A deacidification device and method for producing dimethyl phosphite

Abstract

The present invention relates to the field of fine chemical technology, and discloses a deacidification device and method for producing dimethyl phosphite. The deacidification device and method for producing dimethyl phosphite of the present invention include a motor, a gas outlet, a rotating shaft, a steam outlet, a throwing disc, a reaction liquid outlet, a steam inlet, a liquid collecting pipe, a jacket and a reaction liquid inlet, and are characterized in that: the deacidification device is composed of more than two stages of reducing throwing discs, and the diameter of the throwing discs gradually decreases from top to bottom along the deacidification device, and a liquid collecting pipe is arranged on the inner wall surface of the deacidification device above the side of each stage of throwing disc. The deacidification device and method of the present invention adopt multi-stage reducing throwing discs, preventing the channeling flow and dry wall phenomena that occur in the lower half of the deacidification device due to the gradual reduction of the liquid material during the deacidification process, making the liquid film distribution more uniform, improving the hydrogen chloride removal efficiency and the yield and quality of dimethyl phosphite. At the same time, the design that the inner diameter of the deacidification device gradually decreases from top to bottom effectively reduces the steam consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemical industry, and particularly relates to a deacidification device for producing dimethyl phosphite and a using method thereof. Background Art

[0002] Dimethyl phosphite, also known as dimethyl phosphorous acid, is an important raw material for the production of pesticides such as insecticides, trichlorfon, dichlorvos, and glyphosate, and can also be used in the production of plastic auxiliaries, dye additives, flame retardants, etc.

[0003] At present, dimethyl phosphite in industry is mainly obtained by using methanol and phosphorus trichloride as raw materials and adopting a solvent-free continuous production process. The advantages of this production process are fast production speed, low production cost, and low operating cost. However, during the production process, when methanol reacts with phosphorus trichloride to form dimethyl phosphite, a large amount of hydrogen chloride and chloromethane are also generated. And when dimethyl phosphite contacts with hydrogen chloride for a long time, side reactions easily occur to form methyl phosphite monomethyl ester and chloromethane, which in turn affects the yield and quality of dimethyl phosphite. To improve the yield and purity of dimethyl phosphite and reduce the occurrence of side reactions, it is necessary to remove hydrogen chloride from the reaction solution in a timely manner. Therefore, the deacidification process in the production process of dimethyl phosphite is one of the key steps determining its yield and quality. Existing dimethyl phosphite production enterprises mainly use a single-stage / multi-stage disc deacidification device for deacidification, and the obtained dimethyl phosphite has relatively low yield and purity.

[0004] Patent CN 101870712B proposes a method for producing dimethyl phosphite. Phosphorus trichloride and methanol with a molar ratio of 1:(3.0 - 3.1) are respectively continuously injected into the reaction chamber space through their respective injection structures by their corresponding pumping mechanisms and mixed and reacted with each other. Then, the reaction materials are introduced tangentially into a centrifugal cyclone separation device with a pressure lower than the reaction chamber space, so that the non-condensable gas and the condensed liquid product are centrifugally cyclone separated, and the collected liquid substance is dimethyl phosphite. This method can quickly complete the separation of the product, effectively reduce the occurrence of side reactions between hydrogen chloride and dimethyl phosphite, and improve the yield and quality of the product. Patent CN114605469A discloses a high-efficiency synthesis process for producing dimethyl phosphite. By adopting a continuous fractional reaction method, after adding phosphorus trichloride, methanol is added in batches by spraying for reaction, and hydrogen chloride and chloromethane are discharged through a vacuum tube. After deacidification and rectification, dimethyl phosphite is obtained. This production process can discharge products such as hydrogen chloride at a relatively fast speed, reduce the generation of by-products, and improve the yield of dimethyl phosphite.

[0005] Although the above production processes / devices have accelerated the removal rate of hydrogen chloride to a certain extent and improved the yield of dimethyl phosphite, there are still problems such as high steam consumption, incomplete removal of hydrogen chloride, and low yield and purity of dimethyl phosphite. Summary of the Invention

[0006] The object of the present invention is to provide a deacidification device and a use method for producing dimethyl phosphite to solve the above problems. During the production process of dimethyl phosphite, this deacidification device can reduce steam consumption while improving the removal efficiency of hydrogen chloride and the yield and quality of dimethyl phosphite.

[0007] The deacidification device for producing dimethyl phosphite provided by the present invention includes a motor, a gas outlet, a rotating shaft, a steam outlet, a centrifugal disc, centrifugal disc holes, a reaction liquid outlet, a steam inlet, a liquid collecting pipe, a steam jacket, and a reaction liquid inlet.

[0008] The deacidification device is composed of more than two stages of centrifugal discs, and the diameter of the centrifugal discs gradually decreases from top to bottom along the deacidification device. A liquid collecting pipe is provided on the inner wall surface of the deacidification device above the side of each stage of centrifugal disc.

[0009] The ratio of the diameter of the centrifugal disc to the inner diameter of the deacidification device is 0.2 - 0.9, and the inner diameter of the deacidification device gradually decreases from top to bottom.

[0010] The deacidification device is composed of three stages of centrifugal discs. The diameters of the centrifugal discs are 2.0 - 1.8 m, 1.8 - 1.6 m, and 1.6 - 1.4 m from top to bottom in sequence, and gradually decrease.

[0011] The side wall surface of the centrifugal disc is provided with centrifugal disc holes; the shapes of the centrifugal disc holes include circular, rectangular, or polygonal; the aperture of the centrifugal disc holes is 0.5 - 10 mm.

[0012] The shape of the liquid collecting pipe is an inverted frustum of a cone, and the included angle between the liquid collecting pipe and the inner wall surface of the deacidification device α is 20 - 70 degrees.

[0013] Compared with the existing deacidification device, since the inner diameter of the deacidification device of the present invention gradually decreases from top to bottom, the heat exchange area required during the deacidification process is reduced, so the steam consumption is reduced while maintaining the same deacidification temperature.

[0014] Another technical solution of the present invention is to provide a deacidification process for dimethyl phosphite. Using the deacidification device for producing dimethyl phosphite, the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device through the reaction liquid inlet for deacidification. After being centrifuged by the first - stage centrifugal disc, a liquid film is formed on the inner wall of the deacidification device. After the liquid film descends along the inner wall surface under the action of gravity, the obtained liquid material is collected by the liquid collecting pipe and sent to the next - stage centrifugal disc for further centrifugation, film formation, and deacidification. The crude ester after deacidification is collected into a rectification tank, and refined dimethyl phosphite is obtained after rectification.

[0015] Before the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device, the pressure inside the deacidification device is controlled to be -0.10 to -0.05 MPa; the temperature is controlled to be 40 - 90 °C; the rotation speed of the rotating shaft is controlled to be 200 - 800 r / min.

[0016] Before the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device, the pressure inside the deacidification device is controlled to be -0.075 MPa; the temperature is controlled to be 75 °C; the rotation speed of the rotating shaft is controlled to be 500 r / min.

[0017] During the deacidification of dimethyl phosphite, the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device. After being centrifuged by the spinning disc, a liquid film is formed on the inner wall surface of the deacidification device. Under the action of gravity, the liquid film moves downward along the inner wall surface, and after heat exchange with the wall surface, hydrogen chloride gas in the liquid film is removed. Therefore, the control of the temperature inside the deacidification device is very important. Too low a temperature will slow down the removal rate of hydrogen chloride, and too high a temperature will cause a side reaction between dimethyl phosphite and hydrogen chloride, reducing the yield of dimethyl phosphite. The purpose of maintaining a negative pressure in the deacidification device is to timely extract the generated hydrogen chloride gas to avoid the occurrence of side reactions. Therefore, the magnitude of the negative pressure also determines the removal rate of hydrogen chloride and the final yield of dimethyl phosphite. Although too large a negative pressure inside the deacidification device is beneficial to the timely discharge of hydrogen chloride gas from the deacidification device and avoids the occurrence of side reactions, too high a negative pressure will entrain a large amount of dimethyl phosphite in the discharged hydrogen chloride gas, reducing the yield of dimethyl ester. And too small a negative pressure will cause the generated hydrogen chloride gas not to be discharged in time, resulting in a side reaction with dimethyl ester and reducing the yield of dimethyl ester. The role of the spinning disc is to make the reaction liquid form a uniform liquid film on the inner wall surface of the deacidification device after being centrifuged by the spinning disc, thereby removing hydrogen chloride. The rotation speed of the rotating shaft determines the film-forming effect during the deacidification process, and thus determines the removal efficiency of hydrogen chloride. A lower rotation speed will lead to a poor film-forming effect and affect the removal efficiency of hydrogen chloride. A higher rotation speed is beneficial to the removal of hydrogen chloride, but it will bring higher energy consumption.

[0018] Advantages of the deacidification device and its use method for producing dimethyl phosphite of the present invention:

[0019] The deacidification device and deacidification method for producing dimethyl phosphite of the present invention adopt a multi-stage variable-diameter spinning disc. The diameter of the spinning disc gradually decreases from top to bottom, preventing the channeling flow and dry wall phenomena that occur in the lower half of the deacidification device due to the gradual reduction of the liquid material during the evaporation process. The liquid film distribution is more uniform, reducing steam consumption while improving the hydrogen chloride removal efficiency, as well as the yield and quality of dimethyl phosphite, and can be widely applied in fields such as chemical industry, pharmaceuticals, and water treatment. Description of the Drawings

[0020] Figure 1 . Schematic structural diagram of the deacidification device for dimethyl phosphite of the present invention.

[0021] Figure 2 . Schematic diagram of the centrifugal disk structure of the present invention.

[0022] Figure 3 . Schematic diagram of the liquid collecting pipe structure.

[0023] Figure 4 . Schematic diagram of the structure of the existing deacidification device for dimethyl phosphite.

[0024] Reference numerals

[0025] 1. Motor, 2. Gas outlet, 3. Rotating shaft, 4. Steam outlet, 5. Centrifugal disk, 51. Centrifugal disk holes, 6. Reaction liquid outlet, 7. Steam inlet, 8. Liquid collecting pipe, 9. Steam jacket, 10. Reaction liquid inlet, 11. Inner wall surface of the deacidification device α Angle between the liquid collecting pipe and the inner wall of the deacidification device. Detailed implementation manners

[0026] Example 1

[0027] As shown in the Figure 1 device, a deacidification device for producing dimethyl phosphite, comprising a motor 1, a gas outlet 2, a rotating shaft 3, a steam outlet 4, a centrifugal disk 5, a reaction liquid outlet 6, a steam inlet 7, a liquid collecting pipe 8, a jacket 9 and a reaction liquid inlet 10. There are three - stage centrifugal disks 5 inside the deacidification device. The upper part of the deacidification device has a diameter of 2 m, the bottom diameter is 1.2 m, and the height is 3.5 m. The diameters of the first - stage, second - stage and third - stage centrifugal disks are 1.8 m, 1.6 m and 1.4 m respectively. The side wall surface of the centrifugal disk 5 is evenly distributed with a plurality of circular centrifugal disk holes 51 with a diameter of 5 mm. A liquid collecting pipe 8 is provided on the inner wall surface of the deacidification device above the side of each stage of the centrifugal disk 5. The angle between the liquid collecting pipe 8 and the inner wall of the deacidification device α is 45 degrees.

[0028] A steam jacket 9 is arranged outside the deacidification device. A steam inlet 7 is arranged at the lower part of the steam jacket 9, and a steam outlet 4 is arranged at the upper part. A reaction liquid inlet 10 is arranged at the upper part of the deacidification device, a gas outlet 2 is arranged at the top of the deacidification device, and a reaction liquid outlet is arranged at the bottom of the deacidification device. Inevitably, an electrode 1 and a driven rotating shaft 3 are arranged on the deacidification device.

[0029] The dimethyl phosphite deacidification process using the said device comprises the following steps:

[0030] First, turn on the vacuum pump connected to the deacidification device to make the pressure in the kettle reach - 0.075 MPa. Start the motor and adjust the rotating speed of the rotating shaft to 500 revolutions per minute. Adjust the steam flow rate of the steam inlet 7 to make the temperature in the deacidification device about 75 °C, and wait for the pressure, rotating speed and temperature to be stable;

[0031] Secondly, the reaction solution after the reaction of phosphorus trichloride and methanol enters the deacidification device through the reaction solution inlet 10 for deacidification. After being centrifuged by the first-stage spinning disk, a liquid film is formed on the inner wall of the deacidification device. Under the action of gravity, the liquid film descends along the inner wall surface to a certain height, and then the liquid material is collected by the liquid collecting pipe 8 and further centrifuged, formed into a film, and deacidified by the second-stage and third-stage spinning disks. The crude ester after deacidification is collected into the rectification tank, and refined dimethyl phosphite is obtained after rectification.

[0032] The process for the reaction of phosphorus trichloride and methanol is as follows: 1 mol / L phosphorus trichloride and 3 mol / L methanol solution are continuously injected into the esterification reaction kettle through their respective spraying structures by their corresponding pumping mechanisms and mixed and reacted with each other. The flow rates of phosphorus trichloride and methanol are both 50 L / min.

[0033] It is experimentally measured that the purity of dimethyl phosphite is 99.2%, the yield is 98.6%, and 0.095 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process. Compared with the existing deacidification device (Comparative Example 1), the purity and yield of dimethyl phosphite are increased by 2.79% and 2.92% respectively, and the steam consumption is reduced by 13.64%.

[0034] Comparative Example 1

[0035] As Figure 4 shown in the device, the diameter of the deacidification device is 2 m, the height is 3.5 m, and it is internally provided with three-stage spinning disks. The diameters of the first-stage, second-stage, and third-stage spinning disks are all 1.8 m. The liquid collecting pipe is not provided inside the device, and other conditions are the same as those in Example 1. It is experimentally measured that the purity of dimethyl phosphite is 96.5%, the yield is 95.8%, and 0.11 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process.

[0036] Example 2

[0037] Adjust the rotation speed of the rotating shaft to 400 revolutions per minute, and other conditions are the same as those in Example 1. It is experimentally measured that the purity of dimethyl phosphite is 98.3%, the yield is 98.1%, and 0.105 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process. Compared with the existing deacidification device (Comparative Example 2), the purity and yield of dimethyl phosphite are increased by 2.18% and 2.62% respectively, and the steam consumption is reduced by 11.02%.

[0038] Comparative Example 2

[0039] Adjust the rotation speed of the rotating shaft to 400 revolutions per minute, and other conditions are the same as those in Comparative Example 1. It is experimentally measured that the purity of dimethyl phosphite is 96.1%, the yield is 95.6%, and 0.118 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process.

[0040] Example 3

[0041] The diameter of the round holes of the three-stage centrifugal disk in the deacidification device is 3 mm, and the others are the same as in Example 1. It is experimentally measured that the purity of dimethyl phosphite is 99.4%, the yield is 98.9%, and 0.098 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process. Compared with the existing deacidification device (Comparative Example 1), the purity and yield of dimethyl phosphite are increased by 2.69% and 2.91% respectively, and the steam consumption is reduced by 14.04%.

[0042] Comparative Example 3

[0043] The diameter of the round holes of the three-stage centrifugal disk in the deacidification device is 3 mm, and the others are the same as in Comparative Example 1. It is experimentally measured that the purity of dimethyl phosphite is 96.8%, the yield is 96.1%, and 0.114 tons of steam is consumed per ton of dimethyl phosphite during the deacidification process.

Claims

1. A deacidification device for producing dimethyl phosphite, comprising a motor (1), a gas outlet (2), a rotating shaft (3), a steam outlet (4), a centrifugal disc (5), a reaction liquid outlet (6), a steam inlet (7), a liquid collecting pipe (8), a steam jacket (9) and a reaction liquid inlet (10), characterized in that: The deacidification device is composed of more than two levels of centrifugal discs (5), and the diameter of the centrifugal discs (5) gradually decreases from top to bottom along the deacidification device. A liquid collecting pipe (8) is arranged on the inner wall surface of the deacidification device above the side of each level of centrifugal disc (5); the deacidification device is composed of three levels of centrifugal discs (5), and the diameters of the centrifugal discs (5) are 2.0 - 1.8 m, 1.8 - 1.6 m, and 1.6 - 1.4 m from top to bottom in sequence and gradually decrease. The side wall surface of the centrifugal disc (5) is provided with centrifugal disc holes (51); the aperture of the centrifugal disc holes (51) is 0.5 - 10 mm.

2. The deacidification device for producing dimethyl phosphite according to claim 1, characterized in that: The ratio of the diameter of the centrifugal disc (5) to the inner diameter of the deacidification device is 0.2 - 0.9, and the inner diameter of the deacidification device gradually decreases from top to bottom.

3. The deacidification device for producing dimethyl phosphite according to claim 1, characterized in that: The shapes of the centrifugal disc holes (51) include circular, rectangular, or polygonal.

4. The deacidification device for producing dimethyl phosphite according to claim 1, characterized in that: The liquid collecting pipe (8) is in the shape of an inverted frustum of a cone, and the included angle between the liquid collecting pipe (8) and the inner wall surface of the deacidification device α is 20 to 70 degrees.

5. The deacidification device for producing dimethyl phosphite according to any one of claims 1-4, and the deacidification process of dimethyl phosphite is carried out by using the said device, characterized in that: The reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device through the reaction liquid inlet for deacidification. After being centrifuged by the first-level centrifugal disc, a liquid film is formed on the inner wall of the deacidification device. After the liquid film descends along the inner wall surface under the action of gravity, the obtained liquid material is collected by the liquid collecting pipe and sent to the next-level centrifugal disc for further centrifugation, film formation, and deacidification. The crude ester after deacidification is collected into a rectification tank, and refined dimethyl phosphite is obtained after rectification.

6. The deacidification device for producing dimethyl phosphite according to claim 5, wherein: Before the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device, the pressure in the deacidification device is controlled to be -0.10 - -0.05 MPa; the temperature is controlled to be 40 - 90 °C; the rotation speed of the rotating shaft is controlled to be 200 - 800 r / min.

7. The deacidification device for producing dimethyl phosphite according to claim 6, characterized in that: Before the reaction liquid after the reaction of phosphorus trichloride and methanol enters the deacidification device, the pressure in the deacidification device is controlled to be -0.075 MPa; the temperature is controlled to be 75 °C; the rotation speed of the rotating shaft is controlled to be 500 r / min.

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