JPH02250850A - Purification of naphthalenecarboxylic acid - Google Patents

Abstract

PURPOSE:To produce the title compound by oxidizing a substituted naphthalene with an O2 gas in the presence of oxidizing catalysts of heavy metals of Ce, Co and Mn and bromine in a liquid phase, distilling away a solvent from the reaction product, dissolving the resulting substance in an alkali aqueous solution, recovering the insoluble catalyst, circulating and reusing the catalyst. CONSTITUTION:In obtaining a naphthalenecarboxylic acid(NCA) by oxidizing a substituted naphthalene with a molecular oxygen-containing gas in a solvent containing a lower aliphatic monocarboxylic acid by using oxidizing catalysts comprising a heavy metal consisting of cerium, cobalt and manganese and bromine in a liquid phase, the solvent is distilled away from the reaction product, an alkali aqueous solution is added to the resulting substance, a formed naphthalenecarboxylic acid is dissolved in the alkali aqueous solution and insoluble cerium, cobalt and manganese are recovered and effectively recycled and used. Consequently, the heavy metal catalysts can be recovered in high recovery ratio, a catalytic cost is inexpensive and this method is industrially advantageous.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention involves the oxidation of substituted naphthalene with a molecular oxygen-containing gas in a solvent containing a lower aliphatic carboxylic acid in the presence of an oxidation catalyst consisting of a heavy metal and bromine. The present invention also relates to a method for recovering and recycling a heavy metal catalyst used as an oxidation catalyst in a method for producing naphthalene carboxylic acid (hereinafter referred to as "rNCA").

[Prior Art] NCA, such as naphthoic acid, is used as a raw material for photographic chemicals and dyes, and naphthalene dicarboxylic acids, especially 2.6 monomer, are used as polyethylene naphthalate, which is used in the production of films and textile products with excellent heat resistance. It is used as a raw material for polyester, polyamide, etc.

Furthermore, naphthalenetricarboxylic acid and naphthalenetetracarboxylic acid are seen as promising raw materials for highly functional resins and the like.

Conventionally, many proposals have been made as methods for manufacturing NCA. For example, a method of oxidizing alkylnaphthalenes and acylnaphthalenes with a molecular oxygen-containing gas in a solvent containing a lower aliphatic monocarboxylic acid such as acetic acid in the presence of a catalyst consisting of heavy metals consisting of cobalt and manganese and bromine (Tokuko Showa) 4g-43893, JP 56-21017, JP 59-13495, JP 49-
42654, JP 60-89445, JP 60-89446), or a method in which the oxidation reaction is carried out using a heavy metal consisting of cobalt and cerium and bromine as a catalyst (JP 62-212344). Publications) etc. are known.

As a result of extensive testing and research into the production of naphthalene dicarboxylic acid, the present inventors found that by using cerium in combination with cobalt and manganese as a heavy metal catalyst, compared to the case of using known cobalt and manganese, the synergistic effect of We found that naphthalene dicarboxylic acid can be produced in high yield, and that there is almost no clogging of the oxygen-containing gas blowing pipe or adhesion of reaction products to the inner wall of the reaction vessel, which occurs when cobalt and manganese are used. A patent application (Japanese Patent Application No. 62-319394) was filed.

However, if the oxidation reaction is carried out economically on an industrial scale,
In order to produce NCAs at low cost, it is very important to recover and recycle heavy metal catalysts.

As a method for recovering cobalt and manganese, in the production of terephthalic acid by liquid phase oxidation of P-xylene, the solvent is recovered from the filtrate from which the generated terephthalic acid is separated, and then the carbonate is recovered from the residue ( (Japanese Patent Publication No. 46-14339, Japanese Patent Application Laid-Open No. 47-34088), or by-products of the oxidation reaction that are harmful to the oxidation reaction and are recovered at the same time as the used cobalt and manganese are removed by re-oxidizing them with molecular oxygen. However, a method for restoring the activity of cobalt and manganese (Japanese Unexamined Patent Publication No. 106986/1986) is known.

There are few cases in which cerium has been used as a type of heavy metal catalyst in oxidation reactions of alkylnaphthalenes, etc., and currently no method of recovering and recycling cerium has been studied. Further, a method of recovering cobalt and manganese at the same time as cerium to restore their activity and then recycling them has not yet been studied.

[Problems to be solved] This invention solves the problem of NCA by liquid phase oxidation of substituted naphthalene, etc.
in the production of naphthalene dicarboxylic acid, especially naphthalene dicarboxylic acid.
The purpose of the present invention is to provide a method for simultaneously recovering and recycling cerium, manganese, and cobalt used as heavy metal catalysts.

[Means for Solving the Problems] The present inventors have discovered that cerium is used as one of the heavy metal catalysts in the production of NCA by liquid phase oxidation of alkylnaphthalenes, etc.
As a result of extensive testing and research on methods for recovering heavy metal catalysts when used as seeds, we found that in the above-mentioned method for producing NCA using cerium, cobalt, and manganese as heavy metal catalysts, after separating the target NCA from the reaction products, the reaction mother liquor is recovered. When an attempt was made to separate and recover the lower aliphatic monocarboxylic acid, which is the solvent, and recover the heavy metal catalyst using a known method from the reaction mother liquor concentrate after the solvent was separated and recovered, it was found that almost all of the cobalt and manganese were recovered. On the other hand, only 0.1 mo1% of the charged amount of cerium could be recovered.

As a result of various tests and studies regarding the cause, it was determined that cerium did not remain in the reaction mother liquor concentrate, but was accompanied by the target product, NCA.

That is, the target product NCA separated from the reaction mixture
When the cerium content was measured, it was found that almost the entire amount of cerium was contained in NCA.

Therefore, we conducted extensive research on a method of recovering cerium from the separated cerium-containing NCA using a known organic solvent and taking advantage of the difference in solubility, but it was not possible to separate cerium with a high yield. there were.

In other words, N is a substance that dissolves NCA.

N-dimethyl, acetamide, N,N-dimethylformamide, dimethyl sulfoxide, etc. are known, but none of them have very high solubility and are expensive, so they are not economical methods for industrial use.

Furthermore, we investigated a solvent that does not dissolve NCA but dissolves cerium, but we were unable to find any.

Therefore, the present inventors focused on the fact that NCA becomes water-soluble if it is made into an alkali salt, and from the concentrated reaction mother liquor in which lower aliphatic carboxylic acids are separated and recovered from the reaction product, cerium is used as an alkali-insoluble component, and cobalt and manganese are When conducting tests to see if they could be recovered together, it was surprisingly discovered that the two could be separated extremely efficiently and almost all of cerium, cobalt and manganese could be recovered at the same time, leading to the present invention.

That is, this invention oxidizes substituted naphthalene in a solvent containing a lower aliphatic monocarboxylic acid, using a heavy metal consisting of cerium, cobalt and manganese, and bromine as an oxidation catalyst, and a molecular oxygen-containing gas to produce naphthalene carboxylic acid. In the manufacturing method, after distilling off the solvent from the reaction product produced by the oxidation reaction, an aqueous alkali solution is added to dissolve the naphthalene carboxylic acid, and insoluble cerium, cobalt and manganese are recovered and recycled. This is a characteristic method for producing naphthalenecarboxylic acid.

The substituted naphthalene that is the raw material in this invention is:
Alkyl groups such as methyl group, ethyl group and isopropyl group, or acyl groups such as acetyl group and formyl group,
All isomers having more than one can be used.

As the lower aliphatic monocarboxylic acid used in this invention, acetic acid, propionic acid, butyric acid, etc. can be used, but acetic acid is preferable.

As the solvent used in combination, a solvent relatively stable against oxidation, such as chlorobenzene and bromobenzene, is used.

As the oxidation catalyst, a heavy metal consisting of cerium, cobalt and manganese and bromine are used in combination. These oxidation catalysts are preferably soluble in solvents, such as cerium,
For cobalt and manganese, acetate, bromide, etc. are preferred, and for bromine, potassium bromide, sodium bromide, etc. are preferred.

NCAs to which the method of the present invention can be applied are compounds having 1 to 4 carboxyl groups, ie, naphthoic acid, naphthalene dicarboxylic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, and isomers thereof.

As the alkali used for recovering the heavy metal catalyst, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, or potassium bicarbonate can be used.

[Function] Substituted naphthalene is oxidized in a liquid phase with a molecular oxygen-containing gas in a solvent containing a lower aliphatic monocarboxylic acid in the presence of a heavy metal consisting of cerium, cobalt and manganese, and an oxidation catalyst consisting of bromine. After the solvent is distilled off from the reaction product, an aqueous alkaline solution is added and the reaction is allowed to proceed for 1 to 3 hours. Although NCA is completely dissolved, cerium, cobalt and manganese are not dissolved and precipitate as insoluble components. Therefore, cerium, cobalt, and manganese can be separated extremely efficiently by performing solid-liquid separation using an ordinary solid-liquid separation device, such as a centrifugal filtration device or a filter press. Even if these recovered heavy metals are recycled as they are for the next oxidation reaction, the effect will be almost the same as the initial one.

[Effects of the Invention] As described above, according to the method of this invention, a heavy metal catalyst consisting of cerium, cobalt and manganese can be simultaneously
It can be recovered with a high recovery rate of 9% or more and recycled, and the cost of the catalyst is low, which is extremely advantageous in industrial implementation.

[Example] Example 1 In a titanium autoclave with a first reaction capacity of 0.52, 4.98 g of cobalt acetate tetrahydrate, 4.89 g of manganese acetate tetrahydrate, and 6 cerium acetate hydrate were added as catalysts. .71 g, potassium bromide 7.14 g, potassium acetate 5.91 g
, 230 g of acetic acid was charged as a solvent, and 71.00 g of 2.6-dipurvylnaphthalene was added for 4 hours while stirring and blowing in excess air at a reaction pressure of 30 kg/cm2・G and a reaction temperature of 200°C. After that, only air was blown in for 1 hour to complete the first oxidation reaction. Acetic acid was distilled off from this reaction product using an evaporator. Then, 1.200 g of a 10% aqueous sodium hydroxide solution was added and dissolved in the residue, and after refluxing for 1 hour, the alkali-insoluble matter was collected by filtration, washed with water, dried, and heavy metals were removed using plasma emission spectrometry. When quantitatively determined, it contained 99.8% of cerium, 99.7% of cobalt, and 99.9% of manganese based on the amount charged.

Further, a 10% aqueous hydrochloric acid solution was added to the filtrate to make it in an acidic range, and solids were precipitated. After separating this solid by filtration and washing with water, it was quantified using liquid chromatography.
, 6-naphthalene dicarboxylic acid was contained in an amount of 92.7 mol % based on the charged 2,6-diituprobylnaphthalene.

Second and subsequent reactions The alkali insoluble matter recovered from the first reaction is used as a substitute for the heavy metal catalyst used in the first reaction, and potassium bromide, potassium acetate, and acetic acid are charged in the same amounts as in the first reaction. ,
2,6-diitubrobylnaphthalene was added in the same manner as in the first time, and the reaction was carried out under the same conditions as in the first time.

After post-treatment in the same manner as the first time, the yield of 2,6-naphthalenecarboxylic acid was 9.
The yields of cerium, cobalt, and manganese were 99.6% for cerium, 99.5% for cobalt, and 99.8% for manganese based on the first charge.

For the third and subsequent reactions, the reaction was repeated 10 times in total under the same conditions as the second reaction.

Note that 2,6-naphthalene dicarboxylic acid and heavy metals were determined in the 5th and 10th tests.

The results are shown in Table 1.

In the first case, a heavy metal catalyst was recovered and recycled at the same time by the same operation, and the reaction was carried out in the same manner.

The results are shown in Table 2.

Table 2 As shown in Table 1, almost the entire amount of cerium, cobalt and manganese can be recovered and recycled at the same time.
Moreover, there is almost no decrease in the yield of 2,6-naphthalenecarboxylic acid.

Example 2 Same as Example 1 except that sodium carbonate was used as the alkali instead of sodium hydroxide.As shown in Table 2, almost the entire amount of the heavy metal catalyst can be recovered and recycled at the same time.

Example 3 As an alkali for heavy metal recovery 1. The same conditions and operations as in Example 1 were carried out except that potassium hydroxide was used.
The heavy metal catalyst was recovered, recycled and used for the same reaction. The results are shown in Table 3.

Table 3 As shown in Table 3, almost the entire amount of heavy metal catalyst can be recovered and recycled at the same time.

Example 4 300 g of acetic acid and 0.8 g of cobalt acetate tetrahydrate were placed in a titanium autoclave with a capacity of 0.52 and equipped with a reflux condenser tube, a gas blowing tube, a gas discharge tube, a raw material supply tube, and a stirrer.
77 g, manganese acetate tetrahydrate 0.862 g, cerium acetate monohydrate 1.18 g, potassium bromide 0.503 g, reaction temperature 160°C, reaction pressure 30 kg/cm.
2.G, methylnaphthalene 0.5g/min and air 1
．． The oxidation reaction was carried out for 1 hour and 40 minutes while supplying 5N27w1n.

After the reaction was completed, acetic acid was distilled off using an evaporator, and 200 g of a 10% aqueous sodium hydroxide solution was added to the residue, dissolved, and then refluxed for 1 hour. After the alkali insoluble matter was collected by filtration, washed with water, and dried, the heavy metals were quantified by plasma emission spectrometry.The results showed that cerium was 99.8%, cobalt was 99.8%, and manganese was 99.8% based on the amount charged. % was included. Also, add 10% to the filtrate.
Aqueous hydrochloric acid solution was added to make the mixture acidic, and a solid precipitated out.

After this solid was filtered and washed with water, it was quantified using liquid gas chromatography, and it was found that the content of naphthoic acid was 88.7 mol % based on the charged methylnaphthalene.

The alkali insoluble matter recovered in the first reaction was used as a substitute for the heavy metal catalyst in the first reaction, and potassium bromide, potassium acetate, and acetic acid were charged in the same amounts as in the first reaction.
Methylnaphthalene was added in the same manner as in the first time, and the reaction was carried out under the same conditions as in the first time.

After post-treatment in the same manner as in the first round, analysis revealed that the yield of naphthoic acid was 88.2%, and the yield of cerium, cobalt, and manganese was 99.9% compared to the amount charged in the first round. 6%, cobalt 99.5%,
The manganese content was 99.8%.

For the third and subsequent reactions, the reactions were repeated one after another under the same conditions as the second reaction, for a total of 10 reactions.

Note that the naphthoic acid and heavy metal catalyst were quantified at the 5th and 10th times. The results are shown in Table 4.

As shown in Table 4, almost the entire amount of the heavy metal catalyst can be recovered and recycled at the same time, and there is almost no decrease in the yield of naphthoic acid.

Table 4

Claims (3)

[Claims] (1) Naphthalene carboxylic acid is produced by oxidizing substituted naphthalene in a solvent containing a lower aliphatic monocarboxylic acid using a molecular oxygen-containing gas using a heavy metal consisting of cerium, cobalt, and manganese and bromine as an oxidation catalyst. The method is characterized in that after the solvent is distilled off from the reaction product produced by the oxidation reaction, an aqueous alkali solution is added to dissolve the naphthalene carboxylic acid, and insoluble cerium, cobalt and manganese are recovered and recycled. A method for producing naphthalenecarboxylic acid. (2) The method according to claim 1, characterized in that a substituted naphthalene substituted with an alkyl group or an acyl group is used. (3) The method according to claim 1 or 2, characterized in that sodium hydroxide, sodium carbonate, potassium hydroxide, potassium hydrogen carbonate, potassium carbonate, or sodium hydrogen carbonate is used as the alkali.