Preparation method of alpha-mo c and product and application thereof

Abstract

The application relates to the technical field of catalysts, in particular to a preparation method of alpha-MoC and products and applications thereof, at least comprising the following steps: S1, providing Mo powder with a purity of greater than or equal to 99.9%; S2, pretreating the Mo powder; and S3, preparing the alpha-MoC by adopting a low-temperature carbonization technology on the pretreated Mo powder. The application discards the traditional multi-step long process and high-temperature high-energy-consumption process, and solves the core pain points of low product purity, poor dispersity, serious pollution and difficulty in large-scale production in the prior art. The obtained alpha-MoC has a purity of greater than or equal to 95%, excellent catalytic activity, a preparation period shortened to 8-12 hours, energy consumption reduced by 70%, wastewater discharge reduced by more than 90%, and is suitable for industrial production and can be widely applied to thermal catalysis scenes such as CO2 resourceization, hydrogen production by reforming of low-carbon compounds, selective hydrogenation of unsaturated hydrocarbons and the like.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a method for preparing α-MoC, its products, and their applications. Background Technology

[0002] α-MoC belongs to the field of transition metal carbide (TMC) materials and application technology. Its core application scenarios cover thermocatalysis (CO2 hydrogenation, water-gas conversion, methanol / ethanol reforming to produce hydrogen, etc.), energy storage (lithium-ion battery anode) and electrocatalysis (hydrogen evolution, oxygen reduction reaction).

[0003] Current α-MoC technology, centered on "molybdenum-based precursor carbonization" and "supported α-MoC construction," while capable of synthesizing and controlling performance, suffers from five major drawbacks: The preparation process is cumbersome and difficult to mass-produce: it requires multiple steps including "precursor preparation - pretreatment - carbonization - post-treatment". The precursor preparation requires raw materials such as molybdate / organomolybdenum complexes, which need to be stirred for 12-24 hours, dried for 12 hours, and calcined for 5 hours, taking 3-5 days and being prone to moisture absorption; the pretreatment (pre-reduction / doping) easily induces MoO. X Or N / O impurities; post-treatment acid washing (e.g., 1M HCl) produces Mo-containing products. 2+ Cl - Wastewater treatment accounts for 20-30% of environmental protection costs.

[0004] Carbonization is high-temperature and high-energy-consuming, making quality control difficult: it requires carbonization at 900-1200℃ for 6-12 hours, with a unit energy consumption of 1200kWh / t (energy cost of 720 yuan per ton), relying on customized graphite furnaces (costing 5-8 times that of ordinary tube furnaces); high temperature causes grain coarsening from <20nm to >100nm, and specific surface area from 150-200m². 2 / g decreased to <50m 2 / g, active sites reduced by more than 70%; CH4 / H2 ratio difficult to control, prone to formation (XRD 2θ=36.5°, 42.3°) or residual metal Mo (2θ=40.5°), the purity of α-MoC is only 60-70%, and the catalytic selectivity is significantly reduced.

[0005] Inefficient use of carbon sources and high pollution: Solid carbon sources (glucose, carbon nanotubes) require a 50-100% excess, with a utilization rate of <40%; gaseous carbon sources (such as 50% CH4 + 50% H2) have only 30% of carbon participating in the reaction; uneven mixing of solid carbon sources easily leads to the formation of MoC2 / MoO. X Acid washing removes residual carbon, producing carbon-containing sludge with COD > 5000 mg / L.

[0006] The product exhibits poor performance and stability: α-MoC nanoparticles have high surface energy (>100 mJ / m²). 2Template-free agglomerates reach 500-1000nm, with an active site exposure rate of only 20-30%; high-temperature carbonization (>800℃) leads to sintering of carbon-supported particles (>200nm); multi-step process results in batch specific surface area deviation >10%, purity deviation >15%, and catalytic rate deviation >25%.

[0007] The equipment requirements are high and the safety risks are significant: a high-temperature furnace and a 99.99% pure Ar protection system are required, with an investment of over 2 million yuan for a single pilot line; at high temperatures, the flow rate (<50mL / min) and pressure (<0.1MPa) of CH4 / H2 (flammable and explosive) must be strictly controlled, and the furnace tubes are prone to carbon buildup and blockage, requiring professionally certified operation. Summary of the Invention

[0008] To address the above problems, the first aspect of the present invention provides a method for preparing α-MoC, comprising at least the following steps: S1. Provide Mo powder with a purity of ≥99.9%; S2. Pre-treat the Mo powder; S3. The α-MoC is prepared by low-temperature carbonization technology on the pretreated Mo powder.

[0009] In one embodiment, the method for preparing the Mo powder includes: Using MoO3 as raw material, a mixed atmosphere is introduced, and the material is reduced in a tube furnace by stepwise heating and cooling to obtain Mo powder with a purity of ≥99.9%.

[0010] In one embodiment, the mixed atmosphere comprises Ar and hydrogen, wherein the volume ratio of Ar to hydrogen is (90-95):(5-10). Examples include 90:5, 90:10, 95:5, and 95:10.

[0011] In one embodiment, the ventilation rate of the mixed atmosphere is 50-200 mL / min.

[0012] In one embodiment, the stepwise heating and reduction step includes: holding at 500-600℃ for 1.5-4 hours, then heating to 750-850℃ and holding for 2-4 hours.

[0013] In one embodiment, the pretreatment step in S2 includes: washing the Mo powder with hydrochloric acid, ultrasonic cleaning, and drying.

[0014] In one embodiment, the preprocessing step in S2 includes: Soak the Mo powder in hydrochloric acid for 3-5 minutes; After adding deionized water and sonicating for 20-30 minutes, filter and separate the Mo powder, transfer it to a beaker containing anhydrous ethanol, and sonicate again for 20-30 minutes. The ultrasonically cleaned Mo powder is dried at 80-90℃ for 2-3 hours.

[0015] In one embodiment, the molar concentration of the hydrochloric acid is 0.5 mol / L.

[0016] In one embodiment, the ultrasound has a frequency of 30 kHz and a power of 200 W.

[0017] In one embodiment, the moisture content of the Mo powder dried in step S2 is < 0.1 wt%.

[0018] In one implementation, step S3 includes: Pretreated Mo powder is placed in a high-vacuum tube furnace, vacuumed, and then mixed gas is introduced. The temperature is raised to 500-550℃ and reacted for 2-5 hours to obtain α-MoC.

[0019] In one embodiment, the mixed gas is H2 and CH4, and the volume ratio of H2 to CH4 is (80-90):(10-20). Examples include 80:20, 85:15, and 90:10.

[0020] In one embodiment, the gas flow rate of the mixed gas is 10-200 mL / min.

[0021] In one embodiment, the flow rate of the mixed gas ensures that the molar ratio of Mo to C is 1:1.

[0022] In one embodiment, the gas pressure of the high-vacuum tube furnace is 1.1 × 10⁻⁶. -3 Pa.

[0023] The second aspect of this invention provides a method for preparing α-MoC, wherein the product has a grain size of 5-20 nm and a specific surface area of ​​180-220 m². 2 / g.

[0024] A third aspect of the present invention provides an application of the product in thermocatalytic reactions in the energy and environmental protection fields.

[0025] The α-MoC prepared by this invention has direct applications focused on thermocatalytic reactions in the energy and environmental protection fields, specifically including the following three categories: 1. Thermocatalytic technology for the resource utilization of carbon dioxide (CO2): Core application scenarios: Reverse water-gas shift reaction (RWGS: CO2+H2→CO+H2O), selective hydrogenation of CO2 to methanol / dimethyl ether, etc.

[0026] Application logic: The α-MoC prepared by this patent has excellent CO2 adsorption and activation capacity (adsorption energy -2.94 eV) and H2 dissociation efficiency (activation energy 0.56 eV), which can efficiently convert CO2 into high-value CO (the core component of syngas) or methanol, solving the problems of low low-temperature activity and poor CO selectivity of existing RWGS catalysts (such as Ni-based and CeO2-based catalysts). It can be directly applied to industrial tail gas CO2 emission reduction and resource utilization scenarios (such as CO2 treatment in steel plants and power plants).

[0027] 2. Thermocatalytic technology for hydrogen production from low-carbon compound reforming: Core application scenarios: methanol aqueous reforming for hydrogen production (APRM: CH3OH+H2O→3H2+CO2), selective partial reforming of ethanol for hydrogen production (C2H5OH+H2O → 2H2+CH3COOH), etc.

[0028] Application logic: α-MoC can synergistically activate the CH bonds of methanol / ethanol and the OH bonds of water through the Mo-C interface, inhibiting the breaking of C-C bonds (avoiding...) Byproducts), the highly dispersed α-MoC (specific surface area 180-220 m²) prepared by this invention 2 The yield of H2 from methanol reforming can reach 171 μmol / (g・s) (6 times that of traditional Pt / Al2O3), which can be directly applied to distributed hydrogen production scenarios (such as on-board hydrogen production in fuel cell vehicles and small hydrogen refueling stations).

[0029] 3. Thermocatalytic technology for selective hydrogenation of unsaturated hydrocarbons: Core application scenarios: selective hydrogenation of acetylene to ethylene (C2H2+H2O / CO→C2H4+CO2), selective hydrogenation of phenylacetylene to styrene (C8H6+H2→C8H8), etc.

[0030] Application Logic: The Mo active sites on the α-MoC surface can precisely adsorb unsaturated hydrocarbons (such as acetylene adsorption energy -3.15 eV). Combined with the OH* generated by H2O dissociation as a mild hydrogen source, it avoids excessive hydrogenation (such as the generation of C2H6). After Au / Pt is loaded onto the α-MoC prepared in this invention, an acetylene conversion rate of >99% and an ethylene selectivity of 83% can be achieved. It can be directly applied to unsaturated hydrocarbon purification scenarios in petrochemicals (such as the removal of trace amounts of acetylene from cracked gas).

[0031] Beneficial effects 1. The process of this invention is simple and efficient, with a low risk of introducing impurities: The integrated process eliminates redundant steps such as precursor preparation, pre-reduction, and acid washing post-treatment in traditional technologies, shortening the preparation cycle from 3-5 days to 8-12 hours and increasing production efficiency by more than 90%.

[0032] This invention uses pure Mo powder as the sole raw material throughout the entire process, without the need to add solvents, dopants, or solid carbon sources. The reaction is controlled solely by a gas atmosphere, and the impurity content of O, N, Cl, etc. in the product is <0.1%, laying the foundation for the synthesis of high-purity α-MoC.

[0033] 2. Low temperature, energy saving, and cost reduction; compatible with conventional equipment: In this invention, the carbonization temperature of 550℃ is reduced by 350-650℃ compared with the traditional technology (900-1200℃), the energy consumption per unit mass of α-MoC is reduced to 350kWh / t, which is 70% lower than the traditional technology, and the energy cost per ton is reduced from 720 yuan to 210 yuan.

[0034] The low-temperature process can directly utilize commonly used high-vacuum tube furnaces (quartz tubes, maximum temperature 800℃) in laboratories / factories, eliminating the need for customized high-temperature graphite furnaces. This reduces equipment procurement costs by more than 80% (only 30,000-50,000 RMB), extends the service life of the furnace tubes from 3 months to more than 1 year, and significantly reduces maintenance costs.

[0035] 3. The product of this invention exhibits excellent performance and outstanding catalytic activity: Precise control of carbonization atmosphere and temperature, XRD detection shows no (2θ=36.5°), metallic Mo (2θ=40.5°) impurity peaks, α-MoC purity ≥95%, CO2 adsorption energy stable at -2.94 eV, CO selectivity in RWGS reaction ≥94%.

[0036] In this invention, a low temperature of 550℃ is used to suppress grain growth, controlling the α-MoC grain size to 5-20 nm and achieving a specific surface area of ​​180-220 m². 2 / g, the active site exposure rate is increased to 60-70%, and the H2 yield in the methanol reforming hydrogen production reaction reaches 171μmol / (g・s), which is 6 times that of the traditional Pt / Al2O3 catalyst.

[0037] 4. Green, environmentally friendly, and clean, meeting dual carbon requirements: In this invention, a mixed gas of 80% H2 and 20% CH4 is matched with an α-MoC stoichiometric ratio (Mo:C=1:1). H2 promotes the dissociation of CH4, increasing the carbon source utilization rate to 60-70%. Unreacted gas can be recycled, reducing carbon source waste.

[0038] The entire process involves no solid carbon source or pickling steps, reducing wastewater discharge by more than 90%, with a COD value of < 50 mg / L, far below the national industrial wastewater discharge standard (100 mg / L), thus achieving clean production.

[0039] 5. Good batch consistency, suitable for large-scale production: The one-step process of this invention is simple and controllable, with different batches of products showing a specific surface area deviation of <5%, a purity deviation of <3%, and a catalytic performance deviation of <8%, meeting the core requirements of industrial production for catalyst stability.

[0040] 550℃ is below the explosion limit of CH4 / H2 mixed gas (650℃), CH4 cracking rate is < 5%, there is no risk of carbon buildup clogging the furnace tube, no additional safety devices are required, and ordinary experimental personnel can operate it after simple training, reducing the safety and labor costs of large-scale production.

[0041] 6. Wide range of applications and high industrialization value: The high-purity, highly dispersed α-MoC provided by this invention can be directly used as a catalyst or support, and is suitable for various industrial-grade thermocatalytic scenarios such as CO2 resource recovery (RWGS reaction), distributed hydrogen production (methanol aqueous reforming), and unsaturated hydrocarbon purification (selective hydrogenation of acetylene). It can replace traditional Ni-based and Pd-based noble metal catalysts and reduce application costs. Attached Figure Description

[0042] Figure 1 The figures show the HAADF-STEM, EDS, and XRD characterizations of the Mo powder prepared in step S1 of Example 1; (a) and (d) are the HAADF-STEM images of the Mo powder, (b) and (e) are the EDS energy spectra of the Mo powder, and (c) is the XRD pattern of the Mo powder.

[0043] Figure 2 The image shows the HAADF-STEM characterization of α-MoC prepared in Example 1.

[0044] Figure 3 The image shows the HAADF-STEM characterization of α-MoC prepared in Example 2. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifying specific conditions in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. Example 1

[0046] The first aspect of this example provides a method for preparing α-MoC, including the following steps: S1. Provide Mo powder with a purity of ≥99.9%; S2. Pre-treat the Mo powder; S3. The α-MoC is prepared by low-temperature carbonization technology on the pretreated Mo powder.

[0047] The method for preparing the Mo powder includes: Using MoO3 as raw material, the temperature was first raised to 550℃ and held for 2.5 h in a mixed atmosphere of Ar (95 wt%) and H2 (5 wt%), followed by raising the temperature to 800℃ and holding for 3 h. Then, the temperature was cooled to room temperature in the furnace to obtain Mo powder with a purity ≥ 99.9%.

[0048] The ventilation rate of the mixed atmosphere is 150 mL / min.

[0049] The preprocessing steps in S2 include: The Mo powder was immersed in 0.5 mol / L hydrochloric acid for 3 minutes; Add 100 mL of deionized water and sonicate for 20 min. Filter and separate the Mo powder, transfer it to a beaker containing 100 mL of anhydrous ethanol, and sonicate again for 20 min. The ultrasonically cleaned Mo powder was dried at 80°C for 2.5 hours.

[0050] The ultrasound has a frequency of 30kHz and a power of 200W.

[0051] The moisture content of the Mo powder dried in step S2 is < 0.1 wt%.

[0052] Step S3 includes: Pretreated Mo powder was placed in a high-vacuum tube furnace, and after evacuation, a mixed gas was introduced. The temperature was raised to 550℃ and reacted for 3.5 hours to obtain α-MoC.

[0053] The mixed gas is H2 and CH4, with a volume ratio of H2:CH4 of 80:20. The gas flow rate is 25 mL / min, ensuring a molar ratio of Mo to C of 1:1.

[0054] The gas pressure of the high-vacuum tube furnace is 1.1 × 10⁻⁶. -3 Pa.

[0055] The second aspect of this example provides a method for preparing α-MoC, resulting in a product with a grain size of 5-20 nm and a specific surface area of ​​180-220 m². 2 / g.

[0056] The third aspect of this example provides an application of the product in thermocatalytic reactions in the energy and environmental protection fields.

[0057] Figure 1HAADF-STEM, EDS and XRD characterization images of the Mo powder prepared in step S1 of Example 1; Figure 1 (a) and (d) are HAADF-STEM images of Mo powder, showing that Mo powder has a uniform nanoscale particle morphology and clearly observes the Mo crystal orientation

[111] without other impurity particles or oxide layers, indicating that the microstructure of Mo powder is uniform. Figure 1 (b) and (e) are EDS spectra of Mo powder. The results show that the percentage of Mo atoms is 99%, and no impurity elements such as O and N were detected, which confirms that the Mo powder has excellent purity. Figure 1 (c) shows the XRD pattern of Mo powder. The XRD diffraction pattern of Mo powder is completely matched with the card [42-1120] of the Powder Diffraction File (PDF). The characteristic diffraction peaks (2θ=40.5°, 47.3°, 69.2°) correspond to the (110), (200), and (211) crystal planes of the body-centered cubic structure Mo. No other phase diffraction peaks appear, indicating that Mo powder is a pure body-centered cubic phase.

[0058] Figure 2 The image shows the HAADF-STEM characterization of α-MoC prepared in Example 1. The image reveals that the product exhibits a typical nanoscale particle aggregation morphology, with particle size concentrated in... Furthermore, high-resolution lattice fringe observation revealed a lattice spacing of 0.22 nm, corresponding to the (002) crystal plane of α-MoC, confirming that the products were all α-MoC phase and contained no... The formation of impurity phases such as metallic Mo indicates that the carbonization process can precisely control the phase purity of α-MoC. Example 2

[0059] The first aspect of this example provides a method for preparing α-MoC, including the following steps: S1. Provide Mo powder with a purity of ≥99.9%; S2. Pre-treat the Mo powder; S3. The α-MoC is prepared by low-temperature carbonization technology on the pretreated Mo powder.

[0060] The method for preparing the Mo powder includes: Using MoO3 as raw material, the temperature was first raised to 550℃ and held for 2.5 h in a mixed atmosphere of Ar (95 wt%) and H2 (5 wt%), followed by raising the temperature to 800℃ and holding for 3 h. Then, the temperature was cooled to room temperature in the furnace to obtain Mo powder with a purity ≥ 99.9%.

[0061] The ventilation rate of the mixed atmosphere is 150 mL / min.

[0062] The preprocessing steps in S2 include: The Mo powder was immersed in 0.5 mol / L hydrochloric acid for 3 minutes; Add 100 mL of deionized water and sonicate for 20 min. Filter and separate the Mo powder, transfer it to a beaker containing 100 mL of anhydrous ethanol, and sonicate again for 20 min. The ultrasonically cleaned Mo powder was dried at 80°C for 2.5 hours.

[0063] The ultrasound has a frequency of 30kHz and a power of 200W.

[0064] The moisture content of the Mo powder dried in step S2 is < 0.1 wt%.

[0065] Step S3 includes: Pretreated Mo powder was placed in a high-vacuum tube furnace, and after evacuation, a mixed gas was introduced, and the temperature was raised to 550°C for reaction. α-MoC was obtained.

[0066] The mixed gas is H2 and CH4, with a volume ratio of H2:CH4 of 80:20. The gas flow rate is 100 mL / min, ensuring a molar ratio of Mo to C of 1:1.

[0067] The gas pressure of the high-vacuum tube furnace is 1.5 × 10⁻⁶. -1 Pa.

[0068] The second aspect of this example provides a The product prepared by the method has a grain size of 10-30 nm and a specific surface area of ​​180-220 m². 2 / g.

[0069] The third aspect of this example provides an application of the product in thermocatalytic reactions in the energy and environmental protection fields.

[0070] Figure 3 The image shows the HAADF-STEM characterization of α-MoC prepared in Example 2. The image reveals that the product exhibits a typical nanoscale particle aggregation morphology, with particle size concentrated in... Furthermore, high-resolution lattice fringe observation revealed a lattice spacing of 0.22 nm, corresponding to the (002) crystal plane of α-MoC, confirming that the products were all α-MoC phase and contained no... The formation of impurity phases such as metallic Mo indicates that the carbonization process can precisely control the phase purity of α-MoC.

[0071] Comparative Example 1 The specific implementation method of this comparative example is the same as that of Example 1, except that the mixed gas of H2 and CH4 is replaced with C2H4 (purity ≥99.9%), and in S3: the gas flow rate is 25 mL / min. After heating to 550℃ and reacting for 3.5 h, the system is kept under vacuum and naturally cooled to obtain the product, which is characterized as follows. (No α-MoC is generated).

[0072] Comparative Example 2 The specific implementation method of this comparative example is the same as that of Example 1, except that the mixed gas of H2 and CH4 is replaced with CO (purity ≥99.9%), and in S3: the gas flow rate is 25 mL / min, and the temperature is increased to... After reacting for 3.5 h, the system was kept under vacuum and allowed to cool naturally to obtain the product, which was characterized as a small amount of β-Mo2C+. (No α-MoC is generated).

[0073] Comparative Example 3 The specific implementation method of this comparative example is the same as that of Example 1, except that the mixed gas of H2 and CH4 is replaced with C4H 10 / H2(C4H 10 In S3 (H2 volume ratio 1:5), the gas flow rate is 25 mL / min, and the temperature is increased to... After reacting for 3.5 h, the system was kept under vacuum and allowed to cool naturally to obtain the product, which was characterized as follows: Mixed phase (no pure α-MoC is formed, and the phase is not uniform).

[0074] Comparative Example 4 The specific implementation method of this comparative example is the same as that of Example 1, except that the mixed gas of H2 and CH4 is replaced with CH4 (purity ≥99.9%), and the gas flow rate in S3 is 25 mL / min. After heating to 550℃ and reacting for 3.5 h, the system is kept under vacuum and naturally cooled to obtain the product, which is characterized as follows. Mixed phase (no pure α-MoC is formed, and the phase is not uniform).

[0075] Comparative Example 5 The specific implementation method of this comparative example is as follows: 1. Provide precursor Mo elemental powder with a purity ≥ 99.9%; 2. Pre-treat the Mo elemental powder: according to the mass ratio 3. Carbonization process: The mixture is placed in a corundum crucible, then placed in a tube furnace, and an Ar atmosphere is introduced (flow rate 40 mL / min). The temperature is increased to 700℃ at a rate of 5℃ / min, and the reaction is carried out at a constant temperature. After cooling, the product was washed three times (50 mL each time) with deionized water to remove the molten salt. The filter cake was collected by filtration and dried at 120 °C for 3 h to obtain the product, which was characterized as amorphous carbides and... Mixed phase (improper carbon source morphology, unable to generate α-MoC, and disordered phase composition).

[0076] Comparative Example 6 The specific implementation method of this comparative example is the same as that of Example 1, except that the precursor used is MoO3 powder (purity ≥99.9%). Specifically, S3 is as follows: the pretreated MoO3 powder is placed in a high vacuum tube furnace, and the vacuum is first evacuated to a pressure of 1×10⁻⁶. -4 Pa was introduced, and a 5% H2 / Ar mixed gas was introduced at a flow rate of 40 mL / min. The temperature was increased to 400℃ at a rate of 10℃ / min for pre-reduction for 1 h. After pre-reduction, the gas was switched to an 80:20 H2 / CH4 mixed gas at a flow rate of 60 mL / min to ensure that the molar ratio of Mo to C in the system was 1:1.2. The temperature was increased to 550℃ at a rate of 5℃ / min, and the reaction was carried out at a constant temperature for 3.5 h. After the system was kept under vacuum and allowed to cool naturally, the product was obtained and characterized as follows. Mixed phase (not a single phase).

[0077] Comparative Example 7 The specific implementation method of this comparative example is the same as that of Example 1, except that the precursor used is MoO2 powder (purity ≥99.9%). The specific reaction is as follows: 1. Additive loading (the pretreated MoO2 powder and RhCl3 solution are impregnated in equal volumes at room temperature for 6 hours, and then evaporated at 80°C for 2 hours to obtain the Rh / MoO2 precursor (Rh loading 0.01wt%)); 2. The Rh / MoO2 precursor is placed in a high vacuum tube furnace, and the vacuum is first evacuated to a pressure of 1×10⁻⁶. -4 Pa, a H2 / CH4 mixed gas with a volume ratio of 80:20 is introduced, and the gas flow rate is controlled at 60 mL / min to ensure that the molar ratio of Mo to C in the system is [value missing]. The temperature was increased to 700℃ at 5℃ / min, and the reaction was carried out at a constant temperature for 2 hours. After the system was kept under vacuum and cooled naturally, the product was characterized as a mixed phase of α-MoC + β-Mo2C (the phases were not singular).

[0078] Comparative Example 8 The specific implementation method of this comparative example is the same as that of Example 1, except that the precursor used is hydrogen molybdenum bronze (HMO) (purity ≥99.9%). S3: The pretreated HMO powder is placed in an atmospheric pressure tube furnace. Ar gas (flow rate 40 mL / min) is first introduced and the temperature is raised to 400°C at 10°C / min, and held for 30 min to remove air impurities. Then, the mixture of H2 / CH4 gas with a volume ratio of 80:20 is switched to, the gas flow rate is controlled at 60 mL / min, and the temperature is raised to 550°C at 5°C / min. The reaction is carried out at a constant temperature. After the system was kept under vacuum and allowed to cool naturally, the product was characterized as a mixed phase of α-MoC + β-Mo2C (the phases were not singular).

[0079] Comparative Example 9 The specific implementation method of this comparative example is the same as that of Example 1, except that the precursor used is MoO3 powder (purity ≥99.9%). S3: The pretreated MoO3 powder is placed in a high vacuum tube furnace, and the vacuum is first evacuated to a pressure of 1×10⁻⁶. -4 Pa, a 5% H2 / Ar mixed gas is introduced, with the gas flow rate controlled at 40 mL / min, and the temperature is increased to 400℃ at 10℃ / min for pre-reduction for 1 h; after pre-reduction, the mixture is switched to an 80:20 H2 / CH4 mixed gas, with the gas flow rate controlled at 60 mL / min, ensuring that the molar ratio of Mo to C in the system is 1:1.2, and the temperature is increased to 400℃ at 5℃ / min. After reacting at a constant temperature for 2 hours, the system was kept under vacuum and allowed to cool naturally to obtain the product, which was characterized as a small amount of β-Mo2C+. Mixed phase (not a single phase).

[0080] Comparative Example 10 The specific implementation method of this comparative example is the same as that of Example 1, except that the precursor used is MoO3 powder (purity ≥99.9%). S3: The pretreated MoO3 powder is placed in a high vacuum tube furnace, and the vacuum is first evacuated to a pressure of 1×10⁻⁶. -4 A mixture of H2 / CH4 gas (95:5 volume ratio) was introduced at a flow rate of 60 mL / min to ensure a molar ratio of Mo to C of 1:1.2. The temperature was increased to 550℃ at a rate of 5℃ / min, and the reaction was maintained at this temperature for 2 hours. After natural cooling under vacuum, the product was obtained and characterized as follows. Mixed phase (not a single phase).

Claims

1. A method for preparing α-MoC, characterized in that, At least the following steps are included: S1. Provide Mo powder with a purity of ≥99.9%; S2. Pre-treat the Mo powder; S3. The α-MoC is prepared by low-temperature carbonization technology on the pretreated Mo powder.

2. The method for preparing α-MoC according to claim 1, characterized in that, The method for preparing the Mo powder includes: Using MoO3 as raw material, a mixed atmosphere is introduced, and the material is reduced in a tube furnace by stepwise heating and cooling to obtain Mo powder with a purity of ≥99.9%.

3. The method for preparing α-MoC according to claim 2, characterized in that, The mixed atmosphere comprises Ar and hydrogen, wherein the volume ratio of Ar to hydrogen is (90-95):(5-10).

4. The method for preparing α-MoC according to claim 2, characterized in that, The stepwise heating and reduction process includes: holding at 500-600℃ for 1.5-4 hours, then heating to 750-850℃ and holding for 2-4 hours.

5. The method for preparing α-MoC according to claim 1, characterized in that, The pretreatment step in S2 includes: washing the Mo powder with hydrochloric acid, ultrasonic cleaning, and drying.

6. The method for preparing α-MoC according to claim 5, characterized in that, The preprocessing steps in S2 include: Soak the Mo powder in hydrochloric acid for 3-5 minutes; After adding deionized water and sonicating for 20-30 minutes, filter and separate the Mo powder, transfer it to a beaker containing anhydrous ethanol, and sonicate again for 20-30 minutes. The ultrasonically cleaned Mo powder is dried at 80-90℃ for 2-3 hours.

7. The method for preparing α-MoC according to claim 1, characterized in that, Step S3 includes: Pretreated Mo powder is placed in a high-vacuum tube furnace, and after evacuation, a mixed gas is introduced. The temperature is raised to 500-550℃ and reacted for 1-5 hours to obtain α-MoC.

8. The method for preparing α-MoC according to claim 7, characterized in that, The mixed gas is H2 and CH4, and the volume ratio of H2 to CH4 is (80-90):(10-20).

9. A product prepared by the method for preparing α-MoC according to any one of claims 1-8, characterized in that, The product has a grain size of 5-20 nm and a specific surface area of ​​180-220 m². 2 / g.

10. An application of the product according to claim 9, characterized in that, It is used in thermocatalytic reactions in the fields of energy and environmental protection.

Images