Microwave-assisted method for preparing porous nano carbon material

Abstract

The invention provides a microwave-assisted method for preparing a porous nano carbon material. The microwave-assisted method comprises the following steps: (1) mixing a heavy oil product with an organic solvent, and performing ultrasonic treatment in an ultrasonic instrument until the solution is uniform to obtain a mixed solution; (2) adding a template agent into the mixed solution, continuously performing ultrasonic treatment to prepare uniformly mixed slurry, and evaporating to remove redundant toluene in the uniformly mixed slurry; (3) putting the slurry into a microwave generation device, setting a heating temperature, introducing inert gas, and starting the microwave generation device after the temperature rises to the set temperature, so as to obtain a sample; and (4) washing the sample with hydrochloric acid and distilled water, and drying to obtain the porous nano carbon material. According to the method, the reaction temperature can be reduced, the reaction time can be shortened and the conditionality of the preparation process can be reduced while the oil slurry is subjected to high value-added utilization by utilizing the microwave reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocarbon materials, and particularly relates to a method for preparing porous nanocarbon materials by microwave assistance. Background Art

[0002] As a new type of carbon material, nanocarbon materials have many unique properties, including unique morphological structures, high specific surface areas, low diffusion distances, high electrical conductivity and ionic conductivity, controllable synthesis and doping, etc. Therefore, nanocarbon materials have great application prospects in high-reversible-capacity, high-power-density, long-cycle-stability, and high-safety lithium-ion batteries. As one of the most promising energy storage devices, lithium-ion batteries have been widely used in portable electronic devices. However, the use of traditional electrode materials results in insufficient energy density and power density, poor durability, and high cost of the battery, which limits its large-scale application in electric vehicles and other fields. The development of nanocarbon materials provides an opportunity for designing new energy storage materials suitable for lithium-ion batteries. Therefore, nanocarbon materials represented by fullerenes, carbon nanotubes, graphene, and porous carbon have extremely high application value.

[0003] Chinese Patent CN111977633A discloses a method for preparing phosphorus / oxygen-doped nanoporous carbon materials by microwave method. (1) A carbon source, a phosphorus source, and a microwave absorber are uniformly mixed in different proportions to obtain a mixture; (2) The dispersant and the above mixture are placed in a microwave reactor, and a microwave reaction occurs in an air atmosphere. After the product is naturally cooled, the product is washed with acid and water to remove impurities and dried to obtain phosphorus / oxygen-doped nanoporous carbon materials. This technology is different from catalytic slurry with low added value. The carbon source used in the preparation method is potassium citrate, which has a higher price, 3-4 times that of catalytic slurry, resulting in high production costs. At the same time, the nanoporous carbon materials inevitably doped in the product during the production process cannot be removed, and it has great limitations in application.

[0004] Chinese Patent CN114094058A discloses a method for preparing a lithium phosphide electrode based on the microwave method, including the following steps: S1, phenyl lithium phosphate is ground by an air flow mill, and the ground phenyl lithium phosphate particles are filtered through a sieve with a mesh size of 600 to 2000; S2, the material obtained in S1 is placed in an inert atmosphere for heat treatment, and the treatment temperature is 300 to 500 °C; S3, the material obtained in S2 is subjected to microwave treatment, the microwave power is 400 to 1000 W, and the treatment time is 0.5 to 3 h; S4, the material obtained in S3 is mixed with carbon fiber and polyvinylidene fluoride, and the mass ratio of the three is 90:5:5 to 65:25:10. Using N-methylpyrrolidone as a solvent, stirring for 3 h, and coating the mixed material on a copper foil as an electrode material. This technology has a complex preparation process, a too long microwave treatment time used, a large gap between the raw materials and products and the present invention, and different actual purposes.

[0005] Chinese Patent CN113666411A discloses a method for preparing a lithium battery anode material by microwave method, which is a composite of ultrafine oxides and carbon. The method is as follows: First, prepare a salt solution to infiltrate metal ions into a metal-organic framework material (MOF); use suction filtration to separate the MOF material infiltrated with ions from the solution, and dry it to obtain the MOF material infiltrated with ions; Second, mix the MOF material infiltrated with ions and graphene, then grind them, and then heat them by microwave for a short time; Third, after the product is washed and purified, a lithium battery anode material composed of a composite of ultrafine oxides and carbon is obtained. The nanoparticle size of the product of the present invention is 2-10 nm, and it can have a high capacity performance under a low oxide load; the preparation process of this technology is complex. In the early stage, it is necessary to soak and mix with an alkali metal-based MOF material. After drying, it is also necessary to grind and mix with graphene directionally. The cost of the required preparation raw materials is much higher than that of the catalytic slurry with low added value.

[0006] Chinese Patent CN111099917A discloses a porous composite material that generates an arc in a microwave and a preparation method. The method includes the following steps: a. Prepare a solution or dispersion of a carbon material and / or a carbon material precursor for loading; b. Immerse an inorganic porous skeleton or an inorganic porous skeleton precursor in the solution or dispersion of step a, so that the pores of the inorganic porous skeleton or the inorganic porous skeleton precursor are filled with the solution or dispersion; the carbon material and / or the carbon material precursor account for 0.001%-99.999% of the total mass of the inorganic porous skeleton material or the inorganic porous skeleton material precursor and the carbon material and / or the carbon material precursor, preferably 0.01%-99.99%, more preferably 0.1%-99.9%; c. Take out the porous material obtained in step b, heat it, and dry it. The carbon material or the carbon material precursor precipitates or solidifies and is loaded on the inorganic porous skeleton or the inorganic porous skeleton precursor; the heating and drying temperature is 50-250 °C, preferably 60-200 °C, more preferably 80-180 °C; the power of the microwave in step c is 1W-100KW, preferably 500W-10KW, and the microwave time is 2-200min, preferably 20-200min; this technology requires complex raw materials, including inorganic porous skeleton materials, carbon materials, carbonizable organic substances, and inorganic substances of non-metals and non-metal compounds. Among them, the carbonizable organic substances are organic polymer compounds, including natural organic polymer compounds and synthetic polymer compounds, dispersions and other raw materials. The preparation process is complex, and the required raw materials are quite different from the low-value-added oil slurry.

[0007] In the prior art, the reaction conditions of the direct carbonization method are harsh and the energy consumption is too high. For the direct microwave reaction method, the microwave energy has a weak response to liquid oils, and the efficiency is greatly reduced. Summary of the Invention

[0008] The object of the present invention is to provide a method for preparing porous nanocarbon materials by microwave assistance. This method improves the response intensity of the reaction system to microwaves through pre-carbonization, and while highly valuably utilizing the slurry by microwave-enhanced reaction, it can reduce the reaction temperature, shorten the reaction time, and reduce the conditional nature of the preparation process.

[0009] To achieve the above object, the present invention provides a method for preparing porous nanocarbon materials by microwave assistance, comprising the following steps:

[0010] (1) Mix heavy oil products with an organic solvent and place them in an ultrasonic instrument to ultrasonically treat until the solution is uniform to obtain a mixed solution;

[0011] (2) Add a template agent to the mixed solution, continue ultrasonic treatment to make a uniformly mixed slurry, and evaporate to remove the excess organic solvent in the uniformly mixed slurry;

[0012] (3) Place the slurry in a microwave generating device, set the heating temperature, introduce an inert gas, and after the temperature rises to the set temperature, complete preliminary carbonization, and then start the microwave generating device to strengthen the reaction process to obtain a sample;

[0013] (4) Wash the sample with hydrochloric acid and distilled water and dry it to obtain a porous nanocarbon material.

[0014] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the heavy oil products are one or more of catalytic cracking slurry, ethylene tar, coal tar, vacuum residue, and deoiled asphalt.

[0015] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the organic solvent is one or more of toluene, petroleum ether, and n-heptane.

[0016] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the dosage ratio of the heavy oil products to toluene is 1:0.5 to 1:20, preferably 1:1 to 1:10, where the heavy oil products are in terms of mass and toluene is in terms of volume.

[0017] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the ultrasonic time in step (1) is greater than 1 min, preferably more than 5 min.

[0018] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the template agent includes metal oxides and / or metal salts. The metal oxides can be iron oxide and / or magnesium oxide, and the metal salts can be sodium chloride and / or potassium chloride.

[0019] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the mass ratio of heavy oil to template agent is 1:1 to 1:40, and preferably the mass ratio is 1:5 to 1:20.

[0020] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, in step (2), the evaporation temperature is 60 to 150 °C, and preferably the evaporation temperature is 80 to 120 °C.

[0021] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, in step (3), the set heating temperature is 400 to 600 °C, and preferably it is 450 to 550 °C.

[0022] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, the inert gas is nitrogen, argon or helium, and the gas flow rate is 80 to 1500 mL / min, and preferably it is 100 to 1000 mL / min.

[0023] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, in step (3), the microwave frequency is 0.2 to 4.0 GHz, preferably 0.3 to 2.0 GHz, and the time is 0.5 to 10 minutes, preferably 0.5 to 8 minutes.

[0024] In the method for preparing porous nanocarbon materials by microwave assistance according to the present invention, in step (4), the hydrochloric acid concentration is 0.5 to 3.0 mol / L, preferably 0.5 to 1.0 mol / L, and the drying temperature is 75 to 120 °C, preferably 80 to 100 °C.

[0025] Advantages of the present invention:

[0026] 1. By using the template agent, the large molecules of the oil product first penetrate into the voids of the layered structure of the template agent. The template agent is used as the main configuration control to affect and modify the morphology, size, etc. of the material, thereby regulating the material properties, and porous carbon materials can be prepared directionally.

[0027] 2. By adjusting the carbonization process and process conditions, the carbonization synthesis of porous nanocarbon materials from heavy oil products is controlled; the template, raw materials and reaction conditions play an important role in the formation of the microstructure and porosity of carbon. By controlling conditions such as the process temperature, type and proportion of the template agent, different porous carbon materials with different morphologies and physical properties can be obtained.

[0028] 3. Through two stages of pre-carbonization and microwave-assisted strengthening reaction, the reaction efficiency is greatly improved. This process is simple, the conditions are mild, it is green and pollution-free, and the cost is low, and it has a wide application prospect and is expected to generate huge economic benefits. Description of the Drawings

[0029] Figure 1X-ray diffraction pattern of the porous nanocarbon material product prepared in Example 1 of the present invention.

[0030] Figure 2 Raman spectrum of the porous nanocarbon material product prepared in Example 1 of the present invention. Detailed implementation manners

[0031] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

[0032] Source of raw materials or equipment: Iron oxide, CP (Shanghai Reagent), ≥98.0%, Shanghai Reagent; Dilute hydrochloric acid, 0.1 mol / L, Shanghai Reagent.

[0033] Evaluation and analysis methods: XRD, RAMAN

[0034] Example 1

[0035] Add 2.5 g of catalytic cracking slurry to 10 ml of toluene, and ultrasonically treat for 10 minutes to form a black mixed solution. Then, 10 g of iron oxide template agent is fully mixed in the mixed solution, and the above mixture is stirred and dried in an oil bath at 90 °C to form a homogeneous mixture and recover toluene. Subsequently, the mixture is heated to 500 °C in a programmed temperature tube furnace under a continuous nitrogen flow at a heating rate of 10 °C / min. Then, turn on the microwave generating device, select a microwave frequency of 1.5 GHz, and continue for 3 min. After cooling to room temperature, react with 1.0 mol / L dilute hydrochloric acid in a magnetic stirring beaker to remove the template agent. The product collected by vacuum filtration is washed with deionized water to remove soluble salts, and the obtained product is dried in an oven at 80 °C for 12 hours to obtain a porous nanocarbon material.

[0036] Example 2

[0037] Add 2.5 g of vacuum residue to 50 ml of toluene, and ultrasonically treat for 15 minutes to form a black mixed solution. Then, 2.5 g of magnesium oxide template agent is fully mixed in the mixed solution, and the above mixture is stirred and dried in an oil bath at 90 °C to form a homogeneous mixture and recover toluene. Subsequently, the mixture is heated to 450 °C in a programmed temperature tube furnace under a continuous nitrogen flow at a heating rate of 10 °C / min. Then, turn on the microwave generating device, select a microwave frequency of 1.0 GHz, and continue for 5 min. After cooling to room temperature, react with 1.0 mol / L dilute hydrochloric acid in a magnetic stirring beaker to remove the template agent. The product collected by vacuum filtration is washed with deionized water to remove soluble salts, and the obtained product is dried in an oven at 100 °C for 8 hours to obtain a porous nanocarbon material.

[0038] Example 3

[0039] Add 5 g of deoiled asphalt to 2.5 ml of toluene and ultrasonically treat for 10 minutes to form a black mixed solution. Then, fully mix 10 g of potassium chloride template agent in the mixed solution. Stir and dry the above mixture in an oil bath at 100 °C to form a homogeneous mixture and recover toluene. Subsequently, heat the mixture to 500 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. Select a microwave frequency of 0.5 GHz and continue for 10 min. After cooling to room temperature, react with 1.0 mol / L dilute hydrochloric acid in a magnetic stirring beaker to fully remove the template agent. Wash the product collected by vacuum filtration with deionized water to remove soluble salts. Dry the obtained product in an oven at 90 °C for 10 hours to obtain a porous nanocarbon material.

[0040] Example 4

[0041] Add 5 g of deoiled asphalt to 15 ml of toluene and ultrasonically treat for 10 minutes to form a black mixed solution. Then, fully mix 200 g of sodium chloride template agent in the mixed solution. Stir and dry the above mixture in an oil bath at 60 °C to form a homogeneous mixture and recover toluene. Subsequently, heat the mixture to 400 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. Select a microwave frequency of 4 GHz and continue for 0.5 min. After cooling to room temperature, react with 1.0 mol / L dilute hydrochloric acid in a magnetic stirring beaker to fully remove the template agent. Wash the product collected by vacuum filtration with deionized water to remove soluble salts. Dry the obtained product in an oven at 90 °C for 10 hours to obtain a porous nanocarbon material.

[0042] Example 5

[0043] Add 2.5 g of vacuum residue to 20 ml of toluene and ultrasonically treat for 15 minutes to form a black mixed solution. Then, fully mix 10 g of potassium chloride and sodium chloride (mass ratio 1:1) template agent in the mixed solution. Stir and dry the above mixture in an oil bath at 150 °C to form a homogeneous mixture and recover toluene. Subsequently, heat the mixture to 600 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. Select a microwave frequency of 2.0 GHz and continue for 1 min. After cooling to room temperature, react with 1.0 mol / L dilute hydrochloric acid in a magnetic stirring beaker to fully remove the template agent. Wash the product collected by vacuum filtration with deionized water to remove soluble salts. Dry the obtained product in an oven at 90 °C for 10 hours to obtain a porous nanocarbon material.

[0044] Example 6

[0045] 5 g of deoiled asphalt was added to 15 ml of toluene, and ultrasonic treatment was carried out for 10 minutes to form a black mixed solution. Then, 10 g of a template agent of potassium chloride and sodium chloride (mass ratio 2:1) was thoroughly mixed in the mixed solution. The above mixture was stirred and dried in an oil bath at 100 °C to form a homogeneous mixture and recover toluene. Subsequently, the mixture was heated to 450 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. The microwave frequency was selected as 1.5 GHz and lasted for 5 min. After cooling to room temperature, 1.0 mol / L dilute hydrochloric acid was used to react fully in a magnetic stirring beaker to remove the template agent. The product collected by vacuum filtration was washed with deionized water to remove soluble salts. The obtained product was dried in an oven at 80 °C for 12 hours to obtain a porous nanocarbon material.

[0046] Example 7

[0047] 2.5 g of coal tar pitch was added to 20 ml of toluene, and ultrasonic treatment was carried out for 15 minutes to form a black mixed solution. Then, 10 g of zinc oxide template agent was thoroughly mixed in the mixed solution. The above mixture was stirred and dried in an oil bath at 100 °C to form a homogeneous mixture and recover toluene. Subsequently, the mixture was heated to 450 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. The microwave frequency was selected as 2.0 GHz and lasted for 1 min. After cooling to room temperature, 1.0 mol / L dilute hydrochloric acid was used to react fully in a magnetic stirring beaker to remove the template agent. The product collected by vacuum filtration was washed with deionized water to remove soluble salts. The obtained product was dried in an oven at 90 °C for 10 hours to obtain a porous nanocarbon material.

[0048] Example 8

[0049] 5 g of coal tar pitch was added to 20 ml of toluene, and ultrasonic treatment was carried out for 15 minutes to form a black mixed solution. Then, 20 g of calcium oxide template agent was thoroughly mixed in the mixed solution. The above mixture was stirred and dried in an oil bath at 100 °C to form a homogeneous mixture and recover toluene. Subsequently, the mixture was heated to 500 °C at a heating rate of 10 °C / min in a programmed temperature tube furnace under a continuous nitrogen flow. The microwave frequency was selected as 1 GHz and lasted for 2.5 min. After cooling to room temperature, 1.0 mol / L dilute hydrochloric acid was used to react fully in a magnetic stirring beaker to remove the template agent. The product collected by vacuum filtration was washed with deionized water to remove soluble salts. The obtained product was dried in an oven at 90 °C for 10 hours to obtain a porous nanocarbon material.

[0050] Comparative Example 1

[0051] Mix 0.5 g of phytic acid, 2 g of potassium citrate, and 2 g of ethanol in a quartz crucible, then place it in a microwave reactor for microwave heating. The reaction power is 500 W and the reaction time is 2 min. After the product cools naturally, treat the product with hydrochloric acid, wash it with water to remove impurities, and dry it in an oven at 60 °C to obtain the phosphorus / oxygen-doped nanoporous carbon material MP / OPC500-0.5.

[0052] Comparative Example 2

[0053] Mix 0.75 g of phytic acid, 2 g of potassium citrate, and 2 g of ethanol in a quartz crucible, then place it in a microwave reactor for microwave heating. The reaction power is 400 W and the reaction time is 2 min. After the product cools naturally, treat the product with hydrochloric acid, wash it with water to remove impurities, and dry it in an oven at 60 °C to obtain the phosphorus / oxygen-doped nanoporous carbon material MP / OPC400-0.75.

[0054] Table 1 Comparative Analysis of XRD and Raman Data for Different Embodiment Cases

[0055]

[0056] From the above data, it can be seen that for the porous nanocarbon materials prepared by this method, the product has a relatively consistent peak position in the carbon material, with an obvious peak at about 25°. The preparation result is relatively stable. The product of the porous carbon material obtained in the comparative example has a lower degree of disorder and better preparation effect.

[0057] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing porous nanocarbon materials using microwave assistance, characterized in that: The following steps are involved: (1) mixing a heavy oil product and an organic solvent and placing the mixture in an ultrasonic instrument and ultrasonicating the mixture until the solution is uniform to obtain a mixed solution; (2) adding a template to the mixed solution, continuing ultrasonic treatment to form a uniform mixed slurry, and evaporating and removing excess solvent in the uniform mixed slurry; (3) placing the slurry in a microwave generator, setting the heating temperature, introducing an inert gas, and completing the preliminary carbonization after the temperature rises to the set temperature, starting the microwave generator, and strengthening the reaction process to obtain a sample; (4) The sample was washed with hydrochloric acid and distilled water and dried to obtain a porous nanocarbon material.

2. The method for preparing porous nanocarbon materials using microwave assistance according to claim 1, characterized in that: The heavy oil product is one or more of catalytic cracking slurry, ethylene tar, coal tar, vacuum residue and deoiled asphalt.

3. The method for preparing porous nanocarbon materials using microwave assistance according to claim 1, characterized in that: The organic solvent is one or more of toluene, petroleum ether and n-heptane.

4. The method for preparing porous nanocarbon materials using microwave assistance according to claim 1, characterized in that: The usage ratio of the heavy oil product to the organic solvent is 1:0.5 to 1:20, wherein the heavy oil product is measured by mass and the organic solvent is measured by volume.

5. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The ultrasonic time in step (1) is greater than 1 min.

6. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The template includes metal oxides and / or metal salts.

7. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The mass ratio of the heavy oil product to the template agent is 1:1 to 1:

40.

8. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The evaporation temperature in step (2) is 60-150°C.

9. The method for preparing porous nanocarbon materials using microwave assistance according to claim 1, characterized in that: The heating temperature set in step (3) is 400-600°C.

10. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The inert gas is nitrogen, argon or helium, and the gas flow rate is 80-1500 mL / min.

11. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: In step (3), the microwave frequency is 0.2 to 4.0 GHz and the time is 0.5 to 10 minutes.

12. The method for preparing porous nano-carbon materials using microwave assistance according to claim 1, characterized in that: The hydrochloric acid concentration in step (4) is 0.5-3.0 mol / L, and the drying temperature is 75-120°C.

Images