阅读说明：本技术 粗2,6-萘二甲酸的精制方法 (Process for refining coarse 2,6-naphthalene dicarboxylic acid ) 是由 朱庆才 张海涛 司丹 于 2020-06-02 设计创作，主要内容包括：本发明粗2,6-萘二甲酸的精制方法,主要解决现有技术中2,6-二异丙基萘空气氧化生成的粗2,6-萘二甲酸中杂质2-乙酰基-6-萘甲酸含量高,影响后续加氢精制的问题。本发明通过粗2,6-萘二甲酸的精制方法,包括在氧化催化剂存在下,以水为溶剂,粗2,6-萘二甲酸与含有CO-(2)和自由氧的混合气体反应,降低粗2,6-萘二甲酸中的2-乙酰基-6-萘甲酸含量,得到精制2,6-萘二甲酸的技术方案,较好的解决了该问题,可用于精制2,6-萘二甲酸的生产中。(The invention relates to a refining method of crude2,6-naphthalene dicarboxylic acid, which mainly solves the problem that the content of impurity 2-acetyl-6-naphthoic acid in the crude2,6-naphthalene dicarboxylic acid generated by air oxidation of 2, 6-diisopropylnaphthalene in the prior art is high, so that the subsequent hydrofining is influenced. The invention relates to a method for refining crude2,6-naphthalene dicarboxylic acid, which comprises reacting crude2,6-naphthalene dicarboxylic acid with a mixture containing CO in the presence of an oxidation catalyst and water as a solvent 2 Reacts with the mixed gas of free oxygen to reduce the content of 2-acetyl-6-naphthoic acid in the crude2,6-naphthalene dicarboxylic acid to obtain the refined 2,6-naphthalene dicarboxylic acid, better solves the problem and can be used in the production of the refined 2,6-naphthalene dicarboxylic acid.)

1. A process for purifying crude2, 6-naphthalenedicarboxylic acid which comprises reacting crude2, 6-naphthalenedicarboxylic acid with a catalyst containing CO in the presence of an oxidation catalyst in the presence of water as a solvent₂Reacting with the mixed gas of free oxygen to reduce the content of 2-acetyl-6-naphthoic acid in the crude2,6-naphthalene dicarboxylic acid, thereby obtaining the refined 2,6-naphthalene dicarboxylic acid.

2. The process as set forth in claim 1, wherein the crude2, 6-naphthalenedicarboxylic acid is obtained by air oxidation of 2, 6-diisopropylnaphthalene over a Co-Mn-Br catalyst.

3. The process as set forth in claim 1 wherein the oxidation catalyst is a noble metal supported catalyst. And/or preferably the noble metal comprises at least one member of the group consisting of palladium, ruthenium and platinum, more preferably palladium. And/or preferably the catalyst support comprises TiO₂。

4. The process as set forth in claim 3 wherein the noble metal loading in the oxidation catalyst is from 0.1 to 1 wt.%.

5. The process as set forth in claim 1, characterized in that the crude2, 6-naphthalenedicarboxylic acid has a 2-acetyl-6-naphthoic acid content of 200 to 20000ppmw, more preferably 500-3000 ppmw.

6. The method as set forth in claim 1, wherein the crude2, 6-naphthalenedicarboxylic acid has a mass concentration of 1 to 10% by weight in the aqueous solution. More preferably 3-5 wt%.

7. The method as set forth in claim 1, wherein the volume ratio of free oxygen to carbon dioxide in the mixed gas is 0.10 to 3.0.

8. The process as claimed in claim 1, wherein the reaction temperature is 250-320 ℃. More preferably 280-300 ℃.

9. The process as claimed in claim 1, wherein the reaction pressure is from 8 to 15 MPa. More preferably 8-10 MPa.

10. The process as claimed in claim 1, wherein the reaction time is from 10 to 60 min. More preferably 25-45 min.

Technical Field

The present invention relates to a method for purifying crude2, 6-naphthalenedicarboxylic acid.

Background

2,6-naphthalene dicarboxylic acid (2,6-NDA) and derivatives thereof are important monomers for preparing various polyesters, polyurethane materials, Liquid Crystal Polymers (LCP) and the like, and particularly polyethylene naphthalate (PEN) prepared by polycondensation of 2,6-NDA and ethylene glycol has wide application prospects in films, packaging containers (especially beer bottles) and industrial fibers. Compared with the polyester material polyethylene terephthalate (PET) which is widely used at present, PEN has more excellent performance and wider application range. In PEN and its key monomer 2,6-NDA, the national improvement Commission "action plan for enhancing core competitiveness of manufacturing industry for three years" (2018-.

Currently, 2,6-NDA is synthesized industrially mainly by oxidizing dialkyl naphthalene in air liquid phase under Co-Mn-Br catalyst, especially the most common synthetic route using 2, 6-dimethyl naphthalene as raw material, for example, 2,6-NDA is prepared by using 2, 6-dimethyl naphthalene (2,6-DMN) in US5183933 (titled: Process for preparation 2,6-naphthalene-dicarboxylic acid), and the yield can reach 93%. However, since the physical properties of 2, 6-dimethylnaphthalene and the physical and chemical properties of 2, 7-dimethylnaphthalene are similar, the separation is difficult, and the cost for obtaining high-purity 2, 6-dimethylnaphthalene is high; in contrast, 2, 6-diisopropylnaphthalene (2,6-DIPN) is easy to separate and purify from the raw material (isomer mixture), the operation cost is relatively low, but the amount of oxidation byproducts is large, and the subsequent product separation is complicated and difficult, so researchers are keen to synthesize 2, 6-naphthalenedicarboxylic acid by using 2, 6-diisopropylnaphthalene as the raw material, and hope to find an economical synthesis route, for example, patent US4681978 (titled: Process for preparing 2,6-naphthalene-dicarboxylic acid) adopts step-by-step heating and pressure oxidation in a reaction kettle, the first step obtains intermediate 6-isopropyl-2-naphthoic acid (NMCA), and the second step reacts under the same conditions, and finally obtains 24% 2, 6-NDA. In patent US4709088 (titled: Process for preparing 2,6-naphthalene-dicarboxylic acid), a semi-continuous method is adopted, 2,6-DIPN as a raw material is continuously put into a mixed solution of a catalyst and a solvent for reaction at a certain speed, and after the feeding is finished, deep oxidation is carried out for 2 hours, so that the yield of 2,6-DNA is 91.7 mol%, and therefore, the semi-continuous operation is very beneficial to the reaction, and the yield of 2,6-NDA can be greatly improved.

As research progresses, researchers have increasingly demanded the kinds and contents of by-products in oxidized products, because the kinds and contents of impurities contained in 2,6-NDA used in the production of PEN by polymerization must meet certain standards in order to meet the requirements of polymerized products. Taking 2,6-NDA produced by taking 2,6-DMN as a raw material as an example, AMOCO has the following requirements on the content of impurities in the oxidized crude product 2, 6-NDA: trimellitic acid <5 wt.%, bromo-2, 6-naphthalenedicarboxylic acid <3 wt.%, 2-formyl-6-naphthoic acid <1 wt.%. Because of different raw materials, crude2, 6-NDA produced by oxidizing 2,6-DIPN has no clear index at present, but a large number of experiments show that the impurities mainly comprise 2-formyl-6-naphthoic acid (2,6-FNA) and 2-acetyl-6-naphthoic acid (2,6-ANA), the contents of the two impurities greatly influence the performance and color of a polymer, and the next step of polymerization can be carried out only by an impurity removal process. There are many methods for refining crude2, 6-naphthalenedicarboxylic acid, among which hydrofinishing is a very efficient and commonly used Method, as described in U.S. Pat. No. 5,5256817 (entitled: Method for purifying a naphthalene-dicarboxylic acid), U.S. Pat. No. 20030088121 (entitled: Method for purifying crop 2,6-naphthalene-dicarboxylic acid), U.S. Pat. No. 6747171 (entitled: Low temperature purification of naphthalene-dicarboxylic acids), and Chinese patent CN101077857 (entitled: Method for producing naphthalenedicarboxylic acid), but these patents are directed to purifying crude2, 6-naphthalenedicarboxylic acid obtained by oxidation of 2, 6-dimethylnaphthalene as a raw material, while two different impurities are not described for crude2, 6-DIPN obtained by oxidation of 2, 6-dinaphthalene, but the raw material is a-2-NDA-6-crude, but the raw material is a different one, since crude2, 6-naphthalenedicarboxylic acid obtained by oxidation of 2,6-DMN as a raw material does not contain 2,6-ANA as an impurity, it is very difficult to purify crude2, 6-NDA containing 2,6-ANA by hydrogenation in such a manner that 2,6-ANA is much more difficult to hydrogenate than 2,6-FNA, and excessive hydrogenation of 2,6-NDA to 2, 6-dicarboxy-1, 2,3, 4-tetrahydronaphthalene (2,6-DCT) is caused if hydrogenation is intensified, as described in U.S. Pat. No. 4,47171 and Chinese patent CN 101077857. Thus, to hydrofinish the crude2, 6-NDA containing the impurity 2,6-ANA, the 2,6-ANA content must first be reduced to a level that ensures that it can be removed during hydrofinishing without affecting the 2, 6-NDA.

Disclosure of Invention

The invention aims to solve the technical problem that the content of 2-acetyl-6-naphthoic acid as an impurity in crude2,6-naphthalene dicarboxylic acid generated by air oxidation of 2, 6-diisopropylnaphthalene in the prior art is high, so that the subsequent hydrofining is influenced, and the problem that the content of 2-acetyl-6-naphthoic acid is reduced by adopting the prior catalytic oxidation and the 2-NA impurity is very high is solved, and the novel method for refining the crude2,6-naphthalene dicarboxylic acid is provided, and the method can not cause the remarkable increase of the 2-NA impurity while the content of the 2-acetyl-6-naphthoic acid is obviously reduced.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a process for purifying crude2, 6-naphthalenedicarboxylic acid which comprises reacting crude2, 6-naphthalenedicarboxylic acid with a catalyst containing CO in the presence of an oxidation catalyst in the presence of water as a solvent₂Reacting with the mixed gas of free oxygen to reduce the content of 2-acetyl-6-naphthoic acid in the crude2,6-naphthalene dicarboxylic acid, thereby obtaining the refined 2,6-naphthalene dicarboxylic acid.

We have found that when 2-acetyl-6-naphthoic acid is removed from crude2, 6-naphthalenedicarboxylic acid using a gas containing oxygen gas containing carbon dioxide as an oxidizing agent, the 2-NA content in the purified product can be significantly reduced as compared with when a gas containing oxygen gas alone is used as the oxidizing agent.

In the technical scheme, the crude2,6-naphthalene dicarboxylic acid is obtained by air oxidation of 2, 6-diisopropyl naphthalene under the catalyst of Co-Mn-Br.

In the above technical scheme, the oxidation catalyst is a noble metal supported catalyst.

In the above-mentioned technical solution, the noble metal preferably includes at least one of the group consisting of palladium, ruthenium, and platinum, and more preferably includes palladium.

In the above technical solution, the catalyst carrier of the noble metal supported catalyst preferably comprises TiO₂。

In the above technical solution, the physical shape of the carrier is not particularly limited, and may be a fine powder having an irregular shape or a granule having a regular shape, and the convenience of subsequent separation is preferable, and the carrier is preferably shaped into a shape such as a sphere, a cylinder, a rectangular parallelepiped, etc., and the size is determined based on the fact that the carrier is not leaked when being put into a basket, and in some embodiments, the diameter is 2 to 5mm (for example, but not limited to, the diameter may be 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4mm, 4.1mm, 4.2mm, 4.3mm, 4.4mm, 4.5mm, 4.6mm, 4.7mm, 4.8mm, 4.9mm, etc.) for the same ratio.

In the technical scheme, the specific surface area of the carrier is preferably 40-120 m²(ii) in terms of/g. For example, but not limited to, a carrier having a specific surface area of 45m²/g、50m²/g、55m²/g、60m²/g、65m²/g、70m²/g、75m²/g、80m²/g、85m²/g、90m²/g、95m²/g、100m²/g、105m²/g、110m²/g、115m²G,/etc.

In the above technical scheme, the preferred pore volume of the carrier is 0.3-0.6cm³(ii) in terms of/g. For example, but not limited to, a carrier pore volume of 0.31cm³/g、0.32cm³/g、0.33cm³/g、0.34cm³/g、0.35cm³/g、0.36cm³/g、0.37cm³/g、0.38cm³/g、0.39cm³/g、0.4cm³/g、0.41cm³/g、0.42cm³/g、0.43cm³/g、0.44cm³/g、0.45cm³/g、0.46cm³/g、0.47cm³/g、0.48cm³/g、0.49cm³/g、0.5cm³/g、0.51cm³/g、0.52cm³/g、0.53cm³/g、0.54cm³/g、0.55cm³/g、0.56cm³/g、0.57cm³/g、0.58cm³/g、0.59cm³/g。

In the technical scheme, the loading amount of the noble metal in the oxidation catalyst is 0.1-1 wt%. Non-limiting examples of the noble metal loading may be 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, etc., but it is preferable to select the loading to be 0.5 wt% from the economical viewpoint.

In the technical scheme, the content of 2-acetyl-6-naphthoic acid in the crude2, 6-naphthalenedicarboxylic acid is 200-20000 ppmw. For example, but not limited to, a 2-acetyl-6-naphthoic acid content in the crude2, 6-naphthalenedicarboxylic acid of 250ppmw, 300ppmw, 350ppmw, 400ppmw, 450ppmw, 500ppmw, 550ppmw, 600ppmw, 650ppmw, 700ppmw, 750ppmw, 800ppmw, 850ppmw, 900ppmw, 950ppmw, 1000ppmw, 1100ppmw, 1200ppmw, 1300ppmw, 1400ppmw, 1500ppmw, 1600ppmw, 1700ppmw, 1800ppmw, 1900ppmw, 2000ppmw, 2100ppmw, 2200ppmw, 2300ppmw, 2400ppmw, 2500ppmw, 2600ppmw, 2700ppmw, 2800, 2900ppmw, 3000ppmw, 4000ppmw, 5000ppmw, 6000ppmw, 7000ppmw, 8000ppmw, 9000, 10000ppmw, 12000, 14000ppmw, 18000ppmw, 3500ppmw, etc.; more preferably 500-3000 ppmw. The 2-acetyl-6-naphthoic acid is obtained by air oxidation of 2, 6-diisopropyl naphthalene under a Co-Mn-Br catalyst, the content of the 2-acetyl-6-naphthoic acid contained in the 2-acetyl-6-naphthoic acid is different according to the catalyst proportion and reaction process conditions used in the air oxidation of the 2, 6-diisopropyl naphthalene, the content of the 2-acetyl-6-naphthoic acid is generally in the range of 200-20000 ppmw, and although the content of the 2-acetyl-6-naphthoic acid is not strictly required when the refining method is used, the content of the 2-acetyl-6-naphthoic acid is generally controlled to be 500-3000ppmw for economy and experimental convenience.

In the above technical solution, the mass concentration of the crude2, 6-naphthalenedicarboxylic acid in the aqueous solution is preferably 1 to 10 wt%. For example, but not limited to, the crude2, 6-naphthalenedicarboxylic acid has a mass concentration in the aqueous solution of 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.0 wt%, etc., more preferably 3 to 5 wt%.

In the above technical solution, the volume ratio of free oxygen to carbon dioxide in the mixed gas is preferably 0.10-3.0. For example, but not limited to, the volume ratio of free oxygen to carbon dioxide in the mixed gas is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, and the like.

From the economic viewpoint, the mixed gas is preferably composed of air and carbon dioxide, and in this case, it is preferably, but not limited to, such as but not limited to, that the volume ratio of air to carbon dioxide is preferably 1 to 10, and more specifically, non-limiting examples of the volume ratio of air to carbon dioxide may be 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, and the like.

In the above technical scheme, the reaction temperature is preferably 250-320 ℃. For example, but not limited to, reaction temperatures of 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃, 300 ℃, 315 ℃, etc., more preferably 280 ℃ and 300 ℃.

In the above technical scheme, the reaction pressure is preferably 8-15 MPa. For example, but not limited to, the reaction pressure is 8.5MPa, 9MPa, 9.5MPa, 10MPa, 10.5MPa, 11MPa, 11.5MPa, 12MPa, 12.5MPa, 13MPa, 13.5MPa, 14MPa, 14.5MPa, etc., more preferably 8 to 10 MPa.

In the above technical scheme, the reaction time is preferably 10-60 min. For example, but not limited to, the reaction time is 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, etc., more preferably 25 to 45 min.

As an example of an implementation, but not limited to, may be:

a method for purifying crude2, 6-naphthalenedicarboxylic acid comprising the steps of:

(1) adding crude2,6-naphthalene dicarboxylic acid containing 2-acetyl-6-naphthoic acid, an oxidation catalyst and water into a reaction kettle;

(2) the temperature of the reaction kettle is controlled at 250 ℃ and 320 ℃ and the pressure is 8-15MPa to ensure that the crude2, 6-naphthalenedicarboxylic acid is partially or completely dissolved, and CO is introduced₂Keeping the reaction for 10-60 min;

(3) after the reaction is finished, filtering the reaction product at normal temperature, and drying the obtained filter cake at the normal pressure of 80-120 ℃ to obtain the 2,6-naphthalene dicarboxylic acid.

The proportion of the crude2, 6-naphthalenedicarboxylic acid and water added in step (1) is such that the 2, 6-naphthalenedicarboxylic acid has at least a certain solubility during the reaction, preferably a complete solubility, which is advantageous for the completion of the reaction, but since the solubility of 2, 6-naphthalenedicarboxylic acid is relatively low and the solubility in water at 280 ℃ is only 6g, the mass concentration of 2, 6-naphthalenedicarboxylic acid in water is preferably controlled to 1 to 10 wt%, more preferably 3 to 5 wt%.

In the above technical scheme, the temperature of the reaction kettle in the step (2) is preferably controlled to be 280-300 ℃, the pressure is preferably controlled to be 8-10MPa, the amount of introduced air can be determined according to 2-acetyl-6-naphthoic acid contained in the crude2,6-naphthalene dicarboxylic acid, generally, 1000ppmw of 2-acetyl-6-naphthoic acid only needs to be introduced with air of not less than 10ml/min, and it is noted that if CO is introduced while air is introduced₂Or directly introducing CO₂The air effect is better, the generation of 2-naphthoic acid can be obviously reduced, wherein CO is₂The ratio of the amount of the nitrogen-containing gas to the amount of the air is 1 (1-10), preferably 1 (3-6), and if other gases such as nitrogen and CO are used, the effect is not obtained. The reaction time in the step (2) is preferably controlled to be 25 to 45 min. After step (2), the reaction product can be isolated and dried by methods well known in the art, and all the methods can achieve the technical effects comparable to those of the present invention. For example, step (2) may be followed by:

(3) after the reaction is finished, filtering the reaction product at normal temperature, and drying the obtained filter cake at 90-110 ℃ under normal pressure to obtain the 2,6-naphthalene dicarboxylic acid.

In a specific embodiment, the contents of 2-acetyl-6-naphthoic acid, 2-formyl-6-naphthoic acid and 2-naphthoic acid are determined by a liquid chromatography external standard method.

The invention adopts crude2,6-naphthalene dicarboxylic acid containing 2-formyl-6-naphthoic acid (2-FNA)1863ppmw, 2-acetyl-6-naphthoic acid (2,6-ANA)2067ppmw as raw material, and 0.5 wt% Pd/TiO₂As a catalyst, introducing CO at the reaction temperature of 280 ℃ and the reaction pressure of 8MPa₂Air (CO) of₂1:4) with air for 30min, the product obtained being analyzed to have a 2-FNA content of 823ppmw, a 2,6-ANA content of 132ppmw and a 2-NA content of 86 ppmw. And a better technical effect is obtained.

Detailed Description

[ example 1 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pd/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 15ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 2 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading of Ru of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Ru/TiO₂The content of Ru in the supported metal catalyst was 0.498 wt% by ICP-AES analysis.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Ru/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 15ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is completed, the cooling system is startedAnd (3) taking out the reaction mixture for filtering after the temperature in the kettle is room temperature, drying the obtained filter cake at 90 ℃ for 6 hours, and sampling to analyze the impurity type and content in the filter cake. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 3 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the Pt loading of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Soaking the carrier for 12h, drying at 100 deg.C for 2h, calcining at 400 deg.C for 3h, and reducing with hydrogen at 250 deg.C for 2h to obtain Pt/TiO₂The Pt content of the catalyst in the supported metal catalyst is 0.496 wt% by adopting ICP-AES analysis.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pt/TiO₂2g of catalyst are put into a 1L reaction kettleStirring, heating to 280 deg.C, controlling the pressure in the reaction kettle at 8MPa, and introducing 60ml/min air and 15ml/min CO when the temperature and pressure in the kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 4 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pd/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 6ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 5 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Per g, preparing an impregnation solution according to the loading of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and thenImpregnation of TiO by equivalent impregnation₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pd/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 10ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 6 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pd/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 20ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ example 7 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled to be 2.75MPa, 1000g 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquor containing crude2, 6-naphthalenedicarboxylic acid is filtered, the reaction product mixed liquor is respectively washed by 60 ℃ acetic acid and 80 ℃ water, the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and after sampling and drying, impurities in the 2-formyl-6-naphthoic acid and the 2-acetyl-6-naphthoic acid are analyzedThe content of (a). The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and Pd/TiO₂Putting 2g of catalyst into a 1L reaction kettle, then starting stirring, heating to 280 ℃, controlling the pressure of the reaction kettle to be 8MPa, and introducing 60ml/min of air and 60ml/min of CO when the temperature and the pressure in the reaction kettle reach₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ COMPARATIVE EXAMPLE 1 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled to be 2.75MPa, 1000g 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, and after the reaction is finished, the mixture containing crude2,6-naphthalene dimethylFiltering the mixed solution of the reaction products of the acid, washing by adopting acetic acid at 60 ℃ and water at 80 ℃, respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and sampling and drying the mixture to analyze the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and 2g of the catalyst are put into a 1L reaction kettle together, then stirring is started, the temperature is raised to 280 ℃, the pressure of the reaction kettle is controlled at 8MPa, and when the temperature and the pressure in the kettle reach, 75ml/min of air is introduced for reaction, and the reaction time is 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ COMPARATIVE EXAMPLE 2 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g acetic acid are mixed and added into a reaction kettle, then stirring is started and the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g 2, 6-diisopropyl naphthalene is heated to a molten stateThen the mixture enters a reaction kettle at the speed of 12g/min, sufficient air is simultaneously introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed solution containing crude2, 6-naphthalenedicarboxylic acid is filtered, and is respectively washed by 60 ℃ acetic acid and 80 ℃ water, the washing acetic acid is 1000g, the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and 2g of the catalyst are put into a 1L reaction kettle together, then stirring is started, the temperature is raised to 280 ℃, the pressure of the reaction kettle is controlled at 8MPa, and after the temperature and the pressure in the reaction kettle are reached, 60ml/min of air and 15ml/min of N are introduced₂The reaction was carried out for 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

[ COMPARATIVE EXAMPLE 3 ]

1. Preparation of crude2, 6-naphthalenedicarboxylic acid sample

311.25g of Co (OAc)₂·4H₂O、306.25g Mn(OAc)₂·4H₂O、297.5g KBr、367.5g CH₃COOK and 7760g of acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 185 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g of 2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 12g/min, sufficient air is introduced for reaction, after the feeding is finished, the reaction temperature and the reaction pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, reaction product mixed liquid containing crude2, 6-naphthalenedicarboxylic acid is filtered, the mixed liquid is respectively washed by 60 ℃ of acetic acid and 80 ℃ of water, the amount of the washing acetic acid is 1000g, the amount of the washing water is 1000g, and the contents of impurities, namely 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid are analyzed after sampling and drying. The crude2, 6-naphthalenedicarboxylic acid was analyzed to have a 2-formyl-6-naphthoic acid (2-FNA) content of 1863ppmw and a 2-acetyl-6-naphthoic acid content of 2067 ppmw.

2. Preparation of the catalyst

In the form of spherical TiO with a diameter of 3mm₂Is a carrier with a specific surface area of 86m²Per g, pore volume of 0.42cm³Preparing an impregnation solution according to the loading amount of Pd of 0.5 wt%, wherein the concentration of metal ions in the impregnation solution is 0.01g/ml, and then impregnating TiO according to an equivalent impregnation method₂Impregnating a carrier for 12h, drying at 100 ℃ for 2h, roasting at 400 ℃ for 3h, and reducing at 250 ℃ for 2h by hydrogen to obtain Pd/TiO₂The catalyst, Pd content in the supported metal catalyst was analyzed by ICP-AES to be 0.498 wt%.

3. Purification of crude2, 6-naphthalenedicarboxylic acid sample

20g of the crude2, 6-naphthalenedicarboxylic acid sample is taken as a raw material, 380g of deionized water and 2g of the catalyst are put into a 1L reaction kettle together, then stirring is started, the temperature is raised to 280 ℃, the pressure of the reaction kettle is controlled at 8MPa, and after the temperature and the pressure in the kettle are reached, 60ml/min of air and 15ml/min of CO are introduced for reaction, wherein the reaction time is 30 min. After the reaction is finished, a cooling system is started, after the temperature in the kettle is room temperature, the reaction mixture is taken out for filtration, the obtained filter cake is dried for 6 hours at the temperature of 90 ℃, and the type and the content of impurities in the filter cake are sampled and analyzed. For convenience, the catalysts used and the results of the analysis are shown in Table 1.

As can be seen from Table 1, TiO loading with Pd, Pt or Ru₂The prepared catalyst can be used for the oxidative purification of crude2, 6-naphthalenedicarboxylic acid, but Pd is more excellent in the effect, and CO is contained₂The oxidation with air can reduce the content of 2,6-ANA impurities, but the oxidation reaction with air only can generate more 2-NA, if the oxidation reaction is carried out with the mixed gas of air and CO, the content of 2,6-ANA cannot be obviously reduced, and more 2-NA can be generated, if the oxidation reaction is carried out with air and N₂The oxidation reaction of the mixed gas (2) also gives a large amount of 2-NA.

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.

TABLE 1

Remarking: 2,6-FNA is 2-formyl-6-naphthoic acid; 2,6-ANA is 2-acetyl-6-naphthoic acid; the 2-NA is 2-naphthoic acid.