KR100545541B1 - Process for producing high purity 2,6-naphthalene dicarboxylic acid - Google Patents

Abstract

The present invention relates to a method for purifying 2,6-naphthalenedicarboxylic acid (hereinafter referred to as NDA) containing impurities produced by the oxidation reaction of 2,6-dimethyl naphthalene, wherein 2,6-dimethyl naphthalene is liquid In the method for purifying the product obtained by oxidation or liquid phase oxidation, 2,6-naphthalenedicarboxylic acid of high purity using 1 to 20 times of organic alcohol based on the weight of 2,6-naphthalenedicarboxylic acid It relates to a method of manufacturing.

In the present invention, an amine or an amine compound component, which is an impurity composed of trimellitic acid, a metal complex (ie, an organic metal complex of cobalt or manganese) and a high molecular weight, is added and dissolved in water or an organic alcohol. Remove by passing through material. The amine salt, which is a product of NDA and the charged amine or amine compound component, is decomposed simultaneously with distillation in a liquid phase of water or organic alcohol at a temperature of 50 to 300 ° C. to obtain NDA again. At this time, the gaseous phase component produced by decomposition is condensed and used again as an amine or an amine compound component. Impurities such as 2-naphthoic acid and methyl naphthoic acid are dissolved in an organic alcohol and removed. Formyl 2-naphthoic acid and brominated NDA components are removed through a high pressure hydrogenation process with controlled hydrogen input under a metal catalyst.

2,6-naphthalene dicarboxylic acid, 2,6-dimethyl naphthalene, liquid phase oxidation

Description

Preparation method of high purity 2,6-naphthalene dicarboxylic acid {Preparation method of purified 2,6-naphthalene dicarboxylic acid}

The present invention provides high-efficiency and high-efficiency naphthalene dicarboxylic acid [2,6-naphthalene dicarboxylic acid (hereinafter referred to as NDA)] that can be used as a monomer for polymerization of polyethylene naphthalate (hereinafter referred to as "PEN"). The present invention relates to a process for the preparation of carbon dioxide, in particular the purification of naphthalene dicarboxylic acid (hereinafter referred to as "coarse NDA") containing impurities produced by oxidation of 2,6-dimethyl naphthalene (hereinafter referred to as "DMN"). It is about a method.

PEN resin is a highly functional resin that exhibits excellent physical properties in the same application as polyethylene terephthalate (hereinafter referred to as "PET"), which is mainly used as a material for fibers, containers, and films. In terms of friendly materials, demand is expected to increase.

PEN resin is much better than PET resin in almost all polymer application properties and processability, but it is difficult to prepare a raw material for PEN polymerization, and technically, high purity of the raw material is difficult due to oxidation.

PEN was commercialized as a biaxially oriented film in 1971, but the price of NDA, its main raw material, was too high and did not lead to demand creation. By 1995, Amoco Corporation produced DMN, produced crude NDA by oxidation of DMN, and high-purity Naphthalene dicarboxylate (hereinafter referred to as "NDC") through methyl esterification reaction. As a series of commercial processes have been developed, the development of PEN into various uses has begun.

As PEN resin has better physical properties than PET resin, the demand for this is rapidly increasing, whereas NDC, a raw material for PEN, is still in short supply compared to potential demand, and coarse NDA is produced by oxidation of DMN. Since then, the commercial technology for producing a high purity NDA capable of polymerization is not known in the art yet.

The present invention relates to a process for producing NDA with high purity in which coarse NDA containing impurities produced by oxidation can be used as monomers for PEN polymerization.

When the DMN is oxidized using well-known cobalt (Co), manganese (Mn) and bromine (Br) -based liquid catalysts and oxygen as the main source of oxidation, 90 to 94 weight percent of coarse NDA It is known to produce (see US Pat. No. 5,183,933 to Harper et al.).

The main impurities contained in the coarse NDA include trimellitic acid, 2-naphthoic acid, methyl naphthoic acid, 2-formyl-6-naphthoic acid, other trace oligomers, indeterminate components, etc. And the bromide (hereinafter referred to as bromide NDA) produced by the organic complex (Metal Complex) of Mn and the bromination reaction are exemplified as representative components.

In particular, the catalyst for oxidation reaction (cobalt, manganese, bromine compound called "MC-based catalyst") has strong color development, so that the color of the NDA can be changed even with a small amount.

When PEN polymerization is carried out using NDA containing some impurities, the degree of polymerization is not significantly reduced or the polymerization is not performed properly, and the color of the polymer or reactant which can be compared with the color B value is not very poor. The molecular weight, melting point, viscosity, gas barrier properties, etc. of the polymeric material also become remarkably poor.

The highest level of purity known to date for coarse NDA achieved by direct oxidation is at least 98% by weight obtained by adjusting the reaction conditions of the DMN oxidation process and the application rate of the catalyst system. Techniques related to the method of obtaining are reported in the patent literature (see US Patent No. 6,268,528 to Machida et al.).

As a method of obtaining a high purity monomer for PEN polymerization, a method of methyl esterifying coarse NDA to obtain a high purity NDC, and applying the same to a process of polymerizing it with ethylene glycol, such as McMahon U.S. Patent No. 6,114,575, et al., Which is already commercialized, is a polymerization method of PEN. This method is the most successful process for producing PEN polymerization raw materials known to date. Meanwhile, US Pat. No. 5,254,719 to Holzhauer et al., US Pat. No. 5,262,560, US Pat. No. 6,013,831 to Machida, and the like describe an improved method for obtaining high purity NDCs.

When PEN is polymerized using high-purity NDC, since the esterified methyl component contained in the NDC is converted into a large amount of methanol, the capital investment cost, raw material cost, etc. of polymerization are high. In addition, the manufacturing process of the NDC also requires a number of process steps, but has the disadvantage of obtaining a high-purity NDC.

On the other hand, if high purity NDA can be produced commercially, it is less expensive to invest in equipment, less raw material cost compared to NDC polymerization method, and can advantageously utilize the existing PET polymerization process, monomer for PEN polymerization, which is the final product. As an advantage, the process step is reduced. Therefore, methods for obtaining high purity NDA are actively developed.

The conventional technique is the method of purifying impure aromatic carboxylic acid using hydrogen gas (see US Patent No. 5,256,817 to Sikkenga et al. And US Patent No. 6,255,525 to Sitkenga et al.). Although there is a difference in technology, it has been widely used in the manufacturing process of purified terephthalic acid, which is a raw material for PET production.

A method of removing impurities from NDA using lower alkanes anhydride having 2 to 5 carbon atoms (see US Patent No. 4,933,491 to Albertins et al.) And a method of removing impurities from NDA using acetic anhydride [ Note: US Pat. No. 5,840,970 to Sμmner II et al. Is particularly effective at removing trimellitic acid, but has the disadvantage that the yield of high purity NDA finally obtained is poor.

In addition, methods of purifying crude NDA by converting it to an amine salt (see US Pat. No. 5,770,764 to Zeitlin et al. And US Pat. No. 5,859,294 to Hashimoto et al.) Particularly improve color. It is a very effective method, and a technique for obtaining a high purity NDA of 99.5% by weight or more when applied to a hydrogenation method and a recrystallization method in a specific solvent has also been developed (see US Patent No. 5,859,294 to Hashimoto et al.).

U.S. Patent No. 5,859,294 to Hashimoto et al. Discloses that coarse NDA is dissolved in an aqueous solution containing aliphatic amine, cycloaliphatic amine or acetonitrile, and the aldehyde compound is contacted with a metal belonging to the group 8 group of the periodic table in an inert gas to decarbonylate it. (decarbonylating reaction) to convert the aldehyde compound into a naphthoic acid compound, and the aqueous solution containing naphthalenedicarboxylic acid amine salt is heated to distill off the amine, or coarse NDA is dissolved in an aqueous solution containing aliphatic amine, cycloaliphatic amine or acetonitrile, and It is reported that high purity NDA of 99.95% or more is obtained by precipitating the crystals of the amine salt in a mixed solvent with an aliphatic ketone, an alicyclic ketone, or acetonitrile and then heating the naphthalenedicarboxylic acid amine salt to distill off the amine. According to the method described in this patent document, the purification process also requires the connection of a considerable process equipment, not only excessive use of amine, but also a loss thereof, and a series of complicated and sophisticated purification operations, In the intermediate process, the crude NDA purification process is followed by crystallization of granular NDA by at least three times of washing and suction filtration or centrifugation, so that the loss of NDA in this process, that is, the yield, may be reduced. In fact, there are technical limitations to use it as a process technology for producing high purity NDA in large quantities.

The present invention relates to a method for purifying coarse NDA produced by the oxidation reaction of DMN. According to the present invention, it is possible to produce high purity NDA from coarse NDA in high yield.

The main impurities contained in the coarse NDA are unknown components including trimellitic acid, 2-naphthoic acid, methyl naphthoic acid, 2-formyl-6-naphthoic acid, other trace oligomers, isomers, and catalyst systems for oxidation reactions. Representative components include organic complexes of Co and Mn produced as by-products and brominated NDA produced by the bromination reaction, and are separated from the coarse NDA containing them by the method according to the present invention and have a purity of 99.0 wt% or more suitable for polymer polymerization. Obtaining high purity NDA in high yield is a technical problem to be achieved by the present invention.

The process according to the invention may consist of a series of processes in a continuous process or in a batch process. It is particularly convenient to configure a continuous process flow.

In addition, the various methods proposed by the present invention are based on the content of NDA in the solid phase of the crude liquor produced by the oxidation reaction, the type of impurities contained and the amount of individual components, the final NDA purity characteristics required, and the type of impurities. Depending on the quantity, some of the methods may not be implemented, the number of times may be repeated, and the order of processing may be changed.

The principal characteristic purification principles of the process according to the invention are as follows, combining the individual properties of the invention according to the coarse compositional properties of the NDA, the economics and ease of process operation, and finally the purified NDA properties required, You can change the order and apply it.

1) Some unreacted material that may form impurities and some of the catalyst components used during the reaction are removed in the course of washing the mother liquor obtained after the oxidation reaction and solid-liquid separation to obtain crude solid NDA.

 2) Impurities consisting of trimellitic acid, metal complexes (i.e., organic complexes of Co or Mn) and substances of high molecular weight are insoluble components in the process of dissolving coarse NDA in water or organic alcohol by adding amine or amine compound components. Remove by passing through solid material.

3) The NDA amine salt, which is the product of NDA produced in 2) above and the charged amine or amine compound component, is further decomposed simultaneously with distillation in a liquid phase at an appropriate temperature to further obtain NDA. At this time, the gaseous component produced by decomposition is condensed and used again as an amine or an amine compound component.

4) Impurities such as 2-naphthoic acid and methyl naphthoic acid are dissolved in organic alcohol and removed. These components have relatively high solubility compared to NDA.                         

5) 2-formyl-6-naphthoic acid and brominated NDA components are removed through a high-pressure hydrogenation process with controlled hydrogen input under a metal catalyst.

On the other hand, in the present invention, the purification by organic alcohol, which is relatively economical and has a very high solvent recovery rate and NDA refining efficiency, may be performed on the oxidized stock solution, on coarse NDA, before the final drying of NDA, or It may be carried out in the middle of the purification, and needs to include the step of purifying a portion of the impurities using organic alcohol.

Preferred organic alcohol compounds for use in the process of the invention are organic alcohol compounds having 10 or less carbon atoms and having hydroxy (-OH) end groups. Of these, methanol, ethanol, propanol, isopropanol, butanol and hexanol are preferable, and methanol and ethanol have high utility in terms of ease of recovery, and the amount of organic alcohol used at this time is based on the weight of the stock solution after oxidation. 0.1 to 20 times, or 0.1 to 20 times based on the weight of NDA contained in the treated material. In addition, the temperature of the alcohol used in the purification or the temperature of the purification process is from room temperature to 250 ℃, the pressure of the solution is from atmospheric pressure to 50 atm corresponding to the saturated water vapor pressure of the organic alcohol.

Purity suitable for the purpose of use of NDA may be formed through the sequential application, repeated application, selective combination application, all applications or only partial application of the processes 1, 2), 3), 4) and 5) claimed in the present invention. have.

According to the present invention, the impurities can be effectively removed, the method is simple, the loss of NDA in the process and the NDA yield are high. White high purity NDA powders having a purity of from 99% to 99.99% by weight of NDA purity from 80% to 99% by weight in the stock solutions obtained in the DMN oxidation reaction can be obtained with minimal loss.

The crude liquid containing the crude NDA produced by the oxidation reaction was washed with acetic acid while the solid was obtained by conventional filtration, filtering or centrifugal separation, and further washed with water to give a conventional filtration, Filtration or centrifugation yields a crude coarse NDA. In this process, the residual amount of reaction such as DMN, a part of the catalyst for oxidation reaction, and a part of impurities are removed.

At this time, NDA is hardly soluble in water, and some micro-sized NDA particles remain in the cleaning liquid during filtration or in the process of filtering and centrifugation, thereby causing a part of yield loss. As conditions for obtaining coarse solid NDA from the stock solution preferred in the present invention, the respective application amounts of acetic acid for washing, water, and organic alcohol are 0.1 to 10 times each, based on the volume of the stock solution formed by the oxidation reaction. Preferably, the temperature of the solution is from room temperature to 250 ° C., and the pressure of the solution is at a level of atmospheric pressure to 50 atm corresponding to at least its saturated vapor pressure. It is also possible to wash with a mixed solution of water, acetic acid and organic alcohol.

Trace impurities such as 2-naphthoic acid and methyl naphthoic acid have been found to be relatively high in solubility in organic alcohols compared to NDA.

Purification may be performed with or first with organic alcohol. Preferred organic alcohol compounds for use in the present invention are organic alcohol compounds having 10 or less carbon atoms and having hydroxy (-OH) terminal groups. Among them, methanol, ethanol, propanol, butanol, isopropanol and hexanol are preferable, and methanol and ethanol have high utility in terms of ease of recovery, and the amount of organic alcohol used at this time is based on the weight of the oxidized stock solution, 0.1 to 20 times, or 0.1 to 20 times based on the weight of NDA contained in the treated material. When purified using the above organic alcohol, the preferred temperature of the alcohol solution and the mixed components is from room temperature to 250 ℃, the preferred pressure is from atmospheric pressure to 50 atm (atm).

Impurities composed of trimellitic acid, metal complexes (i.e., organic complexes of Co or Mn) and substances of high molecular weight are introduced by amine or amine compound components to dissolve coarse NDA while passing through solid materials with insoluble components and adsorbed or removed. You can filter. After removing the impurities, the NDA amine salt may be precipitated by NDA by decomposition and distillation at a temperature of 50 to 300 ° C. in a solution state.

NDA and some of the components included in the NDA react with the amine or amine compound component to form a highly soluble amine salt in most solvents. On the other hand, impurities composed of trimellitic acid, metal complexes (i.e., organic complexes of Co or Mn) and substances of high molecular weight are relatively insoluble in NDA in the solvent even when amine or amine compound components are added. As the amine or amine compound component, methyl amine, dimethyl amine, tetramethyl amine, ethyl amine, dipropyl amine, isopropyl amine, butyl amine, dibutyl amine, 2-ethylhexyl amine, pyridine, piperidine, methyl pyridine, pipe Rollidine, hexamethylene imine, hexamethylene diamine, hexamethylene tetraamine, etc. are mentioned.

The type, amount, and properties of the amine or amine compound used according to the type and content of impurities contained in the NDA were evaluated as being good to use selectively depending on the characteristics of the subsequent filtration process and the economics of the amine or amine compound. For example, using an amine or an amine compound having a high molecular weight lowers the temperature at the time of decomposition distillation of the amine salt and enables the formation of selective solubility, while various components are by-products in the decomposition distillation of the amine salt. As a result, there is a disadvantage in that the recovery rate of the amine, which is generated as a solvent, can be recycled, and the cost is high. The use of low molecular weight amines or amine compounds also dissolves some impurities, lowers the removal efficiency and increases the decomposition distillation temperature, while increasing the recovery of amines that can be recycled. In the case of coarse NDA, when the metal component content is several hundred ppm or more, or the trimellitic acid component is several hundred ppm or more, considering the ease of handling, triethyl amine and trimethyl amine are used in the embodiment of the present invention in an amount of 0.01 to 10 μm. Impurity removal was high in the selective permeable membrane or carbon adsorption layer which can filter the size of.

The amine or amine compound is used in an amount corresponding to a mole of amine functional groups of 1.0 to 1.5 times the number of moles of carboxyl (—COOH) functional groups of NDA. Alternatively, when the amine or amine compound is mixed or the single substance purity is 80% or less, 0.2 to 2 times the amine or amine compound by weight of the NDA is applied. At this time, the amount of water or organic alcohol used is preferably a level of 1 to 20 times the NDA weight.

Impurities insoluble in the amine or the amine compound can be removed by passing through the activated carbon adsorption layer or by selective permeation membrane, filtration, centrifugation, or the like. As a preferable activated carbon adsorption layer, nitrogen adsorption surface area is 300-1500m <2> / g, and the residence time in the adsorption layer of NDA amine salt aqueous solution is 0.1 second on conditions similar to the temperature of the NDA amine aqueous solution around 100 degreeC at normal temperature or normal temperature. It is preferable to determine the flow rate and the amount of the adsorption layer to be maintained at about 120 seconds. As another method, it is preferable to use a selective permeable membrane or a hollow fiber membrane having a filtration degree of 0.1 µm to 10 µm.

Impurities containing 2-formyl-6-naphthoic acid and a brominated NDA component are preferably removed using a high-pressure hydrogenation process in which hydrogen is controlled under a metal catalyst. The metal catalyst used at this time is preferably a supported palladium (Pd) catalyst, a supported platinum (Pt) catalyst or a ruthenium (Ru) catalyst. The loading amount of the platinum and palladium catalyst is preferably 0.1 to 5% by weight, and as the carrier, a gamma-type alumina pellet having a nitrogen adsorption surface area (BET) of 200 to 300 m 2 / g or a nitrogen adsorption surface area (BET) of 500 m 2 / g to Preference is given to activated carbon carriers of 1000 m 2 / g and impact strength of at least 1 kgf / cm 2.

The hydrogenation conditions are 0.1 mol relative to the total amount of NDA in an aqueous solution of NDA or NDA amine salt or acetic acid, organic alcohol, single or mixed solution to be treated at a temperature of 150 ° C to 350 ° C and a pressure of 10 to 100 atm. It is preferred that H ₂ corresponding to% to 300 mol% is mixed with nitrogen and flowed at a total catalyst space velocity (WHSV) of 0.1 to 10 ^{hr −1} . When the reaction temperature and pressure were low, the progress of hydrogenation was very slow, and when the reaction temperature was too high, the amount of impurities estimated by NDA decomposition increased. By the hydrogenation reaction proposed by the present invention, 2-formyl-6-naphthoic acid is mainly converted into the form of methyl naphthoic acid, and the brominated NDA component can be easily converted into NDA. In addition, even when it converts into the NDA amine salt mentioned above, the hydrogenation processing method in this invention can be applied, and it can process similarly even if it does not convert into NDA amine salt separately.

In the hydrogenation reaction of the present invention, some methyl naphthoic acid, 2-naphthoic acid and trimellitic acid may additionally be generated depending on the severity of the reaction and coarse constituents of NDA. At this time, the generated additional impurities and the like are relatively high in solubility in water or the above-described organic alcohol compound, and thus are easily removed through purification. After hydrogenation, the color of the NDA powder obtained by the removal of impurities turns white.

The NDA amine salt, which is a product of the amine or amine compound component introduced for purification, is decomposed simultaneously with distillation in a liquid phase at an appropriate temperature to further obtain NDA.

Decomposition distillation conditions of the NDA amine salt, based on the weight of the NDA amine salt, by dissolving and distilling the amine from the NDA amine salt by applying heat in a state dissolved in 0.1 to 20 times water or organic alcohol, purified NDA Will form a precipitate. The temperature of the solution is adjusted to 50 ° C to 300 ° C by applying heat from the outside. The temperature conditions vary depending on the type of amine or amine compound introduced to form the amine salt, the properties of the decomposition products of the amine salts, and the properties of the solvent.When the temperature is low, decomposition occurs very slowly. Good, but the color of the NDA changes, rather, impurities are produced, and if it exceeds 300 ° C, the precipitated NDA is decomposed again. Therefore, it was evaluated that it is desirable to lower the pressure to lower the decomposition distillation temperature, or to increase the pressure to prevent sudden boiling of the solvent.

Applying the methods described above alone, in combination, or repeatedly applied to obtain the final purified NDA is usually carried out by washing with a solvent containing the final DNA, or by centrifugation or Filtration is applied to finally obtain high purity NDA which is dried to obtain powdery NDA.

2-naphthoic acid, methyl naphthoic acid and the like may be produced during the purification process described above. These impurities are relatively well soluble in organic alcohols compared to NDA and are therefore removed using it as a solvent. Organic alcohols can be used in the final cleaning process or in the purification process. Preferred organic alcohol compounds for use in the present invention are organic alcohol compounds having 10 or less carbon atoms and having hydroxyl (-OH) terminal groups. Among them, methanol, ethanol, propanol, butanol, isopropanol and hexanol are preferable, and methanol and ethanol have high utility in terms of ease of recovery, and the amount of organic alcohol used at this time is based on the weight of the oxidized stock solution, 0.1 to 20 times, or 0.1 to 20 times based on the weight of NDA contained in the treated material. When the purification is performed using the above organic alcohol, the temperature of the alcohol solution and the mixed components is preferably from room temperature to 250 ℃, the pressure is preferably from atmospheric pressure to 50 atm (atm).

Purification methods employed in the present invention may be formed through the sequential application, selective repeat application, selective combination application, all applications or only some applications to form a purity suitable for the purpose of using the NDA.

According to the present invention, the impurities can be effectively removed, the method is simple, the loss of NDA in the process and the yield of NDA are high.

NDA yields or yields are inevitable as more purification or washing processes are inevitable, but yields of 90% to 99% by weight or more, which are suitable for commercial processes, are also possible in the conventional individual processes employed by the present invention. According to the present invention, it can be obtained as a loss as a method for obtaining a high purity white NDA powder having a purity of 99.00% to 99.99% by weight from 80% to 99% by weight of the NDA in the stock solution produced in the DMN oxidation reaction. have.

Hereinafter, although an Example demonstrates this invention concretely, this invention should not be considered limited by these Examples.

Comparative Example 1

2,6-dimethyl naphthalene (hereinafter referred to as "DMN" (99.9%)) was subjected to liquid phase oxidation using a cobalt, manganese and bromine containing catalyst to prepare a stock solution containing NDA.

A catalyst solution for oxidation reaction was prepared by dissolving 18.4 g of cobalt acetate tetrahydrate, 12.3 g of manganese acetate tetrahydrate, and 8.7 g of hydrobromic acid (47% aqueous solution) in 172 g of water and 1792 g of acetic acid. 700 g of a catalyst solution was introduced into a 5.0 L titanium pressure reactor equipped with a reflux condenser, a material transfer pump, and a back pressure regulator. 185 g of 2,6-dimethyl naphthalene was mixed with the catalyst solution, heated to about 80 ° C. externally to dissolve the DMN, and then a pump for raw material transfer was connected.

Nitrogen is substituted, and the temperature is raised and pressurized so that the pressure reactor may have a temperature of 200 ° C. and a pressure of 18 atm. Once the temperature and pressure have stabilized, 540 sccm of oxygen (purity 99.99%) is flowed into the pressure reactor through a mass flow controller while introducing a catalyst and DMN mixed solution into the pressure reactor at a rate of 14.88 g / min. The stirring speed of the pressure reactor was set to about 200 to 500rpm, and the solution mixed with the catalyst and DMN was added to the oxygen for about 30 minutes while maintaining the reaction conditions after the addition was completed.

After slowly lowering the reaction temperature to room temperature, the pressure reactor was decomposed to obtain a stock solution in which NDA and the like were dispersed in fine powder. Subtracting the total charge excluding oxygen from the total sample obtained after the reaction resulted in a weight gain of 69.82 g.

The resulting solution and the amount remaining on the reactor wall were mixed and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. This cake was referred to as sample "A". Sample A was dried to give 252.1 g of sample. 50.0 g of Sample A was washed with 100 cc of acetic acid which is a conventional washing method, filtered under reduced pressure to give a solid, and then the obtained solid was further washed with 100 cc of water, and then filtered under reduced pressure to obtain a solid, which was then dried. This sample was referred to as sample "B".

The obtained sample was analyzed by liquid chromatography (HPLC) to quantify the amount of impurities by an internal standard method to analyze NDA purity. In addition, an element analyzer (ICP) was used to quantitatively analyze the amount of cobalt (Co) and manganese (Mn) remaining in the sample. The analytical results are listed in Table 1 together with the results of the examples. The yield was determined by the ratio of the μA and NDA content of the "A" sample used as the ratio obtained from the final treatment and its NDA content.

Example 1

50.0 g of sample A was placed in a pressure reactor, 100 g of ethanol was added thereto, and then stirred at room temperature for 1 hour at 200 revolutions per minute. The resulting solution was mixed with the remaining amount on the reactor wall and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was referred to as "C" and its amount and components were analyzed.

Example 2

50.0 g of Sample A was placed in a pressure reactor, 100 g of ethanol was added, and then the temperature was raised to 100 ° C. and stirred for 1 hour at 200 revolutions per minute. The resulting solution was mixed with the remaining amount on the reactor wall and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was referred to as "D" and its amount and components were analyzed.

Example 3

25.0 g of Sample B was placed in a pressure reactor, 100 g of ethanol was added, and then the temperature was raised to 100 ° C. and stirred for 1 hour at 100 revolutions per minute. The resulting solution was mixed with the remaining amount on the reactor wall and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was referred to as "E" and its amount and components were analyzed.

Example 4

50.0 g of sample A was placed in a pressure reactor containing 800 g of water, and 27.9 g of tetramethyl amine was added thereto. Agitation was started at 100 revolutions per minute. After 1 hour had elapsed, the solution in the pressure reactor was passed through the solid material adsorption bed at 10 cc / min per minute under a discharge pressure of 3 atm using a pump. The solid material adsorption layer used was a carbon adsorption filter, a carbon filler HS02 manufactured by Hyosung Corporation.

In order to measure the yield, when the residual amount of the pressure reactor was almost gone, 2000 g of water was introduced into the reactor to remove the NDA aqueous solution component remaining in the solid adsorption layer. The amount of NDA aqueous solution in which NDA amine salt was dissolved was 2360 g.

Example 5

The NDA amine salt obtained in Example 4 was cracked and distilled into the NDA component. 1180 g of the NDA aqueous solution obtained in Example 4 was taken and placed in a pressure reactor, and the air remaining in the pressure reactor was replaced with nitrogen for 20 minutes. Distilled water was introduced into the pressure reactor at a rate of 10 cc / min with a high pressure pump while raising the temperature of the pressure reactor to 200 ° C. at room temperature to 1 ° C./min. The pressure in the reactor was maintained at 5 atmospheres using a pressure regulator, and the resulting gas component was condensed while being discharged out of the pressure reactor to collect the liquid component. When the temperature of the pressure reactor reached 200 ° C, cracking distillation conditions were maintained for about 1 hour. Thereafter, the pressure reactor was decomposed at about 80 ° C. while the reactor was slowly cooled, the resulting solution was mixed with the remaining amount on the reactor wall, and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was called "F" and its amount and components were analyzed.

Example 6

10.0 g of Sample A was decomposed and distilled in Example 5, 800 g of condensed water, that is, an aqueous solution containing components such as amines, was charged into a pressure reactor, and 2.8 g of tetramethyl amine was supplemented and added. Agitation was started at 100 revolutions per minute. After 1 hour had elapsed, the solution in the pressure reactor was passed through the solid material adsorption bed at 10 cc / min per minute under a discharge pressure of 3 atm using a pump. The solid material adsorption layer used was a carbon adsorption filter, a carbon filler HS02 manufactured by Hyosung Corporation.

In order to measure the yield, when the residual amount of the pressure reactor was almost gone, 2000 g of water was further added to the reactor to remove the remaining NDA aqueous solution component in the solid adsorption layer. The amount of NDA aqueous solution in which NDA amine salt was dissolved was 2230 g. The resulting NDA amine salt was cracked and distilled into NDA components. The obtained NDA aqueous solution was put into a pressure reactor, and the air remaining in the pressure reactor was replaced with nitrogen for 20 minutes. Distilled water was introduced into the pressure reactor at a rate of 10 cc / min with a high pressure pump while raising the temperature of the pressure reactor to 200 ° C. at 1 ° C./min per minute. The pressure in the reactor was maintained at 5 atmospheres using a pressure regulator, and the resulting gas component was condensed while being discharged out of the pressure reactor to collect the liquid component. When the temperature of the pressure reactor reached 200 ° C, cracking distillation conditions were maintained for about 1 hour. Thereafter, the reactor was decomposed at about 80 ° C. while the pressure reactor was slowly cooled, the resulting solution was mixed with the remaining amount on the reactor wall, and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was referred to as "G" and its amount and components were analyzed.

Example 7

50.0 g of sample A was placed in a pressure reactor containing 800 g of ethanol, and 27.9 g of tetramethyl amine was added thereto. Agitation was started at 100 revolutions per minute. After 1 hour had elapsed, the solution in the pressure reactor was passed through the solid material adsorption bed at 10 cc / min per minute under a discharge pressure of 3 atm using a pump. The solid material adsorption layer used was a carbon adsorption filter, a carbon filler HS02 manufactured by Hyosung Corporation.

In order to measure the yield, when the residual amount of the pressure reactor was almost gone, 2000 g of water was further added to the reactor to remove the remaining NDA aqueous solution component in the solid adsorption layer. The amount of NDA aqueous solution in which NDA amine salt was dissolved was 2240 g.

Example 8

The NDA amine salt dissolved in the alcohol obtained in Example 7 was decomposed and distilled into the NDA component. 1120 g of the NDA solution obtained in Example 7 was taken and placed in a pressure reactor, and the air remaining in the pressure reactor was replaced with nitrogen for 20 minutes. Distilled water was introduced into the pressure reactor at a rate of 10 cc / min with a high pressure pump while raising the temperature of the pressure reactor to 200 ° C. at 1 ° C./min per minute. The pressure in the reactor was maintained at 5 atmospheres using a pressure regulator, and the resulting gas component was condensed while being discharged out of the pressure reactor to collect the liquid component. When the temperature of the pressure reactor reached 150 ° C., cracking distillation conditions were maintained for about 30 minutes. Thereafter, the reactor was decomposed at about 80 ° C. while the reactor was slowly cooled, the resulting solution was mixed with the remaining amount on the reactor wall, and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was referred to as "H" and its amount and components were analyzed.

Example 9

Hydrogenation treatment was performed on the aqueous NDA amine salt solution obtained in Example 4. 1180 g of the NDA aqueous solution obtained in Example 4 was taken and placed in a pressure reactor containing 5 wt% of palladium (Pd) activated carbon catalyst, and the air remaining in the pressure reactor was replaced with hydrogen for 30 minutes. The hydrogen was adjusted to 200 sccm through a mass flow controller while raising the temperature of the pressure reactor to 250 ° C. The pressure of the reactor was maintained at 80 atm using a pressure regulator. Hydrogenation was carried out for 2 hours. Thereafter, the reactor was decomposed at about 80 ° C. while slowly cooling the reactor, and the resulting solution was passed through a carbon adsorption layer at 10 cc / min per minute using a pump. This solution was subjected to decomposition distillation as in Example 5. Thereafter, the resulting mixture was filtered under reduced pressure to obtain a solid cake. The purified NDA sample was referred to as "I" and its amount and components were analyzed.

Example 10

Hydrogenation treatment was performed on the aqueous NDA amine salt solution obtained in Example 7. 1120 g of the NDA solution obtained in Example 7 was taken and placed in a pressure reactor containing 5 wt% of palladium (Pd) activated carbon catalyst, and the air remaining in the pressure reactor was replaced with hydrogen for 30 minutes. The hydrogen was adjusted to 200 sccm through a mass flow controller while raising the temperature of the pressure reactor to 250 ° C. The pressure in the reactor was maintained at 80 atmospheres using a pressure regulator. Hydrogenation was carried out for 2 hours. Thereafter, the reactor was decomposed at about 80 ° C. while the reactor was slowly cooled, and the resulting solution was passed through a carbon adsorption layer at 10 cc / min per minute using a pump. This solution was subjected to decomposition distillation as in Example 5. Thereafter, the resulting mixture was filtered under reduced pressure to obtain a solid cake. The purified NDA sample was called "J" and its amount and components were analyzed.

Example 11

The purified NDA "I" obtained in Example 9 was taken and ethanol was further mixed to effect alcohol washing. 10.0 g of sample I was placed in a pressure reactor, 200 g of ethanol was added, the temperature was raised to 100 ° C., and stirred for 1 hour at 200 revolutions per minute. The obtained solution and the remaining amount on the reactor wall were mixed and filtered under reduced pressure using a 1 μm filter paper to obtain a solid cake. The purified NDA sample was called "K" and its amount and components were analyzed.

This example is an experiment to compare the utility of the alcohol only required by the present invention, the purified "K" sample was composed of a single component (100% purity) within the HPLC analysis limit used in the present invention. On the other hand, in Example 9, NDA sample I (purity 99.86%) contained some amount of methyl naphthoic acid and 2-naphthoic acid, but was found to be almost removed by the process of the present invention.

Sample classification A B C D E Processing method Comparative Example 1 Comparative Example 1 Example 1 Example 2 Example 3 ¹⁾ Component Analysis Table 2,6-naphthalenedicarboxylic acid (% by weight) 95.48 96.52 97.34 97.90 98.11 Trimellitic acid (% by weight) 1.10 0.95 0.53 0.49 0.37 2-formyl-6-naphthoic acid (% by weight) 0.90 0.55 0.56 0.52 0.53 Methylnaphthoic Acid (wt%) 0.30 0.29 0.26 0.11 0.07 2-naphthoic acid (% by weight) 0.20 0.21 0.17 0.07 0.05 Bromo-2,6-naphthalenedicarboxylic acid (% by weight) 0.82 0.82 0.83 0.81 0.83 ²⁾ Other unidentified substances (% by weight) 1.20 0.66 0.31 0.11 Trace amount Cobalt (wtppm) Manganese (wtppm) 1824 1233 892 562 537 453 436 373 345 287 Yield comparison table 2,6-naphthalenedicarboxylic acid yield (% by weight) Reference content 99.1% 98.7% 97.4% 97.2%

1) Component analysis is quantitative analysis by liquid chromatography (HPLC).

   The content of cobalt and manganese is quantitatively analyzed by elemental analyzer (ICP).

2) An unidentified substance is actually present but not identified in the analysis.

   Quantitative error. Trace analysis is a trace substance that is present but difficult to quantify.

3) Yield is calculated as the ratio of the amount of A sample used and the NDA content according to Equation 1 obtained by the final treatment and the NDA content thereof.

                       Obtained Cake Amount (g) x NDA Component Ratio (wt%)

         Yield = ------------------------------------------------ ------------

       A sample amount (g) × A sample content ratio (95.48% by weight) used in the Examples

Sample classification F G H I J Processing method Example 5 Example 6 Example 8 Example 9 Example 10 ¹⁾ Component Analysis Table 2,6-naphthalenedicarboxylic acid (% by weight) 99.21 99.37 99.72 99.86 99.94 Trimellitic acid (% by weight) 0.01 0.01 0.00 0.00 0.01 2-formyl-6-naphthoic acid (% by weight) 0.22 0.12 0.09 0.00 0.01 Methylnaphthoic Acid (wt%) 0.21 0.22 0.01 0.05 0.01 2-naphthoic acid (% by weight) 0.11 0.09 0.01 0.07 0.01 Bromo-2,6-naphthalenedicarboxylic acid (% by weight) 0.23 0.21 0.07 0.00 0.00 ²⁾ Other unidentified substances (% by weight) Trace amount Trace amount 0.10 - - Cobalt (wtppm) Manganese (wtppm) 89 71 104 98 76 52 29 32 31 24 Yield comparison table 2,6-naphthalenedicarboxylic acid yield (% by weight) 93.6% 92.9% 93.7% 92.4% 91.6%

1) Component analysis is quantitative analysis by liquid chromatography (HPLC).

   Cobalt and manganese content are quantitatively analyzed by Elemental Analyzer (ICP).

2) An unidentified substance is actually present but not identified in the analysis.

   Quantitative error. Trace analysis is a trace substance that is present but difficult to quantify.

3) Yield is calculated as the ratio of the amount of A sample used and the NDA content according to Equation 2 obtained by the final treatment and the NDA content thereof.

                       Obtained Cake Amount (g) x NDA Component Ratio (wt%)

        Yield = ------------------------------------------------ ------------

       A sample amount (g) × A sample content ratio (95.48% by weight) used in the Examples

The present invention relates to a method for purifying coarse NDA produced by the oxidation reaction of DMN, and it is possible to produce high purity NDA from coarse NDA by the purification method of the present invention.

Purification methods according to the present invention may be formed through the sequential application, selective iterations, selective combinations, all or part of the application, the purity suited to the purpose of the NDA can be effectively removed, impurities can be effectively removed, the process is simple but the process In addition, the NDA loss is low, the NDA yield is high, economical purification is possible, and high-purity NDA is commercialized by mass purification.

Claims (9)

delete delete  In the method for liquid-phase oxidation of 2,6-dimethyl naphthalene or purifying the obtained product to produce high purity 2,6-naphthalenedicarboxylic acid, 0.1 to 20 times the amount of one or more organic alcohols selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol and hexanol, based on the weight of 2,6-dimethyl naphthalene, After the organic alcohol is added, high purity 2,6-naphthalene, characterized in that the step of separating into a solid and a liquid through a temperature condition of 0 to 250 ℃ and a pressure condition of 50 to 50 atm (atm) Method for producing dicarboxylic acid. 4. The method of claim 3, wherein 0.2 to 2 times the amount of amine or amine compound is added based on the weight of 2,6-dimethyl naphthalene to remove components that are not soluble in water or organic alcohol. Method for producing 2,6-naphthalenedicarboxylic acid. The method according to claim 3, wherein when removing the insoluble components, a solid adsorption layer is used, a selective permeable membrane is used, or a solid component having a size of 0.01 to 10 µm is separated from the liquid phase. , Method for producing high purity 2,6-naphthalenedicarboxylic acid. The method according to claim 3, wherein the amine or amine compound used is an organic compound which can form a soluble salt with 2,6-dimethyl naphthalene in water or an organic alcohol, and has a nitrogen (N) component in molecular structure, Method for producing high purity 2,6-naphthalenedicarboxylic acid. delete The method of claim 6, The amine or amine compound and 2,6-dimethyl naphthalene are subjected to the process of decomposing the soluble salt formed in water or organic alcohol at 50 ° C to 300 ° C, but again using the liquid component collected by condensation or cooling when decomposing. A process for producing high purity 2,6-naphthalenedicarboxylic acid, characterized by the above-mentioned. The ruthenium (Ru) compound according to claim 3 or 4, wherein a platinum (Pt) or palladium (Pd) supported catalyst is used or based on the amount of 2,6-dimethyl naphthalene, High purity, characterized in that the hydrogen is introduced at a temperature of 150 ℃ to 300 ℃ and a pressure of 0.5 to 200 atm, based on the amount of 2,6-dimethyl naphthalene, 0.1 to 300 mol% Method for producing 2,6-naphthalenedicarboxylic acid.