阅读说明：本技术 2,6-萘二甲酸的提纯方法 (Method for purifying 2, 6-naphthalene dicarboxylic acid ) 是由 秦春曦 陈亮 张洪福 于 2019-10-23 设计创作，主要内容包括：本发明提供了一种2,6-萘二甲酸的提纯方法,包括：步骤A：将粗2,6-萘二甲酸与脂肪醇混合,进行酯化反应；步骤B：结晶析出2,6-萘二甲酸二烷基酯,固液分离；步骤C：将步骤B中固液分离得到的2,6-萘二甲酸二烷基酯与水混合,添加磷酸酯类化合物和/或聚丙烯酰胺类化合物,进行水解使得2,6-萘二甲酸结晶析出。本发明的提纯方法获得的2,6-NDA颗粒性良好,其颗粒粒径大于100μm,且该工艺流程简洁高效,容易实现连续化生产,适合工业应用。(The invention provides a method for purifying 2, 6-naphthalene dicarboxylic acid, which comprises the following steps: step A: mixing crude 2, 6-naphthalene dicarboxylic acid and fatty alcohol to perform esterification reaction; and B: crystallizing and separating out the 2, 6-naphthalenedicarboxylic acid dialkyl ester, and carrying out solid-liquid separation; and C: and C, mixing the dialkyl 2, 6-naphthalenedicarboxylate obtained by solid-liquid separation in the step B with water, adding a phosphate compound and/or a polyacrylamide compound, and hydrolyzing to separate out 2, 6-naphthalenedicarboxylic acid crystals. The 2,6-NDA obtained by the purification method has good granularity, the particle size of the particles is more than 100 mu m, the process flow is simple and efficient, the continuous production is easy to realize, and the method is suitable for industrial application.)

1. A method for purifying 2, 6-naphthalenedicarboxylic acid, comprising:

step A: mixing crude 2, 6-naphthalene dicarboxylic acid and fatty alcohol to perform esterification reaction;

and B: cooling the esterification reaction mixture obtained in the step A, separating out the 2, 6-naphthalenedicarboxylic acid dialkyl ester, and carrying out solid-liquid separation to obtain the 2, 6-naphthalenedicarboxylic acid dialkyl ester;

and C: a dialkyl 2, 6-naphthalenedicarboxylate is mixed with water to form a slurry, and a phosphate compound and/or a polyacrylamide compound are added to the slurry to hydrolyze the mixture and crystallize the 2, 6-naphthalenedicarboxylate.

2. The process according to claim 1, characterized in that the fatty alcohol is selected from at least one of the fatty alcohols from C1 to C15, preferably from methanol and/or ethanol.

3. The method according to claim 1 or 2, wherein the phosphate compound has a structure represented by formula (I),

wherein R is₁、R₂And R₃The same or different, each independently selected from hydrogen, C1-C15 alkyl, hydroxy-substituted C1-C15 alkyl and C6-C15 aryl; r₁、R₂And R₃At least one of which is hydrogen or hydroxy-substituted C1-C15 alkyl,

preferably, the phosphate ester compound is di (2-ethylhexyl) phosphate.

4. The method according to any one of claims 1 to 3, wherein the phosphate compound is added in an amount of 0.01 to 10 wt% based on the mass of the dialkyl 2, 6-naphthalenedicarboxylate; and/or the addition amount of the polyacrylamide compound is 0.01-10 wt% of the mass of the dialkyl 2, 6-naphthalenedicarboxylate.

5. The method according to any one of claims 1 to 4, wherein in step A, the catalyst of the esterification reaction is selected from any one of protonic acid, ionic liquid and metal compound; preferably, when the catalyst of the esterification reaction is protonic acid and/or ionic liquid, the temperature of the esterification reaction is 80-150 ℃, and when the catalyst of the esterification reaction is metal compound, the temperature of the esterification reaction is 150-350 ℃, and preferably 10-80 ℃ lower than the temperature of the hydrolysis.

6. The process according to any one of claims 1 to 5, wherein in step B, the crystallization temperature is from-10 ℃ to 100 ℃, preferably from 0 ℃ to 80 ℃; and/or the purity of the dialkyl 2, 6-naphthalenedicarboxylate is greater than 95%, preferably greater than 98%, and/or the solid color value B of the dialkyl 2, 6-naphthalenedicarboxylate is between-25 and + 25.

7. The method according to any one of claims 1 to 6, wherein in step C, the temperature of the hydrolysis is 200-350 ℃, preferably 230-280 ℃; and/or

In the hydrolysis, the mass ratio of water to the dialkyl 2, 6-naphthalenedicarboxylate is (0.1-10): 1, preferably (1-5): 1; and/or

The hydrolysis time is 0.1-5h, preferably 0.2-1 h.

8. The method according to any of claims 1-7, characterized in that the method further comprises a step D: c, performing solid-liquid separation on the 2, 6-naphthalenedicarboxylic acid obtained in the step C, washing with water and drying, preferably, using a liquid phase obtained after the solid-liquid separation for preheating the esterification reaction raw material in the step A, cooling the liquid phase to the esterification temperature, performing solid-liquid separation, returning the obtained solid to the hydrolysis crystallization kettle, and distilling out fatty alcohol from the obtained liquid phase for the esterification reaction again; and/or

The method also comprises decoloring after the esterification reaction of the step A, and preferably, the decoloring is performed by adopting activated carbon or ion resin adsorption.

9. The process according to any one of claims 1 to 8, characterized in that in step D the temperature of the solid-liquid separation is greater than 100 ℃, preferably greater than 200 ℃, more preferably the same as the temperature of the hydrolysis in step C.

10. Use of a process according to any one of claims 1 to 9 for removing impurities from crude 2, 6-naphthalenedicarboxylic acid.

Technical Field

The invention relates to the field of purification of 2, 6-naphthalenedicarboxylic acid, in particular to a method for purifying 2, 6-naphthalenedicarboxylic acid.

Background

Compared with the traditional polyethylene terephthalate (PET), the benzene ring in the polyethylene naphthalate (PEN) system is replaced by a naphthalene ring with better rigidity, so that the PEN has more excellent performance compared with the PET, and the potential application of the PEN covers all fields in which the PET can be applied and can provide better performance. The key to the production of PEN is to obtain polymer grade monomers. PEN production can take two routes, one is the direct polymerization of 2,6-NDA with ethylene glycol; the other is the ester exchange polymerization of 2,6-NDC and ethylene glycol. Although the first route is simple in process, the melting point of the monomer 2,6-NDA is as high as 310 ℃, and the vapor pressure is low, so that the monomer has certain solubility only in organic solvents such as nitrogen-nitrogen Dimethylacetamide (DMAC), and the like, and the 2,6-NDA is difficult to purify by adopting an efficient separation method; the second route involves first esterifying 2,6-NDA with methanol and then purifying the esterification product and polymerizing it with ethylene glycol, which is relatively complicated compared to the first route and produces methanol as a byproduct of the polymerization process.

The reported methods for obtaining polymerization-grade 2,6-NDA include adduct crystallization, near-critical water crystallization, supercritical water crystallization, acid-base purification, and esterification hydrolysis. Chinese patent CN 102070442 reports an adduct crystallization process, which indicates that 2,6-NDA can form adduct crystals with nitrogen such as dimethylacetamide and N-methylpyrrolidone at a temperature below 60 ℃, so that 2,6-NDA can be dissolved at about 50 ℃, and then 2,6-NDA can be purified by cooling crystallization. However, in the process, colored impurities such as 2-formyl-6-naphthoic acid or 2-acetyl-6-naphthoic acid and the like also form adduct crystals with the organic solvents, so that the two colored impurities cannot be effectively removed, the color of the product is yellowish, and the problem of solvent residue is serious by adopting the process, so that the product meeting the polymerization requirement is difficult to obtain.

US patent US 3888921 reports an acid-base purification process. The crude 2,6-NDA is first dissolved in an aqueous solution of an alkaline substance, and the 2,6-NDA is crystallized and precipitated by adjusting the pH. However, in this process, the color-developing impurities are removed by decolorizing with activated carbon, and the resulting particles are fine and difficult to filter.

U.S. Pat. No. 4, 5563294 reports a process for obtaining 2,6-NDA by hydrolysis of esterification products, wherein purified 2,6-NDC is hydrolyzed in water at a temperature of at least 230 ℃ to obtain 2,6-NDA, and the hydrolysis products are at least 10% soluble in water. However, in this method, the starting 2,6-NDC must be a purified product, and the obtained 2,6-NDA particles are aggregated seriously. Chinese patent CN1680264 adopts hydrophobic solvent and water as solvent to hydrolyze 2,6-NDC under alkaline condition, the whole hydrolysis process is carried out in two steps, the first step hydrolyzes at least 80% of 2,6-NDC under low water content, then the second step hydrolyzes after adding water, and the hydrolyzed 2,6-NDA alkali salt solution is acid-separated. The process is complex, acid and alkali are introduced, a large amount of wastewater is generated, and the obtained 2,6-NDA particles are fine and are not easy to filter.

As can be seen from the above, the known 2,6-NDA purification process has the problems of low space utilization rate of a crystallizer due to large solvent consumption, low solubility of 2,6-NDA, difficulty in filtering the obtained 2,6-NDA particles and the like.

Disclosure of Invention

Based on the defects of the purification process, the invention provides a method for efficiently purifying 2, 6-naphthalenedicarboxylic acid, the invention adopts pure water to hydrolyze 2, 6-naphthalenedicarboxylic acid dialkyl ester which does not reach the refining target, and phosphate ester or polyacrylamide substances are added in the hydrolysis process, so that 2,6-NDA generated in the hydrolysis process can not be polymerized, and impurities are still dissolved in water in the hydrolysis process, thereby achieving the purpose of purifying 2, 6-NDA.

The first aspect of the present invention provides a method for purifying 2, 6-naphthalenedicarboxylic acid, comprising:

step A: mixing crude 2, 6-naphthalene dicarboxylic acid and fatty alcohol to perform esterification reaction;

and B: cooling the esterification reaction mixture obtained in the step A, separating out the 2, 6-naphthalenedicarboxylic acid dialkyl ester, and carrying out solid-liquid separation to obtain the 2, 6-naphthalenedicarboxylic acid dialkyl ester;

and C: a dialkyl 2, 6-naphthalenedicarboxylate is mixed with water to form a slurry, and a phosphate compound and/or a polyacrylamide compound are added to the slurry to hydrolyze the mixture and crystallize the 2, 6-naphthalenedicarboxylate.

According to some embodiments of the invention, the hydrolysis and crystallization are carried out simultaneously and in the same reactor.

According to some embodiments of the invention, the hydrolysis and crystallization process comprises a crystal growth process.

According to some embodiments of the invention, the method further comprises performing a decolorization after the esterification reaction of step a.

According to some embodiments of the invention, the decolorizing is carried out by adsorption on activated carbon or ionic resin.

According to some embodiments of the invention, the fatty alcohol is selected from at least one of the fatty alcohols of C1-C15.

According to a preferred embodiment of the invention, the fatty alcohol is selected from methanol and/or ethanol.

According to some embodiments of the present invention, the phosphate compound has a structure represented by formula (I),

wherein R is₁、R₂And R₃The same or different, each independently selected from hydrogen, C1-C15 alkyl, hydroxy-substituted C1-C15 alkyl and C6-C15 aryl; r₁、R₂And R₃At least one of which is hydrogen or hydroxy-substituted C1-C15 alkyl.

According to a preferred embodiment of the present invention, the phosphate ester compound is bis (2-ethylhexyl) phosphate.

According to some embodiments of the present invention, the phosphate ester compound is added in an amount of 0.01 to 10 wt% based on the mass of the dialkyl 2, 6-naphthalenedicarboxylate.

According to some embodiments of the invention, the polyacrylamide-based compound is selected from at least one of cationic polyacrylamide and anionic polyacrylamide.

According to some embodiments of the invention, the polyacrylamide-based compound is added in an amount of 0.01 to 10 wt% based on the mass of the dialkyl 2, 6-naphthalenedicarboxylate.

According to some embodiments of the invention, in step a, the esterification reaction may be carried out in any form.

According to some embodiments of the invention, in step a, the catalyst of the esterification reaction is selected from any one of a protic acid, an ionic liquid, and a metal compound.

According to some embodiments of the invention, when the catalyst of the esterification reaction is a protic acid and/or an ionic liquid, the temperature of the esterification reaction is between 80 and 150 ℃.

According to some embodiments of the present invention, when the catalyst for the esterification reaction is a metal compound, the temperature of the esterification reaction is 150-350 ℃.

According to a preferred embodiment of the present invention, when the catalyst of the esterification reaction is a metal compound, it is preferably 10 to 80 ℃ lower than the temperature of the hydrolysis.

According to some embodiments of the invention, in step B, the crystallization temperature is-10 to 100 ℃.

According to a preferred embodiment of the invention, in step B, the crystallization temperature is between 0 and 80 ℃.

According to some embodiments of the invention, the purity of the dialkyl 2, 6-naphthalenedicarboxylate in step B is greater than 95%.

According to a preferred embodiment of the present invention, in step B, the purity of the dialkyl 2, 6-naphthalenedicarboxylate is greater than 98%.

According to some embodiments of the invention, the dialkyl 2, 6-naphthalenedicarboxylate has a solid color value B of between-25 and + 25. The solid color values described in this invention are the L/A/B values of the product solids, where B represents a yellow-blue color and the greater the B value the more yellow.

According to some embodiments of the invention, the temperature of the hydrolysis in step C is 200-350 ℃.

According to a preferred embodiment of the present invention, in step C, the temperature of the hydrolysis is 230-280 ℃.

According to some embodiments of the invention, in step C, the mass ratio of water to dialkyl 2, 6-naphthalenedicarboxylate in said hydrolysis is (0.1-10): 1.

according to a preferred embodiment of the present invention, in step C, the mass ratio of water to dialkyl 2, 6-naphthalenedicarboxylate in said hydrolysis is (1-5): 1.

according to some embodiments of the invention, in step C, the hydrolysis time is between 0.1 and 5 h.

According to a preferred embodiment of the invention, in step C, the hydrolysis time is between 0.2 and 1 h.

According to some embodiments of the invention, in step D, the temperature of the solid-liquid separation is greater than 100 ℃.

According to a preferred embodiment of the invention, in step D, the temperature of the solid-liquid separation is greater than 200 ℃.

According to a preferred embodiment of the present invention, in step D, the temperature of the solid-liquid separation is the same as the temperature of the hydrolysis in step C.

According to some embodiments of the invention, the method further comprises step D: and D, carrying out solid-liquid separation on the 2, 6-naphthalenedicarboxylic acid obtained in the step C, washing with water and drying.

According to some embodiments of the present invention, the liquid phase after the solid-liquid separation is used for preheating the esterification reaction raw material in the step a, the liquid phase is cooled to the esterification temperature and then subjected to solid-liquid separation, the obtained solid is returned to the hydrolysis crystallization kettle, and the fatty alcohol distilled from the obtained liquid phase is used for the esterification reaction again.

A second aspect of the present invention provides a use of the method according to the first aspect for removing impurities from crude 2, 6-naphthalenedicarboxylic acid.

By adopting the process, the following beneficial effects can be obtained:

the hydrolysis raw material of the invention does not need to be refined 2, 6-naphthalenedicarboxylic acid dialkyl ester, and the hydrolysis process is a reaction crystallization process, thereby playing a role in purification; the obtained 2,6-NDA has good granularity, and the particle size of the particles is more than 100 mu m; the process flow is simple and efficient, continuous production is easy to realize, and the method is suitable for industrial application.

Drawings

Fig. 1 is a flow diagram of a purification method according to one embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the following description.

The following examples and comparative examples were conducted using the same crude 2,6-NDA starting material, and the crude 2,6-NDA starting material was quantitatively analyzed by liquid chromatography to obtain the starting material composition shown in Table 1.

TABLE 1 crude 2,6-NDA feed composition

Example 1

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, heating to 240 ℃ for reaction for 2 hours, filtering at 240 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 2.

TABLE 2 product compositions N1 and N2

Example 2

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 1 wt% of bis (2-ethylhexyl) phosphate, heating to 240 ℃ for reaction for 2 hours, filtering at 240 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 3.

TABLE 3 product compositions N1 and N2

Example 3

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 240 ℃ for 3h, and cooling to 140 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 20 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 3 wt% of lauryl alcohol phosphate, heating to 250 ℃ for reaction for 1h, filtering at 250 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 4.

TABLE 4 product compositions N1 and N2

Example 4

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon into a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 0.1 wt% of cationic polyacrylamide (molecular weight of 400-1200 ten thousand, provided by river chemical industry), heating to 230 ℃ for reaction for 3 hours, filtering at 230 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 5.

TABLE 5 product compositions N1 and N2

Example 5

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 0.1 wt% of bis (2-ethylhexyl) phosphate, heating to 240 ℃ for reaction for 2 hours, filtering at 240 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 6.

TABLE 6 product compositions N1 and N2

Example 6

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 5 wt% of bis (2-ethylhexyl) phosphate, heating to 240 ℃ for reaction for 2 hours, filtering at 240 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 7.

TABLE 7 product compositions N1 and N2

Example 7

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 250 ℃ for 2h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 30 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 7:1, adding 10 wt% of trioctyl phosphate, heating to 260 ℃ for reaction for 1h, filtering at 260 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 8.

TABLE 8 product compositions N1 and N2

Example 8

Weighing 100g of the raw materials and 500g of ethanol, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 1 wt% of bis (2-ethylhexyl) phosphate, heating to 240 ℃ for reaction for 2 hours, filtering at 240 ℃ after the reaction is finished to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 9.

TABLE 9 product compositions N1 and N2

Example 9

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 1 wt% of bis (2-ethylhexyl) phosphate, heating to 300 ℃ for reaction for 1h, cooling to 140 ℃ after the reaction is finished, filtering to obtain refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 10.

TABLE 10 product compositions N1 and N2

Example 10

Weighing 100g and 500g of the raw materials, carrying out esterification reaction at 230 ℃ for 5h, and cooling to 130 ℃ after the reaction. Adding 10g of activated carbon by using a slurry pump for decolorization, cooling and crystallizing the decolorized solution, wherein the crystallization end point temperature is 10 ℃ to obtain solid 2,6-NDC (recorded as N1), preparing the obtained N1 solid into slurry with water according to the liquid-solid ratio of 5:1, adding 1 wt% of bis (2-ethylhexyl) phosphate, heating to 350 ℃ for reaction for 2 hours, filtering at 350 ℃ after the reaction is finished, obtaining refined 2,6-NDA (recorded as N2), and analyzing products N1 and N2, wherein the results are shown in Table 11.

TABLE 11 product compositions N1 and N2

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.