Copper oxide / graphene catalyst and its preparation method, application and use method

Abstract

This invention relates to the field of catalyst preparation, and discloses a copper oxide / graphene catalyst, its preparation method, application, and usage method. The catalyst is prepared by the following steps: graphene is blended with anhydrous ethanol and ultrasonically mixed to form a brown-black solution; divalent copper salt is added to the brown-black solution, ultrasonication is continued, and the reaction is stirred to obtain a reaction solution; the reaction solution is cooled to room temperature, the precipitate is collected by centrifugation and washed, and then freeze-dried to obtain the copper oxide / graphene catalyst, which includes a copper oxide-supported graphene carrier. The graphene has a planar sheet structure. The copper oxide / graphene catalyst is used to catalyze C-N coupling reactions. The sheet structure of the graphene supports copper oxide through a π-π stacking manner, and retains its catalytic function after multiple cycles.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, and more particularly to a copper oxide / graphene catalyst, its preparation method, application, and usage. Background Technology

[0002] The construction of CN bonds plays an important role in the fields of organic drug synthesis, materials chemistry, and biomolecular science. The introduction of transition metals provides a rapid and convenient synthetic method for constructing CN bonds to synthesize complex molecules. Although traditional homogeneous catalysts have high reaction efficiency, they require a lot of time and money for separation, recycling, and reuse. Heterogeneous catalysts prepared by immobilizing transition metals on porous materials such as graphene and metal-organic frameworks (MOFs) are easier to separate, recover, and reuse in organic reactions.

[0003] Multilayer graphene, with its planar two-dimensional sheet structure, has a large specific surface area that facilitates the transport of substances. It can support many substances through π-π stacking, and has broad application prospects in fields such as photoelectrocatalysis and drug carriers. Transition metal catalysts, especially copper oxides and complexes, have advantages such as strong stability in chemical reactions, wide availability, abundant reserves in nature, and relatively low price. Using graphene as a support to support transition metal catalysts is a research hotspot. How to improve the uniformity and robustness of the loading to improve catalytic efficiency has become a technical challenge for this type of heterogeneous catalyst.

[0004] Chinese patent 201610067430.4 discloses a method for preparing cubic copper oxide / graphene nanocomposite materials. The method involves a simple one-pot reduction process, in which copper sulfate pentahydrate and graphene oxide are ultrasonically dispersed in water, stirred evenly in a water bath at 50–60°C, and then precipitated with sodium hydroxide dropwise to form copper hydroxide precipitate. A glucose solution is added for reduction, followed by centrifugation, washing, and drying to obtain a cubic cuprous oxide / graphene photocatalyst for the visible light degradation of methyl orange. However, the catalytic spectrum of this patented photocatalyst is too small, and its application prospects cannot cover the CN-coupled reaction for the synthesis of N-aryl heterocyclic compounds. Summary of the Invention

[0005] To address the lack of catalysts in existing technologies for the CN-coupling reaction of N-aryl heterocyclic compounds, this invention provides a copper oxide / graphene catalyst for catalyzing the CN-coupling reaction of N-aryl heterocyclic compounds, offering advantages such as high catalytic efficiency and reusability. This invention also provides a method for preparing the copper oxide / graphene catalyst, which, when used for the CN-coupling reaction of N-aryl heterocyclic compounds, exhibits high catalytic efficiency and reusability. Furthermore, this invention proposes an application of the copper oxide / graphene catalyst for catalyzing the CN-coupling reaction of N-aryl heterocyclic compounds, also demonstrating high catalytic efficiency and reusability.

[0006] This invention is achieved through the following technical solution:

[0007] A copper oxide / graphene catalyst includes a copper oxide-supported graphene carrier having a planar sheet structure, the copper oxide / graphene catalyst being used to catalyze a CN coupling reaction.

[0008] Preferably, the graphene sheet structure is achieved by π-π stacking or by loading copper oxide with interlayer electrostatic force.

[0009] Preferably, the copper oxide / graphene catalyst retains its catalytic function after being recycled multiple times.

[0010] A method for preparing a copper oxide / graphene catalyst includes the following steps:

[0011] 1) Graphene and anhydrous ethanol were blended and sonicated to form a brown-black solution;

[0012] 2) Add the divalent copper salt to the brown-black solution prepared in step 1), continue sonicating, and then stir to obtain the reaction solution;

[0013] 3) Cool the reaction solution prepared in step 2) to room temperature, centrifuge to collect the precipitate and wash it, then freeze-dry to obtain the oxidation product. Copper / graphene catalyst.

[0014] Preferably, the mass-to-volume ratio of graphene to anhydrous ethanol in step 1) is 1:100 to 1:1000 g / mL; the ultrasonic power density is 0.3 to 0.6 W / cm³. 2 The frequency is between 20 and 80 kHz, and the ultrasound time is between 30 and 60 minutes.

[0015] Preferably, in step 2), the mass ratio of graphene to divalent copper salt is 2:1 to 1:4, and the divalent copper salt includes one or more of copper sulfate, copper nitrate, copper chloride, acetone, and their hydrates; the ultrasonic power density is 0.3 to 0.6 W / cm³. 2The frequency is between 20 and 80 kHz, the continuous ultrasound time is 5 to 15 minutes, the reaction temperature is 40 to 80°C, and the reaction time is 12 to 36 hours.

[0016] Preferably, in step 3), the centrifugation speed is 4000-8000 rpm, the centrifugation time is 5-15 min, and the freeze-drying time is 4-12 h.

[0017] The application of the above-described copper oxide / graphene catalyst or the copper oxide / graphene catalyst prepared by the above-described preparation method in catalysis, wherein the catalyst is used for CN coupling reaction in the catalytic synthesis of N-aryl heterocyclic compounds.

[0018] Preferably, the raw materials for the reaction of synthesizing N-aryl heterocyclic compounds include halobenzenes and their derivatives, phenylboronic acid and its derivatives, imidazoles and their derivatives, and piperazines and their derivatives.

[0019] Preferably, the reaction formula for synthesizing the N-aryl heterocyclic compound is as follows:

[0020]

[0021] Wherein, R1 and R2 are one of hydrogen, alkyl, alkoxy, aryl, amino, hydroxyl, and nitro; and R3 and R4 are one of hydrogen, alkyl, alkoxy, and aryl.

[0022] A method for using the copper oxide / graphene catalyst in catalytic applications, comprising the following steps:

[0023] (1) The copper oxide / graphene catalyst is placed in a high-pressure reactor, the raw materials for the synthesis of N-aryl heterocyclic compounds and the base are added, then the solvent is added, ultrasonically dispersed, and the reaction solution II is obtained by solvothermal reaction.

[0024] (2) Cool the reaction solution II prepared in step (1) to room temperature, adjust the pH value to neutral, centrifuge and take the supernatant, and perform chromatographic analysis to obtain the catalytic efficiency of the copper oxide / graphene catalyst.

[0025] Preferably, in step (1), the mixing ratio of the copper oxide / graphene catalyst and the raw material for the synthesis of N-aryl heterocyclic compounds is 2.5–7.5 g: 1 mol; the molar ratio of the raw material for the synthesis of N-aryl heterocyclic compounds to the base is 6: 1–8; the mixing ratio of the base to the solvent is 0.005–0.02 mol: 5–15 g; the ultrasonic dispersion time is 5–30 min; the solvothermal reaction temperature is 100–150 °C; and the reaction time is 6–18 h.

[0026] Preferably, in step (2), the centrifugation speed is 4000-8000 rpm and the centrifugation time is 5-15 min.

[0027] The beneficial effects of this invention are:

[0028] (1) The present invention uses graphene as a carrier and divalent copper salt to prepare copper oxide catalyst. It has a wide catalytic spectrum and can cover the CN coupling reaction between one or more of halobenzenes and their derivatives, phenylboronic acid and its derivatives, imidazole and its derivatives, and piperazine and its derivatives with excellent catalytic efficiency.

[0029] (2) In this invention, copper oxide catalyst is prepared by using graphene as a carrier and divalent copper salt. By utilizing the huge specific surface area and abundant planar interlayer structure of graphene, copper oxide is stacked in the graphene layered structure through interlayer electrostatic forces, which makes the load reliable, not easy to fall off and fail, and still maintains high catalytic efficiency after repeated use.

[0030] (3) This invention uses graphene as a carrier to prepare copper oxide catalyst from divalent copper salt. The preparation process is simple, low cost, and the reaction conditions are environmentally friendly, which is conducive to industrial promotion. Attached Figure Description

[0031] Figure 1 The XRD patterns of graphene (a), copper oxide / graphene catalyst (b), and Cu(OAc)2·4H2O (c) are shown in comparison.

[0032] Figure 2 Zeta potential characterization of graphene (a) and copper oxide / graphene catalyst (b).

[0033] Figure 3 XPS comparison spectra of graphene (a), copper oxide / graphene catalyst (b), and a locally magnified XPS spectrum of copper oxide / graphene catalyst (c).

[0034] Figure 4 This is a gas chromatographic retention time diagram of each substance in Example 5. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Unless otherwise specified, the means used in the embodiments are conventional means in the art. The terms "comprising," "including," or any other variations thereof used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not explicitly listed or elements inherent to such a composition, step, method, article, or apparatus. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. The experimental materials used in the embodiments and comparative examples of this invention are all commercially available products.

[0036] Quantitative determination of catalytic efficiency was performed using gas chromatography. The gas chromatographic conditions were as follows: a SP-6800A gas chromatograph manufactured by Shandong Lunan Ruihong Chemical Instrument Co., Ltd. was used for qualitative and quantitative analysis of the reaction products. The chromatographic column used was a TDX-01 (30m×25μm×0.25μm) capillary column; the injection chamber temperature was 250℃; the detector temperature was 250℃; a programmed temperature rise was used, with an initial column temperature of 180℃, held for 1 minute, then increased to 240℃ at 20℃ / min, held for 1 minute, then increased to 270℃ at 30℃ / min; N2 was used as the carrier gas; and a flame ionization detector was used.

[0037] Example 1

[0038] A method for preparing a copper oxide / graphene catalyst includes the following steps:

[0039] 1) Graphene and anhydrous ethanol were blended and ultrasonicated to form a brown-black solution. The mass-to-volume ratio of graphene to anhydrous ethanol was 1:100 g / mL, and the ultrasonic power density was 0.3 W / cm³. 2 Between 20kHz and 30min;

[0040] 2) Add copper sulfate to the brown-black solution prepared in step 1), with a graphene to copper sulfate mass ratio of 1:4, and continue sonication at an ultrasonic power density of 0.3 W / cm³. 2 Between 20kHz and 5min, the reaction was stirred at 40℃ for 12h to obtain reaction solution I;

[0041] 3) Cool the reaction solution I prepared in step 2) to room temperature, centrifuge at 4000 rpm for 5 min to collect the precipitate and wash it, then freeze-dry for 4 h to obtain the copper oxide / graphene catalyst.

[0042] Example 2

[0043] A method for preparing a copper oxide / graphene catalyst includes the following steps:

[0044] 1) Graphene and anhydrous ethanol were blended and ultrasonicated to form a brown-black solution. The mass-to-volume ratio of graphene to anhydrous ethanol was 1:1000 g / mL, and the ultrasonic power density was 0.6 W / cm³. 2 Between 80kHz and 80min;

[0045] 2) Add copper nitrate to the brown-black solution prepared in step 1), with a graphene to copper nitrate mass ratio of 2:1, and continue sonication at an ultrasonic power density of 0.6 W / cm³. 2 Between 80kHz and 15min, the reaction was stirred at 80℃ for 36h to obtain reaction solution I.

[0046] 3) Cool the reaction solution I prepared in step 2) to room temperature, centrifuge at 8000 rpm for 15 min to collect the precipitate and wash it, then freeze-dry for 12 h to obtain the copper oxide / graphene catalyst.

[0047] Example 3

[0048] A method for preparing a copper oxide / graphene catalyst includes the following steps:

[0049] 1) Graphene and anhydrous ethanol were blended and ultrasonicated to form a brown-black solution. The mass-to-volume ratio of graphene to anhydrous ethanol was 1:500 g / mL, and the ultrasonic power density was 0.5 W / cm³. 2 The frequencies were between 50 kHz and 45 min, respectively.

[0050] 2) Add copper acetate to the brown-black solution prepared in step 1), with a graphene to copper acetate mass ratio of 1:1, and continue sonication at an ultrasonic power density of 0.5 W / cm³. 2 Between 50kHz and 10min, the mixture was stirred at 60℃ for 24h to obtain reaction solution I.

[0051] 3) Cool the reaction solution I prepared in step 2) to room temperature, centrifuge at 6000 rpm for 10 min to collect the precipitate and wash it, then freeze-dry for 8 h to obtain the copper oxide / graphene catalyst.

[0052] Example 4

[0053] A method of using the copper oxide / graphene catalyst prepared in Example 3 in the catalytic reaction of N-aryl heterocyclic compounds includes the following steps:

[0054] 0.05 g of copper oxide / graphene catalyst was placed in a high-pressure reactor, along with 0.01 mol of iodobenzene, 0.02 mol of imidazole, 0.02 mol of sodium hydroxide, and 5 g of dioxane solvent. The reactor was then placed in an ultrasonic device for dispersion for 30 minutes. The sealed reactor was then placed in a 130°C electric heating drying oven and reacted at a constant temperature for 12 hours before being removed and cooled to room temperature. The pH of the solution was then adjusted to neutral with dilute hydrochloric acid. The mixture was then centrifuged at 4000 RPM for 5 minutes, and the supernatant was used for direct quantitative analysis using gas chromatography.

[0055] Example 5

[0056] A method of using the copper oxide / graphene catalyst prepared in Example 3 in the catalytic reaction of N-aryl heterocyclic compounds includes the following steps:

[0057] 0.05 g of copper oxide / graphene supported catalyst was placed in a polytetrafluoroethylene liner of a stainless steel high-pressure reactor. Then, 0.01 mol of phenylboronic acid, 0.02 mol of imidazole, and 0.02 mol of sodium hydroxide were added sequentially, followed by 5 g of dioxane solvent. The reactor was then placed in an ultrasonic device for dispersion for 30 minutes. The sealed reactor was then placed in a 130°C electric heating drying oven and reacted at a constant temperature for 12 hours before being removed and cooled to room temperature. The pH of the solution was then adjusted to neutral with dilute hydrochloric acid. The mixture was then centrifuged at 4000 RPM for 5 minutes, and the supernatant was taken for direct quantitative analysis using gas chromatography.

[0058] Comparative Example 1

[0059] The difference from Example 4 is that iodobenzene is replaced by bromobenzene.

[0060] Comparative Example 2

[0061] The difference from Example 4 is that iodobenzene is replaced by chlorobenzene.

[0062] Comparative Example 3

[0063] The difference from Example 4 is that the iodobenzene is made from... replace.

[0064] Comparative Example 4

[0065] The difference from Example 4 is that the iodobenzene is made from... replace.

[0066] Comparative Example 5

[0067] The difference from Example 4 is that the iodobenzene is made from... replace.

[0068] Comparative Example 6

[0069] The difference from Example 4 is that the iodobenzene is made from... replace.

[0070] Comparative Example 7

[0071] The difference from Example 4 is that the iodobenzene is made from... replace.

[0072] Comparative Example 8

[0073] The difference from Example 4 is that the iodobenzene is made from... replace.

[0074] Comparative Example 9

[0075] The difference from Example 4 is that dioxane is replaced by dimethyl sulfoxide.

[0076] Comparative Example 10

[0077] The difference from Example 4 is that dioxane is replaced by n-butanol.

[0078] Comparative Example 11

[0079] The difference from Example 4 is that dioxane is replaced by N-methylpyrrolidone.

[0080] Comparative Example 12

[0081] The difference from Example 4 is that dioxane is replaced by N,N'-dimethylformamide.

[0082] Comparative Example 13

[0083] The difference from Example 4 is that sodium hydroxide is replaced by potassium carbonate.

[0084] Comparative Example 14

[0085] The difference from Example 4 is that sodium hydroxide is replaced by sodium phosphate.

[0086] Comparative Example 15

[0087] The difference from Example 4 is that sodium hydroxide is replaced with sodium methoxide.

[0088] The N-aryl heterocyclic compounds catalyzed in Examples 4-5 and Comparative Examples 1-15 were then detected by gas chromatography. Figure 4 The gas chromatographic retention time diagrams of each substance in Example 5 are shown below, and the gas chromatographic retention times of the substances in Example 4 are shown in Table 1:

[0089] Table 1 Retention times of each substance in the reaction system

[0090]

[0091] The data for raw material conversion rate, product selectivity, and theoretical product yield were calculated using the area normalization method and are shown in Tables 2 to 5.

[0092] Table 2. Detection data after catalytic reaction of N-aryl heterocyclic compounds in Examples 4-5.

[0093] raw material Raw material conversion rate Product selectivity theoretical yield of product Example 4 Iodobenzene 98.6％ 93.6％ 92.3％ Example 5 phenylboronic acid 98.8％ 94.1％ 93.0％

[0094] Table 3. Detection data after catalytic reaction of N-aryl heterocyclic compounds in Examples 3 and Comparative Examples 1-8.

[0095]

[0096] Table 4. Results of the influence of solvent type on Examples 3 and Comparative Examples 9-12

[0097]

[0098] Table 5. Results of the influence of alkali type on Example 3 and Comparative Examples 13-15

[0099] Types of alkalis Raw material conversion rate Product selectivity theoretical yield of product Example 3 Sodium hydroxide 98.6％ 93.6％ 92.3％ Comparative Example 13 Potassium carbonate 86.3％ 48.9％ 42.2％ Comparative Example 14 Sodium phosphate 64.9％ 66.1％ 42.9％ Comparative Example 15 Sodium methoxide 59.4％ 58.3％ 34.6％

[0100] Table 6 Comparison of products prepared under different catalyst cycle numbers

[0101]

[0102] As shown in Table 2, the conversion rate, product selectivity, and theoretical yield of the raw materials obtained in Example 4 (using iodobenzene) and Example 5 (using phenylboronic acid) were all above 90%. Comparing the raw materials obtained in Table 3 by replacing iodobenzene in Example 4 with various halogenated benzenes, the conversion rate, product selectivity, and theoretical yield of Comparative Examples 4 and 5 were the highest, approaching 100%, while Comparative Example 2 was the lowest, with a conversion rate below 15% and a product selectivity and theoretical yield even lower, below 2%. Other data also showed significant differences, with no significant correlation or regularity. It is impossible to deduce the catalytic effect of copper oxide / graphene solely from the similarity of molecular structures. It is evident that the catalytic efficiency of copper oxide / graphene catalysts varies for different raw materials, and the current experimental data cannot be simply generalized or predicted. As shown in Table 4, the different types of solvents have a significant impact on catalytic efficiency, with dioxane in Example 3 having the most significant effect. The results showed that the conversion rate of the raw materials, the selectivity of the products, and the theoretical yield were all above 90%. However, the data continued to decline from Comparative Examples 9 to 12. When N,N'-dimethylformamide was used as the solvent in Comparative Example 12, the yield was significantly lower than 60%. As shown in Table 5, the type of alkali significantly affected the catalytic effect. Sodium hydroxide in Example 3 was the best, with the conversion rate of the raw materials, the selectivity of the products, and the theoretical yield all above 90%. However, the data continued to decline from Comparative Examples 13 to 15. When sodium methoxide was used as the alkali in Comparative Example 15, the yield was significantly lower than 60%. As shown in Table 6, after five repeated uses, the conversion rate of the raw materials, the selectivity of the products, and the theoretical yield of the copper oxide / graphene catalyst all declined, but the decline was no more than 5% each time. This shows that the copper oxide / graphene of the present invention has good durability for recycling and reuse, and can be recycled and reused multiple times, effectively saving costs.

[0103] like Figures 1-2 As shown, the XRD patterns and Zeta potentials of graphene (a), copper oxide / graphene catalyst (b), and Cu(OAc)2·4H2O (c) are compared together. The XRD patterns of graphene and copper oxide / graphene are very similar. The main difference is that the double peaks of the original graphene, which are between 30° and 40°, red-shift to between 40° and 50° after the reaction to form copper oxide / graphene. The density of the sharp peaks of copper oxide / graphene between 50° and 60° increases significantly. In addition, the Zeta potential of graphene is negative, while that of copper oxide / graphene is positive. The larger the absolute value of the Zeta potential, the more stable the catalyst particles are in suspension. Figure 3 The XPS spectrum shown shows a characteristic peak indicating Cu 2p between 925 eV and 965 eV in the binding energy of copper oxide / graphene compared to graphene. Figure 4 The gas chromatographic retention time diagrams of each substance in Example 5 are shown.

[0104] The above embodiments are merely examples of several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent.

[0105] For those skilled in the art, various modifications and improvements can be made without departing from the concept of this invention, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An application of a copper oxide / graphene catalyst in the CN coupling reaction during the catalytic synthesis of N-aryl heterocyclic compounds, characterized in that, The copper oxide / graphene catalyst comprises graphene supported on copper oxide. The graphene has a planar layered structure, and copper oxide is stacked within the graphene layered structure through interlayer electrostatic forces. The reaction formula for synthesizing N-aryl heterocyclic compounds is shown in the figure below: Wherein, R1 is one of hydrogen, alkyl, alkoxy, aryl, amino, hydroxyl, and nitro; R3 is one of hydrogen, alkyl, alkoxy, and aryl; and the copper oxide / graphene catalyst retains its catalytic function after multiple cycles of use. The preparation steps of the copper oxide / graphene catalyst are as follows: 1) Graphene and anhydrous ethanol were mixed and sonicated for 30-60 minutes to form a brown-black solution; 2) Add the divalent copper salt to the brown-black solution prepared in step 1), continue sonicating for 5 to 15 minutes, and then continue stirring at 40℃ to 80℃ for 12 to 36 hours to obtain reaction solution I; 3) Cool the reaction solution I prepared in step 2) to room temperature, centrifuge to collect the precipitate and wash it, then freeze-dry to obtain the copper oxide / graphene catalyst.

2. The application according to claim 1, characterized in that, In step 1), the mass-to-volume ratio of graphene to anhydrous ethanol is 1:100 to 1:1000 g / mL; the ultrasonic power density is 0.3 to 0.6 W / cm³. 2 The frequency is between 20 and 80 kHz.

3. The application according to claim 2, characterized in that, In step 2), the mass ratio of graphene to divalent copper salt is 2:1 to 1:4, and the divalent copper salt includes one or more of copper sulfate, copper nitrate, copper chloride, acetone, and their hydrates; the ultrasonic power density is 0.3 to 0.6 W / cm³. 2 The frequency is between 20 and 80 kHz.

4. The application according to claim 1, characterized in that, In step 3), the centrifugation speed is 4000-8000 rpm, the centrifugation time is 5-15 min, and the freeze-drying time is 4-12 h.

5. An application according to any one of claims 1 to 4, characterized in that, The method of using the copper oxide / graphene catalyst in the aforementioned application includes the following steps: (1) The copper oxide / graphene catalyst is placed in a high-pressure reactor, the raw materials for the synthesis of N-aryl heterocyclic compounds and the base are added, then the solvent is added, ultrasonically dispersed, and the reaction solution II is obtained by solvothermal reaction. (2) Cool the reaction solution II prepared in step (1) to room temperature, adjust the pH value to neutral, centrifuge and take the supernatant, and perform chromatographic analysis to obtain the catalytic efficiency of the copper oxide / graphene catalyst.

6. The application according to claim 5, characterized in that, In step (1), the mixing ratio of the copper oxide / graphene catalyst and the raw material for the synthesis of N-aryl heterocyclic compounds is 2.5–7.5 g: 1 mol; the molar ratio of the raw material for the synthesis of N-aryl heterocyclic compounds to the base is 6:1–8; the mixing ratio of the base to the solvent is 0.005–0.02 mol: 5–15 g; the ultrasonic dispersion time is 5–30 min; the solvothermal reaction temperature is 100–150 °C; and the reaction time is 6–18 h.

7. The application according to claim 5, characterized in that, In step (2), the centrifugation speed is 4000-8000 rpm and the centrifugation time is 5-15 min.

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