Preparation method of lauryl betaine

Abstract

The invention discloses a lauryl betaine preparation method, which comprises: 1, preparing sodium monochloroacetate: adding 30-40 g of monochloroacetic acid into a three-neck flask provided with a thermometer and a stirrer, adding a proper amount of water to dissolve, uniformly stirring, slowly adding 240-280 g of a 20% alkaline solution into the monochloroacetic acid solution, stirring while controlling the pH value to be 6.5-7.0, and carrying out a reaction for 2-3 h to obtain sodium monochloroacetate; the reaction temperature is controlled below 60 DEG C until the neutralization is complete; 2, 60-75 g of dodecyl dimethyl tertiary amine is added into the sodium monochloroacetate solution to ensure complete dissolution, the temperature of a reaction system is controlled to range from 60 DEG C to 85 DEG C to react for 5-12 h in an oil bath provided with a temperature controller, 50 ml of 80% ethanol solution is added, and full stirring is conducted; 3, after the reaction is completed, the solution is naturally cooled to the room temperature. Filtering, washing and drying to obtain lauryl betaine, and distilling to obtain purified lauryl betaine. By coordinating the specific reaction conditions and process in the preparation process, the content of active substances in lauryl betaine is high, and the appearance reaches the standard.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to a preparation method of lauryl betaine. BACKGROUND

[0002] Lauryl betaine (also known as "dodecyldimethylbetaine") is an amphoteric surfactant, which has good washing, foaming, softening, antistatic, dispersing and sterilization and disinfection properties. It can remain stable in a wide pH range and can be mixed with anionic, cationic and non-ionic surfactants, and is therefore widely used in the fields of shampoo, shower gel, fabric finishing agent, dyeing aid, calcium soap dispersant, dry cleaning surfactant and metal corrosion inhibitor.

[0003] With the increasing demand of consumers for the performance of daily chemical products, especially the pursuit of mildness, environmental protection and high efficiency, the market demand for amphoteric surfactants such as lauryl betaine is increasing. The product not only can provide excellent cleaning effect, but also has the characteristics of low toxicity and low irritation, and is suitable for manufacturing non-irritating conditioning shampoo, fiber softener and antistatic agent.

[0004] The preparation of lauryl betaine is usually realized by chemical reaction, mainly involving quaternization reaction. In the reaction process, monochloroacetic acid (or sodium chloroacetate) and tertiary amine (such as a mixture of N,N-dimethyldodecylamine and N,N-dimethyltetradecylamine) are reacted under certain conditions to generate the target product. In the reaction process, liquid alkali (such as sodium hydroxide or potassium hydroxide) is used as a neutralizing agent to adjust the pH value of the reaction system and promote the reaction.

[0005] Patent document (CN102924307A) discloses a preparation method of lauryl betaine, which comprises the following preparation steps: adding monochloroacetic acid and liquid alkali in a reaction kettle, stirring the reaction liquid at a speed of 100 r / min at room temperature, then adding tertiary amine after 2 h of reaction, and heating to 60 DEG C, and then reacting for 8 h at the temperature to obtain the product lauryl betaine.

[0006] The reaction time of the preparation process is relatively short, the system temperature control is unreasonable, and the feeding mode is not deeply studied, and the fine control is insufficient, resulting in low product quality, low conversion rate, high product cost and unqualified appearance. SUMMARY

[0007] Based on the improvement of the prior art and the fine control of the preparation process of lauryl betaine, the application is completed.

[0008] The application relates to a preparation method of lauryl betaine, which comprises the following steps:

[0009] Step 1: Preparation of sodium monochloroacetate

[0010] Dissolution and mixing: In a three-necked flask equipped with a thermometer and a stirrer, 30-40 g of monochloroacetic acid was added and dissolved in an appropriate amount of water, and stirred until uniform,

[0011] Neutralization reaction: 240-280 g of a 20% alkaline solution was slowly added to the monochloroacetic acid solution while stirring, and the pH was controlled at 6.5-7.0, and the reaction temperature was controlled below 60°C until complete neutralization, to obtain a sodium monochloroacetate solution;

[0012] Step 2: Condensation reaction

[0013] Dissolution: 60-75 g of dodecyl dimethyl tertiary amine was added to the sodium monochloroacetate solution to ensure complete dissolution,

[0014] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 60-85°C for 5-12 h, 50 ml of 80% ethanol solution was added, and the reaction system was stirred thoroughly to make it uniform;

[0015] Step 3: Post-treatment

[0016] Post-treatment: After the reaction was completed, the solution was allowed to cool naturally to room temperature. Filtration, washing and drying treatment were performed to obtain lauryl betaine,

[0017] Purification: Distillation was performed to obtain purified lauryl betaine.

[0018] As a preferred implementation method, in the step 2, the dodecyl dimethyl tertiary amine was added to the sodium monochloroacetate solution at once.

[0019] As a preferred implementation method, in the step 2, the temperature of the reaction system was controlled at 70-80°C, and the reaction time was 5-10 h.

[0020] As a preferred implementation method, wherein the reaction time is 5.5-10 h.

[0021] As a preferred implementation method, wherein in the step 1, the pH is controlled at 7.0.

[0022] As a preferred implementation method, wherein in the step 1, the alkaline solution in the neutralization reaction is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide.

[0023] As a preferred implementation method, wherein in the step 1, the alkaline solution in the neutralization reaction is sodium hydroxide.

[0024] The present application also relates to a lauryl betaine prepared by the method of any one of the above.

[0025] Inventive effects

[0026] The present application coordinates specific reaction conditions and processes in the preparation process, so that the lauryl betaine has high active substance content and meets the standard in appearance. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0028] The terms "first", "second", and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those described herein, and the objects distinguished by "first", "second", etc. are usually a class, and are not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / ", generally indicates that the front and rear associated objects are in an "or" relationship.

[0029] Embodiment 1

[0030] Step 1 : Preparation of sodium monochloroacetate

[0031] Dissolution and mixing: In a three-necked flask equipped with a thermometer and a stirrer, 32 g of monochloroacetic acid was added and dissolved in an appropriate amount of water, and stirred uniformly.

[0032] Neutralization reaction: 250 g of 20% sodium hydroxide solution was slowly added to the monochloroacetic acid solution while stirring, and the pH value was controlled at 7.0, and the reaction temperature was controlled below 60°C until the neutralization was complete, to prepare a sodium monochloroacetate solution.

[0033] Step 2: Condensation reaction

[0034] Dissolution: 70 g of dodecyl dimethyl tertiary amine was added to the above-mentioned sodium monochloroacetate solution at one time to ensure complete dissolution.

[0035] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 70°C for 10 h, 50 ml of 80% ethanol solution was added, and the reaction system was stirred uniformly.

[0036] Step 3: Work-up

[0037] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 45 g of lauryl betaine.

[0038] Purification: 44.97 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0039] Qualitative analysis

[0040] (1) Bromophenol blue method (for cation standardization)

[0041] Step 1: Prepare BS-12 aqueous solution

[0042] Take a certain amount of BS-12, add an appropriate amount of distilled water, stir thoroughly to dissolve until a 10% BS-12 aqueous solution is formed, ensuring that the solution is uniform and free of obvious undissolved particles.

[0043] Step 2: Sampling and Reagent Addition

[0044] Sampling: Using a micropipette or dropper, accurately take 1 drop of the sample from the prepared 10% BS-12 aqueous solution and place it in a clean test tube or cuvette.

[0045] Add bromophenol blue solution: Add 5 ml of 0.1% bromophenol blue solution to the sample.

[0046] Add chloroform: Then, add 5 ml of chloroform to the mixture.

[0047] Step 3: Acidification and Shaking

[0048] Add dilute hydrochloric acid: Use a dropper to add a few drops of dilute hydrochloric acid (0.1M HCl) to the mixture drop by drop until the color begins to change or the preset acidity condition is reached.

[0049] Vigorous shaking: Seal the test tube or cuvette and shake vigorously to thoroughly mix the aqueous and chloroform phases. During shaking, bromophenol blue combines with the quaternary ammonium cations in BS-12 to form a blue complex soluble in chloroform.

[0050] Step 4: Observe the color change

[0051] Procedure: After the two phases have separated and stabilized, observe the color of the chloroform layer. If the chloroform layer is blue, it indicates that the BS-12 sample contains a quaternary ammonium salt cation structure.

[0052] Quantitative analysis

[0053] 1. Sample preparation

[0054] Weigh approximately 0.2 g of BS-12 sample using a precise balance, and transfer the weighed sample to a 100 ml Erlenmeyer flask. The Erlenmeyer flask is advantageous for observation during mixing and titration due to its shape.

[0055] 2. Dissolve the sample

[0056] Add distilled water: Add 20 ml of distilled water to the Erlenmeyer flask and gently shake the flask to promote sample dissolution.

[0057] 3. Adjust the pH value

[0058] Add indicator: Add 2-3 drops of 0.1% Benzene Red Purple 4B indicator.

[0059] Adjust pH: Use 1N (i.e., 1 mol / L) hydrochloric acid, add about 10 drops drop by drop to adjust the pH of the solution to within ±2.

[0060] 4. Add titration aid

[0061] Add nitrobenzene: Add 5-6 drops of nitrobenzene to the solution as a titration aid.

[0062] 5. Perform titration

[0063] Titration procedure: Titrate with a 0.02N (i.e., 0.02 mol / L) phosphotungstic acid solution.

[0064] Observe the color change: As phosphotungstic acid is added, the color of the solution will gradually change from red to blue.

[0065] Determining the endpoint: The titration is considered to have reached the endpoint when the solution color changes completely from red to blue, and this color change no longer changes after adding a small amount of phosphotungstic acid.

[0066] 6. Calculation Results

[0067] Record the data: Record the volume of phosphotungstic acid consumed during the titration process.

[0068] Content calculation: The content of BS-12 in the sample is calculated based on the concentration of phosphotungstic acid, the titration volume, and the reaction relationship between BS-12 and phosphotungstic acid.

[0069] Calculation formula:

[0070]

[0071] (Where, N: equivalent concentration of phosphotungstic acid, V: number of milliliters of phosphotungstic acid consumed, M: molecular weight of BS-12, W: weight of sample)

[0072] The volume of phosphotungstic acid consumed in the above titration process in Example 1 was recorded as 15.29 ml. Based on the calculation, the BS-12 content of Example 1 was 48%.

[0073] Example 2

[0074] Step 1 : Preparation of sodium monochloroacetate

[0075] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0076] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0077] Step 2: Condensation reaction

[0078] Dissolution: Add 70g of dodecyl dimethyl tertiary amine to the above sodium monochloroacetate solution at once to ensure complete dissolution.

[0079] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 75℃ and the reaction was carried out for 10 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0080] Step 3: Work-up

[0081] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. The solution was then filtered, washed, and dried to obtain 42 g of lauryl betaine.

[0082] Purification: 41.94 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0083] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Example 2 was recorded as 14.65 ml. The BS-12 content of Example 2 was calculated to be 46%.

[0084] Example 3

[0085] Step 1 : Preparation of sodium monochloroacetate

[0086] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0087] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0088] Step 2: Condensation reaction

[0089] Dissolution: Add 70g of dodecyl dimethyl tertiary amine to the above sodium monochloroacetate solution at once to ensure complete dissolution.

[0090] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system is controlled at 80℃ and the reaction is carried out for 10 hours. Then, 50 ml of 80% ethanol solution is added and the mixture is stirred thoroughly to make the reaction system homogeneous.

[0091] Step 3: Work-up

[0092] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. The solution was then filtered, washed, and dried to obtain 42 g of lauryl betaine.

[0093] Purification: 41.89 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0094] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Example 3 was recorded as 12.74 ml. The BS-12 content of Example 3 was calculated to be 40%.

[0095] Example 4

[0096] Step 1 : Preparation of sodium monochloroacetate

[0097] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0098] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0099] Step 2: Condensation reaction

[0100] Dissolution: Add 70g of dodecyl dimethyl tertiary amine to the above sodium monochloroacetate solution at once to ensure complete dissolution.

[0101] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 70℃ and the reaction was carried out for 7.5 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0102] Step 3: Work-up

[0103] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 46 g of lauryl betaine.

[0104] Purification: 45.97 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0105] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Example 4 was recorded as 13.38 ml. The BS-12 content of Example 4 was calculated to be 42%.

[0106] Example 5

[0107] Step 1 : Preparation of sodium monochloroacetate

[0108] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0109] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0110] Step 2: Condensation reaction

[0111] Dissolution: Add 70g of dodecyl dimethyl tertiary amine to the above sodium monochloroacetate solution at once to ensure complete dissolution.

[0112] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 70℃ and the reaction was carried out for 5.5 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0113] Step 3: Work-up

[0114] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 44 g of lauryl betaine.

[0115] Purification: 43.98 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0116] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Example 5 was recorded as 13.69 ml. The BS-12 content of Example 5 was calculated to be 43%.

[0117] Comparative Example 1

[0118] Step 1 : Preparation of sodium monochloroacetate

[0119] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0120] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0121] Step 2: Condensation reaction

[0122] Dissolution: Slowly add dodecyl dimethyl tertiary amine dropwise to the above sodium monochloroacetate solution until the amount added is 70g, ensuring complete dissolution.

[0123] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system is controlled at 70℃ and the reaction is carried out for 10 hours. 50 ml of 80% ethanol solution is added and the mixture is stirred thoroughly to make the reaction system homogeneous.

[0124] Step 3: Work-up

[0125] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 37 g of lauryl betaine.

[0126] Purification: Distillation yielded 36.66 g of purified lauryl betaine (BS-12).

[0127] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 1 was recorded as 10.83 ml. The BS-12 content of Comparative Example 1 was calculated to be 34%.

[0128] Comparative Example 2

[0129] Step 1 : Preparation of sodium monochloroacetate

[0130] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0131] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0132] Step 2: Condensation reaction

[0133] Dissolution: Slowly add dodecyl dimethyl tertiary amine dropwise to the above sodium monochloroacetate solution until the amount added is 70g, ensuring complete dissolution.

[0134] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 70℃ and the reaction was carried out for 4 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0135] Step 3: Work-up

[0136] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 46 g of lauryl betaine.

[0137] Purification: 45.33 g of purified lauryl betaine (BS-12) was obtained by distillation.

[0138] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 2 was recorded as 9.55 ml. The BS-12 content of Comparative Example 2 was calculated to be 30%.

[0139] Comparative Example 3

[0140] Step 1 : Preparation of sodium monochloroacetate

[0141] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0142] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0143] Step 2: Condensation reaction

[0144] Dissolution: Add 70g of dodecyl dimethyl tertiary amine to the above sodium monochloroacetate solution at once to ensure complete dissolution.

[0145] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 70℃ and the reaction was carried out for 15 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0146] Step 3: Work-up

[0147] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. The solution was then filtered, washed, and dried to obtain 39 g of lauryl betaine.

[0148] Purification: Distillation yielded 38.24 g of purified lauryl betaine (BS-12).

[0149] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 3 was recorded as 9.55 ml. The BS-12 content of Comparative Example 3 was calculated to be 31%.

[0150] Comparative Example 4

[0151] Step 1 : Preparation of sodium monochloroacetate

[0152] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0153] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0154] Step 2: Condensation reaction

[0155] Dissolution: Slowly add dodecyl dimethyl tertiary amine dropwise to the above sodium monochloroacetate solution until the amount added is 70g, ensuring complete dissolution.

[0156] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system is controlled at 80℃ and the reaction is carried out for 15 hours. 50 ml of 80% ethanol solution is added and the mixture is stirred thoroughly to make the reaction system homogeneous.

[0157] Step 3: Work-up

[0158] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. The solution was then filtered, washed, and dried to obtain 38 g of lauryl betaine.

[0159] Purification: Distillation yielded 37.73 g of purified lauryl betaine (BS-12).

[0160] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 4 was recorded as 10.19 ml. The BS-12 content of Comparative Example 4 was calculated to be 32%.

[0161] Comparative Example 5

[0162] Step 1 : Preparation of sodium monochloroacetate

[0163] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0164] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0165] Step 2: Condensation reaction

[0166] Dissolution: Slowly add dodecyl dimethyl tertiary amine dropwise to the above sodium monochloroacetate solution until the amount added is 70g, ensuring complete dissolution.

[0167] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 60℃ and the reaction was carried out for 8 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0168] Step 3: Work-up

[0169] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. The solution was then filtered, washed, and dried to obtain 39 g of lauryl betaine.

[0170] Purification: Distillation yielded 38.33 g of purified lauryl betaine (BS-12).

[0171] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 5 was recorded as 7.64 ml. The BS-12 content of Comparative Example 5 was calculated to be 24%.

[0172] Comparative Example 6

[0173] Step 1 : Preparation of sodium monochloroacetate

[0174] Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 32g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous.

[0175] Neutralization reaction: Slowly add 250g of 20% sodium hydroxide solution to the monochloroacetic acid solution while stirring, control the pH value to 7.0, and control the reaction temperature to below 60℃ until neutralization is complete to obtain sodium monochloroacetate solution.

[0176] Step 2: Condensation reaction

[0177] Dissolution: Slowly add dodecyl dimethyl tertiary amine dropwise to the above sodium monochloroacetate solution until the amount added is 70g, ensuring complete dissolution.

[0178] Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system was controlled at 60℃ and the reaction was carried out for 8 hours. 50 ml of 80% ethanol solution was added and the mixture was stirred thoroughly to make the reaction system homogeneous.

[0179] Step 3: Work-up

[0180] Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain 37 g of lauryl betaine.

[0181] Purification: Distillation yielded 36.49 g of purified lauryl betaine (BS-12).

[0182] The same quantitative analysis was performed as in Example 1 above. The volume of phosphotungstic acid consumed in the titration process of Comparative Example 6 was recorded as 9.24 ml. The BS-12 content of Comparative Example 5 was calculated to be 29%.

[0183] As can be seen from Examples 1-5 and Comparative Examples 1-6 above, the present invention achieves an increase in BS-12 content by controlling the temperature of the condensation reaction system at 70-80°C and the reaction time at 5.5-10h, and then adding dodecyl dimethyl tertiary amine to the system in one step. As can be seen from Examples 1-5, the calculated BS-12 content in these examples is all above 40%.

[0184] As can be seen from Comparative Examples 1-6, the addition of dodecyl dimethyl tertiary amine in Comparative Examples 1-2 and 4-5, by slowly adding the dodecyl dimethyl tertiary amine dropwise to the sodium monochloroacetate solution instead of adding it all at once, resulted in a sharp increase in the free amine content in the product, leading to a significant decrease in the content of BS-12. Furthermore, the short reaction time in Comparative Example 2 resulted in incomplete condensation, low product conversion, and reduced final product yield. The reaction times of Comparative Examples 3 and 4 were 15 hours, which was too long and might reduce the purity and content of BS-12 due to excessive reaction or increased side reactions. The reaction system temperature in Comparative Example 5 was too low, resulting in a reduced reaction rate, prolonged reaction time, and even incomplete reaction, leading to a significant decrease in yield and potentially introducing more impurities. The system temperature in Comparative Example 6 was too high, leading to an increase in unwanted side reactions and a decrease in the content of the target product, BS-12.

[0185] Step 1 : Preparation of sodium monochloroacetate Step 2: Condensation reaction Step 3: Work-up Step 1 : Preparation of sodium monochloroacetate Step 2: Condensation reaction Step 3: Work-up Appearance test

[0186] The appearance of BS-12 in Examples 1-5 and Comparative Examples 1-5 was visually inspected, and the pH value was measured. The results are shown in Table 1 below:

[0187]

[0188]

[0189] As can be seen from the table above, the BS-12 obtained in Examples 1 to 5 meets the normal standard, while the BS-12 obtained in Comparative Examples 1 to 3, although transparent, appears dark yellow, and the BS-12 obtained in Comparative Examples 4 to 6 has a brown and cloudy appearance, which does not meet the appearance standard of the finished product at all.

[0190] The embodiments of this application have been described above, but this application is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing lauryl betaine, characterized in that, The method includes the following steps: Step 1: Preparation of sodium monochloroacetate Dissolving and mixing: In a three-necked flask equipped with a thermometer and a stirrer, add 30-40 g of monochloroacetic acid, add an appropriate amount of water to dissolve, and stir until homogeneous. Neutralization reaction: Slowly add 240-280g of 20% alkaline solution to the monochloroacetic acid solution while stirring, control the pH value to 6.5-7.0, and control the reaction temperature to below 60℃ until neutralization is complete, to obtain sodium monochloroacetate solution; Step 2: Condensation reaction Dissolution: Add 60-75g of dodecyl dimethyl tertiary amine to the sodium monochloroacetate solution, ensuring complete dissolution. Reaction: In an oil bath equipped with a temperature controller, the temperature of the reaction system is controlled at 60℃~85℃ for 5h~12h. 50ml of 80% ethanol solution is added and the mixture is stirred thoroughly to make the reaction system homogeneous. Step 3: Post-processing Post-treatment: After the reaction was complete, the solution was allowed to cool naturally to room temperature. It was then filtered, washed, and dried to obtain lauryl betaine. Purification: Distillation yielded purified lauryl betaine.

2. The method for preparing lauryl betaine according to claim 1, wherein, In step 2, dodecyl dimethyl tertiary amine is added to the sodium monochloroacetate solution in a single step.

3. The method for preparing lauryl betaine according to claim 1 or 2, wherein, In step 2, the temperature of the reaction system is controlled at 70℃~80℃, and the reaction time is 5h~10h.

4. The method for preparing lauryl betaine according to claim 3, wherein, The reaction time is 5.5h to 10h.

5. The method for preparing lauryl betaine according to claim 1, wherein, In step 1, the pH value is controlled to be 7.

0.

6. The method for preparing lauryl betaine according to claim 1, wherein, In step 1, the alkaline solution in the neutralization reaction is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide.

7. The method for preparing lauryl betaine according to claim 6, wherein, In step 1, the alkaline solution in the neutralization reaction is sodium hydroxide.

8. A lauryl betaine, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

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