Synthetic method of methylparaben
By using a strong acid cation exchange resin as a catalyst during the synthesis of methylparaben and removing moisture by distillation, the problems of long reaction time and low yield in the existing synthesis methods are solved, and efficient methylparaben synthesis is achieved, with improved yield and catalysts being recycled.
Patent Information
- Application Number
- CN202411970545.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-03-28
AI Technical Summary
In the existing methylparaben synthesis method, the reaction time is long and the yield is difficult to improve. It is mainly because methanol and water are not azeotropic, which causes water to accumulate in the reaction system, reduce the concentration of methanol and catalyst, and thus slow down the reaction rate.
Strong acid cation exchange resin is used as a catalyst, and water is continuously removed through distillation during the synthesis process, so that the reaction equilibrium is shifted to the right, and the yield of methylparaben is increased. The method includes adding a catalyst and heating the treatment by retrieving the methanol solution several times until the reaction is complete, filtering and recovering the catalyst, and finally obtaining methylparaben ester by distillation.
The water is removed by distillation, maintaining high concentrations of methanol and catalysts, which significantly improves the yield of methylparaben and simplifies the post-treatment process, and the catalyst can be recycled, in line with the concept of green chemistry.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of methyl paraben synthesis, and in particular to a method for synthesizing methyl paraben. Background Art
[0002] Parabens, also known as parabens, are a type of safe and effective preservatives used internationally and are widely used in food, cosmetics, and pharmaceutical industries. Parabens, sodium benzoate, and potassium sorbate are the three major internationally used preservatives. Except for parabens, the others are acidic preservatives, that is, they have good preservative effects under acidic conditions. Parabens have a wide pH range of use and have good preservative effects within the range of pH = 3 to 8. At the same time, it also has the characteristics of low toxicity, high efficiency, and low dosage. It is one of the food preservatives that my country focuses on developing. Commonly used ones are methyl paraben, ethyl paraben, and propyl paraben. At present, in some European and American countries, methyl paraben is a widely used preservative, and has been widely used in food, medicine, cosmetics and other fields.
[0003] Generally, the synthesis of methylparaben is based on the reaction of p-hydroxybenzoic acid and excess methanol under the catalysis of concentrated sulfuric acid. A large amount of concentrated sulfuric acid needs to be repeatedly washed and removed with concentrated NaOH and NaCO3 solutions, resulting in complex separation and purification and serious equipment corrosion. In order to solve this problem, a large number of studies have used solid acids, super solid acids, and loaded acids as catalysts.
[0004] Although the use of these catalysts solves the above problems, whether liquid acid or solid acid catalyst is used, it faces a problem: since methanol cannot be azeotropic with water and methanol has a low boiling point, it is difficult to find a suitable dehydrating agent. As the reaction proceeds, more and more water is added to the reaction system, which makes the concentration of methanol and catalyst lower and lower, and the reaction becomes slower and slower. Therefore, the synthesis reaction time of methyl paraben is long and the yield is difficult to improve. Summary of the invention
[0005] In order to improve the defects of the existing methyl paraben synthesis reaction time being long and the yield being difficult to improve, the present application provides a method for synthesizing methyl paraben.
[0006] A method for synthesizing methyl paraben, comprising the following synthesis method: Taking p-hydroxybenzoic acid and methanol as raw materials, adding catalyst materials and heating them to reflux reaction; After the methanol solution is distilled out, methanol is continued to be added and stirred for reaction, the above steps are repeated and the methanol solution is recovered multiple times until the p-hydroxybenzoic acid is completely reacted, the reaction is stopped and filtered, the filtrate is collected and the catalyst material is recovered, the methanol is distilled off, and crystals are precipitated to prepare methyl paraben; The catalyst material includes a strong acid cation exchange resin.
[0007] By adopting the above technical scheme, the present application adopts a strong acid cation exchange resin as a catalyst, and distills out water during the synthesis process, so that the water in the reaction system is continuously removed, and the reaction balance is continuously shifted to the right, which is conducive to improving the yield of methyl paraben. In addition, the concentrations of methanol and the catalyst in the later stage of the reaction are almost unchanged, and the reaction rate is not affected. The cation exchange resin catalyst simplifies the post-processing process and can be recycled.
[0008] Furthermore, the strong acid cation exchange resin is T-62 MP DRY catalyst grade strong acid cation exchange resin.
[0009] Through the above technical solution, this application uses T-62 MP DRY strong acid cation exchange resin, whose internal structure is specially designed to have a large specific surface area and high acid density. These characteristics make it show excellent activity and selectivity when catalyzing esterification reactions, and can effectively promote the reaction between p-hydroxybenzoic acid and methanol at a lower temperature. At the same time, the T-62 MP DRY catalyst used in this application can be put into use again after simple cleaning and regeneration after use. This not only reduces the emission of waste, but also reduces the consumption of raw materials, which is in line with the concept of green chemistry.
[0010] Furthermore, the mass ratio of the catalyst material to p-hydroxybenzoic acid is (2-3):3.
[0011] Through the above technical solution, the present application further optimizes the mass ratio of catalyst material to p-hydroxybenzoic acid. According to Le Chatelier principle, increasing the amount of catalyst can promote the reaction in the positive direction to a certain extent. However, with the increase of catalyst concentration, the growth of reaction rate is not a linear relationship, but gradually tends to saturation. Within this range, the ratio of (2-3): 3 can ensure sufficient catalytic activity without wasting resources.
[0012] Furthermore, the molar ratio of the p-hydroxybenzoic acid to the total amount of methanol is 1:(3-6).
[0013] Through the above technical scheme, the present application optimizes the molar ratio of p-hydroxybenzoic acid to the total amount of methanol. The setting of this ratio is intended to ensure that there is enough methanol to drive the esterification reaction during the reaction and to minimize the generation of by-products. A higher methanol molar ratio helps to ensure that all p-hydroxybenzoic acid can react fully and reduce the presence of unreacted substrate.
[0014] Furthermore, after the heating reflux reaction for 50-80 minutes, the methanol solution is recovered.
[0015] Furthermore, the heating reflux reaction temperature is >80°C.
[0016] Furthermore, in the multiple times of recovering the methanol solution, the temperature of the methanol solution recovered for the last time is 90°C.
[0017] By adopting the above technical scheme, the present application further optimizes the heating reflux reaction temperature, at which the strong acid cation exchange resin shows higher catalytic activity at a higher temperature. This is because high temperature enhances the energy of the active sites on the resin surface, making it more effective in adsorbing and activating reactant molecules. In addition, high temperature can also prevent the catalyst from being deactivated or poisoned due to low temperature, ensuring that it remains efficient throughout the reaction process. At the same time, the present application further adjusts the temperature of the last recovery of the methanol solution, which helps to ensure that all the p-hydroxybenzoic acid has been fully reacted and the methanol is thoroughly distilled out. Operation within this temperature range can effectively avoid the problem of incomplete reaction or decreased product purity caused by residual methanol.
[0018] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application uses a strong acidic cation exchange resin as a catalyst, and distills out water during the synthesis process, so that the water in the reaction system is continuously removed, and the reaction equilibrium is continuously shifted to the right, which is beneficial to the increase in the yield of methyl paraben. In addition, the concentrations of methanol and the catalyst are almost unchanged in the later stage of the reaction, and the reaction rate is not affected. The cation exchange resin catalyst simplifies the post-processing process and can be recycled; 2. This application uses T-62 MP DRY strong acid cation exchange resin, whose internal structure is specially designed and has a large specific surface area and high acid density. These characteristics make it exhibit excellent activity and selectivity when catalyzing esterification reactions, and can effectively promote the reaction between p-hydroxybenzoic acid and methanol at a lower temperature. At the same time, the T-62 MP DRY catalyst used in this application can be put into use again after simple cleaning and regeneration. This not only reduces the emission of waste, but also reduces the consumption of raw materials, which is in line with the concept of green chemistry; 3. This application further optimizes the mass ratio of catalyst material to p-hydroxybenzoic acid. According to Le Chatelier principle, increasing the amount of catalyst can promote the reaction in the positive direction to a certain extent. However, with the increase of catalyst concentration, the growth of reaction rate is not a linear relationship, but gradually tends to saturation. Within this range, the ratio of (2-3): 3 can ensure sufficient catalytic activity without wasting resources; 4. The present application further optimizes the heating reflux reaction temperature, at which the strong acid cation exchange resin exhibits higher catalytic activity at higher temperatures. This is because high temperature enhances the energy of the active sites on the resin surface, allowing it to more effectively adsorb and activate reactant molecules. In addition, high temperature can also prevent the catalyst from being deactivated or poisoned by low temperature, ensuring that it remains efficient throughout the entire reaction process. At the same time, the present application further adjusts the temperature of the last recovery of the methanol solution, which helps to ensure that all the p-hydroxybenzoic acid has been fully reacted and the methanol has been thoroughly distilled out. Operations within this temperature range can effectively avoid problems such as incomplete reactions or decreased product purity due to residual methanol. DETAILED DESCRIPTION
[0019] The present application is further described in detail below with reference to the embodiments.
[0020] In the examples of the present application, the raw materials and instruments used are as follows, but not limited thereto. Raw materials not otherwise specified are of analytical grade.
[0021] T-62 MP DRY strong acid cation exchange resin: Kehaisi (Beijing) Technology Co., Ltd.
[0022] Example 1 A method for synthesizing methyl paraben, comprising the following synthesis method: According to the mass ratio of 1:6, 1000g of p-hydroxybenzoic acid and 6000g of methanol are taken as raw materials, 1000g of T-62 MPDRY strong acid cation exchange resin is first added, 2200g of methanol is added while stirring, and then all the p-hydroxybenzoic acid is added, stirred and mixed, and the temperature is raised to 85°C, and the mixture is heated and refluxed for 1h, and the mixture of methanol and water is recovered; 2000g of methanol is added for the second time, stirring and reacting is continued, the temperature is raised to 90°C, and the mixture is heated and refluxed for 1h, and the mixture of methanol and water is recovered; 1800g of methanol is added for the third time, stirring and reacting is continued, the temperature is raised to 87°C, and the mixture is heated and refluxed for 1h, and the mixture of methanol and water is recovered, the filtrate is filtered and collected, and the excess methanol is distilled off and crystals are precipitated to prepare methyl paraben.
[0023] Example 2 A method for synthesizing methyl paraben, comprising the following synthesis method: Take 1000g of p-hydroxybenzoic acid and 4500g of methanol as raw materials, first add 833g of T-62 MP DRY strong acid cation exchange resin, add 1700g of methanol while stirring, then add all the p-hydroxybenzoic acid, stir and mix, heat to 85°C, heat and reflux for 1h, and recover the mixture of methanol and water; add 1500g of methanol for the second time, continue to stir and react, heat to 90°C, heat and reflux for 1h, and recover the mixture of methanol and water; add 1300g of methanol for the third time, continue to stir and react, heat to 88°C, heat and reflux for 1h, recover the mixture of methanol and water, filter and collect the filtrate, distill to remove excess methanol, precipitate crystals, and prepare methyl paraben.
[0024] Example 3 A method for synthesizing methyl paraben, comprising the following synthesis method: Take 1000g of p-hydroxybenzoic acid and 3000g of methanol as raw materials, first add 666g of T-62 MP DRY strong acid cation exchange resin, add 1200g of methanol while stirring, then add all the p-hydroxybenzoic acid, stir and mix, heat to 85°C, heat and reflux for 1h, and recover the mixture of methanol and water; add 1000g of methanol for the second time, continue to stir and react, heat to 90°C, heat and reflux for 1h, and recover the mixture of methanol and water; add 800g of methanol for the third time, continue to stir and react, heat to 90°C, heat and reflux for 1h, recover the mixture of methanol and water, filter and collect the filtrate, distill to remove excess methanol, precipitate crystals, and prepare methyl paraben.
[0025] Performance Testing The performance of methylparaben prepared in Examples 1-3 was tested, and the content of methylparaben in the heat preservation and reflux for 1h, 2h and 3h was tested respectively. The results are shown in Table 1 below: Table 1 Performance test table
[0026] From the above examples 1-3, combined with the test results in Table 1, it can be found that: First, it can be found from Examples 1-3 that the present application uses a strong acid cation exchange resin as a catalyst and distills out water during the synthesis process, so that the water in the reaction system is continuously removed and the reaction equilibrium is continuously shifted to the right, which is beneficial to the increase in the yield of methyl paraben.
[0027] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.
[0028] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.
[0029] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.
[0030] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.
Claims
1. A method for synthesizing methylparaben, characterized in that: The following synthesis methods are included: Taking p-hydroxybenzoic acid and methanol as raw materials, adding catalyst materials and heating them to reflux reaction; After the methanol solution is distilled out, methanol is continued to be added and stirred for reaction, the above steps are repeated and the methanol solution is recovered multiple times until the p-hydroxybenzoic acid is completely reacted, the reaction is stopped and filtered, the filtrate is collected and the catalyst material is recovered, the methanol is distilled off, and crystals are precipitated to prepare methyl paraben; The catalyst material includes a strong acid cation exchange resin.
2. A method for synthesizing methylparaben according to claim 1, characterized in that: The strong acid cation exchange resin is T-62 MP DRY catalyst grade strong acid cation exchange resin.
3. A method for synthesizing methylparaben according to claim 1, characterized in that: The mass ratio of the catalyst material to p-hydroxybenzoic acid is (2-3):
3.
4. A method for synthesizing methylparaben according to claim 1, characterized in that: The molar ratio of the p-hydroxybenzoic acid to the total amount of methanol is 1:(3-6).
5. A method for synthesizing methylparaben according to claim 1, characterized in that: After the heating reflux reaction for 50-80 minutes, the methanol solution is recovered.
6. A method for synthesizing methylparaben according to claim 1, characterized in that: The heating reflux reaction temperature is >80°C.
7. A method for synthesizing methylparaben according to claim 1, characterized in that: In the multiple recovering of the methanol solution, the temperature of the methanol solution recovered for the last time is 90°C.