JPH08310992A - Method for producing naphthalenedicarboxylic acid - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Continuous production of crude naphthalenedicarboxylic acid with good solid-liquid separation, with stable yield, and no problems such as clogging of piping during operation. A manufacturing method is provided. [Structure] Dialkylnaphthalene 8, a catalyst solution 11 composed of a cobalt salt and a manganese salt dissolved in acetic acid and / or propionic acid, and a bromine compound, and chlorobenzene 1
0 and compressed air 9 are continuously supplied to the oxidation reaction tank 1 to cause an oxidation reaction of the dialkylnaphthalene to generate naphthalene dicarboxylic acid, and the off gas 12 generated during the reaction is guided to the first condenser 2 to 60- Partially condensate at 150 ° C. and the condensate is circulated to the oxidation reaction tank 1, while the reaction solution is continuously withdrawn from the oxidation reaction tank 1 and separated into 20 solids and 23 to obtain crude naphthalenedicarboxylic acid and a catalyst solution. The catalyst solution 25 is a continuous production method of naphthalenedicarboxylic acid supplemented with a catalyst and circulated in the oxidation reaction tank 1.

Description

Detailed Description of the Invention

[0001]

The present invention relates to naphthalenedicarboxylic acid (hereinafter also referred to as "NDCA") by liquid-phase oxidation of diisopropylnaphthalene (hereinafter sometimes referred to as "DIPN") with molecular oxygen. There is). NDCA is a polyethylene naphthalate (PE) that has excellent properties as an engineering plastic, such as high heat resistance, chemical resistance and strength, good gas barrier properties, and low oxygen and carbon dioxide passage rates.
It is a raw material for producing polyesters and polyamides such as N).

[0002]

2. Description of the Related Art A method for producing NDCA by liquid-phase oxidation of DIPN with molecular oxygen in the presence of a catalyst composed of a heavy metal such as cobalt and manganese and a bromine compound is known, and various proposals have been made ( JP-A-1-12124
No. 0, JP-A-63-250344, JP-A-1
-160943, JP-A-60-89445, JP-A-60-89446, etc.).

For example, in JP-A-60-89445, a heavy metal composed of cobalt and / or manganese and bromine are contained in a solvent containing 2,6-DIPN in at least 50% by weight of acetic acid and / or propionic acid. A liquid-phase air oxidation method is disclosed in which at least 0.2 mol of the heavy metal is used per mol of 2,6-DIPN in the presence of a catalyst. JP-A-60-89446 discloses the heavy metal as a solvent. A liquid phase air oxidation process is disclosed in which at least 1% by weight is present. As represented by these methods, what is common to the conventional methods is that a heavy metal catalyst of cobalt and manganese and a bromine compound are used in large amounts with respect to 2,6-DIPN, and they consist of cobalt, manganese, and a bromine compound. The batch method in which DIPN and air are supplied to the catalyst solution for a certain period of time and only air is continuously supplied to complete the oxidation (post-oxidation), and the NDCA produced is held in the oxidation tank, and is not extracted There is a point.

Another point common to the conventional methods is that the reaction temperature and the reaction pressure are high. For example, in the examples described in JP-A-60-89445 and JP-A-60-89446, the reaction temperature is 160 to 200 ° C.,
The reaction pressure is 20 to 30 kg / cm ² G.
In the example described in Japanese Patent No. 121240, 180 to 200
° C., the reaction pressure was 15~30kg / cm ² G, in the embodiment of JP 63-250344 JP, 180
˜200 ° C., the reaction pressure is 15 kg / cm ² G, and in the example described in JP-A-1-160943, 200
C., 30 kg / cm ² G.

Since these methods employ the batch oxidation method, there is a problem that the production rate of NDCA is extremely low. That is, DIPN is not supplied during post-oxidation, and it is necessary to take out NDCA from the oxidation tank after the oxidation is completed. During that time, NDCA is not newly produced. There is a fatal drawback due to the batch oxidation method that the NDCA production rate (STY) converted per unit time and per unit capacity of the oxidation tank is low. In order to solve the drawback, measures have been taken to increase the oxidation rate under conditions of high temperature and high pressure, but as a result, combustion loss of acetic acid and / or propionic acid as a solvent (generation of carbon dioxide due to oxidation) is significantly caused. Is causing a new problem. Further, in the batch oxidation method, water by-produced in the oxidation process remains in the reaction solution (catalyst solution containing NDCA in a slurry state), so if the catalyst solution after NDCA is separated by filtration is reused, In the recycling stage, although the NDCA yield is certainly high, the NDCA produced by the oxidation reaction and suspended in the reaction solution as a slurry is collected by solid-liquid separation using a filter or centrifuge. As the generated catalyst (acetic acid solution containing heavy metal salts such as cobalt salt and manganese salt and bromine compound) is circulated in the oxidation tank, a large amount of water generated by the oxidation reaction is accumulated in the catalyst solution, resulting in the initial catalytic activity. It becomes difficult to maintain the NDCA yield, and the NDCA yield decreases over time as water accumulates, and at the same time, the amount of impurity by-products increases, which not only reduces the yield of the product NDCA, but also the purity and the hue. In fact it comes happening undesirable in terms of industrial production, etc. cause.

As a means for solving such a situation, chlorobenzene or benzene is supplied to a solution for causing an oxidation reaction, and a gas phase discharged from the oxidation reaction solution is cooled and condensed to form chlorobenzene or benzene. A method for producing naphthalenedicarboxylic acid is developed in which the chlorobenzene or benzene-rich phase of the condensate that is separated into a rich phase and a water-rich phase circulates in the oxidation reaction solution, and the water-rich phase is extracted from the system. (JP-A-6-72949)
Issue).

[0007]

This method drastically reduces the activity decrease in the circulating use of the catalyst, and makes it possible to decrease the reaction temperature and the pressure, but the yield is unstable. However, there are problems such as poor separation in the solid-liquid separator and blockage in the oxidation reaction tank and piping.

The object of the present invention is to solve these problems, to obtain a crude naphthalene dicarboxylic acid having a good solid-liquid separation property in a stable yield, and to cause problems such as clogging of pipes during operation. An object of the present invention is to provide a continuous method for producing naphthalenedicarboxylic acid.

[0009]

The present invention provides a method for continuously producing naphthalenedicarboxylic acid that achieves the above-mentioned object, including a dialkylnaphthalene, a cobalt salt and a manganese salt dissolved in acetic acid and / or propionic acid, and A catalyst solution consisting of a bromine compound, chlorobenzene and compressed air are continuously supplied to an oxidation reaction tank to oxidize a dialkylnaphthalene to generate naphthalenedicarboxylic acid, and off-gas generated during the reaction is a downflow first. 1 leading to a condenser for partial condensation and circulating the condensate in an oxidation reaction tank, while the reaction solution is continuously withdrawn from the oxidation reaction tank and solid-liquid separated to obtain crude naphthalenedicarboxylic acid and a catalyst solution, In the continuous production method of naphthalenedicarboxylic acid in which the catalyst solution is replenished with the catalyst and circulated in the oxidation reaction tank, the oxidation reaction tank The total concentration of cobalt and manganese metal in the reaction solution inside is in the range of 5 to 10% by weight, based on the total number of moles of cobalt and manganese metal in the reaction solution inside the oxidation reaction tank. , So that the number of moles of bromine atoms is in the range of 1/8 to 1/2, and the moles of cobalt and manganese metal per unit time to which the supplemental amount in the catalyst solution circulated in the oxidation reaction tank is added. The number of moles of the dialkylnaphthalene continuously supplied to the oxidation reaction tank is 0.5 to
The volume of the reaction solution occupying the oxidation reaction tank so that the molar ratio is within the range of 2.0 per unit time of the acetic acid and / or propionic acid solution containing naphthalenedicarboxylic acid and the catalyst continuously discharged from the oxidation reaction tank By controlling the calculated average residence time to be in the range of 3 to 7 hours by dividing by the discharge volume of
The reaction is carried out at a reaction temperature of ℃ or higher and 180 ℃ or lower at a reaction pressure of less than 10 kg / cm ² (gauge pressure), and the first condenser partially condenses in the range of 60 to 150 ° C. Lead to the second condenser to fully condense,
The feature is that the water produced by the oxidation reaction is continuously withdrawn from the system from the oxidation reactor.

Dialkylnaphthalene is diisopropylnaphthalene, isopropylethylnaphthalene, diethylnaphthalene, ethylmethylnaphthalene, dimethylnaphthalene, isopropylmethylnaphthalene, sec-butylisopropylnaphthalene, disec-butylnaphthalene,
sec-butylethylnaphthalene, sec-butylmethylnaphthalene, di-tert-butylnaphthalene, te
Examples thereof include rt-butylisopropylnaphthalene, tert-butylethylnaphthalene, and tert-butylmethylnaphthalene. As diisopropyl naphthalene (DIPN), 2,6-isomer, 2,7-isomer, all isomers, and a mixture thereof can be used. Formylnaphthoic acid, acetylnaphthoic acid,
You may use the oxidation derivative such as isopropyl naphthoic acid as a raw material. The amount of DIPN supplied may be 1 to 40% by weight based on the solvent used.

Acetic acid and / or propionic acid are used as the solvent. The most preferred solvent is acetic acid.

The presence of water is acceptable to some extent, but the presence of a large amount of water inhibits oxidation and is not preferred. The water content is preferably 7 times or less, and more preferably 5 times or less, the total molar amount of heavy metals such as cobalt and manganese. If it exceeds 7 times by mole, the catalytic activity is remarkably reduced and the NDCA yield is reduced. Further, it was found that the produced naphthalenedicarboxylic acid (solid slurry) has increased stickiness and adheres thickly to the walls of the oxidation tank and the pipe, which causes clogging.

Therefore, the amount and condensation of chlorobenzene and benzene supplied to the oxidation reaction solution are adjusted so that the molar amount of water is not more than 7 times the total molar amount of heavy metals such as cobalt and manganese in the oxidation reaction solution. It is necessary to determine the circulation rate of chlorobenzene or a benzene-rich phase in the liquid.

As the oxidation catalyst, a heavy metal salt of cobalt or manganese and a bromine compound are used in combination. Examples of these heavy metals include oxides, hydroxides, carbonates, organic acid salts, and halides. Among these, organic acid salts,
Acetate is particularly preferred. As a bromine compound, bromine (B
r ₂ ), hydrogen bromide, an inorganic bromine compound such as a hydrogen bromide salt,
Alkyl bromides such as methyl bromide, ethyl bromide, propyl bromide, ethylene bromide and the like can be mentioned. Among these, hydrogen bromide, sodium bromide, potassium bromide, ammonium bromide, cobalt bromide and manganese bromide are particularly preferable.

By using cobalt and manganese together, a higher catalytic action is recognized as compared with the case where cobalt or manganese is used alone. The ratio of each heavy metal used as a catalyst is 0.1 ≦ Co / (Co + Mn) in atomic ratio.
≦ 0.9, preferably 0.2 ≦ Co / (Co + Mn)
≦ 0.7. Outside this range, the yield of NDCA decreases.

The feed amount of heavy metal, which is the total of cobalt and manganese, to the DIPN continuously fed to the reaction tank is expressed as a molar ratio, and 0.5 ≦ (Co + Mn) / DI
PN ≦ 2.0. Below this range, not only the NDCA yield decreases and the amount of by-product trimellitic acid (TMA) significantly increases, but also trimellitic acid forms a complex with heavy metals such as cobalt and manganese, and the catalyst loss amount is reduced. Will increase. When the amount is more than this range, a large amount of the catalyst is used, so that the produced and precipitated NDCA is accompanied by a heavy metal, which not only lowers the purity of the NDCA but also leads to catalyst loss. In addition, the reaction tank becomes large and NDCA
Industrially unfavorable situations occur, such as a decrease in productivity and the deposition and blocking of the catalyst in the blowing tube of the molecular oxygen-containing gas. The above range is characteristic when performing a continuous oxidation reaction, and the reason is not clear, but batch oxidation (feeding diisopropyl naphthalene as a raw material and air to the catalyst solution previously charged in the oxidation tank to perform the oxidation reaction However, in the method in which naphthalenedicarboxylic acid is stored in the oxidation tank instead of being extracted from the oxidation tank, 1.0
≦ (Co + Mn) /DIPN≦4.0, which is characteristic, while a large amount of catalyst is required.

In addition to facilitating the oxidation reaction, there is an optimum range of cobalt and manganese catalysts in the acetic acid and / or propionic acid solution. The reason for this is not clear, but the oxidation must be carried out so that the total concentration of cobalt and manganese metals in the reaction liquid present inside the oxidation tank is in the range of 5 to 10% by weight. That is, if it is less than 5%, the cobalt and manganese catalysts cannot efficiently oxidize the dialkylnaphthalene, so that the yield of naphthalene dicarboxylic acid decreases. When it exceeds 10%, the cobalt and manganese catalyst concentration exceeds the solubility, the catalyst is deposited inside the oxidation tank, and the catalyst is clogged at the outlet of the oxidation tank, which makes the oxidation operation difficult.

A part of the catalyst used in the oxidation reaction forms an unnecessary complex with trimellitic acid and acetic acid and / or propionic acid, which are by-products of the oxidation reaction, and precipitates together with NDCA. Therefore, the amount of the catalyst effective for the oxidation reaction dissolved in the solvent becomes insufficient. To make up for it, it is necessary to supplement with fresh catalyst. Cobalt and manganese heavy metals entrained in NDCA can be recovered almost quantitatively by washing with an aqueous solution containing an acid component such as sulfuric acid.
By adding carbonate to the aqueous solution to make it alkaline, it is possible to recover cobalt carbonate and manganese almost quantitatively. This carbonate can be directly dissolved in acetic acid and / or propionic acid solution and recycled to the oxidation tank, and its catalytic activity is comparable to that of the fresh product.

There is a suitable range for the amount of the bromine compound that is an oxidation reaction accelerator used with respect to the total amount of heavy metals such as cobalt and manganese. This range is expressed as a molar ratio,
1/8 ≦ Br / (Co + Mn) ≦ 1/2. Below this range, the oxidation reaction does not proceed smoothly and the NDCA yield decreases. Above this range, the addition reaction of bromine to the naphthalene ring will occur, resulting in a decrease in NDCA yield, a decrease in NDCA purity and quality deterioration, and an increase in the amount of methyl bromide entrained in the exhaust gas. It is not preferable because it causes pollution problems.

The supply amount of chlorobenzene to the oxidation reaction tank is 100 to 1 with respect to 100 parts by weight of water produced by the oxidation reaction.
000 parts by weight, more preferably 250 to 750 parts by weight. If the amount of chlorobenzene supplied is less than 100 parts by weight, water cannot be efficiently removed from the oxidation tank, and water accumulates in the circulating catalyst, degrading the catalytic activity. Even if more than 1000 parts by weight of chlorobenzene is supplied, the efficiency of removing the oxidation product water does not increase, but rather, the cooling capacity increases due to the increase in the amount of chlorobenzene, and the chlorbenzene circulation equipment expands in economic terms. This leads to an increase in cost, which is not preferable.

As the molecular oxygen-containing gas, air can be used as it is. Further, oxygen or air diluted with an inert gas can be used.

As the molecular oxygen-containing gas, air can be used as it is. Further, oxygen or air diluted with an inert gas can be used. The oxygen partial pressure is preferably 0.2 to ² kg / cm ² .

The reaction temperature is 160 to 180 ° C. Below this range, the oxidation of DIPN to the oxidation intermediate proceeds rapidly, but the oxidation of the oxidation intermediate to NDCA does not proceed smoothly, and the NDCA yield decreases. If it exceeds this range, the loss of combustion of acetic acid as a solvent increases, which is not economically preferable.

The pressure to be used may be at least a pressure capable of maintaining the liquid phase in the reaction tank, but 10 kg / cm ²
When it is G or more, the loss of combustion of acetic acid and / or propionic acid which constitutes the solvent increases, so the amount is made less than 10 kg / cm ² G.

The role of the first condenser is to condense water but not acetic acid and / or propionic acid among the gas phase components entrained in the offgas of the oxidation reaction tank. Therefore, under the condition that the pressure in the oxidation reaction tank is 8 Kg / cm ² G, the temperature at the outlet of the first condenser is controlled in the range of 60 to 150 ° C, preferably in the range of 80 to 140 ° C. When the temperature exceeds this temperature range, the partial condensation amount decreases, and the acetic acid amount entering the second condenser remarkably increases. As a result, the amount of acetic acid circulated from the first condenser to the oxidation reaction tank extremely decreases, and the oxidation reaction tank operates. Cannot be done. On the other hand, when the temperature falls from the above temperature range, the amount of circulating acetic acid increases, but the amount of water partially condensed also increases, and a large amount of water is circulated to the oxidation reaction tank, making it difficult to effectively remove water. Next, NDCA
After the solid-liquid separation, water is accumulated in the recovered catalyst liquid, and the catalytic activity is significantly reduced.

The condensate collected in the second condenser is subjected to a distillation separation operation to obtain a chlorobenzene / water mixture as a top fraction and acetic acid and / or propionic acid as a bottom fraction. The chlorobenzene / water mixture is phase-separated and recovered as a chlorobenzene phase and an aqueous phase. Distillation may be either ordinary batch distillation or continuous distillation,
It doesn't matter. The distillation column may be either a packed column or a tray type without any problem. The distillation conditions may be atmospheric pressure or reduced pressure.

By dividing the volume occupied by the reaction solution in the oxidation reaction tank by the discharge volume of the acetic acid and / or propionic acid solution containing naphthalenedicarboxylic acid and the catalyst continuously discharged from the oxidation reaction tank per unit time, It is necessary to operate so that the calculated average residence time is in the range of 3 to 7 hours. Below this range, the state of incomplete oxidation remains, the amount of intermediate increases, and the NDCA yield decreases. Above this range, the product is placed in the oxidized state for longer than the reaction time required for complete oxidation, resulting in increased impurities and NDCA.
Yield decreases.

Solid-liquid separation of the reaction liquid extracted from the oxidation reaction tank may be carried out by a filtration system or a centrifugal separation system. The complete condensate discharged from the second condenser is supplied to a distillation column, and acetic acid and / or propionic acid separated at the bottom of the column is used as a washing liquid for the crude NDCA solid-liquid separated and / or a catalyst liquid solid-liquid separated. It is preferable to use it as a diluent.

A catalyst is attached to the crude NDCA and can be recovered by washing with acetic acid and / or propionic acid recovered at the bottom of the column. At that time, there is no need to use fresh acetic acid and / or propionic acid, which is economical. In the catalyst liquid discharged from the oxidation reaction tank, acetic acid and / or propionic acid is distilled out from the oxidation reaction tank, so that the catalyst metal is concentrated. It is economically extremely advantageous to use a column bottom recovery liquid without using fresh acetic acid and / or propionic acid as the diluent.

[0030]

【Example】

Example 1 The apparatus shown in FIG. 1 was used. The oxidation reaction tank (1) was titanium-lined and had a volume of 13.7 liters, and was equipped with a disc turbine type multistage stirring blade. The oxidation reaction tank (1) has a DIPN supply line (8), an air supply line (9), a chlorobenzene supply line (10), a catalyst circulation line (11), an off-gas discharge line (12) and a solvent circulation line (13). ) Is connected.

The off-gas discharge line (12) has a first condenser
(2) is connected, and a partial condensate liquid receiver (3) is connected underneath. The bottom of the partial condensate receiver (3) is connected to the solvent circulation line (13) via the first condensate circulation pump (6). The off-gas discharge line of the first condenser is the second condenser
It is connected to (7) and from there is further connected to a gas-liquid separator (4). The off-gas discharge line is connected to the upper part of the gas-liquid separator (4), and the pipe from the receiver (5) is connected to the bottom part. The receiver (5) is connected to a distillation column (14), a solvent discharge line (15) is provided at the bottom of the distillation column (14), and a chlorobenzene / water mixture discharge line is provided at the top of the column.
(16) are connected respectively. The chlorobenzene / water mixture discharge line (16) is connected to a phase separator (17),
Above the phase separator (17) is the oxidation product water discharge line (18).
At the bottom, chlorobenzene circulation lines (19) are connected, respectively. This chlorobenzene circulation line
The other end of (19) goes through a pump to supply chlorobenzene.
It is connected to (10).

A first oxidation product storage tank (21) and a second oxidation product storage tank (22) are connected in series to the bottom of the oxidation reaction tank (1) via a reactant discharge line (20). These storage tanks (21) and (22) have solvent discharge lines for the distillation column (14).
(15) is connected. The second oxidation product storage tank (22) is connected to the solid-liquid separator (23). Solid-liquid separator
The catalyst discharge line (1) of the distillation column (14) is further provided in (23).
5), the crude NDCA discharge line (24) and the catalyst liquid discharge line (25) are connected. The catalyst liquid discharge line (25) is connected to the catalyst circulation tank (26), and from there, the catalyst circulation line
It is connected to the oxidation reaction tank (1) via (11). A catalyst replenishment line (27) is connected to the catalyst circulation tank (26).

2,6-DIPN is supplied from the DIPN supply line (8), chlorobenzene is supplied from the chlorobenzene supply line (10) to the oxidation reaction tank (1), and a catalyst circulation line is provided.
(11) The catalyst was supplied to start the NDCA manufacturing operation.
The weight per hour is as shown in the mass balance table of Table 1.

[0034]

[Table 1]

A part of the catalyst used for the oxidation reaction forms a complex with trimellitic acid (TMA), which is an oxidation byproduct, to form N.
Since it precipitates together with DCA, while adding a replenishment catalyst via the catalyst replenishment line (27) so that the amounts of cobalt acetate (anhydrous salt equivalent) and manganese acetate (anhydrous salt equivalent) in the circulating catalyst are always constant, It ran continuously. In addition, air pressurized by a compressor was supplied from the air supply line (9), and continuous operation was performed at 170 ° C. and 8 Kg / cm ² G.

The amount of cooling water was controlled so that the outlet temperature of the first condenser (2) was 128 ° C., and the gas phase components of the oxidation reaction tank which were entrained in the off gas were partially condensed. Partial condensate is the receiver (3)
Stored in the oxidation reaction tank via the circulation pump (6) while adjusting the frequency so that the liquid level of the receiver (3) becomes constant.
It was continuously circulated in (1). The partial condensate circulated in the oxidation reaction tank was mainly composed of acetic acid. The components not condensed in the first condenser (2) are cooled to 35 ° C. in the second condenser (7),
Completely condensed.

This condensate is stored in a receiver (5), then once recovered under normal pressure, and then supplied to a continuous distillation column (14) made of SUS317L with a theoretical plate number of 65 (sieve tray), Chlorobenzene and water were recovered from the top, and the chlorobenzene phase was recycled to the oxidation reaction tank (1). The acetic acid at the bottom of the column was used as a wash acetic acid for NDCA. The NDCA yield (DIPN standard) after 10 hours from the start of continuous operation by the catalyst circulation was 85%, but when the catalyst circulation was continued continuously, the yield started to improve and after 10 hours, ND
The CA yield was stable at 90%. The trimellitic acid yield is 6
%Met. During that time, no decrease in the activity of the circulating catalyst was observed. The crude NDCA was a free-flowing pale yellow powder and had good solid-liquid separation from the catalyst. In addition, the acetic acid combustion loss weight calculated from Table 1 is the NDCA produced.
The weight per unit weight was very small, 0.071, which proved the economic merit of this method.

Reactant discharge line (20) of the oxidation reaction tank (1)
Analysis of the composition of the reaction product (FIG. 1, I) discharged from the reactor revealed that the total concentration of cobalt and manganese metal was 7.5% by weight, and the molar ratio of Br to the total number of moles of cobalt and manganese was 0.25. there were.

Cobalt and manganese contained in the catalyst liquid (FIG. 1, K) circulated in the oxidation reaction tank (1) relative to the molar amount of diisopropylnaphthalene (FIG. 1, A) supplied to the oxidation reaction tank (1). The ratio of the total molar amounts of the metals was 1.1.

The average residence time was 5.6 hours.

As described above, the partial condensate containing acetic acid as the main component, which is recovered by adding chlorobenzene to increase the evaporation amount of the oxidation product water and partially condensing the off-gas entrained component, is used in the oxidation reaction tank (1 ), The oxidation product water is completely condensed in the subsequent second condenser (7), and if extracted to the outside of the system,
Oxidized water can be easily removed from the oxidation system, and even if the catalyst is circulated, the filterability of NDCA does not deteriorate, the catalytic activity does not decrease, and a high NDCA yield can be maintained for a long time. done.

Examples 2 to 7 Using the equipment described in Example 1, under the same conditions as the reaction temperature and reaction pressure and the first condenser outlet temperature described in Example 1,
The operation was carried out. The following table shows the operation factors and operation results in that case.

[0043]

[Table 2]

The filterability of the crude NDCA in the solid-liquid separator (23) is good, and there is no clogging of the crude NDCA or the catalyst in the oxidation reaction tank (1) or other tanks or pipes, and it can be used for a long time. , Stable operation was possible.

Comparative Example 1 The same apparatus and the same operation as in Example 1 were carried out except that chlorobenzene was not supplied and the pump of the chlorobenzene circulation line (19) was not operated.

The amount of water escaped from the second condenser (7) is far below the theoretical amount of water produced by oxidation, and as a result, the oxidation reaction tank (1) passes through the solid-liquid separator (23). The water content in the circulating catalyst liquid circulated in the above was larger than that in Example 1, and increased as the catalyst circulation time became longer.

The NDCA yield was 85% after 10 hours from the start of the catalyst circulation, but after 20 hours the NDCA yield was 79%.
Fell to. When the catalyst circulation was further continued, water was further accumulated, and the NDCA yield decreased to 70% after 30 hours. The catalyst activity was clearly reduced, and the solid-liquid separator
The crude NDCA obtained from (23) also changed into a sticky brown solid, and the filterability deteriorated.

Comparative Example 2 The outlet temperature of the first condensate (2) of Example 1 was changed from 128 ° C to 16 ° C.
The same operation as in Example 1 was performed except that the temperature was raised to 0 ° C. to increase the amount of water flowing through the second condenser (7). As a result, the amount of acetic acid returning from the partial condensate liquid receiver (3) to the oxidation reaction tank (1) decreases, the liquid level of the oxidation reaction tank drops sharply, and the solid-liquid separator ( The line up to 23) was clogged with the catalyst and NDCA, impairing the stability of continuous oxidation, and operation became impossible.

Comparative Example 3 The same operation as in Example 1 was carried out except that the outlet temperature of the first condenser (2) was set to 50 ° C. As a result, the amount of liquid partially condensed increased, and the amount of complete condensation in the second condenser (7) decreased.

As a result, the amount of water escaped is less than the theoretical amount of water produced by oxidation, and as a result, the circulating catalyst liquid circulated to the oxidation reaction tank (1) via the solid-liquid separator (23) is circulated. The water content was larger than that in Example 1, and increased as the catalyst circulation time became longer.

The NDCA yield was 75% after 10 hours from the start of the catalyst circulation, but when the catalyst circulation was continued, more water was accumulated, and after 20 hours, the NDCA yield was 50 to 50%.
It fell to 60%. The catalytic activity was clearly decreased, and the crude NDCA obtained from the solid-liquid separator (23) was also changed to a sticky brown solid and the filterability was deteriorated.

Comparative Examples 4 to 11 Using the equipment described in Example 1, under the same conditions as the reaction temperature and reaction pressure and the first condenser outlet temperature described in Example 1,
The operation was carried out. The following table shows the operation factors and operation results in that case.

[0053]

[Table 3]

When operating under conditions outside the scope of the present invention,
An unfavorable situation occurs for stable operation, such as a reduction in NDCA yield, a shutdown due to blockage of the catalyst, and a shutdown due to poor solid-liquid separation in the filter.

[0055]

According to the present invention, crude naphthalene dicarboxylic acid having good solid-liquid separation can be obtained by a continuous method in a stable yield, and there is no problem such as clogging of piping during operation.

[Brief description of drawings]

FIG. 1 is a flow sheet showing a configuration of an apparatus used in an example of the present invention.

[Explanation of symbols]

 1 ... Oxidation reaction tank 2 ... 1st condenser 3 ... Partial condensate liquid receiver 4 ... Gas-liquid separator 5 ... Receiver 6 ... 1st condensate liquid circulation pump 7 ... 2nd condenser 8 ...... DIPN supply line 9 ...... Air supply line 10 ... Chlorobenzene supply line 11 ... Catalyst circulation line 12 ... Off gas discharge line 13 ... Solvent circulation line 14 ... Distillation column 15 ... Solvent discharge line 16 ... Chlorobenzene / water mixture discharge line 17 ... Phase separator 18 ... Oxidation product water discharge line 19 ... Chlorobenzene circulation line 20 ... Reactant discharge line 21 ... First oxidation product storage tank 22 ... Second oxidation product storage tank 23 ... Solid-liquid separator 24 ... Crude NCDA Discharge line 25 ... Catalyst liquid discharge line 26 ... Catalyst circulation tank 27 ... Catalyst replenishment line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Kato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A catalyst solution comprising a dialkylnaphthalene, a cobalt salt and a manganese salt dissolved in acetic acid and / or propionic acid, and a bromine compound, chlorobenzene and compressed air are continuously supplied to an oxidation reaction tank to dialkylnaphthalene. To produce naphthalenedicarboxylic acid, the off-gas generated during the reaction is guided to the first condenser in the downward flow to be partially condensed, and the condensate is circulated in the oxidation reaction tank, while the reaction solution is oxidized. Crude naphthalenedicarboxylic acid and a catalyst liquid are obtained by continuously extracting from the reaction tank and performing solid-liquid separation, and the catalyst solution is supplemented with a catalyst and circulated in the oxidation reaction tank in the continuous production method of naphthalenedicarboxylic acid Oxidation so that the total concentration of cobalt and manganese metal in the reaction liquid existing in the tank is in the range of 5 to 10% by weight. It is circulated to the oxidation reaction tank so that the molar ratio of bromine atoms to the total molar ratio of cobalt and manganese metal present in the reaction solution is 1/8 to 1/2. The number of moles of cobalt and manganese metal to which the replenisher in the catalyst liquid is added per unit time is 0.5 to a mole ratio with respect to the number of moles of dialkylnaphthalene continuously supplied to the oxidation reaction tank per unit time.
The volume of the reaction solution that occupies the oxidation reaction tank so that the molar ratio is in the range of 2.0 per unit time of the acetic acid and / or propionic acid solution containing the naphthalene dicarboxylic acid and the catalyst continuously discharged from the oxidation reaction tank By controlling the calculated average residence time to be in the range of 3 to 7 hours by dividing by the discharge volume of
° C. by oxidation under the conditions of reaction pressure of higher than 180 ° C. The following reaction temperature 10 kg / cm ² (gauge pressure), in the first condenser causes the partial condensation in the range of 60 to 150 ° C., the non-condensable components Lead to the second condenser to fully condense,
A method for producing naphthalenedicarboxylic acid, which comprises continuously extracting water produced by an oxidation reaction from the oxidation reactor to the outside of the system. 2. The condensate discharged from the second condenser is distilled, and the chlorobenzene / water component separated at the top of the column is phase-separated, and then the chlorobenzene phase is circulated to the oxidation reaction tank, and the water phase is Acetic acid and / or propionic acid separated from the system and separated at the bottom of the column is used as a washing solution for crude naphthalenedicarboxylic acid solid-liquid separated from the reaction solution continuously discharged from the oxidation reaction tank and / or after solid-liquid separation As a diluent for the catalyst liquid of
The method for producing naphthalenedicarboxylic acid according to claim 1, which is reused.