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

Abstract

The invention discloses a method for preparing 2, 6-naphthalic acid by oxidizing 2, 6-diisopropylnaphthalene, which comprises the following steps: carrying out oxidation reaction on 2, 6-diisopropylnaphthalene and air under the action of a Co-Mn-Br catalyst and an accelerant to obtain 2, 6-naphthalic acid, and the accelerant comprises Zr, Ni and CO2. In the accelerant used by the invention, CO2 can form carbonate peroxide in a solution, and Co < 2 + > and Mn < 2 + > are promoted to be oxidized to generate Co < 3 + > and Mn < 3 + >, so that the reaction rate of a free radical chain is accelerated. Zr and Ni have similar effects and can form a weak complex with Co, Co-Mn dimer and monomer balance are redistributed, and the synergistic reduction effect of Co and Mn is strengthened. Meanwhile, CO2, Zr or Ni can play a synergistic promoting role, the reaction rate is increased, and the reaction proceeding degree is improved, so that the yield and purity of the product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, and in particular to a method for preparing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-diisopropylnaphthalene. Background Art

[0002] 2,6-Naphthalene dicarboxylic acid (2,6-NDA) has a similar structure to terephthalic acid and is an important monomer for preparing various polymer materials such as polyester and polyurethane. The polyamide material prepared by replacing terephthalic acid has better heat resistance and higher strength. The new liquid crystal polymer material prepared by it shows better heat resistance, flame retardancy and processability than ordinary liquid crystal polyester, and can be widely used in aerospace, automotive and circuit motherboard fields that have high requirements for temperature and temperature difference changes. At the same time, 2,6-NDA is also an important intermediate in electronics, medicine, dyes, pesticides, etc.

[0003] At present, the main methods for preparing 2,6-naphthalene dicarboxylic acid are 2,6-dimethylnaphthalene oxidation method and 2,6-diisopropylnaphthalene oxidation method. The reaction processes of these two methods are similar. Co-Mn-Br ternary catalyst is used, and a certain amount of air is introduced under the conditions of 180-220℃ and 2-5 MPa for reaction. The 2,6-dimethylnaphthalene oxidation method has high yield and purity and high production efficiency. Amoco has established a production device using this method. The problem with this method is that the raw materials 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene have similar physical and chemical properties and are difficult to separate, resulting in expensive raw materials and high production costs. The raw material price of 2,6-diisopropylnaphthalene oxidation method is relatively cheap and the operating cost is low. From the perspective of industrial production and economic cost, the 2,6-diisopropylnaphthalene oxidation method has better development prospects than the 2,6-dimethylnaphthalene oxidation method. However, its problem is that the reaction time is long, and the yield and purity are relatively low, with a yield of 63-75% and a purity of 88-93%. How to optimize reaction conditions, speed up reaction rate, and improve product yield and purity is currently a hot topic. Summary of the invention

[0004] In order to solve the problem of low purity and yield of the preparation method of 2,6-naphthalene dicarboxylic acid in the prior art, the purpose of the present invention is to provide a method for preparing 2,6-naphthalene dicarboxylic acid by oxidizing 2,6-diisopropylnaphthalene, which increases the reaction rate, shortens the reaction time, and improves the synergistic activity of the Co-Mn-Br catalyst by adding a certain amount of zirconium acetate or nickel acetate and CO2, thereby achieving the purpose of improving the yield and purity of the product. The problem of low yield and purity of the product of the 2,6-diisopropylnaphthalene oxidation method can be effectively solved, which is conducive to promoting the industrial application of the method and laying a solid foundation for the subsequent promotion and application of high-performance polyester materials.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene comprises the following steps: 2,6-diisopropylnaphthalene is oxidized with air in the presence of a Co-Mn-Br catalyst and a promoter to obtain 2,6-naphthalenedicarboxylic acid, wherein the promoter includes Zr, Ni and CO2.

[0006] A further improvement of the present invention is that the promoter is a mixture of zirconium acetate, nickel acetate and CO2.

[0007] A further improvement of the present invention is that the mass ratio of zirconium acetate to nickel acetate is 0.03-0.81:0.28-0.85, and the CO2 partial pressure is 0.2-0.5 MPa.

[0008] A further improvement of the present invention is that the Co-Mn-Br catalyst is a mixture of cobalt acetate, manganese acetate, potassium acetate and potassium bromide.

[0009] A further improvement of the present invention is that the mass ratio of cobalt acetate: manganese acetate: potassium acetate: potassium bromide is 1.80-4.45: 1.80-4.45: 2.24-4.86: 1.52-3.20.

[0010] A further improvement of the present invention is that the solvent is a mixed solvent of propionic acid and acetic acid, and the mass ratio of 2,6-diisopropylnaphthalene to the solvent is 50-100:300-700.

[0011] A further improvement of the present invention is that the mass ratio of propionic acid to acetic acid is 150-350:150-350. A further improvement of the present invention is that the reaction temperature is 180-200° C. and the reaction time is 1-3 h.

[0012] A further improvement of the present invention is that the air inlet flow rate is 10-15 L / min and the reaction pressure is 2-2.5 MPa.

[0013] A further improvement of the present invention is that the yield of 2,6-naphthalene dicarboxylic acid is 87.5-93.2%, and the purity of 2,6-naphthalene dicarboxylic acid is 92.4-96.2%.

[0014] Compared with the prior art, the present invention has the following beneficial effects: Among the promoters used in the present invention, CO2 can form peroxycarbonate in the solution to promote the 2+ and Mn 2+ Oxidation to generate Co 3+ , Mn 3+Thereby accelerating the reaction rate of the free radical chain. Zr and Ni have similar effects, and can form a weak complex with Co, redistribute the balance of Co-Mn dimers and monomers, and strengthen the synergistic reduction effect of Co and Mn. The simultaneous use of CO2, Zr or Ni can play a synergistic role, accelerate the reaction rate, increase the degree of reaction, and thus improve the yield and purity of the product. The specific advantages of the present invention are as follows: The yield and purity of the product are high. The yield of 2,6-naphthalenedicarboxylic acid prepared by the method provided by the present invention is 87.5-93.2%, and the purity is 93.4-96.2%, which is greatly improved compared with the yield of 63-75% and the purity of 88-93% in the current technology, effectively solving the problem of low yield and purity of the current 2,6-diisopropylnaphthalene oxidation method, and is conducive to the industrial application of the method and the promotion of high-performance polyester materials.

[0015] Further, the reaction time is short. The present invention provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene using CO2, zirconium acetate and nickel acetate as promoters. The reaction time of the conventional method for oxidizing 2,6-diisopropylnaphthalene to 2,6-naphthalene dicarboxylic acid is generally 3-5 hours. The reaction time of the method is 1-3 hours, which greatly shortens the reaction time, improves product production capacity, saves energy consumption during the reaction, and has great economic benefits and commercial value.

[0016] Furthermore, excessive partial pressure of CO2 will affect the flow of oxygen into the reactor, thereby reducing the oxidation rate and incomplete oxidation. Excessive Zr ions or Ni ions will affect the formation of Co-Mn dimers, reduce catalyst activity, and thus reduce the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The nuclear magnetic spectrum of 2,6-naphthalene dicarboxylic acid prepared by the present invention. DETAILED DESCRIPTION

[0018] The present invention will be described more fully below in conjunction with the embodiments. However, the present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0019] The oxidation of 2,6-diisopropylnaphthalene to 2,6-naphthalenedicarboxylic acid has always had the problem of low yield and purity, which is not conducive to industrial production and application. By changing the catalyst ratio and adding a certain amount of promoter, the yield and purity of the product can be improved while shortening the reaction time, which can greatly improve production efficiency, reduce production costs, and promote the development of high-performance polyester materials.

[0020] The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to the present invention comprises the following steps: (1) The oxidation method of 2,6-naphthalene dicarboxylic acid is as follows: 2,6-diisopropylnaphthalene is used as a reaction raw material, and an oxidation reaction occurs with air in a high-temperature and high-pressure titanium reactor under the synergistic effect of a catalyst and a promoter. After the reaction is completed, the obtained mixture is cooled and crystallized, centrifuged and filtered, and vacuum dried to obtain 2,6-naphthalene dicarboxylic acid, i.e., 2,6-NDA crystals.

[0021] Specifically, by weight, replace the air in the kettle with nitrogen at room temperature, gradually heat it to 180°C after the air is completely replaced, continue to introduce nitrogen to pressurize it to 2 MPa, then introduce CO2 and air, control the partial pressure of CO2 to 0.2-0.5 MPa, and introduce air flow rate to 10-15 L / min. By weight, take 50-100 parts of 2,6-diisopropylnaphthalene, 1.80-4.45 parts of cobalt acetate, 1.80-4.45 parts of manganese acetate, 2.24-4.86 parts of potassium acetate, 1.52-3.20 parts of potassium bromide, 0.03-0.81 parts of zirconium acetate or 0.28-0.85 parts of nickel acetate, 150-350 parts of propionic acid, and 150-350 parts of acetic acid. Add part of the solvent, catalyst and promoter to the reactor. After the air replacement, heating and pressurization operations are completed, dissolve 2,6-diisopropylnaphthalene in the remaining solvent and use a plunger pump to pump it into the reactor at a certain rate. The feed amount is 0.05-0.07 mol / h. During the feeding process, the temperature in the reactor is controlled to be 180-220°C and the pressure is 2.0-2.5 MPa. After the feeding is completed, react for 1-3 hours to obtain a mixture containing 2,6-naphthalene dicarboxylic acid crystals. The mixture containing 2,6-naphthalene dicarboxylic acid crystals is cooled and crystallized at 10-20°C, centrifuged and filtered, washed 3 times with hot acetic acid at 60-70°C, and dried at 100-120°C for 2-3 hours to obtain 2,6-naphthalene dicarboxylic acid crystals.

[0022] The yield of the 2,6-naphthalene dicarboxylic acid product is 87.5-93.2% and the purity is 92.4-96.2%.

[0023] The technical solution of the present invention is described in detail below through specific embodiments: Example 1 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.82 g of nickel acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0024] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0025] Weigh and use Agilent 1100 high performance liquid chromatography to determine its yield and purity. The external standard method is used for determination. The mobile phase is methanol, water containing 0.1% (volume fraction) phosphoric acid and acetonitrile. The mobile phase volume is 1 mL / min. The column temperature is 30°C. The elution gradient is shown in Table 1 below: Table 1 Mobile phase elution gradient for high performance chromatography analysis

[0026] The yield calculation formula of 2,6-NDA is:

[0027] The yield and purity of 2,6-NDA crystals are shown in Table 2 below: Table 2 Yield and purity of 2,6-NDA crystals obtained in Example 1

[0028] See also Figure 1 It can be seen that the impurity peaks mainly appear at positions 7-9 and 10, and the total impurity content is about 3%. It can be seen that the 2,6-naphthalene dicarboxylic acid prepared by the patented method has a higher purity and a lower impurity content.

[0029] Example 2 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.35 g of cobalt acetate, 4.27 g of manganese acetate, 4.84 g of potassium acetate, 3.18 g of potassium bromide, and 0.85 g of nickel acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0030] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0031] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 3 below: Table 3 Yield and purity of 2,6-NDA crystals obtained in Example 2

[0032] Example 3 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0033] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0034] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 4 below: Table 4 Yield and purity of 2,6-NDA crystals obtained in Example 3

[0035] Example 4 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.07 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0036] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0037] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 5 below: Table 5 Yield and purity of 2,6-NDA crystals obtained in Example 4

[0038] Example 5 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 15L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0039] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0040] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 6 below: Table 6 Yield and purity of 2,6-NDA crystals obtained in Example 5

[0041] Example 6 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.82 g of nickel acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.0 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0042] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0043] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 7 below: Table 7 Yield and purity of 2,6-NDA crystals obtained in Example 6

[0044] Example 7 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 200℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0045] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0046] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 8 below: Table 8 Yield and purity of 2,6-NDA crystals obtained in Example 7

[0047] Example 8 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 3.86 g of cobalt acetate, 3.75 g of manganese acetate, 4.34 g of potassium acetate, 2.51 g of potassium bromide, and 0.56 g of nickel acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0048] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0049] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 9 below: Table 9 Yield and purity of 2,6-NDA crystals obtained in Example 8

[0050] Example 9 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.5 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0051] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0052] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 10 below: Table 10 Yield and purity of 2,6-NDA crystals obtained in Example 9

[0053] Example 10 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 50 g of 2,6-diisopropylnaphthalene, 150 g of propionic acid, 300 g of acetic acid, 1.8 g of cobalt acetate, 3.3 g of manganese acetate, 4.86 g of potassium acetate, 1.52 g of potassium bromide, and 0.28 g of nickel acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 50 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 200°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.06 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 12 L / min, control the reactor temperature to 180°C, the pressure to 2.0 MPa, and the CO2 partial pressure to 0.2 MPa. Maintain this condition for 1 hour and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0054] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 20°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0055] Embodiment 11 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 70 g of 2,6-diisopropylnaphthalene, 300 g of propionic acid, 250 g of acetic acid, 4.45 g of cobalt acetate, 1.8 g of manganese acetate, 2.24 g of potassium acetate, 3.2 g of potassium bromide, and 0.03 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 220°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 13 L / min, control the reactor temperature to 220°C, the pressure to 2.3 MPa, and the CO2 partial pressure to 0.4 MPa. Maintain this condition for 2 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0056] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 15°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 70°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for 2 hours to obtain 2,6-NDA crystals.

[0057] Example 12 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 85 g of 2,6-diisopropylnaphthalene, 200 g of propionic acid, 150 g of acetic acid, 3.5 g of cobalt acetate, 4.45 g of manganese acetate, 3.5 g of potassium acetate, 2.3 g of potassium bromide, and 0.81 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 50 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 190°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.07 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 14 L / min, control the reactor temperature to 200°C, the pressure to 2.4 MPa, and the CO2 partial pressure to 0.5 MPa. Maintain this condition for 1.5 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0058] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 65°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0059] Comparative Example 1 This comparative example provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.82 g of nickel acetate. Open the lid of the titanium reactor and add all the cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, propionic acid, and acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve and control the reactor to heat up to 180°C. Open the air valve and CO2 valve, adjust the air flow rate to 10 L / min, control the reactor temperature to 190°C, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.5 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0060] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0061] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 11 below: Table 11 Yield and purity of 2,6-NDA crystals obtained in Comparative Example 1

[0062] Comparative Example 2 This comparative example provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.85 g of cobalt acetate, 4.62 g of manganese acetate, 4.98 g of potassium acetate, 3.43 g of potassium bromide, and 0.96 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0063] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0064] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 12 below: Table 12 Yield and purity of 2,6-NDA crystals obtained in Comparative Example 2

[0065] Comparative Example 3 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.10 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 220℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.35 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0066] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0067] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 13 below: Table 13 Yield and purity of 2,6-NDA crystals obtained in Comparative Example 3

[0068] Comparative Example 4 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. Open the air valve and CO2 valve at the same time, adjust the air flow rate to 10L / min, control the reactor temperature to 190℃, the pressure to 2.5 MPa, and the CO2 partial pressure to 0.7 MPa. Maintain this condition for 3 hours and then end the reaction. Close the air valve and CO2 valve, cool down, and obtain a mixed material.

[0069] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0070] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 14 below: Table 14 Yield and purity of 2,6-NDA crystals obtained in Comparative Example 4

[0071] Comparative Example 5 The present embodiment provides a method for preparing 2,6-naphthalene dicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, comprising the following steps: (1) Take 100 g of 2,6-diisopropylnaphthalene, 350 g of propionic acid, 350 g of acetic acid, 4.17 g of cobalt acetate, 4.08 g of manganese acetate, 4.61 g of potassium acetate, 2.80 g of potassium bromide, and 0.71 g of zirconium acetate. Open the lid of the titanium reactor and add cobalt acetate, manganese acetate, potassium acetate, potassium bromide, nickel acetate, 100 g of propionic acid, and 100 g of acetic acid into the reactor. After closing the lid, open the nitrogen valve of the reactor, replace the air in the reactor with nitrogen and pressurize it to 2.0 MPa, then close the nitrogen valve, control the reactor to heat up to 180°C, dissolve the raw material 2,6-diisopropylnaphthalene in the remaining propionic acid and acetic acid mixed solvent, and after the preparation is completed, use a plunger pump to pump it into the reactor at a feed rate of 0.05 mol / h. At the same time, open the air valve, adjust the air flow rate to 10 L / min, and control the reactor temperature to 190°C and the pressure to 2.5 MPa. The reaction was terminated after maintaining the reaction conditions for 3 hours, and the air valve was closed to cool the mixture to obtain a mixed material.

[0072] (2) Low-temperature heat transfer oil is introduced into the reactor coil to control the cooling crystallization temperature to 10°C. After the crystallization is complete, the reactor is opened to release the mixed material, and a solid product is obtained by centrifugation. The product is washed twice with 60°C hot acetic acid, filtered, and placed in a vacuum oven set at 100°C for two hours to obtain 2,6-NDA crystals.

[0073] The yield and purity of the product 2,6-NDA were determined by the method shown in Example 1. The results are shown in Table 15 below: Table 15 Yield and purity of 2,6-NDA crystals obtained in Comparative Example 5

[0074] According to the above Examples 1-12 and Comparative Examples 1-5, it can be seen from Comparative Example 1 that the reaction effect is very poor under intermittent conditions without using a pump, and the yield and purity are greatly reduced.

[0075] It can be seen from Comparative Example 2 that an excessive amount of zirconium acetate will affect the formation of the catalyst complex, thereby reducing the yield and purity.

[0076] It can be seen from Comparative Example 3 that too high a temperature will affect the degree of reaction, increase side reactions, and reduce the yield and purity.

[0077] It can be seen from Comparative Example 4 that excessive CO2 causes peroxycarbonate to affect the complex of the Co-Mn-Br ternary catalyst, thereby reducing the yield and purity.

[0078] It can be seen from Comparative Example 5 that not adding CO2 will reduce the yield and purity, indicating that the addition of an appropriate amount of CO2 will promote the reaction to a certain extent.

[0079] The present invention uses nickel acetate or zirconium acetate and CO2 as promoters to greatly improve the yield and purity of 2,6-NDA, and can effectively solve the shortcomings of insufficient yield and low purity of the current 2,6-diisopropylnaphthalene oxidation method. At the same time, the method can also accelerate the reaction rate, shorten the reaction time, increase the production capacity and reduce the energy consumption, and has broad industrial application prospects and commercial value.

[0080] The invention discloses a method for preparing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-diisopropylnaphthalene. The method uses a mixed solution of acetic acid and propionic acid as a solvent, nickel acetate or zirconium acetate and CO2 as promoters on the basis of a Co-Mn-Br ternary catalyst, can improve the yield and purity of the product while shortening the reaction time, is beneficial to the industrial application of the process, and lays a foundation for the development of high-performance polyester materials.

[0081] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene, characterized in that: The following steps are involved: 2,6-diisopropylnaphthalene is oxidized with air in the presence of a Co-Mn-Br catalyst and a promoter to obtain 2,6-naphthalenedicarboxylic acid, wherein the promoter includes Zr, Ni and CO2.

2. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The promoter is a mixture of zirconium acetate, nickel acetate and CO2.

3. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 2, is characterized in that: The mass ratio of zirconium acetate to nickel acetate is 0.03-0.81:0.28-0.85, and the CO2 partial pressure is 0.2-0.5 MPa.

4. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The Co-Mn-Br catalyst is a mixture of cobalt acetate, manganese acetate, potassium acetate and potassium bromide.

5. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 4, characterized in that: Mass ratio of cobalt acetate: manganese acetate: potassium acetate: potassium bromide = 1.80-4.45: 1.80-4.45: 2.24-4.86: 1.52-3.

20.

6. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The solvent is a mixed solvent of propionic acid and acetic acid, and the mass ratio of 2,6-diisopropylnaphthalene to the solvent is 50-100:300-700.

7. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 6, characterized in that: The mass ratio of propionic acid to acetic acid is 150-350:150-350.

8. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The reaction temperature is 180-200°C and the reaction time is 1-3 h.

9. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The air inlet flow rate is 10-15 L / min, and the reaction pressure is 2-2.5 MPa.

10. The method for preparing 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene according to claim 1, characterized in that: The yield of 2,6-naphthalene dicarboxylic acid is 87.5-93.2%, and the purity of 2,6-naphthalene dicarboxylic acid is 92.4-96.2%.

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