Preparation method for and use of nanoporous carbon material having continuous structure

Abstract

Disclosed in the present invention are a preparation method for and the use of a nanoporous carbon material having a continuous structure. The preparation method comprises: mixing an aromatic reactant and a strong dehydrating agent, and then heating the resulting mixture to a molten state, wherein the aromatic reactant is an aromatic compound containing both a nitryl and an amino, or an aromatic mixture obtained by mixing a nitryl-containing compound with an amino-containing compound; and then subjecting the aromatic reactant in the molten state and the strong dehydrating agent to a second instance of heating to 220-1000ºC within 30 s to 50 min, and fully reacting same, so as to obtain a nanoporous carbon material having a continuous structure. The cost of raw materials is low, the preparation conditions are simple, and the preparation speed is fast. The nanoporous carbon material having a continuous structure is used in preparation of a fireproof thermal-insulation material, a solar heat-absorbing material, a seawater purification material, a battery electrode material and an adsorbing material. The carbon material has a density as low as 1 g / L, and also has a large specific surface area of 200-400 m2 / g.

Description

Preparation method and application of nanoporous carbon material with continuous structure Technical Field

[0001] The present invention relates to a carbon material, a preparation method of the carbon material and applications thereof, and in particular to a preparation method and applications of a nanoporous carbon material with a continuous structure. Background Art

[0002] The diversity of carbon materials and their excellent physical and chemical properties have led to their widespread application across numerous interdisciplinary fields. Low-dimensional carbon materials (0D, 1D, and 2D) are often limited in their catalytic activity due to their large contact and thermal resistances, resulting in undesirable electrical and thermal conductivity, low effective surface area, and weak mechanical properties. Therefore, constructing three-dimensional nanoporous carbon materials with continuous structures can provide abundant active sites, large surface area, high porosity, a multidimensional conductive network, and strong mechanical stability for various catalytic reactions.

[0003] Among the existing methods for preparing porous carbon materials, template-based organic synthesis and chemical vapor deposition are commonly used methods. The template-based organic synthesis method requires the removal of the template agent and the steps are complicated; while the chemical vapor deposition method requires a certain nano-metal catalyst to provide conditions for the melting and precipitation of carbon elements to prepare low-dimensional carbon nanomaterials, and its preparation cost requirements are relatively high.

[0004] In order to overcome the weaknesses of the above-mentioned preparation method, the patent publication with patent announcement number CN106784876B discloses a method for preparing a carbon aerogel catalyst with high oxygen reduction performance in one step by polymerizing and carbonizing p-nitroaniline and concentrated sulfuric acid. The specific method is as follows: p-nitroaniline and concentrated sulfuric acid are uniformly mixed in a certain proportion, carbonized at 700-1100°C for 0.5-3h in a tubular furnace under inert gas protection, and the black aerogel-like product is taken out after cooling to room temperature to obtain an N, S-doped carbon aerogel catalyst with high oxygen reduction performance; however, this method is used to prepare an aerogel with catalytic performance, so the conditions in the preparation process are subject to multiple restrictions. The high preparation temperature and long carbonization time result in a high cost for preparing porous carbon materials, reduced preparation efficiency and unfavorable for expanded production.

[0005] Summary of the Invention

[0006] Objectives of the invention: The first objective of the present invention is to provide a method for preparing a nanoporous carbon material with a continuous structure, which has a simple preparation process and low cost;

[0007] The second object of the present invention is to provide an application of the above-mentioned nanoporous carbon material with a continuous structure.

[0008] Technical solution: The method for preparing a nanoporous carbon material with a continuous structure described in the present invention comprises the following steps:

[0009] (1) mixing an aromatic reactant with a strong dehydrating agent and heating the mixture to a molten state; the aromatic reactant is an aromatic compound containing both a nitro group and an amino group, or an aromatic mixture obtained by mixing a compound containing a nitro group and a compound containing an amino group;

[0010] (2) The molten aromatic reactant and the strong dehydrating agent are heated to 220-1000° C. within 30 seconds to 50 minutes to fully react to obtain a nanoporous carbon material with a continuous structure.

[0011] Further, the compound containing both nitro and amino groups includes: nitroaniline, specifically o-nitroaniline, m-nitroaniline, p-nitroaniline; methylnitroaniline, specifically 3-methyl-2-nitroaniline, 3-methyl-4-nitroaniline, 4-methyl-2-nitroaniline, 2-methyl-6-nitroaniline, 2-methyl-4-nitroaniline, 5-methyl-2-nitroaniline and other isomers; fluoronitroaniline, specifically 2-fluoro-4-nitroaniline, 3-fluoro-4-nitroaniline, 2,6-difluoro-p-nitroaniline, etc.; chloronitroaniline; nitronaphthylamine, specifically 2-nitronaphthylamine, 3-nitronaphthylamine, 4-nitronaphthylamine, 5-nitronaphthylamine, etc. -nitronaphthylamine; the compound containing nitro in the mixture is: one or more of 1-chloro-4-nitronaphthalene, 2-methyl-1-nitronaphthalene, 3-methyl-1-nitronaphthalene, 1-methyl-4-nitronaphthalene, 1-fluoro-2-nitrobenzene, o-nitrotoluene, m-nitrotoluene, p-nitrotoluene, o-nitrochlorobenzene, m-nitrochlorobenzene, p-nitrochlorobenzene, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, etc.; the compound containing amino in the mixture is: one or more of 1-chloro-2-naphthylamine, 2-chloro-1-naphthylamine, aniline, o-aminotoluene, m-aminotoluene, p-aminotoluene, o-chloroaniline, m-chloroaniline, p-chloroaniline, etc.

[0012] Furthermore, the strong dehydrating agent is one or more of concentrated sulfuric acid, fuming sulfuric acid, phosphorus pentoxide, phosphoric acid, sodium hydroxide, and calcium oxide.

[0013] Furthermore, the temperature at which the molten state is maintained in step (1) is not higher than 210°C.

[0014] Furthermore, the reaction temperature in step (2) is 220-500°C, wherein the volume change of the carbon material is the largest at 500°C. The higher the temperature between 220-500°C, the greater the change in the volume expansion of the carbon material. After exceeding 500°C, the change in the volume expansion of the carbon material no longer increases significantly. Therefore, the preferred temperature for controlling the volume expansion is 220-500°C. If you want to obtain the maximum volume, the optimal temperature is 500°C.

[0015] Furthermore, in step (2), the reaction heating rate is 1°C / min to 100°C / s, wherein the volume expansion change of the carbon material is the largest at 50°C / s, and the higher the heating rate, the greater the volume change of the carbon material. However, when the heating rate exceeds 50°C / s, the change in the volume expansion of the carbon material gradually decreases.

[0016] Furthermore, the mass ratio of the aromatic compound to the strong dehydrating agent is in the range of 1:0.2-5, wherein when the dehydrating agent is concentrated sulfuric acid, the carbon material with the largest volume expansion is obtained at a mass ratio of 1:1.2; when the dehydrating agent is phosphorus pentoxide, the carbon material with the largest volume expansion is obtained at a mass ratio of 1:2; for example, the aromatic compound is one or both of o-nitroaniline or p-nitroaniline, the strong dehydrating agent is concentrated sulfuric acid, and the mass ratio of the two is 1:0.2-5, wherein 1:1.2 is the optimal condition; the aromatic compound is one or both of o-nitroaniline or p-nitroaniline, the strong dehydrating agent is phosphorus pentoxide, and the mass ratio of the two is 1:0.2-5, wherein 1:2 is the optimal condition; the aromatic compound is one or more compounds containing both nitro and amino groups, the strong dehydrating agent is concentrated sulfuric acid, and the mass ratio of the two is 1:0.2-5, wherein 1:1.2 is the optimal condition.

[0017] Furthermore, when the aromatic reactant is an aromatic mixture obtained by mixing a nitro-containing compound and an amino-containing compound, the nitro-containing compound and the amino-containing compound are mixed in equal proportions according to the amount of substances.

[0018] The above-mentioned nanoporous carbon material with a continuous structure is used in the preparation of fireproof and heat-insulating materials, solar heat-absorbing materials, seawater purification materials, battery electrode materials and adsorption materials.

[0019] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: 1. The preparation method of the present invention utilizes organic synthesis and inorganic high-temperature carbonization to achieve a continuous structure of nanoporous carbon materials based on dehydration expansion of metal-free carbon sources; and the method has low preparation cost, simple preparation conditions and high efficiency, and can be commercialized on a large scale; the carbon material prepared by this method has a minimum density of 1g / L, which is ultra-low, and has a density of 200-400m 2 / g of large specific surface area, with excellent adsorption performance; 2. The carbon material prepared by this method has a photothermal conversion efficiency of 82%, can quickly heat up under extremely short light conditions, achieve the effect of local heating, and the unique bubble chamber structure can maintain heat preservation to prevent heat loss, and can be used as a high-efficiency heating and heat preservation material. The larger the volume of the same mass, the larger the area that the material per unit mass can be evenly dispersed, thereby absorbing more solar energy; 3. The carbon material prepared by this method has a high photothermal conversion efficiency. The carbon material can be used in the field of water evaporation purification, and can reduce the actual seawater ion concentration to below 4 orders of magnitude. It has an excellent salt desorption effect, meets the demand standards of organisms for clean water resources, and can be applied to salt water purification projects in saline-alkali lands. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a scanning electron microscope image of the carbon material prepared in Example 1;

[0021] FIG2 is a BET graph of specific surface area test of the carbon materials prepared in Example 1 and Example 92;

[0022] FIG3 is a BET trend diagram of the specific surface area test of the carbon material obtained in Example 1 as the preparation temperature changes;

[0023] FIG4 is a temperature change curve diagram of the photothermal conversion experiment of the carbon material prepared in Example 1;

[0024] FIG5 is a comparison chart of ion concentration changes before and after the carbon material prepared in Example 1 is applied to seawater desalination;

[0025] FIG6 is a comparison chart of water evaporation rates of the carbon material prepared in Example 1 applied to samples with different specific surface areas;

[0026] FIG7 is a linear sweep voltammetry curve obtained by testing oxygen reduction of the carbon material electrode prepared in Example 1;

[0027] FIG8 is a trend diagram of the volume change of the carbon material obtained by changing the heating rate of the carbon material in Example 93. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0029] Example 1

[0030] Step 1: Place 3g of o-nitroaniline in a porcelain boat and add 3.68g of concentrated sulfuric acid in a mass ratio of 1:1.2. Place the boat in the center of the heating plate and heat it to 210°C. Once the o-nitroaniline is completely melted, heat it again.

[0031] Step 2: The temperature was raised to 500°C for the second time within 30 seconds. The mixed solution boiled and expanded rapidly during the 10-second reaction process, with the volume expanding to 220 times that of the raw material, obtaining a three-dimensional nanoporous carbon material with a continuous structure as shown in Figure 1a. It can be seen that the prepared three-dimensional carbon material is formed by the mutual squeezing of carbon bubbles, and the average diameter of these bubbles is about 50μm. The BET trend diagram of the carbon material changing with temperature can be seen in Figure 3. The BET increases significantly from 210°C to 300°C and tends to equilibrium after 300°C.

[0032] The preparation methods of Examples 2-91 are basically the same as those of Example 1, except that the aromatic reactants, strong dehydrating agents and mass ratios used are set according to the contents of Table 1. When the aromatic reactant is an aromatic mixture containing both nitro and amino groups, the nitro-containing and amino-containing compounds are mixed in equal proportions according to the amount of substance; the morphology of the carbon materials prepared in each example is a continuous porous bubble structure.

[0033] Example 92

[0034] The preparation method was essentially the same as in Example 1, except that the secondary heating temperatures were 210°C, 300°C, and 400°C, respectively. At 210°C, the reaction took 20-30 minutes to complete, as shown in Figure 2a. At 300°C, the reaction took 5 minutes to complete, as shown in Figure 2b. At 400°C, the reaction took 1 minute to complete, as shown in Figure 2c. The higher the temperature, the faster the reaction rate. There was no significant difference in reaction rate at 500°C and above, as shown in Figure 2d for the BET data of the reaction completed at 500°C.

[0035] Example 93

[0036] The preparation methods are basically the same as those in Example 1, except that when the temperature is raised to 500°C for the second time, the change in the heating rate affects the volume of the carbon material. FIG8 shows the volume change process of the carbon material when the heating rate is in the range of 0-80°C / s. As shown in FIG8 , the volume change of the obtained carbon material becomes more obvious as the heating rate gradually increases. When the heating rate is 50°C / s, the volume change of the carbon material is the largest. After the heating rate is higher than 50°C / s, the volume change of the carbon material decreases.

[0037] As can be seen from Table 1, the expansion volume of the carbon materials prepared using concentrated sulfuric acid and fuming sulfuric acid as dehydrating agents is better than that of other dehydrating agents.

[0038] It can be seen from Examples 1-3, 9-10, 19-21, 27-29, 39-41, and 83-85 in Table 1 that when the aromatic reactants react with concentrated sulfuric acid, the expanded volume of the carbon material first increases and then decreases as the amount of concentrated sulfuric acid added increases.

[0039] As can be seen from Table 1, the expanded volume of the carbon material generated by the reaction of o-nitroaniline, p-nitroaniline or a mixture thereof with concentrated sulfuric acid or fuming sulfuric acid is more than 150 times the volume of the raw material; in Examples 83-91, the expanded volume of the carbon material generated by the reaction of methyl nitroaniline compounds as aromatic reactants with concentrated sulfuric acid is 55 times or more than that of the raw material, slightly less than that of o-nitroaniline and p-nitroaniline. Taking Example 83 as an example, the electron microscope scanning image of the carbon material prepared therefrom is shown in Figure 1d; in Examples 27-32, the expanded volume of the carbon material generated by the reaction of nitro naphthylamine compounds as aromatic reactants with concentrated sulfuric acid is 18 times or more than that of the raw material. Taking Example 27 as an example, the electron microscope scanning image of the carbon material prepared therefrom is shown in Figure 1b As shown; in Examples 33-35, the carbon materials generated by the reaction of nitronaphthalene compounds as aromatic reactants with concentrated sulfuric acid do not expand significantly, and have smaller specific surface area and pore size; in Examples 39-43, the carbon materials generated by the reaction of fluoronitroaniline compounds as aromatic reactants with concentrated sulfuric acid have an expansion volume that is 40 times or more of that of the raw material. For the rest, when fluoronitroaniline, the compound containing nitro group in the mixture, and the compound containing amino group in the mixture are used as aromatic reactants and react with concentrated sulfuric acid, the obtained carbon materials still have a certain expansion volume, but the expansion effect is slightly lower than that of other aromatic reactants; Taking Example 37 as an example, the electron microscope scanning image of the prepared carbon material is shown in Figure 1c.

[0040] Table 1

[0041] The carbon materials prepared in Examples 1, 44 and 84 were tested for solar water evaporation efficiency. -2 Under the sunlight intensity of 1.5, 2.5 and 3.5 respectively, the water loss rate of the samples containing saturated water was 1.23, 0.82 and 0.39 kgm -2 The specific surface areas of the carbon materials of Examples 1, 44, and 84 decrease in sequence, indicating that samples with high specific surface areas are conducive to the evaporation of water.

[0042] Take the carbon material of Example 1 and prepare a 1 mg / ml carbon material aqueous solution, ultrasonically disperse it, take 1 ml of the aqueous solution and drop it into a quartz cuvette, and use an 808 nm laser with an intensity of 1 kWm -2 After 60 minutes of irradiation, the solution was shielded from light for another 60 minutes, and then cooled naturally. The photothermal conversion efficiency of the carbon material was found to be 82% through cooling curve fitting. This extremely high photothermal conversion efficiency allows the material to rapidly heat up under illumination, achieving a localized high-temperature heating effect, as shown in Figure 4.

[0043] The actual solar desalination capacity of the carbon material of Example 1 was tested using East China Sea seawater as a test sample. OGN was used as a solar water evaporation filter for seawater desalination. The four main ions Na + Mg 2+ , K + and Ca 2+ It was found that the concentration of the above ions was significantly reduced by about four orders of magnitude after seawater desalination. The significant reduction in ion concentration means that the material has the ability to purify water efficiently and meets the demand standards of organisms for clean water resources, as shown in Figure 5.

[0044] The carbon material catalyst of Example 1 was made into a working electrode with a loading of 0.204 mg cm -2 The oxygen reduction performance of the catalyst was tested using a rotating disk electrode under 0.1 m KOH conditions, and the oxygen reduction linear sweep voltammetry curves were obtained at different rotation speeds. The overpotential generated at 1600 rpm was 525 mV, indicating excellent electrocatalytic oxygen reduction activity, as shown in Figure 7.

Claims

1. A method for preparing a nanoporous carbon material having a continuous structure, characterized in that: The following steps are involved: (1) mixing an aromatic reactant with a strong dehydrating agent and heating the mixture to a molten state; the aromatic reactant is an aromatic compound containing both a nitro group and an amino group, or an aromatic mixture obtained by mixing a compound containing a nitro group and a compound containing an amino group; (2) The molten aromatic reactant and the strong dehydrating agent are heated to 220-1000° C. within 30 seconds to 50 minutes to fully react to obtain a nanoporous carbon material with a continuous structure.

2. The method for preparing carbon material according to claim 1, characterized in that: The aromatic compounds containing both nitro and amino groups include: nitroaniline, methylnitroaniline, fluoronitroaniline, chloronitroaniline, and nitronaphthylamine; The nitro-containing compound in the aromatic mixture includes one or more of 1-chloro-4-nitronaphthalene, 2-methyl-1-nitronaphthalene, 3-methyl-1-nitronaphthalene, 1-methyl-4-nitronaphthalene, 1-fluoro-2-nitrobenzene, o-nitrotoluene, m-nitrotoluene, p-nitrotoluene, o-nitrochlorobenzene, m-nitrochlorobenzene, p-nitrochlorobenzene, o-nitrobenzaldehyde, m-nitrobenzaldehyde, and p-nitrobenzaldehyde; The amino-containing compounds in the aromatic mixture include: one or more of 1-chloro-2-naphthylamine, 2-chloro-1-naphthylamine, aniline, o-aminotoluene, m-aminotoluene, p-aminotoluene, o-chloroaniline, m-chloroaniline, and p-chloroaniline.

3. The method for preparing carbon material according to claim 2, characterized in that: The strong dehydrating agent is one or more of concentrated sulfuric acid, fuming sulfuric acid, phosphorus pentoxide, phosphoric acid, sodium hydroxide, and calcium oxide.

4. The method for preparing carbon material according to claim 1, characterized in that: The reaction temperature of step (2) is 500-1000°C.

5. The method for preparing carbon material according to claim 1, characterized in that: The mass ratio of the aromatic reactant to the strong dehydrating agent is in the range of 1:0.2-5.

6. The method for preparing carbon material according to claim 1, characterized in that: When the aromatic reactant is an aromatic mixture obtained by mixing a nitro-containing compound and an amino-containing compound, the nitro-containing compound and the amino-containing compound are mixed in equal proportions according to the amount of substances.

7. The method for preparing carbon material according to claim 1, characterized in that: The reaction temperature rise rate in step (2) is 1°C / min-100°C / s.

8. The method for preparing carbon material according to claim 7, characterized in that: The reaction temperature rise rate in step (2) is 50°C / s.

9. A nanoporous carbon material with a continuous structure prepared according to the method according to any one of claims 1 to 8.

10. Application of a nanoporous carbon material with a continuous structure in the preparation of fireproof and heat-insulating materials, solar heat-absorbing materials, seawater purification materials, battery electrode materials and adsorption materials.

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