Air polymerization inhibition system for acrylic acid esterification reaction

Abstract

The utility model belongs to the technical field of acrylic acid esterification reaction systems, and particularly relates to an air polymerization inhibition system for acrylic acid esterification reaction. The air polymerization inhibition system for the acrylic acid esterification reaction comprises a reaction kettle, an air inlet in the upper portion of the reaction kettle is connected with an air pipeline, the reaction kettle is provided with a pipeline connected with a dehydrating tower, the dehydrating tower is provided with a return pipeline connected with the reaction kettle, and the top of the dehydrating tower is connected with a reaction return tank through a first-stage condenser. The first-stage condenser is connected with the second-stage condenser; an air inward extending pipe is arranged at the air inlet of the reaction kettle, a double-layer distributor is arranged on the air inward extending pipe, and a stirrer is arranged in the reaction kettle. According to the air polymerization inhibition system for the acrylic acid esterification reaction, the double-layer distributor, the double-layer stirring paddle and the guide plate are arranged and matched with the optimized return pipeline, so that uniform dispersion and microbubbling of air are realized, the contact area and the contact efficiency of the air and materials are improved, the polymerization inhibition effect is enhanced, and the dosage of a chemical polymerization inhibitor is reduced.

Description

Technical Field

[0001] This utility model belongs to the technical field of acrylic acid esterification reaction system, specifically relating to an air polymerization inhibition system for acrylic acid esterification reaction. Background Technology

[0002] In the field of direct esterification, ester products formed by the reaction of unsaturated acid raw materials such as acrylic acid and methacrylic acid with alcohols, due to their unsaturated double bond structure, possess excellent light resistance, water resistance, and oil resistance, and are widely used in downstream industries such as coatings, resins, and automotive paints. However, during this type of reaction, raw materials and products are prone to self-polymerization or copolymerization, leading to decreased product quality, equipment blockage, and consequently, lower reaction conversion rates, thus affecting production efficiency.

[0003] To suppress polymerization, existing technologies generally employ the addition of chemical polymerization inhibitors (such as p-hydroxyanisole, hydroquinone, copper acetate, etc.). However, relying solely on chemical polymerization inhibitors cannot completely eliminate the risk of polymerization, and the polymerization inhibition effect remains insufficient.

[0004] CN218924658U discloses a system for improving the polymerization of materials in a butyl acrylate esterification reactor. This system employs a combination of a diester and a dehydration tower. It introduces inhibitory air through four channels into the reboiler and the bottom of chambers a and b of the two esterification reactors. Simultaneously, it adds inhibitory agent through two pipelines to chamber a of the first esterification reactor and the top reflux pipeline of the dehydration tower. Combined with a negative pressure environment to lower the reaction temperature, and an overflow pipeline for continuous material transport between the two reactors, along with multiple sets of spray pipelines to enhance material mixing, it effectively reduces pipeline blockage, lowers the self-polymerization of raw materials, and significantly improves the conversion rate of acrylic acid. However, this system directly introduces air through four pipelines. Although multiple spray pipelines are provided, the contact area between air and material is limited. Furthermore, the use of a diester with two chambers increases the complexity of the reaction device and easily creates dead zones in material circulation. Even with inhibitory measures, localized polymerization cannot be avoided, which increases operating costs and makes the operation of the device more difficult.

[0005] In summary, although adding air can further inhibit the polymerization reaction of acrylic acid and methacrylic acid materials, the traditional method of introducing air cannot fully utilize the inhibitory effect of air. Therefore, there is an urgent need for an air inhibition system that can achieve uniform air dispersion and improve the inhibition effect, thereby increasing the efficiency of air inhibition while reducing the amount of chemical inhibitors used and lowering production costs. Utility Model Content

[0006] To overcome the problems of uneven air dispersion and poor polymerization inhibition efficiency in the existing technology, this utility model provides an air polymerization inhibition system for acrylic acid esterification reaction.

[0007] To achieve the above objectives, the technical solution of this utility model is as follows:

[0008] An air-based polymerization inhibition system for acrylate esterification includes a reactor and a dehydration tower. The reactor has an air inlet connected to an air pipeline. The reactor is also equipped with a pipeline connected to the dehydration tower. The top of the dehydration tower is connected to a reaction reflux tank via a primary condenser. The primary condenser has an outlet connected to a secondary condenser. The secondary condenser has a liquid outlet connected to the reaction reflux tank. The secondary condenser also has a gas outlet connected to a tail gas pipeline. The tail gas pipeline has a branch that returns to the reactor's air inlet, and a three-way valve is installed at the branch. The dehydration tower has a reflux pipeline connected to the upper part of the reactor; the reflux pipeline has an internally extended pipe structure. An internally extended air pipe is installed at the reactor's air inlet, and a double-layer distributor is installed on the internally extended air pipe. The reactor has a built-in agitator with double-layer impellers arranged from top to bottom, and both layers of distributors are located below the impellers.

[0009] Preferably, the double-layer distributor includes an upper annular distributor and a lower distribution disk. The bottom of the upper annular distributor is uniformly provided with multiple inclined gas outlet nozzles, with the gas outlets of the gas outlet nozzles facing the inner wall of the reactor. Further, a ring of gas outlet nozzles is distributed circumferentially along the bottom. The lower distribution disk has an annular structure, and its upper surface is uniformly provided with multiple umbrella-shaped gas outlets. Each umbrella-shaped gas outlet consists of a gas outlet pipe and an umbrella-shaped guide head fixed to the top of the gas outlet pipe. Further, a stainless steel mesh sintered filter element is installed at the gas outlet end of the gas outlet pipe to form uniform microbubbles. The umbrella-shaped guide head is fixed to the outer edge of the gas outlet pipe by a bracket, and its function is to prevent the liquid in the reactor from backflowing and clogging the gas outlet pipe.

[0010] Preferably, the liquid outlet end of the inner extension pipe structure in the return pipeline is connected to an annular pipe, and a liquid outlet hole is provided at the bottom of the annular pipe. Further, the annular pipe is located below the upper annular distributor.

[0011] Preferably, a support frame is provided on the inner wall of the bottom of the reactor and connected to the lower distribution plate, and a guide plate is provided on the inner side wall of the reactor, with the guide plate located on the opposite side of the air extension pipe.

[0012] Preferably, the upper part of the reactor is also connected to the raw material tank area via a raw material pipeline for feeding raw materials such as acrylic acid.

[0013] Preferably, the bottom of the reactor is connected to an external pump via a pipeline, and the reactor jacket is connected to a steam pipeline.

[0014] Preferably, the reaction reflux tank is equipped with an overflow plate, with one side of the overflow plate being the reflux liquid zone and the other side being the sedimentation and separation zone; the bottom of the reaction reflux tank is equipped with a pipeline connected to a reflux pump, which is connected to the upper part of the dehydration tower; the bottom of the sedimentation and separation zone is equipped with a pipeline connected to a water tank.

[0015] Preferably, both the reaction vessel and the reaction reflux tank are equipped with level gauges.

[0016] Preferably, a sampling port is also provided on the exhaust pipe, which is located at the front end of the three-way valve and is used to detect the oxygen content in the exhaust gas.

[0017] Preferably, a wire mesh demister is installed at the top of the dehydration tower.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] This invention relates to an air-based polymerization inhibition system for acrylate esterification reactions. By installing an air extension pipe with a double-layer distributor at the air inlet of the reactor, along with a double-layer stirring paddle and guide plate, and optimizing the dehydration tower reflux pipeline to an extension pipe structure with an annular pipe, uniform air dispersion and microbubbling are achieved. This increases the contact area and efficiency between air and materials, effectively enhancing the polymerization inhibition effect. Furthermore, single-reactor operation simplifies the reaction apparatus, avoids the formation of dead zones in material circulation, reduces the risk of localized polymerization, and lowers the amount of chemical polymerization inhibitor used while improving polymerization inhibition efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the air polymerization inhibition system for the acrylate esterification reaction of this utility model;

[0021] Figure 2 This is an enlarged view of point A inside the reactor in this utility model;

[0022] Figure 3 This is an enlarged view of point B inside the reactor in this utility model.

[0023] In the diagram: 1. Reactor; 101. Stirrer; 102. Upper annular distributor; 103. Lower distribution plate; 104. Support frame; 105. Baffle plate; 106. Umbrella-shaped gas outlet; 1061. Gas outlet pipe; 1062. Sintered filter element; 1063. Support; 1064. Umbrella-shaped guide head; 107. Gas outlet nozzle; 2. Dehydration tower; 3. Primary condenser; 4. Reaction reflux tank; 5. Secondary condenser; 6. Tail gas pipeline; 7. Reflux pump; 8. External pump; 9. Water tank; 10. Level gauge; 11. Air pipeline; 12. Raw material pipeline; 13. Steam pipeline; 14. Sampling port; 15. Raw material tank area; 16. Wire mesh demister; 17. Three-way valve; 18. Reflux pipeline; 181. Annular pipe. Detailed Implementation

[0024] The specific technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0025] like Figures 1-3As shown, the air-inhibiting polymerization system for acrylate esterification reaction of this utility model includes a reactor 1 and a dehydration tower 2. The upper air inlet of the reactor 1 is connected to an air pipeline 11. The reactor 1 is provided with a pipeline connected to the dehydration tower 2. The top of the dehydration tower 2 is connected to the reaction reflux tank 4 through a primary condenser 3. The primary condenser 3 is provided with an air outlet connected to a secondary condenser 5. The secondary condenser 5 is provided with a gas outlet connected to a tail gas pipeline 6. The dehydration tower 2 is provided with a reflux pipeline 18 connected to the upper part of the reactor 1. The reflux pipeline 18 has an internal extension pipe structure. A wire mesh demister 16 is provided at the top of the dehydration tower 2. An internal air extension pipe is provided at the air inlet of the reactor 1. A double-layer distributor is provided on the internal air extension pipe. The reactor 1 has a built-in stirrer 101. The stirrer 101 has a double-layer stirring paddle from top to bottom. Both layers of distributors are located below the stirring paddles.

[0026] The double-layer distributor includes an upper annular distributor 102 and a lower distribution disk 103. The bottom of the upper annular distributor 102 is evenly provided with multiple inclined air outlet nozzles 107, and the air outlets of the air outlet nozzles 107 face the inner wall of the vessel. The lower distribution disk 103 has an annular structure, and its upper surface is evenly provided with multiple umbrella-shaped air outlets 106. Each umbrella-shaped air outlet 106 consists of an air outlet pipe 1061 and an umbrella-shaped guide head 1064 fixed to the top of the air outlet pipe 1061. A stainless steel mesh sintered filter element 1062 is installed at the air outlet end of the air outlet pipe 1061, and the umbrella-shaped guide head 1064 is fixed to the outer edge of the air outlet pipe 1061 by a bracket 1063.

[0027] The outlet end of the return pipe 18 is connected to the annular pipe 181, and the bottom of the annular pipe 181 is provided with an outlet hole. The annular pipe 181 is located below the upper annular distributor 102.

[0028] A support frame 104 is provided on the inner wall of the bottom of the reactor 1 and is connected to the lower distribution plate 103. A guide plate 105 is provided on the inner side wall of the reactor 1, and the guide plate 105 is located on the opposite side of the air extension pipe.

[0029] The upper part of the reactor 1 is also connected to the raw material tank area 15 through the raw material pipeline 12, and the bottom is connected to the external pump 8 through the pipeline. The jacket of the reactor 1 is connected to the steam pipeline 13.

[0030] The secondary condenser 5 is also equipped with a liquid outlet connected to the reaction reflux tank 4. The reaction reflux tank 4 is equipped with an overflow plate, with one side of the overflow plate being the reflux liquid zone and the other side being the sedimentation and separation zone. The bottom reflux liquid zone of the reaction reflux tank 4 is equipped with a pipeline connected to the reflux pump 7, which is connected to the upper part of the dehydration tower 2. The bottom of the sedimentation and separation zone is equipped with a pipeline connected to the water tank 9.

[0031] The exhaust gas pipeline 6 is provided with a branch that returns to the gas inlet of the reactor 1. A three-way valve 17 is provided at the branch. A sampling port 14 is also provided on the exhaust gas pipeline 6.

[0032] Both the reaction vessel 1 and the reaction reflux tank 4 are equipped with level gauges 10.

[0033] The air-based polymerization inhibition system for the aforementioned acrylate esterification reaction, using acrylic acid and trimethylolpropane as examples, operates as follows:

[0034] After the system check is completed, the raw materials are fed in. Acrylic acid (containing 100ppm polymerization inhibitor), trimethylolpropane, catalyst, chemical polymerization inhibitor and dehydrating agent are transported from raw material tank area 15 to reactor 1 through raw material pipeline 12. During the feeding process, the feeding amount is monitored in real time by level gauge 10 of reactor 1 to ensure that each raw material enters the reaction system according to the process ratio.

[0035] After the raw materials are fed, the steam pipe 13 of the jacket of the reactor 1 is turned on to introduce steam to heat the material in the reactor 1. At the same time, the stirrer 101 is turned on. While heating and stirring are started, air enters the air inlet at the top of the reactor 1 through the air pipe 11 and is transported to the double-layer distributor located at the bottom of the double-layer stirring paddle through the air extension pipe at the air inlet.

[0036] In the double-layer distributor, the upper annular distributor 102 diverts air to multiple inclined air outlet nozzles 107, with the nozzle outlets facing the inner wall of the vessel, allowing some air to flow and disperse along the vessel wall. The lower distribution plate 103 distributes air through multiple umbrella-shaped air outlets 106. The air is first divided into uniform microbubbles by the sintered filter element 1062 of the umbrella-shaped air outlet 106, and then blocked by the umbrella-shaped guide head 1064 before entering the material from multiple directions. During this process, in order to prevent the formation of a stirring vacuum zone, a guide plate 105 is set on the inner wall of the vessel on the opposite side of the air extension tube, which works in conjunction with the double-layer stirring paddle to further promote the uniform diffusion of air bubbles in the material and realize the efficient role of air as a polymerization inhibitor.

[0037] The raw materials undergo esterification under the action of a catalyst and a dehydrating agent to produce trimethylolpropane trimethacrylate and water. The water produced in the reaction forms an azeotrope with the dehydrating agent and enters the dehydration tower 2 through the pipeline connecting the reaction vessel 1 and the dehydration tower 2. After separation in the dehydration tower 2, the azeotrope vapor is distilled off from the top of the tower. The wire mesh demister 16 at the top of the tower first captures the liquid droplets in the vapor, and then the vapor enters the first-stage condenser 3 and the second-stage condenser 5 for condensation. The condensed liquid enters the reaction reflux tank 4, and the tail gas enters the tail gas pipeline 6. The oxygen content in the tail gas is detected through the sampling port 14. After detection, it is controlled by the three-way valve 17 to be circulated or directly transported to the tail gas treatment unit.

[0038] The material entering the reaction reflux tank 4 is separated inside the tank. The reflux liquid zone on one side of the overflow plate collects the organic phase, such as water-containing agent, and enters the reflux pump 7 through the bottom pipeline. The reflux pump 7 then transports the material back to the dehydration tower 2. The sedimentation and separation zone on the other side of the overflow plate collects the aqueous phase, which is discharged into the water tank 9 for storage through the bottom pipeline.

[0039] The liquid material at the bottom of the dehydration tower 2 returns to the reactor 1 through the reflux pipe 18. The inner extension pipe structure of the reflux pipe 18 transports the material to the annular pipe 181, and the annular pipe 181 is located below the upper annular distributor 102. Driven by the air sprayed from the upper annular distributor 102, and with the stirring action of the agitator, the reflux material is quickly mixed with the original material in the reactor to avoid excessive local raw material concentration that may cause polymerization.

[0040] Once the esterification reaction reaches the set conversion rate, the steam pipeline 13 is closed, and the liquid material in the reactor 1 enters the external pump 8 through the bottom pipeline, which then transports it to the subsequent processing steps. The air pipeline 11 valve can only be closed when the liquid level is at the bottom of the lower distribution plate 103 to avoid the risk of local polymerization due to interruption of air supply when the liquid level is higher than the lower distribution plate 103, and to prevent the liquid from blocking the umbrella-shaped air outlet 106 due to interruption of air supply. When the liquid level drops to the bottom of the lower distribution plate 103, the amount of material is small, and the risk of polymerization is significantly reduced. At this time, the air pipeline 11 valve can be closed.

Claims

1. An air-based polymerization inhibition system for acrylate esterification reaction, characterized in that, The reactor includes a reactor (1) and a dehydration tower (2). The upper air inlet of the reactor (1) is connected to an air pipeline (11). The reactor (1) is equipped with a pipeline connected to the dehydration tower (2). The top of the dehydration tower (2) is connected to the reaction reflux tank (4) through a primary condenser (3). The primary condenser (3) is equipped with an outlet connected to a secondary condenser (5). The secondary condenser (5) is equipped with a gas outlet connected to a tail gas pipeline (6). The dehydration tower (2) is equipped with a reflux pipeline (18) connected to the upper part of the reactor (1). The reflux pipeline (18) has an internal extension pipe structure. The reactor (1) is equipped with an air inlet pipe and a double-layer distributor. The reactor (1) has a built-in stirrer (101) with a double-layer stirring paddle from top to bottom. The double-layer distributor is located at the bottom of the stirring paddle.

2. The air-inhibitory polymerization system for acrylate esterification reaction according to claim 1, characterized in that, The double-layer distributor includes an upper annular distributor (102) and a lower distribution plate (103). Multiple inclined air outlet nozzles (107) are evenly arranged at the bottom of the upper annular distributor (102), and the air outlet of the air outlet nozzles (107) faces the inner wall of the vessel.

3. The air polymerization inhibition system for acrylate esterification reaction according to claim 2, characterized in that, The lower distribution plate (103) has a ring structure, and multiple umbrella-shaped air outlets (106) are evenly arranged on the upper surface. Each umbrella-shaped air outlet (106) consists of an air outlet pipe (1061) and an umbrella-shaped guide head (1064) fixed to the top of the air outlet pipe (1061). A stainless steel mesh sintered filter element (1062) is installed at the air outlet end of the air outlet pipe (1061), and the umbrella-shaped guide head (1064) is fixed to the outer edge of the air outlet pipe (1061) by a bracket (1063).

4. The air polymerization inhibition system for acrylate esterification reaction according to claim 2, characterized in that, The outlet end of the return pipe (18) is connected to the ring pipe (181), and the bottom of the ring pipe (181) is provided with an outlet hole. The ring pipe (181) is located below the upper ring distributor (102).

5. The air polymerization inhibition system for acrylate esterification reaction according to claim 3, characterized in that, The bottom inner wall of the reactor (1) is provided with a support frame (104) connected to the lower distribution plate (103). The inner side wall of the reactor (1) is provided with a guide plate (105), which is located on the opposite side of the air extension pipe.

6. The air polymerization inhibition system for acrylate esterification reaction according to claim 1, characterized in that, The upper part of the reactor (1) is connected to the raw material tank area (15) through the raw material pipeline (12), and the bottom is connected to the external pump (8) through the pipeline. The jacket of the reactor (1) is connected to the steam pipeline (13).

7. The air polymerization inhibition system for acrylate esterification reaction according to claim 1, characterized in that, The secondary condenser (5) is also provided with a liquid outlet connected to the reaction reflux tank (4). The reaction reflux tank (4) is provided with an overflow plate inside. One side of the overflow plate is the reflux liquid area, and the other side is the sedimentation and separation liquid area. The bottom reflux liquid area of ​​the reaction reflux tank (4) is provided with a pipeline connected to the reflux pump (7). The reflux pump (7) is connected to the upper part of the dehydration tower (2). The bottom of the sedimentation and separation liquid area is provided with a pipeline connected to the water tank (9).

8. The air polymerization inhibition system for acrylate esterification reaction according to claim 1, characterized in that, The exhaust gas pipeline (6) is provided with a branch that returns to the inlet of the reactor (1). A three-way valve (17) is provided at the branch. A sampling port (14) is also provided on the exhaust gas pipeline (6).

9. The air-inhibitory polymerization system for acrylate esterification reaction according to claim 1, characterized in that, Both the reactor (1) and the reaction reflux tank (4) are equipped with level gauges (10).

10. The air polymerization inhibition system for acrylate esterification reaction according to claim 1, characterized in that, A wire mesh demister (16) is installed at the top of the dehydration tower (2).

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