Preparation method and application of mesoporous aza-carbon loaded Me-W catalyst

Abstract

The invention discloses a preparation method and application of a mesoporous aza-carbon loaded Me-W catalyst, and the preparation method comprises the following steps: adding Me oxide or metal salt into ammonium tungstate, grinding uniformly, then adding a carrier and a salt template, grinding and mixing uniformly to obtain a mixture, covering the mixture with another salt template, and then calcining; and after the calcination is completed, washing and drying the calcined solid in sequence to obtain the mesoporous aza-carbon loaded Me-W catalyst. The salt template is used for pore forming, so that active components of the meso-porous nitrogen-doped carbon loaded Me-W catalyst are highly dispersed, aggregation and sintering are avoided, and the specific surface area and catalytic activity of the catalyst are greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, and particularly relates to a mesoporous nitrogen-doped carbon-supported Me-W catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As one of the most important chemical intermediates, benzaldehyde is widely used in fields such as the pigment, pharmaceutical, and food industries. Industrially, the classical method for constructing benzaldehyde is through the toluene chlorination hydrolysis method, which uses toluene as a raw material and obtains benzaldehyde through processes such as chlorination and hydrolysis. However, in these two processes, trace amounts of chlorine will inevitably exist in the product benzaldehyde, which greatly limits the application of the product in high-quality pharmaceutical processes. Therefore, developing a chlorine-free benzaldehyde preparation process has important application value and prospects.

[0003] Whether in basic research or in the industrial field, the conversion of alcohols to aldehydes or ketones is one of the most important and challenging functional group conversions. Compared with existing industrial processes involving halogens, the catalytic selective oxidation of benzyl alcohol to benzaldehyde is a more preferred route for providing high-quality benzaldehyde. Currently, many catalysts have been developed for the oxidation of benzyl alcohol to produce benzaldehyde. However, these processes are still greatly hindered because their disadvantages need to be overcome. For example, the use of expensive rare metals, the need for organic solvents, additional additives, and the problem of catalyst recovery. In this context, developing inexpensive and easily recyclable heterogeneous non-noble metal catalysts for the oxidation of benzyl alcohol to produce benzaldehyde has become an effective strategy. For example, in 2017, Fan et al. prepared supported Pd-Ni bimetallic nanoparticles by the solid-phase alloying method. Adding Ni to Pd can weaken the dissociative adsorption of benzyl alcohol and the cleavage of the C-O bond, and by removing hydrogen with oxygen on the Ni surface to inhibit the formation of the C-H bond, the formation of toluene in the solvent-free benzyl alcohol oxidation reaction can be effectively inhibited, thereby improving the selectivity and productivity for benzaldehyde (Chinese Journal of Catalysis, 2017, 38, 1870-1879). In 2020, Chen et al. prepared an atomically MnO x modified Pd nanoparticle catalyst, which showed high activity and selectivity in the reaction of benzyl alcohol oxidation to produce benzaldehyde. The MnOx coating structure selectively passivated the Pd(111) surface, avoiding the decarbonylation reaction of benzaldehyde. MnO x modified Pd catalyst had a TOF of 31561 h -1 , which was 8.7 times that of the unmodified Pd catalyst. At the same time, the maximum conversion of benzyl alcohol and the yield of benzaldehyde were increased to 84.7% and 76.5% respectively (Journal of Catalysis, 2020, 386, 60-69). However, the conversion of benzyl alcohol and the selectivity of benzaldehyde need to be further improved.

[0004] WO3, as a non-noble metal catalyst, has been widely used in various oxidation reactions. However, pure WO3 shows poor catalytic activity in the reaction of oxidizing benzyl alcohol to benzaldehyde. Therefore, other metal nanoparticles (NPs) such as Cu, Zn, Ni, Pt, etc. are usually used to modify the surface of WO3 to improve its catalytic activity. However, during the actual reaction process, the aggregation and sintering of metal nanoparticles (NPs) usually lead to the loss of catalytic performance. Therefore, metal NPs with catalytic activity are usually encapsulated on carriers with a high specific surface area to solve the above problems, thereby improving catalytic activity and stability. Mesoporous carbon materials are often used as carriers to improve catalytic activity and selectivity due to their large specific surface area, low cost, high carrier mobility, etc. And nitrogen doping can further reduce the activation energy, thus obtaining materials with higher catalytic performance than pure carbon-based catalysts. Therefore, loading the Me-W metal composite catalyst on mesoporous nitrogen-doped carbon materials is expected to obtain a catalyst with high selectivity and conversion rate.

[0005] Traditionally, the preparation of mesoporous carbon materials usually adopts the hard template method (using magnesium oxide, mesoporous or colloidal silica, etc. as templates); the soft template method (using block copolymers, metal-organic frameworks (MOFs), etc. as templates), etc. However, these methods usually use some corrosive reagents to remove the template agent, which will inevitably corrode the equipment, and these methods usually have disadvantages such as high cost and complex technology. Therefore, there is still a need to develop a preparation process for mesoporous nitrogen-doped carbon-supported Me-W catalysts with simple process, low cost, high conversion rate and selectivity. Summary of the Invention

[0006] Aiming at the problems existing in the prior art in the field, such as low conversion rate, low selectivity in the process of tungsten oxide catalyzing the oxidation of benzyl alcohol, small specific surface area of tungsten oxide, and few catalytic sites, the present invention provides a preparation method of mesoporous nitrogen-doped carbon-supported Me-W catalyst. The salt template agent is used to create pores in the nitrogen-doped carbon material, and ammonium tungstate and metal oxide or metal salt precursors are calcined with the catalyst carrier, and then the salt template is removed to leave pores, obtaining the mesoporous nitrogen-doped carbon-supported Me-W catalyst, which can well solve the problems of sintering and aggregation of metal nanoparticles under high-temperature calcination, thereby greatly increasing the specific surface area of the catalyst and providing more active sites for the catalytic oxidation reaction. These advantages can ultimately enable the catalyst to exhibit excellent stability and catalytic activity in the reaction of selectively oxidizing benzyl alcohol to benzaldehyde. By applying it to the catalytic oxidation reaction of benzyl alcohol, the catalyst shows extremely high selectivity for the target product benzaldehyde, the reaction process conditions are mild, and the operation is simple. Moreover, the catalyst preparation process is simple, and it can be recycled by simple centrifugation later, with good cycle stability, showing good industrial application potential.

[0007] A preparation method of a mesoporous nitrogen-doped carbon-supported Me-W catalyst, comprising the steps of:

[0008] (1) Adding Me oxide or metal salt to ammonium tungstate and grinding evenly, then adding a carrier precursor and a salt template and grinding and mixing evenly to obtain a mixture, then covering the mixture with another salt template, and then performing calcination; wherein, the carrier precursor is at least one of melamine, urea, glucose monohydrate, and dicyandiamide, preferably a mixture of melamine, urea, and glucose monohydrate.

[0009] (2) Taking the solid generated in step (1), washing, drying, and grinding to obtain the mesoporous nitrogen-doped carbon-supported Me-W catalyst.

[0010] The inventors found through experiments that the mesoporous nitrogen-doped carbon material obtained by calcining a mixture of melamine, urea, and glucose monohydrate has a better effect than using them alone. The pore-forming effect of using a mixture of sodium chloride and potassium chloride as the salt template is better than using them alone.

[0011] In step (1), Me is an oxide and / or chloride and / or nitrate formed by one of Zn, Se, Sn, Cr, Zr, Fe, or Cu as a metal element. In the present invention, ZnO is preferred.

[0012] In step (1): The molar amount of the Me metal element, the molar amount of the ammonium tungstate, the total mass of the carrier precursor, and the total mass of the salt template are in the ratio of (0.1 - 0.8) mmol∶1 mmol∶(2 - 6) g∶(20 - 50) g.

[0013] In step (1): The mass ratio of melamine, urea, and glucose monohydrate is (0.5 - 2)∶(0.5 - 2)∶1.

[0014] In step (1): The mass ratio of sodium chloride and potassium chloride is (0.5 - 2)∶(0.5 - 2).

[0015] The calcination temperature in step (1) is 600 - 900 °C, preferably 800 - 900 °C; the calcination duration is 4 - 6 h. Preferably 5 - 6 h.

[0016] In step (2): The drying temperature is 60 - 120 °C, preferably 80 - 100 °C; the drying duration is 4 - 12 h, preferably 8 - 12 h.

[0017] The catalyst is composed of Me, tungsten oxide, and mesoporous nitrogen-doped carbon.

[0018] The present invention also provides the application of the mesoporous nitrogen-doped carbon-supported Me-W catalyst in the catalytic oxidation of benzyl alcohol to prepare benzaldehyde.

[0019] Among them, the method for catalytic oxidation of benzyl alcohol to prepare benzaldehyde is as follows: After mixing the Me-W catalyst supported on mesoporous nitrogen-doped carbon, a solvent, hydrogen peroxide and benzyl alcohol, a catalytic oxidation reaction is carried out at 40-90 °C (preferably 60-80 °C) to obtain the target product benzaldehyde.

[0020] The solvent is preferably at least one of acetonitrile, dichloromethane, and water, and more preferably water. Using water as the solvent has the advantages of safety, low cost, non-toxicity, and no pollution, which conforms to the concept of modern green chemistry. The reaction product can be extracted and separated into layers, and the post-treatment process is extremely simple.

[0021] The volume ratio of the benzyl alcohol, the hydrogen peroxide and the solvent is preferably 1:(1-5):(1-40), and more preferably 1:(1-3):(1-30).

[0022] The mass ratio of the benzyl alcohol to the catalyst is preferably 1:(0.1-0.5).

[0023] The reaction time of the catalytic oxidation reaction is preferably 1-8 h, and more preferably 4-6 h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention provides a class of Me-W catalysts supported on mesoporous nitrogen-doped carbon. The preparation method of this catalyst is simple, the raw materials are easy to obtain and the price is low, and it can be recovered by simple centrifugation.

[0026] 2. The loading of mesoporous nitrogen-doped carbon enables the active components of the catalytic material to be highly dispersed, avoiding sintering and aggregation, and also greatly increasing the specific surface area of the active components, thereby improving the catalytic activity and stability.

[0027] 3. The doping of additional metal elements can, on the one hand, modify the surface of tungsten oxide to improve the catalytic activity, and on the other hand, play a synergistic role during the catalytic reaction process.

[0028] 4. The reaction conditions for the preparation of benzaldehyde from benzyl alcohol provided by the present invention are mild, and both the reaction conversion rate and selectivity are greatly improved. Under preferred conditions, when the Zn-W catalytic material supported on mesoporous nitrogen-doped carbon prepared with ZnO as the additional metal element is provided by the present invention, the selectivity of benzaldehyde is higher, which is particularly suitable for the catalytic oxidation reaction of preparing benzaldehyde from benzyl alcohol. Description of the Drawings

[0029] Figure 1 It is the X-ray diffraction (XRD) pattern of the Zn-W supported on mesoporous nitrogen-doped carbon prepared in Example 1. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operating methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. The raw materials used in the following specific embodiments are all purchased from the market. Unless otherwise specified, room temperature is represented as 25°C.

[0031] Example 1

[0032] The first step: Preparation of Zn-W catalyst supported on mesoporous nitrogen-doped carbon:

[0033] The above-mentioned Zn-W catalyst supported on mesoporous nitrogen-doped carbon was prepared by physical grinding method. Weigh 8.1 mg of zinc oxide (0.1 mmol), 1.5 g of ammonium tungstate (0.5 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), and 1 g of glucose monohydrate (5 mmol) according to the molar ratio of 0.2∶1∶25.5∶12.2∶10; add 3.3 g of sodium chloride and 3.3 g of potassium chloride according to the mass ratio of 1∶1, and physically mix the above substances only using an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, the mixture was transferred to a crucible and covered with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1∶1) mixture, and then the mixture was calcined in air at 800°C for 5 h (heating rate 10°C / min), cooled to room temperature, and 200 mL of deionized water was added to the mixture to soak until the salt template was completely dissolved. Subsequently, the remaining solid was washed with deionized water to thoroughly wash away the salt template. The remaining solid was transferred to an oven and dried at 80°C for 12 h to obtain the Zn-W catalyst supported on mesoporous nitrogen-doped carbon (denoted as S1 catalyst).

[0034] The second step, catalytic oxidation reaction: In a 5 mL reaction tube, take the S1 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%), and react at 80°C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol was 92.1%, the selectivity of benzaldehyde was 92.4%, and the yield was 85.1%

[0035] Comparative Example 1

[0036] First step: catalyst preparation: The method was similar to that of Example 1, except that zinc oxide was not added (while keeping the molar ratios of other substances unchanged). 1.5 g of ammonium tungstate (0.5 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), 1 g of glucose monohydrate (5 mmol); 3.3 g of sodium chloride and 3.3 g of potassium chloride were added in a mass ratio of 1:1. The above substances were physically mixed using only an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, the mixture was transferred to a crucible and covered with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1:1) mixture, and then the mixture was calcined in air at 800 °C for 5 h (heating rate 10 °C / min), cooled to room temperature, and 200 mL of deionized water was added to the mixture and soaked until the salt template was completely dissolved. Subsequently, the remaining solid was washed with deionized water to thoroughly wash away the salt template. The remaining solid was transferred to an oven and dried at 80 °C for 12 h to obtain a mesoporous nitrogen-doped carbon-supported WO3 catalyst (denoted as D1 catalyst).

[0037] Second step, catalytic oxidation reaction: In a 5 mL reaction tube, take the D1 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%), and react at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol was 92.6%, the selectivity for benzaldehyde was 84.3%, and the yield was 78.1%

[0038] Comparative Example 2

[0039] First step: catalyst preparation: The method was similar to that of Example 1, except that ammonium tungstate was not added (while keeping the molar ratios of other substances unchanged). Weigh 8.1 mg of zinc oxide (0.1 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), 1 g of glucose monohydrate (5 mmol); 3.3 g of sodium chloride and 3.3 g of potassium chloride were added in a mass ratio of 1:1. The above substances were physically mixed using only an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, the mixture was transferred to a crucible and covered with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1:1) mixture, and then the mixture was calcined in air at 800 °C for 5 h (heating rate 10 °C / min), cooled to room temperature, and 200 mL of deionized water was added to the mixture and soaked until the salt template was completely dissolved. Subsequently, the remaining solid was washed with deionized water to thoroughly wash away the salt template. The remaining solid was transferred to an oven and dried at 80 °C for 12 h to obtain a mesoporous nitrogen-doped carbon-supported ZnO catalyst (denoted as D2 catalyst).

[0040] Step 2, Catalytic Oxidation Reaction: In a 5 mL reaction tube, take the D2 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 4.7%, the selectivity for benzaldehyde is 44.7%, and the yield is 2.1%

[0041] Example 2

[0042] First step, Preparation of Mesoporous N-Doped Carbon Supported Zn-W Catalyst:

[0043] The above mesoporous N-doped carbon supported Zn-W catalyst was prepared by physical grinding method. Weigh 16.2 mg of zinc oxide (0.2 mmol), 1.5 g of ammonium tungstate (0.5 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), and 1 g of glucose monohydrate (5 mmol) according to the molar ratio of 0.4∶1∶25.5∶12.2∶10; add 3.3 g of sodium chloride and 3.3 g of potassium chloride according to the mass ratio of 1∶1, and physically mix the above substances using only an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, transfer the mixture to a crucible, cover it with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1∶1) mixture, and then calcine the mixture in air at 800 °C for 5 h (heating rate 10 °C / min). Cool to room temperature, add 200 mL of deionized water to the mixture and soak until the salt template completely dissolves. Subsequently, wash the remaining solid with deionized water to thoroughly remove the salt template. Transfer the remaining solid to an oven and dry at 80 °C for 12 h to obtain the mesoporous N-doped carbon supported Zn-W catalyst (denoted as S2 catalyst).

[0044] Step 2, Catalytic Oxidation Reaction: In a 5 mL reaction tube, take the S2 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 84.0%, the selectivity for benzaldehyde is 84.3%, and the yield is 70.8%

[0045] Example 3

[0046] First step, Preparation of Mesoporous N-Doped Carbon Supported Zn-W Catalyst:

[0047] The above-mentioned Zn-W catalyst supported on mesoporous nitrogen-doped carbon was prepared by a physical grinding method. Weigh 24.3 mg of zinc oxide (0.3 mmol), 1.5 g of ammonium tungstate (0.5 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), and 1 g of glucose monohydrate (5 mmol) according to a molar ratio of 0.6∶1∶25.5∶12.2∶10; add 3.3 g of sodium chloride and 3.3 g of potassium chloride according to a mass ratio of 1∶1, and physically mix the above substances using only an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, transfer the mixture to a crucible, cover it with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1∶1) mixture, then calcine the mixture in air at 800 °C for 5 h (heating rate 10 °C / min), cool to room temperature, add 200 mL of deionized water to the mixture and soak until the salt template completely dissolves. Subsequently, wash the remaining solid with deionized water to thoroughly wash away the salt template. Transfer the remaining solid to an oven and dry at 80 °C for 12 h to obtain the Zn-W catalyst supported on mesoporous nitrogen-doped carbon (denoted as S3 catalyst).

[0048] Second step, catalytic oxidation reaction: In a 5 mL reaction tube, take the S3 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%), and react at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol was 94.8%, the selectivity of benzaldehyde was 77.5%, and the yield was 73.4%

[0049] Example 4

[0050] First step, preparation of the Zn-W catalyst supported on mesoporous nitrogen-doped carbon:

[0051] The above-mentioned Zn-W catalyst supported on mesoporous nitrogen-doped carbon was prepared by physical grinding method. Weigh 32.4 mg of zinc oxide (0.4 mmol), 1.5 g of ammonium tungstate (0.5 mmol), 0.77 g of urea (12.75 mmol), 0.77 g of melamine (5.1 mmol), and 1 g of glucose monohydrate (5 mmol) according to the molar ratio of 0.8∶1∶25.5∶12.2∶10; add 3.3 g of sodium chloride and 3.3 g of potassium chloride according to the mass ratio of 1∶1, and physically mix the above substances using only an agate mortar. To ensure thorough mixing, all batches were ground for at least 2 h. Subsequently, the mixture was transferred to a crucible and covered with an additional 12 g of sodium chloride / potassium chloride (mass ratio 1∶1) mixture, and then the mixture was calcined in air at 800 °C for 5 h (heating rate: 10 °C / min), cooled to room temperature, and 200 mL of deionized water was added to the mixture and soaked until the salt template was completely dissolved. Subsequently, the remaining solid was washed with deionized water to thoroughly wash away the salt template. The remaining solid was transferred to an oven and dried at 80 °C for 12 h to obtain the Zn-W catalyst supported on mesoporous nitrogen-doped carbon (denoted as S4 catalyst).

[0052] Second step, catalytic oxidation reaction: In a 5 mL reaction tube, take the S4 catalyst (10 mg) obtained in the first step and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%), and react at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol was 91.1%, the selectivity of benzaldehyde was 81.0%, and the yield was 73.8%.

[0053] Example 5

[0054] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 80 °C for 2 h. By gas phase analysis, the conversion rate of benzyl alcohol was 78.6%, the selectivity of benzaldehyde was 91.2%, and the yield was 71.7%.

[0055] Example 6

[0056] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol was 93.3%, the selectivity of benzaldehyde was 90.0%, and the yield was 84.0%.

[0057] Example 7

[0058] Take S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 80 °C for 6 h. By gas phase analysis, the conversion rate of benzyl alcohol is 98.2%, the selectivity of benzaldehyde is 66.1%, and the yield is 64.9%. When the reaction time is short, the selectivity increases probably because the target product benzaldehyde generated at this time is not over-oxidized to acid, so the selectivity is high. However, due to the short reaction time, less substrate is converted, resulting in a low conversion rate. When the reaction time is too long, although the conversion rate of benzyl alcohol is close to 100%, it will cause the over-oxidation of benzaldehyde to acid, resulting in a decrease in the selectivity of benzaldehyde and a decrease in the yield at the same time.

[0059] Example 8

[0060] Take S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 40 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 14.3%, the selectivity of benzaldehyde is 79.7%, and the yield is 11.4%.

[0061] Example 9

[0062] Take S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 60 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 49.1%, the selectivity of benzaldehyde is 89.7%, and the yield is 44.1%.

[0063] Example 10

[0064] Take S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, then add hydrogen peroxide (141.7 mg, concentration 30 wt%), and react at 90 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 98.3%, the selectivity of benzaldehyde is 62.9%, and the yield is 61.8%. Low temperature is not conducive to the oxidation of benzyl alcohol, resulting in a decrease in the conversion rate of benzyl alcohol; too high a temperature will cause the over-oxidation of benzaldehyde to acid, so it will lead to a decrease in the selectivity and yield of benzaldehyde. The same conclusion can also be obtained in the amount of hydrogen peroxide used, and Examples 11 - 14 show this change.

[0065] Example 11

[0066] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (28.3 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 18.3%, the selectivity for benzaldehyde is 83.6%, and the yield is 15.3%.

[0067] Example 12

[0068] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (56.7 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 40.5%, the selectivity for benzaldehyde is 92.6%, and the yield is 37.5%.

[0069] Example 13

[0070] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 92.1%, the selectivity for benzaldehyde is 92.4%, and the yield is 85.1%.

[0071] Example 14

[0072] Take the S1 catalyst (10 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (170.0 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 91.7%, the selectivity for benzaldehyde is 90.2%, and the yield is 82.7%.

[0073] Example 15

[0074] Take the S1 catalyst (5 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 80.6%, the selectivity for benzaldehyde is 88.7%, and the yield is 71.5%.

[0075] Example 15

[0076] Take the S1 catalyst (15 mg) and benzyl alcohol (54 mg, 0.5 mmol), add 1 mL of deionized water, and then add hydrogen peroxide (113.4 mg, concentration 30 wt%). React at 80 °C for 4 h. By gas phase analysis, the conversion rate of benzyl alcohol is 96.4%, the selectivity for benzaldehyde is 86.3%, and the yield is 73.2%.

[0077] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims

1. A method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst, characterized in that: Includes steps: (1) adding Me oxide or metal salt to ammonium tungstate and grinding them evenly, then adding a carrier precursor and a salt template and grinding and mixing them evenly to obtain a mixture, then covering the mixture with another salt template, and then calcining; wherein the carrier precursor is at least one of melamine, urea, glucose monohydrate, and melamine; (2) Taking the solid generated in step (1), washing, drying and grinding it in sequence to obtain a mesoporous nitrogen-carbon supported Me-W catalyst.

2. The method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 1, characterized in that: In step (1), Me is an oxide and / or chloride and / or nitrate formed by one of the metal elements selected from Zn, Se, Sn, Cr, Zr, Fe and Cu.

3. The method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 1, characterized in that: In step (1): The ratio of the molar amount of the metal element in Me to the molar amount of the ammonium tungstate, the total mass of the carrier precursor and the total mass of the salt template is 0.1-0.8 mmol: 1 mmol: 2-6 g: 20-50 g.

4. The method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 1, characterized in that: In step (1), the salt template is at least one of sodium chloride and potassium chloride.

5. The method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 1, characterized in that: The calcination temperature in step (1) is 600-900° C., and the calcination time is 4-6 hours.

6. The method for preparing a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 1, characterized in that: In step (2), the drying temperature is 60 to 120° C. and the drying time is 4 to 12 hours.

7. Use of a mesoporous nitrogen-carbon-supported Me-W catalyst prepared according to the preparation method of any one of claims 1 to 6 in catalytic oxidation of benzyl alcohol to prepare benzaldehyde.

8. Use of a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 7 in catalytic oxidation of benzyl alcohol to prepare benzaldehyde, characterized in that: The mesoporous nitrogen-doped carbon-supported Me-W catalyst, solvent, hydrogen peroxide and benzyl alcohol are uniformly mixed, and then a catalytic oxidation reaction is carried out at 40-90° C. to obtain the target product benzaldehyde.

9. Use of a mesoporous nitrogen-carbon supported Me-W catalyst according to claim 8 in catalytic oxidation of benzyl alcohol to prepare benzaldehyde, characterized in that: The solvent is at least one of acetonitrile, dichloromethane and water; The volume ratio of the benzyl alcohol, the hydrogen peroxide and the solvent is 1:1-5:1-40; The mass ratio of the benzyl alcohol to the catalyst is 1:0.1-0.5; The duration of the catalytic oxidation reaction is 1 to 8 hours.

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