Preparation method of nucleating agent for high specific capacity mesophase carbon microbead

Abstract

The application relates to a preparation method of a high specific capacity type mesophase carbon microsphere nucleating agent. Purified raw material oil is obtained by removing solid impurities from raw material oil through solid-liquid separation treatment; light phase distillate oil is cut off from the purified raw material oil through distillation, and medium oil is obtained; heavy oil obtained by removing impurities from the medium oil through boiling bed multi-stage catalytic hydrogenation or heavy oil obtained by cutting off the front distillate before 370 DEG C from the medium oil after fixed bed catalytic hydrocracking; the two kinds of heavy oil are filtered through solvent oil according to certain proportions, and the nucleating agent is obtained. Compared with the previous nucleating agent preparation process, the nucleating agent has higher purity, excellent electrochemical performance, and the process is easy to realize, and the product quality is stable.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation, and particularly relates to a method for preparing a nucleating agent for high specific capacity mesophase carbon microspheres. Background Technology

[0002] Mesophase carbon microspheres are a novel type of carbon material. Due to their layered molecular parallel stacking structure, combined with spherical characteristics, small and uniformly distributed sphere diameter, and high electrical and thermal conductivity and surface activity, they have become the preferred raw material for high-strength, high-density isotropic graphite materials, lithium-ion secondary battery electrode materials, high specific surface area activated carbon materials, and high-performance liquid chromatography (HPLC) packing materials. They have been widely applied in the semiconductor, chemical, machinery, nuclear energy, new energy, and environmental protection industries.

[0003] The main methods for preparing mesophase carbon microspheres include thermal polycondensation, emulsification, suspension polymerization, and other methods. Thermal polycondensation involves the thermal treatment of polycyclic aromatic hydrocarbons to produce mesophase microspheres, which are dispersed in the mother liquor of the reaction system. These microspheres are then separated from the mother liquor using appropriate methods. Nuclei are formed during the formation of the mesophase microspheres, and the nucleation process is divided into homogeneous nucleation and heterogeneous nucleation. The process of coal tar pitch containing a significant amount of QI forming the nuclei for mesophase carbon microspheres is heterogeneous nucleation, which mainly occurs in the early stages of mesophase formation. The process of coal tar pitch containing almost no QI forming the nuclei for mesophase carbon microspheres is homogeneous nucleation, which occurs throughout the entire process of mesophase formation and development. The QI in the raw material has a polycyclic aromatic hydrocarbon structure similar to that of mesophase carbon microspheres, which can reduce the activation energy required for the formation of mesophase carbon microspheres. It acts as a nucleus during the nucleation process, so the formation of nuclei in heterogeneous nucleation is almost simultaneous. Given a fixed reaction time, the growth time of each microsphere is almost the same, resulting in a more uniform particle size distribution of the mesophase carbon microspheres formed by heterogeneous nucleation. In homogeneous nucleation, coal tar pitch first undergoes thermal decomposition and thermal dehydrogenation condensation to form planar large aromatic lamellar molecules. These large aromatic lamellar molecules then begin to stack layer by layer under the influence of π-π electronic forces and van der Waals forces to form the nucleus of the mesophase carbon microsphere. Therefore, in homogeneous nucleation, the formation of nuclei is not simultaneous but occurs at different times; some nuclei form earlier, while others form later. This results in different growth times for the mesophase carbon microspheres, leading to large differences in particle size and an uneven particle size distribution.

[0004] Nucleating agents play a crucial role in the formation and growth of mesophase carbon microspheres, providing seed crystals and preventing sphere coalescing. Nucleating agents include physical and chemical additives. Physical additives, such as carbon black and flake graphite, do not react with polycyclic aromatic hydrocarbons (PAHs); they merely influence mesophase growth physically through their shape and size. Furthermore, some additives, such as Al₂O₃, quartz, and mica, possess typical surface features or external morphologies, thus acting as crystallization centers to induce the formation of mesophase carbon microspheres with different morphologies and microstructures. Chemical additives, such as boron and ferrocene, can react with PAH molecules and accelerate the formation of mesophase pitch. Chemical additives typically bind to large aromatic hydrocarbon molecules through chemical bonds.

[0005] Mesophase carbon microspheres (MCMBs) have stood out among numerous lithium-ion battery anode materials due to their unique layered structure, excellent conductivity, and high packing density, attracting widespread attention and research from scholars and now achieving commercial applications. However, MCMBs also have inherent drawbacks, such as lower theoretical specific capacity and poor rate performance, which limit their application in power batteries. To expand the application scope of MCMBs, it is urgent to optimize and adjust the preparation process of MCMBs. By adding nucleating agents of different types and properties to the raw material pitch, the yield, particle size distribution, and structure of MCMBs can be controlled. This effectively controls the growth conditions of MCMBs, improves the product yield, reduces costs, and optimizes the performance of MCMBs. This research direction has always been a key focus of MCMB research and development. Summary of the Invention

[0006] This invention provides a method for preparing a nucleating agent for high-specific-capacity mesophase carbon microspheres. The produced nucleating agent possesses high purity, high graphitization degree, easy dispersibility, and excellent thermal reactivity. Adding this nucleating agent to the raw material mother liquor effectively controls the particle size of the carbon microspheres and improves the yield of mesophase carbon microspheres. Furthermore, the mesophase carbon microspheres prepared using this nucleating agent exhibit small specific surface area, high purity, and high specific capacity. Compared with previous nucleating agent preparation processes, this invention provides a nucleating agent with higher purity and superior electrochemical performance, and the process is easy to implement and the product quality is stable.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for preparing a nucleating agent for high specific capacity mesophase carbon microspheres includes the following steps:

[0009] 1) The raw oil is purified by removing solid impurities through solid-liquid separation.

[0010] The feedstock includes ethylene residue, catalytic cracking slurry, medium- and low-temperature coal tar pitch, high-temperature coal tar pitch, light coking oil, and heavy coking oil.

[0011] Solid-liquid separation methods include centrifugal separation, extraction separation, and pressure filtration separation.

[0012] The purified raw material oil has an ash content of <0.5% and a quinoline-insoluble content of <0.1%.

[0013] 2) The purified feedstock oil is distilled to remove the light phase oil to obtain medium oil; the light phase oil is the distillate with a distillation range of 170-220℃.

[0014] 3) Heavy oil A is obtained by multi-stage catalytic hydrocracking of medium oil in a fluidized bed to remove impurities; or heavy oil B is obtained by removing the pre-370℃ fraction from the tail oil obtained by fixed-bed catalytic hydrocracking of medium oil after vacuum distillation.

[0015] The fluidized bed multi-stage catalytic hydroremoval process involves using a series of dual or multi-tube reactors, where the first stage reaction temperature is 240–320℃, and the second or subsequent stages reaction temperature is 250–400℃. The heavy oil A obtained from the fluidized bed multi-stage catalytic hydroremoval process has an ash content of <0.3%, a toluene-insoluble content of ≥30%, and a quinoline-insoluble content of ≥10%.

[0016] Fixed-bed catalytic hydrocracking uses a fixed-bed reactor with a reaction temperature of 240–380℃. The tail oil obtained after fixed-bed catalytic hydrocracking is then subjected to vacuum distillation to remove the pre-370℃ fraction, resulting in heavy oil B with an ash content of <0.3%, a toluene-insoluble content of ≥40%, and a quinoline-insoluble content of ≥20%.

[0017] 4) Mix one or both of the two heavy oils obtained in step 3), and then filter them through solvent oil to obtain a nucleating agent.

[0018] If two heavy oils are mixed, the mass ratio should be heavy oil A: heavy oil B = 1:0.1~10.

[0019] The mass ratio of heavy oil to solvent oil is 1:0.2 to 4.

[0020] Solvent oils include crude benzene, toluene, xylene, wash oil, anthracene oil, dianthracene oil, heavy coking oil, light coking oil, and pyridine.

[0021] The nucleating agent product prepared by this invention has an ash content of <0.1%, a toluene-insoluble content of >70%, a quinoline-insoluble content of >40%, a quinoline-insoluble particle size distribution D50 of 1-4 μm, a purity of ≥95%, and a graphitization degree of ≥92%.

[0022] All percentage contents in this invention are mass percentage contents.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1) The product of this invention is a special nucleating agent for preparing high specific capacity mesophase carbon microspheres, which has properties such as high purity, high graphitization degree, easy dispersibility and excellent thermal reactivity.

[0025] 2) By adding this nucleating agent to the raw material mother liquor, the particle size of carbon microspheres can be effectively controlled, and the yield of mesophase carbon microspheres can be improved.

[0026] 3) The specific surface area of ​​the mesophase carbon microspheres prepared by this nucleating agent is ≤2m². 2 / g, purity ≥95%, specific capacity ≥320mAh / g. It features small specific surface area, high purity, and high specific capacity.

[0027] 4) Compared with previous nucleating agent preparation processes, this invention has higher nucleating agent purity, better electrochemical performance, and the process is easy to implement and the product quality is stable. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the specific implementation methods of this invention will be further described below in conjunction with the embodiments. The following embodiments are used to specifically illustrate the content of this invention. These embodiments are only general descriptions of the content of this invention and do not limit the content of this invention.

[0029] Example 1:

[0030] Medium- and low-temperature coal tar pitch was heated to 50°C, centrifuged at 1000 rad / min, and centrifuged through a 300-mesh sieve to remove solid impurities, yielding purified feedstock oil with an ash content of 0.48% and a quinoline-insoluble content of 0.08%. The purified feedstock oil was then introduced into a distillation vessel, held at a final gas phase temperature of 170°C for 1 hour, and the bottom of the vessel yielded medium-quality oil. This medium-quality oil underwent two-stage hydrogenation in a fluidized bed to remove impurities, yielding heavy oil A. The first stage reaction temperature was 240°C, and the second stage reaction temperature was 320°C. Heavy oil A had an ash content of 0.15%, a toluene-insoluble content of 40%, and a quinoline-insoluble content of 30%. Heavy oil and wash oil were mixed at a mass ratio of 1:0.8 and filtered at 120°C. The filter cake served as a nucleating agent, with an ash content of 0.05%, a toluene-insoluble content of 80.2%, a quinoline-insoluble content of 86.3%, and a D50 of 1.2 μm. The purity is 95.6%, and the degree of graphitization is 92.8%. The specific surface area of ​​the mesophase carbon microspheres prepared using this nucleating agent is 2.0 m². 2 / g, purity is 95.3%, specific capacity is 322mAh / g.

[0031] Example 2:

[0032] High-temperature coal tar was heated to 60℃, centrifuged at 1200 rad / min, and centrifuged through a 300-mesh sieve to remove solid impurities, yielding purified feed oil with an ash content of 0.1% and a quinoline-insoluble content of 0.03%. The purified feed oil was then introduced into a distillation vessel, held at a final gas phase temperature of 220℃ for 2 hours, and the bottom of the vessel yielded medium-quality oil. This medium-quality oil underwent two-stage hydrogenation in a fluidized bed to remove impurities, yielding heavy oil A. The first stage reaction temperature was 280℃, and the second stage reaction temperature was 360℃. The heavy oil had an ash content of 0.05%, a toluene-insoluble content of 53.2%, and a quinoline-insoluble content of 22.3%. Heavy oil A was then mixed with crude benzene at a mass ratio of 1:1.2 and filtered at 130℃. The filter cake served as a nucleating agent, with an ash content of 0.03%, a toluene-insoluble content of 92.6%, a quinoline-insoluble content of 68.3%, and a D50 of 2.3 μm. The purity was 97.2%, and the degree of graphitization was 94.2%. The specific surface area of ​​the mesophase carbon microspheres prepared using this nucleating agent was 1.96 m². 2 / g, purity is 96.1%, and specific capacity is 325mAh / g.

[0033] Example 3:

[0034] Ethylene residue oil was heated to 60°C and centrifuged at 1200 rad / min using a 400-mesh sieve to remove solid impurities, yielding purified feedstock oil with an ash content of 0.32% and a quinoline-insoluble content of 0.05%. The purified feedstock oil was then introduced into a distillation vessel, held at a final vapor temperature of 180°C for 1.5 hours, yielding medium-quality oil at the bottom. This medium-quality oil was further subjected to fixed-bed hydrocracking to obtain heavy oil B, with a reaction temperature of 360°C. Heavy oil B had an ash content of 0.15%, a toluene-insoluble content of 63.1%, and a quinoline-insoluble content of 47.3%. Heavy oil B was then filtered with coking light oil at a mass ratio of 1:2 at 100°C. The filter cake served as a nucleating agent, with an ash content of 0.05%, a toluene-insoluble content of 82.6%, a quinoline-insoluble content of 73.3%, and a D50 of 2.1 μm. The purity was 96.1%, and the degree of graphitization was 92.8%. The specific surface area of ​​the mesophase carbon microspheres prepared using this nucleating agent was 1.87 m². 2 / g, purity is 96.3%, and specific capacity is 324mAh / g.

[0035] Example 4:

[0036] The catalytic cracking slurry was heated to 90°C and centrifuged at 1200 rad / min using a 400-mesh sieve to remove solid impurities, resulting in purified feedstock oil with an ash content of 0.27% and a quinoline-insoluble content of 0.03%. The purified feedstock oil was then introduced into a distillation vessel, held at a final vapor temperature of 180°C for 1.5 hours, yielding medium-quality oil at the bottom. This medium-quality oil was further processed by fixed-bed hydrocracking to obtain heavy oil B, with a reaction temperature of 340°C. The heavy oil had an ash content of 0.15%, a toluene-insoluble content of 40.1%, and a quinoline-insoluble content of 27.3%. Heavy oil B was then filtered with pyridine at a mass ratio of 1:2 at 100°C. The filter cake served as a nucleating agent, with an ash content of 0.05%, a toluene-insoluble content of 72.6%, a quinoline-insoluble content of 53.3%, and a D50 of 3.06 μm. The purity was 97.3%, and the degree of graphitization was 93.7%. The specific surface area of ​​the mesophase carbon microspheres prepared using this nucleating agent was 1.94 m². 2 / g, purity is 97.3%, specific capacity is 322mAh / g.

[0037] Example 5:

[0038] Heavy coking oil was heated to 60°C and centrifuged at 1200 rad / min using a 400-mesh sieve to remove solid impurities, yielding purified feedstock oil with an ash content of 0.12% and a quinoline-insoluble content of 0.01%. The purified feedstock oil was then introduced into a distillation vessel, held at a final vapor temperature of 180°C for 3 hours, and the bottom of the vessel yielded medium-quality oil. This medium-quality oil was then subjected to two-stage hydrogenation in a fluidized bed to remove impurities, yielding heavy oil A. The first stage reaction temperature was 240°C, and the second stage reaction temperature was 320°C. Heavy oil A had an ash content of 0.15%, a toluene-insoluble content of 40%, and a quinoline-insoluble content of [missing information]. The content is 30%; medium oil is hydrocracking in a fixed bed to obtain heavy oil B, where the reaction temperature is 390℃, the ash content of the heavy oil is 0.05%, the toluene-insoluble content is 79.1%, and the quinoline-insoluble content is 67.3%; heavy oil A and heavy oil B are mixed at a mass ratio of 1:1 and then filtered with toluene at a mass ratio of 1:2.5 at 90℃. The filter cake is the nucleating agent, with an ash content of 0.01%, a toluene-insoluble content of 95.6%, a quinoline-insoluble content of 83.3%, a D50 of 2.5μm, a purity of 98.1%, and a graphitization degree of 93.2%. The specific surface area of ​​the mesophase carbon microspheres prepared by this nucleating agent is 1.76m². 2 / g, purity is 98.3%, and specific capacity is 330mAh / g.

Claims

1. A method for producing a nucleating agent for high specific capacity meso- carbon microbeads, characterized by comprising the steps of: The method comprises the following steps: ​ 1) removing solid impurities from raw oil by solid-liquid separation treatment to obtain purified raw oil; The raw oil comprises one or more of ethylene residue, catalytic cracking slurry oil, medium-low temperature coal tar pitch, high temperature coal tar pitch, coking light oil, and coking heavy oil; 2) removing light phase distillate oil from the purified raw oil by distillation to obtain medium oil; The ash content of the purified raw oil is less than 0.5%, and the quinoline insoluble content is less than 0.1%; The light phase distillate oil in the above step 2) has a distillation range of 170-220°C; 3) removing impurities from the medium oil by boiling bed multi-stage catalytic hydrogenation to obtain heavy oil A, or removing impurities from tail oil obtained by fixed bed catalytic hydrocracking of the medium oil by vacuum distillation to obtain heavy oil B; The reaction temperature of the first stage of the boiling bed multi-stage catalytic hydrogenation is 240-320°C, and the reaction temperature of the second stage or subsequent stages is 250-400°C; The reaction temperature of the fixed bed catalytic hydrocracking is 240-380°C; 4) mixing one or both of the two heavy oils obtained in step 3) and filtering with solvent oil to obtain a nucleating agent.

2. The method for producing a nucleating agent for high specific capacity meso- carbon microbeads according to claim 1, characterized by, The solid-liquid separation treatment in the above step 1) comprises centrifugal separation, extraction separation, extraction separation, and pressure filtration separation.

3. The method for producing a nucleating agent for high specific capacity meso- carbon microbeads according to claim 1, characterized by, The boiling bed multi-stage catalytic hydrogenation in the above step 3) adopts a double or multi-tube reactor series mode; The heavy oil A obtained by boiling bed multi-stage catalytic hydrogenation has an ash content of less than 0.3%, a toluene insoluble content of greater than or equal to 30%, and a quinoline insoluble content of greater than or equal to 10%.

4. The method for producing a nucleating agent for high specific capacity meso- carbon microbeads according to claim 1, characterized by, The fixed bed catalytic hydrocracking in the above step 3) adopts a fixed bed reactor; the heavy oil B obtained by removing impurities from tail oil obtained by fixed bed catalytic hydrocracking by vacuum distillation has an ash content of less than 0.3%, a toluene insoluble content of greater than or equal to 40%, and a quinoline insoluble content of greater than or equal to 20%.

5. The method for producing a nucleating agent for high specific capacity meso- carbon microbeads according to claim 1, characterized by, In the above step 4), the two heavy oils are mixed in a mass ratio of heavy oil A:heavy oil B=1:0.1-10.

6. The method for producing a nucleating agent for high specific capacity meso- carbon microbeads according to claim 1 or 5, characterized by, In the above step 4), the mass ratio of heavy oil to solvent oil is heavy oil:solvent oil=1:0.2-4; The solvent oil comprises crude benzene, toluene, xylene, wash oil, one anthracene oil, two anthracene oil, coking heavy oil, coking light oil, and pyridine.

7. A nucleating agent produced by the production method of the nucleating agent for high-capacity meso-phase carbon microbeads according to any one of claims 1 to 6, characterized by The nucleating agent has an ash content of less than 0.1%, a toluene insoluble content of greater than 70%, a quinoline insoluble content of greater than 40%, a quinoline insoluble particle size distribution D50 of 1-4µm, a purity of greater than or equal to 95%, and a graphitization degree of greater than or equal to 92%.