Preparation method and application of petroleum asphalt-based porous carbon material

Abstract

The invention provides a preparation method and application of a petroleum asphalt-based porous carbon material, and belongs to the technical field of porous carbon materials. The preparation method comprises the following steps: by taking petroleum asphalt as a carbon precursor, stirring and pre-oxidizing the petroleum asphalt and molten salt at a certain temperature, then pre-carbonizing, washing away the molten salt, and carbonizing with KOH to prepare the petroleum asphalt-based porous carbon material. The petroleum asphalt with low carbon yield (11%) is converted into the petroleum asphalt-based porous carbon material with obviously improved carbon yield (up to 30%) through an efficient and convenient method. When the petroleum asphalt-based porous carbon material prepared by the method provided by the invention is used as an electrode material of a lithium ion battery / zinc ion capacitor, the petroleum asphalt-based porous carbon material shows excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of porous carbon materials, and in particular to a preparation method and application of a petroleum asphalt-based porous carbon material. Background Art

[0002] Asphalt is a complex, dark brown mixture composed of hydrocarbons of varying molecular weights and their non-metallic derivatives. It is primarily categorized into three types: coal tar pitch, petroleum tar pitch, and natural asphalt. Petroleum tar pitch, a product of crude oil processing, is a black or dark brown, viscous liquid, semi-solid, or solid at room temperature. It is primarily used in road, building, and water conservancy projects, but its utilization value is relatively low. To further enhance the high-value-added utilization of petroleum tar pitch, converting this inexpensive material into porous carbon materials for electrodes with high conductivity, large surface area, and adjustable porosity is an effective approach.

[0003] Among the various methods for preparing porous carbon materials, the molten salt method can avoid the use of environmentally polluting acids and alkalis in the process of removing the template. It can be removed by washing with water. It is a simple and green method for synthesizing porous carbon materials. It is simple to operate and efficient. It has been widely used in the preparation of electrode materials in the field of energy storage. Han et al. (Materials Chemistry and Physics, 2021, 265, 124491) mixed coal tar and molten salt (NaCl and ZnCl2) evenly and pre-oxidized them. Then, they mixed them with KOH and pyrolyzed them to prepare coal tar-based porous carbon materials. The combined action of molten salt and activator gives the carbon material a highly developed, interconnected pore structure, which helps to provide abundant active sites, promote the rapid transfer of charges, and make the porous carbon material exhibit 320 F g -1 Wang et al. (Chemical Engineering Journal, 2023, 455, 140540) mixed coal tar pitch with molten salt (NaCl and KCl) in DMF solvent, dried it, and pyrolyzed it to prepare porous carbon nanosheets. When the porous carbon nanosheets were used as the negative electrode material for sodium ion batteries, they showed a high specific capacitance at 0.1A g -1 The current density is 313.6 mAh g -1 However, how to prepare petroleum pitch-based porous carbon materials with excellent performance for lithium-ion batteries / zinc-ion capacitors through the molten salt method remains to be further explored. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing a petroleum asphalt-based porous carbon material with excellent lithium / zinc storage performance and its application by a molten salt method. The method for preparing the petroleum asphalt-based porous carbon material provided by the present invention is simple to operate and efficient. Petroleum asphalt is used as a carbon precursor, which is stirred with a molten salt at a certain temperature for pre-oxidation treatment, followed by pre-carbonization. After washing away the molten salt, the petroleum asphalt-based porous carbon material is carbonized with KOH to obtain the petroleum asphalt-based porous carbon material. The petroleum asphalt-based porous carbon material prepared by this method exhibits high initial efficiency and capacity when used as an electrode material for lithium-ion batteries / zinc-ion capacitors.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing a petroleum pitch-based porous carbon material, comprising the following steps: (1) Pre-oxidation treatment of petroleum asphalt and molten salt is carried out by stirring at 130-250 °C to obtain a pre-oxidation product; (2) subjecting the pre-oxidation product obtained in step (1) to a pre-carbonization treatment at a temperature between 350°C and 500°C to obtain a pre-carbonized product; (3) After washing away the molten salt from the pre-carbonized product, the product is mixed with an activator and carbonized to obtain a petroleum asphalt-based porous carbon material.

[0006] Preferably, the petroleum asphalt in step (1) contains 7-10% asphaltenes, 30-45% colloids, 28-31% aromatics, and 15-30% saturates.

[0007] Preferably, the mass ratio of petroleum asphalt to molten salt in step (1) is 1:1-1:10, and the pre-oxidation treatment time is 5-16 h.

[0008] Preferably, the type of the molten salt in step (1) is any one of NaCl−KCl, KCl−ZnCl2, KCl−CaCl2, Na2CO3−K2CO3, CaCl2−NaCl, LiNO3−KNO3 and ZnCl2−NaCl, and the mass ratio of the two salts is 1:1~1:3.

[0009] Preferably, the heating rate of the temperature in step (2) to the pre-carbonization temperature is 2-10°C / min, and the pre-carbonization time is 1-3 h.

[0010] Preferably, the activating agent in step (3) includes at least one of KOH, K2CO3, KHCO3, K3C6H5O7, KC2H3O2, K2C2O4, NaOH, Na2CO3 and ZnCl2.

[0011] Preferably, the mass ratio of petroleum asphalt to activator in step (3) is 1:1 to 1:6.

[0012] Preferably, the carbonization atmosphere in step (3) is an inert atmosphere, including at least one of nitrogen, helium, argon, neon and xenon, the carbonization temperature is 650~1000℃, the heating rate is 2~10℃ / min, and the carbonization time is 1~5h.

[0013] The present invention also provides a petroleum pitch-based porous carbon material prepared by the preparation method described in the above technical solution and its application in lithium ion battery / zinc ion capacitor electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the thermogravimetric curve of the petroleum asphalt used in Example 1 of the present invention; Figure 2 This is a SEM image of the petroleum pitch-based porous carbon material prepared in Example 1 of the present invention; Figure 3 This is the N2 adsorption-desorption curve of the petroleum pitch-based porous carbon material prepared in Example 1 of the present invention; Figure 4 This is the pore size distribution curve of the petroleum pitch-based porous carbon material prepared in Example 1 of the present invention; Figure 5 The charge and discharge curve of the lithium-ion battery prepared in Application Example 1 of the present invention at 0.1 C; Figure 6 This is a cycling performance diagram of the lithium-ion battery prepared in Application Example 1 of the present invention at 5 C; Figure 7 This is a rate performance diagram of the zinc ion capacitor prepared in Application Example 2 of the present invention; DETAILED DESCRIPTION

[0015] The present invention provides a method for preparing a petroleum pitch-based porous carbon material, comprising the following steps: (1) Pre-oxidation treatment of petroleum asphalt and molten salt at 150-250 °C is performed by stirring to obtain a pre-oxidation product; (2) subjecting the pre-oxidation product obtained in step (1) to a pre-carbonization treatment at a temperature between 350°C and 500°C to obtain a pre-carbonized product; (3) After washing away the molten salt from the pre-carbonized product, the product is mixed with an activator and carbonized to obtain a petroleum asphalt-based porous carbon material.

[0016] In the present invention, the pre-oxidation treatment is preferably performed by heating and stirring or heating and stirring with air, more preferably heating and stirring with air. In the present invention, the pre-oxidation treatment of heating and stirring with air can accelerate the pre-oxidation process of the asphalt, resulting in more complete and uniform oxidation.

[0017] In the present invention, the mass ratio of the petroleum asphalt to the molten salt is preferably 1:1 to 1:10, more preferably 1:1 to 1:4.

[0018] In the present invention, the pre-oxidation treatment time is preferably 5 to 16 hours, more preferably 9 to 12 hours. In the present invention, when the pre-oxidation time is in the range of 9 to 12 hours, it is more conducive to the pre-oxidation of petroleum asphalt and is conducive to improving the carbon yield of petroleum asphalt.

[0019] In the present invention, when the petroleum asphalt and the molten salt are subjected to heating and stirring for pre-oxidation treatment, the selected heating equipment is not particularly limited, and any heating equipment that is well known to those skilled in the art and can meet the heating conditions can be selected.

[0020] In the present invention, the method for removing molten salts is preferably to heat the sample in a 90°C water bath for 3 hours, then filter and wash the sample several times with 90°C deionized water until the solution is neutral. Alternatively, the sample can be directly filtered and washed several times with deionized water until the solution is neutral. To save time, the first method is preferred for removing molten salts.

[0021] In the present invention, the pre-carbonization temperature is preferably 350-500°C, more preferably 400-450°C; the pre-carbonization time is preferably 1-3 hours, more preferably 2-3 hours; and the heating rate to the pre-carbonization temperature is preferably 2-10°C / min, more preferably 3-6°C / min. In the present invention, when the pre-carbonization temperature, time, and heating rate are within the above ranges, the pre-carbonized product is more conducive to subsequent activation.

[0022] In the present invention, the activating agent is preferably at least one of KOH, K2CO3, KHCO3, K3C6H5O7, KC2H3O2, K2C2O4, NaOH, Na2CO3, and ZnCl2, and more preferably at least one of KOH and NaOH. In the present invention, when the activating agent is at least one of KOH and NaOH, it is more conducive to improving the activation efficiency and preparing a carbon material with a rich pore structure.

[0023] In the present invention, the mass ratio of the petroleum pitch to the activator is preferably 1:1 to 1:6, more preferably 1:2 to 1:4. In the present invention, when the mass ratio of the petroleum pitch to the activator is within the above range, it is more conducive to preparing an ideal carbon material.

[0024] In the present invention, the carbonization temperature is preferably 650-1000°C, more preferably 700-900°C; the carbonization time is preferably 1-5 hours, more preferably 2-3 hours; and the heating rate to the carbonization temperature is preferably 2-10°C / min, more preferably 5-8°C / min. In the present invention, when the carbonization temperature, time, and heating rate are within the above ranges, a petroleum pitch-based porous carbon material with excellent electrochemical properties can be obtained.

[0025] In the present invention, the prepared petroleum pitch-based porous carbon material is subjected to impurity removal. This impurity removal involves soaking the carbonized product in a dilute HCl solution for 3-10 hours, followed by filtration, washing several times with deionized water, and drying. The concentration of the dilute HCl solution is not particularly limited; concentrations commonly used by those skilled in the art can be used. The drying method described in the present invention can be any of vacuum drying, oven drying, and freeze drying.

[0026] The present invention also provides the use of the petroleum pitch-based porous carbon material described in the above technical solution in lithium ion battery / zinc ion capacitor electrode materials.

[0027] The present invention does not specifically limit the application method of the petroleum pitch-based porous carbon material in the lithium ion battery / zinc ion capacitor electrode material. Carbon materials well known to those skilled in the art can be used as the application method in the above two systems.

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0029] 30 g of petroleum pitch was added to a three-necked flask placed in an oil bath. The temperature was adjusted to 230°C. After the petroleum pitch softened, 30 g of NaCl-KCl (mass ratio of NaCl to KCl: 1:1) was added and stirred for 11 hours under air. The hot product was poured into a corundum boat, cooled, and then pre-carbonized in a tube furnace. Pre-carbonization conditions were heating to 450°C at 5°C / min under high-purity argon and holding for 2 hours. After removing the molten salt by washing with deionized water (using 90°C hot water every 3 hours), the pre-carbonized product was dried in an 80°C oven. 5 g of the dried sample and 20 g of KOH were stirred in a stirrer 10 times, each time for 5 seconds, to obtain a uniformly dispersed mixture. The mixture was then heated to 800°C at 5°C / min under high-purity argon and held for 2 hours. After cooling naturally to room temperature, the carbonized sample was collected and immersed in a hot 1 M HCl solution for 6 hours to remove impurities. It was then washed several times with deionized water and dried at 60°C for 12 hours to obtain a petroleum pitch-based porous carbon material. The carbon yield from the petroleum pitch was calculated to be 30%.

[0030] Thermogravimetric analysis was used to observe the pyrolysis behavior of petroleum asphalt. Figure 1 As shown in Figure 2, it can be seen that the carbon yield of petroleum asphalt is only 11%.

[0031] The morphology of petroleum asphalt-based porous carbon materials was characterized by SEM. Figure 2 As shown. Figure 2 It can be seen that the carbon material has a rich pore structure.

[0032] The petroleum asphalt-based porous carbon material was tested using a nitrogen adsorption specific surface area tester, and the isothermal adsorption-desorption curves were obtained as follows: Figure 3 As shown. Figure 3 It can be seen that the specific surface area of ​​petroleum asphalt-based porous carbon material is 1991.1 m 2 / g, and a pore volume of 0.72 cm 3 / g. The pore size distribution curve of petroleum pitch-based porous carbon materials is as follows Figure 4 As shown, it can be seen that its micropores and mesopores are mainly distributed in the sizes of 0.7 and 2.6 nm, respectively.

[0033] 40 mg of the petroleum pitch-based porous carbon material and 5 mg of the conductive carbon black prepared in Example 1 were taken and ground thoroughly, and mixed with sodium carboxymethyl cellulose in a mass ratio of 8:1:1, ground to a uniform slurry, and then the slurry was evenly scraped onto the current collector copper foil. After drying, it was cut into (12×12) mm 2The electrode was dried at 120°C under vacuum for 10 hours and then transferred to a glove box for later use. The battery was assembled in an Ar atmosphere glove box, using a metallic lithium sheet as the counter electrode, a celgard membrane as the separator, and 1M LiPF6 + EC / DEC (V:V = 1:1) as the electrolyte, forming a lithium-ion half-cell.

[0034] The battery prepared in Example 1 was subjected to a charge and discharge performance test under the following conditions: the charge and discharge mode was rate charge; the current density was 0.1C; the discharge cut-off voltage was 0.001 V, and the charge cut-off voltage was 3 V. The rate charge and discharge curve of the battery prepared in Example 1 is shown in FIG. Figure 5 As shown. Figure 5 It can be seen that the reversible specific capacity of the battery prepared in Application Example 1 is 356.5 mAh g -1 , the first coulombic efficiency is 75.5%.

[0035] The cycle performance test of the battery prepared in Example 1 was conducted under the following conditions: the charging mode was rate charging, the current density was 5 C, the discharge cut-off voltage was 0.001 V, and the charge cut-off voltage was 3 V. The cycle curve of the battery prepared in Example 1 is shown in FIG. Figure 6 As shown. Figure 6 It can be seen that the capacity of the battery prepared in Application Example 1 is 133.3 mAh g after 1500 cycles. -1 The capacity retention rate is 85.6%, indicating that the material has good cycle stability.

[0036] The petroleum pitch-based porous carbon material prepared in Example 1 was mixed with acetylene black and PTFE in a mass ratio of 8:1:1 to prepare a positive electrode mixture slurry, which was then dried at 65°C for 30 minutes. The dried slurry was rolled into a circular sheet and further dried at 65°C for 5 hours. Finally, the circular sheet was pressed onto flexible graphite paper and cut into (10×10) mm 2 The pole piece is spare (mass loading of active material is ~1.6 mg cm -2 A zinc ion capacitor was assembled using coal tar pitch-based porous carbon as the positive electrode, Zn foil as the negative electrode, Whatman GF / D (glass fiber) as the separator, and 1 M Zn(CF3SO3)2 aqueous solution as the electrolyte, and then assembled into a CR2032 button cell.

[0037] The zinc ion capacitor prepared in Example 2 was subjected to rate performance test. The test conditions were as follows: the charging mode was rate charging, and the charging speeds were 0.2, 0.5, 1, 2, 5, 10 and 20 A g -1 The current density was cycled for 10 cycles and then returned to 0.2 A g -1, the discharge cut-off voltage is 0.2 V, and the charge cut-off voltage is 1.8 V. The results are as follows Figure 3 As shown. Figure 3 It can be seen that the zinc ion capacitor prepared in Example 1 has the following characteristics at 0.2, 0.5, 1, 2, 5, 10 and 20 A g -1 The specific capacities are 145.5, 125.1, 111.7, 99.8, 82.5, 67.6, and 50.1 mAh g -1 , and finally recovered to 0.2 A g -1 The specific capacity is 145.3 mAh g -1 , indicating that it has good rate performance and electrochemical reversibility. Example 2

[0038] 30 g of petroleum pitch was added to a three-necked flask placed in an oil bath. The temperature was adjusted to 230°C. After the petroleum pitch softened, 60 g of KCl-ZnCl2 (with a mass ratio of NaCl to KCl of 1:1) was added. The mixture was stirred for 9 hours under air. The hot product was poured into a corundum boat, cooled, and then pre-carbonized in a tube furnace. Pre-carbonization conditions were heating to 500°C at 5°C / min under high-purity argon and holding for 2 hours. After removing the molten salt by washing with deionized water (using 90°C hot water every 3 hours), the pre-carbonized product was dried in an 80°C oven. 5 g of the dried sample and 20 g of KOH were stirred in a stirrer 10 times, each for 5 seconds, to obtain a uniformly dispersed mixture. The mixture was then heated to 800°C at 5°C / min under high-purity argon and held for 2 hours. After naturally cooling to room temperature, the carbonized samples were collected and immersed in a 1 M HCl hot solution for 6 h to remove impurities. They were then washed with deionized water several times and dried at 60 °C for 12 h to obtain petroleum pitch-based porous carbon materials. Example 3

[0039] 30 g of petroleum pitch was added to a three-necked flask placed in an oil bath. The temperature was adjusted to 230°C. After the petroleum pitch softened, 30 g of NaCl-KCl (mass ratio of NaCl to KCl: 1:1) was added and stirred for 10 hours under air. The hot product was poured into a corundum boat, cooled, and then pre-carbonized in a tube furnace. Pre-carbonization conditions were heating to 400°C at 5°C / min under high-purity argon and holding for 3 hours. After removing the molten salt by washing with deionized water (using 90°C hot water every 3 hours), the pre-carbonized product was dried in an 80°C oven. The dried sample (5 g) and 20 g of KHCO₃ were stirred in a stirrer 10 times, each for 5 seconds, to obtain a uniformly dispersed mixture. The mixture was then heated to 800°C at 5°C / min under high-purity argon and held for 2 hours. After naturally cooling to room temperature, the carbonized samples were collected and immersed in a 1 M HCl hot solution for 6 h to remove impurities. They were then washed with deionized water several times and dried at 60 °C for 12 h to obtain petroleum pitch-based porous carbon materials.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a petroleum pitch-based porous carbon material, comprising the following steps: (1) Pre-oxidation treatment of petroleum asphalt and molten salt is carried out by stirring at 130-250 °C to obtain a pre-oxidation product; (2) subjecting the pre-oxidation product obtained in step (1) to a pre-carbonization treatment at a temperature between 350°C and 500°C to obtain a pre-carbonized product; (3) After washing away the molten salt from the pre-carbonized product, the product is mixed with an activator and carbonized to obtain a petroleum asphalt-based porous carbon material.

2. The preparation method according to claim 1, characterized in that The petroleum asphalt in step (1) contains 7-10% asphaltenes, 30-45% colloids, 28-31% aromatics, and 15-30% saturates.

3. The preparation method according to claim 1, wherein The mass ratio of petroleum asphalt to molten salt in step (1) is 1:1-1:10, and the pre-oxidation treatment time is 5-16 h.

4. The preparation method according to claim 1, characterized in that The type of the molten salt in step (1) is any one of NaCl-KCl, KCl-ZnCl2, KCl-CaCl2, Na2CO3-K2CO3, CaCl2-NaCl, LiNO3-KNO3 and ZnCl2-NaCl, and the mass ratio of the two salts is 1:1~1:

3.

5. The preparation method according to claim 1, wherein The heating rate of the step (2) to the pre-carbonization temperature is 2-10°C / min, and the pre-carbonization time is 1-3 h.

6. The preparation method according to claim 1, characterized in that The activator in step (3) includes at least one of KOH, K2CO3, KHCO3, K3C6H5O7, KC2H3O2, K2C2O4, NaOH, Na2CO3 and ZnCl2.

7. The preparation method according to claim 1, characterized in that The mass ratio of petroleum asphalt to activator in step (3) is 1:1 to 1:

6.

8. The preparation method according to claim 1, wherein The carbonization atmosphere in step (3) is an inert atmosphere, including at least one of nitrogen, helium, argon, neon and xenon. The carbonization temperature is 650-1000°C, the heating rate is 2-10°C / min, and the carbonization time is 1-5 h.

9. A petroleum pitch-based porous carbon material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the petroleum pitch-based porous carbon material according to claim 9 in negative electrode materials for lithium-ion batteries and positive electrode materials for zinc-ion hybrid capacitors.

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