Porous carbon materials and their preparation methods and uses

Abstract

The present invention provides a porous carbon material and a preparation method and use thereof. The preparation method includes the steps of obtaining a fraction of ethylene tar at 250°C to 550°C, hydrotreating the fraction to obtain hydropurified ethylene tar, pre-carbonizing a part of the hydropurified ethylene tar to obtain coke, and mixing the remainder of the hydropurified ethylene tar with the coke to form a mixture, activating the mixture, and obtaining a porous carbon material. The preparation method can realize the preparation of high-purity porous carbon, and the preparation process is simple and low cost.

Description

[Technical Field]

[0001] This application relates to the field of carbon materials technology, and in particular to porous carbon materials and their preparation methods and uses. [Background technology]

[0002] Electric double layer capacitors (EDLCs) are a new type of energy storage device with high power density and excellent cycle stability, and porous carbon is widely used as an electrode material for EDLCs.

[0003] Electric double-layer capacitors achieve extremely high capacitance by using an electric double-layer structure consisting of a porous carbon electrode and an electrolyte. The electrodes in electric double-layer capacitors are made of porous carbon materials. Supercapacitors store electrical energy by adsorbing ions in an electrolyte solution onto the porous carbon, and release electrical energy by desorbing ions from the porous carbon back into the electrolyte solution. Adsorption and desorption are purely physical processes, and theoretically, they have an almost infinite charge / discharge life. However, porous carbon materials often lack high purity and contain large amounts of impurities, including non-metallic elements such as sulfur, nitrogen, and oxygen, and metallic elements such as iron, nickel, and magnesium. These impurities chemically react with the solvent and solutes in the electrolyte solution, resulting in poor device stability and reduced capacity and service life.

[0004] The raw materials, additives, and preparation process conditions for porous carbon preparation significantly affect the purity of the resulting porous carbon. The raw materials used to prepare porous carbon are mainly biomass, coal, and petroleum-processed derivatives. Biomass and coal contain large amounts of impurities, such as ash and heavy metals, that are difficult to remove. Among petroleum-processed derivatives, ethylene tar has the advantage of low ash content and low metallic and non-metallic impurities. However, ethylene tar contains a large amount of unsaturated olefins, has poor thermal stability, and is easily oxidized during the preparation of porous carbon, resulting in the introduction of new impurities. In conventional techniques, ethylene tar is typically used to prepare porous carbon after removing light components. For example, Patent Document CN106672966A discloses a method for preparing porous carbon using ethylene tar, which involves pretreating ethylene tar, removing the light components in n-heptane reflux, pre-oxidizing the precursor to a porous carbon material, and finally carbonizing and acid-washing the precursor to obtain a porous carbon material using a template method. However, the invention described in this patent, which utilizes a template method, is expensive to prepare.

[0005] Therefore, how to prepare high-purity porous carbon materials while reducing costs has become a hot topic of research among those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned drawbacks, the present application provides a method for preparing a porous carbon material, which can realize the preparation of highly pure porous carbon and has the advantages of a simple preparation process and low cost.

[0007] The present application further provides a porous carbon material, which is produced using the above-mentioned preparation method and has advantages such as high purity and excellent stability.

[0008] The present application further provides an electric double layer capacitor, which employs the porous carbon material as an electrode and has advantages such as high energy efficiency and excellent cycle stability. [Means for solving the problem]

[0009] In a first aspect, the present application provides a method for preparing a porous carbon material, the method comprising the steps of obtaining a fraction of ethylene tar at 250°C to 550°C, and subjecting the fraction to hydrotreatment to obtain hydropurified ethylene tar; subjecting a portion of the hydropurified ethylene tar to a preliminary carbonization treatment to obtain coke; and mixing the remainder of the hydropurified ethylene tar with the coke to form a mixture, and subjecting the mixture to an activation treatment to obtain a porous carbon material.

[0010] According to one embodiment of the present application, the preliminary carbonization treatment is carried out in an inert atmosphere, and the temperature of the preliminary carbonization treatment is 300°C to 800°C.

[0011] According to one embodiment of the present application, the mass ratio of the coke to the remainder of the hydrorefined ethylene tar is 1:(0.01 to 0.8).

[0012] According to one embodiment of the present application, the mixture is subjected to an activation treatment using an activator, and the activator includes at least one of an alkaline compound, water vapor, and carbon dioxide.

[0013] According to one embodiment of the present application, the activation treatment conditions are a temperature of 600° C. to 900° C. and a time of 0.5 to 3 hours.

[0014] According to one embodiment of the present application, a fraction of ethylene tar in the range of 350°C to 450°C is obtained.

[0015] According to one embodiment of the present application, the step of activating the mixture to obtain the primary porous carbon further includes the step of performing a deoxidation purification treatment on the primary porous carbon to obtain a porous carbon material.

[0016] According to one embodiment of the present application, the deoxidation and purification treatment is carried out in a vacuum reducing atmosphere, and the conditions for the deoxidation and purification treatment are a degree of vacuum of −0.1 MPa to −0.01 MPa, a temperature of 300° C. to 900° C., and a time of 0.5 hours to 3 hours.

[0017] In a second aspect, the present application provides a porous carbon material prepared by the above-described preparation method.

[0018] In a third aspect, the present application provides an electric double layer capacitor, the electrodes of which contain the porous carbon material described above. [Effects of the Invention]

[0019] The implementation of the present application has at least the following beneficial effects:

[0020] The method for preparing a porous carbon material provided by the present application involves obtaining a fraction of ethylene tar at 250°C to 550°C, removing impurities such as light components and ash, and then subjecting the fraction to hydrotreatment, which further removes unsaturated structures such as sulfur and nitrogen, resulting in hydrorefined ethylene tar with an extremely low impurity content and excellent stability, making it less susceptible to oxidative degradation in subsequent treatment processes. The present application uses coke obtained by preliminary carbonization as the main carbon source, and the remainder of the hydrorefined ethylene tar as a modifier. This modifier not only enables the molding of the mixture but also fills the gaps between coke particles, thereby increasing the density of the product. Furthermore, because hydrorefined ethylene tar has a structure similar to that of coke, the two can be uniformly fused during subsequent calcination, improving the stability of the product and preventing the introduction of new impurities. The method for preparing a porous carbon material provided by the present application also has the advantages of a simple preparation method and a high utilization rate of the ethylene tar raw material, making it suitable for mass production and industrial production.

[0021] The porous carbon material provided by the present application is prepared using the above method and has advantages such as high purity and excellent stability, and can be applied in technical fields such as supercapacitors, biomedicine, and catalysis, particularly as an electrode material for electric double layer capacitors, which has the advantages of high energy efficiency and excellent cycle stability. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a flowchart of a method for preparing a porous carbon material in one embodiment of the present application. [Figure 2] 3 shows charge and discharge curves of the double layer capacitor according to Example 1. [Figure 3] 1 is a cycle performance curve of the double layer capacitor in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0023] The specific embodiments listed below are intended to illustrate the principles and features of the present application, and are not intended to limit the scope of the present application. Any other embodiments that can be obtained by a person skilled in the art based on the examples of the present application without any creative work fall within the scope of protection of the present application.

[0024] As shown in FIG. 1 , the present application provides a method for preparing a porous carbon material, which includes the steps of obtaining a fraction of ethylene tar at 250°C to 550°C, and subjecting the fraction to hydrotreating to obtain hydropurified ethylene tar, subjecting a portion of the hydropurified ethylene tar to a preliminary carbonization treatment to obtain coke, and mixing the remainder of the hydropurified ethylene tar with the coke to form a mixture, and subjecting the mixture to an activation treatment to obtain a porous carbon material.

[0025] According to the method provided by the present application, hydrotreated ethylene tar with a low impurity content and a high carbon content can be obtained by fractionating and hydrotreating a fraction. A portion of the hydrotreated ethylene tar is subjected to a preliminary carbonization treatment to obtain a tar, which is used as a carbon source, and the remainder of the hydrotreated ethylene tar is used as a modifier to prepare a porous carbon material. The method according to the present application not only enables the advanced processing and utilization of ethylene tar, but also increases the purity of the porous carbon material. Furthermore, the method according to the present application has the advantages of low cost and simple operation, and is suitable for mass production and industrial production.

[0026] The present invention uses ethylene tar, which is widely available and inexpensive, as a raw material. The ethylene tar of the present invention is a product of high-temperature condensation in a process for preparing ethylene by cracking. Sources of ethylene tar include, but are not limited to, ethylene tar produced by ethylene production units in oil refineries, small-scale experimental cracking units, and medium-scale experimental cracking units.

[0027] In some examples of the present application, the selected ethylene tar may be one or a mixture of multiple types, and the mass content of carbon in the ethylene tar is 90% or more, the mass content of sulfur is less than 0.5%, the mass content of nitrogen is less than 0.5%, and the total mass content of metals (iron, aluminum, nickel, copper, etc.) is less than 500 mg / kg, and preferably the mass content of carbon in the ethylene tar is 92% or more, the mass content of sulfur is less than 0.2%, the mass content of nitrogen is less than 0.2%, and the total mass content of metals (iron, aluminum, nickel, copper, etc.) is less than 100 mg / kg.

[0028] Conventional fractional distillation methods can be used to obtain fractions of ethylene tar, and impurities such as light components and ash can be removed from the ethylene tar by fractional distillation. Fractional distillation includes, but is not limited to, atmospheric distillation and reduced pressure distillation. In the fractional distillation process, fractionation is performed according to temperature, and a fraction is obtained from the ethylene tar at 250°C to 550°C. The fractionation point is preferably 300°C to 500°C, and more preferably 350°C to 450°C.

[0029] In the present invention, an ethylene tar fraction is subjected to a hydrotreating treatment to further remove unsaturated structures such as sulfur and nitrogen therein, thereby obtaining hydropurified ethylene tar having a high carbon content and excellent stability, and preventing oxidative deterioration of the ethylene tar in the subsequent treatment.

[0030] The hydrotreating process includes, but is not limited to, fixed bed hydrotreating and slurry bed hydrotreating, i.e., it may be carried out in a fixed bed reactor or a slurry bed reactor.

[0031] The above hydrotreating can be carried out under the usual hydrotreating conditions in the art, for example, a temperature of 300°C to 450°C, a pressure of 10 MPa to 16 MPa, and a space velocity of 1 h -1 The hydrogen-to-oil ratio can be set to 800:1.

[0032] The preliminary carbonization treatment in the present application can be carried out in an inert atmosphere, and the inert atmosphere can be at least one of nitrogen gas, argon gas, helium gas, and carbon dioxide.

[0033] In some embodiments, the temperature of the pre-carbonization treatment is between 300°C and 800°C, with a temperature of between 400°C and 550°C being preferred.

[0034] The above pre-carbonization treatment can be carried out in conventional calcination equipment, and equipment that can be used includes, but is not limited to, sintering furnaces such as tube furnaces and box furnaces, or coking equipment.

[0035] To facilitate subsequent mixing of the reaction raw materials, a crushing process is usually further included after the preliminary carbonization process, which results in a coke particle size of 0.1 micrometers to 10 millimeters, preferably 1 micrometer to 1000 micrometers, and more preferably 20 micrometers to 200 micrometers.

[0036] The above-mentioned grinding process can be carried out in conventional grinding equipment, including but not limited to at least one of a mechanical grinder and an airflow grinder, and is preferably carried out in a mechanical grinder having a metal contamination prevention coating, the metal contamination prevention coating comprising ceramic or tungsten carbide.

[0037] The process of mixing the remainder of the hydrotreated ethylene tar with the coke to form a mixture in the present application can be carried out in an inert atmosphere. In some embodiments, the mass ratio of the coke to the remainder of the hydrotreated ethylene tar is 1:(0.01-0.8), preferably 1:(0.05-0.2).

[0038] The above mixing process includes, but is not limited to, manual mixing, mechanical mixing, etc. Preferably, an inert gas is purged into the sealed mixing vessel, or the operation is carried out in an inert atmosphere glove box.

[0039] In the process of forming the mixture, the remaining hydrorefined ethylene tar can be used as a modifier. This allows it to act as an adhesive to form coke, solving the problem of ordinary adhesives being structurally unstable and introducing new impurities. It can also act as a filler to fill the gaps between coke particles and increase the density of the product. Meanwhile, the remainder of the hydrorefined ethylene tar is a precursor to coke, and the two are highly compatible, allowing them to fuse uniformly in the subsequent calcination process. This solves the problem of uneven mixing that exists when preparing porous carbon materials using conventional methods, avoids the introduction of new impurities, and is advantageous for forming products with high purity, uniform structure, and stability.

[0040] The activation treatment can be a conventional physical activation method, a chemical activation method, or a combination of the two methods. In some embodiments, the mixture is generally activated using an activator, which accordingly includes at least one of an alkaline compound, steam, and carbon dioxide. In a specific embodiment of the present invention, an alkaline substance such as potassium hydroxide can be used as the activator. Mixing the hydrotreated ethylene tar residue, coke, and an alkaline substance to form a mixture and then performing chemical activation is advantageous for increasing the specific surface area of ​​the porous carbon material. Physical activation can also be performed using steam or carbon dioxide as an activator. This physical activation can be achieved simply by controlling the atmosphere in the furnace without adding an alkaline substance during mixing. For example, the hydrotreated ethylene tar residue and coke can be mixed to form a mixture, and the mixture can be activated in an atmosphere containing steam or carbon dioxide. Because the porous carbon material prepared using the physical activation method has a relatively small specific surface area, combining physical activation and chemical activation is preferred.

[0041] In a specific embodiment of the present invention, the remainder of the hydrotreated ethylene tar, coke, and an alkaline compound are mixed to form a mixture. The alkaline compound includes at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, zinc chloride, calcium hydroxide, and sodium bicarbonate. The mass ratio of the coke to the alkaline compound is 1:(0-6), preferably 1:(1-3). The alkaline compound may be a solid powder, and for example, the particle size may be 0.1 micrometers to 5 millimeters, preferably 20 micrometers to 500 micrometers.

[0042] In the specific implementation process described above, an alkaline compound is selected as the activator for the activation treatment. Hydropurified ethylene tar also acts as a coating agent, uniformly coating the surface of the activator, preventing the activator from coming into contact with water or carbon dioxide in the air during material transfer, which can cause inactivation. It also prevents alkali metal atoms from dissipating during the temperature rise of the activation treatment, which is beneficial for improving activation efficiency and increasing the specific surface area of ​​the porous carbon. Furthermore, the hydropurified ethylene tar's function as a coating agent can prevent oxygen from the air from entering the mixture, which could lead to a high oxygen content.

[0043] The porous carbon precursor according to the present application is in the form of a pillar or a block. To obtain a well-formed product, a molding process is usually further included before the activation process. The molding process can be carried out using conventional equipment, such as an extruder or a tablet press. When a certain pressure is applied using an extruder or a tablet press, the mixture is molded into a pillar or a block.

[0044] In the present application, the activation treatment temperature is 600° C. or higher, and the activation treatment conditions are preferably a temperature of 600° C. to 900° C., a pressure of 0.01 MPa to 0.3 MPa, and a time of 0.5 to 3 hours.

[0045] The activation treatment can be carried out in an inert atmosphere, and the activation atmosphere contains at least one of nitrogen gas, argon gas, helium gas, carbon dioxide, and water vapor.

[0046] The activation treatment can be carried out in a conventional firing apparatus, including, but not limited to, an atmospheric furnace filled with the above atmosphere and capable of reaching a temperature of 600°C or higher.

[0047] The pressure for the activation treatment is preferably between 0.1 MPa and 0.3 MPa, and can be carried out, for example, at normal pressure.

[0048] In the specific process of the present application, the activated product is usually washed, filtered, dried, and pulverized after the activation treatment to remove excess activator and other impurities. Preferably, it is first washed with an acid solution, and then washed with pure water until it becomes neutral. The purpose of drying is to remove excess moisture, and the drying temperature is preferably 100°C to 200°C. The pulverization process can be carried out using a mechanical pulverizer, and the particle size after pulverization is preferably 2 μm to 50 μm.

[0049] As shown in Figure 1, in the present application, the mixture is subjected to an activation treatment to further remove oxygen elements and volatile components therein. The step of obtaining primary porous carbon further includes a step of performing a deoxidation purification treatment on the primary porous carbon to obtain a porous carbon material.

[0050] The conditions for the deoxidation and purification treatment are a degree of vacuum of -0.1 MPa to -0.01 MPa, preferably -0.01 MPa, a temperature of 300°C to 900°C, and a time of 0.5 to 3 hours.

[0051] The deoxidation and purification treatment is carried out in a vacuum reducing atmosphere and can be carried out in a vacuum-operated atmosphere furnace or a vacuum-operated reactor. For example, after placing the primary porous carbon in a furnace, the furnace is sealed and the air inside the furnace is first removed to create a vacuum. Then, the vacuum system and the furnace are disconnected, and a reducing gas is slowly introduced into the furnace to raise the temperature and carry out the reduction reaction. The supply of reducing gas is maintained until the end of the reaction, and the product is cooled to room temperature. After cooling, the product is removed from the furnace and sealed and packaged to obtain a porous carbon material. The time for drawing a vacuum inside the furnace can be 120 to 480 seconds.

[0052] In the above deoxidation purification treatment, the reducing gas may be at least one of hydrogen gas, methane, ethylene, and propylene. The flow rate of the reducing gas is preferably 1 mL / min to 2000 mL / min. The reducing gas is preferably a reducing gas containing an inert gas with a volume fraction of 1% to 50%, and the inert gas may be nitrogen gas, argon gas, or the like.

[0053] The present invention further performs purification treatments such as deoxidation and purification, and then performs hydrodeoxidation by first evacuating the mixture and then filling it with a reducing gas, which increases the deoxidation efficiency and solves the problems of uneven and incomplete deoxidation that occur in the conventional atmospheric pressure replacement method.

[0054] The present application further provides a porous carbon material prepared by the above-mentioned preparation method, which has the advantages of high purity, uniform structure and stability, and is particularly applicable to technical fields such as supercapacitors, biomedicine, and catalysis.

[0055] The specific surface area of ​​the above porous carbon material is 500m 2 / g~3500m 2 / g, and the total pore volume is 0.1 cm 3 / g~5cm 3 / g, the oxygen content is less than 1wt%, the ash content is less than 0.1wt%, the metal contents (iron, nickel, cobalt, copper, aluminum, sodium, potassium) are each less than 20mg / kg, and the total metal content is less than 50mg / kg.

[0056] The present invention further provides an electric double layer capacitor, which employs the porous carbon material as an electrode and has the advantages of high energy efficiency and excellent cycle stability. Specifically, the electric double layer capacitor has an initial discharge specific capacity of 20 F / g or more in an organic electrolyte liquid system, or an initial discharge specific capacity of 40 F / g or more in an inorganic electrolyte liquid system.

[0057] In the above electric double layer capacitor, the electrode material can be prepared by mixing a porous carbon material, an adhesive, conductive carbon black, etc. in a certain ratio to form a slurry, and then applying the slurry to a substrate to form an electrode.

[0058] Hereinafter, preferred embodiments of the present application will be described in detail with reference to examples. It should be understood that the following examples are provided for illustrative purposes only and are not intended to limit the scope of the present application. Those skilled in the art can make various modifications and substitutions to the present application without departing from the spirit and scope of the present application.

[0059] The experimental methods used in the examples and comparative examples of the present application are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the examples are commercially available unless otherwise specified.

[0060] Example 1 The method for preparing a porous carbon material provided by this example includes the following steps. (1) Ethylene tar obtained from an ethylene unit manufactured by Daqing Petrochemical Co., Ltd. is selected, and a distillation fraction is separated from the ethylene tar using a true boiling point distillation apparatus. The distillate in the range of 350°C to 450°C is separated, and the distillate is hydrotreated using a fixed-bed hydrogenation apparatus. The hydrotreatment conditions are a reaction temperature of 300°C, a reaction pressure of 10 MPa, and a space velocity of 1 h -1 a hydrogen-to-oil ratio of 800:1 to obtain hydrorefined ethylene tar.

[0061] (2) A portion of the hydrorefined ethylene tar is placed in a tank-type coking reactor and subjected to a preliminary carbonization treatment. The reactor atmosphere is filled with high-purity nitrogen gas, and the temperature is increased to 500°C at a rate of 2°C / min. The mixture is then treated at this constant temperature for 480 minutes. The product is taken out from the bottom of the reactor and crushed using a ball mill with a ball mill pot and tungsten carbide balls to obtain coke with a particle size D50 range of 20-50μm.

[0062] (3) A mixture is obtained by mixing the coke and the remaining part of the hydrorefined ethylene tar under nitrogen gas as a protective gas. Potassium hydroxide is used as an activator, and the coke, potassium hydroxide, and the remaining part of the hydrorefined ethylene tar are mixed in a mass ratio of 1:2.5:0.2. The potassium hydroxide is a pulverized powder with a D50 particle size range of 20-50 μm. A rotary mechanical agitator lined with tetrafluoroethylene material is used as the mixing device. Pressing the above three-component mixture into a cylindrical shaped blank with a diameter of 2 cm and a height of 1 cm under a pressure of 5 MPa using a powder tablet press.

[0063] (4) The raw material was placed in a corundum crucible with a lid, and the crucible was placed in a tubular furnace for activation treatment. The activation treatment conditions were a high-purity nitrogen gas atmosphere, a heating rate of 5°C / min, a temperature of 800°C, a time of 120 minutes, and a pressure of 0.01 MPa. The calcined product is taken out and placed in a 5% hydrochloric acid solution with stirring for 5 hours. After filtration, it is washed with pure water three times. Finally, the solid product is collected by filtration and dried at 100°C for 24 hours to obtain a dry product.

[0064] (5) The dried product is placed in a quartz crucible, which is then placed in a quartz tube vacuum furnace for deoxidation and purification. Specifically, the air in the furnace is evacuated to -0.1 MPa and the vacuum is maintained for 30 minutes. After this, reducing gas (hydrogen gas, ethylene, and argon gas in a volume ratio of 1:1:8, flow rate 10 mL / min) is slowly introduced into the furnace. At this time, heating is initiated, with a temperature increase rate of 5°C / min, a temperature of 700°C, and a constant temperature time of 120 minutes. After the reaction is complete, the material is allowed to cool naturally to obtain a porous carbon material.

[0065] The double layer capacitor provided by this example uses the porous carbon material provided by Example 1 as an electrode material, and the assembly of the double layer capacitor includes the following steps. 1) Mixing porous carbon material, polytetrafluoroethylene adhesive, and conductive carbon black (JPD600, commercially purchased) in a mass ratio of 9:0.5:0.5, using pure water as a dispersant, and stirring uniformly to obtain a slurry. 2) A process of uniformly applying the above slurry to a foam nickel electrode plate with a diameter of 13 mm, and then drying it in a vacuum oven at 120°C for 6 hours to obtain an electrode. 3) Take two electrodes of the same mass, use 6 mol / L potassium hydroxide solution as the electrolyte, use glass fiber filter paper as the separator, and use a CR2032 button battery case as the container, and assemble them using a button battery sealing machine to obtain a double layer capacitor.

[0066] The electrochemical performance of the above double layer capacitor was tested using an electrochemical workstation, and the test results are shown in Figures 2 and 3.

[0067] Example 2 The method for preparing a porous carbon material provided by this example includes the same steps as in Example 1, with the following substitutions compared to Example 1: In step (3), the step of "using potassium hydroxide as an activator" is replaced with the step of "using water vapor as an activator." Furthermore, the molding treatment in step (3) is replaced with the step of "extruding the mixture into particles with a diameter of 2 to 5 mm and a length of 2 to 5 mm using an extruder to obtain a porous carbon precursor." The method includes the same steps as in Example 1, with the exception that the activation treatment conditions in step (4) are changed from "pressure 0.01 MPa" to "pressure 0.02 MPa."

[0068] Example 3 The method for preparing a porous carbon material provided by this example includes the following substitutions compared to Example 1, but otherwise includes the same steps as Example 1. Step (1) is as follows: ethylene tar is selected from an ethylene unit manufactured by Fushun Petrochemical Co., Ltd., and a fraction is separated from the ethylene tar using a vacuum distillation apparatus. A fraction in the range of 300 to 350°C is separated, and the fraction is subjected to hydrotreating using a slurry bed hydrotreating apparatus. The hydrotreating conditions are a temperature of 450°C, a pressure of 16 MPa, and a space velocity of 1 h -1 , the hydrogen-oil ratio is set to 800:1, and hydropurified ethylene tar is obtained. The double layer capacitor provided by this example is assembled under the same conditions as in Example 1, except that the porous carbon material in Example 1 is replaced with the porous carbon material prepared in Example 3.

[0069] Example 4 The method for preparing a porous carbon material provided by this example includes the same steps as in Example 1, except that step (5) in Example 1 is omitted.

[0070] Comparative Example 1 The method for preparing a porous carbon material provided by this example includes the same steps as those of Example 1, except that step (1) of Example 1 is omitted, ethylene tar is directly used in step (2), the remainder of the hydropurified ethylene tar is not added in step (3), and step (5) is omitted.

[0071] Comparative Example 2 The method for preparing a porous carbon material provided by this example includes the same steps as in Example 1, except that the remainder of the ethylene tar hydropurified in step (3) of Example 1 is not added, and step (5) is omitted.

[0072] Comparative Example 3 The method for preparing a porous carbon material provided by this example includes the same steps as those of Example 2, except that instead of adding the remainder of the hydrorefined ethylene tar in step (3) of Example 2, asphalt currently commonly used in the industry (commercial product, powdery, softening point 250°C) is used as an additive in the same mass ratio, and step (5) is omitted (i.e., deoxidation purification treatment is not performed).

[0073] [Table 1]

[0074] As can be seen from Table 1, the ash content, metal content, and non-metal content of the porous carbon material in Comparative Example 1 are much higher than those in the Examples. In other words, by performing preparative treatment and hydrotreating the ethylene tar, the impurity content of the product can be significantly reduced. Furthermore, as can be seen from Examples 1 and 4, deoxidation purification can further reduce the oxygen content in the material. Compared to Example 1, Comparative Example 2 does not contain hydropurified ethylene tar for coating the activator. Therefore, alkali metal atoms may dissipate from the activator at high temperatures. This reduces the activation efficiency of the activator and reduces the specific surface area of ​​the material when the ratio of activator to carbon source is the same. Furthermore, because hydropurified ethylene tar is not added for coating the activator, oxygen enters the mixture during the reaction, causing an increase in the oxygen content. Without deoxidation, it is impossible to remove the oxygen. In Comparative Example 3, asphalt was added as an adhesive, impurities contained in asphalt were mixed into the product during preparation, and at the same time, the oxygen content was high, so the coating effect of asphalt was inferior to that of hydrorefined ethylene tar.

[0075] Figure 2 shows the charge / discharge curve of the double layer capacitor of Example 1. At a charge / discharge current of 1 A / g, the capacitance of the capacitor is 238 F / g, and the charge / discharge curve of the capacitor maintains a well-symmetrical curve without distortion. In other words, the electrode material exhibits a purely physical process of electric double layer adsorption during charge / discharge. Furthermore, since the electrolyte does not chemically react with the electrode material, it can be proven that the porous carbon material of the present invention contains very little impurities such as non-carbon elements.

[0076] Figure 3 shows the cycle performance curve of the double layer capacitor in Example 3. When the double layer capacitor was cycled for 20,000 cycles at a charge / discharge current of 5 A / g, the capacity retention rate of the capacitor was 99%. Since the adsorption / desorption that occurs on the surface of the electrode material is highly reversible, the porous carbon material according to the present invention has a low impurity content, very stable properties, and excellent recyclability.

[0077] The method for preparing a porous carbon material provided by the present application makes it possible to prepare a porous carbon material with a low impurity content and high purity, and also makes full use of ethylene tar, thereby reducing the cost of the preparation process.

[0078] The preferred specific embodiments and test verifications of the present application have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes based on the concept of the present application without any creative efforts. Therefore, any technical solutions that those skilled in the art can obtain according to the concept of the present application through logical analysis, reasoning, or limited experiments based on the prior art should be included in the scope of protection determined by the claims.

[0079] This application claims priority from a Chinese patent application bearing application number 202211007821.9 and entitled "Porous carbon material and its preparation method and use" filed with the China Patent Office on August 22, 2022, the entire contents of which are incorporated herein by reference.

Claims

1. obtaining a fraction of ethylene tar at 250°C to 550°C, and subjecting the fraction to hydrotreatment to obtain hydropurified ethylene tar; a step of subjecting a portion of the hydrorefined ethylene tar to a preliminary carbonization treatment to obtain coke; mixing the remainder of the hydrorefined ethylene tar with the coke to form a mixture, and then activating the mixture to obtain a porous carbon material; A method for preparing a porous carbon material, comprising:

2. 2. The method according to claim 1, wherein the pre-carbonization is carried out in an inert atmosphere at a temperature of 300°C to 800°C.

3. 2. The method according to claim 1, wherein the mass ratio of the coke to the remainder of the hydrotreated ethylene tar is 1:(0.01-0.8).

4. 2. The method according to claim 1, wherein the mixture is subjected to the activation treatment using an activator, and the activator comprises at least one of an alkaline compound, water vapor, and carbon dioxide.

5. The preparation method according to claim 1, wherein the activation treatment is carried out at a temperature of 600°C to 900°C for a time of 0.5 to 3 hours.

6. The preparation method according to claim 1, wherein the ethylene tar fraction is obtained in the range of 350°C to 450°C.

7. The preparation method according to claim 1, further comprising the steps of: subjecting the mixture to an activation treatment to obtain primary porous carbon; and subjecting the primary porous carbon to a deoxidation purification treatment to obtain the porous carbon material.

8. 8. The method according to claim 7, wherein the deoxidation and purification treatment is carried out in a vacuum reducing atmosphere, and the conditions for the deoxidation and purification treatment are a degree of vacuum of −0.1 MPa to −0.01 MPa, a temperature of 300° C. to 900° C., and a time of 0.5 hours to 3 hours.

9. The preparation method described in claim 1, wherein the mass ratio of the coke to the remainder of the hydrorefined ethylene tar is 1:0.2.

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