Reactor device for enhancing heat dissipation in cyclohexene oxidation process

Abstract

The invention relates to the field of chemical reaction devices, aims to overcome the defects of an existing high-pressure reaction kettle type device, and provides a stirring reaction device for chemical production, which can continuously and accurately feed materials in a reaction process and can control reaction temperature uniformity and reaction temperature accuracy. According to the device, materials are continuously replenished through the hollow rotating shaft and the stirring paddle blades with the small holes, so that the replenished materials are fully mixed with reaction liquid, and the uniformity of the reaction temperature is maintained. The stirring paddle blades at the uppermost end and the lowermost end are respectively designed in a downward pressing manner and an upward raising manner, so that the material mixing uniformity is further enhanced. In addition, the device is provided with a flow controller and a temperature sensor, the feeding rate and the heating rate can be automatically adjusted according to the temperature of a reaction system, and the reaction temperature runaway phenomenon is effectively prevented. The S-shaped condensing coil is used for conveying cold energy, and the temperature in the reaction container is accurately controlled by regulating and controlling the circulating rate and temperature of circulating condensate. The method innovatively solves the key problems in chemical production, improves the product quality, and has wide popularization and application values.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis and relates to chemical equipment technology, in particular to a reaction device capable of accurately controlling the reaction temperature of preparing adipic acid by oxidizing cyclohexene with hydrogen peroxide. Background Art

[0002] Adipic acid is a high-value-added fine chemical product, primarily used in the fields of nylon salts, polyurethanes, plasticizers, pharmaceuticals, pesticides, and food additives. Depending on the raw materials used, there are five main methods for the industrial production of adipic acid: the phenol method, the cyclohexane method, the cyclohexene method, the butadiene method, and the biosynthesis method. Currently, the cyclohexane method and the cyclohexene method are the main methods for the industrial production of adipic acid. Both methods use nitric acid as the oxidant, resulting in severe equipment corrosion during the production process. They also release large amounts of N2O gas, nitric acid vapor, and highly concentrated waste acid liquid, seriously polluting the environment. In response to the increasingly serious problem of environmental pollution, finding a clean process for the synthesis of adipic acid is of great economic and social significance. In recent years, a new process for the one-step preparation of adipic acid using cyclohexene as the raw material and hydrogen peroxide as the oxidant has attracted increasing attention. This production process is simple, has a high yield, and is clean and pollution-free during the reaction, making it an ideal alternative to existing adipic acid production methods.

[0003] Currently reported, publicly available reactions for the one-step production of adipic acid from cyclohexene with hydrogen peroxide are mostly conducted in sealed reactors, with the reaction temperature generally controlled at 80-120°C, using organic solvents such as dichloromethane or 1,2-dichloroethane as the reaction solvent. The reaction process for producing adipic acid from cyclohexene with hydrogen peroxide is shown above. During the reaction, intermediates such as epoxycyclohexane, trans-1,2-cyclohexanediol, 2-hydroxycyclohexanone, 7-hydroxy-2-polycaprolactone, and adipic anhydride are produced. Because this reaction is exothermic, a large amount of heat is released. If this heat is not removed promptly, the temperature in the reactor will continue to rise. When the reaction system temperature reaches a certain critical temperature, ring-opening polymerization of the intermediate epoxycyclohexane and ring-opening copolymerization of epoxycyclohexane with adipic anhydride will occur. Because the polymerization reaction is exothermic and has a relatively fast reaction rate, the occurrence of the polymerization reaction will cause the temperature and pressure in the reactor to rise rapidly. Failure to remove the reaction heat and pressure from the reactor promptly can pose a risk. Furthermore, the occurrence of polymerization reactions can also lead to a decrease in adipic acid yield. Therefore, rationally designing the reactor structure and reaction process, precisely controlling the reaction temperature within the reactor during the reaction, ensuring a smooth chemical reaction, and preventing polymerization are crucial for the large-scale application of the one-step hydrogen peroxide oxidation process for adipic acid.

[0004] Currently used high-pressure reactors generally adopt a one-time feeding method or continuous feeding from the bottom sampling port during the reaction process. The raw materials are stirred by the stirring paddle to form a vortex to mix the materials. This mixing method is only conducive to the mixing of liquids in the horizontal direction, while the vertical liquid mixing effect is poor. During the heating reaction process, local overheating is prone to occur, resulting in temperature runaway, which causes uneven temperature distribution of the materials in the reaction vessel, easily triggering side reactions and hindering the progress of the reaction. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of existing high-pressure reactors and provide a stirring reaction device for chemical production that can continuously and accurately feed materials during the reaction process and can control the uniformity and accuracy of the reaction temperature.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A reaction apparatus for precisely controlling the reaction temperature of adipic acid produced by the one-step oxidation of cyclohexene with hydrogen peroxide, comprising a reaction vessel, a controller, a flow controller, a heating controller, a temperature sensor, a pressure sensor, a pressure gauge, and a safety blasting device. The reaction vessel is a hollow cylindrical structure, with a first feed inlet and a second feed inlet at the top and a discharge outlet at the bottom, each equipped with a valve. A serpentine coil is disposed within the reaction vessel, surrounding the inner wall of the reaction vessel. A rotating shaft is provided within the reaction vessel, with multiple sets of stirring paddles mounted on the shaft. A second feed inlet is provided at the top of the reaction vessel, each equipped with a valve. A temperature sensor is provided within the reaction vessel. A cavity is defined between the outer wall of the reaction vessel and the inner wall of the reaction apparatus, housing a heating module connected to the temperature sensor. The flow controller, temperature sensor, pressure sensor, drive motor, and thermal oil controller are all connected to the controller.

[0008] Furthermore, the top of the reaction vessel is provided with an inlet and an outlet of a serpentine coil, which are connected to the outlet and the inlet of the cooling circulating liquid respectively; the temperature of the cooling circulating liquid can be freely adjusted between -20°C and 150°C, preferably between 40°C and 90°C.

[0009] Furthermore, the multiple groups of stirring paddles have different modes, wherein the top layer of stirring paddle blades is a downward pressure design, which will generate downward pressure on the material during use; the bottom layer of stirring paddle blades is an upward lifting design, which will generate upward pressure on the material during use, thereby making the material mixing more even; the other stirring paddle blades are flat paddle blades; the distances between the multiple groups of stirring paddle blades are equal.

[0010] Furthermore, the upper end of the rotating shaft is connected to the driving motor by a transmission chain or a transmission belt; the driving motor is connected to the controller.

[0011] Furthermore, the rotating shaft and the stirring paddle blades are both hollow structures, and the stirring paddle blades have evenly distributed small holes on the upper and lower sides, with a pore size range of 0.01-1mm, preferably 0.1-0.5mm; the upper port of the hollow rotating shaft is the first feed port, which is connected to the feed flow controller; the flow controller can accurately control the addition rate of the material at the feed port.

[0012] Furthermore, the second feed port is connected to a pressure gauge, a pressure sensor and a safety blasting device. The pressure range of the pressure gauge is 0-15 MPa, which can accurately display the real-time pressure in the reaction vessel; the alarm pressure setting value of the safety blasting device is 0.1-12.5 MPa, preferably 10 MPa. When the pressure exceeds the pressure alarm setting value, the safety blasting device will automatically start to release the pressure in the reaction vessel, so that the pressure in the reaction vessel is within a safe range.

[0013] Furthermore, the distance between the position where the temperature sensor is inserted into the reaction container and the bottom of the reaction container is 1 / 10-1 / 2 of the height of the reaction container.

[0014] Furthermore, the heating method is thermal oil heating, steam heating or electric heating.

[0015] Furthermore, the controller is connected to a flow controller, a temperature sensor, and a pressure sensor, each capable of displaying corresponding values. When the temperature sensor indicates a temperature exceeding a set temperature range, the controller adjusts the feed flow rate of the first feed port via the flow controller, typically reducing the feed rate or stopping the feed. Simultaneously, the controller controls the heating device via the temperature sensor, typically reducing the heating rate or stopping the heating. Furthermore, the temperature within the reaction vessel is adjusted by adjusting the circulation rate or temperature of the circulating condensate, typically by increasing the circulation speed or reducing the condensate temperature, thereby lowering the temperature within the reaction vessel.

[0016] In particular, the reaction device is also suitable for preparing glutaric acid by oxidizing cyclopentene with hydrogen peroxide in one step, preparing pimelic acid by oxidizing cycloheptene with hydrogen peroxide in one step, and other similar reactions.

[0017] Compared with the prior art, this application has the following advantages and beneficial effects:

[0018] 1. This technical solution uses a hollow rotating shaft and stirring blades. Materials are continuously added during the reaction process through small holes evenly distributed on the stirring blades. Since the stirring blades are evenly distributed in the reaction vessel, the added materials can be mixed with the reaction liquid in a timely manner to ensure the uniformity of the reaction temperature.

[0019] 2. In this technical solution, the uppermost stirring paddle blade uses a downward pressure type, and the lowermost stirring paddle blade uses an upward lifting type, which can make the materials mixed more evenly and ensure the uniformity of the reaction temperature.

[0020] 3. This technical solution uses a flow controller to control the first feed port. When the temperature of the reaction system exceeds the set temperature, the flow controller will reduce the feed rate or stop feeding, thereby effectively controlling the reaction rate and reducing the reaction temperature.

[0021] 4. This technical solution uses a temperature sensor to control and detect the temperature inside the reaction container. When the temperature inside the reaction container exceeds the set temperature, the controller will reduce the heating rate or stop heating through the temperature sensor, thereby effectively controlling the temperature inside the reaction container.

[0022] 5. This technical solution transports cold air into the reaction vessel by setting a serpentine condensing coil, thereby reducing the temperature inside the reaction vessel and preventing temperature runaway in the reaction vessel. At the same time, the temperature inside the reaction vessel can be effectively regulated by controlling the circulation rate and temperature of the circulating condensate.

[0023] Therefore, the present invention is not only innovative but also can achieve relatively precise control of the temperature in the reaction vessel, enhance the uniformity of stirring and mixing, and enhance the uniformity of heat exchange. It has practical significance for controlling the reaction rate, preventing reaction temperature runaway, and improving product quality. It is suitable for further promotion and application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0026] Example 1:

[0027] Take 4g of quaternary ammonium salt phosphotungstic heteropolyacid catalyst confined by hollow molecular sieve, add it to a 1L reaction vessel through the second feed port, then add 666mL of 30% hydrogen peroxide solution through the second feed port, and then close the second feed port valve; Set the stirring speed of the motor to 800rpm and stir for 30min until uniform. Set the heating target temperature of the reaction vessel electric heating device to 90°C, the heating power to 20mW / min, and the setting reaction time to 6h; A condensate with a temperature of 90°C is introduced into the serpentine condensing coil, and the condensate circulation rate is 50mL / min. After the setting parameters are completed, start the heating device until the temperature in the reactor reaches 90°C. Place 144mL of cyclohexene in a high-pressure vessel, connect the first feed port, set the flow rate of the flow controller to 1mL / min, and pump cyclohexene into the reaction vessel according to the set flow rate through a high-pressure feed pump, and the reaction starts. Temperature monitoring within the reaction vessel during the reaction revealed that the temperature of the reaction system remained stable within the range of 89-91°C throughout the 6-hour reaction. After the reaction was completed, the second feed port was opened while hot to slowly vent the pressure within the reaction vessel. The discharge port was then opened to discharge the reaction mixture, and the catalyst was filtered while hot. The reaction mixture was allowed to stand at low temperature for 5 hours, and the crude adipic acid was collected, dried, and weighed. The calculated adipic acid yield was 74%. Extraction of 1 mL of the reaction solution with 1 mL of dichloromethane and subsequent gas chromatography analysis revealed no characteristic peaks for cyclohexene, confirming a cyclohexene conversion rate of 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments.

[0029] Figure 1 It is a structural schematic diagram of the present invention.

[0030] Figure 1 Middle: 1 reaction vessel body, 2 rotating shaft, 3 first feed port, 4 flow controller, 5 motor, 6 heating module, 7 serpentine coil, 8 serpentine coil inlet, 9 serpentine coil outlet, 10 second feed port, 11 pressure gauge, 12 safety blasting device, 13 heating controller, 14 discharge port, 15 temperature sensor, 16 stirring paddle blade.

Claims

1. A reactor device for enhancing heat dissipation during cyclohexene oxidation, characterized in that: It includes a reaction vessel body with a hollow cylindrical structure, a controller, a flow controller, a heating controller, a temperature sensor, a pressure sensor, a pressure gauge and a safety blasting device; the top of the reaction vessel is provided with a first feed port and a second feed port, and the bottom is provided with a discharge port with a valve; the interior is provided with a serpentine coil surrounding the inner wall and multiple groups of stirring paddles with different modes; the outside is provided with a heating module connected to the temperature sensor.

2. The stirring reaction device according to claim 1, characterized in that: The inlet and outlet of the serpentine coil are respectively connected to a cooling circulating liquid system, and the temperature range can be adjusted from -20°C to 150°C, preferably from 40°C to 90°C.

3. The stirring reaction device according to claim 1, characterized in that: The multiple groups of stirring paddles include a downward pressure design at the top, an upward lift design at the bottom, and flat blades, and the distances between the stirring paddles are equal.

4. The stirring reaction device according to claim 1, characterized in that: The rotating shaft is connected to the driving motor through a transmission chain or a belt, and the rotating shaft and the stirring paddle thereon are both hollow structures, and the stirring paddle is provided with a small hole with an aperture of 0.01-1 mm.

5. The stirring reaction device according to claim 1, characterized in that: A flow controller is provided at the first feed inlet, which can accurately control the material addition rate.

6. The stirring reaction device according to claim 1, characterized in that: The second feed port is provided with a pressure gauge, a pressure sensor and a safety explosion device, wherein the pressure range of the pressure gauge is 0-15 MPa, and the alarm pressure setting value of the safety explosion device is 0.1-12.5 MPa, preferably 10 MPa.

7. The stirring reaction device according to claim 1, characterized in that: The distance between the position where the temperature sensor is inserted into the reaction container and the bottom is 1 / 10 to 1 / 2 of the height of the reaction container.

8. The stirring reaction device according to claim 1, characterized in that: The heating method can be thermal oil heating, steam heating or electric heating.

9. The stirring reaction device according to claim 1, characterized in that: The controller is connected to a flow controller, a temperature sensor, and a pressure sensor, and can automatically adjust a feed rate, a heating rate, or start a safety blasting device when an abnormality is detected.

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