Preparation method of coal pitch-based porous carbon material and application thereof

Abstract

The application discloses a method for preparing coal-tar pitch-based porous carbon by using double-salt compounds (K2CO3 and Na2CO3) and potassium hydroxide and application thereof. The pore diameter of the material activated by KOH is adjusted by adding K2CO3 and Na2CO3, and the sputtering and eruption of the sample in the activation process is avoided, and the equipment is not corroded. The application comprises the following steps: after coal tar that is crushed is uniformly mixed with an activating agent, simple one-step activation is carried out at high temperature, wherein the specific surface area of the porous carbon material can reach about 2000 m 2 / g, and the pore volume is between 0.98 and 1.29 cm 3 / g. When the porous carbon material is used as an electrode material of a super capacitor, the material shows high specific capacitance and good rate performance. The application provides a preparation method of high-specific-surface-area porous carbon, and the reaction process is mild.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry and energy materials, and provides a method and application for preparing coal tar pitch-based porous carbon using potassium hydroxide assisted by dual salt compounds (K2CO3, Na2CO3). Background Technology

[0002] The overuse of fossil fuels has caused a serious energy crisis and environmental pollution. To promote the sustainable development of Earth's resources, various renewable energy sources have been developed, such as wind power, solar power, and tidal power.

[0003] However, the supply of these renewable energy sources is unstable, necessitating the development of efficient and stable energy storage devices. Supercapacitors have attracted widespread attention from researchers due to their advantages such as high safety, long charge / discharge lifespan, fast charging speed, high power density, and wide operating temperature range. Electrode materials, as a crucial component of supercapacitors, have a significant impact on their energy storage performance. Therefore, developing a high-performance supercapacitor electrode material is the most direct way to improve supercapacitor performance. Among these materials, porous carbon is currently widely studied due to its wide availability, low cost, environmental friendliness, and diverse structures.

[0004] Coal tar pitch, a byproduct of coal tar distillation, has a high carbon content and is a high-quality carbon source. Coal resources dominate my country's energy consumption structure, and the country is the largest producer of coal tar, thus generating a large amount of coal tar pitch annually. Using coal tar pitch as a carbon source to prepare porous carbon can not only increase the added value of coal tar pitch but also reduce the preparation cost of porous carbon. Currently, coal tar pitch-based porous carbon is mainly obtained through chemical activation using strong alkali potassium hydroxide as an activator. Pure potassium hydroxide reacts violently during activation, producing an "alkali explosion" phenomenon, posing a safety hazard. Furthermore, KOH activation can damage the material's structure, forming more useless pores. Patent literature "Method and Application of Preparing Three-Dimensional Porous Graphene Sheets Using Low-Temperature Dual Salt Compounds (CN 113307254 A)" discloses a method for preparing flower-like porous carbon with three-dimensional porous graphene-like sheets grown on the surface using biochar as raw material and K2CO3 and Na2CO3 as activators. This method avoids the problems caused by potassium hydroxide activation, but the specific capacity of the porous carbon formed when applied to activate coal tar pitch carbon is relatively low. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing coal tar pitch-based porous carbon. The method involves using a dual-salt activator, K₂CO₃ and Na₂CO₃, to assist potassium hydroxide in the preparation of coal tar pitch-based porous carbon materials. The addition of K₂CO₃ and Na₂CO₃ adjusts the pore size of the material after activation with KOH, and also avoids sample sputtering and eruption during the activation process.

[0006] The second objective of this invention is to provide a coal tar pitch-based porous carbon obtained by the above preparation method. This porous carbon material has a high specific surface area and high pore volume, and the porous carbon electrode prepared from it exhibits excellent electrochemical performance.

[0007] The technical solution is as follows:

[0008] A method for preparing coal tar pitch-based porous carbon materials with high specific surface area using potassium hydroxide assisted by a dual-salt activator includes the following steps:

[0009] Step 1: Place the coal tar pitch carbon raw material in a pulverizer and pulverize it into powder;

[0010] Step 2: Take a certain mass of crushed coal tar pitch carbon and mix it evenly with KOH, K2CO3 and Na2CO3 according to the mass ratio;

[0011] Step 3: Place the mixed raw materials obtained in Step 2 into a tube furnace under a nitrogen atmosphere, heat to the reaction temperature to carry out the activation reaction, and then cool to room temperature before taking it out.

[0012] Step 4: The product obtained in Step 3 is heated and acid-washed in a water bath with dilute hydrochloric acid solution for a certain period of time, and then washed with deionized water until the solution becomes neutral.

[0013] Step 5: After drying the product obtained in Step 4, the coal tar pitch-based porous carbon material is obtained.

[0014] Preferably, in step 1, the particle size of the powdered carbon particles is 2-50 µm.

[0015] Preferably, in step 2, the mass ratio of coal tar pitch carbon powder to activator is 1:1-1:10, wherein the molar ratio of K2CO3 to Na2CO3 is 0:1 to 1:0, and the mass ratio of coal tar pitch carbon to potassium hydroxide is 1:0-1:2.

[0016] Preferably, in step 3, the activation temperature is 600 ℃-1000 ℃, the activation reaction time is 5 h, and the heating rate is 5 ℃ / min.

[0017] Preferably, in step 4, the concentration of hydrochloric acid is 0.5-2 mol / L, and the stirring time is 5-10 h.

[0018] Preferably, the product obtained in step 5 is placed in a freeze dryer for 5-24 hours.

[0019] The present invention also discloses a coal tar pitch-based porous carbon material, which is obtained by the above-mentioned method of preparing coal tar pitch-based porous carbon material with potassium hydroxide assisted by a double salt compound. The material is characterized by having a high specific surface area and abundant pore structure.

[0020] This invention also provides the application of coal tar pitch-based porous carbon obtained by the above method in supercapacitors, characterized by exhibiting high specific capacitance and rate performance. Beneficial effects

[0021] 1. Coal tar pitch-based porous carbon materials were prepared using a simple, environmentally friendly, low-temperature, and easily industrialized method.

[0022] 2. The method for preparing coal tar pitch-based porous carbon provided by the present invention uses coal tar pitch as raw material and double salt-assisted KOH as an activator, and the reaction process is mild;

[0023] 3. The prepared porous carbon material has a high specific surface area and abundant porous structure, which can provide more electrochemical active sites; when used as an electrode material for supercapacitors, it exhibits high specific capacity and good rate performance. Attached Figure Description

[0024] Figure 1 The nitrogen adsorption-desorption curves are for the porous carbon material prepared in Example 1.

[0025] Figure 2 This is a pore size distribution diagram of the porous carbon material prepared in Example 1.

[0026] Figure 3 The graph shows the three-electrode constant current charge-discharge curves of the porous carbon material electrode prepared in Example 1.

[0027] Figure 4 This is a rate performance diagram of the porous carbon material electrode prepared in Example 1.

[0028] Figure 5 This is a scanning electron microscope image of the porous carbon prepared in Example 3. Implementation

[0029] To better understand the present invention, the following detailed description, in conjunction with specific embodiments and accompanying drawings, further explains the present invention, but the embodiments do not limit the present invention in any way.

[0030] A method for preparing coal tar pitch-based porous carbon materials with high specific surface area using potassium hydroxide assisted by a dual-salt activator includes the following steps:

[0031] Step 1: Place the coal tar pitch carbon raw material in a pulverizer and pulverize it into powder;

[0032] Step 2: Take a certain mass of crushed coal tar pitch carbon and mix it evenly with KOH, K2CO3 and Na2CO3 according to the mass ratio;

[0033] Step 3: Place the mixed raw materials obtained in Step 2 into a tube furnace under a nitrogen atmosphere, heat to the reaction temperature to carry out the activation reaction, and then cool to room temperature before taking it out.

[0034] Step 4: The product obtained in step 3 is heated and acid-washed in a water bath with dilute hydrochloric acid solution for a certain period of time, and then washed with deionized water until the solution becomes neutral.

[0035] Step 5: After drying the product obtained in step 4, the coal tar pitch-based porous carbon material is obtained. Example

[0036] (1) Weigh 200 g of block coal tar pitch and place it in a pulverizer to pulverize for 5 min until it becomes powder.

[0037] (2) Mix the powdered raw materials with K2CO3 / Na2CO3 and KOH in a mass ratio of 1:2:2, wherein the molar ratio of K2CO3 and Na2CO3 is 0.45:0.55.

[0038] (3) The mixed material was activated in a tube furnace under a nitrogen atmosphere at an activation temperature of 750 °C for 5 h with a heating rate of 5 °C / min. After activation, the mixture was allowed to cool naturally to room temperature.

[0039] (4) The activated material was washed with 1 mol / L HCl solution and deionized water until the solution was neutral. Finally, it was dried in a freeze dryer for 12 h to obtain coal tar pitch-based porous carbon.

[0040] (5) Fabrication of electrode materials. The prepared porous carbon material, acetylene black and binder polytetrafluoroethylene are mixed in a mass ratio of 80:10:10, ground evenly and rolled into sheets. The sheets are then dried in a vacuum drying oven at 80℃ for 24 h. A sheet with a mass of 1-2 mg is then cut and pressed onto the nickel foam.

[0041] (6) The electrochemical performance of the obtained materials was tested using a three-electrode system, with 6 M KOH solution as the electrolyte, a platinum sheet as the counter electrode, and saturated silver chloride as the reference electrode. Electrochemical tests were performed using a Chenhua electrochemical workstation. Cyclic voltammetry was set with a voltage range of -1.0 V to -0.2 V and a scan rate of 20 mV / s; impedance testing was set with a frequency range of 100 kHz to 0.1 Hz and an initial voltage; constant current charge-discharge performance testing was set with a voltage range of -1.0 V to -0.2 V and a current density of 1 A / g.

[0042] The porous carbon material obtained through Example 1 is shown in the attached figure, wherein, Figure 1The figure shows the nitrogen adsorption-desorption curve of the activated product. As can be seen from the figure, the sample exhibits a high adsorption capacity when P / P0 < 0.1, indicating that there is a rich microporous structure in the sample, with a specific surface area of ​​2094.7 m2 / g.

[0043] Figure 2 The pore size distribution diagram of the activated product clearly shows that the sample mainly contains a large number of micropores and some mesopores.

[0044] Figure 3 The three-electrode galvanostatic charge-discharge curves of the prepared porous carbon material electrode show a high specific capacitance of 169 F / g in 6 M KOH solution at a current density of 1 A / g.

[0045] Figure 4 The diagram shows the rate performance of the prepared porous carbon material electrode. Example

[0046] (1) Weigh 200 g of block coal tar pitch and place it in a pulverizer to pulverize for 5 min until it becomes powder.

[0047] (2) Mix the powdered raw materials with K2CO3 / Na2CO3 and KOH in a mass ratio of 1:2:2, wherein the molar ratio of K2CO3 and Na2CO3 is 0.45:0.55.

[0048] (3) The mixed material was activated in a tube furnace under a nitrogen atmosphere at an activation temperature of 850 °C for 5 h with a heating rate of 5 °C / min. After activation, the mixture was allowed to cool naturally to room temperature.

[0049] (4) The activated material was washed with 1 mol / L HCl solution and deionized water until the solution was neutral. Finally, it was dried in a freeze dryer for 12 h to obtain coal tar pitch-based porous carbon.

[0050] Analysis of the coal tar pitch-based porous carbon prepared in the above embodiments showed that as the activation temperature increased, the microporous structure in the material collapsed to form mesopores, resulting in a decrease in specific surface area. Example

[0051] (1) Weigh 200 g of block coal tar pitch and place it in a pulverizer to pulverize for 5 min until it becomes powder.

[0052] (2) Mix the powdered raw materials with K2CO3 / Na2CO3 and KOH in a mass ratio of 1:2:2, wherein the molar ratio of K2CO3 and Na2CO3 is 0.45:0.55.

[0053] (3) The mixed material was activated in a tube furnace under a nitrogen atmosphere at an activation temperature of 950 °C for 5 h with a heating rate of 5 °C / min. After activation, the mixture was allowed to cool naturally to room temperature.

[0054] (4) The activated material was washed with 1 mol / L HCl solution and deionized water until the solution was neutral. Finally, it was dried in a freeze dryer for 12 h to obtain coal tar pitch-based porous carbon.

[0055] Analysis of the coal tar pitch-based porous carbon prepared in the above embodiments showed that excessively high activation temperature caused a large number of microporous structures formed in the material to collapse and form mesopores, resulting in a decrease in specific surface area. Example

[0056] (1) Weigh 200 g of block coal tar pitch and place it in a pulverizer to pulverize for 5 min until it becomes powder.

[0057] (2) Mix the powdered raw materials with K2CO3 / Na2CO3 at a mass ratio of 1:4, wherein the molar ratio of K2CO3 to Na2CO3 is 0.45:0.55.

[0058] (3) The mixed material was activated in a tube furnace under a nitrogen atmosphere at an activation temperature of 950 °C for 5 h with a heating rate of 5 °C / min. After activation, the mixture was allowed to cool naturally to room temperature.

[0059] (4) The activated material was washed with 1 mol / L HCl solution and deionized water until the solution was neutral. Finally, it was dried in a freeze dryer for 12 h to obtain coal tar pitch-based porous carbon.

[0060] Analysis of the coal tar pitch-based porous carbon prepared in the above examples showed that the microporous structure of the sample prepared by using only two salts as activators was greatly reduced, resulting in a significant decrease in specific surface area.

[0061] The specific data of the coal tar pitch-based porous carbon obtained in Test Examples 1-4 are shown in Table 1:

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the method for preparing coal tar pitch-based porous carbon using the dual-salt assisted potassium hydroxide activation provided by this invention can yield coal tar pitch-based porous carbon with high specific surface area and large pore volume. The coal tar pitch-based porous carbon prepared using the scheme in Example 1 exhibits superior capacitance performance when used as a supercapacitor electrode.

[0065] The embodiments described above are merely examples for illustrating the present invention and should not be construed as limiting the implementation of the present invention. For those skilled in the art, any modifications, equivalent substitutions, and improvements within the core technical scope of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing coal tar pitch-based porous carbon materials using potassium hydroxide assisted by a dual-salt compound, characterized in that, Includes the following steps: Step 1: Place the coal tar pitch raw material in a pulverizer and pulverize it into powder; the particle size of the powdered carbon particles is 2-50 μm; Step 2: Take a certain mass of pulverized coal tar pitch and mix it evenly with activators KOH, K2CO3 and Na2CO3 in the mass ratio; the mass ratio of coal tar pitch powder to activator is 1:1 to 1:10, wherein the molar ratio of K2CO3 to Na2CO3 is 0:1 to 1:0, and the amount of K2CO3 and Na2CO3 is not 0; the mass ratio of coal tar pitch to KOH is 1:0 to 1:2, and the amount of KOH is not 0. Step 3: Place the mixed raw materials obtained in Step 2 into a tube furnace under a nitrogen atmosphere, heat to the reaction temperature to carry out the activation reaction, and then cool to room temperature before taking it out. Step 4: The product obtained in Step 3 is acid-washed with dilute hydrochloric acid solution in a water bath for a certain period of time, and then washed with deionized water until the solution is neutral; the activation reaction temperature is 600 ℃-1000 ℃, the activation reaction time is 5 h, and the heating rate is 5 ℃ / min. Step 5: After drying the product obtained in step 4, the porous carbon material is obtained.

2. The method according to claim 1, characterized in that: In step 4, the concentration of hydrochloric acid is 0.5-2 mol / L, and the stirring time is 5-10 h.

3. The method according to claim 1, characterized in that: The product obtained in step 5 is placed in a freeze dryer for 5-24 hours.

4. A coal tar pitch-based porous carbon material, obtained by the method described in any one of claims 1-3, which uses a dual-salt compound-assisted KOH preparation method for coal tar pitch-based porous carbon materials, characterized in that: It has a high specific surface area and abundant pore structure.

5. A supercapacitor, characterized by: Including the coal tar pitch-based porous carbon material as described in claim 4.

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