A microchannel reactor for the production of diethyl maleate and a process for the production thereof

Abstract

The application discloses a maleic acid diethyl ester micro-channel reactor and a production process thereof, the reactor is connected at the head and tail by a plurality of units with the same structure, the unit comprises a unit pipe and a screen, the screen is internally filled with a granular catalyst, a liquid passing channel is formed in the center of the screen, one end of the liquid passing channel is sealed, and a centrifugal impeller for drawing the inside of the liquid passing channel into negative pressure is arranged at the other end of the liquid passing channel. The application synchronously carries out modular treatment through the integrated tubular reactor and the catalyst, so that the application is convenient to disassemble and assemble, the replacement efficiency is improved, and the waste problem caused by the whole waste of the high-activity catalyst can be avoided.

Description

Technical Field

[0001] This invention relates to the field of esterification reaction technology, and in particular to a microchannel reactor for diethyl maleate and its production process. Background Technology

[0002] Diethyl maleate is an unsaturated dicarboxylic acid diester used in fine chemical industries such as the production of malathion, plasticizers, and diethyl succinate. Current production methods typically use a batch process in a reactor with concentrated sulfuric acid for catalytic reaction. This process is highly corrosive, requires sophisticated equipment, causes significant environmental pollution, and generates large amounts of acidic wastewater during post-treatment. The latest technology uses solid acid in a tubular microchannel reactor for synthesis. While this effectively solves the acidic wastewater pollution problem, the solid acid catalyst is encapsulated in the pipes at both ends by a grid or filter. The solid acid catalyst, which is preferentially contacted by the feed liquid, is easily deactivated due to various issues, making replacement and disassembly inconvenient. Patent 202423026719.0 discloses a tubular reactor designed for easy disassembly and maintenance, achieving rapid replacement through a quick-release structure. However, this method does not eliminate the existing structure where the catalyst is blocked at both ends by a grid. After quick disassembly, the entire catalyst still needs to be emptied for replacement, making modular and rapid catalyst replacement impossible. This results in low production efficiency and waste of a large amount of highly active catalyst. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a diethyl maleate microchannel reactor and its production process to solve the problems of the inability to modularly disassemble and replace solid acid catalysts and the low efficiency of continuous production in the prior art.

[0004] The objective of this invention is achieved through the following technical solution: a diethyl maleate microchannel reactor, wherein the reactor consists of multiple units with identical structures connected end to end, each unit including a unit tube and a screen, the screen being filled with particulate catalyst, a liquid passage being formed in the center of the screen, one end of the liquid passage being sealed, and the other end of the liquid passage being provided with a centrifugal impeller to create a negative pressure inside it.

[0005] Preferably, the liquid passage is provided with a rotating shaft that drives the centrifugal impeller to rotate, one end of the screen is sealed with a front sealing plate, a gear ring is fixedly provided on the front sealing plate, a sun gear is provided on the rotating shaft, and a planetary gear and a planet carrier are provided between the gear ring and the sun gear and meshed with it. The planet carrier is fixedly connected to the inner wall of the unit tube.

[0006] Preferably, the screen is provided with multiple thrust blades, which are arranged at intervals around the tail end of the screen. The thrust blades push the fluid in a direction opposite to the overall fluid movement direction in the reactor.

[0007] Preferably, the unit tube is provided with multiple screens, a front sealing plate, and a centrifugal impeller. The screens and the impeller are alternately mounted on the outside of the rotating shaft, and the screens rotate synchronously.

[0008] Preferably, a connecting rod is fixedly provided at the tail end of the screen, and the other end of the connecting rod is inserted into the screen located at the rear.

[0009] Preferably, the tail end of the rotating shaft is fitted with a rear limiting plate, and the rear limiting plate is provided with a second slot that matches the connecting rod.

[0010] Preferably, a motor is fixedly mounted on the outside of the unit tube, and the output end of the motor is connected to the rotating shaft by a bevel gear.

[0011] Preferably, the planetary carrier is provided with a limiting rod, and the inner wall of the unit tube is provided with a first slot that matches the limiting rod.

[0012] Preferably, the planetary carrier is disc-shaped, and the planetary carrier is rotatably connected to the gear ring in a sealed manner.

[0013] A process for producing diethyl maleate includes the following steps. S1. Maleic anhydride and ethanol are introduced into a tubular reactor to carry out a monoesterification reaction; S2. The monoesterification product is passed into the microchannel reactor and subjected to a mixed-flow reaction using a solid acid catalyst to generate the dieesterification product. This invention has the following advantages: Advantages of this invention: 1. This invention designs the reactor as a series of identical units connected end to end. Each unit contains an independent screen and granular catalyst filled within it. The screens are connected by interlocking rods. This solves the problem in the prior art where solid acid catalysts are encapsulated in the pipes from both ends through a grid, making modular and quick replacement impossible and resulting in low production efficiency. This invention enables modular and quick replacement of the catalyst, significantly shortening the replacement time, reducing the labor intensity of operators, and avoiding the waste caused by the complete disposal of highly active catalysts, thus significantly improving the efficiency of continuous production. 2. By designing a liquid passage in the center of the screen and cooperating with a centrifugal impeller, the reaction liquid can be made to contact the reaction with the dense particulate catalyst. This solves the problem that the reaction liquid in the existing tubular reactor tends to flow directly along the tube wall and form a channel in the rear. It ensures full contact between the reaction liquid and the solid acid catalyst, and improves the efficiency of the catalytic reaction and the conversion rate of raw materials. 3. By designing a planetary deceleration structure to drive the screen and internal granular catalyst to rotate at low speed, it can rotate at different speeds from the shaft. This not only ensures the continuous effect of centrifugal negative pressure, but also ensures the integrity of the internal granular catalyst by low-speed rotation. It also solves the problem of local channeling and poor mass transfer caused by uneven catalyst filling, which affects the catalytic reaction effect, and greatly enhances the solid-liquid mass transfer effect. 4. The rotating screen, in conjunction with the reverse-push blades, solves the technical problem that the centrifugal force generated by the centrifugal impeller greatly increases the flow rate of the reaction liquid, which is not conducive to the full reaction. This allows multiple cycles of reaction to be formed in the pipeline, significantly improving the generation efficiency of diesterization products and the overall conversion rate, enabling the system to operate continuously and stably. 5. This invention modularizes the traditional integrated tubular reactor and catalyst simultaneously, allowing users to flexibly increase or decrease the number of units according to actual production needs, achieving linear scaling up of reactor throughput as required; at the same time, each unit can independently and precisely control the reaction temperature, meeting the process requirements of precise temperature control for the diethyl maleate esterification reaction, further improving the stability and batch consistency of the final product quality. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the unit three-dimensional structure of the present invention; Figure 2 yes Figure 1 A schematic diagram of the cross-sectional structure; Figure 3 yes Figure 1 A schematic diagram of the internal structure.

[0015] In the diagram, 1. Unit tube; 2. Flange; 3. Motor; 4. Shaft; 5. Screen; 6. Granular catalyst; 7. Front sealing plate; 8. Liquid passage; 9. Centrifugal impeller; 10. Sun gear; 11. Planetary gears; 12. Planetary carrier; 13. Gear ring; 14. Limiting rod; 15. First slot; 16. Linkage rod; 17. Rear limiting plate; 18. Second slot; 19. Thrust blade; 20. Limiting pin. Detailed Implementation

[0016] 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, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0018] A diethyl maleate microchannel reactor, the reactor being composed of multiple structurally identical units connected end to end, such as... Figure 1 , Figure 2 As shown, each unit includes a unit tube 1, a screen 5, and a rotating shaft 4. Flanges 2 are provided at both ends of the unit tube 1, and the unit tubes 1 are connected via flanges 2. The unit tube 1 can be temperature-controlled by installing a heat exchange jacket. The existing jacket structure is not shown in the figure. The screen 5 is a cylindrical structure, with a diameter smaller than that of the unit tube 1. The screen 5 is hollow inside and has multiple liquid passage holes on both its inner and outer circumferential surfaces. The screen 5 is filled with granular catalyst 6, which is a solid acid catalyst. The left end of the screen 5 is sealed with a... The front sealing plate 7 and the center of the screen 5 form a liquid passage 8. The front sealing plate 7 seals the left end of the liquid passage 8. The other end of the liquid passage 8 is equipped with a centrifugal impeller 9. The central inlet of the centrifugal impeller 9 is directly opposite the outlet of the liquid passage 8. The rotation of the centrifugal impeller 9 draws a negative pressure inside the liquid passage 8, so that the reaction liquid outside the screen 5 can pass through the screen 5 and come into contact with the particulate catalyst 6 to react and finally enter the liquid passage 8. This avoids the problem of the reaction liquid flowing directly along the inner wall of the unit tube 1 to the rear, thus completing the second step of the esterification reaction.

[0019] The rotating shaft 4 is installed in the liquid passage 8 and drives the centrifugal impeller 9 to rotate. The gear ring 13 is fixedly installed on the front sealing plate 7. The sun gear 10 is installed on the rotating shaft 4. Three planetary gears 11 and a planet carrier 12 are installed between the gear ring 13 and the sun gear 10 and mesh with them. The planet carrier 12 is disc-shaped. The planet carrier 12 is sealed and rotates to connect with the gear ring 13, so that the planet carrier 12, the gear ring 13 and the front sealing plate 7 together seal the planetary gears 11 and the sun gear 10. The planetary reduction mechanism can drive the screen 5 to rotate. The low speed ensures the integrity of the internal granules. At the same time, the rotating granules can not only mix the reaction liquid, but also avoid the channeling problem caused by uneven filling, thus promoting the efficient catalytic reaction.

[0020] like Figure 3Multiple thrust blades 19 are installed on the screen 5. The thrust blades 19 are arranged at intervals around the tail end of the screen 5. The installation direction of the thrust blades 19 must ensure that the direction of the fluid movement is opposite to the overall direction of the fluid movement in the reactor. The centrifugal force generated by the centrifugal impeller 9 will greatly accelerate the flow rate, which is not conducive to the contact reaction. By setting the thrust blades 19, part of the fluid generated by centrifugation can be guided back to react with the catalyst again, realizing the cyclic reaction. The reverse fluid movement can also counteract the channeling problem along the inner wall of the unit tube 1.

[0021] Only one screen 5 is installed inside unit tube 1. Disassembling and assembling one flange 2 can only replace one catalyst and one screen 5. To improve disassembly and assembly efficiency, multiple screens 5, front sealing plates 7, and centrifugal impellers 9 are installed inside unit tube 1. The screens 5 and impellers are alternately mounted on the outside of the rotating shaft 4. To enable the screens 5 to rotate synchronously, a connecting rod 16 is fixedly provided at the tail end of the screen 5. The other end of the connecting rod 16 is inserted into the front sealing plate 7 located on the rear screen 5. A rear limiting plate 17 is fitted at the tail end of the rotating shaft 4. Both the rear limiting plate 17 and the front sealing plate 7 are disc-shaped. The rear limiting plate 17 and the front sealing plate 7 are provided with a second slot 18 that matches the connecting rod 16. The screens 5 at the front and rear are connected and linked through the second slot 18. A motor 3 is fixedly installed outside unit tube 1. The output end of the motor 3 passes through and rotates to connect unit tube 1. The output end of motor 3 is connected to shaft 4 via bevel gear meshing. The bevel gear meshing connection structure can be sealed and protected by a square sealing structure. The output end can be connected via various quick-release structures such as plug-in. The final installed rear limiting plate is rotatably connected to the square sealing structure. Centrifugal impeller 9 is mounted on shaft 4. It can be fixed in position by a limiting pin 20 passing through the shaft sleeve of centrifugal impeller 9 and shaft 4, which facilitates subsequent disassembly. Of course, it can also be fixed by other existing methods. Limiting rod 14 is installed on planetary carrier 12. The inner wall of unit tube 1 is provided with a first slot 15 that matches the limiting rod 14. The first slot 15 is composed of two parallel limiting blocks, which allows the limiting rod 14 to slide left and right and finally be locked inside, thus fixing planetary carrier 12. The combination of multiple quick-release structures can realize the rapid disassembly and assembly of catalyst.

[0022] Working principle: Start motor 3, motor 3 drives shaft 4 to rotate, shaft 4 drives centrifugal impeller 9 and sun gear 10 to rotate. The rotation of centrifugal impeller 9 generates negative pressure, causing the reaction liquid outside screen 5 to pass through dense granular catalyst 6 under pressure for catalytic reaction. Subsequently, it is drawn into liquid passage 8, and then enters centrifugal impeller 9 and is thrown out. The rotation of sun gear 10 drives gear ring 13 to rotate through planetary gear 11. Gear ring 13 drives screen 5 and the internal granular catalyst 6 to rotate at a reduced speed. The rotation of granular catalyst 6 agitates and mixes the reaction liquid. The rotation of screen 5 drives the reverse thrust blade 19 to rotate. Part of the reaction liquid thrown out by centrifugal impeller 9 is transported in the reverse direction for recycling, and the other part flows backward.

[0023] A process for producing diethyl maleate includes the following steps. S1. Maleic anhydride and ethanol are introduced into a tubular reactor and subjected to a monoesterification reaction under controlled temperature. S2. The monoesterification product is introduced into the microchannel reactor. The reaction solution is mixed with the particulate catalyst 6 through the rotating screen 5. After being extracted by the centrifugal impeller 9, a portion is recycled for a secondary reaction, and the remainder flows backward. The reactor continuously circulates, so that the entire system continuously and stably generates the diesterification product.

[0024] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A diethyl maleate microchannel reactor, characterized in that: The reactor consists of multiple identical units connected end to end. Each unit includes a unit tube (1) and a screen (5). The screen (5) is filled with particulate catalyst (6). A liquid passage (8) is formed in the center of the screen (5). One end of the liquid passage (8) is sealed, and the other end of the liquid passage (8) is provided with a centrifugal impeller (9) that draws the inside of the liquid passage into negative pressure.

2. The diethyl maleate microchannel reactor according to claim 1, characterized in that: The liquid passage (8) is provided with a rotating shaft (4) that drives the centrifugal impeller (9) to rotate. One end of the screen (5) is sealed with a front sealing plate (7). A gear ring (13) is fixed on the front sealing plate (7). A sun gear (10) is provided on the rotating shaft (4). A planetary gear (11) and a planet carrier (12) are provided between the gear ring (13) and the sun gear (10) and mesh with it. The planet carrier (12) is fixedly connected to the inner wall of the unit tube (1).

3. The diethyl maleate microchannel reactor according to claim 2, characterized in that: The screen (5) is provided with multiple thrust blades (19), which are arranged around the tail end of the screen (5) at intervals. The thrust blades (19) push the fluid to move in the opposite direction to the overall fluid movement direction in the reactor.

4. The diethyl maleate microchannel reactor according to claim 3, characterized in that: The unit tube (1) is equipped with multiple screens (5), a front sealing plate (7), and a centrifugal impeller (9). The screens (5) and the impeller are alternately mounted on the outside of the rotating shaft (4), and the screens (5) rotate synchronously.

5. A diethyl maleate microchannel reactor according to claim 4, characterized in that: The tail end of the screen (5) is fixedly provided with a connecting rod (16), and the other end of the connecting rod (16) is inserted into the screen (5) located behind it.

6. A diethyl maleate microchannel reactor according to claim 5, characterized in that: The tail end of the rotating shaft (4) is fitted with a rear limiting plate (17), and the rear limiting plate (17) is provided with a second slot (18) that matches the connecting rod (16).

7. A diethyl maleate microchannel reactor according to claim 2, characterized in that: The unit tube (1) is fixedly equipped with a motor (3), and the output end of the motor (3) is connected to the rotating shaft (4) by a bevel gear.

8. A diethyl maleate microchannel reactor according to claim 2, characterized in that: The planetary carrier (12) is provided with a limiting rod (14), and the inner wall of the unit tube (1) is provided with a first slot (15) that matches the limiting rod (14).

9. A diethyl maleate microchannel reactor according to claim 8, characterized in that: The planet carrier (12) is disc-shaped and is sealed and rotatably connected to the gear ring (13).

10. A process for producing diethyl maleate, based on the reactor described in any one of claims 1-9, characterized in that, Includes the following steps, S1. Maleic anhydride and ethanol are introduced into a tubular reactor to carry out a monoesterification reaction; S2. The monoesterification product is introduced into the microchannel reactor and subjected to a mixed-flow reaction using a solid acid catalyst to generate a diesterification product.

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