Pentaerythritol efficient synthesis system and synthesis method using same

Abstract

Provided in the present invention are a pentaerythritol efficient synthesis system and a synthesis method using same. The efficient synthesis system comprises a multi-stage reactor, wherein a plurality of enhancement units and a plurality of liquid level sensors are vertically arranged inside the multi-stage reactor; a plurality of grids or a plurality of screen plates are arranged in the middle section of the interior of the multi-stage reactor; an acetaldehyde feed port is arranged at the top of the multi-stage reactor, and the acetaldehyde feed port is introduced into the enhancement units; a diverter feed port and a mixed liquid feed port are respectively arranged on two sides of the top of the multi-stage reactor; a communication pipe is further arranged outside the multi-stage reactor, and the communication pipe is further provided with a valve; a control system for receiving data sent back from the liquid level sensors and controlling the valve to open or close is further arranged outside the multi-stage reactor; and a discharge port is arranged at the bottom of the multi-stage reactor. The efficient synthesis system of the present invention features a high yield and a high purity by means of the enhancement units and the liquid level sensors.

Description

An efficient synthetic system and method for pentaerythritol Technical Field

[0001] This invention belongs to the field of pentaerythritol production technology, specifically to a highly efficient synthesis system and method for pentaerythritol. Background Technology

[0002] Pentaerythritol is an important organic chemical raw material widely used in resin, coating, chemical, pharmaceutical, and defense industries. It is primarily used to produce lubricants, plasticizers, surfactants, emulsifiers, pharmaceuticals, pesticides, and explosives. Currently, deep-processed pentaerythritol products are under development, including initiators for polyester polyols, components for flame-retardant coatings, intermediates for epoxy crosslinking agents, stabilizers for polyvinyl chloride, intermediates for oil-modified amino surface coatings (amino alkyd resins), olefin antioxidants, and pentaerythritol triacrylates. Pentaerythritol phosphate and phosphite esters are used as flame retardants, antioxidants, or heat stabilizers in polymer production, while pentaerythritol acrylates are widely used in radiation-cured coatings and fast-drying printing inks, and also in the manufacture of water-soluble alkyd resins. Its polymer emulsions can be used as adhesives.

[0003] Currently, sodium hydroxide is widely used as a catalyst in traditional industries. However, this traditional process presents several problems. The synthesis of pentaerythritol in traditional processes involves two steps: the first step, the Aldel reaction, is endothermic, while the second step, the Cannizzaro reaction, is exothermic. The condensation process requires a gradual temperature rise curve; otherwise, side reactions will occur. Especially when the temperature exceeds 20°C, the reaction rate accelerates, the heat of reaction is difficult to remove in time, side reactions accelerate, and byproducts increase, leading to a decrease in pentaerythritol yield and increasing the difficulty of subsequent separation processes, thus affecting product output and quality. Furthermore, the strong base catalytic system causes severe corrosion to equipment. The formaldehyde required for the reaction is always an aqueous solution, resulting in a high water load in the entire process. During distillation, the high latent heat of water causes high energy consumption, and the excessive water content in the reaction system prolongs the reaction time.

[0004] In view of this, the present invention is hereby proposed.

[0005] Summary of the Invention

[0006] The primary objective of this invention is to provide a highly efficient synthesis system for pentaerythritol. This highly efficient synthesis system, through the setup of multiple enhanced units, grids, sensors, and valves, achieves more uniform mixing of the reaction system, a more thorough reaction, reduced backmixing leading to higher product purity, and increased contact area between raw materials via enhanced units, thereby improving reaction rate and product yield. Furthermore, the use of an external circulation system allows for timely removal of reaction heat, enabling precise control of the reaction temperature, reducing the generation of reaction byproducts, and facilitating subsequent purification and separation.

[0007] The second objective of this invention is to provide a method for synthesizing pentaerythritol, which is simple to operate, has mild operating conditions, and produces a high yield and high purity of product.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] A high-efficiency synthesis system for pentaerythritol includes a multi-stage reactor. Multiple intensifier units and a liquid level sensor are vertically arranged inside the multi-stage reactor. A multi-layer grid is installed in the middle section of the multi-stage reactor. An acetaldehyde inlet is located at the top of the multi-stage reactor, leading into the intensifier units. A distributor inlet and a mixed liquid inlet are respectively located on both sides of the top of the multi-stage reactor. A connecting pipe with valves is also installed outside the multi-stage reactor. A control system for receiving data from the liquid level sensor and controlling the opening and closing of the valves is also located outside the multi-stage reactor. An outlet is located at the bottom of the multi-stage reactor.

[0010] Preferably, as a further feasible option, the multi-stage reactor is a two-stage reactor, and the two-stage reactor is provided with two intensifier units and two liquid level sensors; wherein, the first-stage reactor includes a first intensifier unit disposed at the top of the multi-stage reactor and a first liquid level sensor disposed on the inner wall above the first intensifier unit, the first liquid level sensor being used to detect the liquid level height in the first-stage reactor.

[0011] The second-stage reactor includes a second intensifier unit disposed at the bottom of the two-stage reactor and a second liquid level sensor disposed on the inner wall above the second intensifier unit. The second liquid level sensor is used to detect the liquid level height in the second-stage reactor.

[0012] In the pentaerythritol synthesis system of this invention, since the raw materials used in this invention are normally two immiscible liquids in contact with each other, the reaction between the two is insufficient due to the small phase interface area between the raw materials during the traditional synthesis of pentaerythritol. Furthermore, since the condensation of formaldehyde and acetaldehyde is a multi-stage condensation reaction, in order to make the reaction more complete and increase the reaction rate, this invention sets up a multi-stage reactor, preferably a two-stage reactor, to make the reaction more complete and thorough. By using an enhanced unit to increase the reaction area between the formaldehyde and acetaldehyde reaction liquids, the progress of the reaction process and the yield of the reaction can be increased. In this invention, the two-stage reactor setup ensures that the condensation of formaldehyde and acetaldehyde does not stop at an intermediate step, minimizing the generation of byproducts and improving the purity of the final product. This facilitates subsequent separation and purification. This is because the invention incorporates a first liquid level sensor and an intensifier unit in the first-stage reactor. After the acetaldehyde and sodium hydroxide catalyst entering from the top of the multi-stage reactor are uniformly mixed with the formaldehyde metered in by a metering pump, the first intensifier unit processes them into extremely small droplets, increasing the interphase area and enhancing contact between them. This design increases the contact area and time between the raw materials and the reactor as they descend through the first-stage reactor. Catalysis further enhances the reaction, leading to a more complete and efficient conversion of the raw materials into more intermediate products. As the raw material mixture, processed into droplets, descends through the two-stage reactors, it gradually fills the first-stage reactor. The reaction liquid from the first-stage reactor is then transported to the second-stage reactor via external conveying channels. A grid in the middle of the multi-stage reactor prevents back-mixing between the first and second-stage reactors. The mixture entering the second-stage reactor is then processed by an intensifier unit, increasing the interphase area between the reactants and ultimately converting the intermediate product into pentaerythritol. Therefore, this invention, by using a two-stage reactor and an intensifier unit, increases the interphase area between the raw materials, resulting in a more complete and efficient reaction.

[0013] Preferably, as a further feasible option, the multi-layer grid or multi-layer sieve plate has 3-7 layers;

[0014] Preferably, the number of layers is 5;

[0015] The distance between the grille and the second strengthening unit is twice the distance between the grille and the second liquid level sensor;

[0016] The distance between the second liquid level sensor and the second strengthening unit is three times the distance between the second liquid level sensor and the grid.

[0017] Preferably, as a further feasible option, the distance between the first liquid level sensor and the first intensifier unit is three times the distance between the first liquid level sensor and the top of the two-stage reactor.

[0018] Furthermore, this invention addresses the issue of the final step in the synthesis of pentaerythritol, where the intermediate product is converted into pentaerythritol. This final step involves excessive formaldehyde and a strongly exothermic reaction. To prevent backmixing between the first and second stage reactors, which could lead to excessively vigorous reactions and side reactions in the first stage reactor, making subsequent separation and purification of byproducts difficult, this invention uses a control system connected to the first and second liquid level sensors to control the opening and closing of valves on the connecting pipe. During the reaction in the first stage reactor to generate the intermediate product, the valves are closed, ensuring the reaction liquid inside the first stage reactor reacts fully after being processed by the first intensifier unit. The presence of a grid prevents backmixing between the liquid in the second stage reactor and the liquid in the first stage reactor. The grid design... The setup is preferably multi-layered, and more preferably, the grid or sieve plate is set with 5 layers to ensure that the liquids inside the second-stage reactor and the first-stage reactor do not back-mix, thus affecting the reaction degree inside the first-stage reactor. The first liquid level sensor is set up to display the position of the liquid level inside the first-stage reactor in real time through the control system set outside the two-stage reactor. When the liquid level inside the first-stage reactor reaches a specified height, the control interface will control the valve to open, so that the reaction liquid inside the first-stage reactor can flow smoothly into the second-stage reactor. The second liquid level reactor set up inside the second-stage reactor will also display the position of the liquid level inside the second-stage reactor in real time through the control system. When the liquid level inside the second-stage reactor reaches a specified position, the control system will control the valve to close, thereby preventing the reaction liquid in the first-stage reactor from being over-transferred to the second-stage reactor.

[0019] Therefore, it can be understood that the liquid level sensor, intensifier unit, grid, and valve settings are crucial for this invention. The installation location of the liquid level sensor is also subject to certain limitations. The intensifier unit increases the interphase area between raw materials, thereby increasing the contact area and extending the contact time, leading to a more complete and thorough reaction. The liquid level sensor displays the real-time liquid level positions inside the first and second stage reactors, facilitating valve control and ensuring smooth transfer of the reaction liquid from the first to the second stage reactor. Furthermore, the grid effectively prevents backmixing between the first and second stage reactors during this transfer process, which could intensify the reaction in the first stage reactor, increase byproducts, and affect product purity. The placement of the liquid level sensor is crucial in this invention. When the distance between the first liquid level sensor and the first intensifier unit is three times the distance between the first liquid level sensor and the top of the two-stage reactor, the pentaerythritol synthesized by the efficient synthesis system of this invention has higher purity and yield. This is because when the raw material enters through the feed inlet at the top of the multi-stage reactor, the valve is closed to prevent excessively vigorous reactions inside the first-stage reactor, thus avoiding numerous side reactions. At this time, the mixed liquid inside the first-stage reactor cannot enter the second-stage reactor. As the raw material mixture gradually fills the first-stage reactor, the first liquid level sensor transmits the liquid level position inside the first-stage reactor in real time. When the liquid level reaches a critical point... At this point, the control system will control the opening of the valve to transfer the liquid inside the first-stage reactor to the second-stage reactor through the connecting pipe. Therefore, if the first liquid level sensor is set close to the first intensifier unit, the liquid reaction is violent in the vicinity of the intensifier unit, and the raw materials will collide violently after being processed by the intensifier unit. Setting the first liquid level sensor close to the first intensifier unit can easily lead to damage to the liquid level sensor, thus making it impossible to obtain the real-time liquid level height inside the first-stage reactor. As a result, the first liquid level sensor cannot transmit the liquid level height back to the control system in time to control the opening of the valve, resulting in insufficient reaction of the raw material mixture inside the first-stage reactor and the generation of many side reactions, which reduces the yield of reactants and affects the purity of the product.If the distance between the first liquid level sensor and the top of the multi-stage reactor is set too far, the control system will be too close to the sensor. Since there is a time lag between the sensor and the control system in opening the valve, a large distance will prevent the control system from opening the valve in time. This would prevent the reaction liquid from flowing smoothly from the first-stage reactor into the second-stage reactor, causing the first-stage reactor to become overfilled. This would disrupt the external circulation system outside the first-stage reactor, preventing the timely removal of heat and leading to side reactions. Therefore, a certain distance is needed between the first liquid level sensor and the tops of both reactors to prevent the valve from opening too late due to overfilling of the first-stage reactor. The distance between the bar screen and the second intensifier unit is twice the distance between the bar screen and the second liquid level sensor, and the distance between the second liquid level sensor and the second intensifier unit is... A distance three times the distance between the sensor and the grid is necessary to allow sufficient space for valve closure, ensuring timely valve closing and preventing backmixing between the first and second stage reactors due to prolonged valve opening. This would exacerbate the reaction in the first stage reactor, leading to a series of side reactions. If the distance between the second liquid level sensor and the second intensifier unit is too close, the intense reaction at close range could cause a violent impact, damaging the sensor and preventing valve closure, resulting in backmixing between the first and second stage reactors and affecting product yield and purity. Conversely, if the distance is too great, the distance between the sensor and the grid will be too short. Since there is a time difference in transmission between the sensor and the control system, a suitable distance is needed to ensure timely valve closure and prevent overfilling of the second stage reactor with reaction liquid.

[0020] Preferably, as a further feasible option, a formaldehyde inlet is provided above the first strengthening unit, the formaldehyde inlet leads into the first strengthening unit, a formaldehyde feed metering pump is connected to the first strengthening unit through the formaldehyde inlet, and a mixer is provided between the formaldehyde inlet and the formaldehyde feed metering pump.

[0021] Preferably, as a further feasible option, a first circulating discharge port is provided below the first intensifier unit, the first circulating discharge port leads into the first intensifier unit, a first circulating pump is connected to the first intensifier unit through the first circulating discharge port, and the first circulating pump is connected to the mixer through a heat exchanger.

[0022] Preferably, as a further feasible option, a second circulating pump inlet is provided above the second intensifier unit, the second circulating pump inlet leads into the second intensifier unit, the second circulating pump is connected to the second intensifier unit through the second circulating pump inlet, the second circulating pump is connected to a connecting pipe located at the center of the outside of the two-stage reactor through a heat exchanger, and the second circulating pump extracts the liquid in the second-stage reactor through the discharge port.

[0023] Preferably, as a further feasible option, it also includes a distillation column, a recrystallization unit, a storage tank, and a filter connected in sequence;

[0024] The distillation column is connected to the multi-stage reactor.

[0025] This invention also incorporates a circulation-heat exchange system outside the reactor to promptly remove heat from the reactor, preventing numerous side reactions caused by excessively high internal temperatures. This is because, in the reaction system of this invention, formaldehyde is often used in excess, and the condensation reaction is a strongly exothermic process. When the temperature in the reaction system is too high, many byproducts that are detrimental to the subsequent separation and purification of pentaerythritol are often generated during the synthesis. Therefore, to improve product purity and minimize the generation of side reactions, this invention uses a circulation-heat exchange system outside the reactor. This allows the liquid inside the first and second stage reactors to be promptly extracted by a circulation pump, then transferred back to the reactor after heat exchange in a heat exchanger. This significantly reduces the reaction temperature inside the reactor, resulting in more uniform mixing of the reaction system, a more thorough and complete reaction, and better control of the reactor temperature, thus preventing the generation of more byproducts.

[0026] Therefore, it can be understood that in the operation of the pentaerythritol high-efficiency synthesis system of the present invention, the catalysts sodium hydroxide and acetaldehyde first enter the multi-stage reactor from the acetaldehyde inlet at the top of the multi-stage reactor. Then, they are mixed evenly with metered formaldehyde and enter the first intensifier unit inside the first-stage reactor. After processing by the first intensifier unit, the mixture of the three is processed into small droplets, increasing the interphase area between the reactants, thereby making the reaction more complete and generating more intermediate products. The intermediate products descend inside the reactor in the form of small droplets. When the valve is closed, the mixing of the raw materials... The liquid gradually fills the first-stage reactor. The first liquid level sensor displays the liquid level inside the first-stage reactor in real time through a control system installed outside the multi-stage reactors. As the liquid level gradually reaches a critical value, the control system opens the valve, allowing the reaction liquid inside the first-stage reactor to be simultaneously transported to the second-stage reactor via a connecting pipe. Then, through a second enhancement unit installed inside the second-stage reactor, the interphase area between formaldehyde and the intermediate product is increased, allowing the intermediate product to be fully converted into pentaerythritol. When the liquid level inside the second-stage reactor reaches a critical value, the control system closes the valve. During the reaction, the external circulation system of the first and second stage reactors uses a circulation pump to extract a portion of the reaction liquid from the reactors. After heat exchange in a heat exchanger, this liquid is mixed with formaldehyde, which is metered in by a metering pump, and then returned to the reaction system via a mixer to ensure a stable reaction temperature. The final reaction liquid then enters the middle section of a distillation column through a circulation channel in the middle of the multi-stage reactor for distillation. The top of the distillation column contains a small amount of formaldehyde and most of the water. The mixture collected from the top is then passed through a distributor to remove most of the water before re-entering the multi-stage reactor through the distributor's inlet. The internal system recycles the substances, while the substance collected from the bottom of the distillation column is a mixture of pentaerythritol, water, and sodium hydroxide. This mixture then flows out through the bottom of the distillation column to a recrystallization unit for purification. The mixture obtained from the bottom of the column is added to the recrystallization unit to purify pentaerythritol. The solid-liquid mixture obtained after purification is then filtered through a filter. The filter residue is the final product, crude pentaerythritol, while the filtrate is an aqueous solution of sodium hydroxide. The filtrate can be purified and then recycled into the multi-stage reactor through the mixed liquid inlet at the top of the multi-stage reactor.

[0027] The intensification unit of the present invention belongs to the prior art. Although some are pneumatic, some are hydraulic, and some are pneumatic-hydraulic linkage, the difference between the types is mainly selected according to the specific working conditions. In addition, the connection between the intensification reactor and other equipment, including the connection structure and connection position, depends on the structure of the intensification reactor and is not limited thereto.

[0028] The present invention also provides a method for synthesizing the aforementioned pentaerythritol, comprising the following steps:

[0029] Acetaldehyde, catalyst, and metered formaldehyde are subjected to a multi-stage reaction. The multi-stage reaction enhances the mass transfer area of ​​the reaction system and reduces backmixing.

[0030] Preferably, as a further feasible option, the temperature of the multi-stage reaction is 25℃-35℃, and the reaction time is 1h-2h.

[0031] The method for synthesizing pentaerythritol of this invention improves reaction efficiency and product yield by employing a multi-stage reactor. Furthermore, the external circulation system significantly reduces the temperature within the multi-stage reactor, minimizing byproduct generation and increasing product purity. Since formaldehyde and acetaldehyde are immiscible, the enhanced unit increases the interphase area between the two phases, thereby accelerating the reaction and increasing the yield. The completely reacted reaction liquid is then cooled via the external circulation system of the multi-stage reactor. Because this condensation reaction is exothermic and involves the excessive use of formaldehyde, a large amount of heat is generated during the reaction. To ensure a complete reaction, an external circulation system is used. This system fully utilizes excess formaldehyde and promptly removes excess heat, maintaining the temperature inside the multi-stage reactor at 25°C-35°C. During continuous circulation, a metering pump continuously and quantitatively replenishes formaldehyde, maintaining stable reaction progress while ensuring a higher yield of pentaerythritol.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The pentaerythritol high-efficiency synthesis system of the present invention, through the setting of multiple enhanced units, grid, sensor and chamber door, makes the reaction system more uniformly mixed, the reaction more thorough, reduces backmixing and makes the product purer. Furthermore, the enhanced units increase the contact area between raw materials, thereby improving the reaction rate and product yield. In addition, the external circulation system can remove the reaction heat in time to accurately control the reaction temperature, reduce the generation of reaction by-products, and facilitate subsequent purification and separation.

[0034] (2) The present invention provides a method for synthesizing pentaerythritol, which is simple to operate, has mild operating conditions, and produces high product yield and high purity. Attached Figure Description

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 is a schematic diagram of the structure of a high-efficiency synthesis system for pentaerythritol according to the present invention.

[0037] The attached diagram lists the components represented by each number as follows:

[0038] In the diagram: 1. Diverter inlet; 2. Acetaldehyde inlet; 3. Mixed liquid inlet; 4. First liquid level sensor; 5. First intensifier unit; 6. Formaldehyde inlet; 7. Mixer; 8. Multistage reactor; 9. Control system; 10. Second liquid level sensor; 11. Second intensifier unit; 12. Discharge outlet; 13. Second circulation pump inlet; 14. Second circulation pump; 15. Heat exchanger; 16. Conveying pipeline; 17. First circulation pump; 18. Heat exchanger; 19. Metering pump; 20. Diverter; 21. Grille; 22. Distillation column; 23. Recrystallization unit; 24. Filter; 25. Pentaerythritol storage tank; 26. First circulation pump outlet; 27. Valve; 28. Heat exchanger; 29. ​​Connecting pipe. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. To more clearly illustrate the technical solutions in this invention, specific embodiments are described below.

[0042] Example 1

[0043] Please refer to Figure 1, which shows a high-efficiency synthesis system for pentaerythritol, including: 1. a distributor inlet; 2. an acetaldehyde inlet; 3. a mixed liquid inlet; 4. a first liquid level sensor; 5. a first intensifier unit; 6. a formaldehyde inlet; 7. a mixer; 8. a multi-stage reactor; 9. a control system; 10. a second liquid level sensor; 11. a second intensifier unit; 12. a discharge outlet; 13. a second circulating pump inlet; 14. a second circulating pump; 15. a heat exchanger; 16. a conveying pipeline; 17. a first circulating pump; 18. a heat exchanger; 19. a metering pump; 20. a distributor; 21. a grid; 22. a distillation column; 23. a recrystallization unit; 24. a filter; 25. a pentaerythritol storage tank; 26. a first circulating pump discharge outlet; 27. a valve; 28. a heat exchanger; and 29. a connecting pipe.

[0044] The efficient synthesis process for pentaerythritol is as follows: Acetaldehyde, the raw material, is fed into the multi-stage reactor 8 at a rate of 196 kg / h, along with sodium hydroxide aqueous solution as a catalyst, through acetaldehyde inlet 2. Then, formaldehyde, metered by metering pump 19 and fed through formaldehyde inlet 6 at a rate of 120 kg / h, is mixed thoroughly and processed into small droplets by the first intensifier unit 5 inside the first-stage reactor. This increases the interphase area between the reactants, allowing formaldehyde and acetaldehyde to react in the first-stage reactor and be converted into intermediate products for pentaerythritol synthesis. At this time, valve 27 on the conveying pipeline 16 is closed. As the raw material continuously enters the first-stage reactor, the first liquid level sensor 4 inside the reactor displays the liquid level in real time via a control system 9 located outside the reactor. When the liquid level reaches a critical value, the external control system 9 controls valve 27. 7 is opened, allowing the liquid in the first-stage reactor to smoothly enter the second-stage reactor through the connecting pipe 29. Then, it is processed by the second enhancement unit 11 set in the second-stage reactor, which increases the phase interface area between the intermediate product and formaldehyde, so that the intermediate product can be more fully and completely converted into pentaerythritol. When the liquid in the second-stage reactor reaches the boundary value, the external control system 9 can control the valve 27 to close. Due to the setting of the grid 21, which is set to a 5-layer grid, the reaction liquid in the first-stage reactor and the reaction liquid in the second-stage reactor will not be back-mixed. As the reaction in the first-stage reactor proceeds, the first circulation pump 17 will draw 30% of the liquid in the first-stage reactor through the first circulation pump outlet 26, which will be heat exchanged through the heat exchanger 18. After being mixed evenly with the formaldehyde entering through the metering pump in the mixer 7, it will enter the multi-stage reactor through the formaldehyde inlet.During the reaction in the second-stage reactor, the second circulation pump 14 also draws 30% of the liquid from the second-stage reactor through the outlet 12. After heat exchange in the heat exchanger 15, the liquid enters the multi-stage reactor through the inlet 13 of the second circulation pump to continue the reaction. The final reaction liquid obtained in the second-stage reactor, after being drawn out by the second circulation pump 14, enters the distillation column 22 through the conveying pipe 16 for distillation. At this time, a small amount of formaldehyde and most of the water will be collected from the top of the distillation column 22. The mixture collected from the top of the column will pass through the distributor 20 to remove most of the water, and the remaining liquid will be... The feed enters the reactor again through the feed inlet 1 of the distillation column to react. The bottom product of the distillation column 22 is a mixture of pentaerythritol, water, and sodium hydroxide. This mixture flows out through the bottom of the distillation column 22 and is transferred to the recrystallization unit 23 for purification. After purification in the recrystallization unit 23, the resulting solid-liquid mixture is filtered through the filter 24. The filter residue is crude pentaerythritol, which is then transferred through the filter 24 to the pentaerythritol storage tank 25 for storage. The filtrate, after purification, can be recycled into the multi-stage reactor through the mixed liquid feed inlet 3 located at the top of the multi-stage reactor.

[0045] Example 2

[0046] The only difference between this embodiment and Embodiment 1 is that the first liquid level sensor is placed at the center of the first-stage reactor.

[0047] Example 3

[0048] The only difference between this embodiment and Embodiment 1 is that the second liquid level sensor is placed at the center of the second-stage reactor.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that the first liquid level sensor is not provided.

[0051] Comparative Example 2

[0052] The only difference between this comparative example and Example 1 is that no grille is provided.

[0053] Comparative Example 3

[0054] The only difference between this comparative example and Example 1 is that the grid is set to two layers.

[0055] Comparative Example 4

[0056] The only difference between this comparative example and Example 1 is that a second liquid level sensor is not provided.

[0057] Comparative Example 5

[0058] The only difference between this comparative example and Example 1 is that the first strengthening unit is not provided.

[0059] Comparative Example 6

[0060] The only difference between this comparative example and Example 1 is that a second intensifier unit is not provided.

[0061] Comparative Example 7

[0062] The only difference between this comparative example and Example 1 is that a second circulation pump and heat exchanger are not provided.

[0063] Comparative Example 8

[0064] The only difference between this comparative example and Example 1 is that the first circulation pump and heat exchanger are not included.

[0065] Comparative Example 9

[0066] The only difference between this comparative example and Example 1 is that it does not include a first circulation pump, a second circulation pump, and a corresponding heat exchanger.

[0067] Table 1 compares the product yield and conversion rate of the embodiments and comparative examples of the present invention:

[0068] The yield calculation formula is: Yield = Amount of reacted material / Total input.

[0069] The formula for calculating conversion rate is: Conversion rate = Amount of product generated in the reaction / Amount of product theoretically generated.

[0070] By comparing Examples 1-3 and Comparative Examples 1-3, it can be seen that the placement of the liquid level sensor, grid, and valves in this invention is very important. This is because the liquid level sensor can display the position of the liquid level inside the first-stage reactor and the second-stage reactor in real time, which facilitates the control of the opening and closing of the valves. This allows the reaction liquid inside the first-stage reactor to be transferred to the second-stage reactor through the connecting pipe. The grid prevents the mixed liquid inside the second-stage reactor from back-mixing with the mixed liquid inside the first-stage reactor, which would intensify the reaction in the first-stage reactor, thereby increasing the amount of by-products and affecting the purity of the product. The placement of the liquid level sensor is crucial in this invention. A certain distance must be maintained between the first liquid level sensor and the first intensifier unit (3 times the distance between the first liquid level sensor and the top of the two-stage reactor) to prevent the valve from opening too late due to excessive mixing in the first-stage reactor. Similarly, a distance of twice the distance between the grid and the second intensifier unit (2 times the distance between the grid and the second liquid level sensor), and three times the distance between the second liquid level sensor and the second intensifier unit (3 times the distance between the second liquid level sensor and the grid), allows sufficient space for valve closure, ensuring timely valve closure and preventing excessive mixing in the second-stage reactor due to prolonged valve opening.

[0071] Comparing Example 1 and Comparative Examples 4-5, it can be seen that the setup of the first and second intensifying units of this invention is crucial. This is because the raw materials used in this invention are normally two immiscible liquids in contact with each other. Therefore, in the traditional synthesis of pentaerythritol, the small interphase area between the raw materials leads to insufficient reaction. Furthermore, since the condensation of formaldehyde and acetaldehyde is a multi-stage condensation reaction, to ensure a more complete and efficient reaction and increase the reaction rate, the first intensifying unit processes the two materials into small droplets, thereby increasing the interphase area and contact between them. This allows for greater contact area and time as the raw materials descend within the two-stage reactor. Under the catalysis of the catalyst, the reaction between the raw materials proceeds more thoroughly, resulting in the conversion of more intermediate products. The intensifying unit in the second-stage reactor further increases the interphase area between the reactants, ultimately converting the intermediate products into pentaerythritol.

[0072] By comparing Example 1 and Comparative Examples 6-8, it can be seen that the external circulation system set up in this invention is extremely important. This is because, during the reaction process, due to the exothermic nature of the condensation reaction and the excessive use of formaldehyde, the reaction temperature inside the multi-stage reactor is relatively high. In order to ensure that the reaction can proceed completely, an external circulation system is adopted. Through external circulation, excess formaldehyde is fully utilized and excess heat is removed in a timely manner. At the same time, the reaction system is also thoroughly mixed. During the reaction process in the second-stage reactor, this invention uses the external circulation system to extract part of the reaction liquid using a second circulation pump. Heat exchange is carried out through a heat exchanger connected to the second circulation pump, which greatly reduces the reaction temperature inside the multi-stage reactor and reduces the generation of by-products. Through such an external circulation system, the temperature inside the multi-stage reactor can be maintained at 25℃-35℃.

[0073] Therefore, the high-efficiency synthesis system of the present invention, through the setting of multiple intensifying units, grids, liquid level sensors, and valves, makes the reaction system more uniformly mixed, the reaction more thorough, reduces backmixing and results in higher product purity. Furthermore, by increasing the contact area between raw materials through the intensifying units, the reaction rate and product yield are improved. Moreover, by using an external circulation system, the reaction heat can be removed in a timely manner, thereby accurately controlling the reaction temperature, reducing the generation of reaction by-products, and facilitating subsequent purification and separation.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly efficient synthetic system for pentaerythritol, characterized in that, The reactor includes a multi-stage reactor, inside which multiple intensifier units and liquid level sensors are vertically arranged. Multiple layers of grids or sieves are installed in the middle section of the reactor. An acetaldehyde inlet is located at the top of the reactor, leading into the intensifier units. A distributor inlet and a mixed liquid inlet are respectively located on both sides of the top of the reactor. A connecting pipe with valves is also installed outside the reactor. A control system for receiving data from the liquid level sensors and controlling the opening and closing of the valves is also located outside the reactor. An outlet is located at the bottom of the reactor.

2. The high-efficiency synthesis system according to claim 1, characterized in that, The multi-stage reactor is a two-stage reactor, and the two-stage reactor is equipped with two intensifier units and two liquid level sensors. The first-stage reactor includes a first intensifier unit installed at the top of the multi-stage reactor and a first liquid level sensor installed on the inner wall above the first intensifier unit. The first liquid level sensor is used to detect the liquid level height in the first-stage reactor. The second-stage reactor includes a second intensifier unit disposed at the bottom of the two-stage reactor and a second liquid level sensor disposed on the inner wall above the second intensifier unit. The second liquid level sensor is used to detect the liquid level height in the second-stage reactor.

3. The high-efficiency synthesis system according to claim 1, characterized in that, The number of layers in the multi-layer grid or multi-layer sieve plate is 3-7; Preferably, the number of layers is 5; The distance between the grille and the second strengthening unit is twice the distance between the grille and the second liquid level sensor; The distance between the second liquid level sensor and the second strengthening unit is three times the distance between the second liquid level sensor and the grid.

4. The high-efficiency synthesis system according to claim 2, characterized in that, The distance between the first liquid level sensor and the first intensifier unit is three times the distance between the first liquid level sensor and the top of the two-stage reactor.

5. The high-efficiency synthesis system according to claim 2, characterized in that, A formaldehyde inlet is provided above the first enhancement unit, and the formaldehyde inlet leads into the first enhancement unit. A formaldehyde feed metering pump is connected to the first enhancement unit through the formaldehyde inlet, and a mixer is provided between the formaldehyde inlet and the formaldehyde feed metering pump.

6. The high-efficiency synthesis system according to claim 2, characterized in that, A first circulation outlet is provided below the first intensifier unit, and the first circulation outlet leads into the first intensifier unit. A first circulation pump is connected to the first intensifier unit through the first circulation outlet, and the first circulation pump is connected to the mixer through a heat exchanger.

7. The high-efficiency synthesis system according to claim 2, characterized in that, A second circulation pump inlet is provided above the second intensifier unit. The second circulation pump inlet leads into the second intensifier unit. The second circulation pump is connected to the second intensifier unit through the second circulation pump inlet. The second circulation pump is connected to the conveying pipeline located at the center of the outside of the two-stage reactor through a heat exchanger. The second circulation pump extracts the liquid in the second-stage reactor through the discharge port.

8. The high-efficiency synthesis system according to claim 1, characterized in that, It also includes a distillation column, a recrystallization unit, a storage tank, and a filter connected in sequence; The distillation column is connected to the multi-stage reactor.

9. A method for synthesizing pentaerythritol, characterized in that, The method employs the system described in any one of claims 1-8, and the method includes the following steps: subjecting acetaldehyde, catalyst, and metered formaldehyde to a multi-stage reaction, thereby enhancing the mass transfer area of ​​the reaction system and reducing backmixing through the multi-stage reaction.

10. The synthesis method according to claim 9, characterized in that, The temperature of the multi-stage reaction is 25℃-35℃, and the reaction time is 1h-2h.

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