A process for the preparation of hexamethylenediamine

Abstract

The application discloses a preparation method of hexamethylene diamine, which comprises the following steps: 1) catalyst pretreatment: mixing a hydrogenation catalyst and a modifier, and treating under a nitrogen atmosphere for 0.5-2h to obtain a modified catalyst; and 2) hydrogenation reaction: hydrogenating adiponitrile into hexamethylene diamine in the presence of the modified catalyst. The hexamethylene diamine prepared by the method has the advantages of good catalyst stability, high product yield and low DCH generation amount, and the problem of frequent shutdown of a device can be avoided due to the non-introduction of inorganic alkali.

Description

Technical Field

[0001] This invention relates to a preparation method, and more particularly to a method for preparing hexamethylenediamine. Background Technology

[0002] Hexamethylenediamine is an important chemical raw material, mainly used in the production of nylon 66 and HDI (1,6-hexamethylenediisocyanate). Currently, there are two main industrial production methods for hexamethylenediamine: the high-pressure method and the low-pressure method.

[0003] The low-pressure process offers mild conditions and high safety, making it the preferred choice for most manufacturers both domestically and internationally. This process typically uses nickel or cobalt catalysts. While nickel catalysts are cheaper than cobalt catalysts, as reported in the literature "Deactivation of nitrilehydrogenation catalysts: New mechanistic insight from a nylon recycle process," nickel catalysts require the addition of inorganic bases such as NaOH or KOH as co-catalysts during use; otherwise, they will rapidly deactivate. However, a significant drawback is that during post-processing, as moisture is removed, inorganic bases precipitate and adhere to the inner walls of process pipelines and the trays of the distillation column. This necessitates periodic shutdowns for water distillation to remove the bases, impacting the operation of the unit.

[0004] To address this issue, patents CN108084035A and CN109647419A disclose Ni / Al2O3 catalysts modified with rare earth metal oxides and alkaline earth metal oxides for the hydrogenation reaction of adiponitrile, which can avoid the addition of inorganic base co-catalysts from the source; however, the yield of hexamethylenediamine is low. Patent CN116178174A discloses a low-energy-consumption method for purifying hexamethylenediamine. This method uses an ionic liquid to extract hexamethylenediamine from the alkaline aqueous phase before distillation, achieving the purpose of removing alkali and avoiding a series of problems in subsequent distillation. However, the preparation and processing of ionic liquids are complex.

[0005] Another prominent problem in the process of preparing hexamethylenediamine by hydrogenation of adiponitrile is the generation of the byproduct 1,2-cyclohexamethylenediamine (DCH). The boiling points of DCH and the product hexamethylenediamine are very close, making separation difficult and resulting in high energy consumption and product loss during purification.

[0006] Patent CN115335356A discloses a method for hydrogenating adiponitrile using Raney nickel as a catalyst and KOH and basic compounds (including basic hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide) as co-catalysts. CN115298161A discloses a method for modifying Raney nickel catalysts using CO or CO2 in a liquid medium. Both methods can reduce DCH production to some extent, but their effects are limited, with DCH content still exceeding 1000 ppm. Furthermore, the catalyst activity decreases significantly after modification with CO or CO2. Summary of the Invention

[0007] To address the above technical problems, this invention proposes a method for preparing hexamethylenediamine. The method for preparing hexamethylenediamine using this invention offers advantages such as good catalyst stability, high product yield, and low DCH formation, and avoids frequent plant shutdowns by eliminating the need for inorganic bases.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing hexamethylenediamine includes the following steps:

[0010] 1) Catalyst pretreatment: The hydrogenation catalyst and the modifier are mixed and treated under a nitrogen atmosphere for 0.5-2 hours to obtain the modified catalyst;

[0011] 2) Hydrogenation reaction: In the presence of a modified catalyst, adiponitrile is hydrogenated to produce hexamethylenediamine;

[0012] The modifier is water and / or alcohol with an adiponitrile content of 50-200 ppm;

[0013] Preferably, the amount of the modifier added is 5-50 times the mass of the hydrogenation catalyst.

[0014] It has been surprisingly discovered that pretreating hydrogenation catalysts with a modifier containing trace amounts of adiponitrile can maintain catalyst activity to a certain extent, improve the catalyst's stable operating cycle, and, most notably, significantly reduce the amount of DCH generated, which is beneficial for improving product quality and yield.

[0015] As a preferred embodiment, the reaction conditions for the hydrogenation of adiponitrile are: reaction temperature 50-100℃, preferably 70-90℃, hydrogen partial pressure during the reaction is 1-8MPa, preferably 2-5MPa, gauge pressure.

[0016] As a preferred embodiment, the adiponitrile hydrogenation reaction is carried out in a mixed solvent composed of liquid ammonia and water; liquid ammonia and water as a mixed solvent is the main alternative to conventional inorganic bases in this invention, on the one hand maintaining an alkaline environment, and on the other hand extracting the product hexamethylenediamine into the aqueous phase to accelerate the reaction.

[0017] Preferably, the mass ratio of liquid ammonia to water in the mixed solvent is (3-50):1, more preferably (6-30):1.

[0018] As a preferred embodiment, in step 2), the mass ratio of adiponitrile to the mixed solvent is 1:(1-6), preferably 1:(2-4).

[0019] Preferably, the feed flow rate of the adiponitrile is 0.5-20 g / g. cat h, preferably 0.5-12g / g cat ·h.

[0020] As a preferred embodiment, the hydrogenation reaction is carried out in a fluidized bed, fixed bed, or stirred reactor, and optionally in a batch, continuous, or semi-continuous reaction mode; the corresponding catalyst feeding method is a one-time feeding, and the powdered catalyst or the molded catalyst can be added to the reactor at once, depending on the reactor type.

[0021] In a preferred embodiment, the hydrogenation catalyst is selected from one or more of Raney nickel and supported metal Ni catalysts.

[0022] In a preferred embodiment, the hydrogenation catalyst is a SiO2-supported metal Ni catalyst prepared by direct reduction method;

[0023] Preferably, in the above catalyst, the loading of metallic Ni in the support is 20-40 wt%.

[0024] As a preferred embodiment, the direct reduction method specifically comprises:

[0025] The precursor of metallic Ni was dissolved in water and SiO2 support was added. The mixture was ultrasonically treated at room temperature for 1-2 hours, filtered and dried to obtain catalyst powder, which was then optionally prepared into a molded body.

[0026] Preferably, the drying conditions are: drying at 60-100℃ for 12-24 hours.

[0027] In this invention, the Ni / SiO2 catalyst prepared by direct reduction can retain the structure of nickel silicate, which can serve as a catalyst anchoring agent, to the greatest extent, thereby significantly improving the catalyst activity and stability. Combined with the modification treatment of the modifier mentioned above, the stability of the catalyst after long-term use is comprehensively improved, the amount of DCH generated is reduced, and the product yield and quality are improved.

[0028] In a preferred embodiment, the precursor of metallic Ni is one or more of Ni nitrate, sulfate, and hydrochloride.

[0029] As a preferred embodiment, the SiO2-supported Ni catalyst prepared by the direct reduction method is applied to the hydrogenation reaction after being activated by hydrogen.

[0030] For example, the reaction conditions for hydrogen activation can be to activate the catalyst with pure hydrogen at 300-400°C for 8-12 hours. Since hydrogen activation is a relatively conventional catalyst activation method in the art, it will not be described in detail here. The above is merely one of the feasible operating conditions applicable to this reaction provided by the present invention, but it should not be construed as any limitation on the protection of this invention.

[0031] The hydrogenation preparation of hexamethylenediamine using the method of this invention not only features high catalyst activity, few byproducts, and high product selectivity, but also long catalyst lifetime and good stability, which is beneficial for extending the reaction cycle. Furthermore, compared with conventional techniques, this method avoids the use of inorganic bases, solving the problems of complex post-processing and long downtime cleaning cycles in existing technologies, and has significant advantages in application. Detailed Implementation

[0032] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0033] Unless otherwise specified, the raw materials and reagents used in the following examples and comparative examples were all purchased through commercial channels.

[0034] In the following embodiments, the reaction solution was analyzed by gas chromatography under the following conditions: Agilent DB-5 column, injection port 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 temperature program as follows: hold at 50°C for 2 min, increase to 80°C at 5°C / min, then increase to 280°C at 15°C / min and hold for 10 min.

[0035] The hydrogenation catalysts provided in the following preparation examples were all activated for 10 hours in a hydrogen environment at 350°C before being used in the hydrogenation reaction.

[0036]

Preparation of Example 1

[0037] Preparation of hydrogenation catalyst C1:

[0038] 14.9 g of Ni(NO3)2·6H2O was dissolved in 20.0 g of deionized water, and 10.0 g of SiO2 support was weighed and added to the solution. The solution mixture was sonicated at room temperature for 2 h, filtered, and then dried in an oven at 80 °C for 12 h to obtain the hydrogenation catalyst C1.

[0039]

Preparation of Example 2

[0040] Preparation of hydrogenation catalyst C2:

[0041] 9.9 g of Ni(NO3)2·6H2O was dissolved in 13.4 g of deionized water, and 8.0 g of SiO2 support was weighed and added to the solution. The solution mixture was sonicated at room temperature for 1 h, filtered, and then dried in an oven at 80 °C for 24 h to obtain the hydrogenation catalyst C2.

[0042] [Preparation Example 3]

[0043] Preparation of hydrogenation catalyst C3:

[0044] 19.8 g of Ni(NO3)2·6H2O was dissolved in 26.7 g of deionized water, and 10.0 g of SiO2 support was weighed and added to the solution. The solution mixture was sonicated at room temperature for 2 h, filtered, and then dried in an oven at 80 °C for 18 h to obtain the hydrogenation catalyst C3.

[0045] [Preparation Example 4]

[0046] Preparation of C4 hydrogenation catalyst:

[0047] 14.9 g of Ni(NO3)2·6H2O was dissolved in 20.0 g of deionized water, and 10.0 g of SiO2 support was weighed and added to the solution. The solution mixture was sonicated at room temperature for 2 h, filtered, and then dried in an oven at 80 °C for 12 h. Finally, it was calcined at 550 °C for 6 h to obtain the hydrogenation catalyst C4.

[0048] The following examples and comparative examples were used to prepare hexamethylenediamine:

[0049]

Example 1

[0050] (1) Catalyst pretreatment

[0051] 10g of hydrogenation catalyst C1 was added to the reactor, followed by 100g of water containing 100ppm adiponitrile. The mixture was stirred for 1 hour under a nitrogen atmosphere. The water in the reactor was then filtered out to obtain the modified catalyst.

[0052] (2) Hydrogenation reaction

[0053] Add 12.5g of deionized water to the catalyst-containing reactor. Purge the reactor three times with 1MPa nitrogen and three times with 1MPa hydrogen. Then, transfer 187.5g of liquid ammonia into the reactor. Start the stirrer at 1000rpm and begin the heating program to raise the reactor temperature to 70℃. At this point, open the hydrogen valve to introduce hydrogen into the reactor and adjust the hydrogen partial pressure to 3.0MPa. Next, open the adiponitrile feed pump and feed line valve, introducing adiponitrile at a rate of 6g / g. catThe adiponitrile was added to the reactor at a flow rate of h for hydrogenation. During the reaction, water was circulated through the internal coil to remove the heat of reaction. When the adiponitrile feed reached 67g, the feed was stopped, and the reaction ended when the hydrogen flow meter reading reached 0. The reactor was cooled to room temperature, stirring was stopped, and the reactor was discharged to atmospheric pressure. It was then purged three times with 1MPa nitrogen. The material in the reactor was filtered out through a bottom-mounted tube with a filter head, and samples were taken for analysis. The calculated yield of hexamethylenediamine was 99.07%, and the DCH content was 0.030%.

[0054] (3) Loop test

[0055] The hydrogenation reaction was repeated 10 times using the same method as in step (2). Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 98.83% and the DCH content was 0.042%.

[0056]

Example 2

[0057] (1) Catalyst pretreatment

[0058] 10g of hydrogenation catalyst C2 was added to the reactor, followed by 300g of water containing 50ppm adiponitrile. The mixture was stirred for 2 hours under a nitrogen atmosphere. The water in the reactor was then filtered out to obtain the modified catalyst.

[0059] (2) Hydrogenation reaction

[0060] Add 6.5g of deionized water to the catalyst-containing reactor. Purge the reactor three times with 1MPa nitrogen and three times with 1MPa hydrogen. Then, transfer 193.5g of liquid ammonia into the reactor. Start the stirrer at 800rpm and begin the heating program to raise the reactor temperature to 90℃. At this point, open the hydrogen valve to introduce hydrogen into the reactor and adjust the hydrogen partial pressure to 5.0MPa. Next, open the adiponitrile feed pump and feed line valve, introducing adiponitrile at a rate of 12g / g. cat The adiponitrile was added to the reactor at a flow rate of h for hydrogenation. During the reaction, water was circulated through the internal coil to remove the heat of reaction. When the adiponitrile feed reached 100g, the feed was stopped, and the reaction ended when the hydrogen flow meter reading reached 0. The reactor was cooled to room temperature, stirring was stopped, and the reactor was discharged to atmospheric pressure. It was then purged three times with 1MPa nitrogen. The material in the reactor was filtered out through a bottom-mounted tube with a filter head, and samples were taken for analysis. The calculated yield of hexamethylenediamine was 99.52%, and the DCH content was 0.042%.

[0061] (3) Loop test

[0062] The hydrogenation reaction was repeated 10 times using the same method as in step (2). Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 99.18%, and the DCH content was 0.031%.

[0063]

Example 3

[0064] (1) Catalyst pretreatment

[0065] 10g of hydrogenation catalyst C3 was added to the reactor, followed by 200g of ethanol containing 200ppm adiponitrile. The mixture was stirred for 1.5h under a nitrogen atmosphere. The ethanol in the reactor was then filtered out to obtain the modified catalyst.

[0066] (2) Hydrogenation reaction

[0067] Add 28.6 g of deionized water to the catalyst-containing reactor. Purge the reactor three times with 1 MPa nitrogen gas, then three times with 1 MPa hydrogen gas. Afterward, transfer 171.4 g of liquid ammonia into the reactor. Start the stirrer at 900 rpm and begin the heating program to raise the reactor temperature to 80°C. At this point, open the hydrogen valve to introduce hydrogen into the reactor, adjusting the hydrogen partial pressure to 2.0 MPa. Next, open the adiponitrile feed pump and feed line valve, introducing adiponitrile at a rate of 0.5 g / g. cat The adiponitrile was added to the reactor at a flow rate of h for hydrogenation. During the reaction, water was circulated through the internal coil to remove the heat of reaction. When the adiponitrile feed reached 50g, the feed was stopped, and the reaction ended when the hydrogen flow meter reading reached 0. The reactor was cooled to room temperature, stirring was stopped, and the reactor was discharged to atmospheric pressure. It was then purged three times with 1MPa nitrogen. The material in the reactor was filtered out through a bottom-mounted tube with a filter head, and samples were taken for analysis. The calculated yield of hexamethylenediamine was 99.15%, and the DCH content was 0.037%.

[0068] (3) Loop test

[0069] The hydrogenation reaction was repeated 10 times using the same method as in step (2). Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 98.73% and the DCH content was 0.044%.

[0070]

Example 4

[0071] (1) Catalyst pretreatment

[0072] 10g of hydrogenation catalyst C4 was added to the reactor, followed by 100g of water containing 100ppm adiponitrile. The mixture was stirred for 1 hour under a nitrogen atmosphere. The water in the reactor was then filtered out to obtain the modified catalyst.

[0073] (2) Hydrogenation reaction

[0074] Add 12.5g of deionized water to the catalyst-containing reactor. Purge the reactor three times with 1MPa nitrogen and three times with 1MPa hydrogen. Then, transfer 187.5g of liquid ammonia into the reactor. Start the stirrer at 1000rpm and begin the heating program to raise the reactor temperature to 70℃. At this point, open the hydrogen valve to introduce hydrogen into the reactor and adjust the hydrogen partial pressure to 3.0MPa. Next, open the adiponitrile feed pump and feed line valve, introducing adiponitrile at a rate of 6g / g. cat The adiponitrile was added to the reactor at a flow rate of h for hydrogenation. During the reaction, water was circulated through the internal coil to remove the heat of reaction. When the adiponitrile feed reached 67g, the feed was stopped, and the reaction ended when the hydrogen flow meter reading reached 0. The reactor was cooled to room temperature, stirring was stopped, and the reactor was discharged to atmospheric pressure. It was then purged three times with 1MPa nitrogen. The material in the reactor was filtered out through a bottom-mounted tube with a filter head, and samples were taken for analysis. The calculated yield of hexamethylenediamine was 95.71%, and the DCH content was 0.077%.

[0075] (3) Loop test

[0076] The hydrogenation reaction was repeated 10 times using the same method as in step (2). Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 92.26%, and the DCH content was 0.18%.

[0077]

Example 5

[0078] (1) Catalyst pretreatment

[0079] 10g of Raney nickel catalyst (Jingjiang Hongpeng Catalyst Co., Ltd.) was added to the reactor, followed by 100g of water containing 100ppm adiponitrile. The mixture was stirred for 1 hour under a nitrogen atmosphere. The water in the reactor was then filtered out to obtain the modified catalyst.

[0080] (2) Hydrogenation reaction

[0081] Add 12.5g of deionized water to the catalyst-containing reactor. Purge the reactor three times with 1MPa nitrogen and three times with 1MPa hydrogen. Then, transfer 187.5g of liquid ammonia into the reactor. Start the stirrer at 1000rpm and begin the heating program to raise the reactor temperature to 70℃. At this point, open the hydrogen valve to introduce hydrogen into the reactor and adjust the hydrogen partial pressure to 3.0MPa. Next, open the adiponitrile feed pump and feed line valve, introducing adiponitrile at a rate of 6g / g. catThe adiponitrile was added to the reactor at a flow rate of h for hydrogenation. During the reaction, water was circulated through the internal coil to remove the heat of reaction. When the adiponitrile feed reached 67g, the feed was stopped, and the reaction ended when the hydrogen flow meter reading reached 0. The reactor was cooled to room temperature, stirring was stopped, and the reactor was discharged to atmospheric pressure. It was then purged three times with 1MPa nitrogen. The material in the reactor was filtered out through a bottom-mounted tube with a filter head, and samples were taken for analysis. The calculated yield of hexamethylenediamine was 96.22%, and the DCH content was 0.066%.

[0082] (3) Loop test

[0083] The hydrogenation reaction was repeated 10 times using the same method as in step (2). Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 93.28%, and the DCH content was 0.14%.

[0084] Comparative Example 1

[0085] Hexamethylenediamine was prepared by hydrogenation reaction using almost the same method as in Example 1, except that the water containing 100 ppm adiponitrile was replaced with deionized water during catalyst pretreatment. After the reaction, samples were taken for analysis, and the calculated yield of hexamethylenediamine was 93.11%, with a DCH content of 0.35%.

[0086] The hydrogenation reaction was then repeated five times using the same method. Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 88.47%, and the DCH content was 0.91%.

[0087] Comparative Example 2

[0088] Hexamethylenediamine was prepared by hydrogenation reaction using almost the same method as in Example 1, except that water containing 100 ppm adiponitrile was replaced with water containing 100 ppm liquid ammonia during catalyst pretreatment. After the reaction, samples were taken for analysis, and the calculated yield of hexamethylenediamine was 93.81%, with a DCH content of 0.33%.

[0089] The hydrogenation reaction was then repeated five times using the same method. Finally, samples were taken for analysis, and the yield of hexamethylenediamine was calculated to be 89.51%, and the DCH content was 0.90%.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of hexamethylenediamine, characterized in that, The method comprises the following steps: 1) catalyst pretreatment: mixing the hydrogenation catalyst and the modifier, treating under nitrogen atmosphere for 0.5-2h to obtain a modified catalyst; 2) hydrogenation reaction: hydrogenating adiponitrile in the presence of the modified catalyst to obtain hexamethylenediamine; The modifier is water and / or alcohol containing 50-200ppm of adiponitrile; The hydrogenation catalyst is a supported metal Ni catalyst.

2. The process for the preparation of hexamethylenediamine according to claim 1, characterized in that, The amount of the modifier added is 5-50 times the mass of the hydrogenation catalyst.

3. The method of claim 1, wherein the method is carried out at a temperature of from 20 °C to 100 °C. The reaction conditions for the hydrogenation of adiponitrile are: reaction temperature 50-100℃, hydrogen partial pressure 1-8MPa during the reaction.

4. The process for the preparation of hexamethylenediamine according to claim 3, characterized in that, The reaction conditions for the hydrogenation of adiponitrile are: reaction temperature 70-90℃, hydrogen partial pressure 2-5MPa during the reaction.

5. The method of claim 1, wherein the method is carried out at a temperature of from 50 °C to 150 °C. The hydrogenation reaction of adiponitrile is carried out in a mixed solvent composed of liquid ammonia and water.

6. The process for the preparation of hexamethylenediamine according to claim 5, characterized in that, The mass ratio of liquid ammonia to water in the mixed solvent is (3-50):

1.

7. The process for the preparation of hexamethylenediamine according to claim 6, characterized in that, The mass ratio of liquid ammonia to water in the mixed solvent is (6-30):

1.

8. The process for the preparation of hexamethylenediamine according to any one of claims 5 to 7, characterized in that, In step 2), the mass ratio of adiponitrile to mixed solvent is 1:(1-6).

9. The method of claim 8, wherein the method further comprises, In step 2), the mass ratio of adiponitrile to mixed solvent is 1:(2-4).

10. The method of claim 8, wherein the method is carried out at a temperature of from 20 °C to 100 °C. The feed flow rate of said adiponitrile is 0.5-20 g / g cat • h.

11. The method of claim 10, wherein the method is carried out at a temperature of from 20 °C to 100 °C. The feed flow rate of said adiponitrile is 0.5-12 g / g cat • h.

12. The process for the preparation of hexamethylenediamine according to any one of claims 1 to 7, characterized in that, The hydrogenation reaction is carried out in a fluidized bed, a fixed bed or a stirred tank reactor.

13. The method of claim 1, wherein the method is carried out at a temperature of from 20 °C to 100 °C. The hydrogenation catalyst is a SiO2-supported metal Ni catalyst prepared by direct reduction method.

14. The method for preparing hexamethylenediamine according to claim 13, characterized in that, In the catalyst, the loading amount of metal Ni in the carrier is 20-40wt%.

15. The method of claim 13, wherein the method is carried out at a temperature of from 50 °C to 150 °C. The direct reduction method is specifically as follows: Dissolving a precursor of metal Ni in water, adding a SiO2 carrier, ultrasonic treatment at room temperature for 1-2h, filtering and drying to obtain a catalyst powder, and optionally preparing a shaped body.

16. The method of claim 15, wherein the 1,6-hexanediamine is prepared by the process of claim 1. The drying conditions are: drying at 60-100℃ for 12-24h.

17. The method for preparing hexamethylenediamine according to claim 15, characterized in that, The precursor of metal Ni is one or more of nitrate, sulfate and hydrochloride of Ni.

18. The method of claim any one of claims 13-17, wherein, The SiO2-supported metal Ni catalyst prepared by the direct reduction method is applied to the hydrogenation reaction after hydrogen activation.