A method for producing a sulfated surfactant

Abstract

This invention belongs to the field of surfactant preparation technology, specifically relating to a method for preparing a sulfate ester salt type surfactant. The method includes the following steps: olefins and concentrated sulfuric acid are separately introduced into a microchannel reactor equipped with a catalyst section and mixed and reacted under ultrasonic conditions to obtain an intermediate product; an aqueous solution of NaOH or KOH is added to the intermediate product, the temperature is raised to 90-105℃, and the mixture is stirred and refluxed for 1-2 hours to obtain the sulfate ester salt type surfactant. This invention combines a microchannel reactor with fine chemical synthesis and successfully synthesizes secondary alkyl sulfates. By accelerating the reaction with a catalyst and ultrasound, increasing the phase contact area, and controlling the reaction temperature at a low level, the degree of olefin sulfation is greatly improved, thereby increasing the yield of secondary alkyl sulfates. The method is safe, environmentally friendly, easy to operate, simple in process, and easy to control. It is expected that production can be scaled up to industrial scale through array arrangement.

Description

Technical Field

[0001] This invention belongs to the field of surfactant preparation technology, specifically relating to a method for preparing a sulfate ester salt type surfactant. Background Technology

[0002] Alkyl sulfates are an important class of anionic surfactants, often exhibiting good surface activity. Secondary alkyl sulfates, due to their structural difference—with -OSO3Na bonded to the secondary carbon atom of the alkyl chain—possess excellent solubility and wetting properties, and are generally used to prepare liquid or paste-like detergents. In previous processes, secondary alkyl sulfates were prepared by reacting olefins or secondary alcohols with concentrated sulfuric acid, followed by neutralization of the intermediate secondary alkyl sulfate ester with an aqueous alkaline solution. The preparation process of secondary alkyl sulfates was complex and yielded low results due to the incomplete reaction of the olefin or secondary alcohol in the first step caused by the low phase contact area between the olefin and sulfuric acid, as well as the formation of dialkyl sulfates during neutralization.

[0003] In the first step, the content of unreacted olefins or secondary alcohols may reach 40% or even more. To avoid affecting the subsequent neutralization process, it is necessary to separate the unreacted olefins or secondary alcohols using organic solvents. However, the formation of emulsions and gels during the separation process, as well as the possible hydrolysis of secondary alkyl sulfates, makes the extraction process extremely complex. Therefore, improving the conversion rate of the first step reaction is crucial. Summary of the Invention

[0004] The present invention aims to solve the above problems and provides a method for preparing a sulfate ester salt type surfactant, which can effectively improve the conversion rate of sulfation reaction of olefins.

[0005] According to the technical solution of the present invention, the method for preparing the sulfate ester salt type surfactant is as follows:

[0006] Includes the following steps,

[0007] S1: The olefin and concentrated sulfuric acid are separately introduced into a microchannel reactor with a catalyst section and mixed and reacted under ultrasonic conditions to obtain an intermediate product.

[0008] S2: Add an aqueous solution of NaOH or KOH to the intermediate product, heat to 90-105℃, and stir under reflux for 1-2 hours to obtain the sulfate ester salt type surfactant; the general structural formula of the sulfate ester salt type surfactant is as follows:

[0009]

[0010] In the formula, M is metal Na or K, and n = 9-15.

[0011] Furthermore, the olefin is a straight-chain olefin or an olefin having one branch.

[0012] Furthermore, in step S1, the molar ratio of the introduced olefin and concentrated sulfuric acid is 1:1.05-1:1.3, for example, it can be 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, or any two of these ranges.

[0013] Furthermore, the channel material of the microchannel reactor is polytetrafluoroethylene, with an inner diameter of 2-3 mm and an outer diameter of 3-4 mm.

[0014] Furthermore, in step S1, the flow rates of both the olefin and concentrated sulfuric acid are 0.5-2 mL / min, the introduction time is 25-35 min, and the reaction temperature is 10-40℃.

[0015] Furthermore, in step S1, the catalyst is a molecular sieve catalyst, such as a tubular mesoporous molecular sieve catalyst.

[0016] Furthermore, the microchannel reactor is provided with alternating pipe sections and catalyst sections, and the catalyst sections are provided with the catalyst.

[0017] Specifically, the pipeline section includes a spiral pipeline, the catalyst section includes a flexible tube and a catalyst wrapped inside the flexible tube, and the pipeline section and the catalyst section are connected by a reducing valve.

[0018] In step S1, the catalyst section and the pipeline section are arranged alternately.

[0019] This invention utilizes a microchannel reactor equipped with a catalyst to perform the sulfation reaction of olefins, using olefins and concentrated sulfuric acid as starting materials under optimal temperature and reactant ratios, thereby improving the conversion rate. Temperature significantly affects olefin sulfation; generally, lower temperatures result in fewer side reactions and higher yields. Compared to chemical reactions conducted in conventional reaction vessels, microchannel reactors offer the following advantages: smaller microchannel width and depth lead to extremely short diffusion distances between reactants, resulting in rapid mass transfer and thorough mixing within a short time; smaller specific surface area leads to higher heat exchange efficiency and easier temperature maintenance; and reaction conditions such as reactant ratios, reaction time, and flow rate are easily controlled. The first step of the reaction is completed using a microchannel reactor, leveraging the faster mass transfer rate and lower, more constant reaction temperature to enhance the conversion rate of this initial reaction.

[0020] Furthermore, the temperatures of the olefins and concentrated sulfuric acid introduced into the microchannel reactor are 10-40°C. Specifically, the olefins and concentrated sulfuric acid can be kept at a temperature of 10-40°C before introduction, and the time depends on the amount introduced, for example, 20 minutes.

[0021] Furthermore, the concentration of the aqueous solution of NaOH or KOH is 10-30%.

[0022] Furthermore, in step S2, the molar ratio of the added NaOH or KOH to the concentrated sulfuric acid introduced in step S1 is 2:1.

[0023] Furthermore, in step S2, considering that the presence of a large amount of water will affect the subsequent separation, produce an unpleasant odor during the subsequent separation, and also cause a large number of bubbles to be generated during the distillation process, ethanol can be added as a solvent and dispersant along with the added NaOH or KOH aqueous solution, and the amount of water used can be greatly reduced.

[0024] Furthermore, the amount of ethanol added is 10-40% of the volume of the NaOH or KOH aqueous solution.

[0025] Furthermore, step S2, after reflux, also includes the steps of purifying and drying the product. Specifically, the obtained product is treated with petroleum ether and ethanol, and then dried to obtain the purified product, which yields a sulfate ester salt type surfactant.

[0026] The technical solution of the present invention has the following advantages compared with the prior art:

[0027] By combining microchannel reactors with fine chemical synthesis, secondary alkyl sulfates were successfully synthesized. Microchannel reactors offer advantages such as large specific surface area and rapid heat transfer, overcoming the difficulty of mixing in the first-step reaction. They also rapidly transfer heat released during the reaction, reducing side reactions such as over-sulfonation and improving the conversion rate of the first-step reaction. A catalyst is used to accelerate the reaction rate of the first step, while the strong vibration, high acceleration, strong cavitation effect, and stirring effect generated by ultrasound accelerate the mixing of concentrated sulfuric acid and olefins. Furthermore, by controlling low reaction temperature and reaction time, the degree of olefin sulfation is significantly improved, thereby increasing the yield of secondary alkyl sulfates. The process also features consistent material residence time, good product quality stability, high safety, environmental friendliness, convenient operation, simple process, and easy control. It is expected that production can be scaled up to industrial scale through array arrangement.

[0028] The types of raw materials can be adjusted according to different product requirements, simplifying the process engineering, saving the time required for the first step of the reaction, reducing costs, and also reducing the difficulty of subsequent neutralization and separation processes. Attached Figure Description

[0029] Figure 1 The graph shows the change in the conversion rate of the first step reaction as a function of the molar ratio of concentrated sulfuric acid to olefins.

[0030] Figure 2 The graph shows the change in the conversion rate of the first step reaction as a function of the dropping time.

[0031] Figure 3 This is a graph showing the change in the conversion rate of the first step reaction over time.

[0032] Figure 4 This is a graph showing the change in the conversion rate of the first step reaction as a function of reaction temperature.

[0033] Figure 5 This is a schematic diagram of the pipe section and catalyst section in a microchannel reactor. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0035] This invention provides a method for preparing a sulfate ester salt type surfactant, wherein the general structural formula of the sulfate ester salt type surfactant is as follows:

[0036]

[0037] Where M is metal Na or K, and n = 9-15;

[0038] Includes the following steps,

[0039] Step 1, sulfation reaction: Add a straight-chain olefin or an olefin with only one branch to two containers and concentrated sulfuric acid respectively. Feed the olefin and concentrated sulfuric acid into the two inlets of the microchannel reactor. The molar ratio of the olefin to the concentrated sulfuric acid is 1:1.05-1:1.3. Use two plunger pumps to pump the materials into the microchannel reactor with the catalyst, and use a three-way ball valve to mix them into one stream under ultrasonic conditions. Control the reaction temperature between 10-40℃, and the flow rates of the two streams are both 0.5-2 mL / min. After the reaction is completed, the intermediate product can be obtained.

[0040] Step 2, neutralization reaction: Prepare an alkaline aqueous solution (20%) of a certain concentration using deionized water, and adjust the pH value of the intermediate product with the alkaline aqueous solution. Control the reaction temperature at 25-40℃, stir magnetically for 1-2 hours, and then reflux at 102℃ for 2 hours to complete the reaction.

[0041] Considering that the presence of a large amount of water will affect subsequent separation, produce an unpleasant odor during the subsequent separation, and also cause a large number of bubbles to be generated during the distillation process, ethanol can be added as a solvent and dispersant, and the amount of water used can be greatly reduced.

[0042] Step 3: After treating the product from Step 2 with petroleum ether and ethanol, the purified product obtained by drying can be used to obtain a sulfate ester salt type surfactant.

[0043] like Figure 5 As shown, the microchannel reactor includes alternating pipe sections and catalyst sections. The pipe sections include spiral pipes, and the catalyst sections include flexible tubes and catalyst wrapped inside the flexible tubes. The pipe sections and catalyst sections are connected by a reducing valve.

[0044] Example 1: Preparation of secondary dodecyl surfactant

[0045] Step 1: Add dodecene and concentrated sulfuric acid to two containers respectively, and keep the temperature constant at 20°C for 20 min. The molar ratio of concentrated sulfuric acid to olefin is 1:1.1. Feed the materials into the two inlets of the microchannel reactor. The inner diameter of the microchannel reactor is 2-3 mm and the outer diameter is 3-4 mm. The catalyst is a tubular mesoporous molecular sieve catalyst (Xi'an Ruixi Biotechnology Co., Ltd.). Use two plunger pumps to pump the materials into the microchannel reactor separately, and use a three-way ball valve to mix them into one stream under ultrasonic conditions. Control the reaction temperature at 20°C, and the flow rate of both streams is 0.5 mL / min. The material is completely introduced in 30 min, and then held for 5 min after complete introduction to obtain the intermediate product.

[0046] The chemical formulas involved in the reaction are as follows:

[0047]

[0048] Step 2, Neutralization process: Neutralize the pH of the intermediate product with a 20% NaOH aqueous solution, with a molar ratio of NaOH to concentrated sulfuric acid of 2:1. Add NaOH solution and 8 mL of ethanol, stir magnetically, and reflux at 102°C for 2 hours to complete the reaction.

[0049] The chemical formulas involved in the reaction are as follows:

[0050]

[0051] Step 3: After treating the product from Step 2 with petroleum ether and ethanol, the purified product obtained by drying is the secondary dodecyl surfactant with a CMC (critical micelle concentration) of 0.24 g / L.

[0052] Example 2: Preparation of hexadecyl surfactant

[0053] Step 1: Add hexadecene and concentrated sulfuric acid to two containers respectively, and keep them at 10°C for 20 minutes. The molar ratio of concentrated sulfuric acid to olefin is 1:1.1. Feed the materials into the microchannel reactor through two inlets. The inner diameter of the microchannel reactor is 2-3 mm and the outer diameter is 3-4 mm. The catalyst is a molecular sieve catalyst. Use two plunger pumps to pump the materials into the microchannel reactor separately, and use a three-way ball valve to mix them into one stream under ultrasonic conditions. Control the reaction temperature at 10°C, and the flow rate of both streams is 1 mL / min. The material is completely introduced for 30 minutes, and then held for 5 minutes after complete introduction to obtain the intermediate product.

[0054] Step 2, Neutralization process: Neutralize the pH of the intermediate product with a 20% NaOH aqueous solution, with a molar ratio of NaOH to concentrated sulfuric acid of 2:1. Add NaOH solution and 5-10 mL of ethanol, and reflux at 100°C for 2 hours with magnetic stirring until the reaction is complete.

[0055] Step 3: After treating the product from Step 2 with petroleum ether and ethanol, the purified product obtained by drying is the hexadecyl surfactant with a CMC of 0.029 g / L.

[0056] Example 3: Effect of molar ratio on the conversion rate of the first step reaction

[0057] Concentrated sulfuric acid was used as the sulfation reagent to react with a straight-chain olefin (dodecene), with sulfuric acid in relative excess. The reaction temperature was controlled at 20℃, the flow rate at 0.5 mL / min, and the mixture was ultrasonically mixed. A microchannel reactor with a catalyst was used, and the effect of the molar ratio on the conversion rate of the first step reaction was investigated over a 30-minute infusion time.

[0058] The results are as follows Figure 1 As shown, under the same reaction temperature and reaction time, the conversion rate gradually increases with the increase of the molar ratio of concentrated sulfuric acid to olefins. The rate of increase slows down after the molar ratio reaches 1:1.05. After the molar ratio reaches 1.1, the conversion rate decreases, the amount of byproducts increases, and the subsequent neutralization step increases the amount of alkali used, leading to a higher content of inorganic salts.

[0059] Example 4: Effect of reaction time (inlet time and residence time) on the conversion rate of the first step reaction

[0060] Concentrated sulfuric acid was used as the sulfation reagent to react with a straight-chain olefin (dodecene), with sulfuric acid in relative excess. The reaction temperature was controlled at 20℃, the molar ratio of olefin to concentrated sulfuric acid was 1:1.1, the flow rate was 0.5 mL / min, and the mixture was ultrasonically mixed. The effect of the catalyst introduction time on the conversion rate of the first step reaction was investigated in a microchannel reactor with a catalyst (after complete introduction, a 10-min hold period was observed). The results are as follows: Figure 2As shown, when the reaction molar ratio and reaction temperature are the same, the reaction conversion rate first increases and then decreases, reaching a maximum of 84.14% at 30 min. After that, the conversion rate decreases with the extension of the dropping time.

[0061] Based on this, the reaction temperature was controlled at 20℃, and the molar ratio of olefin to concentrated sulfuric acid was 1:1.1. The effect of residence time after the introduction of sulfuric acid on the reaction conversion rate was further investigated. The results are as follows: Figure 3 As shown, when the reaction molar ratio and reaction temperature are the same, the conversion rate gradually decreases with increasing residence time, assuming a 30-minute inlet time. The highest conversion rate is 98.21% immediately after the addition is complete; thereafter, extending the residence time leads to side reactions and a decrease in the content of the target product. Therefore, considering both time cost and the yield of the target product, the optimal reaction time is when the inlet is completely filled.

[0062] Example 5: Effect of reaction temperature on the conversion rate of the first step reaction

[0063] Concentrated sulfuric acid was used as the sulfation reagent to react with a straight-chain olefin (dodecene). The molar ratio of olefin to concentrated sulfuric acid was controlled at 1:1.1, the flow rate was 0.5 mL / min, the mixture was ultrasonically mixed, and the reaction time was 30 min. The effect of reaction temperature on the conversion rate was investigated.

[0064] The results are as follows Figure 4 As shown, when the reaction molar ratio and reaction temperature are the same, the yield decreases with increasing reaction temperature. This may be because lower reaction temperatures result in fewer side reactions, thus leading to higher yields.

[0065] Example 6: Effects of Catalyst and Ultrasonic Treatment on the Reaction

[0066] Concentrated sulfuric acid was used as the sulfation reagent to react with a straight-chain olefin (dodecene) under the following conditions: reaction temperature 20℃, molar ratio 1:1.1. Without ultrasonic mixing and without a catalyst, the conversion rate was 48.16% after 15 minutes. With a catalyst, the conversion rate was 60.72%. With ultrasonic mixing and a catalyst, the conversion rate was 70.82%.

[0067] In summary, this invention prepares a class of alkyl sulfate surfactants with different carbon chain lengths through sulfation and neutralization reactions. It also improves existing preparation processes, reducing raw material usage and increasing yield to a certain extent. The resulting products exhibit good water solubility, surface tension, wetting, and emulsifying properties. The reaction conditions involved in this invention are mild, the reaction cycle is short, and the post-processing is simple, facilitating subsequent industrial production.

[0068] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for producing a sulfated surfactant, characterized by, The structural general formula of the sulfate surfactant is as follows: ， Wherein, M is metal Na or K, n=9-15; The method comprises the following steps, S1: passing olefin and concentrated sulfuric acid into a micro-channel reactor with a catalyst respectively, mixing and reacting under ultrasonic environment to obtain an intermediate product; the micro-channel reactor has a channel inner diameter of 2-3 mm and an outer diameter of 3-4 mm; the flow rate of the olefin and the concentrated sulfuric acid is both 0.5-2 mL / min, the time for passing in is 25-35 min, and the reaction temperature is 10-40 ℃; the olefin is linear olefin; the molar ratio of the olefin to the concentrated sulfuric acid is 1:1.05-1:1.3; and the catalyst is a molecular sieve catalyst; S2: adding an aqueous solution of NaOH or KOH to the intermediate product, heating to 90-105 ℃, and refluxing under ultrasonic auxiliary stirring for 1-2 h to obtain the sulfate surfactant.

2. The production method according to claim 1, wherein The micro-channel reactor is provided with alternately arranged pipe sections and catalyst sections, and the catalyst sections are provided with the catalyst.

3. The production method according to claim 1, wherein In the step S2, the molar ratio of the added NaOH or KOH to the concentrated sulfuric acid passed in in the step S1 is 2:

1.

4. The production method according to claim 1, wherein In the step S2, the aqueous solution of NaOH or KOH is added while adding ethanol as a solvent and dispersant.

5. The production method according to claim 1, wherein In the step S2, after refluxing, the product is further purified and dried. In the step S2, after refluxing, the product is further purified and dried.

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