Preparation method and application of catalyst for hydrogenation of nitrile to hexamethylenediamine based on polypyrrole-derived carbon fiber supported with nickel

Abstract

The present invention provides a preparation method and application of a nitrile compound hydrogenation catalyst based on polypyrrole-derived carbon fiber loaded with metallic nickel. The catalyst is formed by uniformly dispersing metallic nickel on the surface of the carrier using PPy-derived carbon fiber as a carrier through a loading process to prepare a PPy-derived carbon fiber precursor; after active nickel metal salt and a precipitant are dissolved in water, PPy-derived carbon fiber is added as a precursor, hydrothermal stirring, centrifugal filtration, and low-temperature drying; highly dispersed nickel-loaded PPy catalyst is obtained through high-temperature calcination. The catalyst prepared by the method provided by the present invention is applicable to the selective hydrogenation of nitrile compounds to synthesize amine compounds, in particular, the hydrogenation of adiponitrile or 6-aminocapronitrile to prepare hexamethylenediamine, and the catalyst is based on PPy-derived carbon fiber as a carrier, and utilizes the rich nitrogen defects and pore structure of PPy to achieve metal capture and high-stability dispersion, as well as the conductive properties provided by the PPy-derived carbon layer itself to promote electron transmission, thereby improving catalyst activity.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing hexamethylenediamine by catalytic hydrogenation of nitrile compounds, and in particular to a preparation method and application of a nitrile hydrogenation catalyst for preparing hexamethylenediamine based on polypyrrole-derived carbon fiber loaded with metallic nickel. Background Art

[0002] Amine compounds are an important class of intermediates, widely used in the synthesis of pesticides, pharmaceuticals, textiles, and polymer materials. Hexamethylenediamine, containing two amino groups and exhibiting relatively active chemical properties, can be condensed with adipic acid to produce poly(hexamethylenediamine adipamide), also known as nylon 66. Nylon 66 has a large market demand for a wide range of applications, including photovoltaic auxiliary materials, photovoltaic transmission materials, semiconductor packaging, and display components. Currently, hexamethylenediamine is primarily obtained by hydrogenating adiponitrile. Partial hydrogenation of adiponitrile occurs primarily through gas-phase and liquid-phase catalytic hydrogenation, primarily using Raney-type catalysts, unsupported nickel-based catalysts, and supported nickel-based catalysts.

[0003] Raney catalysts have been used in industry. CN1139392 and CN103977819, respectively, disclose that Raney catalysts perform well in all aspects of hydrogenating nitrile compounds to produce amines. However, due to their poor resistance to poisons and mechanical properties, Raney catalysts are easily broken during reaction stirring and liquid impact, resulting in a short catalyst lifespan. This makes subsequent processing and filtration difficult, making complete removal from solutions difficult in industry. Furthermore, the resulting small particles can clog reactors, among other drawbacks.

[0004] In recent years, PPy-derived carbon fibers have been explored for use in catalyst supports due to their porous structure, high specific surface area, and rich nitrogen doping. As the active component of hydrogenation catalysts, metallic nickel has the advantages of high catalytic activity and good stability. However, traditional catalyst supports, such as activated carbon, have problems such as limited specific surface area and uneven pore size distribution, which restrict the improvement of their catalytic performance. Therefore, the development of a catalyst based on PPy-derived carbon fibers loaded with metallic nickel is of great significance for improving the catalytic efficiency and product purity of nitrile hydrogenation reactions.

[0005] This invention provides an adiponitrile / 6-aminocapronitrile hydrogenation catalyst and its preparation method. By utilizing PPy-derived carbon fibers as a carrier and combining them with the high catalytic activity of nickel, this catalyst achieves an efficient and stable hydrogenation reaction. This catalyst not only improves reaction conversion and product purity but also exhibits excellent stability and reusability, providing a new solution for the industrial production of hexamethylenediamine.

[0006] Purpose of the Invention

[0007] In response to the above technical problems, the present invention provides a method for preparing a nickel-supported nitrile hydrogenation catalyst to hexamethylenediamine based on polypyrrole-derived carbon fibers. The catalyst prepared by this method uses PPy-derived carbon fibers as a carrier. The catalyst utilizes the abundant nitrogen defects and pore structure of PPy to capture and stabilize metal dispersion, while the conductive properties of the PPy-derived carbon layer itself promote electron transport, thereby enhancing catalytic activity. Furthermore, the catalyst avoids the use of precious metals as active components, resulting in low cost, high catalyst activity, and selectivity after repeated reactions, demonstrating good stability.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following specific technical solutions:

[0009] A method for preparing a nitrile hydrogenation catalyst to hexamethylenediamine based on PPy-derived carbon fiber-supported nickel is characterized by adopting a hydrothermal method, and the specific steps are as follows:

[0010] (1) Preparation of PPy-derived carbon fiber precursor;

[0011] (2) After dissolving the active nickel metal salt and the precipitant in water, PPy-derived carbon fibers are added as a precursor, hydrothermally stirred, centrifugally filtered, and dried at low temperature;

[0012] (3) After high-temperature calcination, highly dispersed nickel-loaded PPy catalyst was obtained.

[0013] In the present invention, in step (1), the preparation method of the PPy-derived carbon fiber precursor is:

[0014] 1) Add hydrochloric acid to ultrapure water. In an ice-water bath, add hexadecyltrimethylammonium bromide to the solution and stir until dissolved.

[0015] 2) Add ammonium persulfate to the above solution and stir until the solution turns milky white. Then add pyrrole dropwise and stir at room temperature for 3-5 hours to obtain a black flocculent product.

[0016] 3) Washing with anhydrous ethanol and ultrapure water, filtering multiple times, placing the resulting product in a vacuum drying oven at 80-100°C for 24-30 hours, and grinding to obtain black powder polypyrrole.

[0017] In the present invention, in step (2), the nickel metal salt is one of nickel chloride, nickel nitrate, nickel bromide, and nickelous hydroxide, wherein the metal loading is 3%-10%.

[0018] In the present invention, in step (2), the precipitant is one or more of Na2CO3, NaOH, NH3·H2O, and urea, and the molar ratio of the precipitant to the loaded metal is 0.5-3:1.

[0019] In the present invention, in step (2), the hydrothermal temperature is 45-200° C., and the hydrothermal time is 2-12 h.

[0020] In the present invention, in steps (2) and (3), the drying temperature is 45-120°C, the calcination temperature is 600-800°C, the calcination atmosphere is argon atmosphere, and the calcination time is 2-8 h.

[0021] The catalyst prepared by the above preparation method is applied to the reaction of hydrogenating nitriles to generate hexylamine, and the specific steps are: adding the raw material liquid and the catalyst obtained after reduction into a reactor, and reacting the raw material liquid and hydrogen under the catalytic action of the catalyst at a certain reaction temperature and pressure to generate hexamethylenediamine.

[0022] Preferably, the catalyst reduction temperature range is 400-700°C, the reduction time is 2-6 h, and the reducing gas is H2 or H2 / N2.

[0023] Preferably, the nitrile compound is one of adiponitrile or 6-aminocapronitrile.

[0024] Preferably, the raw material liquid is a nitrile-solvent mixture, the solvent is one or more of methanol, ethanol, propanol, and isopropanol, and the mass concentration of the nitrile compound is 5-80 wt%.

[0025] Preferably, the hydrogenation reaction conditions are: reaction temperature of 60-130°C; reaction pressure of 2.0-5.0 MPa.

[0026] The reduced catalyst can also be first placed in a fixed bed for hydrogenation reaction. The method is to place the reduced catalyst in a fixed bed, introduce the raw material liquid, and react at a reaction temperature of 60-130 ºC and a reaction pressure of 2.0-5.0 MPa to produce hexamethylenediamine.

[0027] The beneficial effects of the present invention are:

[0028] (1) The rich nitrogen defects and pore structure of PPy-derived carbon fibers are utilized to achieve metal capture and highly stable dispersion, and the conductive properties of PPy-derived carbon itself promote electron transport and improve catalyst activity.

[0029] (2) Using nickel as the loading metal avoids the use of precious metals and reduces process costs. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the examples. It should also be understood that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of the present invention. The specific mass, reaction time, temperature, process parameters, etc. in the examples are only examples within the appropriate ranges, and any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the scope of the present invention.

[0031] Unless otherwise specified, the raw materials and reagents in the following examples and comparative examples were purchased from commercial sources.

[0032] Example 1

[0033] Preparation of PPy-derived carbon fiber precursor: Add 90 ml of hydrochloric acid to 200 ml of ultrapure water. In an ice-water bath, add 1 g of hexadecyltrimethylammonium bromide to the solution and stir for 10 min until dissolved. Then add 1.5 g of ammonium persulfate to the above solution and stir for 20 min until the solution becomes milky white. Subsequently, 2.0 mL of pyrrole is added dropwise and stirred at room temperature for 5 h to obtain black flocs. The product is washed with anhydrous ethanol and ultrapure water in turn and filtered several times. The resulting product is placed in a vacuum drying oven and vacuum dried at 80 °C for 24 h. After grinding, black powder polypyrrole PPy-derived carbon fiber is obtained.

[0034] Catalyst preparation: Weigh 0.006 mol nickel bromide and 0.02 mol Na2CO3 and dissolve them in 50 ml deionized water. After stirring evenly, add 10 g PPy-derived carbon fiber and continue stirring to obtain a uniform mixture. The mixture is then hydrothermally aged at 120 °C for 8 h. After cooling, filtering, and drying, the precursor is heated to 700 °C at 5 °C / min under argon atmosphere and calcined for 3 h to obtain a 3%-Ni / NC-700 catalyst.

[0035] Catalyst Performance Evaluation: The 3%-Ni / NC-700 catalyst was first reduced under a H2 atmosphere at 500°C for 3 h to completely reduce the nickel metal. A 20 wt% adiponitrile / isopropanol solution and 0.5 g of the 3%-Ni / NC-700 catalyst were then added to an autoclave. The autoclave was sealed and filled with hydrogen at 1 MPa for three replacement cycles before the pressure was increased to 4.0 MPa. The hydrogen cylinder was opened to maintain a constant pressure in the autoclave while the temperature was raised. Once the autoclave temperature reached and stabilized at 100°C, the magnetic stirrer was activated and the reaction timer was started. After a 4-h reaction, the reaction mixture was cooled to room temperature and the pressure was released. The reaction products were analyzed by gas chromatography (Table 1).

[0036] Example 2:

[0037] Catalyst preparation: 0.01 mol of nickel nitrate hexahydrate and 0.02 mol of urea were weighed and dissolved in 50 ml of deionized water. After stirring, 10 g of PPy-derived carbon fiber (prepared in Example 1) was added and stirred to obtain a uniform mixture. The mixture was then hydrothermally aged at 120°C for 8 h. After cooling, filtering, and drying, the precursor was heated to 700°C at 5°C / min under an argon atmosphere and calcined for 3 h to obtain a 5%-Ni / NC-700 catalyst.

[0038] Catalyst performance evaluation: 2.0 g of 5%-Ni / NC-700 catalyst was loaded into a fixed bed and reduced under H2 atmosphere at 500 °C for 3 h. After the reduction was completed and the temperature dropped to the experimental temperature, 30 wt% 6-aminocapronitrile / ethanol solution was used as the raw material. The reaction temperature was 100 °C, the reaction pressure was 4 MPa, and the mass space velocity was set to 2.0 h -1 , hydrogenation was carried out under the condition that the molar ratio of hydrogen to adiponitrile was set to 30 to obtain a hexamethylenediamine reaction liquid, which was analyzed by gas chromatography. The results are shown in Table 1.

[0039] Example 3:

[0040] Catalyst preparation: 0.014 mol nickel chloride and 0.02 mol NH3·H2O were weighed and dissolved in 50 ml deionized water. After stirring, 10 g PPy-derived carbon fibers (prepared in Example 1) were added and stirred to obtain a uniform mixture. The mixture was then hydrothermally aged at 120°C for 8 h. After cooling, filtering, and drying, the resulting precursor was heated to 700°C at 5°C / min under an argon atmosphere and calcined for 3 h to obtain an 8%-Ni / NC-700 catalyst.

[0041] Catalyst Performance Evaluation: The 8%-Ni / NC-700 catalyst was first reduced under a H2 atmosphere at 500°C for 3 h to completely reduce the nickel metal. A 20 wt% adiponitrile / isopropanol solution and 0.5 g of the 8%-Ni / NC-700 catalyst were then added to an autoclave. The autoclave was sealed and filled with hydrogen at 1 MPa for three replacement cycles before the pressure was increased to 4.0 MPa. The hydrogen cylinder was opened to maintain a constant pressure in the autoclave while the temperature was raised. Once the autoclave temperature stabilized at 100°C, the magnetic stirrer was activated and the reaction timer was started. After a 4-h reaction, the reaction mixture was cooled to room temperature and the pressure was released. The reaction products were analyzed by gas chromatography (Table 1).

[0042] Example 4:

[0043] Catalyst preparation: 0.006 mol nickel bromide and 0.02 mol Na2CO3 were weighed and dissolved in 50 ml deionized water. After stirring evenly, 10 g PPy-derived carbon fiber (prepared in Example 1) was added and stirred continuously to obtain a uniform mixture. The mixture was then hydrothermally aged at 120°C for 4 h. After cooling, filtering, and drying, the precursor was heated to 700°C at 5°C / min under an argon atmosphere and calcined for 3 h to obtain a 3%-Ni / NC-700-2 catalyst.

[0044] Catalyst Performance Evaluation: The 3%-Ni / NC-700-2 catalyst was first reduced under a H2 atmosphere at 500°C for 3 h to completely reduce the nickel metal. A 20 wt% adiponitrile / isopropanol solution and 0.5 g of the 3%-Ni / NC-700-2 catalyst were then added to an autoclave. The autoclave was sealed and filled with hydrogen at 1 MPa for three replacement cycles before the pressure was increased to 4.0 MPa. The hydrogen cylinder was opened to maintain a constant pressure in the autoclave while the temperature was raised. Once the autoclave temperature reached and stabilized at 100°C, the magnetic stirrer was activated and the reaction timer was started. After a 4-h reaction, the reaction mixture was cooled to room temperature and the pressure was released. The reaction products were analyzed by gas chromatography (Table 1).

[0045] Example 5:

[0046] Catalyst preparation: Weigh 0.014 mol nickel chloride and 0.02 mol ammonia water and dissolve them in 50 ml deionized water. After stirring evenly, add 10 g PPy-derived carbon fiber (prepared in Example 1) and continue stirring to obtain a uniform mixture. The mixture is then hydrothermally aged at 120°C for 8 h. After cooling, filtering, and drying, the resulting precursor is heated to 700°C at 5°C / min under an argon atmosphere and calcined for 5 h to obtain an 8%-Ni / NC-700-2 catalyst.

[0047] Catalyst Performance Evaluation: The 8%-Ni / NC-700-2 catalyst was first reduced under a H2 atmosphere at 500°C for 3 h to completely reduce the nickel metal. A 15 wt% adiponitrile / isopropanol solution and 0.5 g of the 8%-Ni / NC-700-2 catalyst were then added to an autoclave. The autoclave was sealed and filled with hydrogen at 1 MPa for three replacement cycles before the pressure was increased to 4.0 MPa. The hydrogen cylinder was opened to maintain a constant pressure in the autoclave while the temperature was raised. Once the autoclave temperature reached and stabilized at 100°C, the magnetic stirrer was activated and the reaction timer was started. After a 4-h reaction, the reaction mixture was cooled to room temperature and the pressure was released. The reaction products were analyzed by gas chromatography (Table 1).

[0048] Example 6:

[0049] Catalyst preparation: 0.01 mol of nickel nitrate hexahydrate and 0.02 mol of urea were weighed and dissolved in 50 ml of deionized water. After stirring, 10 g of PPy-derived carbon fiber (prepared in Example 1) was added and stirred to obtain a uniform mixture. The mixture was then hydrothermally aged at 120°C for 8 h. After cooling, filtering, and drying, the precursor was heated to 800°C at 5°C / min under an argon atmosphere and calcined for 3 h to obtain a 5%-Ni / NC-800 catalyst.

[0050] Catalyst performance evaluation: 2.0 g of 5%-Ni / NC-800 catalyst was loaded into a fixed bed and reduced under H2 atmosphere at 500 °C for 3 h. After the reduction was completed and the temperature dropped to the experimental temperature, 50 wt% 6-aminocapronitrile / ethanol solution was used as the raw material. The reaction temperature was 100 °C, the reaction pressure was 4 MPa, and the mass space velocity was set to 2.0 h -1 , hydrogenation was carried out under the condition that the molar ratio of hydrogen to adiponitrile was set to 30 to obtain a hexamethylenediamine reaction liquid, which was analyzed by gas chromatography. The results are shown in Table 1.

[0051] Example 7:

[0052] Catalyst preparation: 0.01 mol of nickel nitrate hexahydrate and 0.02 mol of urea were weighed and dissolved in 50 ml of deionized water. After stirring, 10 g of PPy-derived carbon fiber (prepared in Example 1) was added and stirred to obtain a uniform mixture. The mixture was then hydrothermally aged at 120°C for 8 h. After cooling, filtering, and drying, the precursor was heated to 600°C at 5°C / min under an argon atmosphere and calcined for 3 h to obtain a 5%-Ni / NC-600 catalyst.

[0053] Catalyst performance evaluation: 2.0 g of 5%-Ni / NC-600 catalyst was loaded into a fixed bed and reduced under H2 atmosphere at 500 °C for 3 h. After the reduction was completed and the temperature dropped to the experimental temperature, 30 wt% 6-aminocapronitrile / ethanol solution was used as the raw material. The reaction temperature was 100 °C, the reaction pressure was 4 MPa, and the mass space velocity was set to 2.0 h -1 , hydrogenation was carried out under the condition that the molar ratio of hydrogen to adiponitrile was set to 30 to obtain a hexamethylenediamine reaction liquid, which was analyzed by gas chromatography. The results are shown in Table 1.

[0054] Comparative Example 1:

[0055] Catalyst preparation: The catalyst preparation was similar to that in Example 1, except that the PPy was first calcined at 800° C. under an inert atmosphere before loading nickel metal.

[0056] The catalyst performance evaluation was consistent with that in Example 1. The evaluation results are shown in Table 1.

[0057] Comparative Example 2:

[0058] Catalyst preparation: The catalyst preparation was similar to that in Example 3, except that PPy was replaced with graphite carbon.

[0059] The catalyst performance evaluation was consistent with that in Example 3. The evaluation results are shown in Table 1.

[0060] Comparative Example 3:

[0061] Catalyst preparation: The catalyst preparation was similar to that in Example 2, except that PPy was replaced with carbon fiber.

[0062] The catalyst performance evaluation was consistent with that in Example 2. The evaluation results are shown in Table 1.

[0063] Comparative Example 4:

[0064] Catalyst preparation: The catalyst preparation was similar to that in Example 6, except that PPy was replaced with carbon nanotubes.

[0065] The catalyst performance evaluation was consistent with that in Example 6. The evaluation results are shown in Table 1.

[0066] Comparison of the results of Example 1 with Comparative Example 1 shows that the catalytic effect of the nickel metal loaded on the precursor after PPy is first calcined to form carbon fibers is lower than that without calcination, which indicates that the carbon fiber structure formed by calcining PPy is not conducive to the loading of nickel metal; comparison of the results of Examples 2, 3, 6 and Comparative Examples 2-4 shows that the nitrile hydrogenation catalyst with PPy-derived carbon fibers as carriers is more effective than other carbon carriers. This is because when other carbon carriers load nickel metal, the metal is prone to agglomeration, resulting in larger particle size and weak metal-carrier interaction, while the rich nitrogen defects and micro / mesoporous structure of PPy-derived carbon fibers are conducive to the capture and highly stable dispersion of metal precursors, so the catalyst prepared with other carbon carriers is weaker than that of PPy-derived carbon fibers.

[0067] Table 1. Evaluation results of the catalysts prepared in different examples for the synthesis of hexamethylenediamine

[0068]

[0069] Example 8

[0070] Recycling experiment of the 5%-Ni / NC-700 catalyst of Example 2:

[0071] First, 0.25 g of 5%-Ni / NC-700 catalyst was reduced under H2 atmosphere at 500°C for 3 h to completely reduce the nickel metal. Then, a 10 wt% adiponitrile / isopropanol solution and 0.25 g of 5%-Ni / NC-700 catalyst were added to the autoclave. The autoclave was sealed and filled with hydrogen at 1 MPa for 3-5 times. After that, it was placed in a heating mantle. When the temperature in the autoclave reached 100°C, the hydrogen pressure was increased to 4.0 MPa, the magnetic stirrer was turned on, and the reaction timer was started. After the reaction was allowed to proceed for 4 h, the reaction was cooled to room temperature, the reaction pressure was released, and the product was filtered and analyzed by gas chromatography. The catalyst was recovered, dried, and reduced, and the above steps were repeated. The conversion selectivity for each use is shown in Table 2:

[0072] Table 2. Recycling experimental results of 5%-Ni / NC-700 catalyst

[0073]

Claims

1. A method for preparing a PPy-derived carbon fiber-supported nickel catalyst, characterized in that: The specific steps are as follows: (1) Preparing a PPy-derived carbon fiber precursor. The preparation method of the PPy-derived carbon fiber precursor is as follows: 1) Add hydrochloric acid to water. In an ice-water bath, add hexadecyltrimethylammonium bromide to the solution and stir until dissolved. 2) Add ammonium persulfate to the above solution and stir until the solution turns milky white. Then add pyrrole dropwise and stir at room temperature for 3 hours to obtain a black flocculent product. 3) Washing with anhydrous ethanol and ultrapure water, filtering multiple times, vacuum drying the resulting product, and grinding to obtain black powder polypyrrole; (2) After dissolving the active nickel metal salt and the precipitant in water, add the PPy-derived carbon fiber precursor, stir and hydrothermally react, centrifuge and filter, and dry at low temperature. The hydrothermal temperature is 120 ° C and the hydrothermal time is 2-12 h; (3) After high-temperature calcination, highly dispersed nickel-loaded PPy catalyst was obtained.

2. The preparation method according to claim 1, characterized in that The nickel metal salt is one of nickel chloride, nickel nitrate, nickel bromide and nickelous hydroxide, wherein the metal loading amount is 3%-10%.

3. The preparation method according to claim 1, characterized in that The precipitant is one or more of Na2CO3, NaOH, NH3·H2O and urea, and the molar ratio of the precipitant to the loaded metal is 0.5-3:

1.

4. The preparation method according to claim 1, characterized in that The drying temperature is 45-120° C., the calcination temperature is 600-800° C., the calcination atmosphere is argon atmosphere, and the calcination time is 2-8 h.

5. Use of the catalyst prepared according to the preparation method according to any one of claims 1 to 4 in the hydrogenation reaction of nitrile compounds to produce hexamethylenediamine.

6. The use according to claim 5, characterized in that The catalyst is first subjected to a reduction reaction before the nitrile hydrogenation reaction to generate hexamethylenediamine. The reduction reaction is to reduce the catalyst at a temperature range of 400-700° C. and a reducing gas of H 2 or H 2 / N 2 for 2-6 hours.

7. The use according to claim 5, characterized in that The nitrile compound is one of adiponitrile or 6-aminocapronitrile; during the hydrogenation reaction, the nitrile compound is dissolved in an alcohol solvent, which is one or more of methanol, ethanol, propanol, and isopropanol, wherein the mass concentration of the nitrile compound is 10-60 wt%.

8. The use according to claim 5, characterized in that The hydrogenation reaction conditions are: reaction temperature of 60-130°C; reaction pressure of 2.0-5.0 MPa.

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