A method for preparing thiodipropionic acid using a series of dynamic kettle reactors

Abstract

The application discloses a method for preparing thiodipropionic acid by using a series connection dynamic kettle type reactor, S1 reaction liquid configuration, S2 feeding, S3 heat exchange, S4 residence, and S5 discharging; after reaction residence for a certain time, the material is discharged from the first dynamic kettle type reactor, enters the second dynamic kettle type reactor, and after further acidification reaction, thiodipropionic acid liquid is obtained. The preparation method can effectively solve the problems of high content of acrylic acid polymer, low raw material conversion rate, low yield, safety risk and the like in the traditional process; the thiodipropionic acid is generally prepared by using an intermittent reaction kettle in the prior art, and the application provides a method for preparing thiodipropionic acid by using a series connection dynamic kettle type reactor, so that the amount of acrylic acid is reduced, energy consumption is saved, the content of polyacrylic acid is reduced, and the yield and quality of finished products are improved.

Description

Technical Field

[0001] This invention relates to the field of thiodipropionic acid preparation technology, and in particular to a method for preparing thiodipropionic acid using a series dynamic batch reactor. Background Technology

[0002] 3,3'-Thiodipropionic acid, commonly known as thiodipropionic acid or thiodipropionate, is an intermediate in the synthesis of thioester antioxidants. Currently, the main processes for preparing thiodipropionic acid in China are the acrylic acid process and the acrylonitrile process. The acrylic acid process is widely used due to its inexpensive raw materials, simple process, and high yield. The acrylic acid process involves reacting acrylic acid with sodium sulfide under alkaline conditions via a Michael addition reaction to obtain sodium thiodipropionate. After acidification, crystallization, spin drying, rinsing, and drying, pure thiodipropionic acid is obtained. The reaction equation is as follows: Figure 4 As shown:

[0003] Depending on the reaction mode, reactions are divided into batch reactions and continuous reactions. Currently, the reported and adopted reactions are all batch reactions. Batch reactions have the advantages of simple equipment, flexible operation, and high conversion rate. However, they also have disadvantages such as requiring more supporting equipment, high energy consumption, frequent start-up and shutdown, heavy workload, frequent personnel contact with materials which are not conducive to safety, management, and low production capacity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing thiodipropionic acid using a series dynamic batch reactor, so as to reduce the amount of acrylic acid used, reduce the polyacrylic acid content, and improve the yield and quality of the finished product.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing thiodipropionic acid using a series dynamic batch reactor includes the following steps:

[0007] S1, Preparation of reaction solution: Prepare aqueous solutions of sodium sulfide and sodium hydroxide separately. Adjust the content of sodium sulfide aqueous solution to 27-29% and the concentration of sodium hydroxide solution to 25-30% according to experimental requirements.

[0008] S2, Feeding: 27-29% sodium sulfide aqueous solution, sodium hydroxide aqueous solution, and acrylic acid are fed into the reactors separately. The ratio of the two phases is adjusted to maintain a sodium sulfide to acrylic acid feed molar ratio of 1:2.03. The feed is introduced into the reaction zone of the first dynamic batch reactor at room temperature via a pump, and the feed rate is controlled. The sodium hydroxide aqueous solution, as another phase, is pumped into the first dynamic batch reactor at room temperature to adjust the pH value. The sulfuric acid solution, as another phase, is pumped into the second dynamic batch reactor at room temperature, and the feed rates of both phases are controlled, maintaining a 1:1 molar ratio with the first dynamic batch reactor. Temperature and pH values ​​are monitored online or offline at all times, and the feed rate of the sulfuric acid solution is adjusted according to the pH value.

[0009] S3, heat exchange: During the reaction process, a temperature controller is used to control the temperature, so that the temperature of the first step reaction is maintained at 70℃-80℃;

[0010] S4, Residence: After the two phases are mixed, the residence time of the reaction liquid is 60s-600s, and the reaction is carried out under normal pressure.

[0011] S5, Discharge: After the reaction has been held for a certain period of time, the material is discharged from the first dynamic batch reactor and enters the second dynamic batch reactor for further acidification to obtain thiodipropionic acid solution.

[0012] Preferably, the reactor in S2 includes a first dynamic batch reactor and a second dynamic batch reactor. Both the first and second dynamic batch reactors are equipped with built-in coils on their exteriors. The two built-in coils maintain a constant temperature system for the first and second dynamic batch reactors through a heat exchange mechanism. The bottom of the first and second dynamic batch reactors are respectively provided with a first reaction zone and a second reaction zone. Both the first and second dynamic batch reactors are equipped with motors and shafts. The motors are fixedly connected to the shafts. The lower end of the shafts extends into the first and second reaction zones and is fixed with multiple stirring blades. The first and second dynamic batch reactors are connected by a conveying pipe.

[0013] Preferably, the first dynamic batch reactor and the second dynamic batch reactor are each equipped with a temperature sensor and a pH sensor.

[0014] Preferably, the heat exchange mechanism includes a heat exchange box, a heat exchange component installed inside the heat exchange box, a water pump installed on the heat exchange box, a spiral tube embedded in the built-in coil, an outlet pipe and an inlet pipe respectively installed at both ends of the spiral tube, the outlet pipe being connected to the heat exchange box, the inlet end of the water pump being connected to the heat exchange box, and the inlet pipe being connected to the outlet end of the water pump.

[0015] Preferably, the first dynamic batch reactor is equipped with a first material inlet pipe, a second material inlet pipe, and a third material inlet pipe.

[0016] Preferably, the second dynamic batch reactor is equipped with a fourth material inlet pipe and a product outlet pipe.

[0017] Preferably, the inner surfaces of the first dynamic batch reactor and the second dynamic batch reactor are configured as cylindrical structures.

[0018] Preferably, flow valves are provided on the first material inlet pipe, the second material inlet pipe, the third material inlet pipe, the fourth material inlet pipe, and the product outlet pipe.

[0019] Preferably, both the first and second dynamic batch reactors are equipped with four fixed rods, with a guide tube fixed to the upper end of each fixed rod. The shaft extends into the guide tube and has multiple fan blades fixed on it.

[0020] Preferably, a power motor is installed at the bottom of the heat exchange box, and a drive rod is fixedly connected to the output end of the power motor. The drive rod passes through the heat exchange box and is rotatably connected to it. Multiple stirring rods are fixed on the drive rod.

[0021] Compared with the prior art, the beneficial effects of this invention are as follows:

[0022] The preparation method of the present invention can effectively solve the problems of high acrylic polymer content, low raw material conversion rate, low yield, and safety risks in traditional processes. In the prior art, batch reactors are generally used to prepare thiodipropionic acid. The present invention provides a method for preparing thiodipropionic acid using a series dynamic batch reactor, so as to reduce the amount of acrylic acid used, save energy and reduce consumption, reduce the polyacrylic acid content, and improve the yield and quality of the finished product. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure in the method for preparing thiodipropionic acid using a series dynamic batch reactor proposed in Example 1;

[0024] Figure 2 This is a schematic diagram of the structure of a method for preparing thiodipropionic acid using a series dynamic batch reactor as proposed in Example 2;

[0025] Figure 3 This is a schematic diagram of the structure in the method for preparing thiodipropionic acid using a series dynamic batch reactor proposed in Example 3;

[0026] Figure 4 The reaction equation is from the existing technology.

[0027] In the diagram: 1 First dynamic batch reactor, 2 Second dynamic batch reactor, 3 Built-in coil, 4 First reaction zone, 5 Liquid outlet pipe, 6 Liquid inlet pipe, 7 Water pump, 8 Product discharge pipe, 9 Fourth material inlet pipe, 10 Stirring blades, 11 Heat exchanger, 12 Temperature sensor, 13 pH sensor, 14 Motor, 15 Shaft, 16 First material inlet pipe, 17 Second material inlet pipe, 18 Third material inlet pipe, 19 Second reaction zone, 20 Guide tube, 21 Fixed rod, 22 Heat exchanger, 23 Power motor, 24 Drive rod, 25 Stirring rod, 26 Conveying pipe, 27 Spiral tube, 28 Fan blades. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Example 1

[0030] Reference Figure 1 A method for preparing thiodipropionic acid using a series dynamic batch reactor includes the following steps:

[0031] S1, Preparation of reaction solution: Prepare aqueous solutions of sodium sulfide and sodium hydroxide separately. Adjust the content of sodium sulfide aqueous solution to 27-29% and the concentration of sodium hydroxide solution to 25-30% according to experimental requirements.

[0032] S2, Feeding: 27-29% sodium sulfide aqueous solution, sodium hydroxide aqueous solution, and acrylic acid are fed into the reactors separately. The ratio of the two phases is adjusted to maintain a molar ratio of sodium sulfide to acrylic acid of 1:2.03. The materials are fed into the reaction zone of the first dynamic batch reactor 1 at room temperature via pump, and the feed rate is controlled. Sodium hydroxide aqueous solution is pumped into the first dynamic batch reactor 1 at room temperature as another phase to adjust the pH value. Sulfuric acid solution is pumped into the second dynamic batch reactor 2 at room temperature as another phase, and the feed rates of the two phases are controlled, maintaining a molar ratio of 1:1 with the materials fed into the first dynamic batch reactor 1. Temperature and pH value are monitored online or offline at any time, and the feed rate of sulfuric acid solution is adjusted according to the pH value.

[0033] S3, heat exchange: During the reaction process, a temperature controller is used to control the temperature, so that the temperature of the first step reaction is maintained at 70℃-80℃;

[0034] S4, Residence: After the two phases are mixed, the residence time of the reaction liquid is 60s-600s, and the reaction is carried out under normal pressure.

[0035] S5, Discharge: After the reaction has been held for a certain period of time, the material is discharged from the first dynamic batch reactor 1 and enters the second dynamic batch reactor 2 for further acidification reaction to obtain thiodipropionic acid solution.

[0036] The reactor in S2 of this invention includes a first dynamic batch reactor 1 and a second dynamic batch reactor 2. Both the first dynamic batch reactor 1 and the second dynamic batch reactor 2 are equipped with a temperature sensor 12 and a pH sensor 13. The inner surfaces of the first dynamic batch reactor 1 and the second dynamic batch reactor 2 are cylindrical. The first dynamic batch reactor 1 is equipped with a first material inlet pipe 16, a second material inlet pipe 17, and a third material inlet pipe 18. The second dynamic batch reactor 2 is equipped with a fourth material inlet pipe 9 and a product outlet pipe 8. Furthermore, each of the first material inlet pipe 16, the second material inlet pipe 17, the third material inlet pipe 18, the fourth material inlet pipe 9, and the product outlet pipe 8 is equipped with a flow valve, which is connected to a PLC controller. The temperature and pH sensors and the rotating motor are also connected to the PLC controller.

[0037] Both the first dynamic batch reactor 1 and the second dynamic batch reactor 2 are equipped with built-in coils 3. The two built-in coils 3 maintain a constant temperature system for the first dynamic batch reactor 1 and the second dynamic batch reactor 2 through a heat exchange mechanism. The heat exchange mechanism includes a heat exchange box 11, in which heat exchange elements 22 are installed. The heat exchange elements 22 are suitable for both cooling and heating and can be controlled electrically, or by circulating water, electricity, and steam. A water pump 7 is installed on the heat exchange box 11. A spiral tube 27 is embedded in the built-in coils 3. A liquid outlet pipe 5 and a liquid inlet pipe 6 are respectively installed at both ends of the spiral tube 27. The liquid outlet pipe 5 is connected to the heat exchange box 11. The liquid inlet end of the water pump 7 is connected to the heat exchange box 11, and the liquid inlet pipe 6 is connected to the liquid outlet end of the water pump 7. The medium in the heat exchange box 11 is heat transfer oil.

[0038] The bottom of the first dynamic batch reactor 1 and the second dynamic batch reactor 2 are respectively provided with a first reaction zone 4 and a second reaction zone 19. Both the first dynamic batch reactor 1 and the second dynamic batch reactor 2 are equipped with motors 14 and shafts 15. The motors 14 are fixedly connected to the shafts 15. The lower end of the shafts 15 extends into the first reaction zone 4 and the second reaction zone 19 and is fixed with multiple stirring blades 10. The first dynamic batch reactor 1 and the second dynamic batch reactor 2 are connected by a conveying pipe 26.

[0039] First, two materials are introduced into the first reaction zone 4 of the first dynamic batch reactor 1 through the first material inlet pipe 16, the second material inlet pipe 17, and the third material inlet pipe 18 in proportion. Under the action of the motor 14 driving shaft 15 and the stirring blades 10, the materials undergo preliminary mixing reaction. In the first reaction zone 4 of the first dynamic batch reactor 1, the high-speed rotation generates shear force, which allows the materials to pass through a large specific surface area, achieving instantaneous uniform mixing and efficient heat transfer, thereby greatly enhancing the reaction rate and reaction efficiency.

[0040] In summary, the series dynamic batch reactor of this application ensures uniform heating and mixing of materials during the reaction, reduces acrylic acid polymerization, avoids polymer formation, and improves reaction efficiency. The temperature controller employs an integrated heating and cooling unit for precise temperature control, appropriately increasing the reaction rate. The reactor equipment of this application has a small footprint, saving land, and the PLC control system is easy to operate, highly automated, and saves manpower.

[0041] Table 1: Comparison of data on the preparation of thiodipropionic acid between a series dynamic batch reactor and a traditional batch reactor;

[0042]

[0043] Analysis of the data in Table 1 shows that when using the reactor described above, compared with traditional batch reactors, the content of polyacrylic acid by-product can be reduced, product stability and quality can be improved, and a very high yield can be achieved.

[0044] Example 2

[0045] Reference Figure 2The difference between this embodiment and embodiment 1 is that in this embodiment, four fixed rods 21 are installed in both the first dynamic batch reactor 1 and the second dynamic batch reactor 2. A guide tube 20 is fixed to the upper end of the fixed rod 21, and a shaft 15 extends into the guide tube 20. Multiple fan blades 28 are fixed on the shaft 15. The rotation of the shaft 15 drives the fan blades 28 to rotate, which creates a negative pressure in the guide tube 20. Therefore, the mixed liquid can flow upward through the guide tube 20 to achieve internal circulation, thereby making the mixing more thorough.

[0046] Example 3

[0047] Reference Figure 3 The difference between this embodiment and embodiments 1 and 2 is that a power motor 23 is installed at the bottom of the heat exchange box 11 in this embodiment. The output end of the power motor 23 is fixedly connected to a drive rod 24. The drive rod 24 passes through the heat exchange box 11 and is rotatably connected to it. Multiple stirring rods 25 are fixed on the drive rod 24. The power motor 23 drives the drive rod 24 and the stirring rods 25 to rotate, which can stir the return medium and make the temperature of the circulating medium more uniform. The heat exchange element 22 in the heat exchange box 11 is suitable for both cooling and heating and can be controlled by electricity or by circulating water, electricity and steam.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing thiodipropionic acid using a series dynamic batch reactor, characterized in that, Includes the following steps: S1, Preparation of reaction solution: Prepare aqueous solutions of sodium sulfide and sodium hydroxide separately. Adjust the content of sodium sulfide aqueous solution to 27-29% and the concentration of sodium hydroxide solution to 25-30% according to experimental requirements. S2, Feeding: 27-29% sodium sulfide aqueous solution, sodium hydroxide aqueous solution and acrylic acid are fed into the reactor respectively. The ratio of the two phase raw materials is adjusted so that the molar ratio of sodium sulfide to acrylic acid is controlled at 1:2.

03. The materials are fed into the reaction zone of the first dynamic batch reactor (1) at room temperature by pump, and the feeding speed of the materials is controlled. Sodium hydroxide aqueous solution is pumped into the first dynamic batch reactor (1) at room temperature as another phase material to adjust the pH value. Sulfuric acid solution is pumped into the second dynamic batch reactor (2) at room temperature as another phase material, and the feeding speed of the two phase materials is controlled. The molar ratio of the materials fed into the first dynamic batch reactor (1) is 1:

1. The temperature and pH value are monitored online or offline at any time, and the feeding amount of sulfuric acid solution is adjusted according to the pH value. S3, heat exchange: During the reaction process, a temperature controller is used to control the temperature, so that the temperature of the first step reaction is maintained at 70℃-80℃; S4, Residence: After the two phases are mixed, the residence time of the reaction liquid is 60s-600s, and the reaction is carried out under normal pressure. S5, Discharge: After the reaction has been held for a certain period of time, the material is discharged from the first dynamic batch reactor (1) and enters the second dynamic batch reactor (2) for further acidification to obtain thiodipropionic acid solution.

2. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The reactor in S2 includes a first dynamic batch reactor (1) and a second dynamic batch reactor (2). Both the first dynamic batch reactor (1) and the second dynamic batch reactor (2) are equipped with built-in coils (3). The two built-in coils (3) maintain the constant temperature system of the first dynamic batch reactor (1) and the second dynamic batch reactor (2) through a heat exchange mechanism. The bottom of the first dynamic batch reactor (1) and the second dynamic batch reactor (2) are respectively provided with a first reaction zone (4) and a second reaction zone (19). Both the first dynamic batch reactor (1) and the second dynamic batch reactor (2) are equipped with motors (14). Both the first dynamic batch reactor (1) and the second dynamic batch reactor (2) are equipped with shafts (15). The motors (14) are fixedly connected to the shafts (15). The lower end of the shafts (15) extends into the first reaction zone (4) and the second reaction zone (19) and is fixed with multiple stirring blades (10). The first dynamic batch reactor (1) and the second dynamic batch reactor (2) are connected by a conveying pipe (26).

3. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, Temperature sensor (12) and pH sensor (13) are installed on the first dynamic batch reactor (1) and the second dynamic batch reactor (2).

4. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The heat exchange mechanism includes a heat exchange box (11), a heat exchange component (22) is installed inside the heat exchange box (11), a water pump (7) is installed on the heat exchange box (11), a spiral tube (27) is embedded in the built-in coil (3), and an outlet pipe (5) and an inlet pipe (6) are respectively installed at both ends of the spiral tube (27). The outlet pipe (5) is connected to the heat exchange box (11), the inlet end of the water pump (7) is connected to the heat exchange box (11), and the inlet pipe (6) is connected to the outlet end of the water pump (7).

5. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The first dynamic batch reactor (1) is equipped with a first material inlet pipe (16), a second material inlet pipe (17) and a third material inlet pipe (18).

6. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The second dynamic batch reactor (2) is equipped with a fourth material inlet pipe (9) and a product outlet pipe (8).

7. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The inner surfaces of the first dynamic batch reactor (1) and the second dynamic batch reactor (2) are configured as cylindrical structures.

8. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, Flow valves are provided on the first material inlet pipe (16), the second material inlet pipe (17), the third material inlet pipe (18), the fourth material inlet pipe (9), and the product outlet pipe (8).

9. The method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 1, characterized in that, The first dynamic batch reactor (1) and the second dynamic batch reactor (2) are each equipped with four fixed rods (21). The upper end of the fixed rod (21) is fixed with a guide tube (20). The shaft (15) extends into the guide tube (20). Multiple fan blades (28) are fixed on the shaft (15).

10. A method for preparing thiodipropionic acid using a series dynamic batch reactor according to claim 4, characterized in that, A power motor (23) is installed at the bottom of the heat exchange box (11). A drive rod (24) is fixedly connected to the output end of the power motor (23). The drive rod (24) passes through the heat exchange box (11) and is rotatably connected to it. Multiple stirring rods (25) are fixed on the drive rod (24).

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