Efficient synthesis system of pentaerythritol

Abstract

The utility model provides an efficient synthesis system of pentaerythritol, which comprises a multi-stage reactor, a plurality of strengthening units and a liquid level sensor are vertically arranged in the multi-stage reactor, and a plurality of layers of grids or sieve plates are arranged in the middle section in the multi-stage reactor. An acetaldehyde feeding hole is formed in the top of the multi-stage reactor, the acetaldehyde feeding hole is communicated into the strengthening unit, a flow divider feeding hole and a mixed liquid feeding hole are respectively formed in two sides of the top of the multi-stage reactor, a communicating pipe is further arranged outside the multi-stage reactor, a valve is further arranged on the communicating pipe, and the flow divider feeding hole is communicated with the mixed liquid feeding hole. A control system used for receiving data sent back by the liquid level sensor and controlling the valve to be opened or closed is further arranged outside the multi-stage reactor, and a discharging opening is formed in the bottom of the multi-stage reactor. The efficient synthesis system disclosed by the utility model has the characteristics of high yield and high purity by applying the strengthening unit and the liquid level sensor.

Description

Technical Field

[0001] The utility model belongs to the technical field of pentaerythritol production, in particular to a high-efficiency synthesis system of pentaerythritol. Background Art

[0002] Pentaerythritol is an important organic chemical raw material, widely used in resin, coating, chemical, pharmaceutical and other industrial sectors. Pentaerythritol is mainly used to produce lubricants, plasticizers, surfactants, emulsifiers, medicines, pesticides, explosives, etc. At present, deep-processing products of pentaerythritol are being developed, including initiators for polyester polyols, components of flame-retardant coatings, epoxy crosslinking agent intermediates, polyvinyl chloride stabilizers, oil-modified amino surface coatings (amino alkyd resins) intermediates, olefin antioxidants and pentaerythritol triacrylate, etc. The phosphate and phosphite esters of pentaerythritol are used as flame retardants, antioxidants or heat stabilizers in polymer production, while pentaerythritol acrylate is widely used in radiation-cured coatings and quick-drying printing inks, and is also used to make water-soluble alkyd resins, and its polymer emulsion can be used as an adhesive.

[0003] At present, sodium hydroxide is widely used as a catalyst in traditional industries, but there are many problems in traditional industries. In the traditional process, the synthesis of pentaerythritol is carried out in two steps. The first step, the Alder reaction, is an endothermic reaction, and the second step, the Cannizzaro reaction, is an exothermic reaction. The condensation process requires a gentle temperature rise curve, otherwise side reactions will occur. Especially when the temperature exceeds 20°C, the reaction rate increases, the reaction heat is difficult to remove in time, the side reactions accelerate, the by-products increase, the yield of pentaerythritol decreases, and the difficulty of the subsequent separation process is increased, affecting the yield and quality of the product; the strong base catalytic system corrodes the equipment more seriously; and the formaldehyde required for the reaction is all formaldehyde aqueous solution, which leads to a large water load in the entire process. In the distillation process, the high latent heat of water causes high energy consumption, and the excessive amount of water in the reaction system makes the reaction time longer.

[0004] In view of this, the present utility model is proposed. Summary of the invention

[0005] The first purpose of the utility model is to provide an efficient synthesis system of pentaerythritol. The efficient synthesis system of the utility model makes the reaction system more evenly mixed, the reaction is more thoroughly carried out, and the backmixing is reduced to make the product purity higher. The contact area between the raw materials is increased by the enhanced unit, thereby improving the reaction rate and product yield. The reaction heat can be removed in time by using an external circulation system, thereby accurately controlling the reaction temperature, reducing the generation of reaction by-products, and facilitating subsequent purification and separation.

[0006] In order to achieve the above-mentioned purpose of the utility model, the following technical solutions are specially adopted:

[0007] A high-efficiency synthesis system of pentaerythritol comprises a multistage reactor, wherein a plurality of strengthening units and liquid level sensors are vertically arranged inside the multistage reactor, a multilayer grid is arranged in the middle section inside the multistage reactor, an acetaldehyde feed port is arranged at the top of the multistage reactor, the acetaldehyde feed port leads to the strengthening unit, a diverter feed port and a mixed liquid feed port are arranged at both sides of the top of the multistage reactor, a connecting pipe is arranged outside the multistage reactor, a valve is arranged on the connecting pipe, a control system for receiving data sent back by the liquid level sensor and controlling the opening or closing of the valve is arranged outside the multistage reactor, and a discharge port is arranged at the bottom of the multistage reactor.

[0008] Preferably, as a further implementable solution, the multi-stage reactor is a two-stage reactor, and two strengthening units and two liquid level sensors are arranged inside the two-stage reactor; wherein the first-stage reactor comprises a first strengthening unit arranged at the top of the multi-stage reactor and a first liquid level sensor arranged on the inner wall above the first strengthening unit, and the first liquid level sensor is used to detect the liquid level height of the first-stage reactor;

[0009] The second stage reactor comprises a second strengthening unit arranged at the bottom of the two-stage reactor and a second liquid level sensor arranged on the inner wall above the second strengthening unit, wherein the second liquid level sensor is used to detect the liquid level height of the second stage reactor.

[0010] In the pentaerythritol synthesis system of the utility model, since the raw materials used in the utility model are two mutually insoluble liquids under normal circumstances, when performing the traditional synthesis of pentaerythritol, the reaction between the two is insufficient due to the small interfacial area between the raw materials used, and since the condensation of formaldehyde and acetaldehyde is a multi-stage condensation reaction, in order to make the reaction of the two more sufficient and complete and to increase the reaction rate, the utility model sets a multi-stage reactor, and preferably sets a two-stage reactor so that the reaction can be more sufficient and thorough, and adopts an enhanced unit to increase the reaction area between the formaldehyde and acetaldehyde reaction liquids, thereby increasing the progress of the reaction process and the yield of the reaction. The arrangement of the two-stage reactor in the utility model can ensure that the condensation of formaldehyde and acetaldehyde will not stop in the middle step, can greatly reduce the generation of by-products, improve the purity of the final product, and thus facilitate subsequent separation and purification. This is because the utility model arranges the first liquid level sensor and the strengthening unit in the first-stage reactor, so that the acetaldehyde and sodium hydroxide catalyst entering through the top of the multi-stage reactor and the formaldehyde entering through the metering pump are mixed evenly, and then the two are processed into extremely small droplets through the treatment of the first strengthening unit, thereby increasing the interfacial area between the two, so that the contact between the two is increased. The contact area and contact time of the raw materials can be increased when the raw materials are lowered inside the first-stage reactor, and the reaction between the raw materials can be carried out more fully and thoroughly under the catalysis of the catalyst, so that the raw materials can be converted into more intermediate products, and in the descending process of the raw material mixture processed into droplets in the two-stage reactor, the mixture of the raw materials gradually fills the first-stage reactor, and then the reaction liquid inside the first-stage reactor is transported to the second-stage reactor through the conveying channel arranged outside the multi-stage reactor, and the grid arranged in the middle section of the multi-stage reactor avoids the reaction liquid in the first-stage reactor and the second-stage reactor from mixing back. And the mixed liquid entering the second-stage reactor will be processed by the strengthening unit arranged inside the second-stage reactor, and the interfacial area between the reactants is increased so that the intermediate product is finally converted into pentaerythritol. Therefore, in the utility model, by arranging the two-stage reactor and the strengthening unit, the interfacial area between the raw materials is increased, so that the reaction is more fully and thoroughly.

[0011] Preferably, as a further implementable solution, the number of layers of the multi-layer grid or multi-layer sieve plate is 3-7 layers;

[0012] Preferably, the number of layers is 5;

[0013] The distance between the grid and the second strengthening unit is twice the distance between the grid and the second liquid level sensor;

[0014] 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.

[0015] Preferably, as a further implementable solution, the distance between the first liquid level sensor and the first enhancement unit is 3 times the distance between the first liquid level sensor and the top of the two-stage reactor.

[0016] Moreover, the last step reaction of the synthesis of pentaerythritol in the utility model, i.e., the conversion of the intermediate product into pentaerythritol, is relatively intense, and due to the excessive use of formaldehyde and the strong exothermic reaction in the last step, in order to avoid back-mixing of the reaction system between the first-stage reactor and the second-stage reactor, which makes the reaction in the first-stage reactor relatively intense and produces side reactions, making it inconvenient for subsequent separation and purification of the produced by-products, the utility model controls the opening and closing of the valve arranged on the connecting pipe through a control system connected to the first liquid level sensor and the second liquid level sensor. During the process of the first-stage reactor reacting to generate the intermediate product, the valve is in a closed state, so that the reaction liquid inside the first-stage reactor can fully react after being processed by the first intensification unit, and the presence of the grid will prevent the liquid in the second-stage reactor from back-mixing with the liquid in the first-stage reactor, and the grid The arrangement is preferably multi-layered, and preferably the grid or sieve plate is arranged in 5 layers, so as to ensure that the liquid inside the second-stage reactor and the first-stage reactor will not be mixed back, thereby affecting the reaction degree inside the first-stage reactor, and the arrangement of the first liquid level sensor will display the position of the liquid level inside the first-stage reactor in real time through the control system arranged outside the two-stage reactor. When the liquid level position inside the first-stage reactor reaches the specified height, the control interface will control the valve to open, so that the reaction liquid inside the first-stage reactor can flow smoothly to the second-stage reactor, and the second liquid level reactor arranged 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, and when the liquid level inside the second-stage reactor reaches the specified position, the control system will control the valve to close, so as to avoid the reaction liquid in the first-stage reactor from being excessively transported to the second-stage reactor.

[0017] Therefore, it can be known that for the utility model, the setting of the liquid level sensor, the strengthening unit, the grid and the valve is very important for the utility model, wherein the installation position of the liquid level sensor is also subject to certain limitations. The setting of the strengthening unit can increase the interfacial area between the raw materials, thereby increasing the contact area between the raw materials, prolonging the contact time between the two and enabling the reaction to be more sufficient and thorough, while the setting of the liquid level sensor can display the position of the liquid levels inside the first-stage reactor and the second-stage reactor in real time, thereby facilitating the control of the opening and closing of the valve, so that the reaction liquid inside the first-stage reactor can be smoothly transported to the second-stage reactor, and during the transportation process, due to the presence of the grid, it is possible to well avoid back-mixing between the first-stage reactor and the second-stage reactor, causing the reaction of the first-stage reactor to intensify, thereby increasing the by-products and affecting the product purity. The location of the liquid level sensor is very important for the present invention. When the distance between the first liquid level sensor and the first intensification 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 high-efficiency synthesis system of the present invention has higher purity and higher yield. This is because when the raw materials enter through the feed port at the top of the multi-stage reactor, in order to avoid excessively violent reactions inside the first-stage reactor and thus produce many side reactions, the valve is in a closed state. 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 will transmit the liquid level position inside the first-stage reactor in real time. When the liquid level position reaches a When the critical point is reached, 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 at a position close to the first enhanced unit, the liquid at a position close to the enhanced unit will react violently, and the raw materials will collide violently after being processed by the enhanced unit. The first liquid level sensor is set close to the first enhanced unit, which may easily cause the liquid level sensor to be damaged, so that the real-time liquid level inside the first-stage reactor cannot be obtained, so that the first liquid level sensor cannot transmit the liquid level 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 many side reactions, which reduce the yield of the reactants and affect the purity of the products;If the distance is set too far, the distance between the first liquid level sensor and the top of the multi-stage reactor will be closer. Since there is a certain time difference between the first liquid level sensor and the control system in the process of controlling the opening of the valve, if the first liquid level sensor is set at a long distance, the control system will not be able to control the valve opening in time, so that the reaction liquid inside the first-stage reactor cannot flow smoothly into the second-stage reactor, resulting in the reaction liquid inside the first-stage reactor being too full, causing the external circulation system set outside the first-stage reactor to fail to work normally, resulting in the inability to remove the heat inside the first-stage reactor in time, causing side reactions. Therefore, a certain distance needs to be created between the first liquid level sensor and the top of the two-stage reactor to avoid the valve being opened too late due to the mixed liquid inside the first-stage reactor being too full, and the distance between the grid and the second enhanced unit is twice the distance between the grid and the second liquid level sensor, and the distance between the second liquid level sensor and the second enhanced unit is Only when the distance between the second liquid level sensor and the grid is three times the distance between the sensor and the grid, a certain space can be reserved when controlling the valve to close, so that the valve can be closed in time to avoid the back mixing between the first-stage reactor and the second-stage reactor due to the long-term opening of the valve, which intensifies the reaction in the first-stage reactor and produces a series of side reactions. If the distance between the second liquid level sensor and the second enhanced unit is too close, the violent reaction of the second enhanced unit at close range will produce a violent collision, thereby causing damage to the second liquid level sensor, and the closure of the valve cannot be controlled, resulting in back mixing between the second-stage reactor and the first-stage reactor, affecting the product yield and purity; if the distance is set too far, the distance between the second liquid level sensor and the grid will be shorter. Since there is a certain time difference in the transmission between the second liquid level sensor and the control system, the distance between the second liquid level sensor and the grid needs to be appropriate, so that the control system can control the valve to close in time to avoid the reaction liquid inside the second-stage reactor from being too full. ;

[0018] Preferably, as a further implementable scheme, a formaldehyde feed inlet is arranged above the first strengthening unit, the formaldehyde feed inlet leads into the first strengthening unit, a formaldehyde feed metering pump is connected to the first strengthening unit through the formaldehyde feed inlet, and a mixer is arranged between the formaldehyde feed inlet and the formaldehyde feed metering pump.

[0019] Preferably, as a further implementable solution, a first circulation outlet is provided below the first strengthening unit, the first circulation outlet leads into the first strengthening unit, a first circulation pump is connected to the first strengthening unit through the first circulation outlet, and the first circulation pump is connected to the mixer through a heat exchanger.

[0020] Preferably, as a further implementable scheme, a second circulation pump feed port is arranged above the second strengthening unit, the second circulation pump feed port leads to the second strengthening unit, the second circulation pump is connected to the second strengthening unit through the second circulation pump feed port, the second circulation pump is connected to the connecting pipe arranged at the outer center of the two-stage reactor through a heat exchanger, and the second circulation pump extracts the liquid in the second-stage reactor through the discharge port.

[0021] Preferably, as a further implementable solution, it further comprises a distillation tower, a recrystallization device, a storage tank and a filter connected in sequence;

[0022] The distillation tower is connected to the multi-stage reactor.

[0023] The utility model also sets a circulation-heat exchange system outside the reactor, which can timely remove the heat inside the reactor to avoid many side reactions caused by the excessively high temperature inside the reactor. This is because in the reaction system of the utility model, the amount of formaldehyde used is often excessive, and the condensation reaction is a highly exothermic process. When the temperature in the reaction system is too high, many by-products that are not conducive to the subsequent separation and purification of the product are often produced during the synthesis of pentaerythritol. Therefore, in order to improve the purity of the product and reduce the generation of side reactions as much as possible, the utility model sets a circulation-heat exchange system outside the reactor, so that the liquid inside the first-stage reactor and the second-stage reactor can be timely pumped out by a circulation pump, and then transferred to the reactor after heat exchange through a heat exchanger. This can greatly reduce the reaction temperature inside the reactor, so that the reaction system can be mixed more evenly, the reaction can be carried out more thoroughly and fully, and the temperature in the reactor can be well controlled, avoiding the generation of more by-products.

[0024] Therefore, it can be known that in the working process of a high-efficiency synthesis system of pentaerythritol of the utility model, first, the catalyst sodium hydroxide and acetaldehyde will enter the multi-stage reactor from the acetaldehyde feed port at the top of the multi-stage reactor, and then be evenly mixed with the formaldehyde added after metering and enter the first strengthening unit inside the first-stage reactor. After being processed by the first strengthening unit, the mixture of the three will be processed into small droplets, increasing the interfacial area between the reactants so that the reaction is more complete and more intermediate products are generated. When the intermediate products descend in the form of small droplets inside the reactor, when the valve is in a closed state, the mixture of the raw materials The compound will gradually fill the first-stage reactor, and the first liquid level sensor will display the liquid level position inside the first-stage reactor in real time through the control system set outside the multi-stage reactor. As the liquid level gradually reaches the critical value, the control system will control the opening of the valve, so that the reaction liquid inside the first-stage reactor is simultaneously transported to the second-stage reactor through the connecting pipe, and then through the second strengthening unit set inside the second-stage reactor, the interface area between formaldehyde and the intermediate product is increased, so that the intermediate product can be fully converted into pentaerythritol. When the liquid inside the second-stage reactor reaches the critical value, the control system will control the valve to close. During the reaction process, the external circulation system of the first-stage reactor and the second-stage reactor will extract part of the reaction liquid inside the reactor by means of a circulation pump, and after heat exchange through a heat exchanger, it will be mixed with formaldehyde quantitatively added by a metering pump through a mixer and then returned to the reaction system to ensure that the temperature of the reaction system remains stable; then the final reaction liquid will enter the middle section of the distillation tower through a circulation channel arranged in the middle section of the multi-stage reactor for distillation, wherein a small amount of formaldehyde and most of the water are extracted from the top of the distillation tower, and then the mixture extracted from the top of the tower will pass through a splitter to remove most of the water and then enter the multi-stage reactor again through the feed port of the splitter. The solid-liquid mixture obtained by the recrystallization device is filtered through a filter, and the filter residue is the final product, crude pentaerythritol, and the filtrate is an aqueous sodium hydroxide solution. After being purified, the filtrate can enter the multistage reactor through the mixed liquid feed port at the top of the multistage reactor for recycling.

[0025] The strengthening unit of the utility model belongs to the existing technology. Although some are pneumatic type, some are hydraulic type, and some are gas-liquid linkage type, the difference between the types is mainly selected according to different specific working conditions. In addition, the connection between the strengthening reactor and the reactor, as well as other equipment, including the connection structure and the connection position, depends on the structure of the strengthening reactor and is not limited to this.

[0026] Compared with the prior art, the beneficial effects of the utility model are:

[0027] (1) The utility model discloses a highly efficient pentaerythritol synthesis system, which makes the reaction system more evenly mixed and the reaction more thorough by setting up multiple strengthening units, grids, sensors and doors, thereby reducing backmixing and making the product purity higher. The strengthening units increase the contact area between the raw materials, thereby improving the reaction rate and product yield. The external circulation system can be used to remove the reaction heat in time, thereby accurately controlling the reaction temperature, reducing the generation of reaction by-products, and facilitating subsequent purification and separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limiting of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0029] Figure 1 The utility model is a schematic structural diagram of a high-efficiency synthesis system of pentaerythritol.

[0030] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0031] In the figure: 1. feed port of diverter; 2. feed port of acetaldehyde; 3. feed port of mixed liquid; 4. first liquid level sensor; 5. first strengthening unit; 6. feed port of formaldehyde; 7. mixer; 8. multi-stage reactor; 9. control system; 10. second liquid level sensor; 11. second strengthening unit; 12. discharge port; 13. feed port of second circulation pump; 14. second circulation pump; 15. heat exchanger; 16. conveying pipeline; 17. first circulation pump; 18. heat exchanger; 19. metering pump; 20. diverter; 21. grid; 22. distillation tower; 23. recrystallization device; 24. filter; 25. pentaerythritol storage tank; 26. discharge port of first circulation pump; 27. valve; 28. heat exchanger; 29. ​​connecting pipe. DETAILED DESCRIPTION

[0032] The technical solution of the utility model will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the utility model, rather than all of the embodiments, and are only used to illustrate the utility model, and should not be considered as limiting the scope of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the utility model. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0033] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below.

[0036] Example 1

[0037] See also Figure 1As shown, a high-efficiency synthesis system of pentaerythritol includes 1. a feed port of a splitter; 2. a feed port of acetaldehyde; 3. a feed port of a mixed liquid; 4. a first liquid level sensor; 5. a first strengthening unit; 6. a feed port of formaldehyde; 7. a mixer; 8. a multi-stage reactor; 9. a control system; 10. a second liquid level sensor; 11. a second strengthening unit; 12. a discharge port; 13. a feed port of a second circulation pump; 14. a second circulation pump; 15. a heat exchanger; 16. a conveying pipeline; 17. a first circulation pump; 18. a heat exchanger; 19. a metering pump; 20. a splitter; 21. a grid; 22. a distillation tower; 23. a recrystallization device; 24. a filter; 25. a pentaerythritol storage tank; 26. a discharge port of a first circulation pump; 27. a valve; 28. a heat exchanger; 29. ​​a connecting pipe.

[0038] The reaction process of the efficient synthesis of pentaerythritol is as follows: the raw material acetaldehyde in an amount of 196 kg / h and the catalyst sodium hydroxide aqueous solution first enter the multi-stage reactor 8 through the acetaldehyde feed port 2, and then are mixed evenly with the formaldehyde added by the metering pump 19 at an amount of 120 kg / h through the formaldehyde feed port 6, and then processed into small droplets by the first strengthening unit 5 arranged inside the first-stage reactor, so that the interfacial area between the reactants is increased so that formaldehyde and acetaldehyde can be converted into the intermediate product of synthesizing pentaerythritol after the reaction in the first-stage reactor. At this time, the valve 27 arranged on the conveying pipeline 16 is in a closed state. As the raw material continues to enter the first-stage reactor, the first liquid level sensor 4 arranged inside the first-stage reactor will display the liquid level position inside the first reactor in real time through the control system 9 arranged outside the reactor. When the liquid level reaches the critical value, the external control system 9 can control the valve 2 7 is opened, so that the liquid in the first-stage reactor can smoothly enter the second-stage reactor through the connecting pipe 29, and then is processed by the second strengthening unit 11 set in the second-stage reactor to increase the interfacial area between the intermediate product and formaldehyde, so that the intermediate product can be more fully and thoroughly converted into pentaerythritol. When the liquid surface in the second-stage reactor reaches the critical value, the external control system 9 can control the valve 27 to close, and due to the setting of the grid 21 and the grid being set as a 5-layer grid at this time, the reaction liquid in the first-stage reactor and the reaction liquid in the second-stage reactor will not be mixed back. As the reaction in the first-stage reactor proceeds, the first circulation pump 17 will extract 30% of the liquid in the first-stage reactor through the first circulation pump discharge port 26, exchange heat through the heat exchanger 18, and after being evenly mixed with the formaldehyde entering through the metering pump in the mixer 7, enter the multi-stage reactor through the formaldehyde feed port;When the reaction occurs in the second stage reactor, the second circulation pump 14 will also pump out 30% of the liquid in the second stage reactor through the discharge port 12, and after heat exchange through the heat exchanger 15, enter the multi-stage reactor through the second circulation pump feed port 13 to continue the reaction. The reaction liquid finally obtained by the reaction in the second stage reactor will be pumped out through the second circulation pump 14 and then enter the distillation tower 22 through the delivery pipeline 16 for distillation. At this time, a small amount of formaldehyde and most of the water will be extracted from the top of the distillation tower 22, and the mixture extracted from the top of the tower will pass through the splitter 20 to remove most of the water, and the remaining liquid will pass through The liquid enters the reactor again from the feed port 1 of the diverter for reaction, and the mixture of pentaerythritol, water and sodium hydroxide is extracted from the bottom of the distillation tower 22. The mixture is transferred to the recrystallization device 23 through the bottom flow of the distillation tower 22 for purification. After the solid-liquid mixture is purified by the recrystallization device 23, it is filtered through the filter 24. The filter residue is the crude pentaerythritol. The crude pentaerythritol is transferred to the pentaerythritol storage tank 25 through the filter 24 to store the pentaerythritol. After the filtrate is purified, it can enter the multi-stage reactor through the mixed liquid feed port 3 set at the top of the multi-stage reactor for recycling. ;

[0039] Example 2

[0040] The only difference between this embodiment and Embodiment 1 is that the first liquid level sensor is arranged at the center of the first-stage reactor.

[0041] Example 3

[0042] The only difference between this embodiment and Embodiment 1 is that the second liquid level sensor is arranged at the center of the second-stage reactor.

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 1 is that the first liquid level sensor is not provided.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 1 is that no grille is provided.

[0047] Comparative Example 3

[0048] The difference between this comparative example and Example 1 is that the grid is provided in two layers.

[0049] Comparative Example 4

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

[0051] Comparative Example 5

[0052] The difference between this comparative example and Example 1 is that the first strengthening unit is not provided.

[0053] Comparative Example 6

[0054] The difference between this comparative example and Example 1 is that the second strengthening unit is not provided.

[0055] Comparative Example 7

[0056] The difference between this comparative example and Example 1 is that the second circulation pump and the heat exchanger are not provided.

[0057] Comparative Example 8

[0058] The difference between this comparative example and Example 1 is that the first circulation pump and the heat exchanger are not provided.

[0059] Comparative Example 9

[0060] The difference between this comparative example and Example 1 is that the first circulation pump, the second circulation pump and the corresponding heat exchanger are not provided.

[0061] Table 1 is a comparison of the product yield and conversion rate of the utility model embodiment and the comparative example:

[0062] The yield calculation formula is: yield = amount of reacted material / total input

[0063] The conversion rate is calculated as follows: Conversion rate = amount of product generated by the reaction / theoretical amount of product generated

[0064]

[0065] By comparing Examples 1-3 and Comparative Examples 1-3, it can be known that the liquid level sensor, grid, liquid level sensor and valve arrangement positions provided in the present invention are very important for the present invention. This is because the liquid level sensor can display the positions of the liquid levels inside the first-stage reactor and the second-stage reactor in real time, thereby facilitating the control of the opening and closing of the valve, so that the reaction liquid inside the first-stage reactor can be transmitted to the second-stage reactor through the connecting pipe, and the grid arrangement will prevent the mixed liquid inside the second-stage reactor from being back-mixed with the mixed liquid in the first-stage reactor, thereby intensifying the reaction in the first-stage reactor, thereby increasing the by-products and affecting the product purity. The setting position of the liquid level sensor is very important for the utility model. When the distance between the first liquid level sensor and the first strengthening unit is 3 times the distance between the first liquid level sensor and the top of the two-stage reactor, a certain distance can be created between the first-stage reactor and the top of the two-stage reactor to avoid the valve from being opened too timely due to excessive filling of the mixed liquid inside the first-stage reactor. When the distance between the grid and the second strengthening unit is 2 times the distance between the grid and the second liquid level sensor, and the distance between the second liquid level sensor and the second strengthening unit is 3 times the distance between the second liquid level sensor and the grid, a certain space can be reserved when controlling the valve to close, so that the valve can be closed in time to avoid excessive filling of the liquid inside the second-stage reactor due to the long-term opening of the valve.

[0066] By comparing Example 1 with Comparative Examples 4-5, it can be known that the arrangement of the first strengthening unit and the second strengthening unit of the utility model is very important for the utility model. This is because the raw materials used in the utility model are two mutually insoluble liquids under normal circumstances. Therefore, when performing the traditional synthesis of pentaerythritol, the reaction between the two is insufficient due to the small interfacial area between the raw materials used. Moreover, since the condensation of formaldehyde and acetaldehyde is a multi-stage condensation reaction, in order to make the reaction of the two more sufficient and complete and to increase the reaction rate, the utility model can process the two into small droplets through the treatment of the first strengthening unit, thereby increasing the interfacial area between the two, increasing the contact between the two, and increasing the contact area and contact time between the two when the raw materials descend inside the two-stage reactor. Under the catalysis of the catalyst, the reaction between the raw materials can be carried out more fully and thoroughly, so that the raw materials can be converted into more intermediate products. Through the treatment of the strengthening unit arranged in the second-stage reactor, the interfacial area between the reactants is increased so that the intermediate products are finally converted into pentaerythritol.

[0067] By comparing Example 1 and Comparative Examples 6-8, it can be known that the external circulation system provided in the utility model is extremely important. This is because during the reaction process, the condensation reaction is an exothermic reaction and the excessive use of formaldehyde causes the reaction temperature inside the multi-stage reactor to be high. In order to allow the reaction to proceed thoroughly, an external circulation system is adopted. The excess formaldehyde is fully utilized and the excess heat is removed in time through the external circulation method, and the reaction system is also fully mixed. During the reaction process in the second-stage reactor, the utility model uses the external circulation system to extract part of the reaction liquid using the second circulation pump, and performs heat exchange through the 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 always maintained at 25°C-35°C.

[0068] Therefore, the efficient synthesis system of the utility model makes the reaction system more evenly mixed, the reaction is more thoroughly carried out, and the backmixing is reduced to make the product purity higher through the setting of multiple strengthening units, grids, liquid level sensors and valves, and the contact area between the raw materials is increased by the strengthening units, thereby improving the reaction rate and product yield, and the reaction heat can be removed in time by using an external circulation system to accurately control the reaction temperature, reduce the generation of reaction by-products, and facilitate subsequent purification and separation.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. An efficient synthesis system of pentaerythritol, characterized in that: It comprises a multi-stage reactor, wherein a plurality of strengthening units and liquid level sensors are vertically arranged inside the multi-stage reactor, a multi-layer grid or a multi-layer sieve plate is arranged in the middle section inside the multi-stage reactor, an acetaldehyde feed port is arranged at the top of the multi-stage reactor, and the acetaldehyde feed port leads to the strengthening unit, a diverter feed port and a mixed liquid feed port are arranged on both sides of the top of the multi-stage reactor respectively, a connecting pipe is also arranged outside the multi-stage reactor, a valve is also arranged on the connecting pipe, a control system for receiving data sent back by the liquid level sensor and controlling the opening or closing of the valve is also arranged outside the multi-stage reactor, and a discharge port is arranged at the bottom of the multi-stage reactor.

2. The efficient synthesis system according to claim 1, characterized in that: The multistage reactor is a two-stage reactor, and two strengthening units and two liquid level sensors are arranged inside the two-stage reactor; wherein the first-stage reactor comprises a first strengthening unit arranged at the top of the multistage reactor and a first liquid level sensor arranged on the inner wall above the first strengthening unit, and the first liquid level sensor is used to detect the liquid level height of the first-stage reactor; The second stage reactor comprises a second strengthening unit arranged at the bottom of the two-stage reactor and a second liquid level sensor arranged on the inner wall above the second strengthening unit, wherein the second liquid level sensor is used to detect the liquid level height of the second stage reactor.

3. The efficient synthesis system according to claim 1, characterized in that: The number of layers of the multi-layer grid or multi-layer sieve plate is 3-7; The distance between the grid and the second strengthening unit is twice the distance between the grid 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 efficient synthesis system according to claim 3, characterized in that: The number of layers is 5.

5. The efficient synthesis system according to claim 2, characterized in that: The distance between the first liquid level sensor and the first enhancement unit is three times the distance between the first liquid level sensor and the top of the two-stage reactor.

6. The efficient synthesis system according to claim 2, characterized in that: A formaldehyde feed inlet is arranged above the first strengthening unit, the formaldehyde feed inlet leads into the first strengthening unit, a formaldehyde feed metering pump is connected to the first strengthening unit through the formaldehyde feed inlet, and a mixer is arranged between the formaldehyde feed inlet and the formaldehyde feed metering pump.

7. The efficient synthesis system according to claim 2, characterized in that: A first circulation outlet is provided below the first strengthening unit, the first circulation outlet leads into the first strengthening unit, a first circulation pump is connected to the first strengthening unit through the first circulation outlet, and the first circulation pump is connected to the mixer through a heat exchanger.

8. The efficient synthesis system according to claim 2, characterized in that: A second circulation pump feed port is arranged above the second strengthening unit, and the second circulation pump feed port leads to the second strengthening unit. The second circulation pump is connected to the second strengthening unit through the second circulation pump feed port. The second circulation pump is connected to the delivery pipeline arranged at the center of the outside of the two-stage reactor through a heat exchanger, and the second circulation pump extracts the liquid in the second-stage reactor through the discharge port.

9. The efficient synthesis system according to claim 1, characterized in that: It also includes a distillation tower, a recrystallization device, a storage tank and a filter which are connected in sequence; the distillation tower is connected to the multi-stage reactor.

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