Process for the production of hexamethylenediamine by hydrogenation of aminocapronitrile

Abstract

This invention relates to a method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile, comprising the following steps: in a tubular fixed-bed reactor, a feed liquid containing aminohexanonitrile and hydrogen gas are subjected to a hydrogenation reaction in countercurrent contact in the presence of a platinum-palladium supported catalyst. This invention enhances mass transfer through gas-liquid countercurrent contact, ensuring sufficient hydrogen concentration throughout the bed and avoiding side reactions caused by localized hydrogen deficiency in traditional co-current processes. Simultaneously, the continuously hydrogen-rich reaction environment facilitates the full utilization of the high cyano hydrogenation activity and hexamethylenediamine selectivity of the platinum-palladium supported catalyst, thereby effectively suppressing intramolecular cyclization, condensation, and C-N bond hydrogenolysis side reactions under alkali-free conditions throughout the process, simultaneously achieving an aminohexanonitrile conversion >98.5% and a hexamethylenediamine selectivity >98.5%.

Description

Technical Field

[0001] This invention relates to the field of organic chemical technology, and in particular to a method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile. Background Technology

[0002] Hexamethylenediamine is a key monomer for the synthesis of nylon 66 and polyurethane curing agents. The mainstream industrial production route is the preparation of hexamethylenediamine by catalytic hydrogenation of aminohexanonitrile. Currently, the most widely used industrial application is the Raney nickel suspension reactor hydrogenation process, but this process has the following defects in long-term operation: (1) In order to suppress cyclization side reactions, strong alkaline additives such as sodium hydroxide must be added during the production process. On the one hand, the residual alkali metal ions in the product will greatly increase the complexity of the post-processing process, making it difficult to stably meet the purity index requirements of high-end polymer grade products; on the other hand, a large amount of alkaline waste liquid will be generated, resulting in a large load on the treatment of waste and high environmental protection costs; (2) Raney nickel catalyst has poor mechanical strength and is easily pulverized and lost during the reaction process; (3) The reactor is an intermittent operation mode, which cannot achieve continuous operation. The capacity of a single unit is limited, making it difficult to meet the needs of large-scale continuous production.

[0003] To address the shortcomings of batch-type processes, fixed-bed hydrogenation based on precious metal catalysts has become an important direction for improvement. However, this process also has certain bottlenecks. On the one hand, existing precious metal fixed-bed hydrogenation processes generally adopt a co-flow approach, where the feed liquid and hydrogen flow in the same direction through the catalyst bed. Hydrogen is rapidly consumed in the upper part of the bed, and the hydrogen partial pressure in the lower part of the bed is significantly reduced. This easily leads to insufficient local hydrogen concentration and a decrease in the gas-liquid-solid three-phase mass transfer efficiency, which in turn induces intramolecular cyclization of aminohexanonitrile to generate byproducts such as hexamethyleneimine and polyamines. It is difficult to simultaneously achieve a feed conversion rate and product selectivity of 98.5%. On the other hand, cyano hydrogenation is a strongly exothermic process. Traditional fixed beds mostly use high-temperature heat exchange with heat transfer oil to remove heat. The heat exchange temperature difference is large, and the bed temperature is difficult to control, which easily causes local temperature runaway in the bed, thereby inducing CN bond hydrogen decomposition side reactions.

[0004] Therefore, it is necessary to further improve the existing method for the catalytic hydrogenation of aminohexanonitrile to prepare hexamethylenediamine. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile.

[0006] The technical solution adopted in this invention is as follows: This invention provides a method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile, comprising the following steps: In a tubular fixed-bed reactor, a hydrogenation reaction is carried out by countercurrent contact of a feed liquid containing aminohexanonitrile and hydrogen gas in the presence of a platinum-palladium supported catalyst.

[0007] Preferably, the raw material solution containing aminohexadione is prepared by mixing an alcohol solvent and aminohexadione in a mass ratio of 1 to 100:1.

[0008] Preferably, the molar ratio of hydrogen to aminohexanonitrile is 3~50:1.

[0009] Preferably, the mass ratio of platinum to palladium in the platinum-palladium supported catalyst is 1:5 to 5:1, and the total loading of platinum and palladium is 0.1 to 10 wt%. The support for the platinum-palladium supported catalyst is selected from one or a combination of two or more of activated carbon, alumina, and silica.

[0010] Preferably, the preparation of the platinum-palladium supported catalyst includes the following steps: using an equal-volume impregnation method, the support is impregnated in a platinum-palladium mixed precursor salt solution, and then the impregnated support is sequentially dried, calcined, and reduced to obtain the catalyst.

[0011] Preferably, the spray density of the aminohexanonitrile-containing raw material solution is 0.5~10m. 3 / (m 2 h), the volume hourly space velocity (VHSV) of the aminohexanonitrile-containing feed solution is 0.1~5 h⁻¹. -1 .

[0012] Preferably, the volume hourly space velocity of the hydrogen gas is 100-5000 h⁻¹. -1 .

[0013] Preferably, the reaction pressure of the hydrogenation reaction is absolute pressure of 0.5~3MPa, and the reaction temperature of the hydrogenation reaction is 50~90℃.

[0014] Preferably, the heat exchange medium in the shell side of the tubular fixed-bed reactor is demineralized water at 25~95℃.

[0015] The beneficial effects of this invention are: (1) This invention enhances mass transfer by using gas-liquid countercurrent contact, ensuring sufficient hydrogen concentration throughout the bed and avoiding side reactions caused by local hydrogen deficiency in traditional co-current processes. At the same time, the continuously hydrogen-rich reaction environment is conducive to the full utilization of the high cyano hydrogenation activity and hexamethylenediamine selectivity of the platinum-palladium supported catalyst, thereby effectively suppressing side reactions such as intramolecular cyclization, condensation and CN bond hydrogenolysis under alkali-free conditions throughout the process, and simultaneously achieving an aminohexanonitrile conversion rate >98.5% and a hexamethylenediamine selectivity >98.5%.

[0016] (2) The present invention achieves uniform and controllable bed temperature by constant temperature heat transfer of low temperature demineralized water, eliminates the local temperature run-off phenomenon that is easy to be generated by traditional heat transfer oil heat exchange, and further suppresses the side reaction of CN bond hydrogen decomposition.

[0017] (3) No alkaline additives are required throughout the process of this invention. On the one hand, the generation of alkaline waste liquid is eliminated from the source, which greatly reduces the load of waste treatment and environmental protection costs. On the other hand, the product does not contain alkali metal impurities. Combined with the high hexamethylenediamine selectivity of this invention, crude hexamethylenediamine can reach the polymerization grade purity standard by conventional distillation, which significantly simplifies the post-processing process and reduces separation energy consumption.

[0018] (4) The present invention adopts a tubular fixed bed reactor, and the platinum-palladium supported catalyst has high mechanical strength, which effectively avoids catalyst pulverization and loss, and can achieve long-term continuous operation. Detailed Implementation

[0019] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0020] This invention provides a method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile, comprising the following steps: In a tubular fixed-bed reactor, a hydrogenation reaction is carried out by countercurrent contact of a feed liquid containing aminohexanonitrile and hydrogen gas in the presence of a platinum-palladium supported catalyst.

[0021] In fixed-bed hydrogenation processes, although countercurrent contact theoretically has the advantage of enhanced mass transfer, it is rarely used in long-term practice. The main reasons include: (1) the drag effect of the rising gas flow on the falling liquid easily causes flooding, channeling and flow deviation, resulting in a narrow stable operating window; (2) the continuous disturbance of the bed by the rising gas flow intensifies the collision wear and pulverization of catalyst particles, and the fine powder generated can also clog downstream equipment and shorten the operating cycle of the unit; (3) countercurrent operation requires the addition of complex gas-liquid distributors, anti-fluidization internals, etc., which increases the investment and operating costs of supporting equipment. Therefore, industrial-scale production basically adopts the trickle bed operation mode of gas-liquid co-flow (or pre-mixed co-flow feeding). This invention innovatively employs a countercurrent contact mode where the feed liquid flows from top to bottom and hydrogen flows from bottom to top. By using a platinum-palladium supported catalyst with both high catalytic performance and high mechanical strength, and supplemented by a tubular fixed-bed shell-side low-temperature demineralized water isothermal heat transfer system, it effectively overcomes the engineering risks of countercurrent operation. Simultaneously, it solves the dual side reaction inducements in traditional co-current processes: concentrated exothermic heat in the upper section of the bed leading to high-temperature hotspots, and decreased hydrogen partial pressure in the lower section of the bed causing incomplete hydrogenation. This significantly improves feed conversion and target product selectivity. Ultimately, this invention achieves simultaneous aminohexanonitrile conversion and hexamethylenediamine selectivity exceeding 98.5% under mild conditions, and the unit can achieve long-term stable operation for 3000-8000 hours after a single catalyst loading.

[0022] After the hydrogenation reaction is completed, the tail hydrogen discharged from the top of the reactor is separated, condensed, and recycled to replenish fresh hydrogen. The reaction liquid containing hexamethylenediamine collected from the bottom of the reactor is subjected to flash evaporation to recover the solvent and distillation to remove light and heavy components and impurities, thereby obtaining polymer-grade hexamethylenediamine. In this invention, the recovery rate of platinum and palladium precious metals in the spent catalyst is >95%, both the solvent and tail hydrogen can be recycled, the demineralized water heat transfer medium is inexpensive and the by-product low-pressure hot water can be recovered, and the multi-stage synergy reduces the overall operating cost, making it suitable for large-scale industrial production of high-quality hexamethylenediamine.

[0023] In a preferred embodiment, the feed liquid containing aminohexanonitrile is prepared by mixing an alcohol solvent and aminohexanonitrile at a mass ratio of 1 to 100:1. This invention uses an alcohol solvent as the reaction solvent, which can effectively dilute the reaction system, reduce viscosity, and improve gas-liquid-solid mass transfer efficiency. For example, the mass ratio of alcohol solvent to aminohexanonitrile can be 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, etc.; the alcohol solvent can be methanol, ethanol, etc.

[0024] In a preferred embodiment, the molar ratio of hydrogen to aminohexanonitrile is 3 to 50:1. For example, the molar ratio of hydrogen to aminohexanonitrile can be 3:1, 10:1, 20:1, 30:1, 40:1, 50:1, etc.

[0025] In a preferred embodiment, the mass ratio of platinum to palladium in the platinum-palladium supported catalyst is 1:5 to 5:1, and the total loading of platinum and palladium is 0.1 to 10 wt%. The support for platinum-palladium supported catalysts is selected from one or a combination of two or more of activated carbon, alumina, and silica.

[0026] This invention employs a platinum-palladium bimetallic synergistic catalysis method, exhibiting high activity and selectivity for cyano hydrogenation. It achieves efficient catalysis under mild conditions with low loading, reducing exothermic load. Simultaneously, the catalyst possesses high mechanical strength and excellent wear resistance, significantly reducing particle pulverization and loss, ensuring long-term stable operation in countercurrent flow. For example, the mass ratio of platinum to palladium in the platinum-palladium supported catalyst can be 1:5, 1:2, 1:1, 2:1, 5:1, etc.; the total loading of platinum and palladium can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc.

[0027] In a preferred embodiment, the preparation of the platinum-palladium supported catalyst includes the following steps: impregnating the support in a platinum-palladium mixed precursor salt solution using an equal-volume impregnation method, and then sequentially subjecting the impregnated support to drying, calcination, and reduction treatments to obtain the catalyst. This invention employs an impregnation-reduction method for preparing the platinum-palladium supported catalyst. First, the platinum-palladium active components are uniformly adsorbed into the pores of the support through impregnation. Then, residual solvents are removed through drying and calcination, converting the platinum-palladium precursor into oxides. Finally, the platinum-palladium oxides are reduced to a highly active metallic state to obtain the catalyst. This invention does not impose particular limitations on the preparation of the platinum-palladium mixed precursor salt solution or the conditions for impregnation, drying, calcination, and reduction treatment. For example, the platinum-palladium mixed precursor salt solution can be prepared by first preparing a 0.01~1.0 mol / L platinum precursor salt solution and a 0.01~1.0 mol / L palladium precursor salt solution separately, and then mixing them. The impregnation temperature can be 25~60℃, and the impregnation time can be 4~24 h. The drying temperature can be 100~120℃, and the drying time can be 4~12 h. The calcination temperature can be 300~450℃, and the calcination time can be 2~6 h. The reduction treatment temperature can be 200~350℃, and the reduction treatment time can be 2~8 h. The reduction treatment atmosphere can be hydrogen. Furthermore, the molding specifications of the obtained platinum-palladium supported catalyst are not particularly limited; it can be spherical or cylindrical particles with a diameter of 2~5 mm.

[0028] In a preferred embodiment, the spray density of the feed solution containing aminohexanonitrile is 0.5~10 m³. 3 / (m 2 h), the volume hourly space velocity (VHSV) of the feed solution containing aminohexanonitrile is 0.1~5h. -1 For example, the spray density of the feed solution containing aminohexanonitrile can be 0.5 m³. 3 / (m 2 h), 1m 3 / (m 2 h), 2m 3 / (m 2 h), 3m 3 / (m 2 h), 4m 3 / (m 2 h), 5m 3 / (m 2 h), 6m 3 / (m 2 h), 7m 3 / (m 2 h), 8m 3 / (m 2 h), 9m 3 / (m 2 h), 10m 3 / (m 2 h), etc.; the volume hourly space velocity (VHSV) of the feed solution containing aminohexanonitrile can be 0.1 h⁻¹. -1 0.5h -1 1h -1 2h -1 3h -1 4h -1 5h -1 6h -1 7h -1 8h -1 9h -1 10h -1 wait.

[0029] In a preferred embodiment, the volume hourly space velocity (VHSV) of hydrogen is 100–5000 h⁻¹. -1 For example, the volume hourly space velocity (VHSV) of hydrogen can be 100 h⁻¹. -1 500h -1 1000h -1 1500h -1 2000h -1 2500h -1 3000h -1 3500h -1 4000h -1 4500h -1 5000h -1 wait.

[0030] This invention selects and combines liquid-phase feed parameters and gas-phase feed parameters within the above-mentioned range. By controlling the gas-liquid load, the fluid dynamics of the bed are stabilized within a safe operating window far from the flooding zone, which is beneficial for the long-term stable operation of the countercurrent catalytic hydrogenation reaction.

[0031] In a preferred embodiment, the hydrogenation reaction pressure is absolute 0.5~3 MPa, and the hydrogenation reaction temperature is 50~90°C. This invention selects reaction pressures and temperatures within the above ranges to ensure both the hydrogenation reaction rate and selectivity, while the mild temperature and pressure conditions also help maintain the stability of countercurrent operation.

[0032] In a preferred embodiment, the heat exchange medium in the shell side of the tubular fixed-bed reactor is demineralized water at 25-95°C. This invention removes a large amount of heat released from the hydrogenation reaction by isothermal heat transfer using demineralized water at a low temperature of 25-95°C, utilizing both vaporization and sensible heat transfer. This heat transfer method offers high temperature control precision, resulting in a uniform temperature distribution within the bed, eliminating localized temperature runaway, and effectively suppressing CN-bond hydrogenolysis side reactions. Simultaneously, the uniform temperature field ensures the stability of fluid properties within the bed, further enhancing the stability of countercurrent operation and the selectivity of hexamethylenediamine. The demineralized water can be processed using a closed-loop circulation heat exchange mode, and the low-pressure hot water produced as a byproduct during the heat exchange process can be uniformly recycled and reused.

[0033] Preparation Examples 1-3: Preparation of Catalysts Preparation Example 1 Coconut shell activated carbon was used as a carrier, with a platinum to palladium mass ratio of 1:1 and a total platinum and palladium loading of 0.5 wt%.

[0034] Equal volumes of 0.1 mol / L chloroplatinic acid solution and 0.1 mol / L palladium chloride solution (dissolved in 0.1 mol / L dilute hydrochloric acid) were mixed to obtain a platinum-palladium mixed precursor salt solution. Coconut shell activated carbon was pre-dried at 100 °C and impregnated in the platinum-palladium mixed precursor salt solution at 30 °C for 12 h using an equal-volume impregnation method. The impregnated support was first dried at 110 °C for 6 h, then placed in an air atmosphere and calcined at 400 °C for 4 h, and finally placed in a hydrogen atmosphere and reduced at 300 °C for 4 h to obtain a platinum-palladium supported catalyst, denoted as C-1.

[0035] Preparation Example 2 Using γ-Al2O3 as a support, the mass ratio of platinum to palladium was 2:1, and the total loading of platinum and palladium was 3wt%.

[0036] Equal volumes of 0.4 mol / L chloroplatinic acid solution and 0.2 mol / L palladium chloride solution (dissolved in 0.1 mol / L dilute hydrochloric acid) were mixed to obtain a platinum-palladium mixed precursor salt solution. γ-Al2O3 was pre-dried at 100 °C and impregnated in the platinum-palladium mixed precursor salt solution at 40 °C for 8 h using an equal-volume impregnation method. The impregnated support was first dried at 120 °C for 4 h, then placed in an air atmosphere and calcined at 450 °C for 3 h, and finally placed in a hydrogen atmosphere and reduced at 350 °C for 3 h to obtain a platinum-palladium supported catalyst, denoted as C-2.

[0037] Preparation Example 3 Using silica as a carrier, the mass ratio of platinum to palladium is 1:4, and the total loading of platinum and palladium is 8 wt%.

[0038] Equal volumes of 0.2 mol / L chloroplatinic acid solution and 0.8 mol / L palladium chloride solution (dissolved in 0.1 mol / L dilute hydrochloric acid) were mixed to obtain a platinum-palladium mixed precursor salt solution. Silica was pre-dried at 100 °C and impregnated in the platinum-palladium mixed precursor salt solution at 35 °C for 10 h using an equal-volume impregnation method. The impregnated support was first dried at 105 °C for 8 h, then placed in an air atmosphere and calcined at 350 °C for 5 h, and finally placed in a hydrogen atmosphere and reduced at 250 °C for 6 h to obtain a platinum-palladium supported catalyst, denoted as C-3.

[0039] Comparative Preparation Example 1 The difference between this preparation example and Preparation Example 1 is that coconut shell activated carbon is used as the support, the total platinum loading is 0.5 wt%, and the preparation is carried out according to the method of Preparation Example 1 to obtain a platinum single metal supported catalyst, denoted as C-4.

[0040] Example 1 A method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile includes the following steps: The platinum-palladium supported catalyst C-1 from Preparation Example 1 was packed into a tubular fixed-bed reactor. Using methanol as a solvent, methanol and aminohexanonitrile were mixed at a mass ratio of 10:1 to prepare a feed solution containing aminohexanonitrile. The feed solution was then introduced into a 2m... 3 / (m 2 The spray density (h) and 0.5h -1 A volume hourly space velocity (VHSV) of 1000 h⁻¹ is sprayed from the top of the reactor onto the catalyst bed from top to bottom, with hydrogen gas flowing at a velocity of 1000 h⁻¹. -1 The volume hourly space velocity (VHSV) passes through the catalyst bed from bottom to top in the reactor. The molar ratio of hydrogen to aminohexanonitrile is controlled at 10:1, and the reaction pressure is absolute at 1.5 MPa. Deionized water at 55–60 °C is circulated in the shell side of the reactor for heat transfer, and the bed reaction temperature is controlled at 60 °C. The feed liquid containing aminohexanonitrile and hydrogen undergo a countercurrent hydrogenation reaction in the catalyst bed. After 48 hours of stable operation, the reaction liquid was analyzed, showing an aminohexanonitrile conversion rate of 99.2% and a hexamethylenediamine selectivity of 99.0%.

[0041] Example 2 A method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile includes the following steps: The platinum-palladium supported catalyst C-2 from Preparation Example 2 was packed into a tubular fixed-bed reactor. Using ethanol as a solvent, ethanol and aminohexanonitrile were mixed at a mass ratio of 20:1 to prepare a feed solution containing aminohexanonitrile. The feed solution was then pumped into a 3m³... 3 / (m 2 The spray density (h) is 0.8h. -1 A volume hourly space velocity (VHSV) of 1500 h⁻¹ is sprayed from the top of the reactor onto the catalyst bed, with hydrogen gas flowing downwards at a velocity of 1500 h⁻¹. -1The volume hourly space velocity (VHSV) passes through the catalyst bed from bottom to top in the reactor. The molar ratio of hydrogen to aminohexanonitrile is controlled at 15:1, and the reaction pressure is absolute at 2 MPa. Deionized water at 65-70°C is circulated in the reactor shell side for heat transfer, and the bed reaction temperature is controlled at 70°C. The feed liquid containing aminohexanonitrile and hydrogen undergo a countercurrent hydrogenation reaction in the catalyst bed. After 48 hours of stable operation, the reaction liquid was analyzed, showing an aminohexanonitrile conversion rate of 99.5% and a hexamethylenediamine selectivity of 98.8%.

[0042] Example 3 A method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile includes the following steps: The platinum-palladium supported catalyst C-3 from Preparation Example 3 was packed into a tubular fixed-bed reactor. Using methanol as a solvent, methanol and aminohexanonitrile were mixed at a mass ratio of 50:1 to prepare a feed solution containing aminohexanonitrile. The feed solution was then introduced into a 1m³ flow rate. 3 / (m 2 The spray density (h) is 0.3h. -1 A volume hourly space velocity (VHSV) of 800 h⁻¹ is sprayed from the top of the reactor onto the catalyst bed from top to bottom, with hydrogen gas flowing at a velocity of 800 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen gas flows from the bottom of the reactor upwards through the catalyst bed. The molar ratio of hydrogen to aminohexanonitrile is controlled at 20:1, and the reaction pressure is absolute at 0.8 MPa. Deionized water at 45–50 °C is circulated in the shell side of the reactor for heat transfer, and the bed reaction temperature is controlled at 50 °C. The feed liquid containing aminohexanonitrile and hydrogen gas undergo a countercurrent hydrogenation reaction in the catalyst bed. After 48 hours of stable operation, the reaction liquid was analyzed, showing an aminohexanonitrile conversion rate of 98.8% and a hexamethylenediamine selectivity of 98.6%.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that the feeding method is different. In this example, both the raw material liquid and hydrogen are fed from the top of the reactor in a parallel flow from top to bottom. The other steps remain unchanged.

[0044] After the device operated stably for 48 hours, the reaction solution was tested, and the conversion rate of aminohexanonitrile was 97.2%, and the selectivity of hexamethylenediamine was 96.1%.

[0045] Comparative Example 2 This comparative example employs a Raney nickel batch reactor hydrogenation process, comprising the following steps: Methanol and aminohexanonitrile are mixed at a mass ratio of 10:1 using methanol as the solvent. Then, 1% NaOH (by mass of aminohexanonitrile) is added, and the mixture is stirred until homogeneous. The mixture is then transferred to a batch reactor, and Raney nickel catalyst (3% by mass of aminohexanonitrile) is added. The reactor is sealed. The air inside is replaced three times each with nitrogen and hydrogen. Stirring is then initiated, and the temperature is raised to 80°C. Hydrogen is then introduced, maintaining a reaction pressure of 2.5 MPa and a stirring speed of 800 rpm for 4 hours. After the reaction, the reaction solution is filtered and analyzed. The conversion rate of aminohexanonitrile is 98.1%, and the selectivity for hexamethylenediamine is 97.3%.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that the catalyst is different; the platinum monometallic supported catalyst C-4 from Comparative Preparation Example 1 is used in an equal amount to replace the platinum-palladium supported catalyst C-1 from Preparation Example 1. All other steps remain unchanged.

[0047] After the device operated stably for 48 hours, the reaction solution was tested, and the conversion rate of aminohexanonitrile was 97.1%, and the selectivity of hexamethylenediamine was 96.0%.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile, characterized in that, Includes the following steps: In a tubular fixed-bed reactor, a hydrogenation reaction is carried out by countercurrent contact of a feed liquid containing aminohexanonitrile and hydrogen gas in the presence of a platinum-palladium supported catalyst.

2. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The raw material solution containing aminohexanonitrile is prepared by mixing an alcohol solvent and aminohexanonitrile in a mass ratio of 1 to 100:

1.

3. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The molar ratio of hydrogen to aminohexanonitrile is 3~50:

1.

4. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The platinum-palladium supported catalyst has a platinum to palladium mass ratio of 1:5 to 5:1, and the total loading of platinum and palladium is 0.1 to 10 wt%. The support for the platinum-palladium supported catalyst is selected from one or a combination of two or more of activated carbon, alumina, and silica.

5. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile as described in claim 1 or 4, characterized in that, The preparation of the platinum-palladium supported catalyst includes the following steps: using an equal-volume impregnation method, the support is impregnated in a platinum-palladium mixed precursor salt solution, and then the impregnated support is successively dried, calcined, and reduced to obtain the catalyst.

6. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The spray density of the aminohexanonitrile-containing feed solution is 0.5~10 m³. 3 / (m 2 h), the volume hourly space velocity (VHSV) of the aminohexanonitrile-containing feed solution is 0.1~5 h⁻¹. -1 .

7. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The volume hourly space velocity of the hydrogen gas is 100-5000 h⁻¹. -1 .

8. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The reaction pressure of the hydrogenation reaction is absolute pressure 0.5~3MPa, and the reaction temperature of the hydrogenation reaction is 50~90℃.

9. The method for preparing hexamethylenediamine by hydrogenation of aminohexanonitrile according to claim 1, characterized in that, The heat exchange medium in the shell side of the tubular fixed-bed reactor is demineralized water at 25~95℃.