Chemical formula: Mo2C
English: Molybdenum Carbide
Melting point: 2615
Appearance: gray black
Molecular weight: 204
Boiling point: 2690
Water solubility: insoluble
Currently, the main chemical methods for preparing molybdenum carbide include compound high-temperature decomposition method, temperature programmed reaction method, high-temperature carbon reduction method of molybdenum oxide, and gas-phase reaction of metal molybdenum compounds with certain volatility. At present, the widely used method is the temperature programmed reaction (TPRe), which uses transition metal oxides mixed with carbon sources and hydrogen as raw materials and undergoes a process similar to the temperature programmed reduction process. At a set temperature, the transition metal oxides undergo a reaction process of reduction and carbonization (carburization). Commonly used carbon source materials include methane, ethane, ethylene, or carbon oxides (CO, CO2), and the reaction temperature is generally controlled between 400 to 1000 ℃. Liang et al. synthesized nano molybdenum carbide using high surface area carbon materials as carbon sources through temperature programmed reduction method. 1. The program heating method uses ammonium molybdate to decompose at 500 ℃ to prepare MoO3. The alumina carrier is immersed in ammonium molybdate and ammonia aqueous solution, stirred for 0.5 hours, placed at room temperature for 24 hours, evaporated in a water bath at 80-90 ℃, dried at 115 ℃ for 12 hours, and calcined at 500 ℃ for 4 hours to prepare supported molybdenum trioxide precursor. Using the method of programmed heating, molybdenum carbide was prepared using n-hexane as the carbonization raw material. The programmed heating process involves increasing the room temperature to 300 ℃, with a heating rate of 10 ℃/min; Increase from 300 ℃ to 600 ℃, with a heating rate of 1 ℃/min; Maintain a constant temperature for 2 hours at 600 ℃. 2. Gas phase method: The gas phase method generally uses high specific surface area activated carbon (with a specific surface area greater than 200m2/g) and transition metal volatile compounds, which are stoichiometric and fed into a flowing reactor. The reaction takes place at a high temperature of 900-1400 ℃ for a certain period of time, cooled in an inert gas, and the carbides are recovered. A mixture of high specific surface carbon and MoO3 was heated to 800 ℃ in argon gas to sublimate and adsorb MoO3 onto the carbon. Mo2C was prepared by reacting at 1300 ℃ for a certain time. It has been reported that MoO3 and 1150m2/g of carbon were reacted at a C/Mo molar ratio of 6:1 to obtain a hexagonal Mo2C, with a specific surface area of up to 213m2/g. Leclercq et al. evaporated volatile metal compounds into containers containing low-pressure carbon hydrides and directly carbonized them at high temperatures to produce carbides. By changing the gas composition in the reactor and the type of metal compound precursor, different carbides and carbon oxides are prepared. Nagai et al. used this method to prepare Mo2C/Al2O3 catalysts with activity three times higher than the impregnation method under 973K vacuum conditions. But the disadvantage of this method is that the conditions are difficult to control and the synthesis amount is small. 3. Thermal decomposition method refers to the process of reacting transition metal oxides or halides with designated organic compounds to form metal organic compounds, which are then subjected to thermal decomposition reaction in an inert atmosphere. Bayer Company uses it to react with organic compounds containing two hydroxyl groups, remove excess organic compounds, and decompose into metal carbides under vacuum or inert gas. Sehwartzkopf et al. directly carbonized metal oxide powders at high temperatures, but the resulting samples had a lower specific surface area. At present, the preparation of molybdenum carbide is developing towards high specific surface area and high dispersibility for practical use. 4. Liquid phase reaction method: Low temperature liquid phase reaction method refers to the process of dissolving a series of substances in a suitable solvent, allowing them to undergo chemical reactions under relatively mild conditions.
1. Cutting tools: Molybdenum carbide has extremely high hardness and wear resistance, making it widely used in the manufacturing of high hardness cutting tools, such as drills, milling cutters, turning tools, etc.
2. Electronic materials: Molybdenum carbide has low electrical resistivity, good thermal stability, and low coefficient of thermal expansion, making it suitable for use as semiconductor materials and energy storage materials. Molybdenum carbide has good conductivity and high-temperature stability, so it is widely used in the manufacturing of electronic materials, such as electrodes, capacitors, etc.
3. Aerospace: Molybdenum carbide has excellent corrosion resistance and high-temperature stability, making it widely used in the aerospace field, such as manufacturing engine components, combustion chambers, etc.
4. Molybdenum carbide can also be used as a coating material, which can effectively improve surface hardness and corrosion resistance, and is used to manufacture special coatings such as acid alkali resistance and corrosion resistance.
5. Molybdenum carbide catalytic performance: It has been found that molybdenum carbide has high initial catalytic activity in benzene hydrogenation reactions. Although the catalyst gradually deactivates as the reaction progresses, its steady-state conversion frequency (TOF) can still be compared to precious metals Pt or Ru. Under normal pressure and reaction conditions of 300 ℃, α- The catalytic activity of MoC-x for thiophene hydrodesulfurization reaction is similar to that of commonly used hydrodesulfurization catalyst molybdenum sulfide. The main catalytic reaction types of catalyst molybdenum carbide are: (1) hydrogenation and hydrolysis reaction; (2) Hydrodesulfurization HDS and hydrodenitrogenation HDN reaction; (3) Isomerization reaction; (4) Hydrocarbon conversion and synthesis reactions; (5) Application in ammonia synthesis.
This product should be sealed and stored in a dry and cool environment, and should not be exposed to the air for a long time. It should prevent aggregation due to moisture, which can affect its dispersion performance and usage effect. It should also avoid heavy pressure, avoid contact with oxidants, and be transported as ordinary goods.