Preparation method of high-salt-tolerance and low-dioxane straight-chain primary alcohol polyoxyethylene ether sodium sulfate

Abstract

The invention provides a preparation method of high-salt-tolerance and low-dioxane straight-chain primary alcohol polyoxyethylene ether sodium sulfate, and relates to the technical field of chemical engineering, and the preparation method comprises the following steps: 1, mixing straight-chain primary alcohol with a solid acid catalyst, heating and slowly adding ethylene oxide in a nitrogen atmosphere, and aging after dropwise adding to obtain straight-chain primary alcohol polyoxyethylene ether; 2, SO3 / air mixed gas is used as a sulfating agent, and sulfating reaction is carried out on the SO3 / air mixed gas and straight-chain primary alcohol polyoxyethylene ether; and 3, neutralizing and mixing a product obtained after the sulfation reaction with a neutralizing agent and water, and then carrying out vacuum steam stripping treatment to obtain the high-salt-tolerance and low-dioxane type straight-chain primary alcohol polyoxyethylene ether sodium sulfate. According to the method, the ethoxylation reaction is carried out under the catalysis of the solid acid catalyst, the number of EO in polyether is effectively controlled, then the dioxane content in the straight-chain primary alcohol polyoxyethylene ether sodium sulfate can be effectively reduced by optimizing the conditions in the sulfation reaction without additives, and the salt resistance of the product is good.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and particularly relates to a preparation method of linear primary alcohol polyoxyethylene ether sulfate with high salt tolerance and low dioxane content. Background Art

[0002] As a commonly used anionic surfactant, linear primary alcohol polyoxyethylene ether sulfate has excellent surface activity, detergency, emulsification performance, biodegradability, etc. These advantages make it widely used in the daily chemical field.

[0003] At present, there are the following problems in the application of linear primary alcohol polyoxyethylene ether sulfate: First, since by-products such as dioxane are generated during the sulfation process of linear primary alcohol polyether, and dioxane is a class 2B carcinogen recognized by the International Agency for Research on Cancer (IARC), this severely restricts the application and development of linear primary alcohol polyoxyethylene ether sulfate in the daily chemical field. At present, relevant domestic and foreign institutions have clearly stipulated the dioxane content in alcohol ether sulfates. The industry standard in China requires that the dioxane content in linear primary alcohol ether sulfate shall not be higher than 70 mg / kg (calculated based on the product). With the improvement of people's safety awareness, the daily chemical field, especially the high-end washing and care industry, has put forward more stringent procurement standards for the dioxane content in linear primary alcohol ether sulfate. At present, the dioxane content in conventional linear primary alcohol polyoxyethylene ether sulfate products on the market is 25 - 30 mg / kg and there are problems such as large fluctuations in indicators, which can no longer meet the requirements of high-end customers. Second, when linear primary alcohol polyoxyethylene ether sulfate is used in daily chemical products, it often comes into contact with water sources of different hardness. Hard water contains relatively high concentrations of metal ions such as calcium, magnesium, and sodium (i.e., salts). Therefore, the salt tolerance of linear primary alcohol polyoxyethylene ether sulfate will affect its solubility and surface activity in a hard water environment. However, the EO chain distribution of linear primary alcohol polyoxyethylene ether sulfate prepared by the current method is relatively wide, resulting in poor salt tolerance. Therefore, how to reduce the dioxane content in the product has important research significance.

[0004] Chinese Patent No. 202111627710.3 provides a method for improving the dioxane content in fatty alcohol polyoxyethylene ether sulfate. In the existing process, when reaching the sulfonation step, a mixed material of fatty alcohol polyoxyethylene ether and alkylbenzene reacts with SO3 in a film reactor to undergo sulfonation reaction; after the sulfonation reaction is completed, the output material enters the neutralization system and is immediately neutralized to obtain the product fatty alcohol polyoxyethylene ether sulfate. Chinese Patent No. 201711161827.0 provides a production process for high-quality fatty alcohol polyoxyethylene ether sulfate with high active matter content, light color, and low dioxane residue, which includes the following steps: 1) Dissolve an appropriate amount of sulfonation stabilizer in fatty alcohol polyoxyethylene ether in advance; 2) According to the existing sulfonation production process of fatty alcohol polyoxyethylene ether sulfate, on the existing gas-phase SO3 film sulfonation device, sulfonate the fatty alcohol polyoxyethylene ether pre-dissolved with sulfonation stabilizer; 3) After sulfonation, the acid ester does not need to be aged and directly enters the neutralization system, and fatty alcohol polyoxyethylene ether sulfate is produced according to the existing neutralization process. In the above existing technologies, a certain amount of additives are added in the sulfonation stage to ensure the stability of the sulfonation process. Although it can reduce the dioxane residue in the organic material product to a certain extent, it will increase the preparation cost of the product, and the additives may enter the wastewater, increasing the generation amount of organic wastewater and the wastewater treatment cost. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: aiming at the deficiencies in the existing technology, to provide a preparation method of high-salt-tolerant and low-dioxane linear primary alcohol polyoxyethylene ether sulfate. In this method, the ethoxylation reaction is carried out under the catalysis of a solid acid catalyst to effectively control the number of EO in the polyether, and then by optimizing the conditions in the sulfation reaction, without additives, the dioxane content in the linear primary alcohol polyoxyethylene ether sulfate can be effectively reduced, and the surface performance of the product is good.

[0006] To solve the above technical problems, the technical solution of the present invention is: A preparation method of high-salt-tolerant and low-dioxane linear primary alcohol polyoxyethylene ether sulfate, which includes the following steps: I. Mix linear primary alcohol with a solid acid catalyst, slowly raise the temperature and add ethylene oxide under a nitrogen atmosphere, and carry out an aging treatment for 2 - 4 h after the dropping is completed to obtain linear primary alcohol polyoxyethylene ether; II. Use a SO3 / air mixed gas as a sulfating agent to carry out a sulfation reaction with linear primary alcohol polyoxyethylene ether; III. After the product of the sulfation reaction is neutralized and mixed with a neutralizing agent and water, carry out vacuum stripping treatment. A part of the material after vacuum stripping treatment is recycled to the neutralization mixing step, and the discharged material after vacuum stripping treatment is high-salt-tolerant and low-dioxane linear primary alcohol polyoxyethylene ether sulfate.

[0007] Preferably, the straight-chain primary alcohol is one of 1-decanol, 1-dodecanol, and 1-tetradecanol; the solid acid catalyst is one of titanium oxide-based solid acid and titanium oxide-zirconium oxide-based solid acid; the addition amount of the solid acid is 0.1-0.2 wt% of the mass of the straight-chain primary alcohol.

[0008] Preferably, the dropping temperature of ethylene oxide is 120-130 °C, and the dropping rate is 40-60 kg / h; the molar ratio of the straight-chain primary alcohol to ethylene oxide is 1:(1-3).

[0009] Preferably, when the straight-chain primary alcohol is mixed with the solid acid catalyst, it further includes a step of introducing nitrogen into the reaction vessel for replacement, and the dropping process and aging process of ethylene oxide are both carried out under a nitrogen atmosphere.

[0010] Preferably, after aging, it further includes steps of cooling and degassing and filtration; the conditions for cooling and degassing are: the temperature is 100 °C, and the time is 20-30 min.

[0011] Preferably, a multi-tube film sulfonation reactor is used for the sulfation reaction. The length of a single reaction tube of the multi-tube film sulfonation reactor is 6 m, and the inner diameter is 2-3 cm.

[0012] Preferably, the flow rate of the straight-chain primary alcohol polyoxyethylene ether in a single reaction tube is 24-28 kg / h, the residence time of the straight-chain primary alcohol polyoxyethylene ether in the reaction tube is 2-3 s, and the molar ratio of SO3 to the straight-chain primary alcohol polyoxyethylene ether is (1-1.05):1; during the sulfation reaction, the inlet and outlet temperatures of the circulating cooling water on the outer wall of the reaction tube are 24-28 °C, and the temperature difference between the inlet temperature and the outlet temperature of the circulating cooling water is less than 1 °C.

[0013] Preferably, the neutralizing agent is one of sodium hydroxide, potassium hydroxide, ammonia water, and monoethanolamine, and the temperature for neutralizing and mixing is 60-80 °C.

[0014] Preferably, the temperature of vacuum stripping is 60-80 °C, the vacuum degree is -0.095 to -0.07 MPa, the pH of the discharged material after vacuum stripping treatment is 9-10, and the effective content of the target product is 68-72 wt%.

[0015] Preferably, the mass ratio of the recycled material to the discharged material after vacuum stripping treatment is (20-25):1.

[0016] Due to the adoption of the above technical solution, the beneficial effects of the present invention are: The present invention provides a method for preparing linear primary alcohol polyoxyethylene ether sulfate with high salt tolerance and low dioxane content. Using linear primary alcohol and ethylene oxide as raw materials, ethoxylation reaction is carried out under the catalysis of a solid acid catalyst. By optimizing the temperature, time, raw material ratio of the ethoxylation reaction and the dropping rate of ethylene oxide, the content of alcohol ethers with >4EO and the content of polyethylene glycol in the linear primary alcohol polyoxyethylene ether are effectively reduced, thereby reducing the generation of dioxane in the subsequent sulfation reaction. In the sulfation reaction of the present invention, by optimizing the flow rate of the linear primary alcohol polyoxyethylene ether, its residence time in the reaction tube, the inlet and outlet temperatures and the temperature difference of the circulating cooling water on the outer wall of the reaction tube, the stability of the liquid film formed by the linear primary alcohol polyoxyethylene ether on the reaction tube is improved, ensuring the stable progress of the sulfation reaction, further reducing the occurrence of side reactions and reducing the dioxane content in the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0018] Figure 1 For the influence of the type of ethoxylation catalyst on the EO distribution. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present invention, the following will further describe the solutions of the present invention. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0020] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0021] In order to further understand the present invention, the following describes the preferred implementation schemes of the present invention in combination with embodiments. However, it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention.

[0022] The preparation of the solid acid catalyst described in the following examples and comparative examples is as follows: I. Preparation of titanium oxide type solid acid catalyst: 1 kg of titanium hydroxide was added to 20 kg of sulfuric acid solution with a concentration of 3 mol / L, impregnated at room temperature for 4 h and then filtered. The obtained filter cake was calcined in a muffle furnace at 850 °C for 5 h, then cooled to 130 °C, taken out and cooled to room temperature in a dryer to obtain a titanium oxide-based solid acid catalyst.

[0023] II. Preparation of titanium oxide-zirconium oxide-based solid acid catalyst: 0.74 kg of titanium hydroxide and 0.26 kg were added to 20 kg of sulfuric acid solution with a concentration of 3 mol / L, heated to 60 °C and stirred until completely dissolved. After cooling to room temperature, concentrated ammonia water was added for precipitation until the pH of the solution reached 9-10. After standing and impregnating for 4 h, it was filtered. The obtained filter cake was calcined in a muffle furnace at 900 °C for 5 h, then cooled to 130 °C, taken out and cooled to room temperature in a dryer, thus obtained. Example 1

[0024] (1) 0.15 kg of titanium oxide-based solid acid catalyst and 100 kg of 1-decanol were added into a reaction kettle. Nitrogen was introduced into the reaction kettle for replacement twice. After heating to 130 °C, 55.7 kg of ethylene oxide was slowly added dropwise into the reaction kettle. The addition of ethylene oxide was completed within 1 h. After the addition was completed, it was aged at a constant temperature for 3 h. After the aging was completed, the temperature was lowered to 100 °C for degassing for 30 min, and then the temperature was lowered to 50 °C for filtration and discharging to obtain 1-decanol polyoxyethylene ether; (2) 1-decanol polyoxyethylene ether formed a liquid film flowing from top to bottom (about 1 mm thick) on the inner wall of the reaction tube of a multi-tube film sulfonation reactor. The liquid film was in gas-liquid contact reaction with SO3 / air mixed gas (SO3 volume fraction was 3.0%) to obtain 1-decanol polyoxyethylene ether sulfate. The flow rate of 1-decanol polyoxyethylene ether in a single reaction tube was 26 kg / h, the residence time of 1-decanol polyoxyethylene ether in the reaction tube was 2 s, the inlet temperature of the circulating cooling water on the outer wall of the reaction tube was 25.0 °C, the outlet temperature of the cooling water was 25.3 °C, and the molar ratio of SO3 to 1-decanol polyoxyethylene ether was 1.02:1; (3) After 1-decanol polyoxyethylene ether sulfate, 32 wt% sodium hydroxide aqueous solution and water were neutralized and mixed at 70 °C, then vacuum stripping treatment was carried out under the conditions of a vacuum degree of -0.09 MPa and a temperature of 70 °C. Part of the recycled material from the vacuum stripping treatment was recycled to the neutralization and mixing process, and the remaining discharged material was homogenized for 4 h. The mass ratio of the recycled material to the discharged material was 22:1; the pH of the discharged material from the vacuum stripping treatment was 9.5, and the effective content of the target product was 70 wt%, to obtain high salt-tolerant and low dioxane-type linear primary alcohol polyoxyethylene ether sodium sulfate, whose molecular formula was C 10 H 21 O-(C2H4O)2-SO3Na. Example 2

[0025] (1) Add 0.15 kg of titanium oxide-based solid acid catalyst and 100 kg of 1-dodecanol into the reaction kettle. Purge the reaction kettle with nitrogen twice, heat up to 130 °C, and then slowly drip 47.3 kg of ethylene oxide into the reaction kettle. The dripping time of ethylene oxide is 1 h. After the dripping is completed, keep the temperature constant for aging for 3 h. After the aging is completed, cool down to 100 °C for degassing for 30 min, and then cool down to 50 °C for filtration and discharging to obtain 1-dodecanol polyoxyethylene ether; (2) The 1-dodecanol polyoxyethylene ether forms a downward-flowing liquid film (about 1 mm thick) on the inner wall of the reaction tube of the multi-tube film sulfonation reactor. The liquid film undergoes a gas-liquid contact reaction with the SO3 / air mixed gas (the volume fraction of SO3 is 3.0%) to generate 1-dodecanol polyoxyethylene ether sulfate. The flow rate of 1-dodecanol polyoxyethylene ether in a single reaction tube is 26 kg / h, the residence time of 1-dodecanol polyoxyethylene ether in the reaction tube is 2 s, the inlet temperature of the circulating cooling water on the outer wall of the reaction tube is 25.0 °C, the outlet temperature is 25.3 °C, and the molar ratio of SO3 to 1-dodecanol polyoxyethylene ether is 1.02:1; (3) After neutralizing and mixing 1-dodecanol polyoxyethylene ether sulfate, 32 wt% sodium hydroxide aqueous solution, and water at 70 °C, vacuum stripping treatment is carried out under the conditions of a vacuum degree of -0.09 MPa and a temperature of 70 °C. A part of the recycled material from the vacuum stripping treatment is recycled to the neutralization and mixing process, and the remaining discharged material is homogenized for 4 h. The mass ratio of the recycled material to the discharged material is 22:1; the pH of the discharged material from the vacuum stripping treatment is 9.5, and the effective content of the target product is 70 wt%. Obtain high-salt-tolerant and low-dioxane linear primary alcohol polyoxyethylene ether sulfate, and its molecular formula is C 12 H 25 O-(C2H4O)2-SO3Na. Example 3

[0026] The difference between this example and Example 2 is that an equal amount of 1-tetradecanol is used to replace 1-dodecanol, and other conditions are the same as those in Example 2. Example 4

[0027] The difference between this example and Example 2 is that an equal amount of titanium oxide-zirconium oxide-based solid acid catalyst is used to replace the titanium oxide-based solid acid catalyst, and other operations are the same as those in Example 2.

[0028] Comparative Example 1 The difference between this comparative example and Example 2 is that an equal amount of potassium hydroxide is used to replace the titanium oxide-based solid acid catalyst, and other conditions are the same as those in Example 2.

[0029] Comparative Example 2 The difference between this comparative example and Example 2 is that the flow rate of 1-dodecanol polyoxyethylene ether is 18 kg / h, and other conditions are the same as those in Example 2.

[0030] Comparative Example 3 The difference between this comparative example and Example 2 is that the flow rate of 1-dodecanol polyoxyethylene ether is 32 kg / h, and other conditions are the same as those in Example 2.

[0031] Comparative Example 4 The difference between this comparative example and Example 4 is that the inlet temperature of the circulating cooling water in the reaction tube is 20.0 °C, and the outlet temperature of the circulating cooling water is 20.3 °C, and other conditions are the same as those in Example 4.

[0032] Comparative Example 5 The difference between this comparative example and Example 2 is that the inlet temperature of the circulating cooling water in the reaction tube is 32.0 °C, and the outlet temperature of the circulating cooling water is 32.3 °C, and other conditions are the same as those in Example 2.

[0033] Comparative Example 6 The difference between this comparative example and Example 2 is that the mass ratio of the recycled material to the discharged material during the vacuum stripping treatment is 15:1, and other conditions are the same as those in Example 2.

[0034] Comparative Example 7 The difference between this comparative example and Example 2 is that during the preparation of 1-dodecanol polyoxyethylene ether, the dropping rate of ethylene oxide is 35 kg / h, and other operations are the same as those in Example 2.

[0035] Comparative Example 8 The difference between this comparative example and Example 2 is that during the preparation of 1-dodecanol polyoxyethylene ether, the dropping rate of ethylene oxide is 65 kg / h, and other operations are the same as those in Example 2.

[0036] Test 1: The performance parameters of the 1-dodecanol polyoxyethylene ether prepared in Example 2, Example 4, Comparative Example 1, and Comparative Examples 7-8 are shown in Table 1. The influence of the type of catalyst during the ethoxylation process on the number of EO in the linear primary alcohol polyoxyethylene ether is as Figure 1 shown.

[0037] Table 1

[0038] As can be seen from the test results in Table 1, in order to control the contents of polyethylene glycol and alcohol ethers with >4 EO in 1-dodecanol polyoxyethylene ether, the conditions of the ethoxylation reaction need to be strictly controlled. Specifically, the dropping rate of ethylene oxide and the type of catalyst are relatively critical conditions. If the dropping rate of ethylene oxide is too fast, the local concentration in the reaction system will be too high. When high-concentration ethylene oxide contacts with alcohol molecules, the reaction is incomplete, and the unreacted ethylene oxide may undergo self-polymerization reaction to generate polyethylene glycol, thus increasing the content of polyethylene glycol in 1-dodecanol polyoxyethylene ether. When ethylene oxide is added dropwise slowly, during the dropping process, ethylene oxide gradually reacts with alcohol molecules, and each EO unit has enough time to add to the alcohol chain to form a more uniform chain length. The unreacted ethylene oxide in the aging stage continues to participate in the reaction, promoting the formation of alcohol ethers with a specific number of EOs. Therefore, in order to ensure the contents of polyethylene glycol and alcohol ethers with >4 EO in 1-dodecanol polyoxyethylene ether, the dropping rate of ethylene oxide is controlled at 40-60 kg / h.

[0039] For the type of catalyst, as can be seen from the data in Example 2, Example 4, and Comparative Example 1, titanium oxide type and titanium oxide-zirconium oxide type solid acids can effectively reduce the contents of polyethylene glycol and alcohol ethers with >4 EO in linear primary alcohol polyoxyethylene ether. From Figure 1 it can be seen that the contents of high-EO alcohol ethers and polyethylene glycol are important factors for generating dioxane, and titanium oxide type and titanium oxide-zirconium oxide type solid acids can effectively reduce the content of high-EO alcohol ethers in linear primary alcohol type polyoxyethylene ether.

[0040] Test Two: Detect the dioxane in the target product according to the standard of GB / T 26388-2011 (Determination of Residual Dioxane in Surfactants - Gas Chromatography Method).

[0041] Test Three: Take n g of sodium chloride in (88 - n) g of water and stir until completely dissolved. Then add 12 g of the target product and stir at 25 °C until completely dissolved. Observe whether the aqueous solution of the sample containing sodium chloride is clear and transparent. When n g of sodium chloride is added, it is clear and transparent, while when n + 1 g is added, turbidity appears. At this time, the salt tolerance of the sample is determined to be n%.

[0042] The above test results are shown in Table 2.

[0043] Table 2

[0044] As can be seen from the test results in Table 2, through optimizing the conditions of the ethoxylation and sulfation reactions, the product prepared by the present invention has a low dioxane content and good salt tolerance performance.

[0045] In Comparative Example 1, an alkaline potassium hydroxide catalyst was used, and the content of dioxane increased significantly, indicating that the alkaline catalyst would promote the formation of high EO alcohol ethers and the self-polymerization of ethylene oxide to form polyethylene glycol, thus leading to an increase in the amount of dioxane generated during the sulfonation process. In Comparative Examples 2-3, whether the flow rate of 1-dodecanol polyoxyethylene ether was too small or too large would affect the content of dioxane. When the flow rate was too small, the liquid film formed on the inner wall of each reaction tube was prone to over-sulfonation due to film breakage during the sulfonation reaction, resulting in an increase in the amount of dioxane generated. When the flow rate was too fast, the liquid film formed on the inner wall of each reaction tube was too thick, which would cause the situation that when SO3 reacted with the gas-liquid interface of the liquid film, the inside of the liquid film had not yet reacted while the outside had been over-sulfonated, thus leading to an increase in the amount of dioxane generated. In Comparative Examples 4-5, too low or too high inlet and outlet temperatures of the circulating cooling water in the reaction tube would also increase the content of dioxane in the dispersant. Because when the inlet and outlet temperatures of the circulating cooling water in the reaction tube were relatively low, the occurrence of sulfonation side reactions would be significantly reduced, thus reducing the amount of dioxane generated. While when the inlet and outlet temperatures of the circulating cooling water were relatively high, the side reactions would be accelerated. Moreover, under low-temperature conditions, the degree of sulfonation would decrease slightly and the salt tolerance would also decrease slightly. In Comparative Example 6, when the recycle ratio was low, the stripping efficiency was low and the residue of low-boiling impurity dioxane increased. In Comparative Example 8, when the dropping rate of ethylene oxide was too high, it would lead to a too high local concentration of ethylene oxide and its self-polymerization to form polyethylene glycol, thus resulting in an increase in the amount of dioxane generated during the sulfonation process. The salt tolerance of Comparative Example 8 and conventional AES was significantly lower than that of Examples 1, 2, and 3. This was because the amount of polyethylene glycol generated during the ethoxylation process in Comparative Example 8 increased, and the content of primary alcohol sulfate in the subsequent sulfonation process would be significantly higher than that in the examples, thus reducing the salt tolerance.

[0046] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The descriptions of the above examples are only used to help understand the method of the present invention and its core idea, including the best mode, and also enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field of the present invention, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A preparation method of linear primary alcohol polyoxyethylene ether sulfate with high salt tolerance and low dioxane content, characterized in that, It includes the following steps: Mix the linear primary alcohol with a solid acid catalyst. Under a nitrogen atmosphere, slowly raise the temperature and add ethylene oxide dropwise. After the dropping is completed, carry out an aging treatment for 2 - 4 h to obtain a linear primary alcohol polyoxyethylene ether; Use a SO3 / air mixed gas as a sulfating agent to carry out a sulfation reaction with the linear primary alcohol polyoxyethylene ether; The product after the sulfation reaction is neutralized and mixed with a neutralizing agent and water, and then subjected to vacuum stripping treatment. A part of the material after the vacuum stripping treatment is recycled back to the neutralization and mixing step, and the discharged material obtained by the vacuum stripping treatment is a high salt - resistant and low - dioxane type sodium linear primary alcohol polyoxyethylene ether sulfate.

2. The preparation method of a high salt-tolerant and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The linear primary alcohol is one of 1 - decanol, 1 - dodecanol, and 1 - tetradecanol; the solid acid catalyst is one of a titanium oxide - type solid acid and a titanium oxide - zirconium oxide - type solid acid; the addition amount of the solid acid catalyst is 0.1 - 0.2 wt% of the mass of the linear primary alcohol.

3. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The dropping temperature of ethylene oxide is 120 - 130 °C, and the dropping rate is 40 - 60 kg / h; the molar ratio of the linear primary alcohol to ethylene oxide is 1:(1 - 3).

4. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: After mixing the linear primary alcohol with the solid acid catalyst, it also includes a step of introducing nitrogen into the reaction vessel for replacement, and the dropping process and the aging process of ethylene oxide are both carried out under a nitrogen atmosphere.

5. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: After the aging is completed, it also includes steps of cooling and degassing, and filtration; the conditions for cooling and degassing are: the temperature is 100 °C, and the time is 20 - 30 min.

6. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: A multi - tube film - type sulfonation reactor is used for the sulfation reaction. The length of a single reaction tube of the multi - tube film - type sulfonation reactor is 6 m, and the inner diameter is 2 - 3 cm.

7. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The flow rate of the linear primary alcohol polyoxyethylene ether in a single reaction tube is 24 - 28 kg / h, the residence time of the linear primary alcohol polyoxyethylene ether in the reaction tube is 2 - 3 s, and the molar ratio of SO3 to the linear primary alcohol polyoxyethylene ether is (1 - 1.05):1; during the sulfation reaction, the inlet and outlet temperatures of the circulating cooling water on the outer wall of the reaction tube are 24 - 28 °C, and the temperature difference between the inlet and outlet of the circulating cooling water is less than 1 °C.

8. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The neutralizing agent is one of sodium hydroxide, potassium hydroxide, ammonia water, and monoethanolamine, and the temperature for neutralization and mixing is 60 - 80 °C.

9. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The temperature for vacuum stripping is 60 - 80 °C, the vacuum degree is - 0.095 to - 0.07 MPa, the pH of the discharged material after the vacuum stripping treatment is 9 - 10, and the effective content of the target product is 68 - 72 wt%.

10. The preparation method of a high salt tolerance and low dioxane linear primary alcohol polyoxyethylene ether sulfate according to claim 1, characterized in that: The mass ratio of the recycled material to the discharged material after the true - air stripping treatment is (20 - 25):1.

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