A cobalt-based bifunctional catalyst, a preparation method and application thereof

Abstract

The application discloses a cobalt-based bifunctional catalyst and a preparation method and application thereof, and specifically relates to the following steps: S1, preparing a metal precursor solution; S2, preparing a template solution; S3, preparing a precipitant solution; S4, mixing the template solution with the metal precursor solution, and then adding the precipitant solution to perform a pre-precipitation reaction; S5, adding high-temperature deionized water with a temperature of 60-100 DEG C to the solution after the pre-precipitation to perform a first-stage ball milling, and forming a metal hydroxide-template ordered composite; S6, adding a hydrogen peroxide solution to the metal hydroxide-template ordered composite to perform a second-stage ball milling, and obtaining a mixture; S7, drying the mixture, and then removing the template to obtain a catalyst precursor powder; and S8, activating the catalyst precursor powder to obtain the cobalt-based bifunctional catalyst. The prepared catalyst solves the problem of catalytic efficiency reduction caused by metal agglomeration, and improves the selectivity of piperazine and derivatives thereof.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a cobalt-based bifunctional catalyst, its preparation method, and its application. Background Technology

[0002] Piperazine and its derivatives (methylpiperazine, ethylpiperazine, aminoethylpiperazine, hydroxyethylpiperazine) are key intermediates in fine chemicals, pharmaceuticals, pesticides, and polymer materials. Selective reductive amination of ethylene glycol to prepare organic amines with high added value is a synthetic route with high atom economy and environmental friendliness, but the products of ethylene glycol amination reaction are complex and diverse.

[0003] Currently, the core technological bottleneck in the amination reaction of ethylene glycol lies in the development of highly efficient catalysts. Existing catalytic systems are mainly divided into noble metal-based catalysts and transition metal-based catalysts. Although noble metal-based catalysts have high catalytic activity and selectivity, the scarcity and high price of noble metal resources lead to high catalyst costs, making it difficult to meet the economic requirements of large-scale industrial production. Among transition metal-based catalysts, nickel-based and cobalt-based catalysts have become research hotspots due to their low cost and relatively considerable activity, but they still have many key drawbacks: Traditional preparation methods, such as impregnation, make it difficult to precisely control the size of metal particles, easily causing metal agglomeration, resulting in insufficient exposure of active sites and decreased catalytic efficiency. The interaction between the support and the active metal component is weak, and metal loss and sintering are prone to occur during the reaction. The catalyst has a short lifespan and is difficult to regenerate. Some processes need to be carried out under high temperature and high pressure, which places high demands on equipment materials, significantly increasing energy consumption and safety risks. At the same time, the product selectivity is poor, and more by-products are generated, increasing the cost and difficulty of subsequent separation and purification. Summary of the Invention

[0004] The purpose of this invention is to provide a cobalt-based bifunctional catalyst, its preparation method, and its application. The preparation process does not require harsh high-pressure equipment and is carried out under mild conditions. The prepared cobalt-based metal bifunctional catalyst with ordered mesoporous structures solves the problem of decreased catalytic efficiency caused by metal agglomeration and improves the selectivity of piperazine and its derivatives.

[0005] This invention adopts the following technical solution: a method for preparing a cobalt-based bifunctional catalyst, comprising the following steps: Step S1: Dissolve the cobalt source compound and the aluminum source compound in deionized water to prepare a metal precursor solution; Step S2: Dissolve the template agent in deionized water to prepare a template agent solution or dispersion; Step S3: Prepare the precipitant solution; Step S4: Mix the template agent solution from step S2 with the metal precursor solution from step S1, and then add the precipitant solution from step S3 to carry out a pre-precipitation reaction to obtain a pre-precipitated solution. Step S5: Add high-temperature deionized water at 60~100℃ to the pre-precipitated solution in step S4, and perform the first stage ball milling to form a metal hydroxide-template ordered complex; Step S6: Add a 5%~30% hydrogen peroxide solution to the metal hydroxide-template ordered composite from step 5, and perform a second-stage ball milling to obtain a mixture; Step S7: Dry the mixture from step S6, then remove the template agent to obtain catalyst precursor powder; Step S8: Activate the catalyst precursor powder from step S7 to obtain a cobalt-based bifunctional catalyst.

[0006] Furthermore, the template agent in step S2 is a soft template agent, selected from one or more of block copolymer P123, block copolymer F127, hexadecyltrimethylammonium bromide, polyethylene glycol, and polyethyleneimine.

[0007] Furthermore, the mass ratio of the soft template agent to the total metal ions in the metal precursor solution is 0.01:1 ~ 2:1.

[0008] Furthermore, in step S5, the rotation speed of the ball mill in the first stage is 100~800 r / min, and the ball milling time is 0.5~8h; the temperature of the high-temperature deionized water is 60~100℃.

[0009] Furthermore, in step S6, the solid-liquid ratio of the solid to the hydrogen peroxide solution in the ball milling system is 1:20 ~ 20:1 g / mL, the ball milling speed in the second stage is 100~800 r / min, and the ball milling time is 0.5~8 h.

[0010] Furthermore, the method for removing the template agent is as follows: in step S7, the template agent is removed by solvent extraction or programmed temperature calcination.

[0011] Further, the activation process in step S8 is as follows: the catalyst precursor powder is calcined in an air atmosphere at a temperature of 300~800℃ for 0.5~8 h; after calcination, it is reduced and activated in a hydrogen atmosphere at a temperature of 200~600℃ for 0.5~8 h.

[0012] Further, the cobalt source compound in step S1 is one or more of cobalt nitrate hexahydrate, cobalt sulfate heptahydrate, cobalt acetate tetrahydrate, and cobalt acetylacetonate; the aluminum source compound is one or more of aluminum nitrate nonahydrate, aluminum sulfate octadecahydrate, aluminum ammonium sulfate dodecahydrate, and sodium aluminate; the cobalt source compound and the aluminum source compound are in a cobalt-aluminum molar ratio of 0.05:1 to 4:1.

[0013] This invention also discloses a cobalt-based bifunctional catalyst prepared by the above-mentioned method.

[0014] This invention also discloses the use of the cobalt-based bifunctional catalyst prepared by the above-mentioned method for selective reduction amination of ethylene glycol to prepare organic amines, wherein the organic amines include piperazine, methylpiperazine, ethylpiperazine, aminoethylpiperazine, or hydroxyethylpiperazine.

[0015] The beneficial effects of this invention are: 1. Template-mechanical-chemical synergistic construction of ordered mesoporous and microporous structures: A template agent is introduced in the pre-precipitation stage, and the synergistic effect of ball milling mechanical force and high-temperature hydrothermal heat promotes the orderly assembly of metal precursors under the guidance of the template; after template removal, an ordered mesoporous and microporous structure is obtained with narrow pore size distribution and good pore wall stability. 2. Shape-selective catalysis significantly improves piperazine selectivity: The pore size of the ordered mesoporous and microporous structures of this cobalt-based bifunctional catalyst matches the molecular size of ethylenediamine (approximately 0.43 nm) and piperazine (approximately 0.6 nm). The reaction intermediate ethylenediamine is confined within the pores, and under the directional effect of acidic sites (surface hydroxyl groups) on the pore walls, it is easier to undergo intramolecular cyclization to generate piperazine, while chain byproducts, such as diethylenetriamine and triethylenediamine oligomers, are difficult to generate due to steric hindrance; experiments show that the selectivity of piperazine and its derivatives can be improved to over 75%. 3. In-situ hydrogen peroxide modification in the later stage of ball milling to construct surface hydroxyl groups and defects: Hydrogen peroxide is added in the later stage of ball milling, and the mechanical force of ball milling promotes uniform etching and hydroxylation of the composite surface by hydrogen peroxide, realizing the introduction of surface hydroxyl groups and oxygen vacancies in one step; the surface hydroxyl groups, as acidic sites, form a metal-acid bifunctional synergy with the hydrogenation sites of metallic cobalt, significantly improving the conversion rate of ethylene glycol and the selectivity of the target product. 4. Simple process, mild conditions, and easy scale-up: Precipitation, ordered assembly, and surface modification are integrated into the ball milling process, avoiding the cumbersome operation of traditional multi-step and long-term stirring; in addition, the raw materials are inexpensive and readily available, and there is no need for harsh high-temperature and high-pressure equipment, which has good prospects for industrial scale-up. Attached Figure Description

[0016] Figure 1 Co prepared in Example 1 0.5 Al1O x Pore ​​size distribution diagram of the -PEI-Bm-H catalyst.

[0017] Figure 2 Co prepared in Example 1 0.5 Al1O x TEM characterization of the -PEI-Bm-H catalyst. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] In this invention, room temperature refers to the temperature inside the laboratory during the experiment.

[0020] This invention discloses a method for preparing a cobalt-based bifunctional catalyst, comprising the following steps: Step S1: Dissolve the cobalt source compound and the aluminum source compound in deionized water at a cobalt-aluminum molar ratio of 0.05:1 to 4:1 to prepare a metal precursor solution; Step S2: Dissolve the template agent in deionized water to prepare a template agent solution or dispersion; Step S3: Prepare a precipitant solution. The selected precipitant is one or more of urea, ammonium carbonate, ammonium bicarbonate, and ammonia water. Step S4: Mix the template agent solution from step S2 with the metal precursor solution from step S1, and then add the precipitant solution from step S3 to carry out a pre-precipitation reaction to obtain a pre-precipitated solution.

[0021] Step S5: Add high-temperature deionized water (60-100℃) to the pre-precipitated solution in step S4 and perform the first stage of ball milling. Under the guidance of the template agent, the metal ions undergo in-situ hydrolysis, condensation, and ordered assembly to form a metal hydroxide-template ordered complex.

[0022] Step S6: Add 5%~30% hydrogen peroxide solution to the metal hydroxide-template ordered composite in step 5, and perform a second-stage ball milling to perform in-situ etching and hydroxylation modification on the surface of the composite to obtain a mixture.

[0023] Step S7: Allow the mixture from Step S6 to stand for aging, filter, and wash the solid precipitate with deionized water until the filtrate is neutral, obtaining a filter cake; dry the filter cake in an oven at 75°C overnight. Place the dried powder in a muffle furnace and calcine it at 550°C for 5 h under air atmosphere at a rate of 1°C / min to remove the polyethyleneimine template, obtaining a catalyst precursor powder with an ordered mesoporous and microporous structure and a surface rich in hydroxyl groups; the soft template agent is removed by solvent extraction or programmed temperature calcination.

[0024] Step S8: The catalyst precursor powder from step S7 is calcined in an air atmosphere and then reduced and activated in a hydrogen atmosphere to obtain a cobalt-based metal bifunctional catalyst with ordered mesoporous structures.

[0025] The cobalt source compound in step S1 is one or more of cobalt nitrate hexahydrate, cobalt sulfate heptahydrate, cobalt acetate tetrahydrate, and cobalt acetylacetonate; the aluminum source compound is one or more of aluminum nitrate nonahydrate, aluminum sulfate octadecahydrate, aluminum ammonium sulfate dodecahydrate, and sodium aluminate.

[0026] In addition to cobalt nitrate hexahydrate, which is a commonly used cobalt source, other cobalt sources are also introduced: cobalt sulfate heptahydrate is a major industrial cobalt salt with large production capacity and a mature supply chain. Its procurement cost is significantly lower than that of cobalt nitrate, making it the preferred cost reduction solution for large-scale catalyst production and a conventional alternative in cobalt-based catalyst patents; cobalt acetate tetrahydrate has a milder and more controllable precipitation process, and the acetate ion is a weak acid ion with a natural pH buffering capacity in aqueous solution; cobalt acetylacetonate achieves high metal dispersion, and the acetylacetonate ion is a strong chelating ligand, with cobalt ions existing in the form of a stable complex. During the precipitation process, the metal ion release rate is extremely slow, and the nucleation is uniform.

[0027] Besides aluminum nitrate nonahydrate, which is a commonly used aluminum source, other aluminum sources are also introduced: aluminum sulfate octadecahydrate is one of the largest and lowest-priced aluminum sources, with stable bulk supply and raw material costs far lower than aluminum nitrate, making it a core cost-reduction option for the industrial-scale production of catalysts; ammonium aluminum sulfate dodecahydrate gradually dissociates in solution to release Al3+, and the co-precipitation process is smoother when combined with a precipitant, allowing cobalt and aluminum components to be uniformly mixed at the atomic level, avoiding phase separation caused by local aluminum enrichment, and improving the uniformity of catalyst components. Sodium aluminate has a purer and more controllable surface acidity. After precipitation, aluminate ions are directly converted into aluminum hydroxide, without introducing strong acid anions such as nitrate and sulfate ions. After calcination, there are no strong acidic residual sites on the catalyst surface, and the acidity comes only from controllable surface hydroxyl groups.

[0028] The template agent in step S2 is a soft template agent, selected from one or more of block copolymer P123, block copolymer F127, hexadecyltrimethylammonium bromide, polyethylene glycol, and polyethyleneimine. The mass ratio of the soft template agent to the total metal ions in the metal precursor solution is 0.01:1 to 2:1.

[0029] Soft template agents can form ordered micelle structures through molecular self-assembly, and their interaction with metal precursors is tunable. Template removal conditions are mild and impurities are not easily introduced. Furthermore, the pore size and degree of order can be flexibly controlled by the type and amount of template agent. Compared with hard template agents, no subsequent strong base or strong acid etching is required to remove the template, making the process simpler and more suitable for large-scale preparation.

[0030] Template agents with lower molecular weights can completely dissolve in water to form a clear solution, while some template agents with higher molecular weights can form a uniform and stable colloidal dispersion. Both systems can achieve template-guided assembly.

[0031] In step S5, the ball milling speed in the first stage is 100~800 r / min, and the ball milling time is 0.5~8 h; the temperature of the high-temperature deionized water is 60~100℃.

[0032] In step S6, the solid-liquid ratio of the solid to the hydrogen peroxide solution in the ball milling system is 1:20 ~ 20:1 g / mL, the ball milling speed in the second stage is 100~800 r / min, and the ball milling time is 0.5~8 h.

[0033] In step S8, the calcination temperature is 300~800℃ and the calcination time is 0.5~8 h; the reduction temperature is 200~600℃ and the reduction time is 0.5~8 h.

[0034] To further illustrate the performance of the cobalt-based bifunctional catalyst in this invention, the following examples are provided. In each example, the raw materials used are commercially available conventional raw materials, and room temperature refers to the temperature during laboratory experiments.

[0035] Example 1 Step S1: At room temperature, weigh 0.02 mol of cobalt nitrate hexahydrate and 0.04 mol of aluminum nitrate nonahydrate (cobalt-aluminum molar ratio 0.5:1), dissolve them in 50 mL of deionized water, and stir until completely dissolved to obtain a metal precursor solution.

[0036] Step S2: Weigh 0.113 g of polyethyleneimine and dissolve it in 50 mL of deionized water. Stir until clear to obtain the template agent solution. The mass ratio of the template agent polyethyleneimine to the total metal ions is 0.05:1.

[0037] Step S3: Weigh 6.25 g of urea and dissolve it in 50 mL of deionized water to obtain a precipitant solution.

[0038] Step S4: Mix the template agent solution with the metal precursor solution and stir at room temperature for 30 min; then add the urea solution dropwise to the above mixture for pre-precipitation to obtain the pre-precipitated solution.

[0039] Step S5: Transfer the pre-precipitated solution to a ball mill jar, add 20 mL of high-temperature deionized water at 95℃, set the ball mill speed to 600 r / min, and perform the first stage of ball milling for 2 h. Under the guidance of the template agent, the metal ions undergo in-situ hydrolysis, condensation and ordered assembly to form a metal hydroxide-template ordered complex. Step S6: After the first stage of ball milling is completed, add 15 mL of 15% hydrogen peroxide solution (solid-liquid ratio of approximately 1:8, based on the mass of solids) to the ball milling jar, and continue the second stage of ball milling at 600 r / min to perform in-situ etching and hydroxylation modification on the surface of the composite. The ball milling time is 1 h to obtain a mixture.

[0040] Step S7: Remove the mixture, allow it to stand at room temperature for 4 hours to age, and wash it with deionized water until the filtrate is neutral to obtain a filter cake. Dry the filter cake in an oven at 75°C overnight; place the dried powder in a muffle furnace and calcine it at 550°C for 5 hours under air atmosphere at a rate of 1°C / min to remove the polyethyleneimine template, thereby obtaining a catalyst precursor powder with an ordered mesoporous structure.

[0041] Step S8: The precursor powder is calcined in air at a rate of 5°C / min to 400°C for 2 h, then switched to a hydrogen atmosphere and reduced at a rate of 5°C / min to 500°C for 2 h. After natural cooling, the catalyst is obtained and denoted as Co. 0.5 Al1O x -PEI-Bm-H.

[0042] Example 2 The difference between this embodiment and Embodiment 1 is that the template agent selected in step S2 is different; P123 template agent is used instead. All other aspects are the same.

[0043] Step S2: Weigh 0.045g of block copolymer P123 (EO) 20 PO 70 EO 20 Dissolve the template agent in 50 mL of deionized water to obtain a template agent solution; the mass ratio of template agent to total metal ions is 0.02:1.

[0044] The resulting catalyst is denoted as Co. 0.5 Al1O x -P123-Bm-H.

[0045] Example 3 The difference between this embodiment and Embodiment 1 is that the template agent selected in step S2 is different, while everything else is the same. The composite template agent used is a combination of F127 and polyethyleneimine.

[0046] Step S2: Weigh 0.056 g of F127 and 0.057 g of PEI (molecular weight 1800 Da) and dissolve them together in 50 mL of deionized water to obtain a composite template agent solution.

[0047] The resulting catalyst is denoted as Co. 0.5 Al1O x -F127 / PEI-Bm-H.

[0048] Example 4 The difference between this embodiment and Embodiment 1 is that a low cobalt-aluminum molar ratio is used in step S1, while all other aspects are the same.

[0049] Step S1: Weigh 0.005 mol of cobalt nitrate hexahydrate and 0.1 mol of aluminum nitrate nonahydrate (cobalt-aluminum molar ratio of 0.05:1), the rest is the same as in Example 1. The resulting catalyst is denoted as Co. 0.05 Al1O x -PEI-Bm-H.

[0050] Example 5 The difference between this embodiment and Embodiment 1 is that a high cobalt-aluminum molar ratio is used in step S1, while all other aspects are the same.

[0051] Step S1: Weigh 0.08 mol of cobalt nitrate hexahydrate and 0.02 mol of aluminum nitrate nonahydrate (cobalt-aluminum molar ratio 4:1). The resulting catalyst is denoted as Co4Al1O. x -PEI-Bm-H.

[0052] Example 6 The difference between this embodiment and Embodiment 1 is that ammonium carbonate precipitant is used in step S3, while all other steps are the same.

[0053] Step S3: Weigh 7.69 g of ammonium carbonate to prepare a precipitant solution.

[0054] The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-CA.

[0055] Example 7 The difference between this embodiment and Embodiment 1 is that the precipitant in step S3 is urea and ammonium bicarbonate, while all other aspects are the same.

[0056] Step S3: Weigh 3.125 g of urea and 2.5 g of ammonium bicarbonate and dissolve them in 50 mL of deionized water. The mass ratio of urea to ammonium bicarbonate is approximately 1.25:1, yielding a composite precipitant solution. The rest is the same as in Example 1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-HU / AB.

[0057] Example 8 The difference between this embodiment and Embodiment 1 is the cobalt source compound and the aluminum source compound in step S1; all other aspects are the same.

[0058] Step S1: Weigh 0.01 mol of cobalt nitrate hexahydrate and 0.01 mol of cobalt sulfate heptahydrate (molar ratio 1:1), mix with 0.04 mol of aluminum nitrate nonahydrate, and dissolve in deionized water, maintaining the total cobalt-aluminum molar ratio of 0.5:1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-CoNS.

[0059] Example 9 The difference between this embodiment and Embodiment 1 is the cobalt source compound and the aluminum source compound in step S1; all other aspects are the same.

[0060] Step S1: Weigh 0.01 mol of cobalt acetate tetrahydrate and 0.01 mol of cobalt acetylacetonate (molar ratio 1:1), mix with 0.04 mol of aluminum nitrate nonahydrate, and dissolve in deionized water. The total cobalt-aluminum molar ratio remains 0.5:1. The rest is the same as in Example 1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-CoAC / (acac).

[0061] Example 10 The difference between this embodiment and Embodiment 1 is the cobalt source compound and the aluminum source compound in step S1; all other aspects are the same.

[0062] Step S1: Weigh 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of aluminum nitrate nonahydrate, and 0.02 mol of aluminum sulfate octahydrate (aluminum source molar ratio 1:1), with a total cobalt-aluminum molar ratio of 0.5:1. Dissolve in 50 mL of deionized water and stir until completely dissolved to obtain a metal precursor solution. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-AlNS.

[0063] Example 11 The difference between this embodiment and Embodiment 1 is the cobalt source compound and the aluminum source compound in step S1; all other aspects are the same.

[0064] Step S1: Weigh 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium aluminate, and 0.02 mol of ammonium aluminum sulfate dodecahydrate (aluminum source molar ratio 1:1), with a total cobalt-aluminum molar ratio of 0.5:1. Dissolve in 50 mL of deionized water and stir until completely dissolved to obtain a metal precursor solution. The rest is the same as in Example 1. The obtained catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-AlNa / NH4S.

[0065] Example 12 The difference between this embodiment and Embodiment 1 is the template agent in step S2; all other aspects are the same.

[0066] Step S2: Weigh 0.0226 g of polyethyleneimine and dissolve it in 50 mL of deionized water. The molar ratio of template agent to total metal ions is 0.01:1. The rest is the same as in Example 1. The resulting catalyst is denoted as Co. 0.5 Al1O x-PEI-0.01-Bm-H.

[0067] Example 13 The difference between this embodiment and Embodiment 1 is that the amount of the template agent polyethyleneimine used in step S2 is different, while all other aspects are the same.

[0068] Step S2: Weigh 4.516 g of polyethyleneimine and dissolve it in deionized water. The molar ratio of template agent to total metal ions is 2:1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-2-Bm-H.

[0069] Example 14 The difference between this embodiment and Embodiment 1 is that the template agent in step S2 is different, but everything else is the same.

[0070] Step S2: Weigh 0.678 g of PEG and 0.339 g of CTAB (mass ratio 2:1) and dissolve them in 50 mL of deionized water to obtain a composite template agent solution. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEG / CTAB-Bm-H.

[0071] Example 15 The difference between this embodiment and Embodiment 1 is that the concentration of the hydrogen peroxide solution in step S6 is different, but everything else is the same.

[0072] Step S6: Add a 5% (w / w) hydrogen peroxide solution with a solid-liquid ratio of 20:1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-5%.

[0073] Example 16 The difference between this embodiment and Embodiment 1 is that the concentration of the hydrogen peroxide solution in step S6 is different, but everything else is the same.

[0074] Step S6: Add a 30% (w / w) hydrogen peroxide solution with a solid-liquid ratio of 1:20. All other parameters are the same as in Example 1. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm-H-30%.

[0075] Comparative Example 1 This embodiment is identical to Example 1 except that no template agent is added. The resulting catalyst is denoted as Co. 0.5 Al1O x -Bm-H (No template).

[0076] Comparative Example 2 This embodiment is identical to Example 1 except that hydrogen peroxide is not added during the second stage of ball milling. The resulting catalyst is denoted as Co. 0.5 Al1O x -PEI-Bm (without H2O2).

[0077] Comparative Example 3 In this embodiment, after the first stage of ball milling, hydrogen peroxide was not added. Instead, the washed, dried, and template-removed precursor powder was separately added to 15 mL of a 15% (w / w) hydrogen peroxide solution, stirred at 40°C for 4 h, then filtered, washed, dried, and subsequently calcined and reduced. Everything else was exactly the same as in Example 1. The resulting catalyst was denoted as Co. 0.5 Al1O x -PEI-H2O2-post.

[0078] Comparative Example 4 This embodiment uses a conventional coprecipitation method, without ball milling, templates, or hydrogen peroxide, as detailed below: At room temperature, weigh 0.02 mol cobalt nitrate hexahydrate and 0.04 mol aluminum nitrate nonahydrate (cobalt-aluminum molar ratio 0.5:1), dissolve them in 50 mL of deionized water, and stir until completely dissolved to obtain a metal precursor solution.

[0079] Weigh 6.25 g of urea and dissolve it in 50 mL of deionized water to obtain a precipitant solution.

[0080] Add the urea solution dropwise into the metal precursor solution and stir at a constant temperature of 90°C for 5 hours.

[0081] Aged for 4 hours, washed until neutral, filtered, and dried at 75°C overnight.

[0082] The dried powder was calcined directly in air at 400°C for 2 h, followed by reduction with hydrogen at 500°C for 2 h. The resulting catalyst was denoted as Co. 0.5 Al1O x -CP.

[0083] Comparative Example 5 This embodiment involves ball milling but without a template or hydrogen peroxide, as detailed below: At room temperature, weigh 0.02 mol cobalt nitrate hexahydrate and 0.04 mol aluminum nitrate nonahydrate (cobalt-aluminum molar ratio 0.5:1), dissolve them in 50 mL of deionized water, and stir until completely dissolved to obtain a metal precursor solution.

[0084] Weigh 0.113 g of polyethyleneimine and dissolve it in 50 mL of deionized water. Stir until clear to obtain a template agent solution. The mass ratio of template agent to total metal ions is 0.05:1.

[0085] Weigh 6.25 g of urea and dissolve it in 50 mL of deionized water to obtain a precipitant solution.

[0086] The metal precursor solution was mixed with urea solution and heated to 85°C with stirring to obtain a turbid liquid. The turbid liquid was transferred to a ball mill jar, and 95°C deionized water was added. The mixture was ball-milled at 400 r / min for 3 h (without a second stage of hydrogen peroxide ball milling). Subsequent washing, drying, calcination, and reduction were performed as in Example 1. The resulting catalyst is denoted as Co. 0.5 Al1O x -Bm (no template, no H2O2).

[0087] To verify the performance of the catalyst prepared in this invention, a catalyst performance evaluation was conducted: Evaluation method: A 50 mL stainless steel high-pressure reactor was used. 1.0 g of the reduced catalyst prepared in each example and comparative example was weighed and added to a feed solution consisting of 5 g ethylene glycol and 16 g 25% ammonia (ammonia-to-ethanol molar ratio 3:1). After sealing, the reactor was purged with hydrogen five times, and the pressure was increased to 3 MPa. The reactor was stirred at 800 r / min and heated to 195 °C at 5 °C / min, and reacted for 12 h. After cooling, the product was collected and analyzed by gas chromatography (area normalization method). The data are shown in Table 1.

[0088] Table 1. Ethylene glycol conversion and selectivity of piperazine derivatives

[0089] As shown in Table 1: The catalyst prepared using the method of this invention exhibits significantly improved overall performance, effectively addressing the core issues of low conversion and selectivity in ethylene glycol amination. Except for Example 4, where the ethylene glycol conversion rate was 76.3% due to the lower limit of the cobalt-aluminum ratio, the ethylene glycol conversion rates in all other examples exceeded 85%, and the selectivity of piperazine and its derivatives exceeded 75%. In the preferred example 1, the ethylene glycol conversion rate reached 95.2%, and the selectivity of piperazine and its derivatives reached 89.2%, far superior to the conventional co-precipitation method (Comparative Example 4, conversion rate 62.5%, selectivity 39.2%) and the simple ball milling process (Comparative Example 5, conversion rate 68.9%, selectivity 46.6%), fully verifying that the preparation method of this invention can simultaneously and significantly improve both reaction activity and target product selectivity.

[0090] 2. The template-guided ordered mesoporous structure exhibits a significant shape-selective catalytic effect, solving the problem of insufficient selectivity in ethylenediamine cyclization. Comparing Example 1 and Comparative Example 1 (without template), the selectivity of piperazine and its derivatives increased from 55% to 89.2% after the introduction of the template, while the selectivity of ethylenediamine decreased from 32.5% to 8.1%. This indicates that the ordered channels confine the reaction intermediates, promoting the intramolecular cyclization of ethylenediamine to form piperazine, while inhibiting the formation of macromolecular byproducts. Different types of soft templates and composite template systems (Examples 2, 3, and 14) all achieved significant improvements in selectivity, verifying the universality of the soft template system. The molar ratio of template to metal ions is effective across the entire range of 0.01:1 to 2:1, perfectly matching the scope defined in the claims.

[0091] 3. Ball milling in-situ hydrogen peroxide modification constructs a metal-acid bifunctional synergistic system, solving the problems of metal particle agglomeration and insufficient active sites. Comparing Example 1 and Comparative Example 2 (without hydrogen peroxide modification), the ethylene glycol conversion rate increased from 81.5% to 95.2% after in-situ hydrogen peroxide modification, and the selectivity of piperazine and its derivatives increased from 66.7% to 89.2%, demonstrating that the hydroxyl groups introduced on the surface act as acidic sites, forming a bifunctional synergy with the hydrogenation sites of cobalt metal, while simultaneously promoting the amination of alcohols and the cyclization of intermediates. Comparing Example 1 and Comparative Example 3 (hydrogen peroxide post-treatment), the catalytic effect of ball milling in-situ modification is significantly better than that of the post-treatment method, indicating that the mechanical force of ball milling promotes uniform etching and hydroxyl grafting on the particle surface by hydrogen peroxide, resulting in more complete modification. At the same time, the mechanical dispersion effect inhibits metal grain agglomeration and increases the exposure of active sites.

[0092] The catalyst in Example 1 was characterized, such as Figure 1 As shown, by Figure 1 It is evident that the catalyst's pore size is primarily concentrated around 0.5 nm, exhibiting an extremely narrow pore size distribution and a full width at half maximum (FWHM) of less than 1 nm. This further demonstrates that the ordered mesoporous structure formed under template guidance has uniform size, enabling precise shape-selective catalysis. The ordered pore size matches the molecular size of ethylenediamine and piperazine, forming the structural basis for the high selectivity of piperazine.

[0093] like Figure 2 The image shown is a TEM characterization image of the catalyst in Example 1. It can be observed from the image that the catalyst exhibits an ordered mesoporous channel structure with regular channel orientation, proving that the template-guided assembly effect is good. The cobalt particles are uniformly dispersed in the channel framework, with the particle size concentrated in 5~8 nm, and there is no obvious large particle agglomeration. This indicates that the confinement effect of the ordered channels effectively inhibits the growth and agglomeration of metal grains, ensuring the full exposure of active sites, which is consistent with the result of high catalytic activity.

Claims

1. A method for preparing a cobalt-based bifunctional catalyst, characterized in that, Includes the following steps: Step S1: Dissolve the cobalt source compound and the aluminum source compound in deionized water to prepare a metal precursor solution; Step S2: Dissolve the template agent in deionized water to prepare a template agent solution or dispersion; Step S3: Prepare the precipitant solution; Step S4: Mix the template agent solution from step S2 with the metal precursor solution from step S1, and then add the precipitant solution from step S3 to carry out a pre-precipitation reaction to obtain a pre-precipitated solution. Step S5: Add high-temperature deionized water at 60~100℃ to the pre-precipitated solution in step S4, and perform first-stage ball milling to form a metal hydroxide-template ordered composite. Step S6: Add a 5%~30% hydrogen peroxide solution to the metal hydroxide-template ordered composite from step 5, and perform a second-stage ball milling to obtain a mixture; Step S7: Dry the mixture from step S6, then remove the template agent to obtain catalyst precursor powder; Step S8: Activate the catalyst precursor powder from step S7 to obtain a cobalt-based bifunctional catalyst.

2. The method for preparing a cobalt-based bifunctional catalyst as described in claim 1, characterized in that, The template agent in step S2 is a soft template agent, selected from one or more of block copolymer P123, block copolymer F127, hexadecyltrimethylammonium bromide, polyethylene glycol, and polyethyleneimine.

3. The method for preparing a cobalt-based bifunctional catalyst as described in claim 2, characterized in that, The mass ratio of the soft template agent to the total metal ions in the metal precursor solution is 0.01:1 to 2:

1.

4. The method for preparing a cobalt-based bifunctional catalyst as described in claim 3, characterized in that, In step S5, the ball milling speed in the first stage is 100~800 r / min, and the ball milling time is 0.5~8 h; the temperature of the high-temperature deionized water is 60~100℃.

5. The method for preparing a cobalt-based bifunctional catalyst as described in claim 4, characterized in that, In step S6, the solid-liquid ratio of the solid to the hydrogen peroxide solution in the ball milling system is 1:20 ~ 20:1 g / mL, the ball milling speed in the second stage is 100~800 r / min, and the ball milling time is 0.5~8 h.

6. The method for preparing a cobalt-based bifunctional catalyst as described in claim 5, characterized in that, The method for removing the template agent is as follows: in step S7, solvent extraction or programmed temperature calcination is used for removal.

7. The method for preparing a cobalt-based bifunctional catalyst as described in claim 6, characterized in that, The activation process in step S8 is as follows: the catalyst precursor powder is calcined in an air atmosphere at a temperature of 300~800℃ for 0.5~8 h; after calcination, it is reduced and activated in a hydrogen atmosphere at a temperature of 200~600℃ for 0.5~8 h.

8. The method for preparing a cobalt-based bifunctional catalyst as described in claim 7, characterized in that, The cobalt source compound in step S1 is one or more of cobalt nitrate hexahydrate, cobalt sulfate heptahydrate, cobalt acetate tetrahydrate, and cobalt acetylacetone; the aluminum source compound is one or more of aluminum nitrate nonahydrate, aluminum sulfate octadecahydrate, aluminum ammonium sulfate dodecahydrate, and sodium aluminate; the cobalt source compound and the aluminum source compound are in a cobalt-aluminum molar ratio of 0.05:1 to 4:

1.

9. A cobalt-based bifunctional catalyst prepared according to any one of the preparation methods of a cobalt-based bifunctional catalyst according to claims 1-8.

10. A cobalt-based bifunctional catalyst prepared according to the method for preparing a cobalt-based bifunctional catalyst according to any one of claims 1-8, or the cobalt-based bifunctional catalyst according to claim 9, characterized in that, In the selective reductive amination of ethylene glycol to prepare organic amines, the organic amines include piperazine, methylpiperazine, ethylpiperazine, aminoethylpiperazine, or hydroxyethylpiperazine.

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