One-pot synthesis of naphthalene dicarboxylic acid

Abstract

This invention discloses a one-pot method for synthesizing naphthalenedicarboxylic acid, aiming to solve the problems of complex synthesis processes and insufficient product purity in existing naphthalenedicarboxylic acid synthesis methods. The method involves: 1. Mixing 2,6-dimethylnaphthalene, an organic solvent, and a catalyst, introducing chlorine gas, and performing photochlorination under ultraviolet light to obtain a chlorinated reaction solution; 2. Adding the chlorinated reaction solution to an autoclave, then adding a water / alkali system, introducing nitrogen gas, and reacting under sealed conditions at a temperature of 85-150°C. The reactants are placed in pure water and heated to 140-160°C under sealed conditions to obtain naphthalenedicarboxylic acid; wherein the catalyst is azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide. This invention provides a green and efficient method for synthesizing naphthalenedicarboxylic acid, using dimethylnaphthalene as a starting material, and synthesizing naphthalenedicarboxylic acid in a one-pot process through photochlorination and hydrolysis, achieving a naphthalenedicarboxylic acid content of over 99%.

Description

Technical Field

[0001] This invention relates to a method for synthesizing naphthalenedicarboxylic acid. Background Technology

[0002] 2,6-Dicarboxynaphthalene, abbreviated as naphthalenedicarboxylic acid, is an important monomer for high-performance PEN, PBN, liquid crystal polymers (LCP), and polyurethane resins, and can improve various properties of polymeric materials. The novel polyester materials PEN / PBN possess good rigidity and high strength, and are superior in mechanical properties, heat resistance, gas barrier properties, and chemical stability. Liquid crystal polymers (LCP) feature high thermal stability, excellent environmental flame retardancy, extremely low water absorption, short molding cycles, and low shrinkage, contributing to the development of thinner and more complex electronic devices. With the rapid commercialization of the aerospace industry and 5G technology, the demand for terminal products is increasing rapidly, thus the demand for polymeric materials with better performance characteristics is growing even more significantly.

[0003] Numerous studies have been conducted both domestically and internationally on the chemical synthesis of naphthalenedicarboxylic acid (NDA). Currently, the main method employed is the oxidation of dialkylnaphthalene. For example, US Patent 5183933 reports the synthesis of NDA using 2,6-dimethylnaphthalene via cobalt-manganese-bromine catalytic oxidation. However, obtaining large quantities of high-purity 2,6-dimethylnaphthalene is challenging. US Patent 4709088 reports the catalytic oxidation of 2,6-diisopropylnaphthalene, a more readily synthesizable raw material, to obtain NDA, which is also the primary production process used by foreign companies. In China, research on NDA processes is primarily focused on laboratory studies, with no reports of large-scale production. Examples include the air oxidation method reported in patent CN113620799A filed by China Petroleum & Chemical Corporation, and the micron-catalyzed synthesis and oxidation of diisopropylnaphthalene to NDA by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, in patent CN114558611A. The above synthesis processes involve dangerous and complex processes such as high temperature and high pressure, insufficient product purity due to residual metal impurities, and harsh industrial production conditions. Exploring new synthesis routes has more important research significance and economic value. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of complex synthesis process and insufficient product purity in existing methods for synthesizing naphthalene dicarboxylic acid, and to provide a one-pot method for synthesizing naphthalene dicarboxylic acid.

[0005] The one-pot synthesis method of naphthalenedicarboxylic acid of the present invention is implemented according to the following steps:

[0006] Step 1: Mix 2,6-dimethylnaphthalene, organic solvent and catalyst to obtain a reaction solution. Pass chlorine gas into the reaction solution and carry out photochlorination under ultraviolet light to obtain a chlorinated reaction solution.

[0007] Step 2: Add the chlorination reaction solution to the autoclave, then add the water / alkali system, purge with nitrogen gas and react at 85-150℃ under sealed conditions. Filter to obtain the reactants, place the reactants in pure water, heat to 140-160℃ under sealed conditions to react, cool and filter to obtain naphthalenedicarboxylic acid.

[0008] The catalyst is azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

[0009] This invention provides a green and efficient method for synthesizing naphthalenedicarboxylic acid. Unlike the high-temperature and high-pressure catalytic oxidation of alkyl groups, this invention uses dimethylnaphthalene as a starting material and synthesizes naphthalenedicarboxylic acid in a one-pot process by photocatalytic chlorination to form benzyl chloride and then hydrolyzing it. The reaction conditions are mild, avoiding product purity issues caused by metal ion impurities, and the process is easy to control, showing promise for industrialization. Attached Figure Description

[0010] Figure 1 NMR of naphthalenedicarboxylic acid obtained in Example 1 1 H spectrum;

[0011] Figure 2 NMR of naphthalenedicarboxylic acid obtained in Example 1 13 C-spectrum. Detailed Implementation

[0012] Specific Implementation Method 1: The one-pot synthesis method for naphthalenedicarboxylic acid in this implementation method is carried out according to the following steps:

[0013] Step 1: Mix 2,6-dimethylnaphthalene, organic solvent and catalyst to obtain a reaction solution. Pass chlorine gas into the reaction solution and carry out photochlorination under ultraviolet light to obtain a chlorinated reaction solution.

[0014] Step 2: Add the chlorination reaction solution to the autoclave, then add the water / alkali system, purge with nitrogen gas and react at 85-150℃ under sealed conditions. Filter to obtain the reactants, place the reactants in pure water, heat to 140-160℃ under sealed conditions to react, cool and filter to obtain naphthalenedicarboxylic acid.

[0015] The catalyst is azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

[0016] The reaction formula for the synthesis of naphthalenedicarboxylic acid in this embodiment is as follows:

[0017] .

[0018] This embodiment introduces a green photochemical method to synthesize naphthalenedicarboxylic acid in a simple and efficient manner, which demonstrates the value of green chemistry compared to traditional processes.

[0019] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the organic solvent mentioned in step one is chlorobenzene, dichlorobenzene, dichloroethane, or tetrachloroethylene.

[0020] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that chlorine gas is introduced into the reaction solution through a pressure reducer in step 1.

[0021] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the temperature for controlling the photo-chlorination reaction in step one is 5-25℃.

[0022] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the photo-chlorination time under ultraviolet light in step 1 is 3-8 hours.

[0023] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the mass ratio of 2,6-dimethylnaphthalene, organic solvent, and catalyst in step one is 1:(8-20):(0.05-0.02).

[0024] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the water / alkali system in step two is one or a mixture of water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium ethoxide aqueous solution, sodium methoxide aqueous solution, and sodium tert-butoxide aqueous solution.

[0025] This embodiment preferably uses an alkaline system, such as an aqueous solution of sodium hydroxide or an aqueous solution of sodium ethoxide.

[0026] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the mass ratio of the water / alkali system added to 2,6-dimethylnaphthalene is 2-10:1.

[0027] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that nitrogen gas is introduced in step two and the reaction is carried out at a temperature of 85-150°C for 3-8 hours under sealed conditions.

[0028] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that in step 2, the mixture is heated in a sealed environment to 140-160°C for 2.5-3.5 hours.

[0029] Example 1: The one-pot synthesis method for naphthalenedicarboxylic acid in this example is carried out according to the following steps:

[0030] Step 1: Mix 10g of 2,6-dimethylnaphthalene, 100g of dichlorobenzene and 0.2g of azobisisobutyronitrile in a photoreactor, cool to 6°C to obtain a reaction solution, introduce chlorine gas into the reaction solution through a pressure reducer, turn on a 200W ultraviolet lamp to irradiate, and carry out photo-chlorination for 8 hours to obtain a chlorinated reaction solution.

[0031] Step 2: Add the chlorination reaction solution obtained in Step 1 to a high-pressure reactor, then add 20 mL of water, purge with nitrogen gas, and react at 120°C for 3.5 hours under sealed conditions. Filter to obtain the reactant, place the reactant in 150 mL of pure water, heat to 150°C under sealed conditions for 3 hours, cool and filter to obtain naphthalenedicarboxylic acid.

[0032] The product of this embodiment has a naphthalene dicarboxylic acid content (purity) of 99.5% and a yield of 65%.

[0033] The NMR spectrometry of the naphthalene dimethyl obtained in this embodiment 1 H spectrum Figure 1 As shown, 1 ¹H NMR (400 MHz, DMSO-d⁶) δ 13.29 (s, 1H), 8.69 (s, 1H), 8.23 ​​(d, J = 8.6 Hz, 1H), 8.07 (d, J = 8.5 Hz, 1H). 13 C spectrum as shown Figure 2 As shown, 13 C NMR (101 MHz, DMSO-d6) δ 167.71, 134.65, 130.68,130.61, 130.22, 126.41.

[0034] Example 2: The one-pot synthesis method for naphthalenedicarboxylic acid in this example is carried out according to the following steps:

[0035] Step 1: Mix 10g of 2,6-dimethylnaphthalene, 100g of dichlorobenzene and 0.5g of benzoyl peroxide in a photoreactor, cool to 6°C to obtain a reaction solution, introduce chlorine gas into the reaction solution through a pressure reducer, turn on a 400W ultraviolet lamp to irradiate, and carry out photo-chlorination for 6 hours to obtain a chlorinated reaction solution.

[0036] Step 2: Add the chlorination reaction solution obtained in Step 1 to a high-pressure reactor, then add 20 mL of 40% sodium hydroxide aqueous solution. Purge with nitrogen gas and react at 100°C for 3 hours under sealed conditions. After cooling, add an appropriate amount of dilute sulfuric acid to adjust the pH of the solution to 6, stir for 1 hour, filter to obtain the reactant, place the reactant in 150 mL of pure water, heat to 150°C under sealed conditions for 3 hours, cool and filter to obtain naphthalenedicarboxylic acid.

[0037] The product of this embodiment contains 99.6% naphthalenecarboxylic acid and has a yield of 83%.

[0038] Example 3: The one-pot synthesis method for naphthalenedicarboxylic acid in this example is implemented according to the following steps:

[0039] Step 1: Mix 10g of 2,6-dimethylnaphthalene, 100g of chlorobenzene and 0.5g of benzoyl peroxide in a photoreactor, cool to 6°C to obtain a reaction solution, slowly introduce chlorine gas into the reaction solution through a pressure reducer, turn on a 400W ultraviolet lamp to irradiate, and carry out photo-chlorination for 6 hours to obtain a chlorinated reaction solution.

[0040] Step 2: Add the chlorination reaction solution obtained in Step 1 to a high-pressure reactor, then add 10g of sodium ethoxide and 10g of water. Under nitrogen gas and sealed conditions, react at 95°C for 3 hours. After cooling, add an appropriate amount of dilute sulfuric acid to adjust the pH of the solution to 6-7, stir for 1 hour, filter to obtain the reactant, place the reactant in 150mL of pure water, seal and heat to 150°C for 3 hours, cool and filter to obtain naphthalenedicarboxylic acid.

[0041] The product of this embodiment contains 99.6% naphthalenecarboxylic acid and has a yield of 85%.

Claims

1. A method for one-pot synthesis of naphthalenedicarboxylic acid, characterized in that... The one-pot synthesis method for naphthalenedicarboxylic acid is carried out according to the following steps: Step 1: Mix 2,6-dimethylnaphthalene, organic solvent and catalyst to obtain a reaction solution. Pass chlorine gas into the reaction solution and carry out photochlorination under ultraviolet light to obtain a chlorinated reaction solution. Step 2: Add the chlorination reaction solution to the autoclave, then add the water / alkali system, purge with nitrogen gas and react at 85-150℃ under sealed conditions. Filter to obtain the reactants, place the reactants in pure water, heat to 140-160℃ under sealed conditions to react, cool and filter to obtain naphthalenedicarboxylic acid. The catalyst is azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

2. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... The organic solvent mentioned in step one is chlorobenzene, dichlorobenzene, dichloroethane, or tetrachloroethylene.

3. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step one, chlorine gas is introduced into the reaction solution through a pressure reducer.

4. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step one, the temperature for the photo-chlorination reaction is controlled to be 5-25℃.

5. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step one, the photo-chlorination reaction under ultraviolet light takes 3-8 hours.

6. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step one, the mass ratio of 2,6-dimethylnaphthalene, organic solvent and catalyst is 1:(8-20):(0.05-0.02).

7. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step two, the water / alkali system is one or a mixture of water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium ethoxide aqueous solution, sodium methoxide aqueous solution, and sodium tert-butoxide aqueous solution.

8. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... The mass ratio of the water / alkali system added to 2,6-dimethylnaphthalene is 2-10:

1.

9. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step two, nitrogen gas is introduced and the reaction is carried out under sealed conditions at a temperature of 85-150℃ for 3-8 hours.

10. The method for one-pot synthesis of naphthalenedicarboxylic acid according to claim 1, characterized in that... In step two, the mixture is heated in a sealed container to 140-160℃ for 2.5-3.5 hours to carry out the reaction.

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