Cobalt-copper bimetal-loaded nitrogen-doped carbon nanotube material and preparation method thereof

Abstract

The invention discloses a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals and a preparation method of the nitrogen-doped carbon nanotube material. The method comprises the following steps: adding 2-methylimidazole, cobaltous acetate and cupric acetate into deionized water, ultrasonically dissolving and mixing, standing, washing and drying to obtain a CoCu-ZIF material; and then, calcining the material in a reducing atmosphere, an oxidizing atmosphere and a reducing atmosphere in sequence to obtain the CoCu-coated NCNT material without the carbon film covering metal. Compared with a C / CoCu-coated NCNT material covered with a carbon film and generated only through calcination of reducing gas, in the prepared material, cobalt-copper bimetal active sites are exposed more sufficiently, which means that the usage amount of a catalyst can be reduced on the basis of realizing high catalytic activity, so that the material is more economical.

Description

Technical Field

[0001] The present invention belongs to the field of non-noble metal catalytic hydrogenation, and specifically relates to the preparation of a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals as a catalyst for the selective hydrogenation of phenylacetylene. Background Art

[0002] Styrene, as a key monomer, plays an irreplaceable role in the preparation of various materials such as styrene-butadiene rubber, polystyrene, and expanded polystyrene. It can also be used as a comonomer in the synthesis of various engineering plastics with wide applications. This compound is mainly prepared by the dehydrogenation of ethylbenzene, and trace amounts of phenylacetylene impurities naturally exist in the raw material ethylbenzene. This characteristic highlights the importance of the process for the selective hydrogenation of phenylacetylene to styrene in industrial production - this process can not only improve the quality of polyolefin products but also effectively reduce the poisoning effect of by-products on polymerization catalysts. Industrially, Lindlar catalysts (mainly composed of Pd-CaCO3-Pb(OAc)2) are generally used for alkyne hydrogenation reactions, but this system has significant defects: on the one hand, the lead acetate component is toxic, and on the other hand, the high cost of palladium metal also restricts its application. Non-noble metal catalyst systems based on earth-abundant elements (such as Fe, Co, Ni, Cu, etc.) can significantly reduce the cost of selective semi-hydrogenation of phenylacetylene, but their catalytic performance is significantly insufficient: compared with palladium-based catalysts, such materials generally have problems such as harsh reaction conditions, low selectivity, and poor activity. Therefore, developing non-noble metal catalysts with high activity, high selectivity, and long lifespan through strategies such as electronic structure regulation, interface engineering, and support optimization has become a technical bottleneck that urgently needs to be broken through in the current industrial catalysis field.

[0003] Metal-organic framework materials (MOFs) are crystalline porous compounds formed by the coordination assembly of organic ligands and metal centers, and have become common precursors for the preparation of various porous functional materials (including metal-based materials, metal carbides / oxides / phosphides, metal / metal oxide nanoparticles, and carbon-supported metal catalysts). Among them, cobalt-based catalysts prepared by pyrolysis using cobalt-based zeolitic imidazolate framework (ZIF-67) as a precursor show good application prospects in the selective hydrogenation of phenylacetylene due to their precisely tunable micro-nano morphology and hierarchical pore structure. However, studies have shown that there is a carbon film on the surface of the nanoparticles generated by pyrolysis, which hinders the contact of reactants and hydrogen molecules with active sites and significantly weakens the catalytic performance.

[0004] In the Chinese invention patent with application number CN202011640032.X and titled "Co@NCNT materials prepared by reduction-oxidation-reduction strategy and preparation method thereof", ZIF-67 is calcined in a reducing atmosphere to obtain a cobalt-based catalyst covered with a carbon film, and then the carbon film covering the surface of the cobalt nanoparticles is removed by an oxidizing atmosphere, and finally calcined by a reducing atmosphere to obtain a fully exposed cobalt nanoparticle catalyst. The problem is that the adsorption energy of cobalt metal alone on styrene is too large, and failure to desorb in time leads to excessive hydrogenation reaction. Therefore, how to prepare ZIF-67-derived cobalt-based catalysts with high catalytic activity and selectivity through a simple and efficient method is still a technology that urgently needs to break through the difficulties in this field. Summary of the invention

[0005] In view of the problems existing in the existing methods, the present invention provides a nitrogen-doped carbon nanotube material loaded with cobalt-copper bimetallic, a preparation method and an application thereof, which improves the selectivity and activity of the catalyst in the hydrogenation of phenylacetylene by the synergistic effect and electronic effect of the Co-Cu bimetallic components in the cobalt-copper alloy catalyst and the removal of the carbon film coated with the metal by multi-stage calcination.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] The present invention provides a method for preparing a nitrogen-doped carbon nanotube material loaded with cobalt-copper bimetallic materials, comprising the following steps:

[0008] (1) adding 2-methylimidazole to deionized water and dissolving it uniformly by ultrasonication to obtain an organic ligand solution; dissolving cobalt acetate and copper acetate in deionized water to obtain a metal salt solution;

[0009] (2) adding the metal salt solution of step (1) to the organic ligand solution, stirring and mixing, standing and then centrifuging, washing and drying the precipitate to obtain a CoCu-ZIF material;

[0010] (3) The CoCu-ZIF material described in step (2) is calcined in a reducing atmosphere, an oxidizing atmosphere, and a reducing atmosphere to obtain a nitrogen-doped carbon nanotube material loaded with cobalt-copper bimetallic.

[0011] Furthermore, in step (1), the ratio of cobalt acetate, copper acetate and deionized water is (3-6) mmol: (0.21-0.72) mmol: 10 mL, the ratio of 2-methylimidazole and deionized water is (21-60) mmol: 10 mL, and the ultrasonic dissolution time is 20-50 min.

[0012] Furthermore, in step (2), the mixing order is to pour the metal salt solution into the organic ligand solution. The volume ratio of the metal salt solution to the organic ligand solution is 2-10:5-10.

[0013] Further, in step (2), the stirring temperature is 20 - 30°C, and the standing time is 10 - 30 min.

[0014] Further, in step (2), the centrifugation speed is 4000 - 6000 r / min, the centrifugation time is 2 - 5 min, the washing liquid is 20 - 40 mL of methanol, and the precipitate is centrifugally washed 2 times; the drying temperature is 60 - 75°C, and drying is carried out for 18 - 24 h.

[0015] Further, in step (3), the reducing atmosphere is a hydrogen - argon mixture, the volume fraction of hydrogen is 10%, and the gas flow rate is 40 - 60 mL / min; the temperature of the calcination treatment is 600 - 800°C, the calcination time is 2 - 5 h, and the heating rate is 2 - 5°C / min.

[0016] Further, in step (3), the oxidizing atmosphere is an oxygen - argon mixture, the volume fraction of oxygen is 3% - 10%, preferably 3%; the gas flow rate is 40 - 60 mL / min, the calcination temperature is 200 - 300°C, and the calcination time is 10 - 60 min.

[0017] Further, in step (3), the reducing atmosphere is a hydrogen - argon mixture, the volume fraction of hydrogen is 10% - 20%, preferably 10%, the gas flow rate is 40 - 60 mL / min, the calcination temperature is 250 - 300°C, and the calcination time is 2 - 5 h.

[0018] The present invention provides a cobalt - copper bimetallic nitrogen - doped carbon nanotube material. The cobalt - copper bimetallic nitrogen - doped carbon nanotube material has a hollow dodecahedron structure. The hollow carbon carrier is composed of carbon nanotubes. The top of the carbon nanotube is a cobalt - copper bimetallic nanoparticle with a diameter of 10 - 17 nm. The cavity diameter is 700 - 900 nm, and the thickness of the hollow carbon layer is 80 - 250 nm; in the selective hydrogenation reaction of phenylacetylene, the selectivity of the cobalt - copper bimetallic nitrogen - doped carbon nanotube material is 70% - 92%.

[0019] Compared with Co@NCNT prepared by directly calcining ZIF - 67, the CoCu@NCNT material has highly dispersed, highly active, and high - density - distributed cobalt - copper bimetallic active sites, and the selectivity for the selective hydrogenation reaction of phenylacetylene reaches 92%. In addition, compared with the C / CoCu@NCNT material with a carbon - film - covered structure generated only by calcination with a reducing gas, in the material prepared by the present invention, the cobalt - copper bimetallic active sites are more fully exposed, which means that on the basis of achieving high catalytic activity, the amount of catalyst used can be reduced, so it is also more economical.

[0020] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0021] (1) The present invention uses a bimetallic catalyst prepared from two non-noble metals to replace the noble metal catalyst, significantly reducing the catalyst cost.

[0022] (2) The preparation method provided by the present invention is simple. Copper ions are added during the synthesis of the MOFs precursor to replace part of the cobalt ions. A cobalt-copper alloy catalyst is synthesized by calcination. By utilizing the synergistic effect of the cobalt-copper bimetal and multi-stage calcination to remove the carbon film coated on the surface of the metal nanoparticles, more active sites are exposed, and the reaction activity and the selectivity of styrene are significantly improved in the catalytic selective hydrogenation of phenylacetylene, with the selectivity reaching 92%. It shows that the catalyst has excellent activity and selectivity in the selective hydrogenation reaction of phenylacetylene. Description of the Drawings

[0023] Figure 1 X-ray photoelectron spectroscopy (XPS) diagram of the 1# CoCu@NCNT material prepared in Example 1;

[0024] Figure 2 Scanning electron microscopy (SEM) diagram of the 1# CoCu@NCNT material prepared in Example 1;

[0025] Figures 3a to 3e Elemental mapping (EDS) diagram of the 1# CoCu@NCNT material prepared in Example 1;

[0026] Figure 4 a is the transmission electron microscopy (TEM) diagram of the 1# CoCu@NCNT material prepared in Example 1;

[0027] Figure 4 b is the transmission electron microscopy (TEM) diagram of the 4# C / CoCu@NCNT material prepared in Example 4;

[0028] Figure 4 c is the transmission electron microscopy (TEM) diagram of the 7# C / CoCu@NC material prepared in Example 7;

[0029] Figure 5 Hydrogenation performance test diagram of phenylacetylene for the 1# CoCu@NCNT material prepared in Example 1, the 4# C / CoCu@NCNT material prepared in Example 4, the 7# C / CoCu@NC material prepared in Example 7, and the Co@NCNT material without copper doping. Detailed Embodiments

[0030] The embodiments of the present invention are described in detail below with reference to specific examples, but the scope of rights and protection of the present invention are not limited thereto. It should be noted that the operation steps not described in detail herein can be understood or completed by personnel in the relevant technical field based on the prior art. If the supplier information of the chemical reagents or experimental equipment involved is not indicated, they are deemed to be standardized commodities that can be obtained through market channels.

[0031] Example 1

[0032] This embodiment provides a method for preparing a nitrogen-doped carbon nanotube material loaded with cobalt-copper bimetallic materials, comprising the following steps:

[0033] (1) 0.05 mol of 2-methylimidazole was added to 10 mL of deionized water and dissolved by ultrasonication for 20 min to obtain a 2-methylimidazole solution; 0.005 mol of cobalt acetate and 0.0006 mol of copper acetate were dissolved in deionized water to obtain a metal salt solution.

[0034] (2) adding the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; standing for 10 min to obtain a CoCu-ZIF suspension; centrifuging the obtained CoCu-ZIF suspension at 4000 r / min for 2 min, washing it several times by centrifugation with anhydrous methanol, and drying it at 60° C. for 14 h to obtain a CoCu-ZIF material.

[0035] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tube furnace, and in a hydrogen-argon atmosphere, heat it to 800°C at a rate of 2°C / min, calcine it at 800°C for 3 h, cool it to 250°C, switch the calcination gas to an oxygen-argon mixture, calcine it at 250°C for 30 min, then switch the gas to a hydrogen-argon mixture, heat it to 300°C at a rate of 2°C / min, calcine it at 300°C for 3 h, cool it to room temperature and take it out to obtain 1#CoCu / NCNT material.

[0036] Figure 1 This is the X-ray photoelectron spectrum (XPS) of 1#CoCu@NCNT material prepared in Example 1. The presence of orbital peaks of Cu and Co indicates the successful preparation of cobalt-copper bimetallic material.

[0037] Figure 2 , Figures 3a to 3e and Figure 4Figure a shows the SEM image, elemental mapping (EDS) image, and TEM image of the 1# CoCu@NCNT material prepared in Example 1. Through image analysis, it can be seen that the obtained material is a hollow dodecahedron structure. The hollow carbon carrier is composed of carbon nanotubes. At the top of the carbon nanotubes are cobalt-copper bimetallic nanoparticles with a diameter of 12 nm. The cavity diameter is 700 nm, and the thickness of the hollow carbon layer is 80 nm. The EDS image proves that the cobalt-copper bimetallic sites are evenly distributed on the surface of the material. Figure 4 Figure b is the TEM image of the 4# C / CoCu@NCNT material prepared in Example 4. It can be seen from the figure that the morphology is similar to that of the material in Example 1, but the thickness of the hollow carbon carrier of the material in Example 4 without calcination in an oxidizing atmosphere is 200 nm. Figure 4 Figure c is the TEM image of the 7# CoCu@NC material prepared in Example 7. The 7# CoCu@NC material is a solid polyhedron structure with a thick carbon layer wrapping metal nanoparticles. By comparing with Example 4, it can be seen that the hydrogen-argon atmosphere is the key to the appearance of the hollow carbon structure composed of carbon nanotubes.

[0038] Figure 5 Figure shows the performance test diagrams of the 1# CoCu@NCNT, 4# C / CoCu@NCNT, 7# CoCu@NC materials prepared in Example 1 and Example 4, and the Co@NCNT material prepared without copper doping for the hydrogenation of phenylacetylene to styrene. By analyzing the images, it can be seen that the hydrogenation activity of the 7# CoCu@NC material is the worst, only 7%, because the thick carbon layer hinders the contact between the active sites and the reactants, but the selectivity is higher than that of the Co@NCNT material without copper doping. The 1# CoCu@NCNT and Co@NCNT have the highest catalytic activity, and the conversion rates of phenylacetylene are 94% and 98% respectively in 3.5 h. They are superior to the hydrogenation catalytic performance of the 4# C / CoCu@NCNT material, indicating that more metal active sites are successfully exposed during the calcination process in an oxidizing atmosphere. However, the selectivity of styrene for the CoCu@NCNT material is better than that of the Co@NCNT, which are 92% and 73% respectively, indicating that this catalyst has more excellent performance in the selective hydrogenation reaction of phenylacetylene.

[0039] Example 2

[0040] This example provides a preparation method of a nitrogen-doped carbon nanotube material loaded with cobalt-copper bimetal, including the following steps:

[0041] (1) Add 0.06 mol of 2-methylimidazole to 10 mL of deionized water and dissolve it by ultrasonic treatment for 20 min to obtain a 2-methylimidazole solution; dissolve 0.005 mol of cobalt acetate and 0.0006 mol of copper acetate in deionized water to obtain a metal salt solution.

[0042] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 15 min to obtain a CoCu-ZIF suspension. Centrifuge the obtained CoCu-ZIF suspension at 5000 r / min for 2 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 70 °C for 15 h to obtain the CoCu-ZIF material.

[0043] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tube furnace, under a hydrogen-argon atmosphere, heat it at a heating rate of 2 °C / min to 700 °C, calcine it at 700 °C for 2.5 h, cool it to 250 °C, switch the calcination gas to an oxygen-argon mixture, calcine it at 250 °C for 40 min, then switch the gas to a hydrogen-argon mixture, heat it at a heating rate of 2 °C / min to 300 °C, calcine it at 300 °C for 3 h, cool it to room temperature and take it out to obtain the 2# CoCu / NCNT material.

[0044] Example 3

[0045] This example provides a preparation method of a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals, including the following steps:

[0046] (1) Add 0.06 mol of 2-methylimidazole to 10 mL of deionized water, dissolve it by ultrasonic treatment for 20 min to obtain a 2-methylimidazole solution; dissolve 0.0055 mol of cobalt acetate and 0.0005 mol of copper acetate in deionized water to obtain a metal salt solution.

[0047] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 20 min to obtain a CoCu-ZIF suspension. Centrifuge the obtained CoCu-ZIF suspension at 6000 r / min for 1 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 70 °C for 18 h to obtain the CoCu-ZIF material.

[0048] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tube furnace, under a hydrogen-argon atmosphere, heat it at a heating rate of 2 °C / min to 600 °C, calcine it at 600 °C for 3 h, cool it to 250 °C, switch the calcination gas to an oxygen-argon mixture, calcine it at 250 °C for 50 min, then switch the gas to a hydrogen-argon mixture, heat it at a heating rate of 2 °C / min to 290 °C, calcine it at 290 °C for 3 h, cool it to room temperature and take it out to obtain the 3# CoCu / NCNT material.

[0049] Example 4

[0050] This example provides a preparation method of a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals, including the following steps:

[0051] (1) Add 0.05 mol of 2-methylimidazole to 10 mL of deionized water and dissolve it by ultrasonic treatment for 20 min to obtain a 2-methylimidazole solution; dissolve 0.005 mol of cobalt acetate and 0.0006 mol of copper acetate in deionized water to obtain a metal salt solution.

[0052] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 10 min to obtain a CoCu-ZIF suspension, centrifuge the obtained CoCu-ZIF suspension at 4000 r / min for 2 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 60 °C for 14 h to obtain a CoCu-ZIF material.

[0053] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tubular furnace, under a hydrogen-argon atmosphere, heat it at a heating rate of 2 °C / min to 800 °C, calcine it at 800 °C for 3 h, cool it to room temperature and then take it out to obtain a 4#C / CoCu@NCNT material.

[0054] Example 5

[0055] This example provides a preparation method of a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals, including the following steps:

[0056] (1) Add 0.07 mol of 2-methylimidazole to 10 mL of deionized water and dissolve it by ultrasonic treatment for 40 min to obtain a 2-methylimidazole solution; dissolve 0.004 mol of cobalt acetate and 0.0006 mol of copper acetate in deionized water to obtain a metal salt solution.

[0057] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 15 min to obtain a CoCu-ZIF suspension, centrifuge the obtained CoCu-ZIF suspension at 4000 r / min for 2 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 70 °C for 14 h to obtain a CoCu-ZIF material.

[0058] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tubular furnace, under a hydrogen-argon atmosphere, heat it at a heating rate of 2 °C / min to 800 °C, calcine it at 750 °C for 3 h, cool it to 250 °C, switch the calcination gas to an oxygen-argon mixed gas, calcine it at 250 °C for 30 min, then switch the gas to a hydrogen-argon mixed gas, heat it at a heating rate of 2 °C / min to 300 °C, calcine it at 300 °C for 3 h, cool it to room temperature and then take it out to obtain a 5#CoCu / NCNT material.

[0059] Example 6

[0060] This embodiment provides a method for preparing a cobalt-copper bimetal-loaded nitrogen-doped carbon nanotube material, comprising the following steps:

[0061] (1) Add 0.03 mol of 2-methylimidazole to 10 mL of deionized water, and ultrasonically dissolve it for 20 min to obtain a 2-methylimidazole solution; dissolve 0.004 mol of cobalt acetate and 0.0006 mol of copper acetate in deionized water to obtain a metal salt solution.

[0062] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 15 min to obtain a CoCu-ZIF suspension, centrifuge the obtained CoCu-ZIF suspension at 6000 r / min for 2 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 65 °C for 15 h to obtain a CoCu-ZIF material.

[0063] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tube furnace, under a hydrogen-argon atmosphere, heat it at a heating rate of 2 °C / min to 700 °C, calcine it at 650 °C for 2 h, cool it to 250 °C, switch the calcination gas to an oxygen-argon mixture, calcine it at 300 °C for 30 min, then switch the gas to a hydrogen-argon mixture, heat it at a heating rate of 2 °C / min to 300 °C, calcine it at 300 °C for 3 h, cool it to room temperature and take it out to obtain the 6# CoCu / NCNT material.

[0064] Example 7

[0065] This embodiment provides a method for preparing a cobalt-copper bimetal-loaded nitrogen-doped carbon nanotube material, comprising the following steps:

[0066] (1) Add 0.06 mol of 2-methylimidazole to 10 mL of deionized water, and ultrasonically dissolve it for 20 min to obtain a 2-methylimidazole solution; dissolve 0.0055 mol of cobalt acetate and 0.0005 mol of copper acetate in deionized water to obtain a metal salt solution.

[0067] (2) Add the metal salt solution in step (1) to the 2-methylimidazole solution to obtain a mixed solution; let it stand for 20 min to obtain a CoCu-ZIF suspension, centrifuge the obtained CoCu-ZIF suspension at 6000 r / min for 1 min, wash it by centrifugation with anhydrous methanol several times, and dry it at 70 °C for 18 h to obtain a CoCu-ZIF material.

[0068] (3) Weigh 0.6 g of the CoCu-ZIF material obtained in step (2) into a quartz boat, place it in a tubular furnace, and under an argon atmosphere, heat it to 800 °C at a heating rate of 2 °C / min, calcine it at 800 °C for 3 h, take it out after cooling to room temperature to obtain the 7# CoCu@NC material.

[0069] Example 8: Test reaction for selective hydrogenation of phenylacetylene catalyzed by cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material

[0070] Add 30 mg of the catalyst (the 1# CoCu / NCNT material prepared in Example 1 or the C / CoCu / NCNT material or Co / NCNT material prepared in Example 4) into a 25 mL Schlenk tube, then add 0.1 mmol of phenylacetylene and 5 mL of ethanol. After the addition is completed, use a vacuum pump to evacuate the air in the tube, and then introduce hydrogen. Then, place the Schlenk tube in an oil bath at 60 °C for heating reaction, adjust the stirrer knob to 25, and let the system react continuously for 3.5 h under a hydrogen environment of 0.1 MPa. After the reaction is completed, take out the black reaction solution in the Schlenk tube and achieve solid-liquid separation by magnetic recovery. Analyze the composition of the obtained liquid with an Agilent gas chromatography-mass spectrometry (GC-MS). Finally, obtain the conversion rate of phenylacetylene and the selectivity of styrene.

[0071] The above embodiments are only specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a cobalt-copper bimetal-loaded nitrogen-doped carbon nanotube material, characterized in that It includes the following steps: (1) Add 2-methylimidazole to deionized water, and ultrasonically dissolve it evenly to obtain an organic ligand solution; dissolve cobalt acetate and copper acetate in deionized water to obtain a metal salt solution; (2) Stir and mix the metal salt solution described in step (1) with the organic ligand solution, let it stand and then centrifuge, wash and dry the precipitate to obtain a CoCu-ZIF material; (3) Calcinate the CoCu-ZIF material described in step (2) successively in a reducing atmosphere, an oxidizing atmosphere, and a reducing atmosphere to obtain a nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals.

2. The preparation method of the cobalt and copper bimetal loaded nitrogen-doped carbon nanotube material according to claim 1, wherein, In step (1), the ratio of cobalt acetate, copper acetate and deionized water in the metal salt solution is (3-6) mmol:(0.21-0.72) mmol:10 mL; the ratio of 2-methylimidazole and deionized water in the organic ligand solution is (21-60) mmol:10 mL.

3. The preparation method of the cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material according to claim 1, wherein In step (1), the time for ultrasonic dissolution is 20-50 min.

4. The preparation method of the cobalt and copper bimetal loaded nitrogen-doped carbon nanotube material according to claim 1, characterized in that, In step (2), the mixing order is to pour the metal salt solution into the organic ligand solution; the volume ratio of the metal salt solution to the organic ligand solution added is 2-10:5-10.

5. The preparation method of the cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material according to claim 1, wherein, In step (2), the stirring temperature is 20-30 °C, and the standing time is 10-30 min.

6. The preparation method of the cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material according to claim 1, characterized in that, In step (2), the centrifugation speed is 4000-6000 r / min, the centrifugation time is 2-5 min, the washing liquid is 20-40 mL of methanol, and the precipitate is centrifuged and washed 2 times; the drying temperature is 60-75 °C, and it is dried for 18-24 h.

7. The preparation method of the cobalt and copper bimetal loaded nitrogen-doped carbon nanotube material according to claim 1, wherein, In step (3), the reducing atmosphere is a hydrogen-argon mixed gas, the volume fraction of hydrogen is 10%-20%, the gas flow rate is 40-60 mL / min; the calcination temperature is 600-800 °C, the calcination time is 2-5 h, and the heating rate is 2-5 °C / min.

8. The preparation method of the cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material according to claim 1, characterized in that In step (3), the oxidizing atmosphere is an oxygen-argon mixed gas, the volume fraction of oxygen is 3%-10%, the gas flow rate is 40-60 mL / min, the calcination temperature is 200-300 °C, and the calcination time is 10-60 min.

9. The preparation method of the cobalt and copper bimetal-loaded nitrogen-doped carbon nanotube material according to claim 1, wherein In step (3), the reducing atmosphere is a hydrogen-argon mixed gas, the volume fraction of hydrogen is 10%-20%, the gas flow rate is 40-60 mL / min, the calcination temperature is 250-300 °C, and the calcination time is 2-5 h.

10. A cobalt-copper bimetallic nitrogen-doped carbon nanotube material prepared by the preparation method according to any one of claims 1-9, characterized in that, The nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals has a hollow dodecahedron structure. The hollow carbon carrier is composed of carbon nanotubes. The top of the carbon nanotubes is cobalt and copper bimetal nanoparticles with a diameter of 10-17 nm. The cavity diameter is 700-900 nm, and the thickness of the hollow carbon layer is 80-250 nm; the selectivity of the nitrogen-doped carbon nanotube material loaded with cobalt and copper bimetals in the selective hydrogenation reaction of phenylacetylene is 70%-92%.

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