A nitrogen-doped porous carbon material, a preparation method and application thereof

Abstract

The application discloses nitrogen-doped porous carbon material and a preparation method and application thereof. The preparation method of the nitrogen-doped porous carbon material comprises the following steps: 1) after biomass waste is crushed, water is added to perform a hydrothermal reaction to obtain porous carbon particles; 2) azotobacter chroococcum is inoculated into an AzuBay nitrogen-free liquid culture medium, and then the porous carbon particles are added to perform biological nitrogen fixation to obtain the porous carbon particles loaded with microbial nitrogen; and 3) the porous carbon particles loaded with microbial nitrogen are placed in a water vapor-carbon dioxide-nitrogen mixed atmosphere to perform activation, and thus the nitrogen-doped porous carbon material is obtained. The nitrogen-doped porous carbon material is prepared by using the azotobacter chroococcum to take the nitrogen in the air as a nitrogen source, without adding an external nitrogen source, and the process is green and environmentally-friendly, and the preparation cost is low. Finally, the nitrogen-doped porous carbon material mainly containing pyrrole nitrogen as a nitrogen-containing functional group can be prepared, and the type of the nitrogen-containing functional group can be flexibly adjusted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon materials, in particular to a nitrogen-doped porous carbon material and a preparation method and application thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) are common air pollutants, which not only cause great harm to human health, but also bring great safety hazards to industrial production processes due to their low boiling point, flammability, volatility and other characteristics, so it is very important to effectively control and reduce VOCs. Adsorption technology has the advantages of low cost and wide adaptability, and is the most widely used method for VOCs treatment at present, and the performance of the adsorbent is crucial. Porous carbon materials are commonly used adsorbents, but they have low adsorption capacity and poor specificity, which limits their further popularization and application. Studies have shown that nitrogen atoms in nitrogen-doped porous carbon materials can affect the electronegativity of surrounding carbon atoms, create defect sites, and provide alkaline surfaces, which are more conducive to the adsorption of VOCs than porous carbon materials and have better application prospects.

[0003] Currently, the preparation methods of nitrogen-doped porous carbon materials mainly include the following two kinds: 1) two-step pyrolysis method: high-nitrogen biomass is directly pyrolyzed at high temperature as a carbon-nitrogen source, and then activated with potassium hydroxide or other activators; 2) three-step pyrolysis method: carbonization of carbon source, then co-pyrolysis with nitrogen source (melamine, urea, nitrogen-containing phosphate, etc.) to achieve nitrogen doping, and then activated with activators. However, both the two-step pyrolysis method and the three-step pyrolysis method have the problems of complex preparation process, strong corrosion of chemical reagents used, secondary pollution, high cost, etc., and cannot effectively adjust the types of nitrogen-containing functional groups in the nitrogen-doped porous carbon material, thereby limiting the large-scale production and use of nitrogen-doped porous carbon materials.

[0004] Therefore, it is of great significance to develop a simple, green, low-cost preparation method of nitrogen-doped porous carbon material, and to prepare nitrogen-doped porous carbon material with flexible adjustment of the types of nitrogen-containing functional groups. SUMMARY

[0005] The present application relates to the technical field of carbon materials, in particular to a nitrogen-doped porous carbon material and a preparation method and application thereof.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A preparation method of a nitrogen-doped porous carbon material comprises the following steps:

[0008] 1) crushing the biomass waste and adding water to perform a hydrothermal reaction to obtain porous carbon particles;

[0009] 2) inoculating Azotobacter chroococcum into Azotobacter nitrogen-free liquid medium, and then adding porous carbon particles to carry out biological nitrogen fixation, to obtain porous carbon particles loaded with microbial nitrogen;

[0010] 3) placing the porous carbon particles loaded with microbial nitrogen in a water vapor-carbon dioxide-nitrogen mixed gas atmosphere to activate, to obtain nitrogen-doped porous carbon material.

[0011] Preferably, the biomass waste in step 1) is at least one of sugarcane residue, branches and leaves, wood chips, and fruit shells.

[0012] Further preferably, the biomass waste in step 1) is sugarcane residue (nitrogen content ≤0.35wt%).

[0013] Preferably, the diameter or length-width of the granular material formed after the biomass waste in step 1) is crushed is 0.5cm-1.5cm.

[0014] Preferably, the mass ratio of the biomass waste to water in step 1) is 1:1-6.

[0015] Preferably, the hydrothermal reaction in step 1) is carried out at a temperature of 130℃-180℃, and the reaction time is 10h-15h.

[0016] Preferably, after the hydrothermal reaction in step 1), the product is further subjected to filtration separation, drying, and sterilization treatment.

[0017] Preferably, the drying is carried out at a temperature of 80℃-110℃.

[0018] Preferably, the sterilization treatment is carried out by ultraviolet lamp irradiation.

[0019] Preferably, the addition amount ratio of the porous carbon particles to the Azotobacter nitrogen-free liquid medium in step 2) is 1g-110g:100mL.

[0020] Preferably, the pH value of the Azotobacter nitrogen-free liquid medium in step 2) is 7.0-7.2, and the specific composition is as follows: yeast extract: 0.5g / L; mannitol: 20g / L; glucose: 5g / L; sodium malate: 5g / L; sucrose: 5g / L; KH2PO4·2H2O: 0.2g / L; MgSO4·7H2O: 0.2g / L; CaSO4·2H2O: 0.1g / L; K2HPO4·3H2O: 0.8g / L; Na2MoO4·2H2O: trace amount; FeCl3·6H2O: trace amount; and the solvent is water.

[0021] Preferably, the Azotobacter nitrogen-free liquid medium in step 2) is subjected to sterilization treatment.

[0022] Preferably, the Azubuije nitrogen-free liquid medium is sterilized by high-temperature sterilization.

[0023] Preferably, the biological nitrogen fixation in step 2) is carried out at a temperature of 25-32°C, and the nitrogen fixation time is 12h-10 days.

[0024] Preferably, the biological nitrogen fixation in step 2) is carried out under oscillation, and the rotation speed of the oscillator is 160-250rpm.

[0025] Preferably, after the biological nitrogen fixation in step 2), the product is further separated by filtration and dried.

[0026] Preferably, the drying is carried out at a temperature of 80-110°C.

[0027] Preferably, in step 3), the volume ratio of water vapor in the water vapor-carbon dioxide-nitrogen mixed gas atmosphere is 13-17%, the volume ratio of carbon dioxide is 23-27%, and the volume ratio of nitrogen is 56-64%.

[0028] Preferably, the activation in step 3) is carried out at a temperature of 600-1000°C, and the activation time is 1-2.5h.

[0029] A nitrogen-doped porous carbon material prepared by the above method.

[0030] An adsorbent comprising the above nitrogen-doped porous carbon material.

[0031] Use of the above nitrogen-doped porous carbon material for adsorbing volatile organic pollutants.

[0032] The present application has the advantages that: the present application uses Azotobacter chroococcum to prepare nitrogen-doped porous carbon material using atmospheric nitrogen as the nitrogen source, without the need for additional nitrogen source, the process is green and environmentally friendly, the preparation cost is low, and nitrogen-doped porous carbon material mainly containing pyrrole nitrogen functional groups can be prepared, and the type of nitrogen-containing functional groups can be flexibly adjusted.

[0033] Specifically:

[0034] 1) The present application uses Azotobacter chroococcum to fix atmospheric nitrogen as a nitrogen source for nitrogen-doped porous carbon material, which has the advantages of simple process, no secondary pollution, low production cost, green and environmentally friendly, etc. compared with existing nitrogen-doping methods (such as chemical nitrogen source method), and can realize planned production, which has a profound impact on industrialization.

[0035] 2) The present application can prepare the porous carbon material with specific nitrogen-containing functional groups by combining microbial treatment with physical activation method, and the regulation of the nitrogen-containing form is more effective than that of the porous carbon material obtained by other methods;

[0036] 3) The raw material adopted by the present application is biomass waste, which is abundant in source and realizes resource recycling;

[0037] 4) The Azotobacter chroococcum adopted by the present application is a microorganism widely existing in nature, which is easy to survive and the required conditions for culture are simple;

[0038] 5) The nitrogen-doped porous carbon material has good adsorption performance, which can not only meet the needs of organic waste gas treatment in different occasions, but also is suitable for catalysis, separation, environmental protection, energy storage, food, medicine and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 XPS graph of the nitrogen-doped porous carbon material and the porous carbon particles of Example 2.

[0040] Figure 2 Pore size distribution graph of the nitrogen-doped porous carbon material of Example 1, the nitrogen-doped porous carbon material and the porous carbon particles of Example 2.

[0041] Figure 3 Nitrogen adsorption-desorption curve of the nitrogen-doped porous carbon material of Example 1, the nitrogen-doped porous carbon material and the porous carbon particles of Example 2.

[0042] Figure 4 XPS graph of the nitrogen-doped porous carbon material of Example 3 and Example 4.

[0043] Figure 5 Pore size distribution graph of the nitrogen-doped porous carbon material of Example 3 and Example 4.

[0044] Figure 6 Nitrogen adsorption-desorption curve of the nitrogen-doped porous carbon material of Example 3 and Example 4.

[0045] Figure 7 Adsorption performance test result graph of the nitrogen-doped porous carbon material and the porous carbon particles of Examples 1-4. DETAILED DESCRIPTION

[0046] The present application will be further explained and described below in combination with specific embodiments.

[0047] The pH value of the Ashby's nitrogen-free liquid medium in Examples 1-4 is 7.2, and the specific composition is as follows: yeast extract: 0.5 g / L; mannitol: 20 g / L; glucose: 5 g / L; sodium malate: 5 g / L; sucrose: 5 g / L; KH2PO4·2H2O: 0.2 g / L; MgSO4·7H2O: 0.2 g / L; CaSO4·2H2O: 0.1 g / L; K2HPO4·3H2O: 0.8 g / L; Na2MoO4·2H2O: trace amount; FeCl3·6H2O: trace amount; and solvent is water.

[0048] The pretreatment process of Azotobacter chroococcum in Examples 1-4 is as follows: 50 μL of Ashby's nitrogen-free liquid medium is used to completely dissolve 1 ampoule (1 mL in volume) of Azotobacter chroococcum freeze-dried powder (purchased from China Industrial Microbial Culture Collection Center), and the obtained bacterial solution is inoculated into a solid culture medium (in gel form, and the preparation raw materials are as follows: Ashby's medium solid component: 2.18 g; agar: 1.5 g; deionized water: 100 mL), and then incubated at 28°C for 24 h until the colonies develop to complete morphology, and then one colony is inoculated into Ashby's nitrogen-free liquid medium, and then incubated at 28°C for 24 h in a constant temperature shaker, and the above operation is repeated for 3 times, and the best active strain is selected after the strain recovers the activity to prepare Azotobacter chroococcum bacterial solution (stored at -20°C for standby use).

[0049] Example 1:

[0050] A nitrogen-doped porous carbon material is prepared by the following method:

[0051] 1) The bagasse is crushed to form particles with a length and width of 0.5 cm-1.5 cm, and then baked at 80°C for 12 h, and then dispersed by adding water in a mass ratio of 1:6, and then subjected to hydrothermal reaction at 180°C for 12 h, filtered, and the obtained solid is placed in an oven and baked at 80°C for 12 h, and then sterilized by irradiation under a UV lamp for 2 h to obtain porous carbon particles (denoted as SC);

[0052] 2) The Ashby's nitrogen-free liquid medium is sterilized at 121°C for 30 min, and then naturally cooled to room temperature, and then inoculated with Azotobacter chroococcum bacterial solution at an inoculation amount of 100 μL / 100 mL, and then porous carbon particles are added in a ratio of 2.18 g:100 mL, and then subjected to vibration culture at 28°C and a rotation speed of 160 rpm in a constant temperature vibration incubator for 12 h, filtered, and the obtained solid is placed in an oven and baked at 80°C for 12 h to obtain porous carbon particles loaded with microbial nitrogen;

[0053] 3) The porous carbon particles loaded with microbial nitrogen were placed in a tube furnace, and a water vapor-carbon dioxide-nitrogen mixed gas atmosphere (volume ratio of water vapor, carbon dioxide, and nitrogen was 15:25:60) was filled. After heating to 800°C at a heating rate of 10°C / min and holding for 2 h, a nitrogen-doped porous carbon material (denoted as SCM-A12) was obtained.

[0054] Example 2:

[0055] A nitrogen-doped porous carbon material (denoted as SCM-A20) was prepared, which was completely identical to Example 1 except that the “cultured for 12 h” in step 2) was adjusted to “cultured for 20 h”.

[0056] Example 3:

[0057] A nitrogen-doped porous carbon material (denoted as SCM-D5) was prepared, which was completely identical to Example 1 except that the “2.18 g of porous carbon particles were added according to the ratio of 2.18 g of porous carbon particles to 100 mL of Ashby’s nitrogen-free liquid medium” in step 2) was adjusted to “109 g of porous carbon particles were added according to the ratio of 109 g of porous carbon particles to 100 mL of Ashby’s nitrogen-free liquid medium”, and the “cultured for 12 h” in step 2) was adjusted to “cultured for 5 days”.

[0058] Example 4:

[0059] A nitrogen-doped porous carbon material (denoted as SCM-D10) was prepared, which was completely identical to Example 1 except that the “2.18 g of porous carbon particles were added according to the ratio of 2.18 g of porous carbon particles to 100 mL of Ashby’s nitrogen-free liquid medium” in step 2) was adjusted to “109 g of porous carbon particles were added according to the ratio of 109 g of porous carbon particles to 100 mL of Ashby’s nitrogen-free liquid medium”, and the “cultured for 12 h” in step 2) was adjusted to “cultured for 10 days”.

[0060] Performance test:

[0061] 1) The X-ray photoelectron spectroscopy (XPS) spectra of the nitrogen-doped porous carbon material (SCM-A20) and the porous carbon particles (SC) of Example 2 are shown in FIG. 1, the XPS peak separation results of N1s and O1s of SCM-A20 and SC are shown in Table 1, the pore size distribution graphs of the nitrogen-doped porous carbon material (SCM-A12) of Example 1, SCM-A20, and SC are shown in FIG. 2, the nitrogen adsorption-desorption curves of SCM-A12, SCM-A20, and SC are shown in FIG. 3, and the specific surface area and pore volume test results of SCM-A12, SCM-A20, and SC are shown in Table 2. Figure 1 Figure 2 Figure 3

[0062] ​​​Table 1 XPS deconvolution results of N1s and O1s of SCM-A20 and SC

[0063]

[0064] Table 2 Specific surface area and pore volume test results of SCM-A12, SCM-A20 and SC

[0065]

[0066] Note: S BET represents specific surface area, V tot represents total pore volume, V mic represents micropore volume, V meso represents mesopore volume, V mic / V tot represents the percentage content of micropore volume.

[0067] From Figures 1 to 3 and Tables 1-2, we can know that:

[0068] a) The specific surface area of the nitrogen-doped porous carbon material (SCM-A12) of Example 1 is 1175.16 m 2 / g, and the total pore volume is 1.098 cm 3 / g;

[0069] b) The proportion of pyrrole nitrogen in the nitrogen-doped porous carbon material (SCM-A20) of Example 2 is 73.30% (compared with SC, the nitrogen content is significantly improved), the specific surface area is 1338.21 m 2 / g, and the total pore volume is 0.634 cm 3 / g (containing a certain proportion of micropores and mesopores, i.e. containing porous structures of different pore sizes).

[0070] 2) The XPS graphs of the nitrogen-doped porous carbon material (SCM-D5) of Example 3 and the nitrogen-doped porous carbon material (SCM-D10) of Example 4 are shown in Figure 4 , the XPS deconvolution results of N1s, O1s and C1s of SCM-D5 and SCM-D10 are shown in Table 3, the pore size distribution graphs of SCM-D5 and SCM-D10 are shown in Figure 5 (SC as a control), the nitrogen adsorption-desorption curves of SCM-D5 and SCM-D10 are shown in Figure 6 (SC as a control), and the specific surface area and pore volume test results of SCM-D5 and SCM-D10 are shown in Table 4.

[0071] Table 3 XPS deconvolution results of N1s, O1s and C1s of SCM-D5 and SCM-D10

[0072]

[0073] Table 4 Specific surface area and pore volume test results of SCM-D5 and SCM-D10

[0074]

[0075] From Figures 4 to 6 and Tables 3-4, it can be seen that:

[0076] a) the proportion of pyrrolic nitrogen in the nitrogen-doped porous carbon material (SCM-D5) of Example 3 was 49.78%, the specific surface area was 1330.61 m 2 / g, and the total pore volume was 0.921 cm 3 / g;

[0077] b) the proportion of pyrrolic nitrogen in the nitrogen-doped porous carbon material (SCM-D10) of Example 4 was 66.03%, the specific surface area was 1193.28 m 2 / g, and the total pore volume was 0.958 cm 3 / g.

[0078] 3) Adsorption performance test: the ethyl acetate concentration (determined by GC) in the adsorption evaluation device was stabilized at 100 ppm, 0.05 g of the nitrogen-doped porous carbon material (SCM-A12, SCM-A20, SCM-D5 and SCM-D10; SC as a control) was loaded, ethyl acetate-nitrogen mixed gas (the concentration of ethyl acetate was 100 ppm) was introduced, the ethyl acetate concentration at the outlet was determined by GC, and the adsorption capacity of the nitrogen-doped porous carbon material for ethyl acetate was calculated. The test results are shown in Figure 7 and Table 5.

[0079] Table 5 Adsorption performance test results of the nitrogen-doped porous carbon materials and porous carbon particles of Examples 1-4

[0080]

[0081] From Figure 7 and Table 5, it can be seen that the adsorption capacities of SCM-A12, SCM-A20, SCM-D5 and SCM-D10 for ethyl acetate were 132.48 mg / g, 165.11 mg / g, 133.60 mg / g and 144.00 mg / g, respectively, all of which were greater than that of SC.

[0082] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, all of which are included in the protection scope of the present application.

Claims

1. A method for producing a nitrogen-doped porous carbon material, characterized by, The method comprises the following steps: 1) crushing biomass waste and adding water to perform a hydrothermal reaction to obtain porous carbon particles; 2) inoculating Azotobacter chroococcum into Azotobacter nitrogen-free liquid medium, adding the porous carbon particles, and performing biological nitrogen fixation to obtain porous carbon particles loaded with microbial nitrogen; 3) placing the porous carbon particles loaded with microbial nitrogen in a water vapor-carbon dioxide-nitrogen mixed atmosphere to perform activation, thereby obtaining nitrogen-doped porous carbon material; In step 3), the volume ratio of water vapor in the water vapor-carbon dioxide-nitrogen mixed atmosphere is 13% to 17%, the volume ratio of carbon dioxide is 23% to 27%, and the volume ratio of nitrogen is 56% to 64%. In step 3), the activation is performed at a temperature of 600°C to 1000°C, and the activation time is 1h to 2.5h.

2. The method of claim 1, wherein: In step 1), the biomass waste is at least one of sugarcane residue, branches and leaves, wood chips, and fruit shells.

3. The production method according to claim 1 or 2, characterized by: In step 1), the hydrothermal reaction is performed at a temperature of 130°C to 180°C, and the reaction time is 10h to 15h.

4. The method of claim 1, wherein: In step 2), the addition amount ratio of the porous carbon particles to the Azotobacter nitrogen-free liquid medium is 1g to 110g:100mL.

5. The production method according to claim 1 or 4, characterized by: In step 2), the biological nitrogen fixation is performed at a temperature of 25°C to 32°C, and the nitrogen fixation time is 12h to 10 days.

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