Preparation method of cheap metal nano Cu complex catalyst
A cost-effective nano-Cu complex catalyst is developed using copper, 3-thiophene propanoic acid, and 2,2'-bipyridine, addressing the high cost of noble metals by providing a stable and efficient catalytic solution for diverse chemical reactions.
Patent Information
- Application Number
- CN202510466816.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-07-15
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Precious metal catalyst resources are scarce and expensive, and are not suitable for large-scale factory applications.
Using the preparation method of cheap metal nanoCu complex catalyst, the nanoCu complex catalyst was obtained by reacting copper acetate, 3-thiophenemalonic acid, 2,2'-bipyridine and polyvinylpyrrolidone in an ethanol-water solvent to form blue needle-like crystals, and the nanoCu complex catalyst was obtained by centrifugation, washing and vacuum drying.
It achieves efficient and stable catalytic effect, is low-cost, and is suitable for a variety of reaction systems, especially Knoevenagel condensation reaction.
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Figure CN120309639A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of catalyst preparation, and specifically to a preparation method of a cheap metal nano Cu complex catalyst. Background Art
[0002] A catalyst generally refers to a substance that increases the reaction rate without changing the total standard Gibbs free energy change of the reaction, or can also be expressed as a substance that can increase the chemical reaction rate in a chemical reaction without changing the chemical equilibrium, and whose own mass and chemical properties do not change before and after the chemical reaction. According to statistics, more than 90% of industrial processes use catalysts, such as chemical engineering, petrochemical, biochemical, environmental protection, etc. There are many types of catalysts. According to the state, they can be divided into liquid catalysts and solid catalysts; according to the phase state of the reaction system, they are divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts include acids, bases, soluble transition metal compounds, and peroxide catalysts.
[0003] In the preparation process of catalysts, due to the high catalytic activity of noble metals, noble metals are commonly used as catalysts. However, noble metal resources are scarce and expensive, and the cost of using noble metal catalysts is relatively high, which is not suitable for large-scale factory applications.
[0004] Therefore, we make improvements and propose a preparation method of a cheap metal nano Cu complex catalyst. Summary of the Invention
[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0006] A preparation method of a cheap metal nano Cu complex catalyst of the present invention includes the following steps:
[0007] S1. Mixing and dissolving: Add copper acetate, 3-thiophene malonic acid, 2,2'-bipyridine, and polyvinylpyrrolidone into an ethanol-water mixed solvent, and stir at room temperature until completely dissolved to obtain a mixed solution;
[0008] S2. Reaction and crystallization: Continuously stir the mixed solution for 2 - 24 hours, and blue needle-like crystals gradually precipitate during the reaction of the mixed solution;
[0009] S3. Separation and purification: Collect the blue needle-like crystals by centrifugation or filtration;
[0010] S4. Washing and drying: Wash the collected blue needle-like crystals with ethanol, and obtain the nano Cu complex catalyst through vacuum drying.
[0011] As a preferred technical solution of the present invention, the chemical formula of the nano-Cu complex catalyst is [Cu(TMA)(bpy)(H2O)], where TMA is 3-thiophene malonic acid, bpy is 2,2'-bipyridine, and TMA and bpy are 0D coordination molecules with a spatial structure, and the central Cu(II) ion has a coordination environment of a distorted tetrahedron.
[0012] As a preferred technical solution of the present invention, the microstructure of the blue needle-like crystals can be observed by electron microscopy characterization, and the microstructure range of the blue needle-like crystals is in the nano-scale.
[0013] As a preferred technical solution of the present invention, the size of the crystals is 50 - 500 nm.
[0014] As a preferred technical solution of the present invention, the test method of the blue needle-like crystals can catalyze the Knoevenagel condensation reaction at room temperature.
[0015] As a preferred technical solution of the present invention, the substrates of the Knoevenagel condensation reaction include a combination of aromatic aldehydes and active methylene compounds, and the catalyst dosage is 0.5% - 5% of the total molar amount of the substrates.
[0016] As a preferred technical solution of the present invention, the volume ratio of ethanol to water is 3:1.
[0017] As a preferred technical solution of the present invention, the molar ratio of copper acetate, 3-thiophene malonic acid, and 2,2'-bipyridine is 1:(0.8 - 1.2):(0.8 - 1.2), and the addition amount of polyvinylpyrrolidone is 0.5% - 5% of the total mass of the reaction system.
[0018] The beneficial effects of the present invention are:
[0019] In the present invention, a cheap metal Cu is used as the catalytic active center site, abandoning the choice of using precious metals in traditional catalysts, and through experiments, it is proved that its catalytic effect is still efficient and stable. Compared with traditional precious metal catalysts, the present invention has low cost, has a significant cost advantage compared with other precious metal catalysts, and is applicable to a variety of reaction systems. Description of the Drawings
[0020] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:
[0021] Figure 1 It is a schematic flow structure diagram of a preparation method of a cheap metal nano-Cu complex catalyst of the present invention; Detailed Embodiments
[0022] The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.
[0023] Embodiment: As Figure 1 shown, a method for preparing a cheap metal nano Cu complex catalyst of the present invention includes the following steps:
[0024] S1. Mixing and dissolving: Copper acetate, 3-thiophene malonic acid, 2,2'-bipyridine, and polyvinylpyrrolidone are added to an ethanol-water mixed solvent and stirred at room temperature until completely dissolved to obtain a mixed solution; copper acetate has a low solubility in pure water but is soluble in ethanol. When adding, copper acetate needs to be added first to dissolve it to avoid local precipitation and the introduction of undissolved metal salt particles; 2,2'-bipyridine, as a bidentate ligand, is prone to form a complex with Cu 2+ If added too early, it may cause the solution to become turbid. It needs to be added slowly after the metal salt is dissolved. 3-thiophene malonic acid also needs to be added after copper acetate. Polyvinylpyrrolidone, as a stabilizer, can inhibit the aggregation of metal particles, so it is added after the system is completely dissolved. When adding, it needs to be added drop by drop and continuously stirred to avoid a sudden increase in the solution viscosity caused by the entanglement of polymer chains.
[0025] The carboxylic acid group of 3-thiophene malonic acid will release H + , which may affect the coordination stability of 2,2'-bipyridine and Cu 2+ . Therefore, during the preparation, it can be considered to adjust the pH to 6-7 with a weak base (such as NaHCO3) to maintain the stability of the coordination structure.
[0026] S2. Reaction crystallization: The mixed solution is continuously stirred for 2-24 hours, and blue needle-shaped crystals gradually precipitate during the reaction; the stirring speed during stirring is 300-500 rpm to avoid violent shearing from damaging crystal nucleation. The blue needle-shaped crystals usually start to precipitate in 12-18 hours. Therefore, existing monitoring equipment needs to be used to monitor the change in the turbidity of the solution in real time. If the solution becomes turbid or non-needle-shaped precipitates appear during the reaction, it needs to be filtered through a 0.22 μm filter membrane and then recrystallization is triggered.
[0027] The reaction temperature is 23°C - 27°C, and the temperature fluctuation needs to be controlled within 1°C, and the temperature of each part needs to be kept uniform. Local overheating may cause irregular crystal morphology.
[0028] S3. Separation and purification: The blue needle-shaped crystals are collected by centrifugation or filtration; centrifugation at 800-1000 rpm for 10-15 minutes can be used, avoiding too high a rotation speed from causing the needle-shaped crystals to break or the structure to deform, and it is preferred to use a polypropylene centrifuge tube to avoid the crystals being broken due to collision with a glass tube.
[0029] S4. Washing and Drying: Wash the collected blue needle-like crystals with ethanol, which can effectively remove the residual polyvinylpyrrolidone and unreacted organic ligands. The nano-Cu complex catalyst is obtained by vacuum drying. The drying temperature should be ≤60 °C to prevent crystal form transformation, and nitrogen is introduced into the vacuum drying oven for protection to avoid the oxidation of Cu 2+ oxidation.
[0030] The chemical formula of the nano-Cu complex catalyst is [Cu(TMA)(bpy)(H2O)], where TMA is 3-thiophene malonic acid, bpy is 2,2'-bipyridine, and TMA and bpy are 0D coordination molecules with a spatial structure. The central Cu(II) ion has a distorted tetrahedral coordination environment.
[0031] The microstructure of the blue needle-like crystals can be observed by electron microscopy characterization. When using an electron microscope for observation, a high-resolution mode needs to be adopted, and the low-dose mode should be turned on to protect sensitive areas. Moreover, the microstructure range of the blue needle-like crystals is in the nanometer size. The size of the crystals is 50 - 500 nm.
[0032] The inspection method of the blue needle-like crystals can be to catalyze the Knoevenagel condensation reaction at room temperature. The substrates of the Knoevenagel condensation reaction include a combination of aromatic aldehydes and active methylene compounds. The catalyst dosage is 0.5% - 5% of the total molar amount of the substrates.
[0033] Before the reaction, the blue needle-like crystals need to be dried to remove the ethanol molecules or water molecules adsorbed on the surface, avoiding the inhibition of the exposure of active sites by solvent residues. During the reaction, benzaldehyde, 4-nitrobenzaldehyde, 4-methoxybenzaldehyde, and furfural can be selected as substrates respectively, and the catalyst prepared in this application is added to compare the catalytic efficiency of each reaction. The experimental results are shown in Table 1 below:
[0034] Substrate type Conversion rate (%) Selectivity (%) Reaction time (h) Benzaldehyde 98 >99 12 4-Nitrobenzaldehyde 97 98 10 4-Methoxybenzaldehyde 85 95 24 Furfural 92 97 15
[0035] The reaction conditions for each reaction in Table 1 above are: 0.5 mol% of the catalyst, reaction temperature 25 °C, and reaction time 12 hours.
[0036] The conversion rate (%) in Table 1 refers to the proportion of the substrate converted into the target product, reflecting the activation ability of the catalyst for the reaction. For example, the conversion rate of benzaldehyde reaches 98%, indicating that nearly all the substrates participate in the reaction.
[0037] The selectivity (%) in Table 1 refers to the proportion of the target product among all the products, reflecting the directional regulation ability of the catalyst. The selectivity of benzaldehyde > 99% indicates that there are very few side reactions.
[0038] In Table 1, the reaction time (h) refers to the duration required to reach the highest conversion rate, reflecting the improvement effect of the catalyst on the reaction rate. An electron-withdrawing group (such as -NO2) can shorten the reaction time to 10 hours, while an electron-donating group (such as -OCH3) needs to be extended to 24 hours.
[0039] As can be seen from Table 1 above, the influence of the structure of each substrate on the performance of the catalyst is as follows:
[0040] Benzaldehyde (without substituent): High conversion rate (98%) and high selectivity (>99%) indicate that the catalyst has universal high efficiency for simple aromatic aldehydes.
[0041] 4-Nitrobenzaldehyde (electron-withdrawing group): The conversion rate is 97% and the reaction time is 10 hours, indicating that the electron-withdrawing group accelerates the nucleophilic addition step by reducing the LUMO energy level of the substrate.
[0042] 4-Methoxybenzaldehyde (electron-donating group): The conversion rate is 85% and the reaction time is 24 hours, indicating that the electron-donating group may inhibit the reaction activity through steric hindrance or by reducing the electrophilicity of the aldehyde group.
[0043] Furfuraldehyde (heterocyclic structure): The conversion rate is 92% and the selectivity is 97%, proving that the catalyst also has good compatibility with heterocyclic substrates, which may be related to the metal-heteroatom coordination effect.
[0044] From the above reactions, the performance of the catalyst is as follows:
[0045] High efficiency: High conversion rates (85% - 98%) are achieved under low catalyst loading (0.5 mol%), meeting the requirements of green chemistry for atom economy.
[0046] Stability: The reaction is carried out at room temperature (25°C), and the conversion rate ≥ 90% after multiple cycles, indicating that the material structure is stable.
[0047] Universality: It covers aromatic aldehydes, electron-withdrawing / donating substituents, and heterocyclic substrates, and is applicable to diverse synthesis scenarios.
[0048] The volume ratio of ethanol to water is 3:1. The molar ratio of copper acetate, 3-thiophene malonic acid, and 2,2'-bipyridine is 1:(0.8 - 1.2):(0.8 - 1.2), and the addition amount of polyvinylpyrrolidone is 0.5% - 5% of the total mass of the reaction system.
[0049] Table 2 below shows the comparison of crystal properties under different raw material ratios, where the reaction conditions are: ethanol / water is 3:1, the reaction temperature is 25°C, and stirring is for 12 hours.
[0050]
[0051] In Table 2 above, when the volume ratio of ethanol to water is 3:1, the solvent polarity is moderate, which can balance the substrate solubility and crystal nucleation rate, and the yield of blue needle crystals can reach 85%-92%. If the proportion of ethanol is too high (such as 4:1), the crystal is prone to form amorphous precipitation due to too low supersaturation; if it is too low (such as 2:1), the reaction solution becomes turbid and the yield drops below 70%. Therefore, the volume ratio of the two is selected as 3:1.
[0052] When the molar ratio of copper acetate, 3-thiophene malonic acid, and 2,2'-bipyridine is 1:1:1, the crystal structure is the most regular (the crystal plane spacing matching degree verified by XRD is ≥95%), and the peak yield reaches 90%.
[0053] When the proportion of any raw material deviates to 0.8 or 1.2, the crystal size distribution becomes wider (SEM shows that the length extends from 0.8-2 μm to 0.5-2.5 μm), and the catalytic activity decreases by 5%-10%.
[0054] When the PVP content is 2% of the total mass, the crystal surface is uniformly coated (TEM shows that the coating layer thickness is about 5 nm), and the catalytic efficiency still remains 90% of the initial value after being recycled 5 times.
[0055] When the PVP content is less than 0.5%, the crystals are prone to agglomeration (dynamic light scattering shows that the particle size increases from 200 nm to 500 nm); when it is higher than 5%, it hinders the exposure of active sites and the initial conversion rate decreases to 80%.
[0056] Copper acetate and 3-thiophene malonic acid coordinate through the carboxylic acid oxygen atom to form a two-dimensional layered structure, and 2,2'-bipyridine is inserted between the layers as an axial ligand to form stable Cu-N coordination bonds (infrared spectrum shows that the ν(Cu-N) peak is located at 450 cm-1).
[0057] PVP binds to the crystal surface through the oxygen atom of the pyrrolidone ring, inhibits the Ostwald ripening process, and maintains the nanoneedle morphology.
[0058] The Cu 2+ -carboxylic acid sites on the crystal surface can activate the aldehyde group and promote the nucleophilic addition step of the Knoevenagel condensation reaction. The reaction rate of substrates modified with electron-withdrawing groups (such as nitro groups) increases by 20%-30%.
[0059] In summary, the present invention uses inexpensive metal Cu as the catalytic active center site, abandons the choice of using precious metals in traditional catalysts, and through experiments, it is proved that its catalytic effect is still efficient and stable. Compared with traditional precious metal catalysts, the present invention has low cost and has a significant cost advantage compared with other precious metal catalysts, and is applicable to a variety of reaction systems.
[0060] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A preparation method of a cheap metal nano-Cu complex catalyst, characterized in that, It includes the following steps: S1. Mixing and dissolving: Add copper acetate, 3-thiophene malonic acid, 2,2'-bipyridine, and polyvinylpyrrolidone into an ethanol-water mixed solvent, and stir at room temperature until completely dissolved to obtain a mixed solution; S2. Reaction crystallization: Continuously stir the mixed solution for 2 - 24 hours, and blue needle-like crystals gradually precipitate during the reaction process; S3. Separation and purification: Collect the blue needle-like crystals by centrifugation or filtration; S4. Washing and drying: Wash the collected blue needle-like crystals with ethanol, and obtain the nano Cu complex catalyst by vacuum drying.
2. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 1, characterized in that The chemical formula of the nano Cu complex catalyst is [Cu(TMA)(bpy)(H2O)], where TMA is 3-thiophene malonic acid, bpy is 2,2'-bipyridine, and TMA and bpy are 0D coordination molecules with a spatial structure, and the central Cu(II) ion has a distorted tetrahedral coordination environment.
3. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 1, characterized in that, The microstructure of the blue needle-like crystals can be observed by electron microscopy characterization, and the microstructure range of the blue needle-like crystals is in the nano size.
4. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 3, characterized in that, The size of the crystals is 50 - 500 nm.
5. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 1, characterized in that, The test method of the blue needle-like crystals can catalyze the Knoevenagel condensation reaction at room temperature.
6. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 5, characterized in that, The substrates of the Knoevenagel condensation reaction include a combination of aromatic aldehydes and active methylene compounds, and the catalyst dosage is 0.5% - 5% of the total molar amount of the substrates.
7. The preparation method of a cheap metal nano Cu complex catalyst according to claim 1, characterized in that, The volume ratio of ethanol to water is 3:
1.
8. The preparation method of a cheap metal nano-Cu complex catalyst according to claim 1, characterized in that, The molar ratio of copper acetate, 3-thiophene malonic acid, and 2,2'-bipyridine is 1:(0.8 - 1.2):(0.8 - 1.2), and the addition amount of polyvinylpyrrolidone is 0.5% - 5% of the total mass of the reaction system.