Cobalt-copper catalyst with nanosheet structure as well as preparation method and application of cobalt-copper catalyst

Abstract

The invention provides a cobalt-copper catalyst with a nanosheet structure and a preparation method and application of the cobalt-copper catalyst, the catalyst contains copper oxide and cobalt oxide, and the catalyst is of the nanosheet structure. The nano-material catalyst provided by the invention has the advantages of larger specific surface area, more interface atoms, higher interface atom diffusion coefficient, preferred crystal face orientation and higher chemical activity. The nano-catalyst provided by the invention has high activity and good selectivity. Compared with nano-particles, the one-dimensional pore structure provided by the porous nanosheet structure can be used as a nano-reactor for catalytic reaction, and the collision among reactant molecules, intermediate products and catalysts is adjusted, so that the reaction kinetics is influenced. The cobalt-copper catalyst disclosed by the invention has efficient hydrogenation activity, such as an effect of preparing alcohol through catalytic hydrogenation of carbon dioxide, is very stable in a long-time reaction, and is relatively mild in catalytic reaction conditions.

Description

Technical Field

[0001] This invention relates to a cobalt-copper catalyst with a nanosheet structure, its preparation method, and its application. Background Technology

[0002] The precise design and synthesis of well-defined nanocrystals are crucial for elucidating the structure-activity relationships of heterogeneous catalysts. Composite nanomaterials composed of two or more nanomodules exhibit performance unmatched by single components in many fields due to the unique functions of each component, the special interfaces between components, and synergistic effects. The CO2 hydrogenation reaction system, in particular, requires the synergistic action of multiple active centers, such as CO2 activation, CC coupling, and the formation of oxidizing compounds.

[0003] Traditional industrial catalyst preparation methods, such as impregnation and precipitation, often encounter problems related to limited contact area / distance between active sites and supports, as well as weak interfacial interactions, thus limiting catalytic activity and selectivity. Ion exchange methods can alter the coordination environment of the original components and establish metal-metal interactions through lattice insertion; this method has been proven to have a significant promoting effect on catalytic reactions. Catalysts prepared using this method can effectively improve catalytic performance and solve the problems of catalyst deactivation and difficulty in controlling product selectivity during the reaction. The literature (Chem.Rev.2020,120,7984-8034) summarizes existing catalytic material systems for the direct hydrogenation of carbon dioxide to alcohols, including copper-based catalysts, noble metal catalysts, and cobalt-based catalysts. However, these systems suffer from harsh reaction conditions, easy catalyst deactivation, and high catalyst costs. Improving reaction conditions, enhancing catalyst stability, and increasing selectivity remain key challenges for this reaction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a novel cobalt-copper catalyst that is particularly suitable for hydrogenation, especially for the direct production of alcohols from carbon dioxide, and has the characteristics of low reaction temperature and good catalyst stability.

[0005] According to a first aspect of the present invention, the present invention provides a cobalt-copper catalyst with a nanosheet structure, the catalyst comprising copper oxide and cobalt oxide, and the catalyst having a nanosheet structure.

[0006] According to a second aspect of the present invention, the present invention provides a method for preparing the catalyst of the present invention, wherein the method comprises: a) subjecting a cobalt source alkaline solution to a first hydrothermal crystallization to obtain intermediate A;

[0007] b) The copper source and intermediate A are combined into a solution and subjected to a second hydrothermal crystallization to obtain intermediate B;

[0008] c) Calcining intermediate B.

[0009] According to a third aspect of the invention, the invention provides the application of the catalyst described herein in hydrogenation, preferably in the hydrogenation conversion of carbon dioxide to alcohols.

[0010] The nanoparticle catalyst of the present invention has high activity and good selectivity. It is speculated that this is because the nanomaterial catalyst of the present invention has more interface atoms, a higher interface atom diffusion coefficient, and a preferred crystal orientation. Moreover, compared with nanoparticles, the porous nanosheet structure provides a one-dimensional pore structure that can serve as a nanoreactor for catalytic reactions, regulating the collisions between reactant molecules, intermediate products and catalysts, thereby affecting the reaction kinetics.

[0011] This invention prepares cobalt hydroxide nanosheets via hydrothermal recrystallization; then, copper species are loaded onto the cobalt hydroxide nanosheets using an ion exchange method to form an integrated nanosheet structure; finally, the nanosheet structure is heat-treated to prepare a cobalt-copper catalyst with a nanosheet structure. This invention mainly utilizes the cobalt hydroxide nanosheet structure, employing an ion exchange method to replace one metal with another metal hydroxide, and synthesizing a nanoscale sheet-like porous structure through heat treatment.

[0012] The present invention describes a method for preparing porous nanosheet-structured catalysts via ion exchange, which is particularly suitable for hydrogenation reactions, especially for the direct hydrogenation of carbon dioxide to alcohols in a fixed-bed reactor. Compared with CuO / Co3O4 catalysts prepared by impregnation, the catalyst prepared by ion exchange significantly improves the alcohol selectivity and exhibits good catalyst stability, achieving better technical results.

[0013] The cobalt-copper catalyst prepared by this method has a high efficiency in hydrogenation, especially in the catalytic hydrogenation of carbon dioxide to alcohol. At the same time, the catalyst is very stable during long-term reactions, and the catalytic reaction conditions are relatively mild. Attached Figure Description

[0014] Figure 1 The X-ray powder diffraction patterns are those of the samples synthesized in Examples 1-9 and Comparative Example 1 of this invention. Figure 1 The X-ray powder diffraction patterns shown in Examples 1-9 are as follows. In all the catalysts, the cobalt phase exists as cobalt tetroxide, and the copper species exhibits characteristic diffraction peaks of copper oxide.

[0015] Figure 2 This is a scanning electron microscope image of the sample synthesized in Example 1 of the present invention. Figure 2 The image shows the porous nanosheet structure synthesized in [Example 1], with a thickness of approximately 30–50 nanometers and a sheet length of approximately 150–300 nanometers.

[0016] Figure 3 This is a transmission electron microscope image of the sample synthesized in Example 1 of the present invention. Figure 3 The image shows the porous nanosheet structure synthesized in [Example 1], wherein the nanosheet structure remains intact and has obvious disordered pores.

[0017] Figure 4 This is an elemental distribution diagram of the synthesized sample in Example 1 of the present invention. Figure 4 The image shows the elemental distribution diagram of Example 1, in which copper species are dispersed very uniformly on cobalt tetroxide nanosheets.

[0018] Figure 5 This is a transmission electron microscope image of the synthesized sample in Comparative Example 1 of this invention. Figure 5 The image shown is a transmission electron microscope image of [Comparative Example 1] after calcination. It can be seen that the nanosheet structure is significantly destroyed, which does not conform to the hexagonal nanosheet structure of the catalyst.

[0019] Figure 6 This is an elemental distribution diagram of the synthesized sample in Comparative Example 1 of the present invention. Figure 6 The elemental distribution diagram of Comparative Example 1 is shown in the figure. It can be seen that the copper species are relatively uniformly dispersed, but some copper species have aggregated, which does not conform to the characteristic of uniform dispersion of Cu catalyst.

[0020] Figure 7 This is a scanning electron microscope image of the synthesized sample in Example 9 of the present invention. Figure 7 The image shown in the scanning electron microscope (SEM) image of Example 9 reveals that the nanosheets have agglomerated and stacked into blocks, which does not conform to the hexagonal nanosheet structure of the catalyst. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] This invention provides a cobalt-copper catalyst with a nanosheet structure, wherein the catalyst contains copper oxide and cobalt oxide, and the catalyst has a nanosheet structure. The catalyst of this invention has a well-defined structure, excellent hydrogenation activity, and is particularly suitable for hydrogenation reactions such as the catalytic hydrogenation of carbon dioxide to alcohols, with high alcohol selectivity.

[0023] In this invention, the composition of the catalyst can be selected from a wide range. This is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the atomic ratio of Co / Cu in the catalyst is 1-16:1, preferably 3-4:1.

[0024] In this invention, any nanosheet structure can be used to achieve the purpose of this invention. According to a preferred embodiment of this invention, the thickness of the nanosheet structure of the catalyst is 30-50 nanometers.

[0025] In this invention, any nanosheet structure can be used to achieve the purpose of this invention. According to a preferred embodiment of this invention, the nanosheet structure of the catalyst is a hexagonal sheet structure.

[0026] In this invention, any nanosheet structure can be used to achieve the purpose of this invention. According to a preferred embodiment of this invention, the diameter of the nanosheet structure of the catalyst is 150-300 nanometers.

[0027] In this invention, there are no special requirements for the form of the copper oxide. This is an illustrative example and does not limit the scope of the invention. According to a preferred embodiment of the invention, the copper oxide is CuO.

[0028] In this invention, there are no special requirements for the form of cobalt oxide. This is an illustrative example and does not limit the scope of the invention. According to a preferred embodiment of the invention, the cobalt oxide is Co3O4.

[0029] The catalyst of this invention has Cu-Co dual active centers that can contact at the atomic level, forming a synergistic catalytic effect, resulting in excellent hydrogenation activity. It is particularly suitable for the catalytic hydrogenation of carbon dioxide to alcohols, with high alcohol selectivity.

[0030] According to a preferred embodiment of the present invention, the thickness of the CuO / Co3O4 nanosheet structure is preferably in the range of 30 to 50 nanometers; the nanostructure is preferably a hexagonal sheet structure; and the diameter of the nanosheet structure is 150 to 300 nanometers.

[0031] Catalysts that satisfy the aforementioned structure can be used in this invention, and there are no special requirements for their preparation methods. According to one embodiment of this invention, this invention provides a method for preparing the catalyst of this invention, wherein the method includes: a) subjecting a cobalt source alkaline solution to a first hydrothermal crystallization to obtain intermediate A;

[0032] b) The copper source and intermediate A are combined into a solution and subjected to a second hydrothermal crystallization to obtain intermediate B;

[0033] c) Calcining intermediate B.

[0034] In this invention, after the first hydrothermal crystallization in step a), the intermediate A is obtained by cooling, washing and drying. There are no special requirements for the cooling, washing and drying methods. Generally, the intermediate A is cooled to room temperature, for example, washed with an inert solvent such as water and then dried.

[0035] In this invention, after the second hydrothermal crystallization in step b), the intermediate B is obtained by cooling, washing, and drying. There are no special requirements for the cooling, washing, and drying methods. Generally, the intermediate is cooled to room temperature, for example, washed with an inert solvent such as water, and then dried.

[0036] The preparation method of this invention involves co-hydrothermally crystallizing a copper source and intermediate A. This method yields a catalyst with the structure of this invention, exhibiting a well-defined structure, excellent hydrogenation activity, and is particularly suitable for the catalytic hydrogenation of carbon dioxide to alcohols, demonstrating high alcohol selectivity.

[0037] In this invention, there are no special requirements for the cobalt source alkaline solution. It is generally formed by introducing water and alkaline substances. In order to form a mixed and homogeneous solution, it can be formed by stirring or appropriate heating.

[0038] In this invention, the aforementioned preparation methods can all achieve the purpose of this invention, and there are no special requirements for the cobalt source alkaline solution, etc. According to a preferred embodiment of this invention, in step a), the solvent I of the cobalt source alkaline solution is a mixture of water and organic amine. More preferably, the weight ratio of water to organic amine is 1-10:1, preferably 2-5:1, for example 2:1, 3:1, 4:1, 5:1, etc. In the examples, 10:3 is used as an example to illustrate the advantages of this invention, but this invention is not limited thereto.

[0039] In this invention, the range of selectable organic amines is relatively wide. For this invention, preferably, the organic amine is one or more of benzylamine and oleylamine. In this invention, it has been found that using both benzylamine and oleylamine as organic amine sources can improve the hydrogenation activity of the catalyst, particularly improving the alcohol selectivity of the catalytic hydrogenation of carbon dioxide to alcohols. According to a preferred embodiment of the invention, the organic amine is preferably a mixture of benzylamine and oleylamine, and the content of each of benzylamine and oleylamine is 30-70% by weight.

[0040] In this invention, the mass ratio of cobalt source to solvent I can be selected from a wide range. This is an illustrative example, but it does not limit the scope of the invention. Preferably, the mass ratio of cobalt source to solvent I is 0.01-0.1:1, more preferably 0.02-0.05:1, for example 0.02:1, 0.03:1, 0.04:1, 0.05:1, etc.

[0041] In this invention, the range of cobalt sources that can be selected is relatively wide. For this invention, the preferred cobalt source is selected from one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetate tetrahydrate.

[0042] In this invention, the conditions for the first hydrothermal crystallization in step a) can be selected from a wide range. For this invention, the first hydrothermal crystallization preferably includes a temperature of 120-180°C, such as 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, and 180°C. All of the above temperatures can achieve the purpose of this invention. The embodiment uses 180°C as an example, but does not limit the scope of this invention.

[0043] In this invention, the selectable range of the first hydrothermal crystallization time is relatively wide, and it is specifically selected and determined according to the first hydrothermal crystallization temperature. For example, in this invention, the first hydrothermal crystallization time is 9-12 hours.

[0044] In this invention, there are no special requirements for the copper source and intermediate A to form a solution. Generally, the copper source can be dissolved in water and then intermediate A can be added. In order to achieve uniform mixing, it can generally be formed by appropriate heating or stirring.

[0045] In this invention, in step b), a solution is formed, and there are no special requirements for the solvent. According to this invention, water is used for example, and other substances can be introduced as needed.

[0046] In this invention, in step b), the weight ratio of solvent to cobalt source in the solution can be selected within a wide range. For this invention, the preferred weight ratio of solvent to copper source in the solution is 40-50:1, for example, 40:1; 41:1; 43:1; 45:1; 47:1; 49:1, etc. All of the above weight ratios can achieve the purpose of this invention. The embodiments provide exemplary examples.

[0047] In this invention, the range of copper sources that can be selected is relatively wide. For this invention, the preferred copper source is one or more of copper nitrate trihydrate, copper chloride dihydrate, and copper acetate monohydrate.

[0048] In this invention, the metal atom ratio of intermediate A and copper source can be selected within a wide range. For this invention, the preferred metal atom ratio of intermediate A and copper source is 1-16:1, and more preferably 3-4:1.

[0049] In this invention, the conditions for the second hydrothermal crystallization in step b) have a wide range of selectable values. For this invention, the second hydrothermal crystallization preferably includes a temperature of 120-180°C, such as 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, and 180°C. All of the above temperatures can achieve the purpose of this invention. The embodiment uses 120°C as an example, but does not limit the scope of this invention.

[0050] In this invention, the selection range of the second hydrothermal crystallization time is relatively wide, and it is specifically selected and determined according to the second hydrothermal crystallization temperature. For example, in this invention, the second hydrothermal crystallization time is 6-12 hours.

[0051] In the preparation of this invention, in order to form a homogeneous mixture, it can generally be achieved by moderate heating or dynamic mixing, which is a well-known technique in the art and will not be described in detail here.

[0052] In this invention, the range of selectable calcination conditions in step c) is relatively wide. For this invention, the preferred calcination conditions in step c) include a temperature of 350-850℃, preferably 350-400℃. Using the aforementioned preferred calcination temperature can significantly improve the alcohol selectivity of the catalyst for the hydrogenation of carbon dioxide to alcohols.

[0053] In this invention, the calcination time in step c) can be adjusted as needed. For this invention, the preferred calcination time is 3-5 hours. In this invention, through calcination, intermediate B dehydrates and forms a special cobalt-copper interface.

[0054] In this invention, there are no special requirements for the atmosphere in which calcination takes place; for example, it is generally an oxygen-containing atmosphere or an air atmosphere.

[0055] This invention does not have any special requirements for the heating rate in the specific roasting process. It is an illustrative example and does not limit the scope of the invention. According to one embodiment of the invention, the heating rate from room temperature to the roasting temperature is 3-10℃ / min.

[0056] The catalyst of the present invention is particularly suitable for hydrogenation, especially the hydrogenation of carbon dioxide to produce alcohols. The present invention provides the application of the catalyst of the present invention in the hydrogenation of carbon dioxide to produce alcohols; preferably, the application steps include: in the presence of the catalyst of the present invention, hydrogenating carbon dioxide and hydrogen.

[0057] In this invention, the operating conditions for the hydrogenation of carbon dioxide to produce alcohols can be selected over a wide range. For this invention, the preferred conditions include: a carbon dioxide to hydrogen molar ratio of 3-4:1, a reaction temperature of 250-275°C, a reaction pressure of 1-2 MPa, and a reaction space velocity of 4000-6000 h⁻¹. -1 .

[0058] The present invention will be described in detail below through examples. In the following examples, the morphology and structure of the catalyst prepared above and the catalyst activity test parameters were measured by STEM, SEM, EDX, XRD, BET, and fixed-bed reactor carbon dioxide hydrogenation test methods; the catalyst morphology was characterized by a SU8010 scanning electron microscope (SEM) manufactured by Hitachi, Japan, with a test operating voltage of 30kV; the catalyst size and morphology were characterized by a Talos F200X scanning transmission electron microscope (STEM) manufactured by Thermo Fisher Scientific, USA. A small amount of powder sample and an appropriate amount of anhydrous ethanol were taken into a sample bottle, ultrasonically dispersed for 10 min, and the mixed solution was dropped onto a copper grid using a capillary tube, dried, and then tested; the phase analysis of the catalyst was performed using an Advance D8 X-ray powder diffractometer (XRD) manufactured by Bruker, Germany, with Cu target K α The X-ray, Vantec-1 detector, and 40 kV and 40 mA were used for testing, with a scanning range of 10°–80° and a scanning step of 2° / min. The catalytic performance of carbon dioxide hydrogenation was tested in a fixed-bed stainless steel reactor, with 0.2 g of catalyst loaded into a reaction tube lined with a quartz liner, and a reaction space velocity of 6 SL·h⁻¹. -1 ·g -1 The reaction pressure was 2 MPa, and the heating rate was 2 °C / min. The catalyst was pretreated under different conditions before performance testing. Liquid products were collected using a cold water bath cold trap. The reaction tail gas was analyzed online using an Agilent GC7890B gas chromatograph, and the liquid products were analyzed offline using an Agilent GC 4890D.

[0059] The copper and cobalt raw materials are commercially available products from Sinopharm Company with brand names 10031-433 and 10026-22-9, while the benzylamine and oleylamine raw materials are commercially available products from Aladdin Company with brand names 100-46-9 and 112-90-3.

[0060]

Example 1

[0061] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0062] 1.2 g of the prepared cobalt hydroxide nanosheets were added to 50 mL of water and a solution containing 0.74 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0063] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 4 / 1).

[0064]

Example 2

[0065] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0066] 1.2 g of the prepared cobalt hydroxide nanosheets were added to 50 mL of water and a solution containing 2.46 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0067] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 1 / 1).

[0068]

Example 3

[0069] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0070] 1.2 g of the prepared cobalt hydroxide nanosheets were added to 50 mL of water and a solution containing 1.23 g of copper nitrate trihydrate, and stirred at room temperature for 0.5 hours. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0071] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 2 / 1).

[0072]

Example 4

[0073] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g benzylamine and 10 g water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0074] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of water and a solution containing 0.986 g of copper nitrate trihydrate, and stirred at room temperature for 0.5 h. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization treatment at 120 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0075] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 3 / 1).

[0076]

Example 5

[0077] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g benzylamine and 10 g water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0078] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of water and a solution containing 0.37 g of copper nitrate trihydrate, and stirred at room temperature for 0.5 h. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization treatment at 120 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0079] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the bulk CuO / Co3O4 material (where the Co / Cu atomic ratio is 8 / 1).

[0080]

Example 6

[0081] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0082] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of water and a solution containing 0.19 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization treatment at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0083] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 16 / 1).

[0084]

Example 7

[0085] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0086] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of water and a solution containing 0.74 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization treatment at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0087] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 550°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 4 / 1).

[0088]

Example 8

[0089] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g benzylamine and 10 g water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0090] 1.2 g of the prepared cobalt hydroxide nanosheets were added to 50 mL of water and a solution containing 0.74 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0091] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 650°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 4 / 1).

[0092]

Example 9

[0093] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g benzylamine and 10 g water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0094] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of water and a solution containing 0.74 g of copper nitrate trihydrate, and stirred at room temperature for half an hour. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization treatment at 120 °C for 12 hours. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain Cu(OH)₂ / Co(OH)₂ nanosheets.

[0095] The Cu(OH)2 / Co(OH)2 nanosheets prepared above were transferred to a muffle furnace and heated to 850°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the porous nanosheet structure CuO / Co3O4 material (where the Co / Cu atomic ratio = 4 / 1).

[0096]

Example 10

[0097] The method is the same as in Example 1, except that the organic amine is a mixture of benzylamine and oleylamine, the total amount of organic amine remains the same, the amount of benzylamine is 30 wt%, the amount of oleylamine is 70 wt%, and all other conditions are the same.

[0098]

Example 11

[0099] The method of Example 1 is the same, except that the organic amine is a mixture of benzylamine and oleylamine, the total amount of organic amine remains the same, the amount of benzylamine is 90 wt%, the amount of oleylamine is 10 wt%, and the other conditions are the same.

[0100] Comparative Example 1

[0101] 0.437 g of cobalt nitrate hexahydrate was added to a mixture of 3 g of benzylamine and 10 g of water, and stirred at 40 °C for 30 min. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal crystallization at 180 °C for 12 h. After natural cooling, the precipitate was collected by centrifugation, thoroughly washed with ultrapure water, and then dried in an oven at 80 °C to obtain cobalt hydroxide nanosheets.

[0102] 1.2 g of the cobalt hydroxide nanosheet material prepared above was added to 50 mL of ethanol and a solution containing 0.74 g of copper nitrate trihydrate, and ultrasonically stirred at room temperature for 0.5 h. The mixture was then dried by rotary evaporation to obtain Cu(NO3)2 / Co(OH)2.

[0103] The Cu(NO3)2 / Co(OH)2 prepared above was transferred to a muffle furnace and heated to 350°C for 3 hours in a static air atmosphere at a heating rate of 5°C / min. After natural cooling, a black powder was obtained, which is the ultrasonic impregnation CuO / Co3O4 material (where Co / Cu = 4 / 1).

[0104] Figure 1 The X-ray powder diffraction patterns are those of the samples synthesized in Examples 1-9 and Comparative Example 1 of this invention. Figure 1 The X-ray powder diffraction patterns shown in Examples 1-9 are as follows. In all the catalysts, the cobalt phase exists as cobalt tetroxide, and the copper species exhibits characteristic diffraction peaks of copper oxide.

[0105] Figure 2 This is a scanning electron microscope image of the sample synthesized in Example 1 of the present invention. Figure 2 The image shows the porous nanosheet structure synthesized in [Example 1], with a thickness of approximately 30–50 nanometers and a sheet length of approximately 150–300 nanometers.

[0106] Figure 3 This is a transmission electron microscope image of the sample synthesized in Example 1 of the present invention. Figure 3 The image shows the porous nanosheet structure synthesized in [Example 1], wherein the nanosheet structure remains intact and has obvious disordered pores.

[0107] Figure 4 This is an elemental distribution diagram of the synthesized sample in Example 1 of the present invention. Figure 4 The image shows the elemental distribution diagram of Example 1, in which copper species are dispersed very uniformly on cobalt tetroxide nanosheets.

[0108] Figure 5 This is a transmission electron microscope image of the synthesized sample in Comparative Example 1 of this invention. Figure 5 The image shown is a transmission electron microscope image of [Comparative Example 1] after calcination. It can be seen that the nanosheet structure is significantly destroyed, which does not conform to the hexagonal nanosheet structure of the catalyst.

[0109] Figure 6 This is an elemental distribution diagram of the synthesized sample in Comparative Example 1 of the present invention. Figure 6 The elemental distribution diagram of Comparative Example 1 is shown in the figure. It can be seen that the copper species are relatively uniformly dispersed, but some copper species have aggregated, which does not conform to the characteristic of uniform dispersion of Cu catalyst.

[0110] Figure 7 This is a scanning electron microscope image of the synthesized sample in Example 9 of the present invention. Figure 7 The image shown in the scanning electron microscope (SEM) image of Example 9 reveals that the nanosheets have agglomerated and stacked into blocks, which does not conform to the hexagonal nanosheet structure of the catalyst.

[0111] Test case

[0112] Performance evaluation of carbon dioxide hydrogenation catalytic reaction: 0.1 g of the prepared catalyst was added to a multiphase fixed-bed microreactor, and carbon dioxide and hydrogen were introduced. Nitrogen was used as an internal standard, and the reaction was heated and carried out. The molar ratio of carbon dioxide to hydrogen was 3:1, the reaction temperature was 250-275℃, the reaction pressure was 2 MPa, and the space velocity was 6 L·g⁻¹. cat -1 ·h -1 The results are shown in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cobalt-copper catalyst with a nanosheet structure, characterized in that, The catalyst contains copper oxide and cobalt oxide, and the catalyst has a nanosheet structure.

2. The catalyst according to claim 1, wherein, The atomic ratio of Co / Cu in this catalyst is 1-16:1, preferably 3-4:

1.

3. The catalyst according to claim 1 or 2, wherein, The thickness of the nanosheet structure of the catalyst is 30–50 nanometers; and / or The catalyst has a hexagonal sheet structure in its nanosheet form; and / or The catalyst has a nanosheet structure with a diameter of 150–300 nanometers; and / or The copper oxide is CuO; and / or The cobalt oxide is Co3O4.

4. A method for preparing the catalyst according to any one of claims 1-3, wherein, The method includes: a) subjecting a cobalt source alkaline solution to a first hydrothermal crystallization to obtain intermediate A; b) The copper source and intermediate A are combined into a solution and subjected to a second hydrothermal crystallization to obtain intermediate B; c) Calcining intermediate B.

5. The preparation method according to claim 4, wherein, In step a), The solvent I of the cobalt source alkaline solution is a mixture of water and organic amine, preferably with a water to organic amine weight ratio of 1-10:1, more preferably 2-5:1; and / or Preferably, the organic amine is one or more of benzylamine and oleylamine; More preferably, the organic amine is a mixture of benzylamine and oleylamine, and the content of each of benzylamine and oleylamine is 30-70% by weight; and / or The mass ratio of cobalt source to solvent I is 0.01-0.1:1, preferably 0.02-0.05:1; and / or The cobalt source is selected from one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetate tetrahydrate.

6. The preparation method according to claim 4 or 5, wherein, In step a), the conditions for the first hydrothermal crystallization include a temperature of 120-180°C and / or a time of 9-12 hours.

7. The preparation method according to any one of claims 4-6, wherein, In step b), The solvent that forms the solution is water; and / or The weight ratio of solvent to cobalt source in the solution is 40-50:1; and / or The copper source is one or more of copper nitrate trihydrate, copper chloride dihydrate, and copper acetate monohydrate; and / or The metal atom ratio of intermediate A and copper source, Co / Cu, is 1-16:1, preferably 3-4:

1.

8. The preparation method according to any one of claims 4-7, wherein, In step b), the conditions for the second hydrothermal crystallization include a temperature of 120-180°C and / or a time of 6-12 hours.

9. The preparation method according to any one of claims 4-8, wherein, In step c), the calcination conditions include: a temperature of 350-850℃, preferably 350-400℃; and / or a time of 3-5h; and / or calcination being carried out in an oxygen-containing atmosphere; and / or a heating rate from room temperature to the calcination temperature of 3-10℃ / min.

10. The use of the catalyst according to any one of claims 1-3 in hydrogenation, preferably in the hydrogenation conversion of carbon dioxide to alcohols; Preferably, the steps for the application of carbon dioxide hydrogenation to produce alcohols include: In the presence of the catalyst described in any one of claims 1-3; The process involves the hydrogenation of carbon dioxide and hydrogen. The operating conditions for the hydrogenation of carbon dioxide to produce alcohols include: a carbon dioxide to hydrogen molar ratio of 3-4:1, a reaction temperature of 250-275℃, a reaction pressure of 1-2 MPa, and a reaction space velocity of 4000-6000 h⁻¹. -1 .

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