Preparation method of 2, 6-naphthalic acid glycol ester

Abstract

The invention discloses a preparation method of 2, 6-naphthalic acid glycol ester, which belongs to the technical field of organic chemical synthesis, and comprises the following steps: firstly, mixing 2, 6-naphthalic acid and ethylene glycol according to a molar ratio of 1: 2 to 1: 3; secondly, 0.1%-0.5% of a catalyst is added into the mixture, and 0.2% of butyl titanate is particularly used as the catalyst in the embodiment; then reacting the mixture at a temperature of 100 DEG C to 150 DEG C for 4 to 6 hours; finally, unreacted ethylene glycol and generated moisture are removed through vacuum distillation, a solid-phase extraction column is used for further purifying the product to improve the purity and yield of the product, the method is characterized in that MOFs is used for carrying out loading treatment on butyl titanate in the aspect of use and treatment of the catalyst, and in addition, by adding magnetic MOFs, the purity of the product is greatly improved. The method realizes rapid recovery and reuse of the catalyst, greatly improves the environmental friendliness and economic benefits of the whole production process, and has important practical value and wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical synthesis, and more specifically to a method for preparing ethylene 2,6-naphthalene dicarboxylate. Background Art

[0002] Ethylene 2,6-naphthalene dicarboxylate is an important chemical compound that is widely used in materials science, medicine, and advanced functional materials. This ester compound has good biocompatibility and chemical stability, making it potentially useful in a variety of applications. For example, in the manufacture of certain high-performance polymers and resins, this ester compound can be used as a monomer or linker to improve the heat resistance and mechanical strength of the material.

[0003] The traditional preparation method of ethylene 2,6-naphthalene dicarboxylate usually includes an esterification reaction, that is, 2,6-naphthalene dicarboxylic acid and ethylene glycol are reacted under the catalysis of acid or base. However, these methods have some disadvantages, such as harsh reaction conditions, poor catalyst selectivity, many side reactions, and complex product separation and purification processes. Therefore, the development of an efficient, environmentally friendly and cost-effective synthesis method is an important demand of the chemical manufacturing industry.

[0004] In recent years, material science has made significant progress in the design and application of catalyst supports. Metal-Organic Frameworks (MOFs) have been widely studied and applied to various catalytic reactions due to their high specific surface area and adjustable pore structure. Especially in esterification reactions, MOFs can improve the dispersion and utilization of catalysts, thereby improving the selectivity and yield of the reaction. Summary of the invention

[0005] 1. Technical problems to be solved

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing ethylene 2,6-naphthalene dicarboxylate. By introducing butyl titanate as a catalyst, under the catalytic action of butyl titanate, side reactions such as polymerization or decomposition can be effectively reduced. Because the selectivity of the catalytic process is higher, the specificity of the reaction is improved. The action of the catalyst allows the reaction to be completed at a lower temperature and in a shorter time, saving energy and reducing by-products produced by thermal decomposition.

[0007] 2. Technical solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] A method for preparing ethylene 2,6-naphthalene dicarboxylate comprises the following steps:

[0010] S1. Mix 2,6-naphthalene dicarboxylic acid and ethylene glycol in a molar ratio of 1:2 to 1:3;

[0011] S2, adding 0.1% to 0.5% (based on the weight of naphthalene dicarboxylic acid) of a catalyst to the reaction mixture, and then mixing uniformly;

[0012] S3, the mixture is reacted at 100° C. to 150° C. for 4 to 6 hours;

[0013] S4. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation, and the reaction product is purified using a solid phase extraction column to improve the purity and yield of the product.

[0014] As a further improvement of the present invention, the catalyst in step S2 is butyl titanate, wherein the addition amount of butyl titanate is 0.2%.

[0015] As a further improvement of the present invention, step S3 is performed in an inert gas atmosphere to prevent oxidation of the raw materials.

[0016] As a further improvement of the present invention, the catalyst is loaded with MOFs before being added, and the amount of MOFs used is 3-5 times the weight of the catalyst.

[0017] As a further improvement of the present invention, the load processing includes the following steps:

[0018] S21, dissolving butyl titanate in a suitable organic solvent, wherein the organic solvent is selected from one of acetone, ethanol or toluene;

[0019] S22, immersing MOFs in a solution of butyl titanate at room temperature for 12 hours;

[0020] S23, then drying under vacuum to remove the solvent to obtain MOFs loaded with butyl titanate;

[0021] S24. Heat-treating MOFs at 120° C. for 3 hours under an inert atmosphere to ensure good bonding between butyl titanate and MOFs.

[0022] As a further improvement of the present invention, before the MOFs are subjected to the loading treatment for the catalyst, the magnetic material is pre-loaded with the magnetic material, wherein the magnetic material is nano Fe3O4 particles, wherein the mass ratio of the nano Fe3O4 particles to the MOFs is 1:5-15.

[0023] As a further improvement of the present invention, the nano Fe3O4 particles are reacted by adding an appropriate amount of ammonia water to iron salts under alkaline conditions, wherein the iron salts are FeCl2 and FeCl3, and the molar ratio is 1:2, the temperature is controlled at 80°C, the reaction time is 1 hour, and finally dried after magnetic separation and washing.

[0024] As a further improvement of the present invention, in step S22, MOFs and nano-Fe3O4 particles are simultaneously immersed in a solution of butyl titanate, and a surfactant is added to stir evenly. The surfactant is sodium dodecyl sulfate, and the mass ratio of the surfactant to the nano-Fe3O4 particles is 1:10.

[0025] As a further improvement of the present invention, in step S3, a rotating uniform magnetic field is applied to the mixture during the reaction to ensure that the reaction proceeds uniformly, and in step S4, MOFs are recovered through the magnetic field after the reaction is completed.

[0026] As a further improvement of the present invention, the operating temperature of the vacuum distillation is 120°C to 140°C and the pressure is 10 to 50 mmHg.

[0027] 3. Beneficial effects

[0028] (1) The present invention introduces butyl titanate as a catalyst. The intermediate formed by butyl titanate and 2,6-naphthalene dicarboxylic acid makes the carboxyl group more easily react with ethylene glycol. The tetravalent cation of titanium forms a coordination bond with the carboxyl oxygen of the carboxylic acid, which reduces the pKa of the carboxyl group and makes the carboxylic acid part a better leaving group, thereby accelerating the reaction process. Secondly, butyl titanate forms a complex with ethylene glycol. This process enhances the nucleophilicity of ethylene glycol and promotes the esterification reaction. Under the catalytic action of butyl titanate, side reactions such as polymerization or decomposition can be effectively reduced because the selectivity of the catalytic process is higher, thereby improving the specificity of the reaction. The action of the catalyst allows the reaction to be completed at a lower temperature and in a shorter time, saving energy and reducing by-products produced by thermal decomposition.

[0029] (2) The present invention uses MOFs to load butyramide. The porosity and high specific surface area in the MOFs structure provide more active sites, improving the catalytic efficiency. The structural characteristics of MOFs make butyramide more evenly dispersed, maximizing its catalytic potential, thereby improving the purity and thermal stability of the product.

[0030] (3) The present invention adds nano-Fe3O4 particles. The nano-particles provide a large number of active catalytic sites due to their large surface area to volume ratio. The use of magnetic particles can quickly remove the catalyst from the reaction system through an external magnetic field, reducing the loss of the catalyst and improving the recovery rate, thereby increasing the catalytic efficiency and simplifying the separation process overall.

[0031] (4) The present invention can ensure uniform distribution of reactants by applying a rotating magnetic field during the reaction process, avoid local overheating or concentration gradient problems, promote uniformity of reaction mixing, and accelerate the reaction rate by improving the mixing effect, thereby achieving the expected chemical conversion rate in a shorter time, thereby increasing the reaction rate and further improving the yield and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of the method of the present invention;

[0033] Figure 2 This is a performance characterization table of the polyphenylene ether products of Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] 2,6-naphthalene dicarboxylic acid and ethylene glycol are mixed in a molar ratio of 1:2, 0.2% (based on the weight of naphthalene dicarboxylic acid) of butyl titanate is added to the reaction mixture, and then mixed evenly. The mixture is reacted at 100° C. for 4 hours in an inert gas atmosphere, and the mixture is stirred. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation. The operating temperature of the vacuum distillation is 120° C. and the pressure is 10 mmHg. The reaction product is purified using a solid phase extraction column to improve the purity and yield of the product, and finally the butyl titanate is recovered.

[0037] Embodiment 2:

[0038] 2,6-naphthalene dicarboxylic acid and ethylene glycol are mixed in a molar ratio of 1:3, 0.2% (based on the weight of naphthalene dicarboxylic acid) of butyl titanate is added to the reaction mixture, and then mixed evenly. The mixture is reacted at 150° C. for 6 hours in an inert gas atmosphere, and the mixture is stirred. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation, and the reaction product is purified using a solid phase extraction column to improve the purity and yield of the product, and finally the butyl titanate is recovered.

[0039] Embodiment 3:

[0040] Different from Example 2, 2,6-naphthalene dicarboxylic acid and ethylene glycol are mixed in a molar ratio of 1:3, and MOFs are used for loading treatment before adding butyl titanate. The amount of MOFs used is 3 times the weight of the catalyst. First, butyl titanate is dissolved in ethanol, and MOFs are immersed in a solution of butyl titanate for 12 hours at room temperature, and then dried under vacuum to remove the solvent to obtain MOFs loaded with butyl titanate. MOFs are heat-treated at a temperature of 120° C. for 3 hours under an inert atmosphere to ensure good bonding between butyl titanate and MOFs. 0.2% (based on the weight of naphthalene dicarboxylic acid) of butyl titanate is added to the reaction mixture and then mixed evenly. The mixture is reacted at 150° C. for 6 hours in an inert gas atmosphere, and the mixture is stirred at the same time. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation, and the reaction product is purified using a solid phase extraction column. Finally, MOFs loaded with butyl titanate are recovered.

[0041] Embodiment 4:

[0042] The difference in Example 3 is that an appropriate amount of ammonia water is added to the iron salt under alkaline conditions to react, wherein the iron salt is FeCl2 and FeCl3, and the molar ratio is 1:2, the temperature is controlled at 80°C, the reaction time is 1 hour, and finally, nano-Fe3O4 particles are obtained by magnetic separation and washing and drying, and the mass ratio of the nano-Fe3O4 particles to the MOFs is 1:5, and the MOFs and the nano-Fe3O4 particles are simultaneously immersed in a solution of butyl titanate, and sodium dodecyl sulfate is added to stir evenly, and the mass ratio of the sodium dodecyl sulfate to the nano-Fe3O4 particles is 1:10, and the mixture is immersed at room temperature for 12 hours, and then dried under vacuum to remove the solvent to obtain a titanium dioxide loaded solution. The MOFs containing butyl titanate and nanomagnetic particles are heat-treated at a temperature of 120° C. for 3 hours under an inert atmosphere to ensure good bonding of butyl titanate, nanomagnetic particles and MOFs. 0.2% (based on the weight of naphthalene dicarboxylic acid) of butyl titanate is added to the reaction mixture and then mixed evenly. The mixture is reacted at 150° C. for 6 hours in an inert gas atmosphere while the mixture is stirred. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation, and the reaction product is purified by a solid phase extraction column. Finally, the MOFs loaded with butyl titanate and nanomagnetic particles are recovered by magnetic separation technology.

[0043] Embodiment 5:

[0044] On the basis of Example 4, a rotating uniform magnetic field is applied to the mixture during the reaction until the reaction is completed, and MOFs loaded with butyl titanate are recovered by magnetic separation technology.

[0045] See also Figure 2 , according to the data analysis in the table:

[0046] The mechanism of action of butyl titanate:

[0047] Activated carboxylic acid: Butyl titanate can react with 2,6-naphthalene dicarboxylic acid to form an intermediate, which is more easily reacted with ethylene glycol. Specifically, the tetravalent positive ion of titanium can form a coordination bond with the carboxyl oxygen of the carboxylic acid, reducing the pKa of the carboxyl group and making the carboxylic acid part a better leaving group.

[0048] Enhance the nucleophilicity of ethylene glycol: Butyl titanate can also enhance the nucleophilicity of ethylene glycol by forming a complex with ethylene glycol, thereby accelerating the esterification reaction.

[0049] Reducing side reactions: Using butyl titanate as a catalyst can also effectively reduce side reactions such as polymerization or decomposition because the catalytic reaction is more selective.

[0050] Improve reaction efficiency: Through the action of the catalyst, the reaction can be completed at a lower temperature and in a shorter time, thus saving energy and reducing by-products produced by thermal decomposition.

[0051] Therefore, in Example 1, butyl titanate as a catalyst exhibited superior catalytic performance and improved the yield and purity of the product.

[0052] Effect of temperature and time: In Example 2 and Example 3, increasing the reaction temperature and time significantly increased the yield and purity of the product compared to Example 1, which indicates that higher reaction temperature and longer time are conducive to the complete reaction.

[0053] Effect of MOFs: The use of MOFs for the loading treatment of butyl titanate in Example 3 further improved the purity and thermal stability of the product because MOFs provided more active sites and improved the catalytic efficiency.

[0054] Addition of nanomagnetic particles: Nanoparticles generally have a larger surface area to volume ratio and provide more active catalytic sites, thereby improving catalytic efficiency. In addition, the use of magnetic particles can simplify the separation process and quickly remove particles from the reaction system through an external magnetic field, which helps to reduce catalyst losses.

[0055] Stirring with a rotating magnetic field: The use of a rotating magnetic field can promote uniform mixing of the reaction, ensure a consistent distribution of the reactants, thereby increasing the reaction rate and reducing local overheating or concentration gradient problems, potentially further improving yield and purity.

[0056] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing ethylene 2,6-naphthalene dicarboxylate, characterized in that: The following steps are involved: S1. Mix 2,6-naphthalene dicarboxylic acid and ethylene glycol in a molar ratio of 1:2 to 1:3; S2, adding 0.1% to 0.5% (based on the weight of naphthalene dicarboxylic acid) of a catalyst to the reaction mixture, and then mixing uniformly; S3, the mixture is reacted at 100° C. to 150° C. for 4 to 6 hours; S4. After the reaction is completed, unreacted ethylene glycol and generated water are removed by vacuum distillation, and the reaction product is purified using a solid phase extraction column to improve the purity and yield of the product.

2. The method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 1, characterized in that: The catalyst in step S2 is butyl titanate, wherein the addition amount of butyl titanate is 0.2%.

3. A method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 1, characterized in that: The step S3 is performed in an inert gas atmosphere to prevent oxidation of the raw materials.

4. A method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 2, characterized in that: The catalyst is loaded with MOFs before being added, and the amount of MOFs used is 3-5 times the weight of the catalyst.

5. A method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 4, characterized in that: The load processing includes the following steps: S21, dissolving butyl titanate in a suitable organic solvent, wherein the organic solvent is selected from one of acetone, ethanol or toluene; S22, immersing MOFs in a solution of butyl titanate at room temperature for 12 hours; S23, then drying under vacuum to remove the solvent to obtain MOFs loaded with butyl titanate; S24. Heat-treating MOFs at 120° C. for 3 hours under an inert atmosphere to ensure good bonding between butyl titanate and MOFs.

6. The method for preparing ethylene 2,6-naphthalate according to claim 4, characterized in that: Before the MOFs are loaded with the catalyst, the magnetic material is pre-loaded, wherein the magnetic material is nano-Fe3O4 particles, wherein the mass ratio of the nano-Fe3O4 particles to the MOFs is 1:5-15.

7. The method for preparing ethylene 2,6-naphthalate according to claim 6, characterized in that: The nano Fe3O4 particles are reacted by adding an appropriate amount of ammonia water to iron salt under alkaline conditions, wherein the iron salt is FeCl2 and FeCl3, and the molar ratio is 1:2, the temperature is controlled at 80°C, the reaction time is 1 hour, and finally the particles are magnetically separated and washed before drying.

8. The method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 7, characterized in that: In the step S22, MOFs and nano-Fe3O4 particles are simultaneously immersed in a solution of butyl titanate, and a surfactant is added to stir the solution evenly. The surfactant is sodium dodecyl sulfate, and the mass ratio of the surfactant to the nano-Fe3O4 particles is 1:

10.

9. The method for preparing ethylene 2,6-naphthalene dicarboxylate according to claim 8, characterized in that: In step S3, a rotating uniform magnetic field is applied to the mixture during the reaction to ensure that the reaction proceeds uniformly, and in step S4, MOFs are recovered through the magnetic field after the reaction is completed.

10. A method for preparing ethylene 2,6-naphthalate according to any one of claims 1 to 9, characterized in that: The operating temperature of the vacuum distillation is 120°C to 140°C and the pressure is 10 to 50 mmHg.

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