A reactor for the preparation of p-acetoxybenzoic acid

Abstract

This invention discloses a reactor for the preparation of p-acetoxybenzoic acid, relating to the field of p-acetoxybenzoic acid preparation technology. Specifically, it includes a reactor body with a stirring structure within it. The inner wall of the reactor body has uniformly arranged axially extending grooves, and a guide plate is movably connected to the inner cavity of each groove. The guide plate is connected to the reactor body via an elastic structure. This application utilizes the synergistic effect of a third magnet and a magnetic sensor to achieve real-time capture of the guide plate's positional changes. The rotation period of the stirring structure is inferred from the positional change period of the guide plate, enabling precise acquisition of the stirring structure's rotation period. This facilitates the controller's adjustment of the stirring structure's rotation speed. Furthermore, the controller can determine whether the guide plate is stuck or has abnormal reset based on the guide plate's reset time interval and final position, improving the reactor's reliability.

Description

Technical Field

[0001] This invention relates to the field of p-acetoxybenzoic acid preparation technology, specifically to a p-acetoxybenzoic acid preparation reactor. Background Technology

[0002] p-Acetoxybenzoic acid, as an important organic synthetic intermediate, is widely used in pharmaceuticals, liquid crystal materials, and polymer modification. Its typical synthetic route usually involves the acylation reaction of p-hydroxybenzoic acid with an acetylation reagent (such as acetyl chloride or acetic anhydride) in the presence of an acidic catalyst. This reaction is mostly a heterogeneous exothermic reaction, placing extremely high demands on the heat transfer efficiency, mixing homogeneity, and catalyst protection of the reaction system.

[0003] Currently, traditional batch reactors are commonly used in industrial production, with anchor-type agitators installed inside to mix materials. However, the flow generated by this type of agitator is mainly concentrated near the wall and the agitator, easily forming a weak flow / quasi-dead zone in the middle of the reactor. This leads to problems such as material settling and localized overheating, affecting the mixing effect. To address this issue, those skilled in the art can easily think of installing baffles on the inner wall of the reactor to improve axial homogenization. However, the raw material system used to prepare p-acetoxybenzoic acid has a high viscosity, and the raw material easily adheres to the inner wall of the reactor. Therefore, existing stirring structures usually include scrapers to remove the adhering material from the reactor wall. This requires the scrapers to be arranged and operate close to the inner wall of the reactor. However, if the radial dimension of the baffle is too small, the ideal guiding effect cannot be achieved; if the radial dimension of the baffle is increased to enhance the guiding effect, it will interfere with and restrict the circumferential movement of the scraper. Therefore, how to balance the hydrodynamic performance of the baffle and the mechanical operating space of the scraper within a limited space has become a technical contradiction that urgently needs to be solved.

[0004] Furthermore, in the catalytic synthesis of p-acetoxybenzoic acid, the stirring speed is a core process parameter, directly determining the uniformity of material mixing, reaction rate, and catalyst working state. Excessive speed intensifies friction and collision between the solid catalyst and materials, the reactor wall, and the stirring structure within the reaction system, causing severe catalyst wear. The worn catalyst exhibits significantly reduced activity and catalytic efficiency, leading not only to incomplete synthesis and substandard product purity but also to increased catalyst loss and significantly increased recovery difficulty, greatly raising production costs. Simultaneously, the fine catalyst impurities generated during wear easily mix into the product, increasing the workload of subsequent purification processes.

[0005] To address catalyst wear caused by uncontrolled stirring speed, existing technologies typically equip the drive motor with encoders and other detection elements. By monitoring the motor's output speed in real time, the actual operating speed of the stirring structure can be indirectly calculated, thus achieving closed-loop speed control. However, under long-term continuous operation, the motor and transmission structure experience continuous mechanical wear and heat generation, leading to problems such as increased transmission clearance, thermal deformation of components, and decreased transmission efficiency. This causes a deviation between the motor's output speed and the actual stirring speed of the stirring structure, resulting in a lack of synchronization between the two speed data. Consequently, the reactor controller cannot achieve precise closed-loop control of the stirring speed, making it difficult to effectively avoid catalyst wear defects caused by excessive speed.

[0006] Based on this, this application proposes a reactor for the preparation of p-acetoxybenzoic acid. Summary of the Invention

[0007] This invention provides a reactor for the preparation of p-acetoxybenzoic acid, which solves the problem mentioned in the background art that the size design of the guide plate and the normal operation of the scraper cannot be simultaneously considered; and that the stirring speed is poorly controlled due to transmission wear, heat deformation, and transmission efficiency decay caused by the indirect calculation of the stirring speed by setting a detection element at the motor end.

[0008] The present invention provides the following technical solution: a reactor for the preparation of p-acetoxybenzoic acid, comprising a reactor body, wherein a stirring structure is provided in the reactor body, and grooves extending axially are uniformly provided on the inner sidewall of the reactor body. A guide plate is movably connected to the inner cavity of the grooves. The guide plate is connected to the reactor body through an elastic structure. The side of the guide plate away from the elastic structure is the guiding side, and the side of the guide plate close to the elastic structure is the sealing side. When the elastic structure is in a free state, the guiding side is located in the inner cavity of the reactor body, and the sealing side seals the grooves. A first magnet is encapsulated inside the flow-guiding side of the guide plate, and a second magnet is encapsulated at the corresponding position of the vertical end of the stirring structure. When the stirring structure drives the second magnet to rotate until it is circumferentially aligned with the first magnet, the first magnet and the second magnet are in a state of magnetic repulsion. The magnetic repulsion force acts on the guide plate, pressing the guide plate into the groove. A third magnet is encapsulated inside the sealing side of the guide plate, and a magnetic sensor is provided inside the groove. The third magnet is located within the detection area of ​​the magnetic sensor, and the magnetic sensor generates a pulse signal as the third magnet moves.

[0009] Preferably, the stirring structure is a frame-type stirring structure, and a scraper is provided on the outer wall of the vertical end of the stirring structure, with the cutting edge of the scraper abutting against the inner wall of the reactor body.

[0010] Preferably, the guide plate is movably connected to the reactor body via a rotating shaft, and the side of the guide plate away from the rotating shaft is an arc-shaped sidewall.

[0011] Preferably, the inner cavity of the groove is provided with a positioning block. When the guide plate contacts the positioning block, the guide plate is located in the inner cavity of the groove. The side of the groove away from the rotating shaft is an arc-shaped surface adapted to the arc-shaped sidewall. The arc-shaped sidewall and the arc-shaped surface are in a fitted state.

[0012] Preferably, the elastic structure includes a positioning rod connected to the inner cavity of the groove, and a torsion spring is movably sleeved on the outer ring of the positioning rod. One end of the torsion spring is connected to the guide plate, and the other end of the torsion spring is connected to the reactor body.

[0013] Preferably, the guide plate has a hollow structure; the axial height of the guide plate covers the area between the upper and lower crossbars of the stirring structure.

[0014] Preferably, the first magnets in each guide plate have the same polarity orientation, and the first magnets are located outside the detection area of ​​the magnetic sensor.

[0015] Preferably, both the first magnet and the second magnet have protective sheets on their surfaces.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This p-acetoxybenzoic acid preparation reactor utilizes a frame-type stirring structure and baffles to improve axial homogenization, facilitate thorough mixing and heat transfer of raw materials, and enhance interfacial reactions between materials, thereby improving the yield and quality of p-acetoxybenzoic acid. Furthermore, the use of like-pole magnetic repulsion achieves non-contact clearance between the baffles and the stirring structure, ensuring that the baffles do not obstruct the operation of the stirring structure and are aligned with the scraper. During this clearance process, the scraper cleans the guide surface, ensuring the effective use of the baffles.

[0017] 2. This p-acetoxybenzoic acid preparation reactor achieves real-time capture of the position change characteristics of the guide plate through the synergistic effect of the third magnet and magnetic sensor. The rotation period of the stirring structure is inferred by the position change period of the guide plate, thus achieving accurate acquisition of the rotation period of the stirring structure. This facilitates the controller to adjust the rotation speed of the stirring structure. Furthermore, the controller can determine whether the guide plate is stuck or has a reset abnormality based on the reset time interval and final position of the guide plate, thereby improving the reliability of the reactor. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the internal structure of a reactor for preparing p-acetoxybenzoic acid according to the present invention. Figure 2 This is a top view of the cross-section of a reactor for preparing p-acetoxybenzoic acid according to the present invention; Figure 3 The structure of this invention Figure 2 Partial cross-sectional view; Figure 4 This is a schematic diagram of the stirring structure of the present invention; Figure 5 This is a schematic diagram of the flow guide plate of the present invention; Figure 6 The structure of this invention Figure 5 Rear view illustration.

[0019] In the diagram: 1. Reactor body; 2. Stirring structure; 3. Second magnet; 4. Baffle plate; 5. Scraper; 6. Rotating shaft; 7. Positioning block; 8. First magnet; 9. Groove; 10. Third magnet; 11. Positioning rod; 12. Magnetic sensor; 13. Torsion spring. Detailed Implementation

[0020] 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. 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.

[0021] This invention provides one embodiment: Please refer to Figures 1-6 A reactor for the preparation of p-acetoxybenzoic acid includes a reactor body 1, which is a p-acetoxybenzoic acid preparation reactor in the prior art, and the model and specifications can be set according to requirements.

[0022] The reactor body 1 is equipped with a stirring structure 2. In the prior art, the reactor is usually equipped with an anchor-type stirring paddle. The flow generated by the rotation of this stirring paddle is mainly concentrated on the wall and near the paddle. Weak flow / quasi-dead zone is easily formed in the middle of the reactor, which leads to problems such as material settling and local overheating. In order to address this problem, the stirring structure 2 in the reactor body 1 is a frame-type stirring structure. The crossbar of the stirring structure 2 is used to stir the middle area of ​​the reactor, thereby improving the stirring effect and alleviating the problem of local overheating.

[0023] A scraper 5 is provided on the outer wall of the vertical end of the stirring structure 2. The cutting edge of the scraper 5 is attached to the inner wall of the reactor body 1. When the stirring structure 2 is rotated under the drive of a power source such as a motor, the stirring structure 2 can drive the scraper 5 to rotate. The scraper 5 is used to scrape off the deposits that adhere to the inner wall of the reactor due to factors such as local overheating. In this embodiment, the cutting edge of the scraper 5 is attached to the inner wall of the reactor with a preset clamping amount of 0.5-2mm to ensure continuous contact between the cutting edge and the wall surface and stable scraping positive pressure during the use of the reactor, thus ensuring the reliability of the scraper 5.

[0024] When uneven mixing and localized overheating occur, theoretically, the overall circulation can be improved by dynamically adjusting the stirring speed. However, due to the low accuracy of stirring speed detection and poor controllability of the actual speed, the reactor cannot adapt to the material mixing requirements of the reaction system by dynamically adjusting the speed, and cannot achieve precise control of the mixing conditions. Furthermore, for anchor-type stirring paddles and frame-type stirring structures, increasing the speed has a poor effect on improving axial circulation. Instead, it significantly increases the linear velocity in the narrow gap between the outer edge of the paddle and the reactor wall, creating a continuous environment of strong mechanical impact and high shear scraping at the wall edge, which greatly aggravates catalyst friction and wear. If the set speed is reduced to avoid the risk of catalyst wear, it is not possible to effectively eliminate the problems of material settling, uneven mixing, and localized overheating. Ultimately, the existing equipment cannot meet the core production requirements of catalyst protection and efficient and uniform material mixing, which seriously restricts the finished product quality and production stability of p-acetoxybenzoic acid.

[0025] To address this issue and further improve the axial mixing effect, this application incorporates a guide plate 4 with active avoidance function within the reactor body 1. This ensures effective flow guidance while preventing interference with the movement of the scraper 5. Specifically, the inner wall of the reactor body 1 is uniformly provided with axially extending grooves 9. The guide plate 4 is movably connected to the inner cavity of the grooves 9. The axial height of the guide plate 4 covers the area between the upper and lower crossbars of the stirring structure 2. The guide plate 4 is connected to the reactor body 1 via a rotating shaft 6. The rotating shaft 6 is movably connected to the reactor body 1 and detachably connected to the guide plate 4. Under external force, the guide plate 4 can rotate axially around the rotating shaft 6.

[0026] The guide plate 4 is connected to the reactor body 1 via an elastic structure. The side of the guide plate 4 away from the elastic structure is the guiding side, and the side of the guide plate 4 closer to the elastic structure is the sealing side. In this embodiment, the elastic structure includes a positioning rod 11 connected to the inner cavity of the groove 9. A torsion spring 13 is movably sleeved on the outer ring of the positioning rod 11. One end of the torsion spring 13 is connected to the guide plate 4, and the other end of the torsion spring 13 is connected to the reactor body 1. When the elastic structure is in a free state, the torsion spring 13 applies a thrust to the guide plate 4. Under the action of this thrust, the guiding side is located in the inner cavity of the reactor body 1, and the guide plate 4 and the reactor body 1 are in a close fit. When the stirring structure 2 stirs the raw material for preparing p-acetoxybenzoic acid in the reactor, the guiding side can guide the raw material, effectively suppressing material sedimentation, improving axial homogenization, and thus improving the stirring effect.

[0027] The guide plate 4 has a hollow structure to reduce its weight and facilitate its rotation. The side of the guide plate 4 away from the rotating shaft 6 is an arc-shaped sidewall, and the side of the groove 9 away from the rotating shaft 6 is an arc-shaped surface that fits the arc-shaped sidewall. The arc-shaped sidewall and the arc-shaped surface are in a close fit, and the guide plate 4 and the groove 9 are sealed by a sealing gasket to effectively intercept the raw material and prevent it from seeping in. The material of the sealing gasket can be set according to requirements.

[0028] A first magnet 8 is encapsulated within the flow guide side, and the first magnets 8 within each flow guide plate 4 have the same polarity orientation. A second magnet 3 is encapsulated at the corresponding position on the vertical end of the stirring structure 2. When the stirring structure 2 drives the second magnet 3 to rotate until it is circumferentially aligned with the first magnet 8, the first magnet 8 and the second magnet 3 are in a state of magnetic repulsion. The magnetic repulsion force acts on the flow guide plate 4, pressing the flow guide plate 4 into the groove 9, forming a clearance for the stirring structure 2 to pass through. During the passage of the stirring structure 2, the scraper 5 can scrape off the adhering material on the flow guide surface of the flow guide plate 4, achieving cleaning of the flow guide surface and ensuring the flow guiding effect of the flow guide plate 4. When the stirring structure 2 and the flow guide plate 4 are in a misaligned state, the flow guide plate 4 can be reset under the action of the torsion spring 13, and the flow guide side remains in a convex state, realizing the flow guiding of materials in the reactor.

[0029] A third magnet 10 is encapsulated within the sealing side, and a magnetic sensor 12 is disposed inside the groove 9. The third magnet 10 is located within the detection area of ​​the magnetic sensor 12, while the first magnet 8 is located outside the detection area of ​​the magnetic sensor 12. The magnetic sensor 12 generates a pulse signal as it moves with the third magnet 10. In use, when the guide plate 4 avoids the stirring structure 2, the guide plate 4 can move the third magnet 10, changing the distance between the third magnet 10 and the magnetic sensor 12, thereby changing the magnetic induction intensity sensed by the magnetic sensor 12. The magnetic sensor 12 outputs a corresponding pulse signal based on the relationship between the magnetic induction intensity and the position between the two. The controller can obtain the real-time rotation speed of the stirring structure 2 based on the frequency or period of the pulse signal. This allows the controller to precisely control the rotation speed of the stirring structure during use, effectively avoiding catalyst wear defects caused by excessive rotation speed. In this embodiment, the magnetic sensor 12 is a Hall sensor.

[0030] The inner cavity of the groove 9 is provided with a positioning block 7, which can limit the movement of the guide plate 4. When the guide plate 4 avoids the stirring structure 2, it contacts the positioning block 7 under the action of magnetic repulsion. At this time, the guide plate 4 is in the avoidance position. When the guide plate 4 resets and fits tightly against the reactor body 1, it is in the working position. The controller can calculate the reset time interval of the guide plate 4 from the avoidance position to the working position based on the received pulse signal and compare it with the preset reset time threshold. When the reset time interval of the guide plate 4 exceeds the set threshold or the guide plate 4 cannot move to the working position, the controller can issue an early warning through the alarm unit such as the alarm on the reactor so as to facilitate timely maintenance.

[0031] In addition, both the first magnet 8 and the second magnet 3 are provided with protective sheets on their surfaces. The protective sheets protect the first magnet 8 and the second magnet 3 from corrosion by the raw materials. The material of the protective sheets can be set according to the requirements.

[0032] As can be seen from the above description, this application improves the axial homogenization effect by utilizing a frame-type stirring structure and a guide plate 4, which facilitates the full mixing and heat transfer of raw materials, increases the interfacial reaction between materials, and thus improves the yield and quality of p-acetoxybenzoic acid.

[0033] In use, this application achieves real-time capture of the position change characteristics of the guide plate through the synergistic effect of the third magnet and the magnetic sensor. The rotation period of the stirring structure is inferred by the position change period of the guide plate, so as to accurately obtain the rotation period of the stirring structure 2. This facilitates the controller to adjust the rotation speed of the stirring structure 2. Furthermore, the controller can determine whether the guide plate is stuck or has a reset abnormality based on the reset time interval and final position of the guide plate, thereby improving the reliability of the reactor.

[0034] In summary: When using this p-acetoxybenzoic acid preparation reactor, the stirring structure 2 agitates the raw materials inside the reactor. The stirring structure 2 drives the scraper 5 to move, scraping away the adhering substances on the inner wall of the reactor. During the stirring process, the guide plate 4 guides the raw materials near the wall, improving the axial homogenization effect. Furthermore, the magnetic repulsion between the first magnet 8 and the second magnet 3 allows the guide plate 4 to be pressed into the groove 9 when the stirring structure 2 rotates the second magnet 3 to be circumferentially aligned with the first magnet 8. This magnetic repulsion avoids the stirring structure 2, facilitating its passage. During the passage of the stirring structure 2, the scraper 5 scrapes away the adhering substances on the guide surface of the guide plate 4, cleaning the guide surface. When the stirring structure 2 and the guide plate 4 are misaligned, the guide plate 4 can be reset under the rebound force of the torsion spring 13, maintaining its convex state and guiding the material inside the reactor.

[0035] During the movement of the guide vane, the distance between the third magnet 10 and the magnetic sensor 12 changes. The magnetic sensor 12 outputs a corresponding pulse signal to the controller based on the detected magnetic induction intensity. The controller can obtain the rotation cycle of the stirring structure based on the frequency or period of the pulse signal, and thus obtain the real-time rotation speed of the stirring structure 2. In use, the controller can achieve precise control of the stirring structure's rotation speed, effectively avoiding catalyst wear defects caused by excessive rotation speed. Furthermore, based on the received pulse signal, the controller can calculate the reset time interval of the guide vane returning from the avoidance position to the working position and compare it with a preset reset time threshold. When the guide vane reset time interval exceeds the set threshold or the guide vane cannot move to the working position, the controller can issue an early warning through alarm units such as alarms installed on the reactor for timely maintenance.

Claims

1. A p-acetoxybenzoic acid production reactor comprising a reactor body (1), characterised in that: The reactor body (1) is provided with a stirring structure (2). The inner sidewall of the reactor body (1) is uniformly provided with grooves (9) extending along the axial direction. The inner cavity of the groove (9) is movably connected to a guide plate (4). The guide plate (4) is connected to the reactor body (1) through an elastic structure. The side of the guide plate (4) away from the elastic structure is the guiding side, and the side of the guide plate (4) close to the elastic structure is the blocking side. When the elastic structure is in a free state, the guiding side is located in the inner cavity of the reactor body (1), and the blocking side blocks the groove (9). The guide plate (4) has a first magnet (8) encapsulated in the guide side, and the stirring structure (2) has a second magnet (3) encapsulated in the corresponding position at the vertical end. When the stirring structure (2) drives the second magnet (3) to rotate to be circumferentially aligned with the first magnet (8), the first magnet (8) and the second magnet (3) are in a state of magnetic repulsion. The magnetic repulsion force acts on the guide plate (4) and presses the guide plate (4) into the groove (9). The guide plate (4) has a third magnet (10) encapsulated in the sealing side, and a magnetic sensor (12) is provided on the inner side of the groove (9). The third magnet (10) is located in the detection area of ​​the magnetic sensor (12), and the magnetic sensor (12) generates a pulse signal as the third magnet (10) moves.

2. A reactor for the production of Acetyl oxybenzoic acid as claimed in claim 1, wherein: The stirring structure (2) is a frame-type stirring structure. A scraper (5) is provided on the outer wall of the vertical end of the stirring structure (2). The cutting edge of the scraper (5) is attached to the inner wall of the reactor body (1).

3. A reactor for the production of Acetyl oxybenzoic acid as claimed in claim 1, wherein: The guide plate (4) is movably connected to the reactor body (1) via a rotating shaft (6), and the side of the guide plate (4) away from the rotating shaft (6) is an arc-shaped sidewall.

4. A reactor for the production of Acetyl oxybenzoic acid as claimed in claim 3, wherein: The inner cavity of the groove (9) is provided with a positioning block (7). When the guide plate (4) contacts the positioning block (7), the guide plate (4) is located in the inner cavity of the groove (9). The side of the groove (9) away from the rotating shaft (6) is an arc-shaped surface adapted to the arc-shaped sidewall. The arc-shaped sidewall and the arc-shaped surface are in a close fit.

5. The reactor for preparing p-acetoxybenzoic acid according to claim 1, characterized in that: The elastic structure includes a positioning rod (11) connected to the inner cavity of the groove (9). A torsion spring (13) is movably sleeved on the outer ring of the positioning rod (11). One end of the torsion spring (13) is connected to the guide plate (4), and the other end of the torsion spring (13) is connected to the reactor body (1).

6. The reactor for preparing p-acetoxybenzoic acid according to claim 2, characterized in that: The guide plate (4) is a hollow structure; the axial height of the guide plate (4) covers the area between the upper and lower crossbars of the stirring structure (2).

7. The reactor for preparing p-acetoxybenzoic acid according to claim 1, characterized in that: The first magnet (8) in each guide plate (4) has the same polarity orientation and is located outside the detection area of ​​the magnetic sensor (12).

8. The reactor for preparing p-acetoxybenzoic acid according to claim 1, characterized in that: Both the first magnet (8) and the second magnet (3) have protective sheets on their surfaces.

Images