Preparation system and preparation method of N-vinylcaprolactam

Abstract

The preparation system comprises a loop type reaction device and a centrifugal pump, the loop type reaction device comprises a circulation pipeline and an oil bath pan, the input end and the output end of the centrifugal pump are both connected with the circulation pipeline, a part of pipe section of the circulation pipeline is located in the oil bath pan, and the other part of pipe section of the circulation pipeline is located in the oil bath pan. A heat-conducting oil pipe sleeves the outer wall of a part of pipe section, outside the oil bath pan, of the circulating pipeline; an oil guide channel is formed between the inner wall of the heat-conducting oil pipe and the outer wall of the circulating pipeline; the circulating pipeline is respectively connected with an acetylene pipeline, a nitrogen pipeline, a vacuum pipeline, a feeding pipe and a discharging pipe, one end, far away from the circulating pipeline, of the feeding pipe is connected with a melting kettle, one end, far away from the circulating pipeline, of the discharging pipe is connected with a storage tank, and valves are arranged on the acetylene pipeline, the nitrogen pipeline, the vacuum pipeline, the feeding pipe and the discharging pipe. According to the preparation system and method provided by the invention, a basic catalyst in a traditional method does not need to be added, and the problem of raw material and product polymerization in traditional preparation is solved.

Description

Technical Field

[0001] The invention relates to the technical field of organic functional monomer preparation, and in particular to a system and method for preparing N-vinyl caprolactam. Background Art

[0002] N-vinyl caprolactam is a kind of alkyl substituted amine. It can be used as a monomer to produce polymers, and can also be used as an intermediate for fine chemicals such as synthetic pesticides. It is an important raw material for the modern materials industry. The homopolymer or copolymer of N-vinyl caprolactam has been widely used in pigment dispersants, detergent additives, cosmetics and pharmaceutical additives, textile processing additives and adhesive additives. It can also be used to stabilize and clarify juice and beer. In particular, in recent years, studies have found that the homopolymer or copolymer of N-vinyl caprolactam has a low critical phase transition temperature. The temperature sensitivity, and its phase transition temperature is just within the physiological temperature range (30-40°C), this feature has aroused great interest, and the application of this type of polymer in biological, pharmaceutical materials and daily chemicals has been extremely extensively studied.

[0003] However, the existing N-vinyl caprolactam preparation methods generally have the problem of easily causing polymerization of raw materials and products, which easily leads to problems such as reduced yield, increased production costs, unstable product quality, etc., causing troubles to producers. Therefore, there is a need for a N-vinyl caprolactam preparation system and preparation method that can reduce product or raw material polymerization and ensure product quality. Summary of the invention

[0004] In order to solve the problems in the background technology, the present invention proposes an N-vinyl caprolactam preparation system, comprising a loop reaction device and a centrifugal pump, wherein the loop reaction device comprises a circulation pipeline and an oil bath pot, the input end and the output end of the centrifugal pump are both connected to the circulation pipeline, a portion of the circulation pipeline is located in the oil bath pot, and a heat transfer oil pipe is sleeved on the outer wall of the portion of the circulation pipeline located outside the oil bath pot, and an oil transfer channel is formed between the inner wall of the heat transfer oil pipe and the outer wall of the circulation pipeline; The circulation pipeline is respectively connected to an acetylene pipeline, a nitrogen pipeline, a vacuum pipeline, a feed pipe and a discharge pipe; the end of the feed pipe away from the circulation pipeline is connected to a melt kettle; the end of the discharge pipe away from the circulation pipeline is connected to a storage tank; the acetylene pipeline, nitrogen pipeline, vacuum pipeline, feed pipe and discharge pipe are all provided with valves. Preferably, the portion of the circulation pipeline located in the oil bath is a spiral coil.

[0005] Preferably, a temperature gauge and a pressure gauge are provided on the circulation pipeline.

[0006] Preferably, the ends of the acetylene pipeline, nitrogen pipeline and vacuum pipeline connected to the circulation pipeline are adjacent to each other, or the ends of the acetylene pipeline, nitrogen pipeline and vacuum pipeline close to the circulation pipeline are connected to the circulation pipeline through the same pipeline, and the pressure gauge is located near the connection between the acetylene pipeline, nitrogen pipeline and vacuum pipeline and the circulation pipeline.

[0007] Preferably, there are at least two loop reaction devices, and two adjacent loop reaction devices are connected by a centrifugal pump. The input end of the centrifugal pump is respectively connected to the circulation pipelines of the two adjacent loop reaction devices through a first feed pipeline, and the output end of the centrifugal pump is respectively connected to the circulation pipelines of the two loop reaction devices through a second feed pipeline. The positions of the connection ends of the first feed pipeline and the second feed pipeline with the centrifugal pump are higher than the positions of the connection ends of the first feed pipeline and the second feed pipeline with the circulation pipeline.

[0008] Preferably, there are two melt kettles, each melt kettle is connected to the feed pipe through a material pipe, and each material pipe is provided with a switch valve; there are two storage tanks, each storage tank is connected to the circulation pipeline through a discharge pipe, and each storage tank is connected by a pipeline, and a valve is provided on the pipeline.

[0009] A method for preparing N-vinyl caprolactam comprises the following steps: S1. Add solid caprolactam into a melt kettle and heat to 85°C to melt the caprolactam; S2. After all the caprolactam is melted, first add TMHPO polymerization inhibitor to the melt kettle, stir and mix for 2 hours, then add tributylphosphine ion liquid catalyst to the melt kettle, stir and mix for 3 hours; After S3, caprolactam, tributylphosphine ionic liquid catalyst and TMHPO polymerization inhibitor are mixed, 100°C hot oil is introduced into the oil guide channel, and the oil bath is started to heat to 100°C; S4. After the temperature stabilizes, open the valve on the vacuum pipeline, and use the vacuum pipeline to evacuate the circulation pipeline. After the pressure in the circulation pipeline reaches the pressure required for suction, close the valve on the vacuum pipeline, and then open the valve on the feed pipe. The circulation pipeline sucks the material in the melt kettle through the vacuum pressure. S5. After the material is sucked in, open the valve on the nitrogen pipeline and introduce nitrogen with a pressure of 0.2MP into the circulation pipeline through the nitrogen pipeline; S6, start the centrifugal pump, the centrifugal pump makes the material in the circulation pipeline circulate in the circulation pipeline; S7. After the material circulates for 30 minutes, open the valve on the acetylene pipeline and introduce acetylene at a pressure of 0.3MP into the circulation pipeline through the acetylene pipeline; S8, continue to circulate the material to react, close the valve on the acetylene pipeline after 3 hours of reaction, discharge the excess acetylene in the circulation pipeline, and obtain a crude product; S9, close the valve and centrifugal pump on the nitrogen pipeline, open the valve on the discharge pipe, and allow the crude product to flow into the storage tank; S10. Send the crude product to a lightness removal tower for separation and purification to obtain N-vinyl caprolactam. During separation and purification, the vacuum degree of the lightness removal tower is controlled at -0.03~-0.06MPa, the reboiler temperature is controlled at 150°C, and the reflux ratio is controlled at 1~4.

[0010] Preferably, the amount of caprolactam added is 15 moles, the amount of tributylphosphine ionic liquid catalyst added is 3 moles, and the amount of TMHPO inhibitor added is 0.15 grams; Or, the amount of caprolactam added is 20 moles, the amount of tributylphosphine ionic liquid catalyst added is 4 moles, and the amount of TMHPO inhibitor added is 0.2 grams; Alternatively, the amount of caprolactam added is 10 moles, the amount of tributylphosphine ionic liquid catalyst added is 2 moles, and the amount of TMHPO inhibitor added is 0.1 g.

[0011] The present invention has the following beneficial effects: The present invention provides a novel method for synthesizing and preparing N-vinyl caprolactam in a loop reaction device under the action of a phosphine ion liquid catalyst and a polymerization inhibitor, which does not require the addition of a basic catalyst in a traditional method, solves the problem of raw material and product polymerization in traditional preparation, does not generate solid waste, is energy-saving and environmentally friendly, does not require high temperature and high pressure, and has mild reaction conditions. At the same time, the phosphine ion liquid catalyst provided by the present invention has less corrosion to equipment, and the catalyst is used to prepare N-vinyl caprolactam, with a small amount of catalyst added, high catalytic efficiency, high conversion rate, easy separation from the product, and safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the system structure under the single-loop reaction of the present invention; Figure 2 It is a schematic diagram of the system structure under the double-loop reaction of the present invention; Figure 3 It is a schematic diagram of the system structure of the present invention under a single-loop reaction in which melt kettles are connected in series.

[0013] Numbers in the figure: 1. Nitrogen pipeline; 2. Acetylene pipeline; 3. Pressure gauge; 4. Temperature gauge; 5. Melt kettle; 6. Centrifugal pump; 7. Oil bath pot; 8. Storage tank; 9. Heat transfer oil pipe; 10. Vacuum pipeline; 11. Circulation pipeline. DETAILED DESCRIPTION

[0014] In order to make the present invention clearer and more understandable, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the given embodiments are only a few of the implementation methods and do not represent all embodiments.

[0015] In this article, the terms "inside, outside, up, down" and so on are established based on the positional relationship shown in the drawings. Depending on the different drawings, the corresponding positional relationship may also change accordingly. Therefore, they cannot be understood as an absolute limitation on the scope of protection.

[0016] Embodiment 1: Combined with Figure 1 Description: This embodiment provides a system for preparing N-vinyl caprolactam, comprising a loop reaction device and a centrifugal pump 6, wherein the loop reaction device comprises a circulation pipeline 11 and an oil bath pot 7, wherein the input end and the output end of the centrifugal pump 6 are both connected to the circulation pipeline 11, wherein a portion of the circulation pipeline 11 is located in the oil bath pot 7, wherein the portion of the circulation pipeline 11 located in the oil bath pot 7 is a spiral coil, and the outer wall of the portion of the circulation pipeline 11 located outside the oil bath pot 7 is sheathed with a heat transfer oil pipe 9, wherein an oil transfer channel is formed between the inner wall of the heat transfer oil pipe 9 and the outer wall of the circulation pipeline 11, and the heat transfer oil pipe 9 can heat the circulation pipeline 11 by introducing hot oil into the oil transfer channel; The circulation pipeline 11 is respectively connected to the acetylene pipeline 2, the nitrogen pipeline 1, the vacuum pipeline 10, the feed pipe and the discharge pipe. The end of the feed pipe away from the circulation pipeline 11 is connected to the melt kettle 5, and the end of the discharge pipe away from the circulation pipeline 11 is connected to the storage tank 8. The acetylene pipeline 2, the nitrogen pipeline 1, the vacuum pipeline 10, the feed pipe and the discharge pipe are all provided with valves, and the closing and opening of each pipeline are controlled by the valves; the circulation pipeline 11 is provided with a thermometer 4 and a pressure gauge 3, the temperature of the circulation pipeline 11 is detected by the thermometer 4, and the pressure in the circulation pipeline 11 is detected by the pressure gauge 3. Specifically, the oil guide channel is connected to the oil bath pot 7 through a pump to take hot oil from the oil bath pot 7 .

[0017] Specifically, the ends of the acetylene pipeline 2, the nitrogen pipeline 1 and the vacuum pipeline 10 connected to the circulation pipeline 11 are adjacent, or the ends of the acetylene pipeline 2, the nitrogen pipeline 1 and the vacuum pipeline 10 close to the circulation pipeline 11 are connected to the circulation pipeline 11 through the same pipeline, and the pressure gauge 3 is located near the connection between the acetylene pipeline 2, the nitrogen pipeline 1 and the vacuum pipeline 10 and the circulation pipeline 11.

[0018] Specifically, the inner diameter of the spiral coil is 6-8 mm and the total length is 8 m.

[0019] Embodiment 2: Combined with Figure 1 and attached Figure 2 It is explained that the N-vinyl caprolactam preparation system provided in this embodiment has the same basic structural properties as the N-vinyl caprolactam preparation system in Example 1, except that there are at least two loop reaction devices in this embodiment, and two adjacent loop reaction devices are connected by a centrifugal pump 6, and the input end of the centrifugal pump 6 is respectively connected to the circulation pipeline 11 of the two adjacent loop reaction devices through the first feed pipeline, and the output end of the centrifugal pump 6 is respectively connected to the circulation pipeline 11 of the two loop reaction devices through the second feed pipeline. The connection of two or more loop reaction devices is realized by the centrifugal pump 6, and then the circulation of materials in each loop reaction device is realized to form a double-loop reaction system or a multi-loop reaction system. The preparation amount and preparation efficiency of N-vinyl caprolactam are improved by the double-loop or multi-loop reaction system, and the industrial mass production of N-vinyl caprolactam is realized.

[0020] The connection ends of the first and second feed pipelines with the centrifugal pump 6 are located higher than the connection ends of the first and second feed pipelines with the circulation pipeline 11, so that the first and second feed pipelines are arranged at an angle to facilitate the flow of materials from the two feed pipelines and reduce material inventory.

[0021] Specifically, the first material conveying pipe and the second material conveying pipe are both provided with ball valves, and the material flow in the material conveying pipe is controlled by controlling the opening of the ball valves.

[0022] Embodiment 3: Combined with Figure 3 It is explained that the N-vinyl caprolactam preparation system provided in this embodiment has the same basic structural properties as the N-vinyl caprolactam preparation system in Example 1, except that in this embodiment, there are two melt kettles 5, each of which is connected to the feed pipe through a material pipe, and each material pipe is provided with a switch valve; there are two storage tanks 8, each of which is connected to the circulation pipeline 11 through a discharge pipe, and the storage tanks 8 are connected by pipelines, and valves are provided on the pipelines.

[0023] By adopting the form of two melting kettles 5 connected in series, the continuous reaction of materials during production can be realized, that is, the time for the materials to be melted and mixed in the melting kettle 5 is usually longer than the time for the materials to react in the circulation pipeline 11. After the materials in one melting kettle 5 are passed into the circulation pipeline 11 for reaction, even if the melting kettle 5 immediately prepares the materials required for the next reaction, it is difficult to complete the preparation after the crude product is obtained. Two melting kettles 5 are set up to prepare or temporarily store materials in advance. When the reaction of the materials in the circulation pipeline 11 is completed, and the previous melting kettle 5 is still preparing the materials, the other melting kettle 5 can pass the prepared materials into the circulation pipeline 11, quickly carry out the next reaction, realize the continuous reaction, and then realize the industrial mass production of N-vinyl caprolactam. If only a single melting kettle 5 is used, only small-batch intermittent production of products can be achieved, and the continuity of production cannot be achieved.

[0024] Embodiment 4: A method for preparing N-vinyl caprolactam comprises the following steps: S1, adding 10 mol of solid caprolactam into the melt kettle 5, and heating to 85°C to melt the caprolactam; S2, after all the caprolactam is melted, 0.1 g of TMHPO inhibitor is added to the melt kettle 5, and the mixture is stirred for 2 hours, and then 2 moles of tributylphosphine ion liquid catalyst is added to the melt kettle 5, and the mixture is stirred for 3 hours; After S3, caprolactam, tributylphosphine ionic liquid catalyst and TMHPO polymerization inhibitor are mixed, 100°C hot oil is introduced into the oil guide channel, and the oil bath pot 7 is started to heat to 100°C; S4. After the temperature is stabilized, the valve on the vacuum pipeline 10 is opened, and the circulation pipeline 11 is evacuated by the vacuum pipeline 10. After the pressure in the circulation pipeline 11 reaches the pressure required for suction, the valve on the vacuum pipeline 10 is closed, and then the valve on the feed pipe is opened, and the circulation pipeline 11 sucks the material in the melt kettle 5 through the vacuum pressure; specifically, the vacuum pressure required for suction is 500Pa; S5. After the material is sucked in, open the valve on the nitrogen pipeline 1, and introduce nitrogen with a pressure of 0.2MP into the circulation pipeline 11 through the nitrogen pipeline 1; S6, starting the centrifugal pump 6, the centrifugal pump 6 makes the material in the circulation pipeline 11 circulate in the circulation pipeline 11; S7, after the material has circulated for 30 minutes, the valve on the acetylene pipeline 2 is opened, and acetylene at a pressure of 0.3MP is introduced into the circulation pipeline 11 through the acetylene pipeline 2; S8, continue to circulate the material to react, close the valve on the acetylene pipeline 2 after reacting for 3 hours, discharge the excess acetylene in the circulation pipeline 11, and obtain a crude product. The conversion rate detected by gas chromatograph is 80%; S9, close the valve on the nitrogen pipeline 1 and the centrifugal pump 6, open the valve on the discharge pipe, and allow the crude product to flow into the storage tank 8; S10. Send the crude product to a lightness removal tower for separation and purification to obtain N-vinyl caprolactam. During separation and purification, the vacuum degree of the lightness removal tower is controlled at -0.03~-0.06MPa, the reboiler temperature is controlled at 150°C, and the reflux ratio is controlled at 1~4.

[0025] Specifically, the circulation pipeline 11 is connected to an explosion-proof diaphragm vacuum pump, the input end of the explosion-proof diaphragm vacuum pump is connected to the circulation pipeline 11, and the output end of the explosion-proof diaphragm vacuum pump is connected to a gas storage tank, and excess acetylene is transported to the gas storage tank through the explosion-proof diaphragm vacuum pump.

[0026] Specifically, a magnetic stirrer is used to perform stirring and mixing.

[0027] Embodiment 5: The method for preparing N-vinyl caprolactam provided in this embodiment has the same steps as the method for preparing N-vinyl caprolactam in Example 4, except that the amount of caprolactam added in this embodiment is 15 mol, the amount of tributyl phosphine ion liquid catalyst added is 3 mol, and the amount of TMHPO inhibitor added is 0.15 g.

[0028] Embodiment 6: The method for preparing N-vinyl caprolactam provided in this embodiment has the same steps as the method for preparing N-vinyl caprolactam in Example 4, except that the amount of caprolactam added is 20 moles, the amount of tributyl phosphine ion liquid catalyst added is 4 moles, and the amount of TMHPO inhibitor added is 0.2 g.

[0029] While embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for preparing N-vinyl caprolactam, characterized in that: The invention comprises a loop reaction device and a centrifugal pump (6), wherein the loop reaction device comprises a circulation pipeline (11) and an oil bath pot (7), wherein the input end and the output end of the centrifugal pump (6) are both connected to the circulation pipeline (11), a portion of the circulation pipeline (11) is located in the oil bath pot (7), a heat transfer oil pipe (9) is sleeved on the outer wall of the portion of the circulation pipeline (11) located outside the oil bath pot (7), and an oil transfer channel is formed between the inner wall of the heat transfer oil pipe (9) and the outer wall of the circulation pipeline (11); The circulation pipeline (11) is respectively connected to an acetylene pipeline (2), a nitrogen pipeline (1), a vacuum pipeline (10), a feed pipe and a discharge pipe; one end of the feed pipe away from the circulation pipeline (11) is connected to a melt kettle (5); one end of the discharge pipe away from the circulation pipeline (11) is connected to a storage tank (8); and valves are provided on the acetylene pipeline (2), the nitrogen pipeline (1), the vacuum pipeline (10), the feed pipe and the discharge pipe.

2. A system for preparing N-vinyl caprolactam according to claim 1, characterized in that: The portion of the circulation pipeline (11) located in the oil bath (7) is a spiral coil.

3. A system for preparing N-vinyl caprolactam according to claim 1, characterized in that: The circulation pipeline (11) is provided with a temperature gauge (4) and a pressure gauge (3).

4. A system for preparing N-vinyl caprolactam according to claim 3, characterized in that: The ends of the acetylene pipeline (2), the nitrogen pipeline (1) and the vacuum pipeline (10) connected to the circulation pipeline (11) are adjacent to each other, or the ends of the acetylene pipeline (2), the nitrogen pipeline (1) and the vacuum pipeline (10) close to the circulation pipeline (11) are connected to the circulation pipeline (11) through the same pipeline, and the pressure gauge (3) is located close to the connection between the acetylene pipeline (2), the nitrogen pipeline (1) and the vacuum pipeline (10) and the circulation pipeline (11).

5. The system for preparing N-vinyl caprolactam according to claim 1, characterized in that: There are at least two loop reaction devices, two adjacent loop reaction devices are connected via a centrifugal pump (6), the input end of the centrifugal pump (6) is respectively connected to the circulation pipelines (11) of the two adjacent loop reaction devices via a first material delivery pipeline, the output end of the centrifugal pump (6) is respectively connected to the circulation pipelines (11) of the two loop reaction devices via a second material delivery pipeline, and the positions of the connection ends of the first material delivery pipeline and the second material delivery pipeline with the centrifugal pump (6) are higher than the positions of the connection ends of the first material delivery pipeline and the second material delivery pipeline with the circulation pipeline (11).

6. A system for preparing N-vinyl caprolactam according to claim 1, characterized in that: There are two melt kettles (5), each melt kettle (5) is connected to a feed pipe through a feed pipe, and each feed pipe is provided with a switch valve; There are two material storage tanks (8), each of which is connected to the circulation pipeline (11) via a discharge pipe, and each of the material storage tanks (8) is connected via a pipeline, and a valve is provided on the pipeline.

7. A method for preparing N-vinyl caprolactam, implemented based on the N-vinyl caprolactam preparation system according to claim 1, characterized in that: The following steps are involved: S1, adding solid caprolactam into a melt kettle (5), and heating to 85°C to melt the caprolactam; S2. After all caprolactam is melted, first add TMHPO polymerization inhibitor to the melt kettle (5), stir and mix for 2 hours, then add tributylphosphine ion liquid catalyst to the melt kettle (5), stir and mix for 3 hours; After S3, caprolactam, tributylphosphine ionic liquid catalyst and TMHPO polymerization inhibitor are mixed, 100°C hot oil is introduced into the oil guide channel, and the oil bath pot (7) is started to heat to 100°C; S4, after the temperature stabilizes, the valve on the vacuum pipeline (10) is opened, and the circulation pipeline (11) is evacuated by the vacuum pipeline (10). After the pressure in the circulation pipeline (11) reaches the pressure required for sucking the material, the valve on the vacuum pipeline (10) is closed, and then the valve on the feed pipe is opened, so that the circulation pipeline (11) sucks the material in the melt kettle (5) through the vacuum pressure; S5. After the material is sucked in, open the valve on the nitrogen pipeline (1) and introduce nitrogen with a pressure of 0.2MP into the circulation pipeline (11) through the nitrogen pipeline (1); S6, starting the centrifugal pump (6), so that the centrifugal pump (6) causes the material in the circulation pipeline (11) to circulate in the circulation pipeline (11); S7. After the material has been circulated for 30 minutes, the valve on the acetylene pipeline (2) is opened, and acetylene at a pressure of 0.3 MPa is introduced into the circulation pipeline (11) through the acetylene pipeline (2); S8, continue to circulate the material to react, close the valve on the acetylene pipeline (2) after reacting for 3 hours, discharge the excess acetylene in the circulation pipeline (11), and obtain a crude product; S9, closing the valve on the nitrogen pipeline (1) and the centrifugal pump (6), and opening the valve on the discharge pipe to allow the crude product to flow into the storage tank (8); S10. Send the crude product to a lightness removal tower for separation and purification to obtain N-vinyl caprolactam. During separation and purification, the vacuum degree of the lightness removal tower is controlled at -0.03~-0.06MPa, the reboiler temperature is controlled at 150°C, and the reflux ratio is controlled at 1~4.

8. A method for preparing N-vinyl caprolactam according to claim 7, characterized in that: The amount of caprolactam added is 15 moles, the amount of tributylphosphine ion liquid catalyst added is 3 moles, and the amount of TMHPO inhibitor added is 0.15 grams; Or, the amount of caprolactam added is 20 moles, the amount of tributylphosphine ionic liquid catalyst added is 4 moles, and the amount of TMHPO inhibitor added is 0.2 grams; Alternatively, the amount of caprolactam added is 10 moles, the amount of tributylphosphine ionic liquid catalyst added is 2 moles, and the amount of TMHPO inhibitor added is 0.1 g.

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