A carbon-modified cobalt-based catalyst, a preparation method thereof, and a preparation method of an organic amine

Abstract

The present application provides a carbon-modified cobalt-based catalyst, a preparation method thereof, and a preparation method of an organic amine. The cobalt-based catalyst comprises a carrier and an active component on at least part of the surface of the carrier; the carrier comprises a carbon material and boron-containing alumina on at least part of the surface of the carbon material; the active component comprises cobalt particles; and the carbon material and the active component are connected by a chemical bond. The cobalt-based catalyst has excellent catalytic activity and service life, and when used in the preparation of an organic amine, the conversion rate of raw materials and the selectivity of products can be improved.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and in particular to a carbon-modified cobalt-based catalyst and its preparation method, as well as a method for preparing organic amines. Background Technology

[0002] Hydrogenation is a key process in the chemical industry for preparing fine chemicals, pharmaceutical intermediates, and new energy materials. In the hydrogenation reaction of organic amine compounds such as 2-methylpentanediamine synthesized using catalysts, the reaction system generally suffers from low hydrogen activation efficiency, poor product selectivity, and frequent side reactions. Furthermore, precise control of the distribution of water molecules and alkaline substances at the reaction interface is required to effectively avoid side reactions such as excessive deammoniation and cyclization. This places high demands on the comprehensive performance of the catalyst.

[0003] Currently, cobalt-based catalysts are commonly used in the industrial preparation of the aforementioned organic amine compounds. These catalysts mostly use traditional inorganic oxides such as alumina and silica as supports, and load the cobalt active component through impregnation or co-precipitation methods. However, existing cobalt-based catalysts have obvious performance defects: on the one hand, the conductivity and pore structure of the support are limited, resulting in a weak overflow effect of hydrogen molecules on the surface of the cobalt-based catalyst. Especially under low-pressure reaction conditions, the intrinsic hydrogenation activity of cobalt-based catalysts is insufficient, making it difficult to meet the needs of industrial production. On the other hand, the electronic structure of the cobalt active center lacks effective regulation, which can easily lead to competitive reactions between the target organic amine product and byproducts such as 3-methylpiperidine. Furthermore, existing technologies require the addition of additional alkali (such as NaOH) to adjust the reaction environment, and excessive alkaline conditions can easily induce new side reactions, further leading to a decrease in product selectivity.

[0004] Therefore, there is a need to provide a catalyst that combines high activity, high selectivity, long lifespan, and low maintenance cost to meet the industrial requirements for the synthesis of organic amine compounds. Summary of the Invention

[0005] This invention provides a carbon-modified cobalt-based catalyst with excellent catalytic activity. When using this cobalt-based catalyst for catalytic hydrogenation, the selectivity of the product can be improved and the probability of side reactions can be reduced.

[0006] This invention provides a method for preparing a carbon-modified cobalt-based catalyst, which can prepare the above-mentioned cobalt-based catalyst. When using the cobalt-based catalyst for catalytic hydrogenation reaction, the selectivity of the product can be improved and the probability of side reactions can be reduced.

[0007] This invention provides a method for preparing organic amine compounds, which can be prepared by hydrogenation reaction using the cobalt-based catalyst described above. This preparation method can improve the selectivity of organic amine compounds and reduce the probability of side reactions.

[0008] A first aspect of the present invention provides a carbon-modified cobalt-based catalyst, comprising a support and an active component located on at least a portion of the surface of the support;

[0009] The carrier comprises a carbon material and boron-containing aluminum oxide located on at least a portion of the surface of the carbon material;

[0010] The active component includes cobalt particles;

[0011] The carbon material is connected to the active component by chemical bonds.

[0012] The carbon-modified cobalt-based catalyst as described above, wherein the active component further includes a cooperating metal element located at least a portion of the surface of the cobalt particles and / or at least a portion of the surface of the support;

[0013] The auxiliary metal element includes at least one of transition metal elements, alkali metal elements, and alkaline earth metal elements.

[0014] The carbon-modified cobalt-based catalyst described above, wherein the support comprises micropores and mesopores, wherein the pore size of the micropores is <2 nm and the pore size of the mesopores is 2~50 nm.

[0015] The carbon-modified cobalt-based catalyst as described above, wherein the mass percentage of cobalt in the carbon-modified cobalt-based catalyst is 10-30%; and / or,

[0016] The cobalt particles have a particle size of <10 nm; and / or,

[0017] The mass percentage of the transition metal element is 0.1-5%; and / or,

[0018] The alkali metal element has a mass percentage content of 0.5% to 5%; and / or,

[0019] The mass percentage content of the alkaline earth metal element is 0.2-6%; and / or,

[0020] The mass ratio of the transition metal element to cobalt element is 0.05~15; and / or,

[0021] The mass ratio of the alkali metal element to cobalt element is 0.06~20; and / or,

[0022] The mass ratio of the alkaline earth metal element to cobalt element is 0.075~20.

[0023] In the carbon-modified cobalt-based catalyst described above, the boron content of the boron-containing alumina is 0.5-2% by mass.

[0024] A second aspect of the present invention provides a method for preparing a carbon-modified cobalt-based catalyst, comprising:

[0025] A carrier is obtained by hydrothermal reaction of functionalized carbon material, boron-containing alumina, and surfactant; the surface of the functionalized carbon material has oxygen-containing functional groups.

[0026] The support is subjected to a first impregnation treatment in a cobalt solution to obtain a catalyst precursor;

[0027] The catalyst precursor is reduced to obtain the carbon-modified cobalt-based catalyst containing cobalt particles.

[0028] In the preparation method described above, the hydrothermal reaction is carried out at a temperature of 120-180°C for a time of 2-4 hours; and / or,

[0029] In the first impregnation treatment, the concentration of the cobalt solution is 0.15~0.5 mol / L, the temperature is 25~30℃, and the time is 2~4 h; and / or,

[0030] In the reduction process, the temperature is 300~500℃ and the time is 2~8h.

[0031] The preparation method described above further includes: subjecting the product obtained from the first impregnation treatment to a second impregnation treatment in a fluxing metal solution to obtain the catalyst precursor;

[0032] The auxiliary metal solution includes at least one of transition metal elements, alkali metal elements, and alkaline earth metal elements.

[0033] In the preparation method described above, in the second impregnation treatment, the concentration of the auxiliary metal solution is 0.05~0.2mol / L, the temperature is 40~70℃, and the time is 1~3h.

[0034] A third aspect of the present invention provides a method for preparing an organic amine compound, comprising: performing a hydrogenation reaction using the above-described carbon-modified cobalt-based catalyst.

[0035] This invention introduces carbon materials into a cobalt-based catalyst, utilizing the chemical bonds formed between the oxygen-containing functional groups on the surface of the carbon materials and the cobalt element. This results in more uniform dispersion of cobalt particles within the carbon-modified cobalt-based catalyst support, thereby enhancing the catalytic activity and lifespan of the carbon-modified cobalt-based catalyst. When the cobalt-based catalyst is used for the preparation of organic amines, the high conductivity of the carbon materials enhances the overflow effect of hydrogen molecules, improving the activation and migration efficiency of hydrogen during the reaction. Simultaneously, the synergistic effect of the basic sites of boron-containing alumina in the cobalt-based catalyst and the hydrophobicity of the carbon materials can dynamically regulate the distribution of water molecules and basic substances at the reaction interface, suppressing side reactions and thus improving the selectivity of the reaction products. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] Existing cobalt-based hydrogenation catalysts suffer from insufficient activity, poor selectivity, and difficulty in controlling side reactions. The inventors discovered that by introducing carbon materials into the catalyst and constructing a "metal-carbon" synergistic system, the catalyst's activity, selectivity, and stability can be synergistically optimized.

[0038] Based on this, in a first aspect, the present invention provides a carbon-modified cobalt-based catalyst, comprising a support and an active component located on at least a portion of the surface of the support;

[0039] The carrier includes a carbon material and boron-containing alumina located on at least a portion of the surface of the carbon material;

[0040] The active components include cobalt particles;

[0041] Carbon materials are connected to active components via chemical bonds.

[0042] Specifically, the carbon-modified cobalt-based catalyst of the present invention is composed of a support and an active component loaded on at least a portion of the surface of the support. The support is a composite structure, which is a composite support based on carbon material and having boron aluminum oxide on at least a portion of the surface of the carbon material; the active component includes cobalt particles, and the surface of the carbon material has oxygen-containing functional groups, such as hydroxyl (-OH) and carboxyl (-COOH), which can form chemical bonds with cobalt atoms in the cobalt particles.

[0043] In the carbon-modified cobalt-based catalyst of the present invention, since the carbon material and cobalt particles are connected by chemical bonds, the cobalt particles can be fixed on the surface of the carbon material, so that the cobalt particles are uniformly dispersed and remain stable on the surface of the carbon material. Therefore, the carbon-modified cobalt-based catalyst of the present invention has excellent catalytic activity and product selectivity, and has a long service life.

[0044] When using the carbon-modified cobalt-based catalyst of this invention for hydrogenation reactions (e.g., hydrogenation of nitrile compounds to prepare organic amines), the high conductivity of the carbon material can enhance the overflow effect of hydrogen molecules, improve the activation and migration efficiency of hydrogen under low pressure conditions, and enable the hydrogenation reaction to have high reactivity even under low pressure conditions. At the same time, the presence of basic sites in boron-containing alumina, combined with the hydrophobicity of the carbon material, dynamically regulates the distribution of water molecules and basic substances at the reaction interface, reduces the dependence of the reaction system on external alkalis (such as sodium hydroxide), and lowers the corrosivity of the reaction system and the risk of by-product formation.

[0045] The carbon-modified cobalt-based catalyst of this invention exhibits high activity, high selectivity and excellent stability in hydrogenation reactions, meeting the high-efficiency requirements of the industrialization of fine chemicals, pharmaceutical intermediates and new energy materials.

[0046] In some implementations, the carbon material includes graphene and / or carbon nanotubes.

[0047] In some embodiments of the present invention, the active component further includes a cooperating metal element located at at least a portion of the surface of the cobalt particles and / or at least a portion of the surface of the support.

[0048] The auxiliary metal element includes at least one of the transition metal elements, alkali metal elements, and alkaline earth metal elements. For example, the transition metal element can be rhenium (Re), the alkali metal element can be cesium (Cs), and the alkaline earth metal element can be strontium (Sr) or barium (Ba).

[0049] Specifically, the auxiliary metal element may be located on at least a portion of the surface of the cobalt particle, or on at least a portion of the surface of the carrier, or simultaneously on at least a portion of the surface of both the cobalt particle and the carrier.

[0050] There is a "metal-carbon" interface between carbon materials and cobalt particles. When the auxiliary metal element includes a transition metal element, an electronic synergistic effect can be formed between cobalt particles. Through electron transfer, the position of the d electron center of cobalt element in carbon-modified cobalt-based catalyst is regulated, thereby improving the catalytic activity of carbon-modified cobalt-based catalyst. When using carbon-modified cobalt-based catalyst for hydrogenation reaction, the excessive adsorption of target product by cobalt active center can be weakened, reducing the probability of side reactions.

[0051] When the auxiliary metal element includes an alkali metal element, the basicity of the alkali metal element itself can synergistically work with the basic sites in the boron-containing alumina in the carbon-modified cobalt-based catalyst. When using the carbon-modified cobalt-based catalyst for hydrogenation reaction, the alkaline microenvironment in the reaction can be adjusted, the dependence of the reaction system on external alkaline substances such as sodium hydroxide can be reduced, and side reactions caused by excessive external alkali can be reduced.

[0052] When the auxiliary metal element includes an alkaline earth metal element, the alkaline earth metal element has moderate alkalinity. When using a carbon-modified cobalt-based catalyst for hydrogenation reaction, it can enhance the adsorption and neutralization capacity of acidic impurities in the reaction system, inhibit the occurrence of side reactions, and thus improve the selectivity of the target product.

[0053] In some embodiments of the present invention, the support includes micropores and mesopores. When the pore size of the micropores is <2 nm and the pore size of the mesopores is 2~50 nm (for example, it can be a range of 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm or any combination thereof), a three-dimensional porous network structure can be formed, providing more loading space for the active components and allowing the active components to be uniformly dispersed in the support, thereby improving the catalytic activity of the carbon-modified cobalt-based catalyst. At the same time, in the hydrogenation reaction, the micropores can preferentially adsorb hydrogen gas and reactant molecules, increasing the contact probability between reactants and active components and improving the conversion efficiency of reactants. The mesopores provide a fast diffusion channel for product molecules, preventing excessive accumulation of products that could lead to reverse reactions. Furthermore, the mesopores can reduce the mass transfer resistance between reactants and products in the carbon-modified cobalt-based catalyst, thereby increasing the reaction rate of the hydrogenation reaction.

[0054] In some embodiments of the present invention, when the mass percentage of cobalt in the carbon-modified cobalt-based catalyst is 10-30% (for example, it can be any of 10%, 15%, 20%, 25%, 30%, or any combination thereof), it can ensure that the cobalt particles are uniformly dispersed on the support surface, providing more sufficient active centers for the carbon-modified cobalt-based catalyst, and further improving the catalytic efficiency and feed conversion rate of the hydrogenation reaction. Further, the mass percentage of cobalt in the carbon-modified cobalt-based catalyst is 15-25%.

[0055] In some embodiments of the present invention, when the cobalt particles have a particle size of <10 nm, they can bind more stably with the oxygen-containing functional groups of carbon materials, and the cobalt particles are more uniformly dispersed on the support surface. This reduces the probability of cobalt particles becoming deactivated due to aggregation and sintering during the hydrogenation reaction, improves the utilization rate of cobalt active centers, and gives the carbon-modified cobalt-based catalyst higher catalytic activity. At the same time, the small-sized cobalt particles can contact the auxiliary metal elements more closely, enhancing the electron transfer effect and further weakening the excessive adsorption of products by the carbon-modified cobalt-based catalyst during the hydrogenation reaction, thereby improving the product yield.

[0056] In some embodiments of the present invention, when the mass percentage of the transition metal element is 0.1-5% (for example, it can be any one of 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or any combination thereof), it can be uniformly distributed on the surface of the cobalt particles and the support, thereby enhancing the electronic synergistic effect between the transition metal and the cobalt particles and further improving the catalytic activity of the carbon-modified cobalt-based catalyst.

[0057] In some embodiments of the present invention, when the mass percentage of alkali metal elements is 0.5% to 5% (for example, it can be any one of 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or any combination thereof), it can better match the alkaline sites in boron-containing alumina, forming a stable alkaline microenvironment during the hydrogenation reaction, further reducing the probability of side reactions.

[0058] In some embodiments of the present invention, when the mass percentage of alkaline earth metal elements is 0.2-6% (for example, it can be any one of 0.2%, 0.7%, 1.2%, 1.7%, 2.2%, 2.7%, 3.2%, 3.7%, 4.2%, 4.7%, 5.2%, 5.7% or any combination thereof), the efficiency of adsorption and neutralization of acidic impurities in the reaction system can be further improved during the hydrogenation reaction while maintaining an alkaline environment in the hydrogenation reaction, thus giving the target product higher selectivity.

[0059] In some embodiments of the present invention, when the mass ratio of transition metal element to cobalt element is 0.05 to 15 (for example, it can be any one of 0.05, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or any combination thereof), the electronic synergistic effect of the "metal-carbon" interface can be further enhanced, so that the carbon-modified cobalt-based catalyst has higher catalytic activity under low pressure conditions.

[0060] In some embodiments of the present invention, when the mass ratio of alkali metal element to cobalt element is 0.06 to 20 (for example, it can be any one or any two of 0.06, 0.1, 0.2, 0.5, 2, 3.5, 5, 6.5, 8, 9.5, 11, 12.5, 14, 15.5, 17, 18.5, 20), the carbon-modified cobalt-based catalyst can maintain excellent catalytic activity while controlling the distribution of water molecules and alkaline substances at the reaction interface in the hydrogenation reaction, preventing unnecessary cyclization side reactions of the raw materials, and giving the target product higher selectivity.

[0061] In some embodiments of the present invention, when the mass ratio of alkaline earth metal elements to cobalt elements is 0.075~20 (for example, it can be any one of 0.075, 0.1, 0.2, 0.5, 2, 3.5, 5, 6.5, 8, 9.5, 11, 12.5, 14, 15.5, 17, 18.5, 20 or any combination thereof), it can be uniformly dispersed on the surface of cobalt particles and the surface of the carrier. It forms a synergy with the hydrophobic properties of carbon materials and the alkaline sites of boron-containing alumina, while adsorbing and neutralizing acidic impurities in the reaction system, and keeping the moisture distribution at the reaction interface balanced, further suppressing the probability of side reactions occurring near the cobalt active center of the raw materials.

[0062] In some embodiments of the present invention, when the mass percentage of boron in the boron-containing alumina is 0.5-2% (for example, it can be any one of 0.5%, 1.0%, 1.5%, 2.0%, or any combination thereof), it can ensure that the boron element is uniformly dispersed in the alumina framework, providing sufficient and uniformly distributed alkaline sites for the carbon-modified cobalt-based catalyst. This makes the carbon-modified cobalt-based catalyst more effective in regulating the distribution of water molecules and alkaline substances at the reaction interface during hydrogenation, thereby having a stronger inhibitory effect on side reactions and further improving the selectivity of the target product.

[0063] Secondly, the present invention provides a method for preparing a carbon-modified cobalt-based catalyst, comprising:

[0064] A carrier is obtained by hydrothermal reaction of functionalized carbon materials, boron-containing alumina, and surfactants; the surface of the functionalized carbon materials has oxygen-containing functional groups.

[0065] The support was placed in a cobalt solution for a first impregnation treatment to obtain the catalyst precursor.

[0066] The catalyst precursor was reduced to obtain a carbon-modified cobalt-based catalyst containing cobalt particles.

[0067] Specifically, in the hydrothermal reaction, under the action of surfactant, the hydrophobic end interacts with the surface of the functionalized carbon material, causing the surfactant to be adsorbed on the surface of the functionalized carbon material, while the hydrophilic end interacts with boron-containing alumina, fixing the boron-containing alumina on the surface of the functionalized carbon material, so that the boron-containing alumina grows uniformly on the surface of the functionalized carbon material and gradually forms a three-dimensional porous network structure, thus obtaining a carrier.

[0068] In the first impregnation process, cobalt ions in the cobalt solution undergo a coordination reaction with oxygen-containing functional groups on the surface of the functionalized carbon material in the support. The oxygen atoms in the oxygen-containing functional groups form chemical bonds with the cobalt ions and anchor the cobalt ions on the surface of the carbon material, thus obtaining the catalyst precursor.

[0069] In the reduction process, cobalt ions in the catalyst precursor are reduced to elemental cobalt. Since stable chemical bonds have been formed between cobalt atoms and oxygen-containing functional groups on the surface of functionalized carbon materials, cobalt atoms cannot freely aggregate and grow. Instead, they undergo small-scale crystallization on the surface of carbon materials, eventually forming cobalt particles with small and uniform particle size, thus obtaining a carbon-modified cobalt-based catalyst containing cobalt particles.

[0070] This invention enables the growth of boron-containing alumina on the surface of carbon materials, enhancing the interfacial bonding strength between the functionalized carbon materials and the boron-containing alumina, improving the stability of the support, and thus improving the stability of the carbon-modified cobalt-based catalyst. At the same time, it enables cobalt ions to coordinate with oxygen-containing functional groups on the surface of the functionalized carbon materials to form chemical bonds, achieving the anchoring and uniform dispersion of cobalt particles on the support surface, thereby improving the catalytic activity of the carbon-modified cobalt-based catalyst.

[0071] The preparation method of the carbon-modified cobalt-based catalyst of the present invention has high process controllability and good repeatability, and can prepare carbon-modified cobalt-based catalysts with excellent catalytic activity and high stability. Moreover, only surfactants need to be added as auxiliary agents, which reduces the raw material preparation cost and operation difficulty for industrial production.

[0072] The present invention does not specifically limit the surfactant, and can be any surfactant commonly used in the art. For example, the surfactant can be hexadecyltrimethylammonium bromide (CTAB).

[0073] The present invention does not specifically limit the cobalt solution, and can be any solution containing cobalt salt commonly used in the art. For example, the cobalt salt can be cobalt nitrate or cobalt sulfate.

[0074] The present invention does not impose any particular limitation on the source of boron-containing alumina; it can be obtained by purchase or prepared by methods known in the art.

[0075] In some embodiments, boron-containing alumina can be prepared by including the following steps:

[0076] A precipitant is added to an aluminate solution at 25-40°C to obtain a precipitate. The precipitate is then mixed with a boron source and aged at 60-90°C to obtain boron-containing alumina.

[0077] In some embodiments, the boron source is at least one of boric acid, borax (sodium tetraborate), and ammonium pentaborate.

[0078] In some embodiments, the aluminate is at least one of sodium aluminate, potassium aluminate, and lithium aluminate.

[0079] In some implementations, the precipitant is carbon dioxide.

[0080] For example, the temperature at which the precipitant is added to the aluminate solution can be a range of 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, or any combination thereof.

[0081] For example, the aging temperature can be a range of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or any combination thereof.

[0082] The present invention does not impose any particular limitation on the source of the functionalized carbon material. It can be obtained by purchase or by methods known in the art, such as mixing carbon material with hydrogen peroxide and then performing an oxidation treatment to obtain the functionalized carbon material.

[0083] In some implementations, the carbon material may be graphene and / or carbon nanotubes.

[0084] The present invention does not particularly limit the reduction treatment method, and can use the reduction treatment method commonly used in the art. For example, the catalyst precursor can be placed in a hydrogen atmosphere for reduction treatment.

[0085] In some embodiments of the present invention, the hydrothermal reaction is carried out at a temperature of 120–180°C, for example, a range of any one or any combination of 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, and 180°C; and for a time of 2–4 hours, for example, a range of any one or any combination of 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours. This temperature and time range allows boron-containing alumina to grow more fully on the surface of the functionalized carbon material, improving the efficiency of the hydrothermal reaction.

[0086] In some embodiments of the present invention, in the first impregnation treatment, the concentration of the cobalt solution is 0.15~0.5 mol / L, for example, it can be any one of 0.15 mol / L, 0.3 mol / L, 0.45 mol / L, 0.5 mol / L, or any combination thereof; the temperature is 25~30°C, for example, it can be any one of 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, or any combination thereof; the time is 2~4 h, for example, it can be any one of 2 h, 2.5 h, 3 h, 3.5 h, 4 h, or any combination thereof. The above-mentioned concentration range, temperature range, and time range allow for a more complete coordination reaction between cobalt ions and the oxygen-containing functional groups on the surface of the functionalized carbon material in the support under mild conditions, resulting in the cobalt ions being stably anchored on the support surface and uniformly distributed on the support surface.

[0087] In some embodiments of the present invention, the reduction process is carried out at a temperature of 300–500°C, for example, any one of 300°C, 350°C, 400°C, 450°C, and 500°C, or any combination thereof; and for a time of 2–8 hours, for example, any one of 2 hours, 3 hours, 4 hours, 6 hours, and 8 hours, or any combination thereof. This temperature and time range allows for the complete reduction of cobalt ions and cooperating metal ions in the catalyst precursor to elemental cobalt and elemental cooperating metal, while conserving energy.

[0088] In some embodiments of the present invention, the method further includes: subjecting the product obtained from the first impregnation treatment to a second impregnation treatment in a fluxing metal solution to obtain a catalyst precursor; the fluxing metal solution includes at least one of a transition metal element, an alkali metal element, and an alkaline earth metal element.

[0089] This invention employs a stepwise impregnation method. First, cobalt ions are loaded onto the support through a first impregnation, preventing the auxiliary metal ions from competing with cobalt ions for strong active sites on the support surface and ensuring that the chemical bonding between cobalt ions and oxygen-containing functional groups remains unaffected. Simultaneously, the auxiliary metal ions are uniformly dispersed in the support and on the surface of the cobalt ions. After reduction treatment, the auxiliary metal ions are reduced to elemental auxiliary metals, which can each exert electron transfer effects and regulate the alkaline microenvironment, achieving synergistic enhancement between the auxiliary metal particles and cobalt particles. This results in the carbon-modified cobalt-based catalyst of this invention exhibiting excellent catalytic activity, as well as higher product selectivity and the ability to suppress side reactions.

[0090] In some embodiments of the present invention, in the second impregnation treatment, the concentration of the auxiliary metal solution is 0.05~0.2 mol / L, for example, it can be any or a combination of 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L; the temperature is 40~70°C, for example, it can be any or a combination of 40°C, 50°C, 60°C, 70°C; and the time is 1~3 h, for example, it can be any or a combination of 1 h, 2 h, 3 h. The above-mentioned concentration range, temperature range, and time range can, while saving energy, allow the auxiliary metal ions to more fully adhere to the carrier surface and the edge of the cobalt ions through electron transfer effect and / or surface coordination.

[0091] In some embodiments, the concentration of the transition metal solution (such as sodium perrhenate solution) is 0.1~0.15 mol / L.

[0092] In some embodiments, the concentration of the alkali metal solution (such as cesium hydroxide solution) is 0.1~0.2 mol / L.

[0093] In some embodiments, the concentration of the alkaline earth metal solution (such as barium nitrate solution) is 0.05~0.1 mol / L.

[0094] In some embodiments, the second impregnation treatment may be performed simultaneously with mechanical stirring or ultrasonic-assisted operation to enable the metal ions to be loaded onto the carrier surface and the edges of the cobalt ions more quickly.

[0095] Thirdly, the present invention provides a method for preparing organic amine compounds, comprising: performing a hydrogenation reaction using the above-mentioned carbon-modified cobalt-based catalyst.

[0096] In the preparation of organic amine compounds, the carbon-modified cobalt-based catalyst support combines the high conductivity of carbon materials with abundant micropores and mesopores, which can enhance the overflow effect of hydrogen molecules. Furthermore, the cobalt particles are dispersed in the support at the nanoscale, fully exposing the cobalt active centers and resulting in strong activation of hydrogen. This allows for faster activation of hydrogen molecules in low-pressure hydrogenation reactions, improving the reaction conversion rate. Simultaneously, the auxiliary metal element can form an electronic synergistic effect with cobalt, and by regulating the alkaline microenvironment in the reaction system through alkaline sites, it can suppress side reactions such as deamination and cyclization, improving the selectivity of organic amine compounds. Moreover, the carbon-modified cobalt-based catalyst of this invention has a stable structure and long service life, reducing the frequency of catalyst replacement and lowering the preparation cost of organic amine compounds.

[0097] This invention does not specifically limit the organic amine compounds; for example, the organic amine compound may be 2-methylpentanediamine.

[0098] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0099] Example 1

[0100] The preparation method of 2-methylpentanediamine in this embodiment includes the following steps:

[0101] (1) Preparation of boron-containing alumina

[0102] Carbon dioxide was introduced into a 0.5 mol / L aluminate solution at 35°C to obtain a precipitate. The precipitate was mixed with a boron source and aged at 80°C for 3 hours to obtain boron-containing alumina. The aluminate was sodium aluminate and the boron source was boric acid.

[0103] (2) Preparation of functionalized carbon materials

[0104] 1g of carbon material was added to 1000mL of a 5% (w / w) hydrogen peroxide aqueous solution, ultrasonically dispersed, and then subjected to stirring oxidation treatment at 100℃ for 24h to obtain a functionalized carbon material precursor. The carbon material included 0.5g of carbon nanotubes and 0.5g of graphene. After cooling the functionalized carbon material precursor to room temperature, it was centrifuged at 8000r / min for 10min. After separating the supernatant, a solid was obtained. The solid was washed three times with deionized water and vacuum dried at 80℃ for 12h to obtain the functionalized carbon material.

[0105] (3) Preparation of carbon-modified cobalt-based catalysts

[0106] 1.0 g of functionalized carbon material, 3.0 g of boron-containing alumina, and 50 mL of 0.05 mol / L CTAB solution were placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150 °C for 4 h to obtain a support. The support was then subjected to a first impregnation treatment in a 0.15 mol / L cobalt nitrate solution at 25 °C for 2 h. Subsequently, it was subjected to a second impregnation treatment in a fluxing metal solution at 55 °C for 2 h to obtain a catalyst precursor. The fluxing metal solution consisted of a 0.12 mol / L sodium perrhenate solution, a 0.15 mol / L cesium nitrate solution, and a 0.10 mol / L barium nitrate solution. The catalyst precursor was then subjected to a reduction treatment in a hydrogen atmosphere at 450 °C for 4 h with a hydrogen flow rate of 200 mL / min to obtain a carbon-modified cobalt-based catalyst.

[0107] (4) Preparation of 2-methylpentanediamine

[0108] 2-Methylglutaronitrile, the carbon-modified cobalt-based catalyst prepared in this example, and ethanol were added to a 500 mL reactor, wherein the mass ratio of 2-methylglutaronitrile to carbon-modified cobalt-based catalyst was 10:1, and the amount of ethanol added was 200 mL. Nitrogen gas was introduced into the reactor to replace the air in the reactor, and this operation was repeated 3 times. After the replacement was completed, hydrogen gas was introduced into the reactor to prepare for the hydrogenation reaction. The hydrogenation reaction was carried out under stirring conditions and a hydrogen atmosphere, with a reaction pressure of 2.5 MPa and a reaction temperature of 85 °C. The hydrogen pressure and reaction temperature were maintained for 1.5 hours. After the reaction was completed, heating was stopped and the temperature and pressure were reduced. The reaction product was then removed from the reactor.

[0109] Example 2

[0110] The preparation method of 2-methylpentanediamine in this embodiment is basically the same as that in Example 1, except that:

[0111] (3) Preparation of carbon-modified cobalt-based catalysts

[0112] 1.0 g of functionalized carbon material, 3.0 g of boron-containing alumina, and 50 mL of 0.05 mol / L CTAB solution were placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150 °C for 4 h to obtain the carrier.

[0113] The support was placed in a 0.15 mol / L cobalt nitrate solution for a first impregnation treatment at 25 °C for 2 h to obtain the catalyst precursor.

[0114] The catalyst precursor was subjected to reduction treatment in a hydrogen atmosphere at a temperature of 450℃ for 4 hours at a hydrogen flow rate of 200 mL / min to obtain a carbon-modified cobalt-based catalyst.

[0115] Example 3

[0116] The preparation method of 2-methylpentanediamine in this embodiment is basically the same as that in Example 1, except that:

[0117] (3) Preparation of carbon-modified cobalt-based catalysts

[0118] 1.0 g of functionalized carbon material, 3.0 g of boron-containing alumina, and 50 mL of 0.01 mol / L (low concentration) CTAB solution were placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120 °C for 2 h to obtain the carrier.

[0119] Example 4

[0120] The preparation method of 2-methylpentanediamine in this embodiment is basically the same as that in Example 1, except that:

[0121] (3) Preparation of carbon-modified cobalt-based catalysts

[0122] 0.2 g of functionalized carbon material, 3.0 g of boron-containing alumina, and 50 mL of 0.05 mol / L CTAB solution were placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150 °C for 4 h to obtain the carrier.

[0123] Example 5

[0124] The preparation method of 2-methylpentanediamine in this embodiment is basically the same as that in Example 1, except that:

[0125] (1) Preparation of boron-containing alumina

[0126] Carbon dioxide was bubbled into a 0.5 mol / L sodium aluminate solution at 35°C to obtain a precipitate. The precipitate was mixed with boric acid (by reducing the amount of boric acid added to achieve a final boron content of 0.3%) and aged at 80°C for 3 hours to obtain boron-containing alumina. The aluminate was sodium aluminate and the boron source was boric acid.

[0127] Comparative Example 1

[0128] The preparation method of 2-methylpentanediamine in this comparative example is basically the same as that in Example 1, except that:

[0129] There is no preparation of carbon materials in (2);

[0130] (3) Preparation of cobalt-based catalysts

[0131] 3.0 g of boron-containing alumina and 50 mL of 0.05 mol / L CTAB solution were placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150 °C for 4 h. After the reaction was completed, the mixture was filtered, washed, and vacuum dried at 80 °C for 12 h to obtain the support.

[0132] The above-mentioned support was subjected to a first impregnation treatment in a 0.15 mol / L cobalt nitrate solution at 25°C for 2 hours; then it was subjected to a second impregnation treatment in a metal-additive solution (containing 0.12 mol / L sodium perrhenate, 0.15 mol / L cesium nitrate and 0.10 mol / L barium nitrate) at 55°C for 2 hours to obtain the catalyst precursor.

[0133] The catalyst precursor was subjected to reduction treatment in a hydrogen atmosphere at a temperature of 450℃ for 4 hours at a hydrogen flow rate of 200 mL / min to obtain a cobalt-based catalyst.

[0134] Performance testing

[0135] The following performance tests were performed on the examples and comparative examples respectively:

[0136] (1) Aperture test

[0137] The carbon-modified cobalt-based catalysts in Examples 1-5 and Comparative Example 1 were subjected to nitrogen adsorption-desorption tests using a fully automated specific surface area analyzer to obtain the pore size of the aforementioned carbon-modified cobalt-based catalysts. The test results are shown in Table 1.

[0138] (2) Cobalt particle size test

[0139] The particle size of the cobalt particles in Examples 1-5 and Comparative Example 1 was tested using transmission electron microscopy (TEM). The specific steps are as follows:

[0140] First, 0.1 g of the reduced carbon-modified cobalt-based catalyst solid powder was placed in 5 mL of anhydrous ethanol. The ultrasonic oscillation power was set to 150 W for 10 min, and the catalyst was uniformly dispersed in the ethanol to obtain a stable suspension. Then, 5 μL of this suspension was drawn up using a capillary tube and dropped onto the surface of a copper mesh with a supporting film. After drying, a standard sample was prepared. The sample was placed under a transmission electron microscope for morphological observation, and high-resolution images of 15 different regions were randomly selected and stored sequentially. Finally, at least 200 active cobalt particles were randomly selected from the obtained images, and their diameters were counted and their arithmetic mean was calculated. This arithmetic mean was used as the average cobalt particle size of the carbon-modified cobalt-based catalyst.

[0141] The test results are shown in Table 1.

[0142] (3) Test of the mass percentage of boron in boron-containing alumina

[0143] The mass percentage of boron in the boron-containing alumina in Examples 1-5 and Comparative Example 1 was tested. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to quantitatively analyze the boron content in the carbon-modified cobalt-based catalyst. The specific steps are as follows:

[0144] First, 1.0 mg of carbon-modified cobalt-based catalyst was weighed and 10 mL of aqua regia was added to it for complete digestion until the catalyst was completely dissolved into a transparent liquid, yielding a digestion solution. The digestion solution was then transferred to a volumetric flask and diluted to 25 mL with deionized water to obtain the test solution. During the detection phase, the test solution was injected into an ICP-OES instrument, which determined the mass concentration of boron in the test solution based on a pre-established boron standard concentration curve. Finally, by combining the measured concentration value with the total mass of the carbon-modified cobalt-based catalyst, the mass percentage of boron in the catalyst was calculated.

[0145] The test results are shown in Table 1.

[0146] Table 1

[0147]

[0148] (4) Selectivity test of 2-methylpentanediamine

[0149] The selectivity of 2-methylpentanediamine in Examples 1-5 and Comparative Example 1 was tested using the following steps:

[0150] After the hydrogenation reaction is complete, the product in the reactor is removed, allowed to stand, and the supernatant is separated. The carbon-modified cobalt-based catalyst precipitated in the lower layer is digested. A quantitative amount of the supernatant is taken, and a quantitative amount of internal standard toluene is added. The mixture is thoroughly mixed, and the unreacted mixture is analyzed by gas chromatography. The chromatographic data are quantified using the internal standard method. Then, the conversion rate of the feedstock and the selectivity of 2-methylpentanediamine are calculated using the following formula:

[0151] Raw material conversion rate % = (Concentration of 2-methylglutaronitrile in raw material - Concentration of 2-methylglutaronitrile in product) / Concentration of 2-methylglutaronitrile in raw material × 100%;

[0152] 2-Methylpentanediamine selectivity % = Concentration of 2-methylpentanediamine / (Concentration of 2-methylpentanedionitrile in feedstock - Concentration of 2-methylpentanedionitrile in product) × 100%.

[0153] The test results are shown in Table 2.

[0154] Table 2

[0155]

[0156] As shown in Table 2, the raw material conversion rate and 2-methylpentanediamine selectivity of the embodiments of the present invention are both better than those of Comparative Example 1. The reason is that the embodiments of the present invention use a support formed by functionalized carbon material and boron-containing alumina. The high conductivity of the carbon material enhances the overflow effect of hydrogen molecules and improves the activation efficiency of the carbon-modified cobalt-based catalyst for hydrogen. Furthermore, the cobalt particles are uniformly dispersed in the support, which makes the contact between the raw material and the cobalt active center more sufficient, thus improving the conversion rate of the raw material. At the same time, the cobalt particles and the carbon material are connected by chemical bonds, and the electronic regulation effect of the auxiliary metal element optimizes the d-electron structure of cobalt, weakening the excessive adsorption of 2-methylpentanediamine. Moreover, the hydrophobic properties of the carbon material and the basic sites of the boron-containing alumina synergistically regulate the distribution of water molecules and basic substances at the reaction interface, inhibiting the occurrence of side reactions such as deamination and cyclization. Therefore, the selectivity of 2-methylpentanediamine is better than that of Comparative Example 1.

[0157] From Examples 1 and 2, it can be concluded that the selectivity of 2-methylpentanediamine in Example 1 is greater than that in Example 2. The reason is that the carbon-modified cobalt-based catalyst in Example 1 includes a cooperating metal element. The electronic regulation effect of the cooperating metal element optimizes the d-electron structure of cobalt, weakens the excessive adsorption of 2-methylpentanediamine, and can further regulate the alkaline microenvironment in the reaction system, thereby reducing the probability of side reactions such as deamination and cyclization, and thus improving the selectivity of 2-methylpentanediamine.

[0158] As can be seen from Examples 1 and 3, the raw material conversion rate and the selectivity of 2-methylpentanediamine in Example 1 are higher than those in Example 2. The reason is that the micropore size of the carbon-modified cobalt-based catalyst support in Example 1 is <2nm, and the mesopore size is 2~50nm. It can provide abundant adsorption sites for hydrogen molecules, so that the raw material can contact the active center more fully and undergo hydrogenation reaction. At the same time, it can provide a smooth mass transfer channel for the reaction products and reduce the retention of the reaction products in the carbon-modified cobalt-based catalyst.

[0159] As can be seen from Examples 1 and 4, the raw material conversion rate of Example 1 is higher than that of Example 4. The reason is that in the carbon-modified cobalt-based catalyst of Example 1, the particle size of cobalt particles is <10nm, which increases the number of exposed cobalt active sites, improves the utilization rate of cobalt active centers, and allows hydrogen molecules and reactants to come into more full contact with cobalt active sites and undergo hydrogenation reaction.

[0160] As can be seen from Examples 1 and 5, the selectivity of 2-methylpentanediamine in Example 1 is higher than that in Example 5. The reason is that in the carbon-modified cobalt-based catalyst of Example 1, the mass percentage of boron in the boron-containing alumina is 0.5~2%. At this ratio, boron can be uniformly doped in the alumina framework, forming sufficient and uniformly distributed alkaline sites in the carbon-modified cobalt-based catalyst. During the hydrogenation reaction, it can work synergistically with the hydrophobic properties of carbon materials to precisely control the distribution of water molecules and alkaline substances at the reaction interface, suppressing the probability of side reactions.

[0161] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A carbon-modified cobalt-based catalyst, characterized in that, Includes a carrier and an active component located on at least a portion of the surface of the carrier; The carrier comprises a carbon material and boron-containing aluminum oxide located on at least a portion of the surface of the carbon material; The active component includes cobalt particles; The carbon material is connected to the active component by chemical bonds.

2. The carbon-modified cobalt-based catalyst according to claim 1, characterized in that, The active component further includes a cooperating metal element, which is located on at least a portion of the surface of the cobalt particles and / or at least a portion of the surface of the support; The auxiliary metal element includes at least one of transition metal elements, alkali metal elements, and alkaline earth metal elements.

3. The carbon-modified cobalt-based catalyst according to claim 1, characterized in that, The carrier includes micropores and mesopores, wherein the pore size of the micropores is <2nm and the pore size of the mesopores is 2~50nm.

4. The carbon-modified cobalt-based catalyst according to claim 2, characterized in that, In the carbon-modified cobalt-based catalyst, the mass percentage of cobalt is 10-30%; and / or, The cobalt particles have a particle size of <10 nm; and / or, The mass percentage of the transition metal element is 0.1-5%; and / or, The alkali metal element has a mass percentage content of 0.5% to 5%; and / or, The mass percentage content of the alkaline earth metal element is 0.2-6%; and / or, The mass ratio of the transition metal element to cobalt element is 0.05~15; and / or, The mass ratio of the alkali metal element to cobalt element is 0.06~20; and / or, The mass ratio of the alkaline earth metal element to cobalt element is 0.075~20.

5. The carbon-modified cobalt-based catalyst according to claim 1, characterized in that, The boron-containing alumina contains 0.5% to 2% boron by mass.

6. A method for preparing a carbon-modified cobalt-based catalyst according to any one of claims 1-5, characterized in that, include: A carrier is obtained by hydrothermal reaction of functionalized carbon materials, boron-containing alumina, and surfactants. The surface of the functionalized carbon material has oxygen-containing functional groups; The support is subjected to a first impregnation treatment in a cobalt solution to obtain a catalyst precursor; The catalyst precursor is reduced to obtain the carbon-modified cobalt-based catalyst containing cobalt particles.

7. The preparation method according to claim 6, characterized in that, In the hydrothermal reaction, the temperature is 120~180℃ and the time is 2~4h; and / or, In the first impregnation treatment, the concentration of the cobalt solution is 0.15~0.5 mol / L, the temperature is 25~30℃, and the time is 2~4 h; and / or, In the reduction process, the temperature is 300~500℃ and the time is 2~8h.

8. The preparation method according to claim 6, characterized in that, Also includes: The product obtained from the first impregnation treatment is subjected to a second impregnation treatment in a fluxing metal solution to obtain the catalyst precursor. The auxiliary metal solution includes at least one of transition metal elements, alkali metal elements, and alkaline earth metal elements.

9. The preparation method according to claim 8, characterized in that, In the second impregnation treatment, the concentration of the auxiliary metal solution is 0.05~0.2mol / L, the temperature is 40~70℃, and the time is 1~3h.

10. A method for preparing an organic amine compound, characterized in that, include: It is obtained by hydrogenation reaction using the carbon-modified cobalt-based catalyst of any one of claims 1-5.

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