A copper-based catalyst based on ZIF-8 derived nitrogen-carbon material and a preparation method and application thereof

Abstract

The application discloses a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material and a preparation method and application thereof, and relates to the field of catalyst preparation. The copper-based catalyst comprises the following components and mass fraction ratios: Cu:Zn:carrier:auxiliary agent = 40-60:10-20:20-40:0-10, wherein the carrier is a ZIF-8 derived nitrogen-carbon material carrier, and the auxiliary agent comprises one or more of Mn, Mg, Zr, Cr, Si, Ce and Al; the preparation method of the catalyst comprises the following steps: preparing ZIF-8 solid; performing high-temperature carbonization treatment on the ZIF-8 solid to obtain a nitrogen-carbon material carrier; loading Zn, Cu and the auxiliary agent on the nitrogen-carbon material carrier in steps by using a deposition precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn by using an impregnation method, and obtaining the copper-based catalyst after calcination; and the catalyst can be applied in the reaction of preparing methanol by carbon dioxide hydrogenation after reduction. The application takes the ZIF-8 derived nitrogen-carbon material as the carrier, loads Cu, Zn and the auxiliary agent by combining the deposition precipitation method with the impregnation method, can optimize metal dispersity and interface structure, and significantly improves the activity and stability of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, and in particular to a copper-based catalyst based on ZIF-8 derived nitrogen-carbon materials, its preparation method, and its application. Background Technology

[0002] The hydrogenation of carbon dioxide to methanol is an important pathway to achieve carbon emission reduction, but existing copper-based catalysts (such as Cu / ZnO / Al2O3) suffer from problems such as active component agglomeration, poor water resistance, and insufficient stability. For example, the H2O generated during the reaction of traditional catalysts can lead to ZnO agglomeration and Cu oxidation deactivation, reducing methanol selectivity and conversion. In addition, existing methods such as impregnation or hydrothermal methods have limited catalyst loading or complex processes, making it difficult to meet industrial requirements. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon materials, its preparation method, and its application. Using ZIF-8 derived nitrogen-carbon materials as a support, the metal dispersion and interfacial structure can be optimized, significantly improving the catalyst's activity and stability.

[0004] The present invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, comprising the following components and mass fraction ratio: Cu:Zn:support:auxiliary agent = 40-60:10-20:20-40:0-10, wherein the support is a ZIF-8 derived nitrogen-carbon material support, and the auxiliary agent includes one or more of Mn, Mg, Zr, Cr, Si, Ce, and Al.

[0005] The present invention also provides a method for preparing a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material as described above, comprising the following steps: preparing ZIF-8 solid; carbonizing the ZIF-8 solid to obtain a nitrogen-carbon material support; loading Zn, Cu and additives onto the nitrogen-carbon material support in steps by deposition precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn by impregnation method, and calcining to obtain a copper-based catalyst.

[0006] In one embodiment of the present invention, the preparation of the ZIF-8 solid includes: dissolving 2-methylimidazole in methanol to prepare solution A; dissolving Zn(NO3)2·6H2O in methanol to prepare solution B; mixing and stirring the solution A and the solution B to obtain a suspension; centrifuging, washing and drying the suspension to obtain ZIF-8 solid.

[0007] In one embodiment of the present invention, the preparation of copper-based catalyst precursor solid by deposition precipitation method includes: dissolving zinc nitrate in deionized water to prepare a first active metal solution; dissolving copper nitrate and auxiliary nitrate in deionized water to prepare a second active metal solution; when selecting an auxiliary agent other than Si, preparing a precipitant solution by mixing one or two of sodium carbonate and sodium hydroxide, or when selecting Si as an auxiliary agent, preparing a precipitant solution by dispersing the nitrogen-carbon material support in ethanol and water to obtain a mixed solution; sequentially adding the first active metal solution, the second active metal solution, and the precipitant solution to the mixed solution to obtain a copper-based catalyst precursor slurry; filtering, washing, and drying the copper-based catalyst precursor slurry to obtain the copper-based catalyst precursor solid.

[0008] In one embodiment of the present invention, the concentrations of the first active metal solution, the second active metal solution, and the precipitant solution are 0.5-2 mol / L, for example, 0.5 mol / L, 1 mol / L, or 2 mol / L; the molar ratio of sodium carbonate to sodium hydroxide is 1-3:1, for example, 1:1, 1.5:1, or 3:1; and the temperature of the mixed solution is 10℃-70℃, for example, 10℃, 30℃, 40℃, or 70℃.

[0009] In one embodiment of the present invention, the order of adding the first active metal solution, the second active metal solution, and the precipitant solution includes: simultaneously adding the first active metal solution and the precipitant solution to the mixed solution to form a precipitate; after the first active metal solution has precipitated completely, continuing to add the second active metal solution to form a copper-based catalyst precursor precipitate; after the second active metal solution has precipitated completely, stopping the addition of the precipitant solution, controlling the temperature and aging the mixture to obtain the copper-based catalyst precursor slurry.

[0010] In one embodiment of the present invention, the pH value of the precipitate and the copper-based catalyst precursor precipitate is 7-10, for example, 7, 8, 9, 10; the temperature is controlled at 10℃-70℃, for example, 10℃, 30℃, 40℃, 70℃; and the aging time is 6h-24h, for example, 6h, 10h, 12h, 16h, 20h, 24h.

[0011] In one embodiment of the present invention, the method of adding Zn by impregnation and calcining to obtain a copper-based catalyst includes: dissolving zinc nitrate in deionized water to prepare a third active metal solution; adding the copper-based catalyst precursor solid to the third active metal solution and stirring for impregnation; removing the solvent by rotary evaporation, drying, and calcining under an inert gas to obtain the copper-based catalyst.

[0012] In one embodiment of the present invention, the concentration of the third active metal solution is 0.05-2 mol / L, for example 0.05 mol / L, 1 mol / L, 2 mol / L; the stirring and impregnation time is 1h-4h, for example 1h, 3h, 4h; the calcination temperature is 300℃-400℃, for example 300℃, 350℃, 400℃; and the calcination time is 4h-12h, for example 4h, 6h, 8h, 10h.

[0013] The present invention also provides an application of the copper-based catalyst based on ZIF-8 derived nitrogen-carbon material as described above, or the copper-based catalyst based on ZIF-8 derived nitrogen-carbon material prepared according to the preparation method described above, which can be applied in the reaction of carbon dioxide hydrogenation to methanol.

[0014] Compared with existing technologies, the present invention has the following beneficial technical effects:

[0015] This invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, its preparation method, and its application. Using ZIF-8 derived nitrogen-carbon material as a support, the high specific surface area and porous structure of ZIF-8 can promote the dispersion of active metals. The nitrogen / oxygen functional groups on the surface are beneficial for metal anchoring, and the hydrophobicity can reduce the oxidation of the catalyst by H2O. By combining deposition and impregnation methods to load Cu, Zn, and additives, the metal dispersion and interfacial structure can be optimized, significantly improving the catalyst's activity and stability. When applied to the reaction of carbon dioxide hydrogenation to methanol, it is beneficial to obtain higher carbon dioxide hydrogenation reaction activity and selectivity for the product methanol. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the application of the copper-based catalyst provided by the present invention in the reaction of carbon dioxide hydrogenation to methanol. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] In the description of this invention, it should be noted that the orientations or positional relationships indicated in this description are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the purpose of facilitating the description of this invention and simplifying the description, and are not intended to indicate or imply that the parts or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0019] Please see Figure 1This invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, comprising the following components and mass fraction ratio: Cu:Zn:support:promoter = 40-60:10-20:20-40:0-10, wherein the support is a ZIF-8 derived nitrogen-carbon material support, and the promoter includes one or more of Mn, Mg, Zr, Cr, Si, Ce, and Al. This invention uses ZIF-8 derived nitrogen-carbon material as a support, loading Cu, Zn, and promoter, which can optimize metal dispersion and interfacial structure, significantly improving the catalyst's activity and stability.

[0020] The copper-based catalyst based on ZIF-8 derived nitrogen-carbon materials provided by this invention can be applied in the reaction of carbon dioxide hydrogenation to methanol. This catalyst exhibits high activity and stability, which is beneficial for obtaining high carbon dioxide hydrogenation reaction activity and selectivity for the methanol product.

[0021] ZIF-8-derived nitrogen-carbon material, used as a carrier, is mainly composed of carbon (C), nitrogen (N), and oxygen (O), maintaining the well-defined rhombic dodecahedral structure of ZIF-8. It possesses a large specific surface area, a layered porous structure, and tunable surface properties. The adjustable size and significant specific surface area facilitate the dispersion of active copper species, increasing the surface area of ​​metallic copper. Furthermore, the high porosity and layered porous structure of this nitrogen-carbon material enhance the mass transfer efficiency of reactant gases CO2 and H2, thereby accelerating the carbon dioxide hydrogenation rate. It is obtained by high-temperature calcination of ZIF-8. The resulting nitrogen-carbon material has abundant nitrogen- and oxygen-containing functional groups on its surface, which is beneficial for the anchoring of copper species, can inhibit the sintering of copper species to a certain extent, improve the dispersion of copper species, and increase the number of copper active sites; it promotes the hydrogen overflow effect on the catalyst surface, thereby promoting the hydrogenation conversion rate of carbon dioxide; the surface of this nitrogen-carbon material has abundant basic sites, which is beneficial for enhancing the adsorption and dissociation of CO2; the nitrogen-carbon material has good hydrophobicity, which is beneficial for the rapid desorption of by-product water, thereby effectively reducing the oxidation effect of water on active species and improving the stability of the catalyst.

[0022] The present invention also provides a method for preparing a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material as described above, comprising the steps of: preparing ZIF-8 solid; carbonizing the ZIF-8 solid at high temperature to obtain a nitrogen-carbon material support; loading Zn, Cu and additives onto the nitrogen-carbon material support in steps by deposition precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn by impregnation method, and calcining to obtain a copper-based catalyst.

[0023] Compared to existing single deposition-precipitation or impregnation methods, the copper-based catalyst prepared by the combination of deposition-precipitation and impregnation methods exhibits better copper particle dispersion and possesses a large number of highly active Cu-ZnO or ZnO-Cu interface structures. During the reduction process, the migration of ZnO can construct more ZnO-Cu interface active sites, effectively enhancing the hydrogenation activity of the catalyst. During the impregnation process, the Cu active sites covered by ZnO can suppress the reverse water-gas shift reaction with Cu as the active site, thereby improving the methanol selectivity of carbon dioxide hydrogenation.

[0024] In one embodiment of the present invention, the preparation of ZIF-8 solid includes: dissolving 2-methylimidazole in methanol to prepare solution A; dissolving Zn(NO3)2·6H2O in methanol to prepare solution B; mixing and stirring solution A and solution B to obtain a suspension; centrifuging, washing, and drying the suspension to obtain ZIF-8 solid. After the ZIF-8 solid is prepared, it is subjected to high-temperature carbonization in an inert gas N2 or Ar, with the temperature controlled at 700-1000℃, to obtain a nitrogen-carbon material support, denoted as NC support.

[0025] In one embodiment of the present invention, the preparation of copper-based catalyst precursor solid by deposition precipitation method includes: dissolving zinc nitrate in deionized water to prepare a first active metal solution; dissolving copper nitrate and auxiliary nitrate in deionized water to prepare a second active metal solution; when the auxiliary agent is selected from one or more of Mn, Mg, Zr, Cr, Ce, and Al, mixing one or two of sodium carbonate and sodium hydroxide to prepare a precipitant solution, or when the auxiliary agent is selected from Si, for example, sodium silicate nonahydrate, because its solution is alkaline, sodium carbonate, sodium hydroxide, and sodium silicate nonahydrate need to be prepared into a precipitant solution; dispersing the nitrogen-carbon material support in ethanol and water to obtain a mixed solution; sequentially adding the first active metal solution, the second active metal solution, and the precipitant solution to the mixed solution to obtain a copper-based catalyst precursor slurry; filtering, washing, and drying the copper-based catalyst precursor slurry to obtain a copper-based catalyst precursor solid.

[0026] In one embodiment of the present invention, the order of adding the first active metal solution, the second active metal solution, and the precipitant solution includes: simultaneously adding the first active metal solution and the precipitant solution to the mixed solution to form a precipitate; after the first active metal solution has precipitated completely, continuing to add the second active metal solution to form a copper-based catalyst precursor precipitate; after the second active metal solution has precipitated completely, stopping the addition of the precipitant solution, controlling the temperature and aging to obtain a copper-based catalyst precursor slurry.

[0027] In one embodiment of the present invention, the method of adding Zn by impregnation and calcining to obtain a copper-based catalyst includes: dissolving zinc nitrate in deionized water to prepare a third active metal solution; adding a copper-based catalyst precursor solid to the third active metal solution and stirring for impregnation; removing the solvent by rotary evaporation, drying, and calcining under an inert gas to obtain the copper-based catalyst.

[0028] Specifically, the preparation method of copper-based catalysts based on ZIF-8 derived nitrogen-carbon materials includes the following steps:

[0029] 13.4 g of 2-methylimidazole (2-meim) was dissolved in 120 ml of methanol to prepare solution A; 12.0 g of Zn(NO3)2·6H2O was dissolved in 360 ml of methanol to prepare solution B; solutions A and B were mixed at room temperature and stirred continuously for 12 h to obtain a white suspension. The suspension was then centrifuged and washed three times with methanol to remove byproducts. Finally, the obtained white ZIF-8 precipitate was dried overnight at 60 °C to obtain ZIF-8 solid; the ZIF-8 solid was placed in a tube furnace and heated at 800 °C with Ar (50 mL·min). -1 The nitrogen-carbon material carrier obtained by heat treatment in the medium for 2 hours is denoted as NC carrier;

[0030] Zinc nitrate is dissolved in deionized water to prepare a first active metal solution with a concentration of 0.5-2 mol / L; copper nitrate and auxiliary nitrate are dissolved in deionized water to prepare a second active metal solution with a concentration of 0.5-2 mol / L; sodium carbonate, sodium hydroxide and / or sodium silicate nonahydrate are dissolved in deionized water (the molar ratio of sodium carbonate to sodium hydroxide is 1-3:1) to prepare a precipitant solution with a concentration of 0.5-2 mol / L.

[0031] A certain mass of NC support was ultrasonically dispersed in a mixed solution of ethanol and water and transferred to a reaction beaker. The temperature was controlled within the range of 10-70℃. Under continuous stirring, a first active metal solution and a precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled to maintain the pH of the system within the range of 7-10, forming a precipitate. After the first active metal solution had precipitated completely, a second active metal solution and a precipitant solution were added dropwise to the reaction beaker using a metering pump, maintaining the pH of the system within the range of 7-10, forming a copper-based catalyst precursor precipitate. After the second active metal solution had been added, the addition of the precipitant solution was stopped, and the temperature was maintained within the range of 10-70℃ for aging for 6-24 hours to obtain a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral and free of sodium ions, and then dried at 120℃ for 12 hours to obtain a solid copper-based catalyst precursor sample.

[0032] Zinc nitrate was dissolved in a certain volume of deionized water to prepare a third active metal solution with a concentration of 0.05-2 mol / L. The copper-based catalyst precursor solid sample was added to the third active metal solution and stirred for 4 hours. The solvent was removed by rotary evaporation and dried at 120°C for 12 hours. Then the sample was transferred to a tube furnace and calcined at 300-400°C for 4-12 hours under Ar atmosphere purging. Finally, the catalyst was obtained by tableting and granulation.

[0033] The present invention will be further illustrated below with reference to the embodiments.

[0034] Example 1

[0035] 13.4 g of 2-methylimidazole (2-meim) was dissolved in 120 ml of methanol, denoted as solution A. 12.0 g of Zn(NO3)2·6H2O was dissolved in 360 ml of methanol, denoted as solution B. Solutions A and B were mixed and stirred continuously at room temperature for 12 h to obtain a white suspension. The suspension was then centrifuged and washed three times with methanol to remove byproducts. Finally, the resulting white ZIF-8 precipitate was dried overnight at 60 °C. The ZIF-8 solid was placed in a tube furnace and heat-treated at 800 °C in an Ar atmosphere for 2 h. The resulting support material is denoted as NC.

[0036] 4.95 g of zinc nitrate hexahydrate was dissolved in deionized water to prepare a first active metal solution with a concentration of 0.5 mol / L; 15.1 g of copper nitrate trihydrate, 1.282 g of magnesium nitrate hexahydrate, and 0.252 g of cerium nitrate hexahydrate were dissolved in deionized water to prepare a second active metal solution with a concentration of 0.5 mol / L; 22.5 g of sodium carbonate, 5.66 g of sodium hydroxide, and 0.947 g of sodium silicate nonahydrate were dissolved in deionized water (the molar ratio of sodium carbonate to sodium hydroxide was 1.5:1) to prepare a precipitant solution with a Na ion concentration of 1.5 mol / L.

[0037] 3.5 g of NC support was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (volume ratio of ethanol to deionized water: 1:2) and transferred to a reaction beaker. The temperature was controlled at 60 °C. Under continuous stirring, the first active metal solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8.5, forming a precipitate. After the first active metal solution had precipitated completely, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8.5, forming a copper-based catalyst precursor precipitate. After the second active metal solution had been added, the addition of the precipitant solution was stopped, and the temperature was maintained at 60 °C for 6 hours to continue aging, obtaining a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral and free of sodium ions, and dried at 120 °C for 12 hours to obtain a solid copper-based catalyst precursor sample.

[0038] 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. The copper-based catalyst precursor solid sample was placed in the third active metal solution and impregnated with stirring at 40 °C for 4 h. Then, the solvent was removed by rotary evaporation, and the sample was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 400 °C for 4 h under Ar atmosphere purging. After granulation, catalyst 1 was obtained. The composition and mass fraction ratio of catalyst 1 were: Cu:ZnO:NC:CeO2:MgO:SiO2 = 40:20:35:1:2:2.

[0039] Example 2

[0040] The synthesis method of the NC vector is the same as in Example 1, and will not be repeated here.

[0041] 3.713 g of zinc nitrate hexahydrate was dissolved in deionized water to prepare a first active metal solution with a concentration of 0.5 mol / L; 16.988 g of copper nitrate trihydrate, 1.923 g of magnesium nitrate hexahydrate, and 1.742 g of zirconium nitrate pentahydrate were dissolved in deionized water to prepare a second active metal solution with a concentration of 0.5 mol / L; 26.08 g of sodium carbonate, 4.92 g of sodium hydroxide, and 0.947 g of sodium silicate nonahydrate were dissolved in deionized water (the molar ratio of sodium carbonate to sodium hydroxide was 2:1) to prepare a precipitant solution with a Na ion concentration of 2 mol / L.

[0042] 3g of NC carrier was ultrasonically dispersed in 80ml of a mixed solution of ethanol and water (volume ratio of ethanol to deionized water: 1:2) and transferred to a reaction beaker. The temperature was controlled at 60℃. Under continuous stirring, the first active metal solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8, forming a precipitate. After the first active metal solution had precipitated completely, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8, forming a copper-based catalyst precursor precipitate. After the second active metal solution had been added, the addition of the precipitant solution was stopped, and the temperature was maintained at 60℃ for 6 hours to continue aging, obtaining a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral and free of sodium ions, and dried at 120℃ for 12 hours to obtain a solid copper-based catalyst precursor sample.

[0043] 1.856 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. The copper-based catalyst precursor solid sample was placed in the third active metal solution and impregnated at 40 °C with stirring for 4 h. The solvent was then removed by rotary evaporation, and the sample was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 400 °C for 4 h under Ar atmosphere purging. After granulation, catalyst 2 was obtained. The composition and mass fraction ratio of catalyst 2 were: Cu:ZnO:NC:ZrO2:MgO:SiO2 = 45:15:30:5:3:2.

[0044] Example 3

[0045] The synthesis method of the NC vector is the same as in Example 1, and will not be repeated here.

[0046] 5.569 g of zinc nitrate hexahydrate was dissolved in deionized water to prepare a first active metal solution with a concentration of 0.8 mol / L; 18.875 g of copper nitrate trihydrate, 1.923 g of magnesium nitrate hexahydrate, and 1.394 g of zirconium nitrate pentahydrate were dissolved in deionized water to prepare a second active metal solution with a concentration of 0.8 mol / L; 28.19 g of sodium carbonate, 5.36 g of sodium hydroxide, and 1.421 g of sodium silicate nonahydrate were dissolved in deionized water (the molar ratio of sodium carbonate to sodium hydroxide was 2:1) to prepare a precipitant solution with a Na ion concentration of 2 mol / L.

[0047] 2g of NC carrier was ultrasonically dispersed in 80ml of a mixed solution of ethanol and water (volume ratio of ethanol to deionized water: 1:2), and transferred to a reaction beaker. The temperature was controlled at 70℃. Under continuous stirring, the first active metal solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8, forming a precipitate. After the first active metal solution had precipitated completely, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant was controlled to maintain the pH of the system at 8, forming a copper-based catalyst precursor precipitate. After the second active metal solution had been added, the addition of the precipitant solution was stopped, and the temperature was maintained at 70℃ for 6 hours to continue aging, obtaining a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral and free of sodium ions, and dried at 120℃ for 12 hours to obtain a solid copper-based catalyst precursor sample.

[0048] 1.856 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. The copper-based catalyst precursor solid sample was placed in this third active metal solution and impregnated at 40 °C with stirring for 4 h. The solvent was then removed by rotary evaporation, and the sample was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 400 °C for 4 h under an Ar atmosphere. After granulation, catalyst 3 was obtained. The composition and mass fraction ratio of catalyst 3 were: Cu:ZnO:NC:ZrO2:MgO:SiO2 = 50:20:20:4:3:3.

[0049] Comparative Example 1

[0050] 18.875g of copper nitrate trihydrate, 7.425g of zinc nitrate hexahydrate, and 8.71g of zirconium nitrate pentahydrate were dissolved in deionized water to prepare an active metal solution with a concentration of 2mol / L; 31.8g of sodium carbonate and 2.368g of sodium silicate nonahydrate were dissolved in deionized water to prepare a precipitant solution with a Na ion concentration of 2mol / L.

[0051] Add 80 ml of deionized water to the reaction beaker, control the temperature at 40℃, and use a metering pump to simultaneously add the active metal solution and the precipitant solution to the reaction beaker under continuous stirring. Control the dropping rate of the precipitant to make the pH of the system 9, so as to form a precipitate.

[0052] After the active metal solution was added dropwise, the addition of the precipitant solution was stopped, and the temperature was maintained at 40℃ for 6 hours to continue aging, obtaining a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral and free of sodium ions, and dried at 120℃ for 12 hours. The sample was then transferred to a muffle furnace and calcined at 350℃ for 4 hours, followed by tableting and granulation to obtain comparative catalyst 1. The composition and mass fraction ratio of comparative catalyst 1 were: Cu:ZnO:ZrO2:SiO2 = 50:20:25:5.

[0053] Comparative Example 2

[0054] The synthesis method of the NC vector is the same as in Example 1, and will not be repeated here.

[0055] 18.875g of copper nitrate trihydrate, 7.425g of zinc nitrate hexahydrate and 3.676g of aluminum nitrate nonahydrate were dissolved in a mixed solvent of deionized water and ethanol (volume ratio of deionized water to ethanol was 2:1) to prepare an active metal solution with a concentration of 1.5 mol / L.

[0056] 2.5 g of NC support was added to the active metal solution and impregnated at 40 °C with stirring for 4 h. The solvent in the above mixture was removed by rotary evaporation, and the mixture was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 350 °C for 4 h under Ar atmosphere purging. After granulation, comparative catalyst 2 was obtained. The composition and mass fraction ratio of comparative catalyst 2 were: Cu:ZnO:Al2O3:NC = 50:20:5:25.

[0057] Comparative Example 3

[0058] 20.1 g of 2-methylimidazole (2-meim) was dissolved in 480 ml of methanol, denoted as solution A. 11.87 g of Co(NO3)2·6H2O was dissolved in 480 ml of methanol, denoted as solution B. Solutions A and B were mixed and stirred at room temperature for 30 min to obtain a purple mixed solution. The solution was sealed with plastic wrap and allowed to stand for 24 h. After standing, the mixed solution was centrifuged, and the resulting purple precipitate was washed three times with anhydrous methanol. The precipitate was then vacuum dried at 60 °C for 6 h to obtain ZIF-67 purple powder.

[0059] ZIF-67 solid powder was placed in a tube furnace, and high-purity argon gas was introduced. The gas was heated from room temperature at a rate of 5°C / min. -1 The calcination rate was increased to 800℃ and maintained for 2 hours. After calcination, the material was naturally cooled, and the resulting carrier material was designated as Co@NC black powder.

[0060] 4.95 g of zinc nitrate hexahydrate was dissolved in deionized water to prepare a first active metal mixed solution with a concentration of 0.5 mol / L;

[0061] Dissolve 15.1g of copper nitrate trihydrate, 1.282g of magnesium nitrate hexahydrate, and 0.252g of cerium nitrate hexahydrate in deionized water to prepare a second active metal mixed solution with a concentration of 0. mol / L;

[0062] Dissolve 22.5g sodium carbonate, 5.66g sodium hydroxide and 0.947g sodium silicate nonahydrate in deionized water (molar ratio of sodium carbonate to sodium hydroxide is 1.5:1) to prepare a precipitant solution with a Na ion concentration of 1.5mol / L.

[0063] 3.5 g of Co@NC carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (volume ratio of ethanol to deionized water was 1:2), and transferred to a reaction beaker. The temperature was controlled at 60 °C. Under continuous stirring, the first active metal mixed solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled to keep the pH of the system at 8.5, thus forming a precipitate.

[0064] After the first active metal solution has precipitated completely, the second active metal mixed solution and the precipitant solution are added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant is controlled to keep the pH of the system at 8.5, forming a catalyst precursor precipitate.

[0065] After the second active metal mixed solution was added dropwise, the addition of the precipitant solution was stopped, and the temperature was maintained at 60 °C for 6 h to continue aging to obtain the catalyst precursor slurry. Then, the catalyst precursor slurry was filtered and washed until it was neutral and free of sodium ions, and then dried at 120 °C for 12 h to obtain the dried precursor sample.

[0066] 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water. The resulting dried precursor sample was placed in this metal salt solution and impregnated at 40 °C with stirring for 4 h. The solvent was then removed by rotary evaporation, and the sample was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 400 °C for 4 h under an Ar atmosphere. After granulation, the sample was pressed into tablets to obtain comparative catalyst 3. The composition and mass fraction ratio of comparative catalyst 3 were: Cu:ZnO:Co@NC:CeO2:MgO:SiO2 = 40:20:35:1:2:2.

[0067] Comparative Example 4

[0068] 2.8 g ZrCl4 and 1.99 g terephthalic acid (H2BDC) were added to a 500 mL beaker, followed by the rapid addition of 40 mL glacial acetic acid and 400 mL N,N-dimethylformamide (DMF). The mixture was sonicated for 0.5 h and then placed in a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE) and reacted at 120 °C for 24 h. The mixture was then cooled to room temperature, centrifuged, and washed three times with DMF and ethanol, respectively, yielding a white precipitate. The white precipitate was dried at 80 °C for 12 h to obtain Uio-66 solid powder.

[0069] Uio-66 solid powder was placed in a tube furnace, and high-purity argon gas was introduced. The gas was heated from room temperature at a rate of 5°C / min. -1 The calcination rate was increased to 700℃ and maintained for 4 hours. After calcination, the material was naturally cooled, and the resulting carrier material was designated as ZrO2@C black powder.

[0070] 4.95 g of zinc nitrate hexahydrate was dissolved in deionized water to prepare a first active metal mixed solution with a concentration of 0.5 mol / L;

[0071] 15.1g of copper nitrate trihydrate, 1.282g of magnesium nitrate hexahydrate, and 0.252g of cerium nitrate hexahydrate were dissolved in deionized water to prepare a second active metal mixed solution with a concentration of 0.5mol / L.

[0072] Dissolve 22.5g sodium carbonate, 5.66g sodium hydroxide and 0.947g sodium silicate nonahydrate in deionized water (molar ratio of sodium carbonate to sodium hydroxide is 1.5:1) to prepare a precipitant solution with a Na ion concentration of 1.5mol / L.

[0073] 3.5 g of ZrO2@C carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (volume ratio of ethanol to deionized water was 1:2), and transferred to a reaction beaker. The temperature was controlled at 60 °C. Under continuous stirring, the first active metal mixed solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled to keep the pH of the system at 8.5, thus forming a precipitate.

[0074] After the first active metal solution has precipitated completely, the second active metal mixed solution and the precipitant solution are added dropwise to the reaction beaker using a metering pump. The dropping rate of the precipitant is controlled to keep the pH of the system at 8.5, forming a catalyst precursor precipitate.

[0075] After the second active metal mixed solution is added dropwise, the addition of the precipitant solution is stopped, and the temperature is maintained at 60℃ for 6 hours to continue aging to obtain the catalyst precursor slurry. Then, the catalyst precursor slurry is filtered and washed until it is neutral and free of sodium ions, and then dried at 120℃ for 12 hours to obtain the dried precursor sample.

[0076] 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water. The resulting dried precursor sample was placed in this metal salt solution and impregnated at 40 °C with stirring for 4 h. The solvent was then removed by rotary evaporation, and the sample was dried at 120 °C for 12 h. The sample was then transferred to a tube furnace and calcined at 400 °C for 4 h under an Ar atmosphere. After compression and granulation, comparative catalyst 4 was obtained. The composition and mass fraction ratio of comparative catalyst 4 were: Cu:ZnO:ZrO2@C:CeO2:MgO:SiO2 = 40:20:35:1:2:2.

[0077] The catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were applied to the reaction of carbon dioxide hydrogenation to methanol, and the performance of the catalysts was tested. Reaction conditions: 240℃, GHSV = 10000 ml / gcat. -1 .h -1 The test results are shown in Table 1. The pressure was 5 MPa, and the H2:CO2:N2 ratio was 69:23:8.

[0078] Table 1. Performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-4

[0079]

[0080] As shown in Table 1, Examples 1-3 are catalysts prepared by the present invention using ZIF-8 derived nitrogen-carbon material as a support, combined with deposition precipitation and impregnation methods to load Cu, Zn, and additives. Comparative Example 1 is the comparative catalyst 1 prepared without ZIF-8 derived nitrogen-carbon material as a support, and Comparative Example 2 is the comparative catalyst 2 prepared using ZIF-8 derived nitrogen-carbon material as a support and a single impregnation method. Comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that catalysts 1-3 exhibit better CO2 conversion, methanol selectivity, and methanol content in the reaction of carbon dioxide hydrogenation to methanol. The space-time yield of catalyst 1-3 was higher than that of comparative catalyst 1-2, and the deactivation rate was lower. Higher CO2 conversion rate means more CO2 is utilized in the reaction, resulting in higher feedstock utilization. Higher methanol selectivity means more CO2 is converted into the target product methanol, leading to higher methanol yield. A higher methanol space-time yield also means higher methanol production in a shorter time or in a smaller reactor. Therefore, catalyst 1-3 exhibits better performance than comparative catalyst 1-2 in the carbon dioxide hydrogenation to methanol reaction; that is, catalyst 1-3 has higher activity and stability. Comparative Example 3 uses Co@NC black... Comparative catalyst 3 was prepared by using black ZrO2@C powder as a support material and loading Cu, Zn, and additives using a combination of deposition / precipitation and impregnation methods. Comparative catalyst 4 was prepared by using ZrO2@C black powder as a support material and loading Cu, Zn, and additives using a combination of deposition / precipitation and impregnation methods. Comparing Examples 1-3 and Comparative Examples 3-4, it can be seen that catalyst 1-3 has higher CO2 conversion rate, methanol selectivity, and methanol space-time yield in the reaction of carbon dioxide hydrogenation to methanol than comparative catalyst 3-4, and its deactivation rate is lower than that of comparative catalyst 3-4. Therefore, Examples 1-3 are preferred. Catalysts 1-3, prepared using ZIF-8 derived nitrogen-carbon materials as supports, exhibit better performance in the reaction of carbon dioxide hydrogenation to methanol compared to comparative catalyst 3 prepared using Co@NC black powder as a support material in comparative example 3 and comparative catalyst 4 prepared using ZrO2@C black powder as a support material in comparative example 4. That is, catalysts 1-3 have higher activity and stability. Therefore, the copper-based catalyst prepared by the present invention using ZIF-8 derived nitrogen-carbon materials as supports and combining deposition precipitation and impregnation methods to load Cu, Zn and additives has good activity and stability.

[0081] As described above, this invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, its preparation method, and its application. Using ZIF-8 derived nitrogen-carbon material as a support, the high specific surface area and porous structure of ZIF-8 derived nitrogen-carbon material promote the dispersion of active metals. The nitrogen / oxygen functional groups on the surface facilitate metal anchoring, and the hydrophobicity reduces the oxidation of the catalyst by H2O. Combining deposition and impregnation methods to load Cu, Zn, and additives optimizes metal dispersion and interfacial structure, significantly improving the catalyst's activity and stability. When applied to the reaction of carbon dioxide hydrogenation to methanol, it is beneficial to obtain higher carbon dioxide hydrogenation reaction activity and selectivity for the product methanol.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, characterized in that, The copper-based catalyst comprises the following components and mass fraction ratio: Cu:Zn:carrier:auxiliary agent=40-60:10-20:20-40:0-10, wherein the carrier is a ZIF-8 derived nitrogen-carbon material carrier, the ZIF-8 derived nitrogen-carbon material carrier is obtained by carbonizing treatment of ZIF-8 solid, the auxiliary agent comprises one or more of Mn, Mg, Zr, Cr, Si, Ce and Al, the copper-based catalyst based on the ZIF-8 derived nitrogen-carbon material is obtained by loading the Zn, Cu and auxiliary agent on the ZIF-8 derived nitrogen-carbon material carrier in steps by using a deposition precipitation method to obtain a copper-based catalyst precursor solid, and then supplementing the Zn by using an impregnation method; The preparation of the copper-based catalyst precursor solid by using the deposition precipitation method comprises the following steps: configuring zinc nitrate into a first active metal solution; configuring copper nitrate and auxiliary agent nitrate into a second active metal solution; when the auxiliary agent is selected except Si, one or both of sodium carbonate and sodium hydroxide are mixed and configured into a precipitant solution, or when Si is selected as the auxiliary agent, sodium carbonate, sodium hydroxide and sodium silicate nonahydrate are configured into a precipitant solution; dispersing the nitrogen-carbon material carrier into a solvent to obtain a mixed solution; sequentially adding the first active metal solution, the second active metal solution and the precipitant solution into the mixed solution to obtain a copper-based catalyst precursor slurry; filtering, washing and drying the copper-based catalyst precursor slurry to obtain the copper-based catalyst precursor solid; the adding sequence of the first active metal solution, the second active metal solution and the precipitant solution comprises: simultaneously adding the first active metal solution and the precipitant solution into the mixed solution to form a precipitate solution; after the first active metal solution is precipitated, the second active metal solution is continuously added to form a copper-based catalyst precursor precipitate solution; after the second active metal solution is precipitated, the adding of the precipitant solution is stopped, the temperature is controlled and aging is performed to obtain the copper-based catalyst precursor slurry.

2. A process for the preparation of a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material as claimed in claim 1, wherein, The preparation of the copper-based catalyst comprises the following steps: preparing a ZIF-8 solid; carbonizing the ZIF-8 solid to obtain a nitrogen-carbon material carrier; loading Zn, Cu and auxiliary agent on the nitrogen-carbon material carrier in steps by using a deposition precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn by using an impregnation method, and then performing calcination to obtain the copper-based catalyst.

3. The preparation method according to claim 2, characterized in that, The preparation of the ZIF-8 solid comprises: dissolving 2-methyl imidazole in methanol to obtain solution A; dissolving Zn(NO3)2·6H2O in methanol to obtain solution B; mixing and stirring the solution A and the solution B to obtain a suspension; centrifuging, washing and drying the suspension to obtain the ZIF-8 solid.

4. The preparation method according to claim 2, characterized in that, The preparation of the copper-based catalyst precursor solid by using the deposition precipitation method comprises: configuring zinc nitrate into a first active metal solution; configuring copper nitrate and auxiliary agent nitrate into a second active metal solution; In the selection of the auxiliary agent except Si, one or both of sodium carbonate and sodium hydroxide are mixed to configure a precipitant solution, or in the selection of Si as the auxiliary agent, sodium carbonate, sodium hydroxide and sodium silicate nonahydrate are configured to configure a precipitant solution; The nitrogen-carbon material carrier is dispersed into a solvent to obtain a mixed solution; The first active metal solution, the second active metal solution and the precipitant solution are sequentially added dropwise in the mixed solution to obtain a copper-based catalyst precursor slurry; The copper-based catalyst precursor slurry is filtered, washed and dried to obtain the copper-based catalyst precursor solid.

5. The production method according to claim 4, characterized by, The concentration of the first active metal solution, the second active metal solution and the precipitant solution is 0.5-2 mol / L, the molar ratio of sodium carbonate to sodium hydroxide is 1-3:1, and the temperature of the mixed solution is 10-70°C.

6. The preparation method according to claim 4, characterized in that, The dropwise adding sequence of the first active metal solution, the second active metal solution and the precipitant solution comprises: The first active metal solution and the precipitant solution are simultaneously added dropwise into the mixed solution to form a precipitate solution; After the first active metal solution is precipitated, the second active metal solution is continuously added dropwise to form a copper-based catalyst precursor precipitate solution; After the second active metal solution is precipitated, the addition of the precipitant solution is stopped, the temperature is controlled and aging is performed to obtain the copper-based catalyst precursor slurry.

7. The production method according to claim 6, wherein The pH value of the precipitate solution and the copper-based catalyst precursor precipitate solution is 7-10, the temperature control is 10-70°C, and the aging time is 6-24h.

8. The preparation method according to claim 2, characterized in that, The impregnation method is used to supplement Zn, and after calcination, a copper-based catalyst is obtained, which comprises: Zinc nitrate is configured to a third active metal solution; The copper-based catalyst precursor solid is added into the third active metal solution for stirring and impregnation; The rotary evaporation is used to remove the solvent, and after drying, calcination is performed under inert gas to obtain a copper-based catalyst.

9. The production method according to claim 8, characterized by, The concentration of the third active metal solution is 0.05-2 mol / L, the stirring and impregnation time is 1-4h, the calcination temperature is 300-400°C, and the calcination time is 4-12h.

10. Use of a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material according to claim 1 or a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material obtained by the preparation process according to any one of claims 2 to 9, characterized in that, The application is applied in the reaction of preparing methanol by carbon dioxide hydrogenation.

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