Carbon-coated copper catalyst, preparation method and application thereof

Abstract

The application discloses a carbon-coated copper catalyst and a preparation method and application thereof, and relates to the technical field of catalysts; the technical scheme is that beta cyclodextrin is used as a carbon source, so that copper-containing active components are uniformly distributed on a carbon coating layer; wherein, the carbon coating layer derived from cyclodextrin pyrolysis can effectively inhibit the migration and agglomeration of copper active sites, so that the catalyst has higher selectivity and better reaction activity, and the improvement of catalytic performance is promoted; the carbon-coated copper catalyst is suitable for catalyzing the hydrogen production reaction of ethanol aqueous-phase reforming, the hydrogen production rate reaches 35.6 mu mol H2 / gcat / s, the hydrogen selectivity is higher than 99.9%, and long-time continuous and stable operation of the hydrogen production of ethanol aqueous-phase reforming can be ensured.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a copper-based catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean and efficient energy form, has enormous development potential. Developing hydrogen energy helps promote the transformation and upgrading of the energy structure, reduce dependence on fossil fuels, and improve the flexibility and security of the energy system. Ethanol aqueous reforming for hydrogen production (alkali-free hydrogen production), as an emerging method, has advantages such as inexpensive and readily available raw materials, relatively mild reaction conditions, and low carbon footprint. Therefore, developing catalysts for ethanol aqueous reforming for hydrogen production is of great significance. Currently, catalysts used in low-temperature methanol aqueous reforming for hydrogen production are mainly precious metal catalysts such as Pt, Pd, Ru, and Rh, which are costly and unsuitable for large-scale industrial production. Copper-based catalysts, on the other hand, are inexpensive and possess good selectivity and catalytic activity, showing promising application prospects in ethanol aqueous reforming for hydrogen production and are expected to become a substitute for precious metal catalysts. However, in the ethanol / water system, the dispersion of copper active sites still needs improvement, and the selectivity for byproducts such as carbon monoxide and methane remains relatively high.

[0003] Existing technology discloses a method for preparing carbon-coated copper catalysts and their applications. This catalyst utilizes carbon-containing organic matter and inorganic copper salt solutions as main raw materials to prepare carbon-coated nano-copper-based catalysts. When applied to the aqueous reforming reaction of ethanol to produce hydrogen, this catalyst can effectively improve the selectivity of hydrogen and its reaction rate. However, due to limitations in the catalyst preparation method, copper active sites are prone to agglomeration and migration during the drying process, ultimately leading to uneven distribution on the support and insufficient catalyst activity. Summary of the Invention

[0004] To overcome the problems of low hydrogen selectivity and poor stability in the existing aqueous reforming of ethanol for hydrogen production, this invention provides a method for preparing a carbon-coated catalyst. By using β-cyclodextrin as a carbon source and controlling the ratio of β-cyclodextrin to copper salt, the carbon-coated copper catalyst is made more stable under hydrothermal conditions and can effectively improve the hydrogen production rate and selectivity, thereby accelerating the catalyst to reach its peak hydrogen production performance and further optimizing its catalytic efficiency.

[0005] Another object of the present invention is to provide a carbon-coated copper catalyst obtained by the above preparation method.

[0006] Another object of the present invention is to provide an application of the above-mentioned carbon-coated copper catalyst in the aqueous reforming of ethanol to produce hydrogen.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] Therefore, the first technical solution provided by this invention is as follows:

[0009] A carbon-coated copper catalyst, the carbon-coated copper catalyst comprising copper-containing nanoparticles and a carbon layer coating the copper-containing nanoparticles;

[0010] Based on a total mass of 100% carbon-coated copper catalyst, the carbon layer accounts for 23.96-25.47% of the total catalyst mass, with the remainder being copper-containing nanoparticles.

[0011] Furthermore, in the aforementioned carbon-coated copper catalyst, the copper-containing nanoparticles are one or any mixture of copper nanoparticles and cuprous oxide nanoparticles.

[0012] Furthermore, in the aforementioned carbon-coated copper catalyst, the total mass of oxygen in the cuprous oxide is 18.08% to 21.31% of the total mass of the carbon-coated copper catalyst.

[0013] Furthermore, in the aforementioned carbon-coated copper catalyst, the medium particle size of the copper-containing nanoparticles is 4–15 nm.

[0014] The carbon-coated copper catalyst of this invention uses an organic carbon layer provided by β-cyclodextrin as a support to provide attachment sites for the active component copper ions, so that the active sites of copper can be uniformly dispersed in the organic carbon layer, which can effectively solve the problem of active component agglomeration and thus improve its reaction rate.

[0015] In the carbon-coated copper-based catalyst, the content of organic carbon support and the content of monovalent copper and zero-valent copper active components are relative. When the carbon content is too high, it will reduce the content of copper nanoparticles in the catalyst, inhibiting its reaction rate and selectivity to hydrogen. When the carbon content is too low, it will lead to an excessive loading of copper active components, resulting in the agglomeration of active copper metal. The copper active sites cannot fully contact the reactants, thus reducing the reaction rate.

[0016] Furthermore, copper nanoparticles are represented by the particle size of the active component, which is simultaneously regulated by the organic carbon content and the interaction forces between the active components. The size of the active copper nanoparticles, the content of organic carbon, and their dispersion state jointly affect the catalytic activity of the carbon-coated copper catalyst in the liquid-phase hydrogen production of ethanol. Only when the number of copper active sites and the organic carbon content reach a relatively stable equilibrium can a suitable particle size of the active component be obtained, thereby improving the dispersion of the active component and enhancing the catalyst activity.

[0017] When the particle size of the active component copper nanoparticles is in the range of 4 to 15 nm, the aggregation energy of the active component is effectively suppressed due to the small crystal particle size. The active component copper nanoparticles can be uniformly distributed on the carbon coating layer, achieving high dispersion of copper active sites, thereby improving the activity and selectivity of the carbon-coated copper catalyst.

[0018] The second technical solution provided by this invention is a method for preparing the above-mentioned nitrogen-doped carbon-coated copper catalyst, comprising the following steps:

[0019] S1. Copper nitrate solution and β-cyclodextrin were mixed and thoroughly complexed, and then dried to obtain Cu-βCD complex;

[0020] The molar ratio of copper nitrate to β-cyclodextrin is (1.4–6.1):1;

[0021] S2. The Cu-βCD composite obtained in S1 is calcined at 200-600℃ for 1-4 hours under an inert gas atmosphere to obtain a carbon-coated copper catalyst precursor.

[0022] S3. The carbon-coated copper-based catalyst precursor is reduced in a hydrogen atmosphere to make the copper active sites uniformly distributed on the carbon coating layer, thus obtaining the carbon-coated copper catalyst.

[0023] Furthermore, in the above-mentioned method for preparing nitrogen-doped carbon-coated copper catalyst, the molar ratio of copper salt to β-cyclodextrin in step S1 is (1.9–5.4):1.

[0024] Furthermore, in the above-mentioned method for preparing nitrogen-doped carbon-coated copper catalyst, the complexation in step S1 is carried out by stirring at 80°C for 12 hours; the drying is carried out by drying at 80°C for 24 hours.

[0025] Furthermore, in the above-mentioned method for preparing nitrogen-doped carbon-coated copper catalyst, the calcination temperature in step S2 is 300–400°C, and the calcination time is 2–3 h.

[0026] Furthermore, in the above-mentioned method for preparing nitrogen-doped carbon-coated copper catalyst, the reduction temperature in step S3 is 250–550 °C.

[0027] The final technical solution provided by this invention is to use the above-mentioned carbon-coated copper catalyst to catalyze the reaction of hydrogen production from ethanol aqueous phase reforming.

[0028] This invention selects β-cyclodextrin as the carbon source (β-CD). β-cyclodextrin is a cyclic oligosaccharide composed of seven glucose units linked by α-1,4-glycosidic bonds. Its molecular shape is slightly conical and ring-like, with a hydrophilic outer surface and a relatively hydrophobic inner cavity. β-cyclodextrin has hydroxyl groups at the C-2 and C-3 positions, which can act as ligands to form coordination bonds with copper ions, readily forming complexes and providing excellent dispersion for copper active sites. Furthermore, calcination of β-cyclodextrin in an inert atmosphere forms a carbon layer, which can effectively coat copper nanoparticles, providing attachment sites for the copper active components and forming a highly loaded and highly dispersed structure, resulting in better catalytic performance.

[0029] In this invention, the particle size, active component loading, and carbon content of copper nanoparticles are all affected by the ratio of copper to β-cyclodextrin. Therefore, in order to obtain the carbon-coated copper catalyst described in this invention, it is necessary to reasonably control the ratio of copper nitrate to β-cyclodextrin so that the active component can still be well dispersed under high loading, the particle size can be stabilized at a small size, and in the case of high-density active component, the migration of active component during the reduction of S2 can be further prevented from causing agglomeration.

[0030] The control of calcination conditions in this invention is to ensure the loading of carbon and copper nanoparticles, and to prevent the active components from agglomerating due to excessively high temperature, or the carbon content from being insufficient due to excessively low temperature.

[0031] The catalyst of this invention is simple to prepare. β-cyclodextrin is used as a carbon source and does not need to be carbonized before being stirred and mixed with the metal compound. By controlling the reaction conditions, the carbon-coated copper catalyst has the characteristics of small particle size, high loading and high dispersion. It can achieve high hydrogen production rate, strong hydrogen selectivity and high catalytic activity. It can be used to rapidly produce high-purity hydrogen, and is especially suitable for the field of hydrogen production by aqueous reforming of ethanol.

[0032] This invention also protects the application of a carbon-coated copper catalyst in the aqueous reforming of ethanol to produce hydrogen.

[0033] The specific application methods are as follows:

[0034] The prepared catalyst was added to a reaction solution of water and ethanol, and hydrogen production was carried out in a batch reactor using argon as a protective gas.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] This invention provides a carbon-coated copper catalyst, which constrains the migration and aggregation of active component copper nanoparticles through the carbon layer and provides attachment sites for the active component, resulting in a highly loaded and highly dispersed nitrogen-doped carbon-coated copper catalyst. By controlling the loading amount, carbon content, and particle size of the active component in the carbon-coated copper catalyst, the catalytic performance of the catalyst is improved, resulting in high catalytic activity and good hydrothermal stability.

[0037] The carbon-coated copper catalyst of the present invention is particularly suitable for the catalysis of methanol liquid-phase reforming to produce hydrogen. It has a high hydrogen production rate and high hydrogen selectivity, with a hydrogen selectivity of more than 99.9% in the produced gas. The hydrogen production rate can reach 35 μmol H2 / gcat / s, and it can operate continuously and stably for 400 hours in a fixed-bed reactor. Attached Figure Description

[0038] Figure 1 This is the infrared spectrum of a carbon-coated copper catalyst.

[0039] Figure 2 The image shows a scanning electron microscope (SEM) image of a carbon-coated copper catalyst (left) and a corresponding HRTEM image of the carbon-coated copper catalyst (right).

[0040] Figure 3 High-angle annular dark-field transmission electron microscopy (HAADF-STEM) image of carbon-coated copper catalyst and magnified HRTEM image of carbon-coated Cu nanoparticle structure.

[0041] Figure 4 This is a comparison chart of the hydrogen production performance of the carbon-coated copper catalyst, the commercial CuZnAl catalyst, and the Raney Cu catalyst in ethanol aqueous reforming.

[0042] Figure 5 XRD patterns of carbon-coated copper catalysts with varying molar ratios of copper nitrate to β-cyclodextrin.

[0043] Figure 6 The images show the XRD patterns of the carbon-coated copper catalyst before and after the reaction. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0045] Example 1

[0046] This embodiment provides a carbon-coated copper catalyst for hydrogen production from ethanol via aqueous phase reforming, which is prepared through the following steps:

[0047] S1. Copper nitrate and β-cyclodextrin are mixed and stirred at 80°C for 12 hours to fully complex, and then dried at 80°C to obtain Cu-CD complex; wherein the molar ratio of copper nitrate and β-cyclodextrin is 4:1;

[0048] S2. The Cu-CD complex in S1 was calcined at 400℃ for 2 hours under a nitrogen atmosphere to obtain a carbon-coated copper precursor;

[0049] S3. Reduce 50 mg of carbon-coated copper catalyst precursor at 350 °C for 2 h at a hydrogen flow rate of 50 ml / min to obtain carbon-coated copper catalyst. The components and their contents in the catalyst are shown in Table 1.

[0050] Example 2

[0051] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the calcination temperature in S2 is 300°C. The components and their contents in this catalyst are shown in Table 1.

[0052] Example 3

[0053] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous reforming. Its preparation method is basically the same as that in Example 1, except that the calcination temperature in S2 is 450°C. The components and their contents in this catalyst are shown in Table 1.

[0054] Example 4

[0055] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the calcination time in S2 is 1 hour. The components and their contents in this catalyst are shown in Table 1.

[0056] Example 5

[0057] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the calcination time in S2 is 3 hours. The components and their contents in this catalyst are shown in Table 1.

[0058] Example 6

[0059] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the calcination time in S2 is 1 hour and the calcination temperature is 300°C. The components and their contents in this catalyst are shown in Table 1.

[0060] Example 7

[0061] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous reforming. Its preparation method is basically the same as that in Example 1, except that the calcination time in S2 is 3 hours and the calcination temperature is 300°C. The components and their contents in this catalyst are shown in Table 1.

[0062] Example 8

[0063] This embodiment provides another carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the calcination time in S2 is 1 hour and the calcination temperature is 300°C. The components and their contents in this catalyst are shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] Infrared spectroscopy analysis of the raw material βCD and Cu-βCD complex was performed (see [reference]). Figure 1 The study determined that copper ions provided by copper nitrate form a complex with β-cyclodextrin through coordination. Infrared spectroscopy observation showed that βCD forms a complex at wavelengths of 3200-3600 cm⁻¹. -1 The signal at this location is the vibration of OH, while the signal at 3200-3600 cm⁻¹ is found on the Cu-βCD complex. -1 The OH vibration signal was significantly weakened. This indicates that the copper ions provided by copper nitrate and β-cyclodextrin may form a complex by coordinating with the oxygen-containing functional group OH, allowing copper nanoparticles to be uniformly distributed on the organic carbon layer after calcination, with small particle size and high dispersibility.

[0068] For scanning electron microscopy (SEM) images of the carbon-coated copper catalyst and the corresponding HRTEM images, please refer to [link to relevant documentation]. Figure 2 SEM observation revealed that the carbon-coated copper catalyst exhibits a thin, blocky structure, indicating a large contact area between the catalyst and the reactants, resulting in a high reaction rate. HRTEM images of the carbon-coated copper catalyst show that the copper nanoparticles are small in size and uniformly distributed, demonstrating highly dispersed active copper loading on the support. This indicates that the catalyst is highly dispersible and effectively catalyzes the aqueous reforming of ethanol to produce hydrogen.

[0069] High-angle annular dark-field transmission electron microscopy (HAADF-STEM) image of carbon-coated copper catalyst and magnified HRTEM image of carbon-coated Cu nanoparticle structure, see reference. Figure 3This shows that the copper nanoparticles in the carbon-coated copper catalyst have a particle size of about 10 nm, are uniformly distributed on the carbon coating layer, and do not accumulate, effectively maintaining a high number of active sites and the long-term stability of the catalyst.

[0070] Comparative Example 1

[0071] The comparative example provides a carbon-coated copper catalyst for hydrogen production from ethanol aqueous phase reforming. Its preparation method is basically the same as that in Example 1, except that the molar ratio of copper nitrate to β-cyclodextrin is 2.6:1. The components and their contents in this catalyst are shown in Table 2.

[0072] Comparative Example 2

[0073] The comparative example provides a carbon-coated copper catalyst for hydrogen production from ethanol aqueous reforming. Its preparation method is basically the same as that in Example 1, except that the molar ratio of copper nitrate to β-cyclodextrin is 3.3:1. The components and their contents in this catalyst are shown in Table 2.

[0074] Comparative Example 3

[0075] The comparative example provides a carbon-coated copper catalyst for hydrogen production from ethanol aqueous reforming. Its preparation method is basically the same as that in Example 1, except that the molar ratio of copper nitrate to β-cyclodextrin is 4.7:1. The components and their contents in this catalyst are shown in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] Note: The copper nanoparticle loading mentioned in this application refers to metallic copper, and the percentage of the total mass of copper in cuprous oxide relative to the total mass of the catalyst.

[0080] Comparative Examples 4-8

[0081] The carbon-coated copper catalysts for hydrogen production from ethanol aqueous reforming provided in Comparative Examples 4-8 are prepared in a manner that is basically the same as that in Example 1, except that the carbon source is different, as detailed in Table 3.

[0082] Table 3

[0083] Comparative Example Organic carbon source Comparative Example 4 glucose Comparative Example 5 Sorbitol Comparative Example 6 Agar Comparative Example 7 Konjac gum Comparative Example 8 Agarose

[0084] Comparative Example 9

[0085] After grinding and crushing the purchased commercial CuZnAl catalyst, 50 mg of the catalyst was weighed and reduced at 350 °C for 2 h at a hydrogen flow rate of 50 ml / min.

[0086] Comparative Example 10

[0087] After grinding and crushing the purchased Raney Cu commercial catalyst, 50 mg of the catalyst was weighed and reduced at 350 °C for 2 h at a hydrogen flow rate of 50 ml / min.

[0088] Result detection

[0089] The catalytic reaction conditions for the carbon-coated copper catalyst in the aqueous reforming of ethanol to produce hydrogen are as follows:

[0090] Add 50 mg of any one of the catalysts described in Examples 1-8 and Comparative Examples 1-10 to a batch reactor and add it to 20 ml of ethanol aqueous solution. Use 2 MPa argon as a protective gas and react at 210 °C for 2 h. After cooling to room temperature, use gas chromatography to quantitatively analyze the gas phase products. The results are shown in Table 4.

[0091] The ethanol-water solution is composed of ethanol and water in a molar ratio of 1:1.

[0092] The hydrogen production rate of the carbon-coated copper catalyst is obtained by calculating the gas production volume using the water displacement method. The hydrogen production rate is the amount of hydrogen produced per gram of catalyst per second. The selectivity is calculated by the amount of H2, CO, and CH4 in the products. For example, the hydrogen selectivity H2 (%) = nH2 * 100% / (nH2 + nCO + nCH4).

[0093] Table 4 Comparison of catalytic effects of each embodiment and comparative example

[0094]

[0095] Examples 1-3 show that when the calcination temperature varies within the range of 300℃ to 450℃, the catalyst calcined at 400℃ exhibits the best performance. A calcination temperature of 400℃ promotes the formation of sufficient pores within the carbon-coated copper catalyst, increasing the specific surface area and active sites, thus resulting in higher catalyst activity. In contrast, the copper nanoparticles in the carbon-coated copper catalyst calcined at 300℃ are difficult to disperse, leading to a lower catalytic rate. In the carbon-coated copper catalyst calcined at 450℃, the copper nanoparticles agglomerate, reducing the reaction area with ethanol and water, and decreasing the reaction rate. Examples 4-8 show that longer calcination times do not necessarily improve catalyst performance. When the calcination time is too short, although the particles are relatively uniformly dispersed, the active components in the catalyst do not fully form an ideal crystal structure, resulting in an imperfect structure and distribution of active sites. This makes it difficult to effectively select the target product in the ethanol-water phase reforming hydrogen production reaction, thus reducing selectivity. Conversely, when the calcination time is too long, the catalyst pore structure collapses, hindering the diffusion of active sites, thereby reducing catalyst activity and the hydrogen production rate. As can be seen from Examples 1 and Comparative Examples 1-3, changing the proportion of β-cyclodextrin providing the carbon source affects the catalyst performance. Increasing or decreasing the proportion of β-cyclodextrin reduces the hydrogen production rate and the selectivity of hydrogen. As can be seen from Examples 1 and Comparative Examples 4-8, catalysts prepared using β-cyclodextrin as an organic carbon source exhibit better hydrogen production performance than catalysts using sorbitol or glutamic acid as organic carbon sources. This is because β-cyclodextrin has a unique cyclic structure that allows it to form inclusion complexes. This structural characteristic enables it to better bind with copper elements during the preparation of copper-based catalysts, forming stable and highly efficient catalytic active centers. Furthermore, different organic carbon sources have varying abilities to promote the dispersion of active metallic copper during coupling, ultimately leading to different hydrogen production rates.

[0096] from Figure 4 As shown in Table 4, the carbon-coated copper catalyst in Example 1 exhibits a 99.79% selectivity for hydrogen and a carbon monoxide selectivity of less than 0.1% in the produced gas at 210°C. This is superior to both the commercial CuZnAl and Raney Cu catalysts, achieving effective separation of reaction products and significantly reducing purification costs. The carbon-coated copper catalyst achieves a hydrogen production rate as high as 35.6 μmol·gcat⁻¹·s⁻¹, which is 1.52 times that of the CuZnAl commercial catalyst under the same conditions and 1.38 times that of the Raney Cu commercial catalyst. This represents a significant breakthrough in the application of non-precious metal catalysts in the aqueous reforming of ethanol for hydrogen production.

[0097] Figure 5The XRD patterns of carbon-coated copper catalysts prepared by varying the ratio of copper nitrate to β-cyclodextrin show that as the molar ratio of Cu to β-cyclodextrin decreases from 4.01 to 2.6, or from 4.0 to 4.7, the characteristic peaks of copper in the XRD patterns gradually become sharper, indicating an increase in the particle size of the copper nanoparticles. When the particle size of the copper nanoparticles increases, the organic carbon cannot effectively coat the active copper component. This leads to the aggregation of copper active sites during sintering, and a decrease in the contact area with ethanol and water. Ultimately, this results in a decrease in the hydrogen production rate and selectivity.

[0098] Figure 6 The images show the XRD patterns of the carbon-coated copper catalyst before and after the reaction. By comparing the XRD patterns of the carbon-coated copper catalyst before and after the reaction, it can be found that the peak sharpness and shape of the XRD patterns do not change much, and the size of the active copper nanoparticles does not increase significantly. This indicates that the carbon-coated copper catalyst has good stability, and its structure remains basically consistent during the reaction.

[0099] It should be noted that although the other embodiments provide relevant descriptions of their corresponding XRD patterns, transmission electron microscope images, and elemental analysis diagrams, their relevant performance is quite similar.

[0100] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a carbon-coated copper catalyst, characterized by, The method comprises the following steps: S1. mixing a copper nitrate solution and β-cyclodextrin, fully complexing, drying to obtain a Cu-βCD complex; The molar ratio of copper nitrate and β-cyclodextrin is (1.4-6.1):

1. S2. calcining the Cu-βCD complex prepared in S1 under an inert gas atmosphere at 200-600°C for 1-4h to obtain a carbon-coated copper catalyst precursor; S3. reducing the carbon-coated copper catalyst precursor in a hydrogen atmosphere to make the copper active sites uniformly distributed on the carbon coating layer to obtain a carbon-coated copper catalyst.

2. The method for preparing the carbon-coated copper catalyst according to claim 1, characterized in that, The molar ratio of copper salt and β-cyclodextrin in step S1 is (1.9-5.4):

1.

3. The method for preparing the carbon-coated copper catalyst according to claim 1, characterized in that, The complexing in step S1 is stirring at 80°C for 12h; and the drying is at 80°C for 24h.

4. The method for preparing the carbon-coated copper catalyst according to claim 1, characterized in that, The calcining temperature in step S2 is 300-400°C, and the calcining time is 2-3h.

5. The method for preparing the carbon-coated copper catalyst according to claim 1, characterized in that, The reduction temperature in step S3 is 250-550°C.

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