A process for removing dioxane from fatty alcohol ether sulfate

Abstract

The present invention discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising: a process for removing dioxane from a fatty alcohol polyoxyethylene ether sulfate material in a vacuum tube-type remover, wherein the material is partially output as a discharge product and partially output as a recycled material through a delivery pump; the recycled material passes through a venturi ejector and enters a neutralizer simultaneously with fatty alcohol polyoxyethylene ether sulfate, alkali, and water for a neutralization reaction; at the same time, a certain flow of mixed gas is delivered through the suction end of the venturi ejector; the outlet material of the neutralizer enters the vacuum tube-type remover through a pipeline, and dioxane in the material is removed under vacuum. The present invention further innovates the original continuous tube vacuum neutralization system by introducing a combination of steam and non-condensable gas before the neutralizer, thereby effectively improving the dioxane removal efficiency of the system; the dioxane residue of the product removed by the system can be reduced from the original 10 mg / kg to 5 mg / kg.

Description

Technical Field

[0001] The present invention relates to a production process of an anionic surfactant, in particular to a process for removing dioxane in the preparation of fatty alcohol ether sulfate with low dioxane content. Background Art

[0002] Dioxane is a colorless, volatile liquid with a molecular formula of C₄H₄O₂ and a relative molecular mass of 88.11. Also known as dioxane and 1,4-dioxane, it has an ether-like odor and is flammable. Its melting point is 11.8°C and boiling point is 101.3°C. It is miscible with water, aromatic hydrocarbons, and most organic solvents. The World Health Organization's International Agency for Research on Cancer lists dioxane as a Class 2B carcinogen, and therefore, standards for various daily chemical products have strict limits on dioxane content.

[0003] During the production of fatty alcohol polyoxyethylene ether sulfate (AES), a certain amount of dioxane is produced due to problems with raw materials and processes. Removing dioxane from the sulfonation production process is one of the technical difficulties in this field.

[0004] There are two traditional methods for removing dioxane. The first involves installing removal equipment during production. After neutralization in the AES, the product is heated and then fed into a turbulent flow degasser, where the dioxane is removed along with the water. However, this method has the following disadvantages: 1. The product is cooled during production, requiring repeated heating, resulting in high energy consumption; 2. After removal, the treatment equipment must be adjusted, resulting in significant investment. Chemithon in the United States and Zhejiang Jilida Chemical Co., Ltd. in China both use this method to remove dioxane from AES.

[0005] The second method uses a dedicated vacuum neutralization system to remove dioxane during the neutralization process. The key feature of this system is that the fatty alcohol ether sulfate, neutralizing agent, and water are precisely metered and fed into the neutralization system. Under high-speed stirring, the materials form a thin film on the inner wall of the neutralizer, completing neutralization at the upper end of the neutralization reactor. Dioxane is removed at the middle and lower ends of the neutralization reactor. However, the disadvantages of this method are: 1. AES easily decomposes in alkaline or acidic environments, requiring high control precision for this equipment; 2. This equipment requires high acid and alkalinity resistance from the materials; 3. The neutralization process is short, resulting in poor system stability and difficulty in adjustment; 4. The amount of water evaporation during the removal process is difficult to control, affecting the flow properties and quality of the product. Ballestra, Italy, uses this method to remove dioxane from AES.

[0006] Both traditional methods remove dioxane in a single pass, with a removal rate of 50%-70%. The dioxane concentration in the AES before removal is ≤150 mg / kg, and the dioxane concentration after removal is ≤50 mg / kg. Currently, the most widely used international standard is that the dioxane concentration in AES products is less than 30 mg / kg, and the US FDA standard is less than 20 mg / kg. Therefore, the two traditional dioxane removal methods cannot meet the existing standards.

[0007] Patent CN101690875A, "A Process for Continuous Vacuum Tube Neutralization to Produce Fatty Alcohol Polyoxyethylene Ether Sulfates with Low Dioxane Content," describes a dioxane removal method that improves upon the two aforementioned methods. The sulfonated fatty alcohol ether sulfate, alkali, and water are metered separately and then fed into a neutralizer along with the material circulating from a vacuum tube spray remover for neutralization. The neutralized material is then pumped back into the vacuum tube spray remover for dioxane removal. A portion of the dioxane-removed product is discharged as the final product, while the remaining portion continues to re-enter the neutralizer as a circulating material for neutralization. The principle behind this method is that dioxane and water form a low-boiling azeotrope, which is then removed along with the water after repeated heating and evaporation. This method involves multiple neutralization and dioxane removal processes, achieving a removal rate exceeding 80%, and producing an AES product with a dioxane concentration of less than 10 mg / kg.

[0008] However, major customers downstream of the supply chain are now placing increasingly stringent demands on the dioxane concentration in AES products. A dioxane concentration of 10 mg / kg can only barely meet these requirements. Therefore, it is urgent to continue reducing the dioxane concentration in AES. Summary of the Invention

[0009] The purpose of the present invention is to overcome the problem of excessively high dioxane content described in the background information and to provide a method for effectively removing dioxane during the production process of fatty alcohol polyoxyethylene ether sulfate.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention provides a process for removing dioxane from fatty alcohol ether sulfate, which comprises the following steps:

[0012] 1) After the dioxane is removed from the vacuum tube remover, the fatty alcohol polyoxyethylene ether sulfate material is output as a discharge product and as a recycled material through a delivery pump;

[0013] 2) After the recycled material passes through the Venturi ejector, it enters the neutralizer together with fatty alcohol polyoxyethylene ether sulfate, alkali and water for neutralization reaction; at the same time, a certain flow of mixed gas is delivered from the suction end of the Venturi ejector;

[0014] 3) The outlet material of the neutralizer enters the vacuum tube remover through a pipeline to remove dioxane from the material under vacuum.

[0015] The method of the present invention is based on patent CN101690875A "A process for producing fatty alcohol polyoxyethylene ether sulfate with low dioxane content by continuous vacuum tube neutralization", and a set of Venturi ejectors is installed at the outlet end of the circulation pump, and a stripping agent is simultaneously introduced into the material.

[0016] The present invention further innovates the existing continuous tubular vacuum neutralization system by introducing a combination of steam and non-condensable gas before the neutralizer, effectively improving the system's dioxin removal efficiency. The dioxin residue in the product removed by this system can be reduced from the original 10mg / kg to 5mg / kg.

[0017] As a preferred embodiment of the present invention, in the step 1), the mass ratio of the recycled material to the discharged product in the fatty alcohol polyoxyethylene ether sulfate material after passing through the vacuum tube remover is 5-20:1.

[0018] As a preferred embodiment of the present invention, in step 2), the mixed gas is a mixture of 0.1-0.3 MPa water vapor and non-condensable gas.

[0019] As a preferred solution of the present invention, in step 2), the mass of the mixed gas added is 0.5%-2% of the mass of the recycled material.

[0020] As a preferred embodiment of the present invention, in step 2), the mass ratio of water vapor to non-condensable gas is 99-99.5:0.5-1.

[0021] As a preferred embodiment of the present invention, the mass ratio of water vapor to non-condensable gas is 99:1.

[0022] As a preferred embodiment of the present invention, the non-condensable gas is air.

[0023] As a preferred solution of the present invention, the outlet of the delivery pump is connected to the inlet of the vacuum tube remover, the material pressure in the system pipeline is 0.3-0.5 MPa (G), and the residence time is 20-60S.

[0024] As a preferred embodiment of the present invention, the equipment for the process of removing dioxane from fatty alcohol ether sulfate includes a vacuum tube remover, a delivery pump, a venturi ejector and a neutralizer. The outlet of the vacuum tube remover is connected to the delivery pump through a pipeline. The delivery pump is divided into two routes, one for the finished product outlet and the other for the recycled material outlet; the recycled material outlet is connected to the venturi ejector, the venturi ejector is connected to the neutralizer, and the neutralizer is connected to the inlet of the vacuum tube remover; wherein the venturi ejector is also provided with a mixed gas inlet, and the neutralizer is also provided with a fatty alcohol polyoxyethylene ether sulfate inlet, an alkali inlet and a water inlet.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) This invention further innovates the existing continuous tubular vacuum neutralization system by introducing a combination of steam and non-condensable gas before the neutralizer, effectively improving the system's dioxin removal efficiency. The residual dioxin in the product after removal by this system can be reduced from the original 10 mg / kg to 5 mg / kg.

[0027] 2) The present invention introduces a combination of steam and non-condensable gas before the neutralizer, thereby increasing the dioxane removal rate and further improving the fluidity of the product.

[0028] 3) The method provided by the present invention requires little modification to the original equipment, and accessories are easy to purchase at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the neutralization process and equipment system of the present invention.

[0030] In the figure, 1 is a vacuum tube remover; 2 is a delivery pump; 3 is an outlet for finished products; 4 is a venturi ejector; 5 is an inlet for mixed gas; 6 is a neutralizer; 7 is an inlet for fatty alcohol polyoxyethylene ether sulfate; 8 is an alkali inlet; and 9 is a water inlet.

[0031] Specific implementation cases

[0032] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further described below in conjunction with specific examples, but the following examples are only preferred embodiments of the present invention, not all. Based on the examples in the embodiments, other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0033] Depend on Figure 1 It can be seen that the working process of the neutralization process system of the present invention is:

[0034] The method of the present invention is based on patent CN101690875A "A process for producing fatty alcohol polyoxyethylene ether sulfate with low dioxane content by continuous vacuum tube neutralization", and a set of Venturi ejectors is installed at the outlet end of the circulation pump, and a stripping agent is simultaneously introduced into the material.

[0035] It includes a vacuum tube remover 1, a delivery pump 2, a venturi ejector 4 and a neutralizer 6. The outlet of the vacuum tube remover 1 is connected to the delivery pump 2 through a pipeline. The delivery pump 2 is divided into two routes, one is a finished product outlet 3, and the other is a recycled material outlet; the recycled material outlet is connected to the venturi ejector 4, the venturi ejector 4 is connected to the neutralizer 6, and the neutralizer 6 is connected to the inlet of the vacuum tube remover 1; wherein, the venturi ejector 4 is also provided with a mixed gas inlet 5, and the neutralizer 6 is also provided with a fatty alcohol polyoxyethylene ether sulfate inlet 7, an alkali inlet 8 and a water inlet 9.

[0036] After dioxane is removed from the vacuum tube remover, the fatty alcohol polyoxyethylene ether sulfate material is partially output as a product through a delivery pump, and partially recycled; the recycled material passes through a venturi ejector and enters a neutralizer simultaneously with fatty alcohol polyoxyethylene ether sulfate, alkali and water for neutralization reaction; at the same time, a certain flow of gas enters the suction end of the venturi ejector; the material at the outlet of the neutralizer enters a vacuum tube remover through a pipeline, and the dioxane therein is removed under vacuum.

[0037] Example 1

[0038] This embodiment discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0039] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is pumped out via a transfer pump, with 15,000 kg / h of this material recycled for reuse, of which 1,517 kg / h is discharged as finished product. The recycled material then flows through a Venturi ejector and a retention tank into a neutralizer. Simultaneously, a 0.25 MPa steam and air mixture (mass ratio of steam to air 99:1) enters the system from the Venturi ejector suction port at a rate of 100 kg / h. After passing through a retention tank, the recycled material enters the neutralizer simultaneously with fatty alcohol polyoxyethylene ether sulfate (680 kg / h), 32% liquid caustic soda (315 kg / h), and water (214 kg / h). After neutralization in the neutralizer, it enters the vacuum tube stripper via a pipeline, where dioxane is removed under vacuum. Here, the neutralization pressure is controlled at 0.4 MPa (G) by the valve in front of the vacuum tube stripper. The material residence time at this pressure is 30 s, and the material temperature after neutralization is 49°C.

[0040] Under this process, the concentration of dioxane in the product is 5 mg / kg, and the viscosity of the product is 5750 mPa.s, see Table 1.

[0041] Example 2

[0042] This embodiment discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0043] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is pumped out via a transfer pump, with a controlled rate of 60,000 kg / h recycled, of which 3,034 kg / h is discharged as finished product. The recycled material then flows through a Venturi ejector and a retention tank into a neutralizer. Simultaneously, a 0.2 MPa steam and air mixture (mass ratio of steam to air 99:1) enters the system from the Venturi ejector suction port at a rate of 400 kg / h. After passing through a retention tank, the recycled material enters the neutralizer simultaneously with fatty alcohol polyoxyethylene ether sulfate (1,340 kg / h), 32% liquid caustic soda (630 kg / h), and water (428 kg / h). After neutralization in the neutralizer, it enters the vacuum tube stripper via a pipeline, where dioxane is removed under vacuum. Here, the neutralization pressure is controlled at 0.5 MPa (G) by the valve in front of the vacuum tube stripper. The material residence time at this pressure is 25 s, and the material temperature after neutralization is 51°C.

[0044] Under this process, the concentration of dioxane in the product is 6 mg / kg, and the viscosity of the product is 5720 mPa.s, see Table 1.

[0045] Comparative Example 1

[0046] This comparative example discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0047] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is discharged via a transfer pump, with a controlled 15,000 kg / h rate for recycling, of which 1,517 kg / h is discharged as finished product. After passing through a retention tank, the recycled material enters a neutralizer along with fatty alcohol polyoxyethylene ether sulfate (680 kg / h), 32% liquid caustic soda (315 kg / h), and water (214 kg / h). After neutralization in the neutralizer, it enters a vacuum tube stripper via a pipeline, where dioxane is removed under vacuum. A valve in front of the vacuum tube stripper controls the neutralization pressure at 0.4 MPa(G), with a retention time of 30 seconds. The post-neutralization temperature is 50°C.

[0048] Under this process, the concentration of dioxane in the product is 13 mg / kg, and the viscosity of the product is 10300 mPa.s, see Table 1.

[0049] Comparative Example 2

[0050] This comparative example discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0051] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is pumped out via a transfer pump, with 15,000 kg / h of this material recycled for reuse, of which 1,517 kg / h is discharged as finished product. The recycled material then flows through a static mixer and a retention tank into a neutralizer. Simultaneously, a 0.25 MPa steam and air mixture (mass ratio of steam to air 99:1) is introduced into the system at a rate of 100 kg / h from the front of the static mixer. After passing through a retention tank, the recycled material enters the neutralizer along with fatty alcohol polyoxyethylene ether sulfate (680 kg / h), 32% liquid caustic soda (315 kg / h), and water (214 kg / h). After neutralization in the neutralizer, it is piped into a vacuum tube stripper, where dioxane is removed under vacuum. A valve in front of the vacuum tube stripper controls the neutralization pressure at 0.4 MPa(G). The material residence time at this pressure is 30 seconds, and the post-neutralization temperature is 49°C.

[0052] Under this process, the concentration of dioxane in the product is 12 mg / kg, and the viscosity of the product is 10100 mPa.s, see Table 1.

[0053] Comparative Example 3

[0054] This comparative example discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0055] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is pumped out via a transfer pump, with 15,000 kg / h of this material recycled for reuse, of which 1,517 kg / h is discharged as finished product. The recycled material then enters the neutralizer via a Venturi ejector through a retention tank. Simultaneously, 0.25 MPa steam at 100 kg / h is introduced from the Venturi ejector's suction port. After passing through the retention tank, the recycled material enters the neutralizer along with fatty alcohol polyoxyethylene ether sulfate (680 kg / h), 32% liquid caustic soda (315 kg / h), and water (214 kg / h). After neutralization in the neutralizer, it enters the vacuum tube stripper via a pipeline, where dioxane is removed under vacuum. A valve in front of the vacuum tube stripper controls the neutralization pressure at 0.4 MPa(G). The material residence time at this pressure is 30 seconds, and the post-neutralization temperature is 49°C.

[0056] Under this process, the concentration of dioxane in the product is 10 mg / kg, and the viscosity of the product is 11050 mPa.s, see Table 1.

[0057] Comparative Example 4

[0058] This comparative example discloses a process for removing dioxane from fatty alcohol ether sulfate, comprising:

[0059] After dioxane removal in a vacuum tube stripper, the fatty alcohol polyoxyethylene ether sulfate material is pumped out via a transfer pump, with 15,000 kg / h of this material recycled for reuse, of which 1,517 kg / h is discharged as finished product. The recycled material then flows directly into the neutralizer via a Venturi ejector. Simultaneously, a 0.25 MPa steam and air mixture (mass ratio of steam to air 99:1) enters the system at a rate of 100 kg / h from the Venturi ejector's intake port. After passing through a retention tank, the recycled material is simultaneously fed into the neutralizer along with fatty alcohol polyoxyethylene ether sulfate (680 kg / h), 32% liquid caustic soda (315 kg / h), and water (214 kg / h). After neutralization in the neutralizer, the material is piped into the vacuum tube stripper, where dioxane is removed under vacuum. A valve in front of the vacuum tube stripper controls the neutralization pressure at 0.4 MPa(G), and the post-neutralization material temperature is 49°C. (It is estimated that the material stays at this pressure for about 10 seconds).

[0060] Under this process, the concentration of dioxane in the product is 11 mg / kg, and the viscosity of the product is 10120 mPa.s, see Table 1.

[0061] Table 1 Test data of examples and comparative examples

[0062] Dioxane concentration (mg / kg) Viscosity (mPa.s) Example 1 5 5750 Example 2 6 5720 Comparative Example 1 13 10300 Comparative Example 2 12 10100 Comparative Example 3 10 11050 Comparative Example 4 11 10120

[0063] Comparing the test data of the examples and comparative examples in Table 1 above, after adding a venturi ejector and introducing a mixture of water vapor and air into the system described in patent CN101690875A "A process for continuous vacuum tube neutralization and production of fatty alcohol polyoxyethylene ether sulfates with low dioxane content," the data from Examples 1 and 2, compared with Comparative Example 1, show that the dioxane concentration of the product is significantly reduced, the viscosity is also reduced, and the fluidity is better. From the data of Comparative Example 2, it can be seen that the addition of a stripping agent without a venturi ejector has a smaller effect on the dioxane concentration and product viscosity, indicating that the special structure of the venturi ejector is the main factor in the stripping agent's effect on the material. The data of Comparative Example 3 show that steam and air are both indispensable in the stripping agent, and steam alone cannot effectively remove dioxane and reduce the material viscosity. The data of Comparative Example 4 show that the residence time of the material has a certain impact on its dioxane removal and viscosity reduction. In summary, the stripping agent must contain a certain amount of air, and the stripping agent must pass through the special structure of the Venturi ejector to effectively act on the material, and the material must stay for a certain time before entering the system.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A process for removing dioxane from fatty alcohol ether sulfate, characterized in that: The removal process comprises the following steps: 1) After the dioxane is removed from the vacuum tube remover, the fatty alcohol polyoxyethylene ether sulfate material is output as a discharge product and as a recycled material through a delivery pump; 2) After the recycled material passes through the Venturi ejector, it enters the neutralizer together with fatty alcohol polyoxyethylene ether sulfate, alkali and water for neutralization reaction; at the same time, a certain flow of mixed gas is delivered from the suction end of the Venturi ejector; 3) The outlet material of the neutralizer enters the vacuum tube remover through a pipeline to remove dioxane from the material under vacuum; In the step 2), the mixed gas is a mixture of 0.1-0.3 MPa water vapor and non-condensable gas; In the step 2), the mass ratio of the water vapor to the non-condensable gas is 99-99.5:0.5-1; The outlet of the delivery pump is connected to the inlet of the vacuum tube remover, the material pressure in the system pipeline is 0.3-0.5MPa, and the residence time is 20-60S; The non-condensable gas is air.

2. A process for removing dioxane from fatty alcohol ether sulfate according to claim 1, characterized in that: In the step 1), the mass ratio of the recycled material to the discharged product in the fatty alcohol polyoxyethylene ether sulfate material after passing through the vacuum tube remover is 5-20:

1.

3. A process for removing dioxane from fatty alcohol ether sulfate according to claim 1, characterized in that: In the step 2), the mass of the added mixed gas is 0.5%-2% of the mass of the recycled material.

4. A process for removing dioxane from fatty alcohol ether sulfate according to claim 1, characterized in that: The mass ratio of the water vapor to the non-condensable gas is 99:

1.

5. A process for removing dioxane from fatty alcohol ether sulfate according to claim 1, characterized in that: The equipment for the process of removing dioxane from fatty alcohol ether sulfate includes a vacuum tube remover, a delivery pump, a venturi ejector and a neutralizer. The outlet of the vacuum tube remover is connected to the delivery pump via a pipeline. The delivery pump is divided into two routes, one for the finished product outlet and the other for the recycled material outlet. The recycled material outlet is connected to the venturi ejector, which is connected to the neutralizer, and the neutralizer is connected to the inlet of the vacuum tube remover. The venturi ejector is also provided with a mixed gas inlet, and the neutralizer is also provided with a fatty alcohol polyoxyethylene ether sulfate inlet, an alkali inlet and a water inlet.

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