A method for preparing dimethyldiallylammonium chloride

Abstract

The application belongs to the technical field of organic synthesis, and specifically discloses a preparation method of dimethyl diallyl ammonium chloride, which comprises the following steps: under the condition that water exists, dimethylamine, an alkaline carrier and allyl chloride are mixed and subjected to a contact reaction to obtain a crude tertiary amine; the alkaline carrier comprises a carrier body and a carbonic acid alkali metal salt loaded on the carrier body; under the condition that an organic solvent exists, the crude tertiary amine and allyl chloride are mixed and subjected to a contact reaction. The method can effectively reduce the hydrolysis of allyl chloride and the generation of dimethylamine hydrochloride in the reaction process, the dimethyl diallyl ammonium chloride product contains almost no other hydrochloride impurities, and the reaction efficiency, the yield and the purity of the dimethyl diallyl ammonium chloride are improved.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing dimethyl diallyl ammonium chloride. Background Technology

[0002] Dimethyl diallyl ammonium chloride (DMDAAC), as an important cationic monomer, possesses excellent water solubility, high positive charge density, and strong adsorption properties in its homopolymers and copolymers, making it widely used in water treatment, oil extraction, papermaking, textiles, and daily chemical industries. In the water treatment industry, DMDAAC polymers can serve as highly efficient flocculants, rapidly adsorbing suspended particles and organic pollutants in water, significantly improving water purification efficiency. In the oil extraction field, it can be used as a drilling fluid treatment agent and oil displacement agent, improving drilling fluid rheology and enhancing oil recovery. Therefore, the research and development of DMDAAC synthesis technology has always been a key focus in the fine chemical industry. Currently, the industrial synthesis of DMDAAC mainly uses dimethylamine and allyl chloride as raw materials. First, dimethylamine is reacted with excess allyl chloride under alkaline conditions to generate monoallyl dimethylamine (MADMA), and then MADMA is further reacted with allyl chloride in a quaternization reaction to generate the target product. However, the reaction efficiency and product yield of producing dimethyl diallyl ammonium chloride using this method still need further improvement. Summary of the Invention

[0003] This patent provides a method for preparing dimethyl diallyl ammonium chloride, which can effectively reduce the hydrolysis of allyl chloride and the generation of dimethylamine hydrochloride during the reaction process, thereby improving the reaction efficiency and the yield and purity of dimethyl diallyl ammonium chloride.

[0004] This invention provides a method for preparing dimethyl diallyl ammonium chloride, the method comprising the following steps: S1. In the presence of water, dimethylamine, an alkaline support, and allyl chloride are mixed and subjected to contact reaction I to obtain crude tertiary amine; The alkaline support includes a support body and an alkali metal carbonate salt loaded on the support body; S2. In the presence of an organic solvent, the crude tertiary amine and allyl chloride are mixed and subjected to contact reaction II.

[0005] Furthermore, the carrier body is selected from at least one of coconut shell activated carbon, MCM-41 molecular sieve and γ-alumina, and the alkali metal carbonate is sodium carbonate and / or potassium carbonate.

[0006] Furthermore, the preparation step of the alkaline carrier includes: contacting the carrier body with an aqueous solution containing an alkali metal carbonate, wherein the content of the alkali metal carbonate in the aqueous solution is 3-25 wt%.

[0007] Furthermore, relative to 1g of the carrier body, the amount of the aqueous solution containing the alkali metal carbonate is 3-20mL.

[0008] Furthermore, in the preparation step of the alkaline carrier, the contact is carried out under stirring conditions, and the contact time is 20-28 hours.

[0009] Furthermore, the preparation steps of the alkaline carrier also include: drying the solid material obtained after contact and then calcining it, wherein the calcination conditions include: a temperature of 400-500℃ and a time of 2-4h.

[0010] Further, in step S1, the mixing step includes: mixing dimethylamine and water to obtain an aqueous dimethylamine solution; mixing an alkaline support and the aqueous dimethylamine solution to obtain a dispersion; and mixing the dispersion with allyl chloride.

[0011] Furthermore, the dispersion is mixed with allyl chloride by adding allyl chloride dropwise into the dispersion.

[0012] Further, in step S1, relative to 1g of the dimethylamine, the amount of the basic support is 0.4-0.6g, and the amount of the allyl chloride is 1.65-1.8g.

[0013] Further, in step S1, the conditions for the contact reaction I include: a temperature of 10-20°C, a stirring rate of 200-300 rpm, and a time of 1-2 h.

[0014] Further, in step S2, the mixing step includes: mixing the crude tertiary amine with an organic solvent to obtain a solution containing the crude tertiary amine, and then mixing the solution containing the crude tertiary amine with allyl chloride.

[0015] Furthermore, the method of mixing the solution containing crude tertiary amine with allyl chloride includes: adding allyl chloride dropwise to the solution containing crude tertiary amine.

[0016] Furthermore, relative to 1g of the dimethylamine, the amount of allyl chloride used in step S2 is 1.65-1.8g.

[0017] Furthermore, the conditions for the contact reaction II include: a temperature of 35-45°C and a time of 1-3 hours.

[0018] Furthermore, the preparation method further includes: dehydrating the crude tertiary amine obtained in step S1.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The method provided by the present invention can effectively prevent the hydrolysis of allyl chloride, avoid the generation of by-products, improve the yield and purity of tertiary amines, and the dimethyl diallyl ammonium chloride product contains almost no other hydrochloride impurities, thereby improving the purity of the synthesized dimethyl diallyl ammonium chloride monomer.

[0020] 2. The method provided by this invention uses an alkaline support, which can not only remove HCl in a timely manner while stabilizing the neutralization reaction, but also convert the generated dimethylamine hydrochloride into free dimethylamine, realizing the regeneration and recycling of amine raw materials, ensuring that there is always sufficient active amine participating in the reaction in the reaction system, and fundamentally solving the technical problem of hydrochloride hindering the reaction. Attached Figure Description

[0021] Figure 1 The yields of tertiary amines and DMDAAC in the examples and comparative examples; Figure 2 The content of allyl alcohol in the tertiary amines of the examples and comparative examples; Figure 3 The image shows the infrared absorption spectrum of the DMDAAC product from Example 1. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this document.

[0023] As mentioned above, the present invention provides a method for preparing dimethyl diallyl ammonium chloride, the method comprising the following steps: S1. In the presence of water, dimethylamine, an alkaline support, and allyl chloride are mixed and subjected to contact reaction I to obtain crude tertiary amine; The alkaline support includes a support body and an alkali metal carbonate salt loaded on the support body; S2. In the presence of an organic solvent, the crude tertiary amine and allyl chloride are mixed and subjected to contact reaction II.

[0024] During their research, the inventors discovered that allyl chloride is easily hydrolyzed under alkaline conditions, and the resulting hydrogen chloride readily reacts with dimethylamine to produce dimethylamine hydrochloride, hindering the reaction. The method provided by this invention utilizes an alkaline support comprising a support body and an alkali metal carbonate salt loaded on the support body. This effectively prevents the hydrolysis of allyl chloride, avoids the generation of byproducts, improves the yield and purity of tertiary amines, and ensures that the dimethyl diallyl ammonium chloride product contains almost no other hydrochloride impurities, thus improving the purity of the synthesized dimethyl diallyl ammonium chloride monomer. Furthermore, it can stably neutralize dimethylamine hydrochloride to generate dimethylamine, achieving a closed-loop reaction system for amine regeneration. This ensures that there is always sufficient active amine participating in the reaction. The porous structure of the support body provides stable loading sites for the alkali metal carbonate salt. During the reaction, as HCl is generated, the alkali metal carbonate salt adsorbed on the support body is released through a mild neutralization reaction, preventing drastic pH fluctuations.

[0025] Preferably, the carrier is selected from at least one of coconut shell activated carbon, MCM-41 molecular sieve, and γ-alumina, and the alkali metal carbonate is sodium carbonate and / or potassium carbonate. During the research, it was found that controlling the carrier to be at least one of coconut shell activated carbon, MCM-41 molecular sieve, and γ-alumina, and controlling the alkali metal carbonate to be sodium carbonate and / or potassium carbonate, can further improve the yield and purity of the prepared dimethyldiallyl ammonium chloride.

[0026] Preferably, the preparation steps of coconut shell activated carbon include: mixing coconut shell powder with alkali and then performing carbonization treatment under an inert gas atmosphere. More preferably, the carbonization treatment conditions include: a temperature of 550-650℃ and a time of 0.5-1.5h. More preferably, the heating rate of the carbonization treatment can be 5-15℃ / min.

[0027] Preferably, the preparation steps of coconut shell activated carbon further include: washing the carbonized product after carbonization treatment. More preferably, the washing includes acid washing and water washing. The acid used for acid washing can be a hydrochloric acid solution.

[0028] Preferably, in the preparation step of coconut shell activated carbon, the alkali can be sodium hydroxide and / or potassium hydroxide, preferably sodium hydroxide. The inert gas can be nitrogen or a gaseous element formed from group 0 elements, such as helium or argon. Preferably, the inert gas is nitrogen.

[0029] Preferably, the preparation steps of the γ-alumina include: mixing a mixture containing aluminum salt and a mixture containing sodium bicarbonate salt, adjusting the pH to alkaline, collecting the precipitate, and calcining the precipitate.

[0030] Preferably, the temperature of the mixing reaction is 60-80°C. The aluminum salt can be aluminum nitrate. The pH of the mixture obtained by adjusting the pH is ≥8. More preferably, the alkaline solution used for adjusting the pH is sodium hydroxide solution.

[0031] Preferably, the preparation step of the γ-alumina further includes: after adjusting the pH to alkaline, stirring the solution obtained by adjusting the pH, and then collecting the precipitate.

[0032] Preferably, the stirring conditions include a temperature of 60-80°C and a time of 2-4 hours.

[0033] Preferably, the calcination conditions include a temperature of 500-600°C and a time of 1.5-2.5h.

[0034] Preferably, the preparation step further includes washing and drying the precipitate before calcination. The washing and drying can be conventional methods in the art. For example, washing can be done by first washing with water and then washing with alcohol, and drying can be done by baking.

[0035] Preferably, the preparation step of the alkaline support includes: contacting the support substrate with an aqueous solution containing an alkali metal carbonate, wherein the content of the alkali metal carbonate in the aqueous solution is 3-25 wt%. This method allows the alkali metal carbonate to be better adsorbed onto the support substrate, thereby further improving the yield and purity of the subsequently prepared dimethyl diallyl ammonium chloride. Further preferably, considering the potential to further improve the yield and purity of the subsequently prepared dimethyl diallyl ammonium chloride, the amount of the aqueous solution containing the alkali metal carbonate is 3-20 mL relative to 1 g of the support substrate.

[0036] According to the present invention, in the preparation process of the alkaline support, the drying method can be any feasible method, such as conventional air drying or oven drying. In a specific embodiment of the present invention, the drying is oven drying, wherein the drying temperature is 30-100°C, and the drying time is not particularly limited, as long as the product to be dried is dried to a constant weight. Preferably, the drying conditions include: a temperature of 60-100°C and a time of 8-20 hours.

[0037] To further enhance the adsorption effect of alkali metal carbonate on the carrier, thereby improving the yield and purity of the subsequently prepared dimethyldiallylammonium chloride, more preferably, in the preparation step of the alkaline carrier, the contact is carried out under stirring conditions, and the contact time is 20-28 hours. Stirring can be manual, mechanical, or magnetic, and the stirring rate can be determined by the experimenter based on the actual situation.

[0038] To further improve the yield and purity of the dimethyl diallyl ammonium chloride obtained in the subsequent preparation, more preferably, when the carrier body is MCM-41 and γ-alumina, the preparation step of the alkaline carrier further includes: drying the solid material obtained after contact and then calcining it, wherein the calcination conditions include: a temperature of 400-500℃ and a time of 2-4h.

[0039] The calcination process can be carried out in any feasible reactor, such as a muffle furnace or a tube furnace. In one specific embodiment of the invention, the calcination process is carried out in a muffle furnace. Preferably, the heating rate of the calcination process is 2-8°C / min.

[0040] Preferably, in step S1, the mixing step includes: mixing dimethylamine and water to obtain an aqueous dimethylamine solution; mixing the basic support and the aqueous dimethylamine solution to obtain a dispersion; and mixing the dispersion with allyl chloride. This method allows for a better reaction between allyl chloride and dimethylamine, thereby further improving the yield and purity of the subsequently produced dimethyl diallyl ammonium chloride. Further preferably, to further improve the yield and purity of the subsequently produced dimethyl diallyl ammonium chloride, the dispersion is mixed with allyl chloride by adding allyl chloride dropwise to the dispersion. Preferably, the dispersion is stirred during the dropwise addition. The stirring speed can be determined by a technician based on the actual situation, as long as the allyl chloride, dimethylamine, and basic support are sufficiently contacted.

[0041] Preferably, the dropping rate of allyl chloride can be 0.2-0.6 g / min. The concentration of the dimethylamine aqueous solution can be 20-60 wt%.

[0042] According to the present invention, the temperature at which the alkaline carrier and the dimethylamine aqueous solution are mixed is 4-12°C.

[0043] Preferably, step S1 further includes: separating the mixture obtained from contact reaction I to obtain the crude tertiary amine as the oil phase. The separation can be carried out in a separatory funnel.

[0044] Preferably, in step S1, the amount of the basic support is 0.4-0.6g relative to 1g of the dimethylamine, and the amount of allyl chloride is 1.65-1.8g. Controlling the amounts of the basic support and allyl chloride within the above ranges improves the reaction efficiency while controlling the reaction cost, thereby further improving the yield and purity of the subsequently obtained dimethyl diallyl ammonium chloride.

[0045] To further improve the reaction effect and thus the yield and purity of the subsequently obtained dimethyldiallyl sodium chloride, preferably, in step S1, the conditions for the contact reaction I include: a temperature of 10-20°C, a stirring rate of 200-300 rpm, and a time of 1-2 h. In the following embodiments of the present invention, the stirring rate is 200 rpm.

[0046] To further improve the yield and purity of the subsequently obtained dimethyldiallyl ammonium chloride, preferably, in step S2, the mixing step includes: mixing the crude tertiary amine with an organic solvent to obtain a solution containing the crude tertiary amine, and then mixing the solution containing the crude tertiary amine with allyl chloride. Further preferably, to further improve the yield and purity of the subsequently obtained dimethyldiallyl ammonium chloride, the method of mixing the solution containing the crude tertiary amine with allyl chloride includes: adding allyl chloride dropwise to the solution containing the crude tertiary amine.

[0047] Preferably, the rate at which allyl chloride is added dropwise to the solution containing crude tertiary amine is 0.2-0.6 g / min. In the following embodiments of the invention, the dropping rate is set to 0.4 g / min.

[0048] Preferably, the organic solvent used in step S2 can be acetone.

[0049] Preferably, the amount of allyl chloride used in step S2 is 1.65-1.8 g relative to 1 g of the dimethylamine. Controlling the amount of allyl chloride within the above range can improve the yield of dimethyl diallyl ammonium chloride while controlling costs.

[0050] To further improve the reaction effect, preferably, the conditions for the contact reaction II include: a temperature of 35-45°C and a time of 1-3 hours.

[0051] Preferably, the preparation method further includes: separating the organic solvent after allowing the mixture obtained from contact reaction II to stand for 0.5-1.5 h.

[0052] Preferably, the preparation method further includes: dehydrating the crude tertiary amine obtained in step S1. This can further improve the reaction effect between the crude tertiary amine and allyl chloride, thereby further improving the yield and purity of the subsequently obtained dimethyl diallyl ammonium chloride. Preferably, the dehydrating agent used in the dehydration treatment is anhydrous magnesium sulfate.

[0053] As a relatively preferred embodiment of the present invention, the preparation method of dimethyl diallyl ammonium chloride includes the following steps: (1) The carrier body is mixed and soaked in a solution containing alkali metal carbonate, and then calcined to obtain an alkaline carrier; (2) Add an alkaline support to the dimethylamine aqueous solution, stir in a cold water bath at 4-12℃ and wait for use. Add allyl chloride dropwise at a rate of 0.2-0.6 g / min, control the reaction temperature at 10-20℃, and stir magnetically for 1-2 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and the oil phase. The upper oil phase is crude tertiary amine. The amount of alkaline support used relative to 1 g of the dimethylamine is 0.4-0.6 g, the amount of allyl chloride used is 1.65-1.8 g, the support body is selected from at least one of coconut shell activated carbon, MCM-41 molecular sieve and γ-alumina, and the alkali metal carbonate is sodium carbonate and / or potassium carbonate. (3) The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate, and then added to a three-necked flask with acetone. Allyl chloride was added dropwise with stirring and reacted at 35-45 °C for 1-3 h. After the reaction was completed, the mixture was allowed to stand for 0.5-1.5 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC). The amount of allyl chloride used is 1.65-1.8g relative to 1g of the dimethylamine.

[0054] The dimethyl diallyl ammonium chloride prepared according to the preferred embodiments of the present invention has good purity and yield.

[0055] The present invention will be further illustrated below through examples and comparative examples. In the present invention, room temperature refers to 25°C (298.15K).

[0056] Example 1: S1 Potassium carbonate was dissolved in deionized water to prepare a 0.5 mol / L impregnation solution. 20 g of MCM-41 molecular sieve was mixed with 80 g of impregnation solution and stirred at room temperature for 24 h to ensure that potassium carbonate was fully adsorbed into the pores. The impregnated sample was dried in an oven at 80 °C for 12 h, and then calcined in a muffle furnace at 450 °C at a rate of 5 °C / min for 3 h to obtain the supported molecular sieve. S2 Take 112.5g of 40wt% dimethylamine aqueous solution, add 20g of the supported molecular sieve, stir in a 10 ℃ cold water bath and set aside. Add 76.5g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 15 ℃, and stir magnetically for 1.5 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 76.5g of allyl chloride was added dropwise under stirring. The reaction was carried out at 40 °C for 2 h. After the reaction was completed, the mixture was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0057] The above-mentioned dimethyl diallyl ammonium chloride was characterized by infrared spectroscopy, such as... Figure 3 As shown, 3087 cm -1 The peak at 1680 cm⁻¹ is the stretching vibration peak of CH in =CH₂. -1 The peak at 877-990 cm⁻¹ is the C=C stretching vibration peak. -1 The CH vibrational peak and CN vibrational peak are at 1015 cm⁻¹. -1 The infrared spectral analysis results were consistent with the structure of DMDAAC. This indicates that the obtained compound is indeed DMDAAC. Since no obvious impurity absorption peaks were found in the infrared spectrum, the synthetic process used is feasible.

[0058] Example 2: S1 Sodium carbonate was dissolved in deionized water to prepare a 0.5 mol / L impregnation solution. 20 g of MCM-41 molecular sieve was mixed with 100 g of impregnation solution and stirred at room temperature for 24 h to ensure that sodium carbonate was fully adsorbed into the pores. The impregnated sample was dried in an oven at 80 °C for 12 h, and then calcined in a muffle furnace at 5 °C / min to 450 °C for 3 h to obtain the supported molecular sieve. S2 Take 112.5g of 40wt% dimethylamine aqueous solution, add 23g of the supported molecular sieve, stir in a 10 ℃ cold water bath and set aside. Add 80g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 18 ℃, and stir magnetically for 1.2 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 80g of allyl chloride was added dropwise under stirring. The reaction was carried out at 45 °C for 1.8h. After the reaction was completed, the mixture was allowed to stand for 1h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0059] Example 3: S1; 80g of dried coconut shell powder was mixed with 160g of NaOH and placed in a tube furnace. Under nitrogen flow rate of 50 mL / min, the mixture was heated to 600℃ at a heating rate of 10℃ / min and held for 1 hour for high-temperature carbonization. After cooling, the mixture was washed with 1M hydrochloric acid to remove impurities, followed by washing with deionized water until the pH value reached 7±0.2. Coconut shell activated carbon was then prepared by freeze-drying. 100g of sodium carbonate was dissolved in deionized water to prepare a 20wt% impregnation solution. The coconut shell activated carbon was mixed with the impregnation solution and stirred in a 60℃ constant temperature water bath for 24 hours, stirring every 30 minutes to remove air bubbles. The impregnated activated carbon was dried in an oven at 80℃ for 2 hours to obtain the loaded carrier activated carbon. S2 Take 112.5g of 40wt% dimethylamine aqueous solution, add 25g of loaded carrier activated carbon, stir in a 10 ℃ cold water bath and set aside. Add 76.5g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 12 ℃, and stir magnetically for 2 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 76.5g of allyl chloride was added dropwise under stirring. The reaction was carried out at 35 °C for 2.5 h. After the reaction was completed, the mixture was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0060] Example 4: S1; 80g of dried coconut shell powder was mixed with 160g of NaOH and placed in a tube furnace. Under nitrogen flow rate of 50 mL / min, the mixture was heated to 600℃ at a heating rate of 10℃ / min and held for 1 hour for high-temperature carbonization. After cooling, the mixture was washed with 1M hydrochloric acid to remove impurities, followed by washing with deionized water until the pH value reached 7±0.2. Coconut shell activated carbon was then prepared by freeze-drying. 100g of potassium carbonate was dissolved in deionized water to prepare a 25wt% impregnation solution. The coconut shell activated carbon was mixed with the impregnation solution and stirred in a 60℃ constant temperature water bath for 24 hours, stirring every 30 minutes to remove air bubbles. The impregnated activated carbon was dried in an oven at 80℃ for 2 hours to obtain the loaded carrier activated carbon. S2 Take 112.5g of 40wt% dimethylamine aqueous solution, add 23g of loaded carrier activated carbon, stir in a 10 ℃ cold water bath and set aside. Add 75g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 15 ℃, and stir magnetically for 1.5 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 75g of allyl chloride was added dropwise under stirring. The reaction was carried out at 40 °C for 2 h. After the reaction was completed, it was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0061] Example 5: S1. 25g of aluminum nitrate and 8g of ammonium bicarbonate were dissolved in 200g of deionized water at room temperature on two different magnetic stirrers. Then, in a reaction vessel on a magnetic stirrer at 70 °C, the two solutions were added dropwise to 100g of deionized water using two droppers until the solution was completely added. Next, 20g of NaOH was dissolved in 100g of deionized water on a magnetic stirrer and added dropwise to the previous solution to adjust the pH of the solution to 8. The precipitate was placed on a magnetic stirrer at 70 °C for 3 hours. After precipitation, the white precipitate was washed three times with deionized water and twice with ethanol to remove all impurities, yielding an alumina product. The alumina product was then transferred to an oven at 70 °C and dried for 12 hours. The alumina product was calcined in a programmable furnace at 550 °C for 2 hours to obtain a γ-alumina support. Potassium carbonate was dissolved in deionized water to prepare a 0.3 mol / L impregnation solution. First, 25g of γ-alumina support was soaked in 80g of impregnation solution for 12h, filtered, and dried at 100 ℃ for 6h. The impregnation was repeated once to improve the uniformity of loading. Then, the loaded γ-alumina support was obtained by calcination at 400 °C for 2h. S2 Take 112.5g of 40% dimethylamine aqueous solution, add 25g of γ-alumina support loaded on it, stir in a 10 ℃ cold water bath and set aside. Add 76.5g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 15 ℃, and stir magnetically for 1.5 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 76.5g of allyl chloride was added dropwise under stirring. The reaction was carried out at 40 °C for 2 h. After the reaction was completed, the mixture was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0062] Example 6: S1. 25g of aluminum nitrate and 8g of ammonium bicarbonate were dissolved in 200g of deionized water at room temperature on two different magnetic stirrers. Then, in a reaction vessel on a magnetic stirrer at 70 °C, the two solutions were added dropwise to 100g of deionized water using two droppers until the solution was completely added. Next, 20g of NaOH was dissolved in 100g of deionized water on a magnetic stirrer and added dropwise to the previous solution to adjust the pH of the solution to 8. The precipitate was placed on a magnetic stirrer at 70 °C for 3 hours. After precipitation, the white precipitate was washed three times with deionized water and twice with ethanol to remove all impurities, yielding an alumina product. The alumina product was then transferred to an oven at 70 °C and dried for 12 hours. The alumina product was calcined in a programmable furnace at 550 °C for 2 hours to obtain a γ-alumina support. Sodium carbonate was dissolved in deionized water to prepare a 0.3 mol / L impregnation solution. First, 25g of γ-alumina support was soaked in 80g of impregnation solution for 12h, filtered, and dried at 100 ℃ for 6h. The impregnation was repeated once to improve the uniformity of loading. Then, the loaded γ-alumina support was obtained by calcination at 400 °C for 2h. S2 Take 112.5g of 40wt% dimethylamine aqueous solution, add 25g of γ-alumina support, stir in a 10℃ cold water bath and set aside. Add 76.5g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 15℃, and stir magnetically for 1.5 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S3 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 76.5g of allyl chloride was added dropwise under stirring. The reaction was carried out at 40 °C for 2 h. After the reaction was completed, the mixture was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0063] Comparative Example 1: S1 Take 112.5g of 40wt% dimethylamine aqueous solution, add 100g of 40wt% sodium hydroxide solution, stir in a 10 ℃ cold water bath and set aside. Add 76.5g of allyl chloride dropwise at a rate of 0.4g / min, control the reaction temperature at 15 ℃, and stir magnetically for 1.5 h to obtain the reaction system. Add the reaction system to a separatory funnel to separate the aqueous phase and oil phase. The upper oil phase is crude tertiary amine. S2 The crude tertiary amine was dried and dehydrated with anhydrous magnesium sulfate. Then, it was added to a three-necked flask with 500g of acetone and 76.5g of allyl chloride was added dropwise under stirring. The reaction was carried out at 40 °C for 2 h. After the reaction was completed, the mixture was allowed to stand for 1 h to precipitate needle-like crystals. The acetone was removed by filtration to obtain dimethyl diallyl ammonium chloride (DMDAAC).

[0064] The yields of tertiary amines and DMDAAC in the above examples and comparative examples are as follows: Figure 1 As shown. By Figure 1 As shown, the yields of tertiary amines and DMDAAC in Examples 1-6 are significantly higher than those in the comparative examples. This indicates that the present invention uses a support loaded with alkali metal carbonate, which can significantly improve the yields of tertiary amines and DMDAAC with almost no side reactions, effectively improving the utilization rate of reaction raw materials. Furthermore, the hydrolysis of allyl chloride is effectively avoided during the reaction process, resulting in no byproducts such as allyl alcohols and allyl aldehydes. The yield and purity of tertiary amines are high. In contrast, sodium hydroxide in Comparative Example 1 caused hydrolysis of allyl chloride, leading to a significant decrease in the yields of tertiary amines and DMDAAC. Moreover, the tertiary amination and quaternization are carried out in two steps. After separation and purification, the impurities generated during tertiary amination remain in the aqueous phase. The separated tertiary amine is then quaternized. The quaternized product does not contain hydrochloride, and the synthesized DMDAAC monomer has high purity and can be used as a monomer in industries such as water treatment and oil extraction.

[0065] The allyl alcohol content in the tertiary amines of Examples 1-6 and the comparative examples was tested using the GC-FID method, and the results are as follows: Figure 2 As shown, the methods in Examples 1-6 effectively reduced the production of allyl alcohol, while the comparative example produced approximately 0.8% allyl alcohol.

[0066] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the contents disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing dimethyl diallyl ammonium chloride, characterized in that, The preparation method includes the following steps: S1. In the presence of water, dimethylamine, an alkaline support, and allyl chloride are mixed and subjected to contact reaction I to obtain crude tertiary amine; The alkaline support includes a support body and an alkali metal carbonate salt loaded on the support body; S2. In the presence of an organic solvent, the crude tertiary amine and allyl chloride are mixed and subjected to contact reaction II.

2. The preparation method according to claim 1, characterized in that, The carrier body is selected from at least one of coconut shell activated carbon, MCM-41 molecular sieve and γ-alumina, and the alkali metal carbonate is sodium carbonate and / or potassium carbonate.

3. The preparation method according to claim 1, characterized in that, The preparation steps of the alkaline carrier include: contacting the carrier body with an aqueous solution containing an alkali metal carbonate, wherein the content of the alkali metal carbonate in the aqueous solution is 3-25 wt%.

4. The preparation method according to claim 3, characterized in that, The amount of the aqueous solution containing the alkali metal carbonate salt used is 3-20 mL relative to 1 g of the carrier bulk; and / or, In the preparation step of the alkaline carrier, the contact is carried out under stirring conditions, and the contact time is 20-28 hours. Preferably, the preparation step of the alkaline carrier further includes: drying the solid material obtained after contact and then calcining it, wherein the calcination conditions include: a temperature of 400-500℃ and a time of 2-4h.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step S1, the mixing step includes: mixing dimethylamine and water to obtain an aqueous dimethylamine solution; mixing an alkaline support and the aqueous dimethylamine solution to obtain a dispersion; and mixing the dispersion with allyl chloride.

6. The preparation method according to any one of claims 1 to 4, characterized in that, In step S1, relative to 1 g of the dimethylamine, the amount of the basic support is 0.4-0.6 g, the amount of the allyl chloride is 1.65-1.8 g, and / or, In step S1, the conditions for the contact reaction I include: a temperature of 10-20°C, a stirring rate of 200-300 rpm, and a time of 1-2 h.

7. The preparation method according to any one of claims 1 to 4, characterized in that, In step S2, the mixing step includes: mixing the crude tertiary amine with an organic solvent to obtain a solution containing the crude tertiary amine, and then mixing the solution containing the crude tertiary amine with allyl chloride; Preferably, the method of mixing the solution containing crude tertiary amine with allyl chloride includes: adding allyl chloride dropwise to the solution containing crude tertiary amine.

8. The preparation method according to any one of claims 1 to 4, characterized in that, The amount of allyl chloride used in step S2 is 1.65-1.8g relative to 1g of the dimethylamine.

9. The preparation method according to any one of claims 1 to 4, characterized in that, The conditions for the contact reaction II include: a temperature of 35-45°C and a time of 1-3 hours.

10. The preparation method according to any one of claims 1 to 4, characterized in that, The preparation method further includes: dehydrating the crude tertiary amine obtained in step S1.

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