Method for preparing hexamethylenediamine through nitrile hydrogenation

Abstract

The invention discloses a method for preparing hexamethylenediamine through nitrile hydrogenation, which comprises the following steps: carrying out hydrogenation reaction on adiponitrile to obtain reaction liquid, and then carrying out post-treatment to obtain the hexamethylenediamine, wherein the hydrogenation reaction system further comprises an adsorbent and mother liquor generated in the post-treatment process. According to the method, the mother liquor containing impurities such as azaheptyl ring Schiff base and nitrile hydrolysis ammoniation byproduct amide is returned to the reactor, and the adsorbent is added in the reaction, so that compared with a production process in which the mother liquor is not recycled, the content of the reaction byproduct AMCPA can be reduced to 5 mg / kg or below, and the polarogram value of the hexamethylenediamine product is smaller than or equal to 20 mmol IB / t-HMD.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing hexamethylenediamine by hydrogenating nitrile. Background Art

[0002] Hexamethylenediamine (HMD) is a versatile compound, common applications are in the preparation of polyamides such as nylon 66 and hexamethylene diisocyanate.

[0003] At present, the main raw material for preparing hexamethylenediamine is adiponitrile. The mainstream process routes for adiponitrile include butadiene cyanation, acrylonitrile electrolysis, and adipic acid amination. All of the above process routes contain an impurity, iminocyclopentanenitrile (ICCP). According to known literature or patents, such as GB1367006, 2-aminomethylcyclopentylamine (AMCPA) generated by hydrogenation of ICCP is difficult to separate from hexamethylenediamine. This impurity will cause the downstream product nylon 66 to have low strength and high color number.

[0004] On the other hand, in addition to the influence of impurities such as AMCPA on the quality of hexamethylenediamine products, another key indicator of hexamethylenediamine is the polarographic value. The impurities that affect the polarographic value mainly include aza-heptane Schiff base (THA), 6-aminocapronitrile, amide, etc. Among them, THA aza-heptane Schiff base has two sources, one is produced from the reaction, and the other is generated by thermal decomposition of materials during the distillation process, so it is difficult to completely remove it from the product by distillation; amide is mainly produced by hydrolysis and amination of nitrile, both of which have an impact on the polarographic value of the product. The traditional control method is to discharge the mother liquor at the bottom of the tower containing the above impurities, resulting in product waste.

[0005] Therefore, it is necessary to develop new technologies to reduce the impact of impurities introduced into raw materials and generated during the distillation process on product quality. Summary of the invention

[0006] In view of the influence of impurities generated during the introduction of raw materials and distillation on product quality in the prior art, the present invention aims to provide a method for preparing hexamethylenediamine by hydrogenating nitrile, wherein the mother liquor generated during the post-treatment process is returned to the reactor and an adsorbent is added at the same time. Compared with the production process that does not adopt the present invention and recycles the mother liquor, the content of by-product AMCPA in the hydrogenation reaction liquid can be reduced to less than 5 mg / kg, and the polarographic value of the hexamethylenediamine product is ≤20 mmol IB / t-HMD.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing hexamethylenediamine by hydrogenating nitrile, wherein the method comprises the following steps: carrying out a hydrogenation reaction on adiponitrile to obtain a reaction liquid, and then performing post-treatment to prepare the product; wherein the hydrogenation reaction system further comprises an adsorbent and a mother liquid produced in the post-treatment process.

[0009] In one embodiment, the mother liquor produced in the post-treatment process mainly comprises hexamethylenediamine, cyclohexylimine, 1,2-cyclohexamethylenediamine, N-ethylhexamethylenediamine, Schiff base, amide, etc.; wherein the Schiff base is mainly azaheptyl Schiff base, and the amide is mainly valeramide, hexamethylenediamine, adipic acid amide, etc.;

[0010] Specifically, the mother liquor contains 10 to 5000 mg / kg of azepine Schiff base and 10 to 5000 mg / kg of amide. Specifically, the content of azepine Schiff base includes but is not limited to 10 mg / kg, 30 mg / kg, 50 mg / kg, 100 mg / kg, 500 mg / kg, 1000 mg / kg, 1500 mg / kg, 2000 mg / kg, 2500 mg / kg, 3000 mg / kg, 3500 mg / kg, 4000 mg / kg, 4500 mg / kg. The content of amide includes but is not limited to 10 mg / kg, 30 mg / kg, 50 mg / kg, 100 mg / kg, 500 mg / kg, 1000 mg / kg, 1500 mg / kg, 2000 mg / kg, 2500 mg / kg, 3000 mg / kg, 3500 mg / kg, 4000 mg / kg, 4500 mg / kg, 5000 mg / kg or the range composed of any two thereof.

[0011] The mother liquor produced in the post-treatment process is a mother liquor obtained by post-treatment of a reaction liquid obtained by hydrogenation of adiponitrile; the mother liquor produced in the post-treatment process can be directly returned to the reactor by setting a bypass to circulate and participate in the hydrogenation reaction, or can be recovered and applied to the next batch of reactions, or can be collected and stored for use in other production lines, and the present invention has no special requirements for this;

[0012] In some specific implementation processes, the post-treatment process includes desolventizing, dehydrating, decoking, delightening, refining and other steps. Accordingly, the mother liquor generated by the post-treatment process after each step includes but is not limited to desolventizing mother liquor, dehydrating mother liquor, decoking mother liquor, product tower bottom mother liquor and the like.

[0013] In one embodiment, the post-treatment process ultimately obtains hexamethylenediamine from the top of the product tower, and the total content of aza-heptyl Schiff base and amide in the mother liquor at the bottom of the product tower is ≤500 mg / kg, for example including but not limited to 500 mg / kg, 450 mg / kg, 400 mg / kg, 350 mg / kg, 300 mg / kg, 250 mg / kg, 200 mg / kg, 150 mg / kg, 100 mg / kg, 50 mg / kg, 30 mg / kg, 20 mg / kg, 10 mg / kg, 1 mg / kg or not detected, etc.

[0014] In one embodiment, the amount of mother liquor added from the post-treatment process is 0.01 to 50 wt% of the amount of adiponitrile feed, for example including but not limited to 0.01 wt%, 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt% or any range therebetween, preferably 1 to 20 wt%.

[0015] In one embodiment, the adsorbent is selected from one or more of magnesium oxide (nano magnesium oxide), activated alumina, diatomaceous earth, calcium carbonate, activated carbon, etc.

[0016] Preferably, the pH value of the adsorbent may be 7.0 to 14.0, for example including but not limited to 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0 or a range between any two thereof, preferably 8 to 12;

[0017] Preferably, the specific surface area of ​​the adsorbent is 50 to 500 m 2 / g, for example, but not limited to 50m 2 / g、100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 350m 2 / g, 400m 2 / g, 450m 2 / g、500m 2 / g or any range between them, preferably 100 to 300 m 2 / g;

[0018] Preferably, the BET pore size of the adsorbent may be 3 to 100 nm, for example including but not limited to 3 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or a range between any two thereof, preferably 5 to 20 nm;

[0019] Preferably, the average particle size of the adsorbent can be 10 to 1000um, for example, including but not limited to 10um, 50um, 100um, 200um, 300um, 400um, 500um, 600um, 700um, 800um, 900um, 1000um or a range between any two of them, preferably 20 to 80um.

[0020] In one embodiment, the adsorbent is added in an amount of 0.01 to 1 wt% of the adiponitrile feed, for example including but not limited to 0.01 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt% or any range therebetween, preferably 0.005 to 0.05 wt%.

[0021] The method for preparing hexamethylenediamine by hydrogenation of nitrile of the present invention, the adiponitrile raw material can be obtained by conventional methods in the art, for example, commercially obtained or self-made adiponitrile by conventional methods in the art, and the self-made method can be butadiene method, acrylonitrile method, adipic acid method, etc.; limited by factors such as preparation process, the commercially purchased or self-made adiponitrile raw material by conventional methods in the art usually has trace impurities such as iminocyclopentanenitrile (ICCP) remaining, and generally speaking, the commercially purchased or self-made adiponitrile raw material usually contains 10 to 100 mg / kg of ICCP. 2-aminomethylcyclopentylamine (AMCPA) generated by hydrogenation of ICCP is difficult to separate from hexamethylenediamine, and the impurity will cause the strength of downstream products such as nylon 66 to decrease and the color number to increase.

[0022] The present invention experimentally found that by adding a certain adsorbent to the reaction, ICCP in the raw material, amides and other impurities generated in the mother liquor and the reaction can be enriched into the adsorbent pores by chemical adsorption at the reaction temperature, thereby avoiding the hydrogenation of impurities to generate undesirable by-product AMCPA, reducing the poisoning of the catalyst, and reducing the amount of by-products generated. At the same time, the azepine Schiff base introduced into the mother liquor can be hydrogenated to generate cycloheximide (HMI), which is easy to separate from the product, thereby reducing the product polarographic value.

[0023] In one embodiment, the hydrogenation reaction has a reaction temperature of 60 to 100°C, preferably 65 to 85°C; and a reaction pressure of 1.5 to 5MPa, preferably 2.0 to 3.5MPa; specifically, the reaction temperature includes but is not limited to 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or a range between any two thereof, and the reaction temperature includes but is not limited to 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa, or a range between any two thereof;

[0024] Preferably, the feed space velocity is 0.5-5 g / g cat. / h based on the total amount of adiponitrile and the mother liquor produced in the post-treatment process, for example, including but not limited to 0.5 g / g cat. / h, 1 g / g cat. / h, 1.5 g / g cat. / h, 2 g / g cat. / h, 2.5 g / g cat. / h, 3 g / g cat. / h, 3.5 g / g cat. / h, 4 g / g cat. / h, 4.5 g / g cat. / h, 5 g / g cat. / h or a range composed of any two thereof; more preferably, the reaction is stopped after the feeding is completed by continuing the insulation reaction for 5-30 min, for example, including but not limited to 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min or a range composed of any two thereof;

[0025] During the above hydrogenation reaction, the amount of hydrogen added satisfies the reaction pressure (ie, hydrogen is charged into the reactor and the hydrogen is pressurized to a preset reaction pressure).

[0026] In one embodiment, the hydrogenation reaction system further comprises raw materials such as solvents, catalysts, and additives;

[0027] Specifically, a method for preparing hexamethylenediamine by hydrogenating nitrile is to mix adiponitrile with a solvent, a catalyst, an auxiliary agent, an adsorbent and a mother liquor produced in a post-treatment process, introduce hydrogen to carry out a hydrogenation reaction to obtain a reaction liquid, and then carry out post-treatments such as desolvation, dehydration, decoking, light removal, and refining to obtain hexamethylenediamine. The relevant conditions of the reaction are defined in the foregoing. For other operation and process conditions in the preparation method of the present invention, and the devices used therein, all can be selected according to the corresponding conventional methods in the art, and there is no particular limitation on this. The technician can optimize the process based on the known process in the prior art according to actual needs. Specifically, for example, the conditions listed in the following embodiments of the present invention can be used.

[0028] In one embodiment, the catalyst is selected from one or more of a skeleton nickel or skeleton cobalt catalyst, preferably a skeleton nickel catalyst;

[0029] Preferably, the catalyst is added in an amount of 5 to 50 wt% of the amount of adiponitrile, for example including but not limited to 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt% or any range therebetween, preferably 15 to 30 wt%.

[0030] In the actual production process, part of the catalyst in the reactor needs to be replaced regularly to maintain the reaction activity. During the catalyst discharge process, the adsorbent in the system can be discharged from the reactor together with the catalyst, and then the catalyst and adsorbent in the system are adjusted to the required amount.

[0031] In one embodiment, the solvent can be selected conventionally in the field, and there is no special requirement for its type and amount. For example, the solvent can be one or more of methanol, ethanol, propanol, isopropanol, tetrahydrofuran, etc., preferably ethanol and / or methanol; preferably, the amount of the solvent added is 0.2 to 5 times the mass of adiponitrile, for example, including but not limited to 0.2 times, 0.5 times, 1 times, 2 times, 3 times, 4 times, 5 times or a range composed of any two thereof.

[0032] In one embodiment, the auxiliary agent is selected from one or more of NaOH, KOH, CsOH, tetramethylammonium hydroxide, etc.; preferably, the amount of the auxiliary agent added is 0.1 to 5 wt% of the amount of adiponitrile, for example, including but not limited to, for example, including but not limited to 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt% or a range composed of any two thereof or a range composed of any two thereof.

[0033] In one embodiment, according to the method for preparing hexamethylenediamine by hydrogenation of nitrile as described above, a conventional reactor in the art can be used for hydrogenation reaction. For example, the reactor used can be a gas-liquid-solid three-phase fluidized bed reactor or a kettle reactor, preferably a kettle reactor.

[0034] After the hydrogenation reaction described above in the present invention is stopped, the mother liquor composition is sampled and analyzed. Based on the mass ratio after removing the solvent, the by-product AMCPA content is reduced to less than 5 mg / kg.

[0035] After the hydrogenation reaction is stopped, the hexamethylenediamine is prepared by post-treatments such as desolvation, dehydration, decoking, light removal, and refining, wherein the post-treatments such as desolvation, dehydration, decoking, light removal, and refining are conventional operations in the field, and the parameters can be designed in common ways, which will not be described in detail. The polarographic value of the hexamethylenediamine product thus prepared can be reduced to less than 20 mmol IB / t-HMD, and in the polarographic value unit, IB represents isobutyraldehyde.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. By feeding the mother liquor generated in the post-treatment process into the reactor for reuse, the discharge of the distillation mother liquor can be reduced, thereby reducing the waste of hexamethylenediamine products and improving the economic efficiency of the product.

[0038] 2. By adding an adsorbent to the reaction system, impurities such as ICCP and amide can be enriched in the pores of the adsorbent at the reaction temperature, thereby avoiding the hydrogenation of impurities to generate undesirable byproduct AMCPA and reducing the poisoning of the catalyst. At the same time, the impurity aza-heptyl Schiff base can be converted into HMI by hydrogenation and easily separated from the product, thereby obtaining a low polarographic value product. DETAILED DESCRIPTION

[0039] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0040] Unless otherwise specified, the reagents, materials, instruments and analytical methods used in the following examples are conventional reagents, conventional materials, conventional instruments and conventional analytical methods in the art, which can be obtained commercially, and the reagents involved can also be synthesized by conventional methods in the art. The specific conditions of the experimental methods not shown in the following examples are all conventional operating conditions.

[0041] The main sources of raw materials are as follows:

[0042]

[0043] The mother liquor produced by the post-treatment process of the adiponitrile hydrogenation reaction includes desolventizing, dehydrating, decoking, light removal, refining, etc. The mother liquor obtained is specifically as follows:

[0044] Desolventizing mother liquor: azepine Schiff base 125 mg / kg, amide content 4517 mg / kg;

[0045] Dehydrated mother liquor: Azaheptane Schiff base 113 mg / kg, amide content 4871 mg / kg;

[0046] Decoking mother liquor: 198 mg / kg of aza-heptyl Schiff base, 3846 mg / kg of amide content;

[0047] Product tower mother liquor: 98 mg / kg of aza-heptyl Schiff base and 2563 mg / kg of amide content;

[0048] Light removal mother liquor: Azaheptane Schiff base 87 mg / kg, amide content 2351 mg / kg.

[0049] In the following examples, the reaction liquid components were analyzed by gas chromatography under the following conditions: Agilent DB-5 chromatographic column, inlet temperature 280°C, FID detector temperature 300°C, column flow rate 1.5 ml / min, hydrogen flow rate 30 ml / min, air flow rate 400 ml / min, and the programmed temperature was maintained at 50°C for 2 min, increased to 80°C at 5°C / min, and then increased to 280°C at 15°C / min and maintained for 10 min.

[0050] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0051] Example 1

[0052] Add 300 g of ethanol, 3 g of NaOH, 30 g of Raney nickel catalyst (wet weight), 0.1 g of magnesium oxide powder (pH = 8-10, average particle size 30 μm, specific gravity 198 μm) into the reactor. 2 / g, pore size 5.6nm), adiponitrile and desolventizing mother liquor were fed at a space velocity of 0.5g / gcat. / h, and hydrogen was passed through and the temperature was increased to carry out hydrogenation reaction.

[0053] The reaction conditions are: 85°C, 2.5MPa, the feed amount is 200g of adiponitrile, and the desolventizing mother liquor is 40g. After the feeding is completed, the reaction is extended for 10min to stop the reaction. The composition of the reaction liquid is sampled and analyzed to remove the solvent ratio. The HMD content is 98.8wt% and the AMCPA content is 1mg / kg.

[0054] The reaction liquid is successively subjected to desolventizing, dehydrating, decoking, light removing and refining, and a mother liquor at the bottom of a refining tower (i.e., a product tower) is obtained, wherein the total content of THA and amide is 426 mg / kg. A hexamethylenediamine product is obtained from the top of the tower, and the polarographic value is 15 mmol IB / t-HMD.

[0055] Example 2

[0056] Add 300 g methanol, 6 g KOH, 60 g Raney nickel catalyst (wet weight), 0.02 g activated carbon powder (pH = 7-10, average particle size 300 μm, specific gravity 495 μm) into the reactor. 2 / g, pore size 3nm), adiponitrile and dehydrated mother liquor were fed at a space velocity of 1.5g / gcat. / h, and hydrogen was introduced for hydrogenation reaction.

[0057] The reaction conditions were: 60° C., 5 MPa, a feed amount of 200 g of adiponitrile and 32 g of dehydrated mother liquor. After the feed was completed, the reaction was extended for 5 min to stop the reaction. The composition of the reaction liquid was sampled and analyzed to remove the solvent ratio. The HMD content was 99.0 wt % and the AMCPA content was 3 mg / kg.

[0058] The reaction liquid is successively subjected to desolventizing, dehydrating, decoking, light removing and refining, and a product tower bottom mother liquor is obtained at the bottom of a refining tower, wherein the total content of THA and amide is 357 mg / kg, and a hexamethylenediamine product is obtained from the top of the tower, and the polarographic value is 10 mmol IB / t-HMD.

[0059] Example 3

[0060] Add 300 g of ethanol, 2 g of CsOH, 20 g of Raney nickel catalyst (wet weight), 1 g of γ-alumina powder (pH = 7-8, average particle size 10 μm, specific gravity 70 μm) into the reactor. 2 / g, pore size 9nm), adiponitrile and decoking mother liquor were fed at a space velocity of 2.5g / g cat. / h, and hydrogen was introduced for hydrogenation reaction.

[0061] The reaction conditions are: 71°C, 4.6MPa, the feed amount is 200g of adiponitrile, and the decoking mother liquor is 20g. After the feeding is completed, the reaction is extended for 15min to stop the reaction. The composition of the reaction liquid is sampled and analyzed to remove the solvent ratio. The HMD content is 98.7wt% and the AMCPA content is 4mg / kg.

[0062] The reaction liquid is successively subjected to desolventizing, dehydrating, decoking, light removing and refining to obtain a product tower bottom mother liquor at the bottom of a refining tower, wherein the total content of THA and amide is 475 mg / kg, and a hexamethylenediamine product is obtained from the top of the tower, and the polarographic value is 16 mmol IB / t-HMD.

[0063] Example 4

[0064] Add 300 g of ethanol, 4 g of tetramethylammonium hydroxide pentahydrate, 40 g of Raney nickel catalyst (wet weight), 0.4 g of diatomaceous earth powder (pH = 7-8, average particle size 50 μm, specific surface area 92 μm) into the reactor. 2 / g, pore size 8.6nm), adiponitrile and product tower mother liquor are fed at a space velocity of 4g / g cat. / h, and hydrogen is introduced for hydrogenation reaction.

[0065] The reaction conditions are: 90°C, 3.3MPa, the feed amount is 200g of adiponitrile, and the product tower mother liquor is 10g. After the feeding is completed, the reaction is extended for 30min to stop the reaction. The composition of the reaction liquid is sampled and analyzed to remove the solvent ratio. The HMD content is 98.5wt% and the AMCPA content is 3mg / kg.

[0066] The reaction liquid is successively subjected to desolventizing, dehydrating, decoking, light removing and refining, and a product tower bottom mother liquor is obtained at the bottom of a refining tower, wherein the total content of THA and amide is 481 mg / kg, and a hexamethylenediamine product is obtained from the top of the tower, and the polarographic value is 19 mmol IB / t-HMD.

[0067] Example 5

[0068] Add 300g methanol, 1g NaOH, 10g Raney nickel catalyst (wet weight), 2g calcium carbonate powder (pH = 8-9, average particle size 25um, specific surface area 55m) into the reactor. 2 / g, pore size 50nm), adiponitrile and light removal mother liquor were fed at a space velocity of 5g / g cat. / h, and hydrogen was introduced for hydrogenation reaction.

[0069] The reaction conditions are: 100°C, 1.5 MPa, a feed amount of 200 g of adiponitrile, and 2 g of light mother liquor. After the feeding is completed, the reaction is extended for 20 minutes to stop the reaction. The composition of the reaction liquid is sampled and analyzed to remove the solvent ratio. The HMD content is 98.8wt% and the AMCPA content is 2mg / kg.

[0070] The reaction liquid is successively subjected to desolventizing, dehydrating, decoking, light removing and refining, and a product tower bottom mother liquor is obtained at the bottom of a refining tower, wherein the total content of THA and amide is 465 mg / kg, and a hexamethylenediamine product is obtained from the top of the tower, and the polarographic value is 16 mmol IB / t-HMD.

[0071] Comparative Example 1

[0072] Refer to the method of Example 4, the only difference is that no adsorbent is added to the hydrogenation reaction, and other operations and conditions remain unchanged. The composition of the reaction liquid was sampled and analyzed, and the solvent ratio was removed, where the HMD content was 96.3wt%, and the AMCPA content was 20mg / kg. The total content of THA and amide in the mother liquor at the bottom of the desolvation product tower was 992mg / kg, and the polarographic value of the product obtained by distillation was 59mmol IB / t-HMD.

[0073] Comparative Example 2

[0074] The method of Example 4 is referred to, except that the recovered post-treatment mother liquor is not added to the reaction system, and other operations and conditions remain unchanged.

[0075] The composition of the reaction solution was analyzed by sampling, and the HMD content was 98.5wt% and the AMCPA content was 17mg / kg after removing the solvent. The total content of THA and amide in the mother liquor at the bottom of the tower after desolventization was 1257mg / kg, and the polarographic value of the product obtained by distillation was 80mmol IB / t-HMD.

[0076] Comparative Example 3

[0077] Refer to the method of Example 4, except that no adsorbent and mother liquor are added, and other operations and conditions remain unchanged.

[0078] The composition of the reaction solution was analyzed by sampling, and the HMD content was 98.5wt% and the AMCPA content was 28mg / kg after removing the solvent. The total content of THA and amide in the mother liquor at the bottom of the tower after desolventization was 1381mg / kg, and the polarographic value of the product obtained by distillation was 95mmol IB / t-HMD.

[0079] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing hexamethylenediamine by hydrogenating nitrile, characterized in that: The reaction liquid is obtained by hydrogenating adiponitrile and then post-processed to obtain the product; wherein the hydrogenation reaction system also includes an adsorbent and a mother liquid generated in the post-processing process.

2. The method according to claim 1, characterized in that The mother liquor produced in the post-treatment process contains 10-5000 mg / kg of azepane Schiff base and 10-5000 mg / kg of amide.

3. The method according to claim 1 or 2, characterized in that: The amount of the mother liquor generated in the post-treatment process is 0.01 to 50 wt % of the adiponitrile feed, preferably 1 to 20 wt %.

4. The method according to claim 1, characterized in that: The adsorbent is selected from one or more of magnesium oxide, activated alumina, diatomaceous earth, calcium carbonate, activated carbon, etc. Preferably, the pH value of the adsorbent may be 7.0 to 14.0, preferably 8 to 12; Preferably, the specific surface area of ​​the adsorbent is 50 to 500 m 2 / g, preferably 100 to 300 m 2 / g; Preferably, the BET pore size of the adsorbent may be 3 to 100 nm, preferably 5 to 20 nm; Preferably, the average particle size of the adsorbent may be 10 to 1000 um, preferably 20 to 80 um.

5. The method according to claim 1 or 4, characterized in that: The adsorbent addition amount is 0.01-1 wt % of the adiponitrile feed amount, preferably 0.005-0.05 wt %.

6. The method according to claim 1, characterized in that The hydrogenation reaction has a reaction temperature of 60 to 100°C, preferably 65 to 85°C; a reaction pressure of 1.5 to 5 MPa, preferably 2.0 to 3.5 MPa; Preferably, the feed space velocity is 0.5 to 5 g / gcat. / h based on the total amount of adiponitrile and mother liquor produced in the post-treatment process; more preferably, the reaction is stopped after the reaction is continued for 5 to 30 minutes after the feeding is completed.

7. The method according to claim 1, characterized in that The hydrogenation reaction system comprises a catalyst, wherein the catalyst is selected from one or more of a skeleton nickel catalyst or a skeleton cobalt catalyst, preferably a skeleton nickel catalyst; Preferably, the catalyst is added in an amount of 5 to 50 wt %, preferably 15 to 30 wt %, of the amount of adiponitrile used.

8. The method according to claim 1, characterized in that The hydrogenation reaction system comprises a solvent, and the solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, and tetrahydrofuran, preferably ethanol and / or methanol; Preferably, the amount of the solvent added is 0.2 to 5 times the mass of adiponitrile.

9. The method according to claim 1, characterized in that: The hydrogenation reaction system comprises an auxiliary agent, and the auxiliary agent is selected from one or more of NaOH, KOH, CsOH, and tetramethylammonium hydroxide; Preferably, the amount of the auxiliary agent added is 0.1 to 5 wt % of the amount of adiponitrile used.

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