Closed-loop reaction method and system for continuously producing glycidyl methacrylate

Abstract

The invention provides a ring-closing reaction method and a ring-closing reaction system for continuously producing glycidyl methacrylate. The ring-closure reaction method comprises the following steps: feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under the condition of introducing nitrogen, and carrying out ring-closure reaction to generate glycidyl methacrylate. The closed-loop reaction system comprises a plug flow reactor, a rectifying tower, a first-stage condenser, a second-stage condenser, a split-phase tank, a first feeding pipeline, a second feeding pipeline and a third feeding pipeline which are communicated with one another; the plug flow reactor is a tubular reactor, is provided with a dripping hole at the top, a liquid phase inlet at the first end and an air hole at the bottom, and is respectively communicated with first, second and third feeding pipelines; a gas-phase inlet in the lower part of the rectifying tower is connected with the plug flow reactor. According to the closed-loop reaction method and the closed-loop reaction system, the selectivity of the target product can be improved, the number of equipment is reduced, the cost is reduced, and energy is saved.

Description

Technical Field

[0001] The invention belongs to the field of organic matter production, and in particular relates to a closed-loop reaction method and a system for continuously producing glycidyl methacrylate. Background Art

[0002] Glycidyl methacrylate (GMA for short) is a special acrylic ester monomer that has both carbon-carbon double bonds and epoxy groups, making it highly active. Therefore, it is widely used in the field of acrylic resin coatings. It is now mainly used to produce powder coatings, epoxy adhesives, rubber industry, etc. The GMA production processes reported in industry mainly include neutralization condensation, ester exchange, and ring opening and closing.

[0003] Neutralization condensation is the solution currently adopted by most manufacturers. The advantages of this solution are that the catalyst is easy to obtain, the reaction time is short (2-4h), and the yield is high (92-97%); but the whole reaction system has high requirements for water content, and the reaction steps are long, involving dust addition and dust explosion, intermittent operation, and high labor intensity. The ester exchange method uses methyl methacrylate and glycidol as raw materials, which has great advantages in raw material conversion utilization rate and product yield, and has a high atomic utilization rate; but the source of glycidol raw materials is limited, expensive, and toxic. Secondly, the stability of glycidol is poor, and the reaction process is difficult to control. The open-loop closed-loop method is that methacrylic acid and epichlorohydrin are esterified under the action of a catalyst to generate methacrylic acid-2-hydroxy-3-chloropropyl ester (also known as 3-chloro-2-hydroxy-methylacrylate, referred to as CHPMA), and then the generated intermediate is reacted with sodium hydroxide to remove sodium chloride, and the product is refined. The amount of epichlorohydrin used in this solution can be greatly reduced. Compared with the first two intermittent process routes, the open-loop and closed-loop method is a continuous production route with mild reaction conditions and higher safety, which has obvious advantages.

[0004] The closed-loop reaction step of the open-loop closed-loop method for producing GMA reported in CN202211044078 adopts a multi-kettle series connection method, and the water content in the reactor is controlled by a distillation tower connected to the closed-loop reactor. US005245057A adopts a ten-kettle series connection method for GMA closed-loop reaction. The multi-kettle series connection method consumes a large amount of stirring power, and salt is easily deposited in the reactor, requiring regular maintenance, increasing costs, and the reaction effect is still not as good as that of a plug flow reactor. Zong Min et al. ("Process and Kinetic Study on the Preparation of Epichlorohydrin by Cyclization of Dichloropropanol", Guangzhou Chemistry, 2008, 33 (2): 32-36) experimentally verified that chloride salts promote the hydrolysis of epichlorohydrin. Salts in the closed-loop reaction solution are easy to deposit, and an 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. Based on the many problems existing in the closed-loop reaction part of the current open-loop and closed-loop GMA production route, it is urgent to design a new continuous production reactor and reaction process to replace the existing reactor and existing reaction process, so as to achieve continuous and stable production of glycidyl methacrylate in a safer and more environmentally friendly way, while maximizing the selectivity of the reaction target product. Summary of the invention

[0005] The first object of the present invention is to provide a closed-loop reaction method for continuously producing glycidyl methacrylate, which is simple and easy to operate, has high reaction selectivity, reduces moving equipment, and is more energy-efficient in the overall process;

[0006] The second object of the present invention is to provide a closed-loop reaction system for continuously producing glycidyl methacrylate. The closed-loop reaction system has a simple structure and can improve reaction selectivity and reduce moving equipment during use.

[0007] To achieve the first object of the present invention, the following technical solutions are adopted:

[0008] A closed-loop reaction method for continuously producing glycidyl methacrylate comprises feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under the condition of nitrogen gas introduction to carry out a closed-loop reaction to generate glycidyl methacrylate.

[0009] Preferably, the ring-closing reaction method comprises the following steps:

[0010] (1) feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction liquid and an alkali metal hydroxide solution into a plug flow reactor under nitrogen flow to carry out a ring-closing reaction to generate glycidyl methacrylate, and outputting the glycidyl methacrylate reaction liquid and a gas phase material containing epichlorohydrin, water and nitrogen;

[0011] (2) passing the gaseous material output from step (1) into a distillation tower for distillation separation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the top, and outputting a liquid material containing epichlorohydrin from the bottom;

[0012] (3) sending the gaseous material output from step (2) to a primary condenser for first-stage condensation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the bottom, and outputting a liquid material containing epichlorohydrin from the bottom and refluxing to a distillation tower;

[0013] (4) sending the gaseous material output from step (3) to a secondary condenser for second-stage condensation, outputting a gaseous material containing nitrogen from the bottom, and outputting a liquid material containing water and epichlorohydrin from the bottom;

[0014] (5) The liquid phase material output from step (4) is sent to a phase separation tank for oil-water phase separation, the water 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 refluxed to the distillation tower.

[0015] The closed-loop reaction method of the present invention, preferably, in the closed-loop reaction, the alkali metal hydroxide solution is dripped and fed from the top of the plug flow reactor, preferably fed in multiple stages from the first end to the second end of the plug flow reactor; preferably, the feed amount 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 amount; and / or,

[0016] In the ring-closing 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 is introduced from the bottom of the plug flow reactor, preferably in multiple stages from the first end to the second end of the plug flow reactor.

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

[0019] The reaction conditions of the ring-closing 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.

[0020] The ring-closing reaction method of the present invention, preferably, the ring-closing reaction method also includes:

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

[0022] To achieve the second object of the present invention, a closed-loop reaction system for continuously producing glycidyl methacrylate is also provided.

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

[0024] The plug flow reactor is a tubular reactor, with a drip hole on the top, a liquid phase inlet on the first end, a liquid phase overflow port on the second end, and an air hole on the bottom, and the drip hole, the liquid phase inlet and the air hole are respectively connected to the first feed pipeline, the second feed pipeline and the third feed pipeline, and are used to respectively drip feed an alkali metal hydroxide solution from the top, feed 3-chloro-2-hydroxy-methyl methacrylate reaction liquid from the first end, and introduce nitrogen from the bottom, so that when nitrogen is introduced, a ring-closing reaction of the 3-chloro-2-hydroxy-methyl methacrylate reaction liquid and the alkali metal hydroxide occurs to generate glycidyl methacrylate, which is output from the liquid phase overflow port on the second end, and a gaseous material containing epichlorohydrin, water and nitrogen is output from the top;

[0025] The lower part of the distillation tower is provided with a gas phase inlet, and is connected to the gas phase outlet of the plug flow reactor through a pipeline, for feeding the gas phase material from the plug flow reactor and performing distillation separation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the top, and outputting the liquid phase material containing epichlorohydrin 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 tower through a pipeline, and is used to feed the gas phase material from the distillation tower and perform the first stage condensation on it, output the gas phase material containing epichlorohydrin, water and nitrogen from the bottom, and output the liquid phase material containing epichlorohydrin from the bottom and reflux to the distillation tower;

[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, for feeding the gas phase material from the primary condenser and performing the second stage condensation on it, outputting the gas phase material containing nitrogen from the bottom, and outputting the liquid phase material containing water and epichlorohydrin from the bottom;

[0028] A liquid phase inlet is provided at the top of the phase separation tank and is connected to the liquid phase outlet of the secondary condenser through a pipeline, so as to receive the liquid phase material from the secondary condenser and perform oil-water phase separation on it, discharge the water phase material from the bottom water phase outlet, and discharge the oil phase material containing epichlorohydrin from the bottom oil phase outlet and reflux to the distillation tower.

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

[0030] In the closed-loop reaction system of the present invention, preferably, the top of the plug flow reactor is further provided with a return port, and the return port and the drip hole are arranged staggered;

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

[0032] In the closed-loop reaction system of the present invention, preferably, there are a plurality of 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 correspondingly arranged at the bottom of the plug flow reactor, and the third feed pipeline is connected to the gas distribution pipes through the air holes.

[0034] The present invention also provides a closed-loop reaction method for continuously producing glycidyl methacrylate by utilizing the closed-loop reaction system.

[0035] The beneficial effects of the present invention are:

[0036] (1) The closed-loop reaction method and closed-loop reaction system for continuously producing glycidyl methacrylate of the present invention adopt a plug flow reactor, which is a reactor that is more in line with the reaction mechanism of the target reaction, and 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 is more energy-efficient in the overall process; the closed-loop reaction system has a simple structure, can improve reaction selectivity during use, reduces moving equipment, does not need to set up stirring equipment, and reduces costs.

[0037] (2) The closed-loop reaction method and closed-loop reaction system for continuously producing glycidyl methacrylate of the present invention can realize the continuous production of the target product glycidyl methacrylate and can ensure that the closed-loop reaction part thereof is more stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic structural diagram of a closed-loop reaction system for continuously producing glycidyl methacrylate of the present invention in one embodiment;

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

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

[0041] Figure 4 Schematic diagram of the structure of the reaction system used in Comparative Example 1. DETAILED DESCRIPTION

[0042] The technical scheme and its effects of the present invention are further described below in conjunction with specific implementation modes / examples and drawings. The following implementation modes / examples are only used to illustrate the contents of the present invention, and the invention is not limited to the following implementation modes or examples. Simple changes made to the present invention by applying the concept of the present invention are within the scope of protection claimed by the present invention.

[0043] The present invention provides a closed-loop reaction method for continuously producing glycidyl methacrylate, such as Figure 1-3 As shown, the ring-closing reaction method includes feeding 3-chloro-2-hydroxy-propyl methacrylate reaction solution and alkali metal hydroxide solution into a plug flow reactor under the condition of nitrogen gas to carry out a ring-closing reaction to generate glycidyl methacrylate.

[0044] The present invention adopts a plug flow reactor, which is a reactor that is more in line with the reaction mechanism of the target reaction. Its application can further improve the selectivity of the target product, reduce moving equipment and reduce costs.

[0045] Those skilled in the art will appreciate that the 3-chloro-2-hydroxy-propyl methacrylate reaction solution can be prepared by ring-opening reaction of methacrylic acid and epichlorohydrin under catalyst conditions or by other feasible methods, and 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 is used as a reactant to undergo a ring-closing reaction with an alkali metal hydroxide solution to generate glycidyl methacrylate, and the epichlorohydrin is used as a solvent.

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

[0047] In one embodiment, the ring-closing reaction method comprises the following steps:

[0048] (1) feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction liquid and an alkali metal hydroxide solution into a plug flow reactor under nitrogen flow to carry out a ring-closing reaction to generate glycidyl methacrylate, and outputting the glycidyl methacrylate reaction liquid and a gas phase material containing epichlorohydrin, water and nitrogen;

[0049] (2) passing the gaseous material output from step (1) into a distillation tower for distillation separation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the top, and outputting a liquid material containing epichlorohydrin from the bottom (the liquid material output from the bottom of the distillation tower mainly contains epichlorohydrin, with a purity of ≥99%);

[0050] (3) sending the gaseous material output from step (2) to a primary condenser for first-stage condensation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the bottom, and outputting a liquid material containing epichlorohydrin from the bottom (the liquid material output from the bottom of the primary condenser is mainly epichlorohydrin, with a purity of ≥99%) and refluxing to a distillation tower;

[0051] (4) sending the gaseous material output from step (3) to a secondary condenser for second-stage condensation, outputting a gaseous material containing nitrogen from the bottom (the gaseous material output from the bottom of the secondary condenser is mainly nitrogen with a purity of ≥99%), and outputting a liquid material containing water and epichlorohydrin from the bottom;

[0052] (5) The liquid phase material outputted from step (4) is sent to a phase separation tank for oil-water phase separation, and the water phase material is discharged from the bottom water phase outlet (the water 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 refluxed to the distillation tower.

[0053] In the present invention, steps (2) to (5) are mainly for discharging water and nitrogen from the gaseous material generated during the ring-closing reaction and recycling the epichlorohydrin therein.

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

[0055] In one embodiment, in the ring-closing reaction, the concentration of the alkali metal hydroxide solution 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 4, 5, 6, 7, 8, 9, 10 and 11 stages; preferably, the feed amount 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 amount, such as 45%, 50%, 55%, 60%, 65%, 70% and 75%.

[0057] In one embodiment, in the ring-closing reaction, the 3-chloro-2-hydroxy-methylacrylate reaction solution is fed from the first end of the plug flow reactor.

[0058] In one embodiment, in the closed-loop reaction, nitrogen is introduced from the bottom 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 4, 5, 6, 7, 8, 9, 10 and 11 stages.

[0059] In one embodiment, in the ring-closing reaction, the molar ratio of the alkali metal hydroxide to the methacrylic acid group in the reaction solution of 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 of the ring-closing 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°C, such as 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C and 85°C; 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 comprises: returning the liquid phase material output from the distillation tower in step (2) to the plug flow reactor in step (1) for reuse; preferably returning 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; preferably, the return position is alternately arranged with the dropwise feeding position of the alkali metal hydroxide solution.

[0065] Those skilled in the art will appreciate that the liquid material output from the distillation tower in step (2) 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 a subsequent separation stage.

[0066] The invention also provides a closed-loop reaction system for continuously producing glycidyl methacrylate.

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

[0068] The plug flow reactor 4 is a tubular reactor, with a drip hole on the top, a liquid phase inlet on the first end, a liquid phase overflow port on the second end, and an air hole on the bottom, and the drip hole, the liquid phase inlet and the air hole are respectively connected to the first feed pipeline 1, the second feed pipeline 2 and the third feed pipeline 3, for respectively dripping an alkali metal hydroxide solution from the top, feeding a 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid from the first end, and introducing nitrogen from the bottom, so that a ring-closing reaction of the 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid and the alkali metal hydroxide occurs under the condition of introducing nitrogen to generate glycidyl methacrylate, which is output from the liquid phase overflow port on the second end, and a gaseous material containing epichlorohydrin, water and nitrogen is output from the top;

[0069] The lower part of the distillation tower 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, for feeding the gas phase material from the plug flow reactor 4 and performing distillation separation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the top, and outputting the liquid phase material containing epichlorohydrin 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 tower 6 through a pipeline, for feeding the gas phase material from the distillation tower 6 and performing the first stage condensation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the bottom, and outputting the liquid phase material containing epichlorohydrin from the bottom and refluxing to the distillation tower 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, for feeding the gas phase material from the primary condenser 7 and performing the second stage condensation on it, outputting the gas phase material containing nitrogen from the bottom, and outputting the liquid phase material containing water and epichlorohydrin from the bottom;

[0072] A liquid phase inlet is provided at the top of the phase separation tank 9 and is connected to the liquid phase outlet of the secondary condenser 8 through a pipeline, so as to receive the liquid phase material from the secondary condenser 8 and perform oil-water phase separation on it, discharge the water phase material from the bottom water phase outlet, and discharge the oil phase material containing epichlorohydrin from the bottom oil phase outlet and reflux to the distillation tower 6.

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

[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 feeding the alkali metal hydroxide solution in stages; preferably, there are 3-12 drip holes, such as 4, 5, 6, 7, 8, 9, 10 and 11, for feeding the alkali metal hydroxide solution in multiple stages.

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

[0076] Those skilled in the art understand that the liquid material output from the distillation tower 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 the subsequent separation stage.

[0077] In one embodiment, there are multiple return ports, and they are spaced apart from the first end to the second end at the top of the plug flow reactor 4, so as to return the liquid-phase material output from the bottom of the distillation tower 6 to the plug flow reactor 4 in stages; 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, so as to return the liquid-phase material output from the bottom of the distillation tower 6 to the plug flow reactor 4 in multiple stages.

[0078] In one embodiment, there are multiple pores, and they 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 pores, so as to introduce nitrogen in stages.

[0079] In one embodiment, a plurality of gas distribution pipes 41 are correspondingly arranged at the bottom of the plug flow reactor 4, and the third feed pipeline 3 is connected to the gas distribution pipe 41 through the air hole, so that nitrogen is introduced from the bottom for bubbling to promote reaction mixing and mass transfer, and avoid salt deposition in the plug flow reactor 4.

[0080] Those skilled in the art will appreciate that the reactors generally used in the prior art are multiple kettles connected in series and equipped with a stirrer device for stirring, which requires more power equipment, consumes a lot of energy and has a high cost. The present invention adopts a plug flow reactor 4 and introduces nitrogen from the bottom thereof for bubbling to avoid mechanical stirring, which can not only improve the selectivity of the reaction, but also reduce power equipment, energy consumption and cost.

[0081] In one embodiment, a gas distribution hole is opened on the tube wall of the gas distribution pipe 41. Preferably, there are multiple gas distribution holes, and they are evenly dispersed on the tube wall of the gas distribution pipe 41. Preferably, the gas distribution holes are opened on the tube wall of the gas distribution pipe 41 along different directions.

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

[0083] In one embodiment, in the plug flow reactor 4, the liquid phase feed port is higher than the liquid phase overflow port.

[0084] In one embodiment, the distillation tower 6 has a theoretical plate number of 5-25, such as 10, 15 and 20.

[0085] The present invention also provides a closed-loop reaction method for continuously producing glycidyl methacrylate by utilizing the closed-loop reaction system.

[0086] like Figure 1-3 As shown, the closed-loop reaction method for continuously producing glycidyl methacrylate using the closed-loop reaction system is as follows:

[0087] (1) feeding the 3-chloro-2-hydroxy-propyl methacrylate reaction liquid from the liquid phase inlet of the first end of the plug flow reactor 4 through the second feeding pipeline 2, and dripping the alkali metal hydroxide solution from the dripping hole at the top of the plug flow reactor 4 through the first feeding pipeline 1, and simultaneously introducing nitrogen from the pores at the bottom of the plug flow reactor 4 and the gas distribution pipe 41 through the third feeding pipeline 3, thereby feeding the 3-chloro-2-hydroxy-propyl methacrylate reaction liquid and the alkali metal hydroxide solution into the plug flow reactor under the condition of nitrogen being introduced to carry out a closed-loop reaction to generate glycidyl methacrylate, and outputting the glycidyl methacrylate reaction liquid and a gas phase material containing epichlorohydrin, water and nitrogen;

[0088] (2) passing the gaseous material outputted from step (1) into a distillation tower for distillation separation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the top, and outputting a liquid material containing epichlorohydrin from the bottom; returning the liquid material outputted from the bottom of the distillation tower 6 from the top to the plug flow reactor 4 through the epichlorohydrin return pipeline 5;

[0089] (3) sending the gaseous material output from step (2) to a primary condenser for first-stage condensation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the bottom, and outputting a liquid material containing epichlorohydrin from the bottom and refluxing to a distillation tower;

[0090] (4) sending the gaseous material output from step (3) to a secondary condenser for second-stage condensation, outputting a gaseous material containing nitrogen from the bottom, and outputting a liquid material containing water and epichlorohydrin from the bottom;

[0091] (5) The liquid phase material output from step (4) is sent to a phase separation tank for oil-water phase separation, the water 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 refluxed to the distillation tower.

[0092] The closed-loop reaction method and closed-loop reaction system for continuously producing glycidyl methacrylate of the present invention adopt a plug flow reactor, which is a reactor that is more in line with the reaction mechanism of the target reaction. The application of the plug flow reactor can further improve the selectivity of the target product, reduce moving equipment, reduce costs, and achieve continuous production of the target product glycidyl methacrylate, and ensure that the closed-loop reaction part thereof is more stable and reliable; the closed-loop reaction method is simple and easy to operate, has high reaction selectivity, reduces moving equipment, and is more energy-efficient in the overall process; the closed-loop reaction system has a simple structure, can improve reaction selectivity during use, reduces moving equipment, does not need to set stirring equipment, and reduces costs.

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

[0094] A 3-chloro-2-hydroxy-propyl methacrylate reaction solution, which contains, by mole percentage, 4.8% of 3-chloro-2-hydroxy-propyl methacrylate, 5.2% of glycidyl methacrylate and 90% of 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 method:

[0100] The 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 continuously producing glycidyl methacrylate shown comprises a plug flow reactor 4, a distillation column 6, a primary condenser 7, a secondary condenser 8 and a phase separation tank 9, as well as a first feed pipeline 1, a second feed pipeline 2 and a third feed pipeline 3, which are connected by pipelines;

[0103] The plug flow reactor 4 is a tubular reactor, the top of which is provided with 7 drip holes spaced from the first end to the second end, the first end of which is provided with a liquid phase inlet, and the bottom of which is provided with 7 air holes spaced from the first end to the second end, and the drip holes, the liquid phase inlet and the air holes are respectively connected to the first feed pipeline 1, the second feed pipeline 2 and the third feed pipeline 3, for respectively dripping the alkali metal hydroxide solution from the top section, feeding the 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid from the first end, and introducing nitrogen from the bottom, so that the 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid and the alkali metal hydroxide undergo a ring-closing reaction to generate methacrylic acid when the nitrogen is introduced. Glycidyl ester is output from the liquid phase overflow port at the second end, and the gas phase material containing epichlorohydrin, water and nitrogen is output from the top; wherein, 7 gas distribution pipes 41 are correspondingly arranged at the bottom of the plug flow reactor 4, and the third feed pipeline 3 is connected to the gas distribution pipe 41 through the air hole; gas distribution holes with different directions are evenly opened on the tube wall of the gas distribution pipe 41; the top of the plug flow reactor 4 is also provided with 7 return ports spaced from the first end to the second end, and the return ports and the drip holes are alternately arranged; in the plug flow reactor 4, its liquid phase feed port is higher than its liquid phase overflow port; an outer jacket 42 is provided on the outer wall of the lower part of the plug flow reactor 4;

[0104] The lower part of the distillation tower 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, for feeding the gas phase material from the plug flow reactor 4 and performing distillation separation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the top, and outputting the liquid phase material containing epichlorohydrin from the bottom; the theoretical plate number of the distillation tower 6 is 8; an epichlorohydrin return pipeline 5 is provided from the liquid phase outlet of the distillation tower 6 to the return port of the plug flow reactor 4, for returning the liquid phase material output from the bottom of the distillation tower 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 tower 6 through a pipeline, for feeding the gas phase material from the distillation tower 6 and performing the first stage condensation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the bottom, and outputting the liquid phase material containing epichlorohydrin from the bottom and refluxing to the distillation tower 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, for feeding the gas phase material from the primary condenser 7 and performing the second stage condensation on it, outputting the gas phase material containing nitrogen from the bottom, and outputting the liquid phase material containing water and epichlorohydrin from the bottom;

[0107] A liquid phase inlet is provided at the top of the phase separation tank 9 and is connected to the liquid phase outlet of the secondary condenser 8 through a pipeline, so as to receive the liquid phase material from the secondary condenser 8 and perform oil-water phase separation on it, discharge the water phase material from the bottom water phase outlet, and discharge the oil phase material containing epichlorohydrin from the bottom oil phase outlet and reflux to the distillation tower 6.

[0108] The closed-loop reaction method for continuously producing glycidyl methacrylate using the closed-loop reaction system A1 comprises the following steps:

[0109] (1) feeding the 3-chloro-2-hydroxy-propyl methacrylate reaction liquid from the liquid phase inlet of the first end of the plug flow reactor 4 through the second feeding pipeline 2, and dripping the alkali metal hydroxide solution from the dripping hole at the top of the plug flow reactor 4 in 7 sections through the first feeding pipeline 1, and at the same time, introducing nitrogen from the pores at the bottom of the plug flow reactor 4 and the gas distribution pipe 41 in 7 sections through the third feeding pipeline 3, so that the 3-chloro-2-hydroxy-propyl methacrylate reaction liquid and the alkali metal hydroxide solution are fed into the plug flow reactor under the condition of nitrogen being introduced to carry out a closed-loop reaction to generate glycidyl methacrylate, and outputting the glycidyl methacrylate reaction liquid B1 and a gas phase material containing epichlorohydrin, water and nitrogen;

[0110] (2) passing the gaseous material outputted from step (1) into a distillation tower for distillation separation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the top, and outputting a liquid material containing epichlorohydrin from the bottom; returning the liquid material outputted from the bottom of the distillation tower 6 from the top section 7 to the plug flow reactor 4 through the epichlorohydrin return pipeline 5;

[0111] (3) sending the gaseous material output from step (2) to a primary condenser for first-stage condensation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the bottom, and outputting a liquid material containing epichlorohydrin from the bottom and refluxing to a distillation tower;

[0112] (4) sending the gaseous material output from step (3) to a secondary condenser for second-stage condensation, outputting a gaseous material containing nitrogen from the bottom, and outputting a liquid material containing water and epichlorohydrin from the bottom;

[0113] (5) sending the liquid phase material output from step (4) to a phase separation tank for oil-water phase separation, discharging the water phase material from the bottom water phase outlet, discharging the oil phase material containing epichlorohydrin from the bottom oil phase outlet and refluxing to the distillation tower; wherein,

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

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

[0116] In step (1), an alkali metal hydroxide solution is added dropwise to the plug flow reactor from the first end to the second end of the top of the plug flow reactor in 7 sections according to 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 and measured to determine the selectivity of glycidyl methacrylate. The measurement results are shown in Table 1.

[0118] Embodiment 2 (S2)

[0119] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 50 wt% NaOH aqueous solution;

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

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

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

[0124] Embodiment 3 (S3)

[0125] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 30 wt % NaOH aqueous solution;

[0127] In step (1), the alkali metal hydroxide solution is evenly added dropwise into the plug flow reactor from the dripping hole at the top of the plug flow reactor 4 in 7 sections;

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

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

[0130] Embodiment 4 (S4)

[0131] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 50 wt% NaOH aqueous solution;

[0133] In step (1), the alkali metal hydroxide solution is evenly added dropwise into the plug flow reactor from the dripping hole at the top of the plug flow reactor 4 in 7 sections;

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

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

[0136] Embodiment 5 (S5)

[0137] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 50 wt% NaOH aqueous solution;

[0139] In step (1), the alkali metal hydroxide solution is evenly added dropwise into the plug flow reactor from the dripping hole at the top of the plug flow reactor 4 in 7 sections;

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

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

[0142] Embodiment 6 (S6)

[0143] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing reaction method described in Example 1 only in that:

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

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

[0146] In step (1), the alkali metal hydroxide solution is evenly added dropwise into the plug flow reactor from the dripping hole at the top of the plug flow reactor 4 in 7 sections;

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

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

[0149] Embodiment 7 (S7)

[0150] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing reaction method described in Example 1 only in that:

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

[0152] In step (1), an alkali metal hydroxide solution is added dropwise to the plug flow reactor from the first end to the second end of the top of the plug flow reactor in 7 sections according to a mass ratio of 2:2:2:1:1:1:1;

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

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

[0155] Embodiment 8 (S8)

[0156] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 50 wt% NaOH aqueous solution;

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

[0159] In step (1), an alkali metal hydroxide solution is added dropwise to the plug flow reactor from the first end to the second end of the top of the plug flow reactor in 7 sections according to a mass ratio of 2:2:2:1:1:1:1;

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

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

[0162] Embodiment 9 (S9)

[0163] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 50 wt% NaOH aqueous solution;

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

[0166] In step (1), an alkali metal hydroxide solution is added dropwise to the plug flow reactor from the first end to the second end of the top of the plug flow reactor in 7 sections according to a mass ratio of 2:2:2:1:1:1:1;

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

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

[0169] Embodiment 10 (S10)

[0170] The ring-closing reaction method for continuously producing glycidyl methacrylate using the above-mentioned ring-closing reaction system A1 is different from the ring-closing 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 30 wt % NaOH aqueous solution;

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

[0173] In step (1), an alkali metal hydroxide solution is added dropwise to the plug flow reactor from the first end to the second end of the top of the plug flow reactor in 7 sections according to a mass ratio of 2:2:2:1:1:1:1;

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

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

[0176] Comparative Example 1 (D1)

[0177] Use Figure 4The system shown in the figure adopts a continuous reactor 4' with a baffle 3' (the number of baffles is 5), and a negative pressure is drawn on the continuous reactor 4' to control the pressure in the continuous reactor 4' to be 12 kPaA, and the 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid is fed into the continuous reactor 4' from the liquid phase inlet of the first end thereof along the second feed pipeline 2', and a 50 wt % NaOH aqueous solution (alkali metal hydroxide solution) is evenly added dropwise from the drip hole on the top thereof along the first feed pipeline 1' in 6 sections to generate a closed-loop reaction to generate glycidyl methacrylate, which is discharged from the liquid phase overflow port at the second end, and the molar ratio of the alkali metal hydroxide to the methacrylic acid group in the 3-chloro-2-hydroxy-methacrylate propyl ester reaction liquid is 1.04:1, and the temperature of the reaction liquid is controlled to be 45°C, The reaction liquid stays in the continuous reactor 4' for 10 hours. The gaseous material containing epichlorohydrin and water outputted from the continuous reactor 4' is passed into a distillation tower 6' (with 10 plates) for distillation separation. The gaseous material containing epichlorohydrin and water is outputted from the top, and the liquid material containing epichlorohydrin is outputted from the bottom and returned to the continuous reactor 4' from the top of the first end of the continuous reactor 4' through an epichlorohydrin return pipeline 5'; the gaseous material outputted from the distillation tower 6' is sent to a condenser 7' (with -15°C ethylene glycol aqueous solution as its condensation medium) for condensation and phase separation, water is discharged, and epichlorohydrin is refluxed to the distillation tower 6'; after the NaOH aqueous solution is added dropwise, the reaction is terminated, and a glycidyl methacrylate reaction liquid B1' is outputted.

[0178] The obtained glycidyl methacrylate reaction solution B1' was analyzed and measured to determine the selectivity of glycidyl methacrylate. The measurement 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 and measured to obtain the selectivity data of glycidyl methacrylate. The analysis and measurement results are shown in Table 1.

[0181] Table 1 Selectivity of glycidyl methacrylate

[0182] Example Selectivity of glycidyl methacrylate (wt%) 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] According to Table 1, in the ring-closing reaction methods of Examples 1-10, the selectivity of glycidyl methacrylate is greater than 97.62 wt %, which is significantly improved compared with Comparative Example 1.

[0184] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications and adjustments may be made to the present invention. These modifications and adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A ring-closing reaction method for continuously producing glycidyl methacrylate, characterized in that: The ring-closing reaction method comprises feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction solution and an alkali metal hydroxide solution into a plug flow reactor under the condition of introducing nitrogen gas to carry out a ring-closing reaction to generate glycidyl methacrylate.

2. The closed-loop reaction method according to claim 1, characterized in that: The closed-loop reaction method comprises the following steps: (1) feeding a 3-chloro-2-hydroxy-propyl methacrylate reaction liquid and an alkali metal hydroxide solution into a plug flow reactor under nitrogen flow to carry out a ring-closing reaction to generate glycidyl methacrylate, and outputting the glycidyl methacrylate reaction liquid and a gas phase material containing epichlorohydrin, water and nitrogen; (2) passing the gaseous material output from step (1) into a distillation tower for distillation separation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the top, and outputting a liquid material containing epichlorohydrin from the bottom; (3) sending the gaseous material output from step (2) to a primary condenser for first-stage condensation, outputting a gaseous material containing epichlorohydrin, water and nitrogen from the bottom, and outputting a liquid material containing epichlorohydrin from the bottom and refluxing to a distillation tower; (4) sending the gaseous material output from step (3) to a secondary condenser for second-stage condensation, outputting a gaseous material containing nitrogen from the bottom, and outputting a liquid material containing water and epichlorohydrin from the bottom; (5) The liquid phase material output from step (4) is sent to a phase separation tank for oil-water phase separation, the water 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 refluxed to the distillation tower.

3. The ring-closing reaction method according to claim 1 or 2, characterized in that: 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, the amount of the alkali metal hydroxide solution fed from the first end to the middle of the plug flow reactor is 40-80% of the total feed amount; and / or, In the ring-closing reaction, the 3-chloro-2-hydroxy-propyl methacrylate reaction solution is fed from the first end of the plug flow reactor; and / or, In the closed-loop reaction, nitrogen is introduced from the bottom of the plug flow reactor, preferably in multiple stages from the first end to the second end of the plug flow reactor.

4. The ring-closing reaction method according to any one of claims 1 to 3, characterized in that: In the ring-closing reaction, the molar ratio of the alkali metal hydroxide to the methacrylic acid group in the reaction solution of 3-chloro-2-hydroxy-propyl methacrylate is (0.9-1.4):1; and / or, The reaction conditions of the ring-closing 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 comprises: returning the liquid phase material output from the distillation tower in step (2) to the plug flow reactor in step (1); preferably, returning the liquid phase material in multiple stages from the first end to the second end of the plug flow reactor.

6. A closed-loop reaction system for continuously producing glycidyl methacrylate, characterized in that: The closed-loop reaction system comprises a plug flow reactor (4), a distillation tower (6), a primary condenser (7), a secondary condenser (8) and a phase separation tank (9) which are connected by pipelines, and a first feed pipeline (1), a second feed pipeline (2) and a third feed pipeline (3); The plug flow reactor (4) is a tubular reactor, the top of which is provided with a drip hole, the first end of which is provided with a liquid phase inlet, the second end of which is provided with a liquid phase overflow port, and the bottom of which is provided with an air hole, and the drip hole, the liquid phase inlet and the air hole are respectively connected to the first feed pipeline (1), the second feed pipeline (2) and the third feed pipeline (3), and are used to respectively drip feed an alkali metal hydroxide solution from the top, feed 3-chloro-2-hydroxy-methyl methacrylate reaction liquid from the first end, and introduce nitrogen from the bottom, so that when nitrogen is introduced, a ring-closing reaction of the 3-chloro-2-hydroxy-methyl methacrylate reaction liquid and the alkali metal hydroxide occurs to generate glycidyl methacrylate, which is output from the liquid phase overflow port at the second end, and a gaseous material containing epichlorohydrin, water and nitrogen is output from the top; The lower part of the distillation tower (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, for feeding the gas phase material from the plug flow reactor (4) and performing distillation separation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the top, and outputting the liquid phase material containing epichlorohydrin 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 tower (6) through a pipeline, for feeding the gas phase material from the distillation tower (6) and performing the first stage condensation on it, outputting the gas phase material containing epichlorohydrin, water and nitrogen from the bottom, and outputting the liquid phase material containing epichlorohydrin from the bottom and refluxing it to the distillation tower (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, for feeding the gas phase material from the primary condenser (7) and performing a second-stage condensation on the gas phase material, outputting the gas phase material containing nitrogen from the bottom, and outputting the liquid phase material containing water and epichlorohydrin from the bottom; The phase separation tank (9) is provided with a liquid phase inlet at the top thereof, and is connected to the liquid phase outlet of the secondary condenser (8) through a pipeline, so as to receive the liquid phase material from the secondary condenser (8) and separate the liquid phase material into oil and water phases, discharge the water phase material from the bottom water phase outlet, and discharge the oil phase material containing epichlorohydrin from the bottom oil phase outlet and reflux to the distillation tower (6).

7. The closed-loop reaction system according to claim 6, characterized in that: There are a plurality of drip holes, which are arranged at intervals from the first end to the second end at the top of the plug flow reactor (4) and are used for feeding the alkali metal hydroxide solution in stages.

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

9. The closed-loop reaction system according to any one of claims 6 to 8, characterized in that: There are a plurality of pores, which are arranged at intervals from the first end to the second end at the bottom of the plug flow reactor (4); Preferably, a plurality of gas distribution pipes (41) are correspondingly arranged at the bottom of the plug flow reactor (4), and the third feed pipeline (3) is connected to the gas distribution pipes (41) through the gas holes.

10. A ring-closing reaction method for continuously producing glycidyl methacrylate using the ring-closing reaction system as claimed in any one of claims 6 to 9.

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