Porous carbon material loaded bimetallic CuCo / C composite material, preparation method and application in methanol carbonylation
By loading bimetallic CuCo/C composite materials on porous carbon materials and introducing nitrogen-containing groups, the problem of copper-based catalyst agglomeration in methanol oxidation carbonylation reaction is solved, and catalytic activity and stability are improved, which significantly improves the reaction efficiency and product selectivity.
Patent Information
- Application Number
- CN202510354631.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2025-06-24
AI Technical Summary
Existing copper-based catalysts are prone to agglomeration and oxidation of copper nanoparticles in methanol oxidation carbonylation reaction, resulting in a reduction in catalytic activity and an increase in production costs.
Freeze-drying and calcining methods were used to prepare bimetallic CuCo/C composites supported by porous carbon material, and copper-cobalt was supported on its surface, and nitrogen-containing groups were introduced to improve the stability and catalytic performance of the catalyst.
By limiting the synergistic effects of structure and nitrogen doping, the agglomeration of copper nanoparticles is effectively prevented, catalytic activity and stability are improved, and the efficiency and product selectivity of methanol oxidation carbonylation reaction are significantly improved.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of porous carbon materials, and specifically relates to the application of a bimetallic CuCo / C composite material supported on a porous carbon material and a preparation method thereof in methanol carbonylation. Background Art
[0002] With the increasing demand for efficient and environmentally friendly solutions in various industries, the market prospect of DMC has become very broad. Especially in the current global environment dedicated to achieving the "dual carbon" goal, DMC is gradually becoming one of the important options for the upgrading of many chemical products due to its excellent physical and chemical properties and environmentally friendly characteristics. In traditional commercial copper-based chlorine-containing catalysts, the loss of Cl − is extremely likely to cause catalyst deactivation and equipment corrosion problems, which to a certain extent increases the production cost. The catalyst prepared with chlorine-free copper as the copper source has good catalytic activity. Although it can fundamentally solve the problems caused by the loss of Cl − the loss and aggregation of copper nanoparticles during the liquid-phase reaction process have become one of the main obstacles to the commercialization of this new type of catalyst. Therefore, choosing a suitable catalyst support to improve and enhance the dispersion and stability of copper nanoparticles is a key issue in the methanol oxidative carbonylation reaction.
[0003] Carbon materials such as graphene, activated carbon (AC), etc. usually have a large specific surface area, which can provide more anchoring sites for the active metal copper, enabling Cu nanoparticles to be evenly dispersed on its surface, increasing the effective contact area between the catalytic active center and the reactants, and thus significantly improving the catalytic activity. Using carbon materials to support copper-based catalysts for the oxidative carbonylation of methanol to prepare high-value-added chemical products such as dimethyl carbonate is an important development direction for the clean and efficient utilization of coal. However, the copper nanoparticles in the carbon material-supported Cu-based catalysts are prone to agglomeration and oxidation during the methanol oxidative carbonylation catalysis process. Controlling the Cu species through heteroatom doping and the structural limitation of the carbon material support to develop highly efficient carbon material-supported Cu-based catalysts is the key to the industrialization of the synthesis of DMC by methanol oxidative carbonylation.
[0004] Through the confinement effect of porous carbon materials, active copper species can be confined in the pores of the materials, which can effectively prevent the aggregation of copper particles and improve the catalytic activity. Since the cavities existing inside the hollow bell-shaped nanomaterials can be used as nanoreactors, these cavities can provide a favorable homogeneous environment for the encapsulated core components. In addition, the geometric space confinement effect in the support material can effectively prevent the aggregation and leaching of the active copper core components. Most of the reported methods for stabilizing copper nanoparticles, such as embedding in inert carriers, are mainly aimed at forming a confinement system. Based on this confinement effect, the selection and regulation of copper nanoparticles provide an effective way to solve the stability problem. However, the construction process of the confinement space in most porous carbon materials is complex and costly, and these preparation methods are highly specific for coating noble metal nanoparticles. To meet the demands for nanomaterials with confinement effects in multiple fields, especially non-noble metal catalysts widely used in scientific research and industrial fields, it is of great significance to propose a simple and general synthesis strategy.
[0005] Through the structural confinement of carbon materials and the doping of nitrogen species, the copper particles in the catalyst can be effectively controlled, thereby enhancing the catalytic performance. The doped nitrogen species can enhance the charge transfer ability and promote the adsorption of reaction gases, especially CO, on the active copper sites on the catalyst surface, and then continuously accelerate the rate-determining step of CO insertion. In the catalytic reaction, the encapsulation of graphene can significantly improve the stability and recyclability of the catalyst. When metal nanoparticles are encapsulated in graphene, the existence of the space confinement effect can effectively prevent the aggregation of copper nanoparticles. Secondly, the metal nanomaterials encapsulated by graphene have unique electron transport capabilities and interfacial catalytic characteristics. The effective electron transfer from the metal to the shell layer can enhance the catalytic activity of the material in specific reaction processes. The introduction of nitrogen species can provide more anchoring sites for active metals and improve the dispersion of metal nanoparticles. The improvement of the catalytic activity of copper-based catalysts supported on nitrogen-doped carbon materials is mainly attributed to the synergistic catalytic effect between the confinement structure and nitrogen species, which not only promotes the dispersion of copper nanoparticles but also reduces the possibility of leaching, agglomeration, and oxidation of active copper species during the reaction. Therefore, there is an urgent need to develop new technologies that combine confinement technology and doping technology to fully utilize the dual advantages of space confinement and heteroatom doping. In summary, utilizing the defects in nitrogen-doped carbon materials is an effective way to improve the catalytic activity of carbon-supported copper-based catalysts. Summary of the Invention
[0006] The object of the present invention is to provide a porous carbon material-supported bimetallic CuCo / C composite material and its preparation method. CuCo-NC is obtained by freeze-drying and calcination methods and copper cobalt is loaded on the surface. Nitrogen-containing groups are introduced into the carbon material carrier to promote the stability of copper cobalt species nanoparticles in the methanol oxidative carbonylation reaction and improve its catalytic performance.
[0007] To achieve the above object, the present invention adopts the following specific technical solutions: A bimetallic CuCo / C composite material supported on a porous carbon material, and its preparation method includes the following steps: (1) Stir a certain amount of NaCl, glucose, copper nitrate trihydrate and cobalt nitrate hexahydrate in deionized water, then react in an oil bath for 1 to 5 hours, and cool the product to room temperature; (2) Place the cooled liquid in a container and freeze it, quickly freeze it into a solid with liquid nitrogen and then transfer it to a freeze dryer, evacuate and perform freeze drying; (3) Calcinate the freeze-dried product in a tube furnace under a nitrogen atmosphere, at a temperature of 700 °C to 1000 °C, for 1 to 5 hours, preferably 2 hours; (4) Add water to the calcined product, ultrasonicate, stir, filter and wash to easily remove the sodium chloride template; (5) After drying in a vacuum oven at 50 °C, the obtained product is CuCo-NC.
[0008] Further, in step (1), the reaction temperature in the oil bath is 50 °C to 100 °C, preferably 75 °C; the time is 1 to 5 hours, preferably 2 hours; Further, in step (2), the freeze drying is carried out under vacuum, at a temperature of -90 °C to -40 °C, preferably -80 °C, and the time is 10 to 15 hours, preferably 12 hours; Further, in step (3), the calcination is carried out in a nitrogen atmosphere, the heating rate is 5 °C / min, the temperature is 700 °C to 1000 °C, preferably 900 °C; In the present invention, the stirring is mechanical stirring, and the reduction reaction is carried out under a nitrogen atmosphere.
[0009] The present invention first prepares a uniformly porous and high specific surface area CuCo-NC material by freeze drying and calcination methods. It can be used as an excellent carrier to support copper and cobalt. The higher specific surface area is beneficial for the catalyst to contact with the reactants CO and methanol, which is beneficial for the reaction to proceed.
[0010] The present invention applies a quantitative bimetallic CuCo / C composite material supported to methanol carbonylation, uses gas chromatography to detect the generated concentration of dimethyl carbonate, and finds the optimal conditions for methanol oxidative carbonylation.
[0011] Advantages of the present invention: 1. Innovatively adopt the green template agent sodium chloride, improve the problem that other types of hard templates (such as SiO2, PMMA, etc.) are difficult to remove, and prepare a porous nitrogen-doped carbon material; 2. The problem of easy aggregation of copper nanoparticles was stabilized by using bimetal (the interaction between Cu and Co), the reactive sites were increased, and the reaction performance was enhanced. 3. The in-situ synthesis method was adopted in this invention, which is simple to prepare and easy to realize batch production. Description of the Drawings
[0012] Figure 1 Electron transmission image (TEM), STEM, and EDS mapping images of CuCo-NC; Figure 2 XRD of Cu-NC, Co-NC, and CuCo-NC; Figure 3 Reaction performance of Cu-NC, Co-NC, and CuCo-NC in the liquid-phase oxidative carbonylation of methanol. Detailed Description of the Invention
[0013] This patent invented a preparation method of copper-cobalt nanoparticles supported on nitrogen-doped carbon and explored its application in the oxidative carbonylation of methanol. The specific method is as follows: (1) A composite material of porous nitrogen-doped carbon supported with copper-cobalt nanoparticles was prepared by the template method; (2) The prepared material was applied to the performance evaluation of the oxidative carbonylation of methanol. Example Preparation of a composite material of porous nitrogen-doped carbon supported with copper-cobalt nanoparticles, and the specific steps are as follows: 1. Preparation of Co-NC catalyst First, weigh 17 g of sodium chloride, 1.24 g of glucose, 3.6 g of dicyandiamide, and 320 mg of cobalt nitrate hexahydrate and add them to 200 ml of deionized water. Then, place the solution in an oil bath and heat it to 75 °C and keep it for 2 h (rotation speed is 300 rpm), and then cool the product to room temperature. Put the cooled liquid into a container and freeze it, quickly freeze-dry it into a solid with liquid nitrogen and then transfer it to a freeze dryer, evacuate and conduct freeze-drying (-80 °C, 24 h). Place the freeze-dried product in a tubular furnace under N2 atmosphere and heat the precursor powder to 800 °C at a heating rate of 5 °C / min and keep it for 3 hours. After cooling to room temperature, wash the powder with deionized water to remove the sodium chloride template, then filter and place it in a vacuum oven at 50 °C for drying for 6 h. Then, heat the powder in a tubular furnace under N2 atmosphere again at a heating rate of 5 °C / min to 900 °C and keep it for 1 hour, and cool it to room temperature to obtain the Co-NC catalyst.
[0014] 2. Preparation of Cu-NC catalyst First, weigh 17 g of sodium chloride, 1.24 g of glucose, 3.6 g of dicyandiamide, and 960 mg of copper nitrate trihydrate, and add them to 200 ml of deionized water. Then, place the solution in an oil bath and heat it to 75 °C and maintain for 2 h (rotation speed is 300 rpm), and then cool the product to room temperature. Put the cooled liquid into a container and freeze it, quickly freeze-dry it into a solid with liquid nitrogen, then transfer it to a freeze dryer, evacuate and perform freeze-drying (-80 °C, 24 h). Place the freeze-dried product in a tubular furnace under N2 atmosphere and heat the precursor powder to 800 °C at a heating rate of 5 °C / min and maintain for 3 hours. After cooling to room temperature, wash the powder with deionized water to remove the sodium chloride template, then filter and place it in a vacuum oven at 50 °C for 6 h. Then, heat the powder in a tubular furnace under N2 atmosphere again to 900 °C at a heating rate of 5 °C / min and maintain for 1 hour, and cool to room temperature to obtain the Cu-NC catalyst.
[0015] 3. Preparation of CuCo-NC catalyst To investigate the effect of different Co / Cu ratios on the catalytic performance of the liquid-phase oxidative carbonylation of methanol to dimethyl carbonate, a series of copper-cobalt supported NC catalysts with different Co / Cu ratios were prepared using copper nitrate and cobalt nitrate. Taking the CuCo-NC catalyst as an example: First, weigh 17 g of sodium chloride, 1.24 g of glucose, 3.6 g of dicyandiamide, 960 mg of copper nitrate trihydrate, and 1485.957 mg of cobalt nitrate hexahydrate, and add them to 200 ml of deionized water. Then, place the solution in an oil bath and heat it to 75 °C and maintain for 2 h (rotation speed is 300 rpm), and then cool the product to room temperature. Put the cooled liquid into a container and freeze it, quickly freeze-dry it into a solid with liquid nitrogen, then transfer it to a freeze dryer, evacuate and perform freeze-drying (-80 °C, 24 h). Place the freeze-dried product in a tubular furnace under N2 atmosphere and heat the precursor powder to 800 °C at a heating rate of 5 °C / min and maintain for 3 hours. After cooling to room temperature, wash the powder with deionized water to remove the sodium chloride template, then filter and place it in a vacuum oven at 50 °C for 6 h. Then, heat the powder in a tubular furnace under N2 atmosphere again to 900 °C at a heating rate of 5 °C / min and maintain for 1 hour, and cool to room temperature to obtain the CuCo-NC catalyst.
[0016] The dispersion of copper and cobalt nanoparticles in the prepared CuCo-NC catalyst was observed by TEM images, and the results are as Figure 1As shown. It can be seen from the figure that the prepared catalyst exhibits an obvious porous structure, with uniformly distributed pores visible in the image. These pores are of moderate size and regular shape, constituting the porous network of the catalyst. Further observation reveals that metal nanoparticles are uniformly dispersed in these porous structures, with uniform particle sizes and no significant agglomeration. At the same time, through energy-dispersive X-ray spectroscopy (EDS) elemental mapping analysis, the distribution of metal elements on the catalyst support is uniform, without local enrichment, further confirming the uniform dispersion of metal nanoparticles in the porous material. These results together indicate that the interaction between nitrogen and copper and cobalt inhibits the aggregation of metal particles, promotes the uniform distribution of elements, and thus enhances the activity and stability of the CuCo-NC catalyst.
[0017] In the X-ray diffraction (XRD) pattern analysis ( Figure 2 ), we observed that the diffraction peaks of the prepared samples showed good agreement with the standard cards PDF#04-0386 and PDF#15-0806 of copper-cobalt alloy. The diffraction peaks at approximately 2θ angles of 44.3°, 51.5°, and 76.0° in the pattern are consistent with the Cu-Co in PDF#04-0386 and PDF#15-0806, indicating that copper and cobalt elements form an alloy structure. The intensity and position of the diffraction peaks match the characteristic peaks in the standard cards, and no obvious impurity peaks are seen, confirming the successful synthesis of the copper-cobalt alloy catalyst. By comparing the experimental pattern with the standard cards, we determined the crystal structure of the copper-cobalt alloy in the catalyst.
[0018] Application Example: Performance Evaluation of Methanol Oxidative Carbonylation The methanol oxidative carbonylation reaction was carried out in a 25 ml stainless steel autoclave. Before each experiment, a mixed solution of the catalyst, biphenyl, and methanol was first added to the autoclave, and it was purged with CO three times before the reaction to remove the residual air in the reactor. Then, CO and O2 were charged into the autoclave in proportion to the required pressure. After heating to a certain temperature (80 - 120 °C), stirring (300 r / min) was started. After the autoclave was cooled to room temperature, the remaining mixed gas in the autoclave was emptied, and the reaction liquid and the remaining gas mixture in the autoclave were collected and subjected to chromatographic analysis.
[0019] From Figure 3 the catalyst evaluation results, it can be seen that the DMC selectivity of the three catalysts is higher than 90%, and the DMC selectivity of the CuCo-NC catalyst is as high as 98%.
[0020] The methanol conversion rate of the Cu-NC catalyst reached 1.38% at 2 h of reaction, while the methanol conversion rate of the Co-NC catalyst was only 1.29% at 2 h of reaction. The methanol conversion rate of the copper-cobalt catalyst supported on the modified carbon carrier (CuCo-NC) increased significantly, reaching as high as 6.94% at 2 h of reaction.
[0021] The space-time yield of the Cu-NC catalyst reached 0.75 g / (g·h) at 2 h of reaction, while the space-time yield of the Co-NC catalyst was only 0.67 g / (g·h) at 2 h of reaction. The space-time yield of the copper-cobalt catalyst supported on the modified carbon carrier (CuCo-NC) increased significantly, reaching as high as 3.61 g / (g·h) at 2 h of reaction.
[0022] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.
Claims
1. A method for preparing a bimetallic CuCo / C composite material supported by a porous carbon material, characterized in that: The following steps are involved: (1) NaCl, glucose, copper nitrate trihydrate and cobalt nitrate hexahydrate are stirred in deionized water, then reacted in an oil bath, and the product is cooled to room temperature; (2) placing the cooled liquid into a container and freezing it, quickly freezing it into a solid with liquid nitrogen, and then transferring it to a freeze dryer, vacuuming it, and freeze-drying it; (3) calcining the freeze-dried product in a tube furnace under a nitrogen atmosphere; (4) After calcination, the product is ultrasonically added with water, stirred, filtered, and washed to easily remove the sodium chloride template; (5) After drying in a vacuum oven at 50 °C, the product obtained was CuCo-NC.
2. The preparation method according to claim 1, characterized in that: Step (1) The reaction temperature in the oil bath is 50°C to 100°C.
3. The preparation method according to claim 1, characterized in that: The reaction time in step (1) in the oil bath is 1-5 hours.
4. The preparation method according to claim 1, characterized in that: Step (2) freeze drying is carried out under vacuum at a temperature of -90°C to -40°C.
5. The preparation method according to claim 1, characterized in that: Step (2) freeze drying is carried out under vacuum for 10-15 hours.
6. The preparation method according to claim 1, characterized in that: Step (3) calcination is carried out in a nitrogen atmosphere, with a heating rate of 5°C / min and a temperature of 700°C to 1000°C.
7. The preparation method according to claim 1, characterized in that: Step (3) calcination is carried out in a nitrogen atmosphere for 1-5 hours.
8. A bimetallic CuCo / C composite material supported by a porous carbon material obtained by the preparation method according to any one of claims 1 to 7.
9. Use of the bimetallic CuCo / C composite material supported by the porous carbon material as claimed in claim 8 in methanol carbonylation.