Nitrogen-doped carbon-coated copper catalysts and their preparation methods, and methods for producing nitrile via aldehyde-ammonia oxidation.

Abstract

This invention discloses a nitrogen-doped carbon-coated copper catalyst, its preparation method, and its application. The aim is to provide a nitrogen-doped carbon-coated copper catalyst for the oxidation of aldehydes to nitrile. The catalyst is prepared from a precursor using copper chloride, melamine, and sodium lignosulfonate, which is then subjected to pyrolysis and carbonization. When the nitrogen-doped carbon-coated copper catalyst prepared using this method is applied to the catalytic oxidation of aldehydes to nitrile, it exhibits both high catalytic activity and high selectivity for nitriles, and more importantly, it maintains good stability. This invention belongs to the field of catalyst technology.

Description

Technical Field

[0001] This invention discloses a catalyst, specifically a nitrogen-doped carbon-coated copper catalyst. This invention also discloses the preparation method and application of the nitrogen-doped carbon-coated copper catalyst, belonging to the field of catalyst technology. Background Technology

[0002] With increasing environmental awareness and the implementation of sustainable development strategies, green chemistry is gaining more and more attention in chemical production. Aldehydes are important biomass derivatives, and the ammoxidation of aldehydes to nitriles is a crucial pathway for achieving high-value utilization of biomass, aligning with sustainable development goals. Nitriles are a class of high-value and important chemicals with wide applications in pharmaceuticals, polymer industries, and agrochemicals. More importantly, nitriles are highly reactive entities capable of participating in various chemical reactions. Therefore, in recent years, the synthesis of nitriles has attracted great interest from both academia and industry. Among various nitrile synthesis methods, the ammoxidation of aldehydes using molecular oxygen (or air) as the sole oxidant and NH3 as the sole nitrogen source is a green and sustainable route for obtaining nitriles. This method boasts high atom and step economy because water is the only byproduct throughout the process.

[0003] Although a series of homogeneous catalysts, such as Cu / TEMPO and Fe / TEMPO, have been developed, exhibiting excellent catalytic activity, catalyst recovery and product separation remain challenges. In this regard, heterogeneous catalysts offer advantages due to their superior recoverability, separability, and stability. Therefore, a range of noble metal heterogeneous catalysts have been used for the ammoxidation of aldehydes to nitrile. However, their inherently high cost, limited availability, and toxicity necessitate the replacement with more earth-rich metal catalysts.

[0004] Cu-based catalysts possess advantages such as abundant resources, low cost, high activity, and good selectivity. In the oxidative coupling reaction of aldehydes and ammonia to nitrile, Cu-based catalysts can effectively promote the oxidative coupling reaction of aldehydes and ammonia to generate the target nitrile compounds, while exhibiting good substrate adaptability and mild reaction conditions.

[0005] However, due to the inherent structural problems of copper, it suffers from poor hydrothermal stability and is prone to sintering and deactivation. To address the hydrothermal stability issue, existing technologies have attempted to coat catalysts with carbon supports, utilizing the hydrothermal stabilizing properties of the carbon layer to improve the poor hydrothermal stability of copper. However, the carbon-coated catalysts obtained by current preparation methods still suffer from insufficient dispersibility, and the byproduct amide exhibits high selectivity.

[0006] For example, existing technology discloses a coated copper oxide nanoparticle material (Senthamarai, T. et al. Cu-Oxide Nanoparticles Catalyzed Synthesis of Nitriles and Amides from Alcohols and Ammonia in Presence of Air. Advanced Sustainable Systems 6, 2200263 (2022)). This material is prepared using DMF (N,N-diformamide) and copper nitrate trihydrate as the main raw materials and is used in the ammonia oxidation to nitrile reaction to improve the selectivity for nitrile. However, the preparation process of this catalyst is complex, energy-intensive, and requires harsh reaction conditions, including high reaction temperature and long reaction time. Summary of the Invention

[0007] Therefore, the first objective of this invention is to provide a method for preparing a nitrogen-doped carbon-coated copper catalyst. This method first prepares a precursor using copper chloride, melamine, and sodium lignosulfonate as raw materials, and then pyrolyzes and carbonizes the precursor to obtain the catalyst. This method is simple to prepare and the raw materials are readily available.

[0008] The second objective of this invention is to provide a nitrogen-doped carbon-coated copper catalyst that exhibits high catalytic activity and excellent stability for the ammonia oxidation of aldehydes to nitrile, while also possessing high selectivity for the reaction.

[0009] Another object of the present invention is to provide the application and method of nitrogen-doped carbon-coated copper catalyst in the catalytic oxidation reaction of aldehydes with ammonia to produce nitrile compounds.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] The first aspect of this invention provides a method for preparing a nitrogen-doped carbon-coated copper catalyst, comprising the following steps:

[0012] S1. Copper chloride, melamine and sodium lignosulfonate are ball-milled and mixed evenly to obtain a catalyst precursor; the mass ratio of copper chloride, melamine and sodium lignosulfonate is 1:(5-8):(5-8).

[0013] S2. The mixture obtained in step S1 is ball-milled to obtain a catalyst precursor. The precursor is pyrolyzed under an inert atmosphere, and after washing and drying, a nitrogen-doped carbon-coated copper catalyst is obtained.

[0014] In step S2, the pyrolysis process aims to convert the carbon source into a carbon support composite, while simultaneously converting Cu... 2+ Reduced to Cu 0 or Cu+ The multivalent state properties of Cu provide additional advantages in catalytic performance. The purpose of washing is to remove impurities from the surface of the solid obtained after pyrolysis.

[0015] Preferably, the mass ratio of copper chloride, melamine and sodium lignosulfonate in S1 is 1:5:5.

[0016] The proportions of Cu, N, and C sources are controlled by adjusting the mass ratio of copper chloride, melamine, and sodium lignosulfonate. When step S2 is fully completed, Cu nanoparticles can be completely coated on the carbon support. It is worth noting that although carbon itself does not directly participate in the catalytic oxidation of aldehydes to nitrile, its appropriate content in the catalyst is crucial for maintaining catalytic activity. Excessive carbon source addition will result in an overly thick carbon layer, which may negatively impact catalyst activity; conversely, insufficient carbon source addition will fail to fully utilize the isolating effect of the carbon layer, thus failing to effectively prevent the aggregation of active components. Furthermore, too low a carbon content, besides hindering Cu dispersion, will also reduce catalyst stability; however, excessively high carbon content will reduce the exposure of active components, decreasing catalyst selectivity and catalytic efficiency.

[0017] Preferably, in step S2, the pyrolysis temperature is 800-1000°C; more preferably, the pyrolysis temperature is 900°C.

[0018] Preferably, in step S2, the pyrolysis time is 1 to 2 hours, and more preferably 1 hour.

[0019] During pyrolysis, temperature and time control are crucial for catalyst performance. Appropriate pyrolysis temperature and time ensure sufficient carbon content and effective coating of active components. If the pyrolysis temperature is too low, the copper salt and carbon source fail to achieve a complete pyrolysis reaction, preventing the formation of a catalyst with high coating thickness, and also affecting the compactness of the carbon layer particles. If the pyrolysis temperature is too high, copper metal may sinter, forming larger particles. Both situations will significantly reduce the catalytic activity of the catalyst.

[0020] Preferably, the inert atmosphere described in step S2 includes, but is not limited to, a nitrogen atmosphere.

[0021] A second aspect of the present invention provides a nitrogen-doped carbon-coated copper catalyst prepared using the preparation method described in the first aspect. Its active components include Cu nanoparticles, a carbon support, and nitrogen.

[0022] Preferably, the Cu nanoparticles of the present invention are derived from copper chloride; the nitrogen source is derived from melamine; and the carbon source is mainly derived from sodium lignosulfonate.

[0023] The third aspect of this invention provides the application of the nitrogen-doped carbon-coated copper catalyst described in the second aspect in the oxidation of aldehydes to nitrile.

[0024] Preferably, the aldehyde is one of benzaldehyde, p-chlorobenzaldehyde, p-methylbenzaldehyde, p-anisaldehyde, 2-naphthaldehyde, and furfural.

[0025] The fourth aspect of the present invention provides a method for catalytic ammonia oxidation of aldehydes to produce nitrile, specifically: adding aldehyde and ammonia water to acetonitrile solvent, then adding the nitrogen-doped carbon-coated copper catalyst described in the second aspect, and then reacting the resulting mixture under 0.5-1 MPa oxygen for 6-10 h.

[0026] Preferably, the reaction temperature is 35°C.

[0027] Preferably, the ratio of the nitrogen-doped carbon-coated copper catalyst to aldehydes and ammonia is 90–110 mg: 0.5 mmol: 100–200 μL.

[0028] Compared with existing technologies, the technical solution provided by this invention has the following technical advantages:

[0029] 1. The nitrogen-doped carbon-coated copper catalyst prepared in this invention comprises active component Cu nanoparticles, a carbon support, and nitrogen. The carbon support effectively prevents the migration and aggregation of the active component Cu nanoparticles, ensuring uniform dispersion of Cu nanoparticles on the carbon support. Nitrogen doping introduces defect sites and nitrogen species, which can serve as growth sites for metallic Cu. Through the anchoring effect of N atoms on Cu, the interaction between the Cu active component and the support is enhanced, thereby promoting the stability of the catalyst.

[0030] 2. The technical solution provided by the present invention successfully prepared a nitrogen-doped carbon-coated copper catalyst by ball milling and pyrolysis. The Cu metal coated on the catalyst is uniformly distributed. Due to the high dispersion of Cu nanoparticles in the prepared catalyst, more catalytic active sites can be provided, thereby effectively improving the activation ability of oxygen and enabling it to efficiently catalyze the oxidation of aldehydes to nitriles.

[0031] 3. The nitrogen-doped carbon-coated copper catalyst provided by this invention exhibits high catalytic activity and high selectivity for nitrile in the aldehyde-ammonia oxidation reaction. More importantly, it maintains good stability, solving the problems of catalyst instability and low nitrile selectivity of existing Cu-based catalysts in the aldehyde-ammonia oxidation reaction, and has broad application prospects. Furthermore, the nitrogen-doped carbon-coated copper catalyst of this invention enables efficient catalytic oxidation of aldehydes to nitrile using a non-precious metal catalyst at a low temperature of 35℃, which plays an important role in promoting the development and application of aldehyde-ammonia oxidation technology. Attached Figure Description

[0032] Figure 1 TEM image of the catalyst prepared in Example 1;

[0033] Figure 2 TEM image of the catalyst prepared in Example 2;

[0034] Figure 3 TEM image of the catalyst prepared in Example 3;

[0035] Figure 4 TEM image of the catalyst prepared in Example 4;

[0036] Figure 5 TEM image of the catalyst prepared in Example 5;

[0037] Figure 6 TEM image of the catalyst prepared in Example 6;

[0038] Figure 7 TEM image of the catalyst prepared in Comparative Example 2;

[0039] Figure 8 TEM image of the catalyst prepared in Comparative Example 3;

[0040] Figure 9 TEM image of the catalyst prepared in Comparative Example 4;

[0041] Figure 10 TEM image of the catalyst prepared in Comparative Example 5;

[0042] Figure 11 The XPS full spectrum of the catalyst obtained in Example 2;

[0043] Figure 12 The graph shows the cycle stability test results of the catalyst obtained in Example 2. Detailed Implementation

[0044] The following detailed description of specific embodiments is provided in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0045] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments can be purchased through conventional commercial channels unless otherwise specified.

[0046] Example 1: A method for preparing a nitrogen-doped carbon-coated copper catalyst

[0047] (1) Copper chloride, melamine and sodium lignosulfonate were placed in an agate ball milling jar (with an appropriate amount of agate ball milling beads) at a mass ratio of 1:5:5. The agate ball milling jar was then placed in a planetary ball mill and milled at a speed of 300 rpm with alternating forward and reverse rotation for 10 hours (specifically, 30 minutes forward rotation, 5 minutes rest, and then 30 minutes reverse rotation, for a total of 10 hours). The catalyst precursor was then obtained.

[0048] (2) The precursor obtained in step (1) is placed in a nitrogen atmosphere and heated to 800°C for 1 hour at a heating rate of 5°C / min. After the pyrolysis is completed, a copper-doped carbon material composite is obtained.

[0049] (3) The copper-doped carbon material composite prepared in step (2) was washed five times by centrifugation with ultrapure water for 4 minutes each time to remove impurities on the solid surface, and then dried in a vacuum oven at 60°C for 12 hours at -0.08 MPa to obtain a nitrogen-doped carbon-coated copper catalyst.

[0050] Example 2

[0051] The reaction steps, reaction substrates, and process conditions of Example 2 are the same as those of Example 1, the difference being that the pyrolysis temperature is 900℃.

[0052] Example 3

[0053] The reaction steps, reaction substrates, and process conditions of Example 3 are the same as those of Example 1, except that the pyrolysis temperature is 1000℃.

[0054] The main process parameters of the nitrogen-doped carbon-coated copper catalysts in Examples 1-3 are shown in Table 1.

[0055] Table 1

[0056] Example Copper chloride: Melamine: Sodium lignosulfonate (mass ratio) Pyrolysis temperature / °C Example 1 1:5:5 800 Example 2 1:5:5 900 Example 3 1:5:5 1000

[0057] Example 4

[0058] Example 3 and Example 1 have the same reaction steps, reaction substrates and process conditions. The difference is that the mass ratio of copper chloride: melamine: sodium lignosulfonate is 1:8:8.

[0059] Example 5

[0060] Example 2 and Example 1 have the same reaction steps, reaction substrates and process conditions. The difference is that the mass ratio of copper chloride: melamine: sodium lignosulfonate is 1:8:8.

[0061] Example 6

[0062] Example 6 is identical to Example 1 in terms of reaction steps, reaction substrates, and process conditions. The difference lies in the mass ratio of copper chloride: melamine: sodium lignosulfonate, which is 1:8:8.

[0063] The main process parameters of the nitrogen-doped carbon-coated copper catalysts in Examples 4-6 are shown in Table 2.

[0064] Table 2

[0065] Example Copper chloride: Melamine: Sodium lignosulfonate (mass ratio) Pyrolysis temperature / °C Example 4 1:8:8 800 Example 5 1:8:8 900 Example 6 1:8:8 1000

[0066] Example 7

[0067] Example 7 and Example 1 have the same reaction steps, reaction substrates, and process conditions. The difference is that the ball milling speed is 200 rpm.

[0068] Example 8

[0069] The reaction steps, reaction substrates, and process conditions of Example 8 are the same as those of Example 1, the only difference being that the ball milling speed is 400 rpm.

[0070] Example 9

[0071] The reaction steps, reaction substrates, and process conditions of Example 9 are the same as those of Example 1, the only difference being that the ball milling time is 6 hours.

[0072] Example 10

[0073] The reaction steps, reaction substrates, and process conditions of Example 10 are the same as those of Example 1, except that the ball milling time is 8 hours.

[0074] Comparative Example 1

[0075] This comparative example provides a commercial platinum-carbon catalyst, specifically a 5% Pt / C catalyst, purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0076] Comparative Example 2

[0077] The reaction steps, reaction substrates, and process conditions of this comparative example are the same as those of Example 1, except that the pyrolysis temperature is 600°C.

[0078] Comparative Example 3

[0079] The reaction steps, reaction substrates, and process conditions of this comparative example are the same as those of Example 1, except that the pyrolysis temperature is 700°C.

[0080] Comparative Example 4

[0081] (1) Melamine and sodium lignosulfonate were placed in an agate ball milling jar (with an appropriate amount of agate ball milling beads) at a mass ratio of 5:5. The agate ball milling jar was then placed in a planetary ball mill and milled at a speed of 300 rpm for 10 hours by alternating forward and reverse rotation (specifically, 30 minutes forward rotation, 5 minutes rest, and then 30 minutes reverse rotation, for a total of 10 hours). The catalyst precursor was then obtained.

[0082] (2) The precursor obtained in step (1) is placed in a nitrogen atmosphere and heated to 900°C for 1 hour at a heating rate of 5°C / min. After the pyrolysis is completed, a carbon-doped composite material is obtained.

[0083] (3) The carbon-doped composite material prepared in step (2) was washed five times by centrifugation with ultrapure water for 4 minutes each time to remove impurities on the solid surface, and then dried in a vacuum oven at 60°C for 12 hours at -0.08 MPa to obtain a nitrogen-doped carbon-coated catalyst.

[0084] Comparative Example 5

[0085] (1) Copper chloride and sodium lignosulfonate were placed in an agate ball milling jar (with an appropriate amount of agate ball milling beads) at a mass ratio of 1:10. The agate ball milling jar was then placed in a planetary ball mill and milled at a speed of 300 rpm for 10 hours by alternating forward and reverse rotation (specifically, 30 minutes forward rotation, 5 minutes rest, and then 30 minutes reverse rotation, for a total of 10 hours). The catalyst precursor was then obtained.

[0086] (2) The precursor obtained in step (1) is placed in a nitrogen atmosphere and heated to 900°C for 1 hour at a heating rate of 5°C / min. After the pyrolysis is completed, a copper-doped carbon material composite is obtained.

[0087] (3) The copper-doped carbon material composite prepared in step (2) was washed five times by centrifugation with ultrapure water for 4 minutes each time to remove impurities on the solid surface, and then dried in a vacuum oven at 60°C for 12 hours at -0.08 MPa to obtain a nitrogen-doped carbon-coated copper catalyst.

[0088] To investigate the performance of the catalyst provided in this application, the characterization test results of the catalyst provided in this application are presented below.

[0089] TEM images of the catalysts prepared in Examples 1-3 are shown in the attached images. Figures 1 to 3 ,Depend on Figures 1 to 3 It can be seen that Cu nanoparticles are uniformly dispersed on the nitrogen-carbon sheet, indicating that the nitrogen-doped carbon-coated copper catalyst is a high-density and highly dispersed copper-based catalyst. The high-density and highly dispersed Cu sites efficiently promote the ammoxidation reaction of aldehydes.

[0090] TEM images of the catalysts prepared in Examples 4-6 are shown in the attached images. Figures 4-6 ,Depend on Figures 4 to 6It can be seen that the Cu nanoparticles of the prepared catalyst are anchored on the carbon support in a highly dispersed form. This high dispersion ensures the full exposure of a large number of active sites, promoting the ammonia oxidation of aldehydes.

[0091] The XPS full spectrum of the catalyst obtained in Example 2 is shown in the figure. Figure 11 The presence of Cu, C, N, and O elements in the catalyst can be seen from the figure.

[0092] TEM images of the catalysts prepared in Comparative Examples 2 and 3 are shown in the figure. Figures 7-8 ,Depend on Figures 7-8 It can be seen that there are few or almost no Cu nanoparticles on the carbon support, indicating that the catalyst will not be completely pyrolyzed at lower calcination temperatures, resulting in low Cu coating and thus low reactivity in the reaction.

[0093] TEM image of the catalyst prepared in Comparative Example 4 is shown in Figure 4. Figure 9 ,Depend on Figure 9 It can be seen that the catalyst does not contain Cu nanoparticles.

[0094] TEM image of the catalyst prepared in Comparative Example 5 is shown in Figure 5. Figure 10 ,Depend on Figure 10 It can be seen that Cu nanoparticles agglomerate together, indicating that the introduction of nitrogen species can disperse Cu nanoparticles on the carbon support.

[0095] Application Example 1: Nitrogen-doped carbon-coated Cu catalyst catalyzes the ammoxidation of aldehydes to nitrile.

[0096] 0.5 mmol of substrate (benzaldehyde) and 150 μL of ammonia were added to 3 mL of acetonitrile, followed by 100 mg of nitrogen-doped carbon-coated Cu catalyst prepared in Example 1. The mixture was then placed in a 25 mL high-temperature and high-pressure reactor and reacted at 35 °C and 1 MPa oxygen for 8 h. Finally, the reaction solution was analyzed by gas chromatography, and the results are shown in Table 3.

[0097] Application Examples 2-10

[0098] The nitrogen-doped carbon-coated Cu catalysts used in Examples 2-10 to catalyze the oxidation of aldehydes to nitrile via amine oxidation are the same as those used in Example 1. The difference is that the nitrogen-doped carbon-coated Cu catalysts prepared by any of the preparation methods in Examples 2-10 are used instead of the nitrogen-doped carbon-coated Cu catalysts prepared in Example 1 to catalyze the oxidation of aldehydes to nitrile via amine oxidation. Specific parameters and results are shown in Table 3.

[0099] Application Examples 11-14

[0100] Application Examples 11-14 provide the nitrogen-doped carbon-coated Cu catalyst prepared in Example 2 for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference lies in the specific substrate used. The specific parameters and results are shown in Table 3.

[0101] Application Example 15

[0102] The reaction steps, reaction substrates, reaction conditions, and catalysts used in Application Example 15 are the same as those in Application Example 2. The difference is that the reaction temperature is 30°C. For specific parameters and results, please refer to Table 3.

[0103] Application Example 16

[0104] The reaction steps, reaction substrates, reaction conditions, and catalysts used in Application Example 16 are the same as those in Application Example 2. The difference is that the reaction temperature is 40°C. For specific parameters and results, please refer to Table 3.

[0105] Application Example 17

[0106] Application Example 17 is identical to Application Example 2 in terms of reaction steps, reaction substrate, reaction conditions, and catalyst used. The difference is that the reaction time is 6 hours. For specific parameters and results, please refer to Table 3.

[0107] Application Example 18

[0108] The reaction steps, reaction substrates, reaction conditions, and catalysts used in Application Example 18 are the same as those in Application Example 2. The difference is that the reaction time is 10 hours. For specific parameters and results, please refer to Table 3.

[0109] Application Example 19

[0110] The reaction steps, reaction substrates, reaction conditions, and catalysts used in Application Example 19 are the same as those in Application Example 2. The difference is that the amount of catalyst used is 90 mg. For specific parameters and results, please refer to Table 3.

[0111] Application Example 20

[0112] Application Example 20 is identical to Application Example 2 in terms of reaction steps, reaction substrate, reaction conditions, and catalyst used, except that the amount of catalyst used is 110 mg; see Table 3 for specific parameters and results.

[0113] Application Example 21

[0114] The reaction steps, reaction substrates, reaction conditions, and catalysts used in Application Example 21 are the same as those in Application Example 2. The difference is that the amount of ammonia water used is 100 μl. For specific parameters and results, please refer to Table 3.

[0115] Application Example 22

[0116] Application Example 22 is identical to Application Example 2 in terms of reaction steps, reaction substrate, reaction conditions, and catalyst used, except that the amount of ammonia water used is 200 μl; see Table 3 for specific parameters and results.

[0117] Comparative Application Example 1

[0118] Comparative Application Example 1 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the catalyst provided in Comparative Example 1 is used instead of the catalyst in Application Example 1. Specific parameters and results are shown in Table 3.

[0119] Comparative Application Example 2

[0120] Comparative Application Example 2 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the catalyst provided in Comparative Example 2 is used instead of the catalyst in Application Example 1. Specific parameters and results are shown in Table 3.

[0121] Comparative Application Example 3

[0122] Comparative Application Example 3 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the catalyst provided in Comparative Example 3 is used instead of the catalyst in Application Example 1. Specific parameters and results are shown in Table 3.

[0123] Comparative Application Example 4

[0124] Comparative Application Example 4 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the catalyst provided in Comparative Example 4 is used instead of the catalyst in Application Example 1. Specific parameters and results are shown in Table 3.

[0125] Comparative Application Example 5

[0126] Comparative Application Example 5 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the catalyst provided in Comparative Example 5 is used instead of the catalyst in Application Example 1. Specific parameters and results are shown in Table 3.

[0127] Comparative Application Example 6

[0128] Comparative Application Example 6 provides a nitrogen-doped carbon-coated Cu catalyst for the catalytic oxidation of aldehydes to nitrile. The reaction process, process parameters, and amounts of each substance are the same as in Application Example 1. The difference is that the reaction time is 2 hours. Specific parameters and results are shown in Table 3.

[0129] Table 3

[0130]

[0131]

[0132] Table 3 shows that a nitrogen-doped carbon-coated copper catalyst with excellent catalytic activity can be successfully prepared when the ratio of raw materials copper chloride, melamine, and sodium lignosulfonate is controlled at 1:5:5. However, adding too little Cu source leads to a decrease in the performance of the obtained catalyst. Furthermore, if the pyrolysis temperature is too low, the Cu salt and carbon source cannot be fully pyrolyzed, failing to form a high coating amount and reducing the catalyst's catalytic activity. If the pyrolysis temperature is too high, the carbon content decreases, and Cu metal sinters to form large particles, reducing the final reactant conversion rate and nitrile yield.

[0133] Application Example 1 and Comparative Example 1 demonstrate that the nitrogen-doped carbon-coated copper catalyst outperforms the commercial platinum-carbon catalyst (5% Pt / C). The catalyst exhibits superior catalytic performance, achieving highly efficient catalytic oxidation of aldehydes to nitrile using a non-precious metal catalyst at 35°C. This represents a significant technological breakthrough, improving nitrile yield while maintaining catalytic efficiency.

[0134] To verify the reusability of the nitrogen-doped carbon-coated Cu catalyst provided in this application, the nitrogen-doped carbon-coated Cu catalyst was used to catalyze the oxidation of aldehydes to nitrile via ammonia oxidation, following the method in Application Example 2. After the reaction, the catalyst and solution mixture was placed in a 50 mL centrifuge tube and centrifuged for 3-5 min for solid-liquid separation. Ultrapure water was added to the separated solid, and the mixture was stirred for 3 min before centrifugation for further solid-liquid separation. The catalyst was washed three times with ultrapure water and then twice with anhydrous ethanol. The catalyst was then dried in a vacuum drying oven at 60°C for 12 h to obtain the catalyst after one reaction. The reaction process and catalyst recovery process were repeated five times. The conversion rate of benzaldehyde and the yield of benzonitrile were measured for each reaction. The results are shown in the attached document. Figure 12 , Figure 12 The data shows that the catalyst still has high catalytic activity and stability after five consecutive reactions.

[0135] In summary, the nitrogen-doped carbon catalyst prepared by the method of this invention has both high catalytic activity and high selectivity for nitriles. More importantly, it can maintain good stability, which solves the problems of catalyst instability and low nitrile selectivity of existing noble metal catalysts in the aldehyde-ammonia oxidation reaction, and has broad application prospects.

[0136] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation, characterized in that, Aldehyde compounds, solvents, ammonia, and a nitrogen-doped carbon-coated copper catalyst are placed in a reactor and reacted at an oxygen pressure of 0.5-1 MPa and a temperature of 30-40°C for 6-10 hours to obtain the target product. The nitrogen-doped carbon-coated copper catalyst is prepared by the following steps: S1. Copper chloride, melamine and sodium lignosulfonate solids are mixed and complexed by ball milling to obtain a catalyst precursor. S2. The catalyst precursor in S1 is pyrolyzed under an inert atmosphere, and the resulting solid powder is washed and dried to obtain a nitrogen-doped carbon-coated copper catalyst. The mass ratio of copper chloride, melamine and sodium lignosulfonate is 1:(5-8):(5-8).

2. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, The aldehyde compound is one or any combination of benzaldehyde, p-methylbenzaldehyde, p-anisaldehyde, 2-methoxybenzaldehyde, p-chlorobenzaldehyde, and 2-naphthaldehyde.

3. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, The ratio of nitrogen-doped carbon-coated copper catalyst, aldehyde compound, and ammonia water is 90–110 mg: 0.5 mmol: 100–200 μL.

4. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, The solvent is acetonitrile.

5. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, In step S1, the ball milling involves first placing a mixture of copper chloride, melamine, and sodium lignosulfonate into an agate ball milling jar equipped with agate grinding beads, and then placing the ball milling jar into a planetary ball mill for alternating forward and reverse ball milling; the ball milling speed is 200-400 rpm, and the ball milling time is 6-10 hours.

6. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, In step S2, the pyrolysis temperature is 800–1000°C, the inert flow rate is 100 mL / min, and the pyrolysis time is 1–2 h.

7. The method for preparing nitrile compounds by reacting aldehydes with ammonia oxidation according to claim 1, characterized in that, In step S2, the washing involves centrifuging with ultrapure water 3-5 times, each time for 3-5 minutes; the drying involves drying in a vacuum drying oven at 60°C for 12 hours.

Images