A method for preparing a three-chain alkyl quaternary ammonium salt

Abstract

The present invention discloses a preparation method of a tri-long-chain alkyl quaternary ammonium salt, which comprises the following steps: adding a tri-long-chain alkyl tertiary amine with a content greater than 97%, isopropanol, sodium borohydride, and propylene oxide into a reaction kettle, displacing with nitrogen three times, heating to 110-120 °C, and introducing methyl chloride for reaction; after the introduction of methyl chloride is completed, keep warm for 4 hours, take a sample for detection, when the detected free amine content is less than 0.5% and the hydrochloride content is less than 0.5%, and the color is less than 2 Gardner, it is qualified. After the detection is qualified, cool down to 85-90 °C to recover methyl chloride. After the recovery of methyl chloride is completed, cool down and discharge the material, evaporate the solvent with a rotary evaporator, and dry to obtain tri-long-chain alkyl ammonium chloride. The present invention shortens the reaction time, reduces the content of unreacted free amine, and reduces the generation of by-product hydrochloride, thereby increasing the content of tri-long-chain alkyl quaternary ammonium salt, and at the same time recycling the excessive methyl chloride.

Description

Technical Field

[0001] This invention belongs to the field of quaternary ammonium salt synthesis technology, specifically relating to a method for preparing a three-long-chain alkyl quaternary ammonium salt. Background Technology

[0002] Aliphatic quaternary ammonium salts are an important component of cationic surfactants and are widely used in textiles as leveling agents and antistatic agents, mineral processing flotation agents, agricultural fertilizers as anti-caking agents, crop herbicides, metal preservatives, pigment dispersants, hair conditioners, and cosmetic emulsifiers.

[0003] The general molecular structural formula of aliphatic quaternary ammonium salts is R4N. + X - R is usually an alkyl group or other group, X - As halide anions, the commonly used quaternary ammonium salts are mainly single-chain and double-chain aliphatic quaternary ammonium salts. Their main preparation method is to react single-chain or double-chain aliphatic tertiary amines with quaternizing agents. Triple-chain alkyl quaternary ammonium salts are prepared by reacting triple-chain alkyl tertiary amines with quaternizing agents. They are widely used as metal extractants and phase transfer catalysts. Due to the large steric hindrance of their triple-chain structure, the reaction is relatively difficult, and the synthesis process often has the characteristics of long reaction time and low conversion rate. In particular, it is difficult to obtain quaternary ammonium salts with a content of more than 95%, light color, and low content of free amine and hydrochloride. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for preparing a three-long-chain alkyl quaternary ammonium salt. This method involves increasing the amount of chloromethane as the quaternizing agent, adding suitable auxiliaries, and changing other reaction conditions to obtain the three-long-chain alkyl quaternary ammonium salt. After the reaction is complete, the excess chloromethane is recovered and used for the next batch of quaternization reaction, ultimately yielding a three-long-chain alkyl quaternary ammonium salt with high content and light color.

[0005] The specific technical solution is as follows:

[0006] A method for preparing a three-chain alkyl quaternary ammonium salt includes the following steps:

[0007] 1) Add three long-chain alkyl tertiary amines, isopropanol, sodium borohydride and propylene oxide with a content greater than 97% to the reaction vessel, purge with nitrogen three times, raise the temperature to 110-120℃, and introduce chloromethane to carry out the reaction.

[0008] 2) After the chloromethane is passed through, keep it at the temperature for 4 hours, take a sample for testing. When the free amine content is less than 0.5% and the hydrochloride content is less than 0.5%, and the color is less than 2 Gardner, it is considered qualified. After the test is qualified, cool down to 85~90℃ to recover the chloromethane. After the chloromethane is recovered, cool down and discharge the material. Use a rotary evaporator to evaporate the solvent and dry it to obtain tri-long-chain alkyl ammonium chloride.

[0009] Furthermore, the amount of isopropanol added is 30-50% of the total material, the amount of sodium borohydride added is 0.03-0.05% of the total material, the amount of propylene oxide added is 0.2-0.4% of the total material, and the molar ratio of chloromethane to tri-long-chain alkyl tertiary amine is 1.2-1.4:1.

[0010] Furthermore, chloromethane is passed through for 1 hour, and the reaction pressure is 0.4-0.5 MPa.

[0011] Furthermore, the three long-chain alkyl tertiary amines are trioctyl tertiary amines, trioctyldecyl tertiary amines, tridecyl tertiary amines, tri(dodecyl) tertiary amines, tri(tetradecyl) tertiary amines, or tri(hexadecyl) tertiary amines.

[0012] Furthermore, the chloromethane recovery process includes the following steps: opening the connecting valve between the reaction vessel and the chloromethane recovery vessel; a reflux condensation device is installed between the reaction vessel and the chloromethane recovery vessel; during the recovery process, isopropanol in the reaction vessel is condensed and refluxed back to the reaction vessel, while chloromethane evaporates into the recovery vessel and is absorbed by the solvent; a chloromethane recovery rate of 90% or higher is considered the end of the recovery process.

[0013] Furthermore, the solvent in the chloromethane recovery vessel is isopropanol.

[0014] Furthermore, the temperature of the recovery vessel is 25-35℃.

[0015] The beneficial effects of this invention are: while shortening the reaction time, reducing the content of unreacted free amines and reducing the generation of byproduct hydrochloride, thereby increasing the content of tri-chain alkyl quaternary ammonium salts, and simultaneously recovering and reusing excess chloromethane. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0017] Example 1

[0018] Preparation of trioctylammonium chloride

[0019] 400g of 97.5% pure trioctyl tertiary amine, 195.9g of isopropanol, 0.2g of sodium borohydride, and 1.3g of propylene oxide were added to a reaction vessel. The reaction vessel was purged with nitrogen three times. The temperature was raised to 110℃, and 68.5g of chloromethane was passed through the vessel over one hour. The reaction pressure was 0.4 MPa. The amount of isopropanol added was 30% of the total amount, sodium borohydride was 0.03%, and propylene oxide was 0.2%. The molar ratio of chloromethane to the tri-long-chain alkyl tertiary amine was 1.2:1. After the chloromethane was passed through, the mixture was kept at approximately 110℃ for 4 hours. The sample was taken and tested. The free amine content was 0.29%, the hydrochloride content was 0.32%, and the color was less than 1 Gardner. The temperature was lowered to 85℃ to begin chloromethane recovery. The amount of isopropanol in the recovery vessel was 200g. The temperature of the chloromethane recovery vessel was maintained at 25℃. The recovery process was carried out at 85℃ for 3 hours. At the end of the recovery, 210.4g of chloromethane-isopropanol solution was obtained, with a theoretical chloromethane recovery rate of 91%. After chloromethane recovery was complete, the reaction vessel was cooled to 60℃ and discharged. The solvent in the crude quaternary ammonium salt was evaporated using a rotary evaporator and dried to obtain trioctylammonium chloride. Titration analysis showed that the quaternary ammonium salt content was 96.2%.

[0020] Example 2

[0021] Preparation of Trioctyldecylammonium Chloride

[0022] 350g of 97.4% pure trioctyldecyl tertiary amine, 210.4g of the chloromethane isopropanol solution recovered in Example 1, 63.1g of fresh isopropanol, 0.27g of sodium borohydride, and 2.0g of propylene oxide were added to a reaction vessel. The reaction vessel was purged with nitrogen three times. The temperature was raised to 115°C, and 47.7g of chloromethane was passed through the vessel over one hour. The reaction pressure was 0.45 MPa. The amount of isopropanol added was 40% of the total amount, sodium borohydride was 0.04% of the total amount, and propylene oxide was 0.3% of the total amount. The molar ratio of chloromethane to tri-long-chain alkyl tertiary amine was 1.3:1. After the chloromethane was passed through the vessel, the temperature was maintained at approximately 115°C for 4 hours. Samples were taken and tested. The free amine content was 0.36%, the hydrochloride content was 0.28%, and the color was 1 Gardner. The temperature was lowered to 88℃ to begin the recovery of chloromethane. The amount of isopropanol in the recovery vessel was 300g, and the temperature of the chloromethane recovery vessel was maintained at 30℃. The recovery process was carried out at a reaction vessel temperature of 88℃ for 2.5 hours. After the recovery was completed, 312.3g of chloromethane isopropanol solution was obtained, with a theoretical recovery rate of 92% for chloromethane. After the chloromethane recovery was completed, the reaction vessel was cooled to 62℃ and the product was discharged. The solvent in the crude quaternary ammonium salt was evaporated using a rotary evaporator and dried to obtain trioctyldecylammonium chloride. The quaternary ammonium salt content was determined by titration to be 96.1%.

[0023] Example 3

[0024] Preparation of tri(twelfyl)alkylammonium chloride

[0025] 300g of tri(dodecyl)amine with a purity of 97.6%, 312.3g of chloromethane isopropanol solution recovered in Example 2, 29g of fresh isopropanol, 0.34g of sodium borohydride, and 2.7g of propylene oxide were added to a reactor. The reactor was purged with nitrogen three times. The temperature was raised to 120°C, and 28.4g of chloromethane was passed through the reactor over one hour. The reaction pressure was 0.5 MPa. The amount of isopropanol added was 50% of the total amount, sodium borohydride was 0.05% of the total amount, and propylene oxide was 0.4% of the total amount. The molar ratio of chloromethane to tri-long-chain alkyl tertiary amine was 1.4:1. After the chloromethane was passed through the reactor, the temperature was maintained at approximately 120°C for 4 hours. Samples were taken and tested. The free amine content was 0.42%, and the hydrochloride content was 0.21%. The color was 1 Gardner. The temperature was lowered to 90℃ to begin chloromethane recovery. The amount of isopropanol in the recovery vessel was 300g, and the temperature of the chloromethane recovery vessel was 35℃. During the recovery process, the temperature of the reaction vessel was maintained at 90℃ for 2 hours. After the recovery was completed, 310.6g of chloromethane isopropanol solution was obtained, with a theoretical recovery rate of 91.5% for chloromethane. After the chloromethane recovery was completed, the reaction vessel was cooled to 65℃ and discharged. The solvent in the crude quaternary ammonium salt was evaporated using a rotary evaporator and dried to obtain tri(dodecyl)ammonium chloride. The quaternary ammonium salt content was determined by titration to be 96.2%.

[0026] Comparative Example 1

[0027] Preparation of Trioctyldecylammonium Chloride

[0028] 350g of 97.4% pure trioctyldecyl tertiary amine and 263.1g of isopropanol were added to a reaction vessel. The reaction vessel was purged with nitrogen three times. The temperature was raised to 90℃, and 49.1g of chloromethane was passed through the vessel over one hour. The reaction pressure was 0.35 MPa. The amount of isopropanol added was 40% of the total material. The molar ratio of chloromethane to the tri-long-chain alkyl tertiary amine was 1.1:1. After the chloromethane was passed through, the reaction vessel was kept at approximately 90℃ for 5 hours. Samples were taken and tested to find that the free amine content was 1.9% and the hydrochloride content was 2.6%, with a color of 3 Gardner. After the chloromethane was recovered, the reaction vessel was cooled to 60℃ and the product was discharged. The isopropanol solvent in the crude quaternary ammonium salt was evaporated using a rotary evaporator. The product was dried to obtain trioctyldecyl ammonium chloride, and the quaternary ammonium salt content was determined by titration to be 91.8%.

[0029] Comparative Example 2

[0030] Preparation of tri(twelfyl)alkylammonium chloride

[0031] 300g of tri(dodecyl)amine with a purity of 97.3% and 329g of isopropanol were added to a reaction vessel. The reaction vessel was purged with nitrogen three times. The temperature was raised to 100℃, and 29.1g of chloromethane was passed through the vessel over one hour. The reaction pressure was 0.3 MPa. The amount of isopropanol added was 50% of the total material. The molar ratio of chloromethane to tri(dodecyl)amine was 1:1. After the chloromethane was passed through, the temperature was maintained at approximately 100℃ for 12 hours. Samples were taken and tested to find that the free amine content was 1.6% and the hydrochloride content was 2.8%, with a color of 4 Gardner. The mixture was cooled to 65℃ and discharged. The isopropanol solvent in the crude quaternary ammonium salt was evaporated using a rotary evaporator and dried to obtain tri(dodecyl)ammonium chloride. The quaternary ammonium salt content was determined by titration to be 91.6%.

[0032] When the amount of chloromethane added is small and the temperature is low, the reaction time is long and the free amine concentration is high. Without the addition of auxiliary agents, the hydrochloride content is high and the color is dark, resulting in a low overall quaternary ammonium salt content.

Claims

1. A method for preparing a three-chain alkyl quaternary ammonium salt, characterized in that... Includes the following steps: 1) Add three long-chain alkyl tertiary amines, isopropanol, sodium borohydride and propylene oxide with a content greater than 97% to the reaction vessel, purge with nitrogen three times, raise the temperature to 110-120℃, and introduce chloromethane to carry out the reaction. 2) After the chloromethane is passed through, keep it at the temperature for 4 hours, take a sample for testing. When the free amine content is less than 0.5% and the hydrochloride content is less than 0.5%, and the color is less than 2 Gardner, it is considered qualified. After passing the test, cool down to 85~90℃ to recover the chloromethane. After the chloromethane is recovered, cool down and discharge the material. Use a rotary evaporator to evaporate the solvent and dry it to obtain tri-long-chain alkyl ammonium chloride. The amount of propylene oxide added is 0.2-0.4% of the total material weight; The chloromethane recovery process includes the following steps: opening the connecting valve between the reaction vessel and the chloromethane recovery vessel; a reflux condensation device is installed between the reaction vessel and the chloromethane recovery vessel; isopropanol in the reaction vessel is condensed and refluxed back into the reaction vessel; chloromethane evaporates into the chloromethane recovery vessel and is absorbed by the solvent; a chloromethane recovery rate of over 90% is considered the end of the recovery process. The solvent in the chloromethane recovery reactor is isopropanol, and the temperature of the chloromethane recovery reactor is 25-35℃. The three long-chain alkyl tertiary amines are trioctyl tertiary amine, trioctyldecyl tertiary amine, tridecyl tertiary amine, tri(dodecyl) tertiary amine, tri(tetradecyl) tertiary amine or tri(hexadecyl) tertiary amine.

2. The method for preparing a three-chain alkyl quaternary ammonium salt as described in claim 1, characterized in that... The amount of isopropanol added is 30-50% of the total material weight, the amount of sodium borohydride added is 0.03-0.05% of the total material weight, and the molar ratio of chloromethane to tri-long-chain alkyl tertiary amine is 1.2~1.4:

1.

3. The method for preparing a three-chain alkyl quaternary ammonium salt as described in claim 2, characterized in that... Chloromethane is passed through in 1 hour, and the reaction pressure is 0.4-0.5 MPa.