An apparatus for synthesizing chloromethyl isopropyl carbonate and its method of use

Abstract

This invention relates to the field of chloromethyl isopropyl carbonate synthesis technology, specifically to a synthesis apparatus and method for chloromethyl isopropyl carbonate. The apparatus includes a reactor, with a metering cylinder fixed to its upper end and connected thereto. A hopper is fitted around the outside of the metering cylinder, and a sliding ring is slidably sealed to the metering cylinder. A drive mechanism is provided at the upper end of the reactor to drive the hopper to move vertically. The drive mechanism and the hopper are rotatably connected via a rotating shaft. A gap is provided between the sliding ring and the hopper to allow the hopper to rotate. The sliding ring and the hopper are connected by an elastic diaphragm. This invention, through the reciprocating motion of the hopper, enables the multiple, metered addition of paraformaldehyde from the hopper into the reactor, preventing the paraformaldehyde from clumping within the reactor, reducing stirring time and energy consumption, and ensuring the quality of the produced chloromethyl isopropyl carbonate.

Description

Technical Field

[0001] This invention relates to the field of chloromethyl isopropyl carbonate synthesis technology, specifically to a synthesis apparatus for chloromethyl isopropyl carbonate and its usage method. Background Technology

[0002] The synthesis method of chloromethyl isopropyl carbonate is as follows: isopropyl chloroformate and paraformaldehyde are reacted in a mass ratio of 1.02:1 with an alkylimidazolium ionic liquid catalyst at a temperature of 10℃–40℃. The resulting reactants are then subjected to solvent removal and vacuum distillation to obtain high-purity chloromethyl isopropyl carbonate. In the synthesis process, isopropyl chloroformate and the alkylimidazolium ionic liquid catalyst are first mixed to form a preliminary mixture. Then, paraformaldehyde powder is added to the preliminary mixture. Because the paraformaldehyde is in powder form, adding it directly to the preliminary mixture all at once requires prolonged stirring to disperse the powder. This synthesis method is inefficient, involves long stirring times, and increases energy consumption. Furthermore, the powdered paraformaldehyde tends to clump together, making it difficult to mix effectively with the preliminary mixture and potentially affecting the quality of the chloromethyl isopropyl carbonate. Summary of the Invention

[0003] The technical problem to be solved by the present invention is a synthesis apparatus and method thereof for chloromethyl isopropyl carbonate that can intermittently and quantitatively add powdered paraformaldehyde to a preliminary mixture, reduce stirring time and energy consumption, prevent paraformaldehyde from clumping in the preliminary mixture, and ensure the quality of chloromethyl isopropyl carbonate.

[0004] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0005] A synthesis apparatus for chloromethyl isopropyl carbonate includes a reactor, a metering cylinder fixed to the upper end of the reactor and communicating with it, a hopper sleeved on the outside of the metering cylinder, a sliding ring slidably sealed to the metering cylinder, a drive mechanism for driving the hopper to move vertically at the upper end of the reactor, the drive mechanism and the hopper being rotatably connected via a rotating shaft, a gap allowing the hopper to rotate between the sliding ring and the hopper, the sliding ring and the hopper being connected by an elastic diaphragm that seals the gap, a second magnet fixed to the lower end of the hopper, the second magnet and the rotating shaft forming a 90-degree angle in the circumferential direction of the reactor, a plurality of first magnets evenly fixed in the vertical direction facing the second magnet on the metering cylinder, the magnetic poles of adjacent first magnets facing the second magnet being opposite, the magnetic poles of the lowermost first magnet and the opposite ends of the second magnet being the same, a circular hole opening at the lower end of the metering cylinder, a turntable elastically rotatably sealed to the lower end of the metering cylinder, an arc-shaped hole opening on the turntable, the arc-shaped hole allowing communication with the circular hole after the turntable rotates, and a drive assembly for driving the turntable to rotate on the metering cylinder.

[0006] Specifically, the driving mechanism includes a telescopic cylinder fixed to the upper end of the reactor. The telescopic cylinder is vertically arranged, and a connecting block is fixed on the telescopic rod of the telescopic cylinder. The rotating shaft is rotatably connected to the connecting block and the rotating shaft is rotatably connected to the hopper.

[0007] Specifically, a rotating rod concentric with the upper end of the turntable is fixed, the rotating rod is rotatably connected to the lower end of the metering cylinder, and a torsion spring is sleeved on the rotating rod, which is rotatably connected to the metering cylinder and the turntable.

[0008] Specifically, the driving assembly includes an arc-shaped groove at the lower end of the metering cylinder, which is concentric with the turntable. An arc-shaped slider is slidably engaged within the arc-shaped groove. An arc-shaped first liquid groove is machined at the lower end of the metering cylinder, which is connected to and concentric with the arc-shaped groove. An arc-shaped rod is slidably and sealed within the first liquid groove, and the arc-shaped rod is fixedly connected to the arc-shaped slider. A second liquid groove is provided on the side of the metering cylinder facing away from the first magnet, corresponding to the lowermost first magnet. The length direction of the second liquid groove is parallel to the radial direction of the metering cylinder. A sliding block is slidably and sealed within the second liquid groove, with the sliding block partially protruding to the outside of the metering cylinder. The second liquid groove and the first liquid groove are connected through a channel to form a driving channel. The driving channel between the sliding block and the arc-shaped rod is filled with extrusion liquid.

[0009] Specifically, the first magnet is embedded and fixed on the metering cylinder, with the outer side of the first magnet flush with the outer edge of the metering cylinder.

[0010] Specifically, the upper surface of the bottom plate of the metering cylinder is inclined, and the circular hole is opened at the lowest point of the inclined surface.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] 1. This invention enables the repeated and quantitative addition of paraformaldehyde from the hopper to the reactor through the reciprocating motion of the hopper, which can prevent the paraformaldehyde from clumping in the reactor, reduce the stirring time, reduce the energy consumption required for stirring, and ensure the quality of the produced chloromethyl isopropyl carbonate.

[0013] 2. After the paraformaldehyde in the metering cylinder is added into the reactor, the upward movement of the hopper causes the metering cylinder to vibrate. This causes the paraformaldehyde adhering to the inner wall of the metering cylinder to fall off and be discharged into the reactor through the connecting part of the round hole and the arc hole before the round hole and the arc hole completely intersect, thus ensuring the accuracy of the metered addition of paraformaldehyde.

[0014] 3. During the upward and downward movement of the hopper, the hopper can vibrate, which can cause the paraformaldehyde adhering to the inner wall of the hopper to fall off and cause the paraformaldehyde in the hopper to gather towards the center of the hopper, ensuring that the paraformaldehyde can effectively enter the metering cylinder and that there is enough paraformaldehyde to enter the metering cylinder.

[0015] 4. After the paraformaldehyde in the hopper enters the metering cylinder, the hopper vibrates as it descends. The paraformaldehyde that comes out from the top of the metering cylinder falls into the collection hopper, ensuring that the amount of paraformaldehyde added to the reactor each time is the same. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the present invention.

[0017] Figure 2 This is a cross-sectional view of the hopper and metering cylinder in operation.

[0018] Figure 3 This is a cross-sectional view of the sliding ring and the metering cylinder in operation.

[0019] Figure 4 This is a cross-sectional view of the turntable and the metering cylinder in operation.

[0020] Figure 5 This is a cross-sectional view of the first liquid tank in conjunction with the arc-shaped rod.

[0021] Figure 6 This is a schematic diagram showing the connection between the circular hole and the arc-shaped hole.

[0022] The names of the parts in the attached diagram are:

[0023] 1. Reactor; 2. Hopper; 3. Connecting block; 4. Telescopic cylinder; 5. Metering cylinder; 6. First magnet; 7. Second magnet; 8. Elastic diaphragm; 9. Sliding ring; 10. Circular hole; 11. Turntable; 12. Rotating rod; 13. Arc-shaped hole; 14. Arc-shaped groove; 15. First liquid tank; 16. Arc-shaped slider; 17. Arc-shaped rod; 18. Second liquid tank; 19. Sliding block. Detailed Implementation

[0024] like Figure 1 , Figure 2 and Figure 3 As shown, a synthesis apparatus for chloromethyl isopropyl carbonate includes a reactor 1, with a metering cylinder 5 fixed to and communicating with the upper end of the reactor 1. A hopper 2 is fitted around the outside of the metering cylinder 5. A sliding ring 9 is slidably sealed to the metering cylinder 5. A drive mechanism for driving the hopper 2 to move vertically is provided at the upper end of the reactor 1, and the drive mechanism is rotatably connected to the hopper 2 via a rotating shaft. The drive mechanism includes two telescopic cylinders 4 fixed to the upper end of the reactor 1, located on the front and rear sides of the hopper 2 respectively. The telescopic cylinders 4 are vertically arranged, and a connecting block 3 is fixed to the telescopic rod of the telescopic cylinder 4. A longitudinal rotating shaft is rotatably connected to the connecting block 3, and the rotating shaft is rotatably connected to the hopper 2.

[0025] like Figure 1 As shown, a gap is provided between the sliding ring 9 and the hopper 2 to allow the hopper 2 to rotate. The sliding ring 9 and the hopper 2 are connected by an elastic diaphragm 8, which seals the gap. A second magnet 7 is fixed to the lower left side of the hopper 2, and the angle between the second magnet 7 and the rotating shaft in the circumferential direction of the reactor 1 is 90 degrees. Multiple first magnets 6 are evenly distributed and fixed in the vertical direction on the left side of the metering cylinder 5. The first magnets 6 are embedded and fixed on the metering cylinder 5, and the outer side of the first magnet 6 is flush with the outer edge of the metering cylinder 5. The magnetic poles of two adjacent first magnets 6 facing the second magnet 7 are opposite, and the magnetic poles of the opposite ends of the bottom first magnet 6 and the second magnet 7 are the same. For example, if the magnetic pole of the bottom first magnet 6 facing the second magnet 7 is N, then the magnetic pole of the second magnet 7 facing the first magnet 6 is also N. From bottom to top, the magnetic poles of the first magnets 6 facing the second magnet 7 are N, S, N, S, N, S...

[0026] A circular hole 10 is provided at the lower end of the metering cylinder 5. The upper surface of the bottom plate of the metering cylinder 5 is inclined, and the circular hole 10 is located at the lowest point of the inclined surface. A turntable 11 is elastically rotatably and sealingly connected to the lower end of the metering cylinder 5. An arc-shaped hole 13 is provided on the turntable 11. The arc-shaped hole 13 is allowed to communicate with the circular hole 10 after the turntable 11 rotates. A drive assembly for driving the turntable 11 to rotate is provided on the metering cylinder 5.

[0027] like Figure 4 , Figure 5 and Figure 6As shown, a rotating rod 12, concentric with the upper end of the turntable 11, is fixed to the upper end of the turntable 11. The rotating rod 12 is rotatably connected to the lower end of the metering cylinder 5. A torsion spring is sleeved on the rotating rod 12, and the metering cylinder 5 and the turntable 11 are connected by the torsion spring. One end of the torsion spring is fixedly connected to the metering cylinder 5, and the other end of the torsion spring is fixedly connected to the turntable 11.

[0028] The drive assembly includes an arc-shaped groove 14 formed at the lower end of the metering cylinder 5, concentric with the turntable 11. An arc-shaped slider 16 is slidably engaged within the arc-shaped groove 14. An arc-shaped first liquid groove 15 is machined at the lower end of the metering cylinder 5, communicating with and concentrically connected to the arc-shaped groove 14. An arc-shaped rod 17 is slidably and sealed within the first liquid groove 15, and is fixedly connected to the arc-shaped slider 16. A second liquid groove 18 is formed on the right side of the metering cylinder 5, corresponding to the lowermost first magnet 6, with the length direction of the second liquid groove 18 parallel to the radial direction of the metering cylinder 5. A sliding block 19 is slidably and sealed within the second liquid groove 18, with a portion of the sliding block 19 protruding to the outside of the metering cylinder 5. The second liquid groove 18 and the first liquid groove 15 are connected by a channel to form a drive channel, which is filled with extrusion fluid between the sliding block 19 and the arc-shaped rod 17.

[0029] In the production of chloromethyl isopropyl carbonate, isopropyl chloroformate and alkyl imidazole ionic liquid are added to reactor 1, and a certain amount of paraformaldehyde is added to hopper 2.

[0030] The telescopic cylinder 4 is activated, causing the hopper 2 to move upwards. As the hopper 2 moves upwards, the elastic diaphragm 8 and the sliding ring 9 also move upwards. During this upward movement, the hopper 2 oscillates left and right around its axis due to the attraction and repulsion of the second magnet 7 by multiple first magnets 6. During this upward and oscillating motion, the lower end of the hopper 2 intermittently strikes the metering cylinder 5, causing intermittent vibrations. The paraformaldehyde inside the hopper 2 accumulates towards its center, and the paraformaldehyde adhering to the inner wall of the hopper 2 detaches. When the upper end of the metering cylinder 5 is aligned with the upper end of the sliding ring 9, the telescopic cylinder 4 reaches its maximum upward position, and the paraformaldehyde inside the hopper 2 enters the metering cylinder 5. During the upward and downward movement of the hopper 2, the hopper 2 can vibrate, which can cause the paraformaldehyde adhering to the inner wall of the hopper 2 to fall off and cause the paraformaldehyde in the hopper 2 to gather towards the center of the hopper 2, ensuring that the paraformaldehyde can effectively enter the metering cylinder 5 and that there is enough paraformaldehyde to enter the metering cylinder 5.

[0031] Then, the telescopic cylinder 4 is activated, causing the hopper 2 to descend. As the hopper 2 descends, the elastic diaphragm 8 and the sliding ring 9 also descend. During this descent, the hopper 2 swings left and right around its axis due to the attraction and repulsion of the second magnet 7 by multiple first magnets 6. During the upward movement and swinging motion of the hopper 2, the lower end of the hopper 2 intermittently taps the metering cylinder 5. When the volume of paraformaldehyde in the hopper 2 exceeds the volume of the metering cylinder 5, and the upper end of the metering cylinder 5 exceeds the upper surface of the paraformaldehyde in the hopper 2, excess paraformaldehyde will escape from the upper end of the metering cylinder 5. The hopper 2 and the metering cylinder 5 will vibrate intermittently, and the paraformaldehyde escaping from the upper end of the metering cylinder 5 will fall back into the hopper 2.

[0032] After the paraformaldehyde in the hopper 2 enters the metering cylinder 5, the hopper 2 causes the metering cylinder 5 to vibrate as it descends. The paraformaldehyde that overflows from the top of the metering cylinder 5 falls back into the hopper 2, gradually leveling the top surface of the metering cylinder 5. This ensures that the amount of paraformaldehyde added to the reactor 1 by the metering cylinder 5 is always the same.

[0033] When the second magnet 7 aligns with the bottommost first magnet 6, the hopper 2 swings left and right under the repulsive force between them. The lower end of the hopper 2 can also press the sliding block 19 into the second liquid tank 18. During this movement, the sliding block 19 drives the arc-shaped rod 17, the arc-shaped slider 16, and the turntable 11 to rotate via the pressing liquid. The torsion spring stores energy after the turntable 11 rotates. When the arc-shaped hole 13 connects with the round hole 10, the paraformaldehyde in the metering cylinder 5 can enter the reactor 1 through the round hole 10 and the arc-shaped hole 13.

[0034] After the paraformaldehyde in the metering cylinder 5 is added into the reactor 1, the telescopic cylinder 4 is activated, causing the hopper 2 to move upward. Once the hopper 2 moves upward, the lower end of the hopper 2 loses its squeezing effect on the sliding block 19. Under the elastic force of the torsion spring and the friction between the turntable 11 and the metering cylinder 5, the turntable 11 slowly rotates back to its original position. During this slow rotation, the turntable 11 drives the sliding block 19 to return to its original position via the arc-shaped slider 16, the arc-shaped rod 17, and the squeezing liquid. As the hopper 2 moves upward, under the attraction and repulsion of the second magnet 7 by multiple first magnets 6, the hopper 2 swings left and right around its axis. As the hopper 2 moves upward and swings left and right, its lower end intermittently taps the metering cylinder 5, causing it to vibrate intermittently. During this vibration, the paraformaldehyde adhering to the inner wall of the metering cylinder 5 detaches and is discharged into the reactor 1 through the connecting part of the round hole 10 and the arc-shaped hole 13 before they completely intersect. After the paraformaldehyde in the metering cylinder 5 is added into the reactor 1, the upward movement of the hopper 2 causes the metering cylinder 5 to vibrate, allowing the paraformaldehyde adhering to its inner wall to detach and be discharged into the reactor 1 through the connecting part of the round hole 10 and the arc-shaped hole 13 before they completely intersect, thus ensuring the accuracy of the metered addition of paraformaldehyde.

[0035] The reciprocating motion of the hopper 2 allows for the quantitative and intermittent addition of paraformaldehyde.

[0036] The present invention enables the multiple and quantitative addition of paraformaldehyde in the hopper 2 to the reactor 1 through the reciprocating up and down motion of the hopper 2, which can prevent the paraformaldehyde from clumping in the reactor 1, reduce the stirring time, reduce the energy consumption required for stirring, and ensure the quality of the produced chloromethyl isopropyl carbonate.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An apparatus for synthesizing chloromethyl isopropyl carbonate, comprising a reactor (1), characterized in that, A metering cylinder (5) is fixed to the upper end of the reactor (1) and communicates with it. A hopper (2) is sleeved on the outside of the metering cylinder (5). A sliding ring (9) is slidably sealed on the metering cylinder (5). A driving mechanism for driving the hopper (2) to move vertically is provided at the upper end of the reactor (1). The driving mechanism is rotatably connected to the hopper (2) through a rotating shaft. A gap is provided between the sliding ring (9) and the hopper (2) to allow the hopper (2) to rotate. The sliding ring (9) and the hopper (2) are connected by an elastic diaphragm (8). The elastic diaphragm (8) seals the gap. A second magnet (7) is fixed to the lower end of the hopper (2). The second magnet (7) and the rotating shaft are connected in the reactor (1) The included angle in the circumferential direction is 90 degrees. Multiple first magnets (6) are evenly distributed and fixed in the vertical direction on the side of the metering cylinder (5) facing the second magnet (7). The magnetic poles of two adjacent first magnets (6) facing the second magnet (7) are opposite. The magnetic poles of the bottom first magnet (6) and the opposite end of the second magnet (7) are the same. A round hole (10) is opened at the lower end of the metering cylinder (5). A turntable (11) is elastically rotatably sealed at the lower end of the metering cylinder (5). An arc-shaped hole (13) is opened on the turntable (11). The arc-shaped hole (13) is allowed to communicate with the round hole (10) after the turntable (11) rotates. A drive component for driving the turntable (11) to rotate is provided on the metering cylinder (5).

2. The apparatus for synthesizing chloromethyl isopropyl carbonate according to claim 1, characterized in that, The driving mechanism includes a telescopic cylinder (4) fixed to the upper end of the reactor (1). The telescopic cylinder (4) is set vertically. A connecting block (3) is fixed on the telescopic rod of the telescopic cylinder (4). The rotating shaft is rotatably connected to the connecting block (3) and rotatably connected to the hopper (2).

3. The apparatus for synthesizing chloromethyl isopropyl carbonate according to claim 1, characterized in that, The upper end of the turntable (11) is fixed with a rotating rod (12) concentric with it. The rotating rod (12) is rotatably connected to the lower end of the metering cylinder (5). A torsion spring is sleeved on the rotating rod (12). The metering cylinder (5) and the turntable (11) are connected by the torsion spring.

4. The apparatus for synthesizing chloromethyl isopropyl carbonate according to claim 1, characterized in that, The driving assembly includes an arc-shaped groove (14) at the lower end of the metering cylinder (5), the arc-shaped groove (14) being concentric with the turntable (11), an arc-shaped slider (16) being slidably engaged within the arc-shaped groove (14), an arc-shaped first liquid groove (15) being machined at the lower end of the metering cylinder (5), the first liquid groove (15) being connected to and concentric with the arc-shaped groove (14), an arc-shaped rod (17) being slidably and sealed within the first liquid groove (15), the arc-shaped rod (17) being fixedly connected to the arc-shaped slider (16), and the metering cylinder (5) facing away from the first magnet (6). A second liquid tank (18) is provided on one side of the metering cylinder (5). The second liquid tank (18) corresponds to the first magnet (6) at the bottom. The length direction of the second liquid tank (18) is parallel to the radial direction of the metering cylinder (5). A sliding block (19) is slidably sealed inside the second liquid tank (18). Part of the sliding block (19) protrudes to the outside of the metering cylinder (5). The second liquid tank (18) and the first liquid tank (15) are connected through a channel to form a driving channel. The driving channel between the sliding block (19) and the arc rod (17) is filled with extrusion liquid.

5. The apparatus for synthesizing chloromethyl isopropyl carbonate according to claim 1, characterized in that, The first magnet (6) is embedded and fixed on the metering cylinder (5), and the outer side of the first magnet (6) is flush with the outer edge of the metering cylinder (5).

6. The apparatus for synthesizing chloromethyl isopropyl carbonate according to claim 1, characterized in that, The bottom plate of the metering cylinder (5) has an inclined surface at the top, and the circular hole (10) is located at the lowest point of the inclined surface.

7. A method of using the apparatus for synthesizing chloromethyl isopropyl carbonate according to any one of claims 1-6, characterized in that, Isopropyl chloroformate and alkylimidazolium ionic liquid are added to reactor (1), and a measured amount of paraformaldehyde is added to hopper (2). The telescopic cylinder (4) is activated, causing the telescopic cylinder (4) to drive hopper (2) upward. When hopper (2) moves upward, elastic diaphragm (8) and sliding ring (9) move upward as well. During the upward movement of hopper (2), under the attraction and repulsion of multiple first magnets (6) on second magnets (7), hopper (2) will swing around the axis. During the upward movement and swinging of hopper (2), the lower end of hopper (2) will contact the metering cylinder (5). Intermittent tapping causes intermittent vibrations in the hopper (2) and metering cylinder (5). The paraformaldehyde in the hopper (2) accumulates towards the center, and the paraformaldehyde adhering to the inner wall of the hopper (2) falls off. When the upper end of the metering cylinder (5) is aligned with the upper end of the sliding ring (9), the telescopic rod of the telescopic cylinder (4) reaches its maximum upward position, and the paraformaldehyde in the hopper (2) enters the metering cylinder (5). Then, the telescopic cylinder (4) is activated, causing it to drive the hopper (2) downwards. As the hopper (2) descends, the elastic diaphragm (8) and... As the sliding ring (9) moves downward, the hopper (2) swings around the axis under the attraction and repulsion of the second magnet (7) by the multiple first magnets (6). During the upward movement and swinging of the hopper (2), the lower end of the hopper (2) intermittently strikes the metering cylinder (5), causing intermittent vibrations between the hopper (2) and the metering cylinder (5). The paraformaldehyde emanating from the upper end of the metering cylinder (5) falls into the collection hopper. When the second magnet (7) corresponds to the bottom first magnet (6), the second magnet (7) and the bottom first magnet... Under the repulsive force of iron (6), the hopper (2) swings, and the lower end of the hopper (2) can squeeze the sliding block (19) to move into the second liquid tank (18). During the process of the sliding block (19) moving into the second liquid tank (18), the sliding block (19) drives the arc rod (17), the arc slider (16) and the turntable (11) to rotate through the squeezing liquid. After the turntable (11) rotates, the torsion spring stores the force. When the arc hole (13) is connected to the round hole (10), the paraformaldehyde in the metering cylinder (5) can enter the reactor (1) through the round hole (10) and the arc hole (13).After the paraformaldehyde in the metering cylinder (5) is added into the reactor (1), the telescopic cylinder (4) is activated, causing the telescopic cylinder (4) to drive the hopper (2) upward. After the hopper (2) moves upward, the lower end of the hopper (2) loses its squeezing effect on the sliding block (19). Under the elastic force of the torsion spring, the turntable (11) slowly rotates back to its original position. During the slow rotation of the turntable (11), the turntable (11) drives the sliding block (19) to move back to its original position through the arc-shaped slider (16), the arc-shaped rod (17), and the squeezing liquid. During the upward movement of the hopper (2), multiple first magnets (6) interact with the second magnets (7). Under the influence of adsorption and repulsion, the hopper (2) swings around the axis. During the upward movement and swinging of the hopper (2), the lower end of the hopper (2) intermittently taps the metering cylinder (5), causing the metering cylinder (5) to vibrate intermittently. During the intermittent vibration of the metering cylinder (5), the paraformaldehyde adhering to the inner wall of the metering cylinder (5) will fall off and be discharged into the reactor (1) through the connecting part of the round hole (10) and the arc hole (13) before the round hole (10) and the arc hole (13) completely intersect. The intermittent quantitative addition of paraformaldehyde can be achieved during the up-and-down reciprocating motion of the hopper (2).

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