Preparation method of sodium p-styrenesulfonate

Abstract

The invention belongs to the technical field of synthesis of organic sulfonate, and particularly relates to a preparation method of sodium p-styrenesulfonate. The preparation method comprises the following steps: dissolving pyridine in an organic solvent A, and introducing sulfur trioxide into the organic solvent A for complexing to obtain a sulfur trioxide-pyridine complex; dissolving styrene in an organic solvent B, and adding a polymerization inhibitor to obtain a styrene solution; adding a styrene solution into the sulfur trioxide-pyridine complex to carry out primary sulfonation, and heating to carry out secondary sulfonation; washing, extracting, alkalizing, concentrating, crystallizing and drying to obtain sodium p-styrenesulfonate. The bromination step in the original synthesis route is avoided, and the problems of high energy consumption, high operation difficulty and insufficient atom economy in the original synthesis route are further improved by redesigning the synthesis route and reasonably selecting the raw materials and the polymerization inhibitor.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic sulfonate synthesis, and specifically relates to a preparation method of sodium p-styrenesulfonate. Background Art

[0002] Sodium p-styrenesulfonate is an important organic reagent. Its molecular structure contains a sulfonic acid group and a styryl group, thus endowing it with water solubility, ionic properties and reactivity. It has a wide range of applications in the fields of papermaking, textiles, medicine, electronics, etc.

[0003] At present, there are many synthesis methods of sodium p-styrenesulfonate. For example, Chinese Patent CN106946745A discloses a preparation method of sodium p-styrenesulfonate. Its basic principle is that β-bromoethylbenzene is sulfonated, debrominated and crystallized and purified to obtain high-purity sodium p-styrenesulfonate. The specific steps of the preparation method are as follows: After preheating bromoethylbenzene, it is continuously reacted with diluted sulfur trioxide in a vertical tube reactor at a temperature controlled at 80-110°C to generate bromoethylbenzene sulfonic acid; bromoethylbenzene sulfonic acid is neutralized with liquid alkali in a high-speed homogenizing pump, and the temperature is raised to remove bromine to generate liquid sodium p-styrenesulfonate; the liquid sodium p-styrenesulfonate is cooled and crystallized, centrifuged and dried to obtain sodium p-styrenesulfonate.

[0004] Another example is the experimental principle of preparing sodium p-styrenesulfonate described in "Preparation of Sodium p-Styrenesulfonate" (Wang Peng, Wang Mingchang, Henan Chemical Industry, No. 11, 2001, pp. 19-20). The basic principle is bromination, sulfonation and salting out; that is, ethylbenzene and carbon tetrachloride are mixed, and bromine is added dropwise under ultraviolet light irradiation to form α-bromoethylbenzene through bromination reaction; α-bromoethylbenzene and fuming sulfuric acid are sulfonated in a low-temperature environment to generate a sulfonic acid intermediate; finally, it is salted out with NaCl, filtered and dried to obtain sodium p-styrenesulfonate.

[0005] The above synthesis routes still require multiple steps of reactions such as sulfonation and bromination. These reactions have high temperature requirements and large energy consumption; the raw materials used in the reactions or the generated by-products (such as bromine, SO 3 ) etc. all have certain toxicity and corrosiveness, the operating conditions are harsh, and the equipment cost is also relatively high; in addition, the difficulty and cost of purifying and reusing the generated by-products (such as sulfuric acid, bromine, etc.) are relatively high, and they are generally treated as waste, which will inevitably affect the atom economy during industrial production. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of sodium p-styrenesulfonate to further improve the problems faced by the current preparation method of sodium p-styrenesulfonate in terms of energy consumption, operation difficulty and atom economy.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: The preparation method of sodium p-styrenesulfonate according to the present invention: Dissolve pyridine in organic solvent A, and pass sulfur trioxide into it for complexation to obtain a sulfur trioxide-pyridine complex; dissolve styrene in organic solvent B, and add an inhibitor thereto to obtain a styrene solution; add the styrene solution to the sulfur trioxide-pyridine complex for primary sulfonation, and raise the temperature for secondary sulfonation; then, through washing with water, extraction, alkalization, concentration crystallization, and drying, sodium p-styrenesulfonate is obtained.

[0008] Among them: The organic solvent A is one of dichloroethane, dichloromethane, and tetrachloroethane, and the volume ratio of organic solvent A to pyridine is (2-5):1.

[0009] The molar ratio of pyridine to sulfur trioxide is (1.0-3.0):1, the complexation temperature is 15-45 °C, and the complexation time is 30-120 min.

[0010] The organic solvent B is one of dichloroethane, dichloromethane, and tetrachloroethane, and organic solvent A and organic solvent B are the same solvent. The volume ratio of organic solvent B to styrene is (2-5):1.

[0011] The inhibitor is 4,6-dinitro-2-sec-butylphenol or 2,6-dinitro-4-methylphenol, and the concentration of the inhibitor in the styrene solution is 1000-5000 ppm.

[0012] The molar ratio of styrene to sulfur trioxide is (1.00-1.25):1.

[0013] The temperature of the primary sulfonation is 0-10 °C, and the time of the primary sulfonation is 90-120 min.

[0014] The temperature of the secondary sulfonation is 50-65 °C, and the time of the secondary sulfonation is 45-60 min.

[0015] During alkalization, the temperature is controlled at 10-30 °C. After alkalization, the pH is 9.0-12.0.

[0016] The drying temperature is 40-75 °C.

[0017] The reaction equation of the present invention is as follows:

[0018] The beneficial effects of the present invention are as follows: (1) In the preparation method of the present invention, by redesigning the synthesis route and reasonably selecting raw materials to avoid the bromination step, the safety, environmental protection, and economy are significantly improved: 1. The present invention does not involve bromides and completely abandons the bromine (Br2 ), highly toxic and corrosive reagents such as ethyl bromide, to avoid the generation of bromine-containing waste liquids (such as HBr, organic bromides). Since the treatment of bromine-containing waste liquids is difficult and costly, the present invention can effectively reduce environmental hazards and save production costs. 2. The present invention uses sulfur trioxide-pyridine complex to replace free SO 3 : By complexing pyridine with SO 3 , the activity of SO 3 is reduced, and a large amount of SO 3 escaping simultaneously causes intense exothermic reaction and disulfonation or polysulfonation side reactions, improving operation safety and product yield. 3. Since the sulfonation of styrene is a typical electrophilic substitution reaction, the sulfonic acid group preferentially substitutes the para position of the vinyl group. However, when the local concentration of SO 3 is too high, disulfonation or polysulfonation side reactions will also occur. The present invention designs stepwise temperature control for sulfonation. The first sulfonation is carried out at a low temperature to ensure that the sulfonic acid group is accurately introduced into the para position of the vinyl group, reducing side reactions; the second sulfonation is carried out at an elevated temperature to improve the sulfonation reaction efficiency, promote the completion of the sulfonation reaction, and avoid the problem of over-sulfonation caused by directly heating to a high temperature.

[0019] (2) The inhibitor (i.e., 4,6-dinitro-2-sec-butylphenol or 2,6-dinitro-4-methylphenol) in the present invention can not only prevent the self-polymerization of styrene and improve atom economy; at the same time, it also has the functions of assisting phase separation, optimizing the post-treatment efficiency, and stabilizing the sulfonation intermediate to inhibit side reactions: In the post-treatment stage after the second sulfonation, the inhibitor in the present invention contains groups with both lipophilicity (benzene ring, nitro group) and weak hydrophilicity (phenolic hydroxyl group), which can act as surfactants in the subsequent water washing step, promoting the rapid stratification of the organic phase and the water phase, reducing emulsification phenomena, and improving extraction efficiency; at the same time, in the alkalization stage, the inhibitor can be converted into water-soluble phenolate in an alkaline environment, and its ionic strength can enhance the salting-out effect of the water phase, helping sodium styrene sulfonate to precipitate from the water phase and improving the crystallization efficiency. This characteristic enables it to effectively cope with the adverse effects of scale-up effects during subsequent large-scale production.

[0020] The stability of sulfur trioxide-pyridine complex and the sulfonation intermediate during the sulfonation reaction depends on a weakly acidic environment. The phenolic hydroxyl group of the nitrophenol inhibitor in the present invention can be partially dissociated in a weakly acidic system. Especially in a large reaction kettle, since the present invention reacts in an organic system with a high viscosity, there may sometimes be a situation where the local H + concentration increases. The nitrophenol oxyanion can quickly combine with H + to generate a neutral phenolic hydroxyl group, consuming excess protons and regulating the local H + concentration, avoiding the decomposition of sulfur trioxide-pyridine complex or sulfonic acid intermediate caused by enhanced local acidity; the inhibitor in the present invention can complex metal ions, nitro group (-NO 2) and phenolic hydroxyl groups can complex with trace metal ions (such as Fe introduced by equipment corrosion 3+ , Cu 2+ ), preventing metal ion-catalyzed oxidation side reactions (such as styrene epoxidation) and further improving the product stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the infrared spectrum of the sodium p-styrenesulfonate finished product in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be specifically described and illustrated below in conjunction with examples.

[0023] Example 1 Add 12 mol of pyridine to the reaction kettle, add 2900 mL of dichloroethane, turn on the stirrer and temperature control device, and introduce 10 mol of sulfur trioxide into the reaction kettle. During the introduction process, maintain the temperature at 25 °C, and keep the temperature for 60 min after the introduction to obtain a sulfur trioxide-pyridine complex.

[0024] Take 10 mol of styrene, dissolve it in 4000 mL of dichloroethane, add 6.07 g of the inhibitor 2,6-dinitro-4-methylphenol, and stir to dissolve to obtain a styrene solution. Slowly drop the styrene solution into the sulfur trioxide-pyridine for the first sulfonation, and the dropping time is 60 min; keep the solution temperature at 0 °C during the dropping; after the dropping is completed, keep the temperature at 0 °C and continue to stir for 60 min; then raise the temperature to 60 °C for the second sulfonation, and continue to stir for 60 min to obtain a reaction solution.

[0025] Cool the reaction solution to 30 °C, slowly drop 1000 mL of deionized water while stirring, stir for 10 min, let it stand for stratification, and separate the lower aqueous phase; extract the aqueous phase 2 times with 2000 mL of dichloroethane, remove the organic phase, and retain the purified aqueous phase; transfer the purified aqueous phase to another clean reaction kettle, control the temperature at 30 °C, slowly drop 48 wt.% sodium hydroxide solution to pH = 10 while stirring, and stir for 3 min; then transfer it to a vacuum for concentration until the concentration reaches 40 - 50%. Let the concentrated solution cool naturally to room temperature to precipitate white crystals. Filter the crystals by suction and wash them with a small amount of ice water. Dry the crystals in vacuo at 40 °C to obtain 2081.5 g of the sodium p-styrenesulfonate finished product.

[0026] Perform infrared detection on the finished product. The infrared spectrum is as Figure 1 shown, confirming the obtained sodium p-styrenesulfonate. The purity is detected by chemical titration (iodometric method) to be 84.2%, and the calculated yield is 85.0%.

[0027] Example 2 Add 10 mol of pyridine to the reaction kettle, and add 4000 mL of dichloromethane. Start the stirrer and temperature control device, and introduce 10 mol of sulfur trioxide into the reaction kettle. During the introduction process, maintain the temperature at 45 °C. After the introduction is completed, keep the temperature for 30 min to obtain sulfur trioxide - pyridine complex.

[0028] Take 12.5 mol of styrene, dissolve it in 2900 mL of dichloromethane, add 15.45 g of inhibitor 2,6 - dinitro - 4 - methylphenol, and stir to dissolve to obtain a styrene solution. Slowly drop the styrene solution into sulfur trioxide - pyridine for the first sulfonation, and the dropping time is 60 min; keep the solution temperature at 8 °C during the dropping; after the dropping is completed, keep the temperature at 8 °C and continue to stir for 30 min to complete the first sulfonation; then raise the temperature to 65 °C for the second sulfonation, and continue to stir for 48 min to obtain the reaction solution.

[0029] Cool the reaction solution to 20 °C, slowly drop 1000 mL of deionized water, stir for 10 min, let it stand for liquid - liquid separation, and separate out the lower aqueous phase; extract the aqueous phase 2 times with 2000 mL of dichloroethane to remove the organic phase and retain the purified aqueous phase; transfer the purified aqueous phase to another clean reaction kettle, control the temperature at 20 °C, and slowly drop 48 wt.% sodium hydroxide solution under stirring until the pH = 9, and stir for 3 min; then transfer it to be concentrated under vacuum conditions until the concentration reaches 40 - 50%. Let the concentrated solution cool naturally to room temperature to precipitate white crystals. Filter the crystals by suction and wash them with a small amount of ice water. Dry the crystals under vacuum at 75 °C to obtain 2067.9 g of sodium p - styrenesulfonate finished product.

[0030] Detect the purity by chemical titration method (iodometric method) as 82.1%, and calculate the yield as 82.3%.

[0031] Example 3 Add 30 mol of pyridine to the reaction kettle, and add 4840 mL of tetrachloroethane. Start the stirrer and temperature control device, and introduce 10 mol of sulfur trioxide into the reaction kettle. During the introduction process, maintain the temperature at 15 °C. After the introduction is completed, keep the temperature for 120 min to obtain sulfur trioxide - pyridine complex.

[0032] Take 11 mol of styrene, dissolve it in 5730 mL of tetrachloroethane, add 52.00 g of inhibitor 4,6 - dinitro - 2 - sec - butylphenol, and stir to dissolve to obtain a styrene solution. Slowly drop the styrene solution into sulfur trioxide - pyridine for the first sulfonation, and the dropping time is 60 min; keep the solution temperature at 10 °C during the dropping; after the dropping is completed, keep the temperature at 10 °C and continue to stir for 50 min to complete the first sulfonation; then raise the temperature to 50 °C for the second sulfonation, and continue to stir for 45 min to obtain the reaction solution.

[0033] Cool the reaction solution to 10°C, slowly add 1000 mL of deionized water dropwise, stir for 10 min, let it stand for phase separation, and separate the lower aqueous phase; extract the aqueous phase twice with 2000 mL of dichloroethane, remove the organic phase, and retain the purified aqueous phase; transfer the purified aqueous phase to another clean reaction kettle, control the temperature at 10°C, and slowly add 48 wt.% sodium hydroxide solution dropwise with stirring until the pH reaches 12, and stir for 3 min; then transfer it to be concentrated under vacuum conditions until the concentration reaches 40 - 50%. Let the concentrated solution cool naturally to room temperature to precipitate white crystals. Filter the crystals by suction and wash them with a small amount of ice water. Dry the crystals under vacuum at 65°C to obtain 2080.5 g of the finished product of sodium p-styrenesulfonate.

[0034] The purity was detected by chemical titration method (iodometric method) to be 83.2%, and the yield was calculated to be 84.0%.

[0035] Comparative Example 1 Replace the inhibitor with 2,6-di-tert-butyl-p-cresol, and keep the remaining steps and raw materials the same as in Example 1 to prepare the final product. Test the final product by chemical titration method (iodometric method), the purity is 81.6%, and the yield is calculated to be 62.3%.

[0036] Comparative Example 2 Replace the inhibitor with hydroquinone, and keep the remaining steps and raw materials the same as in Example 1 to prepare the final product. Test the final product by chemical titration method (iodometric method), the purity is 79.3%, and the yield is calculated to be 51.8%.

[0037] Comparative Example 3 Preparation of sodium p-styrenesulfonate using bromine-containing reagent Add 520 g of ethylbenzene, 18 g of anhydrous aluminum chloride and 1250 mL of dichloroethane to a 2500 mL reaction kettle, heat to 135.5°C, add 850 g of liquid bromine dropwise, and the dropping time is 55 min. After the reaction is completed, cool the reactants, wash them 3 times with sodium bicarbonate and water respectively, and obtain 608 g of α-bromoethylbenzene after drying, filtering and vacuum distillation.

[0038] Pass excessive fuming sulfuric acid into 608 g of α-bromoethylbenzene, control the temperature ≤ 5°C. After passing, pressurize with inert gas to 0.8 MPa and heat to 20°C, stir for 30 min, cool to 0°C, add 550 g of sodium bicarbonate and stir for 1 h. After multiple suction filtration, washing and drying, obtain the final product. Test the final product by chemical titration method (iodometric method), the purity is 75.3%, and the yield is calculated to be 71.1%.

[0039] Comparative Example 4 The styrene solution was slowly added dropwise to sulfur trioxide - pyridine for sulfonation, and the dropping time was 60 min; during the dropping, the solution temperature was maintained at 50 °C; after the dropping was completed, the temperature was maintained at 50 °C, and stirring was continued for 95 min to obtain a reaction solution. The remaining steps and raw materials were the same as those in Example 1. The final product was prepared, and the final product was tested by chemical titration method (iodometric method), with a purity of 83.5%, and the calculated yield was 74.6%.

[0040] Implementation effect The reaction conditions in the examples of the present invention are simple and the temperature is moderate. The raw materials used, such as styrene (boiling point 145 °C), pyridine (boiling point 115 °C), sulfur trioxide (≤45 °C when sulfur trioxide is introduced, and sulfur trioxide is in a liquid state at this time), etc., have controllable volatility and toxicity, and the reaction by - products have the advantages of low post - treatment difficulty and relatively low VOCs, which conform to the development trend of green chemistry; in the examples of the present invention, the synthesis process can be carried out at room temperature without complex operations such as low temperature or pressurization, with low equipment investment and simple operation conditions; in the examples of the present invention, the yield of sodium styrene sulfonate is high, the atomic utilization rate of raw materials is high, and there is no situation where atoms such as bromine and chlorine are discharged as waste, which has more advantages in large - scale production.

[0041] In Comparative Example 1, the polymerization inhibitor was replaced with 2,6 - di - tert - butyl - p - cresol (BHT). Due to the large steric hindrance of the two tert - butyl groups, the phenolic hydroxyl group has low reaction activity, weak ability to capture free radicals, and does not have an acidic regulation function. Therefore, 2,6 - di - tert - butyl - p - cresol cannot promote crystallization by adjusting the ionic strength, resulting in a decrease in the subsequent concentration and crystallization efficiency. Infrared spectrum detection of the reaction solution after crystallization in Comparative Example 1 shows that part of sodium styrene sulfonate will remain in the reaction solution, thus affecting the yield of the crystallization link and increasing the mother liquor circulation cost during industrial production.

[0042] In Comparative Example 2, the polymerization inhibitor was replaced with hydroquinone (HQ): it has strong hydrophilicity and low solubility in solvents such as dichloroethane, and uneven distribution leads to local inhibition failure, affecting the yield of sodium styrene sulfonate. It has no nitro group and cannot complex metal ions, and is easily oxidized to quinone impurities, affecting the purity of the sodium styrene sulfonate product.

[0043] Comparative Example 3 used a bromine - containing reagent to prepare sodium styrene sulfonate. It can be seen that the operating conditions of this synthesis route are harsh, bromine - containing wastewater will be generated, the equipment investment is large and the yield is not high. Generally, the factors affecting the yield are: styrene contains double bonds and is prone to self - polymerization reaction under acidic conditions (fuming sulfuric acid) to generate polymer impurities such as polystyrene, resulting in raw material loss. Since it is necessary to ensure the reaction efficiency, fuming sulfuric acid generally needs to be in excess during industrial production, and the reaction will release a large amount of heat, making it difficult to control the temperature.

[0044] Comparative Example 4 only used one - step sulfonation to directly obtain a reaction solution and directly heated it to a relatively high temperature for sulfonation, which easily led to local SO3 At too high a concentration, disulfonation or polysulfonation side reactions are more likely to occur; in the primary sulfonation of the present invention, it is carried out at a relatively low temperature of 0 to 10 °C, and the sulfur trioxide-pyridine complex slowly releases SO 3 , reducing the disulfonation or polysulfonation side reactions caused by too high a local concentration of SO 3 In the secondary sulfonation of the present invention, the temperature is raised to 50 to 65 °C. At this time, SO 3 After the primary sulfonation, there is basically no problem of too high a local concentration. The secondary sulfonation is only used to accelerate the monosulfonation reaction, rather than over-activating SO 3 , thereby avoiding the generation of more by-products.

Claims

1. A method for preparing sodium p-styrene sulfonate, characterized in that: Pyridine is dissolved in an organic solvent A, and sulfur trioxide is introduced therein for complexation to obtain a sulfur trioxide-pyridine complex; styrene is dissolved in an organic solvent B, and a polymerization inhibitor is added therein to obtain a styrene solution; The styrene solution is added to a sulfur trioxide-pyridine complex for primary sulfonation, and the temperature is increased for secondary sulfonation; and then the solution is washed with water, extracted, alkalized, concentrated, crystallized and dried to obtain sodium p-styrene sulfonate.

2. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The organic solvent A is one of dichloroethane, dichloromethane and tetrachloroethane, and the volume ratio of the organic solvent A to pyridine is (2-5):

1.

3. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The molar ratio of pyridine to sulfur trioxide is (1~3):1, the complexation temperature is 15~45°C, and the complexation time is 30~120min.

4. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The organic solvent B is one of dichloroethane, dichloromethane and tetrachloroethane, and the organic solvent A and the organic solvent B are the same solvent, and the volume ratio of the organic solvent B to styrene is (2-5):

1.

5. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The inhibitor is 4,6-dinitro-2-sec-butylphenol or 2,6-dinitro-4-methylphenol, and the concentration of the inhibitor in the styrene solution is 1000-5000 ppm.

6. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The molar ratio of styrene to sulfur trioxide is (1~1.25):

1.

7. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The primary sulfonation temperature is 0~10℃, and the primary sulfonation time is 90~120min.

8. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein The secondary sulfonation temperature is 50~65℃, and the secondary sulfonation time is 45~60min.

9. The method for preparing sodium p-styrene sulfonate according to claim 1, wherein During alkalization, the temperature is controlled at 10~30℃. After alkalization, the pH is 9.0~12.

0.

10. The method for preparing sodium p-styrene sulfonate according to claim 1, characterized in that: The drying temperature is 40~75℃.

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