L] and the residence time was 4 [hr]. Table-6 shows the catalyst composition fluctuation range of the recovered catalyst solution (B) in the recovered catalyst tank, and the catalyst mixture liquid (C) at the catalyst preparation tank outlet was sampled 48 times in 2 hours to analyze the concentration fluctuation range at 48 points. did. Cobalt ions and manganese ions were analyzed using an atomic absorption spectrometer, and bromide ions were analyzed by titration with silver nitrate. Table 7 shows the standard deviation and coefficient of variation of the catalyst composition and the quality of the resulting crude isophthalic acid crystals. There was no significant change in the oxygen consumption of the liquid phase oxidation reaction, especially the post-oxidation reaction. There was no change in the quality of the crude isophthalic acid crystals.

<Comparative Example 1>
The analysis of the recovered catalyst solution (B) in the recovered catalyst tank is not an on-line analysis. Instead, the recovered catalyst solution (B) is manually sampled and the concentration of heavy metal ions is measured using an atomic absorption spectrometer as usual. Was carried out in the same manner as in Example 1.
Specifically, the analysis was performed as follows.
The sampled recovered catalyst solution (B) is weighed in a 100 ml glass container with an electronic balance and put in an appropriate amount. About 2 ml of 20% by mass hydrochloric acid (constant boiling point, iron-free hydrochloric acid) for precision analysis and pure water are added to measure. The diluted sample was weighed and diluted with an electronic balance so that the concentration of heavy metal ions was about 1 ppm. A calibration curve was prepared using standard samples of 0 ppm, 1 ppm, and 2 ppm, and the concentration of the diluted sample was measured. The concentration of cobalt and manganese ions was determined by multiplying the concentration of the diluted sample by the dilution factor.
For the bromide ion concentration, place a Teflon (registered trademark) stirrer in a 200 ml beaker, add an appropriate amount of sample, add pure water to make the liquid in the beaker about 150 ml, add about 2 ml of 60% nitric acid, and add silver nitrate. Precipitation titration was performed using an automatic titration apparatus, and bromide ion concentration was determined. The moisture was measured by the Karl Fischer method.
Although the fluctuation range of the catalyst composition of the recovered catalyst solution (B) could be measured in the same manner as in Example 1, the manual analysis operation was complicated and time-consuming.

<Comparative example 2>
The operation was performed in the same manner as in Example 1 except that the average effective volume of the recovered catalyst solution tank was 90 [L] and the residence time was 1 [hr]. Table 8 shows the fluctuation range of the catalyst composition of the recovered catalyst solution (B) in the recovered catalyst tank.
In addition, for confirmation, the catalyst mixed solution (C) at the outlet of the catalyst preparation tank was sampled 48 times in 2 hours, and the results of analyzing the concentration fluctuation range at 48 points are shown. Cobalt ions and manganese ions were analyzed using an atomic absorption spectrometer, and bromide ions were analyzed by titration with silver nitrate. Table 9 shows the standard deviation and coefficient of variation of the catalyst composition and the quality of the resulting crude isophthalic acid crystals. Variations were observed in the oxygen consumption of the liquid phase oxidation reaction, especially the post-oxidation reaction. In addition, the quality of the crude isophthalic acid crystals varied greatly.

<Example 3>
In water-containing acetic acid having a water concentration of 5% by mass, liquid phase oxidation of 2,6-dimethylnaphthalene in the presence of 3000 ppm cobalt ions, 1500 ppm manganese ions and 5000 ppm bromide ions in a single step with air (reaction temperature 200 [° C.], The reaction pressure is 1.37 [MPaG]) to obtain a crude 2,6-naphthalenedicarboxylic acid slurry (concentration of 2,6-naphthalenedicarboxylic acid of 15% by mass, moisture concentration of hydrous acetic acid as a dispersion medium of 8% by mass). Then, it was led to a two-stage crystallization tank connected in series, and the pressure was reduced successively to obtain a crude 2,6-naphthalenedicarboxylic acid slurry under atmospheric pressure. This slurry was subjected to solid-liquid separation to obtain a crude 2,6-naphthalenedicarboxylic acid cake and an oxidation reaction mother liquor. In addition, a sufficient amount of an oxidation reaction mother liquor was prepared for the next liquid phase oxidation using the catalyst recovery process and the recovered catalyst liquid (B). The catalyst composition of the oxidation reaction mother liquor is shown in Table-10.

  50% of the oxidation reaction mother liquor is recycled to the reaction system as a recycled mother liquor, and 50% of the purge mother liquor that is not recycled is cross-flow filtered using a ceramic filter to produce fine crystals mainly composed of 2,6-naphthalenedicarboxylic acid. Removal gave a filtrate. In order to improve the recovery rate of the catalyst component in the catalyst recovery step, an aqueous hydrobromic acid solution was added to the filtrate. The composition of the catalyst component of this bromine added purge mother liquor is shown in Table-11.

By circulating 80 ° C. hot water through the jacket of the pyridine ring-containing chelate resin tower in which the pretreated pyridine ring-containing chelate resin 150 [L] is packed in a glass double tube, the pyridine ring-containing chelate resin is obtained. Was kept at 80 ° C.
The bromine-added purge mother liquor was passed from the top of the pyridine ring-containing chelate resin tower downward for 120 minutes at a flow rate of 125 [L / hr] [adsorption step].
Thereafter, hydrous acetic acid having a water concentration of 7.0% by mass was passed from the top of the tower downward for 10 minutes at a flow rate of 100 [L / hr] [recovery step].
After the recovery step, hydrous acetic acid having a water concentration of 35.0% by mass was passed from the top of the tower downward for 100 minutes at a flow rate of 90 [L / hr] [elution step].
When the elution step was completed, a substitution solution (hydrous acetic acid having a water concentration of 7.0% by mass) was passed from the top of the column downward for 10 minutes at a flow rate of 100 [L / hr] [substitution step].
This cycle of adsorption process → recovery process → elution process → replacement process → (adsorption process) was repeated at 240 minutes / cycle.
In addition, the effluent from the chelate resin tower has an effluent from the chelate resin tower because the catalyst component eluting in the elution step is collected for 110 minutes in the recovery catalyst liquid tank, and there is almost no elution of the catalyst component. Was sent to the purge solution tank for 130 minutes.

  The recovered catalyst solution (A) obtained in the elution step was sent to a recovered catalyst solution tank equipped with a stirrer. The average flow rate of the recovered catalyst solution (A) fed was 90 [L / hr], and the average liquid level of the recovered catalyst solution tank was 50% (average effective volume at this time 180 [L]). The residence time is 2 [hr]. Table-12 shows the fluctuation range of the concentration of the catalyst component in the recovered catalyst solution (A). The measurement of the catalyst component, etc. is performed 48 times in 2 hours, and the concentration fluctuation range of 48 points is shown.

回収触媒液槽に２時間滞留させた後の回収触媒液(B)を予めリサイクル母液と共に混合して触媒調合槽へ送液し、液相酸化を行い、２，６−ナフタレンジカルボン酸を製造した。回収触媒液(B)の流量は回収触媒液(A)の平均流量と同じ９０［Ｌ／ｈｒ］とした。この回収触媒液(B) を回収触媒槽にオンライン接続された赤外分光計と自動滴定装置により、触媒組成及び水分濃度を分析した。触媒組成の平均値を表−１３に示す。触媒成分などの測定は２時間で４８回サンプリングを行い４８点の濃度変動幅を示したものである。

The recovered catalyst solution (B) that was retained in the recovered catalyst solution tank for 2 hours was mixed with the recycle mother liquor in advance and sent to the catalyst preparation tank, and liquid phase oxidation was performed to produce 2,6-naphthalenedicarboxylic acid. . The flow rate of the recovered catalyst solution (B) was 90 [L / hr], which is the same as the average flow rate of the recovered catalyst solution (A). The recovered catalyst solution (B) was analyzed for catalyst composition and water concentration using an infrared spectrometer and an automatic titrator connected online to the recovered catalyst tank. The average value of the catalyst composition is shown in Table-13. The measurement of the catalyst component and the like is performed by sampling 48 times in 2 hours and showing the concentration fluctuation range of 48 points.

Table 13 shows the standard deviation and coefficient of variation of the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude 2,6-naphthalenedicarboxylic acid crystals. The quality mentioned here means the absorbance (hue value, referred to as OD ₄₀₀ ) at a wavelength of 400 nm of a solution of 2,6-naphthalenedicarboxylic acid dissolved in an alkali and formylnaphthoic acid (abbreviated as FNA) as an oxidation reaction intermediate. ) Content.

<Example 4>
The operation was performed in the same manner as in Example 3 except that the average effective volume of the recovered catalyst solution tank was 360 [L] and the residence time was 4 [hr]. Table-15 shows the catalyst composition fluctuation range of the recovered catalyst solution (B), and Table-16 shows the standard deviation and coefficient of variation of the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude 2,6-naphthalenedicarboxylic acid crystals. Show. There was no significant change in the oxygen consumption of the liquid phase oxidation reaction. There was no change in the quality of the crude 2,6-naphthalenedicarboxylic acid crystals.

<Comparative Example 3>
The operation was performed in the same manner as in Example 3 except that the average effective volume of the recovered catalyst solution tank was 90 [L] and the residence time was 1 [hr]. Table-17 shows the catalyst composition fluctuation range of the recovered catalyst solution (B), and Table-18 shows the standard deviation and coefficient of variation in the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude 2,6-naphthalenedicarboxylic acid crystals. Show. Variations were observed in the oxygen consumption of the liquid phase oxidation reaction. In addition, the quality of the crude 2,6-naphthalenedicarboxylic acid crystal varied greatly.

As described above, in the apparatus for producing aromatic carboxylic acid, by recovering and recycling the catalyst component by the method of the present invention, the 3-CBA content in the crude isophthalic acid crystal and the crude 2,6-naphthalenedicarboxylic acid crystal It is possible to easily suppress substances related to quality, such as FNA content, and variation coefficients of hue values OD ₃₄₀ and OD ₄₀₀ .

According to the present invention, an aromatic carboxylic acid having a stable quality can be easily and efficiently produced industrially advantageously.

Claims (6)

Fragrance excluding terephthalic acid by liquid-phase oxidation of an alkyl group-containing aromatic hydrocarbon using a molecular oxygen-containing gas in the presence of a catalyst containing a heavy metal compound and a bromine compound in a hydrous acetic acid solvent having a moisture content of 1 to 15% by mass. In the method for producing an aromatic carboxylic acid, an oxidation reaction slurry obtained by liquid phase oxidation is cooled and separated into an aromatic carboxylic acid crystal and an oxidation reaction mother liquor, and 25 to 95% of the oxidation reaction mother liquor is used as a recycle mother liquor. When the catalyst component is recovered from the purge mother liquor by purging the remaining oxidation reaction mother liquor out of the system as a purge mother liquor through circulation in the liquid phase oxidation reaction system,
(I) an adsorption step of contacting the purge mother liquor with a pyridine ring-containing chelate resin to adsorb heavy metal ions and bromide ions derived from the catalyst;
(II) An elution step in which a recovered catalyst solution (A) is obtained by bringing the hydrated acetic acid or water into contact with the pyridine ring-containing chelate resin adsorbing the catalyst component in step (I) to elute the heavy metal ions and bromide ions. Switch by formula,
(III) The recovered catalyst solution (A) is retained in the recovered catalyst solution tank for 1.5 to 6 hours, and the recovered catalyst solution (B) from the recovered catalyst solution tank is mixed with the recycle mother liquor in the catalyst preparation tank, Having a step of circulating to the liquid phase oxidation reaction system,
Measure the cobalt ion concentration and water concentration, manganese ion and bromide ion concentration of the recovered catalyst solution (B) with an infrared analyzer and a fully automatic titrator connected online at the following (i) or (ii) A process for producing an aromatic carboxylic acid characterized by comprising:
(i) A part of the closed pipe that is pulled out from the pipe connected to the lower part of the recovered catalyst tank and returned to the catalyst recovery tank
(ii) Part of piping connected from the recovered catalyst tank to the catalyst preparation tank   The recovered catalyst solution (A) from step (II) and a part or all of the recycled mother liquor are previously mixed in the recovered catalyst solution tank, and the catalyst mixture solution (C) obtained by mixing is mixed for 1.5 to 6 hours. Fully automatic titrator with on-line connection of manganese ion and bromide ion concentration by analyzing the concentration of cobalt ion in the catalyst mixture (C) with an infrared analyzer connected online to the catalyst solution tank The method for producing an aromatic carboxylic acid according to claim 1, wherein the concentration is analyzed and introduced into a catalyst preparation tank.   Concentration of cobalt ion, manganese ion and bromide ion A catalyst solution containing cobalt ion or manganese ion and / or bromide ion in a known catalyst recovery solution (B) or catalyst mixture (C) A method for producing an aromatic carboxylic acid according to claim 1 or 2, comprising a step of replenishing accordingly.   The coefficient of variation of each concentration of cobalt ion, manganese ion and bromide ion at the catalyst preparation tank outlet when the recovered catalyst solution (B) from step (III) is returned to the catalyst preparation tank is 5% or less. The manufacturing method of aromatic carboxylic acid in any one of 1-3.   Aromatic carboxylic acids are benzoic acid, phthalic acid, isophthalic acid, metatoluic acid, trimesic acid, 3,5-dimethylbenzoic acid, trimellitic acid, pyromellitic acid, 1,5-naphthalenedicarboxylic acid and 2,6-naphthalene It is at least 1 type chosen from dicarboxylic acid, The manufacturing method of aromatic carboxylic acid in any one of Claims 1-4.   The method for producing an aromatic carboxylic acid according to any one of claims 1 to 4, wherein the aromatic carboxylic acid is isophthalic acid or 2,6-naphthalenedicarboxylic acid.