Reaction mixture for the preparation of 2,6-naphthalene dicarboxylic acid and crude 2,6-naphthalene dicarboxylic acid, product and process for its preparation

Abstract

The application discloses a reaction mixture for preparing 2,6-naphthalene dicarboxylic acid and a 2,6-naphthalene dicarboxylic acid crude product, a product and a preparation method thereof. By adding a small amount of a reaction aid into raw materials of a 2,6-diisopropyl naphthalene oxidation reaction, the 2,6-diisopropyl naphthalene oxidation reaction can be effectively promoted, a side reaction can be reduced, the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid crude product can be effectively improved, and the contents of key impurities 2-methyl-6-naphthalene carboxylic acid and 2-acetyl-6-naphthalene carboxylic acid can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the technical field of 2,6-naphthalenedicarboxylic acid synthesis, and more specifically, to a reaction mixture for preparing 2,6-naphthalenedicarboxylic acid, crude 2,6-naphthalenedicarboxylic acid, the product, and methods thereof. Background Technology

[0002] Polyethylene 2,6-naphthalenedicarboxylate (PEN) is a high-end new polyester material that began to be commercialized in the 1990s. Similar to polyethylene terephthalate (PET), both can be used for films, fibers, hollow containers and sheets, but PEN has better overall performance and a broader potential market, so it has received continuous and in-depth attention from polyester companies and research institutions around the world.

[0003] The main methods for producing PEN include: transesterification (transesterification and polycondensation of dimethyl 2,6-naphthalenedicarboxylate (2,6-NDC) with ethylene glycol (EG)) and direct polymerization (polymerization of 2,6-naphthalenedicarboxylate (2,6-NDCA) with EG). Direct polymerization has advantages over transesterification, such as a simpler process route, milder reaction conditions, and lower energy and material consumption. Liquid-phase oxidation of 2,6-dialkylnaphthalene is the main method for preparing the raw material 2,6-NDCA, including liquid-phase oxidation of 2,6-dimethylnaphthalene (2,6-DMN) and 2,6-diisopropylnaphthalene (2,6-DIPN).

[0004] Compared to 2,6-DMN, 2,6-DIPN is easier to separate and purify from the raw materials (mixture of isomers), and its market price is only about one-fifth of that of the former. However, the oxidation process of 2,6-DIPN is more difficult and complex, resulting in lower purity of the oxidation products and more types and contents of impurities, which makes the subsequent purification process more difficult. However, in the long run, the liquid phase oxidation method of 2,6-DIPN is also a highly competitive process route.

[0005] The existing technical literature, "Liquid-phase air oxidation of 2,6-diisopropylnaphthalene to 2,6-naphthalenedicarboxylic acid" (Jin Haibo, Han Zhansheng. [J]. Journal of Chemical Industry and Engineering, 2007(58)), discloses a method for preparing 2,6-naphthalenedicarboxylic acid, which uses a stirred reactor. As mentioned above, this method results in lower purity of the oxidation product and a greater variety and content of impurities, making subsequent purification processes more difficult.

[0006] Therefore, how to increase the purity of 2,6-naphthoic acid in crude 2,6-naphthoic acid while reducing the content of other impurities, especially the content of key impurities 2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid, is a key technical problem that needs to be solved. Summary of the Invention

[0007] To address the problems in existing technologies, this invention proposes a reaction mixture for preparing 2,6-naphthalenedicarboxylic acid, as well as crude 2,6-naphthalenedicarboxylic acid, the product, and a method thereof. By adding a small amount of reaction aid to the raw materials in the oxidation reaction of 2,6-diisopropylnaphthalene, this invention effectively promotes the oxidation reaction of 2,6-diisopropylnaphthalene, reduces side reactions, thereby effectively improving the purity of 2,6-naphthalenedicarboxylic acid in the crude product and effectively reducing the content of key impurities 2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid.

[0008] One object of the present invention is to provide a reaction mixture for the oxidation of 2,6-diisopropylnaphthalene to prepare 2,6-naphthalenedicarboxylic acid, comprising the following components: 2,6-diisopropylnaphthalene, a catalyst composition, a reaction aid, and a solvent;

[0009] The reaction aid has the structural formula shown in Formula I:

[0010]

[0011] Among them, R1 to R6 may be the same or different, each independently selected from H or C1 to C10 alkyl groups, and at least one of R1 to R6 is an alkyl group.

[0012] In this invention, the reaction aid is a benzene-based substance, which not only facilitates the dissolution of 2,6-diisopropylnaphthalene but also participates in the reaction. Benzene-based substances are more easily oxidized than 2,6-diisopropylnaphthalene and can form active factors. Their products also provide crystal nuclei for the oxidation products of 2,6-diisopropylnaphthalene, making it easier and more complete to oxidize 2,6-diisopropylnaphthalene to obtain the target product, thereby reducing the possibility of by-products and improving the purity of 2,6-naphthalenedicarboxylic acid.

[0013] In this invention, the significant difference between the crystal nuclei generated by the reaction aid and the solubility of 2,6-naphthalenedicarboxylic acid makes them easy to separate and purify without affecting the purity of the 2,6-naphthalenedicarboxylic acid product.

[0014] In the reaction aids described in this invention, preferably,

[0015] The reaction aids R1 to R6 may be the same or different, each independently selected from H or C1 to C5 alkyl groups, and at least one alkyl group among R1 to R6; preferably, each independently selected from H or C1 to C3 alkyl groups, and at least one alkyl group among R1 to R6.

[0016] Preferably,

[0017] At least one alkyl group is selected from R1 to R6; more preferably,

[0018] Of R1 to R6, only one is an alkyl group, and the rest are hydrogen. More preferably, the reaction auxiliaries are selected from at least one of toluene, cumene, and n-propylbenzene; or...

[0019] Two of the R1 to R6 are alkyl groups, and the remainder are hydrogen. More preferably, the reaction aid is selected from at least one of o-xylene, m-xylene, p-xylene, ethyl methylbenzene, and diethylbenzene.

[0020] In the catalyst composition of the present invention, preferably,

[0021] The active components of the catalyst composition include manganese, bromine, cobalt, and optionally potassium; preferably,

[0022] The manganese element in the catalyst composition is selected from at least one of manganese carboxylate; more preferably, the manganese carboxylate is selected from at least one of manganese saturated fatty acids; even more preferably, the manganese saturated fatty acid is selected from at least one of C1-C5 saturated fatty acids; even more preferably, the manganese fatty acid is at least one of manganese formate, manganese acetate, and manganese propionate; and / or,

[0023] The bromine element is selected from bromides; more preferably from at least one of potassium bromide, tetrabromoethane, and ammonium bromide; and / or,

[0024] The potassium element is selected from potassium carboxylate; more preferably, the potassium carboxylate is selected from at least one of potassium saturated fatty acids; even more preferably, the potassium saturated fatty acid is selected from at least one of C1-C5 potassium saturated fatty acids; even more preferably, the potassium saturated fatty acid is at least one of potassium formate, potassium acetate, and potassium propionate; and / or,

[0025] The cobalt element is selected from cobalt carboxylate; more preferably, the cobalt carboxylate is selected from at least one of saturated fatty acid cobalt; more preferably, the saturated fatty acid cobalt is selected from at least one of C1 to C5 saturated fatty acid cobalt; and more preferably, the saturated fatty acid cobalt is at least one of cobalt formate, cobalt acetate, and cobalt propionate.

[0026] In this invention, manganese, bromine and cobalt are the main active ingredients and must be present, while potassium is a co-catalyst, which helps the catalyst to function.

[0027] The preparation method of the catalyst composition of the present invention includes thoroughly mixing the compound containing manganese, bromine, cobalt, and optionally potassium according to the content of each component of the catalyst composition of the present invention as described above.

[0028] The catalyst of this invention does not contain copper. The addition of copper is not conducive to promoting the preparation of 2,6-naphthalenedicarboxylic acid and subsequent purification process in this invention.

[0029] In the solvents described in this invention, preferably,

[0030] The solvent comprises at least one of a carboxylic acid and optionally water; preferably, the water content in the solvent is ≤8 wt%; more preferably, the carboxylic acid is selected from at least one of alkyl carboxylic acids; even more preferably, the carboxylic acid is selected from at least one of C2-C6 saturated fatty acids; further preferably, the carboxylic acid is selected from at least one of acetic acid and propionic acid; and / or,

[0031] In this invention, a small amount of water may be included, but its weight content in the reaction mixture shall not exceed 8%, otherwise the oxidation reaction will be difficult to carry out.

[0032] In the reaction aids described in this invention, preferably,

[0033] The weight ratio of the reaction auxiliary to 2,6-diisopropylnaphthalene is 0.005 to 0.06:1, preferably (0.01 to 0.025):1 or (0.015 to 0.052):1, for example, it can be 0.005:1, 0.008:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.04:1, 0.05:1, 0.052:1, or 0.06:1.

[0034] In the preferred range (0.01-0.025):1 of this invention, even a small amount of the reaction aid added results in a significant removal effect on impurities. In the preferred range (0.015-0.052):1 of this invention, the greater the mass of the reaction aid added within this range, the better the removal effect on impurities.

[0035] In the catalyst composition of the present invention, preferably, the weight ratio of the catalyst composition to 2,6-diisopropylnaphthalene is (5-11):1, more preferably (7-9):1;

[0036] Preferably,

[0037] In the catalyst composition, the molar ratio of cobalt to manganese is (0.3–3.0):1, preferably (0.4–2.5):1; and / or,

[0038] The molar ratio of bromine to manganese is (1–3):1, preferably (1.5–2.5):1; and / or,

[0039] When the catalyst composition contains potassium, the molar ratio of potassium to manganese is (3-7):1, preferably (4-6):1.

[0040] In the solvents described in this invention, preferably,

[0041] The weight ratio of the solvent to 2,6-diisopropylnaphthalene is (5-10):1, preferably (6-8):1.

[0042] A second objective of this invention is to provide a method for preparing 2,6-naphthalenedicarboxylic acid, comprising the following steps:

[0043] The reaction mixture for the oxidation of 2,6-diisopropylnaphthalene to prepare 2,6-naphthalenedicarboxylic acid, as described in one of the objectives of this invention, is used as the reactant to undergo an oxidation reaction with an oxidant to obtain a crude product containing 2,6-naphthalenedicarboxylic acid. Optionally, post-processing is performed to prepare the product containing 2,6-naphthalenedicarboxylic acid.

[0044] Specifically, the method for preparing 2,6-naphthalenedicarboxylic acid according to the present invention includes thoroughly mixing the reaction mixture and then contacting it with an oxidant to carry out an oxidation reaction. More preferably, it includes: thoroughly mixing the catalyst component and the solvent and preheating it to a solution state; thoroughly mixing 2,6-diisopropylnaphthalene and the reaction promoter and preheating it to a solution state; thoroughly mixing the above-mentioned mixed solution of catalyst component and solvent with the mixed solution of reaction mixture and then contacting it with an oxidant to carry out an oxidation reaction to obtain a crude product containing 2,6-naphthalenedicarboxylic acid, optionally followed by post-processing to prepare the product containing 2,6-naphthalenedicarboxylic acid.

[0045] In the method of the present invention, the post-processing of the crude reaction product containing 2,6-naphthalenedicarboxylic acid can be carried out using existing conventional impurity removal methods. Specifically, the post-processing in this invention can be performed on 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry, sequentially as follows: heating to 120°C and then directly filtering under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; adding 50g of acetic acid to filter cake 1 and mixing thoroughly, heating to 120°C and then filtering under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; adding 25g of acetic acid to filter cake 2, heating to 120°C and then filtering under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; adding 50g of pure water to filter cake 3, heating to 160°C and then filtering under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; adding 25g of pure water to filter cake 4, heating to 160°C and then filtering under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; and placing filter cake 5 in an oven at 120°C for 24h to dry.

[0046] The post-treatment of the crude 2,6-naphthalenedicarboxylic acid reaction product described above in this invention mainly removes the catalyst, co-catalyst, solvent, and auxiliary oxidation products (benzoic acid, phthalic acid, and isophthalic acid) contained in the crude 2,6-naphthalenedicarboxylic acid oxidation slurry. This is a routine separation operation, a pretreatment for subsequent analysis, and will not significantly affect the purity of 2,6-naphthalenedicarboxylic acid in the product, nor will it significantly affect the content of key impurities 2-methyl-6-naphthalenedicarboxylic acid and 2-acetyl-6-naphthalenedicarboxylic acid.

[0047] In the preparation method described in this invention, preferably,

[0048] The oxidant is selected from at least one oxygen-containing gas. Preferably, in this invention, to ensure that the oxygen content in the exhaust gas does not exceed the standard, otherwise there will be an explosion hazard, the oxygen volume content in the oxygen-containing gas is 18-25%, preferably 20-23%; more preferably, the oxidant is air.

[0049] Preferably,

[0050] The molar ratio of oxygen in the oxidant to 2,6-diisopropylnaphthalene in the reaction mixture is (4-6):1, preferably (4.5-5.5):1; more preferably,

[0051] Based on 1000g of 2,6-diisopropylnaphthalene and reaction aids, the flow rate of the oxidant under standard conditions was 9.0L / min-11.0L / min.

[0052] In the preparation method described in this invention, preferably,

[0053] The oxidation reaction is carried out at a temperature of 170–230°C, preferably 180–210°C, for example, 170, 180, 190, 200, 210, 220, or 230°C; and / or,

[0054] The pressure of the oxidation reaction is 2.0–4.5 MPa, preferably 2.5–4.0 MPa, for example, 2.0, 2.5, 3.0, 3.5, 4.0, or 4.5 MPa; and / or,

[0055] The oxidation reaction time is 0.5 to 2.5 hours, preferably 0.75 to 2.0 hours, for example, 0.5, 0.75, 1, 1.5, 2, or 2.5 hours.

[0056] A third objective of this invention is to provide a crude or finished product of 2,6-naphthalenedicarboxylic acid prepared by the reaction mixture for the oxidation of 2,6-diisopropylnaphthalene as described in one objective of this invention, or by the preparation method described in another objective of this invention.

[0057] In the crude 2,6-naphthalenedicarboxylic acid of the present invention, preferably,

[0058] The crude 2,6-naphthalenedicarboxylic acid contains 5-15 wt% 2,6-naphthalenedicarboxylic acid, preferably 8-12 wt%.

[0059] Preferably,

[0060] The content of 2-methyl-6-naphthoic acid is 50–200 ppm, preferably 80–150 ppm; and / or,

[0061] The content of 2-acetyl-6-naphthoic acid is 10 to 100 ppm, preferably 20 to 80 ppm.

[0062] In the 2,6-naphthalenedicarboxylic acid product of the present invention, preferably,

[0063] In the 2,6-naphthalenedicarboxylic acid product, the content of 2,6-naphthalenedicarboxylic acid is ≥97.35wt%, preferably 97.35wt% to 98.8wt%;

[0064] More preferably,

[0065] The content of 2-methyl-6-naphthoic acid is ≤1187 ppm, preferably 899.49~1187 ppm; and / or,

[0066] The content of 2-acetyl-6-naphthoic acid is ≤402.64ppm, preferably 285.52~402.64ppm.

[0067] The reaction system for preparing 2,6-naphthalenedicarboxylic acid by the preparation method described in the second objective of this invention includes an oxidation reactor, a gas phase inlet pipeline, a liquid phase raw material inlet pipeline, a tail gas outlet pipeline, and a product outlet pipeline.

[0068] The outlets of the gas phase inlet pipeline and the liquid phase feed inlet pipeline are respectively connected to the feed inlet of the oxidation reactor; the outlet of the oxidation reactor is respectively connected to the feed inlet of the tail gas outlet pipeline and the crude product outlet pipeline.

[0069] The liquid phase feedstock in the liquid phase feedstock inlet pipeline consists of a catalyst composition, 2,6-diisopropylnaphthalene, reaction aids, and solvents; the gas phase feedstock in the gas phase feedstock inlet pipeline is an oxidant. The oxidant and liquid phase feedstock are introduced through the gas phase feedstock inlet pipeline and the liquid phase feedstock inlet pipeline, and continuously contact each other in the oxidation reactor to carry out the oxidation reaction. The oxidized 2,6-naphthalenedicarboxylic acid slurry is output from the product outlet pipeline of the oxidation reactor, and the oxidized oxygen-containing tail gas is output from the tail gas outlet pipeline.

[0070] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0071] Compared with the prior art, the present invention has the following advantages:

[0072] This invention effectively promotes the oxidation reaction of 2,6-diisopropylnaphthalene by adding a small amount of reaction aid to the raw materials of the oxidation reaction, reduces side reactions, thereby effectively improving the purity of 2,6-naphthalenedicarboxylic acid in crude 2,6-naphthalenedicarboxylic acid and effectively reducing the content of key impurities 2-methyl-6-naphthalenedicarboxylic acid and 2-acetyl-6-naphthalenedicarboxylic acid.

[0073] The process of this invention is simple and can effectively reduce the content of key impurities 2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid, which means that the energy consumption of subsequent impurity removal steps is greatly reduced, and the corresponding process cost can also be greatly reduced. Detailed Implementation

[0074] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0075] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0076] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0077] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0078] Purity analysis method for 2,6-naphthalenedicarboxylic acid (2,6-NDCA) in the product: Quantitative determination was performed using Agilent 1260 high-performance liquid chromatography (HPLC). Qualitative analysis: A standard 2,6-NDCA sample was tested by HPLC to obtain a chromatogram. Under the same conditions, the dried product was tested by HPLC to obtain a chromatogram. Comparative analysis showed that the retention time and peak shape were completely consistent with the standard, proving that the main product is 2,6-NDCA. Quantitative analysis (purity determination): The peak area of ​​2,6-naphthalenedicarboxylic acid was measured using a standard sample of known purity, and then the peak area of ​​2,6-naphthalenedicarboxylic acid in the sample was measured. The comparison of the two results yielded the purity of the sample.

[0079] Impurity analysis in the product: Quantitative analysis was performed using Agilent 1260 high-performance liquid chromatography (HPLC). Based on literature and mass spectrometry analysis results, the key impurities (2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid, which significantly affect the color and polymerization of the final purified product 2,6-NDCA) and their elution times were identified. The peak areas of the key impurities were measured using a standard of known purity, and then the peak areas of the key impurities in the sample were measured. Comparison of these two measurements yielded the content of the key impurities in the sample.

[0080]

Example 1

[0081] Preparation of catalyst solution: 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g potassium bromide, 4.50g potassium acetate, and 85.60g acetic acid (solvent) per 100g. Stir the catalyst thoroughly and preheat to 100°C to form a solution. Preparation of oxidizing feedstock: 98.52g 2,6-diisopropylnaphthalene and 1.48g p-xylene per 100g. Stir the oxidizing feedstock thoroughly and preheat to 100°C to melt it into a liquid state.

[0082] 1015.00g of the above-mentioned oxidizing raw material and 8176.92g of the above-mentioned catalyst solution were added to the oxidation reactor beforehand. The stirrer was turned on and its speed was set to 60 rpm. When the temperature reached 160℃, air was introduced into the oxidation reactor at a flow rate of 10.0L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 200℃. After reacting for 30 minutes, the liquid 2,6- Diisopropylnaphthalene and catalyst solution were added to the bottom of the oxidation reactor through the 2,6-diisopropylnaphthalene feed inlet and catalyst inlet at rates of 10.15 g / min and 81.77 g / min, respectively (the purpose of this step is to enable continuous reaction and continuous product production in actual production). After reacting for 60 minutes, crude 2,6-naphthalenedicarboxylic acid slurry was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 91.92 g / min (crude 2,6-naphthalenedicarboxylic acid oxidation slurry), and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. Based on 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry, the following treatments were performed sequentially: After heating to 120℃, the mixture was directly filtered at a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered at a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered at a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered at a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered at a pressure difference of 0.2MPa for 5min to obtain filter cake 4. Filter cake 5 was obtained by pressure filtration at MPa for 5 min. Filter cake 5 was placed in an oven at 120℃ for 24 h to dry. The dried sample was then sent for analysis. In this invention, the post-treatment of the crude 2,6-naphthalenedicarboxylic acid oxidized slurry mainly removes the catalyst, co-catalyst, solvent, and auxiliary oxidation products (benzoic acid, phthalic acid, and isophthalic acid) contained in the crude 2,6-naphthalenedicarboxylic acid oxidized slurry. This is a routine separation operation and a pretreatment for subsequent analysis. It will not significantly affect the purity of 2,6-naphthalenedicarboxylic acid in the product, nor will it significantly affect the content of key impurities 2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid. The specific analytical results are shown in Table 1.

[0083]

Example 2

[0084] Catalyst composition: 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g potassium bromide, 4.50g potassium acetate, and 85.60g acetic acid (100g total). The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 99.00g 2,6-diisopropylnaphthalene and 1.00g p-xylene (100g total). The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0085] 1010.00g of the above-mentioned oxidizing raw material and 8176.92g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 10.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 200°C. After reacting for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet, respectively, at rates of 10.10 g / min and 81.77 g / min. After reacting for 60 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 91.87 g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. Based on 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry, the following treatments were performed sequentially: The slurry was heated to 120℃ and then directly filtered under a pressure difference of 0.5MPa for 10 minutes to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed; the mixture was then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5 minutes to obtain filter cake 2; 25g of acetic acid was added to filter cake 2. After heating to 120℃, filter under a pressure difference of 0.2MPa for 5 minutes to obtain filter cake 3; add 50g of pure water to filter cake 3, heat to 160℃, and filter under a pressure difference of 0.2MPa for 5 minutes to obtain filter cake 4; add 25g of pure water to filter cake 4, heat to 160℃, and filter under a pressure difference of 0.2MPa for 5 minutes to obtain filter cake 5; place filter cake 5 in an oven at 120℃ for 24 hours to dry, and send the dried sample for analysis. The analysis results are shown in Table 1.

[0086]

Example 3

[0087] Catalyst composition: 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g potassium bromide, 4.50g potassium acetate, and 85.60g acetic acid (100g total). The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 98.00g 2,6-diisopropylnaphthalene and 2.00g p-xylene (100g total). The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0088] 1020.00g of the above-mentioned oxidizing raw material and 8176.92g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 10.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 200°C. After reacting for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet, respectively, at rates of 10.20 g / min and 81.77 g / min. After reacting for 60 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 91.97 g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0089]

Example 4

[0090] Catalyst composition: 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g potassium bromide, 4.50g potassium acetate, and 85.60g acetic acid (100g total). The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 95.00g 2,6-diisopropylnaphthalene and 5.00g p-xylene (100g total). The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0091] 1050.00g of the above-mentioned oxidizing raw material and 8176.92g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 10.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 200°C. After reacting for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet, respectively, at rates of 10.50 g / min and 81.77 g / min. After reacting for 60 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 92.27 g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0092]

Example 5

[0093] Catalyst composition: 2.22g cobalt propionate, 4.04g manganese acetate tetrahydrate, 3.64g tetrabromoethane, 4.50g potassium acetate, with the balance being acetic acid, based on a total weight of 100g. The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 97.00g 2,6-diisopropylnaphthalene, 3.00g toluene, based on a total weight of 100g. The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0094] 1000.00g of the above-mentioned oxidizing raw material and 7000g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 9.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 170°C. After reacting for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor at rates of 10.00 g / min and 70.00 g / min, respectively, through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet. After reacting for 120 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 80.00 g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0095]

Example 6

[0096] Catalyst composition: 2.22g cobalt propionate, 4.04g manganese propionate, 3.64g ammonium bromide, 4.50g potassium propionate, with the balance being propionic acid, based on a total weight of 100g. The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 96.00g 2,6-diisopropylnaphthalene, 4.00g m-xylene, based on a total weight of 100g. The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0097] 900.00g of the above-mentioned oxidizing raw material and 6300g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 9.0L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 230°C. After reacting for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor at rates of 9.00g / min and 63.00g / min, respectively, through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet. After reacting for 45 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 72.00g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0098]

Example 7

[0099] Catalyst composition: 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g ammonium bromide, and the balance being propionic acid, per 100g total weight. The catalyst was thoroughly stirred and preheated to 100°C to form a solution. Oxidizing feedstock: 97.50g 2,6-diisopropylnaphthalene, 2.50g o-xylene, per 100g total weight. The oxidizing feedstock was thoroughly stirred and preheated to 100°C to melt it into a liquid state.

[0100] 900.00g of the above-mentioned oxidizing raw material and 6300g of the above-mentioned catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 9.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa, and the tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 230°C. After reacting for 45 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor through the 2,6-diisopropylnaphthalene raw material inlet and the catalyst inlet, respectively, at rates of 9.00 g / min and 63.00 g / min. After reacting for 45 minutes, crude 2,6-naphthalenedicarboxylic acid slurry (crude 2,6-naphthalenedicarboxylic acid oxidation slurry) was continuously discharged from the crude 2,6-naphthalenedicarboxylic acid slurry outlet at a rate of 72.00 g / min, and the crude 2,6-naphthalenedicarboxylic acid oxidation slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0101] Comparative Example 1

[0102] Preparation of the catalyst composition: Based on a total weight of 100g, 2.22g cobalt acetate tetrahydrate, 4.04g manganese acetate tetrahydrate, 3.64g potassium bromide, 4.50g potassium acetate, and 85.60g acetic acid. The catalyst was thoroughly stirred and preheated to 100°C to form a solution. A certain amount of 2,6-diisopropylnaphthalene was preheated to 100°C to melt it into a liquid state.

[0103] 1015.00g of 2,6-diisopropylnaphthalene and 8176.92g of the above catalyst composition were added to the oxidation reactor beforehand. The agitator was turned on and its speed was set to 60 rpm. When the temperature reached 160°C, air was introduced into the oxidation reactor at a flow rate of 10.0 L / min (standard state). The back pressure valve after the tail gas outlet was adjusted to control the pressure inside the reactor to 4.0 MPa. The tail gas generated by the reaction was continuously discharged through the tail gas outlet. The reaction temperature was controlled at 200°C. After the reaction was carried out for 30 minutes, liquid 2,6-diisopropylnaphthalene and the catalyst were added to the bottom of the oxidation reactor at rates of 10.15 g / min and 81.77 g / min, respectively, through the 2,6-diisopropylnaphthalene feed inlet and the catalyst inlet. After reacting for 30 minutes, the crude 2,6-naphthalenedicarboxylic acid slurry was continuously discharged from the outlet at a rate of 91.92 g / min (crude 2,6-naphthalenedicarboxylic acid oxidized slurry), and the crude 2,6-naphthalenedicarboxylic acid oxidized slurry was collected. 100g of the above-mentioned crude 2,6-naphthalenedicarboxylic acid oxidized slurry was processed sequentially as follows: After heating to 120℃, it was directly filtered under a pressure difference of 0.5MPa for 10min to obtain filter cake 1; 50g of acetic acid was added to filter cake 1 and thoroughly mixed, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 2; 25g of acetic acid was added to filter cake 2, then heated to 120℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 3; 50g of pure water was added to filter cake 3, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 4; 25g of pure water was added to filter cake 4, then heated to 160℃ and filtered under a pressure difference of 0.2MPa for 5min to obtain filter cake 5; filter cake 5 was placed in an oven at 120℃ for 24h to dry, and the dried sample was sent for analysis. The analysis results are shown in Table 1.

[0104] Table 1 Summary of analysis results for crude 2,6-naphthalenedicarboxylic acid oxidized slurry samples

[0105]

[0106]

[0107] For 2,6-naphthoic acid products, although the content of impurities such as 2-methyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid is not high, their content will greatly affect the energy consumption of subsequent purification and separation. If the content can be reduced by several hundred ppm, it can be said that the impurity removal effect has been significantly improved, which is a great technological advancement in this field.

[0108] As can be seen from the results in Table 1 above, compared with Comparative Example 1, the addition of p-xylene in Example 1 can effectively improve the purity of 2,6-naphthalenedicarboxylic acid and reduce the impurity content in the product, showing a significant improvement effect.

[0109] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A reaction mixture for the oxidation of 2,6-diisopropylnaphthalene to prepare 2,6-naphthalenedicarboxylic acid, comprising the following components: 2,6-diisopropylnaphthalene, a catalyst composition, a reaction aid, and a solvent; wherein the reaction aid has the structural formula shown in Formula I: Formula I; in, R1 to R6 may be the same or different, each independently selected from H or C1 to C10 alkyl groups, and at least one of R1 to R6 is an alkyl group.

2. The reaction mixture according to claim 1, characterized in that: The reaction aids R1 to R6 may be the same or different, each independently selected from H or C1 to C5 alkyl groups, and at least one of R1 to R6 is an alkyl group.

3. The reaction mixture according to claim 1, characterized in that: The reaction aids R1 to R6 may be the same or different, each independently selected from H or C1 to C3 alkyl groups, and at least one of R1 to R6 is an alkyl group.

4. The reaction mixture according to claim 2, characterized in that: Of R1 to R6, only one is an alkyl group, and the rest are hydrogen; or, Two of R1 to R6 are alkyl groups, and the rest are hydrogen.

5. The reaction mixture according to claim 4, characterized in that: The reaction aid is selected from at least one of toluene, cumene, and n-propylbenzene; or, The reaction aid is selected from at least one of o-xylene, m-xylene, p-xylene, ethyl methylbenzene, and diethylbenzene.

6. The reaction mixture according to claim 1, characterized in that: The active components of the catalyst composition include manganese, bromine, cobalt, and optionally potassium.

7. The reaction mixture according to claim 6, characterized in that: The manganese element in the catalyst composition is selected from at least one of manganese carboxylate; and / or, The bromine element is selected from bromides; and / or, Potassium is selected from potassium carboxylate; and / or, The cobalt element is selected from cobalt carboxylate.

8. The reaction mixture according to claim 7, characterized in that: The manganese carboxylate is selected from at least one of the manganese saturated fatty acids; and / or, The bromine element is selected from at least one of potassium bromide, tetrabromoethane, and ammonium bromide; and / or, The potassium carboxylate is selected from at least one of the potassium saturated fatty acids; and / or The cobalt carboxylate is selected from at least one of the saturated fatty acid cobalt.

9. The reaction mixture according to claim 8, characterized in that: The saturated fatty acid manganese is selected from at least one of C1-C5 saturated fatty acid manganese; and / or, The potassium saturated fatty acid is selected from at least one of C1-C5 saturated fatty acid potassiums; and / or, The saturated fatty acid cobalt is selected from at least one of the C1 to C5 saturated fatty acid cobalt.

10. The reaction mixture according to claim 9, characterized in that: The saturated fatty acid manganese is at least one of manganese formate, manganese acetate, and manganese propionate; and / or, The saturated fatty acid potassium is at least one of potassium formate, potassium acetate, and potassium propionate; and / or, The saturated fatty acid cobalt is at least one of cobalt formate, cobalt acetate, and cobalt propionate.

11. The reaction mixture according to claim 1, characterized in that: The solvent includes at least one of carboxylic acids and optionally water.

12. The reaction mixture according to claim 11, characterized in that: The water content in the solvent is ≤8wt%.

13. The reaction mixture according to claim 12, characterized in that: The carboxylic acid is selected from at least one of saturated fatty acids.

14. The reaction mixture according to claim 13, characterized in that: The carboxylic acid is selected from at least one of C2-C6 saturated fatty acids.

15. The reaction mixture according to claim 14, characterized in that: The carboxylic acid is selected from at least one of acetic acid and propionic acid.

16. The reaction mixture according to claim 1, characterized in that: The weight ratio of the reaction aid to 2,6-diisopropylnaphthalene is (0.005~0.06):

1.

17. The reaction mixture according to claim 16, characterized in that: The weight ratio of the reaction aid to 2,6-diisopropylnaphthalene is (0.01~0.025):1 or (0.015-0.052):

1.

18. The reaction mixture according to claim 1, characterized in that: The catalyst composition is in a weight ratio of (5~11):1 with 2,6-diisopropylnaphthalene.

19. The reaction mixture according to claim 18, characterized in that: The catalyst composition is in a weight ratio of (7~9):1 to 2,6-diisopropylnaphthalene.

20. The reaction mixture according to claim 19, characterized in that: In the catalyst composition, the molar ratio of cobalt to manganese is (0.3~3.0):1; and / or, The molar ratio of bromine to manganese is (1~3):1; and / or, When the catalyst composition contains potassium, the molar ratio of potassium to manganese is (3~7):

1.

21. The reaction mixture according to claim 20, characterized in that: In the catalyst composition, the molar ratio of cobalt to manganese is (0.4~2.5):1; and / or, The molar ratio of bromine to manganese is (1.5~2.5):1; and / or, When the catalyst composition contains potassium, the molar ratio of potassium to manganese is (4~6):

1.

22. The reaction mixture according to claim 1, characterized in that: The weight ratio of the solvent to 2,6-diisopropylnaphthalene is (5~10):

1.

23. The reaction mixture according to claim 22, characterized in that: The weight ratio of the solvent to 2,6-diisopropylnaphthalene is (6~8):

1.

24. A method for preparing 2,6-naphthalenedicarboxylic acid, comprising contacting a reaction mixture containing any one of claims 1-23 for the oxidation of 2,6-diisopropylnaphthalene to prepare 2,6-naphthalenedicarboxylic acid with an oxidizing agent to undergo an oxidation reaction, thereby obtaining a crude reaction product containing 2,6-naphthalenedicarboxylic acid, optionally followed by post-processing to prepare the product containing 2,6-naphthalenedicarboxylic acid.

25. The preparation method according to claim 24, characterized in that: The oxidant is selected from at least one oxygen-containing gas.

26. The preparation method according to claim 25, characterized in that: The oxygen-containing gas has an oxygen volume content of 18-25%.

27. The preparation method according to claim 26, characterized in that: The oxygen-containing gas has an oxygen volume content of 20-23%.

28. The preparation method according to claim 27, characterized in that: The oxidant is air.

29. The preparation method according to claim 25, characterized in that: The molar ratio of oxygen in the oxidant to 2,6-diisopropylnaphthalene in the reaction mixture is (4~6):

1.

30. The preparation method according to claim 29, characterized in that: The molar ratio of oxygen in the oxidant to 2,6-diisopropylnaphthalene in the reaction mixture is (4.5~5.5):

1.

31. The preparation method according to claim 30, characterized in that: Based on 1000g of 2,6-diisopropylnaphthalene and reaction aids, the flow rate of the oxidant under standard conditions was 9.0L / min-11.0L / min.

32. The preparation method according to any one of claims 24 to 31, characterized in that: The oxidation reaction is carried out at a temperature of 170~230℃; and / or, The oxidation reaction is carried out at a pressure of 2.0~4.5 MPa; and / or, The oxidation reaction takes 0.5 to 2.5 hours.

33. The preparation method according to claim 32, characterized in that: The oxidation reaction is carried out at a temperature of 180~210℃; and / or, The oxidation reaction is carried out at a pressure of 2.5–4.0 MPa; and / or, The oxidation reaction takes 0.75 to 2.0 hours.

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