System for separating p-chlorobenzaldehyde and p-chlorobenzoic acid
By using crystallization and sublimation techniques to separate p-chlorobenzaldehyde and p-chlorobenzoic acid in a crystallization tank, the problems of p-chlorobenzaldehyde loss and high cost caused by the water washing method are solved, achieving high-purity separation and clean production.
Patent Information
- Application Number
- CN202511114664.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-11
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, the water washing method for separating p-chlorobenzaldehyde and p-chlorobenzoic acid results in the loss of p-chlorobenzaldehyde and generates a large amount of wastewater from multiple washes, leading to high treatment costs and difficulty in achieving high purity requirements.
A physical method is used, taking advantage of the coagulation and sublimation properties of p-chlorobenzaldehyde and p-chlorobenzoic acid, to crystallize in a crystallization tank and control the temperature with a temperature control device. Combined with inert gas purging and vacuum removal, the separation of p-chlorobenzoic acid is achieved.
This method improves the purity of p-chlorobenzaldehyde, reduces the content of p-chlorobenzoic acid, achieves high-purity separation without the need for water or other solvents, simplifies the operation, and achieves the goal of clean production.
Smart Images
Figure CN120900247A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the chemical technology field, and in particular to a system for separating p-chlorobenzaldehyde and p-chlorobenzoic acid. BACKGROUND
[0002] In the traditional production process of p-chlorobenzaldehyde, p-chlorobenzoic acid is generated during the acid hydrolysis after chlorination reaction, so it is necessary to reduce its content in p-chlorobenzaldehyde through separation treatment.
[0003] The commonly used treatment method is water washing method, which utilizes the solubility of p-chlorobenzoic acid in water to transfer it from p-chlorobenzaldehyde to water phase through water washing. However, this method has obvious defects, because p-chlorobenzaldehyde also has certain water solubility, and part of p-chlorobenzaldehyde will be lost with water during the water washing process, resulting in loss of p-chlorobenzaldehyde.
[0004] To improve this problem, the following optimization scheme exists in the prior art. The p-chlorobenzaldehyde lost in the water solution after water washing is oxidized into p-chlorobenzoic acid (uniformly into the same substance), and then the pH value of the water solution is adjusted, for example, adjusted to acidic conditions, so as to reduce the solubility of p-chlorobenzoic acid, so that it is crystallized and recovered. The remaining wastewater is neutralized by adding alkali and then treated. Through this scheme, the content of p-chlorobenzoic acid in p-chlorobenzaldehyde can be reduced to 0.5%-0.2%.
[0005] If the subsequent product does not have high purity requirements, for example, the content of p-chlorobenzoic acid is allowed to be ≥0.5%, the above treatment can meet the requirements. However, if higher purity is required, for example, the content of p-chlorobenzoic acid is required to be ≤0.2%, further water washing is required to further reduce the content, but such a large number of water washing will produce a large amount of wastewater, and when recovering p-chlorobenzoic acid from the wastewater, due to the large amount of water, the treatment cost will be too high. SUMMARY
[0006] Therefore, the present application provides a system for separating p-chlorobenzaldehyde and p-chlorobenzoic acid, which separates p-chlorobenzaldehyde and p-chlorobenzoic acid by a physical method.
[0007] The system for separating p-chlorobenzaldehyde and p-chlorobenzoic acid provided by the present application comprises: The crystallization tank has multiple coils inside, the outer wall is wrapped by a jacket, and the top and bottom have an upper gas inlet and a lower gas inlet, respectively; The circulating material tank is connected to the bottom of the crystallization tank through a first pipeline and a second pipeline, and connected to the top of the crystallization tank through a third pipeline; the circulating material tank is also connected to a finished product tank; The desublimation tank is connected to the top of the crystallization tank through a fourth pipeline; the inside of the desublimation tank has multiple crystallization trays, and the bottom has a discharge port; A temperature control device is used to control the temperature of the coil, jacket and crystallization tray; The system performs the following separation steps: The stock solution is injected into the crystallization tank until the preset volume is reached; The temperature of the coil and jacket is controlled to crystallize p-chlorobenzoic acid in the stock solution, and the stock solution is circulated in the crystallization tank, third pipeline, circulating tank, first pipeline until the purity of p-chlorobenzoic acid in the stock solution meets the standard; The stock solution in the crystallization tank is controlled to flow through the second pipeline to the circulating tank, and the stock solution in the circulating tank flows to the finished product tank; The temperature of the coil and jacket is controlled to accelerate the volatilization of residual p-chlorobenzoic acid in the crystallization tank, and the upper gas inlet is opened until the volatilized p-chlorobenzoic acid is purged out of the crystallization tank; The fourth pipeline is opened and the desublimation tank and the crystallization tank are vacuumed, the temperature of the coil and jacket is controlled to sublimate p-chlorobenzoic acid in the crystallization tank, and the lower gas inlet is opened to blow the sublimated p-chlorobenzoic acid into the desublimation tank, and the temperature of the crystallization tray is controlled to condense p-chlorobenzoic acid; The p-chlorobenzoic acid on the crystallization tray is treated, and the product is obtained through the discharge port.
[0008] In some embodiments, the system further comprises a storage tank connected to the bottom of the crystallization tank through a fifth pipeline, and a first feeding pump is arranged on the fifth pipeline near the storage tank; The first pipeline is arranged at the bottom of the circulating tank, and a second feeding pump is arranged on the first pipeline near the circulating tank; The crystallization tank has an observation window; The gas source of the upper gas inlet and the lower gas inlet is inert gas; The circulating tank has a sampling port; And / or, the top of the desublimation tank has a vacuum air outlet.
[0009] In some embodiments, the crystallization tank is further connected to the bottom of the storage tank through a sixth pipeline; and the opening of the upper gas inlet until the volatilized p-chlorobenzoic acid is purged out of the crystallization tank comprises: opening the sixth pipeline, and opening the upper gas inlet until the volatilized p-chlorobenzoic acid is purged into the storage tank; And / or, a seventh pipeline is arranged at the outlet of the second feeding pump, and the circulating tank is connected to the finished product tank through the seventh pipeline.
[0010] In some embodiments, the system further comprises a heat exchanger connected to the circulating tank through an eighth pipeline, and the temperature control device is further configured to control the temperature of the heat exchanger. The control of the temperature of the coil and the jacket to accelerate the volatilization of residual p-chlorobenzaldehyde in the crystallization tank, the opening of the upper gas inlet until the volatilized p-chlorobenzaldehyde is purged out of the crystallization tank, comprises: The control of the temperature of the coil and the jacket to accelerate the volatilization of residual p-chlorobenzaldehyde in the crystallization tank, the opening of the second pipeline and the eighth pipeline, the opening of the upper gas inlet to purge the volatilized p-chlorobenzaldehyde to the heat exchanger, and the control of the temperature of the heat exchanger to liquefy p-chlorobenzaldehyde until the heat exchanger is no longer dripping.
[0011] In some embodiments, the control of the temperature of the coil and the jacket to accelerate the volatilization of residual p-chlorobenzaldehyde in the crystallization tank comprises: The temperature of the coil and the jacket is raised until the heat exchanger drips, and the temperature of the coil and the jacket is controlled to be raised by a preset amplitude.
[0012] In some embodiments, the heat exchanger has a drip observation window; and / or, the heat exchanger is further connected to a tail gas absorption system.
[0013] In some embodiments, the flow rate of the circulating flow of the stock solution is greater than or equal to 0.5 cm / min and less than or equal to 1 cm / min; And / or, the vacuum degree when the desublimation tank and the crystallization tank are vacuumized is greater than or equal to 10 kpa and less than or equal to 20 kpa.
[0014] In some embodiments, each of the crystallization discs is provided with a scraper; The top of the desublimation tank is further provided with a motor, and the rotating shaft of the motor is connected with each scraper.
[0015] In some embodiments, the temperature control device is divided into a first temperature control system, a second temperature control system, a third temperature control system, and a fourth temperature control system. The temperature range of the first temperature control system is 48-48.5℃, the temperature range of the second temperature control system is 49-50℃, the temperature range of the third temperature control system is 80-200℃, and the temperature range of the fourth temperature control system is -5-10℃. The control of the temperature of the coil and the jacket to crystallize p-chlorobenzoic acid in the stock solution comprises: controlling the temperature of the coil by the first temperature control system, and controlling the temperature of the jacket by the second temperature control system. controlling the temperature of the coil and the jacket by the third temperature control system; controlling the temperature of the coil and the jacket by the third temperature control system; controlling the temperature of the coil and the jacket by the third temperature control system; controlling the temperature of the coil and the jacket by the third temperature control system;
[0016] In some embodiments, the temperature control medium of the first temperature control system, the second temperature control system, the third temperature control system and / or the fourth temperature control system is ethylene glycol Based on the above technical solutions, the application utilizes the freezing and sublimation characteristics of p-chlorobenzaldehyde and p-chlorobenzoic acid, and separates p-chlorobenzoic acid from p-chlorobenzaldehyde at a proper temperature. Then, according to the sublimation characteristics of p-chlorobenzoic acid, the p-chlorobenzoic acid is sublimated to the condensation tank for condensation by heating. In this way, the two materials are separated, the purity of p-chlorobenzaldehyde is improved, and the purity of p-chlorobenzoic acid is also relatively high. Without adding water or other solvents, no other hazardous waste is generated, the operation is simple, and the purpose of clean production is achieved. BRIEF DESCRIPTION OF DRAWINGS
[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.
[0018] Figure 1 A system structure diagram for separating p-chlorobenzaldehyde and p-chlorobenzoic acid in the embodiments of the application; Figure 2 A structure schematic diagram of a coil in the embodiments of the application; Figure 3 A structure schematic diagram of a crystallization disc in the embodiments of the application; Figure 4 A structure schematic diagram of a scraper in the embodiments of the application; Figure 5 A structure schematic diagram of an ethylene glycol temperature control system in the embodiments of the application. DETAILED DESCRIPTION
[0019] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts are within the scope of the present application.
[0020] It should be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, unless otherwise clear from the context, the singular forms "a", "an" and "the" are intended to include the plural forms.
[0021] It should also be understood that the terms "first", "second", "third", "fourth" and the like (if any) in the specification of the present application, if any, are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence, and cannot be understood as indicating or implying relative importance of the indicated technical features or implying the number of the indicated technical features.
[0022] It should be further understood that the term "and / or" used in the specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.
[0023] The system for separating p-chlorobenzaldehyde and p-chlorobenzoic acid provided by the embodiments of the present application, as shown in Figures 1-5 may include a crystallization tank 110, a circulating material tank 120, a condensation tank 130, a temperature control device 140 and a finished product tank 150.
[0024] The crystallization tank 110 is internally provided with a plurality of coils 111, which play a temperature control role. Exemplarily, the coils 111 are sequentially and uniformly arranged at intervals in the height direction of the crystallization tank 110. The outer wall of the crystallization tank 110 is wrapped by a jacket 112, which also plays a temperature control role. The top and bottom of the crystallization tank 110 are respectively provided with an upper gas inlet and a lower gas inlet. In some embodiments, the gas source of the upper gas inlet and the lower gas inlet can be inert gas, such as nitrogen. It can be understood that the use of inert gas can ensure that the gas does not chemically react with other substances when the gas is used for purging, etc., to ensure the extraction purity. Exemplarily, the crystallization tank 110 can have an observation window through which a user can observe the internal condition of the crystallization tank 110.
[0025] In some embodiments, the system can further include a storage tank 160 connected to the bottom of the crystallization tank 110 through a fifth pipeline 250, and a first feeding pump 161 is arranged on the fifth pipeline 250 close to the storage tank 160. It should be noted that all the pipelines in the embodiments of the present application can be provided with one or more valves to control whether the pipeline is opened or closed, or partially closed. For example, the valve arrangement of each pipeline can be as shown in Figure 1 FIG. 1, and the elements marked by the labels starting with HA in the figure are valves, such as the valve HA123 arranged at the lower air inlet, and the like.
[0026] The circulating tank 120 is connected to the bottom of the crystallization tank 110 through a first pipeline 210 and a second pipeline 220. In some embodiments, the first pipeline 210 is arranged at the bottom of the circulating tank 120, and a second feeding pump 121 is arranged on the first pipeline 210 close to the circulating tank 120, that is, the first pipeline 210 is a feeding pipeline. The circulating tank 120 is connected to the top of the crystallization tank 110 through a third pipeline 230, and the circulating tank 120 is also connected to the finished product tank 150. For example, the circulating tank 120 can have a sampling port, through which a user can take samples and perform purity detection, and the like.
[0027] In some embodiments, the system can further include a heat exchanger 170 connected to the circulating tank 160 through an eighth pipeline 280, for example, the eighth pipeline 280 is arranged at the top of the circulating tank 160.
[0028] The bottom of the desublimation tank 130 is connected to the top of the crystallization tank 110 through a fourth pipeline 240. The desublimation tank 130 has a plurality of crystallization trays 131 inside, which serve as temperature control. For example, the crystallization trays 131 are arranged uniformly and at intervals in the height direction of the desublimation tank 130. The bottom of the desublimation tank 130 also has a discharge port.
[0029] The temperature control device 140 is used to regulate the temperature of the coil pipe 111, the jacket 112 and the crystallization disc 131. In some embodiments, the temperature control device 140 can also be used to regulate the temperature of the heat exchanger 170. In some embodiments, the temperature control device 140 can be divided into four temperature control subsystems, i.e. a first temperature control system, a second temperature control system, a third temperature control system and a fourth temperature control system. The temperature range of the first temperature control system is 48-48.5°C, the temperature range of the second temperature control system is 49-50°C, the temperature range of the third temperature control system is 80-200°C, and the temperature range of the fourth temperature control system is -5-10°C. It can be understood that through the regulation of the four temperature control systems, the temperature control requirements required in the embodiments of the present application can be met. For example, when the first temperature control system regulates the coil pipe 111, the temperature of the coil pipe 111 will be between 48-48.5°C, for example, 48°C, and the other cases are similar. In some embodiments, the temperature control medium of the first temperature control system, the second temperature control system, the third temperature control system and / or the fourth temperature control system is ethylene glycol. For example, as shown in the coil pipe 111, Figure 2 the ethylene glycol at the target temperature (for example, 48°C) flows into the inlet of the coil pipe 111, and flows out from the outlet after winding through the pipe, so as to achieve the purpose of temperature control. For another example, the ethylene glycol at the target temperature (for example, 49°C) flows into the inlet below the jacket 112, and flows out from the outlet when the height of the filled ethylene glycol reaches the height of the outlet, so as to achieve the purpose of temperature control. The temperature control principles of the crystallization disc 131 and the heat exchanger 170 are similar. For example, as shown in the ethylene glycol flowing out of the tank, flowing into the coil pipe 111, the jacket 112, the crystallization disc 131 or the heat exchanger 170, and flowing back into the tank from the coil pipe 111, the jacket 112, the crystallization disc 131 or the heat exchanger 170, so as to achieve the purpose of temperature control. Figure 5
[0030] Based on this, the separation steps of the system are as follows: S1, injecting the raw liquid into the crystallization tank 110 until reaching a preset capacity, the setting of the preset capacity needs to meet the requirements of the circulating flow in step S2, for example, the amount of the raw liquid injected needs to be able to overflow through the third pipeline 230 to the circulating material tank 120. For example, the value of the preset capacity can be two-thirds of the capacity of the circulating material tank 120.
[0031] For example, the first feeding pump 161 can be started, the fifth pipeline 250 is opened, and the raw liquid in the storage tank 160 is injected into the crystallization tank 110. Of course, after the injection is completed, the first feeding pump 161 can be stopped, and the fifth pipeline 250 is closed. It should be noted that the raw liquid refers to untreated p-chlorobenzaldehyde, and contains a certain concentration of p-chlorobenzoic acid, for example, the concentration of p-chlorobenzoic acid is 0.8%.
[0032] S2, controlling the temperature of the coil pipe 111 and the jacket 112 to crystallize p-chlorobenzoic acid in the original solution, and controlling the circulation of the original solution in the crystallization tank 110, the third pipeline 230, the circulation tank 120, and the first pipeline 210 until the purity of p-chlorobenzaldehyde in the original solution reaches the standard.
[0033] Since the melting point of p-chlorobenzaldehyde is 47-49°C, but the melting point of p-chlorobenzoic acid is much higher than 49°C, the physical property can be used to cool and crystallize the original solution.
[0034] On the one hand, the circulation of the original solution can be controlled, which is convenient for crystallization. In some embodiments, the circulation of the original solution can be controlled slowly, for example, the flow rate of the circulation of the original solution is greater than or equal to 0.5 cm / min and less than or equal to 1 cm / min, such as 0.5 cm / min. Illustratively, the second feeding pump 121 can be started, and the third pipeline 230 and the first pipeline 210 are opened. Under the driving of the second feeding pump 121, the original solution circulates. On the other hand, the temperature of the coil pipe 111 and the jacket 112 can be controlled, so that the p-chlorobenzaldehyde in the original solution flowing through is still liquid, but the p-chlorobenzoic acid crystallizes. Since the contact area of the coil pipe 111 is much larger than the outer wall of the crystallization tank 110, the p-chlorobenzoic acid mainly crystallizes on the surface of the coil pipe 111.
[0035] It can be understood that through continuous circulation and crystallization, the content of p-chlorobenzoic acid in the original solution will be lower and lower, that is, the purity of p-chlorobenzaldehyde in the original solution will be higher and higher. It is worth mentioning that this process uses physical properties and does not involve other chemical reactions, that is, no other substances are generated. Therefore, the purity of p-chlorobenzaldehyde can reach a very high degree, for example, the content of p-chlorobenzoic acid is less than 0.1%. Illustratively, during the circulation and crystallization process, the user can take samples of the original solution through the sampling port multiple times, and detect the purity of p-chlorobenzaldehyde in the sample solution. When the purity reaches the standard (for example, the content of p-chlorobenzoic acid is less than 0.1%), the circulation is stopped. Of course, after the purity of p-chlorobenzaldehyde in the original solution reaches the standard, the circulation can be stopped, for example, the third pipeline 230 is closed.
[0036] In some embodiments, in step S1, the temperature of the coil pipe 111 and the jacket 112 is controlled to crystallize p-chlorobenzoic acid in the original solution. The temperature control method can be that the temperature of the coil pipe 111 is controlled by the first temperature control system, and the temperature of the jacket 112 is controlled by the second temperature control system. Since the p-chlorobenzoic acid mainly crystallizes on the surface of the coil pipe 111, the heat exchange of the coil pipe 111 is more, so the temperature of the jacket 112 can be slightly higher than that of the coil pipe 111 to supplement the heat and achieve the technical purpose of maintaining the temperature stable. Illustratively, the temperature of the coil pipe 111 can be 48°C, and the temperature of the jacket 112 can be 49°C.
[0037] S3, control the mother liquor in the crystallization tank 110 to flow to the circulating tank 120 through the second pipeline 220, and the mother liquor in the circulating tank 120 flows to the finished product tank 150.
[0038] After step S2, the purity of p-chlorobenzaldehyde in the mother liquor has reached the standard, and the mother liquor can be collected through the circulating tank 120. Therefore, on the one hand, the mother liquor in the circulating tank 120 can flow to the finished product tank 150, and on the other hand, the mother liquor in the crystallization tank 110 can flow back to the circulating tank 120. It should be noted that since the first pipeline 210 is used for circulating flow, it is generally not suitable for backflow, so the second pipeline 220 can be opened to control the mother liquor in the crystallization tank 110 to flow to the circulating tank 120 through the second pipeline 220, and of course the second pipeline 220 can be closed when the backflow is completed. It can be understood that in this way, the p-chlorobenzaldehyde with a purity reaching the standard is obtained and placed in the finished product tank 150.
[0039] In some embodiments, the second feeding pump 121 is provided with a seventh pipeline 270, and the circulating tank 120 is connected to the finished product tank 150 through the seventh pipeline 270. In this way, when the mother liquor in the circulating tank 120 is transported to the finished product tank 150, the second feeding pump 121 can be directly used, without the need to additionally set up a pump. For example, after the transportation of the finished product tank 150 is completed, the second feeding pump 121 can be stopped, the seventh pipeline 270 can be closed, and the first pipeline 210 can be completely closed, and the like.
[0040] S4, control the temperature of the coil 111 and the jacket 112 to accelerate the volatilization of the residual p-chlorobenzaldehyde in the crystallization tank 110, and open the upper air inlet until the volatilized p-chlorobenzaldehyde is blown out of the crystallization tank 110.
[0041] After step S3, the extraction of p-chlorobenzaldehyde has been completed in the embodiments of the present application, but the extraction of p-chlorobenzoic acid still needs to be continued. After the extraction of p-chlorobenzaldehyde is completed, there is usually residual p-chlorobenzaldehyde in the crystallization tank 110, and the residual p-chlorobenzaldehyde mainly exists in the form of liquid. Therefore, it is necessary to remove the residual p-chlorobenzaldehyde as much as possible, so that the purity of the extracted p-chlorobenzoic acid is higher.
[0042] Specifically, the boiling point of p-chlorobenzaldehyde is about 213°C. If p-chlorobenzaldehyde is evaporated by heating to this temperature, although the purpose of removal can be achieved, at this temperature, although the temperature has not reached the boiling point of p-chlorobenzoic acid, the sublimation rate of p-chlorobenzoic acid will be very fast, which will cause a certain loss of p-chlorobenzoic acid.
[0043] In order to reduce the loss of p-chlorobenzoic acid as much as possible, the temperature of the coil 111 and the jacket 112 is controlled to a certain extent in the embodiments of the present application, so as to accelerate the volatilization of the residual p-chlorobenzaldehyde and reduce the sublimation of p-chlorobenzoic acid as much as possible. At the same time, the upper inlet is opened to introduce and purge the gas, for example, to purge with nitrogen, so as to not only blow out the volatilized p-chlorobenzaldehyde from the crystallization tank 110, but also further accelerate the volatilization of p-chlorobenzaldehyde after purging, so as to reduce the sublimation of p-chlorobenzoic acid as much as possible. It can be understood that the residual p-chlorobenzaldehyde is removed after the purging is completed, and such treatment can retain p-chlorobenzoic acid to a large extent, that is, the residual component in the crystallization tank 110 is basically p-chlorobenzoic acid.
[0044] In some embodiments, in step S4, the temperature of the coil 111 and the jacket 112 is controlled to accelerate the volatilization of the residual p-chlorobenzaldehyde in the crystallization tank 110. The temperature control mode can be that the temperature of the coil 111 and the jacket 112 is controlled by the third temperature control system. For example, the temperature of the coil 111 and the jacket 112 can be controlled to be between 120-160°C, for example, 120°C, 140°C, 160°C, etc. Alternatively, the temperature of the coil 111 and the jacket 112 is first controlled to a certain temperature, for example, 120°C, and maintained for a period of time, and then controlled to a certain temperature, for example, 160°C, until the purging is completed.
[0045] In some embodiments, the crystallization tank 110 is also connected to the bottom of the storage tank 160 through the sixth pipeline 230. Based on this, opening the upper inlet until the volatilized p-chlorobenzaldehyde is purged out of the crystallization tank 110 can be that the sixth pipeline 230 is opened, and the upper inlet is opened until the volatilized p-chlorobenzaldehyde is purged into the storage tank 160.
[0046] Since the fifth pipeline 250 is a material conveying pipeline, it is generally not suitable for reflux, and therefore the sixth pipeline 230 is provided for reflux. In this way, the volatilized p-chlorobenzaldehyde can be purged into the storage tank 160 and returned to the untreated raw liquid.
[0047] In other embodiments, when the system includes the heat exchanger 170, controlling the temperature of the coil 111 and the jacket 112 to accelerate the volatilization of the residual p-chlorobenzaldehyde in the crystallization tank 110 and opening the upper inlet until the volatilized p-chlorobenzaldehyde is purged out of the crystallization tank can be that the temperature of the coil 111 and the jacket 112 is controlled to accelerate the volatilization of the residual p-chlorobenzaldehyde in the crystallization tank 110, the second pipeline 220 and the eighth pipeline 280 are opened, and the upper inlet is opened to purge the volatilized p-chlorobenzaldehyde into the heat exchanger 170; and the temperature of the heat exchanger 170 is controlled to liquefy the p-chlorobenzaldehyde, and the purging is stopped after the heat exchanger 170 no longer has the dripping phenomenon.
[0048] In order to visually observe the volatilization of p-chlorobenzaldehyde, the volatilized p-chlorobenzaldehyde is blown into the heat exchanger 170. At the same time, the temperature of the heat exchanger 170 is controlled so that the p-chlorobenzaldehyde is liquefied. In this way, as the p-chlorobenzaldehyde is liquefied, the heat exchanger 170 will have a dripping phenomenon. It can be understood that when the heat exchanger 170 no longer has the dripping phenomenon, at this time, there is basically no residual p-chlorobenzaldehyde, and the blowing can be stopped. At this time, the crystallization tank 110 is basically full of p-chlorobenzoic acid, so that the purity of the p-chlorobenzoic acid obtained subsequently is relatively high. Exemplarily, the heat exchanger 170 can have a dripping observation window, so that the dripping phenomenon can be known through the dripping observation window. Exemplarily, the heat exchanger 170 is also connected with a tail gas absorption system, because the p-chlorobenzaldehyde blown into the heat exchanger 170 carries a small amount of p-chlorobenzoic acid, and there can also be a small amount of p-chlorobenzaldehyde that is not liquefied, so the tail gas absorption system is provided to process and avoid environmental pollution.
[0049] In some embodiments, the temperature of the heat exchanger 170 is controlled to liquefy the p-chlorobenzaldehyde, and the temperature control manner can be that the temperature of the heat exchanger 170 is controlled by the second temperature control system. Exemplarily, the temperature of the heat exchanger 170 can be controlled to 49°C, so that the p-chlorobenzaldehyde can be liquefied.
[0050] In some embodiments, the temperature of the coil 111 and the jacket 112 is controlled to accelerate the volatilization of the residual p-chlorobenzaldehyde in the crystallization tank 110, which can be that the temperature of the coil 111 and the jacket 112 is increased until the heat exchanger 170 has a dripping phenomenon, and then the coil 111 and the jacket 112 are controlled to increase the temperature by a preset amplitude. Exemplarily, the temperature of the coil 111 and the jacket 112 can be slowly increased to 120°C, when the condensate is seen to drop down through the dripping observation window of the heat exchanger 170, the temperature of the coil 111 and the jacket 112 is slowly increased to 160°C, the dripping phenomenon is accelerated until no condensate drops down.
[0051] S5, open the fourth pipeline 240 to communicate the crystallization tank 110 and the desublimation tank 130; vacuumize the desublimation tank 130 and the crystallization tank 110, control the temperature of the coil 111 and the jacket 112 to sublimate the p-chlorobenzoic acid in the crystallization tank 110; open the lower gas inlet to blow the sublimated p-chlorobenzoic acid into the desublimation tank 130, and control the temperature of the crystallization disc 131 to desublimate the p-chlorobenzoic acid.
[0052] After step S4, the components left in the crystallization tank 110 are substantially p-chlorobenzoic acid, and are in solid state, mainly adhering to the surface of the coil 111. Since the coil 111 is not convenient for scraping, the p-chlorobenzoic acid is transferred into the desublimation tank 130 in the embodiments of the present application. Specifically, the fourth pipeline 240 is first opened to connect the crystallization tank 110 and the desublimation tank 130. Then, on one hand, the desublimation tank 130 and the crystallization tank 110 are vacuumized, because the vacuum environment can lower the sublimation temperature of the p-chlorobenzoic acid, for example, the vacuum degree of the vacuumization of the desublimation tank 130 and the crystallization tank 110 is greater than or equal to 10 kPa and less than or equal to 20 kPa, such as 20 kPa; on the other hand, the temperature of the coil 111 and the jacket 112 is controlled to sublimate the p-chlorobenzoic acid in the crystallization tank 110, for example, the temperature of the coil 111 and the jacket 112 is controlled to be 180°C, so that the p-chlorobenzoic acid sublimates under the vacuum environment and at this temperature. Exemplarily, the top of the desublimation tank 130 has a vacuum exhaust port, through which the vacuum extraction can be achieved.
[0053] Then, the sublimated p-chlorobenzoic acid needs to be transferred into the desublimation tank 130, so the sublimated p-chlorobenzoic acid can be blown into the desublimation tank 130 through the lower air inlet, for example, by blowing with nitrogen. It should be noted that the vacuumization should also be maintained during the blowing. At the same time, the temperature of the crystallization plate 131 is controlled to desublimate the p-chlorobenzoic acid, for example, the temperature of the crystallization plate 131 is controlled to be 0°C. In this way, with the sublimation, blowing and desublimation, the p-chlorobenzoic acid in the crystallization tank 110 can be transferred to the plurality of crystallization plates 131 in the desublimation tank 130. Exemplarily, the surface of the coil 111 can be observed through the observation window of the crystallization tank 110, if the surface of the coil 111 is substantially free of the adhered p-chlorobenzoic acid, it indicates that the transfer of the p-chlorobenzoic acid is substantially completed.
[0054] In some embodiments, in step S4, the temperature of the coil 111 and the jacket 113 is controlled to sublimate the p-chlorobenzoic acid in the crystallization tank 110, and the temperature control manner can be: the temperature of the coil 111 and the jacket 113 is controlled by the third temperature control system, for example, the temperature of the coil 111 and the jacket 113 is controlled to be about 180°C, which can make the solid p-chlorobenzoic acid sublimate in cooperation with a certain vacuum environment.
[0055] In some embodiments, in step S4, the temperature of the crystallization plate 131 is controlled to desublimate the p-chlorobenzoic acid, and the temperature control manner can be: the temperature of the crystallization plate 131 is controlled by the fourth temperature control system, for example, the temperature of the crystallization plate 131 is controlled to be about 0°C, so that the gaseous p-chlorobenzoic acid contacts the crystallization plate 131 to desublimate and adhere to the crystallization plate 131.
[0056] S6, the p-chlorobenzoic acid on the crystallization plate 131 is treated, and is obtained through the discharge port.
[0057] After step S5, the p-chlorobenzoic acid in the raw solution injected this time is basically all on the crystallization tray 131, and after the above-mentioned steps, the purity of the p-chlorobenzoic acid is also very high, for example, the purity is ≥98%. In this way, the p-chlorobenzoic acid on the crystallization tray 131 can be processed and obtained through the discharge port. In some embodiments, as shown in Figure 4 Each crystallization tray 131 is provided with a scraper, for example, a cross-shaped scraper, and the top of the desublimation tank 130 is also provided with a motor, the rotating shaft of the motor is connected with each scraper. In this way, the motor can be started to drive each scraper to rotate to scrape the p-chlorobenzoic acid on the crystallization tray 131. Exemplarily, a small hole can be arranged on the crystallization tray 131, so that the scraped p-chlorobenzoic acid falls to the bottom of the desublimation tank 130.
[0058] As can be seen from the above, the embodiments of the present application utilize the freezing and sublimation characteristics of p-chlorobenzaldehyde and p-chlorobenzoic acid, and the p-chlorobenzoic acid is crystallized out from the p-chlorobenzaldehyde at a proper temperature, and then according to the sublimation characteristics of the p-chlorobenzoic acid, the p-chlorobenzoic acid is sublimated to the desublimation tank for desublimation by heating, so as to separate the two materials, the purity of the p-chlorobenzaldehyde is improved, and the purity of the separated p-chlorobenzoic acid is also relatively high. Without adding water or other solvents, no other hazardous waste is generated, the operation is simple, and the purpose of clean production is achieved.
[0059] Based on the above-mentioned embodiments, the system in the embodiments of the present application can be exemplarily implemented as follows: Open the valve HA-101, the valve HA-102, the valve HA-103, the valve HA-104, and the valve HA-105, start the first feeding pump 161, and inject 200 liters of raw solution containing chlorobenzaldehyde into the crystallization tank 110, wherein the content of p-chlorobenzoic acid is 0.8%. With the injection, the raw solution will overflow into the circulating tank 120 until the overflow stops, for example, the overflow stops at two-thirds of the height, the first feeding pump 161 is stopped, and the valve HA-101 and the valve HA-102 are closed.
[0060] Open the valve HA-106, the valve HA-107, and the valve HA-108, open the second feeding pump 121, and let the raw solution flow slowly in the crystallization tank 110 and the circulating tank 120 at a flow rate of 0.5 cm / min. Let the first temperature control system (hereinafter referred to as A1 glycol temperature control system) act on the coil pipe 111, and let the second temperature control system (hereinafter referred to as A2 glycol temperature control system) act on the jacket 112. Then, sampling can be taken from the sampling port of the circulating tank 120 every 2 hours to detect the content of p-chlorobenzoic acid, and about 8 to 10 times of sampling is required. When the content of p-chlorobenzoic acid is reduced to below 0.1%, for example, the quality index requirement of the product is met, and the valve HA-108 is closed.
[0061] Open the valve HA-110, the valve HA-111, the valve HA-112, send the raw solution into the product storage tank 150, that is, send the qualified p-chlorobenzaldehyde into the product storage tank 150. After completion, stop the second feeding pump 121, close the valve HA-104, the valve HA-105, the valve HA-106, the valve HA-107, the valve HA-110.
[0062] Let the third temperature control system (hereinafter referred to as A3 glycol temperature control system) act on the coil 111, the jacket 112, and let the A2 glycol temperature control system act on the heat exchanger 170. Open the valve HA-119, the valve HA-120, the valve HA-121, and open the valve HA-124 to use nitrogen to blow. For example, first let the coil 111, the jacket 112 slowly warm up to 120℃, and after the condensate can be seen to drop through the drop observation window of the heat exchanger 170, let the coil 111, the jacket 112 slowly warm up to 120℃ for 5-8 hours, until the condensate cannot be seen to drop through the drop observation window of the heat exchanger 170, close the valve HA-103, the valve HA-111, the valve HA-112, the valve HA-119, the valve HA-120, the valve HA-121, the valve HA-124.
[0063] Open the valve HA-115, the valve HA-116, connect the crystallization tank 110 and the condensation tank 130. Open the valve HA-122, vacuumize the crystallization tank 110 and the condensation tank 130, for example, vacuumize to 20kpa. Let the fourth temperature control system (hereinafter referred to as A4 glycol temperature control system) act on the crystallization disc 131, for example 0℃, and let the temperature of the coil 111, the jacket 112 rise to 180℃. Open the valve HA-123 to use nitrogen to blow, and maintain the vacuum environment, for example, maintain between 10-20kpa. In this way, the p-chlorobenzoic acid on the coil 111 will gradually decrease, and the p-chlorobenzoic acid condensed on the crystallization disc 131 will become more and more. When the p-chlorobenzoic acid on the surface of the coil 111 decreases to expose the surface of the coil 111, stop the A3 glycol temperature control system, stop vacuumizing, and close the valve HA-122. Continue to introduce nitrogen for 1-3 hours, so that the inside of the crystallization tank 110 and the condensation tank 130 returns to normal pressure, close the valve HA-115, the valve HA-116, the valve HA-123, and stop the A4 glycol temperature control system.
[0064] Open the valve HA-117, start the motor, and the scraper will scrape the p-chlorobenzoic acid on the crystallization disc 131 down and bag it, thus completing the separation of p-chlorobenzaldehyde and p-chlorobenzoic acid.
[0065] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims
1. A system for separating p-chlorobenzaldehyde from p-chlorobenzoic acid, characterized by, The system comprises: a crystallization tank with multiple coils inside and an outer wall wrapped by a jacket, and an upper inlet and a lower inlet at the top and bottom respectively; a circulating tank connected to the bottom of the crystallization tank through a first pipeline and a second pipeline, and connected to the top of the crystallization tank through a third pipeline; the circulating tank is also connected to a finished product tank; a desublimation tank connected to the top of the crystallization tank through a fourth pipeline; the desublimation tank has multiple crystallization trays inside and a discharge port at the bottom; a temperature control device for controlling the temperature of the coils, the jacket and the crystallization trays; the separation steps of the system are as follows: injecting a raw solution into the crystallization tank until a preset volume is reached; controlling the temperature of the coils and the jacket to crystallize p-chlorobenzoic acid in the raw solution, and controlling the circulation of the raw solution in the crystallization tank, the third pipeline, the circulating tank, the first pipeline, until the purity of p-chlorobenzoic acid in the raw solution meets the standard; controlling the raw solution in the crystallization tank to flow to the circulating tank through the second pipeline, and controlling the raw solution in the circulating tank to flow to the finished product tank; controlling the temperature of the coils and the jacket to accelerate the volatilization of residual p-chlorobenzoic acid in the crystallization tank, and opening the upper inlet until the volatilized p-chlorobenzoic acid is purged out of the crystallization tank; opening the fourth pipeline and performing vacuumization on the desublimation tank and the crystallization tank, controlling the temperature of the coils and the jacket to sublimate p-chlorobenzoic acid in the crystallization tank, and opening the lower inlet to purge the sublimated p-chlorobenzoic acid into the desublimation tank, and controlling the temperature of the crystallization trays to desublimate p-chlorobenzoic acid; processing p-chlorobenzoic acid on the crystallization trays, and obtaining the product through the discharge port.
2. The system of claim 1, wherein, The system further comprises a storage tank connected to the bottom of the crystallization tank through a fifth pipeline, and a first feeding pump arranged on the fifth pipeline near the storage tank; the first pipeline is arranged at the bottom of the circulating tank, and a second feeding pump is arranged on the first pipeline near the circulating tank; the crystallization tank has an observation window; the gas source of the upper inlet and the lower inlet is inert gas; the circulating tank has a sampling port; and / or, the top of the desublimation tank has a vacuum air outlet.
3. The system of claim 2, wherein, the crystallization tank is also connected to the bottom of the storage tank through a sixth pipeline; the step of opening the upper inlet until the volatilized p-chlorobenzoic acid is purged out of the crystallization tank comprises: opening the sixth pipeline, and opening the upper inlet until the volatilized p-chlorobenzoic acid is purged into the storage tank; and / or, a seventh pipeline is arranged at the outlet of the second feeding pump, and the circulating tank is connected to the finished product tank through the seventh pipeline.
4. The system of claim 1, wherein, The system further comprises a heat exchanger connected to the circulating tank through an eighth pipeline, and the temperature control device is also used to control the temperature of the heat exchanger; the step of controlling the temperature of the coils and the jacket to accelerate the volatilization of residual p-chlorobenzoic acid in the crystallization tank, and opening the upper inlet until the volatilized p-chlorobenzoic acid is purged out of the crystallization tank comprises: controlling the temperature of the coil and the jacket to accelerate volatilization of residual p-chlorobenzaldehyde in the crystallization tank, opening the second pipeline and the eighth pipeline, opening the upper gas inlet to blow off the volatilized p-chlorobenzaldehyde to the heat exchanger; and, controlling the temperature of the heat exchanger to liquefy the p-chlorobenzaldehyde until the heat exchanger no longer has a dripping phenomenon to stop blowing.
5. The system of claim 4, wherein, The control of the temperature of the coil and the jacket to accelerate volatilization of residual p-chlorobenzaldehyde in the crystallization tank comprises: Raising the temperature of the coil and the jacket until the heat exchanger has a dripping phenomenon, and controlling the coil and the jacket to raise the temperature by a preset amplitude.
6. The system of claim 4, wherein, The heat exchanger has a dripping observation window; and / or, the heat exchanger is further connected with a tail gas absorption system.
7. The system of claim 1, wherein, The flow rate of the circulating flow of the stock solution is greater than or equal to 0.5 cm / min and less than or equal to 1 cm / min; And / or, the vacuum degree when the desublimation tank and the crystallization tank are vacuumized is greater than or equal to 10 kpa and less than or equal to 20 kpa.
8. The system of claim 1, wherein, Each of the crystallization discs is provided with a scraper; The top of the desublimation tank is further provided with a motor, and the rotating shaft of the motor is connected with each scraper.
9. The system of claim 1 or 4, wherein, The temperature control device is divided into a first temperature control system, a second temperature control system, a third temperature control system and a fourth temperature control system. The temperature range of the first temperature control system is 48-48.5℃, the temperature range of the second temperature control system is 49-50℃, the temperature range of the third temperature control system is 80-200℃, and the temperature range of the fourth temperature control system is -5-10℃. The control of the temperature of the coil and the jacket to crystallize p-chlorobenzoic acid in the stock solution comprises: controlling the temperature of the coil by the first temperature control system and controlling the temperature of the jacket by the second temperature control system. The control of the temperature of the coil and the jacket to accelerate volatilization of residual p-chlorobenzaldehyde in the crystallization tank comprises: controlling the temperature of the coil and the jacket by the third temperature control system. The control of the temperature of the coil and the jacket to sublimate p-chlorobenzoic acid in the crystallization tank comprises: controlling the temperature of the coil and the jacket by the third temperature control system. The control of the temperature of the crystallization disc to desublimate p-chlorobenzoic acid comprises: controlling the temperature of the crystallization disc by the fourth temperature control system. The control of the temperature of the heat exchanger to liquefy p-chlorobenzaldehyde comprises: controlling the temperature of the heat exchanger by the second temperature control system.
10. The system of claim 8, wherein, The temperature control medium of the first temperature control system, the second temperature control system, the third temperature control system and / or the fourth temperature control system is ethylene glycol.