A process for the highly selective preparation of 1,5-naphthalenedisulfonic acid and salts thereof

Abstract

The application provides a method for preparing 1,5-naphthalene disulfonic acid and a salt thereof with high selectivity. The method comprises the following steps: taking naphthalene as a core raw material, preparing a 1,5-naphthalene disulfonic acid sulfonated solution by adopting a segmented dropwise adding sulfonation process in the presence of a catalyst in an organic solvent and with chlorosulfonic acid as a sulfonating agent; purifying the 1,5-naphthalene disulfonic acid sulfonated solution by salting out with a sodium chloride aqueous solution, and obtaining high-purity 1,5-naphthalene disulfonic acid by low-temperature crystallization and filtration; and finally, neutralizing the 1,5-naphthalene disulfonic acid with sodium sulfite to prepare sodium 1,5-naphthalene disulfonate. By controlling the type of catalyst, the dropwise adding speed of the sulfonating agent and the reaction temperature, the generation of naphthalene disulfonic acid isomers is effectively inhibited, and the selectivity of the 1,5-naphthalene disulfonic acid product is greatly improved. Meanwhile, the sodium chloride aqueous solution can be recycled, and the discharge of three wastes is reduced. The preparation method is environmentally friendly and efficient, and the production cost is much lower than that of a traditional process.

Description

Technical Field

[0001] This invention relates to the field of organic chemical synthesis technology, specifically to a sulfonation method for aromatic compounds, and particularly to a method for highly selectively preparing 1,5-naphthalenedisulfonic acid and its salts. Background Technology

[0002] Naphthalene disulfonic acid and its sodium salt are important chemical intermediates of naphthalene after sulfonation and neutralization. The disulfonic acid group contained in its molecular structure has strong reactivity and can undergo further substitution, coupling and other reactions. It has important applications in many fields such as construction, chemical industry, medicine and dyes.

[0003] Currently, the industrial preparation of naphthalene disulfonic acid compounds mostly adopts the stepwise sulfonation method with concentrated sulfuric acid. This method uses a large amount of sulfuric acid, and the reaction process generates a large amount of waste acid and wastewater, which puts great pressure on the environment. The sulfonation reaction has poor selectivity, and the product will generate a large number of isomers, which increases the difficulty and cost of subsequent separation and purification.

[0004] Patent CN108752244A discloses a process for producing 2-naphthol using a double sulfonation technique with waste sulfuric acid and sulfur trioxide. The process involves a primary sulfonation reaction of waste sulfuric acid with naphthalene, followed by the introduction of sulfur trioxide. Sulfur trioxide reacts with water to generate sulfuric acid, promoting a secondary sulfonation reaction in the forward direction. This sulfuric acid then further sulfonates unreacted naphthalene in the system, thereby increasing the yield of the sulfonated product. The problem with this process is that sulfur trioxide is directly introduced into the sulfonation reaction system during the secondary sulfonation. The theory is that sulfur trioxide reacts with water to generate sulfuric acid, which then first sulfonates the naphthalene, promoting the reaction in the forward direction. However, in reality, sulfur trioxide has extremely high reactivity. Directly introducing sulfur trioxide leads to a direct reaction between the naphthalene and sulfur trioxide in the sulfonation system, generating a large amount of polysulfonic naphthalene. Furthermore, while using SO3 as a sulfonating agent effectively reduces waste acid, issues related to tail gas treatment and wastewater remain. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for highly selectively preparing 1,5-naphthalenedisulfonic acid and its salts, so as to solve the technical problems of low purity, low yield and high emissions of 1,5-naphthalenedisulfonic acid in the prior art.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for highly selectively preparing 1,5-naphthalenedisulfonic acid and its salts specifically includes the following steps:

[0008] Step 1: Using naphthalene as raw material, chlorosulfonic acid is selected as the sulfonating agent and a catalyst is added. The inert organic solvent is cooled to -5 ~ -10℃, and naphthalene and catalyst are added under stirring. After complete dissolution, chlorosulfonic acid is slowly added dropwise, and the reaction is maintained at -5 ~ -10℃ for 2 hours. Chlorosulfonic acid is added dropwise again, and the reaction is maintained at the same temperature for 2 hours. The temperature is slowly raised to 50 ~ 60℃ and the reaction is maintained at 4 hours to obtain a sulfonated liquid mainly composed of 1,5-naphthalenedisulfonic acid.

[0009] Step 2: Separate the organic solvent containing excess chlorosulfonic acid from the sulfonated liquid obtained in Step 1, add sodium chloride aqueous solution to the residue, stir and keep the reaction at 40-50℃ for 1 hour, then slowly stir until the temperature of the reaction solution reaches 5-10℃, let it stand in a low temperature environment for 1-2 hours, filter, and vacuum dry to obtain high-purity 1,5-naphthalenedisulfonic acid.

[0010] Step 3: Dissolve the 1,5-naphthalenedisulfonic acid obtained in Step 2 in deionized water, add sodium sulfite, control the reaction temperature at 70-80℃, adjust the pH to 6.5-7.5, cool to crystallize, filter and dry to obtain sodium 1,5-naphthalenedisulfonic acid product.

[0011] In this invention, the chlorosulfonic acid used in the sulfonation process is used to enhance the sulfonation activity and improve the conversion rate of naphthalene.

[0012] Optionally, in step 1, the molar ratio of naphthalene to chlorosulfonic acid is 1:2.0~4.0.

[0013] Optionally, in step 1, the inert organic solvent includes dichloromethane, dichloroethane, tetrachloroethane, petroleum ether, and nitromethane.

[0014] Optionally, in step 1, the molar ratio of naphthalene to organic solvent is 1:15~20.

[0015] In this invention, a catalyst is added during the sulfonation reaction to suppress secondary sulfonation at the non-1,5-position through steric hindrance, or to improve the selectivity of 1,5-naphthalenedisulfonic acid through a solid acid catalyst.

[0016] Optionally, in step 1, the catalyst includes AlCl3, FeCl3, V2O5, phosphotungstic acid, and zeolite molecular sieve.

[0017] Optionally, in step 1, the amount of catalyst used is 2 to 5% of the mass of naphthalene.

[0018] In this invention, the sulfonation product of the sulfonation reaction is purified using an aqueous sodium chloride solution to remove most of the isomerization products from the sulfonation product.

[0019] Optionally, in step 2, the mass concentration of the sodium chloride aqueous solution is 10 to 30%.

[0020] Optionally, in step 2, the volume ratio of the sodium chloride aqueous solution to the sulfonation solution is 1.2 ~ 2.0 : 1.

[0021] Optionally, in step 2, the sodium chloride aqueous solution obtained by filtration can be recycled in the salting-out step 2.

[0022] In this invention, the crude salting-out product and sodium sulfite are mixed and reacted at high temperature, and then filtered to obtain crude sodium 1,5-naphthalenedisulfonate.

[0023] Optionally, in step 3, the molar ratio of 1,5-naphthalenedisulfonic acid to sodium sulfite is 1:1.0~1.5.

[0024] Optionally, in step 3, the cooling crystallization time is 1 to 2 hours.

[0025] Optionally, in step 3, the mother liquor obtained by filtering the sodium 1,5-naphthalenedisulfonate aqueous solution can be recycled in step 3.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. In a highly selective preparation method for 1,5-naphthalenedisulfonic acid and its salts according to the present invention, naphthalene and chlorosulfonic acid undergo a sulfonation reaction in a sulfonation reactor, followed by solid-liquid separation with the addition of an aqueous sodium chloride solution to obtain 1,5-naphthalenedisulfonic acid; when the chlorosulfonic acid is fed in stages, the feeding rate can be controlled to control the reaction rate and exothermic rate, thereby improving the purity of 1,5-naphthalenedisulfonic acid; the method uses chlorosulfonic acid to sulfonate naphthalene to produce 1,5-naphthalenedisulfonic acid, avoiding the generation of waste acid, eliminating complex separation steps, solving the problems of tail gas treatment and solvent recovery, reducing solvent loss, and significantly reducing production costs, making it suitable for large-scale production.

[0028] 2. The purity of the 1,5-naphthalenedisulfonic acid produced by this invention can reach over 97%, and the yield can reach over 95%. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] The technical terms “first”, “second”, etc. in this application are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0031] The reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0032] The technical term "and / or" in this application is only a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0033] In addition, the character " / " in this application generally indicates that the objects before and after it are in an "or" relationship.

[0034] In this application, "multiple" means two or more (including two), and "at least one" means one or more.

[0035] It should be noted that, unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0036] Example 1

[0037] Step 1: Set up a mechanically stirred reaction apparatus equipped with an ice-salt bath and heating. In a 500ml four-necked flask (equipped with a dropping funnel, thermometer, and condenser), add 5g of naphthalene and 50ml of 1,2-dichloroethane. After the naphthalene is completely dissolved, add 0.15g of HZSM-5 zeolite catalyst, cool to -5℃, and slowly add 7.0g of chlorosulfonic acid dropwise. After the addition is complete, maintain the ice bath at -5℃ and stir for 2 hours. Add another 7.0g of chlorosulfonic acid dropwise and stir, maintaining the temperature at -5℃, and stir for another 2 hours. Switch to a water bath, and once the reaction solution temperature reaches approximately 15℃, begin heating, raising the temperature to 50℃. Stir the reaction for 4 hours.

[0038] Step 2: Separate the organic solvent containing excess chlorosulfonic acid from the sulfonated liquid obtained in Step 1, place it in a 50°C water bath, and add 70 ml of 18% sodium chloride aqueous solution dropwise to the residue. Stir thoroughly for 1 hour. Place the four-necked flask in an ice bath at approximately 0°C, stir slowly at low temperature until the reaction system temperature reaches below 10°C, and let it stand at low temperature for 1 hour. Filter, and recycle the filtrate for the next salting-out in Step 2 to obtain 14.73 g of crude 1,5-naphthalenedisulfonic acid.

[0039] Step 3: Add 14.73 g of crude 1,5-naphthalenedisulfonic acid obtained in Step 2 to 50 ml of deionized water and stir to dissolve. Add 6 g of sodium sulfite while stirring. React at 80°C for 2 hours. After the neutralization reaction is complete, cool to room temperature and allow to crystallize for 2 hours. Collect the crystals by vacuum filtration to obtain 12.56 g of sodium 1,5-naphthalenedisulfonic acid with a purity of 98.91% and a yield of 96.76%.

[0040] Example 2

[0041] This example provides a highly selective method for preparing 1,5-naphthalenedisulfonic acid and its salts, which is basically the same as in Example 1. The difference is that the sulfonating agent in step 1, the sulfonation reaction, is 14g of concentrated sulfuric acid, which ultimately yields 10.56g of sodium 1,5-naphthalenedisulfonic acid. The purity of the obtained product is 90.10%, and the yield is 81.36%.

[0042] Example 3

[0043] This example provides a highly selective method for preparing 1,5-naphthalenedisulfonic acid and its salts, which is basically the same as in Example 1. The difference is that the sulfonating agent in step 1, the sulfonation reaction, is 12g of chlorosulfonic acid, and the final product is 11.72g of sodium 1,5-naphthalenedisulfonic acid. The purity of the product is 95.31%, and the yield is 90.29%.

[0044] Example 4

[0045] This example provides a highly selective method for preparing 1,5-naphthalenedisulfonic acid and its salts, which is basically the same as in Example 1. The difference is that the solvent for the sulfonation reaction in step 1 is 50 ml of dichloromethane, which ultimately yields 12.03 g of sodium 1,5-naphthalenedisulfonic acid. The purity of the product is 95.79%, and the yield is 92.68%.

[0046] Example 5

[0047] Step 1: Using a 500ml four-port reaction apparatus, add 5g naphthalene and 50ml dichloromethane solvent, stir until completely dissolved, then add 0.12g AlCl3 and cool to -8℃. Control the dropping rate at 0.5g / min, add chlorosulfonic acid in two drops, 6.4g each time, and maintain the reaction temperature at -8℃ for 2h after each addition. After both additions are completed, slowly raise the temperature to 50℃ and maintain the reaction temperature for 4h to prepare the sulfonated solution.

[0048] Step 2: Remove the organic solvent from the sulfonation solution by rotary evaporation. Place the material in a 50°C water bath and add 70 ml of a 20% sodium chloride aqueous solution. Maintain the temperature at 50°C and stir for 1 hour. Slowly cool to 5°C, let stand at low temperature for 1 hour, filter and dry to obtain 16.04 g of 1,5-naphthalenedisulfonic acid dry material.

[0049] Step 3: Dissolve all of the above 1,5-naphthalenedisulfonic acid in 50ml of deionized water, add 5.5g of sodium sulfite, control the reaction temperature at 70℃, keep the reaction at the temperature, cool and crystallize for 1.5h, filter and dry to obtain 12.18g of the product with a purity of 98.07% and a yield of 93.85%.

[0050] Example 6

[0051] Step 1: Add 5g naphthalene and 50ml tetrachloroethane solvent to a 500ml four-port reaction apparatus. After stirring and dissolving, do not add a catalyst and cool to -10℃. Control the dropping rate at 0.7g / min and add 6.0g chlorosulfonic acid in two portions. After each addition, maintain the temperature at -10℃ for 2 hours. After the reaction is complete, raise the temperature to 50℃ and maintain the temperature for 4 hours to obtain the sulfonated solution.

[0052] Step 2: Remove organic solvent by rotary evaporation. Place the material in a 50°C water bath and add 70ml of a 20% sodium chloride aqueous solution. Maintain the temperature at 50°C and stir for 1 hour. Slowly cool to 5°C, let stand at low temperature for 2 hours, and filter and dry to obtain 12.38g of 1,5-naphthalenedisulfonic acid.

[0053] Step 3: Dissolve all of the above 1,5-naphthalenedisulfonic acid in 50ml of deionized water, add 6.5g of sodium sulfite, control the reaction temperature at 70℃, keep the reaction at this temperature, cool and crystallize for 1.5h, filter and dry to obtain 10.52g of the finished product with a purity of 89.60% and a yield of 81.30%.

[0054] In summary, the preparation method of the present invention improves the purity of 1,5-naphthalenedisulfonic acid and its sodium salt, and further increases their yield. Furthermore, the preparation process of 1,5-naphthalenedisulfonic acid and its sodium salt allows for the recycling of brine and neutralization solution, effectively reducing raw material consumption and waste emissions, while balancing product quality and production economics, fully meeting the needs of large-scale industrial production.

[0055] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for highly selectively preparing 1,5-naphthalenedisulfonic acid and its salts, characterized in that: It includes the following steps: (1) Low-temperature sulfonation reaction: Naphthalene is dissolved in an inert organic solvent, cooled to -5 ~ -10℃, catalyst is added with stirring, chlorosulfonic acid is slowly added dropwise, and the reaction is carried out at a constant temperature of -5 ~ -10℃ for time t1. Chlorosulfonic acid was added dropwise, and the reaction was carried out at the same temperature for time t2. Then the temperature was slowly increased to 50-60°C, and the reaction was carried out at the same temperature for time t3. The catalyst was recovered by filtration to prepare a sulfonated liquid with 1,5-naphthalenedisulfonic acid as the main component. (2) Preparation of 1,5-naphthalenedisulfonic acid: Remove the organic solvent containing excess chlorosulfonic acid from the sulfonation liquid, add sodium chloride aqueous solution to the remaining material, stir and keep warm at 40~50℃ for t4 time, then stir slowly and cool down to 5~10℃, let stand at low temperature for t5 time, filter and vacuum dry to obtain high-purity 1,5-naphthalenedisulfonic acid; (3) Preparation of sodium 1,5-naphthalenedisulfonic acid by salt formation: Dissolve the obtained 1,5-naphthalenedisulfonic acid in deionized water, add sodium sulfite, control the reaction temperature at 70 ~ 80℃, adjust the pH value of the system to 6.5 ~ 7.5; cool and crystallize for t6 time, filter and dry to obtain sodium 1,5-naphthalenedisulfonic acid.

2. The method according to claim 1, characterized in that: In step (1), the ratio of naphthalene to chlorosulfonic acid is 1:2.0 ~ 4.0 according to the molar ratio meter.

3. The method according to claim 1, characterized in that: The inert organic solvent is selected from any one of dichloromethane, dichloroethane, tetrachloroethane, petroleum ether, and nitromethane.

4. The method according to claim 1, characterized in that: The catalyst is selected from one or more Lewis acids, transition metal oxides, solid acids or heteropoly acids; and / or, the amount of catalyst used is 2 to 5% of the mass of naphthalene.

5. The method according to claim 1, characterized in that: The catalyst is selected from one or more of AlCl3, FeCl3, V2O5, phosphotungstic acid, and zeolite molecular sieves.

6. The method according to claim 1, characterized in that: In step (1), t1 = 2 ~ 3h; and / or, t2 = 2 ~ 3h; and / or, t3 = 4 ~ 5h.

7. The method according to claim 1, characterized in that: In step (2), the mass concentration of the sodium chloride aqueous solution is 10-30%; and / or, The volume ratio of sodium chloride aqueous solution to sulfonation solution is 1.2 ~ 2.0 :

1.

8. The method according to claim 1, characterized in that: In step (2), t4 = 4 ~ 5h; and / or t5 = 1 ~ 2h.

9. The method according to claim 1, characterized in that: In step (3), the ratio of 1,5-naphthalenedisulfonic acid to sodium sulfite is 1:1.0~1.5 according to the molar ratio.

10. The method according to claim 1, characterized in that: In step (3), t6 = 1 ~ 2 h.