Synthesis method of 2-fluoroacrylic acid

Abstract

The invention provides a synthetic method of 2-fluoroacrylic acid. Relates to the technical field of 2-fluoroacrylic acid synthesis. The method comprises the following steps: S1, taking 2-fluoropropionic acid as a raw material, specifically an oxidation method; reagents: 2-fluoropropionic acid, an oxidizing agent, a catalyst and an organic solvent; instruments comprise a reaction container, a reflux condensation pipe, a stirring device, a thermometer and a heating device. 2-fluoropropionic acid is selected as a raw material, an appropriate reaction container is selected, a chemical reaction kettle can be preferentially selected as the reaction container, in the process of adding a toxic or irritant reagent, inert gas is added to protect the reagent in the process of adding the reagent again, it is guaranteed that the reagent is safer when entering the reaction kettle, and the reaction is more stable. The inert gas (specifically preferably nitrogen and the like) is mixed with the reagent to enter in a linkage integrated manner in the adding process, so that the stability of the reagent during passing can be well ensured, the density of the reagent can be reduced, and reaction is not easy to form.

Description

Technical Field

[0001] The invention relates to the technical field of 2-fluoroacrylic acid synthesis, and in particular to a method for synthesizing 2-fluoroacrylic acid. Background Art

[0002] 2-Fluoroacrylic acid is a colorless liquid with a pungent odor. It is an organic compound with an allyl structure. Its molecular formula is C3H3FO2 and its molecular weight is 90.05. It is a strong acidic substance with certain dangers. It can cause irritation and corrosion when in contact with the skin and eyes.

[0003] 2-Fluoroacrylic acid is an important raw material for organic synthesis. It is widely used in some specific chemical reactions. It can be used as an organic synthesis intermediate and a pharmaceutical intermediate for synthesizing drugs, pesticides, dyes, polymers and other chemicals. It plays an important role in the chemical synthesis industry. There are many methods for synthesizing 2-fluoroacrylic acid, such as direct fluorination using acrylic acid as raw material, indirect fluorination, oxidation using 2-fluoropropionic acid as raw material, halogenation followed by elimination, and synthesis through cyclopropane intermediates.

[0004] In the existing synthesis methods, especially when using 2-fluoropropionic acid as a raw material for oxidation synthesis, toxic or irritating reagents are added. The reagents are very likely to react with the outside world during the addition process. Therefore, it is not convenient to add protection for some unstable reagents.

[0005] Therefore, it is necessary to provide a method for synthesizing 2-fluoroacrylic acid to solve the above technical problems. Summary of the invention

[0006] The invention provides a method for synthesizing 2-fluoroacrylic acid, which solves the technical problem in the related art that toxic or irritating reagents are very likely to react with the outside world during the addition process, making it inconvenient to protect them.

[0007] In order to solve the above technical problems, the present invention provides a method for synthesizing 2-fluoroacrylic acid, characterized in that it comprises the following steps:

[0008] Step S1: using 2-fluoropropionic acid as a raw material, specifically an oxidation method;

[0009] Reagents: 2-fluoropropionic acid, oxidant, catalyst, organic solvent;

[0010] Instruments: reaction vessel, reflux condenser, stirring device, thermometer, heating device;

[0011] Select 2-fluoropropionic acid as a raw material, select a suitable reaction container, and the reaction container can preferably be a chemical reactor;

[0012] Step S2: In a reaction container, dissolve 2-fluoropropionic acid in an organic solvent, wherein the organic solvent may be selected from one part of ethyl acetate or one part of toluene;

[0013] Add an oxidant, such as potassium permanganate, potassium dichromate, etc., and then drop an appropriate amount of sulfuric acid as a catalyst, and react under heating reflux conditions. During the reaction, the temperature and reaction progress must be closely monitored, and the reaction progress can be monitored by the TLC method;

[0014] Step S3: Stirring is required during the reaction to ensure that the reaction proceeds fully;

[0015] After the reaction is completed, cool to room temperature, pour the reaction solution into a separatory funnel, add a portion of water for extraction, separate the organic phase and the aqueous phase, the aqueous phase can be extracted again with an organic solvent, combine the organic phases, dry the organic phase with a desiccant such as anhydrous sodium sulfate, and filter to remove the desiccant.

[0016] Step S4: Purification: Purify the dried organic phase by distillation, rectification or the like, collect fractions in the corresponding boiling point range, and obtain a 2-fluoroacrylic acid product;

[0017] Purifying the separated 2-fluoroacrylic acid to remove impurities such as unreacted raw materials, by-products and solvents, and the purification method may include recrystallization, column chromatography, etc.;

[0018] Note:

[0019] The selection of oxidants and catalysts is crucial. Different oxidants and catalysts may affect the yield and selectivity of the reaction and need to be optimized according to specific circumstances.

[0020] The control of reaction temperature and time also has a great influence on the reaction results. Too high temperature or too long reaction time may lead to an increase in side reactions and reduce the purity and yield of the product.

[0021] The entire experimental operation process must be carried out in a well-ventilated environment, because some reagents are toxic or irritating, and attention must be paid to safety issues such as fire prevention and explosion prevention.

[0022] Step S5: During the operation of the above steps, some reagents are toxic or irritating. Therefore, in view of this situation, when adding toxic or irritating reagents, it is necessary to add inert gas to protect the reagents and ensure that the reagents are safer when entering the reaction container.

[0023] The step S5 of the synthesis method of 2-fluoroacrylic acid needs to be implemented in a reaction kettle and a adding mechanism when passing an inert gas;

[0024] A top plate is installed on the top of the reactor by bolts, a sealing ring is provided between the upper surface of the reactor and the lower surface of the top plate, a protective cover is installed on the top of the top plate by bolts, and a driving mechanism is installed inside the protective cover;

[0025] The driving mechanism comprises a positioning plate fixedly mounted on the upper surface of the top plate and located inside the protective cover, a motor is installed on one side of the top plate and located on one side of the positioning plate by bolts, a first gear is connected to the keyway of the output shaft of the motor, a rotating rod is rotatably connected inside the positioning plate, and a second gear is fixed to the outer wall of the rotating rod;

[0026] The adding mechanism includes a mounting bracket fixedly arranged on the upper surface of the protective cover, a cam is connected to the top keyway of the rotating rod, a connecting plate is rotatably connected to the upper surface of the cam, a horizontally movable slide is slidably connected to the outside of the mounting bracket, a first extrusion barrel and a second extrusion barrel are fixedly arranged on the outside of the mounting bracket and on the left side of the slide, piston rods are slidably connected to the insides of the first extrusion barrel and the second extrusion barrel respectively, a second one-way valve and a first one-way valve are respectively installed on the outer walls of the first extrusion barrel and the second extrusion barrel, a third one-way valve is installed on the outer walls of the first extrusion barrel and the second extrusion barrel and on one side of the second one-way valve and the first one-way valve, the inlet ends of the two third one-way valves are both sealed with the first pipeline and the second pipeline, the outlet end of the first one-way valve is sealed with the upper pipe, and the outlet end of the second one-way valve is sealed with the inlet pipe.

[0027] Preferably, the first gear and the second gear are meshed with each other, and the outer wall of the rotating rod is rotationally connected to the axis of the protective cover.

[0028] Preferably, the left end of the connecting plate is rotatably connected to the outer wall of the slide plate, the outer wall of the slide plate is fixedly connected to the two piston rods, the outlet end of the upper tube is sealably installed with the inlet tube, and the outlet end of the inlet tube is sealably installed with the outer wall of the reactor.

[0029] Preferably, a hollow tube is rotatably connected to the axis of the top plate, a third gear is fixedly provided on the top of the hollow tube, and connecting rods are fixedly provided on both sides of the hollow tube;

[0030] The reactor is provided with a stirring mechanism inside, the stirring mechanism comprising a turntable, a rotating frame is rotatably connected to the axis of the turntable, connecting plates are rotatably connected to both sides of the rotating frame, two limiting grooves are provided inside the turntable, sliding blocks are slidably connected to the inside of the two limiting grooves, a fixing rod is fixed at the axis of the bottom of the turntable, a bottom plate is fixed at the bottom of the fixing rod, two connecting grooves are provided inside the bottom plate, connecting blocks are slidably connected to the inside of the two connecting grooves, stirring plates are rotatably connected to the inside of the two connecting blocks, a rotating gear is fixed at the middle position of the top of the two stirring plates, and two racks are fixed on the lower surface of the turntable.

[0031] Preferably, the first gear and the third gear are meshed with each other, the bottom end of the rotating rod passes through the interior of the hollow tube and extends to the upper surface of the rotating frame and is connected to the keyway of the rotating frame, and the bottom ends of the two connecting rods are fixedly connected to the upper surface of the turntable.

[0032] Preferably, the two connecting plates are rotatably connected to the upper surfaces of the two sliding blocks, and the bottom of the bottom plate is rotatably connected to the inner bottom of the reactor.

[0033] Preferably, the axes of the two rotating gears are rotatably connected to the two sliding blocks, and the two rotating gears and the two racks are meshed with each other.

[0034] Compared with the related art, the synthesis method of 2-fluoroacrylic acid provided by the present invention has the following beneficial effects:

[0035] The oxidation method using 2-fluoropropionic acid as a raw material requires the addition of an oxidant, a catalyst and an organic solvent during the synthesis process. Some of the reagents are toxic or irritating. Therefore, in view of this situation, in the process of adding toxic or irritating reagents, it is necessary to add an inert gas to protect the reagents during the addition process to ensure that the reagents are safer when entering the reactor. In addition, some reagents enter the reactor from the outside through pipelines. In the process of adding the inert gas (specifically, nitrogen, etc., is preferably used), the inert gas and the reagents are mixed and entered in a linked and integrated manner. This can well ensure the stability of the reagents when passing through, reduce the density between the reagents, and make it less likely to form a reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0037] Figure 1The overall schematic diagram of the reaction kettle and the adding mechanism provided by the present invention;

[0038] Figure 2 for Figure 1 The schematic diagram of the cross-sectional structure of the reactor shown;

[0039] Figure 3 for Figure 1 The schematic diagram of the reactor, top plate and protective cover is shown;

[0040] Figure 4 for Figure 2 The schematic diagram of the driving mechanism structure shown;

[0041] Figure 5 for Figure 2 Schematic diagram of the initial working state of the stirring mechanism shown;

[0042] Figure 6 for Figure 5 The schematic diagram of the structure viewed from above is shown;

[0043] Figure 7 for Figure 5 The schematic diagram of the working state of the stirring mechanism when rotating and stirring is shown;

[0044] Figure 8 for Figure 5 Detailed connection structure diagram of the connecting frame and connecting plate shown;

[0045] Fig. 9 for Figure 6 Detailed structural diagram of the rack and rotating gear connection shown;

[0046] Fig.10 for Figure 1 Schematic diagram of the joining institution structure shown.

[0047] Description of Figure Numbers:

[0048] 1. Reactor, 2. Top plate, 3. Protective cover;

[0049] 4. driving mechanism, 41. positioning plate, 42. motor, 43. first gear, 44. rotating rod, 45. second gear, 46. hollow tube, 47. third gear, 48. connecting rod;

[0050] 5. stirring mechanism, 51. turntable, 52. rotating frame, 53. limiting groove, 54. sliding block, 55. connecting plate, 56. fixing rod, 57. bottom plate, 58. connecting groove, 59. connecting block, 510. stirring plate, 511. rotating gear, 512. rack;

[0051] 6. Joining mechanism, 61. Cam, 62. Connecting plate, 63. Mounting frame, 64. First extrusion barrel, 65. Second extrusion barrel, 66. Slide plate, 67. Piston rod, 68. First one-way valve, 69. Second one-way valve, 610. Third one-way valve, 611. First pipeline, 612. Second pipeline, 613. Upper pipe, 614. Inlet pipe;

[0052] 7. Sealing ring. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The invention provides a method for synthesizing 2-fluoroacrylic acid.

[0055] First embodiment:

[0056] A method for synthesizing 2-fluoroacrylic acid comprises the following steps:

[0057] Step S1: using 2-fluoropropionic acid as a raw material, specifically an oxidation method;

[0058] Reagents: 2-fluoropropionic acid, oxidant, catalyst, organic solvent;

[0059] Instruments: reaction vessel, reflux condenser, stirring device, thermometer, heating device;

[0060] Select 2-fluoropropionic acid as a raw material, select a suitable reaction container, and the reaction container can preferably be a chemical reactor;

[0061] Step S2: In a reaction container, dissolve 2-fluoropropionic acid in an organic solvent, wherein the organic solvent may be selected from one part of ethyl acetate or one part of toluene;

[0062] Add an oxidant, such as potassium permanganate, potassium dichromate, etc., and then drop an appropriate amount of sulfuric acid as a catalyst, and react under heating reflux conditions. During the reaction, the temperature and reaction progress must be closely monitored, and the reaction progress can be monitored by the TLC method;

[0063] Step S3: Stirring is required during the reaction to ensure that the reaction proceeds fully;

[0064] After the reaction is completed, cool to room temperature, pour the reaction solution into a separatory funnel, add a portion of water for extraction, separate the organic phase and the aqueous phase, the aqueous phase can be extracted again with an organic solvent, combine the organic phases, dry the organic phase with a desiccant such as anhydrous sodium sulfate, and filter to remove the desiccant.

[0065] Step S4: Purification: Purify the dried organic phase by distillation, rectification or the like, collect fractions in the corresponding boiling point range, and obtain a 2-fluoroacrylic acid product;

[0066] Purifying the separated 2-fluoroacrylic acid to remove impurities such as unreacted raw materials, by-products and solvents, and the purification method may include recrystallization, column chromatography, etc.;

[0067] Note:

[0068] The selection of oxidants and catalysts is crucial. Different oxidants and catalysts may affect the yield and selectivity of the reaction and need to be optimized according to specific circumstances.

[0069] The control of reaction temperature and time also has a great influence on the reaction results. Too high temperature or too long reaction time may lead to an increase in side reactions and reduce the purity and yield of the product.

[0070] The entire experimental operation process must be carried out in a well-ventilated environment, because some reagents are toxic or irritating, and attention must be paid to safety issues such as fire prevention and explosion prevention.

[0071] Step S5: During the operation of the above steps, some reagents are toxic or irritating. Therefore, in view of this situation, when adding the toxic or irritating reagents, it is necessary to add inert gas to protect the reagents.

[0072] This embodiment: The oxidation method using 2-fluoropropionic acid as a raw material requires the addition of an oxidant, a catalyst and an organic solvent during the synthesis process. Some reagents are toxic or irritating. Therefore, in view of this situation, in the process of adding toxic or irritating reagents, it is necessary to add an inert gas to protect the reagents during the process of adding the reagents to ensure that the reagents are safer when entering the reactor. In addition, some reagents enter the reactor from the outside through pipelines. In the process of adding the inert gas (specifically, nitrogen, etc. may be preferred), the inert gas and the reagents are mixed and introduced in a linked and integrated manner. This can well ensure the stability of the reagents when passing through, reduce the density between the reagents, and make it less easy to form a reaction.

[0073] Second embodiment:

[0074] See also Figure 1 , Figure 2 , Figure 4 and Fig.10, the step S5 of the synthesis method of 2-fluoroacrylic acid needs to be implemented in the reaction kettle 1 and the adding mechanism 6 when passing the inert gas;

[0075] A top plate 2 is installed on the top of the reactor 1 by bolts, a sealing ring 7 is provided between the upper surface of the reactor 1 and the lower surface of the top plate 2, a protective cover 3 is installed on the top of the top plate 2 by bolts, and a driving mechanism 4 is installed inside the protective cover 3;

[0076] The driving mechanism 4 includes a positioning plate 41 fixedly mounted on the upper surface of the top plate 2 and located inside the protective cover 3, a motor 42 is installed on one side of the top plate 2 and located on one side of the positioning plate 41 by bolts, a first gear 43 is connected to the keyway of the output shaft of the motor 42, a rotating rod 44 is rotatably connected inside the positioning plate 41, and a second gear 45 is fixedly mounted on the outer wall of the rotating rod 44;

[0077] See also Figure 2 and Figure 4 : The motor 42 starts to control the first gear 43 to rotate. When the first gear 43 rotates, it engages and controls the second gear 45 to drive the rotating rod 44 to rotate. When the rotating rod 44 rotates, it drives the cam 61 at the top to rotate.

[0078] The adding mechanism 6 comprises a mounting frame 63 fixedly arranged on the upper surface of the protective cover 3, a cam 61 is connected to the top keyway of the rotating rod 44, a connecting plate 62 is rotatably connected to the upper surface of the cam 61, a horizontally movable slide plate 66 is slidably connected to the outside of the mounting frame 63, a first extrusion tube 64 and a second extrusion tube 65 are fixedly arranged on the outside of the mounting frame 63 and on the left side of the slide plate 66, piston rods 67 are slidably connected to the inside of the first extrusion tube 64 and the second extrusion tube 65 respectively, a second one-way valve 69 and a first one-way valve 68 are respectively installed on the outer walls of the first extrusion tube 64 and the second extrusion tube 65, a third one-way valve 610 is installed on the outer walls of the first extrusion tube 64 and the second extrusion tube and on one side of the second one-way valve 69 and the first one-way valve 68, the inlet ends of the two third one-way valves 610 are both sealed with a first pipe 611 and a second pipe 612, the outlet end of the first one-way valve 68 is sealed with an upper pipe 613, and the outlet end of the second one-way valve 69 is sealed with an inlet pipe 614.

[0079] See also Fig.10 : During the rotation process, the cam 61 pulls the connecting plate 62 to control the entire slide plate 66 to drive the two piston rods 67 to reciprocate left and right along the horizontal direction of the mounting frame 63;

[0080] The reagent mainly enters the first extrusion tube 64 through the first pipe 611, and the inert gas mainly enters the second extrusion tube 65 through the second pipe 612. When the two piston rods 67 are pumping, the inert gas and the reagent will be simultaneously drawn into the first extrusion tube 64 and the second extrusion tube 65 through the third one-way valve 610. After that, the two piston rods 67 will change from pumping to pushing. During the pushing process, the inert gas and the reagent will enter the upper tube 613 and the inlet tube 614 from the first extrusion tube 64 and the second extrusion tube 65 through the first one-way valve 68 and the second one-way valve 69, so that the reagent mixed with the inert gas can enter the reactor 1.

[0081] The first gear 43 and the second gear 45 are meshed with each other, and the outer wall of the rotating rod 44 is rotatably connected to the axis of the protective cover 3 .

[0082] The left end of the connecting plate 62 is rotatably connected to the outer wall of the slide plate 66, the outer wall of the slide plate 66 is fixedly connected to two piston rods 67, the outlet end of the upper tube 613 is sealed to the inlet tube 614, and the outlet end of the inlet tube 614 is sealed to the outer wall of the reactor 1.

[0083] It can be understood that the two third one-way valves 610 move unidirectionally from the first pipe 611 and the second pipe 612 to the inside of the first extrusion tube 64 and the second extrusion tube 65, so that the medium can enter during the extraction process, but the medium cannot enter the first pipe 611 and the second pipe 612 during the pushing process. Since the first one-way valve 68 and the second one-way valve 69 move unidirectionally in the interior of the first extrusion tube 64 and the second extrusion tube 65 into the upward tube 613 and the inlet tube 614, extrusion can only be achieved by pushing.

[0084] Combination Figure 3 It can be seen that the inlet of the inlet pipe 614 is located in the middle of the reactor 1 .

[0085] Third embodiment:

[0086] See also Figure 4 and Fig. 9 A hollow tube 46 is rotatably connected to the axis of the top plate 2, a third gear 47 is fixed to the top of the hollow tube 46, and connecting rods 48 are fixed to both sides of the hollow tube 46;

[0087] A stirring mechanism 5 is installed inside the reactor 1, and the stirring mechanism 5 includes a turntable 51, a rotating frame 52 is rotatably connected to the axis of the turntable 51, and connecting plates 55 are rotatably connected to both sides of the rotating frame 52. Two limiting grooves 53 are provided inside the turntable 51, and sliders 54 are slidably connected inside the two limiting grooves 53. A fixing rod 56 is fixed at the bottom axis of the turntable 51, and a bottom plate 57 is fixed at the bottom of the fixing rod 56. Two connecting grooves 58 are provided inside the bottom plate 57, and connecting blocks 59 are slidably connected inside the two connecting grooves 58. A stirring plate 510 is rotatably connected inside the two connecting blocks 59. A rotating gear 511 is fixed at the middle position of the top of the two stirring plates 510, and two racks 512 are fixed on the lower surface of the turntable 51.

[0088] See also Figure 4 : During the rotation process, the first gear 43 will also mesh with and control the third gear 47 to drive the hollow tube 46 so that the connecting rods 48 on both sides rotate, and at the same time, the rotating rod 44 and the hollow tube 46 will rotate in conjunction;

[0089] See also Figure 5 and Figure 7 : When the rotating rod 44 rotates, it will drive the rotating frame 52 at the bottom to rotate on the rotating disk 51, and the rotating frame 52 will control the two connecting plates 55 to synchronously pull the slider 54 along the horizontal direction of the limiting groove 53 to perform left and right reciprocating motion;

[0090] See also Figure 6 and Fig.10 : When the two sliders 54 are sliding, the rotating gear 511 inside the slider 54 will mesh and rotate on the rack 512, and the stirring plate 510 will be controlled to rotate during the rotation. During the rotation of the stirring plate 510, the hollow tube 46 will also drive the entire turntable 51 to rotate.

[0091] The first gear 43 and the third gear 47 are meshed with each other, the bottom end of the rotating rod 44 passes through the interior of the hollow tube 46 and extends to the upper surface of the rotating frame 52 and is connected to the keyway of the rotating frame 52, and the bottom ends of the two connecting rods 48 are fixedly connected to the upper surface of the turntable 51.

[0092] The two connecting plates 55 are rotatably connected to the upper surfaces of the two sliding blocks 54 , and the bottom of the bottom plate 57 is rotatably connected to the inner bottom of the reactor 1 .

[0093] The two rotating gears 511 are rotatably connected to the two sliding blocks 54 at their axes, and the two rotating gears 511 and the two racks 512 are meshed with each other.

[0094] Understandable: Combination Figure 8It can be seen that since the hinge positions of the two connecting plates 55 and the rotating frame 52 are at the same distance from the axis of the rotating frame 52, when the rotating frame 52 rotates due to eccentricity, the movement trajectories of the two connecting plates 55 are the same. Secondly, there is no obstruction when the two connecting plates 55 and the rotating frame 52 rotate, so there will be no interference during rotation.

[0095] This embodiment: Compared with the traditional stirring design, in the first embodiment, repeated stirring is required during the synthesis process, so a driving setting is adopted to form a bidirectional rotation. The rotation of the rotating rod 44 is responsible for controlling the rotating frame 52 to change the slider 54 so that the positions of its two stirring plates 510 change synchronously. When the two stirring plates 510 are displaced, they will also form self-rotation. At the same time, during the self-rotation, the hollow tube 46 will drive the entire turntable 51 to rotate. Therefore, such a design can ensure that the stirring plate 510 contacts the synthetic reagent in the reactor 1 to the greatest extent, ensuring that the stirring synthesis is more sufficient and stable. Compared with the traditional stirring method, this case can also rotate during the movement of the stirring plate 510, and the whole can also rotate, thereby maximizing the rotating contact surface and avoiding the generation of large resistance.

[0096] Please refer to Figures 1 to 10 The working principle of the synthesis method of 2-fluoroacrylic acid provided by the present invention is as follows:

[0097] Step S1: The process flow of the first embodiment is all implemented in the reactor 1. When an unstable reagent is added, the motor 42 starts to control the first gear 43 to rotate. When the first gear 43 rotates, it engages and controls the second gear 45 to drive the rotating rod 44 to rotate. When the rotating rod 44 rotates, it drives the cam 61 at the top to rotate. During the rotation process, the cam 61 pulls the connecting plate 62 to control the entire slide 66 to drive the two piston rods 67 to reciprocate left and right along the horizontal direction of the mounting frame 63. The first pipe 611 mainly enters the reagent into the first extrusion cylinder 64, and the first extrusion cylinder 64 is driven by the first extruder 64. The second pipeline 612 mainly allows the inert gas to enter the second extrusion tube 65. When the two piston rods 67 are pumping, the inert gas and the reagent will be simultaneously extracted into the first extrusion tube 64 and the second extrusion tube 65 through the third one-way valve 610. After that, the two piston rods 67 will change from pumping to pushing. During the pushing process, the inert gas and the reagent will enter the upper tube 613 and the inlet tube 614 from the first extrusion tube 64 and the second extrusion tube 65 through the first one-way valve 68 and the second one-way valve 69, so that the reagent mixed with the inert gas can enter the reactor 1.

[0098] Step S2: During operation of the first embodiment, the synthesis process requires repeated rotation and stirring. In order to ensure that the stirring achieves the maximum effect, the first gear 43 will also engage and control the third gear 47 to drive the hollow tube 46 during the rotation process to rotate the connecting rods 48 on both sides. At the same time, the rotating rod 44 and the hollow tube 46 will rotate in conjunction. When the rotating rod 44 rotates, it will drive the rotating frame 52 at the bottom to rotate on the turntable 51. The rotating frame 52 will control the two connecting plates 55 to synchronously pull the slider 54 to perform left and right reciprocating motion along the horizontal direction of the limit groove 53. When the two sliders 54 are in the process of sliding motion, the rotating gear 511 inside the slider 54 will engage and rotate on the rack 512, and the stirring plate 510 will be controlled to rotate during the rotation process. During the rotation of the stirring plate 510, the hollow tube 46 will also drive the entire turntable 51 to rotate. At the same time, the hollow tube 46 will also drive the entire turntable 51 to rotate.

[0099] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for synthesizing 2-fluoroacrylic acid, characterized in that: The steps include: Step S1: using 2-fluoropropionic acid as a raw material, specifically an oxidation method; Reagents: 2-fluoropropionic acid, oxidant, catalyst, organic solvent; Instruments: reaction vessel, reflux condenser, stirring device, thermometer, heating device; Select 2-fluoropropionic acid as a raw material, select a suitable reaction container, and the reaction container can preferably be a chemical reactor; Step S2: In a reaction container, dissolve 2-fluoropropionic acid in an organic solvent, wherein the organic solvent may be selected from one part of ethyl acetate or one part of toluene; Add an oxidant, such as potassium permanganate, potassium dichromate, etc., and then drop an appropriate amount of sulfuric acid as a catalyst, and react under heating reflux conditions. During the reaction, the temperature and reaction progress must be closely monitored, and the reaction progress can be monitored by the TLC method; Step S3: Stirring is required during the reaction to ensure that the reaction proceeds fully; After the reaction is completed, cool to room temperature, pour the reaction solution into a separatory funnel, add a portion of water for extraction, separate the organic phase and the aqueous phase, the aqueous phase can be extracted again with an organic solvent, combine the organic phases, dry the organic phase with a desiccant such as anhydrous sodium sulfate, and filter to remove the desiccant. Step S4: Purification: Purify the dried organic phase by distillation, rectification or the like, collect fractions in the corresponding boiling point range, and obtain a 2-fluoroacrylic acid product; Purifying the separated 2-fluoroacrylic acid to remove impurities such as unreacted raw materials, by-products and solvents, and the purification method may include recrystallization, column chromatography, etc.; Note: The selection of oxidants and catalysts is crucial. Different oxidants and catalysts may affect the yield and selectivity of the reaction and need to be optimized according to specific circumstances. The control of reaction temperature and time also has a great influence on the reaction results. Too high temperature or too long reaction time may lead to an increase in side reactions and reduce the purity and yield of the product. The entire experimental operation process must be carried out in a well-ventilated environment, because some reagents are toxic or irritating, and attention must be paid to safety issues such as fire prevention and explosion prevention. Step S5: During the operation of the above steps, some reagents are toxic or irritating. Therefore, in view of this situation, when adding the toxic or irritating reagents, it is necessary to add inert gas to protect the reagents.

2. The method for synthesizing 2-fluoroacrylic acid according to claim 1, characterized in that: The step S5 of the synthesis method of 2-fluoroacrylic acid needs to be implemented in a reaction kettle and a adding mechanism when passing an inert gas; A top plate is installed on the top of the reactor by bolts, a sealing ring is provided between the upper surface of the reactor and the lower surface of the top plate, a protective cover is installed on the top of the top plate by bolts, and a driving mechanism is installed inside the protective cover; The driving mechanism comprises a positioning plate fixedly mounted on the upper surface of the top plate and located inside the protective cover, a motor is installed on one side of the top plate and located on one side of the positioning plate by bolts, a first gear is connected to the keyway of the output shaft of the motor, a rotating rod is rotatably connected inside the positioning plate, and a second gear is fixed to the outer wall of the rotating rod; The adding mechanism includes a mounting bracket fixedly arranged on the upper surface of the protective cover, a cam is connected to the top keyway of the rotating rod, a connecting plate is rotatably connected to the upper surface of the cam, a horizontally movable slide is slidably connected to the outside of the mounting bracket, a first extrusion barrel and a second extrusion barrel are fixedly arranged on the outside of the mounting bracket and on the left side of the slide, piston rods are slidably connected to the insides of the first extrusion barrel and the second extrusion barrel respectively, a second one-way valve and a first one-way valve are respectively installed on the outer walls of the first extrusion barrel and the second extrusion barrel, a third one-way valve is installed on the outer walls of the first extrusion barrel and the second extrusion barrel and on one side of the second one-way valve and the first one-way valve, the inlet ends of the two third one-way valves are both sealed with the first pipeline and the second pipeline, the outlet end of the first one-way valve is sealed with the upper pipe, and the outlet end of the second one-way valve is sealed with the inlet pipe.

3. The method for synthesizing 2-fluoroacrylic acid according to claim 2, characterized in that: The first gear and the second gear are meshed with each other, and the outer wall of the rotating rod is rotationally connected to the axis of the protective cover.

4. The method for synthesizing 2-fluoroacrylic acid according to claim 2, characterized in that: The left end of the connecting plate is rotatably connected to the outer wall of the slide plate, the outer wall of the slide plate is fixedly connected to two piston rods, the outlet end of the upper tube is sealed to the inlet tube, and the outlet end of the inlet tube is sealed to the outer wall of the reactor.

5. The method for synthesizing 2-fluoroacrylic acid according to claim 2, characterized in that: A hollow tube is rotatably connected to the axis of the top plate, a third gear is fixedly arranged on the top of the hollow tube, and connecting rods are fixedly arranged on both sides of the hollow tube; The reactor is provided with a stirring mechanism inside, the stirring mechanism comprising a turntable, a rotating frame is rotatably connected to the axis of the turntable, connecting plates are rotatably connected to both sides of the rotating frame, two limiting grooves are provided inside the turntable, sliding blocks are slidably connected to the inside of the two limiting grooves, a fixing rod is fixed at the axis of the bottom of the turntable, a bottom plate is fixed at the bottom of the fixing rod, two connecting grooves are provided inside the bottom plate, connecting blocks are slidably connected to the inside of the two connecting grooves, stirring plates are rotatably connected to the inside of the two connecting blocks, a rotating gear is fixed at the middle position of the top of the two stirring plates, and two racks are fixed on the lower surface of the turntable.

6. The method for synthesizing 2-fluoroacrylic acid according to claim 4, characterized in that: The first gear and the third gear are meshed with each other, the bottom end of the rotating rod passes through the interior of the hollow tube and extends to the upper surface of the rotating frame and is connected to the keyway of the rotating frame, and the bottom ends of the two connecting rods are fixedly connected to the upper surface of the turntable.

7. The method for synthesizing 2-fluoroacrylic acid according to claim 1, characterized in that: The two connecting plates are rotatably connected to the upper surfaces of the two sliding blocks, and the bottom of the bottom plate is rotatably connected to the inner bottom of the reaction kettle.

8. The method for synthesizing 2-fluoroacrylic acid according to claim 7, characterized in that: The two rotating gears are rotatably connected to the two sliding blocks at their axles, and the two rotating gears and the two racks are meshed with each other.

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