Method for preparing molybdenum carbide by using molybdenum sulfide as raw material

Abstract

The invention relates to a method for preparing molybdenum carbide by taking molybdenum sulfide as a raw material, and belongs to the technical field of inorganic material preparation. The method comprises the following steps: preparing a molybdenum-containing compound, an iron-containing compound and carbonaceous reducing agents with different particle sizes; mixing a large-particle-size carbonaceous reducing agent with part of the raw materials, filling the mixture into a central area of the pressing block, and applying relatively high pressure for compaction; mixing the fine-particle-size carbonaceous reducing agent with the remaining raw materials, filling an outer layer area of the pressing block with the mixture, and applying relatively low pressure for compaction; reacting for 1-20 hours at the temperature of 1000-1300 DEG C in an inert atmosphere; and carrying out acid leaching, filtering and drying on the reaction product to obtain the high-purity molybdenum carbide. Through collaborative optimization of partition density and particle size distribution, dynamic release of a carbon source and regulation and control of a reaction path are achieved, side reactions and impurity generation are effectively inhibited, the purity of the main phase MoC is remarkably improved, the process is simple, the cost is low, the method is suitable for industrial production, and the obtained molybdenum carbide can be used for preparing catalyst materials.

Description

Technical Field

[0001] This application relates to the field of inorganic material preparation, specifically to a method for preparing molybdenum carbide using molybdenum sulfide as a raw material. Background Technology

[0002] Molybdenum carbide (Mo2C) is an inorganic material that combines high hardness, high melting point, and excellent catalytic properties, and is widely used in energy catalysis, hard alloys, and other fields. Existing methods for preparing molybdenum carbide mainly include temperature-programmed reaction, high-temperature synthesis, sol-gel method, chemical vapor deposition, and carbothermal reduction.

[0003] The traditional carbothermal reduction method is widely used due to its advantages such as simple process and readily available raw materials. However, due to uneven distribution of reducing agent, uniform particle size and uniform briquette density, side reactions and impurities are prone to occur during the reaction process, making it difficult to obtain high-purity molybdenum carbide.

[0004] In actual production, how to effectively improve the purity of the main phase of molybdenum carbide and suppress the formation of impurity phases and by-products while ensuring simple processes and controllable costs has become a technical issue of concern in this field. Summary of the Invention

[0005] To address the aforementioned core technical issues, this application provides a method for preparing molybdenum carbide using molybdenum sulfide as a raw material.

[0006] The first aspect of this application provides a method for preparing molybdenum carbide from molybdenum sulfide, comprising the following steps:

[0007] The raw materials are prepared, including molybdenum-containing compounds, iron-containing compounds, and carbonaceous reducing agents, wherein the carbonaceous reducing agents include two types: large-particle-size and fine-particle-size.

[0008] The large-particle-size carbonaceous reducing agent is mixed with some molybdenum-containing and iron-containing compounds, and filled into the central area of ​​the compaction block. A first pressure is applied to compact the block.

[0009] The fine-particle-size carbonaceous reducing agent is mixed with the remaining molybdenum-containing and iron-containing compounds and filled into the outer layer of the compaction block. A second pressure is applied for compaction, wherein the first pressure is greater than the second pressure.

[0010] Under an inert atmosphere, the partitioned briquettes are reacted at 1000-1300°C for 1-20 hours;

[0011] After the reaction, the product was acid-leached, filtered, and dried to obtain high-purity molybdenum carbide.

[0012] Through the aforementioned process of synergistic optimization of partitioned density and particle size distribution, the central region employs a high-density, large-particle-size carbonaceous reducing agent to achieve slow release of the carbon source, ensuring the full progress of the main reaction and preventing the formation of unreacted molybdenum or byproducts due to excessive carbon source consumption. The outer region employs a low-density, fine-particle-size carbonaceous reducing agent, enabling rapid carbon supply in the early stages of the reaction, promoting the volatilization and migration of impurities and byproducts, and further improving product purity. Under the synergistic effect of the two regions, the carbon source release rate and diffusion path achieve dynamic self-adaptation, effectively suppressing the formation of local side reactions and non-target carbides, and significantly improving the purity of the main product Mo2C. This method is simple, low-cost, easy to scale up industrially, and allows for flexible adjustment of partition thickness, density, and particle size ratio to meet the needs of different reaction systems and scales.

[0013] Furthermore, the molybdenum-containing compound is molybdenum disulfide or molybdenum concentrate. Using molybdenum disulfide or molybdenum concentrate as raw material ensures a sufficient and uniform distribution of molybdenum source in the reaction system, which is beneficial to the formation of the main phase molybdenum carbide.

[0014] Furthermore, the iron-containing compound is iron oxide, ferrous oxide, or iron powder. Iron sources with different valence states can be flexibly selected according to actual needs, improving process adaptability.

[0015] Furthermore, the carbonaceous reducing agent is graphite or carbon black. Both graphite and carbon black are common carbon source materials, capable of meeting the requirements of different particle size distributions and reaction kinetics.

[0016] Furthermore, the large-particle-size carbonaceous reducing agent has a D50 of 30-100 μm, and the fine-particle-size carbonaceous reducing agent has a D50 of 1-10 μm. By controlling the particle size distribution of the carbonaceous reducing agent, the carbon source release rate can be precisely controlled.

[0017] Furthermore, the ingredients are prepared according to a total molar ratio of 2:2:10 for molybdenum-containing compounds, iron-containing compounds, and carbonaceous reducing agents, wherein the molar ratio of fine-particle-size carbonaceous reducing agent to large-particle-size carbonaceous reducing agent is 1:3 to 1:5; the distribution ratio of molybdenum-containing compounds and iron-containing compounds in the central and outer regions is consistent with the distribution ratio of carbonaceous reducing agents.

[0018] Furthermore, the first pressure is 8-20 MPa, and the second pressure is 2-8 MPa. Applying different pressures helps to achieve effective control of the zoned density.

[0019] Furthermore, the inert atmosphere is argon or nitrogen. The use of an inert atmosphere protects against the formation of oxidative impurities during the reaction.

[0020] Furthermore, the acid leaching is performed using hydrochloric acid for 0.1-2 hours. Acid leaching removes impurities and residual iron components, further improving product purity.

[0021] The second aspect of this application provides an application of the above-described method in the preparation of catalyst materials. The high-purity molybdenum carbide obtained by this method can be widely used in industrial catalytic reactions such as hydrodenitrogenation, hydrodesulfurization, alkane isomerization, and water-vapor shift, exhibiting excellent catalytic activity and stability.

[0022] The present invention has the following beneficial effects:

[0023] 1. By optimizing the partitioned density and particle size distribution in a coordinated manner, the dynamic release of carbon source and the reaction process were precisely controlled, significantly improving the purity of the main phase of molybdenum carbide.

[0024] 2. By using carbonaceous reducing agents with different particle sizes and densities arranged in zones, side reactions and impurity phase formation are suppressed, thereby improving the uniformity and purity of the product.

[0025] 3. The process is simple, the cost is low, and it is easy to scale up industrially. It is applicable to a variety of raw materials and reaction systems, thus broadening the application fields of high-purity molybdenum carbide. Detailed Implementation

[0026] Example 1: This example provides a method for preparing molybdenum carbide using molybdenum sulfide as a raw material.

[0027] Raw material ratio: Analytical grade MoS2 and Fe2O3 are the main raw materials, and the carbonaceous reducing agent is divided into fine-particle-size graphite (D50=5μm) and large-particle-size graphite (D50=80μm). The total molar ratio of MoS2, Fe2O3 and graphite is 2:2:10, and the molar ratio of fine-particle-size graphite to large-particle-size graphite is 1:3. The distribution ratio of MoS2 and Fe2O3 in the central and outer regions is consistent with the distribution ratio of graphite.

[0028] Preparation method: Large-particle-size graphite was mixed with MoS2 and Fe2O3, filled into the central area of ​​a mold, and compacted under a pressure of 10 MPa. Fine-particle-size graphite was mixed with MoS2 and Fe2O3, filled into the outer layer of the mold, and compacted under a pressure of 4 MPa. The total diameter of the compacted block was 20 mm, the diameter of the central area was 8 mm, and the outer layer thickness was 6 mm. The mixture was heated at 1200°C for 2 h in a tube furnace (argon protection), cooled, and the product was removed. It was then leached with hydrochloric acid for 0.5 h, filtered, and dried to obtain high-purity molybdenum carbide. XRD analysis showed that the Mo2C main phase content was 99.6%, the particle size D50 was 4.8 μm, and the standard deviation of particle size uniformity was 0.7 μm.

[0029] Example 2

[0030] Similar to Example 1, only the amount of large-particle-size graphite in the central region was increased, while the amount of fine-particle-size graphite was decreased (molar ratio 1:5), and the other steps remained unchanged. The main phase Mo2C content was approximately 99.7%, the particle size D50 was 4.9 μm, and the uniformity standard deviation was 0.6 μm.

[0031] Example 3

[0032] Same as Example 1, except that the outer fine-grained graphite was replaced with carbon black (D50=3μm), otherwise the same. The main phase Mo2C content was 99.5%, the particle size D50 was 4.7μm, and the uniformity standard deviation was 0.8μm.

[0033] Example 4

[0034] Same as Example 1, but FeO is used instead of Fe2O3 in the central region. The main phase has a Mo2C content of 99.6%, a particle size D50 of 4.8 μm, and a uniformity standard deviation of 0.7 μm.

[0035] Example 5

[0036] Same as Example 1, but the central region density was increased to 14 MPa, while the outer layer density remained unchanged at 4 MPa. The main phase Mo2C content was 99.7%, the particle size D50 was 4.9 μm, and the uniformity standard deviation was 0.6 μm.

[0037] Example 6

[0038] Same as Example 1, but the briquette diameter is increased to 30 mm, and the central region diameter is 10 mm. The main phase Mo2C content is 99.6%, the particle size D50 is 4.8 μm, and the uniformity standard deviation is 0.7 μm.

[0039] III. Comparative Example

[0040] Comparative Example 1: This comparative example does not include the synergistic optimization of partition density and particle size distribution.

[0041] The graphite was made from a completely uniformly mixed fine-grained material, without partitioning or density control, and directly compressed into briquettes (6 MPa) and then reduced according to the original process. The main phase Mo2C content was 98.4%, with obvious residual impurities, a particle size D50 of 5.0 μm, and a uniformity standard deviation of 1.2 μm.

[0042] Comparative Example 2

[0043] All materials were uniformly mixed with large-particle-size graphite and compressed into briquettes (6 MPa), with the rest as before. The main phase Mo2C content was 98.8%, with a relatively high amount of impurities, a particle size D50 of 5.3 μm, and a uniformity standard deviation of 1.4 μm.

[0044] Comparative Example 3

[0045] All briquettes were subjected to high pressure (12 MPa) to achieve uniform density. The main phase Mo2C content was 98.6%, with some unreacted Mo residue. The particle size D50 was 4.9 μm, and the standard deviation of uniformity was 1.1 μm.

[0046] Comparative Example 4

[0047] All briquettes were subjected to low pressure (8 MPa) to achieve uniform density. The main phase Mo2C content was 98.5%, with some unreacted Mo residue. The particle size D50 was 5.1 μm, and the standard deviation of uniformity was 1.3 μm.

[0048] Performance testing methods

[0049] Main phase purity testing: Following GB / T 13223-2018, the purity of the main phase was analyzed using X-ray diffraction (XRD), and the content of impurity elements (S, Fe, C, etc.) was detected using an elemental analyzer. Particle size distribution testing: The particle size distribution was determined using field emission scanning electron microscopy (FE-SEM). 100 particles were counted, and D50 and particle size uniformity were analyzed.

[0050] Table 1. Technical Effects of the Examples and Comparative Examples

[0051] serial number <![CDATA[Main phase Mo2C content (%)]]> Impurity phase content (%) Average particle size D50 (μm) Particle size uniformity (standard deviation, μm) Example 1 99.6 <0.4 4.8 0.7 Example 2 99.7 <0.3 4.9 0.6 Example 3 99.5 <0.5 4.7 0.8 Example 4 99.6 <0.4 4.8 0.7 Example 5 99.7 <0.3 4.9 0.6 Example 6 99.6 <0.4 4.8 0.7 Comparative Example 1 98.4 1.6 5.0 1.2 Comparative Example 2 98.8 1.2 5.3 1.4 Comparative Example 3 98.6 1.4 4.9 1.1 Comparative Example 4 98.5 1.3 5.1 1.3

[0052] Data Analysis

[0053] As shown in Table 1, Examples 1-6 all exhibited extremely high main phase Mo2C content and extremely low impurity phase content, with good particle size distribution uniformity, significantly better than the comparative examples. After synergistic optimization of partitioned density and particle size distribution, the carbon source release rate and diffusion path were effectively controlled, the main reaction was more complete, impurity phase formation was suppressed, and the purity and uniformity of the products were significantly improved.

[0054] Comparative Example 1 did not employ partitioned density and particle size distribution optimization, resulting in excessively rapid and uneven release of the carbon source during the reaction, significant residual impurities, reduced purity of the main phase, and a wider particle size distribution. Comparative Example 2 used a single large-particle graphite, leading to slow carbon source release, incomplete reaction, and a higher concentration of impurities. Comparative Examples 3 and 4 exhibited uniform density, but insufficient reaction in the central region, resulting in unreacted Mo and lower purity of the main phase compared to the examples.

[0055] In the embodiments, adjusting the graphite particle size ratio, pressing pressure, and raw material type can further optimize the purity of the main phase and the particle size uniformity. For example, in Examples 2 and 5, increasing the amount of large-particle-size graphite in the central region or increasing the pressing pressure makes the main reaction more complete, further improving the purity of the main phase. In Example 3, carbon black is used to replace fine-particle-size graphite, further reducing the impurity phase content.

Claims

1. A method for producing molybdenum carbide using molybdenum sulfide as a raw material, characterized by comprising the steps of: The method comprises the following steps: ​ S1: preparing raw materials, which comprise a molybdenum-containing compound, an iron-containing compound and a carbonaceous reducing agent, wherein the carbonaceous reducing agent comprises a large-particle-size carbonaceous reducing agent and a small-particle-size carbonaceous reducing agent; S2: mixing the large-particle-size carbonaceous reducing agent with part of the molybdenum-containing compound and the iron-containing compound, filling the center region of the briquette and compacting by applying a first pressure; S3: mixing the small-particle-size carbonaceous reducing agent with the remaining molybdenum-containing compound and the iron-containing compound, filling the outer region of the briquette and compacting by applying a second pressure, wherein the first pressure is greater than the second pressure; S4: reacting the partitioned briquette at 1000-1300°C for 1-20 hours under an inert atmosphere; S5: after the reaction, performing acid leaching, filtering and drying on the product to obtain high-purity molybdenum carbide.

2. The method of claim 1, wherein, The molybdenum-containing compound is molybdenum disulfide or molybdenum concentrate.

3. The method of claim 1, wherein, The iron-containing compound is iron oxide, ferrous oxide or iron powder.

4. The method of claim 1, wherein, The carbonaceous reducing agent is graphite or carbon black.

5. The method of claim 1, wherein, The D50 of the large-particle-size carbonaceous reducing agent is 30-100 μm, and the D50 of the small-particle-size carbonaceous reducing agent is 1-10 μm.

6. The method of claim 1, wherein, The total molar ratio of the molybdenum-containing compound, the iron-containing compound and the carbonaceous reducing agent is 2:2:10, wherein the molar ratio of the small-particle-size carbonaceous reducing agent to the large-particle-size carbonaceous reducing agent is 1:3-1:5, and the distribution ratio of the molybdenum-containing compound and the iron-containing compound in the center region and the outer region is consistent with the distribution ratio of the carbonaceous reducing agent.

7. The method of claim 1, wherein, The first pressure is 8-20 MPa, and the second pressure is 2-8 MPa.

8. The method of claim 1, wherein, The inert atmosphere is argon or nitrogen.

9. The method of claim 1, wherein, The acid leaching uses hydrochloric acid, and the acid leaching time is 0.1-2 hours.

10. Use of molybdenum carbide prepared by the method of any one of claims 1-9 in the preparation of a catalyst material.