CN113070086A - Nitrogen-doped carbon-loaded molybdenum carbide nano composite material and preparation method and application thereof - Google Patents
Nitrogen-doped carbon-loaded molybdenum carbide nano composite material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a nitrogen-doped carbon-loaded molybdenum carbide nano composite material as well as a preparation method and application thereof. Dissolving molybdate and protein into water, forming a protein-molybdate radical cross-linked network through self-assembly, and then sequentially carrying out freeze drying and pyrolysis to obtain Mo2C/NC nano composite material. Mo2C/NC nanocomposites with nitrogen doping for Mo tuning2The interaction between C and a carbon carrier changes the electron density of Mo sites, so that the d-band center of the metal molybdenum is closer to the Fermi level, the activation of hydrogen (including the cracking of hydrogen and the desorption of active hydrogen) is promoted, and the catalyst shows high catalytic activity and high selectivity in the hydrogenation reduction reaction of the nitroaromatic. Further, Mo2The synthesis method of the C/NC nano composite material is simple, mild in condition, low in cost and beneficial to large-scale production.
Description
Technical Field
The invention relates to a hydrogenation catalytic material, in particular to a nitrogen-doped carbon-loaded molybdenum carbide nano composite material, a preparation method thereof and application of the nitrogen-doped carbon-loaded molybdenum carbide nano composite material in catalyzing hydrogenation reduction of nitroarene into aromatic amine, and belongs to the technical field of hydrogenation catalysis.
Background
Catalytic hydrogenation is of vital importance in the chemical industry for the synthesis of fine and bulk chemicals. The noble metal-based catalyst is widely applied to hydrogenation reaction. However, the high cost and susceptibility to poisoning limit its large-scale application. Transition Metal Carbides (TMC) are of great interest due to their electronic structure and catalytic properties similar to those of noble metals. For example, molybdenum carbide (MoC)x) The catalyst shows good activity in various hydrogenation reactions such as hydrodesulfurization, biomass conversion, dry reforming of methane, CO hydrogenation and the like. However, H of TMCs catalyst2Activation (including H)2Dissociation and desorption of active hydrogen) is the rate control step that determines the catalytic hydrogenation performance. Thus, increasing H in catalytic hydrogenation of TMCs2The activation capacity is very important.
H2The activation on the transition metal depends mainly on the d orbital of the metal, and for supported catalysts, the metal-support interaction (MSI) can adjust the d orbital of the transition metal and improve H2The activation capacity, thereby affecting the catalytic activity. MSI can be adjusted by (but is not limited to) changing the composition and structure of the support, especially for carbon supported catalysts. The physical and chemical properties of the carbon matrix can be adjusted by doping, introducing defects, pore formation, and the like. For example, nitrogen doping can make the carbon matrix an excellent support for supporting the transition metal catalyst. Nitrogen has a smaller atomic radius and a higher electronegativity than carbon. Meanwhile, the interaction between the p orbital of N and the d orbital of metal is stronger than that of C. Thus, when an N-doped Carbon matrix, the interaction between the Carbon support and the metal sites inevitably changes significantly, for example, the wu jun theme group prepared iridium nanoparticles supported on N-doped graphene sheets (Ir @ N-G-750), and Density Functional Theory (DFT) calculations showed that N can stabilize the iridium nanoparticles and enhance the metal-support interaction between the iridium nanoparticles and the graphene support (Shi, r.; Zhao, j.; Liu, s., Carbon 2018,130, 185-195.). The Liangming topic group finds that N can strengthen in Cu loaded with N-doped grapheneThe interaction between Cu and the carbon matrix promotes the adsorption of CO on the carbon surface (Wu, X.; Feng, B.; Li, W., Nano Energy 2019,62, 117-.
Disclosure of Invention
Aiming at the defects of the prior nitroaromatic catalytic hydrogenation technology, the invention aims to provide nitrogen-doped carbon-loaded Mo2C nanocomposite material using nitrogen doping to adjust Mo2The interaction between C and a carbon carrier changes the electron density of Mo sites, so that the d-band center of the metal molybdenum is closer to the Fermi level, the activation of hydrogen (including the cracking of hydrogen and the desorption of active hydrogen) is promoted, and the excellent performance is shown in the hydrogenation reduction reaction of nitro compounds.
The second purpose of the invention is to provide a method for preparing the nitrogen-doped carbon-supported molybdenum carbide nanocomposite material, which has the advantages of mild conditions, simple steps and low cost.
The third purpose of the invention is to provide application of the nitrogen-doped carbon-supported molybdenum carbide nanocomposite, wherein the nitrogen-doped carbon-supported molybdenum carbide nanocomposite is used for hydrogenation reduction of nitroarene to aromatic amine, and shows high-efficiency catalytic activity and selectivity.
In order to achieve the technical purpose, the invention provides a preparation method of a nitrogen-doped carbon-loaded molybdenum carbide nano composite material, which comprises the steps of dissolving molybdate and protein into water, forming a protein-molybdate radical cross-linked network through self-assembly, and then sequentially carrying out freeze drying and pyrolysis to obtain the nitrogen-doped carbon-loaded molybdenum carbide nano composite material.
The preparation key of the nitrogen-doped carbon-loaded molybdenum carbide nanocomposite is that high-nitrogen-content protein is used as a carbon source and a nitrogen source at the same time, polar groups contained in the protein and molybdate can form a protein-molybdate crosslinked network through self-assembly in a solution system, the original structure of a protein-molybdate crosslinked network precursor can be maintained through freeze drying, high-temperature pyrolysis is carried out on the basis, and the precursor is converted into the nitrogen-doped carbon-loaded molybdenum carbide nanocomposite in situ. During the high-temperature pyrolysis process, the conversion of protein into nitrogen-doped carbon carrier and the conversion of molybdenum source are simultaneously realizedAnd forming nano-grade molybdenum carbide particles, realizing in-situ compounding of the nano-grade molybdenum carbide particles and the nitrogen-doped carbon carrier, wherein a very thin nano-nitrogen-doped carbon coating is generated on the surfaces of the nano-grade molybdenum carbide particles in situ, and the molybdenum carbide particles are uniformly dispersed in the nitrogen-doped carbon carrier. Nitrogen in nitrogen-doped carbon can change the electron density of molybdenum sites to make the d-band center of the metal closer to the Fermi level, thereby promoting H2The adsorption and the dissociation of active hydrogen of the molybdenum carbide can greatly improve the catalytic activity of the molybdenum carbide, and the catalyst is found to have no hydrogenation catalytic activity on alkynyl, carbonyl, carboxyl and other groups and show high-selectivity hydrogenation catalysis on nitro, which is unexpected. In addition, protein molecules and molybdate are self-assembled in a solution system to form a protein-molybdate crosslinked network, and the structure of a precursor of the protein-molybdate crosslinked network can be basically maintained through freeze drying and high-temperature carbonization, so that an additional template agent is not required to be introduced, and the preparation process is simplified.
As a preferred embodiment, the molybdate is a conventional water-soluble molybdate, such as ammonium molybdate, sodium molybdate and the like, which are common, and specifically (NH)4)6Mo7O24、Na2MoO4、Li2MoO4、K2MoO4And so on.
As a preferred embodiment, the protein is a nitrogen-rich protein, such as bovine serum albumin, egg white, whey protein, silk protein, and other proteins.
In a preferred embodiment, the weight ratio of molybdate to protein is 1 (1-10), and most preferably 1 (1-1.5).
As a preferred embodiment, the pyrolysis conditions are: in N2Under protection, heating to 700-900 ℃ at a heating rate of 5-30 ℃/min, and preserving heat for 2-7 h. The further preferable pyrolysis temperature is 700-900 ℃. The nitrogen doping amount can be reduced when the temperature is too high, so that the catalytic activity of the nitrogen-doped carbon-loaded molybdenum carbide nano composite material can be influenced, and the carbonization degree is low when the temperature is too low, so that the composite material is not generated.
The invention also provides a nitrogen-doped carbon-loaded molybdenum carbide nano composite material, which is prepared by the preparation method.
As a preferable scheme, the nitrogen-doped carbon-loaded molybdenum carbide nanocomposite is formed by uniformly distributing nano molybdenum carbide particles coated by a nano carbon layer in a nitrogen-doped carbon matrix; the average particle size of the nano molybdenum carbide particles is within the range of 4-14 nanometers. The nitrogen-doped carbon-loaded molybdenum carbide nano composite material (Mo) of the invention2C/NC) of Mo2The average particle size of the C nano particles is small, and the distribution is uniform. Mo2The surface of the C particle is covered with a thin carbon layer which can prevent Mo2The aggregation of the C nano particles can also induce the MSI effect, which is beneficial to improving the hydrogenation catalytic activity.
The invention also provides application of the nitrogen-doped carbon-loaded molybdenum carbide nano composite material in catalyzing hydrogenation reduction of nitroarene into aromatic amine.
As a preferred scheme, the conditions of the hydrogenation reaction are as follows: the pressure is 8-12 bar, and the reaction is carried out for 2-4 h at 105-115 ℃.
The specific structural formula of the nitroarene is as follows:
ArNO2
ar is phenyl or substituted phenyl, or aromatic condensed ring group, or aromatic heterocyclic group, or benzoaromatic heterocyclic group. The substituted phenyl group is a substituent group which contains common substituent groups on a benzene ring, such as alkynyl, acyl, cyano, C1～C10Alkyl, halogen substituents, carboxyl, C1～C10Alkoxy radical, C1～C10Alkylthio, hydroxyl, amido, and the like. Aromatic fused rings such as naphthalene and the like, benzoaromatic heterocyclic groups such as quinoline and the like. The high selectivity reduction of the nitro group in the nitro aromatic hydrocarbon by the nitrogen-doped carbon-loaded molybdenum carbide nano composite material is not influenced by the selection of the aromatic hydrocarbon group in the nitro aromatic hydrocarbon and the introduction of various substituents in the aromatic hydrocarbon group. Of particular interest is the controlled highly selective reduction of a nitro group when the phenyl ring contains two nitro groups.
The nitrogen-doped carbon-supported Mo of the invention2C nanocomposite (Mo)2C/NC) preparation method, specifically comprisingThe method comprises the following steps: weighing 1g of BSA in a beaker, adding 10mL of deionized water, and stirring for dissolving; weighing 1g (NH)4)6Mo7O24·4H2Adding 10mL of deionized water into a centrifugal tube, dissolving by ultrasonic, dropwise adding the formed molybdate solution into BSA while stirring until the mixture is completely and uniformly stirred; transferring the solution into a beaker after stirring, putting the beaker into a freeze drying box until the solvent is completely freeze-dried to obtain a yellow solid after freeze-drying, fully grinding the yellow solid to obtain powder, putting the powder into a porcelain boat, covering the porcelain boat with a cover (another porcelain boat), putting the porcelain boat into a tube furnace, and performing N reaction2Heating to 800 ℃ at the speed of 5 ℃/min in the atmosphere to perform calcination treatment, keeping the temperature for 3 hours, and then cooling to room temperature to obtain black powder named as Mo2C/NC。
Mo of the invention2Use of C/NC nanocomposites for H2The catalytic nitrobenzene hydrogenation reduction reaction is implemented specifically as follows: a mixture of 0.25mmol nitrobenzene, 20mg catalyst and 4mL deionized water was placed in a 50mL stainless steel autoclave with H2Purged three times to remove air, then pressurized to 10bar and reacted at 110 ℃ for 3 h. After the reaction is finished, naturally cooling to room temperature, and removing the residual H2And (4) discharging. The mixture was collected in a centrifuge tube, extracted with ethyl acetate and analyzed by gas chromatography.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1) according to the technical scheme, the protein contains polar groups, the polar groups and molybdate can form a protein-molybdate crosslinked network in a solution system through self-assembly, the original structure of the protein-molybdate crosslinked network precursor can be maintained through freeze drying, a template agent does not need to be additionally introduced, a template removing machine does not need to be subjected to acid or alkali post-treatment, and the simplification of process steps is facilitated.
2) The nitrogen-doped carbon-loaded molybdenum carbide nano composite material is prepared from Mo2The C nano-particle surface is coated with a thin carbon layer, and the characteristic can prevent Mo2Aggregation of C, MSI effect can also be induced, and Mo2The C nano particles are uniformly dispersed in the nitrogen-doped carbon carrier, and nitrogenN in the doped carbon carrier can also adjust Mo2MSI between C and carbon support can promote hydrogen activation.
3) The nitrogen-doped carbon-loaded molybdenum carbide nano composite material is used as a hydrogenation catalyst, can catalyze the hydrogenation reduction reaction of nitro compounds under the action of hydrogen, and has good catalytic activity, selectivity and stability. The N-doped carbon loaded molybdenum carbide nano composite material is mainly based on MSI effect, utilizes N doping to adjust the interaction between the p orbit of N and the d orbit of Mo, increases the electron density of Mo, and is beneficial to H2In the presence of Mo2Activation on C, Mo2The performance of C/NC in hydrogenation catalysis is obviously superior to that of Mo2C and Mo2C/C。
4) The preparation method of the nitrogen-doped carbon-loaded molybdenum carbide nano composite material is simple, easy to operate, environment-friendly and applicable to industrialization, and adopts nontoxic and cheap raw materials without large-scale complex devices.
Drawings
FIG. 1 shows Mo prepared in example 1 of the present invention2Schematic synthesis process of C/NC sample, Mo2Transmission Electron Microscope (TEM) image, HR-TEM image and Mo of C nanoparticles2Element Mapping (Mapping) graph of C/NC: (a) mo prepared for example 12A manufacturing process schematic diagram of the C/NC sample; (b) is Mo2TEM and Mo of C nanoparticles2A C NP size distribution map; (c) and (d) Mo prepared in example 12HR-TEM image of C/NC sample; (e) is Mo2Element Mapping (Mapping) graph of C/NC.
FIG. 2 shows Mo prepared in examples 1 and 2 of the present invention2C/NC、Mo2C/C sample and commercial Mo2X-ray photoelectron Spectroscopy (XPS) graph of C, H2TPR maps and H2-TPD map: (a) sample Mo prepared for example 12N1s XPS peak for C/NC; (b) sample Mo prepared for examples 1,22C/NC、Mo2C/C and Mo commercial products2Mo 3d XPS peak of C; (c) sample Mo prepared for examples 1,22C/NC、Mo2C/C and Mo commercial products2H of C2-a TPR map; (d) are prepared for examples 1 and 2Prepared sample Mo2C/NC、Mo2C/C and Mo commercial products2H of C2-TPD map.
FIG. 3 shows Mo prepared in example 1 of the present invention2Hydrogenation performance diagram of C/NC sample under different conditions: (a) nitrobenzene concentration vs. 8bar H2The effect of the initial hydrogenation rate at 110 ℃, the initial reaction rate was calculated at a conversion below 20%; (b) h at 110 DEG C2Influence of pressure on the nitrobenzene hydrogenation rate; the concentration of nitrobenzene is 5mmol/L, and the dosage of the catalyst is 0.55 mg/mL; the content of the mixture was determined by gas chromatography.
FIG. 4 shows Mo prepared in example 1 of the present invention2Charge density difference map, PDOS map and H for different N configurations in C/NC samples2Free energy profile of dissociation: (a) is Mo2C/NC-0、Mo2C/NC-1、Mo2C/NC-2 and Mo2Charge density differences for the C/NC-3 configuration (yellow and cyan regions represent electron accumulation and depletion, respectively); (b) is Mo2Calculation of predicted density of states of Mo atoms in C/NCs, and (C) predicted density of states of carbon, graphite-N, pyridine-N, and pyrrole-N; (d) is Mo2C/NC-0、Mo2C/NC-1、Mo2C/NC-2 and Mo2C/NC-3 upper H2The free energy distribution of dissociation.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples, but the scope of the present invention is not limited to the following examples.
Example 1
Catalyst sample Mo2C/NC preparation: 1g BSA and 1g (NH)4)6Mo7O24·4H2O was dissolved in 10mL of deionized water. Then, the (NH) is added4)6Mo7O24·4H2And dropwise adding the O solution into the bovine serum albumin aqueous solution, and stirring to form a BSA-Mo network. After stirring was complete, the solution was transferred to a beaker and placed in a freeze drying oven until the solvent was completely lyophilized. Grinding the freeze-dried solid to obtain powder, placing into a porcelain boat, covering with a cover (another porcelain boat), and transferring into a tube furnaceIn the presence of nitrogen gas, at 5 deg.C for min-1Heating the sample to 800 ℃ and holding at 800 ℃ for 3h, and then cooling to room temperature, the sample obtained was named Mo2C/NC。
Example 2 (comparative example)
Catalyst sample Mo2C/C preparation: mixing 1g sucrose and 1g Na2MoO4Dissolved in 10mL of deionized water. Subsequently, Na is added2MoO4The solution is dripped into a sucrose aqueous solution and stirred to form a sucrose-Mo network. After stirring was complete, the solution was transferred to a beaker and placed in a freeze drying oven until the solvent was completely lyophilized. Grinding the freeze-dried solid to obtain powder, placing into a porcelain boat, covering with a cover (another porcelain boat), transferring into a tube furnace, pyrolyzing under nitrogen flow at 5 deg.C for one minute1Heating the sample to 800 ℃ and holding at 800 ℃ for 3h, and then cooling to room temperature, the sample obtained was named Mo2C/C。
N-doped carbon loaded molybdenum carbide (Mo)2C/NC) is shown in FIG. 1 (a). Shown in FIG. 1(b) is Mo2Transmission Electron Microscope (TEM) image of C/NC, Mo2The average particle diameter of the C nanoparticles was 8.23 nm. Shown in FIG. 1(c) is Mo2High resolution transmission electron microscopy (HR-TEM) of C/NC, the surface of these particles being covered with a thin carbon layer, which not only prevents Mo2Aggregation of C, may also induce MSI effects. As shown in FIG. 1(d), the interplanar spacing of these particles was 0.228nm and was directed to the (101) plane of Mo 2C. Shown in FIG. 1(e) is Mo2High angle annular dark field scanning transmission electron microscope (HAADF-STEM) and corresponding Energy Dispersive Spectroscopy (EDS) mapping images of C/NC, Mo can be seen2The size of C is small. Meanwhile, the Mo element is uniformly distributed in the entire carbon matrix.
Shown in FIG. 2(a) is Mo2High resolution XPS spectra of the N1s peak for C/NC, 398.3eV, 399.6eV, 401.3eV correspond to pyridine N, pyrrole N, and graphite N, respectively. Shown in FIG. 2(b) is Mo2High resolution XPS spectra of Mo 3d peak of C/NC. And Mo2C/NC comparison, Mo2C and Mo2Mo 3d binding energy of C/C exhibits positive shiftThis is due to the interaction of Mo and doped N in the carbon support. N doping can alter the electron density of Mo sites, which is in contrast to H2The adsorption and desorption of (a) are closely related. As shown in FIG. 2(c), H is used2TPR temperature programmed reduction method studies the interaction between hydrogen and different catalysts. In addition, the position of the reduction peak may reflect the strength of the metal-support interaction. Mo2C/NC and Mo2There are two peaks in the TPR profile of C/C, and Mo2C has only one peak. Specifically, the peak of the low temperature region is due to reduction of the passivation layer. Higher temperature region corresponding to Mo2C and containing Mo2And (4) decomposing the substance C. And Mo2C and Mo2C/C ratio, Mo2C/NC at 232 ℃ (Mo)2C:243℃、Mo2A first peak of decrease occurs at a lower temperature of 281 ℃ C/C. This indicates that in Mo2C/NC on H2Activation is easier. For higher reduction temperatures (Mo)2C/NC:736℃、Mo2640 ℃ C. indicating Mo2There is a strong interaction between C and N doped carbon carriers. These results are consistent with the results of XPS analysis. As shown in FIG. 2(d), H is used2The adsorption capacity of the catalyst to hydrogen was investigated in a TPD temperature programmed desorption experiment. Mo2C/NC and Mo2H of C/C2Two peaks in the TPD spectrum, and Mo2H of C2-none in the TPD spectrum. Generally, the low temperature signal results from desorption of chemisorbed hydrogen at the metal sites, while the high temperature signal is associated with hydrogen species breakthrough. And Mo2C/C ratio, Mo2C/NC desorption of H at higher temperatures (75 ℃ and 103 ℃)2This means that Mo is2C/NC has stronger hydrogen adsorption capacity. Mo2H overflow temperature of C/NC is lower than Mo2C/C(Mo2C/NC:249℃；Mo2260 ℃ C.), which means that dissociated H species are more readily removed from Mo2C/NC desorption, which shows that N doping can promote H2Adsorption and dissociation. In summary, H2TPD and H2TPR results show that N in the carbon support can regulate Mo2MSI between C and carbon support, which may promote hydrogen activation.
As shown in table 1, hydrogenation activity of the catalyst was examined by using nitrobenzene reduction as a model reaction. In particular, whether it is Mo2C itself or N-doped carbon (NC) shows activity to nitrobenzene hydrogenation catalysis. In contrast, the load type Mo2C shows better catalytic performance. Notably, Mo2C/C conversion and selectivity were 18% and 90%, respectively; mo2The C/NC performance is better, and the conversion rate and the selectivity reach 99 percent. Can reasonably obtain Mo2C reactivity was highly correlated with the support. Wherein, Mo2When the C carrier is on the carbon matrix, the hydrogenation activity of Mo2C is improved mainly by MSI, and the introduction of N in the carbon matrix can further improve Mo2The hydrogenation activity of C is improved, thereby improving the catalytic performance of C. Examine the solvent pair Mo2Influence of C/NC catalytic Activity. In various solvents, including water and various alcohols, Mo2The best performance of C/NC in water.
As shown in Table 2, Mo was investigated2The applicability and the universality of the C/NC for hydrogenation of nitro compounds. Mo2C/NC has very high activity, and all evaluation substrates (17 cases) can be selectively hydrogenated into corresponding amine compounds with high conversion rate. In general, aldehyde groups are easily hydrogenated and easily converted to hydroxyl compounds on noble metal catalysts such as Pt/C. In contrast, for Mo2The C/NC catalyst, 4-nitrobenzaldehyde, was efficiently hydrogenated to 4-aminobenzaldehyde (Table 2, item 2) with 99% conversion and 99% selectivity (selectivity in parentheses). Other unsaturated groups such as halogens, ketones, amides, alkynes, and the like remain during hydrogenation. For example, halonitro compounds can be hydrogenated with up to 99% conversion and 99% selectivity without dehalogenation (table 2, items 6, 7). Mo2The hydrogenation of C/NC para-nitro substituted N heterocycles also showed very high selectivity (Table 2, items 15, 17).
TABLE 1
TABLE 2
As shown in FIG. 4, the Density Functional Theory (DFT) is used to calculate Mo in N-doped pair2MSI and H between C and carrier2Influence of activation and hydrogenation activity. In the presence of Mo2In C/NC, N exists mainly in 3 forms, graphite-N, pyridine-N and pyrrole-N, respectively. First, Mo is compared2The difference in charge density of the C site interaction with N or C. Under the action of N, Mo2The electron transfer between C and the carbon support is significantly enhanced, as both the electron accumulation and depletion regions are scaled up, indicating that N-doped carbon and Mo are comparable to pure carbon2The interaction of C is stronger, which is beneficial to the adsorption of hydrogen. As shown in FIGS. 4(b) and (c), Mo was investigated2Predicted state density of C/NCs (PDOS). For Mo2C/NCs, the d-orbital of Mo contributes most to DOS near the Fermi level. Mo2C/NC-X (X ═ 1,2,3) ratio Mo2C/NC-0 has a higher PDOS; while near the fermi level, the p-orbital of N exhibits a higher DOS than the p-orbital of carbon. This indicates that N doping can enhance the DOS of Mo, thereby providing higher active electrons. Mo2C/NC-0 d band center (E)d) Is 1.93eV, Mo2C/NC-1 is 1.88eV, Mo2C/NC-2 of 1.85eV, Mo2C/NC-3 was 1.84 eV. Obviously, the center of the d-band is closer to the Fermi level after the interaction with N, which is beneficial to the adsorption of hydrogen. In summary, the N dopant can adjust Mo2The initial MSI and carbon support between C is through the interaction between the p orbitals incorporating the N and d orbitals. The interaction can improve the electron density of the molybdenum, and is beneficial to hydrogen adsorption/dissociation, thereby improving the Mo2The catalytic performance of C.
By way of example, the applicant has demonstrated Mo2Preparation method of C/NC nano composite material and p-nitro compound thereofThe effect of the hydrogen reduction reaction. The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all equivalent changes and modifications made in the claims of the present invention should be covered by the present invention, and the protection scope of the present invention is as shown in the claims of the present application.
Claims (7)
1. A preparation method of a nitrogen-doped carbon-loaded molybdenum carbide nano composite material is characterized by comprising the following steps: and dissolving molybdate and protein into water, forming a protein-molybdate cross-linked network through self-assembly, and then sequentially carrying out freeze drying and pyrolysis to obtain the molybdate-molybdate cross-linked network.
2. The method for preparing the nitrogen-doped carbon-supported molybdenum carbide nanocomposite material according to claim 1, wherein the method comprises the following steps:
the molybdate is (NH)4)6Mo7O24、Na2MoO4、Li2MoO4、K2MoO4At least one of them.
The protein is at least one of bovine serum albumin, egg white, whey protein and silk protein.
3. The method for preparing the nitrogen-doped carbon-supported molybdenum carbide nanocomposite material according to claim 1 or 2, wherein the method comprises the following steps: the mass ratio of the molybdate to the protein is 1 (1-10).
4. The method for preparing the nitrogen-doped carbon-supported molybdenum carbide nanocomposite material according to claim 1, wherein the method comprises the following steps: the pyrolysis conditions are as follows: in N2Under protection, heating to 700-900 ℃ at a heating rate of 5-30 ℃/min, and preserving heat for 2-7 h.
5. A nitrogen-doped carbon-loaded molybdenum carbide nano composite material is characterized in that: the preparation method of any one of claims 1 to 4.
6. The nitrogen-doped carbon-supported molybdenum carbide nanocomposite material according to claim 5, wherein: the nano molybdenum carbide particles coated by the nano carbon layer are uniformly distributed in the nitrogen-doped carbon substrate; the average particle size of the nano molybdenum carbide particles is within the range of 4-14 nanometers.
7. The use of the nitrogen-doped carbon-supported molybdenum carbide nanocomposite material according to claim 5 or 6, wherein: the method is applied to catalyzing hydrogenation reduction of nitroaromatic hydrocarbon into aromatic amine.
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