A production process and system for 2,4-D butyric acid

Abstract

The invention discloses a production process and system of 2,4-dichlorobutyric acid, which comprises the following steps: S1: salt-forming reaction, adding 2,4-dichlorophenol into a salt-forming kettle, heating to 45 DEG C, and dripping 32% liquid alkali to prepare a 2,4-dichlorophenol sodium salt solution for standby use; S2: condensation reaction, putting the 2,4-dichlorophenol sodium salt solution formed in the previous step into a condensation kettle, heating to 80 DEG C-110 DEG C, dripping gamma-butyrolactone, refluxing and keeping the temperature at 80 DEG C-110 DEG C for reaction for 3h, cooling after the reaction is completed, crystallizing, filtering and separating 2,4-dichlorophenoxybutyric acid sodium salt crystals, and drying the obtained solid at 70 DEG C and normal pressure after pickling with hydrochloric acid to obtain 2,4-dichlorophenoxybutyric acid. The invention uses industrial phenol and chloroacetic acid as raw materials, adopts a new synthesis technology of condensation first and then chlorination, and the intermediate is directly chlorinated to prepare 2,4-D without separation, with a total yield of 76%, a content of 98% (effective acid), and a melting point of 136.5-140.5° C. There is no dichlorophenol pollution, the process is short, and the cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of 2,4-D butyric acid production, and in particular to a production process and system of 2,4-D butyric acid. Background Art

[0002] The reaction principle of this experiment is that the raw material 2,4-dichlorophenol is salted with liquid alkali, and then reacts with γ-butyrolactone to obtain sodium 2,4-dichlorophenoxybutyrate, which is then acidified with hydrochloric acid to obtain the product 2,4-D butyric acid (2,4-dichlorophenoxybutyric acid).

[0003] The reaction chemical formula is:

[0004]

[0005] The present invention aims to provide a new synthesis technology which uses industrial phenol and chloroacetic acid as raw materials and adopts condensation followed by chlorination. Summary of the invention

[0006] The present invention provides a production process and system for 2,4-D butyric acid, which solves the problems in the background technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A production process of 2,4-D butyric acid comprises the following steps:

[0009] S1: Salt formation reaction

[0010] Add 2,4-dichlorophenol to the salt-forming kettle, raise the temperature to 45°C, and drop 32% liquid caustic soda to prepare 2,4-dichlorophenol sodium salt solution for standby use;

[0011] S2: Condensation reaction

[0012] The 2,4-dichlorophenol sodium salt solution formed in the previous step is put into a condensation kettle, the temperature is raised to 80°C to 110°C, γ-butyrolactone is added dropwise, and the reaction is refluxed and kept warm at 80°C to 110°C for 3 hours. After the reaction is completed, the temperature is lowered and crystallized, and then 2,4-dichlorophenoxybutyric acid sodium salt crystals are separated by filtration. The solid obtained after hydrochloric acid pickling is dried at 70°C under normal pressure to obtain 2,4-dichlorophenoxybutyric acid;

[0013] S3: Mother liquor treatment

[0014] The high-salt mother liquor is acidified by adding 31% hydrochloric acid. After acidification, the mother liquor in the lower layer is completely recovered and used in the condensation section. The upper acid water enters the DCG wastewater treatment process;

[0015] S4: Concentration of salty wastewater

[0016] High-salinity wastewater enters the salt-containing wastewater concentration process, which uses triple-effect evaporation and the condensed water is reused. The concentrated liquid phase is centrifuged, and the residue produced by centrifugation is mainly sodium chloride, a byproduct, and the centrifuged liquid is reused in the high-salinity wastewater concentration process;

[0017] S5: Dry Packaging

[0018] The wet product of 2,4-dichlorophenoxybutyric acid is dried by air flow, and the dried product is transferred to the packaging equipment through the finished product transfer pump.

[0019] Preferably, in S1, the temperature is raised to 80°C and stirred for 0.5h, then the temperature is lowered back to 45°C and kept warm for 0.5h. When the pH value of the reaction sample is 10-12 as detected by pH test paper, the reaction is considered to have reached the end point.

[0020] Preferably, in S2, after the addition of γ-butyrolactone is completed, the temperature is continuously heated to 110°C to 130°C for 3 hours of heat preservation reaction; the pH value is maintained at 10 to 12, and sampling is performed for HPLC monitoring. If 2,4-dichlorophenol is ≤2.0%, the reaction is complete; if it is greater than 2.0%, the reaction is continued for 1 hour, and sampling is performed until 2,4-dichlorophenol is ≤2.0%. After the reaction is completed, the temperature is lowered to room temperature, crystallized, centrifuged and filtered, and the filter cake is sent to the filter cake acidification kettle; the filtrate is sent to the mother liquor acidification kettle and enters the mother liquor treatment process.

[0021] Preferably, in S3, the mother liquor is acidified to a pH value of 1 to 2 as detected by a pH test paper, and part of the 2,4-dichlorophenoxybutyrate sodium and 2,4-dichlorophenol sodium dissolved in the mother liquor is acidified into organic matter, which is then separated and extracted by standing.

[0022] Preferably, in S5, the hot air from the drying process carries 2,4-dichlorophenoxybutyric acid and is discharged from the upper part of the drying equipment, passing through a bag filter. The waste gas discharged from the bag filter is sprayed with three-stage alkaline water and then discharged from a 20m high exhaust pipe.

[0023] A 2,4-D butyric acid production system comprises a salt-forming condensation kettle, a mother liquor acidification kettle and a filter cake acidification kettle, wherein the addition port of the salt-forming condensation kettle is connected to a liquid alkali high-level tank and a gamma-butyrolactone high-level tank, the discharge port of the salt condensation kettle is connected to a first centrifuge, and a mother liquor storage tank is provided between the first centrifuge and the mother liquor acidification kettle.

[0024] Preferably, the mother liquor acidification kettle and the filter cake acidification kettle are both equipped with a hydrochloric acid high-level tank, and a liquid pump is provided between the mother liquor storage tank and the mother liquor acidification kettle.

[0025] Preferably, the liquid outlet of the mother liquor acidification kettle is equipped with an oil phase tank and a water phase tank, a liquid pump is provided between the oil phase tank and the salt condensation kettle, the discharge port of the filter cake acidification kettle is connected to a second centrifuge, and the discharge port of the second centrifuge is connected to the salt-containing wastewater tank.

[0026] Preferably, the tail gas discharge port of the salt-forming condensation reactor is equipped with a tail gas condenser, the bottom end of the tail gas condenser is provided with an air inlet, the top end of the tail gas condenser is provided with an air outlet, a partition plate is fixed at the middle position of the tail gas condenser, the top end of the partition plate is provided with a through hole and is connected with an air cooling pipe, one end of the air cooling pipe extends to the outside of the tail gas condenser and extends back to the inside of the tail gas condenser after passing through the air cooling mechanism, the inside of the tail gas condenser is provided with a first liquid cooling mechanism and a second liquid cooling mechanism above and below the partition plate, respectively, and the first liquid cooling mechanism and the second liquid cooling mechanism both include A plurality of first heat spreaders are arranged equidistantly and fixedly connected to the inner wall of the exhaust gas condenser. A refrigerant inlet duct is arranged near the top of the outside of the exhaust gas condenser. The refrigerant inlet duct enters the inside of the exhaust gas condenser, and serpentines on the top of each first heat spreader in turn, and then extends to the outside of the exhaust gas condenser to communicate with the external duct. The bottom end of the external duct extends to the bottom of the partition plate in the exhaust gas condenser and is connected with the refrigerant exhaust duct. The refrigerant exhaust duct serpentines on each first heat spreader in turn and extends to the outside of the exhaust gas condenser.

[0027] Preferably, an anti-backflow pipe is installed on the inner wall of the bottom end of the tail gas condenser, the anti-backflow pipe is connected to the air inlet, and a shielding cap is fixed on the top of the anti-backflow pipe.

[0028] Preferably, the air cooling mechanism comprises an air cooling box, a second heat spreader is fixed in the air cooling box, one end of the air cooling duct located outside the exhaust gas condenser is serpentinely coated on one side of the second heat spreader, and a heat dissipation fan is installed on the air cooling box.

[0029] Preferably, a first reflux pipe and a second reflux pipe are installed outside the tail gas condenser near the bottom and near the top of the partition plate, respectively, and both the first reflux pipe and the second reflux pipe are connected to the salt-forming condensation kettle.

[0030] The beneficial effects of the present invention are:

[0031] 1. The present invention uses industrial phenol and chloroacetic acid as raw materials, adopts a new synthesis technology of condensation first and then chlorination, and the intermediate is directly chlorinated to produce 2,4-D without separation, with a total yield of 76%, a content of 98% (effective acid), and a melting point of 136.5-140.5°C. There is no pollution from dichlorophenol, the process is short, and the cost is low;

[0032] 2. In the present invention, the tail gas condenser is divided into two upper and lower areas by a partition plate, the heat source flows from bottom to top, and the refrigerant flows from bottom to top. The refrigerant with a lower temperature just entering the air outlet exchanges heat with the heat source with a lower temperature after heat exchange once through the second liquid cooling mechanism. Then, the temperature of the cold source is increased and introduced to the bottom of the partition plate through an external conduit, and heat is exchanged with the heat source with a higher temperature just entering the tail gas condenser. Finally, the cold source flows out through the refrigerant discharge conduit. Both heat exchanges can ensure a large temperature difference between the refrigerant and the heat source, thereby improving the heat exchange efficiency.

[0033] 3. By adding an air cooling mechanism, the gas under the partition plate passes through the second liquid cooling mechanism for the first heat exchange and then enters the air cooling box through the air cooling duct, and dissipates heat through the air cooling box heat dissipation fan. After cooling, it returns to the exhaust gas condenser and then exchanges heat again through the first liquid cooling mechanism. The combination of air cooling and liquid cooling can reduce energy consumption, improve the condensation effect, increase the recovery rate of raw materials, and reduce the waste of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention provides a flow chart of a production process of 2,4-D butyric acid.

[0035] Figure 2 This is a schematic diagram of a 2,4-D butyric acid production system proposed by the present invention.

[0036] Figure 3 This is a detailed diagram of a tail gas condenser in a 2,4-D butyric acid production system proposed by the present invention.

[0037] Figure 4 This is a top view of a tail gas condenser in a 2,4-D butyric acid production system proposed by the present invention.

[0038] Figure 5 This is an enlarged cross-sectional view of a backflow prevention pipe in a production system of 2,4-D butyric acid proposed by the present invention.

[0039] Figure 6 A large cross-section of an air cooling box in a production system of 2,4-D butyric acid proposed by the present invention.

[0040] Numbers in the figure: 1. Liquid alkali high-level tank; 2. γ-butyrolactone high-level tank; 3. Salt-forming condensation kettle; 4. Tail gas condenser; 5. First centrifuge; 6. Mother liquor storage tank; 7. Mother liquor acidification kettle; 8. Filter cake acidification kettle; 9. Oil phase tank; 10. Water phase tank; 11. Second centrifuge; 12. Salt-containing wastewater tank; 13. Air inlet; 14. Air outlet; 15. Refrigerant inlet duct; 16. First heat spreader; 17. Cooling fan; 18. Partition plate; 19. Refrigerant discharge duct; 20. Anti-backflow pipe; 21. Shielding cap; 22. Air cooling box; 23. Second reflux pipe; 24. First reflux pipe; 25. Air cooling duct; 26. Second heat spreader. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0042] Example 1

[0043] a. Salting process: Break the solid 2,4-dichlorophenol, weigh 163g and add it into the salting kettle, start stirring, heat to 80±5℃, add 135g of 32% sodium hydroxide solution, and keep warm for 0.5h. When the pH value of the reaction sample is 10-12, it is considered that the reaction has reached the end point.

[0044] b. Condensation process: transfer all the products of the previous step reaction to the condensation kettle, stir, heat to 80℃~110℃, slowly add quantitative γ-butyrolactone through the high-level tank, continue to heat to 110℃~130℃ and keep warm for 3h after the addition is completed; keep the pH value at 10~12, take samples for HPLC monitoring, if 2,4-dichlorophenol ≤2.0%, the reaction is complete, if >2.0%, continue to react for 1h, take samples for testing until 2,4-dichlorophenol ≤2.0%. After the reaction is completed, cool to room temperature, crystallize, centrifuge and filter, send the filter cake to the filter cake acidification kettle; send the filtrate to the mother liquor acidification kettle and enter the mother liquor treatment process.

[0045] c. Acidification process: put the centrifugal filter cake into the filter cake acidification kettle, add a certain amount of 32% hydrochloric acid, stir and acidify, acidify to the pH test paper detection value of 1-2, then transfer all the materials to the centrifuge for centrifugal filtration and washing of the filter cake. The filter cake is sent to the drying process as a wet product of 2,4-dichlorophenoxybutyric acid. The wet filter cake is dried under reduced pressure at 45°C-55°C, turned over every 4 hours, and sampled after 12 hours to detect the drying loss. If the drying loss is greater than 0.5%, continue drying for 2 hours until the drying loss is ≤0.5%; the filtrate is sent to the sodium chloride refining process as high-salt wastewater.

[0046] Example 2

[0047] a. Salting process: Break solid 2,4-dichlorophenol, weigh 3260g and add it into the salting kettle, start stirring, heat to 80±5℃, add 2700g of 32% sodium hydroxide solution, and keep warm for 0.5h. When the pH value of the reaction sample is 10-12, it is considered that the reaction has reached the end point.

[0048] b. Condensation process: transfer all the products of the previous step reaction to the condensation kettle, stir, heat to 80℃~110℃, slowly add quantitative γ-butyrolactone through the high-level tank, continue to heat to 110℃~130℃ and keep warm for 3h after the addition is completed; keep the pH value at 10~12, take samples for HPLC monitoring, if 2,4-dichlorophenol ≤2.0%, the reaction is complete, if >2.0%, continue to react for 1h, take samples for testing until 2,4-dichlorophenol ≤2.0%. After the reaction is completed, cool to room temperature, crystallize, centrifuge and filter, send the filter cake to the filter cake acidification kettle; send the filtrate to the mother liquor acidification kettle and enter the mother liquor treatment process.

[0049] c. Acidification process: put the centrifugal filter cake into the filter cake acidification kettle, add a certain amount of 32% hydrochloric acid, stir and acidify, acidify to the pH test paper detection value of 1-2, then transfer all the materials to the centrifuge for centrifugal filtration and washing of the filter cake. The filter cake is sent to the drying process as a wet product of 2,4-dichlorophenoxybutyric acid. The wet filter cake is dried under reduced pressure at 45°C-55°C, turned over every 4 hours, and sampled after 12 hours to detect the drying loss. If the drying loss is greater than 0.5%, continue drying for 2 hours until the drying loss is ≤0.5%; the filtrate is sent to the sodium chloride refining process as high-salt wastewater.

[0050] Example 3

[0051] Please refer to Figure 2-6 A 2,4-D butyric acid production system comprises a salt-forming condensation kettle 3, a mother liquor acidification kettle 7 and a filter cake acidification kettle 8, wherein the addition port of the salt-forming condensation kettle 3 is connected with a liquid alkali high-level tank 1 and a γ-butyrolactone high-level tank 2, the discharge port of the salt-forming condensation kettle 3 is connected with a first centrifuge 5, a mother liquor storage tank 6 is arranged between the first centrifuge 5 and the mother liquor acidification kettle 7, a 2,4-dichlorophenol delivery port is arranged at the top of the salt-forming condensation kettle 3, the mother liquor storage tank 6 is used to store the mother liquor separated by the first centrifuge 5, the mother liquor acidification kettle 7 and the filter cake acidification kettle 8 are both equipped with a hydrochloric acid high-level tank, a liquid pump is arranged between the mother liquor storage tank 6 and the mother liquor acidification kettle 7, and the filter cake in the first centrifuge 5 is sent to the filter cake acidification kettle 8 for acidification.

[0052] Among them, the liquid outlet of the mother liquor acidification kettle 7 is installed with an oil phase tank 9 and a water phase tank 10, a liquid pump is provided between the oil phase tank 9 and the salt condensation kettle 3, the discharge port of the filter cake acidification kettle 8 is connected to a second centrifuge 11, and the discharge port of the second centrifuge 11 is connected to a salt-containing wastewater tank 12. The sewage in the water phase tank 10 is discharged after treatment, and the oil phase in the oil phase tank 9 is pumped back to the salt condensation kettle 3 for application.

[0053] Example 4

[0054] Please refer to Figure 2-6The difference between this embodiment and embodiment 3 is that a tail gas condenser 4 is installed at the tail gas discharge port of the salt-forming condensation reactor 3, an air inlet 13 is provided at the bottom end of the tail gas condenser 4, an air outlet 14 is provided at the top end of the tail gas condenser 4, a partition plate 18 is fixed at the middle position of the tail gas condenser 4, a through hole is opened at the top end of the partition plate 18 and an air cooling pipe 25 is connected, one end of the air cooling pipe 25 extends to the outside of the tail gas condenser 4 and extends back to the inside of the tail gas condenser 4 after passing through the air cooling mechanism, and the inside of the tail gas condenser 4 is provided with a first liquid cooling machine above and below the partition plate 18. The first liquid cooling mechanism and the second liquid cooling mechanism each include a plurality of first heat spreaders 16, the plurality of first heat spreaders 16 are equidistantly arranged and fixedly connected to the inner wall of the tail gas condenser 4, a refrigerant inlet conduit 15 is arranged near the top of the outside of the tail gas condenser 4, the refrigerant inlet conduit 15 enters the inside of the tail gas condenser 4, and is successively coiled on the top of each first heat spreader 16, and then extends to the outside of the tail gas condenser 4 to communicate with the outer conduit 20, the bottom end of the outer conduit 20 extends to the bottom of the partition plate 18 in the tail gas condenser 4 and is connected to the refrigerant discharge conduit 1 9 is connected, and the refrigerant discharge conduit 19 is successively coiled on each first heat sink 16 and extends to the outside of the exhaust condenser 4. When cooling by heat transfer, the greater the temperature difference between the heat source and the cold source, the higher the heat exchange efficiency. In the condenser of the prior art, the refrigerant and the heat source are heat-conducted by continuous convection. In the process of convection heat conduction between the refrigerant and the heat source, the refrigerant temperature gradually increases and the heat source temperature decreases. There is an intermediate area where the temperature difference between the refrigerant and the heat source is small, which makes the heat exchange efficiency of this section low, affecting the overall heat exchange efficiency. In the present invention, the exhaust gas condenser 4 is divided into two upper and lower areas by a partition plate 18, the heat source flows from bottom to top, and the refrigerant flows from bottom to top. The refrigerant with a lower temperature just entering the air outlet 14 exchanges heat with the heat source with a lower temperature after heat exchange once through the second liquid cooling mechanism. Then, after the temperature of the cold source is raised, it is introduced to the bottom of the partition plate 18 through the external duct 20, and heat is exchanged with the heat source with a higher temperature just entering the exhaust gas condenser 4, and finally flows out through the refrigerant discharge duct 19. Both heat exchanges can ensure a large temperature difference between the refrigerant and the heat source, thereby improving the heat exchange efficiency.

[0055] Among them, an anti-backflow pipe 20 is installed on the inner wall of the bottom end of the tail gas condenser 4, the anti-backflow pipe 20 is connected to the air inlet 13, and a shielding cap 21 is fixed to the top of the anti-backflow pipe 20. The shielding cap 21 can block the top opening of the anti-backflow pipe 20, thereby preventing the condensed liquid from flowing back from the air inlet 13 to the salt condensation kettle 3.

[0056] Among them, the air cooling mechanism includes an air cooling box 22, in which a second heat spreader 26 is fixed, and an air cooling duct 25 is located at one end of the tail gas condenser 4, and the serpentine coil covers one side of the second heat spreader 26. A heat dissipation fan 17 is installed on the air cooling box 22. The gas below the partition plate 18 enters the air cooling box 22 through the air cooling duct 25 after the initial heat exchange through the second liquid cooling mechanism, and dissipates heat through the heat dissipation fan 17 of the air cooling box 22. After cooling, it returns to the tail gas condenser 4 and then exchanges heat again through the first liquid cooling mechanism. Through the combination of air cooling and liquid cooling, energy consumption can be reduced, the condensation effect can be improved, the recovery rate of raw materials can be improved, and the waste of raw materials can be reduced.

[0057] Among them, the first reflux pipe 24 and the second reflux pipe 23 are respectively installed on the outside of the tail gas condenser 4 near the bottom end and near the top end of the partition plate 18. The first reflux pipe 24 and the second reflux pipe 23 are both connected to the salt-forming condensation kettle 3, and the condensed reaction raw materials are returned to the interior of the salt-forming condensation kettle 3 through the first reflux pipe 24 and the second reflux pipe 23.

[0058] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0059] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A production process of 2,4-D butyric acid, characterized in that: The following steps are involved: S1: Salt formation reaction Add 2,4-dichlorophenol to the salt-forming kettle, raise the temperature to 45°C, and drop 32% liquid caustic soda to prepare 2,4-dichlorophenol sodium salt solution for standby use; S2: Condensation reaction The 2,4-dichlorophenol sodium salt solution formed in the previous step is put into a condensation kettle, the temperature is raised to 80°C-110°C, γ-butyrolactone is added dropwise, and the reaction is refluxed and kept warm at 80°C-110°C for 3 hours. After the reaction is completed, the temperature is lowered and crystallized, and then 2,4-dichlorophenoxybutyric acid sodium salt crystals are separated by filtration. The solid obtained after hydrochloric acid pickling is dried at 70°C under normal pressure to obtain 2,4-dichlorophenoxybutyric acid; S3: Mother liquor treatment The high-salt mother liquor is acidified by adding 31% hydrochloric acid. After acidification, the mother liquor in the lower layer is completely recovered and used in the condensation section, and the acid water in the upper layer enters the DCG wastewater treatment process; S4: Concentration of salty wastewater High-salinity wastewater enters the salt-containing wastewater concentration process, which is concentrated by triple-effect evaporation. The condensed water is reused, and the concentrated liquid phase is centrifuged. The residue produced by centrifugation is mainly sodium chloride, a by-product. The centrifuged liquid is reused in the high-salinity wastewater concentration process. S5: Dry Packaging The wet product of 2,4-dichlorophenoxybutyric acid is dried by air flow, and the dried product is transferred to the packaging equipment through the finished product transfer pump; The production system used in the production process comprises a salt-forming condensation kettle (3), a mother liquor acidification kettle (7) and a filter cake acidification kettle (8), wherein the addition port of the salt-forming condensation kettle (3) is connected to a liquid alkali high-level tank (1) and a γ-butyrolactone high-level tank (2), the discharge port of the salt-forming condensation kettle (3) is connected to a first centrifuge (5), and a mother liquor storage tank (6) is provided between the first centrifuge (5) and the mother liquor acidification kettle (7); The mother liquor acidification kettle (7) and the filter cake acidification kettle (8) are both equipped with a hydrochloric acid high-level tank, and a liquid pump is provided between the mother liquor storage tank (6) and the mother liquor acidification kettle (7); The liquid outlet of the mother liquor acidification kettle (7) is equipped with an oil phase tank (9) and a water phase tank (10), a liquid pump is provided between the oil phase tank (9) and the salt-forming condensation kettle (3), the discharge port of the filter cake acidification kettle (8) is connected to a second centrifuge (11), and the discharge port of the second centrifuge (11) is connected to a salt-containing wastewater tank (12); The tail gas discharge port of the salt-forming condensation reactor (3) is provided with a tail gas condenser (4), the bottom end of the tail gas condenser (4) is provided with an air inlet (13), the top end of the tail gas condenser (4) is provided with an air outlet (14), a partition plate (18) is fixed in the middle position of the tail gas condenser (4), the top end of the partition plate (18) is provided with a through hole and is connected to an air cooling pipe (25), one end of the air cooling pipe (25) extends to the outside of the tail gas condenser (4) and extends back to the inside of the tail gas condenser (4) after passing through the air cooling mechanism, the inside of the tail gas condenser (4) is provided with a first liquid cooling mechanism and a second liquid cooling mechanism respectively located above and below the partition plate (18), the first liquid cooling mechanism and the second liquid cooling mechanism each comprising a plurality of first heat absorbing blocks; Plate (16), a plurality of first heat-spreading plates (16) are equidistantly arranged and fixedly connected to the inner wall of the exhaust gas condenser (4), a refrigerant inlet conduit (15) is arranged near the top of the outside of the exhaust gas condenser (4), the refrigerant inlet conduit (15) enters the inside of the exhaust gas condenser (4), and is successively serpentine-coated on the top of each first heat-spreading plate (16), and then extends to the outside of the exhaust gas condenser (4) and communicates with the external conduit (27), the bottom end of the external conduit (27) extends to the bottom of the partition plate (18) in the exhaust gas condenser (4) and is communicated with the refrigerant discharge conduit (19), and the refrigerant discharge conduit (19) is successively serpentine-coated on each first heat-spreading plate (16) and extends to the outside of the exhaust gas condenser (4).

2. A process for producing 2,4-D butyric acid according to claim 1, characterized in that: In S1, the temperature is raised to 80° C. and stirred for 0.5 h, then the temperature is lowered back to 45° C. and kept warm for 0.5 h. The reaction is sampled and the pH value is 10-12 as determined by pH test paper, which is considered to be the end point of the reaction.

3. A process for producing 2,4-D butyric acid according to claim 1, characterized in that: In the S2, after the addition of γ-butyrolactone is completed, the temperature is continuously heated to 110°C-130°C for 3 hours of heat preservation; the pH value is maintained at 10-12, and sampling is performed for HPLC monitoring. If 2,4-dichlorophenol is ≤2.0%, the reaction is complete; if it is greater than 2.0%, the reaction is continued for 1 hour, and sampling is performed for detection until 2,4-dichlorophenol is ≤2.0%; after the reaction is completed, the temperature is lowered to room temperature, crystallized, centrifuged and filtered, and the filter cake is sent to a filter cake acidifying kettle; the filtrate is sent to a mother liquor acidifying kettle and enters the mother liquor treatment process.

4. A process for producing 2,4-D butyric acid according to claim 1, characterized in that: In S3, the mother liquor is acidified to a pH value of 1-2 as detected by a pH test paper, and part of the 2,4-dichlorophenoxybutyrate sodium and 2,4-dichlorophenol sodium dissolved in the mother liquor is acidified to form organic matter, which is then separated and extracted by standing.

5. The production process of 2,4-D butyric acid according to claim 1, characterized in that: In S5, the hot air from the drying process carries 2,4-dichlorophenoxybutyric acid and is discharged from the upper portion of the drying equipment and passes through a bag filter.

6. A process for producing 2,4-D butyric acid according to claim 1, characterized in that: An anti-backflow pipe (20) is installed on the inner wall of the bottom end of the tail gas condenser (4), the anti-backflow pipe (20) is connected to the air inlet (13), and a shielding cap (21) is fixed on the top end of the anti-backflow pipe (20).

7. A process for producing 2,4-D butyric acid according to claim 1, characterized in that: The air cooling mechanism comprises an air cooling box (22), a second heat spreader (26) is fixed inside the air cooling box (22), one end of the air cooling duct (25) located outside the exhaust gas condenser (4) is covered with a serpentine coil on one side of the second heat spreader (26), and a heat dissipation fan (17) is installed on the air cooling box (22).

8. The production process of 2,4-D butyric acid according to claim 1, characterized in that: A first reflux pipe (24) and a second reflux pipe (23) are respectively installed on the outside of the tail gas condenser (4) near the bottom end and near the top end of the partition plate (18), and the first reflux pipe (24) and the second reflux pipe (23) are both connected to the salt-forming condensation kettle (3).

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