Metallic single-atom-doped copper-based catalysts, methods for their preparation, and uses thereof

Abstract

This invention discloses a copper-based catalyst doped with a single metal atom, its preparation method, and its application. The method uses a water-soluble metal salt as a precursor and prepares a series of copper-based catalysts by reduction with an aqueous sodium borohydride solution. The reaction process uses methanol or other alcohol solutions as the reaction medium and hydrogen source, and the reaction is carried out at 170-210 degrees Celsius, with the reaction product reaching a maximum yield of 99.9%. This method involves the interaction between the single metal atom and metallic copper to promote the efficient hydrogenation and deoxygenation of biomass-derived aldehydes without the addition of external hydrogen. This invention can prepare high-value-added liquid fuels from biomass-derived aldehydes, and features simple catalyst preparation, the ability to transfer hydrogenation in various solvents, high conversion efficiency, and high yield of the target product, showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, and further to the field of biomass energy chemical technology, specifically relating to a copper-based catalyst doped with a single metal atom, its preparation method, and its application. Background Technology

[0002] The depletion of fossil fuels and global climate change have made the search for new renewable resources an urgent priority, with biomass considered a potential alternative. However, biomass-derived chemicals generally have high oxygen content, necessitating the removal of oxygenated compounds to improve their stability and energy density. Biomass-derived molecules such as 5-hydroxymethylfurfural, furfural, vanillin, methyl vanillin, ethyl vanillin, p-anisaldehyde, o-anisaldehyde, m-anisaldehyde, and isovanthanal can be converted into promising liquid biofuels through transfer hydrogenation. However, the complex molecular structures of biomass-derived aldehydes make transfer hydrogenation reduction to ideal liquid biofuels under mild conditions challenging, making the selection of suitable catalysts particularly important. Single-atom catalysts have become a hot topic in heterogeneous catalysis in recent years, attracting widespread attention due to their high efficiency, tunable active centers, and high metal utilization compared to traditional supported nanoparticle catalysts. Previously, many reactions were thought to be catalyzed by clusters or nanoparticles; recent studies have shown that single atoms can exhibit unique thermochemical catalytic activity.

[0003] Currently, biomass-derived aldehydes are mainly produced as liquid biofuels through hydrogenation and deoxygenation via copper-based catalysts, either through transfer hydrogenation or in-situ hydrogen production. Gao et al. prepared a nitrogen-doped carbon-modified copper-based catalyst for the efficient transfer hydrogenolysis of 5-hydroxymethylfurfural to 2,5-dimethylfuran. The most effective NC-Cu / MgAlO catalyst, using cyclohexanol as solvent and hydrogen source, achieved a 2,5-dimethylfuran selectivity greater than 95% after 0.5 hours of reaction at 220°C. Hsiao et al. loaded copper onto different carbon supports to obtain a series of carbon-supported copper catalysts. Using isopropanol as solvent and hydrogen source, they reduced 5-hydroxymethylfurfural to 96% 2,5-dimethylfuran after 10 hours of reaction at 190°C. Fan et al. synthesized highly dispersed copper nanoparticles supported on activated carbon using a one-pot carbothermal method within a temperature range of 400–700 °C. The 15 wt% Cu / AC-600 catalyst showed the best performance. Under conditions of isopropanol as a hydrogen donor and a reaction temperature of 180 °C for 5 hours, vanillin was reduced to 99.1% 2-methoxy-4-methylphenol. In summary, previous copper-based catalysts suffer from drawbacks such as harsh reaction conditions and low catalyst efficiency. Therefore, developing a method to address these issues is essential. Summary of the Invention

[0004] The first objective of this invention is to provide a copper-based catalyst doped with a single metal atom; the second objective is to provide a method for preparing the copper-based catalyst doped with a single metal atom; and the third objective is to provide applications of the copper-based catalyst doped with a single metal atom.

[0005] The first objective of this invention is achieved as follows: the copper-based catalyst doped with metal single atoms is prepared by reducing a precursor solution made by mixing one of the following metals (nickel chloride, cobalt chloride, ferric chloride, zirconium chloride, zirconium oxychloride, tungsten chloride, ammonium molybdate, calcium chloride, magnesium chloride, aluminum chloride, zinc chloride, and tin chloride) with copper chloride using sodium borohydride as a reducing agent, wherein the molar ratio of metallic copper to the other metal is (95~99):(1~5).

[0006] The second objective of this invention is achieved by including the preparation of a bimetallic salt aqueous solution, the preparation of a sodium borohydride aqueous solution, the main reaction, and post-treatment steps, specifically including:

[0007] A. Preparation of bimetallic salt aqueous solution: Weigh the copper salt and another metal salt according to the formula ratio to prepare bimetallic salt aqueous solution a;

[0008] B. Preparation of sodium borohydride aqueous solution: Prepare a 2 mol~10 mol / L sodium borohydride aqueous solution by stirring in an ice bath for 10~30 min to obtain sodium borohydride aqueous solution b;

[0009] C. Main reaction: Sodium borohydride aqueous solution b is added dropwise to bimetallic salt aqueous solution a to form a solid-liquid mixture c;

[0010] D. Post-processing: The solid-liquid mixture c is allowed to stand, filtered and dried to obtain the copper-based catalyst doped with the target metal single atom.

[0011] The third objective of this invention is achieved by the application of the copper-based catalyst doped with a single metal atom in the reductive alcoholysis of biomass-based aldehydes.

[0012] The specific application implementation is as follows:

[0013] (1) Add the substrate biomass-based aldehyde compound to an organic solvent to prepare a reaction substrate solution;

[0014] (2) The reaction substrate solution and the copper-based catalyst doped with metal single atoms are mixed and placed in a sealed container, heated and stirred to carry out the hydrodeoxygenation reaction to obtain the corresponding hydrodeoxygenation product.

[0015] In step (1), the biomass-based aldehyde compound is at least one selected from 5-hydroxymethylfurfural, furfural, vanillin, methyl vanillin, ethyl vanillin, isovanillin, p-anisaldehyde, o-anisaldehyde, and m-anisaldehyde; the organic solvent may be selected from at least one selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, and cyclohexanol; and the mass percentage concentration of the reaction substrate solution may be 2.0% to 20%.

[0016] In step (2), the sealed container is a high-pressure sealed reactor; the reaction temperature is 170-200 degrees Celsius, and the reaction time is 0.5-3 hours; the copper-based catalyst doped with metal single atoms is prepared by reduction with sodium borohydride, wherein sodium borohydride is used as a reducing agent. At least one of the following metal salts, such as nickel chloride, cobalt chloride, iron chloride, zirconium chloride, zirconium oxychloride, tungsten chloride, ammonium molybdate, calcium chloride, magnesium chloride, aluminum chloride, zinc chloride, and tin chloride, is mixed with copper chloride to prepare a precursor solution, and sodium borohydride is used to reduce it to prepare the desired copper-based catalyst doped with metal single atoms, wherein the molar ratio of the bimetallic compounds is 0.1:9.9-0.5:9.5;

[0017] The copper-based catalyst doped with a single metal atom is prepared using the following steps:

[0018] 1) First, prepare an aqueous solution of bimetallic salt, wherein the molar ratio of the bimetallic salt is 0.1:9.9~0.5:9.5.

[0019] 2) Prepare a sodium borohydride aqueous solution of 2 mol / L to 10 mol / L and stir it in an ice bath for 10 to 30 minutes.

[0020] 3) Slowly add the prepared sodium borohydride solution to the bimetallic salt aqueous solution to generate a solid-liquid mixture. After standing for 0.5 to 2 hours, filter and dry to obtain the solid, which is the copper-based catalyst doped with metal single atoms.

[0021] This invention utilizes a copper-based catalyst doped with a single metal atom, exhibiting high reactivity and catalytic efficiency. It can transfer the hydrogenation reduction substrate in various solvents with high product yield, and can reduce a variety of biomass-derived aldehyde compounds. The preparation method is simple and has significant practical application value. This invention relates to the interaction between a single metal atom and copper to promote the efficient hydrogenation and deoxygenation of biomass-derived aldehyde compounds without the addition of external hydrogen gas. This invention can prepare high-value-added products from biomass-derived aldehyde compounds, featuring simple catalyst preparation, high conversion efficiency, and high target product yield, showing promising prospects for industrial application. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0023] The copper-based catalyst doped with metal single atoms described in this invention is prepared by reducing a precursor solution made by mixing one of the following: nickel chloride, cobalt chloride, ferric chloride, zirconium chloride, zirconium oxychloride, tungsten chloride, ammonium molybdate, calcium chloride, magnesium chloride, aluminum chloride, zinc chloride, and tin chloride with copper chloride, using sodium borohydride as a reducing agent. The molar ratio of metallic copper to the other metal is (95~99):(1~5).

[0024] The method for preparing the copper-based catalyst doped with a single metal atom according to the present invention includes the preparation of a bimetallic salt aqueous solution, the preparation of a sodium borohydride aqueous solution, a main reaction, and post-treatment steps, specifically including:

[0025] A. Preparation of bimetallic salt aqueous solution: Weigh the copper salt and another metal salt according to the formula ratio to prepare bimetallic salt aqueous solution a;

[0026] B. Preparation of sodium borohydride aqueous solution: Prepare a 2 mol~10 mol / L sodium borohydride aqueous solution by stirring in an ice bath for 10~30 min to obtain sodium borohydride aqueous solution b;

[0027] C. Main reaction: Sodium borohydride aqueous solution b is added dropwise to bimetallic salt aqueous solution a to form a solid-liquid mixture c;

[0028] D. Post-processing: The solid-liquid mixture c is allowed to stand, filtered and dried to obtain the copper-based catalyst doped with the target metal single atom.

[0029] The application of the copper-based catalyst doped with a single metal atom described in this invention is its application in the reductive alcoholysis of biomass-based aldehyde compounds.

[0030] The reductive alcoholysis of biomass-based aldehydes includes the preparation of the reaction substrate solution and the main reaction steps, specifically including:

[0031] A. Preparation of reaction substrate solution: Add the biomass-based aldehyde compound as the substrate to an organic solvent to prepare reaction substrate solution d;

[0032] B. Main reaction: The reaction substrate solution d and the single-atom doped copper-based catalyst are mixed and placed in a closed reaction vessel, and the mixture is heated and stirred to carry out the catalytic reaction to obtain the corresponding hydrodeoxygenation product.

[0033] The biomass-based aldehyde compounds are one or more of 5-hydroxymethylfurfural, furfural, vanillin, methyl vanillin, ethyl vanillin, isovanillin, p-anisaldehyde, o-anisaldehyde, and m-anisaldehyde.

[0034] The organic solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol, or cyclohexanol.

[0035] The mass percentage concentration of the reaction substrate solution d is 2.0~20%.

[0036] The mass ratio of the single-atom doped copper-based catalyst to the reaction substrate solution d is 1:5 to 2:1.

[0037] The temperature of the catalytic reaction is 150~250℃.

[0038] The catalytic reaction takes 0.5 to 5 hours.

[0039] The invention will be further illustrated below with specific implementation examples:

[0040] Example 1

[0041] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 °C with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 95.3%.

[0042] In the copper-based catalyst A1, which is doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.1:9.9. The preparation method of catalyst A1 includes the following steps: weighing zirconium salt and copper salt in a certain molar ratio to prepare 10 mL of aqueous solution of zirconium oxychloride and copper chloride; preparing 10 mL of aqueous solution of sodium borohydride at 5 mol / L and stirring in an ice bath for 20 minutes. Under ice bath conditions, the sodium borohydride solution is slowly added dropwise to the bimetallic salt aqueous solution. After the addition is complete, a solid-liquid mixture is obtained. After standing for 2 hours, the mixture is filtered and dried to obtain the solid, which is the copper-based catalyst A1 doped with metal single atoms.

[0043] Example 2

[0044] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of ethanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 °C with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 75.5%.

[0045] Example 3

[0046] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of n-propanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 85.5%.

[0047] Example 4

[0048] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography to be 95.6%.

[0049] Example 5

[0050] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of n-butanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 79.6%.

[0051] Example 6

[0052] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of cyclohexanol, and then 0.05 g of copper-based catalyst A1 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 degrees Celsius with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 89.6%.

[0053] Example 7

[0054] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A2 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 °C with stirring to carry out a hydrodeoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 73.2%.

[0055] In the copper-based catalyst A2 doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.2:9.8. The preparation method of catalyst A2 is the same as that of the catalyst in Example 1, except that the proportion of metal salts is different.

[0056] Example 8

[0057] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A3 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170°C with stirring to carry out a hydrogenation and deoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 83.4%.

[0058] In the copper-based catalyst A3 doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.3:9.7. The preparation method of catalyst A3 is the same as that of the catalyst in Example 1, except that the proportion of metal salts is different.

[0059] Example 9

[0060] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A4 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170 °C with stirring to carry out a hydrodeoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography to be 86.2%.

[0061] In the copper-based catalyst A4 doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.4:9.6. The preparation method of catalyst A4 is the same as that of the catalyst in Example 1, except that the proportion of metal salts is different.

[0062] Example 10

[0063] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A5 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170°C with stirring to carry out a hydrodeoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 73.2%.

[0064] In the copper-based catalyst A5, which is doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.5:9.5. The preparation method of catalyst A5 is the same as that of the catalyst in Example 1, except that the proportion of metal salts is different.

[0065] Example 11

[0066] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 170°C with stirring to carry out a hydrodeoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography to be 97.7%.

[0067] In the copper-based catalyst A6 doped with metal single atoms, the molar ratio of zirconium oxychloride to copper chloride is 0.25:9.75. The preparation method of catalyst A6 is the same as that of the catalyst in Example 1, except that the proportion of metal salts is different.

[0068] Example 12

[0069] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 99.7%.

[0070] Example 13

[0071] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 190 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 98.5%.

[0072] Example 14

[0073] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrodeoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 97.4%.

[0074] Example 15

[0075] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of methanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 210 °C with stirring to carry out a hydrodeoxygenation reaction for 0.5 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography to be 94.4%.

[0076] Example 16

[0077] 0.5 g of furfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 2-methylfuran was then detected by gas chromatography to be 99.9%.

[0078] Example 17

[0079] 0.5 g of vanillin was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 2-methoxy-4-methylphenol was then detected by gas chromatography and found to be 95.6%.

[0080] Example 18

[0081] 0.5 g of methyl vanillin was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 3,4-dimethoxytoluene was then detected by gas chromatography and found to be 95.9%.

[0082] Example 19

[0083] 0.5 g of ethyl vanillin was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 3-hydroxy-4-ethoxytoluene was then detected by gas chromatography and found to be 97.8%.

[0084] Example 20

[0085] 0.5 g of isovanthanin was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 3-hydroxy-4-methoxytoluene was then detected by gas chromatography and found to be 98.9%.

[0086] Example 21

[0087] 0.5 g of anisaldehyde was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 4-methoxytoluene was then detected by gas chromatography to be 96.9%.

[0088] Example 22

[0089] 0.5 g of o-anisaldehyde was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 2-methoxytoluene was then detected by gas chromatography to be 96.9%.

[0090] Example 23

[0091] 0.5 g of anisaldehyde was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst A6 with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 200 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 2 hours. The yield of 3-methoxytoluene was then detected by gas chromatography and found to be 96.9%.

[0092] Example 24

[0093] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst B with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 76.9%.

[0094] In the copper-based catalyst B doped with metal single atoms, the molar ratio of nickel chloride to copper chloride is 0.25:9.75. The preparation method of catalyst B is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0095] Example 25

[0096] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst B with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 87.7%.

[0097] In the copper-based catalyst B doped with metal single atoms, the molar ratio of cobalt chloride to copper chloride is 0.25:9.75. The preparation method of catalyst B is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0098] Example 26

[0099] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst B with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 90.2%.

[0100] In the copper-based catalyst C doped with metal single atoms, the molar ratio of ferric chloride to copper chloride is 0.25:9.75. The preparation method of catalyst C is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0101] Example 27

[0102] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst D with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 89.6%.

[0103] In the copper-based catalyst D with metal single-atom doping, the molar ratio of zirconium chloride to copper chloride is 0.25:9.75. The preparation method of catalyst D is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0104] Example 28

[0105] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst E doped with a single metal atom was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 81.2%.

[0106] In the copper-based catalyst E doped with metal single atoms, the molar ratio of tungsten chloride to copper chloride is 0.25:9.75. The preparation method of catalyst E is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0107] Example 29

[0108] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst F with metal single atom doping was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then detected by gas chromatography and found to be 83.7%.

[0109] In the copper-based catalyst F doped with metal single atoms, the molar ratio of ammonium molybdate to copper chloride is 0.25:9.75. The preparation method of catalyst F is the same as that of catalyst in Example 1, except that the type and ratio of metal salt are different.

[0110] Example 30

[0111] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst G doped with a single metal atom was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 69.9%.

[0112] In the copper-based catalyst G doped with metal single atoms, the molar ratio of magnesium chloride to copper chloride is 0.25:9.75. The preparation method of catalyst G is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0113] Example 31

[0114] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst H doped with a single metal atom was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 91.3%.

[0115] In the copper-based catalyst H doped with metal single atoms, the molar ratio of aluminum chloride to copper chloride is 0.25:9.75. The preparation method of catalyst H is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0116] Example 32

[0117] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst I doped with metal single atoms was added and mixed in a sealed high-pressure reactor. The mixture was heated at 180 degrees Celsius and stirred for 3 hours for hydrogenation and deoxygenation reaction. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 93.6%.

[0118] In the copper-based catalyst I with metal single-atom doping, the molar ratio of aluminum chloride to copper chloride is 0.25:9.75. The preparation method of catalyst I is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0119] Example 33

[0120] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst J doped with a single metal atom was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring for 3 hours for hydrogenation and deoxygenation. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 86.9%.

[0121] In the copper-based catalyst J doped with metal single atoms, the molar ratio of aluminum chloride to copper chloride is 0.25:9.75. The preparation method of catalyst J is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0122] Example 34

[0123] 0.5 g of 5-hydroxymethylfurfural was added to 10 mL of isopropanol, and then 0.05 g of copper-based catalyst K doped with a single metal atom was added. The mixture was placed in a sealed high-pressure reactor and heated at 180 degrees Celsius with stirring to carry out a hydrogenation and deoxygenation reaction for 3 hours. The yield of 2,5-dimethylfuran was then determined by gas chromatography to be 79.6%.

[0124] In the copper-based catalyst K doped with metal single atoms, the molar ratio of tin chloride to copper chloride is 0.25:9.75. The preparation method of catalyst K is the same as that of the catalyst in Example 1, except that the type and ratio of metal salt are different.

[0125] This invention utilizes a copper-based catalyst doped with a single metal atom in an alcohol solvent for the transfer hydrogenation catalytic reduction of biomass-derived aldehydes (5-hydroxymethylfurfural, furfural, vanillin, methyl vanillin, ethyl vanillin, p-anisaldehyde, o-anisaldehyde, m-anisaldehyde, and isovanthanal) to prepare liquid biomass fuel. The copper-based catalyst is prepared by reducing a bimetallic salt aqueous solution with sodium borohydride. Compared to other copper-based catalysts, this catalyst is simple to prepare and exhibits good catalytic activity and selectivity, capable of highly active reduction of various biomass-derived aldehydes to corresponding liquid biomass fuels in different transfer hydrogenation solvents. Compared to other copper-based catalysts, the copper-based catalyst doped with a single metal atom in this invention is low-cost and highly effective; the catalyst possesses both reducing and acidic functions, the reaction conditions are mild, the reaction time is short, it is easy to operate, and the yield is high; the reaction uses a monohydric alcohol as a green solvent, resulting in no pollution; and the catalyst can be recycled.

Claims

1. The application of a copper-based catalyst doped with a single metal atom, characterized in that, The application of the copper-based catalyst doped with metal single atoms in the reductive alcoholysis of 5-hydroxymethylfurfural to prepare 2,5-dimethylfuran; The copper-based catalyst doped with metal single atoms is prepared by reducing a precursor solution made by mixing one of the following: nickel chloride, cobalt chloride, ferric chloride, zirconium chloride, zirconium oxychloride, tungsten chloride, ammonium molybdate, magnesium chloride, aluminum chloride, and tin chloride with copper chloride, using sodium borohydride as a reducing agent. The molar ratio of copper to the other metal is (95~99):(1~5).

2. The application of the copper-based catalyst doped with a single metal atom according to claim 1, characterized in that, The preparation method of the copper-based catalyst doped with a single metal atom includes the preparation of a bimetallic salt aqueous solution, the preparation of a sodium borohydride aqueous solution, the main reaction, and post-processing steps, specifically including: A. Preparation of bimetallic salt aqueous solution: Weigh the copper salt and another metal salt according to the formula ratio to prepare bimetallic salt aqueous solution a; B. Preparation of sodium borohydride aqueous solution: Prepare a 2 mol~10 mol / L sodium borohydride aqueous solution by stirring in an ice bath for 10~30 min to obtain sodium borohydride aqueous solution b; C. Main reaction: Sodium borohydride aqueous solution b is added dropwise to bimetallic salt aqueous solution a to form a solid-liquid mixture c; D. Post-processing: The solid-liquid mixture c is allowed to stand, filtered and dried to obtain the copper-based catalyst doped with the target metal single atom.

3. The application of the copper-based catalyst doped with a single metal atom according to claim 1, characterized in that, The 5-hydroxymethylfurfural reductive alcoholysis includes the preparation of the reaction substrate solution and the main reaction steps, specifically including: A. Preparation of reaction substrate solution: The substrate 5-hydroxymethylfurfural is added to an organic solvent to prepare reaction substrate solution d. The organic solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol or cyclohexanol. The mass percentage concentration of reaction substrate solution d is 2.0~20%. The mass ratio of the single-atom doped copper-based catalyst to reaction substrate solution d is 1:5~2:

1. B. Main reaction: The reaction substrate solution d and the copper-based catalyst doped with a single metal atom are mixed and placed in a closed reaction vessel, and the mixture is heated and stirred to carry out a catalytic reaction to obtain the corresponding hydrodeoxygenation product.

4. The application of the copper-based catalyst doped with a single metal atom according to claim 3, characterized in that, The temperature of the catalytic reaction is 150~250℃.

5. The application of the copper-based catalyst doped with a single metal atom according to claim 3, characterized in that, The catalytic reaction takes 0.5 to 5 hours.