Method for preparing heavy oil sodium storage hard carbon negative electrode material

Abstract

The application provides a method for preparing a sodium storage hard carbon negative material from heavy oil, wherein 1wt%-5wt% of an acidic catalyst and an aldehyde crosslinking agent are doped into heavy oil as raw material, and the mixture is subjected to shallow crosslinking polycondensation treatment in a corrosion-resistant reaction kettle; then air oxidation crosslinking is used to obtain isotropic pitch products with good fluidity and low quinoline insoluble content; and carbonization and acid-alkali etching treatment are used to prepare sodium storage hard carbon negative materials with excellent rate performance and long cycle stability. The method uses shallow crosslinking polycondensation by adding an acidic catalyst and an aldehyde crosslinking agent to ensure the utilization rate of small molecules in ethylene tar and significantly improve the yield of the material; the crosslinking polycondensation product is treated by using an oxidation crosslinking process to obtain high-residue isotropic pitch with different softening points and low quinoline insoluble content. On the basis of the above process, the isotropic pitch is treated by using a carbonization-acid-alkali etching process to obtain sodium storage hard carbon negative materials with high battery capacity, excellent rate performance and long cycle stability.

Description

Technical Field

[0001] This invention relates to a method for preparing homogeneous asphalt and sodium-storage hard carbon anode materials from heavy oil. Specifically, heavy oil is used as raw material, and homogeneous asphalt products are obtained through shallow crosslinking-condensation and oxidative crosslinking. The homogeneous asphalt products are then processed through carbonization and acid-base etching processes to obtain sodium-storage hard carbon anode materials. This is a high-quality preparation process for homogeneous asphalt and sodium-storage hard carbon anode materials, belonging to the field of carbon material preparation technology. Background Technology

[0002] With the increasing heavyification of global crude oil resources, a large amount of difficult-to-process heavy oil is generated during petroleum refining. Currently, heavy oil is mainly used for combustion and road paving, with low added value and utilization rate, and is also detrimental to environmental protection. Therefore, how to effectively and rationally utilize heavy oil resources to improve their utilization rate and economic value has become an important research topic. Heavy oil has a complex composition, mainly composed of aromatic compounds, with abundant short side-chain structures. Combined with a high carbon-to-hydrogen ratio and low ash content, these advantages allow it to be converted into high-softening-point asphalt through different preparation methods, thereby obtaining carbon material precursors with different properties. Thermal polycondensation and air oxidation are common asphalt preparation methods. In thermal polycondensation, the change in asphalt properties is mainly due to the evaporation of volatile substances, and dehydrogenation polycondensation is also a significant reaction characteristic. Air oxidation is a simple method for oxidative modification of ethylene tar under medium- and low-temperature conditions. This method promotes molecular polymerization by stimulating free radicals to form cross-linked macromolecules with bridging structures, thereby rapidly increasing the softening point and carbon residue of the product asphalt.

[0003] Carbon precursors possess advantages such as high carbon content, low price, and large yield, making their synthesis into hard carbon energy storage materials with excellent electrochemical performance an ideal approach for achieving high-value-added utilization. The structural design of hard carbon materials significantly affects their various electrochemical properties. Current research on hard carbon materials mainly focuses on improving the specific capacity, initial coulombic efficiency, and cycle stability of sodium-ion batteries. Currently, the inability to simultaneously achieve high battery capacity, excellent rate performance, and long-cycle stability greatly limits the practical application of sodium-ion batteries. CN115849332B discloses a high-rate hard carbon anode material, using biomass polymers as hard carbon precursors, which are mixed with acid anhydride organic compounds in different proportions via a solvent method, followed by a one-step carbonization process to obtain the hard carbon material. CN117049505B proposes forming a porous spherical hard carbon anode material with uniformly dispersed pores by subjecting biomass materials to specific hydrothermal treatment conditions, followed by high-temperature carbonization and alkali treatment. CN118062826A proposes that asphalt is oxidized to obtain oxidized asphalt, and then crosslinked with a mercapto crosslinking agent and an organic sodium salt, followed by heat treatment to obtain hard carbon material. Summary of the Invention

[0004] This invention provides a method for preparing homogeneous asphalt and sodium-storage hard carbon anode materials from heavy oil. Using heavy oil as raw material, a shallow cross-linking-condensation reaction is initiated under low-temperature conditions by doping with a catalyst and a cross-linking agent. The shallow cross-linking-condensation product is further cross-linked by oxidation to prepare high-quality homogeneous asphalt. Using homogeneous asphalt as raw material, a sodium-storage hard carbon anode material with high capacity, rate performance, and long-term stability is prepared through carbonization and acid-base etching. This expands the source of raw materials and represents a high-quality preparation process for sodium-storage hard carbon anode materials.

[0005] To achieve the above objectives, the present invention provides a method for preparing sodium-storage hard carbon anode materials from heavy oil, comprising the following specific steps:

[0006] (1) The raw material is doped with 1wt%-5wt% of an acidic catalyst and 1wt%-5wt% of an aldehyde crosslinking agent and mixed evenly. Under the conditions of inert gas protection, reaction temperature of 80-120℃ and reaction time of 3-5h, a crosslinking-condensation reaction is initiated to obtain a shallow crosslinking condensation product.

[0007] (2) The shallow cross-linked polycondensation product is subjected to a reaction temperature of 270-310℃, a reaction time of 4-10h, and an air flow rate of 4-7ml / (g·min). Through oxygen-induced hydroxyl radicals and methyl radicals, dehydrogenation and cross-linked polycondensation reactions are carried out to obtain isotropic asphalt with an isotropic degree >98%, a carbon residue value ≥45%, and a quinoline insoluble content <0.5%.

[0008] (3) The isotropic asphalt is carbonized for 0.5-2h under an inert atmosphere at a heating rate of 5℃ / min and a temperature of 600-800℃ to form a carbonized product with a preliminary mature carbon skeleton. Then, an etchant is added and mixed with the carbonized product. The mixture is then activated for 0.5-2h under an inert atmosphere at a heating rate of 5℃ / min and a temperature of 800℃. After cooling to room temperature, the sodium storage hard carbon anode material is obtained.

[0009] In step (1) above, the raw material is heavy oil, selected from one or more of FCC slurry oil, vacuum distillate oil, ethylene tar, and medium-low temperature coal tar. The heavy oil has an average molecular weight of 200-500, 2-5 cycloalkane rings, 2-6 aromatic rings, and an aromatic carbon content >40%. The acidic catalyst includes one or more of H2SO4, HNO3, and TsOH, and is added at 1wt% to 5wt% of the raw material. The aldehyde crosslinking agent includes one or more of glutaraldehyde, paraformaldehyde, and propionaldehyde, and is added at 1wt% to 5wt% of the raw material.

[0010] In step (2) above, the reaction temperature is controlled at 270℃ and the reaction time is 4h to produce isotropic asphalt products with a softening point of 150±5℃, a yield of ≥55%, and a carbon residue of ≥48%; the reaction temperature is controlled at 290℃ and the reaction time is 4h to produce isotropic asphalt products with a softening point of 180±5℃, a yield of ≥50%, and a carbon residue of ≥54%; the reaction temperature is controlled at 310℃ and the reaction time is 6h to produce isotropic asphalt products with a softening point of 200±5℃, a yield of ≥44%, and a carbon residue of ≥58%; and the oxidation temperature is controlled at 310℃ and the oxidation time is 10h to produce isotropic asphalt products with a softening point of 250±5℃, a yield of ≥40%, and a carbon residue of ≥70%.

[0011] The etchant mentioned in step (3) above is an acid-base etchant, selected from one or more of KOH, K2CO3, Na2CO3, ZnCl2, and FeCl3. The amount of etchant added is 200wt%-500wt% of the carbonized product. Different carbonization temperatures are selected based on the different softening points of the homogeneous asphalt obtained in step (2). Lower carbonization temperatures are selected for homogeneous asphalt with low softening points, and higher carbonization temperatures are selected for asphalt with high softening points. Different amounts of etchant are added based on the degree of carbonization. At temperatures of 700-800℃, the amount of etchant added is 400wt%-500wt% of the carbonized product; at temperatures of 600-700℃, the amount of etchant added is 200wt%-400wt% of the carbonized product.

[0012] In this invention, changing the carbonization temperature and the amount of etchant added can effectively regulate the multi-scale structure of asphalts with different properties. Low-temperature carbonization is mainly a cross-linking reaction, which can form a rigid three-dimensional network with low porosity. High-temperature carbonization intensifies molecular rearrangement, increases the size of graphite crystallites, reduces interlayer spacing, tends towards an ordered structure, and is more likely to form a dense, highly conductive graphite-like structure. Carbonites obtained at 700℃-800℃ have strong etching resistance due to their dense structure, requiring the addition of etchant at a mass ratio of carbonization product to etchant of 1:4-1:5. Carbonites obtained at 600℃-700℃ may be over-etched due to their loose structure, forming interconnected macropores or collapsed structures. Therefore, etchant should be added at a mass ratio of carbonization product to etchant of 1:2-1:4 to maintain high porosity while promoting the development and distribution of the internal crystal structure of the carbon material. Furthermore, the carbonization process also appropriately reduces the content of oxygen functional groups, promoting the development of the initial microcrystalline structure in the raw material asphalt.

[0013] Based on the properties of isotropic asphalt, carbonization temperature, and etchant usage, the sodium storage hard carbon anode material has a specific capacity of 220-280 mAh / g at a current density of 0.3C, a specific capacity of 203-268 mAh / g at a current density of 1C, and a capacity retention rate of 88%-93% after 200 cycles at a current density of 0.3C.

[0014] The present invention also provides isotropic pitch and sodium-storage hard carbon anode materials prepared by the above method, and the application of the isotropic pitch and sodium-storage hard carbon anode materials in high-performance materials, wherein the high-performance materials include high softening point coated pitch, pitch-based carbon fibers, and sodium-ion batteries.

[0015] This invention employs a combined process of shallow crosslinking-condensation, oxidative crosslinking, carbonization, and acid-base etching to prepare sodium-storage hard carbon anode materials. Due to the complex composition of heavy oil feedstock and the uneven reactivity of different components under high-temperature conditions, direct oxidative crosslinking would lead to the leakage of many small molecules through distillation, reducing feedstock utilization. Therefore, a crosslinking-condensation reaction is first initiated by a catalyst and crosslinking agent. At a relatively low temperature, relying on the acidic environment provided by the catalyst and the oxygen supply from the decomposition of the crosslinking agent, the more reactive light components undergo crosslinking and condensation in the system to form large molecules. This increases the molecular weight and aromaticity of the heavy oil feedstock while improving the overall yield. Next, the temperature is increased, and air is introduced to oxidize and modify the ethylene tar. Oxygen induces free radical reactions and the formation of bridging bonds, forming crosslinked macromolecules, thereby rapidly increasing the softening point and carbon residue of the product asphalt. The introduction of oxygen also limits the formation of quinoline insolubles and aromatic planar molecular structures, ultimately resulting in an excellent isotropic structure. The carbonization process promotes the development of the initial microcrystalline structure in the raw material asphalt, reduces the content of oxygen functional groups, and provides a liquid-phase reaction environment for the assembly of carbon microcrystals. By changing the carbonization temperature and the amount of etchant added, the multi-scale structure of asphalt with different properties can be effectively adjusted. While maintaining high porosity, it promotes the development and distribution of the internal crystal structure of carbon materials, ultimately successfully transforming heavy oil feedstock into layered porous hard carbon with a graphite carbon skeleton. The capacitors constructed from this material exhibit superior capacitance, excellent rate performance, and long-term stability. This method realizes the high-value utilization of inferior heavy oil, solves the problem of large-scale production and utilization of inferior heavy oil, and rationally allocates natural resources.

[0016] The advantages of this invention compared to existing preparation processes are:

[0017] (1) This invention uses heavy oil as raw material, providing a brand-new idea for the large-scale and high-value utilization of heavy oil, promoting the integration of traditional petroleum energy and emerging energy industries, realizing the transformation of its use to "carbon materials", and playing a leading and exemplary role in the transformation and upgrading of refineries and the optimization of product structure.

[0018] (2) By using catalysts and crosslinking agents to initiate the generation of free radicals in aromatic molecules in heavy oil, a crosslinking condensation reaction is induced, achieving crosslinking-condensation at low temperatures. This improves the molecular weight and aromaticity while ensuring the utilization rate of the feedstock molecules. Based on the above process, shallow crosslinking condensation products are used as raw materials. After oxidative crosslinking treatment, the softening point and carbon residue of isotropic asphalt are further improved while inhibiting the formation of quinoline insolubles. By gradually increasing the process operating parameters, the production of isotropic asphalt with high carbon residue at different softening points can be flexibly controlled.

[0019] (3) The carbonization-acid-base etching process is used to treat isotropic asphalt. Compared with direct acid-base etching, it can promote the development of the initial microcrystalline structure in the raw asphalt and appropriately reduce the content of oxygen functional groups, thereby obtaining carbon materials with high porosity and excellent internal crystal structure. The hard carbon materials constructed by it have high battery capacity, excellent rate performance and long cycle stability. Detailed Implementation

[0020] The following describes, in conjunction with embodiments, the method for preparing homogeneous bitumen and sodium-storage hard carbon anode materials from heavy oil provided by the present invention.

[0021] Example 1

[0022] Using medium- and low-temperature coal tar as raw material, 10g of HNO3 and 10g of paraformaldehyde were added to 200g of medium- and low-temperature coal tar. Shallow cross-linking and polycondensation were carried out under nitrogen atmosphere at a reaction temperature of 120℃ for 4 hours. The shallow cross-linking and polycondensation product was then subjected to oxygen-induced free radical reaction at a reaction temperature of 310℃, an air flow rate of 7ml / (g·min), a reaction pressure of atmospheric pressure, and a reaction time of 10 hours to obtain isotropic asphalt. The isotropicity of the prepared isotropic asphalt was... The yield was 98.3%, the softening point was 249℃, the residual carbon value was 71.7%, and the overall yield was 40.4%. The prepared isotropic pitch was carbonized in N2 atmosphere at a heating rate of 5℃ / min to 800℃ for 1h to form a carbonized product with a preliminary mature carbon skeleton. Then, the carbonized product was mixed with K2CO3 at a mass ratio of 1:5 and activated in N2 atmosphere at a heating rate of 5℃ / min to 800℃ for 0.5h. After natural cooling to room temperature, the sodium storage hard carbon anode material was obtained.

[0023] The sodium-storage hard carbon anode material was tested for electrochemical performance in a CR2032 sodium-ion coin cell system using metallic sodium sheet as the positive electrode and 1M NaClO4 (volume ratio EC / DEC = 1:1) as the electrolyte. The sodium-storage hard carbon anode material prepared in Example 1 exhibited a specific capacity of 280.2 mAh / g at 0.3C and 268.3 mAh / g at 1C, with a capacity retention of 93.5% after 200 cycles at 0.3C.

[0024] Example 2

[0025] Using FCC slurry as raw material, 10g of HNO3 and 10g of glutaraldehyde were added to 200g of FCC slurry. Shallow crosslinking-condensation was carried out at a reaction temperature of 100℃ under a nitrogen atmosphere for 5 hours. The shallow crosslinking-condensation product underwent oxygen-induced free radical reaction at a reaction temperature of 310℃, an air flow rate of 6ml / (g·min), a reaction pressure of atmospheric pressure, and a reaction time of 6 hours to obtain isotropic asphalt. The isotropic degree of the prepared isotropic asphalt was 9. The isotropic pitch was carbonized in a N2 atmosphere at a heating rate of 5℃ / min to 700℃ for 1 hour to form a carbonized product with a preliminary mature carbon skeleton. Then, the carbonized product was mixed with NaHCO3 at a mass ratio of 1:4 and activated in a N2 atmosphere at a heating rate of 5℃ / min to 800℃ for 1 hour. After natural cooling to room temperature, the sodium storage hard carbon anode material was obtained.

[0026] According to the electrochemical performance testing method of Example 1, the sodium storage hard carbon anode material prepared in Example 2 has a specific capacity of 273.6 mAh / g at a current density of 0.3C, a specific capacity of 253.8 mAh / g at a current density of 1C, and a capacity retention rate of 92.6% after 200 cycles at a current density of 0.3C.

[0027] Example 3

[0028] Using ethylene tar as raw material, 10g of TsOH and 10g of glutaraldehyde were added to 200g of ethylene tar. The mixture underwent shallow cross-linking-condensation under a nitrogen atmosphere at a reaction temperature of 90℃ for 5h. The shallow cross-linking-condensation product was then subjected to oxygen-induced free radical reaction at a reaction temperature of 290℃, an air flow rate of 6ml / (g·min), a reaction pressure of atmospheric pressure, and a reaction time of 4h to obtain isotropic asphalt. The isotropic degree of the prepared isotropic asphalt was 98%. The isotropic pitch was prepared with a yield of 6%, a softening point of 182℃, a carbon residue of 54.3%, and a comprehensive yield of 50.8%. The prepared isotropic pitch was carbonized in a N2 atmosphere at a heating rate of 5℃ / min to 700℃ for 1 hour to form a carbonized product with a preliminary mature carbon skeleton. The carbonized product was then mixed with Na2CO3 at a mass ratio of 1:3 and activated in a N2 atmosphere at a heating rate of 5℃ / min to 800℃ for 1 hour. After natural cooling to room temperature, the sodium storage hard carbon anode material was obtained.

[0029] According to the electrochemical performance testing method of Example 1, the sodium storage hard carbon anode material prepared in Example 3 has a specific capacity of 250.8 mAh / g at a current density of 0.3C, a specific capacity of 231.9 mAh / g at a current density of 1C, and a capacity retention rate of 91.3% after 200 cycles at a current density of 0.3C.

[0030] Example 4

[0031] Using ethylene tar as raw material, 2g of TsOH and 2g of propionaldehyde were added to 200g of ethylene tar. The mixture underwent shallow crosslinking-condensation at 80℃ under a nitrogen atmosphere for 3 hours. The shallow crosslinking-condensation product was then subjected to oxygen-induced free radical reaction at 270℃, an air flow rate of 4ml / (g·min), a normal pressure, and a reaction time of 4 hours to obtain isotropic asphalt. The isotropic degree of the prepared isotropic asphalt was 98.6%. The softening point was 154℃, the residual carbon value was 48.3%, and the overall yield was 55.8%. The prepared isotropic pitch was carbonized in N2 atmosphere at a heating rate of 5℃ / min to 600℃ for 1h to form a carbonized product with a preliminary mature carbon skeleton. Then, the carbonized product was mixed with Na2CO3 at a mass ratio of 1:2 and activated in N2 atmosphere at a heating rate of 5℃ / min to 800℃ for 2h. After natural cooling to room temperature, the sodium storage hard carbon anode material was obtained.

[0032] According to the electrochemical performance testing method of Example 1, the sodium storage hard carbon anode material prepared in Example 4 has a specific capacity of 220.9 mAh / g at a current density of 0.3C, a specific capacity of 203.1 mAh / g at a current density of 1C, and a capacity retention rate of 88.3% after 200 cycles at a current density of 0.3C.

Claims

1. A method for preparing sodium-storage hard carbon anode material from heavy oil, characterized in that, The specific steps include the following: (1) Add 1wt%-5wt% of acidic catalyst and 1wt%-5wt% of aldehyde crosslinking agent to the raw material and mix them evenly. Under the conditions of inert gas protection, reaction temperature of 80-120℃ and reaction time of 3-5h, initiate crosslinking-condensation reaction to obtain shallow crosslinking condensation product. (2) The shallow cross-linked polycondensation product undergoes oxygen-induced dehydrogenation and cross-linked polycondensation reaction under the conditions of reaction temperature 270-310℃, air flow rate 4-7ml / (g·min) and reaction time 4-10h to obtain isotropic asphalt with an isotropic degree >98%, residual carbon value ≥45%, and quinoline insoluble content <0.5%; (3) Carbonize isotropic asphalt at 600-800℃ for 0.5-2 h under an inert atmosphere with a heating rate of 5℃ / min to form a carbonized product with a preliminary mature carbon skeleton. Then add an etchant and mix it with the carbonized product. Continue to activate it for 0.5-2 h under an inert atmosphere with a heating rate of 5℃ / min and a temperature of 800℃. After cooling to room temperature, obtain sodium storage hard carbon anode material. The raw material in step (1) is heavy oil, including one or more of FCC slurry oil, vacuum distillate oil, ethylene tar, and medium-low temperature coal tar; the average molecular weight of the heavy oil is 200-500, the number of cycloalkanes is 2-5, the number of aromatic rings is 2-6, and the aromatic carbon content is >40%; the acid catalyst includes one or more of H2SO4, HNO3, and TsOH, and the aldehyde crosslinking agent includes one or more of glutaraldehyde, paraformaldehyde, and propionaldehyde.

2. The method for preparing sodium-storage hard carbon anode material from heavy oil according to claim 1, characterized in that: In step (2), the reaction temperature is controlled at 270℃ and the reaction time is 4h to produce isotropic asphalt products with a softening point of 150±5℃, a yield of ≥55%, and a carbon residue of ≥48%; the reaction temperature is controlled at 290℃ and the reaction time is 4h to produce isotropic asphalt products with a softening point of 180±5℃, a yield of ≥50%, and a carbon residue of ≥54%; the reaction temperature is controlled at 310℃ and the reaction time is 6h to produce isotropic asphalt products with a softening point of 200±5℃, a yield of ≥44%, and a carbon residue of ≥58%; and the oxidation temperature is controlled at 310℃ and the oxidation time is 10h to produce isotropic asphalt products with a softening point of 250±5℃, a yield of ≥40%, and a carbon residue of ≥70%.

3. The method for preparing sodium-storage hard carbon anode material from heavy oil according to claim 1, characterized in that: In step (3), the etchant is an acid-base etchant selected from one or more of KOH, K2CO3, Na2CO3, ZnCl2, and FeCl3, and the amount of etchant added is 200wt%-500wt% of the carbonized product.

4. The method for preparing sodium-storage hard carbon anode material from heavy oil according to claim 3, characterized in that: In step (3), the amount of etchant added is 400wt%-500wt% of the carbonized product at a temperature of 700-800℃, and the amount of etchant added is 200wt%-400wt% of the carbonized product at a temperature of 600-700℃.

5. A sodium-storage hard carbon anode material prepared by the method according to any one of claims 1-4, characterized in that: The sodium-storage hard carbon anode material has a specific capacity of 220-280 mAh / g at a current density of 0.3C, a specific capacity of 203-268 mAh / g at a current density of 1C, and a capacity retention rate of 88%-93% after 200 cycles at a current density of 0.3C.

6. The application of the sodium-storing hard carbon anode material according to claim 5 in high-performance materials, characterized in that: The high-performance materials include high softening point coated pitch, pitch-based carbon fiber, and sodium-ion batteries.