Device and method for preparing 6-aminocapronitrile
By designing nozzle atomization and mixing pipe sections, the problems of uneven mixing and high-temperature polymerization in the process of preparing 6-aminohexanoic acid from caprolactam were solved, achieving rapid vaporization and low loss of caprolactam, improving the stability and production efficiency of the equipment, and supporting continuous industrial production.
Patent Information
- Application Number
- CN202410743412.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-07
- Publication Date
- 2025-12-09
AI Technical Summary
Existing technologies for preparing 6-aminohexanonitrile from caprolactam suffer from uneven mixing and high-temperature polymerization decomposition, resulting in high raw material loss, poor equipment stability, and difficulty in achieving continuous industrial-scale production.
By employing nozzle atomization and designing a long mixing tube section, caprolactam and high-temperature ammonia are rapidly mixed and vaporized. The combination of nozzle atomization and mixing tube section achieves uniform mixing and rapid vaporization of caprolactam and high-temperature ammonia, avoiding polymerization and decomposition under prolonged high-temperature conditions.
It effectively reduces the loss of caprolactam raw materials, improves the stability and production efficiency of the equipment, and contributes to continuous production on an industrial scale.
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Figure CN121082199A_ABST
Abstract
Description
Technical Field
[0001] This application relates to an apparatus and method for preparing 6-aminohexanonitrile, belonging to the field of chemical technology. Background Technology
[0002] Hexamethylenediamine (HDMA) is a key chemical intermediate monomer in the synthesis of high-performance material Nylon 66. In addition, HDMA is used in the synthesis of polyamides and is widely used in industrial production as a resin curing agent and a flotation agent in agriculture and mining. Depending on the raw materials, there are three main methods for synthesizing HDMA: the butadiene method, the acrylonitrile method, and the adipic acid method.
[0003] The butadiene process uses butadiene and hydrogen cyanide as raw materials to synthesize adiponitrile, which is then hydrogenated to synthesize hexamethylenediamine. This method is low-cost and produces high-quality products, but it has extremely high requirements for equipment and operation management, and the catalyst preparation is difficult. The technology has long been controlled by developed countries, forming a technological barrier.
[0004] The acrylonitrile process involves the electrolytic dimerization of acrylonitrile to produce adiponitrile, which is then hydrogenated to synthesize hexamethylenediamine. This method uses highly toxic raw materials, is difficult to control, and poses high safety risks; therefore, it has been phased out.
[0005] The adipic acid process uses adipic acid as a raw material, which is ammonified and dehydrated to produce adiponitrile, which is then hydrogenated to synthesize hexamethylenediamine. This method is relatively mature, but the process has high energy consumption, the equipment is prone to corrosion, and the profitability of the plant fluctuates greatly due to the influence of the raw materials.
[0006] In addition to the three methods mentioned above, Toray Industries of Japan developed a caprolactam process for producing hexamethylenediamine in the 1960s. This method uses caprolactam as a raw material, producing 6-aminohexanonitrile through catalytic ammonia dehydration, followed by hydrogenation to obtain hexamethylenediamine. However, this method failed to be widely adopted at the time due to the high cost of caprolactam and was discontinued in 1989. But with improvements in raw material preparation processes and continuous increases in caprolactam production capacity, experts predict that caprolactam production capacity will reach 10 million tons by 2025. With continuously decreasing raw material costs and increasing demand for downstream products, the caprolactam ammonia-hydrogenation process for producing hexamethylenediamine is gradually showing its advantages and has once again become a research hotspot.
[0007] Chinese patent CN113694969 discloses a catalyst system and method for synthesizing hexamethylenediamine. The method uses caprolactam as a raw material and successively introduces substances such as ammonia, hydrogen, and ammonia water into a reaction vessel to produce hexamethylenediamine in one batch.
[0008] Chinese patent CN107739318 discloses a test method for the liquid-phase intermittent synthesis of 6-aminohexanonitrile from caprolactam.
[0009] Chinese patent CN113426377 discloses a Venturi vaporizer for the gas-phase preparation of hexamethylenediamine intermediate 6-aminohexanonitrile. Summary of the Invention
[0010] This application provides an apparatus and method for preparing 6-aminohexanonitrile from caprolactam, which allows caprolactam to vaporize rapidly at a lower temperature, avoiding polymerization and decomposition caused by prolonged high-temperature environment during caprolactam vaporization, effectively reducing the loss of caprolactam raw materials and improving the stability of the apparatus. The apparatus and method have a simple process, high production efficiency, and are conducive to continuous industrial-scale production.
[0011] One aspect of this application provides an apparatus for preparing 6-aminohexanonitrile.
[0012] The device includes a feed pipe, a preheater, and a catalytic reactor connected in sequence;
[0013] The feed pipe is along the direction of ammonia flow and includes a connected feed pipe section and a mixing pipe section;
[0014] Among them, the end of the feed pipe section away from the mixing pipe section is the ammonia feed end, which is equipped with an ammonia inlet;
[0015] The end of the feed pipe section closest to the mixing pipe section is the caprolactam feed end. The caprolactam inlet is located on the pipe wall of the caprolactam feed end, and the axis of the caprolactam inlet is perpendicular to the axis of the feed pipe section.
[0016] The free end of the mixing pipe section away from the feed pipe section is connected to the preheater;
[0017] The device also includes a nozzle component that extends into the cavity of the feed pipe section through a caprolactam inlet;
[0018] The nozzle component includes an atomizing nozzle, the axial direction of the nozzle outlet end of the atomizing nozzle coincides with the axial direction of the feed pipe section, so that the flow direction of caprolactam sprayed from the nozzle outlet end is consistent with the flow direction of ammonia gas.
[0019] Optionally, the mixing pipe section is arranged in a horizontal direction.
[0020] Optionally, the length of the mixing pipe section is L, and the inner diameter of the mixing pipe section is D;
[0021] Where L > 10m, or
[0022] L > 10D.
[0023] Optionally, L > 20m, or
[0024] L > 15D.
[0025] Optionally, the present invention designs a horizontally oriented mixing pipe section with a length greater than 3 to 20 times the pipe diameter or greater than 20 meters, taking the larger value, to ensure that caprolactam and ammonia are fully mixed and exchanged through contact heat, and that the presence of ammonia reduces the bubble point of the mixture. Preferably, the length of the mixing pipe section should be greater than 6 to 12 times the pipe diameter or greater than 10 meters, taking the larger value.
[0026] Optionally, the nozzle component further includes a caprolactam feed pipe;
[0027] The caprolactam feed pipe is fixedly connected to the atomizing nozzle;
[0028] The nozzle outlet end has evenly distributed circular holes on its outlet surface.
[0029] Optionally, in this application, the atomizing nozzle extends deep into the centerline of the welded pipe section, spraying liquid caprolactam from the nozzle hole to rapidly mix with a large amount of high-temperature ammonia gas, and the atomizing nozzle is opened from the front.
[0030] Optionally, the catalytic reactor is a fixed-bed reactor.
[0031] Another aspect of this application provides a method for preparing 6-aminohexanonitrile, the method employing the apparatus described above.
[0032] The method includes:
[0033] Ammonia gas enters through the ammonia inlet and mixes with caprolactam sprayed from the nozzle in the mixing section. After being heated by the preheater, the mixture is introduced into a catalytic reactor containing a catalyst to undergo an ammoniation reaction, yielding 6-aminohexanonitrile.
[0034] Optionally, the molar ratio of ammonia to caprolactam is 1:1 to 60:1.
[0035] Optionally, the molar ratio of ammonia to caprolactam is 5:1 to 25:1.
[0036] Optionally, the molar ratio of ammonia to caprolactam is independently selected from any value of 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 40:1, 50:1, 60:1 or a range between any two of the above.
[0037] Optionally, the temperature of the ammonia gas is 150–400°C.
[0038] Optionally, the temperature of the ammonia gas is 200–350°C.
[0039] Optionally, the temperature of the ammonia gas is independently selected from any value of 150°C, 200°C, 250°C, 278°C, 300°C, 320°C, 350°C, 400°C, or a range between any two of the above.
[0040] Optionally, the temperature of the caprolactam is 80–200°C.
[0041] Optionally, the temperature of the caprolactam is 80–150°C.
[0042] Optionally, the temperature of the caprolactam is independently selected from any value of 80°C, 85°C, 90°C, 95°C, 100°C, 120°C, 150°C, 180°C, 200°C, or a range between any two of the above.
[0043] Optionally, the pressure of the ammoniation reaction is 0.0 to 1.0 MPa.
[0044] Optionally, the pressure of the ammoniation reaction is 0.0 to 0.5 MPa.
[0045] Optionally, the pressure of the ammoniation reaction is independently selected from any value of 0 MPa, 0.03 MPa, 0.06 MPa, 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, or a range between any two of the above.
[0046] Optionally, the temperature of the ammoniation reaction is 250–550°C.
[0047] Optionally, the temperature of the ammoniation reaction is 300–400°C.
[0048] Optionally, the temperature of the ammoniation reaction is independently selected from any value of 250°C, 300°C, 340°C, 400°C, 450°C, 500°C, 550°C, or a range between any two of the above.
[0049] Optionally, the reactor described in this application is a reactor using a solid catalyst, and preferably a fixed-bed reactor.
[0050] As a specific implementation method, this application provides an apparatus and method for preparing intermediates, proposing solutions to the problems of uneven mixing and high-temperature polymerization of caprolactam during the amination of caprolactam to 6-aminohexanonitrile. By using nozzle atomization and designing a straight mixing section, rapid mixing and vaporization of caprolactam and high-temperature ammonia are achieved, avoiding polymerization and decomposition caused by prolonged high-temperature environment during caprolactam vaporization, effectively reducing the loss of caprolactam raw materials and improving the stability of the apparatus.
[0051] The apparatus and method include the following technical solutions:
[0052] The apparatus comprises the following components: a welded pipe section, an atomizing nozzle, a mixing pipe section, a preheater, and a catalytic reactor. High-temperature ammonia gas flows in from the inlet of the welded pipe section. The atomizing nozzle is connected to the welded pipe section and inserted into the centerline. High-pressure caprolactam is introduced into the welded pipe section through the atomizing nozzle, forming caprolactam droplets. The welded pipe section is connected to the mixing pipe section, which maintains a certain length. After a very short flow period, the caprolactam and high-temperature ammonia gas are uniformly mixed and undergo sufficient heat exchange, rapidly vaporizing at a lower temperature to form a gaseous mixed feedstock. The gaseous feedstock is heated to the reaction temperature by the preheater and then fed into the catalytic reactor for ammoniation.
[0053] The beneficial effects that this application can produce include:
[0054] This apparatus and method utilize rapid turbulent mixing to form a low-boiling-point caprolactam-ammonia mixture, allowing caprolactam to vaporize quickly at a lower temperature. This avoids polymerization and decomposition caused by prolonged high-temperature environments during caprolactam vaporization, effectively reducing caprolactam raw material loss and improving the stability of the apparatus. The apparatus and method have a simple process, high production efficiency, and facilitate continuous industrial-scale production. Attached Figure Description
[0055] Figure 1 This is a schematic diagram of an apparatus and method for preparing an intermediate according to this application;
[0056] Figure 2 This is a schematic diagram of the atomizing nozzle described in the device of this application.
[0057] List of components and reference numerals:
[0058] 1. Welded pipe section; 2. Atomizing nozzle; 3. Mixing pipe section; 4. Preheater; 5. Catalytic reactor. Detailed Implementation
[0059] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0060] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.
[0061] In the embodiments of this application, the vaporization rate and yield are calculated as follows:
[0062] Vaporization rate = (Number of moles of gaseous substance in the material / Total number of moles of the material) × 100%;
[0063] Yield = number of moles of caprolactam that form 6-aminohexanonitrile in the feed / total number of moles of caprolactam in the feed.
[0064] Example 1
[0065] This embodiment provides an apparatus for preparing 6-aminohexanonitrile by caprolactam amination, such as... Figure 1 As shown, the device includes a welded pipe section 1, an atomizing nozzle 2, a mixing pipe section 3, a preheater 4, and a catalytic reactor 5 connected in sequence. The welded pipe section 1 has a diameter of 300 mm. The atomizing nozzle 2 is inserted into the centerline of the welded pipe section 1, with the nozzle opening facing forward. A schematic diagram of the nozzle opening is shown below. Figure 2 As shown, multiple circumferentially distributed holes are provided, with the flow direction consistent with the ammonia flow direction. Liquid caprolactam at 85°C is sprayed into welded pipe section 1 through atomizing nozzle 2, mixing with ammonia gas at 278°C in welded pipe section 1, with a molar ratio of ammonia gas to caprolactam of 20:1. Mixing pipe section 3 is a 10m long horizontal pipe. The fully mixed gaseous mixture is heated to 340°C by preheater 4 and sent to catalytic reactor 5, which is a jacketed fixed-bed reactor filled with ZSM-5 solid acid catalyst. The ammoniation reaction occurs at 340°C and 0.03 MPa pressure, and the heat absorbed by the reaction is replenished by a heat transfer medium in the reactor jacket.
[0066] In this example, due to the application of this device and method, the vaporization rate of caprolactam before entering the preheater reaches 99.98%, and the yield of 6-aminohexanonitrile can reach 98.6%.
[0067] Example 2
[0068] This embodiment provides an apparatus for preparing 6-aminohexanonitrile by caprolactam amination, such as... Figure 1 As shown, the device includes a welded pipe section 1, an atomizing nozzle 2, a mixing pipe section 3, a preheater 4, and a catalytic reactor 5 connected in sequence. The welded pipe section 1 has a diameter of 600 mm. The atomizing nozzle 2 is inserted into the centerline of the welded pipe section 1, with the nozzle opening facing forward. A schematic diagram of the nozzle opening is shown below. Figure 2 As shown, multiple circumferentially distributed holes are provided, with the flow direction consistent with the ammonia flow direction. Liquid caprolactam at 95°C is sprayed into welded pipe section 1 through atomizing nozzle 2, mixing with ammonia gas at 320°C in welded pipe section 1, with a molar ratio of ammonia gas to caprolactam of 15:1. Mixing pipe section 3 is a horizontal pipe with a length of 15m. The fully mixed gaseous mixture is heated to 400°C by preheater 4 and sent to catalytic reactor 5. Catalytic reactor 5 is a four-stage segmented inter-stage heated fixed-bed reactor filled with a multi-stage porous aluminum solid catalyst. The ammoniation reaction occurs at 400°C and 0.06 MPa pressure, and the heat absorbed by the reaction is replenished by the heat transfer medium in the inter-stage heater of the reactor.
[0069] In this example, due to the application of this device and method, the vaporization rate of caprolactam before entering the preheater reaches 99.96%, and the yield of 6-aminohexanonitrile can reach 99.0%.
[0070] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. An apparatus for preparing 6-aminohexanonitrile, characterized in that, The device includes a feed pipe, a preheater, and a catalytic reactor connected in sequence; The feed pipe is along the direction of ammonia flow and includes a connected feed pipe section and a mixing pipe section; Among them, the end of the feed pipe section away from the mixing pipe section is the ammonia feed end, which is equipped with an ammonia inlet; The end of the feed pipe section closest to the mixing pipe section is the caprolactam feed end. The caprolactam inlet is located on the pipe wall of the caprolactam feed end, and the axis of the caprolactam inlet is perpendicular to the axis of the feed pipe section. The free end of the mixing pipe section away from the feed pipe section is connected to the preheater; The device also includes a nozzle component that extends into the cavity of the feed pipe section through a caprolactam inlet; The nozzle component includes an atomizing nozzle, the axial direction of the nozzle outlet end of the atomizing nozzle coincides with the axial direction of the feed pipe section, so that the flow direction of caprolactam sprayed from the nozzle outlet end is consistent with the flow direction of ammonia gas.
2. The apparatus according to claim 1, characterized in that, The mixing pipe section is arranged horizontally; Preferably, the length of the mixing pipe section is L, and the inner diameter of the mixing pipe section is D; Where L > 10m, or L > 10D; Preferably, L > 20m, or L > 15D.
3. The apparatus according to claim 1, characterized in that, The nozzle component also includes a caprolactam feed pipe; The caprolactam feed pipe is fixedly connected to the atomizing nozzle; The nozzle outlet end has evenly distributed circular holes on its outlet surface.
4. The apparatus according to claim 1, characterized in that, The catalytic reactor is a fixed-bed reactor.
5. A method for preparing 6-aminohexanonitrile, characterized in that, The method employs the apparatus described in any one of claims 1 to 4. The method includes: Ammonia gas enters through the ammonia inlet and mixes with caprolactam sprayed from the nozzle. After being mixed and vaporized in the mixing section, the mixture is heated by the preheater and then introduced into a catalytic reactor containing a catalyst to undergo an ammoniation reaction, yielding 6-aminohexanonitrile.
6. The method according to claim 5, characterized in that, The molar ratio of ammonia to caprolactam is 1:1 to 60:1; Preferably, the molar ratio of ammonia to caprolactam is 5:1 to 25:
1.
7. The method according to claim 5, characterized in that, The temperature of the ammonia gas is 150–400°C; Preferably, the temperature of the ammonia gas is 200–350°C.
8. The method according to claim 5, characterized in that, The temperature of the caprolactam is 80–200°C; Preferably, the temperature of the caprolactam is 80–150°C.
9. The method according to claim 5, characterized in that, The pressure of the ammoniation reaction is 0.0–1.0 MPa; Preferably, the pressure of the ammoniation reaction is 0.0 to 0.5 MPa.
10. The method according to claim 5, characterized in that, The temperature of the ammoniation reaction is 250–550°C; Preferably, the temperature of the ammoniation reaction is 300–400°C.