JPH0748314A - Continuous production of naphthalenedicarboxylic acid - Google Patents

Abstract

PURPOSE:To provide an efficient production method of naphthalenedicarboxylic acid by circulatively reusing an oxidation reaction catalyst, continuously oxidizing dimethylnaphthalene. CONSTITUTION:In oxidizing dimethylnaphthalene and/or its oxidation derivative with a molecular oxygen-containing gas in a solvent containing at least twice as much as a lower aliphatic carboxylic acid (preferably acetic acid) by weight, having 5-45wt.%, especially 10-30wt.% water content in the presence of an oxidation catalyst composed of a heavy metal, preferably cobalt, manganese and bromine, the catalyst is supplied in such a way that the effective concentration of the heavy metal catalyst prepared by removing o-benzenedicarboxylic acid complex of heavy metal contained in the solvent is made >=0.2wt.%, preferably 0.4-1.0wt.% and almost the whole amount of the reaction mother liquor and/or formed cake is circulated and reused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing naphthalene dicarboxylic acid (hereinafter sometimes abbreviated as NDCA) by oxidizing dimethylnaphthalene and / or its oxidized derivative. For more details,
The present invention relates to an oxidation method in which an oxidation reaction catalyst is recycled.

[0002]

2. Description of the Related Art NDCA and its ester (hereinafter referred to as ND
(Sometimes abbreviated as CA, etc.) is a substance useful as a polymer material, a dye intermediate, and the like. Especially 2,6-NDCA
Polyethylene naphthalate formed from ethylene glycol and the like and ethylene glycol is superior to polyethylene terephthalate in heat resistance, breaking strength, and the like, and has attracted attention as a raw material for films, food packaging materials, and the like. Further, since polybutylene naphthalate resin has a higher crystallization rate and higher wet heat resistance than polybutylene terephthalate resin, NDCA or the like is also useful as a resin raw material.

Conventionally, a method of producing NDCA has been a method of oxidizing dialkylnaphthalene and / or an oxidized derivative thereof with molecular oxygen in a lower aliphatic carboxylic acid solvent using cobalt, manganese, bromine or the like as a catalyst. Many have been proposed.

These methods are classified into a batch system, a semi-continuous system or a continuous system, depending on the reaction mode, and a case where the catalyst is recovered / reused or not.

In order to efficiently produce NDCA on an industrial scale, it is necessary to increase the efficiency as a continuous operation system because the batch-wise or semi-continuous reaction mode has low equipment efficiency and is unsuitable.

Further, in the production of carboxylic acid by liquid-phase oxidation of aromatic hydrocarbon, a relatively expensive catalyst is generally used, so that the catalyst is recycled and reused, that is, the crude NDCA produced is recovered from the reaction mixture. The recycled use of the reaction mother liquor and / or the wash filtrate of the crude NDCA produced is essential for increasing the economic efficiency of the process.

As one of the methods of recovering the oxidation reaction catalyst from the oxidation reaction mixture and recycling it, a method of recovering only the catalyst from the reaction mixture has been proposed. For example, 2,6
In the oxidation reaction of diisopropylnaphthalene, a method of using an alkali to recover the catalyst from the reaction mother liquor when the reaction is carried out using cobalt, manganese, cerium and bromine as a catalyst (JP-A-2-250850) and sulfuric acid are used. Method (JP-A-2-250851) and a method using sulfuric acid and alkali (JP-A-2-25261).
No. 3) is proposed. However, neither of the methods is sufficient in terms of reality and economy in order to inexpensively manufacture NDCA on an industrial scale in terms of corrosiveness with respect to equipment materials or operability.

[0008] As another method of recovering the oxidation reaction catalyst from the oxidation reaction mixture and recycling it, a technique of recycling the reaction filtrate has been proposed. For example, in the oxidation reaction of 2,6-diisopropylnaphthalene, cobalt,
When carrying out the reaction using manganese, cerium and bromine as a catalyst, a method of carrying out a two-step reaction and circulating the reaction filtrate (Japanese Patent Laid-Open No. 4-330039) has been proposed. This method is called post-oxidation. Because it has a process,
The initial investment in the process increases, which is not economically advantageous.

Further, as a method of oxidizing 2,6-diisopropylnaphthalene or 2,6-diethylnaphthalene, a method of reusing the reaction mother liquor has been proposed (Japanese Patent Laid-Open No. 4-2).
No. 66846). The cyclic oxidation reaction by this method is basically possible, but in the case of the oxidation reaction of 2,6-diisopropylnaphthalene and 2,6-diethylnaphthalene, a large amount of cobalt is still present in the crude DNCA after the reaction mother liquor separation. Considering that it is accompanied by manganese, the crude N
It is necessary to reduce the catalyst cost by washing DCA with acetic acid, water or the like to recover these catalysts.

By the way, when the weight loss is dimethylnaphthalene, the above-mentioned document does not describe the oxidation reaction by this method. Therefore, when the present inventors attempted a continuous oxidation method for dimethylnaphthalene, a serious problem that the reaction was stopped at an early stage of circulation (first circulation) occurred.

The inventors of the present invention have made extensive studies on the cause of this problem. Unlike the case of 2,6-diisopropylnaphthalene or 2,6-diethylnaphthalene, the reaction is stopped at the first circulation in the case of dimethylnaphthalene. The phenomenon that occurs is an acid having a dicarboxylic acid at the ortho position such as trimellitic acid, phthalic acid, and methyl-substituted phthalic acid, which are by-products of naphthalene nuclear cleavage (ie, ortho-benzenedicarboxylic acids, hereinafter abbreviated as ODCA). A) forms a chelate-type complex with a heavy metal, which is an oxidation catalyst, and becomes a stable compound, so that the catalytic activity of the heavy metal is impaired, and as a result, it is only possible to supplement the catalyst entrained in the crude NDCA. It was found that the effective amount of catalyst was insufficient.

As a measure for avoiding these problems, a means of using a large amount of heavy metal catalyst can be considered, but in the case of dimethylnaphthalene (as compared with the case of 2,6-diisopropylnaphthalene or 2,6-diethylnaphthalene). However, the proper catalyst concentration is relatively low in view of the yield, and when a large amount of the catalyst is used, the yield of NDCA is rather reduced. Moreover, a part of the heavy metal added in excess is changed during the oxidation reaction, and the produced crude NDCA is colored dark gray to make purification difficult. In addition, combustion of the lower aliphatic carboxylic acid as a solvent This can have the disadvantageous consequence of increased loss.

[0013]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention has as its object the provision of a continuous production method having excellent production efficiency when producing NDCA from dimethylnaphthalene and / or its oxidized derivative. To do.

[0014]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to establish the above method, and have conducted a liquid phase oxidation reaction of dimethylnaphthalene and / or its oxidized derivative using a heavy metal oxidation catalyst and bromine as a catalyst. In addition to replenishing the catalyst entrained in the crude NDCA, at the same time, replenishing the heavy metal oxidation catalyst in an amount equal to the number of moles of the inactive chelate-type complex formed from ODCA and heavy metal oxidation catalyst contained in the reaction mother liquor. In that case, the effective catalyst concentration in the reaction system can be kept constant, NDCA can be continuously produced in high yield, and the total heavy metal concentration in the catalyst liquid is also kept constant as the mother liquor circulation proceeds. The present invention has been completed and the present invention has been completed.

That is, the present invention uses a molecular oxygen-containing gas in the presence of a catalyst composed of a heavy metal and bromine in a solvent of a lower aliphatic carboxylic acid which may contain water, and dimethylnaphthalene and / or its derivative. In the method of oxidizing an oxidized derivative, when the catalyst is recycled and reused, the heavy metal catalyst is supplemented so that the effective concentration of the heavy metal catalyst exhibiting the oxidation activity in the solvent is 0.2% by weight or more, the reaction mother liquor and And / or is a continuous production method of NDCA characterized in that the washing filtrate of the produced cake is circulated and reused.

The present invention will be described in detail below.

The dimethylnaphthalene and / or its oxidized derivative used as the oxidizing raw material in the present invention may be obtained by any method or a mixture thereof. Examples of the oxidized derivative include formylnaphthoic acid and methylnaphthoic acid, but are not limited thereto. Of these, 2,6-body is industrially advantageous. It is preferable that the oxidizing raw material has a high purity, and it is desirable that the purity is 95% or higher, preferably 98% or higher. Components other than 2,6-isomers, for example, isomers such as 2,7-dimethylnaphthalene may be contained as long as possible.

As the solvent in the present invention, an aliphatic monocarboxylic acid having 1 to 5 carbon atoms, that is, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, bromoacetic acid, or the like, or a mixture thereof can be used. Of these solvents, acetic acid and propionic acid are preferred, with acetic acid being most preferred.

The solvent used in the method of the present invention is the above aliphatic monocarboxylic acid containing 5 to 45% by weight, preferably 7 to 35% by weight, and more preferably 10 to 30% by weight of water. . If the water content in the solvent is less than this, the combustion loss of the aliphatic monocarboxylic acid is large, and if it is more than this, the yield of NDCA and the purity are lowered, which is not preferable.

The amount of the solvent used with respect to dimethylnaphthalene and / or its oxidized derivative is usually 2 to 15 times by weight, preferably 3 to 10 times by weight.

The oxidation catalyst used in the present invention is a heavy metal compound and a bromine compound. As the heavy metal oxidation catalyst, cobalt and manganese are used, and if necessary, cerium,
You may add nickel etc. These are used in the form of organic acid salts such as formate salts, acetate salts and propionate salts, halides, hydroxides, oxides, carbonates and the like, and fatty acid salts, particularly acetates and bromides are preferable.

The effective amount of the heavy metal oxidation catalyst in the method of the present invention is a catalytic amount excluding the heavy metal compound component which lost its activity due to the formation of a chelate type complex with ortho-benzenedicarboxylic acid. The concentration used in the solvent is 0.2% by weight or more and 1.5% by weight or less with respect to the solvent,
It is preferably 0.4% by weight or more and 1.0% by weight or less.
If the amount of the effective heavy metal oxidation catalyst used is smaller or larger than the above range, the yield of NDCA is lowered, the purity is lowered, the combustion loss of the lower aliphatic carboxylic acid as a solvent is increased, and the coloring is difficult to purify, which is not preferable. Although the ratio of manganese to cobalt (gram atomic ratio) is not particularly limited,
Considering the yield of DCA and the like, this ratio is preferably 1.0 or less.

On the other hand, the bromine compound may be either an organic compound or an inorganic compound as long as it dissolves in an oxidation reaction system to generate a bromine ion. Specifically, molecular bromine (Br ₂ ), Hydrogen bromide, sodium bromide, potassium bromide, inorganic bromide such as ammonium bromide,
Alternatively, an organic bromide such as a brominated fatty acid such as alkyl bromide or bromoacetic acid can be used. Hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, manganese bromide and the like are particularly preferable examples. Bromine can usually be used in an atomic ratio of 0.01 to 2 with respect to the total weight of the heavy metal oxidation catalyst.

The oxidation reaction temperature in the method of the present invention is 18
It is in the range of 0 to 230 ° C, preferably 190 to 220 ° C. When the reaction temperature is low, the reaction rate is low, and when it is high, side reaction products are increased and the purity of NDCA is decreased. The reaction pressure may be a pressure at which the reaction system is kept in a liquid phase at the reaction temperature, but is usually 10 to 30 kg /
A cm ² G level is suitable.

As the molecular oxygen-containing gas used in the method of the present invention, oxygen gas or any mixed gas obtained by diluting it with an inert gas such as nitrogen is used. Industrially, air is the most available and preferred.

The method of the present invention is effective when applied to any of the batch oxidation method, the semi-continuous oxidation method and the continuous oxidation method, but the effect is particularly large in the case of the continuous oxidation method.

The crude NDCA produced by the oxidation reaction is
The crude NDCA obtained by solid-liquid separation can be obtained on the solid phase side by solid-liquid separation of the reaction product. The crude NDCA is washed with acetic acid or the like, washed with water, and then attached catalyst solution, oxidation reaction intermediate and ODCA catalyst metal. The complex can be removed, and high purification is possible. If necessary, an extremely high-purity NDCA can be obtained by using an ordinary NDCA purification method known as a known method.

[0028]

INDUSTRIAL APPLICABILITY According to the method of the present invention, NDCA can be efficiently and continuously produced on an industrial scale.

[0029]

EXAMPLES The present invention will be specifically described below based on examples. The parts and% in the examples and comparative examples represent parts by weight and% by weight, respectively. The decomposition rate of the lower aliphatic carboxylic acid was determined from the gas chromatographic analysis value of the product composition.

[0030]

Example 1 A gas discharge pipe equipped with a reflux condenser, a gas blowing pipe, a raw material continuous feed pump, a catalyst liquid continuous feed pump,
A titanium autoclave having a product discharge pipe and a stirrer, acetate 160 parts cobalt acetate tetrahydrate _{[Co (OOCCH 3) 2 ·} 4H 2 O] 2.36 parts of manganese acetate tetrahydrate [Mn (OOCCH _{3) 2} · 4H ₂ O] 17 parts 1.26 parts of 47% aqueous hydrogen bromide 0.93 parts water was charged. The water concentration in this catalyst solution is 10%, the effective cobalt concentration and the effective manganese concentration are 0.31%, respectively.
It was 0.16%. While vigorously stirring the catalyst solution under the conditions of a temperature of 200 ° C. and a pressure of 20 kg / cm ² G,
To this, 42 parts of 2,6-dimethylnaphthalene having a purity of 99.5% was continuously fed over 1 hour, and excess compressed air was circulated to carry out an oxidation reaction. After 1 hour from the start of the feeding of 2,6-dimethylnaphthalene, the feeding of the catalyst liquid having the above composition was started while continuing the feeding of 2,6-dimethylnaphthalene. Then, in order to keep the amount of the reaction mixture in the autoclave constant, the reaction was continued while withdrawing a part of the reaction mixture, and the reaction was carried out for a total of 50 hours.

From the reaction mixture withdrawn, mainly NDC
The solid precipitate consisting of A was separated to obtain a reaction mother liquor. The solid precipitate was washed with acetic acid and then separated into solids to obtain a washing filtrate. The separability of the solid precipitate was good. At this time, the yield of NDCA was 93.2 mol%, the yield of ODCA was 3.8 mol%, and the decomposition rate of acetic acid was 5.0%. Further, all of the ODCA contained in the reaction mother liquor and the washing filtrate formed a chelate-type complex with cobalt and manganese to deactivate the catalytic activity. The reaction mother liquor and the washing filtrate were combined and then concentrated to remove excess water. Further, of the cobalt and manganese used, 85% and 70% were contained in the concentrated liquid, respectively.

[0032]

Examples 2 to 11 Cobalt and manganese were added to the concentrated solution obtained in Example 1 such that the inert ODCA metal complex contained therein was equimolar, and the concentrated solution after washing with acetic acid in Example 1 was used. Cobalt and manganese contained in the cake were added at the same ratio, and further cobalt, manganese and hydrobromic acid were added, and acetic acid and water were added so that the effective catalyst concentration became equal to that of the catalyst solution used in Example 1. A catalyst liquid was prepared by adding. The same operation as in Example 1 was performed except that this catalyst solution was used. Hereinafter, the same operation as this was repeated, and the reaction was performed 10 times in total. The separability of the solid precipitate in each reaction was good. In addition, the total cobalt and manganese concentrations in the catalyst solution also reached a certain value, and no accumulation of cobalt and manganese was found in the catalyst solution. Moreover, accumulation of by-products was not observed. The reaction results are shown in Table 1.

[0033]

[Table 1]

As shown in Table 1, by recycling and recycling the reaction mother liquor and the washing filtrate, the NDCA produced from the reaction intermediate dissolved in these liquids can be recovered. It was found that the results were improved in Examples 2 and 3 as compared with Example 1, and maintained a good level thereafter.

[0035]

Comparative Example 1 The same operation as in Example 1 was performed except that cobalt and manganese corresponding to the ODCA metal complex contained in the concentrated liquid obtained in Example 1 were not added. The effective concentration of the heavy metal catalyst in the catalyst liquid was 0.096% by weight of cobalt and 0.047% by weight of manganese. At this time,
40 minutes after the start of feeding 2,6-dimethylnaphthalene, the oxygen class main stopped and the reaction could not be recovered. The conversion rate of 2,6-dimethylnaphthalene was 65%.

[0036]

Comparative Example 2 The same operation as in Example 1 was carried out except that the catalyst solution used in Example 1 was added with 2.16 parts of trimellitic acid as ODCA and the catalyst solution having the following composition was used.

The acetate 160 parts cobalt acetate tetrahydrate _{[Co (OOCCH 3) 2 ·} 4H 2 O] 2.36 parts of manganese acetate tetrahydrate _{[Mn (OOCCH 3) 2 ·} 4H 2 O] 1.26 parts 47% Hydrogen bromide water 0.93 part Trimellitic acid 2.16 parts Water 17 parts At this time, the effective total amount of cobalt and manganese was 0.15% in consideration of the added trimellitic acid. NDCA
The yield was 81.6 mol%.

[0038]

[Comparative Example 3] In the autoclave used in Example 1.

The acetate 160 parts cobalt acetate tetrahydrate _{[Co (OOCCH 3) 2 ·} 4H 2 O] 10.2 parts of manganese acetate tetrahydrate _{[Mn (OOCCH 3) 2 ·} 4H 2 O] 5.43 parts 47% hydrogen bromide water 0.93 parts trimellitic acid 10.2 parts water 13.5 parts were fed. The water concentration in this catalyst solution is 10%, the cobalt concentration and the manganese concentration are 1.3% and 0.64%, respectively.
Met. Example 1 except that a catalyst solution having the above composition was used
The same operation was performed. At this time, the yield of NDCA was 7
It was 4.1 mol%.

[0040]

Example 12 The same operation as in Comparative Example 3 was carried out except that the catalyst solution used in Comparative Example 3 was supplemented with 10.2 parts of trimellitic acid as ODCA and having the following composition.

The acetate 160 parts cobalt acetate tetrahydrate _{[Co (OOCCH 3) 2 ·} 4H 2 O] 10.2 parts of manganese acetate tetrahydrate _{[Mn (OOCCH 3) 2 ·} 4H 2 O] 5.43 parts 47% hydrogen bromide water 0.93 parts water 13.5 parts At this time, the total amount of effective cobalt and manganese in consideration of the added trimellitic acid was 0.45%. After the reaction
The yield of NDCA was 93.1 mol%.

[0042]

Example 13 The same operation as in Example 1 was carried out except that the raw material 2,6-dimethylnaphthalene having a purity of 98.5% was used. At this time, the yield of NDCA based on 2,6-dimethylnaphthalene was 93.0 mol% and ODC
The yield of A was 3.8 mol%, and the decomposition rate of acetic acid was 5.0%. Further, all of the ODCA contained in the reaction mother liquor and the washing filtrate formed a chelate-type complex with cobalt and manganese to deactivate the catalytic activity. The reaction mother liquor and the washing filtrate were combined and then concentrated to remove excess water. Further, of the cobalt and manganese used, 85% and 70% were contained in the concentrated liquid, respectively.

[0043]

Examples 14 to 23 The same operation as in Example 13 was performed using the concentrated liquid obtained in Example 13. Hereinafter, the same operation was repeated, and the reaction was performed 10 times in total. The separability of the solid precipitate in each reaction was good. Also, the total cobalt and manganese concentrations in the catalyst solution have reached a certain level,
No accumulation of cobalt or manganese was found in the catalyst solution. Moreover, accumulation of by-products was not observed. The reaction results are shown in Table 2.

[0044]

[Table 2]

As shown in Table 2, by recycling and recycling the reaction mother liquor and the washing filtrate, the NDCA produced from the reaction intermediate dissolved in these liquids can be recovered. Example 14 compared to 13
It improved in 15 and maintained a good level after that.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Sumitani 77, Kitayoshida-cho, Matsuyama-shi, Ehime Teijin Limited Matsuyama Office

Claims (6)

[Claims] 1. A molecular oxygen-containing gas containing dimethylnaphthalene and / or an oxidized derivative thereof in a solvent containing at least 2 times by weight of a lower aliphatic carboxylic acid in the presence of an oxidation catalyst composed of a heavy metal and bromine. In the oxidation method, when the catalyst is recycled and reused, the catalyst is replenished so that the effective concentration of the heavy metal catalyst excluding the ortho-benzenedicarboxylic acid complex of the heavy metal contained in the solvent is 0.2% by weight or more. Moreover, a continuous process for producing naphthalenedicarboxylic acid, characterized in that almost all the washing filtrate of the reaction mother liquor and / or the produced cake is circulated and reused. 2. The continuous process for producing naphthalenedicarboxylic acid according to claim 1, wherein the heavy metal oxidation catalyst is cobalt and manganese. 3. The continuous process for producing naphthalenedicarboxylic acid according to claim 1, wherein the effective concentration of the heavy metal catalyst in the solvent is 0.4% by weight or more. 4. The continuous process for producing naphthalenedicarboxylic acid according to claim 1, wherein the lower aliphatic carboxylic acid is acetic acid. 5. The continuous process for producing naphthalenedicarboxylic acid according to claim 1, wherein the oxidation is carried out at a reaction temperature of 180 to 230 ° C. 6. The continuous process for producing naphthalenedicarboxylic acid according to claim 1, wherein the water concentration in the solvent is 5 to 45% by weight.