System and method for continuous ammonia hydrogenation of nitrile compounds

Abstract

The invention discloses a system and a method for continuous ammonia hydrogenation of nitrile compounds, and belongs to the technical field of nitrile hydrogenation. According to the system, raw materials, liquid ammonia and hydrogen are mixed, heated by a preheater and then enter a continuous flow hydrogenation reactor, a hydrogenated product is cooled by a cooler and then enters a gas-liquid separator, a liquid phase of the separator is decompressed and then enters an ammonia still, and ammonia gas is discharged from the top of the ammonia still, is liquefied by an ammonia cooler, then enters a liquid ammonia collecting tank and then returns to the system through a liquid ammonia circulating pump. A material at the bottom of the ammonia still is a liquid-phase product and is extracted to a storage tank; a gas phase at the top of the gas-liquid separator is deeply cooled in a deep cooler, so that a small amount of uncondensed ammonia is condensed into a liquid phase to flow into the separator, and hydrogen is discharged from the top of the deep cooler and returns to the system through a circulating hydrogen compressor. The device and the method are suitable for continuous hydrogenation synthesis of corresponding amines from nitrile compounds such as isophthalonitrile, hydroxypropionitrile, N-(2-cyanopropyl)-caprolactam and the like.

Description

Technical Field

[0001] This application relates to a system and method for continuous ammonia hydrogenation of nitrile compounds, belonging to the field of nitrile hydrogenation technology. Background Technology

[0002] Selective hydrogenation of nitrile compounds to prepare amines is an economical and environmentally friendly synthetic route. Amines are very important chemical intermediates with wide applications in the pharmaceutical, pesticide, and coating industries. Taking N-(2-cyanopropyl)-caprolactam as an example, its hydrogenation yields N-(2-aminopropyl)-caprolactam, an intermediate in the production of 1,8-diazabicyclo-bicyclo(5,4,0)-7-undecene (DBU). However, the hydrogenation method for N-(2-cyanopropyl)-caprolactam using a reactor combined with Raney nickel suffers from problems such as low yield, high catalyst loss, high production cost, the flammability of Raney nickel in air, and the potential for explosion in high-pressure hydrogen reactors. Summary of the Invention

[0003] To address at least one of the problems in existing technologies for the selective hydrogenation of nitrile compounds to prepare amine compounds, namely low yield, high catalyst loss, high production cost, flammability of Raney nickel in air, and potential explosion of high-pressure hydrogen reactors, this application proposes a safe, efficient, and continuous system and method for ammonia hydrogenation, applicable to most ammonia hydrogenation reactions of nitrile compounds.

[0004] The technical solution adopted in this application is as follows: According to a first aspect of this application, a system for the continuous hydrogenation of nitrile compounds via ammonia is provided, comprising: The raw material supply unit includes a raw material pipeline, the inlet end of which is connected to a raw material tank, and a raw material pump is installed on the raw material pipeline; A liquid ammonia supply unit includes a liquid ammonia pipeline, the inlet end of which is connected to a liquid ammonia tank, and a liquid ammonia pump is installed on the liquid ammonia pipeline; Hydrogen supply unit, including circulating hydrogen pipeline; The reaction unit includes a preheater, a continuous flow hydrogenation reactor, a cooler, and a separator connected in sequence by pipelines. The outlet sides of the feed pipeline, liquid ammonia pipeline, and circulating hydrogen pipeline are combined and connected to the top of the preheater. The bottom of the preheater is connected to the top of the continuous flow hydrogenation reactor. The lower side of the continuous flow hydrogenation reactor is connected to the top of the cooler. The bottom of the cooler is connected to the middle side of the separator. The ammonia circulation system includes an ammonia stripping tower, an ammonia cooler, and a liquid ammonia collection tank connected sequentially by pipelines. The upper side of the ammonia stripping tower is connected to the bottom of the separator, the top of the ammonia stripping tower is connected to the top of the ammonia cooler, and the bottom of the ammonia cooler is connected to the top of the liquid ammonia collection tank. A nitrogen supply pipeline with a nitrogen pressure reducing valve is installed on the pipeline between the ammonia stripping tower and the ammonia cooler for replenishing nitrogen. The top of the liquid ammonia collection tank is also equipped with a vent pipeline with a back pressure valve for venting gas. A product heat exchanger is installed on the pipeline between the separator and the ammonia stripping tower. A product extraction pipeline is installed at the bottom of the ammonia stripping tower, and the product extraction pipeline passes through the product heat exchanger.

[0005] Optionally, the outlet side of the combined raw material pipeline and liquid ammonia pipeline is then combined with the outlet side of the circulating hydrogen pipeline and connected to the top of the preheater.

[0006] Optionally, the system further includes: The adsorption tank, air cooler, inlet buffer tank, circulating hydrogen compression pump, and exhaust buffer tank are connected sequentially via pipelines. The bottom of the continuous flow hydrogenation reactor is connected to the upper side of the adsorption tank, the top of the adsorption tank is connected to the inlet of the air cooler, the outlet of the air cooler is connected to the middle side of the inlet buffer tank, the top of the inlet buffer tank is connected to the middle side of the exhaust buffer tank, and the circulating hydrogen compression pump is installed on the pipeline between the inlet buffer tank and the exhaust buffer tank. The top of the separator is connected to the middle side of the air intake buffer tank; The top of the exhaust buffer tank is connected to the hydrogen pipeline via a pipeline for recycling and reusing hydrogen.

[0007] Optionally, the bottom of the liquid ammonia collection tank is connected to the receiving liquid ammonia pipeline via a pipeline equipped with a liquid ammonia circulation pump for recycling liquid ammonia. Optionally, the separator may also include a cryogenic device located at the top.

[0008] Optionally, the adsorption tank is filled with an alkaline substance.

[0009] Optionally, the preheater is heated from the outside and filled with ceramic balls inside.

[0010] Optionally, the continuous flow hydrogenation reactor is an adiabatic reactor.

[0011] Optionally, the reboiler of the ammonia stripping tower is equipped with a reboiler; Optionally, the ammonia stripping tower is a packed tower.

[0012] According to a second aspect of this application, a method for continuous ammonia hydrogenation of nitrile compounds is also provided, using the system for continuous ammonia hydrogenation of nitrile compounds described in any of the foregoing claims, the steps of which include: Hydrogen, raw materials, and liquid ammonia are continuously supplied to the reaction unit through a hydrogen supply unit, a raw material supply unit, and a liquid ammonia supply unit, respectively, and the reaction takes place under the action of a catalyst. The reaction products are cooled and separated, and then fed into the ammonia circulation system for product extraction, yielding nitrile compounds.

[0013] Optionally, the mass hourly space velocity (MHSV) of the raw material is 0.2-0.25 h⁻¹. -1 ; The mass hourly space velocity (MSV) of the liquid ammonia is 0.4-0.5 h⁻¹. -1 ; The reaction conditions include: operating temperature of 70°C to 110°C and pressure of 5-7 MPa in the continuous flow hydrogenation reactor; The pressure of the ammonia circulation system is 0.75-0.85 MPa. When the pressure is below 0.75 MPa, nitrogen is supplied through a nitrogen replenishment pipeline with a nitrogen pressure reducing valve. When the pressure is above 0.85 MPa, the gas is discharged through a venting pipeline with a back pressure valve.

[0014] Optionally, hydrogen, raw materials, and liquid ammonia are continuously supplied to the reaction unit through a hydrogen supply unit, a raw material supply unit, and a liquid ammonia supply unit, respectively, including: After liquid ammonia is mixed with the raw materials, it is then mixed with hydrogen.

[0015] Optionally, the step of introducing the ammonia circulation system for product extraction includes: the reaction product entering the ammonia stripping tower, the product being discharged from the bottom of the ammonia stripping tower, and the ammonia gas at the top of the ammonia stripping tower being cryogenically condensed by an ammonia cooler and then flowing into a liquid ammonia collection tank for recycling.

[0016] Optionally, the reaction products are cooled to 40°C by an air cooler and then enter a separator to remove hydrogen. After being preheated to 50°C by a product heat exchanger, they enter an ammonia stripping tower to be heated to 60°C to evaporate ammonia. The ammonia enters an ammonia cooler and is cryogenically condensed at -5°C before flowing into a liquid ammonia collection tank for recycling.

[0017] Optionally, the reaction products are preheated by a product heat exchanger before entering the ammonia stripping tower.

[0018] Optionally, the liquid ammonia in the liquid ammonia collection tank is circulated back into the liquid ammonia pipeline via a liquid ammonia circulation pump.

[0019] Optionally, the reaction products are separated by cooling, comprising: The reaction products discharged from the continuous flow hydrogenation reactor are cooled by a cooler and then enter a separator for gas-liquid separation. The liquid reaction products at the bottom of the separator enter the ammonia circulation system, and the hydrogen at the top of the separator enters the inlet buffer tank, passes through the circulating hydrogen compressor, enters the exhaust buffer tank, and is then circulated back to the circulating hydrogen pipeline.

[0020] Optionally, the gas phase of the separator is separated into hydrogen after passing through a cryogenic device located at the top of the separator to remove unliquefied ammonia.

[0021] Optionally, the step further includes catalyst reduction: Before the continuous introduction of hydrogen, raw materials, and liquid ammonia for reaction, nitrogen is introduced into the continuous ammonia hydrogenation system of the nitrile compounds to purge the atmosphere until the oxygen content is less than 0.5%. Nitrogen is continuously introduced and released while controlling the system temperature and hydrogen concentration to carry out catalyst reduction. After the catalyst reduction is completed, the continuous ammonia hydrogenation system of the nitrile compounds is purged with hydrogen until the nitrogen content is less than 0.5%. Then, hydrogen is continued to be introduced until the pressure reaches 0.5 MPa, and hydrogen circulation is started. Hydrogen is then slowly added until the pressure reaches 4.5 MPa.

[0022] Optionally, the conditions for catalyst reduction include: stepwise heating and hydrogen addition, wherein the heating process and the hydrogen concentration increase process are not carried out simultaneously, the temperature range of heating is 1-500 °C, and the hydrogen concentration range is 0-100%.

[0023] Optionally, the adsorption tank is filled with an alkaline substance to absorb the reduced acidic gas, which then passes through an air cooler and enters the inlet buffer tank for circulation. Optionally, when the raw material is N-(2-cyanopropyl)-caprolactam, the reaction conditions include: an operating temperature of 80°C~100°C, a pressure of 5-7 MPa, and a hydrogen hourly space velocity of 600-1000 ml / (gcat.h) in the continuous flow hydrogenation reactor.

[0024] The beneficial effects of this application include: The system for continuous ammonia hydrogenation of nitrile compounds provided in this application, using N-(2-cyanopropyl)-caprolactam as a raw material, operates at a temperature of 80-100°C, a pressure of ~5 MPa, a feed mass hourly space velocity (MHSV) of 0.2-0.25 h⁻¹, a liquid ammonia hourly space velocity (LHSV) of approximately 0.4 h⁻¹, and a hydrogen hourly space velocity (HHSV) of 600 ml / (gcat·h). The reaction achieves a feed conversion rate >99% and a selectivity >96%. This method allows for continuous nitrile hydrogenation reactions, with ammonia recycling to achieve low energy consumption. It can replicate small-scale experimental results and meet the needs of large-scale applications. With proper planning, energy recovery and reuse can be achieved. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the system for continuous ammonia hydrogenation of nitrile compounds according to this application.

[0026] Attached Figure Labels 1. Raw material tank; 2. Raw material pump; 3. Liquid ammonia tank; 4. Liquid ammonia pump; 5. Preheater; 6. Continuous flow hydrogenation reactor; 7. Cooler; 8. Separator; 9. Inlet buffer tank; 10. Circulating hydrogen compressor; 11. Exhaust buffer tank; 12. Product heat exchanger; 13. Ammonia stripping tower; 14. Ammonia cooler; 15. Liquid ammonia collection tank; 16. Liquid ammonia circulating pump; 17. Adsorption tank; 18. Air cooler.

[0027] M represents electric motor; FC represents flow control; FT represents flow transmitter; LT represents level transmitter; E represents electric heater. Detailed Implementation

[0028] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0030] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0031] To address at least one of the problems in the selective hydrogenation of nitrile compounds to prepare amine compounds, namely low yield, high catalyst loss, high production cost, flammability of Raney nickel in air, and explosion hazard of high-pressure hydrogen reactors, this application provides a safe and efficient system and method for continuous ammonia hydrogenation of nitrile compounds. This system is applicable to most ammonia hydrogenation reactions of nitrile compounds. The nitrile compound feedstock is metered and pressurized by a pump, mixed with liquid ammonia metered and pressurized by a liquid ammonia metering pump, and then mixed with hydrogen from the fresh hydrogen supply line and the circulating hydrogen compressor. After being heated in a preheater, the mixture enters a continuous flow hydrogenation reactor. After hydrogenation, the product is cooled by a cooler and then enters a gas-liquid separator. The liquid phase in the separator is depressurized and enters an ammonia stripping tower. Ammonia gas exits from the top of the ammonia stripping tower, is liquefied by an ammonia cooler, and enters a liquid ammonia collection tank. It is then returned to the system via a liquid ammonia circulation pump. The material at the bottom of the ammonia stripping tower is a liquid product, which is collected and stored in a storage tank. The gas phase at the top of the gas-liquid separator is cryogenically cooled in a cryogenic cooler, causing a small amount of uncondensed ammonia to condense into a liquid phase and flow into the separator. Hydrogen gas exits from the top of the cryogenic cooler and returns to the system via a circulating hydrogen compressor. A bypass (the pipeline between the bottom of the reactor and the adsorption tank) is installed at the bottom of the hydrogenation reactor, connecting to the adsorption tank. An air cooler is installed at the outlet of the adsorption tank, and the gas enters the circulating hydrogen compressor, serving as a catalyst reduction pipeline. This system and method are applicable to the continuous hydrogenation synthesis of corresponding amines from nitrile compounds such as isophthalonitrile, hydroxypropionitrile, and N-(2-cyanopropyl)-caprolactam.

[0032] According to one embodiment of this application, a system for the continuous hydrogenation of nitrile compounds via ammonia, such as... Figure 1 As shown, it includes: The raw material supply unit includes a raw material pipeline, the inlet end of which is connected to a raw material tank 1, and a raw material pump 2 is installed on the raw material pipeline; A liquid ammonia supply unit includes a liquid ammonia pipeline, the inlet end of which is connected to a liquid ammonia tank 3, and a liquid ammonia pump 4 is installed on the liquid ammonia pipeline; Hydrogen supply unit, including circulating hydrogen pipeline; The reaction unit includes a preheater 5, a continuous flow hydrogenation reactor 6, a cooler 7, and a separator 8 connected in sequence by pipelines. The outlet side of the combined raw material pipeline and liquid ammonia pipeline is then connected to the outlet side of the circulating hydrogen pipeline and connected to the top of the preheater 5. The bottom of the preheater 5 is connected to the top of the continuous flow hydrogenation reactor 6. The lower side of the continuous flow hydrogenation reactor 6 is connected to the top of the cooler 7, and the bottom of the cooler 7 is connected to the middle side of the separator 8. The ammonia circulation system includes an ammonia stripping tower 13, an ammonia cooler 14, and a liquid ammonia collection tank 15 connected sequentially by pipelines. The upper side of the ammonia stripping tower 13 is connected to the bottom of the separator 8, the top of the ammonia stripping tower 13 is connected to the top of the ammonia cooler 14, and the bottom of the ammonia cooler 14 is connected to the top of the liquid ammonia collection tank 15. A nitrogen replenishment pipeline with a nitrogen pressure reducing valve is installed on the pipeline between the ammonia stripping tower 13 and the ammonia cooler 14 for replenishing nitrogen. The top of the liquid ammonia collection tank 15 is also equipped with a venting pipeline with a back pressure valve for venting gas. A product heat exchanger 12 is installed on the pipeline between the separator 8 and the ammonia stripping tower 13. A product extraction pipeline is installed at the bottom of the ammonia stripping tower 13, and the product extraction pipeline passes through the product heat exchanger 12.

[0033] The continuous flow hydrogenation reactor 6 is connected in sequence via pipelines to an adsorption tank 17, an air cooler 18, an inlet buffer tank 9, a circulating hydrogen compression pump, and an exhaust buffer tank 11. The bottom of the continuous flow hydrogenation reactor 6 is connected to the upper side of the adsorption tank 17, the top of the adsorption tank 17 is connected to the inlet of the air cooler 18, the outlet of the air cooler 18 is connected to the middle side of the inlet buffer tank 9, and the top of the inlet buffer tank 9 is connected to the middle side of the exhaust buffer tank 11. The circulating hydrogen compression pump is located on the pipeline between the inlet buffer tank 9 and the exhaust buffer tank 11. The top of the separator 8 is connected to the middle side of the intake buffer tank 9; the top of the exhaust buffer tank 11 is connected to the hydrogen pipeline through a pipeline for recycling hydrogen; the catalyst will produce acidic substances or solid particles during the reduction process, which need to be absorbed or separated, so an adsorption tank 17 and an air cooler 18 are provided.

[0034] The bottom of the liquid ammonia collection tank 15 is connected to the receiving liquid ammonia pipeline through a pipeline equipped with a liquid ammonia circulation pump 16, for recycling and reuse of liquid ammonia. The separator 8 is equipped with a cryogenic device at its top. This device is used to cool a small amount of unliquefied ammonia gas to ensure the purity of the circulating hydrogen gas. For example, the temperature of the cryogenic device is approximately 0°C.

[0035] In one embodiment, the adsorption tank 17 is filled with an alkaline substance to absorb the reduced acidic gas, which then passes through the air cooler 18 and enters the intake buffer tank 9 for circulation.

[0036] In one embodiment, the preheater 5 is an external wall heating type, and the interior is filled with ceramic balls; it facilitates gas-liquid mixing and heat transfer, and its main function is to heat the materials while mixing them.

[0037] In one embodiment, the continuous flow hydrogenation reactor 6 is an adiabatic reactor; preferably, the continuous flow hydrogenation reactor 6 is a fixed packed bed adiabatic reactor, with ceramic balls added to the bottom, catalyst added to the middle, and ceramic balls added to the top of the reactor. In one embodiment, the bottom of the ammonia stripping tower 13 is equipped with a reboiler; In one embodiment, the ammonia stripping tower 13 is a packed tower. It is filled with structured packing material, and the internal components can be replaced according to the material properties to accommodate the distillation and separation of different materials.

[0038] According to another embodiment of this application, a method for continuous hydrogenation of nitrile compounds using ammonia is described. Figure 1 The system for the continuous hydrogenation of nitrile compounds via ammonia, as shown, includes the following steps: Hydrogen, raw materials, and liquid ammonia are continuously supplied to the reaction unit through a hydrogen supply unit, a raw material supply unit, and a liquid ammonia supply unit, respectively. The liquid ammonia is mixed with the raw materials and then mixed with hydrogen before entering the reaction unit and reacting under the action of a catalyst. The reaction products are cooled and separated and then fed into the ammonia circulation system for product extraction, yielding nitrile compounds.

[0039] The reaction products are cooled and separated, including: the reaction products discharged from the continuous flow hydrogenation reactor 6 are cooled by the cooler 7 and then enter the separator 8 for gas-liquid separation. The liquid phase reaction products at the bottom of the separator 8 enter the ammonia circulation system. The gas phase of the separator 8 passes through a cryogenic device set at the top of the separator 8 to remove unliquefied ammonia and then separates hydrogen. The hydrogen enters the inlet buffer tank 9 and then passes through the circulating hydrogen compressor 10 and enters the exhaust buffer tank 11 before being circulated back to the circulating hydrogen pipeline.

[0040] The process of introducing the product into the ammonia circulation system includes: the reaction product being preheated by the product heat exchanger 12 and then entering the ammonia stripping tower 13; the product being discharged from the bottom of the ammonia stripping tower 13; the ammonia gas at the top of the ammonia stripping tower 13 being cryogenically condensed by the ammonia cooler 14 and then flowing into the liquid ammonia collection tank 15; and the liquid ammonia in the liquid ammonia collection tank 15 being circulated back into the liquid ammonia pipeline by the liquid ammonia circulation pump 16. The liquid phase at the bottom of the separator 8 is mainly a mixture of product, raw material, and ammonia. After being preheated by the product cooler 7 to a temperature of approximately 50°C, it enters the ammonia stripping tower 13 of the liquid ammonia recovery system. Before the continuous introduction of hydrogen, raw materials, and liquid ammonia for reaction, catalyst reduction is performed: nitrogen is introduced into the continuous ammonia hydrogenation system of the nitrile compounds to purge the atmosphere until the oxygen content is less than 0.5%. Nitrogen is continuously introduced and released while controlling the system temperature and hydrogen concentration for catalyst reduction. The conditions for catalyst reduction include: stepwise heating and hydrogenation, wherein the heating process and the hydrogen concentration increase process are not performed simultaneously. After catalyst reduction, the continuous ammonia hydrogenation system of the nitrile compounds is purged with hydrogen until the nitrogen content is less than 0.5%. Then, hydrogen is continued to be introduced until the pressure reaches 0.5 MPa, and hydrogen circulation is started. Hydrogen is slowly filled until the pressure reaches 4.5 MPa. The amount of nitrogen can be adjusted as needed while continuously introducing and releasing nitrogen. For example, the amount of nitrogen is maintained at 8 Nm3 / h.

[0041] In one embodiment, the mass hourly space velocity (MHSV) of the raw material is 0.2-0.25 h⁻¹. -1 ; The mass hourly space velocity (MSV) of the liquid ammonia is 0.4 h⁻¹. -1 ; The reaction conditions include: the operating temperature in the continuous flow hydrogenation reactor 6 is 70°C~110°C and the pressure is 5MPa; The pressure of the ammonia circulation system is 0.75-0.85 MPa. When the pressure is below 0.75 MPa, nitrogen is supplied through a nitrogen replenishment pipeline with a nitrogen pressure reducing valve. When the pressure is above 0.85 MPa, the gas is discharged through a venting pipeline with a back pressure valve.

[0042] In one embodiment, the reaction product is cooled to 40°C by air cooler 18 and then enters separator 8 to separate and remove hydrogen. After being preheated to 50°C by product heat exchanger 12, it enters ammonia stripping tower 13 to be heated to 60°C to evaporate ammonia. The ammonia enters ammonia cooler 14 and is cryogenically condensed at -5°C before flowing into liquid ammonia collection tank 15 for recycling.

[0043] In one embodiment, the adsorption tank is filled with an alkaline substance to absorb the reduced acidic gas, which then passes through an air cooler 18 and enters the intake buffer tank 9 for circulation. The catalyst needs to be reduced before use, following the principle of raising the temperature without raising the hydrogen, and raising the hydrogen without raising the temperature, with the temperature gradually increased to a maximum of 550°C. During the reduction process, the catalyst will produce acidic substances or solid particles, which need to be absorbed or separated. Therefore, the adsorption tank 17 and the air cooler 18 are provided.

[0044] In one embodiment, when the raw material is N-(2-cyanopropyl)-caprolactam, the reaction conditions include: an operating temperature of 80°C to 100°C, a pressure of 5 MPa, and a hydrogen hourly space velocity of 600 ml / (gcat.h) in the continuous flow hydrogenation reactor 6.

[0045] In one embodiment, the method for continuous hydrogenation of nitrile compounds with ammonia is described using... Figure 1 The system for the continuous hydrogenation of nitrile compounds via ammonia, as shown, includes the following steps: S1: Replace the entire system with nitrogen until the oxygen content is less than 0.5%; S2: Continue charging and releasing nitrogen simultaneously, maintaining a nitrogen level of 8 Nm³. 3 / h; S3: Follow the principle of increasing temperature without increasing hydrogen, and increasing hydrogen without increasing temperature to reduce the catalyst; S4: After the catalyst reduction is completed, replace the entire system with hydrogen until the nitrogen content is less than 0.5%, pressurize to 0.5MPa and start the circulating hydrogen compressor 10; S5: Slowly charge hydrogen into the system until the pressure reaches 4.5 MPa, maintain hydrogen circulation, and control the circulation volume at 600 ml / (gcat.h). S6: Start raw material pump 2 and liquid ammonia pump 4 in sequence, and adjust the raw material mass hourly space velocity to 0.2-0.25 h⁻¹. -1 The mass hourly space velocity (MSV) of liquid ammonia is approximately 0.4 h⁻¹. -1 ; S7: The continuous flow hydrogenation reactor 6 in the reaction unit begins to heat up to 70°C~110°C and maintains operation; S8: After the reaction, the gaseous material enters separator 8. The top cryogenic temperature of separator 8 is set to 0°C to cool the ammonia gas with a relatively low partial pressure and prevent it from being carried into the compressor. Then, the hydrogen gas, with trace amounts of ammonia removed, is compressed to approximately 5.4 MPa by a 10-liter circulating hydrogen compressor and circulated. S9: After the reaction, the liquid material at about 40°C enters the ammonia circulation system through the bottom of separator 8. After preheating, the liquid material is heated to about 50°C and enters the ammonia stripping tower 13. The reboiler of the ammonia stripping tower 13 is set to 60°C, so that the ammonia evaporates into ammonia gas. After being condensed by deep cryogenic cooling at -5°C, it flows into the liquid ammonia collection tank 15 for recycling. S10: In the ammonia circulation system, the pressure is maintained at 0.75-0.85MPa. A nitrogen pressure reducing valve is installed before the ammonia cooler 14. Nitrogen is added when the pressure is lower than 0.75MPa. A back pressure valve is installed on the top of the liquid ammonia collection tank 15. When the pressure is higher than 0.85MPa, the gas is discharged. S11: The reaction has a raw material conversion rate of >99% and a selectivity of >96%.

[0046] Examples 1-3 below are typical cases. Figure 1 The aforementioned system and method for continuous ammonia hydrogenation of nitrile compounds are used for hydrogenation of nitrile compounds.

[0047] Example 1 This embodiment uses N-(2-cyanopropyl)-caprolactam as a raw material to produce N-(2-aminopropyl)-caprolactam via hydrogenation. A 15L volume fixed-bed adiabatic reactor is used in this embodiment for continuous flow hydrogenation, and 10kg of nickel-based supported catalyst is loaded into the reactor. Before startup, the entire system is purged with nitrogen until the oxygen content is less than 0.5%, with nitrogen being continuously charged and released, maintaining a nitrogen flow rate of 8 Nm³. 3 / h, the catalyst bed is under slight positive pressure. Following the principle of increasing temperature without increasing hydrogen production, and increasing hydrogen production without increasing temperature, the catalyst reduction begins, and the temperature increase and hydrogen addition procedure follows Table 1: Table 1

[0048] After catalyst reduction, the system is cooled and purged with hydrogen until the nitrogen content is less than 0.5%. The system is then pressurized to 0.5 MPa and the circulating hydrogen compressor is started. Hydrogen is slowly added to the system and pressurized to 4.5 MPa, maintaining hydrogen circulation at a rate of 600 ml / (gcat.h). The feed pump and liquid ammonia pump are started sequentially, adjusting the feed mass flow rate to 2-2.5 kg / h and the liquid ammonia mass hourly space velocity to approximately 4 L / h. The system temperature is then increased to 70°C-110°C and maintained, with the control system pressure stabilized at 5 MPa. The gaseous material after the reaction enters the separator, with the top cryogenic temperature set to 0°C to cool the ammonia gas with lower partial pressure and prevent it from being carried into the compressor. The hydrogen gas, after trace amounts of ammonia have been removed, is then pressurized to approximately 5.4 MPa by the circulating hydrogen compressor and circulated. A liquid-phase mixture at approximately 40°C enters the ammonia circulation system via a separator. After preheating, the temperature rises to approximately 50°C before entering the ammonia stripping tower. The reboiler in the stripping tower is set to 60°C, causing the ammonia to evaporate into ammonia gas. This gas is then cryogenically condensed at -5°C and flows into a liquid ammonia collection tank for recycling. In the ammonia circulation system, the system pressure is maintained at 0.75-0.85 MPa. A nitrogen pressure reducing valve is installed before the ammonia cooler; nitrogen is added when the pressure drops below 0.75 MPa. A back pressure valve is installed on the top of the liquid ammonia collection tank; exhaust gas is released when the pressure exceeds 0.85 MPa. The reaction has a feed conversion rate >99% and a selectivity >96%.

[0049] Example 2 This embodiment uses 3-methoxypropionitrile as a raw material to produce 3-methoxypropylamine via hydrogenation. The continuous flow hydrogenation reactor used in this embodiment is a 15L volume fixed-bed adiabatic reactor, and the reactor is loaded with 8kg of copper / nickel bimetallic supported catalyst. Before feeding, the catalyst needs to be reduced with hydrogen, following the principle of raising the temperature without raising the hydrogen content, and raising the hydrogen content without raising the temperature. The heating and hydrogenation procedure is as shown in Table 2. Table 2

[0050] After catalyst reduction, the system is cooled and purged with hydrogen until the nitrogen content is less than 0.5%. The system is then pressurized to 0.5 MPa and the circulating hydrogen compressor is started. Hydrogen is slowly added to the system and pressurized to 3.5 MPa, maintaining hydrogen circulation at a rate of 600 ml / (gcat.h). The feed pump and liquid ammonia pump are started sequentially, adjusting the 3-methoxypropionitrile flow rate to 8 kg / h and the liquid ammonia flow rate to approximately 3.2 L / h. The system is then heated to ~80°C and maintained, with the control pressure stabilized at 4 MPa. The gaseous material after the reaction enters the separator, with the top cryogenic temperature set to 0°C to cool the ammonia gas with lower partial pressure and prevent it from being carried into the compressor. The hydrogen gas, after trace amounts of ammonia have been removed, is pressurized to approximately 4.4 MPa by the circulating hydrogen compressor and circulated. The liquid mixture at approximately 40°C enters the ammonia circulation system through the separator for further recycling. The overall yield of this reaction is >96%.

[0051] Example 3 This embodiment uses 3-isopropoxypropionitrile as raw material to produce 3-isopropoxypropylamine via hydrogenation. The reactor used in this embodiment is a 15L fixed-bed adiabatic reactor, and the loading is 8 kg of copper / nickel bimetallic supported catalyst. Before feeding, the catalyst needs to be reduced with hydrogen, following the principle of raising the temperature without raising the hydrogen content, and raising the hydrogen content without raising the temperature. The heating and hydrogenation procedure is as shown in Table 3. Table 3

[0052] After catalyst reduction, the system is cooled and purged with hydrogen until the nitrogen content is less than 0.5%. The system is then pressurized to 0.5 MPa and the circulating hydrogen compressor is started. Hydrogen is slowly added to the system and pressurized to 3.5 MPa, maintaining hydrogen circulation at a rate of 600 ml / (gcat.h). The feed pump and liquid ammonia pump are started sequentially, adjusting the feed mass flow rate to 4 kg / h and the liquid ammonia flow rate to approximately 3.2 L / h. The system temperature is then increased to 80-100°C and maintained, with the control system pressure stabilized at 4 MPa. The gaseous material after the reaction enters the separator, with the top cryogenic temperature set to 0°C to cool the ammonia gas with lower partial pressure and prevent it from being carried into the compressor. The hydrogen gas, after trace amounts of ammonia have been removed, is pressurized to approximately 4.4 MPa by the circulating hydrogen compressor and circulated. The liquid mixture at approximately 40°C enters the ammonia circulation system through the separator for further recycling. The overall yield of this reaction is >94%.

[0053] 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 all fall within the scope of the technical solution.

Claims

1. A system for the continuous hydrogenation of nitrile compounds via ammonia, characterized in that, include: The raw material supply unit includes a raw material pipeline, the inlet end of which is connected to a raw material tank, and a raw material pump is installed on the raw material pipeline; A liquid ammonia supply unit includes a liquid ammonia pipeline, the inlet end of which is connected to a liquid ammonia tank, and a liquid ammonia pump is installed on the liquid ammonia pipeline; Hydrogen supply unit, including circulating hydrogen pipeline; The reaction unit includes a preheater, a continuous flow hydrogenation reactor, a cooler, and a separator connected in sequence by pipelines. The outlet sides of the feed pipeline, liquid ammonia pipeline, and circulating hydrogen pipeline are combined and connected to the top of the preheater. The bottom of the preheater is connected to the top of the continuous flow hydrogenation reactor. The lower side of the continuous flow hydrogenation reactor is connected to the top of the cooler. The bottom of the cooler is connected to the middle side of the separator. The ammonia circulation system includes an ammonia stripping tower, an ammonia cooler, and a liquid ammonia collection tank connected sequentially by pipelines. The upper side of the ammonia stripping tower is connected to the bottom of the separator, the top of the ammonia stripping tower is connected to the top of the ammonia cooler, and the bottom of the ammonia cooler is connected to the top of the liquid ammonia collection tank. A nitrogen supply pipeline with a nitrogen pressure reducing valve is installed on the pipeline between the ammonia stripping tower and the ammonia cooler for replenishing nitrogen. The top of the liquid ammonia collection tank is also equipped with a vent pipeline with a back pressure valve for venting gas. A product heat exchanger is installed on the pipeline between the separator and the ammonia stripping tower. A product extraction pipeline is installed at the bottom of the ammonia stripping tower, and the product extraction pipeline passes through the product heat exchanger.

2. The system for continuous ammonia hydrogenation of nitrile compounds according to claim 1, characterized in that, Also includes: The adsorption tank, air cooler, inlet buffer tank, circulating hydrogen compression pump, and exhaust buffer tank are connected sequentially via pipelines. The bottom of the continuous flow hydrogenation reactor is connected to the upper side of the adsorption tank, the top of the adsorption tank is connected to the inlet of the air cooler, the outlet of the air cooler is connected to the middle side of the inlet buffer tank, the top of the inlet buffer tank is connected to the middle side of the exhaust buffer tank, and the circulating hydrogen compression pump is installed on the pipeline between the inlet buffer tank and the exhaust buffer tank. The top of the separator is connected to the middle side of the air intake buffer tank; The top of the exhaust buffer tank is connected to the hydrogen pipeline via a pipeline for recycling and reusing hydrogen. Preferably, the bottom of the liquid ammonia collection tank is connected to the receiving liquid ammonia pipeline via a pipeline equipped with a liquid ammonia circulation pump, for recycling and reusing liquid ammonia; Preferably, the separator further includes a cryogenic device disposed at the top; Preferably, the adsorption tank is filled with an alkaline substance.

3. The system for continuous ammonia hydrogenation of nitrile compounds according to claim 1, characterized in that, The preheater is heated from the outside and filled with ceramic balls. Preferably, the continuous flow hydrogenation reactor is an adiabatic reactor; Preferably, the bottom of the ammonia stripping tower is equipped with a reboiler; Preferably, the ammonia stripping tower is a packed tower.

4. A method for continuous hydrogenation of nitrile compounds via ammonia, characterized in that, The method uses the system for continuous ammonia hydrogenation of nitrile compounds according to any one of claims 1 to 3, and the steps include: Hydrogen, raw materials, and liquid ammonia are continuously supplied to the reaction unit through a hydrogen supply unit, a raw material supply unit, and a liquid ammonia supply unit, respectively, and the reaction takes place under the action of a catalyst. The reaction products are cooled and separated, and then fed into the ammonia circulation system for product extraction, yielding nitrile compounds.

5. The preparation method according to claim 4, characterized in that, The mass hourly space velocity (MSV) of the raw material is 0.2-0.25 h⁻¹. -1 ; The mass hourly space velocity (MSV) of the liquid ammonia is 0.4-0.5 h⁻¹. -1 ; The reaction conditions include: operating temperature of 70°C to 110°C and pressure of 5-7 MPa in the continuous flow hydrogenation reactor; The pressure of the ammonia circulation system is 0.75-0.85 MPa. When the pressure is below 0.75 MPa, nitrogen is supplied through a nitrogen replenishment pipeline with a nitrogen pressure reducing valve. When the pressure is above 0.85 MPa, the gas is discharged through a venting pipeline with a back pressure valve.

6. The preparation method according to claim 4, characterized in that, The process of introducing the ammonia circulation system for product extraction includes: the reaction product entering the ammonia stripping tower, the product being discharged from the bottom of the ammonia stripping tower, and the ammonia gas at the top of the ammonia stripping tower being cryogenically condensed by an ammonia cooler and then flowing into a liquid ammonia collection tank for recycling. Preferably, the reaction product is cooled to 40°C by an air cooler and then enters a separator to remove hydrogen. After being preheated to 50°C by a product heat exchanger, it enters an ammonia stripping tower to be heated to 60°C to evaporate ammonia. The ammonia enters an ammonia cooler and is cryogenically condensed at -5°C before flowing into a liquid ammonia collection tank for recycling.

7. The preparation method according to claim 6, characterized in that, The reaction products are preheated by a product heat exchanger and then enter the ammonia stripping tower. Preferably, the liquid ammonia in the liquid ammonia collection tank is circulated back into the liquid ammonia pipeline via a liquid ammonia circulation pump.

8. The preparation method according to claim 4, characterized in that, The reaction products are separated by cooling and include: The reaction products discharged from the continuous flow hydrogenation reactor are cooled by a cooler and then enter a separator for gas-liquid separation. The liquid reaction products at the bottom of the separator enter the ammonia circulation system, and the hydrogen at the top of the separator enters the inlet buffer tank, passes through the circulating hydrogen compressor, enters the exhaust buffer tank, and then circulates back to the circulating hydrogen pipeline. Preferably, the gas phase of the separator is separated into hydrogen after passing through a cryogenic device located at the top of the separator to remove unliquefied ammonia.

9. The preparation method according to claim 4, characterized in that, The step also includes catalyst reduction: Before the continuous introduction of hydrogen, raw materials, and liquid ammonia for reaction, nitrogen is introduced into the continuous ammonia hydrogenation system of the nitrile compounds to purge the atmosphere until the oxygen content is less than 0.5%. Nitrogen is continuously introduced and released while controlling the system temperature and hydrogen concentration to carry out catalyst reduction. After the catalyst reduction is completed, the continuous ammonia hydrogenation system of the nitrile compounds is purged with hydrogen until the nitrogen content is less than 0.5%. Then, hydrogen is continued to be introduced until the pressure reaches 0.5 MPa, and hydrogen circulation is started. Hydrogen is then slowly added until the pressure reaches 4.5 MPa. Preferably, the conditions for catalyst reduction include: stepwise heating and hydrogen addition, wherein the heating process and the hydrogen concentration increase process are not carried out simultaneously; Preferably, the adsorption tank is filled with an alkaline substance to absorb the reduced acidic gas, and then enters the intake buffer tank for circulation after passing through an air cooler.

10. The preparation method according to claim 4, characterized in that, When the raw material is N-(2-cyanopropyl)-caprolactam, the reaction conditions include: operating temperature of 80°C~100°C, pressure of 5-7 MPa, and hydrogen space velocity of 600-1000 ml / (gcat.h) in a continuous flow hydrogenation reactor.

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