Doped Cu-based catalyst, preparation method and application of doped Cu-based catalyst in ethanol synthesis

Abstract

The invention relates to the technical field of alcohol synthesis catalysts, in particular to a doped Cu-based catalyst, a preparation method and application of the doped Cu-based catalyst in the aspect of ethanol synthesis. The preparation method comprises the following steps: S1, pretreating mesoporous silica; s2, loading zinc ions on the pretreated mesoporous silica; s3, converting the zinc ions loaded on the mesoporous silica into zinc oxide; s4, treating the mesoporous silica adsorbed with zinc oxide through EDTA (Ethylene Diamine Tetraacetic Acid); s5, performing fixed-point adsorption on the copper ions by zinc oxide on the mesoporous silica; s6, mesoporous silica is removed through alkali treatment, and the doped Cu-based catalyst is prepared through heating reduction. According to the doped Cu-based catalyst prepared by the invention, copper ions and zinc oxide are uniformly distributed, so that the catalytic efficiency of the material on synthesis gas is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of alcohol synthesis catalysts, and specifically to a doped Cu-based catalyst, a preparation method thereof, and an application thereof in synthesizing ethanol. Background Art

[0002] Ethanol is an extremely important chemical raw material, widely used in organic synthesis, dyes, fuels, pharmaceuticals, coatings, and the national defense industry. There are more than a hundred chemical products processed from ethanol as raw materials. In recent years, with the continuous increase in deep-processing products of ethanol and the continuous expansion of chemical application fields, the status of ethanol in the national economy has become increasingly important and prominent.

[0003] Currently, the Cu / ZnO catalyst has achieved a major technological breakthrough from syngas (H2+CO) to ethanol. Ethanol can be obtained without adding alkali metals or Fischer-Tropsch elements in these catalysts, which breaks the traditional understanding of Cu / ZnO as a methanol catalyst, but the ethanol yield is very low. ZnO is an n-type semiconductor. Due to the existence of intrinsic defects such as oxygen vacancies and zinc interstitials, its stoichiometry will deviate. Therefore, doping can change the electronic structure, crystal structure, and surface properties of the Cu / ZnO catalyst, thereby improving its catalytic activity, selectivity, and stability. However, there are still many problems in aspects such as the selection of the type of Cu / ZnO doping material, the control of the doping ratio, and the optimization of the doping method. In the prior art, although the performance of some doped catalysts has been improved to a certain extent, there are defects such as poor doping uniformity, unstable binding with the matrix, complex preparation process, and high cost, which limit their large-scale industrial application.

[0004] Therefore, in view of the problems raised in the above background art, those skilled in the art propose a doped Cu-based catalyst, a preparation method thereof, and an application thereof in synthesizing ethanol. Summary of the Invention

[0005] The purpose of the present invention is to provide a doped Cu-based catalyst, a preparation method thereof, and an application thereof in synthesizing ethanol to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a doped Cu-based catalyst includes the following steps: S1. Dispersing mesoporous silica into a toluene solution containing 3-aminopropyltrimethoxysilane, heating to 50-90°C, refluxing for 5-10 h, then filtering, washing with sufficient toluene, and drying at low temperature to obtain pretreated mesoporous silica; S2. Immerse the pretreated mesoporous silica obtained in step S1 into a zinc nitrate solution with a concentration of 0.5 - 1 mol / L for 3 - 8 h, and then filter to obtain mesoporous silica loaded with zinc ions; S3. Immerse the mesoporous silica loaded with zinc ions obtained in step S2 into ammonia water with a pH of 8 - 10 for 1 - 4 h, then filter, and place the filtered product into a muffle furnace to calcine at 600 - 800 °C for 2 - 5 h to obtain mesoporous silica loaded with zinc oxide; S4. Put the mesoporous silica loaded with zinc oxide obtained in step S3 into an EDTA aqueous solution with a mass fraction of 0.1 - 0.5% and heat it to 40 - 60 °C for reaction for 3 - 6 h, then filter to obtain a filtrate; S5. Put the filtrate obtained in step S4 into a mixture of a copper nitrate solution and a structure assistant and soak for 1 - 2 h, then add sodium carbonate to adjust the pH to 8 - 9, and filter to obtain a crude product; S6. Put the crude product obtained in step S5 into a sodium hydroxide solution with a concentration of 4 - 6 mol / L and heat it to 60 - 80 °C for reaction for 1 - 3 h, then filter, wash the filtered product with sufficient deionized water and dry it at 60 - 100 °C, and put the dried product into a muffle furnace to reduce it in a hydrogen and nitrogen atmosphere at 200 - 300 °C for 2 - 4 h. After reduction, a doped Cu-based catalyst is obtained.

[0007] Further, the mass ratio of silica, 3-aminopropyltrimethoxysilane and toluene in step S1 is 1:(0.1 - 0.5):(50 - 60).

[0008] Further, the mass ratio of the pretreated mesoporous silica to the zinc nitrate solution in step S2 is 1:(30 - 50).

[0009] Further, the mass ratio of the mesoporous silica loaded with zinc ions to ammonia water in step S3 is 1:(10 - 20).

[0010] Further, the mass ratio of the mesoporous silica loaded with zinc oxide to the EDTA aqueous solution in step S4 is 1:(70 - 100).

[0011] Further, the concentration of copper nitrate in step S5 is 0.1 - 0.4 mol / L, the mass ratio of the filtrate to the mixed solution of copper nitrate and the structure assistant is 1:(20 - 30), the structure assistant is a combination of any two of the metal salts of Al, Ga or Cr, specifically aluminum nitrate, gallium nitrate or chromium nitrate, and the concentration of the structure assistant is 0.005 mol / L.

[0012] Further, the mass ratio between the crude product and the sodium hydroxide solution in step S6 is 1:(50 - 100), and the volume ratio between hydrogen and nitrogen is 1:4.

[0013] A doped Cu-based catalyst is prepared by the preparation method of the above-mentioned doped Cu-based catalyst.

[0014] The application of the above-mentioned doped Cu-based catalyst in the synthesis of ethanol.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the present invention, by introducing structural promoters (doping aluminum, gallium, and chromium ions), the catalytic efficiency of the catalyst can be effectively improved. The preparation method of the catalyst is simple and the catalytic stability is strong; 2. In the present invention, mesoporous silica is used as the carrier. First, mesoporous silica is modified by a silane coupling agent to uniformly combine a large amount of zinc ions in the pores of mesoporous silica. Zinc oxide is synthesized in the pores of mesoporous silica by adjusting the pH, and finally a Cu / ZnO catalyst is synthesized; 3. In the present invention, zinc oxide is combined with copper ions. A high-temperature calcination step is introduced in step S3. The high-temperature calcination eliminates the amino groups introduced in step S1 and the hydroxyl groups carried by mesoporous silica itself, weakening the binding ability between copper ions and silica. At the same time, through the complexing action of EDTA, the binding between copper ions and zinc oxide is strengthened. Finally, the mesoporous silica carrier is removed by a strong alkali solution. Description of the Drawings

[0016] Figure 1 It is the process flow chart for preparing the doped Cu-based catalyst in the present invention; Figure 2 It is the XRD pattern of the doped Cu-based catalyst prepared in the present invention; Figure 3 It is the TEM image, HRTEM image, and Cu particle size diagram of the doped Cu-based catalysts prepared in Examples 1 - 4 of the present invention (a1 - d1 are TEM images, a2 - d2 are HRTEM images, and a3 - d3 are Cu particle size histograms). Detailed Embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] Please refer to Figures 1-3 , the present invention provides: Example 1 A preparation method of a doped Cu-based catalyst includes the following steps: S1. Disperse 2.24 g of mesoporous silica into a toluene solution containing 0.448 g of 3-aminopropyltrimethoxysilane and 123.2 g of toluene. Heat to 65 °C and reflux for 9 h. Then filter, wash with sufficient toluene, and dry at low temperature to obtain pretreated mesoporous silica; S2. Immerse 2.12 g of the pretreated mesoporous silica obtained in step S1 into 84.2 g of a zinc nitrate solution with a concentration of 0.8 mol / L for 5.5 h. Then filter to obtain mesoporous silica loaded with zinc ions; S3. Immerse 2.12 g of the mesoporous silica loaded with zinc ions obtained in step S2 into 31.6 g of ammonia water with a pH of 8.5 for 3 h. Then filter, and place the filtered product in a muffle furnace and calcine at 700 °C for 4 h to obtain mesoporous silica loaded with zinc oxide; S4. Put 2.08 g of the mesoporous silica loaded with zinc oxide obtained in step S3 into 176.5 g of an EDTA aqueous solution with a mass fraction of 0.4% and heat to 55 °C for reaction for 4 h. Then filter to obtain a filtrate; S5. Put 1.96 g of the filtrate obtained in step S4 into 54.8 g of a copper nitrate solution with a concentration of 0.2 mol / L and soak for 1.4 h. Then add sodium carbonate to adjust the pH to 8.5 and filter to obtain a crude product; S6. Put 1.85 g of the crude product obtained in step S5 into 108 g of a sodium hydroxide solution with a concentration of 5 mol / L and heat to 75 °C for reaction for 2 h. Then filter, wash the filtered product with sufficient deionized water, dry at 80 °C, put the dried product into a muffle furnace and reduce it in a hydrogen and nitrogen atmosphere at 260 °C for 3 h. The volume ratio between hydrogen and nitrogen is 1:4. After reduction, a doped Cu-based catalyst (abbreviated as CZ) is obtained.

[0019] Example 2 A preparation method of a doped Cu-based catalyst includes the following steps: S1. Disperse 2.54 g of mesoporous silica into a toluene solution containing 0.254 g of 3-aminopropyltrimethoxysilane and 127 g of toluene. Heat to 50 °C and reflux for 5 h. Then filter, wash with sufficient toluene, and dry at low temperature to obtain pretreated mesoporous silica; S2. Immerse the 2.44 g of pretreated mesoporous silica obtained in step S1 into 73.2 g of a zinc nitrate solution with a concentration of 0.5 mol / L for 3 h, and then filter to obtain mesoporous silica loaded with zinc ions; S3. Immerse the 2.25 g of mesoporous silica loaded with zinc ions obtained in step S2 into ammonia water with a pH of 8 for 1 h. The amount of ammonia water used is 22.5 g, and then filter. Place the filtered product in a muffle furnace and calcine it at 600 °C for 2 h to obtain mesoporous silica loaded with zinc oxide; S4. Put the 2.24 g of mesoporous silica loaded with zinc oxide obtained in step S3 into 156.8 g of an EDTA aqueous solution with a mass fraction of 0.1%, heat it to 40 °C and react for 3 h, and then filter to obtain a filtrate; S5. Put the 2.11 g of filtrate obtained in step S4 into 42.2 g of a mixed solution of copper nitrate with a concentration of 0.1 mol / L, aluminum nitrate with a concentration of 0.005 mol / L, and chromium nitrate with a concentration of 0.005 mol / L, soak for 1 h, then add sodium carbonate to adjust the pH to 8, and filter to obtain a crude product; S6. Put the 2.01 g of crude product obtained in step S5 into 100.5 g of a sodium hydroxide solution with a concentration of 4 mol / L, heat it to 60 °C and react for 1 h, and then filter. Wash the filtered product with sufficient deionized water and dry it at 60 °C. Put the dried product into a muffle furnace and reduce it in a hydrogen and nitrogen atmosphere at 200 °C for 2 h. The volume ratio between hydrogen and nitrogen is 1:4. After reduction, a doped Cu-based catalyst (abbreviated as CZAC, A represents Al, and C represents Cr) is obtained.

[0020] Example 3 A preparation method of a doped Cu-based catalyst, comprising the following steps: S1. Disperse 1.96 g of mesoporous silica into a toluene solution containing 3-aminopropyltrimethoxysilane. The amount of 3-aminopropyltrimethoxysilane used is 0.98 g, and the amount of toluene used is 117.6 g. Heat it to 90 °C and reflux for 10 h, and then filter. After washing with sufficient toluene, dry it at low temperature to obtain pretreated mesoporous silica; S2. Immerse the 1.84 g of pretreated mesoporous silica obtained in step S1 into 92 g of a zinc nitrate solution with a concentration of 1 mol / L for 8 h, and then filter to obtain mesoporous silica loaded with zinc ions; S3. Immerse the 1.77 g of mesoporous silica loaded with zinc ions obtained in step S2 into ammonia water with a pH of 10 for 4 h. The amount of ammonia water used is 35.4 g, and then filter. Place the filtered product in a muffle furnace and calcine it at 800 °C for 5 h to obtain mesoporous silica loaded with zinc oxide; S4. Put 1.69 g of mesoporous silica loaded with zinc oxide obtained in step S3 into 169 g of an EDTA aqueous solution with a mass fraction of 0.5%, heat it to 60 °C and react for 6 h, and then filter to obtain a filtrate; S5. Put 1.65 g of the filtrate obtained in step S4 into 49.5 g of a mixed solution of copper nitrate with a concentration of 0.4 mol / L, gallium nitrate with a concentration of 0.005 mol / L, and chromium nitrate with a concentration of 0.005 mol / L, soak for 2 h, then add sodium carbonate to adjust the pH to 9, and filter to obtain a crude product; S6. Put 1.61 g of the crude product obtained in step S5 into 161 g of a sodium hydroxide solution with a concentration of 6 mol / L, heat it to 80 °C and react for 3 h, then filter. Wash the filtered product with sufficient deionized water and dry it at 100 °C. Put the dried product into a muffle furnace and reduce it in a hydrogen and nitrogen atmosphere at 300 °C for 4 h. The volume ratio between hydrogen and nitrogen is 1:4. After reduction, a doped Cu-based catalyst (abbreviated as CZCG, C represents Cr, and G represents Ga) is obtained.

[0021] Example 4 A preparation method of a doped Cu-based catalyst, comprising the following steps: S1. Disperse 2.06 g of mesoporous silica into a toluene solution containing 3-aminopropyltrimethoxysilane. The amount of 3-aminopropyltrimethoxysilane used is 0.62 g, and the amount of toluene used is 116.2 g. Heat it to 75 °C and reflux for 8.5 h. Then filter, wash with sufficient toluene, and dry at low temperature to obtain pretreated mesoporous silica; S2. Soak 1.88 g of the pretreated mesoporous silica obtained in step S1 into 65.8 g of a zinc nitrate solution with a concentration of 0.8 mol / L for 6.5 h, then filter to obtain mesoporous silica loaded with zinc ions; S3. Soak 1.82 g of the mesoporous silica loaded with zinc ions obtained in step S2 into ammonia water with a pH of 9 for 2 h. The amount of ammonia water used is 22.4 g, then filter. Put the filtered product into a muffle furnace and calcine it at 750 °C for 4 h to obtain mesoporous silica loaded with zinc oxide; S4. Put 1.71 g of the mesoporous silica loaded with zinc oxide obtained in step S3 into 164 g of an EDTA aqueous solution with a mass fraction of 0.3%, heat it to 55 °C and react for 4 h, and then filter to obtain a filtrate; S5. Put 1.55 g of the filtrate obtained in step S4 into 38.7 g of a mixed solution of copper nitrate with a concentration of 0.2 mol / L, gallium nitrate with a concentration of 0.005 mol / L, and aluminum nitrate with a concentration of 0.005 mol / L, soak for 1.6 h, then add sodium carbonate to adjust the pH to 8, and filter to obtain a crude product; S6. Put the 1.44 g of crude product obtained in step S5 into 97.6 g of sodium hydroxide solution with a concentration of 5.5 mol / L, heat it to 75 °C and react for 2.5 h, then filter. Wash the filtered product with sufficient deionized water and dry it at 85 °C. Put the dried product into a muffle furnace and reduce it in a hydrogen and nitrogen atmosphere at 280 °C for 3 h. The volume ratio between hydrogen and nitrogen is 1:4. After reduction, a doped Cu-based catalyst (abbreviated as CZAG, where A represents Al and G represents Ga) is obtained.

[0022] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the step of calcining the filtered product in a muffle furnace in step S3 is cancelled, and the remaining steps are exactly the same as those in Example 1.

[0023] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the step of soaking the mesoporous silica loaded with zinc oxide in an EDTA aqueous solution in step S4 is cancelled, and the remaining steps are exactly the same as those in Example 1.

[0024] Comparative Example 3 Compared with Comparative Example 2, Comparative Example 3 also cancels the step of calcining the filtered product in a muffle furnace in step S3, and the remaining steps are exactly the same as those in Comparative Example 2.

[0025] Comparative Example 4 In Comparative Example 4, a catalyst is prepared by a co-precipitation method. The specific operation method is to add sodium carbonate to copper nitrate and zinc nitrate solutions, adjust the pH to 8.5, filter out the precipitate, then perform calcination, and then cool down for reduction. The concentrations of copper nitrate and zinc nitrate, as well as the calcination conditions and reduction conditions in this comparative example are exactly the same as those in Example 1.

[0026] Performance Test Measure 1 mL of catalyst particles and load them into a quartz reaction tube with an inner diameter of 8 mm. Before the activity evaluation, first reduce the catalyst in 20% H2 / N2 at 300 °C in situ for 2 hours. At this time, the gas flow rate is 100 mL / min and the pressure is under atmospheric conditions. After the reduction, introduce the raw material gas (CO + H2) into the reactor, and maintain the reaction pressure at 4 MPa. The inlet flow rate of the syngas is 100 mL / min, and the gas flow ratio is n(H2):n(CO) = 2:1. During the reaction process, use a Hisense GC-950 chromatograph to analyze the composition of the products. In the gas-phase products, online analyze the organic components (C1-C5 hydrocarbons, dimethyl ether, methanol, ethanol) through a flame ionization detector (FID detector, HP-PLOT / Q column), and online analyze the inorganic components (H2, CO, CH4, CO2) through a thermal conductivity detector (TCD detector, TDX-01 column). Use an FID detector (HP-INNOWAX column) to offline detect the alcohols in the liquid-phase products. Among them, the CO conversion formula is as follows: , where i represents all C-containing compounds except CO in the gas-phase and liquid-phase products, n(CO) out represents the amount of CO in the outlet gas (mol), and n i (g) and n i (I) represent the number of carbon atoms of component i in the outlet gas and liquid phase (mol): The space-time yield of ethanol (STY, g·g -1 ·h -1 ) = (ethanol mass / catalyst mass) / reaction time Table 1: CO conversion and space-time yield table of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4

[0027] By comparing and analyzing the data of Example 1 with those of Examples 2-4 in Table 1, it can be seen that the performance of the catalyst is significantly improved by introducing structural promoters (aluminum nitrate, gallium nitrate or chromium nitrate) in the present invention, specifically manifested in that both the space-time yield of ethanol and the CO conversion are significantly increased. Further comparing the data of Example 1 with those of Comparative Examples 1-3, it can be found that through high-temperature calcination and treatment with EDTA, the catalyst performance can be effectively optimized, and the space-time yield of ethanol and the CO conversion are simultaneously improved. In addition, the comparison results between Example 1 and Comparative Example 4 show that compared with the traditional co-precipitation method, the preparation method adopted in the present invention shows significant advantages in catalytic performance.

[0028] Characterization and testing In order to analyze the crystal phase structure of the catalyst, we analyzed their XRD patterns, and the results are as Figure 2As shown. It can be seen from the figure that this series of catalysts have similar structural characteristics, indicating that the introduction of the structural promoter has little effect on the crystal phase structure of the catalyst. Obvious diffraction peaks were observed at 43.4°, 50.5° and 74.1°, corresponding to the (111), (200) and (220) crystal planes of Cu 0 respectively. It is worth noting that no signal peak of ZnO appears in the XRD pattern, indicating that ZnO exists in a highly dispersed or amorphous form in the catalyst. In addition, no diffraction peaks corresponding to Cr, Al and Ga were observed in the XRD pattern of the catalyst, further indicating that the structural promoter exists in a highly dispersed form or is encapsulated in the ZnO matrix.

[0029] Figure 3 (a1-d1, a3-d3) are the TEM images of the catalyst and the corresponding Cu particle size histograms. The black spherical nanoparticles in the catalyst correspond to Cu, and the average particle sizes of Cu in the CZ, CZAC, CZCG and CZAG catalysts are 29.4 nm, 29.1 nm, 28.5 nm and 48.2 nm respectively. It was found that the analysis results of TEM and XRD are not much different and the change trend of the Cu particle size is the same, indicating that there is no essential difference between the two conclusions. In addition, the lattice fringes with lattice spacings of about 0.21 nm and 0.25 nm correspond to the Cu(111) and ZnO(101) crystal planes respectively, and the interface between them can be clearly observed, indicating that an interaction occurs between Cu / ZnO, which is beneficial to the formation of catalytic active sites during the hydrogenation of CO to ethanol Figure 3 (a2-d2)].

[0030] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a doped Cu-based catalyst, characterized in that, It includes the following steps: S1. Disperse mesoporous silica into a toluene solution containing 3-aminopropyltrimethoxysilane, heat it to 50-90 °C, reflux for 5-10 h, then filter. After washing with sufficient toluene, dry it at low temperature to obtain pretreated mesoporous silica; S2. Immerse the pretreated mesoporous silica obtained in step S1 into a zinc nitrate solution with a concentration of 0.5-1 mol / L for 3-8 h, then filter to obtain mesoporous silica loaded with zinc ions; S3. Immerse the mesoporous silica loaded with zinc ions obtained in step S2 into ammonia water with a pH of 8-10 for 1-4 h, then filter. Put the filtered product into a muffle furnace and calcine it at 600-800 °C for 2-5 h to obtain mesoporous silica loaded with zinc oxide; S4. Put the mesoporous silica loaded with zinc oxide obtained in step S3 into an EDTA aqueous solution with a mass fraction of 0.1-0.5%, heat it to 40-60 °C and react for 3-6 h, then filter to obtain a filtrate; S5. Immerse the filtrate obtained in step S4 into a mixed solution of copper nitrate and a structure promoter for 1-2 h, then add sodium carbonate to adjust the pH to 8-9, and filter to obtain a crude product; S6. Put the crude product obtained in step S5 into a sodium hydroxide solution with a concentration of 4-6 mol / L, heat it to 60-80 °C and react for 1-3 h, then filter. Wash the filtered product with sufficient deionized water and dry it at 60-100 °C. Put the dried product into a muffle furnace and reduce it in a hydrogen and nitrogen atmosphere at 200-300 °C for 2-4 h. After reduction, a doped Cu-based catalyst is obtained.

2. The preparation method of the doped Cu-based catalyst according to claim 1, wherein, In step S1, the mass ratio of silica, 3-aminopropyltrimethoxysilane and toluene is 1:(0.1-0.5):(50-60).

3. The preparation method of the doped Cu-based catalyst according to claim 1, characterized in that, In step S2, the mass ratio of the pretreated mesoporous silica to the zinc nitrate solution is 1:(30-50).

4. The preparation method of the doped Cu-based catalyst according to claim 1, characterized in that, In step S3, the mass ratio of the mesoporous silica loaded with zinc ions to the ammonia water is 1:(10-20).

5. The preparation method of the doped Cu-based catalyst according to claim 1, characterized in that, In step S4, the mass ratio of the mesoporous silica loaded with zinc oxide to the EDTA aqueous solution is 1:(70-100).

6. The preparation method of the doped Cu-based catalyst according to claim 1, characterized in that, In step S5, the concentration of copper nitrate is 0.1-0.4 mol / L, and the mass ratio of the filtrate to the mixed solution of copper nitrate and the structure promoter is 1:(20-30). The structure promoter is a combination of any two of the metal salts of Al, Ga or Cr.

7. The preparation method of the doped Cu-based catalyst according to claim 6, characterized in that, The metal salts included in the structure promoter are specifically aluminum nitrate, gallium nitrate or chromium nitrate, and the concentration of the structure promoter is 0.005 mol / L.

8. The preparation method of the doped Cu-based catalyst according to claim 1, wherein, In step S6, the mass ratio of the crude product to the sodium hydroxide solution is 1:(50-100), and the volume ratio of hydrogen to nitrogen is 1:

4.

9. A doped Cu-based catalyst, characterized in that, It is prepared by the preparation method of the doped Cu-based catalyst according to any one of claims 1-8.

10. Application of the doped Cu-based catalyst according to claim 9 in the synthesis of ethanol.

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