Method for preparing high-purity 2, 6-naphthalic acid by oxidizing 2, 6-diisopropylnaphthalene

Abstract

The invention relates to a method for preparing high-purity 2, 6-naphthalic acid by oxidizing 2, 6-diisopropyl naphthalene. The method comprises the following steps: adding 2, 6-diisopropylnaphthalene, a catalyst, a solvent and an additive into a titanium reaction kettle, uniformly mixing, introducing nitrogen to remove oxygen, raising the temperature in the titanium reaction kettle to 150-220 DEG C, and introducing nitrogen to ensure that the pressure in the titanium reaction kettle is 0.5-1 MPa; the solvent is a mixture containing acetic acid and water; pure oxygen is introduced into the titanium reaction kettle, so that the pressure in the titanium reaction kettle is increased to 2.4-3.2 MPa, the reaction system reacts for 1-3 h under the condition that the pure oxygen is continuously introduced, and 2, 6-naphthalic acid is prepared; the 2, 6-naphthalic acid prepared by the method has the advantage of high purity.

Description

Technical Field

[0001] The invention belongs to the technical field of 2,6-naphthalene dicarboxylic acid preparation, and in particular relates to a method for preparing high-purity 2,6-naphthalene dicarboxylic acid by oxidizing 2,6-diisopropylnaphthalene. Background Art

[0002] Polyethylene naphthalate (PEN), a new industrial polyester material with 2,6-naphthalene dicarboxylic acid (2,6-NDA) and ethylene glycol (EG) as monomers, has excellent physical properties, mechanical properties, heat resistance, chemical stability and gas barrier properties. It can be widely used in food packaging, airbags, tires, fibers, electronic components, cell carriers, liquid crystal materials, insulating materials and engineering plastics. It is a polyester material with great application prospects and an important technical direction for industries such as petrochemicals and coal to expand product routes, improve product performance and reduce environmental problems under the background of "dual carbon". At present, the main technical route for the industrial preparation of 2,6-NDA is the catalytic oxidation of 2,6-dimethylnaphthalene (2,6-DMN). However, the cost of the raw material 2,6-DMN is extremely high (its properties are very similar to the isomer 2,7-DMN and it is difficult to separate, resulting in high preparation costs), which limits the large-scale preparation of 2,6-NDA. 2,6-diisopropylnaphthalene (2,6-DIPN) is easy to separate and purify from the raw material (isomer mixture) and has low operating costs. Therefore, from the perspective of industrial production and economic costs, the process route of preparing 2,6-NDA by 2,6-DIPN oxidation is more promising. However, the purity of the crude product of 2,6-NDA prepared by oxidation of 2,6-diisopropylnaphthalene is poor and the yield is low, and its catalytic oxidation system needs to be optimized.

[0003] In order to improve the selectivity of 2,6-DIPN catalytic oxidation and reduce by-products, many researchers have conducted relevant research. The commonly used catalyst system is the Co-Mn-Br ternary homogeneous catalytic system, and the commonly used solvent is acetic acid. Around the secondary oxidation process, researchers have proposed a variety of optimization schemes. For example, Chinese patent CN111068774A uses a variety of nitrogen-containing heterocyclic compounds as catalytic promoters to improve the yield of 2,6-naphthalenedicarboxylic acid; Chinese patent CN113620799A increases the conversion rate of 2,6-diisopropylnaphthalene and the selectivity of 2,6-naphthalenedicarboxylic acid by adding potassium permanganate in the middle of the reaction. However, the optimization of the solvent system has not been considered in the research. Summary of the invention

[0004] In order to solve one or more technical problems existing in the prior art, the present invention provides a method for preparing high-purity 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-diisopropylnaphthalene.

[0005] In a first aspect, the present invention provides a method for oxidizing 2,6-diisopropylnaphthalene to prepare high-purity 2,6-naphthalenedicarboxylic acid, the method comprising the following steps:

[0006] (1) adding 2,6-diisopropylnaphthalene, a catalyst, a solvent and an additive into a titanium reactor and mixing them evenly, then passing nitrogen to remove oxygen and raising the temperature in the titanium reactor to 150-220° C. and passing nitrogen to make the pressure in the titanium reactor 0.5-1 MPa; the solvent is a mixture of acetic acid and water;

[0007] (2) Pure oxygen is introduced into the titanium reactor in step (1) to increase the pressure in the titanium reactor to 2.4-3.2 MPa, and the reaction system is reacted for 1-3 hours while maintaining the continuous introduction of pure oxygen to obtain 2,6-naphthalene dicarboxylic acid.

[0008] Preferably, the catalyst is a mixed salt comprising Co, Mn, Br and K; preferably, the catalyst is a mixed salt comprising Co(OAc)2·4H2O, Mn(OAc)2·4H2O, BrK and CH3COOK.

[0009] Preferably, the molar ratio of Co to Mn in the catalyst is (0.5-2):1; the molar ratio of the sum of the molar amounts of Co and Mn to Br in the catalyst is 1:(0.5-1.5); and the molar ratio of K to Br in the catalyst is (1-4):1.

[0010] Preferably, the mass ratio of the solvent to the catalyst is (5-25):1; and / or the mass ratio of the solvent to the 2,6-diisopropylnaphthalene is (100-1000):1, preferably (100-500):1.

[0011] Preferably, in the solvent, the mass ratio of the acetic acid to the water is (88-98):(2-12).

[0012] Preferably, the solvent is a mixture of acetic acid, water and dimethyl sulfoxide; preferably, the mass ratio of acetic acid, water and dimethyl sulfoxide is (88-98): (2-12): (1-1.5).

[0013] Preferably, the additive is 2,6-naphthalene dicarboxylic acid; preferably, the mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):1.

[0014] Preferably, the additives are 2,6-naphthalene dicarboxylic acid and 1-butyl-3-methylimidazolium bromide.

[0015] Preferably, the mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):1; the mass ratio of the 2,6-naphthalene dicarboxylic acid to the 1-butyl-3-methylimidazolium bromide is 1:(0.05-0.1).

[0016] In a second aspect, the present invention provides high-purity 2,6-naphthalenedicarboxylic acid prepared by the method described in the first aspect of the present invention.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] (1) The present invention mainly solves the problem of low purity of the crude product of 2,6-naphthalene dicarboxylic acid prepared by catalytic oxidation of 2,6-diisopropylnaphthalene. The present invention significantly improves the purity of the crude product by adjusting the type and ratio of the solvent (adjusting the water content in acetic acid), and proposes a new method for preparing high-purity crude 2,6-naphthalene dicarboxylic acid by catalytic oxidation of 2,6-diisopropylnaphthalene, which has the advantage of high purity of the crude 2,6-naphthalene dicarboxylic acid product; the present invention improves the purity and yield of the crude product 2,6-naphthalene dicarboxylic acid by using a mixed solvent of acetic acid and water and adding water, while a system of pure acetic acid or pure propionic acid solvent cannot achieve such a good effect under the same conditions.

[0019] (2) The present invention further adds a small amount of 2,6-naphthalene dicarboxylic acid as an additive to the reaction system. The present invention finds that the addition of a small amount of 2,6-naphthalene dicarboxylic acid is beneficial to improving the purity and yield of the product 2,6-naphthalene dicarboxylic acid.

[0020] (3) In some preferred embodiments of the present invention, the solvent further comprises a small amount of dimethyl sulfoxide. The present invention finds that the introduction of a small amount of dimethyl sulfoxide (DMSO) into a mixed solvent of acetic acid and water can enhance the polarity of the dissolving system, help stabilize the reaction product, improve the selectivity and stability of the reaction, and reduce the occurrence of side reactions, thereby facilitating the improvement of the purity and yield of the target product 2,6-naphthalene dicarboxylic acid. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In a first aspect, the present invention provides a method for oxidizing 2,6-diisopropylnaphthalene to prepare high-purity 2,6-naphthalenedicarboxylic acid, the method comprising the following steps:

[0023] (1) 2,6-diisopropylnaphthalene, a catalyst, a solvent and an additive are added to a titanium reactor and mixed uniformly, and then nitrogen is passed through to deoxygenate and the temperature in the titanium reactor is raised to 150-220°C (for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C) and nitrogen is passed through to make the pressure in the titanium reactor 0.5-1MPa (for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1MPa); the solvent is a mixture comprising acetic acid (i.e., acetic acid) and water; in the present invention, nitrogen (N2) is passed through to exhaust the air in the titanium reactor, the temperature is raised to 150-220°C, preferably 160-220°C, and the nitrogen (N2) pressure is maintained at 0.5-1MPa;

[0024] (2) Pure oxygen (pure oxygen gas) is introduced into the titanium reactor in step (1) so that the pressure in the titanium reactor increases to 2.4-3.2 MPa (for example, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1 or 3.2 MPa) and the reaction system is reacted for 1-3 h (for example, 1, 1.5, 2, 2.5 or 3 h) while maintaining the continuous introduction of pure oxygen to obtain 2,6-naphthalene dicarboxylic acid; in the present invention, nitrogen is turned off and pure oxygen is introduced so that the reaction pressure reaches 2.4-3.2 MPa. During the entire reaction process, a constant pressure connection is maintained and oxygen is continuously introduced so that the reaction system is reacted for 1-3 h at a temperature of 150-220° C. and an oxygen pressure of 2.4-3.2 MPa.

[0025] The invention mainly solves the problem of low purity of a crude product of 2,6-naphthalene dicarboxylic acid prepared by catalytic oxidation of 2,6-diisopropylnaphthalene. The invention significantly improves the purity of the crude product by adjusting the type and ratio of solvents (adjusting the water content in acetic acid), and proposes a new method for preparing high-purity crude 2,6-naphthalene dicarboxylic acid by catalytic oxidation of 2,6-diisopropylnaphthalene. The method has the advantage of high purity of the crude 2,6-naphthalene dicarboxylic acid product. The invention improves the purity and yield of the crude product 2,6-naphthalene dicarboxylic acid by using a mixed solvent of acetic acid and water and by adding water, while a system of pure acetic acid or pure propionic acid solvent cannot achieve such a good effect under the same conditions.

[0026] According to some preferred embodiments, the catalyst is a mixed salt comprising Co, Mn, Br, and K; preferably, the catalyst is a mixed salt comprising cobalt acetate tetrahydrate Co(OAc)2·4H2O, manganese acetate tetrahydrate Mn(OAc)2·4H2O, BrK (potassium bromide KBr) and potassium acetate CH3COOK.

[0027] According to some preferred embodiments, the molar ratio of Co contained in the catalyst to Mn is (0.5-2):1 (for example, 0.5:1, 1:1, 1.5:1 or 2:1); the molar ratio of the sum of the molar amounts of Co and Mn contained in the catalyst to Br is 1:(0.5-1.5) (for example, 1:0.5, 1:0.75, 1:1, 1:1.25 or 1:1.5); the molar ratio of K contained in the catalyst to Br is (1-4):1 (for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1).

[0028] According to some preferred embodiments, the preferred catalyst system is a Co-Mn-Br-K mixed homogeneous catalyst, the ratio (molar ratio) of which is Co:Mn:Br:K=1:1:2:5, the preferred reaction temperature is 170°C, the reaction pressure is 2.8MPa, the oxidant is pure oxygen gas, the stirring speed is 1000r / min, and the reaction time is 2h. During the reaction, pure oxygen is continuously connected to the reactor at the reaction pressure to ensure that the oxidant is sufficient and the pressure is stable. After the reaction is completed, the crude 2,6-naphthalene dicarboxylic acid product is recovered by filtration and washed with acetic acid and water to analyze its purity and calculate its yield.

[0029] According to some preferred embodiments, the mass ratio of the solvent to the catalyst is (5-25):1 (e.g., 5:1, 10:1, 15:1, 20:1 or 25:1); and / or the mass ratio of the solvent to the 2,6-diisopropylnaphthalene is (100-1000):1 (e.g., 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 1000:1), preferably (100-500):1 (e.g., 100:1, 150:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 1000:1). 1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1); in the present invention, in other words, the mass ratio of the 2,6-diisopropylnaphthalene to the solvent is, for example, (0.001-0.01):1, for example, but not limited to, the mass ratio of the raw material (2,6-diisopropylnaphthalene) to the solvent can be 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1 or 0.01:1, etc.

[0030] According to some preferred embodiments, in the solvent, the mass ratio of the acetic acid to the water is (88-98):(2-12) (e.g., 88:12, 90:10, 92:8, 94:6, 96:4 or 98:2); in the present invention, when the solvent consists of acetic acid and water, preferably, the mass percentage of water in the solvent is 2-12%, which is more conducive to ensuring that 2,6-naphthalene dicarboxylic acid with high purity and high yield is obtained. The present invention finds that if the mass percentage of water contained in the solvent is too high, it will affect the purity and yield of the obtained 2,6-naphthalene dicarboxylic acid.

[0031] According to some preferred embodiments, the solvent is a mixture of acetic acid, water and dimethyl sulfoxide; preferably, the mass ratio of the acetic acid, water and dimethyl sulfoxide is (88-98): (2-12): (1-1.5); in the present invention, preferably, the solvent also contains a small amount of dimethyl sulfoxide. The present invention finds that introducing a small amount of dimethyl sulfoxide (DMSO) on the basis of a mixed solvent of acetic acid and water can improve the polarity of the dissolution system, help stabilize the reaction products, improve the selectivity and stability of the reaction, and reduce the occurrence of side reactions, thereby helping to improve the purity and yield of the target product 2,6-naphthalene dicarboxylic acid.

[0032] According to some preferred embodiments, the additive is 2,6-naphthalene dicarboxylic acid; preferably, the mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):1 (for example, 0.0002:1, 0.0003:1, 0.0004:1, 0.0005:1, 0.0006:1, 0.0007:1, 0.0008:1, 0.0009:1 or 0.001:1); the present invention further adds a small amount of 2,6-naphthalene dicarboxylic acid as an additive to the reaction system. The present invention finds that the addition of a small amount of 2,6-naphthalene dicarboxylic acid is beneficial to improving the purity and yield of the product 2,6-naphthalene dicarboxylic acid.

[0033] According to some preferred embodiments, the additives are 2,6-naphthalene dicarboxylic acid and 1-butyl-3-methylimidazolium bromide; the present invention does not specifically limit the source of 1-butyl-3-methylimidazolium bromide, and a product that can be directly purchased can be used. In the present invention, the CAS number of the 1-butyl-3-methylimidazolium bromide is, for example, 85100-77-2.

[0034] According to some preferred embodiments, the mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):1 (for example, 0.0002:1, 0.0003:1, 0.0004:1, 0.0005:1, 0.0006:1, 0.0007:1, 0.0008:1, 0.0009:1 or 0.001:1); the mass ratio of the 2,6-naphthalene dicarboxylic acid to the 1-butyl-3-methylimidazolium bromide is 1:(0.05-0.1) (for example, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or 1:0.1). In the present invention, it is more preferred that the additive is 2,6-naphthalene dicarboxylic acid and 1-butyl-3-methylimidazolium bromide in a mass ratio of 1: (0.05-0.1). The present invention finds that the addition of a small amount of 1-butyl-3-methylimidazolium bromide can effectively improve the solubility of oxygen in the reaction system, while providing better system polarity, which helps to stabilize the reaction product and improve the efficiency of the oxidation process, which helps to improve the purity and yield of 2,6-naphthalene dicarboxylic acid.

[0035] In a second aspect, the present invention provides high-purity 2,6-naphthalenedicarboxylic acid prepared by the method described in the first aspect of the present invention.

[0036] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these embodiments.

[0037] Example 1

[0038] In this example, acetic acid and water (mass ratio 98:2) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0039] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 98 g of acetic acid and 2 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0040] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, raise the temperature to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0041] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0042] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0043] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 97.68% and the yield was 75.72%.

[0044] In the present invention, the purity of 2,6-naphthalene dicarboxylic acid is detected by liquid chromatography, and the yield of 2,6-naphthalene dicarboxylic acid is calculated according to the following formula:

[0045] Yield = [(purity of 2,6-naphthalene dicarboxylic acid in the crude product × mass of the crude product - mass of 2,6-naphthalene dicarboxylic acid added to the reaction) × molecular weight of 2,6-diisopropylnaphthalene / (molecular weight of 2,6-naphthalene dicarboxylic acid × mass of raw material 2,6-diisopropylnaphthalene) × 100%.

[0046] Example 2

[0047] In this example, acetic acid and water (mass ratio 96:4) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0048] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 96 g of acetic acid and 4 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0049] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0050] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0051] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0052] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 97.88% and the yield was 75.96%.

[0053] Example 3

[0054] In this example, acetic acid and water (mass ratio 94:6) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0055] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 94 g of acetic acid and 6 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0056] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, raise the temperature to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0057] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0058] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0059] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 97.84% and the yield was 76.16%.

[0060] Example 4

[0061] In this example, acetic acid and water (mass ratio 90:10) were used as solvents to conduct a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0062] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 90 g of acetic acid and 10 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0063] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0064] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0065] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0066] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 98.09% and the yield was 76.79%.

[0067] Example 5

[0068] In this example, acetic acid and water (mass ratio 88:12) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0069] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 88 g of acetic acid and 12 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0070] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0071] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0072] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0073] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 98.37% and the yield was 76.14%.

[0074] Example 6

[0075] In this example, acetic acid and water (mass ratio 80:20) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0076] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 80 g of acetic acid and 20 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0077] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, raise the temperature to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0078] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0079] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0080] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 96.71% and the yield was 73.22%.

[0081] Example 7

[0082] In this example, acetic acid (acetic acid), water and dimethyl sulfoxide (the mass ratio of acetic acid, water and dimethyl sulfoxide is 88:12:1.2) are used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0083] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 88 g of acetic acid, 12 g of water and 1.2 g of dimethyl sulfoxide, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0084] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0085] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0086] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0087] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 99.06% and the yield was 77.21%.

[0088] Example 8

[0089] In this example, acetic acid and water (mass ratio 88:12) were used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0090] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 0.004 g of 1-butyl-3-methylimidazolium bromide, 88 g of acetic acid and 12 g of water, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0091] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0092] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0093] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0094] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 99.25% and the yield was 77.89%.

[0095] Example 9

[0096] In this example, acetic acid (acetic acid), water and dimethyl sulfoxide (the mass ratio of acetic acid, water and dimethyl sulfoxide is 88:12:1.2) are used as solvents to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0097] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid, 0.004 g of 1-butyl-3-methylimidazolium bromide, 88 g of acetic acid, 12 g of water and 1.2 g of dimethyl sulfoxide, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0098] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, raise the temperature to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0099] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0100] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0101] In this example, through purity analysis and yield calculation, it was determined that the purity of 2,6-naphthalene dicarboxylic acid in the 2,6-naphthalene dicarboxylic acid product was 99.47% and the yield was 78.35%.

[0102] Comparative Example 1

[0103] In this comparative example, acetic acid was used as solvent to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0104] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid and 100 g of acetic acid, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0105] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, heat it to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0106] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0107] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0108] The purity of the 2,6-naphthalene dicarboxylic acid product was 96.25% and the yield was 72.57%.

[0109] Comparative Example 2

[0110] In this comparative example, propionic acid was used as solvent to carry out a catalytic oxidation experiment of 2,6-diisopropylnaphthalene.

[0111] ① Mix 2.49 g of Co(OAc)2·4H2O, 2.45 g of Mn(OAc)2·4H2O, 2.38 g of KBr, 2.94 g of CH3COOK, 0.2 g of 2,6-diisopropylnaphthalene, 0.04 g of 2,6-naphthalenedicarboxylic acid and 100 g of propionic acid, add to a titanium reactor, and stir evenly with a magnetic stirrer at a speed of 1000 r / min.

[0112] ② Continuously introduce nitrogen into the titanium reactor to expel the air in the reactor, then close the reactor, raise the temperature to 170°C, and introduce nitrogen to make the pressure in the reactor 0.8MPa.

[0113] ③ Turn off the nitrogen and turn on the pure oxygen to raise the pressure in the titanium reactor to 2.8MPa. Keep the pure oxygen flowing in so that the reaction system reacts for 2h at a temperature of 170℃ and a pure oxygen pressure of 2.8MPa. During the reaction, the magnetic stirring speed is 1000r / min.

[0114] ④ After the reaction is completed, the titanium reactor is placed in cold water and quickly cooled to room temperature, the mixture containing 2,6-naphthalene dicarboxylic acid is filtered, the solid is collected, and washed with acetic acid and water respectively, and dried to constant weight to obtain the 2,6-naphthalene dicarboxylic acid product, which is weighed, sampled, tested for purity and calculated for yield.

[0115] The purity of the 2,6-naphthalene dicarboxylic acid product was 88.37% and the yield was 68.11%.

[0116] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-purity 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, characterized in that: The method comprises the following steps: (1) adding 2,6-diisopropylnaphthalene, a catalyst, a solvent and an additive into a titanium reactor and mixing them evenly, then passing nitrogen to remove oxygen and raising the temperature in the titanium reactor to 150-220° C. and passing nitrogen to make the pressure in the titanium reactor 0.5-1 MPa; the solvent is a mixture of acetic acid and water; (2) Pure oxygen is introduced into the titanium reactor in step (1) to increase the pressure in the titanium reactor to 2.4-3.2 MPa, and the reaction system is reacted for 1-3 hours while maintaining the continuous introduction of pure oxygen to obtain 2,6-naphthalene dicarboxylic acid.

2. The method according to claim 1, characterized in that: The catalyst is a mixed salt containing Co, Mn, Br and K; Preferably, the catalyst is a mixed salt comprising Co(OAc)2·4H2O, Mn(OAc)2·4H2O, BrK and CH3COOK.

3. The method according to claim 2, characterized in that: The catalyst contains Co and Mn in a molar ratio of (0.5-2):1; The catalyst contains a molar ratio of the sum of the molar amounts of Co and Mn to the molar ratio of the molar amount of Br contained in the catalyst of 1:(0.5-1.5); The catalyst contains K and Br in a molar ratio of (1-4):

1.

4. The method according to claim 1, characterized in that: The mass ratio of the solvent to the catalyst is (5-25):1; and / or The mass ratio of the solvent to the 2,6-diisopropylnaphthalene is (100-1000):1, preferably (100-500):

1.

5. The method according to claim 1, characterized in that: In the solvent, the mass ratio of the acetic acid to the water is (88-98):(2-12).

6. The method according to claim 1, characterized in that: The solvent is a mixture of acetic acid, water and dimethyl sulfoxide; Preferably, the mass ratio of acetic acid, water and dimethyl sulfoxide is (88-98):(2-12):(1-1.5).

7. The method according to claim 1, characterized in that: The additive is 2,6-naphthalene dicarboxylic acid; Preferably, the mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):

1.

8. The method according to claim 1, characterized in that: The additives are 2,6-naphthalene dicarboxylic acid and 1-butyl-3-methylimidazolium bromide.

9. The method according to claim 8, characterized in that: The mass ratio of the 2,6-naphthalene dicarboxylic acid to the solvent is (0.0002-0.001):1; The mass ratio of the 2,6-naphthalene dicarboxylic acid to the 1-butyl-3-methylimidazolium bromide is 1:(0.05-0.1).

10. High-purity 2,6-naphthalenedicarboxylic acid obtained by the method according to any one of claims 1 to 9.