Method for preparing hexamethylenediamine through hydrogenation of 6-aminocapronitrile

Abstract

The invention belongs to the technical field of organic chemical industry, and particularly relates to a method for preparing hexamethylenediamine through hydrogenation of 6-aminocapronitrile. Comprising the following steps: adding a 6-aminocapronitrile solution into a reaction kettle, activating a catalyst through hydrogen, transferring the activated catalyst into the reaction kettle under the protection of nitrogen, sealing, replacing air in the reactor with hydrogen, pressurizing to 1.5-8.0 Mpa, and stirring for reaction; after the reaction is finished, cooling to room temperature, taking a reacted mixture, and carrying out reduced pressure distillation to obtain hexamethylenediamine; the catalyst is an Al2O3 loaded copper-nickel-based catalyst. According to the method, the hexamethylenediamine is prepared by directly hydrogenating the 6-aminocapronitrile serving as the raw material without adding alkali or ammonia water, and the method is simple in production process, high in process safety, low in production cost, high in reaction conversion rate and yield, high in purity of the hexamethylenediamine and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical industry, and specifically relates to a method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile. Background Art

[0002] Hexamethylenediamine is an important chemical raw material. The main use of hexamethylenediamine is to synthesize important industrial products such as nylon 66 and nylon 610, and then make various nylon resins, nylon fibers and polyamide resin inks and other important civilian materials. In addition, hexamethylenediamine is also widely used in mineral oil field demulsifiers, agricultural pesticides, building concrete additives, etc. In addition, hexamethylenediamine can react with carbon phthalate to prepare 6-aminocapronitrile isocyanate, and then continue to polymerize to produce polyurethane materials, which are widely used in the aerospace field. The application scope of hexamethylenediamine is constantly expanding, and the demand for downstream products is increasing, so realizing large-scale industrial production of hexamethylenediamine is now the primary task.

[0003] At present, the production process of hexamethylenediamine mainly includes caprolactam method, butadiene method and adiponitrile catalytic hydrogenation method. The adiponitrile catalytic hydrogenation method for preparing hexamethylenediamine is widely used because of its simple process, high product quality and low production cost. The industrial production method of hexamethylenediamine is mainly adiponitrile catalytic hydrogenation method. 6-aminocapronitrile is an important chemical intermediate, but in the production process of preparing hexamethylenediamine by 6-aminocapronitrile catalytic hydrogenation method, alkali or ammonia water needs to be added to suppress the generation of secondary amine and tertiary amine to improve the selectivity of hexamethylenediamine, so as to maintain the activity and selectivity of the catalyst. A large amount of alkali liquid is discharged in the preparation process, which pollutes the environment, and the alkali or ammonia water corrodes the equipment seriously, and the catalyst is difficult to recover, which reduces the service life of the catalyst. The production cost is too high and is not suitable for industrial production. Therefore, it is of great significance to develop a green synthesis process of hexamethylenediamine. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile. Under the condition of no need to add alkali or ammonia water, 6-aminocapronitrile is used as a raw material and hexamethylenediamine is directly hydrogenated to prepare hexamethylenediamine. The production process is simple, the process safety is high, the service life of the catalyst is improved, the production cost is low, the reaction conversion rate and yield are high, the hexamethylenediamine has high purity, and is suitable for large-scale production.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] A method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile comprises the following steps:

[0007] Add 6-aminocapronitrile solution into a reactor, activate the catalyst with hydrogen, transfer the activated catalyst into the reactor under nitrogen protection, seal the reactor, replace the air in the reactor with hydrogen, pressurize it to 1.5-8.0Mpa, and then stir to react; after the reaction is completed, cool to room temperature, take the reaction mixture, and obtain hexamethylenediamine after reduced pressure distillation;

[0008] The preparation method of the catalyst is as follows: Al2O3 is used as a carrier, copper is used as a first component, nickel is used as a second component, and a rare earth element is used as a third component, and the catalyst is prepared by an impregnation method.

[0009] Preferably, the solvent of the 6-aminocapronitrile solution is ethanol, methanol or water, and the mass concentration of the 6-aminocapronitrile is 5-75%.

[0010] Preferably, the added amount of the catalyst is 1-4% of the total mass of the 6-aminocapronitrile solution.

[0011] Preferably, the reaction is an intermittent reaction or a fixed bed reaction; in the intermittent reaction or the fixed bed reaction, the catalyst activation temperature is 200-280°C, and the activation hydrogen space velocity is 2000-3500h -1 , activation time 5-10h; intermittent reaction temperature 120-500℃; fixed bed reaction temperature 120-500℃, reaction space velocity 0.3-3h -1 .

[0012] Preferably, the dosage ratio of copper, nickel, rare earth elements and Al2O3 in the catalyst is (1-3) mmol: (0.8-2) mmol: (0.8-2) mmol: 1 g.

[0013] Preferably, the rare earth element is La or Ce.

[0014] Preferably, the impregnation method specifically comprises the following steps:

[0015] S1. Dissolving nickel nitrate, copper nitrate and rare earth element nitrate in water to prepare a mixed solution;

[0016] S2, immersing the Al2O3 particles in the mixed solution for 0.5-2h, and then filtering to collect the modified Al2O3;

[0017] S3. calcining the modified Al2O3 at 400-500°C for 2-3h to obtain the catalyst.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention uses 6-aminocapronitrile as a raw material and directly hydrogenates hexamethylenediamine without adding alkali or ammonia water, thereby reducing the impact of alkali solution on the environment and equipment during the preparation of hexamethylenediamine. The production process is simple, the process safety is high, the production cost is low, the reaction conversion rate and yield are high, the hexamethylenediamine is high in purity, there is no three wastes discharged, the equipment investment is low, and it is suitable for large-scale production.

[0020] 2. The preparation method of the catalyst used in the present invention is simple, and it is used for the reaction of hydrogenating 6-aminocapronitrile to synthesize hexamethylenediamine. Compared with the preparation of the Raney nickel catalyst, the cost of the catalyst is low, and the components have different chemical potentials. Under the action of the catalyst, the components exist in the form of ions in the solution and can be mixed in a more orderly manner, with good stability, simple production process and low production cost.

[0021] 3. In the catalyst prepared by the present invention, since copper can be reduced at low temperature, the reduced copper can activate hydrogen atoms and help the reduction of nickel oxide, thereby reducing the reduction temperature of nickel. At the same time, the addition of rare earth elements improves the dispersion of metal copper and nickel, promotes the synergistic effect between copper and nickel, and improves the overall hydrogenation effect of the catalyst. The catalyst provided by the present invention is cheap, easy to obtain and has a long service life. The catalyst after reduction and regeneration still maintains a higher reaction activity than the fresh catalyst. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0024] Example 1

[0025] The catalyst prepared by the impregnation method comprises the following steps:

[0026] S1, taking copper nitrate, nickel nitrate and lanthanum nitrate hexahydrate in a molar ratio of 80mmol:80mmol:40mmol and dissolving them in deionized water to obtain a mixed solution;

[0027] S2, immersing 40 g of Al2O3 particles in the mixed solution for 1 h, and then filtering to collect the modified Al2O3;

[0028] S3. calcining the modified Al2O3 at 500°C for 2h to obtain the catalyst.

[0029] Example 2

[0030] The catalyst prepared by the impregnation method comprises the following steps:

[0031] S1. Weigh nickel nitrate, aluminum nitrate and cerium nitrate hexahydrate in a molar ratio of 120 mmol:80 mmol:40 mmol and dissolve them in deionized water to obtain a mixed solution;

[0032] S2, immersing 40 g of Al2O3 particles in the mixed solution for 2 h, and then filtering to collect the modified Al2O3;

[0033] S3. calcining the modified Al2O3 at 450°C for 2h to obtain the catalyst.

[0034] The pore structure performance of the catalysts in Example 1-2 was calculated using the BET method. The specific surface area of ​​the catalysts prepared in Example 1-2 was in the range of 230-340 m 2 / g, the pore volume and pore diameter are between 0.65-1.43cm 3 / g and between 4.2-5.7nm.

[0035] Example 3

[0036] A method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile comprises the following steps:

[0037] A 30% mass fraction of 6-aminocapronitrile ethanol solution was added to an intermittent reactor, and 20 g of the catalyst prepared in Example 1 was heated and activated with hydrogen on a fixed bed. The catalyst activation temperature was 280° C. and the activation hydrogen space velocity was 2200 h -1 , activation time 8h; then transferred to an intermittent kettle reactor under nitrogen protection, sealed, replaced the air in the kettle with hydrogen, set the reaction temperature of the reactor to 220℃, filled with hydrogen to the set reaction pressure of 6MPa; when the reaction temperature reaches 220℃, start stirring and start timing, the stirring speed is maintained at 600r / min, after 4h of reaction, turn off the stirring and heating device, cool the reactor to room temperature, release the pressure to normal pressure, take the reaction mixture, the conversion rate is 97% according to chromatographic analysis, and the selectivity of hexamethylenediamine is 99.5%. After vacuum distillation and refining, high-purity hexamethylenediamine is obtained.

[0038] Example 4

[0039] A method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile comprises the following steps:

[0040] A 50% mass fraction of 6-aminocapronitrile ethanol solution was added to an intermittent reactor, and 20 g of the catalyst prepared in Example 1 was heated and activated with hydrogen on a fixed bed. The catalyst activation temperature was 280° C. and the activation hydrogen space velocity was 2200 h -1 , activation time 8h; then transferred to an intermittent reactor under nitrogen protection, sealed, replaced the air in the reactor with hydrogen, set the reaction temperature of the reactor to 220℃, filled with hydrogen to the set reaction pressure of 6MPa; when the reaction temperature reaches 220℃, start stirring and start timing, keep the stirring speed at 600r / min, after 4h of reaction, turn off the stirring and heating device, cool the reactor to room temperature, release the pressure to normal pressure, take the reaction mixture, the conversion rate is 98% according to chromatographic analysis, and the selectivity of hexamethylenediamine is 99.5%. After vacuum distillation and refining, high-purity hexamethylenediamine is obtained.

[0041] Example 5

[0042] A method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile comprises the following steps:

[0043] A 75% mass fraction of 6-aminocapronitrile ethanol solution was added to an intermittent reactor, and 20 g of the catalyst prepared in Example 2 was heated and activated with hydrogen on a fixed bed. The catalyst activation temperature was 260° C. and the activation hydrogen space velocity was 2200 h -1 , activation time 8h; then transferred to an intermittent reactor under nitrogen protection, sealed, replaced the air in the reactor with hydrogen, set the reaction temperature of the reactor to 240℃, filled with hydrogen to the set reaction pressure of 6MPa; when the reaction temperature reaches 240℃, start stirring and start timing, keep the stirring speed at 600r / min, react for 4h, turn off the stirring and heating device, cool the reactor to room temperature, release the pressure to normal pressure, take the reaction mixture, the conversion rate is 98% according to chromatographic analysis, and the selectivity of hexamethylenediamine is 99.5%. High-purity hexamethylenediamine is obtained after vacuum distillation and refining.

[0044] Example 6

[0045] The catalyst 20 prepared in Example 1 was loaded into a fixed bed reactor. The catalyst was used after being activated with hydrogen. The activation temperature was 280°C. The temperature was programmed to reach the activation temperature from room temperature for 1 h. The activation hydrogen space velocity was 2200 h -1 , activated for 8h; after the catalyst was activated, the bed temperature dropped to the reaction temperature of 220℃, the system pressure was increased to 6MPa, and a 20% mass fraction of 6-aminocapronitrile ethanol solution was pumped into the reaction system at an air velocity of 1h -1 The reaction mixture was taken, and the conversion rate was 98% and the selectivity of hexamethylenediamine was 99.5% after chromatographic analysis. High-purity hexamethylenediamine was obtained after vacuum distillation and purification.

[0046] Comparative Example 1

[0047] The method for preparing hexamethylenediamine by hydrogenation of 6-aminocapronitrile is the same as that in Example 1, except that a Raney nickel catalyst is used as the catalyst. The reaction mixture is taken, and the conversion rate is 92% and the selectivity of hexamethylenediamine is 95.3% after chromatographic analysis. High-purity hexamethylenediamine is obtained after refining by vacuum distillation.

[0048] In summary, the present invention uses 6-aminocapronitrile as a raw material and adopts the catalyst prepared by the present invention for the reaction of hydrogenating 6-aminocapronitrile to synthesize hexamethylenediamine without adding alkali or ammonia water, and directly hydrogenates hexamethylenediamine. The production process is simple, the process safety is high, the production cost is low, the reaction conversion rate and yield are high, the hexamethylenediamine purity is high, there is no three wastes discharge, the equipment investment is low, and it is suitable for large-scale production. Compared with the preparation of Raney nickel catalyst, the catalyst cost of this method is low, and each component has different chemical potentials. Under the action of the catalyst, each component exists in the form of ions in the solution and can be mixed in a more orderly manner. The catalyst of the present invention is cheap, easy to obtain and has a long service life. Compared with the fresh catalyst, the catalyst after reduction and regeneration still maintains a higher reaction activity.

[0049] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0050] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile, characterized in that: The following steps are involved: Add 6-aminocapronitrile solution into a reactor, activate the catalyst with hydrogen, transfer the activated catalyst into the reactor under nitrogen protection, seal the reactor, replace the air in the reactor with hydrogen, pressurize it to 1.5-8.0Mpa, and then stir to react; after the reaction is completed, cool to room temperature, take the reaction mixture, and obtain hexamethylenediamine after reduced pressure distillation; The preparation method of the catalyst is as follows: Al2O3 is used as a carrier, copper is used as a first component, nickel is used as a second component, and a rare earth element is used as a third component, and the catalyst is prepared by an impregnation method.

2. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The solvent of the 6-aminocapronitrile solution is ethanol, methanol or water, and the mass concentration of the 6-aminocapronitrile is 5-75%.

3. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The added amount of the catalyst is 1-4% of the total mass of the 6-aminocapronitrile solution.

4. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The reaction is an intermittent reaction or a fixed bed reaction; in the intermittent reaction or the fixed bed reaction, the catalyst activation temperature is 200-280°C, and the activation hydrogen space velocity is 2000-3500h -1 , activation time 5-10h; intermittent reaction temperature 120-500℃; fixed bed reaction temperature 120-500℃, reaction space velocity 0.3-3h -1 .

5. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The dosage ratio of copper, nickel, rare earth elements and Al2O3 in the catalyst is (1-3)mmol:(0.8-2)mmol:(0.8-2)mmol:1g.

6. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The rare earth element is La or Ce.

7. The method for preparing hexamethylenediamine by hydrogenating 6-aminocapronitrile according to claim 1, characterized in that: The impregnation method specifically comprises the following steps: S1. Dissolving nickel nitrate, copper nitrate and rare earth element nitrate in water to prepare a mixed solution; S2, immersing the Al2O3 particles in the mixed solution for 0.5-2h, and then filtering to collect the modified Al2O3; S3. calcining the modified Al2O3 at 400-500°C for 2-3h to obtain the catalyst.