A cobalt-based catalyst, its preparation method and use

Abstract

The application provides a cobalt-based catalyst, a preparation method and application thereof. The cobalt-based catalyst comprises a cobalt-based framework formed by cobalt elements and / or aluminum elements, and alkali metal elements, alkaline earth metal elements, boron elements and / or silicon elements existing in the cobalt-based framework, and the alkaline earth metal elements exist in the form of borides and / or silicides. The cobalt-based catalyst provided by the application has high stability, and can improve the selectivity of products in a 2-methylglutaronitrile hydrogenation reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a cobalt-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Dinitrile compounds (such as 2-methylglutaronitrile, MGN) are important intermediates in chemical production, and the hydrogenation reaction thereof can generate amine or piperidine compounds (such as 2-methylpentanediamine MPMD and 3-methylpiperidine 3-MP) with high added value, which are widely used in the fields of medicine, pesticide, and polymer material. However, the hydrogenation reaction of MGN faces the following challenges: poor stability of the catalyst and low selectivity of the product.

[0003] Therefore, it is an urgent technical bottleneck for the current chemical industry to develop a MGN hydrogenation catalyst with good stability and high selectivity. SUMMARY

[0004] The main purpose of the present application is to provide a cobalt-based catalyst with high stability, which can improve the selectivity of the product in the hydrogenation reaction of 2-methylglutaronitrile.

[0005] The present application also provides a preparation method of the cobalt-based catalyst, which can prepare the above-mentioned cobalt-based catalyst and has simple process and low cost.

[0006] The present application also provides a preparation method of 2-methylglutaronitrile and / or 3-methylpiperidine, which uses the above-mentioned catalyst for hydrogenation reaction of 2-methylglutaronitrile, so as to improve the selectivity of the product.

[0007] In the first aspect, the present application provides a cobalt-based catalyst, which comprises a cobalt-based framework formed by cobalt elements and / or aluminum elements, and alkali metal elements, alkaline earth metal elements, boron elements and / or silicon elements existing in the cobalt-based framework, and the alkaline earth metal elements exist in the form of borides and / or silicides.

[0008] The cobalt-based catalyst as described above further comprises at least one of the following: other metal elements of group A, group 1 metal elements, group B metal elements, group B metal elements.

[0009] The cobalt-based catalyst as described above, wherein the mass percentage of the cobalt element is 69% to 95%, the mass percentage of the aluminum element is 3% to 20%, the mass percentage of the alkali metal element is 0.1% to 5%, the mass percentage of the alkaline earth metal element is 0.2% to 6.0%, the molar ratio of the boron element and / or the silicon element to the alkaline earth metal element is (1 to 10):1, the mass ratio of the other metal elements in group A to the cobalt element is (0.1% to 3%):1, the mass ratio of the metal elements in group B to the cobalt element is (1% to 7%):1, the mass ratio of the metal elements in group C to the cobalt element is (1% to 6%):1, and the mass ratio of the metal elements in group D to the cobalt element is (100 ppm to 2000 ppm):1. The mass ratio of the other metal elements in group A to the cobalt element is (0.1% to 3%):1, the mass ratio of the metal elements in group B to the cobalt element is (1% to 7%):1, the mass ratio of the metal elements in group C to the cobalt element is (1% to 6%):1, and the mass ratio of the metal elements in group D to the cobalt element is (100 ppm to 2000 ppm):1. The mass ratio of the metal elements in group B to the cobalt element is (1% to 7%):1, the mass ratio of the metal elements in group C to the cobalt element is (1% to 6%):1, and the mass ratio of the metal elements in group D to the cobalt element is (100 ppm to 2000 ppm):1. The mass ratio of the metal elements in group C to the cobalt element is (1% to 6%):1, and the mass ratio of the metal elements in group D to the cobalt element is (100 ppm to 2000 ppm):1. The mass ratio of the metal elements in group D to the cobalt element is (100 ppm to 2000 ppm):1.

[0010] In a second aspect, the present application provides a preparation method of the cobalt-based catalyst as described above, comprising the following steps:

[0011] 1) Melting a raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder, and stabilizer into an alloy ingot;

[0012] 2) Performing etching treatment on the alloy ingot to obtain a porous skeleton structure;

[0013] 3) Performing impregnation treatment on a system comprising the porous skeleton structure and an alkali metal solution to obtain a cobalt-based catalyst precursor;

[0014] 4) Performing activation treatment on the cobalt-based catalyst precursor to obtain the cobalt-based catalyst.

[0015] The preparation method of the cobalt-based catalyst as described above, wherein the mass percentage of the cobalt powder in the raw material system is 58% to 88%;

[0016] And / or, the mass percentage of the aluminum powder in the raw material system is 10% to 40%;

[0017] And / or, the mass percentage of the alkaline earth metal powder in the raw material system is 0.1% to 5%;

[0018] And / or, the molar ratio of the stabilizer to the alkaline earth metal powder is (1 to 10):1;

[0019] And / or, the stabilizer comprises boron and / or silicon.

[0020] The preparation method of the cobalt-based catalyst as described above, wherein the raw material system further comprises metal elements in group A, metal elements in group C, a group B metal, at least one of the group B metals.

[0021] The preparation method of the cobalt-based catalyst as described above, the smelting of the raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder, and stabilizer into an alloy ingot comprises: under an inert atmosphere, the raw material system is kept at 1500-1700 DEG C for 15-30 min to obtain the alloy ingot.

[0022] The preparation method of the cobalt-based catalyst as described above, the etching treatment of the alloy ingot comprises: under the condition of 70-100 DEG C, the system comprising alkaline solution and the alloy ingot is reacted for 2-8 h to obtain the porous framework structure.

[0023] The mass concentration of the alkaline solution is 20-40%, and the mass ratio of the alloy ingot to the alkaline solution is 1: (5-10).

[0024] The preparation method of the cobalt-based catalyst as described above, the mass concentration of the alkali metal solution is 0.1-1 mol / L.

[0025] And / or, the temperature of the impregnation treatment is 40-70 DEG C.

[0026] And / or, the time of the impregnation treatment is 0.5-2 h.

[0027] In a third aspect, the present application provides a preparation method of 2-methylpentanediamine and / or 3-methylpiperidine, which uses the cobalt-based catalyst as described above or the cobalt-based catalyst prepared by the preparation method of the cobalt-based catalyst as described above to perform hydrogenation reaction on 2-methylglutaronitrile.

[0028] The cobalt-based catalyst provided by the present application has the alkali metal element and the alkaline earth metal element existing in the cobalt-based framework, and the alkaline earth metal element exists in the form of boride and / or silicide, which can improve the stability of the cobalt-based catalyst, and when applied in the hydrogenation reaction of 2-methylglutaronitrile, the selectivity of the product can be improved. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0030] 2-methylglutaronitrile (MGN) is a main by-product in the production process of adiponitrile (ADN), and its catalytic hydrogenation conversion is one of the key paths to realize high-value utilization of resources. In the reaction, skeleton cobalt catalyst is widely studied and applied due to its high catalytic activity and cost-effectiveness. However, the hydrogenation selectivity and activity of the traditional skeleton cobalt catalyst under mild reaction conditions (such as without external alkali, lower pressure) still need to be improved, especially the selectivity of the target primary amine product is often not ideal.

[0031] In order to optimize the performance of the catalyst, the prior art introduces alkali metal (AM, such as Cs, K) and alkaline earth metal (AEM, such as Sr, Ba) and other additives in the cobalt-based catalyst, which can effectively regulate the surface properties of the catalyst and enhance the selectivity of the primary amine. At present, the common method of adding additives mainly depends on the "wet chemical" surface modification technology, that is, after the formation of the skeleton cobalt porous structure, the additives are loaded on the surface of the catalyst by impregnation and other methods. However, in the cobalt-based catalyst prepared by this method, the binding force between the additives and the carrier is limited, and the additives are easy to flow off from the surface of the carrier, resulting in low selectivity of MGN hydrogenation reaction.

[0032] The inventors of the present application found through research that if the alkali metal element and the alkaline earth metal element exist in the cobalt-based skeleton, and the alkaline earth metal element exists in the form of boride and / or silicide, the stability of the cobalt-based catalyst can be significantly improved, and the selectivity of the product in the 2-methylglutaronitrile hydrogenation reaction can be improved.

[0033] In a first aspect, the present application provides a cobalt-based catalyst, which comprises a cobalt-based skeleton formed by cobalt element and / or aluminum element, and an alkali metal element, an alkaline earth metal element, a boron element and / or a silicon element existing in the cobalt-based skeleton, and the alkaline earth metal element exists in the form of boride and / or silicide.

[0034] The cobalt-based catalyst provided by the present application has the alkali metal element and the alkaline earth metal element existing in the cobalt-based skeleton, and the alkaline earth metal element exists in the form of boride and / or silicide, which can improve the stability of the cobalt-based catalyst, and can improve the selectivity of the product in the 2-methylglutaronitrile hydrogenation reaction. This is because the alkali metal element and the alkaline earth metal element exist in the cobalt-based skeleton, which can avoid falling off due to fluid scouring or changes in the reaction environment, that is, the loss of additives. The alkaline earth metal element existing in the form of boride and / or silicide has good resistance to strong alkali corrosion, and the retention rate of the alkaline earth metal element can be greater than 90% during the preparation of the catalyst, and the alkaline earth metal element existing in the form of boride and / or silicide is beneficial to the high dispersion and effective action of the alkali metal element.

[0035] The alkali metal elements (such as Cs and K) in the framework can change the electron cloud density of the cobalt active site through an electronic effect. On the one hand, moderate electron donation can enhance the adsorption capacity of cobalt to the cyan group (-CN) in the MGN, while weakening the excessive adsorption of the product primary amine, thereby avoiding the further hydrogenation of the primary amine to generate by-products such as secondary amine and tertiary amine; on the other hand, the alkali metal can neutralize the acidic sites on the surface of the catalyst, thereby reducing the occurrence of side reactions such as cyan group hydrolysis, and thus improving the selectivity of the primary amine. The electropositivity of the alkaline earth metal elements (such as Sr and Ba) is lower than that of cobalt, and the borides or silicides thereof are dispersed in the framework, thereby forming a local electron-rich region to provide a more suitable active center structure for the hydrogenation of the cyan group. At the same time, the presence of such compounds can regulate the pore size distribution and steric hindrance on the surface of the catalyst, so that the MGN molecule is more easily adsorbed on the active site in a specific orientation, thereby ensuring that both cyan groups can be selectively hydrogenated to generate primary amine, rather than incomplete hydrogenation or side reactions due to steric hindrance.

[0036] Therefore, the cobalt-based catalyst provided by the present application has high long-period operation stability, greatly prolongs the service life, and reduces the catalyst replacement cost and operation load in industrial applications. In the application in the 2-methylglutaronitrile hydrogenation reaction, the selectivity of the product can be improved.

[0037] In some embodiments of the present application, the cobalt-based catalyst further comprises at least one of the following elements in addition to the aluminum element: another metal element in group A, a metal element in group B, a metal element in group B, a metal element in group B.

[0038] Specifically, the at least one metal element in addition to the aluminum element includes at least one of the following: the other metal element in group A includes at least one of gallium (Ga), indium (In) and thallium (Tl); the metal element in group B includes at least one of iron (Fe), nickel (Ni), ruthenium (Ru), rhodium (Rh) and palladium (Pd); the metal element in group B includes at least one of chromium (Cr), molybdenum (Mo) and tungsten (W); the metal element in group B is selected from at least one of copper (Cu), silver (Ag) and gold (Au).

[0039] In the present application, by introducing the above-mentioned metal elements into the cobalt-based catalyst, the electronic structure and geometric configuration of the catalyst can be further optimized, for example, the metal element in group A (such as gallium) can form a solid solution with cobalt to adjust the d-band center position of cobalt and enhance the adsorption capacity to the reaction intermediate; the metal element in group B (such as nickel) can improve the catalytic activity of cobalt through an electronic transfer effect; the metal element in group B (such as chromium) can stabilize the oxidation state of cobalt and inhibit the occurrence of side reactions; and The Group B metal (such as gold) regulates the dispersity of the surface alkali metal through an electronic effect.

[0040] In some embodiments of the present application, in the cobalt-based catalyst, the mass percentage of cobalt element is 69% to 95%, for example, it can be 69%, 70%, 80%, 90%, 95% or a range composed of any two of them, preferably 70% to 85%; this content can maintain the mechanical strength of the cobalt-based framework and also ensure sufficient catalytic active sites.

[0041] The mass percentage of aluminum element is 3% to 20%, for example, it can be 3%, 5%, 10%, 15%, 20% or a range composed of any two of them, preferably 5% to 15%; the residual aluminum in this range is a necessary component to constitute a high-activity porous framework, which not only ensures the high specific surface area of the catalyst, but also maintains its structural stability, preventing excessive collapse during etching.

[0042] The mass percentage of alkali metal element is 0.1% to 5%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or a range composed of any two of them, preferably 0.5% to 2.5%; the mass percentage of alkaline earth metal element is 0.2% to 6.0%, for example, it can be 0.2%, 0.5%, 1%, 3%, 5%, 6.0% or a range composed of any two of them, preferably 0.5% to 2.5%; the additive in this range can effectively regulate the electronic structure of the catalyst and also avoid the shielding of active sites caused by excessive addition. The proportion of alkaline earth metal in the starting material is increased, which reflects the result of effective enrichment of alkaline earth metal due to the formation of stable phases during dealumination.

[0043] The molar ratio of boron element and / or silicon element to alkaline earth metal element is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or a range composed of any two of them; when the cobalt-based catalyst includes boron element, the molar ratio of boron element to alkaline earth metal element is (2-10):1, preferably (5-7):1; under this ratio, the B-alkaline earth metal nano-phase formed shows better stability in strong alkali etching, and its corrosion resistance is due to the fact that the lattice energy of B-alkaline earth metal phase is higher than that of Al-alkaline earth metal phase, so it is preferentially retained during etching. Similarly, when the cobalt-based catalyst includes silicon element, the molar ratio of silicon element to alkaline earth metal element is (1-4):1, preferably (2-3):1.

[0044] The content of the element other than aluminum element is 0.1% to 5%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or a range composed of any two of them, preferably 0.5% to 2.5%; the content of the element other than aluminum element is 0.2% to 6.0%, for example, it can be 0.2%, 0.5%, 1%, 3%, 5%, 6.0% or a range composed of any two of them, preferably 0.5% to 2.5%; the additive in this range can effectively regulate the electronic structure of the catalyst and also avoid the shielding of active sites caused by excessive addition. The mass ratio of the other metal elements in Group A to cobalt is (0.1%-3%):1, for example, 0.1%:1, 0.5%:1, 1%:1, 2%:1, 2.5%:1, 3%:1, or a range consisting of any two of them; The mass ratio of the metal elements in Group B to cobalt is (1%-7%):1, for example, 1%:1, 2%:1, 3%:1, 4%:1, 5%:1, 6%:1, 7%:1, or a range consisting of any two of them; The mass ratio of the metal elements in Group B to cobalt is (1%-6%):1, for example, 1%:1, 2%:1, 3%:1, 4%:1, 5%:1, 6%:1, or a range consisting of any two of them; The mass ratio of the metal elements in Group B to cobalt is (100ppm-2000ppm):1, for example, 100ppm:1, 200ppm:1, 500ppm:1, 700ppm:1, 1000ppm:1, 1500ppm:1, 2000ppm:1, or a range consisting of any two of them. The present application can ensure the synergistic effect of each component while avoiding the shielding of active sites caused by excessive addition.

[0045] In a second aspect, the present application provides a preparation method of the cobalt-based catalyst as described above, comprising the following steps:

[0046] 1) Melting the raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder, and stabilizer into an alloy ingot;

[0047] 2) Etching the alloy ingot to obtain a porous framework structure;

[0048] 3) Immersing the system comprising the porous framework structure and an alkali metal solution to obtain a cobalt-based catalyst precursor;

[0049] 4) Activating the cobalt-based catalyst precursor to obtain a cobalt-based catalyst.

[0050] Specifically, in step 1), the cobalt powder (purity >99.8%, particle size <200 mesh), aluminum powder (purity >99.9%, particle size <200 mesh), alkaline earth metal powder, and stabilizer (such as boron and / or silicon) are placed in a V-type mixer or a three-dimensional mixer, and mixed under the protection of an inert atmosphere (such as nitrogen) for at least 2h to ensure the uniformity of the raw materials. Then, the uniformly mixed powder is transferred to a crucible (such as an alumina or graphite crucible) of a high-frequency vacuum induction melting furnace. The system is vacuumed to 10 -2Pa, and then filled with high-purity argon gas to 0.05 MPa as a protective atmosphere. Start the heating program, melt the raw material system, and ensure that all components are completely melted and form a uniform liquid alloy. In this process, the thermodynamically more dominant stabilizer (boron and / or silicon) will react with the alkaline earth metal in situ to generate boride and / or silicide nanophase wrapped by Co-Al liquid matrix, which is extremely stable in chemical properties. After the melting is completed, the molten alloy liquid is cast into a water-cooled copper mold for rapid cooling to obtain a fine-grained structure. The cooled alloy ingot is coarsely and mediumly crushed in a jaw crusher or hammer crusher, and then finely ground by a ball mill. The crushed alloy ingot is sieved by a standard screen, and the particles in a specific particle size range (such as 100-200 mesh) are collected as raw materials for the subsequent etching step.

[0051] In step 2), the aluminum in the alloy is selectively removed by chemical etching to build a porous framework structure with high specific surface area, and at the same time the alkaline earth metal additive stabilized by the stabilizer is retained.

[0052] In step 3), the porous framework structure is transferred to the impregnation kettle, a certain amount of deionized water is added to form a slurry, and the alkali metal additive (for example, cesium hydroxide (CsOH), potassium hydroxide (KOH), etc.) is prepared into a solution of a certain concentration. In a constant temperature water bath, the alkali metal solution is slowly added to the slurry of the porous framework structure, and stirring is maintained for a certain time. At this time, the support matrix is rich in structure-anchored alkaline earth metal-stabilizer phase, which is beneficial to the high dispersion and effective action of the alkali metal additive, and a cobalt-based catalyst precursor is obtained.

[0053] After the impregnation is completed, the cobalt-based catalyst precursor can be filtered or centrifuged, and washed once or twice with a small amount of deionized water to remove unabsorbed alkali metal ions.

[0054] The obtained filter cake is dried in a vacuum oven at 80°C-120°C for 6h-12h to obtain the final cobalt-based catalyst precursor powder.

[0055] In Step 4), the metal oxides in the cobalt-based catalyst precursor are reduced to a catalytically active metal state to obtain the cobalt-based catalyst. Specifically, the cobalt-based catalyst precursor can be uniformly loaded into a tubular reduction furnace. Under the protection of an inert atmosphere (e.g., high-purity N2or Ar), the temperature is programmed to rise at a certain rate (e.g., 5°C / min to 10°C / min) to a reduction starting temperature (e.g., 250°C). The reduction atmosphere (a mixture of H2with a hydrogen volume fraction of 5% to 100% and N2, or a mixture of H2with a hydrogen volume fraction of 5% to 100% and Ar) is switched on, and the temperature is continued to rise at the same rate to a final reduction temperature of 450°C to 750°C. The temperature is maintained at this temperature for 2 hours to 10 hours to ensure that the metal oxides are fully reduced. After the reduction is completed, the temperature is lowered to room temperature under the protection of an inert atmosphere.

[0056] To facilitate operation and storage, the activated cobalt-based catalyst can be slowly passivated at a low temperature (e.g., room temperature) with an inert gas containing a small amount of oxygen (e.g., a mixture of O2with an oxygen volume fraction of 0.5% to 1% and N2) to form an extremely thin oxide layer on the surface to prevent spontaneous ignition. The final cobalt-based catalyst needs to be sealed and stored in an inert or dry environment.

[0057] In some embodiments of the present application, the mass percentage of cobalt powder in the raw material system is 58% to 88%, for example, it can be 58%, 60%, 65%, 70%, 75%, 80%, 85%, 88%, or a range consisting of any two of them.

[0058] In some embodiments, the mass percentage of aluminum powder in the raw material system is 10% to 40%, for example, it can be 10%, 20%, 25%, 30%, 40%, or a range consisting of any two of them.

[0059] In some embodiments, the mass percentage of alkaline earth metal powder in the raw material system is 0.1% to 5%, for example, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, or a range consisting of any two of them.

[0060] In some embodiments, the molar ratio of the stabilizer to the alkaline earth metal powder is (1 to 10): 1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or a range consisting of any two of them.

[0061] In some embodiments, the stabilizer includes boron and / or silicon.

[0062] By precisely controlling the raw material ratio, the thermodynamic stability of the smelting process can be ensured.

[0063] In some embodiments of the present application, the raw material system further comprises a group A metal, Group metals Group B metals, At least one of Group B metals. This can further optimize the performance of cobalt-based catalysts and further improve the selectivity of products in the hydrogenation reaction of 2-methylglutaronitrile.

[0064] In some embodiments of the present invention, melting a raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder, and stabilizer into an alloy ingot includes: holding the raw material system at 1500°C to 1700°C for 15 min to 30 min under an inert atmosphere to obtain the alloy ingot.

[0065] For example, the temperature can be a range of 1500°C, 1550°C, 1600°C, 1650°C, 1700°C or any two of these; the time can be a range of 15 min, 17 min, 20 min, 22 min, 25 min, 27 min, 30 min or any two of these.

[0066] To ensure that all components are completely melted and form a uniform liquid alloy, the melting temperature must be controlled above the melting point of all components, while avoiding excessively high temperatures that could cause the alloy components to volatilize.

[0067] This invention achieves uniform mixing and phase structure control of raw materials through the above-described smelting process. A smelting temperature of 1500℃~700℃ ensures complete melting of all components, while a holding time of 15min~30min balances phase homogeneity and energy consumption. An inert atmosphere (such as argon) prevents oxidation and ensures preferential reaction between the stabilizer (boron and / or silicon) and alkaline earth metals.

[0068] In some embodiments of the present invention, etching the alloy ingot includes reacting a system comprising an alkaline solution and the alloy ingot at 70°C to 100°C for 2 to 8 hours to obtain a porous framework structure.

[0069] For example, the etching temperature can be a range of 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any two of these; the etching time can be a range of 2h, 3h, 4h, 5h, 6h, 7h, 8h or any two of these.

[0070] The mass concentration of the alkali solution is 20% to 40%, for example, it can be 20%, 25%, 30%, 35%, 40% or any two of them; the mass ratio of the alloy ingot to the alkali solution is 1:(5 to 10), for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any two of them.

[0071] Specifically, in a reaction kettle with mechanical stirring and reflux condenser, an alkali solution with a mass concentration of 20% to 40% (preferably 30%), such as sodium hydroxide aqueous solution, is added. The alloy ingot is slowly added to the alkali solution at a mass ratio of alloy ingot to alkali solution of 1:(5-10) to form a mixture. The addition process will cause an exothermic reaction and generate hydrogen, and the feeding speed needs to be controlled.

[0072] The mixture is heated to 70-100°C (preferably 85°C), and stirred vigorously at this temperature for 2-8h (preferably 6h). During this process, aluminum and part of the active Co-Al phase are selectively dissolved (reaction formula: 2Al+2NaOH+2H2O→2NaAlO2+3H2↑), forming a three-dimensional interconnected porous framework structure. The alkaline earth metal existing in the form of boride and / or silicide is well preserved due to its strong corrosion resistance to alkali, and is finally exposed as the surrounding aluminum matrix disappears, embedded in the newly formed high specific surface area framework, achieving a structural anchoring with a residual rate of greater than 90%.

[0073] After the etching reaction is completed, heating and stirring are stopped, and the powder is allowed to settle naturally. The upper layer of alkali solution is removed by decantation or siphoning. Then a large amount of deionized water is added, and the mixture is stirred, settled, and the supernatant is removed. This washing process is repeated several times until the pH of the washing water approaches neutral (pH 6-8). Finally, the wet filter cake is obtained by filtration or centrifugation.

[0074] The present application optimizes the etching conditions to ensure the selective dissolution of aluminum and the stable preservation of alkaline earth metal elements. Aluminum and Co-Al phase are selectively dissolved to form a three-dimensional interconnected porous framework, while boride and / or silicide phase is preserved due to its strong corrosion resistance to strong alkali.

[0075] In some embodiments of the present application, the mass concentration of the alkali metal solution is 0.1-1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, or a range formed by any two of them.

[0076] In some embodiments, the temperature of the immersion treatment is 40-70°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or a range formed by any two of them.

[0077] In some embodiments, the time of the immersion treatment is 0.5-2h, for example, it can be 0.5h, 0.7h, 1h, 1.5h, 2h, or a range formed by any two of them.

[0078] The conditions of the above impregnation treatment can ensure that the alkali metal is highly dispersed on the structure-anchored alkali earth metal surface to form a synergistic active center and avoid the aggregation effect caused by excessively high concentration.

[0079] In a third aspect, the present application provides a method for preparing 2-methylpentanediamine and / or 3-methylpiperidine, which comprises subjecting 2-methylglutaronitrile to a hydrogenation reaction using the cobalt-based catalyst or the cobalt-based catalyst prepared by the method described above.

[0080] The method for preparing 2-methylpentanediamine and / or 3-methylpiperidine provided by the present application can improve the selectivity of the product 2-methylpentanediamine and / or 3-methylpiperidine by subjecting 2-methylglutaronitrile to a hydrogenation reaction using the cobalt-based catalyst described above.

[0081] The technical solutions of the present application are further described below in combination with specific examples.

[0082] Example 1

[0083] The method for preparing the cobalt-based catalyst of the present example comprises the following steps:

[0084] 1) 750 g of Co powder, 250 g of Al powder, 3.75 g of Ga powder, 22.5 g of Ni powder, 15 g of Cr powder, 0.375 g of Cu powder, 0.375 g of Au powder, 7.5 g of Sr powder and 5.6 g of B powder (to ensure a B:Sr molar ratio of 6:1) are weighed and mixed to obtain a mixed powder.

[0085] The mixed powder is smelted at 1650°C for 20 min under the protection of argon, rapidly water-cooled and cast into a shape, broken and sieved to collect particles of 100-200 mesh to form an alloy ingot.

[0086] 2) In a 5L reaction kettle, 3L of 30% NaOH aqueous solution is heated to 85°C. Under vigorous stirring, 500 g of the alloy ingot is slowly added in batches, and the feeding speed is controlled to maintain the reaction stable. After the feeding is completed, the etching reaction is continued at 85°C for 6 h.

[0087] After the reaction is completed, it is allowed to stand and settle, and the supernatant is removed. Deionized water is added to the original liquid level, and after stirring for 30 min, it is again allowed to settle. This process is repeated about 10 times until the supernatant is neutral as tested by phenothalin test paper, and a porous skeleton structure is obtained.

[0088] 3) Transfer the porous framework structure into a 2L beaker and add 1L of deionized water to form a slurry. Separately, take 22.4g of cesium hydroxide monohydrate (CsOH H2O) and dissolve in 500mL of deionized water to prepare an alkali solution of about 0.15 mol / L. Slowly add the alkali solution into the above slurry at 55℃ and continue to stir the impregnation at this temperature for 1h. Filter, wash twice with 200mL of deionized water, and then dry in a vacuum oven at 110℃ for 12h to obtain a cobalt-based catalyst precursor.

[0089] 4) Load 100g of the cobalt-based catalyst precursor into a tube furnace and heat up to 250℃ at 5℃ / min under N2 atmosphere. Switch to a mixed gas of H2 and N2 with a hydrogen volume fraction of 30% (flow rate 200mL / min) and continue to heat up to 580℃ at 5℃ / min and reduce for 8h at constant temperature.

[0090] 5) Cool down to room temperature under N2 protection and then perform a passivation treatment with a mixed gas of O2 and N2 with an oxygen volume fraction of 1% for 2h to obtain the final cobalt-based catalyst.

[0091] The cobalt-based catalyst comprises a cobalt-based framework formed by cobalt elements and aluminum elements, and alkali elements Cs, alkaline earth elements Ba, and boron elements present in the cobalt-based framework. The alkaline earth elements Ba exist in the form of borides. The cobalt-based catalyst further comprises Ga, Ni, Cr, Cu, and Au.

[0092] In the cobalt-based catalyst, the mass percentage of cobalt elements is 85.3%, the mass percentage of aluminum elements is 4.3%, the mass percentage of alkali elements is 4.25%, the mass percentage of alkaline earth elements is 0.81%, the molar ratio of boron elements to alkaline earth elements is 6:1, the mass ratio of Ga to cobalt elements is 0.5%:1, the mass ratio of Ni to cobalt elements is 3.0%:1, the mass ratio of Cr to cobalt elements is 2.0%:1, the mass ratio of Cu to cobalt elements is 0.05%:1, and the mass ratio of Au to cobalt elements is 0.05%:1.

[0093] Example 2

[0094] The preparation method of the cobalt-based catalyst of this example is basically the same as that of Example 1, except that in step 1), 7.5g of Sr powder and 5.6g of B powder are replaced by 11.8g of Ba powder and 5.6g of B powder.

[0095] The cobalt-based catalyst comprises a cobalt-based framework formed by cobalt elements and aluminum elements, and alkali elements Cs, alkaline earth elements Ba, and boron elements present in the cobalt-based framework. The alkaline earth elements Ba exist in the form of borides. The cobalt-based catalyst further comprises Ga, Ni, Cr, Cu, and Au.

[0096] In the cobalt-based catalyst, the mass percentage of cobalt element is 84.88%, the mass percentage of aluminum element is 4.24%, the mass percentage of alkali metal element is 4.25%, the mass percentage of alkaline earth metal element is 1.27%, the molar ratio of boron element to alkaline earth metal element is 6:1, the mass ratio of Ga to cobalt element is 0.5%:1, the mass ratio of Ni to cobalt element is 3.0%:1, the mass ratio of Cr to cobalt element is 2.0%:1, the mass ratio of Cu to cobalt element is 0.05%:1, and the mass ratio of Au to cobalt element is 0.05%:1.

[0097] Example 3

[0098] The preparation method of the cobalt-based catalyst in this example is basically the same as that in Example 1, except that in step 3), 22.4g of CsOH H2O is replaced by 11.2g of KOH.

[0099] The cobalt-based catalyst includes a cobalt-based framework formed by cobalt element and aluminum element, and alkali metal element K, alkaline earth metal element Sr and boron element existing in the cobalt-based framework. The alkaline earth metal element Sr exists in the form of boride. The cobalt-based catalyst also includes Ga, Ni, Cr, Cu and Au.

[0100] In the cobalt-based catalyst, the mass percentage of cobalt element is 87.36%, the mass percentage of aluminum element is 4.37%, the mass percentage of alkali metal element is 1.92%, the mass percentage of alkaline earth metal element is 0.83%, the molar ratio of boron element to alkaline earth metal element is 6:1, the mass ratio of Ga to cobalt element is 0.5%:1, the mass ratio of Ni to cobalt element is 3.0%:1, the mass ratio of Cr to cobalt element is 2.0%:1, the mass ratio of Cu to cobalt element is 0.05%:1, and the mass ratio of Au to cobalt element is 0.05%:1.

[0101] Example 4

[0102] The preparation method of the cobalt-based catalyst in this example is basically the same as that in Example 1, except that in step 1), 5.6g of B powder is replaced by 4.8g of Si powder (molar ratio of Si to Sr is 2:1).

[0103] The cobalt-based catalyst includes a cobalt-based framework formed by cobalt element and aluminum element, and alkali metal element K, alkaline earth metal element Sr and boron element existing in the cobalt-based framework. The alkaline earth metal element Sr exists in the form of boride. The cobalt-based catalyst also includes Ga, Ni, Cr, Cu and Au.

[0104] In the cobalt-based catalyst, the mass ratio of cobalt element is 85.35%, the mass ratio of aluminum element is 4.27%, the mass ratio of alkali metal element is 4.25%, the mass ratio of alkaline earth metal element is 0.81%, the molar ratio of silicon element to alkaline earth metal element is 2:1, the mass ratio of Ga to cobalt element is 0.5%:1, the mass ratio of Ni to cobalt element is 3.0%:1, the mass ratio of Cr to cobalt element is 2.0%:1, the mass ratio of Cu to cobalt element is 0.05%:1, and the mass ratio of Au to cobalt element is 0.05%:1.

[0105] Comparative Example 1

[0106] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that steps 1) and 3) are omitted.

[0107] Comparative Example 2

[0108] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that step 1) is omitted.

[0109] Comparative Example 3

[0110] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that steps 1) and 3) are omitted, and in step 3), the CsOH solution is replaced with a solution containing 23.5g Sr(NO3)2 for impregnation.

[0111] Comparative Example 4

[0112] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that steps 1) and 3) are omitted, and in step 3), the CsOH solution is replaced with a mixed solution containing 23.5g Sr(NO3)2 and 22.4g CsOH·H2O for impregnation.

[0113] Comparative Example 5

[0114] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that step 1) is omitted, and after step 2) is performed, a solution containing 23.5g Sr(NO3)2 is used for impregnation, and after washing and drying, step 3) is performed.

[0115] Comparative Example 6

[0116] The preparation method of the cobalt-based catalyst of this comparative example is basically the same as that of Example 1, except that step 3) is omitted.

[0117] Comparative Example 7

[0118] The preparation method of the cobalt-based catalyst of the present comparative example is basically the same as that of example 1, except that no B powder is added in step 1), and step 3) is omitted.

[0119] Test example:

[0120] Catalytic performance evaluation device: a high-pressure reaction kettle made of Hastelloy with a content volume of 2 L is used, which is equipped with a magnetic drive stirring device (which can realize a rotation speed of more than 1500 rpm), an embedded cooling coil, a gas sampling pipe, a liquid sampling valve and an automatic temperature / pressure control system.

[0121] In the high-pressure reaction kettle, 100 g of 2-methylglutaronitrile (MGN), 180 g of ethanol and 10 g of the cobalt-based catalyst are added. After replacing air with N2 for 3 times, H2 is filled to 2.5 MPa. Under stirring, the temperature is raised to 75°C, and the constant temperature and pressure reaction is maintained for 1.5 h.

[0122] Product analysis method: after the reaction is completed, the liquid product is taken out after the reaction kettle is cooled to room temperature. A gas chromatograph (GC, model: Agilent 7890B) is used, which is equipped with an HP-5 capillary column and a flame ionization detector (FID), and the products are quantitatively analyzed by an internal standard method (n-dodecane as an internal standard), and the MGN conversion rate, MPMD selectivity, 3-MP selectivity and total selectivity are calculated. The results are shown in Table 1.

[0123] MGN conversion rate (%) = [(raw material MGN concentration - product MGN concentration) / raw material MGN concentration] x 100%;

[0124] MPMD selectivity (%) = [product MPMD concentration / (raw material MGN concentration - product MGN concentration)] x 100%;

[0125] 3-MP selectivity (%) = [product 3-MP concentration / (raw material MGN concentration - product MGN concentration)] x 100%;

[0126] Total selectivity (%) = MPMD selectivity (%) + 3-MP selectivity (%).

[0127] Element content analysis: the actual content of each metal element in the cobalt-based catalyst is accurately measured by an inductively coupled plasma emission spectrometer (ICP-OES) (model: Agilent 720). After the sample is completely dissolved in aqua regia in a microwave digestion instrument, it is diluted and tested, and the residual rate of the alkaline earth metal is calculated accordingly. The results are shown in Table 1.

[0128] Table 1 Residual rate of alkaline earth metal, MGN conversion rate, MPMD selectivity, 3-MP selectivity, initial total selectivity, total selectivity after the 10th cycle, total selectivity attenuation rate of the cobalt-based catalyst of examples 1-4 and comparative examples 1-7

[0129]

[0130] From Table 1, it can be seen that, compared with the comparative examples, the cobalt-based catalyst provided by the present application has alkali metal elements and alkali earth metal elements in the cobalt-based framework, and the alkali earth metal elements exist in the form of borides and / or silicides, which can improve the stability of the cobalt-based catalyst, and when applied in the 2-methylglutaronitrile hydrogenation reaction, the selectivity of the product can be improved.

[0131] Compared with Comparative Example 7, the cobalt-based catalyst of Example 1 has a higher residual rate of alkali earth metal elements, higher catalyst stability, and can improve the selectivity of the product in the 2-methylglutaronitrile hydrogenation reaction. The cobalt-based catalyst in Comparative Example 7 has an effect similar to that of the cobalt-based catalyst without metal oxide as an additive in Comparative Example 1.

[0132] Compared with Comparative Example 5, the cobalt-based catalyst of Example 1 can improve the initial total selectivity of the product in the 2-methylglutaronitrile hydrogenation reaction and reduce the attenuation rate of the total selectivity.

[0133] Finally, it should be noted that: other embodiments of the present application will be readily apparent to those skilled in the art upon considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the application following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art to which the application pertains and as can be applied to the essential features hereinbefore set forth and fall within the scope of the application. The scope of the present application is limited only by the claims appended hereto.

Claims

1. A cobalt-based catalyst characterized in that, The cobalt-based catalyst comprises a cobalt-based framework formed by cobalt elements and / or aluminum elements, alkali metal elements, alkaline earth metal elements, boron elements and / or silicon elements for stabilizing the alkaline earth metal elements, and the alkaline earth metal elements exist in the form of borides and / or silicides; The alkaline earth metal elements are at least one of strontium and barium; In the cobalt-based catalyst, the mass percentage of the cobalt elements is 69% to 95%, the mass percentage of the aluminum elements is 3% to 20%, the mass percentage of the alkali metal elements is 0.1% to 5%, the mass percentage of the alkaline earth metal elements is 0.2% to 6.0%, and the molar ratio of the boron elements and / or silicon elements to the alkaline earth metal elements is (1 to 10):

1.

2. The cobalt-based catalyst of claim 1, wherein The cobalt-based catalyst further comprises at least one of other metal elements of Group IIIA, Group VIII metal elements, Group VI B metal elements and Group IB metal elements in addition to the aluminum elements. The Group VIII metal elements comprise at least one of iron, nickel, ruthenium, rhodium and palladium.

3. The cobalt-based catalyst of claim 2, wherein, The mass ratio of the other metal elements of Group IIIA in addition to the aluminum elements to the cobalt elements is (0.1% to 3%):1, the mass ratio of the Group VIII metal elements to the cobalt elements is (1% to 7%):1, the mass ratio of the Group VI B metal elements to the cobalt elements is (1% to 6%):1, and the mass ratio of the Group IB metal elements to the cobalt elements is (100 ppm to 2000 ppm):

1.

4. A process for the preparation of a cobalt-based catalyst as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: 1) Melting a raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder and a stabilizer into an alloy ingot, wherein the stabilizer comprises boron and / or silicon; 2) Performing etching treatment on the alloy ingot to obtain a porous framework structure; 3) Performing impregnation treatment on a system comprising the porous framework structure and an alkali metal solution to obtain a cobalt-based catalyst precursor; 4) Performing activation treatment on the cobalt-based catalyst precursor to obtain the cobalt-based catalyst.

5. The method of making a cobalt-based catalyst of claim 4, wherein, The mass percentage of the cobalt powder in the raw material system is 58% to 88%; And / or, the mass percentage of the aluminum powder in the raw material system is 10% to 40%; And / or, the mass percentage of the alkaline earth metal powder in the raw material system is 0.1% to 5%; And / or, the molar ratio of the stabilizer to the alkaline earth metal powder is (1 to 10):

1.

6. The method of making a cobalt-based catalyst of claim 4, wherein, The raw material system further comprises at least one of Group IIIA metal, Group VIII metal, Group VI B metal and Group IB metal. The Group VIII metal comprises at least one of iron (Fe), nickel (Ni), ruthenium (Ru), rhodium (Rh) and palladium (Pd).

7. The method of making a cobalt-based catalyst of claim 4, wherein, The melting of the raw material system comprising cobalt powder, aluminum powder, alkaline earth metal powder and a stabilizer into an alloy ingot comprises: under an inert atmosphere, keeping the raw material system at 1500°C to 1700°C for 15 minutes to 30 minutes to obtain the alloy ingot.

8. The method of making a cobalt-based catalyst of claim 4, wherein, The etching treatment on the alloy ingot comprises: reacting a system comprising an alkali solution and the alloy ingot at 70°C to 100°C for 2 hours to 8 hours to obtain the porous framework structure; The mass concentration of the alkali solution is 20-40%, and the mass ratio of the alloy ingot to the alkali solution is 1: (5-10).

9. Process for the preparation of a cobalt-based catalyst according to any one of claims 4 to 8, characterized in that, The mass concentration of the alkali metal solution is 0.1-1 mol / L; And / or, the temperature of the impregnation treatment is 40-70 DEG C. And / or, the time of the impregnation treatment is 0.5-2 hours.

10. A process for the preparation of 2-methylpentanediamine and / or 3-methylpiperidine, characterized in that The cobalt-based catalyst prepared by the method of any one of claims 1-3 or the method of any one of claims 4-9 is used for hydrogenation reaction of 2-methylglutaronitrile.

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