Metal catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a metal catalyst and a preparation method and application thereof. According to the metal catalyst provided by the invention, the metal organic framework material and the introduced metal elements are uniformly dispersed, and the content of the metal elements is regulated, so that enrichment of metal interface sites is realized, and the reaction activity of methanol prepared by hydrogenation of carbon dioxide and the yield of methanol are improved. The preparation method provided by the invention takes the metal organic framework material as a precursor, enriches metal interface sites, and is high in production efficiency, good in safety, low in cost and wide in application prospect. The invention also provides an application of the metal catalyst or the metal catalyst prepared by the preparation method in preparation of methanol by hydrogenation of carbon dioxide. The metal catalyst provided by the invention can improve the reaction activity and product yield of methanol prepared by hydrogenation of carbon dioxide, the methanol product yield is high, and the carbon emission reduction effect is good.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a metal catalyst and a preparation method and application thereof. Background Art

[0002] Recycling carbon dioxide into resources is an important measure towards the goal of "carbon neutrality", and researchers from various countries are also paying attention to the efficient catalytic conversion of carbon dioxide. Methanol, as an important chemical product, is usually produced from synthesis gas in the coal chemical process, but this process usually faces serious carbon dioxide emissions. Studies have shown that methanol can also be produced by combining carbon dioxide with hydrogen. If the hydrogen in this process comes from the electrolysis of water, it is expected to achieve net zero carbon dioxide emissions throughout the process, thereby producing green methanol.

[0003] The hydrogenation of carbon dioxide to produce methanol usually requires the use of catalysts to achieve efficient conversion. Commonly used catalysts include copper-based catalysts, zinc-based catalysts, chromium-based catalysts, and indium-based catalysts. Among them, copper-based catalysts often need to be coupled with other metals to form bimetallic catalysts in order to achieve efficient conversion of carbon dioxide hydrogenation into methanol. However, the copper and other metal elements in the existing copper-based bimetallic catalysts are not evenly dispersed, resulting in an insufficient number of metal interface sites. Summary of the invention

[0004] The object of the present invention is to provide a metal catalyst and a preparation method and application thereof. The metal elements of the metal catalyst provided by the present invention are uniformly dispersed.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a metal catalyst, comprising a metal element and a metal oxide; the metal element is copper; the metal oxide comprises at least one of zinc oxide, zirconium oxide, gallium oxide, indium oxide and aluminum oxide; the molar ratio of the metal in the metal element to the metal in the metal oxide is 0.15 to 5:1; the molar ratio of oxygen to metal in the metal oxide is 1 to 3:1 to 2.

[0007] Preferably, the copper has a particle size of 20 to 35 nm and a specific surface area of ​​10 to 25 m 2 / g.

[0008] Preferably, the metal catalyst is in an irregular octahedral shape; the specific surface area of ​​the metal catalyst is 70 to 300 m 2 / g.

[0009] Preferably, the particle size of the zinc oxide is 10-20 nm; and the zinc oxide is ZnO.

[0010] Preferably, the particle size of the zirconium oxide is 9 to 22 nm; the zirconium oxide is ZrO2.

[0011] Preferably, the particle size of the gallium oxide is 12 to 25 nm; the gallium oxide is Ga2O3.

[0012] Preferably, the particle size of the indium oxide is 15 to 30 nm; the indium oxide is In2O3.

[0013] Preferably, the particle size of the aluminum oxide is 10 to 15 nm; the aluminum oxide is Al2O3.

[0014] The present invention also provides a method for preparing the metal catalyst described in the above scheme, comprising the following steps:

[0015] The copper metal organic framework compound, metal ions and a solvent are mixed and contacted, and then roasted and reduced roasted in sequence to obtain the metal catalyst;

[0016] The metal ion is at least one of zinc ion, zirconium ion, gallium ion, indium ion and aluminum ion.

[0017] The present invention also provides the use of the metal catalyst described in the above scheme or the metal catalyst obtained by the preparation method described in the above scheme in catalyzing the hydrogenation of carbon dioxide to prepare methanol.

[0018] The present invention provides a metal catalyst. The metal catalyst provided by the present invention achieves enrichment of metal interface sites by uniformly dispersing metal organic framework materials and introduced metal elements, and regulating the content of metal elements, thereby improving the reaction activity and product yield of carbon dioxide hydrogenation to methanol.

[0019] The present invention also provides a method for preparing the metal catalyst described in the above scheme. The preparation method provided by the present invention uses metal organic framework materials as precursors, enriches metal interface sites, has high production efficiency, good safety, low cost, and broad application prospects.

[0020] The present invention also provides the use of the metal catalyst described in the above scheme or the metal catalyst obtained by the preparation method described in the above scheme in catalyzing the hydrogenation of carbon dioxide to produce methanol. The metal catalyst provided by the present invention can improve the reaction activity and product yield of the hydrogenation of carbon dioxide to produce methanol, has a high methanol product yield, and has a good carbon emission reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is the XRD spectrum of HKUST-1 support;

[0023] Figure 2 is the XRD spectrum of (Zn)HKUST-1 precursor;

[0024] Figure 3 is the XRD spectrum of ZnO / Cu-MOF-IM-0.5;

[0025] Figure 4 is the XRD spectrum of ZnO / Cu-MOF-IM-0.5 after reduction;

[0026] Figure 5 is the SEM image of HKUST-1 carrier;

[0027] Figure 6 is the SEM image of (Zn)HKUST-1 precursor;

[0028] Figure 7 is the SEM image of ZnO / Cu-MOF-IM-0.5;

[0029] Figure 8 is the SEM image of ZnO / Cu-MOF-IM-0.5 after reduction;

[0030] Fig. 9 This is the EDX image of ZnO / Cu-MOF-IM-0.5 (irregular octahedral morphology);

[0031] Fig.10 This is the EDX image of the reduced ZnO / Cu-MOF-IM-0.5 (irregular octahedral morphology). DETAILED DESCRIPTION

[0032] The present invention provides a metal catalyst, comprising a metal element and a metal oxide; the metal element is copper; the metal oxide comprises at least one of zinc oxide, zirconium oxide, gallium oxide, indium oxide and aluminum oxide; the molar ratio of the metal in the metal element to the metal in the metal oxide is 0.15 to 5:1; the molar ratio of oxygen to metal in the metal oxide is 1 to 3:1 to 2.

[0033] The metal catalyst provided by the present invention comprises a metal element; the particle size of the copper is preferably 20 to 35 nm, specifically 20 nm, 22 nm, 24 nm, 26 nm, 28 nm or 30 nm; the specific surface area of ​​the copper is preferably 10 to 25 m 2 / g, specifically 10m 2 / g, 15m 2 / g, 20m 2 / g or 25m 2 / g.

[0034] The metal catalyst provided by the present invention comprises a metal oxide; the particle size of the zinc oxide is preferably 10 to 20 nm, specifically 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm.

[0035] In the present invention, the zinc oxide is preferably ZnO.

[0036] In the present invention, the particle size of the zirconium oxide is preferably 9 to 22 nm, specifically 9 nm, 12 nm, 15 nm, 18 nm or 22 nm.

[0037] In the present invention, the zirconium oxide is preferably ZrO2.

[0038] In the present invention, the particle size of the gallium is preferably 12 to 25 nm, specifically 12 nm, 15 nm, 18 nm, 21 nm or 25 nm.

[0039] In the present invention, the gallium oxide is preferably Ga2O3.

[0040] In the present invention, the particle size of the indium is preferably 15 to 30 nm, specifically 15 nm, 18 nm, 21 nm, 25 nm, 28 nm or 30 nm.

[0041] In the present invention, the indium oxide is preferably In2O3.

[0042] In the present invention, the particle size of the aluminum is preferably 10 to 15 nm, specifically 10 nm, 11 nm, 12 nm, 13 nm or 15 nm.

[0043] In the present invention, the aluminum oxide is preferably Al2O3.

[0044] In the present invention, the molar ratio of the metal in the metal element to the metal in the metal oxide is preferably 0.15 to 5:1, specifically 0.15:1, 0.2:1, 0.25:1, 0.5:1, 0.8:1, 1:1, 1.25:1, 1.5:1, 1.7:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0045] In the present invention, the molar ratio of oxygen to metal in the metal oxide is preferably 1-3:1-2, specifically 1:1, 1:2, 2:1, 3:1 or 3:2.

[0046] In the present invention, the metal catalyst is preferably Cu and ZnO.

[0047] In the present invention, the shape of the metal catalyst is preferably an irregular octahedron, specifically as Fig. 9 and Fig.10 shown.

[0048] In the present invention, the specific surface area of ​​the metal catalyst is preferably 70 to 300 m 2 / g, specifically 100m 2 / g or 200m 2 / g. The higher the specific surface area of ​​the catalyst, the more conducive it is to the contact and activation of the reactants and active centers.

[0049] The metal catalyst provided by the present invention has an interface site of the metal element of 0.085-0.3 mmol / g, and the interface site is a key active component in the reaction process of preparing methanol by hydrogenation of CO2. The more interface sites there are, the better the reaction performance is. The dispersion of copper is 4-8%, which helps to improve the reaction selectivity.

[0050] The present invention also provides a method for preparing the metal catalyst described in the above scheme, comprising the following steps:

[0051] The copper metal organic framework compound, metal ions and a solvent (referred to as the first solvent) are mixed and contacted (referred to as the first contact), and then calcined and reduction-calcined in sequence to obtain the metal catalyst;

[0052] The metal ion is at least one of zinc ion, zirconium ion, gallium ion, indium ion and aluminum ion.

[0053] In the present invention, the method for preparing the copper metal organic framework compound is preferably: mixing an organic ligand, copper ions and a solvent (referred to as the second solvent) and contacting them (referred to as the second contact).

[0054] In the present invention, the organic ligand preferably includes one or more of dibasic aromatic carboxylic acids and tribasic aromatic carboxylic acids; the dibasic aromatic carboxylic acid is preferably one or both of terephthalic acid and phthalic acid; the tribasic aromatic carboxylic acid is preferably trimesic acid.

[0055] In the present invention, the copper ion is preferably a soluble copper salt; the soluble copper salt preferably includes one or more of copper nitrate, copper nitrate trihydrate, copper acetate and copper chloride, and is more preferably copper nitrate and / or copper acetate.

[0056] In the present invention, the mass ratio of the organic ligand to the copper ion is preferably 1:1-5, specifically 1:1, 1:2, 1:3, 1:4 or 1:5.

[0057] In the present invention, the second solvent preferably includes one or more of amide compounds, alcohol and water; the amide compound is preferably N,N-dimethylformamide; the alcohol preferably includes one or both of ethanol and methanol; the second solvent is more preferably one or more of N,N-dimethylformamide, ethanol and water.

[0058] In the present invention, the mass ratio of the copper ions to the second solvent is preferably 1-5:15-75, specifically 1:15, 1:35, 1:55, 1:75, 3:15, 3:35, 3:55, 3:75, 5:15, 5:35, 5:55 or 5:75.

[0059] In the present invention, the raw materials of the copper metal organic framework compound preferably also include an active agent; the active agent preferably includes one or more of polyvinyl pyrrolidone, γ-methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, and more preferably polyvinyl pyrrolidone; the viscosity average molecular weight of the polyvinyl pyrrolidone is preferably 44000 to 54000, specifically 46000, 48000, 50000 or 52000. In a specific embodiment of the present invention, the polyvinyl pyrrolidone is PVP K-30.

[0060] In the present invention, the mass ratio of the active agent to the copper ions in the copper metal organic framework compound is preferably 3 to 6:1, specifically 3:1, 4:1, 5:1 or 6:1.

[0061] In the present invention, the temperature of the second contact is preferably 60 to 150° C., specifically 80° C., 100° C., 120° C. or 140° C., and the insulation reaction time is preferably 10 to 20 hours, specifically 12 hours, 14 hours, 16 hours or 18 hours. In the second contact process of the present invention, metal ions are mutually constructed into metal organic framework compounds through organic ligands.

[0062] In the present invention, after the second contact, it is preferred that the following steps are further performed: sequentially subjecting the obtained product to solid-liquid separation, washing, drying and grinding; the solid-liquid separation is preferably centrifugation; the washing reagent is preferably methanol; the number of washings is preferably more than 3 times; the drying temperature is preferably 60°C, and the heat preservation and drying time is preferably 12 hours.

[0063] In the present invention, the copper metal organic framework compound is preferably HKUST-1.

[0064] In the present invention, the zinc ion is preferably a soluble zinc salt; the soluble zinc salt preferably includes one or more of zinc nitrate, zinc nitrate hexahydrate, zinc acetate and zinc chloride, and more preferably zinc nitrate and / or zinc acetate.

[0065] In the present invention, the zirconium ion is preferably a soluble zirconium salt; the soluble zirconium salt preferably includes one or more of zirconium nitrate, zirconium chloride and zirconium sulfate.

[0066] In the present invention, the gallium ions are preferably soluble gallium salts; the soluble gallium salts preferably include one or more of gallium nitrate, gallium chloride and gallium sulfate.

[0067] In the present invention, the indium ion is preferably a soluble indium salt; the soluble indium salt preferably includes one or more of indium nitrate, indium chloride and indium sulfate.

[0068] In the present invention, the aluminum ion is preferably a soluble aluminum salt; the soluble aluminum salt preferably includes one or more of aluminum nitrate, aluminum chloride and aluminum sulfate.

[0069] In the present invention, the mass ratio of the copper metal organic framework compound to the metal ion is preferably 2.5 to 10:1, specifically 2.5:1, 3.5:1, 4.5:1, 5.5:1, 6.5:1, 7.5:1, 8.5:1, 9.5:1 or 10:1.

[0070] In the present invention, the first solvent preferably includes one or more of amide compounds, alcohol and water; the amide compound is preferably N,N-dimethylformamide; the alcohol preferably includes one or both of ethanol and methanol; the first solvent is more preferably one or both of ethanol and methanol.

[0071] In the present invention, the mass ratio of the metal ion to the first solvent is preferably 1:250-1000, specifically 1:250, 1:350, 1:450, 1:550, 1:650, 1:750, 1:850, 1:950 or 1:1000.

[0072] In the present invention, the reaction rate of the first contact is preferably 100-1000rpm, specifically 200rpm, 400rpm, 600rpm or 800rpm, the temperature is preferably 50-90°C, specifically 60°C, 70°C or 80°C, and the insulation reaction time is preferably 2-8h, specifically 4h or 6h. In the first contact process of the present invention, the metal ions interact with the copper metal organic framework compound to form a new bimetallic precursor.

[0073] In the present invention, after the first contacting, the obtained product is preferably desolventized; the desolventization is preferably evaporation; and the evaporation temperature is preferably 70°C.

[0074] In the present invention, the calcination atmosphere preferably includes one or both of air and nitrogen; the calcination temperature is preferably 300-600°C, specifically 300°C, 400°C, 500°C or 600°C, and the total insulation reaction time is preferably 2-6h, specifically 2h, 3h, 4h, 5h or 6h.

[0075] In the present invention, the atmosphere of the reduction roasting is preferably hydrogen; the temperature of the reduction roasting is preferably 200-400°C, specifically 200°C, 250°C, 300°C, 350°C or 400°C, and the total insulation reaction time is preferably 1-4h, specifically 1h, 2h, 3h or 4h.

[0076] In the process of calcination and reduction calcination, the bimetallic precursor first undergoes structural destruction of the metal organic framework compound to form a bimetallic oxide, and then the bimetallic oxide forms a metal catalyst under the action of a reducing atmosphere.

[0077] The present invention also provides the use of the metal catalyst described in the above scheme or the metal catalyst obtained by the preparation method described in the above scheme in catalyzing the hydrogenation of carbon dioxide to prepare methanol.

[0078] The metal catalyst provided by the present invention can improve the reaction activity and product yield of preparing methanol by hydrogenating carbon dioxide, has a high methanol product yield, and has a good carbon emission reduction effect.

[0079] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0080] Example 1

[0081] (1) Preparation of HKUST-1 carrier by solvothermal method

[0082] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min and kept at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol for 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%), whose XRD spectrum is shown as follows: Figure 1As shown in the SEM images Figure 5 shown.

[0083] according to Figure 1 and Figure 5 It can be seen that the HKUST-1 carrier prepared in this example has good crystallinity and no impurity peaks, indicating that it has high purity; at the same time, it can be seen from the SEM image that it has a regular octahedral morphology and uniform particle size.

[0084] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0085] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.245 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70 ° C, and the solution was stirred until the solvent was completely evaporated to obtain a (Zn)HKUST-1 precursor, whose XRD spectrum is shown in the following figure. Figure 2 As shown in the SEM images Figure 6 shown.

[0086] according to Figure 2 and Figure 6 It can be seen that after impregnation with Zn, in addition to the XRD crystal phase of HKUST-1, the CuZn-BTC crystal phase also appears, indicating that there is a coordination effect between the Zn species and the ligand and it is distributed in the pores of HKUST-1; at the same time, it can be seen from the SEM image that it still maintains a uniform octahedral morphology, which once again shows that the introduction of Zn will not damage the original HKUST-1 structure.

[0087] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=0.5. Its XRD spectrum is shown in Figure 3 As shown in the SEM images Figure 7 shown.

[0088] according to Figure 3 and Figure 7 It can be seen that after calcination in air, the original HKUST-1 and CuZn-BTC crystal phases disappeared and transformed into CuO, Cu2O and ZnO crystal phases, indicating that the original metal organic framework precursor has been destroyed and formed oxide phases under high temperature calcination in air. At the same time, it can be seen from the SEM image that the original octahedral morphology has been partially destroyed, which again indicates the structural transformation of the precursor.

[0089] (4) The catalyst ZnO / Cu-MOF-0.5 was reduced at 300°C for 2h in a hydrogen atmosphere to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 0.5. Its XRD spectrum is shown in Figure 4 As shown in the SEM images Figure 8 shown.

[0090] according to Figure 4 and Figure 8 It can be seen that the original CuO and Cu2O crystal phases disappear and transform into Cu crystal phases after calcination in hydrogen atmosphere, indicating that the original metal oxides can be reduced under high temperature calcination in hydrogen to form Cu / ZnO interface sites. At the same time, it can be seen from the SEM image that although the octahedral morphology is still destroyed, its morphology has basically not changed significantly compared with the sample calcined in air, indicating that the synthesized material has a certain structural stability.

[0091] Example 2

[0092] (1) Preparation of HKUST-1 carrier by solvothermal method

[0093] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0094] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0095] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.0735 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0096] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=0.15.

[0097] (4) The catalyst ZnO / Cu-MOF-x was reduced in a hydrogen atmosphere at 300°C for 2h to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 0.15.

[0098] Example 3

[0099] (1) Preparation of HKUST-1 carrier by solvothermal method

[0100] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0101] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0102] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.1225 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0103] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=0.25.

[0104] (4) The catalyst ZnO / Cu-MOF-x was reduced in a hydrogen atmosphere at 300°C for 2h to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 0.25.

[0105] Example 4

[0106] (1) Preparation of HKUST-1 carrier by solvothermal method

[0107] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0108] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0109] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.98 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0110] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=2.0.

[0111] (4) The catalyst ZnO / Cu-MOF-x was reduced in a hydrogen atmosphere at 300° C. for 2 h to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 2.0.

[0112] Example 5

[0113] (1) Preparation of HKUST-1 carrier by solvothermal method

[0114] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0115] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0116] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 2.45 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0117] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=5.0.

[0118] (4) The catalyst ZnO / Cu-MOF-x was reduced in a hydrogen atmosphere at 300° C. for 2 h to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 5.0.

[0119] Example 6

[0120] (1) Preparation of HKUST-1 carrier by solvothermal method

[0121] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0122] (2) Synthesis of (Zr)HKUST-1 precursor by impregnation method

[0123] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.3536 g of Zr(NO3)4·5H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zr)HKUST-1 precursor.

[0124] (3) The (Zr)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZrO2 / Cu-MOF-x, where x represents the molar ratio of Zr / Cu, x=0.5.

[0125] (4) The catalyst ZrO2 / Cu-MOF-x was reduced at 300°C for 2h in a hydrogen atmosphere to obtain a metal catalyst ZrO2 / Cu, wherein the Zr / Cu molar ratio was 0.5.

[0126] Example 7

[0127] (1) Preparation of HKUST-1 carrier by solvothermal method

[0128] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min, and kept warm at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed with methanol 3 times, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier (the mass fraction of Cu was 22 wt%).

[0129] (2) Synthesis of (Zn-Al) HKUST-1 precursor by impregnation method

[0130] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.245 g of Zn(NO3)2·6H2O and 0.103 g of Al(NO3)3·9H2O were dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn-Al)HKUST-1 precursor.

[0131] (3) The (Zn-Al)HKUST-1 precursor was calcined at 350 °C in an air atmosphere for 4 h to obtain the catalyst ZnO-Al2O3 / Cu-MOF, in which the molar ratio of Al / Zn / Cu was 1:3:6.

[0132] (4) The catalyst ZnO-Al2O3 / Cu-MOF was reduced at 300°C for 2h in a hydrogen atmosphere to obtain a metal catalyst Al2O3 / ZnO / Cu, wherein the molar ratio of Al / Zn / Cu was 1:3:6.

[0133] Example 8

[0134] (1) Preparation of HKUST-1 carrier by solvothermal method

[0135] 1 g of terephthalic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min and kept at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed 3 times with methanol, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier.

[0136] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0137] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.245 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0138] (3) The (Zn)HKUST-1 precursor was calcined at 350°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=0.5.

[0139] (4) The catalyst ZnO / Cu-MOF-0.5 was reduced at 300°C for 2h in a hydrogen atmosphere to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 0.5.

[0140] Example 9

[0141] (1) Preparation of HKUST-1 carrier by solvothermal method

[0142] 1 g of trimesic acid was dissolved in 30 mL of solvent (15 mL of N,N-dimethylformamide and 15 mL of ethanol) to obtain solution A; 2.077 g of Cu(NO3)2·3H2O and 3 g of polyvinylpyrrolidone (K-30) were dissolved in 15 mL of deionized water to obtain solution B; solution B was slowly dripped into solution A, and the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave after stirring for 30 min and kept at 100°C for 16 h; after the autoclave was cooled, the solvent thermal product was centrifuged and washed 3 times with methanol, dried at 60°C for 12 h, and ground to obtain the HKUST-1 carrier.

[0143] (2) Synthesis of (Zn)HKUST-1 precursor by impregnation method

[0144] 0.5 g of HKUST-1 carrier was mixed with 40 mL of methanol solvent and ultrasonically dispersed for 20 min; 0.245 g of Zn(NO3)2·6H2O was dispersed in 10 mL of methanol solvent and dropped into the above solution, and then the mixed solution was stirred at 600 rpm for 4 h, and then the temperature was raised to 70°C and the solution was stirred until the solvent was completely evaporated to obtain the (Zn)HKUST-1 precursor.

[0145] (3) The (Zn)HKUST-1 precursor was calcined at 600°C in an air atmosphere for 4 h to obtain the catalyst ZnO / Cu-MOF-x, where x represents the molar ratio of Zn / Cu, x=0.5.

[0146] (4) The catalyst ZnO / Cu-MOF-0.5 was reduced at 300°C for 2h in a hydrogen atmosphere to obtain a metal catalyst ZnO / Cu, wherein the Zn / Cu molar ratio was 0.5.

[0147] Comparative Example 1

[0148] The preparation method of this comparative example is the same as that of Example 1, except that the HKUST-1 carrier is replaced with an equal amount of CuO.

[0149] Comparative Example 2

[0150] The preparation method of this comparative example is the same as that of Example 1, except that 0.0245 g Zn(NO3)2·6H2O is added, and x=0.05.

[0151] Comparative Example 3

[0152] The preparation method of this comparative example is the same as that of Example 1, except that: no Zn species are introduced, and the HKUST-1 material is directly calcined.

[0153] Test Example 1

[0154] The metal catalysts prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were characterized in structure, and the results are shown in Table 1. The copper element particle size and zinc element particle size were obtained by XRD test, the catalyst specific surface area was obtained by BET test, and the metal interface sites, copper element specific surface area and copper element dispersion were measured as follows:

[0155] The metal interface sites, copper specific surface area and copper dispersion were measured based on CO2-assisted N2O titration technology. First, 50 mg of catalyst was loaded into a quartz tube, and then heated from 50 ° C to 300 ° C at a rate of 10 ° C / min in a H2 / Ar atmosphere with a volume fraction of 10% at 20 mL / min hydrogen gas. The H2 consumption was detected by the TCD detection module and recorded as N1. After that, the catalyst was cooled to 50 ° C in a 20 mL / min Ar atmosphere for 1 hour, and then the gas was switched to 20 mL / min CO2 / Ar with a volume fraction of 50% carbon dioxide for 30 minutes of adsorption. After that, the gas was switched back to 20 mL / min Ar atmosphere, and the catalyst was heated to 300 ° C for 30 minutes to remove the surface adsorbed species, and then cooled to 50 ° C again and maintained for 1 hour. Next, H2 reduction was performed again according to the initial steps, and the H2 consumption was recorded as N2. The fresh catalyst was titrated with N2O without CO2 assistance. The experimental steps were similar to those of the N2O titration with CO2 assistance, except that the adsorption and desorption of CO2 were eliminated and the H2 reduction consumption in the last step was recorded as N3. Finally, the metal interface sites (mmol / g) can be calculated according to formula (1), and the specific surface area of ​​copper (m 2 / g), the copper dispersion (%) can be calculated by formula (3):

[0156]

[0157]

[0158]

[0159] Among them, N A is Avogadro's constant, w Cu is the mass fraction of copper, M Cu is the molar mass of copper (64 g / mol), 1.47×10 19 Represents the average number of copper atoms per square meter.

[0160] Table 1 Structural parameters of metal catalysts in Examples 1 to 9 and Comparative Examples 1 to 3

[0161]

[0162]

[0163] It can be seen from Table 1 that the strategy of loading Zn element on HKUST-1 as a precursor effectively realizes the regulation of the number of Cu / ZnO interface sites, while maintaining a high Cu dispersion, which is beneficial to the CO2 activation of the catalyst and the production of methanol products.

[0164] Test Example 2

[0165] In a high-pressure fixed-bed reactor, the metal catalysts prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were tested for improving the reaction performance of preparing methanol by hydrogenation of carbon dioxide. The test method was as follows: 50 mg of the metal catalyst and 100 mg of SiO2 were mixed and ground, and then pre-reduced in a 50% H2 / N2 gas flow of 300°C, 0.1 MPa, and 20 mL / min for 2 h; the catalytic performance was detected in a temperature range of 180 to 280°C; the reaction stability was detected under the conditions of 240°C and 3 MPa for 60 h; the outlet pipeline was kept warm at 120°C, and all products were detected by a gas chromatograph (GC2014, Shimadzu Corporation, Japan), which was equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID). The test results are shown in Table 2.

[0166] Table 2 Test results of the reaction performance of preparing methanol by hydrogenation of carbon dioxide in Examples 1 to 9 and Comparative Examples 1 to 3

[0167]

[0168]

[0169] It can be seen from Table 2 that a metal catalyst with good performance can be obtained by adopting the preparation method of the embodiment. This may be because HKUST-1 is used as a precursor to load Zn species, and the constructed metal catalyst has more abundant interface sites, thereby promoting the activation of CO2 and the hydrogenation of reaction intermediates into methanol.

[0170] It can be seen from the above examples that the metal catalyst provided by the present invention improves the reaction activity and product yield of carbon dioxide hydrogenation to methanol.

[0171] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A metal catalyst, characterized in that Including metal elements and metal oxides; The metal element is copper; the metal oxide includes at least one of zinc oxide, zirconium oxide, gallium oxide, indium oxide and aluminum oxide; The molar ratio of the metal in the metal element to the metal in the metal oxide is 0.15-5:1; the molar ratio of oxygen to the metal in the metal oxide is 1-3:1-2.

2. The metal catalyst according to claim 1, characterized in that The copper particle size is 20-35 nm, and the specific surface area is 10-25 m 2 / g.

3. The metal catalyst according to claim 1 or 2, characterized in that The metal catalyst has an irregular octahedral shape; the specific surface area of ​​the metal catalyst is 70 to 300 m 2 / g.

4. The metal catalyst according to claim 1 or 2, characterized in that The particle size of the zinc oxide is 10-20 nm; the zinc oxide is ZnO.

5. The metal catalyst according to claim 1, characterized in that The particle size of the zirconium oxide is 9-22 nm; the zirconium oxide is ZrO2.

6. The metal catalyst according to claim 1 or 5, characterized in that The particle size of the gallium oxide is 12-25 nm; the gallium oxide is Ga2O3.

7. The metal catalyst according to claim 1, characterized in that The particle size of the indium oxide is 15 to 30 nm; the indium oxide is In2O3.

8. The metal catalyst according to claim 1 or 7, characterized in that The particle size of the aluminum oxide is 10-15 nm; the aluminum oxide is Al2O3.

9. The method for preparing the metal catalyst according to any one of claims 1 to 8, characterized in that: The following steps are involved: The copper metal organic framework compound, metal ions and a solvent are mixed and contacted, and then roasted and reduced roasted in sequence to obtain the metal catalyst; The metal ion is at least one of zinc ion, zirconium ion, gallium ion, indium ion and aluminum ion.

10. Use of the metal catalyst according to any one of claims 1 to 8 or the metal catalyst obtained by the preparation method according to claim 9 in catalytic hydrogenation of carbon dioxide to produce methanol.

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