Method for preparing tetramethylammonium bromide by using byproduct methanol in isothiazolinone production process
During the isothiazolinone production process, the by-product methanol is reacted with methane bromide to prepare tetramethylammonium bromide, which solves the problem of difficulty in removing methylamine in methanol and improves the economic value and economic benefits of the product.
Patent Information
- Application Number
- CN202510099102.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2025-05-30
AI Technical Summary
During the production process of isothiazolinone, the by-product methanol contains methylamine, which makes it difficult to effectively remove it and affects the economic benefits of the product.
Tetramethyl ammonium bromide was produced by reacting by-product methanol with methane bromide under specific conditions, and a high-purity methanol solution of tetramethyl ammonium bromide and hydrogen bromide was obtained by distillation and filtration.
The efficient preparation of tetramethylammonium bromide is achieved, which improves the economic value of the product. By recycling the filtrate and methanol, the waste of raw materials is reduced and economic benefits are enhanced.
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of isothiazolinone production, and specifically relates to a method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone. Background Art
[0002] Isothiazolinone preservatives are a mixture of 2-methyl-4-isothiazolin-3-one (MIT), 2-methyl-5-chloro-4-isothiazolin-3-one (CMI), and an inorganic salt stabilizer. This mixture is also known as KATHON, and usually CMI:MIT = 3:1. It is an excellent fungicide, commonly used in finished cosmetics, shampoos, and conditioners, and is a preservative for inhibiting the growth of microorganisms. It has good inhibitory effects on yeasts, fungi, Gram-positive bacteria, heterotrophic bacteria, algae, etc., and is widely used in the sterilization and anti-corrosion treatment of textile, paper-making, oil refining, cosmetics, cleaning agents, oilfield water injection, sewage treatment and other fields. Due to the excellent bactericidal and anti-corrosion effects of isothiazolinone products, many domestic companies produce them. The manufacturing route is to use methyl acrylate as the starting material, and through esterification, acylation, and chlorination reactions to obtain a mixture of 2-methyl-4-isothiazolin-3-one (MI) and 2-methyl-5-chloro-4-isothiazolin-3-one (CMI), and then through compounding with inorganic salts and other auxiliary materials to obtain isothiazolinone (KATHON).
[0003] During the acylation reaction for manufacturing KATHON, a large amount of by-product methanol is generated, which contains approximately 10% methylamine, 0.2% water, and the rest is methanol. Since methylamine in methanol is not easily removed by simple methods, and refining methanol by more complex methods requires mobilizing a large amount of manpower and financial resources, most factories sell it at a very low price and use it for low-grade products with low requirements. Such as being used as a thinner for low-grade paints and coatings, an additive for crude oil products, etc., reducing the economic benefits of the products. Summary of the Invention
[0004] The technical problem to be solved by the present invention is: aiming at the deficiencies existing in the prior art, to provide a method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone, thereby improving the economic benefits of the products.
[0005] To solve the above technical problem, the technical solution of the present invention is:
[0006] A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone, comprising the following steps:
[0007] A: Add the by-product methanol into a reaction kettle, heat it up to 70 - 90 °C, and stir evenly;
[0008] B: Introduce methyl bromide gas into the reactor, control the pressure in the reactor at 0.1 - 0.3 MPa, and react for 2 - 4 h to obtain a reaction solution;
[0009] C: Distill the reaction solution under a vacuum of -0.095 MPa and at a temperature of 45 - 55 °C, and collect the concentrated solution;
[0010] D: Filter the concentrated solution and collect the filter cake to obtain tetramethylammonium bromide.
[0011] Preferably, collect the distillate after distilling the reaction solution to obtain a methanol solution containing hydrogen bromide.
[0012] Preferably, in step C, stop concentration after distilling until the reaction solution turns white and uniform bubbles appear on the liquid surface.
[0013] Preferably, cool the concentrated solution to below 5 °C and then filter in step D.
[0014] Preferably, the filtrate in step D is recycled to the reaction solution of the next batch.
[0015] Preferably, wash the filter cake in step D with methanol and dry it to obtain tetramethylammonium bromide.
[0016] Preferably, the content of tetramethylammonium bromide in step D is > 99.8%, and the moisture content is < 0.2%.
[0017] Preferably, the content of hydrogen bromide in the methanol solution containing hydrogen bromide is > 40%, and the moisture content is < 0.2%.
[0018] Preferably, the molar ratio of methylamine to methyl bromide in step B is 1:3 - 3.02
[0019] Preferably, the methanol collected during the drying process is sold.
[0020] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:
[0021] 1. There are lone electron pairs on the nitrogen atom of methylamine, making it have certain nucleophilicity. The carbon-bromine bond in methyl bromide is a polar bond. The electronegativity of the bromine atom is greater than that of the carbon atom, so the electron cloud is biased towards the bromine atom, making the carbon atom carry partial positive charges. During the nucleophilic reaction, the nitrogen atom of methylamine will attack the carbon atom with partial positive charges in methyl bromide to make the bromine atom leave, generating dimethylamine, trimethylamine, and hydrogen bromide. The reaction equation is as follows:
[0022] CH 3 NH 2 +CH 3 Br→(CH 3 ) 2 NH+HBr
[0023] (CH3 ) 2 NH+CH 3 Br→(CH 3 ) 3 N+HBr
[0024] (CH 3 ) 3 N+CH 3 Br→(CH 3 ) 4 NBr。
[0025] 2. The product tetramethylammonium bromide is commonly used as a phase transfer catalyst, especially suitable for heterogeneous organic transformation reactions. It has good water solubility and solubility in organic solvents, and can transfer reactants between the aqueous phase and the organic phase, thus promoting the progress of the reaction. In addition, tetramethylammonium bromide can also be used as an analytical reagent, mainly for the determination of alkali metals and alkaline earth metals. In other application fields, tetramethylammonium bromide can be used as a flame retardant to improve the flame retardant performance of materials; as a surfactant, it plays a role in sterilization and disinfection in detergents; it can also be used as a wood mildew preventive to prevent wood from mildewing. This patent further illustrates that a methanol solution of hydrogen bromide is also generated while producing tetramethylammonium bromide. The methanol solution of hydrogen bromide is widely used as a brominating agent in organic reactions in etherification reactions and esterification reactions. It is used as a salt-forming agent in the pharmaceutical industry. This greatly improves the economic value of the product.
[0026] 3. The methanol collected during the drying process after washing the filter cake can be sold, and the filtrate is applied to the next batch of reaction solutions, reducing the waste of raw materials, improving the economic benefits of the product, and being environmentally friendly at the same time. Detailed implementation mode
[0027] The present invention will be further described below in conjunction with the embodiments.
[0028] Example 1
[0029] Add 1200 g of the by-product methanol solution obtained from the preparation of cason acylation reaction with a methylamine content of 10.5% w / w into a 2 L autoclave, and seal the reaction kettle. Under stirring, 1157.3 g of methyl bromide is uniformly introduced at 85 °C, and the reaction is carried out at a controlled pressure of 0.2 MPa for 3 h. After the reaction is completed, the vacuum degree is controlled at -0.095 MPa, and methanol distillation is carried out. When the kettle temperature reaches 50 °C, the distillation is stopped. Under stirring, the materials in the kettle are cooled to 5 °C and filtered. The filtrate is applied to the next batch of reaction solutions, and the filter cake is washed with a little methanol and dried. 600.6 g of tetramethylammonium bromide is obtained, with a content of 99.85% and a moisture content of 0.18%; 1457.7 g of a methanol solution of hydrogen bromide is obtained, with a content of 45.12% and a moisture content of 0.18%.
[0030] Example 2
[0031] Add 1200 g of the by-product methanol solution for the preparation of cason acylation reaction with a methylamine content of 10.0% into a 2 L high-pressure reactor, and seal the reactor. Under stirring, uniformly introduce 1102.1 g of methyl bromide at 90 °C, control the pressure at 0.3 MPa, and react for 2 h. After the reaction is completed, control the vacuum degree at -0.095 MPa and carry out methanol distillation. Stop distillation when the reactor temperature reaches 55 °C. Cool the material in the reactor to 5 °C under stirring and filter. The filtrate is recycled to the next batch of reaction solution, and the filter cake is washed with a little methanol and dried. Obtain 571.9 g of tetramethylammonium bromide with a content of 99.91% and a moisture content of 0.17%; obtain 1426.3 g of hydrobromic acid methanol solution with a hydrobromic acid content of 43.91% and a moisture content of 0.16%.
[0032] Example 3
[0033] Add 1200 g of the by-product methanol solution obtained from the preparation of cason acylation reaction with a methylamine content of 10.3% w / w into a 2 L autoclave, and seal the autoclave. Under stirring, uniformly introduce 1130.0 g of methyl bromide at 70 °C, control the pressure at 0.1 MPa, and react for 4 h. After the reaction is completed, control the vacuum degree at -0.095 MPa and carry out methanol distillation. Stop distillation when the reactor temperature reaches 45 °C. Cool the material in the reactor to 5 °C under stirring and filter. The filtrate is recycled to the next batch of reaction solution, and the filter cake is washed with a little methanol and dried. Obtain 582.9 g of tetramethylammonium bromide with a content of 99.88% and a moisture content of 0.15%; obtain 1435.5 g of hydrobromic acid methanol solution with a content of 44.3% and a moisture content of 0.18%.
[0034] It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.
Claims
1. A method for preparing tetramethylammonium bromide using by-product methanol in the production process of isothiazolinone, characterized in that The following steps are involved: A: Add by-product methanol into the reactor, heat to 70-90℃, and stir evenly; B: introduce methyl bromide gas into the reactor, control the pressure in the reactor to 0.1-0.3MPa, react for 2-4h to obtain a reaction liquid; C: The reaction solution is distilled at a vacuum of -0.095 MPa and a temperature of 45-55°C, and the concentrate is collected; D: After filtering the concentrated liquid, collect the filter cake to obtain tetramethylammonium bromide.
2. A method for preparing tetramethylammonium bromide using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The distillate after distillation of the reaction solution is collected to obtain a methanol solution containing hydrogen bromide.
3. A method for preparing tetramethylammonium bromide using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: In step C, the concentration is stopped after the reaction liquid turns white and uniform bubbles are generated on the liquid surface.
4. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The concentrated solution in step D is cooled to below 5°C and then filtered.
5. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The filtrate in step D is returned to the next batch of reaction solution.
6. A method for preparing tetramethylammonium bromide using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The filter cake in step D is washed with methanol and dried to obtain tetramethylammonium bromide.
7. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The content of tetramethylammonium bromide in step D is greater than 99.8%, and the water content is less than 0.2%.
8. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone according to claim 1, characterized in that: The molar ratio of methylamine to methyl bromide in step B is 1:3-3.
02.
9. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone as claimed in claim 2, characterized in that: The content of hydrogen bromide in the methanol solution containing hydrogen bromide is greater than 40%, and the water content is less than 0.2%.
10. A method for preparing tetramethylammonium bromide by using by-product methanol in the production process of isothiazolinone according to claim 6, characterized in that: The methanol collected during the drying process is sold.