A counterflow three-stage methyl acrylate production reaction device and method

Abstract

The present application relates to a kind of countercurrent three-stage methyl acrylate production reaction device and method, it is related to chemical synthesis field, including two groups by upper cavity, middle cavity and lower cavity composition reaction tank and located in the upper cavity temperature control device and middle cavity temperature control device of reaction tank, upper cavity is preheated to 65~70 ℃ by being connected with upper cavity temperature control device, acrylic acid and methanol are all input into upper cavity, middle cavity is located in the lower end of upper cavity and is communicated, catalyst is stored in middle cavity, and nitrogen is passed, middle cavity temperature control device is communicated with middle cavity to make the temperature in middle cavity keep 75 ℃, lower cavity is located in the lower end of middle cavity and is communicated, lower cavity absorbs moisture generated by reaction and exports product to device outside, the present application has the advantages of effectively improving production efficiency.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a countercurrent three-stage methyl acrylate production reactor and method. Background Technology

[0002] In the coatings industry, methyl acrylate can be used to manufacture methyl acrylate-vinyl acetate-styrene terpolymers, acrylic coatings, and floor polishes; in the rubber industry, it can be used to manufacture high-temperature resistant and oil-resistant rubbers; in the organic industry, it can be used as an organic synthesis intermediate and in the manufacture of activators and adhesives; in the plastics industry, it can be used as a monomer for synthetic resins; and in the chemical fiber industry, copolymerization with acrylonitrile can improve the spinnability, thermoplasticity, and dyeing properties of acrylonitrile.

[0003] The esterification reaction of acrylic acid and methanol is the main method for preparing methyl acrylate. This reaction is reversible. To improve production efficiency, it is necessary to take measures to suppress side reactions. The usual practice is to allow one reactant to be in excess or to remove the product causing the reverse reaction from the reaction system in a timely manner. However, the above practices result in high material consumption and difficulty in removing by-products, leading to generally low product yields.

[0004] Therefore, to address the above shortcomings, there is a need to provide a countercurrent three-stage methyl acrylate production reactor and method. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by the present invention is to address the low product yield of current esterification reaction methods.

[0007] (II) Technical Solution

[0008] To solve the above-mentioned technical problems, the present invention provides a countercurrent three-stage methyl acrylate production reaction device, comprising two sets of reaction tanks consisting of an upper chamber, a middle chamber, and a lower chamber, and an upper chamber temperature control device and a middle chamber temperature control device located outside the reaction tanks. The upper chamber is preheated to 65-70°C by being connected to the upper chamber temperature control device. Acrylic acid and methanol are both introduced into the upper chamber. The middle chamber is located at the lower end of the upper chamber and is connected to it. The middle chamber contains a catalyst and is supplied with nitrogen gas. The middle chamber temperature control device is connected to the middle chamber to maintain the temperature inside the middle chamber at 75°C. The lower chamber is located at the lower end of the middle chamber and is connected to it. The lower chamber absorbs the moisture generated during the reaction and outputs the product outside the device.

[0009] As a further explanation of the present invention, preferably, an upper cavity baffle is provided at the upper part of the upper cavity, the upper cavity baffle has holes, and the upper cavity baffle covers the upper cavity discharge pipe.

[0010] As a further explanation of the present invention, preferably, a plurality of ultrasonic low-frequency vibration devices are provided in the upper cavity, the middle cavity and the lower cavity.

[0011] As a further explanation of the present invention, preferably, water-absorbing molecular sieves are provided in the upper cavity and the lower cavity.

[0012] This invention also provides a countercurrent three-stage method for producing methyl acrylate, comprising the following steps:

[0013] Ⅰ. Start the upper chamber temperature control device to pump temperature control liquid into the upper chamber and preheat the upper chamber to 65-75℃. Pass the preheated acrylic acid and methanol into the water-absorbing molecular sieve. After the acrylic acid and methanol are mixed, the upper chamber temperature is maintained at 75℃ by the upper chamber temperature control device, and the mixture of acrylic acid and methanol is passed into the middle chamber.

[0014] II. While the upper cavity is preheating, the middle cavity temperature control device is also activated to preheat the middle cavity and bring the temperature inside the middle cavity to 75°C. The middle cavity receives the mixed liquid introduced from the upper cavity. The mixed liquid reacts with the catalyst. The exothermic reaction is discharged by the middle cavity temperature control device to keep the temperature inside the middle cavity at 75°C. The ultrasonic low-frequency vibration device is turned on to vibrate the catalyst. Nitrogen gas is introduced into the middle cavity during the reaction to prevent the reactants in the reaction liquid from polymerizing, suppress side reactions, and reduce the yield of heavy components.

[0015] Ⅲ. The reaction liquid in the middle cavity flows into the water-absorbing molecular sieve in the lower cavity, and then flows into the upper cavity for further reaction;

[0016] IV. When the reaction time of the reaction liquid reaches the set value, the reaction liquid is discharged from the tank through the lower chamber. After passing through the acrylic acid recovery, alcohol extraction recovery, alcohol distillation and ester refining processes in sequence, qualified products are produced.

[0017] As a further explanation of the present invention, preferably, the feed molar mass ratio of acrylic acid to methanol is (4-6):(3-5).

[0018] As a further explanation of the present invention, preferably, the upper cavity, middle cavity and lower cavity all have liquid entering at the lower end and liquid exiting at the upper end.

[0019] As a further explanation of the present invention, preferably, the nitrogen gas pressure introduced into the middle cavity is 0.05MPa to 0.2MPa.

[0020] As a further explanation of the present invention, preferably, the ultrasonic low-frequency vibration device vibrates at intervals of 5 to 10 minutes after feeding.

[0021] As a further explanation of the present invention, preferably, the water-absorbing molecular sieves in the upper and lower chambers are periodically heated, dehydrated, and regenerated to prevent clogging of the molecular sieves.

[0022] (III) Beneficial Effects

[0023] The above-described technical solution of the present invention has the following advantages:

[0024] The reaction of this invention uses a resin catalyst with high porosity, which easily promotes the positive chemical reaction and inhibits the rate of the reverse reaction and side reaction; and the use of ultrasonic interval vibration reduces problems such as internal channeling and local overheating caused by molecular sieve and catalyst accumulation, thus maintaining the stability of conversion rate and selectivity. Attached Figure Description

[0025] Figure 1 This is a simplified diagram of the device of the present invention.

[0026] In the diagram: 1. Upper cavity; 11. Upper cavity baffle; 12. Upper cavity water-absorbing molecular sieve; 13. Upper cavity ultrasonic low-frequency vibration device; 2. Middle cavity; 21. Middle cavity ultrasonic low-frequency vibration device; 22. Middle cavity feed pipe; 23. Middle cavity discharge pipe; 24. Middle cavity baffle; 3. Lower cavity; 31. Lower cavity water-absorbing molecular sieve; 32. Lower cavity ultrasonic low-frequency vibration device; 33. Lower cavity feed pipe; 34. Lower cavity discharge pipe; 35. Lower cavity baffle; 4. Upper cavity temperature control device; 41. Upper cavity temperature-controlled liquid feed pipe; 42. Upper cavity temperature-controlled liquid discharge pipe; 5. Middle cavity temperature control device; 51. Middle cavity temperature-controlled liquid feed pipe; 52. Middle cavity temperature-controlled liquid discharge pipe; 6. Acrylic acid feed line; 7. Methanol feed line. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] A countercurrent three-stage methyl acrylate production reactor, such as Figure 1 As shown, the reaction vessel includes two sets of reaction vessels consisting of an upper chamber 1, a middle chamber 2, and a lower chamber 3, and upper chamber temperature control devices 4 and 5 located outside the reaction vessels. The effective volume ratio of the three chambers (upper chamber 1, middle chamber 2, and lower chamber 3) is 1.2:1:1.6. The upper chamber 1 is preheated by being connected to the upper chamber temperature control device 4. Acrylic acid and methanol are both introduced into the upper chamber 1. The middle chamber 2 is located at the lower end of the upper chamber 1 and is connected to it. The middle chamber 2 contains the catalyst and is supplied with nitrogen gas. The middle chamber temperature control device 5 is connected to the middle chamber 2 to maintain the temperature inside the middle chamber 2 at 75°C. The lower chamber 3 is located at the lower end of the middle chamber 2 and is connected to it. The lower chamber 3 absorbs the moisture produced by the reaction and outputs the product outside the device.

[0029] like Figure 1 As shown, the upper chamber 1 is mainly used for preheating and mixing reactants, providing initial heat energy for the esterification reaction. From top to bottom, it consists of: an upper chamber discharge pipe, an upper chamber baffle plate 11, an upper chamber water-absorbing molecular sieve 12, an upper chamber manhole, an upper chamber ultrasonic low-frequency vibration device 13, and an upper chamber feed pipe bundle. The upper chamber baffle plate 11 has perforations that completely enclose the discharge port of the upper chamber discharge pipe within the upper chamber. The perforation diameter is smaller than that of the molecular sieve, used to maintain the overflow liquid level in the upper chamber and ensure uniform liquid discharge. The upper chamber ultrasonic low-frequency vibration device 13 vibrates every 5-10 minutes after feeding to prevent molecular sieve clumping and maintain uniform liquid dispersion. The upper chamber manhole is equipped with a viewing window for easy observation of the chamber interior.

[0030] like Figure 1 As shown, the central cavity 2 contains the catalyst and is the main reaction part of the reactor. Besides the catalyst, from top to bottom, it consists of: a central cavity exhaust pipe, a central cavity discharge pipe 23, a central cavity baffle plate 24, a central cavity manhole, a central cavity ultrasonic low-frequency vibration device 21, a central cavity bottom air inlet pipe, and a central cavity feed pipe 22. During the heat treatment or sulfidation of the catalyst in the central cavity, the valves of the central cavity temperature-controlled liquid feed pipe 51 and the central cavity temperature-controlled liquid discharge pipe 52 are first closed, while the valves of the central cavity heating medium feed pipe and the central cavity heating medium discharge pipe are opened, allowing the central cavity heating medium to heat treat or sulfidate the catalyst. The central cavity ultrasonic low-frequency vibration device 21 vibrates every 5-10 minutes after feeding to prevent catalyst agglomeration and maintain uniform catalyst dispersion. The central cavity baffle plate 24 is wrapped around the outlet inside the central cavity discharge pipe 23 to maintain the overflow liquid level in the central cavity. The central cavity manhole is equipped with a viewing window for easy observation of the internal conditions.

[0031] like Figure 1 As shown, the lower chamber 3 is filled with a water-absorbing molecular sieve, mainly used to absorb the water produced by the esterification reaction. From top to bottom, it consists of: lower chamber outlet pipe 34, lower chamber baffle 35, lower chamber water-absorbing molecular sieve 31, lower chamber manhole, lower chamber ultrasonic low-frequency vibration device 32, and lower chamber feed pipe 33. The jacket of the lower chamber water-absorbing molecular sieve 12 has a partition in the middle, which is connected by two rows of central heat exchange pipes. During regeneration, the heating medium enters the jacket through the lower chamber molecular sieve regeneration heating medium feed pipe, fills the other side of the jacket through the central heat exchange pipe, and removes the gas accumulated in the dead corner of the jacket through the lower chamber jacket temperature control and exhaust valve. The heat-exchanged medium is sent out for reheating and circulation through the lower chamber molecular sieve regeneration heating medium outlet pipe.

[0032] like Figure 1As shown, the upper chamber temperature control device 4 consists of an upper chamber temperature control device, an upper chamber temperature control liquid inlet pipe 41, an upper chamber temperature control liquid outlet pipe 42, and an upper chamber jacket temperature regulating and exhaust valve. The jacket has a partition in the middle, which is connected by three rows of central heat exchange pipes. Exhaust is carried out through the upper chamber jacket temperature regulating and exhaust valve. When the upper chamber molecular sieve is heated and regenerated, the valves of the upper chamber temperature control liquid inlet pipe 41 and the upper chamber temperature control liquid outlet pipe 42 are closed first, and the valves of the upper chamber regeneration heating medium inlet pipe and the upper chamber regeneration heating medium outlet pipe are opened. The molecular sieve is heated and regenerated by the high-temperature regeneration heating medium.

[0033] like Figure 1 As shown, the central cavity temperature control device 5 consists of a central cavity temperature control device, a central cavity temperature control liquid inlet pipe 51, a central cavity temperature control liquid outlet pipe 52, and a central cavity jacket temperature regulating and exhaust valve. The jacket has a partition in the middle, which is connected by three rows of central heat exchange pipes. Exhaust is carried out through the central cavity jacket temperature regulating and exhaust valve.

[0034] This invention also provides a countercurrent three-stage method for producing methyl acrylate, the specific steps of which are as follows:

[0035] (1) Feeding and preheating of the upper chamber of the reactor

[0036] Reactor upper chamber preheating: The upper chamber temperature control device is activated, and the temperature-controlled liquid is pumped into the upper chamber temperature-controlled jacket through the upper chamber temperature-controlled liquid inlet pipe 41. The jacket, which is separated in the middle, is filled through the heat exchange pipe in the middle of the chamber, and the gas accumulated in the dead corners is discharged through the upper chamber jacket temperature-adjusting exhaust valves at the four corners, preheating the upper chamber to 65-70℃. After preheating to the set temperature, the reactor is fed. The temperature-controlled liquid is circulated back to the upper chamber temperature control device for reheating through the upper chamber temperature-controlled liquid outlet pipe 42.

[0037] Acrylic acid, preheated to 65-70°C, enters the upper chamber water-absorbing molecular sieve 12 via acrylic acid feed line 6. Methanol, preheated to 65-70°C, enters the upper chamber water-absorbing molecular sieve 12 via methanol feed line 7. The feed molar mass ratio of acrylic acid to methanol is (4-6):(3-5). After the mixed reaction liquid reaches the set liquid level, the process is paused, and the operating parameters of the upper chamber temperature control device are quickly adjusted to normal operating parameters to raise the temperature of the mixed reaction material to 75°C. After starting the feed pump, the mixed reaction liquid enters the upper chamber discharge pipe via the upper chamber baffle 11, maintaining the temperature of the reaction material outlet at the upper chamber discharge pipe at no less than 75°C. After adsorption by the upper chamber water-absorbing molecular sieve 12, the moisture content of the reactants can be initially reduced, providing initial heat energy for the reaction.

[0038] (2) Preheating of reactor cavity and feed reaction

[0039] While feeding into the upper chamber, the reactor middle chamber is preheated: the middle chamber temperature control device is activated, and the temperature control liquid is pumped into the middle chamber temperature control jacket through the middle chamber temperature control liquid feed pipe 51. The jacket, which is separated in the middle, is filled through the heat exchange pipe in the middle chamber, and the gas accumulated in the dead corners is discharged through the temperature adjustment and exhaust valves of the middle chamber jacket at the four corners, preheating the middle chamber to 75°C. After preheating to the set temperature, the upper chamber overflows and feeds the temperature control liquid. The temperature control liquid is circulated back to the middle chamber temperature control device through the middle chamber temperature control liquid discharge pipe 52 for reheating.

[0040] The reaction liquid from the upper chamber enters the catalyst bed through the middle chamber feed pipe 22 and the middle chamber ultrasonic low-frequency vibration device 21, and the temperature rises for reaction. At the same time as feeding, the operating parameters of the middle chamber temperature control device are adjusted to the normal value to promptly discharge the exothermic reaction and maintain the temperature of the middle chamber of the reactor at 75°C. When the reaction liquid reaches half the volume of the middle chamber, the middle chamber air pump is started to fill the chamber with high-purity nitrogen. The high-purity nitrogen enters the catalyst bed of the middle chamber through the middle chamber air inlet pipeline and the bottom air inlet pipe of the middle chamber to prevent the polymerization of reactants, suppress side reactions, and reduce the yield of heavy components. By combining with the middle chamber exhaust pipe, a slightly positive pressure state is maintained in the middle chamber of the reactor, preferably 0.05-0.2 MPa. The reaction liquid overflows through the middle chamber baffle 24 into the middle chamber discharge pipe 23, and then enters the lower chamber feed pipe 33.

[0041] (3) Moisture produced by the adsorption reaction in the lower chamber of the reactor

[0042] The overflow reaction liquid from the upper chamber flows into the feed pipe 33 of the lower chamber. Under the action of nitrogen pressure and reaction liquid pressure, it flows upward and counter-currently through the ultrasonic low-frequency vibration device 32 of the lower chamber into the water-absorbing molecular sieve 31 layer of the lower chamber. The reaction liquid continues to flow upward through the baffle plate 35 of the lower chamber and enters the discharge pipe 34 of the lower chamber. The reaction liquid is then circulated back to the upper chamber for re-reaction.

[0043] (4) Recovery of excess reactants and product purification

[0044] When the reaction time of the reaction liquid reaches the set value, the flow direction of the feed pipe and discharge pipe of each chamber of the reactor is changed by the valve. Finally, the reaction liquid is pumped out of the reactor through the feed pipe 33 of the lower chamber and goes through the acrylic acid recovery, alcohol extraction recovery, alcohol distillation and ester refining process in sequence to produce qualified products.

[0045] (5) Regeneration of molecular sieves in upper and lower chambers

[0046] To ensure the reaction requires a low water content in the reaction solution and prevent molecular sieve blockage, the molecular sieves in the upper and lower chambers are periodically heated and dehydrated for regeneration. During regeneration, the molecular sieves in the upper chamber are first steam-purged through the upper chamber feed pipe, and those in the lower chamber are steam-discharged through the lower chamber discharge pipe, followed by high-temperature drying. Because the heating temperature required for regeneration is higher than the reaction temperature, steam is preferred as the regeneration heat exchange medium. The heat exchange medium enters the heat exchange jackets and central heat exchange pipes of the upper and lower chambers through the upper chamber regeneration heating medium feed pipe and the lower chamber molecular sieve regeneration heating medium feed pipe, respectively, and then exits the upper and lower chambers for recirculation through the upper chamber regeneration heating medium discharge pipe and the lower chamber molecular sieve regeneration heating medium discharge pipe, respectively.

[0047] (6) System Control

[0048] This reactor is equipped with solenoid valves and metering pumps for both liquid and gas phase inlet and outlet. The flow rate is controlled by online automatic valve opening, which realizes automated inlet and outlet, automatic adjustment of reactant ratio and flow direction, and automatic control of reactant flow ratio to optimize conversion rate and product yield.

[0049] The ultrasonic vibration device in this reactor unit, through online electronic control, avoids problems such as catalyst and molecular sieve accumulation and uneven internal liquid flow, while also maximizing the reactor volume. The temperature control device in this reactor unit, also through online electronic control, ensures accurate and sensitive temperature control, shortens heating and cooling times, and guarantees product quality and yield. The use of DCS to control the liquid flow direction enables automatic control of countercurrent reaction, cocurrent venting, and forward and reverse airflow purging, enhancing system safety, reducing the risks of manual operation, and improving production efficiency.

[0050] To verify the feasibility of the above apparatus and method, the following embodiments are provided:

[0051] The embodiments of the present invention use a group of two 25m 3 The reactor will be used as an example for illustration.

[0052] Product Specifications:

[0053]

[0054] Example 1:

[0055] (1) Feeding and preheating of the upper chamber of the reactor

[0056] Acrylic acid and methanol, preheated to 70°C, are fed into the upper chamber of the reactor at a molar mass ratio of 4:3. The operating parameters of the upper chamber temperature control device are quickly adjusted to normal operating parameters, and the temperature of the mixed reaction material is increased to 75°C. After starting the feed pump, the mixed reaction liquid enters the upper chamber discharge pipe through the upper chamber baffle, and the temperature of the reaction material outlet of the upper chamber discharge pipe is maintained at 75°C.

[0057] (2) Preheating of reactor cavity and feed reaction

[0058] While feeding into the upper chamber, the middle chamber of the reactor is preheated to 75°C. After preheating to the set temperature, the upper chamber overflows and feeds the material. The temperature-controlled liquid is circulated back to the temperature control device in the middle chamber through the temperature-controlled liquid outlet pipe of the middle chamber for reheating.

[0059] When the reaction liquid reaches half the volume of the middle cavity, start the middle cavity air pump to fill the cavity with high-purity nitrogen gas, and maintain a slight positive pressure of 0.1 MPa in the middle cavity of the reactor; the reaction liquid overflows through the middle cavity baffle into the middle cavity discharge pipe, and then enters the lower cavity feed pipe.

[0060] (3) Moisture produced by the adsorption reaction in the lower chamber of the reactor

[0061] The overflow reaction liquid from the upper chamber flows into the feed pipe of the lower chamber. Under the action of nitrogen pressure and reaction liquid pressure, it flows upward countercurrently through the ultrasonic low-frequency vibration device in the lower chamber and enters the water-absorbing molecular sieve layer in the lower chamber. The reaction liquid continues to flow upward through the baffle plate in the lower chamber and enters the discharge pipe in the lower chamber. The reaction liquid is then circulated back to the upper chamber for re-reaction.

[0062] (4) Recovery of excess reactants and product purification

[0063] When the reaction time of the reaction liquid reaches the set value, the flow direction of the feed pipe and discharge pipe of each chamber of the reactor is changed by valves. The reaction liquid is finally pumped out of the reactor through the feed pipe of the lower chamber and goes through the acrylic acid recovery, alcohol extraction recovery, alcohol distillation and ester refining process in sequence to produce qualified products. Excess raw materials are recovered and reused.

[0064] Examples 1-4

[0065] (1) Reaction conditions

[0066] 1 4：3 2h 75℃ 75℃ 0.1 MPa 58％ 2 4：3 2.5h 75℃ 75℃ 0.1 MPa 62％ 3 4：3 3h 75℃ 75℃ 0.1 MPa 69％ 4 4：3 3.5h 75℃ 75℃ 0.1 MPa 71％

[0067] (2) Comparison of product properties and product yield

[0068] purity,% 99.7 99.6 99.5 98.1 Colorimetric, in Hazen units (platinum-cobalt color code) 10 10 10 13 Acidity (as acrylic acid), % 0.007 0.009 0.01 0.03 Moisture,% 0.03 0.03 0.04 0.07 Polymerization inhibitor (MEHQ) content, % 0.0112 0.0119 0.0102 0.011 Other ingredients, % 0.2518 0.3491 0.4398 1.789 Product yield, % 57.2 61.3 68.4 69.7

[0069] The above examples illustrate reactions conducted at a pressure of 0.1 MPa. By comparison, the reaction cycle time directly impacts product quality and yield. A shorter reaction cycle time is beneficial for product quality but results in a lower yield and higher production costs; conversely, a longer reaction cycle time is detrimental to product quality but leads to a higher yield and relatively lower production costs.

[0070] Examples 5-8

[0071] (1) Reaction conditions

[0072] 5 3：3 3h 75℃ 75℃ 0.1 MPa 72％ 6 4：3 3h 75℃ 75℃ 0.1 MPa 69.2％ 7 5：3 3h 75℃ 75℃ 0.1 MPa 62.1％ 8 6：3 3h 75℃ 75℃ 0.1 MPa 54.1％

[0073] (2) Comparison of product properties and product yield

[0074]

[0075]

[0076] Examples 5-8 compare the feed molar ratios under reactor pressure of 0.1 MPa and temperature of 75°C. Through comparison of product properties and yields, a feed molar ratio of 4:3 shows a significant advantage in both product yield and properties.

[0077] Examples 9-12

[0078] (1) Reaction conditions

[0079] 9 4：3 3h 75℃ 75℃ 0.05Mpa 63％ 10 4：3 3h 75℃ 75℃ 0.1 MPa 68.3％ 11 4：3 3h 75℃ 75℃ 0.15Mpa 71％ 12 4：3 3h 75℃ 75℃ 0.2 MPa 73.8％

[0080] (2) Comparison of product properties and product yield

[0081] purity,% 99.3 99.5 99.6 99.6 Colorimetric, in Hazen units (platinum-cobalt color code) 11 10 10 10 Acidity (as acrylic acid), % 0.02 0.01 0.009 0.009 Moisture,% 0.08 0.04 0.04 0.04 Polymerization inhibitor (MEHQ) content, % 0.0109 0.0105 0.0104 0.0103 Other ingredients, % 0.5891 0.4395 0.3406 0.3407 Product yield, % 58.9 67.8 69.1 71.1

[0082] Examples 9-12 compare product quality and yield under different reactor pressures. Under optimal conditions, the reactor exhibits a positive trend in the lower pressure range; as the pressure increases, the product quality and yield improve. However, for the equipment, higher pressures require more complex operation and higher-quality materials, as well as a higher-level pneumatic system. Overall, a pressure between 0.1 and 0.15 MPa is more suitable.

[0083] In summary, the production apparatus and method of this invention yield products with a purity of over 99% in most cases, and a product yield that is consistently above 50%, demonstrating high practicality.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A countercurrent three-stage methyl acrylate production reactor, characterized in that: The reaction vessel consists of two sets of reaction vessels, each consisting of an upper chamber (1), a middle chamber (2), and a lower chamber (3), and two temperature control devices (4 and 5) located outside the reaction vessels. The upper chamber (1) is connected to the upper chamber temperature control device (4) to preheat the upper chamber (1) to 65-70°C. Acrylic acid and methanol are both introduced into the upper chamber (1). The upper chamber (1) is equipped with a water-absorbing molecular sieve. The middle chamber (2) is located at the lower end of the upper chamber (1) and is connected to it. The middle chamber (2) contains a catalyst and is supplied with nitrogen gas. The temperature control device (5) is located in the middle chamber. The device (5) is connected to the middle cavity (2) to keep the temperature in the middle cavity (2) at 75°C. The lower cavity (3) is located at the lower end of the middle cavity (2) and is connected to it. The upper cavity (1), the middle cavity (2) and the lower cavity (3) all have liquid entering at the lower end and liquid exiting at the upper end. The lower cavity (3) is equipped with a water-absorbing molecular sieve to absorb the water generated by the esterification reaction. After the water-absorbing molecular sieve absorbs water in the lower cavity (3), the reaction liquid is circulated back to the upper cavity (1) for re-reaction. After the circulation reaction time reaches the set value, the product is output outside the device.

2. The countercurrent three-stage methyl acrylate production reactor according to claim 1, characterized in that: The upper cavity (1) is provided with an upper cavity baffle (11), and the upper cavity baffle (11) has a hole and the upper cavity baffle (11) covers the upper cavity discharge pipe.

3. The countercurrent three-stage methyl acrylate production reactor according to claim 2, characterized in that: Several ultrasonic low-frequency vibration devices are provided in the upper cavity (1), middle cavity (2) and lower cavity (3).

4. A countercurrent three-stage reaction method for producing methyl acrylate, characterized in that: The reaction apparatus according to claim 3 includes the following steps. Ⅰ. Start the upper chamber temperature control device (4) to pump temperature control liquid into the upper chamber (1) and preheat the upper chamber (1) to 65-75°C. Pass the preheated acrylic acid and methanol into the water-absorbing molecular sieve. After the acrylic acid and methanol are mixed, the temperature of the upper chamber (1) is maintained at 75°C by the upper chamber temperature control device (4), and the mixture of acrylic acid and methanol is passed into the middle chamber (2). II. While the upper cavity (1) is preheating, the middle cavity temperature control device (5) is also activated to preheat the middle cavity (2) and make the temperature inside the middle cavity (2) reach 75°C; the middle cavity (2) receives the mixed liquid introduced into the upper cavity (1), the mixed liquid reacts with the catalyst, and the exothermic reaction is discharged by the middle cavity temperature control device (5) so that the temperature inside the middle cavity (2) is always kept at 75°C; the ultrasonic low-frequency vibration device is turned on to make the catalyst vibrate, and nitrogen is introduced into the middle cavity (2) during the reaction to prevent the reaction material in the reaction liquid from polymerizing, suppressing side reactions, and reducing the yield of heavy components; Ⅲ. The reaction liquid in the middle cavity (2) flows into the water-absorbing molecular sieve in the lower cavity (3), and then flows into the upper cavity (1) for further reaction; IV. When the reaction time of the reaction liquid reaches the set value, the reaction liquid is discharged from the tank body through the lower chamber (3). After passing through the acrylic acid recovery, alcohol extraction recovery and alcohol distillation and ester refining processes in sequence, qualified products are produced.

5. The method for producing methyl acrylate in a countercurrent three-stage process according to claim 4, characterized in that: The feed molar mass ratio of acrylic acid to methanol is (4-6):(3-5).

6. The method for producing methyl acrylate in a countercurrent three-stage process according to claim 5, characterized in that: The nitrogen pressure introduced into the middle cavity (2) is 0.05MPa~0.2MPa.

7. The method for producing methyl acrylate in a countercurrent three-stage process according to claim 6, characterized in that: The ultrasonic low-frequency vibration device vibrates every 5 to 10 minutes after feeding.

8. The method for producing methyl acrylate in a countercurrent three-stage process according to claim 7, characterized in that: The water-absorbing molecular sieves in the upper cavity (1) and lower cavity (3) are periodically heated, dehydrated, and regenerated to prevent clogging of the molecular sieves.

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