Copper-based catalyst based on ZIF-8 derived nitrogen-carbon material and preparation method and application of copper-based catalyst

Abstract

The invention discloses a copper-based catalyst based on a ZIF-8 derived nitrogen-carbon material as well as a preparation method and application of the copper-based catalyst, and relates to the field of catalyst preparation. The copper-based catalyst comprises the following components in percentage by mass: 40-60% of Cu, 10-20% of Zn, 20-40% of a carrier and 0-10% of an auxiliary agent, 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 a ZIF-8 solid; performing high-temperature carbonization treatment on the ZIF-8 solid to obtain a nitrogen-carbon material carrier; the preparation method comprises the following steps: loading Zn, Cu and an auxiliary agent on a nitrogen-carbon material carrier step by step by adopting a deposition-precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn through an impregnation method, and roasting to obtain a copper-based catalyst; and after reduction, the catalyst can be applied to a reaction for preparing methanol through carbon dioxide hydrogenation. According to the invention, the ZIF-8 derived nitrogen carbon material is taken as the carrier, Cu, Zn and the auxiliary agent are loaded in combination with a deposition-precipitation method and an impregnation method, the metal dispersity and the interface structure can be optimized, and the activity and the stability of the catalyst are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation, and in particular to a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material, and a preparation method and application thereof. Background Art

[0002] Carbon dioxide hydrogenation to methanol is an important pathway for reducing carbon emissions. However, existing copper-based catalysts (such as Cu / ZnO / Al₂O₃) suffer from issues such as active component agglomeration, poor water resistance, and insufficient stability. For example, the H₂O generated during the reaction of conventional catalysts can cause ZnO agglomeration and copper oxidation deactivation, reducing methanol selectivity and conversion. Furthermore, existing methods, such as impregnation or hydrothermal methods, have limited catalyst loading or complex processes, making them difficult to meet industrial requirements. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, as well as a preparation method and application. Using ZIF-8 derived nitrogen-carbon material as a carrier can optimize the metal dispersion and interface structure, and significantly improve the activity and stability of the catalyst.

[0004] The present invention provides a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material, comprising the following components and mass fraction ratios: Cu:Zn:carrier:additive=40-60:10-20:20-40:0-10, wherein the carrier is a ZIF-8-derived nitrogen-carbon material carrier, and the additive comprises 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 the ZIF-8-derived nitrogen-carbon material as described above, comprising the following steps: preparing a ZIF-8 solid; carbonizing the ZIF-8 solid to obtain a nitrogen-carbon material carrier; loading Zn, Cu and an auxiliary agent on the nitrogen-carbon material carrier in steps using a deposition precipitation method to obtain a copper-based catalyst precursor solid; supplementing Zn by an impregnation method, and obtaining a copper-based catalyst after calcination.

[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 the ZIF-8 solid.

[0007] In one embodiment of the present invention, the preparation of a copper-based catalyst precursor solid by a deposition precipitation method includes: dissolving zinc nitrate in deionized water to form a first active metal solution; dissolving copper nitrate and an auxiliary nitrate in deionized water to form a second active metal solution; when selecting an auxiliary agent other than Si, mixing one or two of sodium carbonate and sodium hydroxide to form a precipitant solution, or when selecting Si as an auxiliary agent, sodium carbonate, sodium hydroxide, and sodium silicate nonahydrate to form a precipitant solution; dispersing the nitrogen-carbon material carrier in ethanol and water to obtain a mixed solution; adding the first active metal solution, the second active metal solution, and the precipitant solution to the mixed solution in sequence 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, and 2 mol / L; the molar ratio of the sodium carbonate to the sodium hydroxide is 1-3:1, for example, 1:1, 1.5:1, and 3:1; and the temperature of the mixed solution is 10°C-70°C, for example, 10°C, 30°C, 40°C, and 70°C.

[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 is precipitated, continuing to add the second active metal solution to form a copper-based catalyst precursor precipitate; after the second active metal solution is precipitated, 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 to be 10°C-70°C, for example, 10°C, 30°C, 40°C, 70°C, and the aging time is 6h-24h, for example, 6h, 10h, 12h, 16h, 20h, 24h.

[0011] In one embodiment of the present invention, the impregnation method supplements Zn, and after calcination, a copper-based catalyst is obtained, which 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, stirring and impregnating; removing the solvent by rotary evaporation, drying, and calcining under inert gas to obtain a 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 1 h-4 h, for example, 1 h, 3 h, 4 h, the calcination temperature is 300 ° C-400 ° C, for example, 300 ° C, 350 ° C, 400 ° C, and the calcination time is 4 h-12 h, for example, 4 h, 6 h, 8 h, 10 h.

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

[0014] Compared with the existing technology, the present invention has the following beneficial technical effects: The present invention provides a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material, as well as a preparation method and application thereof. The ZIF-8-derived nitrogen-carbon material is used as a carrier. The high specific surface area and porous structure of the ZIF-8-derived nitrogen-carbon material can promote the dispersion of active metals. The nitrogen / oxygen functional groups on the surface are conducive to metal anchoring. The hydrophobicity can reduce the oxidation of H2O on the catalyst. The deposition precipitation method and the impregnation method are combined to load Cu, Zn and additives, which can optimize the metal dispersion and interface structure, and significantly improve the activity and stability of the catalyst. The application of the ZIF-8-derived nitrogen-carbon material in the reaction of producing methanol by hydrogenation of carbon dioxide is conducive to obtaining higher carbon dioxide hydrogenation reaction activity and product methanol selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the application of the copper-based catalyst provided by the present invention in the reaction of producing methanol by hydrogenation of carbon dioxide. DETAILED DESCRIPTION

[0016] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0017] In the description of the present 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 convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred parts or elements must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0018] See also Figure 1The present invention provides a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material, comprising the following components and mass fraction ratios: Cu:Zn:support:additive = 40-60:10-20:20-40:0-10, wherein the support is a ZIF-8-derived nitrogen-carbon material support, and the additive comprises one or more of Mn, Mg, Zr, Cr, Si, Ce, and Al. The present invention uses the ZIF-8-derived nitrogen-carbon material as a support, loading Cu, Zn, and the additive, to optimize metal dispersion and interface structure, significantly improving the activity and stability of the catalyst.

[0019] The copper-based catalyst based on ZIF-8-derived nitrogen-carbon materials provided by the present invention can be used in the reaction of hydrogenating carbon dioxide to produce methanol. The catalyst has high activity and stability, which is conducive to achieving high carbon dioxide hydrogenation reaction activity and product methanol selectivity.

[0020] ZIF-8 derived nitrogen-carbon material is used as a carrier, the main components of which are carbon (C), nitrogen (N) and oxygen (O), and it maintains the good rhombic dodecahedron structure of ZIF-8. It has a large specific surface area, a layered porous structure, and adjustable surface properties. The adjustable size and significant specific surface area are conducive to the dispersion of active copper species and increase the surface area of metallic copper. The nitrogen-carbon material has high porosity and a layered porous structure, which is conducive to improving the mass transfer efficiency of the reaction gases CO2 and H2, thereby accelerating the rate of carbon dioxide hydrogenation. It is obtained by high-temperature calcination of ZIF-8. The surface of the obtained nitrogen-carbon material has rich nitrogen- and oxygen-containing functional groups, which are beneficial to 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 the nitrogen-carbon material has rich basic sites, which is beneficial to enhance the adsorption and dissociation of CO2; the nitrogen-carbon material has good hydrophobicity, which is beneficial to the rapid desorption of by-product water, thereby effectively reducing the oxidation effect of water on active species, thereby improving the stability of the catalyst.

[0021] The present invention also provides a method for preparing a copper-based catalyst based on the ZIF-8-derived nitrogen-carbon material as described above, comprising the steps of: preparing a ZIF-8 solid; subjecting the ZIF-8 solid to high-temperature carbonization treatment to obtain a nitrogen-carbon material carrier; using a deposition precipitation method to load Zn, Cu and an auxiliary agent on the nitrogen-carbon material carrier in steps to obtain a copper-based catalyst precursor solid; supplementing Zn by an impregnation method, and obtaining a copper-based catalyst after calcination.

[0022] Compared with the single deposition precipitation method or impregnation method in the existing technology, the copper-based catalyst prepared by the deposition precipitation combined with the impregnation method has better copper particle dispersion and has a Cu-ZnO or ZnO-Cu interface structure with more highly active sites. The migration of ZnO during the reduction process can construct more ZnO-Cu interface active sites, which can effectively improve the hydrogenation activity of the catalyst; during the impregnation process, the Cu active sites covered by ZnO can inhibit the reverse water-gas shift reaction with Cu as the active site, which can improve the methanol selectivity of carbon dioxide hydrogenation.

[0023] In one embodiment of the present invention, the preparation of a 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; and centrifuging, washing, and drying the suspension to obtain a ZIF-8 solid. After the ZIF-8 solid is prepared, it is carbonized at high temperature in an inert atmosphere of N₂ or Ar at a temperature controlled between 700°C and 1000°C to obtain a nitrogen-carbon material support, referred to as an NC support.

[0024] In one embodiment of the present invention, a deposition precipitation method is used to prepare a copper-based catalyst precursor solid, including: dissolving zinc nitrate in deionized water to form a first active metal solution; dissolving copper nitrate and auxiliary nitrate in deionized water to form a second active metal solution; when one or more of Mn, Mg, Zr, Cr, Ce, and Al are selected as the auxiliary agent, one or two of sodium carbonate and sodium hydroxide are mixed to form a precipitant solution, or when Si is selected as the auxiliary agent, for example, sodium silicate nonahydrate, because its solution is alkaline, sodium carbonate, sodium hydroxide, and sodium silicate nonahydrate need to be configured as a precipitant solution; dispersing a nitrogen-carbon material carrier 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.

[0025] 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 is precipitated, continuing to add the second active metal solution to form a copper-based catalyst precursor precipitate; after the second active metal solution is precipitated, stopping the addition of the precipitant solution, controlling the temperature and aging the mixture to obtain a copper-based catalyst precursor slurry.

[0026] In one embodiment of the present invention, Zn is supplemented by an impregnation method, and after calcination, a copper-based catalyst is obtained, which includes: dissolving zinc nitrate in deionized water to prepare a third active metal solution; adding a solid copper-based catalyst precursor to the third active metal solution, stirring and impregnating; removing the solvent by rotary evaporation, drying, and calcining under inert gas to obtain a copper-based catalyst.

[0027] Specifically, the preparation method of the copper-based catalyst based on ZIF-8 derived nitrogen-carbon material comprises the steps of: Solution A was prepared by dissolving 13.4 g of 2-methylimidazole (2-meim) in 120 ml of methanol; solution B was prepared by dissolving 12.0 g of Zn(NO3)2·6H2O in 360 ml of methanol; solution A and solution B were mixed and stirred continuously at room temperature for 12 h to obtain a white suspension, which was then centrifuged and washed three times with methanol to remove by-products. Finally, the obtained white ZIF-8 precipitate was dried at 60 °C overnight 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 ) and heat treated for 2 h, the obtained nitrogen-carbon material carrier material was recorded as NC carrier; Dissolve zinc nitrate in deionized water to prepare a first active metal solution with a concentration of 0.5-2 mol / L; dissolve copper nitrate and auxiliary nitrate in deionized water to prepare a second active metal solution with a concentration of 0.5-2 mol / L; dissolve sodium carbonate, sodium hydroxide and / or sodium silicate nonahydrate 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; A certain mass of NC carrier is ultrasonically dispersed in a mixed solution of ethanol and water, and transferred to a reaction beaker, the temperature is controlled within the range of 10-70°C, and the first active metal solution and the precipitant solution are simultaneously added dropwise to the reaction beaker with a metering pump under continuous stirring, and the dropwise addition rate of the precipitant is controlled so that the pH of the system is within the range of 7-10 to form a precipitate; after the precipitation of the first active metal solution is completed, the second active metal solution and the precipitant solution are respectively added dropwise to the reaction beaker with a metering pump, and the dropwise addition rate of the precipitant is controlled so that the pH of the system is within the range of 7-10 to form a copper-based catalyst precursor precipitate; after the addition of the second active metal solution is completed, the dropwise addition of the precipitant solution is stopped, and the temperature is maintained within the range of 10-70°C for further aging for 6-24h to obtain a copper-based catalyst precursor slurry, and then the copper-based catalyst precursor slurry is filtered and washed until neutral and free of sodium ions, and then dried at 120°C for 12h to obtain a copper-based catalyst precursor solid sample; Zinc nitrate is dissolved in a certain volume of deionized water to prepare a third active metal solution with a concentration of 0.05-2 mol / L, a copper-based catalyst precursor solid sample is added to the third active metal solution, stirred and immersed for 4 hours, the solvent is removed by rotary evaporation, and dried at 120°C for 12 hours. Then, the sample is transferred to a tubular furnace and calcined at 300-400°C for 4-12 hours under Ar atmosphere purge conditions, and then tableted and granulated to obtain a catalyst.

[0028] The present invention will be further described below with reference to the embodiments.

[0029] Example 1 13.4 g of 2-methylimidazole (2-meim) was dissolved in 120 ml of methanol, designated Solution A. 12.0 g of Zn(NO₃)₂·6H₂O was then dissolved in 360 ml of methanol, designated Solution B. Solutions A and B were mixed and stirred continuously at room temperature for 12 hours to produce a white suspension. The suspension was then centrifuged and washed three times with methanol to remove byproducts. The resulting white ZIF-8 precipitate was dried at 60°C overnight. The ZIF-8 solid was then heat-treated in a tube furnace at 800°C in an Ar atmosphere for 2 hours. The resulting support material was designated NC.

[0030] 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; 3.5 g of NC carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (the 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 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 so that the pH of the system was 8.5 to form a precipitate. After the precipitation of the first active metal solution was completed, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled so that the pH of the system was 8.5 to form a copper-based catalyst precursor precipitate. After the addition of the second active metal solution was completed, the addition of the precipitant solution was stopped, and the temperature was maintained at 60 ° C. and the aging was continued for 6 hours to obtain a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until it was neutral and free of sodium ions, and then dried at 120 ° C for 12 hours to obtain a copper-based catalyst precursor solid sample. 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. A solid sample of the copper-based catalyst precursor was placed in the third active metal solution and immersed at 40°C for 4 hours with stirring. The solvent was then removed by rotary evaporation and dried at 120°C for 12 hours. The sample was then transferred to a tube furnace and calcined at 400°C for 4 hours under an Ar atmosphere. Catalyst 1 was then pelletized and pelletized. The components and mass fraction ratio of Catalyst 1 were: Cu:ZnO:NC:CeO2:MgO:SiO2 = 40:20:35:1:2:2.

[0031] Example 2 The synthesis method of the NC carrier is the same as that in Example 1 and will not be repeated here.

[0032] 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; 3 g of NC carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (the volume ratio of ethanol to deionized water was 1:2), and transferred to a reaction beaker. The temperature was controlled at 60°C, and the first active metal solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump under continuous stirring. The dropwise addition rate of the precipitant was controlled so that the pH of the system was 8 to form a precipitate. After the precipitation of the first active metal solution was completed, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled so that the pH of the system was 8 to form a copper-based catalyst precursor precipitate. After the addition of the second active metal solution was completed, the addition of the precipitant solution was stopped, and the temperature was maintained at 60°C for further aging for 6 hours to obtain a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until it was neutral and free of sodium ions, and then dried at 120°C for 12 hours to obtain a copper-based catalyst precursor solid sample.

[0033] 1.856 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. A solid sample of the copper-based catalyst precursor was placed in this third active metal solution and immersed at 40°C with stirring for 4 hours. The solvent was then removed by rotary evaporation and dried at 120°C for 12 hours. The sample was then transferred to a tube furnace and calcined at 400°C for 4 hours under an Ar atmosphere. Catalyst 2 was then pelletized and pelletized. The composition and mass fraction ratio of Catalyst 2 was: Cu:ZnO:NC:ZrO2:MgO:SiO2 = 45:15:30:5:3:2.

[0034] Example 3 The synthesis method of the NC carrier is the same as that in Example 1 and will not be repeated here.

[0035] 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. 2 g of NC carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (the volume ratio of ethanol to deionized water was 1:2), and transferred to a reaction beaker. The temperature was controlled at 70°C, and the first active metal solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump under continuous stirring. The dropwise addition rate of the precipitant was controlled so that the pH of the system was 8 to form a precipitate. After the precipitation of the first active metal solution was completed, the second active metal solution and the precipitant solution were added dropwise to the reaction beaker using a metering pump. The dropwise addition rate of the precipitant was controlled so that the pH of the system was 8 to form a copper-based catalyst precursor precipitate. After the addition of the second active metal solution was completed, the addition of the precipitant solution was stopped, and the temperature was maintained at 70°C for further aging for 6 hours to obtain a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until it was neutral and free of sodium ions, and then dried at 120°C for 12 hours to obtain a copper-based catalyst precursor solid sample.

[0036] 1.856 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water to obtain a third active metal solution. A solid sample of the copper-based catalyst precursor was placed in the third active metal solution and immersed at 40°C for 4 hours with stirring. The solvent was then removed by rotary evaporation and dried at 120°C for 12 hours. The sample was transferred to a tube furnace and calcined at 400°C for 4 hours under an Ar atmosphere purge. Catalyst 3 was then obtained by tableting and granulation. The composition and mass fraction ratio of Catalyst 3 was: Cu:ZnO:NC:ZrO2:MgO:SiO2 = 50:20:20:4:3:3.

[0037] Comparative Example 1 18.875 g of copper nitrate trihydrate, 7.425 g of zinc nitrate hexahydrate, and 8.71 g of zirconium nitrate pentahydrate were dissolved in deionized water to prepare an active metal solution with a concentration of 2 mol / L; 31.8 g of sodium carbonate and 2.368 g of sodium silicate nonahydrate were dissolved in deionized water to prepare a precipitant solution with a Na ion concentration of 2 mol / L; Add 80 ml of deionized water to the reaction beaker, control the temperature at 40°C, and use a metering pump to drop the active metal solution and precipitant solution into the reaction beaker simultaneously under continuous stirring. Control the precipitant addition rate to keep the pH of the system at 9 to form a precipitate. After the active metal solution was added dropwise, the precipitant solution was stopped and the aging process continued for 6 hours while maintaining the temperature within the 40°C range to obtain a copper-based catalyst precursor slurry. The copper-based catalyst precursor slurry was then filtered and washed until neutral with no residual sodium ions. It was then dried at 120°C for 12 hours. The sample was then transferred to a muffle furnace and calcined at 350°C for 4 hours. Comparative Catalyst 1 was then obtained by tableting and granulation. The components and mass fraction ratio of Comparative Catalyst 1 were: Cu:ZnO:ZrO2:SiO2 = 50:20:25:5.

[0038] Comparative Example 2 The synthesis method of the NC carrier is the same as that in Example 1 and will not be repeated here.

[0039] 18.875 g of copper nitrate trihydrate, 7.425 g of zinc nitrate hexahydrate, and 3.676 g of aluminum nitrate nonahydrate were dissolved in a mixed solvent of deionized water and ethanol (the volume ratio of deionized water to ethanol was 2:1) to prepare an active metal solution with a concentration of 1.5 mol / L. 2.5 g of the NC support was added to the active metal solution and impregnated with stirring at 40°C for 4 hours. The mixed solution was subjected to rotary evaporation to remove the solvent and dried at 120°C for 12 hours. The sample was then transferred to a tube furnace and calcined at 350°C for 4 hours under an Ar atmosphere. The sample was then pressed and pelletized to obtain Comparative Catalyst 2. The composition and mass fraction ratio of Comparative Catalyst 2 was: Cu:ZnO:Al2O3:NC = 50:20:5:25. Comparative Example 3 Dissolve 20.1g of 2-methylimidazole (2-meim) in 480ml of methanol (Solution A). Dissolve 11.87g of Co(NO₃)₂·6H₂O in 480ml of methanol (Solution B). Mix Solutions A and B and stir at room temperature for 30 minutes to obtain a purple mixed solution. Seal the solution with plastic wrap and let it stand for 24 hours. After standing for 24 hours, centrifuge the mixed solution. Wash the purple precipitate three times with anhydrous methanol and vacuum dry it at 60°C for 6 hours to obtain a purple ZIF-67 powder.

[0040] The ZIF-67 solid powder was placed in a tube furnace and high-purity argon was introduced from room temperature to a temperature of 5°C min -1 The temperature was raised to 800 °C at a rate of 100 °C and maintained for 2 h. After calcination, the material was naturally cooled to obtain a support material named Co@NC black powder.

[0041] Dissolve 4.95 g of zinc nitrate hexahydrate in deionized water to prepare a first active metal mixed 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 mixed solution having a concentration of 0.1 mol / L. Dissolve 22.5 g of sodium carbonate, 5.66 g of sodium hydroxide, and 0.947 g of sodium silicate nonahydrate in deionized water (the molar ratio of sodium carbonate to sodium hydroxide is 1.5:1) to prepare a precipitant solution with a Na ion concentration of 1.5 mol / L; 3.5 g of the Co@NC carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (the volume ratio of ethanol to deionized water was 1:2) and transferred to a reaction beaker. The temperature was controlled at 60°C. The first active metal mixed solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump under continuous stirring. The precipitant addition rate was controlled to maintain the pH of the system at 8.5 to form a precipitate. After the first active metal solution is precipitated, the second active metal mixed solution and the precipitant solution are added dropwise to the reaction beaker using a metering pump. The precipitant addition rate is controlled to keep the pH of the system at 8.5 to form a catalyst precursor precipitate. After the addition of the second active metal mixed solution is completed, the addition of the precipitant solution is stopped, and the temperature is maintained at 60°C for further aging for 6 hours to obtain a catalyst precursor slurry. The catalyst precursor slurry is then filtered and washed until it is neutral and free of sodium ions, and then dried at 120°C for 12 hours to obtain a dry precursor sample.

[0042] 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water. The resulting dried precursor sample was placed in the metal salt solution and immersed at 40°C with stirring for 4 hours. The solvent was then removed by rotary evaporation and dried at 120°C for 12 hours. The sample was transferred to a tube furnace and calcined at 400°C for 4 hours under an Ar atmosphere. After tableting and granulation, Comparative Catalyst 3 was obtained. The composition and mass fraction ratio of Comparative Catalyst 3 is: Cu:ZnO:Co@NC:CeO2:MgO:SiO2 = 40:20:35:1:2:2; Comparative Example 4 2.8g ZrCl4 and 1.99g terephthalic acid (H2BDC) were added to a 500mL beaker, followed by the rapid addition of 40ml glacial acetic acid and 400ml N,N-dimethylformamide (DMF). The mixture was ultrasonically mixed for 0.5h and then placed in a Teflon-lined stainless steel autoclave and reacted at 120°C for 24h. The mixture was then cooled to room temperature, centrifuged, and washed three times with DMF and ethanol, respectively, to obtain a white precipitate. The resulting precipitate was dried at 80°C for 12h to obtain Uio-66 solid powder.

[0043] Uio-66 solid powder was placed in a tube furnace and high-purity argon was introduced. -1 The temperature was raised to 700 °C at a rate of 100 °C and maintained for 4 h. After calcination, it was naturally cooled. The obtained support material was recorded as ZrO2@C black powder.

[0044] Dissolve 4.95 g of zinc nitrate hexahydrate in deionized water to prepare a first active metal mixed 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 mixed solution with a concentration of 0.5 mol / L; Dissolve 22.5 g of sodium carbonate, 5.66 g of sodium hydroxide, and 0.947 g of sodium silicate nonahydrate in deionized water (the molar ratio of sodium carbonate to sodium hydroxide is 1.5:1) to prepare a precipitant solution with a Na ion concentration of 1.5 mol / L; 3.5 g of the ZrO2@C carrier was ultrasonically dispersed in 80 ml of a mixed solution of ethanol and water (the volume ratio of ethanol to deionized water was 1:2). The solution was then transferred to a reaction beaker and the temperature was controlled at 60°C. The first active metal mixed solution and the precipitant solution were simultaneously added dropwise to the reaction beaker using a metering pump under continuous stirring. The precipitant addition rate was controlled to maintain a pH of 8.5, forming a precipitate. After the first active metal solution is precipitated, the second active metal mixed solution and the precipitant solution are added dropwise to the reaction beaker using a metering pump. The precipitant addition rate is controlled to keep the pH of the system at 8.5 to form a catalyst precursor precipitate. After the addition of the second active metal mixed solution is completed, the addition of the precipitant solution is stopped, and the temperature is maintained at 60°C for further aging for 6 hours to obtain a catalyst precursor slurry. The catalyst precursor slurry is then filtered and washed until it is neutral and free of sodium ions, and then dried at 120°C for 12 hours to obtain a dry precursor sample.

[0045] 2.475 g of zinc nitrate hexahydrate was dissolved in 50 ml of deionized water. The resulting dried precursor sample was placed in the metal salt solution and immersed at 40°C with stirring for 4 hours. The solvent was then removed by rotary evaporation and dried at 120°C for 12 hours. The sample was transferred to a tube furnace and calcined at 400°C for 4 hours under an Ar atmosphere. After tableting and granulation, Comparative Catalyst 4 was obtained. The composition and mass fraction ratio of Comparative Catalyst 4 was: Cu:ZnO:ZrO2@C:CeO2:MgO:SiO2 = 40:20:35:1:2:2.

[0046] The catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were used in the reaction of hydrogenating carbon dioxide to produce methanol to test the performance of the catalysts. The reaction conditions were: 240°C, GHSV = 10000 ml.gcat -1 .h -1 , 5MPa, H2:CO2:N2=69:23:8, test results are shown in Table 1.

[0047] Table 1 Properties of the catalysts prepared in Examples 1-3 and Comparative Examples 1-4

[0048] As can be seen from Table 1, Examples 1-3 are catalysts 1-3 prepared by combining the deposition precipitation method with the impregnation method to load Cu, Zn and additives using ZIF-8 derived nitrogen-carbon materials as carriers. Comparative Example 1 is a comparative catalyst 1 prepared without using ZIF-8 derived nitrogen-carbon materials as carriers. Comparative Example 2 is a comparative catalyst 2 prepared using ZIF-8 derived nitrogen-carbon materials as carriers and a single impregnation method. Comparison of Examples 1-3 and Comparative Example 1-2 shows that the CO2 conversion rate, methanol selectivity, and methanol selectivity of catalysts 1-3 in the reaction of preparing methanol from carbon dioxide hydrogenation are significantly improved. The space-time yield is higher than that of the comparative catalyst 1-2, and the deactivation rate is lower than that of the comparative catalyst 1-2. The high CO2 conversion rate means that more CO2 is utilized in the reaction, the raw material utilization rate is high, and the high methanol selectivity means that more CO2 is converted into the target product methanol, and the methanol yield is higher. The high space-time yield of methanol means that the methanol yield is high in a shorter time or in a smaller reactor. Therefore, the catalyst 1-3 has better performance than the comparative catalyst 1-2 in the reaction of preparing methanol by hydrogenation of carbon dioxide, that is, the activity and stability of the catalyst 1-3 are higher; Comparative Example 3 is a catalyst prepared by using Co@NC black The comparative catalyst 3 is prepared by using ZrO2@C black powder as a carrier material and combining the deposition precipitation method with the impregnation method to load Cu, Zn and auxiliary agents. The comparative catalyst 4 is prepared by using ZrO2@C black powder as a carrier material and combining the deposition precipitation method with the impregnation method to load Cu, Zn and auxiliary agents. Comparing Examples 1-3 and Comparative Examples 3-4, it can be seen that the CO2 conversion rate, methanol selectivity, and methanol space-time yield of catalyst 1-3 in the reaction of preparing methanol by hydrogenation of carbon dioxide are higher than those of comparative catalyst 3-4, and the deactivation rate is lower than that of comparative catalyst 3-4. Therefore, Examples 1-3 are prepared by using ZrO2@C black powder as a carrier material and combining the deposition precipitation method with the impregnation method to load Cu, Zn and auxiliary agents. Catalysts 1-3 prepared using ZIF-8-derived nitrogen-carbon materials as carriers have better performance in the reaction of producing methanol from carbon dioxide hydrogenation than comparative catalyst 3 prepared using Co@NC black powder as carrier material in comparative example 3 and comparative catalyst 4 prepared using ZrO2@C black powder as carrier material in comparative example 4. That is, catalysts 1-3 have higher activity and stability. Therefore, the present invention uses ZIF-8-derived nitrogen-carbon materials as carriers, combines deposition precipitation method with impregnation method to load Cu, Zn and additives, and the copper-based catalyst prepared has good activity and stability.

[0049] From the above description, it can be known that the present invention provides a copper-based catalyst based on ZIF-8 derived nitrogen-carbon material, a preparation method and an application. The ZIF-8 derived nitrogen-carbon material is used as a carrier. The high specific surface area and porous structure of the ZIF-8 derived nitrogen-carbon material can promote the dispersion of active metals. The nitrogen / oxygen functional groups on the surface are conducive to metal anchoring. The hydrophobicity can reduce the oxidation of H2O on the catalyst. The combination of deposition precipitation method and impregnation method to load Cu, Zn and additives can optimize the metal dispersion and interface structure, significantly improve the activity and stability of the catalyst, and its application in the reaction of preparing methanol by hydrogenation of carbon dioxide is conducive to obtaining higher carbon dioxide hydrogenation reaction activity and product methanol selectivity.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A copper-based catalyst based on ZIF-8-derived nitrogen-carbon material, characterized in that: Includes 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 nitrogen-carbon material carrier derived from ZIF-8, and the auxiliary agent includes one or more of Mn, Mg, Zr, Cr, Si, Ce, and Al.

2. A method for preparing a copper-based catalyst based on ZIF-8-derived nitrogen-carbon material according to claim 1, characterized in that: The following steps are involved: Preparation of ZIF-8 solid; Carbonizing the ZIF-8 solid to obtain a nitrogen-carbon material carrier; Zn, Cu and an additive are loaded on the nitrogen-carbon material carrier in steps by a deposition precipitation method to obtain a copper-based catalyst precursor solid; Zn is added by impregnation method and then calcined to obtain a copper-based catalyst.

3. The preparation method according to claim 2, characterized in that The preparation of the ZIF-8 solid comprises: Prepare solution A by dissolving 2-methylimidazole in methanol; Prepare solution B by dissolving Zn(NO3)2·6H2O in methanol; Mixing and stirring the solution A and the solution B to obtain a suspension; The suspension is centrifuged, washed, and dried to obtain ZIF-8 solid.

4. The preparation method according to claim 2, characterized in that The method of preparing the copper-based catalyst precursor solid by the deposition precipitation method comprises: preparing zinc nitrate into a first active metal solution; preparing copper nitrate and auxiliary nitrate into a second active metal solution; When an auxiliary agent other than Si is selected, one or both of sodium carbonate and sodium hydroxide are mixed to form a precipitant solution, or when Si is selected as an auxiliary agent, sodium carbonate, sodium hydroxide and sodium silicate nonahydrate are mixed to form a precipitant solution; dispersing the nitrogen-carbon material carrier in a solvent to obtain a mixed solution; adding the first active metal solution, the second active metal solution, and the precipitant solution dropwise to the mixed solution in sequence 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 preparation method according to claim 4, characterized in that The concentrations of the first active metal solution, the second active metal solution, and the precipitant solution are 0.5-2 mol / L, the molar ratio of the sodium carbonate to the sodium hydroxide is 1-3:1, and the temperature of the mixed solution is 10° C.-70° C.

6. The preparation method according to claim 4, characterized in that The order of adding the first active metal solution, the second active metal solution, and the precipitant solution includes: adding the first active metal solution and the precipitant solution dropwise to the mixed solution simultaneously to form a precipitate; 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; After the precipitation of the second active metal solution is completed, the dropwise addition of the precipitant solution is stopped, the temperature is controlled and the slurry is aged to obtain the copper-based catalyst precursor slurry.

7. The preparation method according to claim 6, characterized in that The pH value of the precipitate solution and the copper-based catalyst precursor precipitate solution is 7-10, the temperature is controlled at 10° C.-70° C., and the aging time is 6 h-24 h.

8. The preparation method according to claim 2, characterized in that The impregnation method supplements Zn, and after calcination, a copper-based catalyst is obtained, which comprises: preparing zinc nitrate into a third active metal solution; adding the copper-based catalyst precursor solid to the third active metal solution, stirring and impregnating; The solvent is removed by rotary evaporation, and the product is dried and calcined under an inert gas to obtain a copper-based catalyst.

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

10. A use of a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material according to claim 1 or a copper-based catalyst based on a ZIF-8-derived nitrogen-carbon material prepared by the preparation method according to any one of claims 2 to 9, characterized in that: It is used in the reaction of producing methanol by hydrogenation of carbon dioxide.

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