Catalyst for preparing 6-aminocapronitrile by ammoniation of caprolactam, preparation method thereof and application thereof in preparing 6-aminocapronitrile by ammoniation

Abstract

The present application discloses a catalyst for preparing 6-aminocapronitrile by ammoniation of caprolactam and a preparation method and its application in preparing 6-aminocapronitrile by ammoniation. The catalyst is a γ-Al2O3 catalyst having a porous structure of the alumina catalyst; the micromorphology of the alumina catalyst is flaky or fibrous; the preparation of the catalyst is achieved by adjusting the aluminum source, the ratio of additives and the crystallization time, and the preparation of γ-Al2O3 with a specific morphology is achieved after high-temperature calcination. The preparation process is simple, the raw materials are easily available, the prepared γ-Al2O3 has high crystallinity, and the morphology, specific surface area and pore size distribution can be flexibly controlled. After the prepared sample is formed, it is used in a fixed bed reactor for the catalytic ammoniation of caprolactam to prepare 6-aminocapronitrile reaction. At 350-450°C and 0.1MPa, the conversion rate of caprolactam is greater than 75%, and the selectivity of 6-aminocapronitrile is greater than 90%.

Description

Technical Field

[0001] The present application relates to a catalyst for preparing 6-aminocapronitrile by ammoniation of caprolactam, a preparation method thereof and application thereof in preparing 6-aminocapronitrile by ammoniation, and belongs to the field of petroleum and chemical industry. Background Art

[0002] 6-aminocapronitrile (ACN) is an important chemical intermediate and an important raw material for preparing hexamethylenediamine. Hexamethylenediamine is mainly used to produce nylon 66 and nylon 610. It can also be used to synthesize polyurethane resins and ion exchange resins, and is used as a curing agent for urea-formaldehyde resins, epoxy resins, etc., and an organic crosslinking agent. Hexamethylenediamine is obtained by hydrogenating 6-aminocapronitrile and hydrogen, and the technology of this reaction is relatively mature. However, there are few patents for preparing 6-aminocapronitrile from caprolactam (CPL) as a raw material.

[0003] The reaction of preparing 6-aminocapronitrile from caprolactam is a continuous amination and dehydration process, which is carried out in the same reactor. Caprolactam and ammonia undergo an amination ring-opening reaction to generate 6-aminocaproamide; 6-aminocaproamide undergoes a dehydration reaction to remove oxygen atoms to generate 6-aminocapronitrile.

[0004] According to the reaction state of caprolactam, it can be divided into gas phase method and liquid phase method. Patent CN107739318A discloses a method and device for preparing 6-aminocapronitrile by caprolactam liquid phase method, which uses phosphoric acid or phosphate as a catalyst, with a caprolactam conversion rate of 58% and a selectivity of 97.8%; Patent CN107602416A mentions a technology for preparing 6-aminocapronitrile by caprolactam gas phase method, but it is in a pressurized state, the reaction conditions are harsh, and it is not suitable for large-scale industrialization.

[0005] The liquid phase method has mild reaction conditions, but the separation of catalyst and product is cumbersome and energy consumption is high. The gas phase method is simple to prepare, there is no problem of separating product and catalyst, and the catalyst used is simple to prepare, but the difficulty is that the stability of the catalyst has not been verified by industrialization. Therefore, it is urgent to develop an economical, efficient and simple catalyst preparation method for the amination of caprolactam to produce 6-aminocapronitrile. Summary of the invention

[0006] Based on the above problems, the object of the present invention is to provide an alumina catalyst for caprolactam amination and a preparation method thereof, wherein the catalyst is a γ-Al 2 O 3The morphology includes flake and fiber; the preparation method of the catalyst is: different aluminum sources, inorganic additives or organic additives are dissolved in water in a certain proportion, and the alumina catalysts with different morphologies and different crystal forms are obtained by adjusting the hydrothermal crystallization conditions and calcination conditions. The catalyst preparation method obtained by this method is simple, the conversion rate of caprolactam is greater than 75%, and the selectivity of 6-aminocapronitrile is greater than 90%.

[0007] In one aspect of the present application, there is provided an alumina catalyst for preparing 6-aminocapronitrile by ammoniation of caprolactam, wherein the alumina catalyst is a porous γ-Al 2 O 3 catalyst;

[0008] The microscopic morphology of the aluminum oxide catalyst is flake or fiber-like.

[0009] Optionally, the pore volume of the alumina catalyst is 0.3 cm 3 / g~0.7cm 3 / g;

[0010] Optionally, the pore size of the alumina catalyst is 2 nm to 50 nm;

[0011] Optionally, the specific surface area of ​​the alumina catalyst is 90 m 2 / g~200m 2 / g;

[0012] Optionally, the sheet layer has a thickness of 30nm to 100nm and an aspect ratio of 1 to 10;

[0013] Optionally, the fiber has an aspect ratio of 10 to 100 and a diameter of 10 nm to 100 nm.

[0014] In another aspect of the present application, a method for preparing the above-mentioned catalyst is provided, the preparation method comprising:

[0015] The aqueous solution containing the aluminum source precursor and the additive is hydrothermally crystallized, dried and calcined to obtain the aluminum oxide catalyst.

[0016] Optionally, the aluminum source precursor is selected from at least one of aluminum nitrate and pseudo-boehmite;

[0017] The additive includes at least one of an organic additive and an inorganic additive.

[0018] Optionally, the inorganic additive is ammonium carbonate;

[0019] The organic additive is selected from at least one of urea, polyethylene glycol and polyvinyl pyrrolidone.

[0020] Optionally, the molar ratio of the aluminum source precursor to the additive is 1:(0.3-9.2);

[0021] Optionally, the upper limit of the molar ratio of the aluminum source precursor to the additive can be independently 1:0.3, 1:1, 1:1.9, 1:2, 1:4, 1:7, 1:9; the lower limit can be independently selected from 1:1, 1:1.9, 1:2, 1:4, 1:7, 1:9, 1:9.2;

[0022] Optionally, the molar ratio of the aluminum source to water is 1:(0.2-4.0);

[0023] Optionally, the upper limit of the molar ratio of the aluminum source to water can be independently selected from 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5; the lower limit can be independently selected from 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4;

[0024] Optionally, the hydrothermal crystallization temperature is 100 to 200° C., and the hydrothermal crystallization time is 2 to 24 hours;

[0025] Optionally, the upper limit of the hydrothermal crystallization temperature may be independently selected from 120°C, 140°C, 160°C, 180°C, and 200°C; the lower limit may be independently selected from 100°C, 120°C, 140°C, 160°C, and 180°C;

[0026] Optionally, the upper limit of the hydrothermal crystallization time can be independently selected from 6h, 12h, 18h, 24h; the lower limit can be independently selected from 2h, 6h, 12h, 18h;

[0027] Optionally, the drying temperature is 60 to 120°C;

[0028] Optionally, the upper limit of the drying temperature can be independently selected from 80°C, 100°C, and 120°C; the lower limit can be independently selected from 60°C, 80°C, and 100°C;

[0029] Optionally, the calcination is carried out in an air atmosphere, the calcination temperature is 500-800° C., the heating rate is 2-8° C. / min, and the calcination time is 2-8 h;

[0030] Optionally, the upper limit of the calcination temperature may be independently selected from 600°C, 700°C, and 800°C; the lower limit may be independently selected from 500°C, 600°C, and 700°C;

[0031] Optionally, the upper limit of the heating rate can be independently selected from 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, and 8°C / min; the lower limit can be independently selected from 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, and 7°C / min;

[0032] Optionally, the upper limit of the calcination time can be independently selected from 4h, 6h, and 8h; the lower limit can be independently selected from 2h, 4h, and 6h;

[0033] As a specific embodiment, the preparation method of the alumina catalyst includes using different aluminum sources, inorganic additives or organic additives to dissolve in water, adjusting the hydrothermal crystallization conditions and calcination temperature to obtain a flaky or fibrous γ-type alumina catalyst, loading the catalyst into a fixed bed, and reacting.

[0034] The specific steps are as follows:

[0035] 1) Dissolve a certain proportion of aluminum source and additives in deionized water, and stir magnetically under water bath heating conditions to obtain a uniform solution;

[0036] 2) The mixed solution in step 1) is placed in a Telfon kettle, and placed in an oven for hydrothermal crystallization at a certain temperature for a certain period of time;

[0037] 3) After the Telfon kettle that has been completely crystallized in step 2) is cooled, the solid product in the kettle is filtered, washed and dried;

[0038] 4) The solid product dried in step 3) is placed in a muffle furnace and calcined at a certain temperature for a certain time in an air atmosphere to obtain Al 2 O 3 product.

[0039] Optionally, in the above scheme, the sheet Al 2 O 3 The aluminum source is aluminum nitrate, and the molar ratio of the aluminum source to the organic additive urea is 1: (0.3-9.2), and the molar ratio of the aluminum source to water is 1: (0.2-4.0).

[0040] Optionally, in the above scheme, the fibrous Al 2 O 3 The aluminum source is selected from at least one of pseudo-boehmite and aluminum nitrate, and the inorganic additive ammonium carbonate [(NH 4 ) 2 CO 3 ] is 1:(0.3~9.2), and the molar ratio of aluminum source to water is: 1:(1.0~4.0).

[0041] Optionally, in the above scheme, 1 to 10 wt % of organic additives such as polyethylene glycol [PEG] and polyvinyl pyrrolidone [PVP] are added.

[0042] Optionally, in the step 2), the hydrothermal crystallization conditions specifically include the following steps:

[0043] Optionally, in the above scheme, prepare the sheet Al 2 O 3 , the hydrothermal crystallization temperature is 160-200°C, and the crystallization time is 2-24h;

[0044] Optionally, in the above scheme, the fibrous Al 2 O 3 , the hydrothermal crystallization temperature is 100-160°C, and the crystallization time is 2-24h;

[0045] Optionally, in step 3), the drying temperature is 60-120°C.

[0046] Optionally, in the above scheme, γ-type Al 2 O 3 The calcination temperature is 500-800°C, the heating rate is 2-8°C / min, and the calcination constant temperature time is 4-6h.

[0047] Another aspect of the present application provides a method for preparing 6-aminocapronitrile by ammoniation of caprolactam, the method comprising: contacting a raw material containing caprolactam and liquid ammonia with a catalyst, and ammoniation and dehydration to prepare 6-aminocapronitrile;

[0048] The catalyst is selected from the above-mentioned alumina catalyst or the alumina catalyst prepared according to the above-mentioned preparation method.

[0049] The aluminum oxide catalyst is pressed into tablets and used for preparing 6-aminocapronitrile by ammoniation of caprolactam.

[0050] Optionally, the reaction temperature of the ammoniation dehydration is 350-450° C.; and the reaction pressure is 0.1-0.5 MPa.

[0051] Optionally, the upper limit of the reaction temperature can be independently selected from 400°C and 450°C; the lower limit can be independently selected from 350°C and 400°C;

[0052] Optionally, the upper limit of the reaction pressure can be independently selected from 0.3MPa and 0.5MPa; the lower limit can be independently selected from 0.1MPa and 0.3MPa;

[0053] Optionally, the caprolactam feed space velocity is 1 to 6 h -1 , liquid ammonia feed space velocity is 5~25h -1 .

[0054] Optionally, the caprolactam feed space velocity upper limit can be independently selected from 2h -1 , 4h -1 , 6h -1 ; The lower limit can be independently selected from 1h -1 , 2h -1 , 4h -1 .

[0055] Optionally, the upper limit of the liquid ammonia feed space velocity can be independently selected from 10h -1 , 15h -1 , 20h -1 , 25h -1 ; The lower limit can be independently selected from 5h -1 , 10h -1 , 15h -1 , 20h -1 .

[0056] The beneficial effects of this application include:

[0057] The catalyst preparation method provided in the present application is simple, green, economical, energy-saving and efficient, and has excellent ammonia dehydration performance. It is applied to the amination of caprolactam to prepare 6-aminocapronitrile, with a caprolactam conversion rate greater than 75% and a 6-aminocapronitrile selectivity greater than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The XRD spectra of the samples prepared in Examples 1 to 3 are shown in FIG.

[0059] Figure 2 This is the SEM spectrum of the sample prepared in Example 1.

[0060] Figure 3 This is the SEM spectrum of the sample prepared in Example 2.

[0061] Figure 4 This is the SEM spectrum of the sample prepared in Example 3. DETAILED DESCRIPTION

[0062] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0063] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0064] In the examples of this application, the conversion rate and selectivity are calculated as follows:

[0065] X=(C t -C 0 ) / C 0

[0066] Y=Ut / ( t -C 0 )

[0067] Where: X represents the conversion rate of caprolactam (%), C t With C 0 represents the caprolactam concentration in the sample after reaction and the initial sample, Y represents the selectivity of 6-aminocapronitrile (%), U t The concentration of caprolactam and 6-aminocapronitrile was analyzed online by gas chromatograph (Agilent 7820A).

[0068] In the examples of the present application, the pore volume, pore diameter and specific surface area were analyzed by a physical adsorption instrument (Micromeritics ASAP2020).

[0069] In the examples of the present application, the morphology, lamella thickness, length and diameter were measured by electron scanning microscopy (Hitachi SU1510).

[0070] Example 1

[0071] According to the aluminum source Al(NO 3 ) 3 9H 2 O: organic additive urea: water with a molar ratio of 1:2:0.5 to prepare the solution. First, weigh a certain amount of Al(NO 3 ) 3 9H 2 O, add deionized water in proportion and stir for 15 minutes, weigh the calculated amount of urea, dissolve it in a certain proportion of deionized water, and transfer it to the beaker containing the aluminum source, and continue stirring for 15 minutes. After the above stirring forms a transparent solution, transfer it to the Telfon kettle lining, and put the kettle into an oven with an oven temperature of 200°C for 24 hours. After the crystallization is completed, wash, filter and dry the solid product at a drying temperature of 120°C. Transfer the dried sample from the oven to a muffle furnace, calcine at a temperature of 600°C, a heating rate of 5°C / min, and keep the temperature constant for 4 hours. The obtained γ-alumina has a flaky morphology, such as Figure 2 As shown, the pore volume is 0.58 cm 3 / g, pore size is 20nm, specific surface area is 112m 2 / g, the flake thickness is 40nm, and the length-width ratio is 1:6.

[0072] Application Example 1

[0073] Take the γ-Al calcined in Example 1 2 O 3 1 g of catalyst was loaded into a fixed bed, the temperature was raised to 400 °C, the reaction pressure was 0.1 MPa, and caprolactam was heated at a space velocity of 4 h-1 Feed, liquid ammonia at a space velocity of 15h -1 The conversion rate of raw material caprolactam was 81%, and the selectivity of product 6-aminocapronitrile was greater than 93%.

[0074] Example 2

[0075] Pseudo-boehmite by aluminum source: Inorganic additives (NH 4 ) 2 CO 3 The solution was prepared in a molar ratio of 1:1.9:1: water. First, a certain amount of calcined pseudo-boehmite and (NH 4 ) 2 CO 3 , add deionized water in proportion and stir for 15 minutes. After the above stirring forms a transparent solution, transfer it to the Telfon kettle lining, and put the kettle into an oven with an oven temperature of 140°C for 6 hours. After the crystallization is completed, wash, filter and dry the solid product at a drying temperature of 120°C. Transfer the dried molecular sieve sample from the oven to a muffle furnace, calcine at a temperature of 600°C, a heating rate of 5°C / min, and keep the temperature constant for 4 hours. The obtained γ-alumina has a fibrous morphology with a pore volume of 0.32cm 3 / g, pore size of 13nm, specific surface area of ​​140m 2 / g, aspect ratio is 30.

[0076] Application Example 2

[0077] Take the γ-Al calcined in Example 2 2 O 3 1 g of catalyst was loaded into a fixed bed, the temperature was raised to 400 °C, the reaction pressure was 0.1 MPa, and caprolactam was heated at a space velocity of 4 h -1 Feed, liquid ammonia at a space velocity of 15h -1 The conversion rate of raw material caprolactam is 80%, and the selectivity of product 6-aminocapronitrile is greater than 85%.

[0078] Example 3

[0079] According to the aluminum source Al(NO 3 ) 3 9H 2 O: organic additive urea: water with a molar ratio of 1:9:3 to prepare the solution. First, weigh a certain amount of Al(NO 3 ) 3 9H 2O and a calculated amount of urea, add deionized water in proportion and stir for 15 minutes. After the above stirring forms a transparent solution, transfer it to the Telfon kettle lining, and put the kettle into an oven at 100°C for 24 hours. After the crystallization is completed, wash, filter and dry the solid product at 120°C. Transfer the dried molecular sieve sample from the oven to a muffle furnace, calcine at 800°C, heat at a rate of 5°C / min, and keep the temperature constant for 4 hours. The resulting γ-alumina has a fibrous morphology with a pore volume of 0.48cm 3 / g, pore size is 26nm, specific surface area is 96m 2 / g, aspect ratio is 60.

[0080] Application Example 3

[0081] Take the γ-Al calcined in Example 3 2 O 3 1 g of catalyst was loaded into a fixed bed and heated to 400 °C at a heating rate of 5 °C / min. -1 Feed, liquid ammonia at a space velocity of 15h -1 The conversion rate of raw material caprolactam is 75%, and the selectivity of product 6-aminocapronitrile is greater than 90%.

[0082] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An alumina catalyst for preparing 6-aminocapronitrile by ammoniation of caprolactam, characterized in that: The alumina catalyst is a γ-Al2O3 catalyst with a porous structure; The microscopic morphology of the alumina catalyst is flake-like or fibrous; The catalyst is obtained by the following steps: hydrothermally crystallizing, drying and calcining an aqueous solution containing an aluminum source precursor and an additive to obtain the aluminum oxide catalyst; The aluminum source precursor is selected from at least one of aluminum nitrate and pseudo-boehmite; The additive includes at least one of an organic additive and an inorganic additive; The inorganic additive is ammonium carbonate; The organic additive is selected from at least one of urea, polyethylene glycol and polyvinyl pyrrolidone; The hydrothermal crystallization temperature is 100 to 200° C., and the hydrothermal crystallization time is 2 to 24 hours; The drying temperature is 60-120°C; The calcination is carried out in an air atmosphere, the calcination temperature is 500-800° C., the heating rate is 2-8° C. / min, and the calcination time is 2-8 hours.

2. The alumina catalyst according to claim 1, characterized in that The pore volume of the alumina catalyst is 0.3 cm 3 / g~0.7cm 3 / g; The pore size of the alumina catalyst is 2nm to 50nm; The specific surface area of ​​the alumina catalyst is 90 m 2 / g~200m 2 / g; The flake layer has a thickness of 30nm to 100nm and an aspect ratio of 1 to 10; The fiber has an aspect ratio of 10 to 100 and a diameter of 10 nm to 100 nm.

3. The alumina catalyst according to claim 1, characterized in that The molar ratio of the aluminum source precursor to the additive is 1:(0.3-9.2), wherein the molar amount of the aluminum source is calculated as the molar amount of the aluminum element, and the molar amount of the additive is calculated as the molar ratio of the aluminum element; The molar ratio of the aluminum source precursor to water is 1:(0.2-4.0), wherein the molar amount of the aluminum source is calculated based on the molar amount of the aluminum element, and the molar amount of water is calculated based on the molar ratio of the aluminum element.

4. The alumina catalyst according to claim 1, characterized in that The hydrothermal crystallization is carried out in a closed hydrothermal reactor.

5. A method for preparing 6-aminocapronitrile by ammoniation of caprolactam, characterized in that: A raw material containing caprolactam and liquid ammonia is contacted with a catalyst, and subjected to ammoniation and dehydration to prepare 6-aminocapronitrile; wherein the catalyst is selected from the alumina catalyst according to any one of claims 1 to 4.

6. The method according to claim 5, characterized in that The reaction temperature of the ammoniation dehydration is 350-450° C.; the reaction pressure is 0.1-0.5 MPa.

7. The method according to claim 5, characterized in that The caprolactam feed space velocity is 1 to 6 h -1 , liquid ammonia feed space velocity is 5~25h -1 .

Images