Preparation method of anionic surfactant sodium dodecyl sulfate

Abstract

The invention belongs to the technical field of high-end reagent synthesis, and particularly relates to a preparation method of an anionic surfactant sodium dodecyl sulfate, which is suitable for the scenes of emulsifiers, flotation agents, soakers and the like in the textile printing and dyeing industry. A traditional synthesis method of sodium dodecyl sulfate often has the problems of harsh reaction conditions (such as high temperature and high pressure), more byproducts, low purity (impurities such as inorganic salt and unreacted alkane residues) and the like, and needs to depend on an additional catalyst, so that the cost and environmental protection pressure are increased. The invention aims to realize high-efficiency, low-consumption and high-purity green synthesis by optimizing a reaction system and a purification process. Under the autocatalysis condition, water, sodium sulfite and 1-bromododecane are mixed for reaction to obtain sodium dodecyl sulfate, and after alcohol purification, the high-purity sodium dodecyl sulfate product with the content of more than or equal to 99.5% can be obtained and can completely meet the specific requirements of serving as a surfactant, a washing agent, an emulsifying agent and a dispersing agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of surfactant synthesis, and relates to a preparation method of an anionic surfactant, sodium dodecyl sulfonate. This method is applicable to textile printing and dyeing, washing, flotation and other industrial applications, and can provide surfactant products with high purity and high efficiency. Background Art

[0002] Surfactants are widely used in many fields such as detergents, textile industry, cosmetics, food, medicine, etc. Among them, anionic surfactants have become one of the mainstream products in the market due to their excellent detergency, emulsification, dispersion and wetting properties. Sodium dodecyl sulfonate (SDS) is an important anionic surfactant, which is widely used in fields such as detergents, textile auxiliaries, flotation agents and emulsifiers. The existing synthesis methods of sodium dodecyl sulfonate are complex in process and prone to produce by-products, which affect the product purity. Therefore, there is an urgent need for a more efficient, environmentally friendly and economical preparation method of sodium dodecyl sulfonate to meet the needs of the high-end surfactant market. Summary of the Invention

[0003] The present invention provides a preparation method of high-purity sodium dodecyl sulfonate. This method is carried out under autocatalytic conditions, without the need for an additional catalyst, which simplifies the reaction system, reduces the production cost, and at the same time improves the purity of the target product.

[0004] The present invention provides a preparation method of high-purity sodium dodecyl sulfonate, which mainly includes the following steps: (1) In a reaction kettle, mix water and sodium sulfite and stir, add 1-bromododecane and carry out the reaction under autocatalytic conditions. The molar ratio of 1-bromododecane to sodium sulfite is 0.6~1:1, and the mass ratio of 1-bromododecane to water is 1:4~12; (2) The temperature of the above reaction system is 130~190 °C, the pressure is 0.2~1.4 MPa, and the reaction time is 1~5 hours; (3) After the reaction is completed, carry out vacuum filtration on the reaction mixture to remove water, and obtain the crude product after cooling; (4) Dissolve the crude product in ethanol, heat the temperature to about 78 °C, the boiling point, add activated carbon for decolorization, filter while it is hot and cool to crystallize, wash and dry the crystalline product in sequence to obtain sodium dodecyl sulfonate with a purity ≥99.5%.

[0005] Advantages and Positive Effects of the Present Invention: The synthesis method of the present invention makes it easier for 1-bromododecane and sodium sulfite to react in the presence of a catalyst. The purified sodium dodecyl sulfonate has good solubility and high purity, and the product content ≥99.5%. It can be completely used for the synthesis of high-end reagents, and has broad market prospects and application values. Detailed implementation mode

[0006] Example 1: Low-temperature, low-pressure, long-time reaction system In a high-pressure reactor, 1-bromododecane (5 g), anhydrous sodium sulfite (4.21 g) and deionized water (40 g) were added in sequence according to a molar ratio of 0.6:1, and stirred to form a homogeneous solution. The reaction system was heated to 130 °C, the pressure was maintained at 0.2 MPa, and the reaction continued for 5 hours. During the reaction, it was a self-catalytic cycle system without the need to add additional catalysts. After the reaction, water was removed by vacuum filtration, and the white crude product was precipitated by cooling to room temperature. The crude product was dissolved in 100 mL of ethanol, heated to about the boiling point of 78 °C, 5 g of activated carbon was added for decolorization for 30 minutes, filtered while hot and cooled for crystallization, and finally recrystallized from ethanol 3 times and dried at 25 °C for 6 hours to obtain sodium dodecyl sulfonate with a purity of 27.65%.

[0007] Example 2: Reaction system under medium temperature conditions The molar ratio of raw materials was adjusted to 0.8:1 (1-bromododecane:sodium sulfite), 50 g of deionized water was added, the reaction temperature was raised to 160 °C, the pressure was increased to 0.8 MPa, and the reaction time was shortened to 3 hours. Other reaction steps and conditions remained unchanged. The purity of the final product reached 99.7%, and the reaction conversion rate was increased to 84.36%.

[0008] Example 3: Reaction system under high temperature conditions The molar ratio of raw materials remained unchanged at 0.8:1 (1-bromododecane:sodium sulfite), 50 g of deionized water was added, the reaction temperature was raised to 190 °C, the pressure was increased to 0.8 MPa, and the reaction time was shortened to 1 hour. Other reaction steps and conditions remained unchanged. The purity of the final product reached 99.5%, and the reaction conversion rate was 70.66%.

[0009] Example 4: Optimal reaction system obtained by response surface method According to the response surface diagram and related data designed by the design-expert program using the response surface method, the optimal reaction conditions were obtained. The molar ratio of the adjusted raw materials was 0.6:1 (1-bromododecane:sodium sulfite), the mass of added water was 47.69 g, the reaction temperature was raised to 172.69 °C, and the reaction time was adjusted to 3.58 hours. Under these conditions, the excessive supply of sodium sulfite accelerated the reaction process, and at the same time, the high temperature promoted the decomposition of by-products, and the purity and yield of the product were significantly improved. The purity of the final product reached 99.7%, and the yield was increased to 99.5%.

Claims

1. A method for preparing anionic surfactant sodium dodecyl sulfate, characterized in that: The following steps are involved: (1) In a reaction kettle, water and sodium sulfite are mixed and stirred, and 1-bromodecane is added; (2) conducting the reaction under autocatalytic conditions, with a reaction temperature of 130-190°C, a pressure of 0.2-1.4 MPa, and a reaction time of 1-5 hours; (3) After the reaction is completed, the reaction mixture is filtered under reduced pressure to remove water, and then cooled to obtain a crude product; (4) dissolving the crude product in ethanol, heating and stirring for a period of time, adding activated carbon for decolorization, filtering while hot and cooling for crystallization; (5) The crystalline product is washed and dried in sequence to obtain sodium dodecyl sulfate with a purity of ≥99.5%.

2. The preparation method according to claim 1, characterized in that: The molar ratio of 1-bromodecane to sodium sulfite in step (1) is 0.6-1:1, and the mass ratio of 1-bromodecane to water is 1:4-12.

3. The preparation method according to claim 1, characterized in that: The reaction temperature in step (2) is 130-190° C., the pressure is 0.2-1.4 MPa, and the reaction time is 1-5 hours.

4. The preparation method according to claim 1, characterized in that: The recrystallization solvent in step (4) is ethanol, which is heated to a boiling point of about 78° C. The amount of activated carbon added is 1 to 3% of the mass of the crude product, and the stirring time is usually 20 to 30 minutes to completely dissolve it.