Method for preparing needle coke by medium-low temperature coal tar pitch composite extraction modification

文档序号:1793715 发布日期:2021-11-05 浏览:20次 中文

阅读说明:本技术 中低温煤焦油沥青复合萃取改质制备针状焦的方法 (Method for preparing needle coke by medium-low temperature coal tar pitch composite extraction modification ) 是由 李冬 徐贤 施俊合 田佳勇 崔楼伟 刘杰 田育成 黄晔 高生辉 高峰 于 2021-08-26 设计创作,主要内容包括:本发明属于煤化工技术领域,涉及一种中低温煤焦油沥青复合萃取改质制备针状焦的方法,包括:1)从中低温煤焦油全馏分中切割出360~540℃馏分段的沥青;2)依次采用有机混合溶剂萃取工艺、离子液体萃取工艺和组分改质工艺,从切割沥青中得到精制沥青;3)在磁场条件下,对精制沥青进行热聚合得到半焦;4)在氮气氛围下,半焦经煅烧、冷却得到针状焦。精制沥青中N含量<2%,O含量为3.5~4.2%,芳香度f-(A)为0.7~0.9。本发明以中低温煤焦油沥青为原料,采用复合萃取改质工艺得到精制沥青,实现原料有效定向调控,提高中间相形成过程中的供氢能力,降低炭化体系黏度,制备的产品结构稳定,纤维含量高。(The invention belongs to the technical field of coal chemical industry, and relates to a method for preparing needle coke by composite extraction and modification of medium-low temperature coal tar pitch, which comprises the following steps: 1) cutting pitch segmented at 360-540 ℃ from the full fraction of the medium-low temperature coal tar; 2) sequentially adopting an organic mixed solvent extraction process, an ionic liquid extraction process and a component modification process to obtain refined asphalt from the cut asphalt; 3) under the condition of a magnetic field, carrying out thermal polymerization on the refined asphalt to obtain semicoke; 4) and calcining and cooling the semicoke in a nitrogen atmosphere to obtain needle coke. N content in refined asphalt<2%, O content of 3.5-4.2%, and aromaticity f A 0.7 to 0.9. The invention takes the medium-low temperature coal tar pitch as the raw material, adopts the composite extraction modification process to obtain the refined pitch, realizes the effective directional regulation and control of the raw material, and improves the hydrogen supply energy in the intermediate phase forming processThe strength, the viscosity of the carbonization system is reduced, and the prepared product has stable structure and high fiber content.)

1. A method for preparing needle coke by medium-low temperature coal tar pitch composite extraction modification is characterized by comprising the following steps:

1) and (3) cutting fractions: cutting pitch segmented at 360-540 ℃ from the full fraction of the medium-low temperature coal tar;

2) and (3) refining asphalt: sequentially adopting an organic mixed solvent extraction process, an ionic liquid extraction process and a component modification process to obtain refined asphalt from the asphalt cut in the step 1);

3) carrying out thermal polymerization on the refined asphalt obtained in the step 2) under the condition of a magnetic field to obtain semicoke;

4) calcining and cooling the semicoke obtained in the step 3) in a nitrogen atmosphere to obtain needle coke.

2. The method for preparing needle coke by performing composite extraction and modification on medium and low temperature coal tar pitch according to claim 1, wherein the refined pitch obtained in the step 2) contains N<2%, O content of 3.5-4.2%, and aromaticity fA0.7 to 0.9.

3. The method for preparing needle coke by performing composite extraction and upgrading on medium and low temperature coal tar pitch according to claim 2, characterized in that the specific process in the step 2) is as follows:

2.1) mixing the asphalt cut in the step 1) with an organic mixed solvent according to a mass ratio of 1: 1.5-5, stirring for 15-40 min at 60-90 ℃, standing for 20-50 min for layering, and taking supernatant to obtain organic extract;

2.2) mixing the organic extraction liquid obtained in the step 2.1) with an ionic liquid according to a mass ratio of 1: 1-3, stirring at 40-90 ℃ for 10-30 min, cooling to room temperature, and performing suction filtration to obtain a filtrate; and adding deionized water into the filtrate, and sequentially carrying out back extraction, separation and reduced pressure distillation to obtain the extracted asphalt, wherein the volume ratio of the filtrate to the deionized water is 1: 4-10;

2.3) adding a modifier into the extracted asphalt obtained in the step 2.2), mixing and placing the mixture in a reaction kettle, wherein the addition amount of the modifier is 5-15 wt% of that of the extracted asphalt; reacting at the constant temperature of 180-200 ℃ for 1-3 h, distilling out light components, cooling to room temperature, and obtaining refined asphalt at the bottom of the kettle.

4. The method for preparing needle coke by performing composite extraction and modification on medium-low temperature coal tar pitch according to claim 3, wherein in the step 2.1), the organic mixed solvent is a mixed solution of n-hexane and toluene, and the mass ratio of the n-hexane to the toluene is 1: 1-4.

5. The method for preparing needle coke by performing composite extraction and upgrading on medium and low temperature coal tar pitch according to claim 4, wherein the ionic liquid adopted in the step 2.2) is [ Bmim ]][Cl]、[Bmim][PF6]、[C4mim][SCN]、[Bmpyrr][Cl]、[Bmmim][Tf2N]、[Emim][EtSO4]、[Bmim]FeCl4、[Bmim][C(CN)3]And [3-mebupy][C(CN)3]One or more of (a).

6. The method for preparing needle coke by performing composite extraction and upgrading on medium and low temperature coal tar pitch according to claim 5, wherein in the step 2.3), the upgrading agent is one or more of tetrahydronaphthalene, mono-anthracene oil, dihydroanthracene, dihydrophenanthrene and decahydronaphthalene.

7. The method for preparing needle coke by performing composite extraction and upgrading on medium and low temperature coal tar pitch according to claim 6, wherein in the step 3), the magnetic field conditions are as follows: the magnetic induction intensity of the magnetic field is 15-30 mT, the magnetic field is applied when the reaction temperature is 400-440 ℃, and the magnetic field is applied for 5-10 s every 10 min;

the thermal polymerization is carried out under the temperature and pressure changing procedure, and the specific conditions are as follows: firstly, heating to 400-440 ℃ at a pressure of 0.5-2 MPa and a heating rate of 2-4 ℃/min, and keeping the temperature for 8-12 h; then, the temperature is raised to 480-520 ℃ at the pressure of 0.5-1 MPa and the temperature rise rate of 0.5-2 ℃/min, and the temperature is kept for 8-12 h.

8. The method for preparing needle coke by performing composite extraction and upgrading on medium and low temperature coal tar pitch according to claim 7, wherein in the step 4), the calcination conditions are as follows: the temperature rise rate is 1-3 ℃/min, the pressure is 0.01-0.03 MPa, the temperature is raised to 1400-1600 ℃, and the calcination is carried out for 6-10 h.

9. The needle coke prepared by the method for preparing the needle coke by the medium and low temperature coal tar pitch composite extraction and modification according to claim 8.

10. The needle coke of claim 9, wherein: the minimum expansion coefficient of the needle coke is 1.36 multiplied by 10-6The resistivity was 568. mu. omega. m at the minimum/. degree.C.

Technical Field

The invention belongs to the technical field of coal chemical industry, and relates to a method for preparing needle coke by performing composite extraction modification on medium-low temperature coal tar pitch.

Background

Needle coke, an important new industrial material, has been widely used in recent years in research on capacitors and lithium ion batteries due to its properties such as high electrical conductivity, low thermal expansion coefficient, corrosion resistance, and high strength, and is a main raw material for manufacturing high-power graphite electrodes, the performance of which is determined to some extent by the quality of needle coke, which is mainly affected by the composition of the raw material.

The medium-low temperature coal tar pitch is characterized by being rich in low-ring aromatic compounds and extremely small in Quinoline Insoluble (QI), and is a high-quality raw material for producing coal-based needle coke. However, the high-reactivity nitrogen-containing and oxygen-containing compounds and other factors which are not beneficial to the formation of the intermediate phase result in poor thermal stability and high system viscosity during carbonization, are not beneficial to the formation, growth and combination of intermediate phase globules, further influence the formation of the intermediate phase, and further deteriorate the performance of the finally obtained needle coke.

At present, the problems of the thermal stability of asphalt, the formation of mesophase and the viscosity of a carbonization system are very important in the refining process of needle coke raw materials. The refining method of the commonly used needle coke raw material mainly comprises the following steps: flash condensation polymerization, vacuum distillation separation, hydrogenation modification, solvent extraction, etc. Patent CN109868146A discloses a method for preparing needle coke raw material by using medium temperature coal pitch as raw material, obtaining a solid-liquid mixture containing mesophase pitch microspheres and de-quinoline insoluble pitch through polymerization and spheroidization, adding coking wash oil into the mixture, performing solid-liquid separation to obtain liquid-phase de-quinoline insoluble pitch, and performing hydro-reforming with hydrogen donor at 350-420 ℃ and 5-15 MPa to remove sulfur, nitrogen, metal and the like and lightly alkylate. Patent CN104232130B discloses a method for preparing needle coke raw material, which comprises heating coal tar pitch and free carbon or components containing free carbon at 320-360 ℃ to react to obtain modified pitch, mixing the modified pitch with washing oil, anthracene oil or quinoline, removing insoluble substances in the mixture by physical separation method, mixing the clarified liquid with any one of petroleum heavy oil, ethylene tar and residual oil extracted by furfural, and then separating. Patent CN100500804C discloses a method for producing needle coke from coal tar distillate, which comprises removing QI from light component solvent oil, distilling under reduced pressure to separate out solvent to obtain refined pitch, placing in a tubular reactor with special structure, and performing thermal polymerization to generate mesophase, and promoting the mesophase to grow in order to obtain needle coke. Patent CN101565630B discloses a method for preparing ordered mesophase needle coke, which uses coal pitch as raw material, and adopts organic solvent, ultrasonic wave and centrifugal separation method to remove insoluble substance, the organic solvent is removed by reduced pressure distillation to obtain refined pitch, and the refined pitch is subjected to thermal polymerization under the action of electric field to promote the molecular orientation of polycyclic aromatic hydrocarbon compound to generate orientation effect.

In the above patents, the needle coke is prepared by treating and refining medium-low temperature coal tar pitch, but there still remains the problem that it is difficult to obtain a mesophase having a stable structure and a wide streamline range, which affects the quality and performance of the needle coke and has high process energy consumption. Therefore, the method has great significance in searching a new method for improving the process and exploring a more reasonable and efficient preparation method.

Disclosure of Invention

Aiming at the technical problems of the existing needle-shaped preparation, the invention provides a method for preparing needle-shaped coke by the composite extraction and modification of medium-low temperature coal tar pitch, which uses the medium-low temperature coal tar pitch as a raw material and adopts a composite extraction and modification process to obtain refined pitch, thereby realizing the effective directional regulation and control of the raw material, improving the hydrogen supply capacity of a system in the mesophase forming process, reducing the viscosity of a carbonization system, and ensuring that the prepared product has stable structure and high fiber content.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for preparing needle coke by medium-low temperature coal tar pitch composite extraction modification is characterized by comprising the following steps:

1) and (3) cutting fractions: cutting pitch segmented at 360-540 ℃ from the full fraction of the medium-low temperature coal tar;

2) and (3) refining asphalt: sequentially adopting an organic mixed solvent extraction process, an ionic liquid extraction process and a component modification process to obtain refined asphalt from the asphalt cut in the step 1);

3) carrying out thermal polymerization on the refined asphalt obtained in the step 2) under the condition of a magnetic field to obtain semicoke;

4) calcining and cooling the semicoke obtained in the step 3) in a nitrogen atmosphere to obtain needle coke.

Further, the refined asphalt obtained in the step 2) has N content<2%, O content of 3.5-4.2%, and aromaticity fA0.7 to 0.9.

Further, the specific process of step 2) is as follows:

2.1) mixing the asphalt cut in the step 1) with an organic mixed solvent according to a mass ratio of 1: 1.5-5, stirring for 15-40 min at 60-90 ℃, standing for 20-50 min for layering, and taking supernatant to obtain organic extract;

2.2) mixing the organic extraction liquid obtained in the step 2.1) with an ionic liquid according to a mass ratio of 1: 1-3, stirring at 40-90 ℃ for 10-30 min, cooling to room temperature, and performing suction filtration to obtain a filtrate; and adding deionized water into the filtrate, and sequentially carrying out back extraction, separation and reduced pressure distillation to obtain the extracted asphalt, wherein the volume ratio of the filtrate to the deionized water is 1: 4-10;

2.3) adding a modifier into the extracted asphalt obtained in the step 2.2), mixing and placing the mixture in a reaction kettle, wherein the addition amount of the modifier is 5-15 wt% of that of the extracted asphalt; reacting at the constant temperature of 180-200 ℃ for 1-3 h, distilling out light components, cooling to room temperature, and obtaining refined asphalt at the bottom of the kettle.

Further, in the step 2.1), the organic mixed solvent is a mixed solution of n-hexane and toluene, and the mass ratio of n-hexane to toluene is 1: 1-4.

Further, the ionic liquid adopted in the step 2.2) is [ Bmim ]][Cl]、[Bmim][BF6]、[C4mim][SCN]、[Bmpyrr][Cl]、[Bmmim][Tf2N]、[Emim][EtSO4]、[Bmim]FeCl4、[Bmim][C(CN)3]And [3-mebupy][C(CN)3]One or more of (a).

Further, in the step 2.3), the modifier is one or more of tetrahydronaphthalene, mono-anthracene oil, dihydroanthracene, dihydrophenanthrene and decahydronaphthalene.

Further, in the step 3), the magnetic field conditions are as follows: the magnetic induction intensity of the magnetic field is 15-30 mT, the magnetic field is applied when the reaction temperature is 400-440 ℃, and the magnetic field is applied for 5-10 s every 10 min;

the thermal polymerization is carried out under the temperature and pressure changing procedure, and the specific conditions are as follows: firstly, heating to 400-440 ℃ at a pressure of 0.5-2 MPa and a heating rate of 2-4 ℃/min, and keeping the temperature for 8-12 h; then, the temperature is raised to 480-520 ℃ at the pressure of 0.5-1 MPa and the temperature rise rate of 0.5-2 ℃/min, and the temperature is kept for 8-12 h.

Further, in the step 4), the calcining conditions are as follows: the temperature rise rate is 1-3 ℃/min, the pressure is 0.01-0.03 MPa, the temperature is raised to 1400-1600 ℃, and the calcination is carried out for 6-10 h.

A needle coke prepared by a method for preparing needle coke by medium-low temperature coal tar pitch composite extraction modification.

Further, the needle coke has a minimum expansion coefficient of 1.36X 10-6/DEG C and a minimum resistivity of 568 mu omega m.

The invention has the beneficial effects that:

1. the method comprises the steps of taking medium-low temperature coal tar pitch segmented at 360-540 ℃ as a raw material, obtaining refined pitch through three steps of a composite extraction modification process, then thermally polymerizing under a magnetic field condition to obtain semicoke, and finally calcining at high temperature to obtain a needle coke product.

2. According to the invention, impurities in the raw materials can be removed through organic mixed solvent extraction, aromatic hydrocarbons are enriched at the same time, nitrogen-containing compounds, oxygen-containing compounds and asphaltenes in the raw materials can be effectively removed through ionic liquid extraction, the improvement of the selectivity of hydrogenation reaction during carbonization, the prolongation of coke formation induction period, the reduction of coke formation temperature point and the improvement of the thermal stability of a carbonization system are facilitated, two-step composite extraction realizes the mutual cooperation of extraction processes, the raw materials are effectively and directionally regulated, and the ionic liquid extraction agent is a green recoverable solvent.

3. On the basis of composite extraction, the invention adopts a component modification process, can improve the hydrogen supply capacity of the system in the intermediate phase forming process, reduce the viscosity of a carbonization system, form more coke-drawing airflow medium and ensure the quality and performance of the final needle coke product.

4. In the invention, the refined asphalt forms a wide-area streamline mesophase in the specific magnetic field and thermal polymerization process, so as to prepare the needle coke with high fiber content, and the expansion coefficient of the needle coke is 1.36 multiplied by 10 at least-6The resistivity is 568 mu omega.m at the minimum, and the performance is better.

Drawings

FIG. 1 is a view showing a structure of a polarized light microscope of a needle coke produced in example 3 of the present invention;

FIG. 2 is a structural view of a scanning electron microscope of the needle coke produced in example 3 of the present invention;

FIG. 3 is a view showing a structure of a polarized light microscope of a needle coke produced in comparative example 3 of the present invention;

FIG. 4 is a structural view of a scanning electron microscope of a needle coke produced in comparative example 3 of the present invention.

Detailed Description

The present invention will now be described in detail with reference to the accompanying drawings and examples.

The method comprises the steps of taking medium-low temperature coal tar pitch segmented at 360-540 ℃ as a raw material, obtaining refined pitch through three steps of a composite extraction and modification process, then thermally polymerizing under a magnetic field condition to obtain semicoke, and finally calcining at high temperature to obtain a needle coke product. The method specifically comprises the following steps:

1) and (3) cutting fractions: cutting pitch segmented at 360-540 ℃ from the full fraction of the medium-low temperature coal tar;

during the operation of the process, the full-fraction medium-low temperature coal tar is placed in a reaction kettle, medium-low temperature coal tar pitch of a 360-540 ℃ distillation section is cut out under reduced pressure, and the pitch of the distillation section is crushed and sieved; preferably 400-500 ℃ fraction;

2) and (3) refining asphalt: sequentially adopting an organic mixed solvent extraction process, an ionic liquid extraction process and a component modification process to obtain refined asphalt from the asphalt cut in the step 1);

the refined asphalt obtained by the invention has N content<2%, O content of 3.5-4.2%, and aromaticity fA0.7 to 0.9.

3) Carrying out thermal polymerization on the refined asphalt obtained in the step 2) under the condition of a magnetic field to obtain semicoke;

the magnetic field conditions were: the magnetic induction intensity of the magnetic field is 15-30 mT, the magnetic field is applied when the reaction temperature is 400-440 ℃, and the magnetic field is applied for 5-10 s every 10 min; the thermal polymerization is carried out under the temperature and pressure changing procedure, and the specific conditions are as follows: firstly, heating to 400-440 ℃ at a pressure of 0.5-2 MPa and a heating rate of 2-4 ℃/min, and keeping the temperature for 8-12 h; then, the temperature is raised to 480-520 ℃ at the pressure of 0.5-1 MPa and the temperature rise rate of 0.5-2 ℃/min, and the temperature is kept for 8-12 h.

4) Calcining and cooling the semicoke obtained in the step 3) in a nitrogen atmosphere to obtain needle coke. The calcination conditions were: the temperature rise rate is 1-3 ℃/min, the pressure is 0.01-0.03 MPa, the temperature is raised to 1400-1600 ℃, and the calcination is carried out for 6-10 h.

Further, the process of refining the asphalt specifically comprises the following steps:

2.1) mixing the asphalt cut in the step 1) with an organic mixed solvent according to a mass ratio of 1: 1.5-5, stirring for 15-40 min at 60-90 ℃, standing for 20-50 min for layering, and taking supernatant to obtain organic extract; the organic mixed solvent is a mixed solution of normal hexane and toluene, and the mass ratio of the normal hexane to the toluene is 1: 1-4.

2.2) mixing the organic extraction liquid obtained in the step 2.1) with an ionic liquid according to a mass ratio of 1: 1-3, stirring at 40-90 ℃ for 10-30 min, cooling to room temperature, and performing suction filtration to obtain a filtrate; and adding deionized water into the filtrate, and sequentially carrying out back extraction, separation and reduced pressure distillation to obtain the extracted asphalt, wherein the volume ratio of the filtrate to the deionized water is 1: 4-10;

in the present invention, the ionic liquid used is [ Bmim ]][Cl](1-butyl-3-methylimidazolyl chloride), [ Bmim [ ]][BF6](1-butyl-3-methylimidazolium hexafluorophosphate) [ C ]4mim][SCN](1-butyl-3-methylimidazolium thiocyanate), [ Bmpyr][Cl](1-butyl-1-methylpyrrolidine chloride), [ Bmmim [ ]][Tf2N](1-butyl-2, 3-methylimidazolium bis (ketoimide)), [ Emim][EtSO4](1-ethyl-3-methylimidazolium ethylsulfate), [ Bmim ]]FeCl4(1-butyl-3-methylimidazolium iron tetrachloride), [ Bmim ]][C(CN)3](1-butyl-3-methylimidazoltrimethylmethane) and [3-mebupy][C(CN)3](3-methyl-N-butylpyridinium tricyanomethanide).

2.3) adding a modifier into the extracted asphalt obtained in the step 2.2), mixing and placing the mixture in a reaction kettle, wherein the addition amount of the modifier is 5-15 wt% of that of the extracted asphalt; reacting at the constant temperature of 180-200 ℃ for 1-3 h, distilling out light components, cooling to room temperature, and obtaining refined asphalt at the bottom of the kettle.

In the invention, the modifier is one or more of tetrahydronaphthalene, anthracene oil, dihydroanthracene, dihydrophenanthrene and decahydronaphthalene.

The invention cuts, crushes and screens the medium-low temperature coal tar pitch as the raw material, and then adopts the composite extraction modification process to obtain the refined pitch, under the condition of magnetic field, the temperature and pressure changing program is adopted to carry out thermal polymerization to obtain the semicoke, and further the needle coke is obtained by high-temperature calcinationViscosity, stable structure of prepared product, high fiber content, and lowest expansion coefficient of needle coke of 1.36 × 10-6The resistivity is 568 mu omega.m at the minimum, and the performance is better.

The preparation process provided by the present invention and the properties of the resulting needle coke product are further illustrated below by several specific sets of examples.

Example 1

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 120g of organic mixed solvent (60g of n-hexane and 60g of toluene) in a beaker, stirring for 15min in a water bath at 60 ℃, standing for 20min, and taking supernatant, namely organic extract;

placing the organic extract and 200g of [ Bmim ] [ Cl ] ionic liquid in a beaker, stirring for 10min under strong magnetic force in water bath at 40 ℃, cooling to room temperature, and filtering out insoluble substances by using a vacuum filtration device; adding deionized water with the volume 4 times that of the filtrate into the filtrate for back extraction, performing suction filtration on a back-extracted solid-liquid mixture by using a vacuum suction filtration device, and separating to obtain an extract; distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

placing 40g of extracted asphalt and 2g of tetrahydronaphthalene in a reaction kettle, controlling the temperature at 180 ℃, keeping the temperature for 1 hour, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 400 ℃ under the condition of controlling the pressure to be 0.5MPa and the heating rate of 2 ℃/min, the magnetism is added for 6s every 10min, the temperature is kept for 8h, and the magnetic induction intensity is 13 mT; then heating to 480 ℃ at the pressure of 0.5MPa and the heating rate of 0.5 ℃/min, and keeping the temperature for 8 hours to obtain semicoke;

4) placing the semicoke in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1400 ℃ under the constant pressure of 0.01MPa at the heating rate of 1 ℃/min, calcining for 5h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

Example 2

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 160g of organic mixed solvent (60g of n-hexane and 100g of toluene) in a beaker, stirring for 20min in a water bath at 70 ℃, standing for 20min, and taking supernatant, namely organic extract;

the organic extract was mixed with 340g of [ Bmim ]][PF6]Placing the ionic liquid in a beaker, stirring for 15min under strong magnetic force in water bath at 50 ℃, cooling to room temperature, filtering out insoluble substances by using a vacuum filtration device, adding deionized water with the volume 5 times that of the filtrate into the filtrate for back extraction, filtering the back-extracted solid-liquid mixture by using the vacuum filtration device, and separating to obtain the extract. Distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

placing 40g of extracted asphalt and 2.8g of dihydroanthracene in a reaction kettle, controlling the temperature at 180 ℃, keeping the temperature for 1.5h, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 420 ℃ under the control of the pressure of 1MPa and the heating rate of 2.5 ℃/min, the magnetism is added for 6s every 10min, the temperature is kept for 9h, and the magnetic induction intensity is 18 mT; then heating to 500 ℃ at the temperature rise rate of 0.5 ℃/min under the pressure of 0.5MPa, and keeping the temperature for 8 hours to obtain semicoke;

4) placing the semicoke in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1450 ℃ at a constant pressure of 0.01MPa at a heating rate of 2 ℃/min, calcining for 6h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

Example 3

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 180g of organic mixed solvent (60g of n-hexane and 120g of toluene) in a beaker, stirring for 20min in a water bath at 75 ℃, standing for 20min, and taking supernatant, namely organic extract;

the organic extract was mixed with 440g ([ Bmim) ([ Bmim ]]FeCl4、[Bmim][Cl]) Placing the ionic liquid in a beaker, stirring for 20min under strong magnetic force in water bath at 60 ℃, cooling to room temperature, and filtering out insoluble substances by using a vacuum filtration device; adding deionized water with the volume 6 times that of the filtrate into the filtrate for back extraction, performing suction filtration on a back-extracted solid-liquid mixture by using a vacuum suction filtration device, and separating to obtain an extract; distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

placing 40g of extracted asphalt and 3.2g of (anthracene oil and tetrahydronaphthalene) in a reaction kettle, controlling the temperature at 190 ℃, keeping the temperature for 1.5h, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 420 ℃ under the condition that the pressure is controlled to be 1.2MPa and the heating rate is controlled to be 3 ℃/min, the magnetism is added for 6s every 10min, the temperature is kept for 10h, and the magnetic induction intensity is 20 mT. Then heating to 510 ℃ at the pressure of 0.5MPa and the heating rate of 1 ℃/min, and keeping the temperature for 10 hours to obtain semicoke;

4) placing the semicoke in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1500 ℃ at constant pressure of 0.01MPa at the heating rate of 3 ℃/min, calcining for 7h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

Example 4

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 240g of organic mixed solvent (80g of n-hexane and 160g of toluene) in a beaker, stirring for 20min in a water bath at 80 ℃, standing for 25min, and taking supernatant, namely organic extract;

mixing the organic extract with 520g of [ Bmmim ]][Tf2N]Placing the ionic liquid in a beaker, stirring for 25min under strong magnetic force in water bath at 65 ℃,the mixture was cooled to room temperature, and insoluble matter was filtered off by a vacuum filtration apparatus. Adding deionized water with the volume 7 times that of the filtrate into the filtrate for back extraction, performing suction filtration on the back-extracted solid-liquid mixture by using a vacuum suction filtration device, and separating to obtain the extract. Distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

placing 40g of extracted asphalt and 4g of (tetrahydronaphthalene and dihydroanthracene) in a reaction kettle, controlling the temperature at 190 ℃, keeping the temperature for 2 hours, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 440 ℃ under the condition that the pressure is controlled to be 1.5MPa and the heating rate is 3 ℃/min, the magnetism is added for 6s every 10min, the temperature is kept for 10h, and the magnetic induction intensity is 24 mT. Then heating to 520 ℃ at the pressure of 0.8MPa and the heating rate of 1 ℃/min, and keeping the temperature for 11 hours to obtain semicoke;

4) finally, the semicoke is placed in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1550 ℃ under the constant pressure of 0.02MPa at the heating rate of 2.5 ℃/min, calcining for 8h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

Example 5

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 240g of organic mixed solvent (80g of n-hexane and 160g of toluene) in a beaker, stirring for 20min in a water bath at 80 ℃, standing for 25min, and taking supernatant, namely organic extract;

the organic extract was mixed with 420g of [ Bmim ]]FeCl4The ionic liquid is placed in a beaker, stirred for 25min under strong magnetic force in water bath at 65 ℃, cooled to room temperature, and insoluble substances are filtered by a vacuum filtration device. Adding deionized water with the volume 8 times that of the filtrate into the filtrate for back extraction, performing suction filtration on the back-extracted solid-liquid mixture by using a vacuum suction filtration device, and separating to obtain the extract. Distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

Placing 40g of extracted asphalt and 3.6g of decalin in a reaction kettle, controlling the temperature at 200 ℃, keeping the temperature for 2 hours, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 430 ℃ under the condition that the pressure is controlled to be 2MPa and the heating rate is 3.5 ℃/min, the magnetism is added for 6s every 10min, the temperature is kept for 8h, and the magnetic induction intensity is 28 mT. Then heating to 500 ℃ at the pressure of 1MPa and the heating rate of 2 ℃/min, and keeping the temperature for 9 hours to obtain semicoke;

4) finally, the semicoke is placed in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1450 ℃ at a constant pressure of 0.02MPa at a heating rate of 3 ℃/min, calcining for 8h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

Example 6

1) Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

2) placing 80g of asphalt and 240g of organic mixed solvent (80g of n-hexane and 160g of toluene) in a beaker, stirring for 20min in a water bath at 80 ℃, standing for 25min, and taking supernatant, namely organic extract;

mixing the organic extract with 440g of 3-mebupy][C(CN)3]Placing the ionic liquid in a beaker, stirring for 25min under strong magnetic force in water bath at 65 ℃, cooling to room temperature, filtering out insoluble substances by using a vacuum filtration device, adding deionized water with the volume 8 times that of the filtrate into the filtrate for back extraction, filtering the back-extracted solid-liquid mixture by using the vacuum filtration device, and separating to obtain an extract; distilling the extract under reduced pressure to remove organic solvent to obtain extracted asphalt;

placing 40g of extracted asphalt and 6g of dihydrophenanthrene in a reaction kettle, controlling the temperature at 200 ℃, keeping the temperature for 2.5 hours, distilling out light components, and cooling to room temperature to obtain refined asphalt;

3) placing the refined asphalt in a reaction kettle in N2Under atmosphere, controlling pressureHeating to 420 ℃ under the condition of the force of 2MPa and the heating rate of 2 ℃/min, magnetizing every 10min for 6s, keeping the temperature for 9h, and controlling the magnetic induction intensity to be 30 mT; then heating to 520 ℃ at the pressure of 1MPa and the heating rate of 1.5 ℃/min, and keeping the temperature for 12h to obtain semicoke;

4) placing the semicoke in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1550 ℃ at a constant pressure of 0.02MPa at a heating rate of 3 ℃/min, calcining for 9h, and cooling to room temperature to obtain the needle coke.

The thermal expansion coefficient, true density and resistivity of the needle coke prepared in this example were determined by the corresponding methods, and the specific results are shown in table 1.

In order to verify the technical effect of the invention, several groups of proportion verification are carried out at present, and the method specifically comprises the following steps:

comparative example 1

The difference from example 1 is that in the case of the composite extraction-modified refined pitch, only the organic solvent is used for thermal extraction, and the ionic liquid extraction and modification are not performed. When the semi-coke is generated by thermal polymerization, a magnetic field is not added; the conditions for obtaining needle coke by semicoke calcination and cooling are different. The raw material is selected from medium-low temperature coal pitch segmented at 360-540 ℃. The rest is the same as in example 1.

Putting 2.6kg of low-temperature coal tar in the full fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction of 360-540 ℃, cooling to room temperature, and crushing. Taking 80g of asphalt, extracting by using an organic mixed solvent to obtain refined asphalt, placing the refined asphalt in a reaction kettle, carrying out thermal polymerization by combining a specific temperature and pressure change program to obtain semi-coke, and calcining at 1500 ℃ to obtain needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

Comparative example 2

The difference from example 2 is that in the case of the composite extraction-upgrading of the purified asphalt, the asphalt is not upgraded. When the semi-coke is generated by thermal polymerization, a magnetic field is not added; the conditions for obtaining needle coke by semicoke calcination and cooling are different. The raw material is selected from medium-low temperature coal pitch segmented at 360-540 ℃. The rest is the same as in example 1.

Putting 2.6kg of low-temperature coal tar in the full fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction of 360-540 ℃, cooling to room temperature, and crushing. Taking 80g of asphalt, extracting by using an organic mixed solvent and an ionic liquid to obtain refined asphalt, placing the refined asphalt in a reaction kettle, carrying out thermal polymerization by combining a specific temperature and pressure changing program to obtain semicoke, and calcining at 1500 ℃ to obtain needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

Comparative example 3

The difference from example 3 is that: the composite extraction modification is only carried out by organic solvent thermal extraction, and the ionic liquid extraction and modification are not carried out. The conditions for obtaining needle coke by semicoke calcination and cooling are different.

The organic solvent extraction, specific magnetic field and thermal polymerization conditions in the comparative example 3 are the same as those in the example 3, and the medium-low temperature coal pitch segmented at the temperature of 360-540 ℃ is selected as the raw material.

Putting 2.6kg of low-temperature coal tar in the full fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction of 360-540 ℃, cooling to room temperature, and crushing. Taking 80g of asphalt, extracting by using an organic mixed solvent to obtain refined asphalt, placing the refined asphalt in a reaction kettle, carrying out thermal polymerization by combining a specific magnetic field and a temperature and pressure changing program to obtain semi-coke, and calcining at 1500 ℃ to obtain needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

Comparative example 4

Different from the embodiment 4, the condition for obtaining needle coke by semicoke calcination and cooling is different, and when the semicoke is generated by thermal polymerization, a magnetic field is not added; the raw material is selected from medium-low temperature coal pitch segmented at 360-540 ℃. The rest is the same as the composite extraction modification process, specific magnetic field and thermal polymerization conditions in the example 4.

Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing; taking 80g of asphalt, obtaining refined asphalt by a composite extraction modification process, placing the refined asphalt in a reaction kettle, and performing thermal polymerization by combining a specific temperature and pressure changing process to obtain semicoke; and calcining the semicoke at 1500 ℃ to obtain needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

Comparative example 5

The difference from example 5 is that no modification was used in the purification of pitch, and no magnetic field was applied in the thermal polymerization to produce semicoke. The raw material is medium-low temperature coal pitch segmented at 360-540 ℃, and the rest is the same as that in the embodiment 5.

Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

placing 80g of asphalt and 240g of organic mixed solvent (80g of n-hexane and 160g of toluene) in a beaker, stirring for 20min in a water bath at 80 ℃, standing for 25min, and taking supernatant, namely organic extract. Carrying out reduced pressure distillation on the extract liquor to remove the organic solvent, thus obtaining extracted asphalt;

placing 40g of extracted asphalt and 3.6g of tetrahydronaphthalene in a reaction kettle, controlling the temperature at 220 ℃, keeping the temperature for 1 hour, distilling out light components, and cooling to room temperature to obtain refined asphalt;

placing the mixture in a reaction kettle at N2Under the atmosphere, the temperature is raised to 430 ℃ at the temperature raising rate of 3.5 ℃/min under the pressure of 2MPa, and the temperature is kept for 8 h. Then heating to 500 ℃ at the temperature rise rate of 2 ℃/min under the pressure of 1MPa, keeping the temperature for 9 hours to obtain semicoke, finally placing the semicoke in a high-temperature calcining furnace, and calcining in N2Under the atmosphere, continuously heating to 1450 ℃ at a constant pressure of 0.02MPa at a heating rate of 3 ℃/min, calcining for 8h, and cooling to room temperature to obtain the needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

Comparative example 6

The difference from example 6 is that no modification is used in the purification of pitch, and no magnetic field is applied and no temperature-variable pressure-variable polymerization is used in the production of semicoke. The rest is the same as in example 6. The raw material is selected from medium-low temperature coal pitch segmented at 360-540 ℃.

Putting 2.6kg of low-temperature coal tar in the whole fraction into a rectifying still, carrying out reduced pressure distillation to obtain a fraction at the temperature of 360-540 ℃, cooling to room temperature, and crushing;

placing 80g of asphalt and 240g of organic mixed solvent (80g of n-hexane and 160g of toluene) in a beaker, stirring for 20min in a water bath at 80 ℃, standing for 25min, and taking supernatant, namely organic extract;

mixing the organic extract with 440g of 3-mebupy][C(CN)3]The ionic liquid is placed in a beaker, stirred for 25min under strong magnetic force in water bath at 65 ℃, cooled to room temperature, and insoluble substances are filtered by a vacuum filtration device. Adding deionized water with the volume 8 times that of the filtrate into the filtrate for back extraction, performing suction filtration on the back-extracted solid-liquid mixture by using a vacuum suction filtration device, and separating to obtain the extract. Distilling the extract under reduced pressure to remove organic solvent to obtain refined asphalt;

placing the refined asphalt in a reaction kettle in N2Under the atmosphere, the temperature is raised to 520 ℃ at the temperature raising rate of 2 ℃/min under the pressure of 1.5MPa, and the temperature is kept for 6h to obtain semicoke;

finally, the semicoke is placed in a high-temperature calcining furnace in N2Under the atmosphere, continuously heating to 1550 ℃ at a constant pressure of 0.02MPa at a heating rate of 3 ℃/min, calcining for 9h, and cooling to room temperature to obtain the needle coke.

The needle coke prepared in this comparative example was measured for thermal expansion coefficient, true density and resistivity by the corresponding methods, and the specific results are shown in table 1.

TABLE 1 physical characteristics of needle coke prepared in examples 1-6 and respective comparative examples

Note: (1) the Coefficient of Thermal Expansion (CTE) was measured in accordance with GB/T3074.4-2016 graphite electrode Coefficient of Thermal Expansion (CTE) measurement method. (2) The true density is determined according to GB/T24203-2009 'carbon material true density determination method'. (3) The resistivity is measured according to GB/T2459-2018 method for measuring resistivity of carbon raw materials and coke.

The comparison of the above tables illustratesThe needle coke has a high fiber content and an ordered structure, and thus has a low thermal expansion coefficient and a low electrical resistivity, and the fiber content and the structure of the needle coke are closely related to the composition of the raw material. The effective directional regulation and control of the raw materials are carried out by adopting a composite extraction modification process, and the discovery that [ Bmim]FeCl4And [ Bmim ]][Cl]The ionic liquid has high heteroatom removal rate in the raw materials, is favorable for improving the thermal stability of a carbonization system and promotes the ordered arrangement of intermediate phases; the addition of anthracene oil and tetrahydronaphthalene (modifier) can improve the hydrogen supply capacity of the system in the intermediate phase forming process, reduce the viscosity of the carbonization system and form more coke-drawing airflow medium; the ionic liquid extraction and the component modification are cooperated, so that the orientation and the order degree of the mesophase structure can be greatly improved, and the needle coke with multiple fiber structures and more consistent orientation is further formed. Therefore, the combined extraction modification, the semi-coke generation under the condition of magnetic field temperature and pressure change and the calcination process are combined to obtain the needle coke with better performance. When the addition amount of the ionic liquid is 169 wt% of the organic extraction liquid and the addition amount of the modifier is 8 wt% of the extracted asphalt, the optimal proportion of the application is that the expansion coefficient of the needle coke is 1.36 multiplied by 10 at the lowest-6The resistivity was 568. mu. omega. m at the minimum/. degree.C.

Further, the microstructures of the needle coke prepared in example 3 and comparative example 3 were observed by a polarizing microscope and a scanning electron microscope, respectively.

1. Conditions of the polarizing microscope: the needle focus was observed for optical texture using a ZEISS Axio scope A1 polarizing microscope. The test results are shown in fig. 1 and 3;

2. conditions of the scanning electron microscope: and (3) observing the microscopic appearance of the needle coke by adopting a ZEISS SIGMA Scanning Electron Microscope (SEM), and spraying gold before detection. See fig. 2 and 4 for test results;

as can be seen from fig. 1 and 3: in the figure 1, the fibers of the needle coke are in a wide-area structure and high in content, and the raw materials are refined by adopting composite extraction modification, so that the obtained raw materials have the characteristics of high aromaticity and low heteroatom content, the hydrogen supply capacity of a system in the formation process of an intermediate phase can be improved, a low-viscosity system is maintained, and the ordered arrangement of the intermediate phase is facilitated; in fig. 3, the fiber structure of the needle coke is mostly mosaic structure and short and thick fiber, because in the process of mesophase inversion, the presence of hetero atoms increases the dipole moment between molecules of the aromatic compound, which causes the rapid increase of the viscosity of the system in the carbonization process, disturbs the accumulation of planar condensed ring aromatic hydrocarbon molecules, is not beneficial to the fusion and growth of mesophase, and causes the generation of mosaic structure.

As can be seen from FIGS. 2 and 4, the fiber appearance structure of the needle-shaped focus in FIG. 2 has clear texture, no mosaic structure, small gaps between the sheets, and directional arrangement. In fig. 4, most of the needle coke has a short and thick fiber appearance structure, an inlaid structure and a loose structure exist, gaps among sheets are large, and the orientation of the sheet structure is poor, because the raw materials are not subjected to compound extraction modification, the raw materials contain S, N, O and other heteroatom compounds, and the heteroatom compounds have strong thermal reactivity in the intermediate phase conversion process, so that the viscosity of a carbonization system is rapidly increased, the stacking of planar condensed ring aromatic hydrocarbon molecules is disturbed, the intermolecular excessive crosslinking is caused, and an inlaid tissue structure is formed.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any equivalent modifications or substitutions made by those skilled in the art within the technical scope of the present invention should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

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