A method for producing petroleum coke

Abstract

This invention discloses a method for preparing petroleum coke, comprising the following steps: pre-sulfurizing a catalyst, followed by hydrodesulfurization treatment with aromatic-enriched oil slurry; then polycondensation treatment, collecting the primary fraction; then secondary fractionation of the primary fraction, collecting the secondary fraction; and finally, delayed coking of the secondary fraction to obtain petroleum coke. In the catalyst preparation process, a porous γ-Al₂O₃ support coated with a chitosan layer is impregnated in a mixed aqueous solution of nickel and molybdenum compounds, followed by calcination to obtain the catalyst. This invention selects a suitable catalyst for hydrodesulfurization and combines it with appropriate process conditions to obtain a fraction with good flowability and containing a suitable amount of cycloalkane structure, achieving simultaneous adjustment of the reaction rate and flowability during delayed coking, ultimately obtaining petroleum coke. The petroleum coke obtained by this invention, after graphitization treatment, exhibits high graphitization degree and high capacity.

Description

Technical Field

[0001] This invention relates to the field of petroleum coke technology, and in particular to a method for preparing petroleum coke. Background Technology

[0002] Petroleum coke needs to undergo graphitization to obtain a layered structure rich in lithium-ion insertion and extraction for use as a negative electrode material in lithium-ion batteries. Aromatic molecules in the feedstock petroleum undergo liquid-phase carbonization to generate a layered mesophase (referred to as secondary QI). These mesophase layers fuse together and then align in a directional manner to obtain highly graphitized petroleum coke. Therefore, the process of preparing petroleum coke from aromatic molecules becomes a key process determining the performance of artificial graphite; and controlling the formation of the mesophase during petroleum coke preparation is extremely important for improving the final performance of artificial graphite.

[0003] In the process of petroleum coke preparation, factors such as the molecular weight and type of aromatics, the formation rate and fluidity of the mesophase, all affect the coalescence and arrangement of the mesophase, thus influencing the performance and structure of the graphitized petroleum coke. Currently, the main methods for producing petroleum coke include: vacuum distillation to remove asphaltenes, enrichment of aromatic molecules, hydrodesulfurization, and delayed coking. Among these, vacuum distillation and hydrodesulfurization primarily improve the performance and structure of the graphitized petroleum coke by adjusting the formation rate of the mesophase; existing methods do not specifically address the fluidity of the mesophase. Furthermore, current hydrodesulfurization treatments result in a high aromatics loss rate, which reduces the performance of the petroleum coke. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for preparing petroleum coke. The present invention selects a suitable catalyst for hydrodesulfurization and combines it with appropriate process conditions to obtain a fraction with good fluidity and containing an appropriate amount of naphthenic structure, thereby achieving a joint adjustment of the reaction rate and fluidity during delayed coking, and finally obtaining petroleum coke. The petroleum coke obtained by the present invention has a high degree of graphitization and high capacity after graphitization treatment.

[0005] This invention proposes a method for preparing petroleum coke, comprising the following steps: taking a catalyst and pre-sulfurizing it, then hydrodesulfurizing it with an aromatics-enriched oil slurry; then performing a polycondensation treatment, collecting the primary fraction, then performing a secondary fractionation on the primary fraction, collecting the secondary fraction; and then taking the secondary fraction for delayed coking to obtain petroleum coke.

[0006] In the catalyst preparation process, a γ-Al2O3 support coated with a chitosan layer is impregnated in a mixed aqueous solution of nickel and molybdenum compounds and then calcined to obtain the catalyst.

[0007] This invention first coats the γ-Al2O3 support with chitosan, followed by impregnation. This process improves the problem of strong interaction between the γ-Al2O3 support and the active metal, which reduces catalytic performance. Furthermore, the multiple active hydroxyl and amino groups in the chitosan can bind and fix with the active metal precursor, allowing the active metal precursor to be uniformly dispersed in the support. After air calcination, the active metal is uniformly dispersed in the support, thereby improving catalytic performance. While effectively removing sulfur, it maintains a low aromatic loss rate and ensures that the hydrodesulfurized oil contains an appropriate amount of cycloalkane structure, improving the oil quality.

[0008] Preferably, during the catalyst preparation process, the specific surface area of ​​the γ-Al₂O₃ support is 290-310 m². 2 / g, 0.55-0.6mL / g, average pore size is 5-5.2nm; thickness of chitosan layer ≤200nm.

[0009] By selecting a γ-Al2O3 support with appropriate properties and a chitosan layer thickness, the catalytic performance of the catalyst can be further improved.

[0010] Preferably, the catalyst contains 4-4.5 wt% NiO and 16-18 wt% MoO3.

[0011] Preferably, during the preparation of the catalyst, it is impregnated at room temperature for 4-6 hours and calcined at 550-600℃ for 3-4 hours.

[0012] Preferably, in the preparation of the catalyst, the nickel compound is nickel nitrate and the molybdenum compound is ammonium molybdate.

[0013] Preferably, the boiling point of the primary fraction is ≤455-490℃; the boiling range of the secondary fraction is ≥360℃.

[0014] The above-mentioned aromatic enriched slurry was prepared from catalytic cracking slurry, and the aromatic content in the aromatic enriched slurry was 30-65 wt%, and the sulfur content was 0.3-0.8 wt%.

[0015] After the above-mentioned hydrodesulfurization treatment, the fraction selected at a suitable temperature has good fluidity, which can improve the graphitization degree of petroleum coke. In addition, the fraction contains an appropriate amount of cycloalkane structure, which can reduce the viscosity growth rate during carbonization, providing more time for the movement and rearrangement of the intermediate phase layers. This achieves a joint adjustment of the reaction rate and fluidity during delayed coking, promoting ordered arrangement, thereby improving the graphitization degree of petroleum coke and thus increasing the capacity of coke for artificial graphite anodes.

[0016] Preferably, the pre-vulcanization conditions are: pre-vulcanization at 380-400℃ for 2-3 hours in a mixed atmosphere of H2S / H2, wherein the volume fraction of H2S in the mixed atmosphere is 10-12v.

[0017] Preferably, the conditions for hydrodesulfurization are as follows: hydrogen flow rate of 800-900 mL / min, feed rate of aromatic enriched oil slurry of 1.8-2.2 mL / min, pressure of 2.5-4.0 MPa, temperature of 300-360℃, and time of 1-2.5 h.

[0018] Preferably, the polycondensation pressure is atmospheric pressure, the polycondensation temperature is 455-490℃, and the holding time is 4-10s; the delayed coking pressure is 0.65-0.74Mpa, the temperature is 480-490℃, and the holding time is 32-36h.

[0019] Preferably, after the petroleum coke is graphitized at 2800-3200℃ for 4-8 hours, its graphitization degree is >97%.

[0020] Beneficial effects:

[0021] This invention involves coating a γ-Al₂O₃ support with chitosan followed by impregnation to reduce the interaction between the active metal and the support, ensuring uniform dispersion of the active metal within the support and improving catalytic performance. This effectively removes sulfur while maintaining a low aromatic hydrocarbon loss rate, and results in hydrodesulfurized oil containing an appropriate amount of cycloalkane structures, thus improving oil quality. Subsequently, fractions at suitable temperatures are selected to obtain fractions with good flowability and containing an appropriate amount of cycloalkane structures. The combination of good flowability and cycloalkane structures allows for the coordinated adjustment of reaction rate and flowability during delayed coking, providing more time for the movement and rearrangement of the intermediate phase layers, thereby increasing the graphitization degree of petroleum coke and improving the capacity of coke used in artificial graphite anodes. Attached Figure Description

[0022] Figure 1 This is a SEM image of the graphitized petroleum coke obtained in Example 1.

[0023] Figure 2 This is a SEM image of the graphitized petroleum coke obtained in Example 2.

[0024] Figure 3 This is a SEM image of the graphitized petroleum coke obtained in Example 3.

[0025] Figure 4 The image shows a SEM image of the graphitized petroleum coke obtained in Comparative Example 1.

[0026] Figure 5 The image shows the SEM image of the graphitized petroleum coke obtained in Comparative Example 3. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0028] Example 1

[0029] A method for preparing petroleum coke includes the following steps:

[0030] The γ-Al₂O₃ support has a specific surface area of ​​304 m². 2 / g, 0.58mL / g, with an average pore size of 5.15nm, was coated with a 1wt% chitosan solution, filtered, and vacuum dried to obtain a γ-Al2O3 support coated with a chitosan layer, wherein the thickness of the chitosan layer was 150nm.

[0031] A γ-Al2O3 support coated with a chitosan layer was added to a mixed aqueous solution of nickel nitrate and ammonium molybdate and impregnated at room temperature for 5 h. After filtration, the solid was calcined at 570 °C for 3.5 h to obtain a catalyst. The catalyst contained 4 wt% NiO and 16 wt% MoO3.

[0032] 5 kg of catalyst was placed in a hydrodesulfurization unit and pre-sulfurized at 390 °C for 2.5 h in a mixed atmosphere of H2S / H2, with a volume fraction of H2S of 11 v%. Then, the temperature was lowered to 250 °C, and hydrogen was introduced until it stabilized. The hydrogen flow rate was controlled at 900 mL / min, and the feed rate of the aromatic enrichment slurry was 2 mL / min. Hydrodesulfurization was carried out at a pressure of 3.5 MPa, a temperature of 330 °C, and a time of 2 h. The hydrodesulfurized oil was collected.

[0033] The hydrodesulfurized oil is transferred to a polycondensation unit, heated to 470°C, and polycondensed for 10 seconds. The top fraction is collected as the primary fraction (boiling point ≤ 470°C). The primary fraction is then subjected to secondary fractionation, and the secondary fraction with a distillation range ≥ 360°C is collected.

[0034] The secondary fraction was collected, and the pressure was adjusted to 0.65 MPa. The temperature was kept at 480℃ for 32 hours for delayed coking to obtain petroleum coke.

[0035] Example 2

[0036] A method for preparing petroleum coke includes the following steps:

[0037] The γ-Al₂O₃ support has a specific surface area of ​​292 m². 2 / g, 0.56mL / g, with an average pore size of 5.05nm, was coated with a 1wt% chitosan solution, filtered, and vacuum dried to obtain a γ-Al2O3 carrier coated with a chitosan layer, wherein the thickness of the chitosan layer was 200nm.

[0038] A γ-Al2O3 support coated with a chitosan layer was added to a mixed aqueous solution of nickel nitrate and ammonium molybdate and impregnated at room temperature for 6 hours. After filtration, the solid was calcined at 550°C for 4 hours to obtain a catalyst. The catalyst contained 4 wt% NiO and 16 wt% MoO3.

[0039] Take 5 kg of catalyst and put it into the hydrodesulfurization unit. In the mixed atmosphere of H2S / H2, pre-sulfurize at 380℃ for 3 h. The volume fraction of H2S in the mixed atmosphere is 10 v%. Then cool down to 250℃, introduce hydrogen gas until it stabilizes, control the hydrogen gas flow rate at 800 mL / min, and the feed rate of aromatic enriched oil slurry at 1.8 mL / min. Perform hydrodesulfurization treatment at a pressure of 2.5 MPa, a temperature of 360℃, and a time of 1 h. Collect the hydrodesulfurized oil.

[0040] The hydrodesulfurized oil is transferred to a polycondensation unit, heated to 480℃, and polycondensed for 7 seconds. The top fraction is collected as the primary fraction (boiling point ≤ 480℃). The primary fraction is then subjected to secondary fractionation, and the secondary fraction with a distillation range ≥ 360℃ is collected.

[0041] The secondary fraction was collected, and the pressure was adjusted to 0.70 MPa. The temperature was maintained at 485℃ for 36 hours to obtain petroleum coke through delayed coking.

[0042] Example 3

[0043] A method for preparing petroleum coke includes the following steps:

[0044] The γ-Al₂O₃ support has a specific surface area of ​​309 m². 2 / g, 0.6mL / g, with an average pore size of 5.2nm, was coated with a 1wt% chitosan solution, filtered, and vacuum dried to obtain a γ-Al2O3 carrier coated with a chitosan layer, wherein the thickness of the chitosan layer was 120nm;

[0045] A γ-Al2O3 support coated with a chitosan layer was added to a mixed aqueous solution of nickel nitrate and ammonium molybdate and impregnated at room temperature for 6 hours. After filtration, the solid was calcined at 600℃ for 3 hours to obtain a catalyst. The catalyst contained 4.5 wt% NiO and 18 wt% MoO3.

[0046] 5 kg of catalyst was placed in a hydrodesulfurization unit and pre-sulfurized at 400 °C for 2 h in a mixed atmosphere of H2S / H2 with a volume fraction of 12 v% of H2S. Then the temperature was lowered to 250 °C, and hydrogen was introduced until it stabilized. The hydrogen flow rate was controlled at 880 mL / min, and the feed rate of the aromatic enrichment slurry was 2.2 mL / min. Hydrodesulfurization was carried out at a pressure of 4.0 MPa, a temperature of 300 °C, and a time of 2.5 h. The hydrodesulfurized oil was collected.

[0047] The hydrodesulfurized oil is transferred to a polycondensation unit, heated to 485℃, and polycondensed for 4 seconds. The top fraction is collected as the primary fraction (boiling point ≤ 485℃). The primary fraction is then subjected to secondary fractionation, and the secondary fraction with a distillation range ≥ 360℃ is collected.

[0048] The secondary fraction was collected, and the pressure was adjusted to 0.74 MPa. The temperature was kept at 490℃ for 32 hours for delayed coking to obtain petroleum coke.

[0049] Comparative Example 1

[0050] The γ-Al2O3 support was directly added to a mixed aqueous solution of nickel nitrate and ammonium molybdate, and the catalyst and petroleum coke were prepared according to the method in Example 1.

[0051] Comparative Example 2

[0052] After hydrodesulfurization, the product is directly subjected to delayed coking treatment to prepare petroleum coke according to the method in Example 1.

[0053] Comparative Example 3

[0054] The γ-Al2O3 support was directly added to a mixed aqueous solution of nickel nitrate and ammonium molybdate, and the catalyst was prepared according to the method of Example 1. After hydrodesulfurization, it was directly subjected to delayed coking treatment, and the petroleum coke was prepared according to the method of Example 1.

[0055] Comparative Example 4

[0056] The boiling point of the first fraction is ≤400℃, the boiling range of the second fraction is ≥360℃, and other conditions are the same as in Example 1.

[0057] Comparative Example 5

[0058] The boiling point of the first fraction is ≤550℃, the boiling range of the second fraction is ≥400℃, and the rest is the same as in Example 1.

[0059] The aromatic enriched oil slurries used in Examples 1-3 and Comparative Examples 1-5 were from the same batch and had the same composition.

[0060] The hydrodesulfurized oils and secondary fractions obtained in Examples 1-3 and Comparative Examples 1-5 were analyzed for their component content. Furthermore, the obtained petroleum coke was graphitized at 3000℃ for 8 hours to obtain artificial graphite, and the degree of graphitization of the artificial graphite was measured. Each artificial graphite was then used to prepare coin cells, and the performance of the cells was examined. The test results are shown in Tables 1-2.

[0061] The method for preparing a coin cell is as follows: Take each artificial graphite and prepare a negative electrode slurry according to the weight ratio of artificial graphite, conductive agent and binder of 95:1:4; uniformly coat the negative electrode slurry onto copper foil and dry it in a vacuum at 60°C to obtain a negative electrode sheet; use lithium sheet as positive electrode and 1mol / L LiPF6 solution as electrolyte solution to assemble coin cells.

[0062] Typical graphs are as follows Figure 1-5 As shown, Figure 1-5 The images shown are, in order, SEM images of the graphitized petroleum coke obtained in Examples 1-3, Comparative Example 1, and Comparative Example 3.

[0063] Depend on Figure 1-5 It can be seen that the petroleum coke in Examples 1-3 has larger granular sheets and a flat cross-section after graphitization; while the petroleum coke in Comparative Examples 1 and 3 has slightly smaller granular sheets and an incomplete cross-section after graphitization.

[0064] Table 1. Component analysis results of hydrodesulfurized oil and secondary fraction.

[0065]

[0066]

[0067] As can be seen from Table 1, the combination of the catalyst and preparation method described in this invention can reduce the loss of aromatics after hydrodesulfurization, increase the content of aromatics in the secondary fraction, and reduce the S content.

[0068] Table 2 Performance test results of petroleum coke after graphitization

[0069]

[0070]

[0071] As can be seen from Table 2, the petroleum coke prepared by the method described in this invention has a high degree of graphitization and good electrochemical performance after graphitization.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing petroleum coke, characterized in that, The process includes the following steps: the catalyst is pre-sulfurized and then hydrodesulfurized with aromatic-enriched oil slurry; then polycondensation is performed to collect the primary fraction; the primary fraction is then subjected to secondary fractionation to collect the secondary fraction; and finally, the secondary fraction is subjected to delayed coking to obtain petroleum coke. In the catalyst preparation process, a γ-Al2O3 support coated with a chitosan layer is impregnated in a mixed aqueous solution of nickel and molybdenum compounds and then calcined to obtain the catalyst. In the preparation of the catalyst, the specific surface area of ​​the γ-Al₂O₃ support is 290-310 m². 2 / g, 0.55-0.6mL / g, average pore size is 5-5.2nm; chitosan layer thickness ≤200nm; The catalyst contains 4-4.5 wt% NiO and 16-18 wt% MoO3. During the preparation of the catalyst, it is impregnated at room temperature for 4-6 hours and calcined at 550-600℃ for 3-4 hours; The pre-vulcanization conditions are as follows: pre-vulcanization at 380-400℃ for 2-3 hours in a mixed atmosphere of H2S / H2, with a volume fraction of H2S of 10-12% in the mixed atmosphere. The boiling point of the primary fraction is ≤490℃; the boiling range of the secondary fraction is ≥360℃. The pressure for polycondensation is atmospheric pressure, the temperature for polycondensation is 455-490℃, and the holding time is 4-10 seconds; the pressure for delayed coking is 0.65-0.74 MPa, the temperature is 480-490℃, and the holding time is 32-36 hours. The conditions for hydrodesulfurization are as follows: hydrogen flow rate of 800-900 mL / min, feed rate of aromatic enriched oil slurry of 1.8-2.2 mL / min, pressure of 2.5-4.0 MPa, temperature of 300-360℃, and time of 1-2.5 h.

2. The method for preparing petroleum coke according to claim 1, characterized in that, In the preparation of the catalyst, the nickel compound is nickel nitrate and the molybdenum compound is ammonium molybdate.

3. The method for preparing petroleum coke according to claim 1 or 2, characterized in that, After being graphitized at 2800-3200℃ for 4-8 hours, the degree of graphitization of petroleum coke is >97%.

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