Method for preparing raw material of carbon material by hydrogenation of cracking tar

Abstract

The invention discloses a method for preparing a carbon material raw material by hydrogenation of cracking tar, which comprises the following steps: taking cracking tar as raw oil, and conveying the cracking tar and hydrogen into a reactor for reaction. The cracking tar is hydrotreated to a stable state, the hydrogenated cracking tar is separated, the obtained heavy residual oil component circularly enters the raw oil feed, and the wax oil component is used as a raw material for preparing carbon materials such as needle coke. The method can realize hydro-conversion of thermally unstable components in the raw materials, deconstructs asphalt residue macromolecular polycyclic aromatic hydrocarbons contained in the cracked tar into tricyclic to tetracyclic polycyclic aromatic hydrocarbons, and makes olefins saturated, on one hand, low-severity hydrotreatment (hydrogen consumption is lower than 1.0%) of the cracked tar is realized, and on the other hand, low-severity hydrotreatment (hydrogen consumption is lower than 1.0%) of the cracked tar is realized; on the other hand, the adverse effect of the asphalt residues on the carbonization process and carbonized products is solved, and the method has extremely high economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical engineering, and particularly relates to a method for hydrogenation upgrading of pyrolysis tar to prepare raw materials for carbon materials. Background Art

[0002] Patent CN112391200B discloses a method for hydrogenation of ethylene pyrolysis tar. In this method, ethylene pyrolysis tar is hydrogenated through a series-connected suspension bed hydrogenation process to convert ethylene pyrolysis tar into monocyclic aromatic hydrocarbons, and then gasoline and diesel fractions are mainly obtained through atmospheric and vacuum distillation. Although this method realizes the full-component hydrogenation conversion of ethylene pyrolysis tar, the conditions adopted are relatively harsh, the hydrogen consumption is high, the hydrogenation cost is too high, and the main products obtained are gasoline and diesel fractions, which have relatively low economic value compared with the raw materials used to prepare carbon materials. Patent CN114381295B discloses a method for preparing high-quality carbon materials from tar. In this method, tar is refined, and refined ethylene tar and catalytic oil are blended with the assistance of a stabilizer to obtain high-quality mesophase pitch and raw materials for producing needle coke. This method does not include the utilization of asphalt residue in tar, resulting in the problem of low tar utilization efficiency. Summary of the Invention

[0003] Aiming at the deficiencies in the above background, the purpose of the present invention is to provide a method for hydrogenation upgrading of pyrolysis tar, which solves the adverse effects of asphalt residue in pyrolysis tar on the carbonization process and carbonization products, improves the utilization efficiency of pyrolysis tar and its asphalt residue, and reduces the carbon dioxide emissions caused by using pyrolysis tar as fuel.

[0004] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0005] A method for preparing raw materials for carbon materials by hydrogenation of pyrolysis tar, which is characterized in that it is carried out according to the following method: In the first step, pyrolysis tar is used as the feed oil, and the feed oil and hydrogen are mixed and input into a reactor for hydrogenation treatment under the reaction conditions with a catalyst present; in the second step, the hydrogenation product is separated, and the obtained wax oil component is used as the raw material for preparing carbon materials such as needle coke, while the heavier residue oil component is recycled into the feed oil in the first step.

[0006] The following is a further optimization and / or improvement of the above technical solution of the invention: The pyrolysis tar is one kind of material or a mixture of multiple materials such as coal tar, biological tar, petroleum pyrolysis tar, etc.

[0007] In the above second step, the output wax oil product is a high-quality raw material rich in three- to four-ring condensed aromatic hydrocarbons and suitable for carbonization to prepare high-grade carbon materials such as needle coke.

[0008] In the first step described above, the hydrogenation reactor is a slurry bed, moving bed, fluidized bed, fixed bed, etc. The hydrogenation reaction conditions are as follows: the hydrogen pressure is not higher than 12 MPa, the temperature is 200 - 450 °C, the residence time is 0.05 - 8 h, and the hydrogen-to-oil volume ratio is 100 - 1000. The preferred parameters are 6 - 9 MPa, 300 - 400 °C, 0.1 - 4 h, and 200 - 600 respectively.

[0009] In the first step described above, the hydrogenation catalyst is one or more sulfides, carbides or nitrides of transition metal elements. When using a slurry bed or fluidized bed, the mass ratio of the catalyst to the pyrolysis tar raw material is 0.00005:1 - 0.05:1, and the preferred mass ratio is 0.0005:1 - 0.01:1.

[0010] In the first step described above, when using a slurry bed or other hydrogenation reactors, the particle size of the catalyst active phase is less than 20 μm, and the preferred size is less than 20 nm.

[0011] In the second step described above, the chemical hydrogen consumption of the hydrogenation reaction is lower than 1.0%, and the preferred value is 0.3 to 0.5%.

[0012] In the second step described above, the separation method of the hydrogenation product includes one method or a combined method of atmospheric and vacuum distillation or high-speed centrifugal separation.

[0013] The beneficial effects of the technical solution of the present invention are as follows:

[0014] 1. The present invention uses pyrolysis tar as a raw material, and through hydrogenation treatment of it, the pitch residue in the raw material is successfully deconstructed into a wax oil component rich in three- to four-ring aromatic hydrocarbons. During the carbonization process, three- to four-ring aromatic hydrocarbons are beneficial to the formation of a macromolecular condensed ring aromatic hydrocarbon structure with better flatness, which further promotes the development of orderly arranged stacking units and carbonaceous mesophase, and an advanced carbon material is obtained.

[0015] 2. The hydrogenation reaction conditions adopted in the present invention are mild and the hydrogen consumption is low, which greatly reduces the production cost. At the same time, the hydrogenation product is used to prepare high-value-added carbon materials such as needle coke, which improves the utilization value of pyrolysis tar.

[0016] 3. The present invention shows an ultra-high pitch residue deconstruction rate. Under the conditions of 8 MPa, 370 °C, 3 h, and a hydrogen-to-oil ratio of 400, the pitch residue deconstruction rate is as high as 98.2%. At the same time, the olefin content is reduced by 99.6%, and the hydrogenation product oil is stable, which greatly improves the low-carbon utilization efficiency of pyrolysis tar resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is the SEM image of the needle coke prepared from the hydrogenated product obtained in Example 1 of the present invention.

[0019] Figure 2 It is the SEM image of the needle coke prepared from the hydrogenated product obtained in Example 2 of the present invention.

[0020] Figure 3 It is the SEM image of the needle coke prepared from the hydrogenated product obtained in Example 3 of the present invention.

[0021] Figure 4 It is the SEM image of the needle coke prepared from the hydrogenated product obtained in Example 4 of the present invention.

[0022] Figure 5 It is the SEM image of the needle coke prepared from the hydrogenated product obtained in Example 5 of the present invention. Specific Embodiments

[0023] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described experimental examples are some experimental examples of the present invention, rather than all of them. Based on the experimental examples in the present invention, all other experimental examples obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention.

[0024] Example 1:

[0025] A method for preparing carbon material raw materials by hydrogenating cracking tar. Ethylene tar is used as the raw material and mixed with the hydrogenation catalyst molybdenum sulfide. The mass ratio of molybdenum sulfide to the raw material oil is 0.005:1. Then it is mixed with hydrogen and enters a hydrogenation reaction suspension bed reactor for hydrogenation treatment to obtain a hydrogenated reactant. The operating conditions of the hydrogenation reaction are: the reaction temperature is 350 °C, the reaction pressure is 6 MPa, the reaction time is 2 h, the hydrogen-to-oil volume ratio is 200:1, and the reaction hydrogen consumption is 0.4%.

[0026] The hydrogenated product is centrifuged and distilled to separate, and the obtained wax oil component is used as the raw material for preparing needle coke. The content of three- to four-ring aromatics in the wax oil component is increased from 42.6% of the initial ethylene tar to 55.3%, and the content of mono- and bi-ring aromatics before and after treatment is 23.6% and 24.2% respectively. See the SEM photo of the prepared needle coke in Figure 1, the needle coke has a regular and dense structure, fewer defect sites such as fractures, and good structural properties. The heavier residue oil components are recycled into the first-stage feedstock.

[0027] This hydrogenation process has low requirements for feedstock and catalysts. Without pre-treating the pyrolysis tar, it can decompose the pitch residue in it, significantly increasing the yield of three- to four-ring aromatic hydrocarbons, and there is no obvious change in the content of mono- and di-ring aromatic hydrocarbons, greatly improving the utilization efficiency of pyrolysis tar.

[0028] Example 2:

[0029] A method for preparing carbon material feedstock by hydrogenating pyrolysis tar. Ethylene tar is used as the feedstock and mixed with the hydrogenation catalyst molybdenum sulfide. The mass ratio of molybdenum sulfide to the feedstock oil is 0.01:1. Then it is mixed with hydrogen and enters a hydrogenation reaction slurry bed reactor for hydrogenation treatment to obtain a hydrogenated reactant. The operating conditions of the hydrogenation reaction are: reaction temperature is 370 °C, reaction pressure is 8 MPa, reaction time is 3 h, hydrogen-to-oil volume ratio is 400:1, and reaction hydrogen consumption is 0.5%.

[0030] The hydrogenated product is centrifuged and separated by distillation. The obtained wax oil component is used as the feedstock for preparing needle coke, and the content of three- to four-ring condensed aromatic hydrocarbons in it is 60.6%. See the SEM photo of the prepared needle coke in Figure 2 , the needle coke has a regular and dense structure and is arranged in a "book page" shape as a whole, showing excellent structural properties. The heavier residue oil components are recycled into the first-stage feedstock.

[0031] Example 3:

[0032] A method for preparing carbon material feedstock by hydrogenating pyrolysis tar. Ethylene tar is used as the feedstock and mixed with the hydrogenation catalyst molybdenum sulfide. The mass ratio of molybdenum sulfide to the feedstock oil is 0.01:1. Then it is mixed with hydrogen and enters a hydrogenation reaction slurry bed reactor for hydrogenation treatment to obtain a hydrogenated reactant. The operating conditions of the hydrogenation reaction are: reaction temperature is 400 °C, reaction pressure is 12 MPa, reaction time is 4 h, hydrogen-to-oil volume ratio is 600:1, and reaction hydrogen consumption is 0.5%.

[0033] The hydrogenated product is centrifuged and separated by distillation. The obtained wax oil component is used as the feedstock for preparing needle coke, and the content of three- to four-ring condensed aromatic hydrocarbons in it is 54.2%. See the SEM photo of the prepared needle coke in Figure 3 , the needle coke structure is relatively dense, but there are some fragmentary defects. The heavier residue oil components are recycled into the first-stage feedstock.

[0034] Example 4:

[0035] The method for preparing carbon material raw materials by hydrogenation of cracked tar uses ethylene tar as raw oil, mixes it with hydrogen and enters a fixed-bed reactor for hydrogenation reaction. In the presence of a hydrogenation catalyst, hydrogenation treatment is carried out to obtain a hydrogenation reaction effluent. The hydrogenation reaction operating conditions are: reaction temperature of 390°C, reaction pressure of 8 MPa, volume space velocity of 1.0 h -1 The hydrogen-oil volume ratio is 600:1. The catalyst loaded in the fixed-bed reactor is a nickel-based catalyst with alumina as the carrier. The active phase particle size is less than 1 μm, and the reaction hydrogen consumption is 0.46%.

[0036] The hydrogenation product was centrifuged and distilled to separate the wax oil component, which was used as the raw material for preparing needle coke. The content of three-ring to four-ring condensed aromatic hydrocarbons was 56.9%. The SEM photo of the prepared needle coke can be found in Figure 4 The needle coke has a regular and dense structure with few defects such as fragmentation and breakage. The heavier residual oil components are recycled into the first step feedstock.

[0037] Example 5:

[0038] The method for preparing carbon material raw materials by hydrogenation of cracked tar uses ethylene tar as raw oil, mixes it with hydrogen, and enters a hydrogenation reaction ebullated bed reactor. In the presence of a hydrogenation catalyst molybdenum sulfide, hydrogenation treatment is carried out to obtain a hydrogenation reaction effluent. The hydrogenation reaction operating conditions are: reaction temperature 390 ° C, reaction pressure 8 MPa, volume space velocity 1.0 h -1 The volume ratio of hydrogen to oil is 600:1, and the hydrogen consumption of the reaction is 0.46%.

[0039] The hydrogenation product was centrifuged and distilled to separate the wax oil component, which was used as the raw material for preparing needle coke. The content of three-ring to four-ring condensed aromatic hydrocarbons was 54.8%. The SEM photo of the prepared needle coke can be found in Figure 5 The needle coke structure is denser and has fewer defects such as fragmentation and breakage. The heavier residual oil components are recycled into the first step feedstock.

[0040] Table 1 shows the results of hydrogenation of cracked tar from Examples 1-5 of the present invention. As can be seen, after hydrogenation of the cracked tar, the carbon material yield reached up to 92.1%, and the asphaltene slag decomposition rate reached 98.2%. This invention not only successfully addresses the difficulty in utilizing asphaltene slag and its adverse effects on the carbonization process and carbonized products, but also offers low implementation difficulty and excellent economic benefits.

[0041] Table 1

[0042] Item Decomposition rate of asphalt residue (%) Yield of carbon material raw material (%) Example 1 97.3 89.5 Example 2 98.2 92.1 Example 3 97.9 86.3 Example 4 96.2 88.6 Example 5 96.3 87.6

[0043] Obviously, the above experimental examples are only illustrations for clear explanation and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for preparing carbon material raw material by hydrogenating cracked tar, comprising the following steps: 1) Using cracked tar as raw oil, the raw oil is mixed with hydrogen and fed into a hydrogenation reactor, and hydrogenated in the presence of a hydrogenation catalyst to obtain a hydrogenated product. The hydrogenation catalyst is one or more sulfides, carbides or nitrides of transition metal elements. The hydrogenation reactor is a suspended bed, a moving bed, an ebullient bed or a fixed bed. The hydrogenation reaction conditions are: hydrogen pressure not higher than 12 MPa, temperature of 200-450°C, residence time of 0.05-8 hours, and hydrogen-to-oil volume ratio of 100-1000; 2) Separating the hydrogenation product obtained in step 1) and using the obtained wax oil component as a raw material for preparing needle coke. The wax oil product has a three- to four-ring condensed aromatic hydrocarbon content exceeding 50%, and is suitable for carbonization to prepare needle coke.

2. The method according to claim 1, wherein: The cracking tar is one or more of coal tar, bio-tar and petroleum cracking tar.

3. The method according to claim 1, wherein: In step 2), the heavier residual oil component is recycled into the first step feed oil.

4. The method according to claim 1, wherein: The hydrogenation reaction conditions are as follows: hydrogen pressure 6-9 MPa, temperature 300-400° C., residence time 0.1-4 h, and hydrogen-to-oil volume ratio 200-600.

5. The method according to claim 1, wherein: When a suspended bed or an ebullating bed is used, the mass ratio of the hydrogenation catalyst to the cracking tar raw material is 0.00005:1 to 0.05:

1.

6. The method according to claim 1, wherein: When a suspension bed or an ebullating bed is used, the particle size of the catalyst active phase of the hydrogenation catalyst is less than 20 μm.

7. The method according to claim 1, wherein: The hydrogen consumption is less than 1.0%.

8. The method according to claim 1, wherein: The separation methods of the hydrogenation products include atmospheric and vacuum distillation and / or high-speed centrifugal separation.

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