Method for reversibly regulating and controlling water solubility of long-chain alkyl sodium sulfonate

Abstract

The invention provides a method for reversibly regulating and controlling the water solubility of long-chain alkyl sodium sulfonate, which comprises the following steps: by taking benzamide tertiary amine hydrochloride (BTACl) as an auxiliary agent, reducing the Krafft temperature (KT) of the long-chain alkyl sodium sulfonate to 25 DEG C or below, promoting the water solubility of the long-chain alkyl sodium sulfonate to be increased so as to exert the normal surfactant function of the long-chain alkyl sodium sulfonate, and then adding alkali to neutralize BTACl so as to obtain the water solubility of the long-chain alkyl sodium sulfonate. The KT of the long-chain alkyl sodium sulfonate is raised to 25 DEG C or above, and the water solubility of the long-chain alkyl sodium sulfonate is reduced, so that the long-chain alkyl sodium sulfonate is crystallized and separated out from an aqueous solution, and the separation, recovery and reutilization of the long-chain alkyl sodium sulfonate are realized. The BTACl used in the invention has a better effect of reversibly regulating and controlling long-chain alkyl sodium sulfonate KT. The method for reversibly regulating and controlling the water solubility of the long-chain alkyl sodium sulfonate can be suitable for any one or a mixture of several of sodium dodecyl sulfate, sodium tetradecyl sulfate and sodium hexadecyl sulfate. The method for reversibly regulating and controlling the water solubility of the long-chain alkyl sodium sulfonate, provided by the invention, is relatively high in speed of regulating and controlling the water solubility of the surfactant. The method for regulating and controlling the water solubility of the long-chain alkyl sodium sulfonate, provided by the invention, is very high in reversibility degree, and the reversible regulation and control frequency can be at least 10 times. According to the method for reversibly regulating and controlling the water solubility of the long-chain alkyl sodium sulfonate, the process of recovering the surfactant is relatively simple, the equipment requirement is relatively low, the cost is relatively low, and the recovery rate of recovering various long-chain alkyl sodium sulfonate is not lower than 96%.

Description

Technical Field

[0001] The invention relates to reversible regulation of the water solubility of a surfactant, in particular to a method for reversibly regulating the Krafft temperature of an anionic surfactant sodium long-chain alkyl sulfonate, and belongs to the technical field of sustainable green fine chemical industry. Background Art

[0002] Surfactants are one of the important fine chemical products, among which anionic surfactants are one of the types of detergent surfactants with the largest output and the widest application. They are widely used in the production of detergents, foaming agents, emulsifiers, solubilizers and wetting agents in various industrial and civil fields. The application performance of anionic surfactants depends greatly on the solubility of anionic surfactants in water. This is because only when the amount of anionic surfactant dissolved in water reaches above its critical micelle concentration can the anionic surfactant dissolved in water form micelles, thereby realizing its washing, foaming, emulsification, solubilization and wetting properties. Fully displayed. Many studies have found that only when the temperature reaches a certain threshold or above, the amount of anionic surfactant dissolved in water can reach its critical micelle concentration. This temperature is the critical micelle temperature of the ionic surfactant, also known as the Krafft temperature (K T , o C). K T The value reflects the high or low water solubility of the anionic surfactant. T It is one of the important performance parameters of anionic surfactants. More importantly, K T Larger anionic surfactants are difficult to use due to their poor water solubility. A typical example is sodium long-chain alkyl sulfonate, such as sodium dodecyl sulfonate. T Up to 37.5 o C. However, the molecular structure of sodium dodecyl sulfate suggests that the biodegradability, acid resistance and hard water resistance of sodium dodecyl sulfate should be better than those of sodium dodecyl sulfate. T The method of converting sodium dodecyl sulfate into K T Lowering to room temperature or below will undoubtedly help sodium dodecyl sulfate and other products with high K TThe application of anionic surfactants in industrial, agricultural and civil fields. From another perspective, up to now, all kinds of detergents and other surfactant-rich products have been discharged into the environment through various channels after use. On the one hand, they bring serious adverse interferences such as foaming, emulsification and adsorption to the sewage disposal system, and on the other hand, they also bring great negative burdens to the environmental ecosystem. What is more serious is that industrial synthesis with petrochemical raw materials derived from petroleum is still the main way for people to obtain anionic surfactants. Therefore, discharging used anionic surfactants into the environment is a great waste of precious resources such as petroleum. Therefore, if an effective method can be proposed to effectively recycle and reuse used anionic surfactants, it will undoubtedly contribute to the low-carbon and sustainable development of the surfactant industry.

[0003] Regarding “K T In view of the current situation that "larger anionic surfactants are difficult to use due to their poor water solubility" and the urgent need for "efficient recovery and reuse of used anionic surfactants" for sustainable development, the present invention proposes a method for reversibly regulating the water solubility of anionic surfactant long-chain alkyl sodium sulfonate, using benzamide tertiary amine hydrochloride as an auxiliary agent, which can reversibly regulate the K of long-chain alkyl sodium sulfonate. T Reduced to 25 o C and below, the water solubility of long-chain alkyl sodium sulfonate increases and it exerts its normal surfactant function. Then, by adding alkali to neutralize the benzamide tertiary amine hydrochloride, the K of long-chain alkyl sodium sulfonate is increased. T Increase to 25 o C or above, reducing the water solubility of long-chain alkyl sodium sulfonate, thereby crystallizing and precipitating from the aqueous solution, and realizing the separation, recovery and reuse of long-chain alkyl sodium sulfonate. Usually, the K of ionic surfactants can be changed by adding inorganic salts, organic salts, and compounding several surfactants. T However, these traditional measures can only achieve a one-way increase in K T Or one-way reduction of K T The present invention provides a method for reversibly regulating the water solubility of anionic surfactant sodium long-chain alkyl sulfonate, which can achieve the effect of sodium long-chain alkyl sulfonate K T Reversible regulation (i.e., by reducing K T Then it can reversely increase K T, and vice versa), therefore, the method for reversibly regulating the water solubility of anionic surfactant long-chain sodium alkyl sulfonate provided by the present invention is essentially different from the traditional method of "adding inorganic salts, organic salts, compounding several surfactants, etc." In addition, there are reports on reversible changes in the water solubility of ionic surfactants through redox (Langmuir, 2020, 36, 3514−3521), CO2 / N2 (ACS SustainableChem. Eng., 2018, 6, 4981−4986) and pH regulation (Chem. Eng. J., 2023, 458, 141297) techniques. However, these reported techniques are only applicable to hydrophobic chains containing selenium (Langmuir, 2020, 36, 3514−3521), amines (ACS Sustainable Chem. Eng., 2018,6, 4981−4986; Chem. Eng. J., 2023, 458, 141297) and other special functional groups are not suitable for traditional surfactants such as long-chain alkyl sodium sulfonate. Therefore, the method for reversibly regulating the water solubility of anionic surfactant long-chain alkyl sodium sulfonate provided by the present invention is also essentially different. T According to a report by Chem. Eng. J., 2021, 417, 129316, this technology can only raise the pH to about 9.57 when using N2 technology to increase the pH, and can only increase the K of sodium dodecane sulfonate. T Reduced to 25 o C and below, for sodium alkyl sulfonates with longer carbon chains (such as sodium tetradecyl sulfonate and sodium hexadecyl sulfonate), it is impossible to achieve K T Reduced to 25 o C and below. In addition, the recovery rate of sodium dodecyl sulfate by this technology is only 92%. In the process of changing pH, gas needs to be blown in to produce obvious foam, which is not conducive to practical operation and is time-consuming. The method for reversibly regulating the water solubility of anionic surfactant long-chain alkyl sodium sulfonate provided by the present invention has a wider range of reversible pH regulation, faster speed, no foam generation, and is conducive to practical operation. T Reduced to 25 o C and below, and the K of sodium alkyl sulfonates with longer carbon chains (including sodium tetradecyl sulfonate and sodium hexadecyl sulfonate) can be T Reduced to 25 oC and below, and the recovery rates of sodium dodecyl sulfonate, sodium tetradecyl sulfonate and sodium hexadecyl sulfonate are all not less than 96%. The molecular structural formulas of sodium dodecyl sulfonate, sodium tetradecyl sulfonate, sodium hexadecyl sulfonate and benzamide tertiary amine hydrochloride of the present invention are shown in the figure below: (Sodium dodecyl sulfate, C12SS), (Sodium Tetradecyl Sulfonate, C14SS), (Sodium hexadecyl sulfate, C16SS) and (Benzamide tertiary amine hydrochloride, BTACl). Summary of the invention

[0004] The purpose of the present invention is to provide a method for reversibly regulating the water solubility of sodium long-chain alkyl sulfonate in view of the shortcomings of the prior art. By using benzamide tertiary amine hydrochloride (BTACl) as an auxiliary agent, the Krafft temperature (K T , o C) Reduced to 25 o C and below, which increases the water solubility of sodium long-chain alkyl sulfonate and enables it to play its normal surfactant function. Then, by adding alkali to neutralize BTACl, the K T Increase to 25 o C or above, the water solubility of the long-chain alkyl sodium sulfonate is reduced, so that it is crystallized from the aqueous solution, thereby realizing the separation, recovery and reuse of the long-chain alkyl sodium sulfonate.

[0005] Furthermore, the method uses benzamide tertiary amine hydrochloride (BTACl) as an auxiliary agent, characterized in that the molar ratio of BTACl to long-chain alkyl sodium sulfonate is in the range of 0.66 to 6.51, and HCl is used to control the pH value of the long-chain alkyl sodium sulfonate aqueous solution to be no higher than 4.4.

[0006] Furthermore, the long-chain alkyl sodium sulfonate is characterized in that it is any one or a mixture of several of sodium dodecyl sulfonate (C12SS), sodium tetradecyl sulfonate (C14SS) and sodium hexadecyl sulfonate (C16SS).

[0007] Furthermore, the neutralization of BTACl by adding alkali is characterized in that sodium hydroxide or potassium hydroxide is used to react with BTACl for neutralization and the pH of the system is controlled within the range of 11.0±0.1.

[0008] Furthermore, the separation, recovery and reuse of the long-chain alkyl sodium sulfonate is characterized in that when the pH is within the range of 11.0±0.1, the long-chain alkyl sodium sulfonate can be precipitated from the system in the form of crystals, and the long-chain alkyl sodium sulfonate can be separated and recovered by conventional filtration, and the recovery rate is not less than 96%.

[0009] The method of the present invention has the following advantages over the prior art: 1. The benzamide tertiary amine hydrochloride (BTACl) used in the present invention can reversibly regulate the long-chain alkyl sulfonate sodium K T The effect is better and can be achieved in a wider temperature range. T reversible regulation.

[0010] 2. The method for reversibly regulating the water solubility of long-chain sodium alkyl sulfonate provided by the present invention is applicable to a wide variety of surfactants, and can be applicable to any one or a mixture of sodium dodecyl sulfonate (C12SS), sodium tetradecyl sulfonate (C14SS) and sodium hexadecyl sulfonate (C16SS).

[0011] 3. The method for reversibly regulating the water solubility of long-chain sodium alkyl sulfonate provided by the present invention is for K T The speed of water solubility regulation of surfactants is fast, and K can be achieved in just tens of seconds or even seconds. T decrease and increase.

[0012] 4. The method for reversibly regulating the water solubility of long-chain sodium alkyl sulfonate provided by the present invention is to regulate K T The process is highly reversible, and the number of reversible controls can reach at least 10 times.

[0013] 5. The method for reversibly regulating the water solubility of long-chain sodium alkyl sulfonate provided by the present invention has a relatively simple process for recovering surfactants, low equipment requirements, low cost, and a high recovery rate for a variety of long-chain sodium alkyl sulfonates (the recovery rate is not less than 96%). BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The benzamide tertiary amine hydrochloride (BTACl) obtained in Example 1 of the present invention is 1 H NMR spectrum.

[0015] Figure 2 The K of C12SS, C14SS and C16SS regulated by BTACl in Examples 2, 3 and 4 of the present invention, respectively T 's effect diagram.

[0016] Figure 3 is the K of BTACl to C12SS in Example 5 of the present invention T Schematic diagram of the effect of reversible regulation. DETAILED DESCRIPTION

[0017] The following is a further description of the method and effect of reversibly regulating the water solubility of long-chain sodium alkyl sulfonate provided by the present invention through specific examples.

[0018] Example 1: Synthesis of Benzamide Tertiary Amine Hydrochloride (BTACl) This example mainly describes the synthesis method of benzamide tertiary amine hydrochloride (BTACl). The specific reaction process is as follows: Under ice bath conditions, take 20 mL of dichloromethane in a three-necked bottle, add NaOH (0.87 g, 21.62 mmol) to dichloromethane and stir, then add N,N-dimethylethylenediamine (2.1 g, 22.68 mmol), and use a constant pressure dropping funnel to drop benzoyl chloride (3.04 g, 21.62 mmol) into the above solution. After the addition is complete, at 25 o C for 6 h. After the reaction, dichloromethane was removed and the concentrated crude product was diluted with petroleum ether (boiling range 30-60 o C) After washing and filtration, 3.48 g of benzamide tertiary amine hydrochloride (BTACl) was obtained with a yield of 83.72%.

[0019] Benzamide tertiary amine hydrochloride (BTACl) 1 H NMR spectrum is shown in Figure 1 .

[0020] Example 2: BTACl reduces the K of C12SS T BTACl was added to the C12SS aqueous solution according to the molar ratio of BTACl to C12SS in the range of 0-3.1, and the pH value of the solution was adjusted to 4.4 with HCl, and the mass percentage of C12SS in the obtained solution was controlled to 1.0%. The obtained sample was placed in a refrigerator to cool until crystals precipitated and then kept at a constant temperature for 12 hours, and then its K was determined by the visual temperature rise method. T Each sample was measured three times and the average value was taken. The experimental results are shown in Figure 2 .Depend on Figure 2 The results show that when the molar ratio of BTACl to C12SS is in the range of 0-3.1, the K T From about 37.5 o C continued to decrease to 6.8 o C near; C12SS K T From about 37.5 o C reduced to 25 oC and below, the amount of BTACl required is about 0.66~3.1 times that of C12SS, that is, when the molar ratio of BTACl to C12SS is in the range of 0.66~3.1, the K of C12SS is T Between 6.8 and 25 o C range.

[0021] The molar ratio of BTACl to C12SS was fixed at 1:1, and the pH value of the solution was adjusted to 4.4 with sulfuric acid and phosphoric acid, respectively. The K of C12SS was measured. T 19.2±0.2 o C and 19.1±0.3 o C, and the result obtained by adjusting the pH to 4.4 with HCl was 19.3±0.1 o C is very close, which shows that the type of inorganic acid used to adjust pH has an effect on the K of C12SS. T The measurement results were not significantly adversely affected, therefore, HCl was used to adjust the pH value of the long-chain alkyl sodium sulfonate aqueous solution in the subsequent examples.

[0022] The molar ratio of BTACl to C12SS was fixed at 1:1, and the pH value of the solution was adjusted to the range of 1.0-4.4 with hydrochloric acid. The K of C12SS was measured. T In 19.3~19.6 o C range, it can be seen that further adjusting the pH value of the C12SS solution from 4.4 to a lower pH level has a significant effect on reducing the K T The meaning of the numerical value is not obvious, therefore, in the subsequent examples, HCl was used to adjust the pH value of the aqueous solution of long-chain sodium alkyl sulfonate to 4.4.

[0023] Example 3: BTACl reduces the K of C14SS T BTACl was added to the C14SS aqueous solution according to the molar ratio of BTACl to C14SS in the range of 0-6.1, and the pH value of the solution was adjusted to 4.4 with HCl, and the mass percentage of C14SS in the obtained solution was controlled to 1.0%. The obtained sample was placed in a refrigerator to cool until crystals precipitated and then kept at a constant temperature for 12 hours, and then its K was determined by the visual temperature rise method. T Each sample was measured three times and the average value was taken. The experimental results are shown in Figure 2 .Depend on Figure 2 The results show that when the molar ratio of BTACl to C14SS is in the range of 0-6.1, the K T From about 46.9 o C continued to decrease to 9.6 o C near; C14SS K T From about 46.9o C reduced to 25 o C and below, the amount of BTACl required is about 1.23~6.1 times that of C14SS, that is, when the molar ratio of BTACl to C12SS is in the range of 1.23~6.1, the K of C14SS is T Between 9.6 and 25 o C range.

[0024] The molar ratio of BTACl to C14SS was fixed at 2:1. After adjusting the pH value of the solution to 4.4 with sulfuric acid and phosphoric acid, the K of C14SS was measured. T 17.4±0.2 o C and 17.3 ± 0.3 o C, and the result obtained by adjusting the pH to 4.4 with HCl was 17.5±0.2 o C is very close, which proves again that the type of inorganic acid used to adjust pH has an important influence on the K of sodium long-chain alkyl sulfonate. T There was no significant adverse effect on the test results.

[0025] The molar ratio of BTACl to C14SS was fixed at 2:1, and the pH value of the solution was adjusted to the range of 1.0-4.4 with hydrochloric acid. The K of C14SS was measured. T At 17.5~17.9 o C range, it was again demonstrated that further adjusting the pH value of the sodium long-chain alkyl sulfonate solution from 4.4 to a lower pH level had an important effect on reducing its K T The meaning of the values ​​is not obvious.

[0026] Example 4: BTACl reduces the K of C16SS T BTACl was added to the C16SS aqueous solution according to the molar ratio of BTACl to C16SS in the range of 0-6.5, and the pH value of the solution was adjusted to 4.4 with HCl, and the mass percentage of C16SS in the obtained solution was controlled to 1.0%. The obtained sample was placed in a refrigerator to cool until crystals precipitated and then kept at a constant temperature for 12 hours, and then its K was determined by the visual temperature rise method. T Each sample was measured three times and the average value was taken. The experimental results are shown in Figure 2 .Depend on Figure 2 The results show that when the molar ratio of BTACl to C16SS is in the range of 0-6.5, the K T From about 53.1 o C continued to decrease to 13.9 o C near; C16SS K T From about 53.1 o C reduced to 25 oC and below, the amount of BTACl required is about 2.0~6.5 times that of C16SS, that is, when the molar ratio of BTACl to C12SS is in the range of 2.0~6.5, the K of C16SS is T Between 13.9 and 25 o C range.

[0027] Example 5: Reversible regulation of K of long-chain sodium alkyl sulfonate T This example mainly illustrates that the neutralization reaction between BTACl and sodium hydroxide (or potassium hydroxide) is used to increase the K of long-chain alkyl sulfonate. T The technical process and effect of long-chain alkyl sulfonate sodium K can be reversibly regulated. T The technical process and effect of the three long-chain alkyl sodium sulfonates C12SS, C14SS and C16SS are described as follows: For a 1.0% mass percent C12SS aqueous solution, the molar ratio of BTACl to C12SS was fixed at 1:1, and the pH value of the solution was adjusted to 4.4 with HCl. At this time, the K of C12SS was measured. T About 19.3 o C; then use sodium hydroxide to neutralize BTACl, and adjust the pH value to 11.0±0.1 with sodium hydroxide, and measure the K of C12SS T About 36.1 o C( Figure 3 A), this is because BTACl reacts with sodium hydroxide to generate benzamide tertiary amine. It can be seen that the K of C12SS can be reduced by neutralizing with sodium hydroxide and keeping the solution pH within the range of 11.0±0.1. T From 19.3 o C increased to 36.1 o C, realized the K of C12SS T On this basis, HCl was used to adjust the pH to 4.4, and the K T Continue to lower the pH, and then use sodium hydroxide to raise the pH to 11.0±0.1. The K T Continue to increase, so as to achieve the K of C12SS T The cyclic reversible regulation can reach at least 10 cycles. Figure 3 A (the base is sodium hydroxide). At the same time, Figure 3 A results suggest that as the number of cycles increases, the K of C12SS corresponding to pH = 4.4 T The value shows a trend of continuous increase. The reason is that during the alternating reaction of HCl and sodium hydroxide, the byproduct sodium chloride continues to accumulate. If the base is changed to potassium hydroxide, the K of the above C12SST The cyclic reversible regulation can still be successfully achieved. Figure 3 B (base is potassium hydroxide), and at least 10 cycles; Figure 3 In B (the base is potassium hydroxide), the above “corresponding to the K of C12SS at pH = 4.4” T The value showed a trend of continuous increase" was well alleviated, but the K of C12SS corresponding to pH = 11.0 ± 0.1 T Numerical ratio Figure 3 The corresponding results in A were reduced, so the reversible regulation of long-chain alkyl sulfonate sodium K T From the perspective of the reversibility of the process, the combination of hydrochloric acid and potassium hydroxide is preferred; from the perspective of long-chain alkyl sulfonate sodium K T From the perspective of the recovery effect, the combination of hydrochloric acid and sodium hydroxide is preferred, which is beneficial to the recovery effect of long-chain sodium alkyl sulfonate.

[0028] For a 0.5% mass percent C14SS aqueous solution, the molar ratio of BTACl to C14SS was fixed at 1:1, and the pH value of the solution was adjusted to 4.4 with HCl. At this time, the K T About 27.9 o C; then use sodium hydroxide to neutralize BTACl, and adjust the pH value to 11.0±0.1 with sodium hydroxide, and measure the K of C14SS T About 52.1 o C, it can be seen that the K of C14SS can be reversibly regulated T It is also achievable.

[0029] For a 0.2% mass percent C16SS aqueous solution, the molar ratio of BTACl to C16SS was fixed at 1:1, and the pH value of the solution was adjusted to 4.4 with HCl. At this time, the K of C16SS was measured. T About 37.3 o C; then use sodium hydroxide to neutralize BTACl, and adjust the pH value to 11.0±0.1 with sodium hydroxide, and measure the K of C16SS T About 55.4 o C, it can be seen that the K of C16SS can be reversibly regulated T It is also achievable.

[0030] Example 6: Recovery of long-chain alkyl sodium sulfonate Prepare a 1.0% C12SS aqueous solution, fix the molar ratio of BTACl to C12SS at 1:1, and adjust the pH value of the solution to 4.4 with HCl. oC; then sodium hydroxide was added to neutralize BTACl, and the pH value was adjusted to 11.0±0.1 with sodium hydroxide. The solution became turbid within 30 seconds. This is because the K T Higher (36.1 o C, Figure 3 A) The precipitation from the aqueous solution is caused by the precipitation. After the precipitation is fully precipitated, it is filtered, washed with cold water and vacuum dried to obtain white flaky C12SS with a recovery rate of 96.8±0.5%. Figure 3 A result suggests that the presence of sodium chloride will further increase the K of C12SS T Therefore, by continuing to add 5% of the total mass of sodium chloride to the mother liquor obtained by the above filtration, a small amount of C12SS can be further recovered, so that the recovery rate of C12SS is increased to 98.8±0.4%.

[0031] Prepare a 1.0% C14SS aqueous solution, fix the molar ratio of BTACl to C14SS at 3:1, and adjust the pH value of the solution to 4.4 with HCl. o C conditions, because the K T About 13.2 o C; sodium hydroxide was then added to neutralize BTACl, and the pH value was adjusted to 11.0±0.1 with sodium hydroxide. The solution became turbid within 13 seconds. This is because the K T Higher (about 52.8 o C), caused by precipitation from aqueous solution, after the precipitation is fully precipitated, it is filtered, washed with cold water and vacuum dried to obtain pale grayish white flaky C14SS with a recovery rate of 98.1±0.3%. It is worth noting that the recovery rate of C14SS only slightly increased to 98.6±0.4% by adding 5% of the total mass of sodium chloride to the mother liquor obtained by the above filtration.

[0032] Prepare a 0.5% C16SS aqueous solution, fix the molar ratio of BTACl to C16SS at 4:1, and adjust the pH value of the solution to 4.4 with HCl. o C conditions, because the K T About 16.7 o C; sodium hydroxide was then added to neutralize BTACl, and the pH value was adjusted to 11.0±0.1 with sodium hydroxide. The solution became turbid within 5 seconds. This is because the K T Higher (about 56.8 oC), caused by precipitation from aqueous solution, after the precipitate is fully precipitated, it is filtered, washed with cold water and vacuum dried to obtain white flaky C16SS with a recovery rate of 98.9±0.1%.

[0033] Example 7: Reversible Control of K of Mixed Long-Chain Alkyl Sodium Sulfonate T and recycling The three kinds of long-chain alkyl sodium sulfonates, C12SS, C14SS and C16SS, were mixed in a molar ratio of 1:1:1 to obtain mixed long-chain alkyl sodium sulfonate, and a mixed long-chain alkyl sodium sulfonate aqueous solution with a mass fraction of 1wt% was prepared. At this time, most of the mixed long-chain alkyl sodium sulfonate in the solution was insoluble, and BTACl was added in a molar ratio of 5:1 to the mixed long-chain alkyl sodium sulfonate. After a little shaking, the mixed long-chain alkyl sodium sulfonate was completely dissolved, and then sodium hydroxide was added to neutralize BTACl, and the pH value was adjusted to 11.0±0.1 with sodium hydroxide. The solution became turbid within 8 seconds. After the precipitate was fully precipitated, it was filtered, washed with cold water and vacuum dried to obtain a white powdery mixed long-chain alkyl sodium sulfonate with a recovery rate of 98.7±0.4%.

[0034] The present invention has been disclosed as above in the form of embodiments, but it is not intended to limit the technical solution of the present invention. Anyone familiar with this field and this technology can make various changes and modifications after the disclosure of the present invention. Therefore, the protection scope of the present invention should be based on the definition of the claims.

Claims

1. A method for reversibly regulating the water solubility of long-chain sodium alkyl sulfonate, characterized in that: The following steps are involved: Benzamide tertiary amine hydrochloride is used as an auxiliary agent, mixed with long-chain alkyl sodium sulfonate, dissolved in water, and hydrochloric acid is added to adjust the pH value to reduce the Krafft temperature of the long-chain alkyl sodium sulfonate to 25 o C and below; By adding alkali to neutralize the benzamide tertiary amine hydrochloride, the Krafft temperature of the long-chain alkyl sulfonate sodium is raised to 25 o C or above, the water solubility of the long-chain alkyl sodium sulfonate is reduced, so that the long-chain alkyl sodium sulfonate is crystallized from the aqueous solution.

2. The method for reversibly regulating the water solubility of long-chain alkyl sodium sulfonate according to claim 1, characterized in that: The molar ratio of benzamide tertiary amine hydrochloride to long-chain alkyl sodium sulfonate is in the range of 0.66-6.51, and hydrochloric acid is used to control the pH value of the long-chain alkyl sodium sulfonate aqueous solution to be no higher than 4.

4.

3. The method for reversibly regulating the water solubility of long-chain alkyl sodium sulfonate according to claim 1, characterized in that: The long-chain alkyl sodium sulfonate is any one of sodium dodecyl sulfonate, sodium tetradecyl sulfonate and sodium hexadecyl sulfonate or a mixture of several of them.

4. The method for reversibly regulating the water solubility of long-chain alkyl sodium sulfonate according to claim 1, characterized in that: In the step 2), sodium hydroxide or potassium hydroxide is used to neutralize the benzamide tertiary amine hydrochloride and the pH of the system is controlled within the range of 11.0±0.

1.

5. The method for reversibly regulating the water solubility of long-chain alkyl sodium sulfonate according to claim 1, characterized in that: In the step 2), the sodium long-chain alkyl sulfonate can be precipitated from the system in the form of crystals, and the sodium long-chain alkyl sulfonate can be separated and recovered by conventional filtration, with a recovery rate of not less than 96%.

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