Pyrazoline continuous production system and method

Abstract

The invention provides a pyrazoline continuous production system and method, belongs to the technical field of chemical raw material preparation, and aims to solve the technical problem that pyrazoline cannot be continuously produced. The pyrazoline continuous production system comprises a storage tank, a ketone hydrazine condensation reaction kettle, a membrane separation dehydration device, a batching tank, a tubular reactor and a pyrazoline collection tank which are connected in sequence, the storage tank comprises a ketone storage tank and a hydrazine storage tank which are arranged in parallel; and the batching tank is also connected with a catalyst storage tank. The oil-water mixture is separated by adopting a membrane separation method, the method is simple and easy to implement, low in energy consumption, simple and clear in technical route, high in universality and capable of continuously separating the ketazine / water mixture and continuously producing the pyrazoline product, the pyrazoline yield is greatly improved, and the method is suitable for industrial production. A new thought different from intermittent reaction production is provided for continuous production of pyrazoline.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical raw material preparation, and in particular relates to a pyrazoline continuous production system and method. Background Art

[0002] Pyrazoline derivatives are a class of nitrogen-containing five-membered heterocyclic compounds. Due to their diverse and unique nitrogen heterocyclic structures, they have many excellent properties and are widely used in the fields of biomedicine, coordination chemistry, high-energy fuels, and optics. The synthesis of pyrazoline derivatives is mainly through the ketazine internal cyclization method, that is, the ketazine undergoes an internal cyclization reaction under the action of a catalyst to synthesize pyrazoline. For example, patent publication number CN115572263A discloses a method for synthesizing pyrazoline by hydrazine salt-catalyzed ketazine cyclization, in which a ketazine compound and a hydrazine salt catalyst are mixed and reacted to obtain a pyrazoline compound.

[0003] According to relevant reference materials, there are three main methods for synthesizing ketazine, namely, sodium hypochlorite oxidation method, hydrogen peroxide oxidation method and hydrazine hydrate method. However, the sodium hypochlorite oxidation method has high equipment requirements due to the strong corrosiveness of sodium hypochlorite, and the hydrogen peroxide method has a low yield of synthesizing ketazine. Relatively speaking, the hydrazine hydrate method has a high yield and a simple synthesis process, and is the mainstream method for synthesizing ketazine. The hydrazine hydrate method uses hydrazine hydrate and ketone as raw materials to produce ketazine through a ketone hydrazine condensation reaction.

[0004] For example, patent publication number CN115869885A discloses a homogeneous and efficient process and reaction device for synthesizing a series of ketone azine products, wherein the reaction device comprises three raw material tanks and a reactor, the raw material tank is connected to the reactor through a feed pipe, and a metering pump is provided on the feed pipe; a distillation tower is connected to the reactor, the distillation tower is connected to a condensing device, the condensing device is connected to an overflow device, and the overflow device is connected to a wastewater storage device. The preparation steps are as follows: ketone, entrainer, and hydrazine hydrate are added to the reaction device for reaction to obtain a series of ketone azine products. However, after the reaction is completed, because of the generation of an aqueous phase, the crude ketone azine needs to be purified, that is, the ketone azine / water mixture is separated. If the separation of ketone azine and water is carried out by traditional distillation, the energy consumption is large, the cost is high, and it is difficult to achieve the continuous progress of the subsequent ketone azine internal cyclization reaction. According to relevant data research, the production process of pyrazoline derivatives is an intermittent reaction with low production capacity. Currently, there is an urgent need to design a set of equipment for continuous production of pyrazoline to solve the problem of continuous production of pyrazoline derivatives and further increase production capacity to meet the strong demand in various fields. Summary of the invention

[0005] Aiming at the technical problem that pyrazoline cannot be produced continuously, the present invention proposes a continuous production system and method for pyrazoline. The oil-water mixture separation of the present invention adopts a membrane separation method, which is simple and easy to implement, has low energy consumption, a simple and clear technical route, strong universality, can continuously separate ketazine / water mixture, and continuously produce pyrazoline products, which greatly improves the pyrazoline production capacity and provides a new idea for the continuous production of pyrazoline that is different from intermittent reaction production.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A pyrazoline continuous production system comprises a storage tank, a ketone-hydrazine condensation reactor, a membrane separation and dehydration device, a batching tank, a tubular reactor and a pyrazoline collecting tank which are connected in sequence; the storage tank comprises a ketone storage tank and a hydrazine storage tank which are arranged in parallel; and the batching tank is also connected to a catalyst storage tank.

[0008] The membrane separation and dehydration device includes a membrane separation storage tank, a membrane pool and a filtrate collecting tank which are connected in sequence; a filter membrane is provided in the membrane pool, and the filter membrane divides the interior of the membrane pool into an upper cavity and a lower cavity; a mixed liquid inlet and a mixed liquid outlet are provided in the upper cavity, and the membrane separation storage tank is connected to the mixed liquid inlet and the mixed liquid outlet respectively; a filtrate outlet is provided in the lower cavity, and the filtrate outlet is connected to the filtrate collecting tank.

[0009] The type of the filtration membrane is an oleophilic and hydrophobic solvent-resistant nanofiltration membrane, which is any one of a modified composite fiber membrane, a modified polyacrylonitrile membrane, and a modified polyimide membrane, and the membrane retention molecular weight is 100 to 200 Da; the tube length of the tubular reactor is 30 meters and the inner diameter of the tube is 2 mm.

[0010] A continuous production method of pyrazoline comprises the following steps:

[0011] S1, respectively transporting ketone and hydrazine hydrate from a ketone storage tank and a hydrazine storage tank to a ketone-hydrazine condensation reaction kettle through metering pumps to obtain a ketone-azo / water mixture;

[0012] S2, continuously conveying the ketazine / water mixture to a membrane separation storage tank, pressurizing it with a pump, passing it through a membrane pool by cross-flow filtration, and obtaining permeate ketazine through membrane filtration in the membrane pool;

[0013] S3, continuously pumping the ketazine into a batching tank through a metering pump, and continuously pumping the catalyst into the batching tank through a metering pump, fully mixing the ketazine and the catalyst in the batching tank and preheating them, pumping the preheated reaction solution into the tubular reactor again, and continuously sending the reaction solution into a pyrazoline collection tank after the reaction is completed to obtain a pyrazoline product.

[0014] The ketone is any one of acetone, 2-pentanone, 2-octanone, 4-methyl-2-pentanone or cyclopropyl methyl ketone.

[0015] The molar ratio of the ketone to the hydrazine hydrate in the ketone-hydrazine condensation reaction kettle is (2-3):1, the reaction temperature is 60-100°C, and the reaction time is 4-12h; the temperature of the mixture during the membrane separation process in the membrane pool is 20-60°C, and the operating pressure of the membrane equipment is 5-60bar.

[0016] The catalyst is a liquid strong acid; the liquid strong acid is any one of nitric acid, sulfuric acid, methanesulfonic acid or trifluoroacetic acid.

[0017] In the step S3, the mass ratio of the catalyst to the ketazine is (1-5):100.

[0018] In step S3, the preheating temperature is 40-100° C. and the time is 0.5-3 hours.

[0019] In the step S3, the reaction temperature in the tubular reactor is 70 to 150° C., and the reaction time is 30 to 240 minutes.

[0020] Beneficial effects of the present invention:

[0021] 1. The reaction yield of synthesizing pyrazoline of the present invention is high. For the synthesis of pyrazoline by the internal cyclization reaction of acetone azine, the selectivity is as high as 99.5%, and the yield is as high as 91.4%. In addition, the continuous production of several other pyrazolines by the continuous production system is listed in this article, and all have good reaction effects and are generally applicable.

[0022] 2. Compared with the traditional distillation to purify ketazine in ketazine / water mixture, the membrane separation technology mentioned in the present invention does not involve phase change in the separation process, has low energy consumption, low maintenance cost, is easy to automate continuous production, is easy to scale up, and is suitable for large-scale application.

[0023] 3. The system mentioned in the present invention can continuously synthesize pyrazoline, which has great advantages over the batch reaction production of pyrazoline, is simple to operate, has certain innovation, and provides a new idea for the separation and purification of oil-water mixture products and subsequent continuous reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1This is a schematic diagram of the structure of the continuous production system of pyrazoline.

[0026] Figure 2 This is a schematic diagram of the structure of the membrane separation and dehydration device.

[0027] In the figure, 1. ketone storage tank; 2. hydrazine storage tank; 3. ketone hydrazine condensation reactor; 4. membrane separation storage tank; 5. membrane pool; 51. transfer pump; 52. unloading valve; 53. membrane inlet pressure gauge; 54. membrane outlet pressure gauge; 55. pressure regulating valve; 6. filtrate collecting tank; 7. catalyst storage tank; 8. batching tank; 9. tubular reactor; 10. pyrazoline collecting tank; 11. metering pump.

[0028] Figure 3 This is a picture of the modified composite fiber membrane.

[0029] Figure 4 This is a picture of modified polyimide film.

[0030] Figure 5 This is a picture of modified polyacrylonitrile membrane.

[0031] Figure 6 This is a diagram showing the separation effect of membrane filtrate and concentrate.

[0032] Figure 7 Acetone azine internal standard.

[0033] Figure 8 It is the internal standard of 2-pentanone azine.

[0034] Fig. 9 It is the internal standard of cyclopropyl methyl ketone azine. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0036] In the embodiment of the present invention, the detection method of ketazine and pyrazoline is GC-internal standard quantitative detection method

[0037] Instrument: Agilent 8890-GC

[0038] Chromatographic column: HP-5 non-polar column

[0039] Gas phase conditions: gas phase injection 1uL; injection port temperature 300℃; split ratio 100:1; column temperature program 50℃ (1min) → 10℃ / min-120℃ (1min) → 15℃ / min-280℃ (9min);

[0040] Reagents: n-nonane (GC, ≥99.5%), anhydrous ethanol (HPLC grade, ≥99.8%), ketazine standard (homemade, 99.5%).

[0041] Internal standard line preparation:

[0042] 1. Use a 1000uL (accuracy 0.2 to 0.6%) pipette to transfer the standard ketazine (400uL, 600uL, 800uL) in sequence, place them in the corresponding 10mL volumetric flasks in sequence, and use a 1 / 10,000 balance to record the mass;

[0043] 2. Use a 1000uL (accuracy 0.2 to 0.6%) pipette to transfer 400uL of the internal standard solution n-nonane, add it to the volumetric flask containing ketazine in step 1, and record the mass using a 1 / 10,000 balance;

[0044] 3. Finally, add ethanol to the volume to the mark, shake and oscillate;

[0045] 4. GC test, and the peak area ratio, i.e. S 内标物 / S 标样 is the vertical axis; mass ratio, i.e. M 内标物 / M 标样 The horizontal axis is the internal standard curve.

[0046] Example 1

[0047] A continuous production system of pyrazoline, such as Figure 1 As shown, it includes a storage tank, a ketone hydrazine condensation reactor 3, a membrane separation dehydration device, a batching tank 8, a tubular reactor 9 and a pyrazoline collection tank 10 connected in sequence; the storage tank includes a ketone storage tank 1 and a hydrazine storage tank 2 arranged in parallel; the ketone storage tank 1 and the hydrazine storage tank 2 are used to store raw ketones and hydrazine hydrates, respectively, and the ketone storage tank 1 and the hydrazine storage tank 2 are connected to the feed port of the ketone hydrazine condensation reactor 3 through a pipeline, and are transported to the ketone hydrazine condensation reactor 3 through a metering pump 11. The ketone hydrazine condensation reactor 3 is a conventional reactor with heating and stirring functions. The batching tank 8 is also connected to the catalyst storage tank 7, and the filtrate filtered by the membrane separation dehydration device is mixed with the catalyst in a certain ratio and transported to the tubular reactor 9 for reaction. The tubular reactor 9 has a tube length of 30 meters and an inner diameter of 2 mm. The product is finally stored in the pyrazoline collection tank 10.

[0048] Specifically, Figure 2As shown, the membrane separation dehydration device includes a membrane separation storage tank 4, a membrane pool 5 and a filtrate collecting tank 6 connected in sequence; the membrane separation storage tank 4 is connected to the liquid outlet of the ketone hydrazine condensation reactor 3, and is used to store a mixture of ketone azine and water. A filter membrane is provided in the membrane pool 5, and the filter membrane divides the interior of the membrane pool 5 into an upper cavity and a lower cavity; a mixed liquid inlet and a mixed liquid outlet are provided in the upper cavity, and the membrane separation storage tank 4 is connected to the mixed liquid inlet and the mixed liquid outlet respectively; a filtrate outlet is provided in the lower cavity, and the filtrate outlet is connected to the filtrate collecting tank 6. The membrane pool 5 is a sealed structure, which can pressurize the upper cavity. A transfer pump 51, a unloading valve 52 and a membrane inlet pressure gauge 53 are provided on the pipeline between the membrane pool 5 and the membrane separation storage tank 4; a membrane outlet pressure gauge 54 and a pressure regulating valve 55 are provided on the pipeline between the mixed liquid outlet and the membrane separation storage tank 4. The pressure and flow rate of the mixture of ketazine and water in the upper cavity of the membrane pool 5 are precisely controlled by the above-mentioned device, and the transfer pump 51 is used to increase the pressure. The pressure regulating valve 55 is adjusted to observe the membrane inlet pressure gauge 53 and the membrane outlet pressure gauge 54. When the system pressure is too high, the unloading valve 52 is used for safe pressure relief. The mixed liquid passes through the membrane pool 5 at a suitable pressure, and the mixture is separated by cross-flow filtration. The permeate ketazine obtained by membrane filtration in the membrane pool 5 is collected in the filtrate collection tank 6, and the intercepted liquid is returned to the oil-water mixed liquid tank for circulation and separation.

[0049] More specifically, the type of the filtration membrane is an oleophilic and hydrophobic solvent-resistant nanofiltration membrane, and the oleophilic and hydrophobic solvent-resistant nanofiltration membrane is a modified composite fiber membrane ( Figure 3 ), modified polyacrylonitrile membrane ( Figure 4 )、Modified polyimide film ( Figure 5 ), the membrane cut-off molecular weight is 100-200Da. The modified composite fiber membrane model is S-3014, the modified polyacrylonitrile membrane model is GC-PANS, and the modified polyimide membrane model is GC-PI200D, all of which were purchased from Guochu Technology (Xiamen) Co., Ltd.

[0050] Example 2

[0051] A method for continuous production of pyrazoline, using the continuous production system of pyrazoline described in Example 1, wherein the filter membrane in the membrane pool 5 is a modified composite fiber membrane, and the steps are:

[0052] S1, acetone and hydrazine hydrate are respectively loaded into the raw material ketone storage tank 1 and the hydrazine storage tank 2, and transported to the 10L ketone hydrazine condensation reactor 3 by the metering pump 11 according to the relationship of the stoichiometric ratio of acetone to hydrazine hydrate of 2:1, and the stirring speed is set to 1000rpm, and then the temperature is raised to 100°C, and the reaction is stopped after 8 hours. The product is an acetone azine / water mixed liquid, which is discharged from the bottom of the ketone hydrazine condensation reactor 3 to the membrane separation storage tank 4 for the next membrane separation stage;

[0053] S2, the acetone azine / water mixed liquid in the separation storage tank is pressurized to a membrane inlet pressure of 50.5 bar by a transfer pump 51 and then passes through the membrane pool 5 in a cross-flow filtration manner. During the membrane separation process, the temperature of the mixed liquid is 25°C, and the acetone azine is collected in the acetone azine collection tank in the form of filtrate. The concentrated liquid is returned to the membrane separation storage tank 4 at a membrane outlet pressure of 50.0 bar for cyclic separation. The filtrate and the concentrated liquid are as follows: Figure 6 As shown. The separation flux of the composite fiber nanofiltration membrane is 9.58 kg·m -2 ·h -1 The filtrate acetone azine was analyzed by Agilent gas chromatography, specifically using an HP-5 column, and the content of various compounds was calculated using the internal standard method based on the standard curve. The selectivity of acetone azine was 99.0%, and the yield was 88.2%.

[0054] S3, the membrane permeate acetone azine is continuously conveyed to the batching tank 8 via the metering pump 11 for 5 kg, the catalyst methanesulfonic acid is loaded into the catalyst storage tank, and the catalyst is conveyed to the batching tank 8 for 200 g via the metering pump 11, the acetone azine and the catalyst are fully mixed in the batching tank 8 and preheated in advance, i.e., the stirring rate is 1000 rpm, and the preheating temperature is 70°C. The reaction liquid after being mixed evenly and preheated for 1 hour is stably pumped into the tubular reactor 9 by a horizontal flow pump, and reacted at 90°C for 200 minutes. After the reaction is completed, it is continuously conveyed to the pyrazoline collection tank 10 to obtain the pyrazoline product. The pyrazoline product is detected and analyzed by Agilent gas chromatography, specifically using an HP-5 column, and the content of various compounds is calculated by the internal standard method according to the standard curve. The internal standard line of acetone azine is as follows: Figure 7 As shown, the internal cyclization performance evaluation showed that the conversion rate of acetone azodicarbonate was 91.9%, the selectivity of 3,3,5-trimethyl-2-pyrazoline was 99.5%, and the yield was 91.4%.

[0055] Comparative Example 1

[0056] A method for producing pyrazoline, which is different from Example 2 in that the acetone azine is crude acetone azine that has not passed through a membrane separation and dehydration device. In the internal cyclization performance evaluation, the acetone azine conversion rate is 80.4%, the 3,3,5-trimethyl-2-pyrazoline selectivity is 89.3%, and the yield is 71.8%.

[0057] Example 3

[0058] A method for continuous production of pyrazoline, using the continuous production system of pyrazoline described in Example 1, wherein the filter membrane in the membrane pool 5 is a modified polyimide membrane, and the steps are:

[0059] S1, 2-pentanone and hydrazine hydrate are respectively loaded into the raw material ketone storage tank 1 and the hydrazine storage tank 2, and transported to the 10L ketone hydrazine condensation reactor 3 by the metering pump 11 according to the relationship of the stoichiometric ratio of 2-pentanone azine to hydrazine hydrate of 2.5:1, and the stirring speed is set to 1000rpm, and then the temperature is raised to 90°C, and the reaction is stopped after 10 hours. The product is a 2-pentanone azine / water mixed liquid, which is discharged from the bottom of the ketone hydrazine condensation reactor 3 to the membrane separation storage tank 4 for the next membrane separation stage;

[0060] S2, the 2-pentanone azine / water mixed liquid in the membrane separation storage tank 4 is pressurized to a membrane inlet pressure of 45.5 bar by the transfer pump 51 and then passes through the membrane pool 5 in a cross-flow filtration manner. The 2-pentanone azine is collected in the 2-pentanone azine collection tank in the form of filtrate. During the membrane separation process, the temperature of the mixed liquid is 40°C, and the concentrated liquid is returned to the membrane separation storage tank 4 at a membrane outlet pressure of 45.0 bar for cyclic separation. The separation flux of the modified polyimide membrane is 7.66 kg·m -2 ·h -1 The filtrate ketazine was analyzed by Agilent gas chromatography, specifically using an HP-5 column, and the content of various compounds was calculated using the internal standard method based on the standard curve. The selectivity of 2-pentanone azine was 95.0%, and the yield was 84.6%.

[0061] S3, the membrane permeate ketone azine is continuously conveyed to the batching tank 8 by the metering pump 11 for 5 kg, the catalyst trifluoroacetic acid is loaded into the catalyst storage tank, and the catalyst is conveyed to the batching tank 8 by the metering pump 11 for 100 g, and the 2-pentanone azine and the catalyst are fully mixed in the batching tank 8 and preheated in advance, that is, the stirring rate is 1000 rpm, and the preheating temperature is 80°C. The reaction liquid after being mixed evenly and preheated for 2 hours is stably pumped into the tubular reactor 9 by a horizontal flow pump, and reacted at 100°C for 120 minutes. After the reaction is completed, it is continuously conveyed to the pyrazoline collection tank 10 to obtain the pyrazoline product, and the internal standard line of 2-pentanone azine is as shown in FIG. Figure 8 As shown, the internal cyclization performance evaluation showed that the conversion rate of 2-pentanone azodicarbonyl was 85.5%, the selectivity of 3,5-dipropyl-5-methyl-2-pyrazoline was 95.8%, and the yield was 81.9%.

[0062] Comparative Example 2

[0063] A method for producing pyrazoline, which is different from Example 3 in that 2-pentanone azine is crude acetone azine that has not passed through a membrane separation and dehydration device. In the internal cyclization performance evaluation, the conversion rate of 2-pentanone azine is 78.6%, the selectivity of 3,3,5-trimethyl-2-pyrazoline is 85.9%, and the yield is 67.5%.

[0064] Example 4

[0065] A method for continuous production of pyrazoline, using the continuous production system of pyrazoline described in Example 1, wherein the filter membrane in the membrane pool 5 is a modified polyacrylonitrile membrane, and the steps are:

[0066] S1, cyclopropyl methyl ketone and hydrazine hydrate are respectively loaded into the raw material ketone storage tank 1 and the hydrazine storage tank 2, and transported to the 10L ketone hydrazine condensation reactor 3 by the metering pump 11 according to the relationship of the stoichiometric ratio of cyclopropyl methyl ketone to hydrazine hydrate of 2.2:1, and the stirring speed is set to 1000rpm, and then the temperature is raised to 80°C, and the reaction is stopped after 5 hours. The product is a cyclopropyl methyl ketone azine / water mixed liquid, which is discharged from the bottom of the reactor to the membrane separation storage tank 4 for the next membrane separation stage;

[0067] S2, the cyclopropyl methyl ketazine / water mixed liquid in the membrane separation storage tank 4 is pressurized to a membrane inlet pressure of 10.5 bar by the transfer pump 51 and then passes through the membrane pool 5 in a cross-flow filtration manner. The cyclopropyl methyl ketazine is collected in the cyclopropyl methyl ketazine collection tank in the form of filtrate. During the membrane separation process, the temperature of the mixed liquid is 30°C, and the concentrated liquid is returned to the membrane separation storage tank 4 at a membrane outlet pressure of 10.0 bar for cyclic separation. The separation flux of the modified polyacrylonitrile membrane is 5.33 kg·m -2 ·h -1 The filtrate refined ketazine was analyzed by Agilent gas chromatography, specifically using an HP-5 column, and the content of various compounds was calculated using the internal standard method based on the standard curve. The selectivity of cyclopropyl methyl ketazine was 91.1%, and the yield was 82.3%.

[0068] S3, the membrane permeate ketazine is continuously conveyed to the batching tank 8 by the metering pump 11 for 5 kg, the catalyst nitric acid is loaded into the catalyst storage tank, and the catalyst is conveyed to the batching tank 8 by the metering pump 11 for 150 g, the cyclopropyl methyl ketazine and the catalyst are fully mixed in the batching tank 8 and preheated in advance, that is, the stirring rate is 1000 rpm, and the preheating temperature is 70°C. The reaction liquid after being mixed evenly and preheated for 1.5 hours is stably pumped into the tubular reactor 9 by the horizontal flow pump, and the reaction time is 40 minutes at 120°C. After the reaction is completed, it is continuously conveyed to the pyrazoline collection tank 10 to obtain the pyrazoline product, and the internal standard line of the cyclopropyl methyl ketazine is as follows: Fig. 9 As shown, the internal cyclization performance evaluation showed that the conversion rate of cyclopropyl methyl ketone azine was 54.4%, the selectivity of 3,5-dicyclopropyl-5-methyl-2-pyrazoline was 94.1%, and the yield was 51.2%.

[0069] Comparative Example 3

[0070] A method for producing pyrazoline, which is different from Example 4 in that the cyclopropyl methyl ketazine is a crude acetone azine that has not been subjected to a membrane separation and dehydration device. In the evaluation of the internal cyclization performance, the conversion rate of the cyclopropyl methyl ketazine is 44.4%, the selectivity of 3,5-dicyclopropyl-5-methyl-2-pyrazoline is 82.8%, and the yield is 36.8%. It can be seen from the comparative example that the yield of the internal cyclization reaction of the crude ketazine without membrane separation and water removal is significantly reduced compared with that of the ketazine after membrane water removal. It is speculated that the reason for the reduction is that the water in the crude ketazine will inhibit the formation of the product pyrazoline, affect the forward reaction, and thus affect the final yield.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pyrazoline continuous production system, characterized in that: The invention comprises a storage tank, a ketone-hydrazine condensation reaction kettle (3), a membrane separation and dehydration device, a batching tank (8), a tubular reactor (9) and a pyrazoline collection tank (10) which are connected in sequence; the storage tank comprises a ketone storage tank (1) and a hydrazine storage tank (2) which are arranged in parallel; and the batching tank (8) is also connected to a catalyst storage tank (7).

2. The pyrazoline continuous production system according to claim 1, characterized in that: The membrane separation dehydration device comprises a membrane separation storage tank (4), a membrane pool (5) and a filtrate collection tank (6) which are connected in sequence; a filter membrane is provided in the membrane pool (5), and the filter membrane divides the interior of the membrane pool (5) into an upper cavity and a lower cavity; a mixed liquid inlet and a mixed liquid outlet are provided in the upper cavity, and the membrane separation storage tank (4) is respectively connected to the mixed liquid inlet and the mixed liquid outlet; and a filtrate outlet is provided in the lower cavity, and the filtrate outlet is connected to the filtrate collection tank (6).

3. The continuous production system of pyrazoline according to claim 2, characterized in that: The type of the filtration membrane is an oleophilic and hydrophobic solvent-resistant nanofiltration membrane, which is any one of a modified composite fiber membrane, a modified polyacrylonitrile membrane, and a modified polyimide membrane, and the membrane has a molecular weight cutoff of 100 to 200 Da.

4. A continuous production method of pyrazoline, characterized in that, The following steps are involved: S1, respectively transporting ketone and hydrazine hydrate from a ketone storage tank (1) and a hydrazine storage tank (2) to a ketone-hydrazine condensation reaction kettle (3) through a metering pump (11), and reacting to obtain a ketone-azine / water mixture; S2, continuously conveying the ketazine / water mixture to a membrane separation storage tank (4), pressurizing it with a pump, passing it through a membrane pool (5) by cross-flow filtration, and obtaining permeate ketazine through membrane filtration in the membrane pool (5); S3, continuously pumping the ketazine into the batching tank (8) through the metering pump (11), and continuously pumping the catalyst into the batching tank (8) through the metering pump (11), fully mixing the ketazine and the catalyst in the batching tank (8) and preheating them, pumping the preheated reaction solution into the tubular reactor (9), and continuously feeding the preheated reaction solution into the pyrazoline collecting tank (10) after the reaction is completed to obtain a pyrazoline product.

5. The continuous production method of pyrazoline according to claim 4, characterized in that: The ketone is any one of acetone, 2-pentanone, 2-octanone, 4-methyl-2-pentanone or cyclopropyl methyl ketone.

6. The continuous production method of pyrazoline according to claim 5, characterized in that: The molar ratio of the ketone to the hydrazine hydrate in the ketone-hydrazine condensation reaction kettle (3) is (2-3):1, the reaction temperature is 60-100°C, and the reaction time is 4-12 hours; the temperature of the mixture during the membrane separation process in the membrane pool (5) is 20-60°C, and the operating pressure of the membrane equipment is 5-60 bar.

7. The continuous production method of pyrazoline according to claim 6, characterized in that: The catalyst is a liquid strong acid; the liquid strong acid is any one of nitric acid, sulfuric acid, methanesulfonic acid or trifluoroacetic acid.

8. The continuous production method of pyrazoline according to claim 7, characterized in that: In the step S3, the mass ratio of the catalyst to the ketazine is (1-5):

100.

9. The continuous production method of pyrazoline according to claim 8, characterized in that: In step S3, the preheating temperature is 40-100° C. and the time is 0.5-3 hours.

10. The continuous production method of pyrazoline according to claim 9, characterized in that: In the step S3, the reaction temperature in the tubular reactor (9) is 70 to 150°C, and the reaction time is 30 to 240 minutes.

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