New technology for pentaerythritol constant-temperature continuous tubular reaction

Abstract

The invention provides a novel process for constant-temperature continuous tubular reaction of pentaerythritol, and relates to the technical field of preparation manufacturing, and the condensation reaction in the process is carried out in a two-section constant-temperature continuous tubular reactor. The method comprises the following steps: neutralizing a continuous tubular reaction solution with acid, evaporating and dehydrating, crystallizing in a crystallizing tank, and filtering and drying crystals to obtain high-purity pentaerythritol. The formaldehyde ratio of the new process is close to the theoretical ratio; continuous production of the device can be realized, and the product quality is stable; the investment cost of an aldehyde tower is reduced, and the product does not need to pass through the aldehyde tower, so that decomposers generated by the product staying at high temperature are reduced; the novel process is good in stability, continuous feeding is achieved, produced pentaerythritol is stable in quality and high in purity, a solution at the bottom is heated, concentrated and dehydrated in an adhesion mode through the neutralization concentration tank, the stirring and discharging processes are simplified, and the processing efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical manufacturing technology, and in particular to a novel process for the isothermal continuous tubular reaction of pentaerythritol. Background Technology

[0002] The isothermal continuous tubular reactor technology for pentaerythritol is an advanced process applied to the chemical production of pentaerythritol. Its core lies in utilizing a specially designed tubular reactor to achieve the continuous aldol condensation of formaldehyde and acetaldehyde under alkaline catalyst and the subsequent Cannizaro reaction under strictly constant temperature conditions. The main application of this technology is the efficient, stable, and large-scale production of high-quality pentaerythritol, a key raw material for manufacturing alkyd resins, polyurethanes, flame retardants, lubricants, PETN, and other products.

[0003] In the existing pentaerythritol production process, the indirect batch reaction is generally used. The indirect batch reaction has the following disadvantages: (1) Excess formaldehyde causes the disproportionation reaction to produce by-products and more impurities during the reaction; (2) Excess formaldehyde requires the addition of a formaldehyde removal tower to recover formaldehyde, which increases the investment in equipment and also increases the amount of electricity, heat and cold energy, resulting in high energy consumption; (3) Indirect batch reaction easily increases the probability of raw materials coming into contact with air during the reaction, which leads to oxidation of raw materials, resulting in high consumption and decreased product quality. It also carries the safety risk of flash explosion caused by contact between chemical raw materials and air; (4) Under high temperature and salt conditions, pentaerythritol will degrade to produce high-boiling-point, high-viscosity products such as lipids, which leads to a decrease in product purity.

[0004] On the other hand, conventional pentaerythritol production processes require neutralization and concentration / dehydration. The neutralization process requires continuous stirring, and the injected neutralization solution cannot be monitored in real time to ensure that the target level is reached. Furthermore, the sampling process is cumbersome and prone to over-neutralization. The subsequent concentration / dehydration process also requires repeated transfer, which increases the probability of contamination. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] Therefore, the purpose of this invention is to provide a new process for the isothermal continuous tubular reaction of pentaerythritol. This invention solves the problem of excessive formaldehyde concentration in batch reactors, eliminating the need for a formaldehyde removal tower to recover excess formaldehyde, thereby reducing costs and energy consumption. The new process reduces the generation of by-products, improves the conversion rate, and thus improves product quality. During neutralization, the solution at the bottom can be heated, concentrated, and dehydrated through adhesion, simplifying the stirring and discharging process and improving processing efficiency.

[0007] To achieve the above objectives, the present invention provides a novel process for the isothermal continuous tubular reaction of pentaerythritol, comprising the following steps:

[0008] S1. The first stage of continuous tubular reaction is carried out. After the formaldehyde and acetaldehyde are mixed in the correct ratio, they are injected into the inlet of the first stage reactor. The reaction is carried out in the pipeline. At the outlet of the first stage, part of the material is returned to the inlet, and the other part of the material is sent to the second stage continuous tubular reactor.

[0009] S2. The second stage of continuous tubular reaction is carried out. The formaldehyde and acetaldehyde are re-ratioed and injected into the inlet of the second stage reactor. The reaction is held in the pipeline. Part of the material at the outlet of the second stage is returned to the inlet, and the other part is sent to the neutralization and concentration tank.

[0010] S3. Add formic acid into the neutralization and concentration tank to adjust the pH value of the internal solution, and start the stirring component inside the neutralization and concentration tank. Use the stirring component to stir and mix the formic acid solution and materials simultaneously. At the rear end of the neutralization and concentration tank, use the sampling mechanism to continuously extract the solution under stirring, and periodically test the extracted solution to obtain the current pH value.

[0011] S4. After the reaction solution is neutralized, the stirring component is controlled to rotate in the opposite direction and the speed is reduced. The stirring component is used to adhere the bottom part of the reaction solution. The inner electric heating system is started to perform thin film evaporation treatment on the adhered solution. The concentrated liquid after evaporation and dehydration is transported to the discharge mechanism along with the stirring component and discharged after being scraped by the discharge mechanism.

[0012] S5. The sample is fed into a crystallization tank for crystallization. The crystalline pentaerythritol is then filtered and dried to obtain high-purity pentaerythritol.

[0013] Furthermore, in step S1, the ratio of formaldehyde to acetaldehyde is 3-3.05:1, the temperature is 45±5℃, the pH at the reactor inlet is controlled at 9.5-10.5, the flow rate is controlled at 0.5-3 m / s, the residence time in the pipeline is 30-45 minutes, and the reflux to extraction ratio is 1-3:1.

[0014] Furthermore, in step S2, the ratio of formaldehyde to acetaldehyde is 1-1.05:1, the temperature is kept constant at 55±5℃, the pH at the reactor inlet is controlled at 10.5-11.5, the flow rate is controlled at 0.5-3 m / s, the residence time in the pipeline is 10-20 minutes, and the reflux to output ratio is 1-2:1; in step S3, formic acid is added to adjust the pH of the reaction solution in the neutralization and concentration tank to 6.8-7.2.

[0015] Furthermore, the neutralization and concentration tank used has a sampling mechanism connected to its rear end, and an end plate is provided at the rear end of the sampling mechanism. An agitation assembly is installed inside the neutralization and concentration tank, and multiple switching mechanisms are embedded on the side of the agitation assembly. There are four switching mechanisms, and each switching mechanism is evenly distributed around the agitation assembly.

[0016] A discharge mechanism is installed on one side of the interior of the neutralization and concentration tank. The discharge mechanism is against one side of the stirring component and is used to scrape and discharge the concentrated reaction liquid adhering to the surface of the neutralization and concentration tank. An electric heating wire is embedded in the top of the interior of the neutralization and concentration tank.

[0017] Furthermore, one end of the neutralization and concentration tank is connected to an injection pipe and a neutralization solution delivery pipe. The neutralization solution delivery pipe is used to deliver formic acid into the interior of the neutralization and concentration tank. The top and bottom of the stirring component are provided with gaps between them and the inner wall of the neutralization and concentration tank, and the liquid level of the injected reaction liquid is lower than the bottom position of the discharge mechanism.

[0018] Furthermore, the agitation component includes:

[0019] The device includes a motor, a rotating disk, and connecting holes. The output end of the motor is connected to a drive shaft, and the end of the drive shaft is fitted with a rotating disk. Connecting holes are provided on both sides of the rotating disk. Switching mechanisms are embedded in the edge of the rotating disk, and there is a gap between two adjacent switching mechanisms. The motor is screwed onto the surface of the neutralization and concentration tank.

[0020] Furthermore, the switching mechanism includes:

[0021] The telescopic cavity, telescopic block, and magnetic plate are provided. The telescopic cavity is located inside the rotating disk. The telescopic block is embedded inside the telescopic cavity, and the magnetic plate is embedded on the inner wall of the telescopic cavity. The connecting hole is connected to the inside of the telescopic cavity, and the side of the telescopic block is in contact with the inner wall of the telescopic cavity.

[0022] The telescopic block has a raised strip on its side, which is used to embed into the inner wall of the telescopic cavity. The telescopic block slides along the inside of the telescopic cavity through the raised strip. A one-way valve is also provided on the inner wall of the telescopic cavity. The one-way valve is connected to the flow channel. The telescopic block extends outward to draw the reaction liquid from the outside into the inside of the telescopic cavity. The telescopic block also retracts towards the inside of the telescopic cavity to push the reaction liquid drawn in into the connecting hole and the inside of the one-way valve.

[0023] The end of the telescopic block is provided with an arc surface, and after the telescopic block is embedded in the telescopic cavity, the surface of the telescopic block is aligned with the surface of the rotating disk. The telescopic block is used to agitate the reaction liquid at the bottom.

[0024] Furthermore, the discharge mechanism includes:

[0025] The tank includes a side scraper, a discharge plate, an elastic lever, a discharge port, a lower hanging plate, and a vertical plate. The lower hanging plate is welded to the inner wall of the neutralization and concentration tank. The top of the lower hanging plate is integrally formed with a discharge plate. The side of the discharge plate is integrally formed with a side scraper. An elastic lever is attached to one end of the discharge plate. The other end of the discharge plate has a discharge port.

[0026] A vertical plate is provided on one side of the lower plate, which is used to push the telescopic block inward. The side scraper abuts against both sides of the rotating disk, and the elastic paddle abuts against the edge of the rotating disk.

[0027] Furthermore, the sampling mechanism includes:

[0028] The system includes an extraction pipe, a pressure pump, a return pipe, and a three-way valve. The pressure pump is screwed to the side of the end plate. One end of the pressure pump is connected to the extraction pipe, and the other end is connected to the return pipe. A three-way valve is installed at the end of the return pipe, and the bottom of the three-way valve is connected to the interior of the neutralization and concentration tank.

[0029] Furthermore, the sampling mechanism also includes:

[0030] The assembly comprises a central rod, stirring blades, a collecting sleeve, and a connecting sleeve. A connecting sleeve is welded to the surface of the end plate, and a central rod is disposed inside the connecting sleeve. A stirring blade is welded to the side of the central rod. A connecting sleeve is integrally formed at the rear end of the stirring assembly and is embedded inside the connecting sleeve. A collecting sleeve is disposed at the bottom of the connecting sleeve. The connecting sleeve is used to transport the reaction liquid extracted from the inside to the inside of the connecting sleeve.

[0031] The technical solution provided by this invention may include the following beneficial effects:

[0032] 1. The formaldehyde ratio in the new isothermal continuous tubular reaction process for pentaerythritol is close to the theoretical ratio; the new process enables continuous production of the equipment and stable product quality; the new process reduces the input cost of the aldehyde tower; the product does not need to pass through the aldehyde tower in the new process, thereby reducing the decomposition products generated by the product staying at high temperature; the new process has good stability, continuous feeding, and produces pentaerythritol with stable quality and high purity.

[0033] 2. This novel isothermal continuous tubular reaction process for pentaerythritol involves conveying formic acid and the reacted materials into a neutralization and concentration tank for stirring and concentration. During this process, the internal stirring component rotates at high speed in the forward direction, automatically triggering the switching mechanism to pop up and stirring the internal mixed solution. When discharging, the switching mechanism is retracted by rotating slowly in the reverse direction. At this point, the solution at the bottom can be heated, concentrated, and dehydrated through adhesion, and then directly discharged. This simplifies the stirring and discharging process and improves processing efficiency.

[0034] 3. The new process of isothermal continuous tubular reaction of pentaerythritol uses an internal switching mechanism in conjunction with a discharge mechanism. During the stirring process, the switching mechanism's repeated extension and retraction piston movement automatically extracts and transports quantitatively from a fixed point at fixed intervals to a sampling mechanism. The sampling mechanism is used to detect and process the extracted material, so as to accurately and in real time determine the neutralization state of the solution.

[0035] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0037] Figure 1 This is a flowchart of a novel process for the isothermal continuous tubular reaction of pentaerythritol proposed in one embodiment of the present invention;

[0038] Figure 2 This is a liquid chromatogram of pentaerythritol synthesized by a novel process according to an embodiment of the present invention;

[0039] Figure 3 This is a structural diagram of the neutralization and concentration equipment in a novel process for the isothermal continuous tubular reaction of pentaerythritol proposed in an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of the sampling mechanism in the neutralization and concentration device structure proposed in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the sampling machine connection in a neutralization and concentration device structure proposed in an embodiment of the present invention;

[0042] Figure 6 This is a structural diagram of the internal structure of the neutralization and concentration tank in a neutralization and concentration device structure proposed in an embodiment of the present invention;

[0043] Figure 7This is a schematic diagram of the agitation component structure in a neutralization and concentration device structure proposed in an embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the discharge mechanism in a neutralization and concentration device structure proposed in an embodiment of the present invention;

[0045] Figure 9 This is the present invention. Figure 6 Enlarged view of region A in the middle;

[0046] As shown in the figure: 1. Neutralization and concentration tank; 2. End plate; 3. Sampling mechanism; 4. Stirring assembly; 5. Injection pipe; 6. Neutralization solution delivery pipe; 7. Connecting sleeve; 8. Extraction pipe; 9. Pressure pump; 10. Return pipe; 11. Three-way valve; 12. Center rod; 13. Stirring blade; 14. Collecting sleeve; 15. Insertion sleeve; 16. Motor; 17. Center hole; 18. Discharge mechanism; 19. Gap; 20. Switching mechanism; 21. Rotating disk; 22. Connecting hole; 23. Side scraper; 24. Discharge plate; 25. Elastic paddle; 26. Discharge port; 27. Lower hanging plate; 28. Vertical plate; 29. ​​Telescopic cavity; 30. Telescopic block; 31. Magnetic suction plate; 32. One-way valve; 33. Guide channel; 34. Inclined plate; 35. Protrusion; 36. Guide hole. Detailed Implementation

[0047] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the invention, and should not be construed as limiting the invention. Rather, embodiments of the invention include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0048] like Figures 1 to 9 As shown, the present invention provides the following embodiments:

[0049] Example 1

[0050] The isothermal continuous tubular production process for pentaerythritol includes the following steps:

[0051] (1) The first stage is a continuous tubular reaction, with the formaldehyde to acetaldehyde ratio controlled at 3.05:1, the temperature at 45℃, the reactor inlet pH controlled at 9.5, and the flow rate controlled at 1 m / s. The pipeline residence time is 40 minutes. Part of the material from the first stage outlet is returned to the inlet, and part is collected to the second stage continuous tubular reactor. The return to collection ratio is 2:1.

[0052] (2) The second stage is a continuous tubular reaction. The ratio of formaldehyde to acetaldehyde is controlled at 1.05:1, the temperature is kept constant at 55℃, the pH at the reactor inlet is controlled at 10.5, and the flow rate is controlled at 1 m / s. The residence time in the pipeline is 15 minutes. Part of the material at the outlet of the second stage is returned to the inlet, and part is collected to the neutralization tank. The return to collection ratio is 1:1.

[0053] (3) Add formic acid to adjust the pH of the reaction solution in the neutralization tank to 7.

[0054] (4) After the neutralized reaction liquid is evaporated and dehydrated, it is then put into a crystallization tank for crystallization. The crystal pentaerythritol is filtered and dried to obtain pentaerythritol with a mass content of 98.5%.

[0055] Example 2

[0056] The isothermal continuous tubular production process for pentaerythritol includes the following steps:

[0057] (1) The first stage is a continuous tubular reaction, with the formaldehyde to acetaldehyde ratio controlled at 3:1, the temperature at 45℃, the reactor inlet pH controlled at 9.5, and the flow rate controlled at 1 m / s. The pipeline residence time is 40 minutes. Part of the material from the first stage outlet is returned to the inlet, and part is collected to the second stage continuous tubular reactor. The return to collection ratio is 2:1.

[0058] (2) The second stage is a continuous tubular reaction, with the formaldehyde to acetaldehyde ratio controlled at 1:1, the temperature kept constant at 55℃, the reactor inlet pH controlled at 10.5, and the flow rate controlled at 1 m / s. The pipeline residence time is 15 minutes. Part of the material from the second stage outlet is returned to the inlet, and part is collected to the neutralization tank. The return to collection ratio is 1:1.

[0059] (3) Add formic acid to adjust the pH of the reaction solution in the neutralization tank to 7.

[0060] (4) After the neutralized reaction solution is evaporated and dehydrated, it is then put into a crystallization tank for crystallization. The pentaerythritol crystals are filtered and dried to obtain pentaerythritol with a mass content of 98.7%.

[0061] Through the above embodiments, the formaldehyde ratio in this process is close to the theoretical ratio; the new process can realize continuous production of the equipment and the product quality is stable; the new process reduces the input cost of the aldehyde tower; the product in the new process does not need to pass through the aldehyde tower, thereby reducing the decomposition products generated by the product staying at high temperature; the new process has good stability, continuous feeding, and produces pentaerythritol with stable quality and high purity.

[0062] Example 3

[0063] In this embodiment, a sampling mechanism 3 is connected to the rear end of the neutralization and concentration tank 1. An end plate 2 is provided at the rear end of the sampling mechanism 3. An agitation assembly 4 is installed inside the neutralization and concentration tank 1. Multiple switching mechanisms 20 are embedded on the side of the agitation assembly 4. There are four switching mechanisms 20, and each switching mechanism 20 is evenly distributed around the agitation assembly 4.

[0064] A discharge mechanism 18 is installed on one side of the interior of the neutralization and concentration tank 1. The discharge mechanism 18 rests against one side of the stirring component 4 and is used to scrape and discharge the concentrated reaction liquid adhering to the surface of the neutralization and concentration tank 1. An electric heating wire is embedded in the top of the interior of the neutralization and concentration tank 1.

[0065] One end of the neutralization and concentration tank 1 is connected to an injection pipe 5 and a neutralization solution delivery pipe 6. The neutralization solution delivery pipe 6 is used to deliver formic acid into the interior of the neutralization and concentration tank 1. The top and bottom ends of the stirring component 4 are provided with gaps 19 between them and the inner wall of the neutralization and concentration tank 1, and the liquid level of the injected reaction liquid is lower than the bottom position of the discharge mechanism 18.

[0066] Specifically, during use, the reacted solution is pumped into the neutralization and concentration tank 1 through the injection pipe 5 at one end until the liquid level approaches the discharge mechanism 18 on the other side. After stopping the injection, the motor 16 is started to control the stirring component 4, while formic acid solution is continuously injected into the inside of the neutralization and concentration tank 1 through the neutralization solution delivery pipe 6. Figure 6 As shown, at this time, the rotating disk 21 is controlled by the motor 16 to rotate counterclockwise, and the speed is controlled until the telescopic block 30 in the switching mechanism 20 extends outward by means of centrifugal effect, so that the solution at the bottom can be stirred. During this process, the sampling mechanism 3 continuously detects the solution sample extracted from the inside until the pH reaches the preset range, and then the injection of formic acid solution can be stopped. At this time, the reverse control motor 16 drives the rotating disk 21 to rotate clockwise and reduces the speed. The telescopic block 30 in each switching mechanism 20 will retract under the action of the inner magnetic attraction structure, and with the rotation of the rotating disk 21, the solution at the bottom will adhere. With the help of the electric heating structure at the top, the solution in the thin film state can be evaporated and dehydrated, and discharged by the discharge mechanism 18.

[0067] In this embodiment, the agitation component 4 includes:

[0068] The motor 16, the rotating disk 21, and the connecting hole 22 are provided. The output end of the motor 16 is connected to the drive shaft. The rotating disk 21 is installed at the end of the drive shaft. The rotating disk 21 has connecting holes 22 on both sides. The switching mechanism 20 is embedded in the edge of the rotating disk 21, and there is a gap between two adjacent switching mechanisms 20. The motor 16 is screwed to the surface of the neutralization and concentration tank 1.

[0069] The switching mechanism 20 includes:

[0070] The telescopic cavity 29, the telescopic block 30, and the magnetic plate 31 are provided. The telescopic cavity 29 is opened inside the rotating disk 21. The telescopic block 30 is embedded inside the telescopic cavity 29, and the magnetic plate 31 is embedded on the inner wall of the telescopic cavity 29. The connecting hole 22 is connected to the inside of the telescopic cavity 29, and the side of the telescopic block 30 is in contact with the inner wall of the telescopic cavity 29.

[0071] The telescopic block 30 has a protruding strip on its side, which is used to embed into the inner wall of the telescopic cavity 29. The telescopic block 30 slides along the inside of the telescopic cavity 29 through the protruding strip. A one-way valve 32 is also provided on the inner wall of the telescopic cavity 29. The one-way valve 32 is connected to the guide channel 33. The telescopic block 30 extends outward to draw the reaction liquid from the outside into the inside of the telescopic cavity 29. The telescopic block 30 also retracts towards the inside of the telescopic cavity 29 to push the reaction liquid drawn in into the inside into the connecting hole 22 and the one-way valve 32.

[0072] The end of the telescopic block 30 is provided with an arc surface, and after the telescopic block 30 is embedded in the telescopic cavity 29, the surface of the telescopic block 30 is aligned with the surface of the rotating disk 21. The telescopic block 30 is used to stir the reaction liquid at the bottom.

[0073] The discharge mechanism 18 includes:

[0074] The tank includes a side scraper 23, a discharge plate 24, an elastic lever 25, a discharge port 26, a lower hanging plate 27, and a vertical plate 28. The lower hanging plate 27 is welded to the inner wall of the neutralization and concentration tank 1. The top of the lower hanging plate 27 is integrally formed with a discharge plate 24. The side of the discharge plate 24 is integrally formed with a side scraper 23. One end of the discharge plate 24 is attached with an elastic lever 25, and the other end of the discharge plate 24 is provided with a discharge port 26.

[0075] A vertical plate 28 is provided on one side of the lower hanging plate 27. The vertical plate 28 is used to push the telescopic block 30 inward. The side scraper abuts against both sides of the rotating disk 21. The elastic paddle 25 is used to abut against the edge of the rotating disk 21.

[0076] By conveying formic acid and the reacted material into the neutralization and concentration tank 1, it is stirred and concentrated. During this process, the internal stirring component 4 rotates at high speed in the forward direction, which automatically pops out the switching mechanism 20 and stirs the mixed solution inside. When discharging, the switching mechanism 20 is retracted by rotating slowly in the reverse direction. At this time, the solution at the bottom can be heated, concentrated and dehydrated by adhesion and then directly discharged, which simplifies the stirring and discharging process and improves processing efficiency.

[0077] Specifically, after starting the motor 16, the drive shaft on the motor 16 will drive the entire rotating disk 21 to rotate. During the rotation of the rotating disk 21, the centrifugal effect will directly cause the telescopic blocks 30 in each switching mechanism 20 to be thrown outward, and finally the telescopic blocks 30 will protrude into the gap 19. At this time, as the rotating disk 21 rotates counterclockwise, the internal solution can be directly stirred.

[0078] During the rotation of the rotating disk 21, a protrusion 35 is provided on one side of the interior of the neutralization and concentration tank 1. A guide hole 36 is provided on the inner side of the protrusion 35. As the rotating disk 21 rotates, the telescopic block 30 contacts the protrusion 35 and is pushed by the inclined plate 34 on the top of the protrusion 35 until the telescopic block 30 is embedded in the telescopic cavity. When the telescopic block 30 passes the position of the protrusion 35, it will be thrown out of the telescopic cavity again by means of centrifugal effect and its own gravity. At this time, the external mixed solution can be directly drawn into the telescopic cavity through the connecting hole 22. As the switching mechanism 20 continues to rotate, when it contacts the vertical plate 28 area on the discharge mechanism 18, it will be pushed by the vertical plate 28 again, causing the telescopic block 30 to retract. At this time, the solution that has been drawn in can be squeezed outward and some solution can pass through the one-way valve 32 into the guide channel 33, and finally enter the sampling mechanism 3 at the rear end for detection or reflux treatment.

[0079] After agitation is complete, the control motor 16 drives the rotating disk 21 to rotate in the opposite direction and reduces the speed until it is too low to throw out the telescopic block 30 that is attracted by the magnetic suction plate 31. During this process, after the solution adheres to the bottom of the rotating disk 21, as it rotates towards the top, the solution in the thin film state adhered to the surface of the rotating disk 21 is evaporated and dehydrated by the electric heating component at the top. Finally, it comes into contact with the side scraper and elastic paddle 25 on the discharge mechanism 18, and the dehydrated concentrate is discharged through the discharge port 26.

[0080] In this embodiment, the sampling mechanism 3 includes:

[0081] The system includes an extraction pipe 8, a pressure pump 9, a return pipe 10, and a three-way valve 11. The pressure pump 9 is screwed to the side of the end plate 2. One end of the pressure pump 9 is connected to the extraction pipe 8, and the other end of the pressure pump 9 is connected to the return pipe 10. The end of the return pipe 10 is equipped with a three-way valve 11, and the bottom of the three-way valve 11 is connected to the interior of the neutralization and concentration tank 1.

[0082] The sampling mechanism 3 also includes:

[0083] The assembly includes a central rod 12, a stirring blade 13, a collecting sleeve 14, and a connecting sleeve 15. A connecting sleeve 7 is welded to the surface of the end plate 2. The central rod 12 is disposed inside the connecting sleeve 7. The stirring blade 13 is welded to the side of the central rod 12. A connecting sleeve 15 is integrally formed at the rear end of the stirring assembly 4. The connecting sleeve 15 is embedded inside the connecting sleeve 7. A collecting sleeve 14 is disposed at the bottom of the connecting sleeve 7. The connecting sleeve 15 is used to transport the reaction liquid extracted from the inside to the inside of the connecting sleeve 7.

[0084] Through the inner switching mechanism 20 in conjunction with the discharge mechanism 18, during the stirring process, the switching mechanism 20 can automatically extract and transport quantitatively from a fixed point at fixed intervals to the sampling mechanism 3 by means of the repeated extension and retraction piston movement of the piston. The sampling mechanism 3 is used to detect and process the extracted material so as to accurately and in real time determine the neutralization state of the current solution.

[0085] Specifically, a portion of the sample extracted through the internal switching mechanism 20 enters the interior of the docking sleeve 7 through the rear insertion sleeve. Since the insertion sleeve rotates synchronously with the rotating disk 21, the central rod 12 inside the docking sleeve 7, in conjunction with the stirring blade 13, can directly agitate the solution inside the insertion sleeve and transport it to the interior of the collecting sleeve 14. The solution is then extracted using the pressure pump 9 and the extraction pipe 8 and finally transported to the return pipe 10. It can then be removed for testing using the three-way valve 11 or directly returned to the interior of the neutralization and concentration tank 1.

[0086] The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0087] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0088] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A new process for the continuous tubular reaction of pentaerythritol at constant temperature, characterized in that, It comprises the following steps: S1, the first stage of continuous tube type reaction is carried out, formaldehyde and acetaldehyde are proportioned, then injected into the inlet position of the first stage reactor, reacted in the pipeline, part of the material at the outlet of the first stage is backflowed to the inlet, and the other part is sent into the second stage of continuous tube type reactor; S2, the second stage of continuous tube type reaction is carried out, formaldehyde and acetaldehyde are proportioned again, then injected into the inlet position of the second stage reactor, reacted in the pipeline, part of the material at the outlet of the second stage is backflowed to the inlet, and the other part is sent into the neutralization and concentration tank; S3, formic acid is added to the inside of the neutralization and concentration tank, the pH value of the internal solution is adjusted, and the stirring assembly inside the neutralization and concentration tank is started, the formic acid solution and the material are stirred and mixed synchronously by the stirring assembly, the solution in the stirring state is continuously extracted at the rear end of the neutralization and concentration tank by the sampling mechanism, and the extracted solution to be detected is detected regularly to obtain the current pH value; S4, after the reaction liquid is neutralized, the stirring assembly is controlled to rotate reversely and the rotating speed is reduced, the bottom part of the reaction liquid is adhered by the stirring assembly, the internal electric heating system is started to perform thin film evaporation treatment on the adhered solution, and the concentrated liquid after evaporation and dehydration is transported to the discharge mechanism by the stirring assembly and discharged after being scraped by the discharge mechanism; S5, sent into the crystallization tank for crystallization, the crystalline pentaerythritol is obtained after the filtering and drying procedures to obtain high-purity pentaerythritol.

2. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 1, characterized by the fact that, In step S1, the proportion of formaldehyde and acetaldehyde is 3-3.05:1, the temperature is 45±5℃, the pH value at the inlet of the reactor is controlled to be 9.5-10.5, the flow rate is controlled to be 0.5-3m / s, the pipeline residence time is 30-45 minutes, and the backflow and production ratio is 1-3:

1.

3. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 2, characterized by the fact that, In step S2, the proportion of formaldehyde and acetaldehyde is 1-1.05:1, the temperature is constant at 55±5℃, the pH value at the inlet of the reactor is controlled to be 10.5-11.5, the flow rate is controlled to be 0.5-3m / s, the pipeline residence time is 10-20 minutes, and the backflow and production ratio is 1-2:1; in step S3, formic acid is added to adjust the pH value of the reaction liquid in the neutralization and concentration tank to 6.8-7.

2.

4. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 1, characterized by the fact that, It comprises a neutralization and concentration tank, a sampling mechanism is connected to the rear end of the neutralization and concentration tank, an end plate is arranged at the rear end of the sampling mechanism, a stirring assembly is installed in the inside of the neutralization and concentration tank, a plurality of switching mechanisms are embedded in the side of the stirring assembly, the number of the switching mechanisms is four, and each switching mechanism is uniformly distributed around the stirring assembly; A discharge mechanism is installed on one side in the inside of the neutralization and concentration tank, the discharge mechanism is abutted on one side of the stirring assembly, and the discharge mechanism is used for scraping and discharging the concentrated reaction liquid adhered to the surface of the neutralization and concentration tank, an electric heating wire is embedded in the top end of the inside of the neutralization and concentration tank.

5. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 4, characterized by the fact that, One end of the neutralization and concentration tank is connected with an injection pipeline and a neutralization solution conveying pipeline, the neutralization solution conveying pipeline is used for conveying formic acid to the inside of the neutralization and concentration tank, gaps are arranged between the top and bottom of the stirring assembly and the inner wall of the neutralization and concentration tank, and the liquid level of the injected reaction liquid is lower than the bottom position of the discharge mechanism.

6. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 4, characterized by the fact that, The stirring assembly comprises: The utility model discloses a motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank.

7. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 6, characterized by the fact that, The switching mechanism comprises: The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank.

8. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 7, characterized by the fact that, The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank.

9. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 6, characterized by the fact that, The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank.

10. The new process for continuous tubular reaction of pentaerythritol at constant temperature according to claim 9, characterized by the fact that, The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank. The utility model relates to a neutralization and concentration tank, including motor, rotating disc and communication hole, the output of motor is connected with drive shaft, the end of drive shaft is installed with rotating disc, and the both sides of rotating disc are all set up with communication hole, and the switching mechanism is embedded to the edge of rotating disc, and is provided with interval between the adjacent two switching mechanisms, and the motor is screwed on the surface of neutralization and concentration tank.

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