Closed loop reaction process and system for continuous production of glycidyl methacrylate

Abstract

The application provides a closed loop reaction method and a closed loop reaction system for continuously producing glycidyl methacrylate. The closed loop reaction method comprises feeding 3-chloro-2-hydroxy-methyl propyl methacrylate reaction solution and alkali hydroxide solution into a plug flow reactor under nitrogen to generate glycidyl methacrylate through a closed loop reaction. The closed loop reaction system comprises a plug flow reactor, a rectifying tower, a first-stage condenser, a second-stage condenser, a phase separation tank and first, second and third feeding pipelines connected in sequence. The plug flow reactor is a tubular reactor, has a liquid inlet at the first end, a gas hole at the bottom and a drop hole at the top, and is connected with the first, second and third feeding pipelines, respectively. The rectifying tower has a gas inlet at the lower part connected with the plug flow reactor. The closed loop reaction method and the closed loop reaction system can improve the selectivity of the target product, reduce the number of moving equipment, reduce the cost, and save energy.

Description

Technical Field

[0001] This invention belongs to the field of organic production, specifically relating to a closed-ring reaction method and system for the continuous production of glycidyl methacrylate. Background Technology

[0002] Glycidyl methacrylate (GMA) is a special acrylate monomer that possesses both carbon-carbon double bonds and epoxy groups, giving it high reactivity. Therefore, it is widely used in the field of acrylic resin coatings, and is currently mainly used in the production of powder coatings, epoxy adhesives, and the rubber industry. The industrially reported GMA production processes mainly include neutralization condensation, transesterification, and ring-opening / ring-closing methods.

[0003] Neutralization condensation is the method currently used by most manufacturers. Its advantages include readily available catalysts, short reaction time (2-4 hours), and high yield (92-97%). However, the entire reaction system requires high water content, has a long reaction process, involves dust feeding and dust explosions, requires intermittent operation, and involves high manual labor intensity. The transesterification method uses methyl methacrylate and glycidyl ether as raw materials, offering significant advantages in raw material conversion and product yield, with high atom utilization. However, glycidyl ether is a limited and expensive raw material with high toxicity, and its stability is poor, making the reaction process difficult to control. The ring-opening and ring-closing method involves the esterification of methacrylic acid and epichlorohydrin under the action of a catalyst to produce 2-hydroxy-3-chloropropyl methacrylate (also known as 3-chloro-2-hydroxy-propyl methacrylate, abbreviated as CHPMA). The resulting intermediate is then reacted with sodium hydroxide to remove sodium chloride, and the product is purified. This method can significantly reduce the amount of epichlorohydrin used. Compared to the two batch process routes, the open-loop and closed-loop methods are continuous production routes with mild reaction conditions and higher safety, giving them significant advantages.

[0004] CN202211044078 reported that the closed-loop reaction step of the open-loop and closed-loop production of GMA adopts a multi-reactor series method, and the water content in the reactor is controlled by a distillation column connected to the closed-loop reactor. US005245057A uses a ten-reactor series method for the GMA closed-loop reaction. The multi-reactor series method consumes a lot of stirring power, and salt is easy to deposit in the reactor, requiring regular maintenance, which increases the cost, and the reaction effect is still not as good as the plug flow reactor. Zong Min et al. ("Process and kinetic study of the preparation of epichlorohydrin by cyclization of dichloropropanol", Guangzhou Chemistry, 2008, 33(2): 32-36) verified through experiments that chloride salts promote the hydrolysis of epichlorohydrin. Salt in the closed-loop reaction solution is easy to deposit, and the increase in salt concentration will greatly increase the viscosity of the closed-loop reaction solution, which not only increases the difficulty of separation and transportation, but also leads to an increase in the conversion rate of side reactions and a decrease in product quality. Given the numerous problems existing in the closed-loop reaction section of the current open-loop and closed-loop GMA production routes, there is an urgent need to design new continuous production reactors and reaction processes to replace existing reactors and reaction processes, so as to achieve continuous and stable production of glycidyl methacrylate that is safer and more environmentally friendly, while maximizing the selectivity of the target product. Summary of the Invention

[0005] The first objective of this invention is to provide a closed-loop reaction method for the continuous production of glycidyl methacrylate, which is simple and easy to operate, has high reaction selectivity, reduces the amount of rotating equipment, and makes the overall process more energy-efficient.

[0006] The second objective of this invention is to provide a closed-loop reaction system for the continuous production of glycidyl methacrylate. This closed-loop reaction system has a simple structure and can improve reaction selectivity and reduce equipment usage during operation.

[0007] To achieve the first objective of this invention, the following technical solution is adopted:

[0008] A method for the continuous production of glycidyl methacrylate via a closed-loop reaction includes feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under nitrogen purging to carry out a closed-loop reaction and generate glycidyl methacrylate.

[0009] Preferably, the closed-loop reaction method includes the following steps:

[0010] (1) Under the condition of nitrogen gas, 3-chloro-2-hydroxy-propyl methacrylate reaction solution and alkali metal hydroxide solution are fed into a plug flow reactor to carry out a closed-loop reaction to generate glycidyl methacrylate, and the glycidyl methacrylate reaction solution and gaseous material containing epichlorohydrin, water and nitrogen are output.

[0011] (2) The gaseous material output in step (1) is fed into a distillation column for distillation separation. A gaseous material containing epichlorohydrin, water and nitrogen is output from the top, and a liquid material containing epichlorohydrin is output from the bottom.

[0012] (3) The gaseous material output in step (2) is sent to the first-stage condenser for first-stage condensation. The gaseous material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid material containing epichlorohydrin is output from the bottom and returned to the distillation column.

[0013] (4) The gaseous material output in step (3) is sent to the secondary condenser for secondary condensation. The gaseous material containing nitrogen is output from the bottom, and the liquid material containing water and epichlorohydrin is output from the bottom.

[0014] (5) The liquid phase material output in step (4) is sent to the phase separation tank for oil-water separation. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column.

[0015] In the closed-loop reaction method of the present invention, preferably, the alkali metal hydroxide solution is fed dropwise from the top of the plug flow reactor, more preferably in multiple stages from the first end to the second end of the plug flow reactor; preferably, the amount of alkali metal hydroxide solution fed from the first end to the middle position of the plug flow reactor is 40-80% of the total feed amount; and / or,

[0016] In the closed-loop reaction, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed from the first end of the plug flow reactor; and / or,

[0017] In the closed-loop reaction, nitrogen gas is introduced from the bottom of the plug flow reactor, preferably in multiple sections from the first end to the second end of the plug flow reactor.

[0018] In the closed-loop reaction method of the present invention, preferably, the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and 3-chloro-2-hydroxy-propyl methacrylate is (0.9-1.4):1; and / or,

[0019] The reaction conditions for the closed-loop reaction include: a reaction pressure of 5-40 kPaA, and / or a reaction temperature of 40-90℃, and / or a reaction time of 3-16 h.

[0020] The closed-loop reaction method of the present invention, preferably, further includes:

[0021] The liquid material output from the distillation column in step (2) is returned to the plug flow reactor in step (1); preferably, it is returned in multiple stages from the first end to the second end of the plug flow reactor.

[0022] To achieve the second objective of this invention, a closed-loop reaction system for the continuous production of glycidyl methacrylate is also provided.

[0023] Preferably, the closed-loop reaction system of the present invention includes a plug flow reactor, a distillation column, a primary condenser, a secondary condenser and a phase separation tank connected by pipelines, as well as a first feed pipeline, a second feed pipeline and a third feed pipeline;

[0024] The plug flow reactor is a tubular reactor with a drip hole at the top, a liquid inlet at the first end, a liquid overflow port at the second end, and a vent at the bottom. The drip hole, the liquid inlet, and the vent are respectively connected to the first feed line, the second feed line, and the third feed line. These lines are used to drip an alkali metal hydroxide solution from the top, feed a 3-chloro-2-hydroxy-propyl methacrylate reaction solution from the first end, and introduce nitrogen gas from the bottom. Under the condition of nitrogen gas introduction, a closed-loop reaction between the 3-chloro-2-hydroxy-propyl methacrylate reaction solution and the alkali metal hydroxide occurs to generate glycidyl methacrylate, which is output from the liquid overflow port at the second end. A gaseous material containing epichlorohydrin, water, and nitrogen gas is output from the top.

[0025] The lower part of the distillation column is provided with a gas phase inlet and is connected to the gas phase outlet of the plug flow reactor through a pipeline. It is used to feed the gas phase material from the plug flow reactor and to distill and separate it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the top, and the liquid phase material containing epichlorohydrin is output from the bottom.

[0026] The top of the primary condenser is provided with a gas phase inlet, which is connected to the gas phase outlet of the distillation column via a pipeline. It is used to feed the gas phase material from the distillation column and perform first-stage condensation on it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid phase material containing epichlorohydrin is output from the bottom and refluxed back to the distillation column.

[0027] The top of the secondary condenser is provided with a gas phase inlet, which is connected to the gas phase outlet of the primary condenser through a pipeline. It is used to feed gas phase material from the primary condenser and perform secondary condensation on it. The gas phase material containing nitrogen is output from the bottom, and the liquid phase material containing water and epichlorohydrin is output from the bottom.

[0028] The top of the phase separation tank is provided with a liquid phase inlet, which is connected to the liquid phase outlet of the secondary condenser through a pipeline. It is used to receive liquid phase material from the secondary condenser and perform oil-water separation. The liquid phase material is discharged from the bottom liquid phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column.

[0029] Preferably, in the closed-loop reaction system of the present invention, there are multiple drip holes, which are spaced apart from the first end to the second end at the top of the plug flow reactor for segmented feeding of alkali metal hydroxide solution.

[0030] Preferably, in the closed-loop reaction system of the present invention, the top of the plug flow reactor is further provided with a return port, which is staggered with the drip hole;

[0031] An epichlorohydrin return pipeline is provided from the liquid phase outlet of the distillation column to the return port of the plug flow reactor, for returning the liquid phase material output from the bottom of the distillation column to the plug flow reactor.

[0032] Preferably, in the closed-loop reaction system of the present invention, there are multiple pores, which are spaced apart from the first end to the second end at the bottom of the plug flow reactor.

[0033] In the closed-loop reaction system of the present invention, preferably, a plurality of gas distribution pipes are provided at the bottom of the plug flow reactor, and the third feed line is connected to the gas distribution pipes through the gas holes.

[0034] The present invention also provides a closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system.

[0035] The beneficial effects of this invention are as follows:

[0036] (1) The closed-loop reaction method and closed-loop reaction system for the continuous production of glycidyl methacrylate of the present invention adopts a plug flow reactor, which is more in line with the reaction mechanism of the target reaction. Its application can further improve the selectivity of the target product. The closed-loop reaction method is simple and easy to operate, has high reaction selectivity, reduces moving equipment, and the overall process is more energy-efficient. The closed-loop reaction system has a simple structure. During use, it can improve reaction selectivity, reduce moving equipment, eliminate the need for stirring equipment, and reduce costs.

[0037] (2) The closed-loop reaction method and closed-loop reaction system for continuous production of glycidyl methacrylate of the present invention can realize the continuous production of the target product glycidyl methacrylate and ensure that its closed-loop reaction part is more stable and reliable. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the closed-loop reaction system for the continuous production of glycidyl methacrylate according to one embodiment of the present invention.

[0039] Figure 2 yes Figure 1 A partial longitudinal section of the plug flow reactor in the closed-loop reaction system shown on the paper.

[0040] Figure 3 yes Figure 1 A cross-sectional view of the plug flow reactor in the closed-loop reaction system shown, along the vertical plane.

[0041] Figure 4 This is a schematic diagram of the reaction system used in Comparative Example 1. Detailed Implementation

[0042] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples and accompanying drawings. The following embodiments / examples are only for illustrating the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0043] This invention provides a closed-ring reaction method for the continuous production of glycidyl methacrylate, such as... Figure 1-3 As shown, the closed-loop reaction method includes feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under nitrogen gas to carry out a closed-loop reaction, generating glycidyl methacrylate.

[0044] This invention uses a plug flow reactor, which is more in line with the reaction mechanism of the target reaction. Its application can further improve the selectivity of the target product, reduce the amount of rotating equipment, and lower costs.

[0045] Those skilled in the art will understand that the 3-chloro-2-hydroxy-propyl methacrylate reaction solution can be prepared by a ring-opening reaction of methacrylic acid and epichlorohydrin under catalytic conditions or by other feasible methods. Preferably, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution comprises 3-chloro-2-hydroxy-propyl methacrylate, glycidyl methacrylate, and unreacted epichlorohydrin. The 3-chloro-2-hydroxy-propyl methacrylate, as a reactant, undergoes a ring-closing reaction with an alkali metal hydroxide solution to generate glycidyl methacrylate, and the epichlorohydrin serves as a solvent.

[0046] Those skilled in the art will understand that when methacrylic acid and epichlorohydrin undergo a ring-opening reaction under catalytic conditions to produce propyl 3-chloro-2-hydroxy-methacrylate, epichlorohydrin is in excess, methacrylic acid reacts 100%, and most of the methacrylic acid is converted to propyl 3-chloro-2-hydroxy-methacrylate, while a small portion is converted to glycidyl methacrylate. Therefore, the resulting propyl 3-chloro-2-hydroxy-methacrylate reaction solution contains propyl 3-chloro-2-hydroxy-methacrylate, glycidyl methacrylate, and unreacted epichlorohydrin.

[0047] In one embodiment, the closed-loop reaction method includes the following steps:

[0048] (1) Under the condition of nitrogen gas, 3-chloro-2-hydroxy-propyl methacrylate reaction solution and alkali metal hydroxide solution are fed into a plug flow reactor to carry out a closed-loop reaction to generate glycidyl methacrylate, and the glycidyl methacrylate reaction solution and gaseous material containing epichlorohydrin, water and nitrogen are output.

[0049] (2) The gaseous material output in step (1) is fed into a distillation column for distillation separation. A gaseous material containing epichlorohydrin, water and nitrogen is output from the top, and a liquid material containing epichlorohydrin is output from the bottom (the liquid material output from the bottom of the distillation column is mainly epichlorohydrin with a purity of ≥99%).

[0050] (3) The gaseous material output in step (2) is sent to the first-stage condenser for first-stage condensation. The gaseous material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid material containing epichlorohydrin is output from the bottom (the liquid material output from the bottom of the first-stage condenser is mainly epichlorohydrin with a purity of ≥99%) and is returned to the distillation column.

[0051] (4) Send the gaseous material output in step (3) to the secondary condenser for secondary condensation. The gaseous material containing nitrogen is output from the bottom (the gaseous material output from the bottom of the secondary condenser is mainly nitrogen with a purity of ≥99%), and the liquid material containing water and epichlorohydrin is output from the bottom.

[0052] (5) The liquid phase material output in step (4) is sent to the phase separation tank for oil-water phase separation. The liquid phase material is discharged from the bottom water phase outlet (the liquid phase material discharged from the bottom of the phase separation tank is mainly water with a purity of ≥99%), and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet (the oil phase material discharged from the bottom of the phase separation tank is mainly epichlorohydrin with a purity of ≥99%) and returned to the distillation column.

[0053] In this invention, steps (2)-(5) are mainly for the purpose of removing water and nitrogen from the gaseous material generated during the closed-loop reaction and reusing the epichlorohydrin therein.

[0054] In one embodiment, the alkali metal hydroxide in the closed-loop reaction includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0055] In one embodiment, the concentration of the alkali metal hydroxide solution in the closed-loop reaction is 20-60%, such as 25%, 30%, 35%, 40%, 45%, 50%, and 55%.

[0056] In one embodiment, in the closed-loop reaction, the alkali metal hydroxide solution is fed dropwise from the top of the plug flow reactor, preferably in multiple stages from the first end to the second end of the plug flow reactor; preferably in 3-12 stages, such as stages 4, 5, 6, 7, 8, 9, 10, and 11; preferably, the amount of alkali metal hydroxide solution fed from the first end to the middle position of the plug flow reactor is 40-80% of the total feed amount, such as 45%, 50%, 55%, 60%, 65%, 70%, and 75%.

[0057] In one embodiment, in the closed-loop reaction, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed from the first end of the plug flow reactor.

[0058] In one embodiment, in the closed-loop reaction, nitrogen gas is introduced from the bottom of the plug flow reactor, preferably in multiple sections from the first end to the second end of the plug flow reactor; preferably in 3-12 sections, such as 4, 5, 6, 7, 8, 9, 10 and 11 sections.

[0059] In one embodiment, in the closed-ring reaction, the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and 3-chloro-2-hydroxy-propyl methacrylate is (0.9-1.4):1, such as 1.0:1, 1.1:1, 1.2:1 and 1.3:1.

[0060] In one embodiment, the reaction conditions for the closed-loop reaction include:

[0061] The reaction pressure is 5-40 kPaA, such as 10 kPaA, 15 kPaA, 20 kPaA, 25 kPaA, 30 kPaA, and 35 kPaA; and / or,

[0062] The reaction temperature is 40-90℃, such as 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, and 85℃; and / or,

[0063] The reaction time is 3-16 hours, such as 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours and 15 hours.

[0064] In one embodiment, the closed-loop reaction method further includes: returning the liquid phase material output from the distillation column in step (2) to the plug flow reactor in step (1) for reuse; preferably returning it in multiple segments from the first end to the second end of the plug flow reactor; preferably in 3-12 segments, such as segments 4, 5, 6, 7, 8, 9, 10 and 11; preferably the return position is alternated with the drop feed position of the alkali metal hydroxide solution.

[0065] Those skilled in the art will understand that the liquid material output from the distillation column in step (2) is mainly epichlorohydrin. It can be returned to the plug flow reactor as a solvent for reuse, thereby reducing the viscosity of the reaction liquid and improving the reaction efficiency. Epichlorohydrin can also be separated and reused in the subsequent separation stage.

[0066] The present invention also provides a closed-loop reaction system for the continuous production of glycidyl methacrylate.

[0067] In one embodiment, the closed-loop reaction system includes a plug flow reactor 4, a distillation column 6, a primary condenser 7, a secondary condenser 8, and a phase separation tank 9 connected by pipelines, as well as a first feed line 1, a second feed line 2, and a third feed line 3.

[0068] The plug flow reactor 4 is a tubular reactor with a drip hole at the top, a liquid inlet at the first end, a liquid overflow port at the second end, and a vent at the bottom. The drip hole, the liquid inlet, and the vent are respectively connected to the first feed line 1, the second feed line 2, and the third feed line 3 for dripping alkali metal hydroxide solution from the top, feeding 3-chloro-2-hydroxy-propyl methacrylate reaction solution from the first end, and introducing nitrogen gas from the bottom. Under the condition of nitrogen gas introduction, a closed-loop reaction between 3-chloro-2-hydroxy-propyl methacrylate reaction solution and alkali metal hydroxide occurs to generate glycidyl methacrylate, which is output from the liquid overflow port at the second end, and a gaseous material containing epichlorohydrin, water, and nitrogen is output from the top.

[0069] The lower part of the distillation column 6 is provided with a gas phase inlet and is connected to the gas phase outlet of the plug flow reactor 4 through a pipeline. It is used to feed the gas phase material from the plug flow reactor 4 and to distill and separate it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the top, and the liquid phase material containing epichlorohydrin is output from the bottom.

[0070] The top of the primary condenser 7 is provided with a gas phase inlet and is connected to the gas phase outlet of the distillation column 6 through a pipeline. It is used to feed the gas phase material from the distillation column 6 and perform first-stage condensation on it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid phase material containing epichlorohydrin is output from the bottom and refluxed back to the distillation column 6.

[0071] The top of the secondary condenser 8 is provided with a gas phase inlet and is connected to the gas phase outlet of the primary condenser 7 through a pipeline. It is used to feed gas phase material from the primary condenser 7 and perform second-stage condensation on it. The gas phase material containing nitrogen is output from the bottom and the liquid phase material containing water and epichlorohydrin is output from the bottom.

[0072] The top of the phase separation tank 9 is provided with a liquid phase inlet and is connected to the liquid phase outlet of the secondary condenser 8 through a pipeline. It is used to receive liquid phase material from the secondary condenser 8 and perform oil-water separation. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column 6.

[0073] In this invention, when condensation is carried out in two stages, the first-stage condenser 7 can use circulating water for condensation, while the second-stage condenser 8 needs to use chilled water for condensation. Compared to the first-stage condensation, which can only use chilled water for condensation, the two-stage condensation of this invention can reduce the use of chilled water, recycle circulating water, reduce energy consumption, and achieve energy saving in the process.

[0074] In one embodiment, there are multiple drip holes, which are spaced apart from the first end to the second end at the top of the plug flow reactor 4 for segmented feeding of alkali metal hydroxide solution; preferably, there are 3-12 drip holes, such as 4, 5, 6, 7, 8, 9, 10 and 11, to feed alkali metal hydroxide solution in multiple segments.

[0075] In one embodiment, the top of the plug flow reactor 4 is also provided with a return port, which is staggered with the drip hole; an epichlorohydrin return pipeline 5 is provided from the liquid phase outlet of the distillation column 6 to the return port of the plug flow reactor 4, for returning the liquid phase material output from the bottom of the distillation column 6 to the plug flow reactor 4 for reuse.

[0076] Those skilled in the art will understand that the liquid material output from the distillation column is mainly epichlorohydrin, which can be returned to the plug flow reactor for reuse as a solvent, thereby reducing the viscosity of the reaction liquid and improving the reaction efficiency. Epichlorohydrin can also be separated and reused in subsequent separation stages.

[0077] In one embodiment, there are multiple return ports, which are spaced apart from the first end to the second end at the top of the plug flow reactor 4, for segmented return of the liquid material output from the bottom of the distillation column 6 to the plug flow reactor 4; preferably, the return ports and the drip holes are alternately arranged; preferably, there are 3-12 return ports, such as 4, 5, 6, 7, 8, 9, 10 and 11, to return the liquid material output from the bottom of the distillation column 6 to the plug flow reactor 4 in multiple segments.

[0078] In one embodiment, there are multiple pores, which are spaced apart from the first end to the second end at the bottom of the plug flow reactor 4; preferably, there are 3-12 pores, such as 4, 5, 6, 7, 8, 9, 10 and 11, to allow nitrogen to be introduced in stages.

[0079] In one embodiment, a plurality of gas distribution pipes 41 are provided at the bottom of the plug flow reactor 4. The third feed line 3 is connected to the gas distribution pipes 41 through the vent, thereby introducing nitrogen gas from the bottom for bubbling to promote reaction mixing and mass transfer, and to avoid salt deposition in the plug flow reactor 4.

[0080] Those skilled in the art will understand that existing reactors typically consist of multiple vessels connected in series, equipped with agitators for stirring, resulting in numerous power sources, high energy consumption, and high costs. This invention, by employing a plug flow reactor 4 and introducing nitrogen gas from its bottom for bubbling, avoids mechanical stirring, thereby improving reaction selectivity, reducing power sources, lowering energy consumption, and reducing costs.

[0081] In one embodiment, gas distribution holes are provided on the wall of the gas distribution pipe 41. Preferably, there are multiple gas distribution holes, which are evenly distributed on the wall of the gas distribution pipe 41. Preferably, the gas distribution holes are provided on the wall of the gas distribution pipe 41 in different directions.

[0082] In one embodiment, the outer wall of the lower part of the plug flow reactor 4 is provided with an outer jacket for heat preservation.

[0083] In one embodiment, the liquid phase inlet of the plug flow reactor 4 is higher than its liquid phase overflow outlet.

[0084] In one embodiment, the number of theoretical plates in the distillation column 6 is 5-25, such as 10, 15, and 20.

[0085] The present invention also provides a closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system.

[0086] like Figures 1-3 As shown, the closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system is as follows:

[0087] (1) The 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed into the liquid phase inlet at the first end of the plug flow reactor 4 through the second feed line 2, and the alkali metal hydroxide solution is fed into the top of the plug flow reactor 4 in segments through the drip hole through the first feed line 1. At the same time, nitrogen gas is introduced into the plug flow reactor 4 in segments through the gas hole and gas distribution pipe 41 at the bottom of the plug flow reactor 4 through the third feed line 3. Thus, under the condition of nitrogen gas, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution and the alkali metal hydroxide solution are fed into the plug flow reactor to carry out a closed-loop reaction to generate glycidyl methacrylate, and the glycidyl methacrylate reaction solution and the gas phase material containing epichlorohydrin, water and nitrogen are output.

[0088] (2) The gaseous material output in step (1) is fed into a distillation column for distillation separation. A gaseous material containing epichlorohydrin, water and nitrogen is output from the top, and a liquid material containing epichlorohydrin is output from the bottom. The liquid material output from the bottom of the distillation column 6 is returned from the top to the plug flow reactor 4 through the epichlorohydrin return pipeline 5.

[0089] (3) The gaseous material output in step (2) is sent to the first-stage condenser for first-stage condensation. The gaseous material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid material containing epichlorohydrin is output from the bottom and returned to the distillation column.

[0090] (4) The gaseous material output in step (3) is sent to the secondary condenser for secondary condensation. The gaseous material containing nitrogen is output from the bottom, and the liquid material containing water and epichlorohydrin is output from the bottom.

[0091] (5) The liquid phase material output in step (4) is sent to the phase separation tank for oil-water separation. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column.

[0092] The closed-loop reaction method and system for the continuous production of glycidyl methacrylate of the present invention employs a plug flow reactor. The plug flow reactor is more consistent with the reaction mechanism of the target reaction, and its application can further improve the selectivity of the target product, reduce moving equipment, lower costs, and achieve continuous production of the target product glycidyl methacrylate. It also ensures a more stable and reliable closed-loop reaction section. The closed-loop reaction method is simple and easy to operate, has high reaction selectivity, reduces moving equipment, and the overall process is more energy-efficient. The closed-loop reaction system has a simple structure, improves reaction selectivity during use, reduces moving equipment, eliminates the need for stirring equipment, and lowers costs.

[0093] The sources of raw materials used in the following examples / comparative examples are as follows:

[0094] A 3-chloro-2-hydroxy-propyl methacrylate reaction solution, wherein, by molar percentage, it contains 4.8% 3-chloro-2-hydroxy-propyl methacrylate, 5.2% glycidyl methacrylate and 90% epichlorohydrin;

[0095] Nitrogen, >99.9%, Wanhua Chemical (Yantai) production base, industrial grade.

[0096] Methacrylic acid, Wanhua Chemical Group Co., Ltd., industrial grade;

[0097] NaOH and KOH aqueous solutions, Wanhua Chemical (Yantai) Chlor-Alkali Thermal Power Co., Ltd., industrial grade;

[0098] Epichlorohydrin, Shandong Haili Chemical Co., Ltd., industrial grade;

[0099] Product analysis methods:

[0100] Gas chromatography analysis used the correction factor method. Instrument manufacturer and model: Shimadzu 1020-plus.

[0101] Example 1 (S1)

[0102] like Figure 1-3 The closed-loop reaction system A1 for the continuous production of glycidyl methacrylate shown includes a plug flow reactor 4, a distillation column 6, a primary condenser 7, a secondary condenser 8 and a phase separation tank 9 connected by pipelines, as well as a first feed line 1, a second feed line 2 and a third feed line 3.

[0103] The plug flow reactor 4 is a tubular reactor with seven drip holes spaced apart from one end to the second end at its top, a liquid inlet at its first end, and seven vent holes spaced apart from one end to the second end at its bottom. The drip holes, the liquid inlet, and the vent holes are respectively connected to the first feed line 1, the second feed line 2, and the third feed line 3. These lines are used to separately feed alkali metal hydroxide solution dropwise from the top, feed 3-chloro-2-hydroxy-propyl methacrylate reaction solution from the first end, and introduce nitrogen gas from the bottom. Under nitrogen gas conditions, a closed-loop reaction occurs between the 3-chloro-2-hydroxy-propyl methacrylate reaction solution and the alkali metal hydroxide to generate methacrylic acid. Glycidyl ester is discharged from the liquid phase overflow port at the second end, and a gaseous material containing epichlorohydrin, water, and nitrogen is discharged from the top. The bottom of the plug flow reactor 4 is also equipped with seven gas distribution pipes 41, and the third feed line 3 is connected to the gas distribution pipes 41 through the gas holes. The walls of the gas distribution pipes 41 are uniformly provided with gas distribution holes facing different directions. The top of the plug flow reactor 4 is also equipped with seven return ports spaced apart from the first end to the second end, alternating with the drip holes. In the plug flow reactor 4, the liquid phase feed port is higher than the liquid phase overflow port. An outer jacket 42 is provided on the lower outer wall of the plug flow reactor 4.

[0104] The lower part of the distillation column 6 is provided with a gas phase inlet, which is connected to the gas phase outlet of the plug flow reactor 4 via a pipeline. It is used to feed the gas phase material from the plug flow reactor 4 and to distill and separate it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the top, and the liquid phase material containing epichlorohydrin is output from the bottom. The theoretical number of plates of the distillation column 6 is 8. An epichlorohydrin return pipeline 5 is provided from the liquid phase outlet of the distillation column 6 to the return port of the plug flow reactor 4, which is used to return the liquid phase material output from the bottom of the distillation column 6 to the plug flow reactor 4.

[0105] The top of the primary condenser 7 is provided with a gas phase inlet and is connected to the gas phase outlet of the distillation column 6 through a pipeline. It is used to feed the gas phase material from the distillation column 6 and perform first-stage condensation on it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid phase material containing epichlorohydrin is output from the bottom and refluxed back to the distillation column 6.

[0106] The top of the secondary condenser 8 is provided with a gas phase inlet and is connected to the gas phase outlet of the primary condenser 7 through a pipeline. It is used to feed gas phase material from the primary condenser 7 and perform second-stage condensation on it. The gas phase material containing nitrogen is output from the bottom and the liquid phase material containing water and epichlorohydrin is output from the bottom.

[0107] The top of the phase separation tank 9 is provided with a liquid phase inlet and is connected to the liquid phase outlet of the secondary condenser 8 through a pipeline. It is used to receive liquid phase material from the secondary condenser 8 and perform oil-water separation. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column 6.

[0108] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 includes the following steps:

[0109] (1) The 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed into the liquid phase inlet at the first end of the plug flow reactor 4 through the second feed line 2, and the alkali metal hydroxide solution is fed into the top of the plug flow reactor 4 through the first feed line 1 in 7 segments through the drip hole. At the same time, nitrogen gas is introduced into the bottom of the plug flow reactor 4 through the gas hole and the gas distribution pipe 41 in 7 segments through the third feed line 3. Thus, under the condition of nitrogen gas, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution and the alkali metal hydroxide solution are fed into the plug flow reactor to carry out a closed-loop reaction to generate glycidyl methacrylate, and the glycidyl methacrylate reaction solution B1 and the gas phase material containing epichlorohydrin, water and nitrogen are output.

[0110] (2) The gaseous material output in step (1) is fed into a distillation column for distillation separation. A gaseous material containing epichlorohydrin, water and nitrogen is output from the top, and a liquid material containing epichlorohydrin is output from the bottom. The liquid material output from the bottom of the distillation column 6 is returned to the plug flow reactor 4 from the top section 7 through the epichlorohydrin return pipeline 5.

[0111] (3) The gaseous material output in step (2) is sent to the first-stage condenser for first-stage condensation. The gaseous material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid material containing epichlorohydrin is output from the bottom and returned to the distillation column.

[0112] (4) The gaseous material output in step (3) is sent to the secondary condenser for secondary condensation. The gaseous material containing nitrogen is output from the bottom, and the liquid material containing water and epichlorohydrin is output from the bottom.

[0113] (5) The liquid phase material output from step (4) is sent to a phase separation tank for oil-water separation. The aqueous phase material is discharged from the bottom aqueous phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and refluxed back to the distillation column; wherein,

[0114] In step (1), the alkali metal hydroxide is KOH, and the alkali metal hydroxide solution is a 50wt% KOH aqueous solution;

[0115] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.02:1;

[0116] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments from the first end to the second end of the top of the reactor at a mass ratio of 1:1:1:1:2:2:2; In step (1), the reaction conditions of the closed-loop reaction include: a reaction pressure of 15 kPaA, a reaction temperature of 63°C, and a reaction time of 4 h.

[0117] The obtained glycidyl methacrylate reaction solution B1 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0118] Example 2 (S2)

[0119] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0120] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0121] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.12:1;

[0122] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 20 kPaA, a reaction temperature of 57°C, and a reaction time of 4.5 h.

[0123] The obtained glycidyl methacrylate reaction solution B2 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0124] Example 3 (S3)

[0125] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0126] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 30wt% NaOH aqueous solution;

[0127] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments through the drip holes at the top of the plug flow reactor 4.

[0128] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 13 kPaA, a reaction temperature of 62°C, and a reaction time of 5.3 h.

[0129] The obtained glycidyl methacrylate reaction solution B3 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0130] Example 4 (S4)

[0131] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0132] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0133] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments through the drip holes at the top of the plug flow reactor 4.

[0134] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 10 kPaA, a reaction temperature of 60°C, and a reaction time of 5.1 h.

[0135] The obtained glycidyl methacrylate reaction solution B4 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0136] Example 5 (S5)

[0137] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0138] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0139] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments through the drip holes at the top of the plug flow reactor 4.

[0140] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 11 kPaA, a reaction temperature of 76°C, and a reaction time of 3.2 h.

[0141] The obtained glycidyl methacrylate reaction solution B5 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0142] Example 6 (S6)

[0143] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0144] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.19:1;

[0145] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0146] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments through the drip holes at the top of the plug flow reactor 4.

[0147] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 10 kPaA, a reaction temperature of 64°C, and a reaction time of 4.9 h.

[0148] The obtained glycidyl methacrylate reaction solution B6 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0149] Example 7 (S7)

[0150] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0151] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1:1;

[0152] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments from the first end to the second end of the top of the reactor at a mass ratio of 2:2:2:1:1:1:1;

[0153] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 10 kPaA, a reaction temperature of 60°C, and a reaction time of 4 h.

[0154] The obtained glycidyl methacrylate reaction solution B7 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0155] Example 8 (S8)

[0156] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0157] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0158] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.03:1;

[0159] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments from the first end to the second end of the top of the reactor at a mass ratio of 2:2:2:1:1:1:1;

[0160] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 20 kPaA, a reaction temperature of 49°C, and a reaction time of 7.5 h.

[0161] The obtained glycidyl methacrylate reaction solution B8 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0162] Example 9 (S9)

[0163] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0164] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 50wt% NaOH aqueous solution;

[0165] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.01:1;

[0166] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments from the first end to the second end of the top of the reactor at a mass ratio of 2:2:2:1:1:1:1;

[0167] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 18 kPaA, a reaction temperature of 56°C, and a reaction time of 9 h.

[0168] The obtained glycidyl methacrylate reaction solution B9 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0169] Example 10 (S10)

[0170] The closed-loop reaction method for the continuous production of glycidyl methacrylate using the aforementioned closed-loop reaction system A1 differs from the closed-loop reaction method described in Example 1 only in that:

[0171] In step (1), the alkali metal hydroxide is NaOH, and the alkali metal hydroxide solution is a 30wt% NaOH aqueous solution;

[0172] In step (1), the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxy-methacrylate is 1.03:1;

[0173] In step (1), the alkali metal hydroxide solution is fed into the plug flow reactor in 7 segments from the first end to the second end of the top of the reactor at a mass ratio of 2:2:2:1:1:1:1;

[0174] In step (1), the reaction conditions for the closed-loop reaction include: a reaction pressure of 25 kPaA, a reaction temperature of 59°C, and a reaction time of 5.2 h.

[0175] The obtained glycidyl methacrylate reaction solution B10 was analyzed to determine the selectivity of glycidyl methacrylate. The results are shown in Table 1.

[0176] Comparative Example 1 (D1)

[0177] Adopting such Figure 4The system shown employs a continuous reactor 4' with five partitions (3'). The reactor 4' is pressurized to 12 kPa. The 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed into the reactor 4' through the liquid inlet at its first end along the second feed line 2'. A 50 wt% NaOH aqueous solution (alkali metal hydroxide solution) is uniformly added dropwise in six segments through the drip hole at the top along the first feed line 1' to induce a closed-loop reaction, producing glycidyl methacrylate. This is discharged from the liquid overflow port at the second end. The molar ratio of alkali metal hydroxide to methacrylic acid groups in the 3-chloro-2-hydroxy-propyl methacrylate reaction solution is 1.04:1. The reaction solution temperature is controlled at 45°C. The reaction liquid resides in the continuous reactor 4' for 10 hours. The gaseous material containing epichlorohydrin and water output from the continuous reactor 4' is fed into the distillation column 6' (with 10 trays) for distillation separation. The gaseous material containing epichlorohydrin and water is output from the top, and the liquid material containing epichlorohydrin is output from the bottom and returned to the continuous reactor 4' from the top of the first end through the epichlorohydrin return pipeline 5'. The gaseous material output from the distillation column 6' is sent to the condenser 7' (with -15℃ ethylene glycol aqueous solution as the condensing medium) for condensation and phase separation. Water is discharged, and epichlorohydrin is refluxed back to the distillation column 6'. After the NaOH aqueous solution is added dropwise, the reaction ends, and glycidyl methacrylate reaction solution B1' is output.

[0178] The obtained glycidyl methacrylate reaction solution B1' was analyzed and the selectivity of glycidyl methacrylate was determined. The results are shown in Table 1.

[0179] Selective results

[0180] The glycidyl methacrylate reaction solutions B1-10 and B1' obtained in Examples 1-10 and Comparative Example 1 were analyzed to obtain selectivity data for glycidyl methacrylate. The analytical results are shown in Table 1.

[0181] Table 1 Selectivity of glycidyl methacrylate

[0182] S1 98.38 S2 97.78 S3 98.12 S4 98.55 S5 97.85 S6 97.62 S7 98.75 S8 98.44 S9 98.56 S10 98.29 D1 92.13

[0183] As shown in Table 1, the selectivity of glycidyl methacrylate in the closed-ring reaction methods of Examples 1-10 is greater than 97.62 wt%, which is a significant improvement compared to Comparative Example 1.

[0184] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as limiting the invention. Those skilled in the art will understand that modifications and adjustments can be made to the invention based on the teachings of this specification. These modifications and adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for the continuous production of glycidyl methacrylate via a closed-ring reaction, characterized in that, The closed-loop reaction method includes feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under nitrogen gas to carry out a closed-loop reaction, generating glycidyl methacrylate; wherein... The alkali metal hydroxide solution is fed dropwise from the top of the plug flow reactor, and is fed in multiple stages from the first end to the second end of the plug flow reactor; Nitrogen gas is introduced from the bottom of the plug flow reactor and is introduced in multiple sections from the first end to the second end of the plug flow reactor.

2. The closed-loop reaction method according to claim 1, characterized in that, The closed-loop reaction method includes the following steps: (1) Under the condition of nitrogen gas, 3-chloro-2-hydroxy-propyl methacrylate reaction solution and alkali metal hydroxide solution are fed into a plug flow reactor to carry out a closed-loop reaction to generate glycidyl methacrylate, and output glycidyl methacrylate reaction solution and gaseous material containing epichlorohydrin, water and nitrogen. (2) The gaseous material output in step (1) is fed into a distillation column for distillation separation. A gaseous material containing epichlorohydrin, water and nitrogen is output from the top, and a liquid material containing epichlorohydrin is output from the bottom. (3) The gaseous material output in step (2) is sent to the first-stage condenser for first-stage condensation. The gaseous material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid material containing epichlorohydrin is output from the bottom and returned to the distillation column. (4) The gaseous material output in step (3) is sent to the secondary condenser for secondary condensation. The gaseous material containing nitrogen is output from the bottom, and the liquid material containing water and epichlorohydrin is output from the bottom. (5) The liquid phase material output in step (4) is sent to the phase separation tank for oil-water separation. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation tower.

3. The closed-loop reaction method according to claim 1 or 2, characterized in that, In the closed-loop reaction, the feed rate of the alkali metal hydroxide solution from the first end to the middle position of the plug flow reactor is 40-80% of the total feed rate; and / or, In the closed-loop reaction, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed from the first end of the plug flow reactor.

4. The closed-loop reaction method according to claim 1 or 2, characterized in that, In the closed-ring reaction, the molar ratio of methacrylic acid groups in the reaction solution of alkali metal hydroxide and propyl 3-chloro-2-hydroxymethacrylate is (0.9-1.4):1; and / or, The reaction conditions for the closed-loop reaction include: a reaction pressure of 5-40 kPaA, and / or a reaction temperature of 40-90 °C, and / or a reaction time of 3-16 h.

5. The closed-loop reaction method according to claim 2, characterized in that, The closed-loop reaction method further includes: returning the liquid phase material output from the distillation column in step (2) to the plug flow reactor in step (1).

6. The closed-loop reaction method according to claim 5, characterized in that, When the liquid material output from the distillation column in step (2) is returned to the plug flow reactor in step (1), it is returned in multiple segments from the first end to the second end of the plug flow reactor.

7. A closed-loop reaction system for the continuous production of glycidyl methacrylate, characterized in that, The closed-loop reaction system includes a plug flow reactor (4), a distillation column (6), a primary condenser (7), a secondary condenser (8), and a phase separation tank (9) connected by pipelines, as well as a first feed line (1), a second feed line (2), and a third feed line (3). The plug flow reactor (4) is a tubular reactor with a drip hole at the top, a liquid inlet at the first end, a liquid overflow port at the second end, and a gas hole at the bottom. The drip hole, the liquid inlet, and the gas hole are respectively connected to the first feed line (1), the second feed line (2), and the third feed line (3) for dripping alkali metal hydroxide solution from the top, feeding 3-chloro-2-hydroxy-propyl methacrylate reaction solution from the first end, and introducing nitrogen gas from the bottom. Under the condition of introducing nitrogen gas, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution and the alkali metal hydroxide undergo a closed-loop reaction to generate glycidyl methacrylate, which is output from the liquid overflow port at the second end, and a gaseous material containing epichlorohydrin, water, and nitrogen gas is output from the top. The lower part of the distillation column (6) is provided with a gas phase inlet and is connected to the gas phase outlet of the plug flow reactor (4) through a pipeline. It is used to feed the gas phase material from the plug flow reactor (4) and to distill and separate it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the top, and the liquid phase material containing epichlorohydrin is output from the bottom. The top of the primary condenser (7) is provided with a gas phase inlet and is connected to the gas phase outlet of the distillation column (6) through a pipeline. It is used to feed the gas phase material from the distillation column (6) and perform first-stage condensation on it. The gas phase material containing epichlorohydrin, water and nitrogen is output from the bottom, and the liquid phase material containing epichlorohydrin is output from the bottom and refluxed back to the distillation column (6). The top of the secondary condenser (8) is provided with a gas phase inlet and is connected to the gas phase outlet of the primary condenser (7) through a pipeline. It is used to feed gas phase material from the primary condenser (7) and perform second-stage condensation on it. The gas phase material containing nitrogen is output from the bottom and the liquid phase material containing water and epichlorohydrin is output from the bottom. The top of the phase separation tank (9) is provided with a liquid phase inlet and is connected to the liquid phase outlet of the secondary condenser (8) through a pipeline. It is used to receive liquid phase material from the secondary condenser (8) and perform oil-water phase separation on it. The liquid phase material is discharged from the bottom water phase outlet, and the oil phase material containing epichlorohydrin is discharged from the bottom oil phase outlet and returned to the distillation column (6).

8. The closed-loop reaction system according to claim 7, characterized in that, The drip holes are multiple and are spaced apart from the first end to the second end at the top of the plug flow reactor (4) for segmented feeding of alkali metal hydroxide solution.

9. The closed-loop reaction system according to claim 7 or 8, characterized in that, The top of the plug flow reactor (4) is also provided with a return port, which is staggered with the drip hole; An epichlorohydrin return pipeline (5) is provided from the liquid phase outlet of the distillation column (6) to the return port of the plug flow reactor (4) for returning the liquid phase material output from the bottom of the distillation column 6 to the plug flow reactor (4).

10. The closed-loop reaction system according to claim 7, characterized in that, The pores are multiple and are spaced apart from the first end to the second end at the bottom of the plug flow reactor (4).

11. The closed-loop reaction system according to claim 10, characterized in that, The bottom of the plug flow reactor (4) is provided with multiple gas distribution pipes (41), and the third feed line (3) is connected to the gas distribution pipes (41) through the air holes.

12. A closed-loop reaction method for the continuous production of glycidyl methacrylate using the closed-loop reaction system as described in any one of claims 7-11.

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