KR20080090670A - Crystallization method of naphthalene dicarboxylic acid and crystal of 2,6-naphthalene dicarboxylic acid obtained by using the same - Google Patents

Abstract

A method for crystallizing naphthalene dicarboxylic acid is provided to obtain 2,6-naphthalene dicarboxylic acid crystals with large and uniform size by crystallizing the naphthalene dicarboxylic acid using an acid from a solution of crude naphthalene dicarboxylic acid purified by microorganism. A method for crystallizing naphthalene dicarboxylic acid comprises the steps of: (a) putting an acidic solution in a reaction solution obtained by purifying crude naphthalene dicarboxylic acid using a microorganism capable of converting 2-formyl-6-naphthoic acid into 2,6-naphthalene dicarboxylic acid at a temperature of 4-150 deg.C at the stirring speed of 0-1,000 rpm to generate crystal of the 2,6-naphthalene dicarboxylic acid with adjusting pH; and (b) stirring the reaction solution at a temperature of 4-150 deg.C at the speed of 0-1,000 rpm for one minute to 5 hours to grow the crystal of the 2,6-naphthalene dicarboxylic acid, wherein the microorganism is Bacillus sp. or Pseudomonas sp. microorganism. Further, the Bacillus sp. is Bacillus sp. F-1(KCTC-10342BP), Bacillus sp. F-3(KCTC-10335BP) or Bacillus subtilis HSB-21(KFCC-11221) and the Pseudomonas sp. is Pseudomonas sp. HN-72(KCTC-10819BP).

Description

Crystallization method of naphthalene dicarboxylic acid and crystal of 2,6-naphthalene dicarboxylic acid obtained by using the same

1 is a micrograph of crystallized 2,6-NDA obtained in Example 1 of the present invention.

2A, 2B and 2C are micrographs of crystallized 2,6-NDA obtained by adding a sulfuric acid solution in Experimental Example 1 of the present invention and maintaining the stirring speed at 50 rpm, 200 rpm, and 800 rpm, respectively.

3A, 3B, and 3C are micrographs of crystallized 2,6-NDA obtained by adding a sulfuric acid solution in Experimental Example 2 of the present invention to a reaction temperature of 15 ° C., 40 ° C., and 80 ° C., respectively.

The present invention relates to a crystallization method of naphthalene dicarboxylic acid, and more particularly to crude naphthalene dicarboxyl microorganisms having the ability to convert 2-formyl-6-naphthoic acid to 2,6-naphthalene dicarboxylic acid. After reacting with acid, 2-formyl-6-naphthoic acid, which is an impurity contained in the crude naphthalene dicarboxylic acid, is converted to 2,6-naphthalene dicarboxylic acid, and then removed. After adjusting the pH of the crude naphthalene dicarboxylic acid to crystallize, the crystals are grown while stirring for a period of time, to obtain 2,6-naphthalene dicarboxylic acid crystals having a large crystal size and a constant or amorphous The crystallization method of naphthalene dicarboxylic acid characterized by the above-mentioned.

Diesters of 2,6-naphthalene dicarboxylic acid and 2,6-naphthalene dicarboxylic acid are useful monomers for preparing various types of polymeric materials such as polyesters and polyamides. For example, poly (ethylene 2,6-) is a high-performance polyester material by condensation reaction of 2,6-naphthalene dicarboxylic acid (NDA) and diester (NDC) of 2,6-naphthalene dicarboxylic acid (NDC) with ethylene glycol. Naphthalate) (hereinafter referred to as PEN). Fibers and films made from PEN have higher strength and better thermal properties than poly (ethylene terephthalate) (hereinafter PET). This makes PEN a very good material for making commercial products such as thin films that can be used to make magnetic recording tapes and electronic components. Films made of PEN are also useful for making food containers, especially food containers for high temperature fillings, due to their good resistance to gas diffusion, in particular carbon dioxide, oxygen and water vapor. It can also be used to make reinforcing fibers useful for making tire cords.

NDC is currently produced by esterifying crude naphthalene dicarboxylic acid (hereinafter cNDA) produced by oxidizing 2,6-dimethylnaphthalene (hereinafter, 2,6-DMN). Currently, NDC is used as a main raw material when synthesizing PEN, but there are some problems compared to using 2,6-naphthalene dicarboxylic acid (hereinafter referred to as NDA) as a raw material. Firstly, water is produced during NDA condensation reaction, while methanol is produced as a by-product in the case of NDC, and there is a risk of explosion. Second, in order to obtain pure NDC during NDC manufacturing process, NDA is esterified to produce NDC through purification process. Therefore, it requires one more step compared to NDA, and thirdly, if you have an existing PET production facility, the use of NDC is not appropriate to use the existing facility. In spite of the disadvantages of NDC, NDC is used instead of NDA in the manufacture of PEN because it is still difficult to produce purified NDA having the purity required for polymerization.

In general, 2,6-NDA is prepared by first oxidizing 2,6-dimethylnaphthalene (2,6-DMN) in the presence of a catalyst. However, cNDA prepared in this way can not be directly used for PEN polymerization instead of NDC because of low purity and must be purified. In particular, in the oxidation of 2,6-DMN, 2-formyl-6-naphthoic acid (hereinafter referred to as FNA), 2-naphthoic acid (hereinafter referred to as NA), trimellitic acid (hereinafter referred to as TMLA), methylnaphthoic acid (hereinafter referred to as CNDA containing various impurities such as MNA) is produced. In particular, the presence of FNA causes the polymerization reaction to stop in the middle, which leads to a decrease in the degree of polymerization, which adversely affects the physical properties of the polymer or causes the coloring of the polyester. Therefore, the FNA must be removed, but there is a difficult problem. .

Therefore, in order to obtain high purity NDA crystals by removing FNA present in cNDA, various purification methods are used.

As a specific example, Japanese Patent Application Laid-Open Nos. 48-68554 and 48-68555 disclose that cNDA is dissolved in an aqueous alkali solution to form a dialkali salt aqueous solution, and then oxidized with alkali dichromate, alkali permanganate and alkali perhalogenate. Disclosed is a method of decolorizing with a solid adsorbent to precipitate with carbon dioxide gas or sulfurous acid gas. Japanese Patent Laid-Open Nos. 52-20993 and 52-20994 dissolve cNDA in an aqueous alkali solution to form an aqueous alkali solution. Then, a method of heat treatment at a temperature of 60-350 ° C., decolorization with a solid adsorbent, and precipitation using carbon dioxide gas or sulfurous acid gas is disclosed.

U.S. Patent No. 6,087,531 also discloses a poly (alkylene naphthalene dicarboxylate) [poly (alkylene naphthalene dicarboxylate)] at 125-400 ℃ basic solution (alkali metal basic solution, hydroxide or alkali metal) Carbonate) and then neutralized with acid at 170-240 ° C. to recover NDA crystals, or the polyester material was dissolved with NaOH or KOH at 170-240 ° C. and then neutralized with acetic acid to recover NDA crystals. And

U.S. Patent No. 6,426,431 describes KH-NDA by treating K ₂ -NDA aqueous solution with CO ₂ at 0-50 ° C. and 0-200 psi to form KH-NDA, and then suspending the KH-NDA in water at a ratio of at least 1: 8. In addition, the method of increasing the purification yield of 2,6-NDA to about 45% by treating with CO ₂ again at 100 ° C. or more (140-160 ° C.) and 100 psi or more (175-250 psi) conditions is disclosed. .

However, in order to obtain NDA crystals, the above-mentioned methods have a problem of low economic efficiency by requiring high temperature and high pressure conditions, a long time treatment, and a large amount of expensive materials, low purification yield, and difficulty in controlling a process. It has been pointed out. In addition, the crystal size of NDA obtained by various methods is 50 μm or less, so the size of the crystal is small, and the volume increases when NDA is added, and a high viscosity slurry solution is formed when reacting with ethylene glycol, causing various problems in the process. There is a problem that there is a coagulation phenomenon in the liver and it is difficult to apply to actual production.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention is to crystallize naphthalene dicarboxylic acid using an acid in a solution obtained by purification of crude naphthalene dicarboxylic acid using a microorganism, the size of crystals Is to provide a 2,6-NDA crystal with large and uniform size.

Another object of the present invention is to provide a 2,6-NDA crystal having a large and uniform size of the crystal obtained by the above method.

One aspect of the present invention for achieving the above object is (a) Zonaphthalene dikar using a microorganism having the ability to convert 2-formyl-6-naphthoic acid to 2,6-naphthalene dicarboxylic acid Adjusting the pH while adding an acidic solution while stirring the reaction solution obtained by purifying the acid at a rate of 0 to 1000 rpm at 4 to 150 ° C. to produce crystals of 2,6-naphthalene dicarboxylic acid; And (b) growing the crystals of 2,6-naphthalene dicarboxylic acid by stirring the reaction solution obtained in step (a) at 4 to 150 ° C. at a rate of 0 to 1000 rpm for 1 minute to 5 hours. It is providing the method of crystallizing naphthalene dicarboxylic acid containing.

Another aspect of the present invention provides a reaction solution obtained by (a) purifying crude naphthalene dicarboxylic acid using a microorganism having the ability to convert 2-formyl-6-naphthoic acid to 2,6-naphthalene dicarboxylic acid. Adjusting the pH while adding an acidic solution while stirring at a speed of 0 to 1000 rpm at 4 to 150 ° C. to produce crystals of 2,6-naphthalene dicarboxylic acid; And (b) growing crystals of 2,6-naphthalene dicarboxylic acid by stirring the reaction solution at a rate of 0 to 1000 rpm while lowering the temperature to 1 to 80 ° C. for 20 minutes to 12 hours. It is to provide a method for crystallizing naphthalene dicarboxylic acid.

Hereinafter, the method for crystallizing naphthalene dicarboxylic acid of the present invention will be described in detail step by step.

(i) step 1: crystallization by acid addition

In this step, first, the microorganism having the ability to convert FNA to NDA is reacted with cNDA, and the reaction solution obtained by converting and removing FNA in the cNDA to NDA is adjusted by adding an acidic solution while stirring at a constant temperature to adjust pH. Crystals of, 6-naphthalene dicarboxylic acid are produced.

First, prior to the crystallization method of the crude naphthalene dicarboxylic acid of the present invention, the process of purifying crude naphthalene dicarboxylic acid using microorganisms will be described in detail.

1) preparing a reaction cell by inoculating a microorganism having the ability to convert FNA to NDA in a liquid medium, shaking culture, and then suspending the cells recovered through centrifugation with physiological saline or distilled water; 2) mixing the crude naphthalene dicarboxylic acid, which is a substrate, with a buffer solution, and then adding an alkaline solution to adjust the pH of the mixed solution to form a purified reaction solution; And 3) converting FNA into NDA by reacting the cells of the microorganism prepared in step 1) with the reaction solution prepared in step 2).

Here, the microorganism is preferably of the genus Bacillus sp . ) Or Pseudomonas sp . Microorganisms belonging to the) may be used, but are not particularly limited thereto, and any microorganism belonging to the present invention may be used without limitation.

Most preferably, Bacillus F-1 (KCTC-10342BP), Bacillus F-3 (KCTC-10335BP), Bacillus subtilis HSB-21 (KFCC-11221) or Pseudomonas genus HN-72 (KCTC-10819BP) For example, the Bacillus genus F-1 and F-3 has been published in the domestic application number 2002-0087819 has been published, the Bacillus subtilis HSB-21 strain has been filed in the domestic application No. 2000-63333 The strain of Pseudomonas genus HN-72 was deposited on June 21, 2005 to the Korea Institute of Bioscience and Biotechnology gene bank of the international depositing institution with the accession number KCTC-10819BP.

The microorganism can be easily cultured using a liquid medium (eg, LB medium, M9 medium, etc.), and can be cultured at a wide range of temperature of 25 to 45 ° C. Preferably it is preferable to incubate at 28 to 35 ℃.

The buffer used in step 2) is not particularly limited, but water, sodium carbonate buffer (Na ₂ O ₃ / NaHCO ₃ ), glycine buffer (Glycine / NaOH), potassium phosphate buffer (KH ₂ PO ₄ / KOH), sodium phosphate buffer (Na ₂ HPO ₄ / NaH ₂ PO ₄ ), succinic acid buffer (Succinic acid / NaOH), sodium acetate buffer (Sodium acetate / Acetic acid), citric acid buffer (Citric acid / Sodium citrate), sodium pyrophosphate buffer (Na ₄ P ₂ O ₇ / HCl), boric acid buffer (Boric acid / NaOH), sodium borate buffer (Sodium borate / HCl) and the like can be used. Preferably, potassium phosphate buffer (KH ₂ PO ₄ -KOH) or boric acid buffer (Boric acid-NaOH) having a buffer range of pH 6.0 to 9.0 may be used. At this time, the concentration of the buffer solution is preferably used at a concentration of 0.01 to 100 mM.

The alkali solution is not necessarily limited, but NaOH or KOH is preferably used, and the pH of the mixed solution is preferably adjusted to 6-10.

The reaction temperature and reaction time in step 3) are preferably 25-50 ° C. and 1 minute-2 hours, and more preferably 35-40 ° C. and 25-40 minutes. In particular, when the reaction temperature is less than 25 ° C or more than 50 ° C, the reactivity is significantly reduced and unsuitable.

On the other hand, there is a close relationship between the FNA content in the cNDA, the cNDA concentration of the reaction solution, and the amount of cells required for complete removal of the FNA. The higher the FNA content in the cNDA and the higher the concentration of cNDA in the reaction solution, It is preferable to use.

Then, a reaction obtained by purifying crude naphthalene dicarboxylic acid using the microorganism in a reactor equipped with a stirrer in order to crystallize amorphous 2,6-NDA present in the cNDA purification solution in which FNA was removed. While stirring the solution at a certain temperature, add an appropriate amount of acidic solution to adjust the pH to a certain range.

At this time, the acidic solution is not particularly limited, sulfuric acid, hydrochloric acid, glacial acetic acid, nitric acid and the like can be used, it is preferable to use sulfuric acid or hydrochloric acid in terms of size and yield of NDA crystals. That is, when sulfuric acid or hydrochloric acid is added, NDA crystals having a uniform size of 100 µm or more can be obtained in high yield.

The pH range is preferably adjusted to pH 1-4 in terms of recovery rate, and the lower the pH, the higher the recovery rate from about 92% to 99.9%.

The reaction temperature is about 4 to 150 ℃, preferably 25 to 120 ℃ suitable for producing a crystal, when the temperature is less than 4 ℃ inside the 2,6-NDA crystal growing faster crystal growth rate during crystal growth The problem is that crystals are formed by mixing different impurities, and when it is more than 150 ° C., crystal growth is very slow during crystal growth, making it difficult to obtain large 2,6-NDA crystals.

The stirring speed is preferably 0 to 1000 rpm, preferably 0 to 400 rpm, more preferably 30 to 200 rpm. If the stirring speed exceeds 1000rpm, it inhibits the growth of the crystal during stirring, and the grown crystal is also broken down, which significantly reduces the size of the crystal.

( ii 2nd step: crystal growth step

After the addition of the acid is completed, the crystals are grown to increase in size by stirring at constant temperature or by decreasing the temperature for a certain time.

That is, in the two-step crystal growth step, while maintaining the temperature of about 4-150 ℃, preferably 25-120 ℃, which is the temperature in the first step of crystal formation step so that the two steps are crystallized at the same temperature Can grow crystals,

Alternatively, the crystals may be grown while lowering the temperature in the second stage to a temperature lower than the temperature in the first stage for a predetermined time. For example, the crystals can be grown while the temperature in the two stages is lowered to about 1-80 ° C., preferably 10-50 ° C. for a period of time.

The time for lowering the temperature is preferably in the range of about 20 minutes to 12 hours, preferably 30 minutes to 3 hours. If the crystal growth step time is too short, the crystallinity is low so that aggregation may occur between individual crystals during the polymerization reaction. Too long a crystal growth step may cause unnecessary energy loss.

In the case where the temperature is kept constant, the reaction time is not particularly limited, but the reaction time is preferably 1 minute to 12 hours, preferably 10 minutes to 3 hours.

As a suitable stirring speed for performing the crystal growth step is preferably carried out at 0 to 1000 rpm, preferably 30 to 200 rpm. If the stirring speed exceeds 1000rpm, it inhibits the growth of the crystal during stirring and the grown crystal is also broken down, which significantly reduces the size of the crystal. At this time, the stirring speed may be the same as or different from the stirring speed in the crystal growth step.

According to the crystallization process of the present invention, uniform 2,6-NDA crystals having a size of 100 μm or more can be obtained, which is economical in terms of manufacturing cost and process, and there is no aggregation phenomenon between the obtained 2,6-NDA individual crystals. It is advantageous in terms of practicality and high recovery rate.

Another mass production of the present invention is to provide 2,6-naphthalene dicarboxylic acid in the crystalline state obtained by the purification method of the present invention. The 2,6-naphthalene dicarboxylic acid provided by this invention can be obtained in a crystalline or amorphous crystal state by adjusting treatment conditions depending on the use and case. In the case of shaping, it is advantageous at the time of the removal of impurities in the washing process for purification of crude naphthalene dicarboxylic acid. In particular, in the case of the shape can have a lattice structure, but is not necessarily limited thereto.

The 2,6-naphthalene dicarboxylic acid crystal produced in the present invention is a large and well-formed crystal form excellent in forming ethylene glycol and a low viscosity slurry because it is in the form of particles having a large and uniform size having an average particle diameter of 100 μm or more, and PEN Is very suitable for filtration, washing and preparation. If the average particle size is small, the product is difficult to handle and power consumption is also high because the slurry formation ability is poor when the slurry is mixed with EG in the PEN polymerization process. Preferably the 2,6-naphthalene dicarboxylic acid crystals of the present invention have an average particle diameter in the range of 100 to 200 μm, more preferably in the range of 110 to 170 μm.

Hereinafter, the specific configuration and operation of the present invention will be described by way of examples, which are intended to illustrate the present invention and should not be construed as limiting the scope of the present invention.

Example 1

First step: On the mountain  Crystal production step

Pseudomonas HN-72 was inoculated into 300 L LB medium and incubated with stirring at 200 rpm in a 30 ° C. fermenter for 22 hours, followed by centrifugation to recover the cells, which were suspended in 50 mM potassium phosphate buffer for reaction. Cells were prepared.

Inject 50 L of 50 mM potassium phosphate buffer into the microbial purification reactor, add 1 to 10 kg of cNDA, and add KOH to NaOH while stirring to adjust the pH of the reaction solution to 8.0, and then add water again. 100 L of a purification reaction solution (cNDA concentration: 1 to 10%, FNA content in cNDA: 0.01 to 4%) was prepared.

While maintaining the reaction solution at 40 ° C., 0.2 to 10 kg / L of the reaction cell was added and then reacted at 40 ° C. for 10 minutes to 2 hours to convert FNA in the cNDA into NDA.

The cNDA purification solution purified in the same manner as described above was adjusted to pH 3.0 by adding a sulfuric acid solution in a crystallization reactor with a stirring device to produce crystals. At this time, the stirring speed was maintained at 350 rpm, the temperature at 65 ℃.

Phase 2: Crystal Growth

The crystals were grown while lowering the temperature of the solution obtained in the first step to 10 ° C. for 2 hours. At this time, the stirring speed was maintained at 150 rpm.

After the crystallization was completed, the crystals were analyzed using a microscope and a particle size analyzer. As a result, the crystallization proceeded well, and it was confirmed that entanglement between individual crystals did not occur. A micrograph of the crystallized NDA is shown in FIG. 1.

Experimental Example  1: mountain type and At the stirring speed  Crystallization reaction

100 ml of the cNDA purified solution obtained in the first step of Example 1 was placed in a reactor equipped with a stirring device, and adjusted to pH 3.0 by adding sulfuric acid, hydrochloric acid, glacial acetic acid, and nitric acid solution, respectively, followed by stirring. Crystals were produced by maintaining the speed at 0, 50, 100, 200, 400, 800, 1000 rpm. Subsequently, the crystal growth reaction was performed for 30 minutes under the same conditions as above. At this time, both the crystal production step and the crystal growth step maintained the same stirring speed, the temperature was maintained at 25 ℃ both steps.

After the crystallization was completed, the crystals were analyzed using a microscope and a particle size analyzer. As a result, all crystallizations were confirmed, and it was confirmed that entanglement between individual crystals did not occur. After adding sulfuric acid solution therein, micrographs of NDA crystals obtained by maintaining the stirring speed at 50 rpm, 200 rpm and 800 rpm, respectively, are shown in FIGS. 2A, 2B and 2C. In addition, the average size of the NDA crystals obtained under each of the above conditions is shown in Table 1 below. As can be seen from the results of Table 1, sulfuric acid and hydrochloric acid showed the best results in the crystallization reaction among the four acid solutions, and the preferred stirring speed was determined to be 0 to 400 rpm.

Experimental Example  2: crystallization reaction according to acid type and temperature condition

The stirring speed was set to 150 rpm and the reaction temperature of the two stages was 4, 15, 25, 40, 60, 80, 100, 120 ℃ except that the experiment was carried out in the same manner as in Experiment 1.

After crystallization was completed, the crystals were analyzed using a microscope and a particle size analyzer. As a result, all crystallizations were confirmed, and it was confirmed that entanglement between individual crystals did not occur. Among them, microscopic pictures of NDA crystals obtained by adding a sulfuric acid solution at a reaction rate of 15 ° C., 40 ° C. and 80 ° C., respectively, are shown in FIGS. 3A, 3B and 3C. In addition, the average size of the NDA crystals obtained under each of the above conditions is shown in Table 2 below. As can be seen from the results of Table 2, sulfuric acid and hydrochloric acid showed the best results in the crystallization reaction among the four acid solutions, and the preferred temperature was determined to be 40 ° C.

Experimental Example  3: acid After addition  Crystallization Reaction with Temperature Change

In the crystallization step by adding acid, the pH range was adjusted to 3 by adding sulfuric acid, hydrochloric acid, glacial acetic acid, and nitric acid, respectively, while maintaining the stirring speed at 350 rpm at temperatures of 40, 60, 80, 100, and 120 ° C. Afterwards, the crystal growth reaction proceeded while gradually lowering the temperature to 10, 20, 40, and 60 ° C. for 20 minutes to 2 hours, respectively. The results are shown in Table 3 below. As can be seen from the results in Table 3 below, the crystal size was improved in all results.

Experimental Example  4: pH  Recovery rate according to condition

Experiments in the same manner as in Experiment 1 except that the crystal forming step and the crystal growth step were adjusted to 50 rpm, the reaction temperature 40 ℃, pH range 1, 2, 3, 4, 5, 6 It was. That is, after performing the crystallization reaction for 30 minutes, a certain amount was taken to compare the recovery rate. The results are shown in Table 4 below. As can be seen from the results of Table 4 below, a recovery rate of 99% or more was obtained under a condition of pH 3 or less, and the lower the pH, the higher the recovery rate.

Although the present invention has been described in detail with reference to the preferred embodiments of the present invention as described above, these are merely exemplary, and those skilled in the art to which the present invention pertains various modifications and equivalents therefrom. It will be appreciated that one other embodiment is possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described in detail through the above examples, NDA crystals having a size of 100 μm or more and uniform crystal size can be obtained by crystallizing crude naphthalene dicarboxylic acid purified using microorganisms, thereby making it economical in terms of manufacturing cost and process. Since there is no agglomeration phenomenon between the obtained NDA individual crystals, there is an advantage of high practicality and recovery.

Claims (13)

(a) The reaction solution obtained by purifying crude naphthalene dicarboxylic acid using a microorganism having the ability to convert 2-formyl-6-naphthoic acid to 2,6-naphthalene dicarboxylic acid was used at 0 to 4 to 150 ° C. Adjusting the pH while adding an acidic solution while stirring at a speed of 1000 to 1000 rpm to generate crystals of 2,6-naphthalene dicarboxylic acid; And (b) growing the crystals of 2,6-naphthalene dicarboxylic acid by stirring the reaction solution at 4 to 150 ° C. at a rate of 0 to 1000 rpm for 1 minute to 5 hours. Method of crystallization. (a) A reaction solution obtained by purifying crude naphthalene dicarboxylic acid using a microorganism having the ability to convert 2-formyl-6-naphthoic acid to 2,6-naphthalene dicarboxylic acid, at 4 to 150 ° C. Adjusting the pH while adding an acidic solution while stirring at a rate of 0 to 1000 rpm to produce crystals of 2,6-naphthalene dicarboxylic acid; And (b) growing the crystals of 2,6-naphthalene dicarboxylic acid by stirring the reaction solution at a rate of 0 to 1000 rpm while lowering the temperature to 1 to 80 ° C. for 20 minutes to 12 hours. Method for crystallization of dicarboxylic acid. The method for crystallizing naphthalene dicarboxylic acid according to claim 1 or 2, wherein the microorganism is a microorganism of the genus Bacillus or Pseudomonas. The method of claim 3, wherein the microorganism is Genus Bacillus F-1 (KCTC-10342BP), Bacillus genus F-3 (KCTC-10335BP), Bacillus subtilis HSB-21 (KFCC-11221), or Pseudomonas genus HN-72 (KCTC-10819BP), characterized in that the crystallization method of naphthalene dicarboxylic acid. The method for crystallizing naphthalene dicarboxylic acid according to claim 1 or 2, wherein the acidic solution of step (a) is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, glacial acetic acid and nitric acid. The method for crystallizing naphthalene dicarboxylic acid according to claim 1 or 2, wherein the pH in the step (a) is adjusted to a range of 1 to 4. The naphthalene dicarboxylic acid according to claim 1 or 2, wherein the stirring speed in step (a) is 0 to 400 rpm, and the stirring speed in step (b) is 30 to 200 rpm. Method of crystallization. The method of claim 1, wherein the reaction temperature and the stirring speed in the step (a) and (b) step is the same, characterized in that the crystallization of naphthalene dicarboxylic acid. 3. The method of claim 2, wherein the stirring speeds in steps (a) and (b) are the same. 2,6-naphthalene dicarboxylic acid crystals obtained by the process according to claim 1. The 2,6-naphthalene dicarboxylic acid crystal according to claim 10, wherein the crystal form is amorphous or amorphous. 12. The 2,6-naphthalene dicarboxylic acid crystal according to claim 11, wherein the form is lattice structure. The 2,6-naphthalene dicarboxylic acid crystal according to claim 10, wherein the crystal has an average particle size of 100 µm or more.

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