A method for preparing sodium lauroyl methyl taurate

Abstract

This invention provides a method for preparing sodium lauroyl methyl taurate, belonging to the field of amino acid surfactant technology. The method uses an organometallic compound as a precursor to prepare a homogeneous sol, which is then gelled, impregnated with sulfuric acid, and calcined at high temperature to obtain a composite solid acid catalyst. This catalyst exhibits excellent performance in the direct dehydration condensation reaction of lauric acid and sodium N-methyl taurate, and the catalyst can be recovered and reused through simple centrifugation. Compared with existing technologies, this process avoids the problems of severe equipment corrosion, chloride ion residue, and inorganic salt byproduct formation associated with traditional acyl chloride methods, while overcoming the difficulties in separating homogeneous catalysts and the high energy consumption of heterogeneous catalysts.

Description

Technical Field

[0001] This invention relates to the field of amino acid surfactant technology, and more particularly to a method for preparing sodium lauroyl methyl taurate. Background Technology

[0002] Surfactants are widely used in the detergent and personal care industries. Sodium lauroyl methyl taurate is an anionic surfactant made from natural lauric acid. It possesses excellent water solubility, acid and alkali resistance, rich foaming properties, and is gentle on the skin and environmentally friendly. It enjoys a continuously growing market demand in high-end personal care products.

[0003] Currently, the industrial production of sodium lauroyl methyl taurate mainly employs indirect synthesis methods, with the fatty acyl chloride method being the most typical. This method prepares the target product through a Schott-Baumann condensation reaction between lauroyl chloride and N-methyl taurate under alkaline conditions. Although the process is relatively mature, it has significant drawbacks. The raw material, lauroyl chloride, is highly reactive and easily hydrolyzed, requiring stringent drying and corrosion resistance from the production equipment. The reaction process is accompanied by the formation of inorganic salts, resulting in a product purity that is typically only around 95%, and residual chloride ions are difficult to completely remove, affecting not only the final product quality but also increasing post-processing costs. Other indirect synthesis routes, such as the fatty acid anhydride method and the fatty acid methyl ester method, while avoiding the direct use of acyl chloride, still face challenges such as the cost and separation difficulties caused by excess anhydride, or demanding reaction conditions and dependence on specific catalysts.

[0004] Existing patented technologies also largely focus on optimizing indirect methods. For example, CN1680305A discloses a method for the direct reaction of fatty acyl chlorides with N-acylmethyl taurine, which, by controlling the solvent ratio and system pH, can achieve a yield of up to 86.65% within 1-6 hours. Meanwhile, patents such as CN110938023A and CN110963947A disclose synthetic routes that use lauric acid derivatives to replace acyl chlorides, aiming to avoid equipment corrosion problems by improving the reactivity of the raw materials.

[0005] In comparison, the direct dehydration condensation method offers a more attractive technical route. This method involves the direct dehydration and amidation of lauric acid and sodium N-methyltaurate, eliminating the need for pre-preparation of active intermediates. It avoids the use of chlorination reagents, the generation of inorganic salt byproducts, and complex purification procedures from the outset, offering significant advantages such as high atom economy, short process flow, and greater adherence to green chemistry principles.

[0006] However, the key to the industrial application of the direct dehydration condensation method lies in developing an efficient catalytic system. Existing technologies, such as patents CN11619904A and CN114031516A, disclose methods for synthesizing N-acyl amino acid surfactants using homogeneous catalysts. While these methods can achieve high yields under relatively mild conditions, the miscibility of the catalyst and product makes them difficult to separate and recover. Catalyst residue not only affects product purity, but also significantly restricts its application in sensitive fields such as cosmetics, and increases production costs and environmental burden.

[0007] While heterogeneous catalytic systems can solve separation problems, their development for specific reactions remains immature. Zeng et al. reported a method for synthesizing sodium lauroyl methyl taurate using catalysts such as boric acid, zinc oxide, and magnesium oxide, achieving a product purity of over 95%. However, these systems typically require harsh conditions such as high temperatures, exhibit insufficient catalytic activity, and their stability and recyclability still need improvement, making it difficult to meet the efficiency and economic requirements of continuous industrial production. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing sodium lauroyl methyl taurate, in order to solve the problems of difficult catalyst recovery and high reaction temperature in the preparation process of sodium lauroyl methyl taurate in the prior art.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing sodium lauroyl methyl taurate, comprising the following steps: 1) Add the precursor to an alcohol solvent to prepare solution 1; 2) Mix ethanol, complexing agent and water to prepare solution 2; 3) Add solution 2 to solution 1 to perform sol-gel, and after the resulting gel has stood, immerse it in sulfuric acid solution or persulfate solution; 4) After drying, the solid material is calcined to obtain a catalyst; 5) Lauric acid, sodium N-methyl taurate, catalyst and liquid paraffin are mixed and reacted. After the reaction is completed, the mixture is centrifuged, extracted, recrystallized and dried in sequence to obtain sodium lauroyl methyl taurate. The precursor comprises two or more of the following: tetrabutyl titanate, zirconium n-propoxide, aluminum isopropoxide, tetraethyl orthosilicate, iron acetylacetone, and cerium nitrate.

[0010] Furthermore, the alcohol solvent comprises one or more of methanol, ethanol, and isopropanol, and the mass ratio of the precursor to the alcohol solvent is 2 to 10.

[0011] Furthermore, the mass ratio of ethanol, complexing agent, and water is 1~3:1~2:1~3; the complexing agent comprises one or more of acetic acid, acetylacetone, nitric acid, and hydrochloric acid.

[0012] Furthermore, the concentration of the sulfuric acid solution or persulfate solution is independently 0.01~2 mol / L, and the immersion time is 6~24 h.

[0013] Furthermore, the calcination temperature is 400~800℃, and the calcination time is 3~6h.

[0014] Furthermore, the molar ratio of lauric acid to sodium N-methyltaurate is 0.5~2.5:1; the mass ratio of lauric acid to liquid paraffin is 0.1~10:1; and the mass ratio of lauric acid to catalyst is 0.05~1:1.

[0015] Furthermore, the reaction temperature is 150~220℃, and the reaction time is 0.5~6h.

[0016] Furthermore, the extractant comprises one or more of cyclohexane, ethyl acetate, dichloromethane, cyclopentane, diethyl ether, and n-heptane.

[0017] Furthermore, the solvent used for recrystallization comprises an organic solvent and water; the organic solvent comprises one or more of ethanol, methanol, acetone, tetrahydrofuran, and isopropanol.

[0018] Furthermore, the mass ratio of the organic solvent to water is 1 to 10:1.

[0019] The beneficial effects of this invention are: 1) The use of solid acid catalysts enables simple separation and efficient recovery of catalysts, which not only solves the problem of difficult separation of traditional homogeneous catalysts, but also reduces production costs and waste emissions.

[0020] 2) The process route is simple and efficient, avoiding the complex purification steps such as desalting required by traditional methods, simplifying the operation process and improving the overall production efficiency. Attached Figure Description

[0021] Figure 1 Infrared spectrum of the catalyst prepared in Example 1 for the preparation of sodium lauroyl methyl taurate; Figure 2 The NMR spectrum is shown for sodium lauroyl methyl taurate prepared in Example 1. Detailed Implementation

[0022] This invention provides a method for preparing sodium lauroyl methyl taurate, comprising the following steps: 1) Add the precursor to an alcohol solvent to prepare solution 1; 2) Mix ethanol, complexing agent and water to prepare solution 2; 3) Add solution 2 to solution 1 to perform sol-gel, and after the resulting gel has stood, immerse it in sulfuric acid solution or persulfate solution; 4) After drying, the solid material is calcined to obtain a catalyst; 5) Lauric acid, sodium N-methyl taurate, catalyst and liquid paraffin are mixed and reacted. After the reaction is completed, the mixture is centrifuged, extracted, recrystallized and dried in sequence to obtain sodium lauroyl methyl taurate. The precursor comprises two or more of the following: tetrabutyl titanate, zirconium n-propoxide, aluminum isopropoxide, tetraethyl orthosilicate, iron acetylacetone, and cerium nitrate.

[0023] In this invention, the precursor is preferably tetrabutyl titanate and zirconium propoxide.

[0024] In this invention, the alcohol solvent comprises one or more of methanol, ethanol and isopropanol, preferably ethanol; the mass ratio of the precursor to the alcohol solvent is 2 to 10, preferably 4 to 5.

[0025] In this invention, the mass ratio of ethanol, complexing agent and water is 1~3:1~2:1~3, preferably 2~3:1.5~2:2~3; the complexing agent includes one or more of acetic acid, acetylacetone, nitric acid and hydrochloric acid, preferably nitric acid.

[0026] In this invention, the concentration of the sulfuric acid solution or persulfate solution is independently 0.01~2 mol / L, preferably 0.5~1.5 mol / L, more preferably 0.8~1.2 mol / L; the immersion time is 6~24 h, preferably 8~20 h, more preferably 12~18 h.

[0027] In this invention, the calcination temperature is 400~800℃, preferably 500~700℃, and more preferably 550~650℃; the calcination time is 3~6h, preferably 4~5h.

[0028] In this invention, the molar ratio of lauric acid to sodium N-methyltaurate is 0.5~2.5:1, preferably 1~2:1, and more preferably 1.5~2:1; the mass ratio of lauric acid to liquid paraffin is 0.1~10:1, preferably 1~9:1, and more preferably 2~6:1; the mass ratio of lauric acid to catalyst is 0.05~1:1, preferably 0.1~0.8:1, and more preferably 0.3~0.5:1.

[0029] In this invention, the reaction temperature is 150~220℃, preferably 160~200℃, and more preferably 170~180℃; the reaction time is 0.5~6h, preferably 1~5h, and more preferably 2~4h.

[0030] In this invention, the extractant comprises one or more of cyclohexane, ethyl acetate, dichloromethane, cyclopentane, diethyl ether, and n-heptane, preferably one or more of cyclohexane, ethyl acetate, and dichloromethane.

[0031] In this invention, the solvent used for recrystallization comprises an organic solvent and water; the organic solvent comprises one or more of ethanol, methanol, acetone, tetrahydrofuran and isopropanol, preferably ethanol.

[0032] In this invention, the mass ratio of the organic solvent to water is 1~10:1, preferably 2~8:1, and more preferably 4~6:1.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] 1) Tetrabutyl titanate and zirconium n-propoxide were added to anhydrous ethanol at a molar ratio of 2:1 to 4 (by mass of the precursor) to obtain solution 1; ethanol, nitric acid, and water were mixed in a ratio of 1:2:1 to obtain solution 2. Solution 2 was added dropwise to solution 1, stirred to form a gel, and allowed to stand overnight. The resulting gel was dried and impregnated with 1 mol / L sulfuric acid solution for 6 hours.

[0036] 2) After drying, remove the solid and place it in a muffle furnace. Calcinate at 500℃ for 3 hours. After cooling to room temperature, the obtained solid is SO4. 2- / ZrO2-TiO2 catalyst.

[0037] 3) Combine 500g lauric acid, 300g sodium N-methyl taurate, and 150g SO4. 2 A mixture of ZrO2-TiO2 catalyst and 100g of liquid paraffin was added to a reaction vessel, and nitrogen gas was introduced to replace the air. The stirring rate was controlled, and the reaction was carried out at 200℃ for 4 hours. After the reaction was completed, the product was dissolved in a mixed solvent of ethyl acetate and water, centrifuged, and separated.

[0038] 4) The lower aqueous layer was dried to obtain the crude product. The crude product was recrystallized from a mixed solution of water and isopropanol in a solvent ratio of 1:5. After filtration and drying, refined sodium lauroyl methyl taurate was obtained. The yield was 83.3% and the purity was 98.1%.

[0039] Example 2

[0040] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 1, the main difference being that 500g of lauric acid, 150g of N-methyl taurate, and 150g of SO4 were used. 2 / ZrO2-TiO2 catalyst, 100g of liquid paraffin were mixed and added to the reactor.

[0041] The yield of sodium lauroyl methyl taurate was 90.2%, and the purity was 98.4%.

[0042] Example 3

[0043] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 1, the main difference being that 500g of lauric acid, 300g of N-methyl taurate, and 150g of SO4 were used. 2- / Fe2O3-ZrO2 catalyst, 100g of liquid paraffin were mixed and added to the reaction vessel.

[0044] The yield of sodium lauroyl methyl taurate was 88.2%, and the purity was 97.9%.

[0045] Example 4

[0046] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 2, the main difference being that the reaction temperature was 170°C and the reaction time was 6 hours.

[0047] The yield of sodium lauroyl methyl taurate was 85.7%, and the purity was 98.2%.

[0048] Example 5

[0049] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 2, the main differences being: the reaction temperature was 180°C, the reaction time was 6 hours, and the catalyst was SO4. 2- / ZrO2-SiO2.

[0050] The yield of sodium lauroyl methyl taurate was 86.8%, and the purity was 98.6%.

[0051] Example 6

[0052] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 1, the main difference being that 500g of lauric acid, 300g of N-methyl taurate, 150g of catalyst, and 200g of liquid paraffin were mixed and added to the reaction vessel.

[0053] The yield of sodium lauroyl methyl taurate was 85.1%, and the purity was 98.7%.

[0054] Example 7

[0055] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 1, the main difference being that 500g of lauric acid, 300g of N-methyl taurate, and 150g of catalyst were added to the reaction vessel without the use of liquid paraffin.

[0056] The yield of sodium lauroyl methyl taurate was 83.8%, and the purity was 98.0%.

[0057] Comparative Example

[0058] Sodium lauroyl methyl taurate was prepared in a manner similar to that in Example 1, the main difference being that 500g of lauric acid, 300g of N-methyl taurate, 100g of liquid paraffin were mixed and added to the reaction vessel without a catalyst.

[0059] The yield of sodium lauroyl methyl taurate was 64.3%, and the purity was 97.9%.

[0060] As can be seen from the above embodiments, this invention provides a method for preparing sodium lauroyl methyl taurate. The method uses an organometallic compound as a precursor to prepare a homogeneous sol, which is then gelled, impregnated with sulfuric acid, and calcined at high temperature to obtain a composite solid acid catalyst. This catalyst exhibits excellent performance in the direct dehydration condensation reaction of lauric acid and N-methyl taurate. The catalyst can be recovered and reused through simple centrifugation. Compared with existing technologies, this process completely avoids the problems of severe equipment corrosion, chloride ion residue, and inorganic salt byproduct formation associated with traditional acyl chloride methods. It also overcomes the drawbacks of difficult separation of homogeneous catalysts and high energy consumption of heterogeneous catalysts. Post-reaction processing only requires conventional steps such as extraction, recrystallization, and drying to obtain a high-purity product. This technology has significant advantages such as catalyst recyclability, simple process flow, and safe and environmentally friendly operation, providing an innovative solution for the green industrial production of sodium lauroyl methyl taurate.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing sodium lauroyl methyl taurate, characterized in that, Includes the following steps: 1) Add the precursor to an alcohol solvent to prepare solution 1; 2) Mix ethanol, complexing agent and water to prepare solution 2; 3) Add solution 2 to solution 1 to perform sol-gel, and after the resulting gel has stood, immerse it in sulfuric acid solution or persulfate solution; 4) After drying, the solid material is calcined to obtain a catalyst; 5) Lauric acid, sodium N-methyl taurate, catalyst and liquid paraffin are mixed and reacted. After the reaction is completed, the mixture is centrifuged, extracted, recrystallized and dried in sequence to obtain sodium lauroyl methyl taurate. The precursor comprises two or more of the following: tetrabutyl titanate, zirconium n-propoxide, aluminum isopropoxide, tetraethyl orthosilicate, iron acetylacetone, and cerium nitrate.

2. The preparation method according to claim 1, characterized in that, The alcohol solvent comprises one or more of methanol, ethanol and isopropanol, and the mass ratio of the precursor to the alcohol solvent is 2 to 10.

3. The preparation method according to claim 2, characterized in that, The mass ratio of ethanol, complexing agent, and water is 1~3:1~2:1~3; the complexing agent comprises one or more of acetic acid, acetylacetone, nitric acid, and hydrochloric acid.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The concentration of the sulfuric acid solution or persulfate solution is independently 0.01~2 mol / L, and the immersion time is 6~24 h.

5. The preparation method according to claim 4, characterized in that, The calcination temperature is 400~800℃, and the calcination time is 3~6h.

6. The preparation method according to claim 1, 2, or 5, characterized in that, The molar ratio of lauric acid to sodium N-methyltaurate is 0.5~2.5:1; the mass ratio of lauric acid to liquid paraffin is 0.1~10:1; and the mass ratio of lauric acid to catalyst is 0.05~1:

1.

7. The preparation method according to claim 6, characterized in that, The reaction temperature is 150~220℃, and the reaction time is 0.5~6h.

8. The preparation method according to claim 7, characterized in that, The extractant comprises one or more of cyclohexane, ethyl acetate, dichloromethane, cyclopentane, diethyl ether, and n-heptane.

9. The preparation method according to claim 1 or 8, characterized in that, The solvent used for recrystallization includes an organic solvent and water; the organic solvent includes one or more of ethanol, methanol, acetone, tetrahydrofuran, and isopropanol.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the organic solvent to water is 1~10:1.

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