Nitrogen and sulfur co-doped carbon material adsorbent as well as preparation method and application thereof

Abstract

The invention provides a nitrogen and sulfur co-doped carbon material adsorbent as well as a preparation method and application thereof, and belongs to the technical field of new materials. According to the simple and efficient synthesis method of the carbon-based adsorbent, hexamethylenetetramine is used for replacing ammonia and formaldehyde to be polymerized with resorcinol to form resin balls, in addition, NH4 < + > released by hydrolysis of hexamethylenetetramine is also a source of nitrogen in a carbon skeleton, and the surface performance of the resin balls can be improved. Meanwhile, thiourea is introduced, nitrogen and sulfur are doped into resin balls at the same time to participate in formation of pore channels, and the pore diameter structure is adjusted. Finally, through activation modification of KOH, the pore structure of the carbon spheres is further adjusted, more micropores beneficial to separation of CO2 / CH4 and CH4 / N2 are generated, and the simple and effective synthesis method provides huge potential for large-scale production of microporous carbon and nitrogen-doped carbon.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a nitrogen and sulfur co-doped carbon material adsorbent and a preparation method and application thereof. Background Art

[0002] With the crisis of depletion of non-renewable resources such as fossil energy and the increasingly serious environmental problems caused by their burning, energy and environmental issues have become bottleneck issues affecting the sustainable development of the world today. People have gradually realized the importance of the two major issues of energy crisis and green environmental protection.

[0003] As an effective alternative to traditional fossil energy, the consumption of natural gas is increasing year by year. The use of natural gas can achieve near-zero carbon emissions. It is not only a convenient and clean energy source, but can also be used as a chemical raw material. Natural gas is a basic raw material for manufacturing a variety of products, and it can also meet people's energy needs in daily life. According to differences in reservoir occurrence, accumulation mechanism, and mining technology, natural gas can be divided into conventional natural gas and unconventional natural gas, of which unconventional natural gas accounts for more than 50% of natural gas resources. Taking coalbed methane (CH 4 The development and utilization of unconventional natural gas represented by CBM (CH) is of great significance for energy conservation and emission reduction. However, the utilization rate of CBM is only about 40%, because low-concentration CBM (CH 4 Less than 30%) is usually discharged directly into the atmosphere as exhaust gas, which not only wastes energy but also pollutes the environment. Therefore, it is urgent to pay attention to the CH 4 Effective utilization of CH 4 In addition, coalbed methane also contains a certain amount of CO 2 and N 2 , which will seriously corrode pipelines and equipment and reduce the calorific value of coalbed methane. Therefore, in order to effectively utilize low-concentration coalbed methane and reduce air pollution, it is necessary to convert CO 2 and N 2 From CH 4 Separate out.

[0004] At present, the technologies used for gas separation and purification include membrane separation, cryogenic distillation, hydrate separation, adsorption separation, etc. Among the above technologies, pressure swing adsorption (PSA) has attracted much attention due to its advantages such as high energy efficiency, low investment cost, and easy control. The performance of the adsorbent is the core of PSA technology and plays an important role in gas adsorption and separation. So far, a variety of porous adsorbents have been developed for the adsorption and separation of CO 2 / N 2 , CO 2 / CH 4 and CH 4 / N 2Binary mixtures such as metal organic frameworks (MOFs), zeolite molecular sieves and carbon-based materials, including activated carbon and carbon molecular sieves. Among them, porous carbon adsorbents have the advantages of simple preparation, low cost, large specific surface area, high porosity, controllable surface function, strong hydrophobicity, alkali resistance and acid resistance.

[0005] Porous carbon adsorbent for CO 2 / N 2 , CO 2 / CH 4 and CH 4 / N 2 Adsorption separation is mainly based on equilibrium adsorption and kinetic adsorption. Considering that gas mixtures have very similar physical properties (such as the same polarity and similar molecular diameters), the adsorbent should meet specific requirements, such as narrow pore size distribution (PSD) and a well-polarized framework. From a kinetic point of view, recent studies have reported that adsorbents with well-defined microporous structures have good performance in separating small gas molecules of similar size [Chem. Eng. J. 2017, 327, 564–572.]. On the other hand, the polarity of the adsorbent framework can enable weak interactions between gas molecules and polar channels, which may further contribute to the separation of gas mixtures. Nitrogen (N) doping is an effective method to adjust the pore size and increase the polarity of the carbon framework. In CO 2 / CH 4 / N 2 There are a lot of reports on selective adsorption [Chem. Eng. J. 2019, 355, 309–319.] Synthesized organic polymers can effectively adjust their pore structure and easily dope heteroatoms into the carbon skeleton to change the physical and chemical properties of the carbon material surface.

[0006] Research on surface modification, pore size optimization, and gas adsorption performance simulation analysis of new activated carbon materials has always attracted much attention. Min Gu et al. prepared a series of granular activated carbons (GACs) with similar surface properties but different pore structures, and used vacuum pressure swing adsorption (VPSA) to extract methane / nitrogen mixture (CH 4 / N 2 ) to enrich methane. The results show that a larger surface area is conducive to CH 4 Enrichment of CH 4 The effective pore size for enrichment is exist The enrichment effect is best within the range [Separation and Purification Technology, 2015, 146: 213-218.]. The main problem of carbon-based adsorbents today is that their irregular structure and the difficulty in adjusting the pore shape and size greatly limit their practical application and separation performance. Summary of the invention

[0007] The purpose of the present invention is to provide a nitrogen and sulfur co-doped carbon material adsorbent and a preparation method and application thereof, which is used to solve the problem that the carbon-based adsorbent in the prior art has irregular structure, difficulty in adjusting pore shape and size, and leads to the absorption of binary mixture CO 2 / N 2 , CH 4 / CO 2 and CH 4 / N 2 The technical problem is that the separation ability is not high.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing a nitrogen and sulfur co-doped carbon material adsorbent, comprising the following steps:

[0010] Step 1), resorcinol, thiourea, citric acid, hexamethylenetetramine and ethanol solution are mixed to obtain a mixed solution;

[0011] Step 2), subjecting the mixed solution to hydrothermal treatment, and then sequentially subjecting the mixed solution to centrifugation, drying, and heat treatment to obtain nitrogen- and sulfur-co-doped carbon spheres;

[0012] Step 3), dispersing the obtained carbon spheres in a KOH solution, and then sequentially centrifuging, drying, and heat treating to obtain a nitrogen and sulfur co-doped carbon material adsorbent.

[0013] Furthermore, in step 1), the molar ratio of thiourea to resorcinol is 0.5 to 2:1;

[0014] The molar ratio of resorcinol, citric acid and hexamethylenetetramine is 1:0.1-0.8:0.5-2;

[0015] In the ethanol solution, the alcohol-water ratio is 0.3-0.6.

[0016] Furthermore, in step 1), the mixing is performed while stirring at a speed of 400 to 600 rpm.

[0017] Furthermore, in step 2), the temperature of the hydrothermal treatment is 100 to 150° C., and the time of the hydrothermal treatment is 20 to 30 hours.

[0018] Furthermore, in step 2), the centrifugal speed is 9000-10000 rpm, and the centrifugal time is 3-5 min;

[0019] The drying temperature is 50-70° C., and the drying time is 12-24 hours.

[0020] Furthermore, in step 2), the heat treatment temperature is 700-900° C., the heat treatment time is 3-6 hours, and the heating rate is 1.5-3° C. / min.

[0021] Further, in step 3), the concentration of the KOH solution is 2-4 wt%;

[0022] The dispersion speed is 600-700 rpm, and the dispersion time is 0.5-2 hours.

[0023] Furthermore, in step 3), the drying temperature is 50 to 70° C. and the drying time is 12 to 24 hours;

[0024] The heat treatment temperature is 600-700° C., the heat treatment time is 2-5 hours, and the heating rate is 0.5-1.5° C. / min.

[0025] The present invention also provides a nitrogen and sulfur co-doped carbon material adsorbent prepared by the above preparation method.

[0026] The present invention also provides a nitrogen and sulfur co-doped carbon material adsorbent for adsorbing and separating a binary mixture CO 2 / N 2 , CO 2 / CH 4 and CH 4 / N 2 Application in.

[0027] Beneficial effects of the present invention:

[0028] The present invention proposes a simple and efficient method for synthesizing a carbon-based adsorbent, wherein hexamethylenetetramine is used to replace ammonia and formaldehyde to polymerize with resorcinol to form resin balls. In addition, NH 4 + It is also the source of nitrogen in the carbon skeleton, which can improve the surface properties of the resin ball. At the same time, thiourea is introduced to dope nitrogen and sulfur into the resin ball at the same time, which participates in the formation of pores and adjusts the pore structure, playing an important role in the enrichment of methane. Finally, through KOH activation modification, the pore structure of the carbon ball is further adjusted to produce more favorable CO 2 / CH 4 and CH 4 / N 2 This simple and effective synthetic method offers great potential for large-scale production of microporous carbon and nitrogen-doped carbon.

[0029] The carbon material is synthesized through a one-pot one-step carbonization route. Not only is the method simple and the synthesis cycle short, but the final synthesized carbon material has a spherical structure, a high specific surface area, regular micropores and nitrogen functional groups, and has high methane adsorption capacity and excellent CO under low pressure and normal pressure.2 / CH 4 and CH 4 / N 2 separation performance, which provides new opportunities for carbon-based materials to achieve high methane enrichment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs CO 2 Adsorption isotherm diagram of

[0031] Figure 2 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs CH 4 Adsorption isotherm diagram of

[0032] Figure 3 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs N 2 Adsorption isotherm diagram of

[0033] Figure 4 CO2 of nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 and undoped carbon material adsorbent RFC obtained in Comparative Example 1 2 / CH 4 Adsorption separation ratio curve of ;

[0034] Figure 5 The CH of the nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 and the undoped carbon material adsorbent RFC obtained in Comparative Example 1 is 4 / N 2 Adsorption separation ratio curve of ;

[0035] Figure 6 CO2 of the carbon material adsorbent RFC-2 obtained in Comparative Example 2 without KOH activation 2 / CH 4 Adsorption separation ratio curve of ;

[0036] Figure 7 CH 4 / N 2 Adsorption separation ratio curve. DETAILED DESCRIPTION

[0037] The present invention provides a method for preparing a nitrogen and sulfur co-doped carbon material adsorbent, comprising the following steps:

[0038] Step 1), resorcinol, thiourea, citric acid, hexamethylenetetramine and ethanol solution are mixed to obtain a mixed solution;

[0039] Step 2), subjecting the mixed solution to hydrothermal treatment, and then sequentially subjecting the mixed solution to centrifugation, drying, and heat treatment to obtain nitrogen- and sulfur-co-doped carbon spheres;

[0040] Step 3), dispersing the obtained carbon spheres in a KOH solution, and then sequentially centrifuging, drying, and heat treating to obtain a nitrogen and sulfur co-doped carbon material adsorbent.

[0041] In the present invention, in step 1), the molar ratio of thiourea to resorcinol is 0.5 to 2:1, preferably 1 to 1.8:1, and more preferably 1.5:1;

[0042] The molar ratio of resorcinol, citric acid and hexamethylenetetramine is 1:0.1-0.8:0.5-2, preferably 1:0.43:0.5-2, and more preferably 1:0.43:1;

[0043] In the ethanol solution, the alcohol-water ratio is 0.3-0.6, preferably 0.4.

[0044] In the present invention, in step 1), the mixing is performed under stirring, and the stirring speed is 400-600 rpm, preferably 500 rpm.

[0045] In the present invention, in step 1), the stirring time is until the solution becomes clear and transparent.

[0046] In the present invention, in step 2), the temperature of the hydrothermal treatment is 100-150°C, preferably 120-140°C, and more preferably 130°C; the time of the hydrothermal treatment is 20-30h, preferably 23-27h, and more preferably 25h.

[0047] In the present invention, in step 2), the hydrothermal treatment is carried out in a hydrothermal autoclave lined with polytetrafluoroethylene.

[0048] In the present invention, in step 2), the centrifugal speed is 9000-10000 rpm, preferably 9500 rpm; the centrifugal time is 3-5 min, preferably 4 min;

[0049] The drying temperature is 50-70° C., preferably 60° C.; the drying time is 12-24 hours, preferably 15-20 hours, and more preferably 18 hours.

[0050] In the present invention, in step 2), the heat treatment temperature is 700-900°C, preferably 750-850°C, and more preferably 800°C; the heat treatment time is 3-6h, preferably 4h; the heating rate is 1.5-3°C / min, preferably 2°C / min.

[0051] In the present invention, in step 2), the heat treatment is performed under a nitrogen atmosphere.

[0052] In the present invention, in step 2), the nitrogen and sulfur co-doped carbon spheres are in powder form.

[0053] In the present invention, in step 3), the concentration of the KOH solution is 2-4wt%, preferably 3wt%;

[0054] The dispersion rotation speed is 600-700 rpm, preferably 650 rpm; the dispersion time is 0.5-2 h, preferably 1-1.5 h, and more preferably 1.2 h.

[0055] In the present invention, in step 3), the drying temperature is 50-70°C, preferably 55-65°C, and more preferably 60°C; the drying time is 12-24h, preferably 15-20h, and more preferably 18h.

[0056] In the present invention, in step 3), the heat treatment temperature is 600-700°C, preferably 630-670°C, and more preferably 650°C; the heat treatment time is 2-5h, preferably 3h; the heating rate is 0.5-1.5°C / min, preferably 1°C / min.

[0057] The present invention also provides a nitrogen and sulfur co-doped carbon material adsorbent prepared by the above preparation method.

[0058] The present invention also provides a nitrogen and sulfur co-doped carbon material adsorbent for adsorbing and separating a binary mixture CO 2 / N 2 , CO 2 / CH 4 and CH 4 / N 2 Application in.

[0059] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] Mix 1 mol of thiourea, 1 mol of resorcinol, 0.43 mol of citric acid, 1 mol of hexamethylenetetramine and an ethanol solution with an alcohol-water ratio of 0.4, and stir at 500 rpm until the solution is clear and transparent. Then transfer the obtained mixed solution to a hydrothermal kettle lined with polytetrafluoroethylene, hydrothermally treat it at 130°C for 25 hours, then centrifuge it at 9500 rpm for 4 minutes, dry it at 60°C for 20 hours, place the obtained resin ball powder in a nitrogen atmosphere, heat it to 800°C at a rate of 1.5°C / min for 4 hours, and obtain nitrogen and sulfur co-doped carbon ball powder;

[0062] The obtained nitrogen and sulfur co-doped carbon ball powder was dispersed in a 2wt% KOH solution at a rotation speed of 600 rpm for 1 hour to obtain a suspension. After centrifugation, it was dried at 60°C for 23 hours and then heat-treated at 650°C for 3 hours to obtain a nitrogen and sulfur co-doped carbon material adsorbent, which was recorded as TURFC-1.

[0063] The carbon material obtained in Example 1 was used as an adsorbent and its performance was tested using a gas adsorption tester.

[0064] Adsorbent pretreatment: Place the adsorbent to be tested in a 120°C oven and dry overnight to remove gas residues on the adsorbent;

[0065] Adsorbent filling: Weigh 2g of adsorbent and place it in the adsorption tank. Use absorbent cotton to seal the top to prevent adsorbent powder from entering the pipeline and affecting the operation of the solenoid valve and the measurement accuracy. Connect the adsorption tank to the adsorption device and wait for measurement;

[0066] Leak detection of adsorption device: Place the adsorption device in a constant temperature water bath at the temperature to be tested, and fill the adsorption device with 0.7MPa of He for leak detection to ensure the airtightness of the gas path;

[0067] Determination of adsorption isotherm: Turn on the measuring device and run it automatically. In the automatic process, first fill the dead volume of the measuring device with helium, and then perform the isotherm measurement of the adsorbent. During the measurement, fill the gas to be measured to the specified pressure. Then measure the corresponding pressure before and after adsorption. 2 and CH 4 The adsorption on the adsorbent is reversible and can be desorbed and regenerated under vacuum. 2 After the adsorption isotherm of CH 4 Determination of isotherms. 2 Gas line changed to CO 2 , can test CO under the same conditions 2 The adsorption isotherm.

[0068] Adsorbent recovery: After the determination process is completed, the adsorbent is taken out and placed in a 120°C oven for drying and regeneration, waiting for subsequent processing.

[0069] Figure 1 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs CO 2 The adsorption isotherm diagram of Figure 2 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs CH 4 The adsorption isotherm diagram of Figure 3 The nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 adsorbs N 2 The adsorption isotherm of Figures 1 to 3 As shown, the carbon material adsorbent TURFC-1 co-doped with nitrogen and sulfur has a carbon dioxide adsorption capacity of 48.88 mL / g, a methane adsorption capacity of 19.54 mL / g, and a nitrogen adsorption capacity of 5.22 mL / g at 0.1 MPa and 30°C; while the carbon material adsorbent RFC without doping has a carbon dioxide adsorption capacity of 37.39 mL / g, a methane adsorption capacity of 17.95 mL / g, and a nitrogen adsorption capacity of 6.24 mL / g at 0.1 MPa and 30°C. It can be seen that the carbon material adsorbent TURFC-1 has better carbon dioxide / methane and methane / nitrogen separation performance.

[0070] Example 2

[0071] 0.5 mol of thiourea, 1 mol of resorcinol, 0.8 mol of citric acid, 2 mol of hexamethylenetetramine and an ethanol solution with an alcohol-water ratio of 0.4 were mixed and stirred at 450 rpm until the solution became clear and transparent. The mixed solution was then transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally treated at 100°C for 30 hours, then centrifuged at 9000 rpm for 5 minutes, dried at 50°C for 12 hours, and the obtained resin ball powder was placed in a nitrogen atmosphere and heated to 700°C at a rate of 2°C / min for 4 hours to obtain nitrogen and sulfur co-doped carbon ball powder;

[0072] The obtained nitrogen and sulfur co-doped carbon ball powder was dispersed in a 2wt% KOH solution at a rotation speed of 600 rpm for 1 hour to obtain a suspension. After centrifugation, it was dried at 60°C for 15 hours and then heat-treated at 600°C for 3 hours to obtain a nitrogen and sulfur co-doped carbon material adsorbent, which was recorded as TURFC-0.5.

[0073] Adsorption isotherm test results: The adsorption capacity of carbon dioxide of nitrogen and sulfur co-doped carbon material adsorbent TURFC-0.5 at 0.1MPa and 30°C is 47.21mL / g, the adsorption capacity of nitrogen is 5.42mL / g, and the adsorption capacity of methane is 19.02mL / g. The carbon dioxide / methane separation ratio at 0.1MPa and 30°C is 2.63, and the methane / nitrogen separation ratio is 3.51.

[0074] Example 3

[0075] 2 mol of thiourea, 1 mol of resorcinol, 0.1 mol of citric acid, 0.5 mol of hexamethylenetetramine and an ethanol solution with an alcohol-water ratio of 0.4 were mixed and stirred at a speed of 550 rpm until the solution became clear and transparent. The obtained mixed solution was then transferred to a hydrothermal kettle lined with polytetrafluoroethylene, hydrothermally treated at 150°C for 20 hours, then centrifuged at a speed of 10,000 rpm for 3 minutes, dried at 70°C for 24 hours, and the obtained resin ball powder was placed in a nitrogen atmosphere, heated to 900°C at a rate of 1.5°C / min for heat treatment for 4 hours to obtain nitrogen and sulfur co-doped carbon ball powder;

[0076] The obtained nitrogen and sulfur co-doped carbon ball powder was dispersed in a 2wt% KOH solution at a rotation speed of 700rpm for 1h to obtain a suspension. After centrifugation, it was dried at 70°C for 12h and then heat treated at 700°C for 3h to obtain a nitrogen and sulfur co-doped carbon material adsorbent, which was recorded as TURFC-2.

[0077] Adsorption isotherm test results: The adsorption capacity of carbon dioxide of nitrogen and sulfur co-doped carbon material adsorbent TURFC-2 at 0.1MPa and 30°C is 47.82mL / g, the adsorption capacity of nitrogen is 5.32mL / g, and the adsorption capacity of methane is 19.18mL / g. The carbon dioxide / methane separation ratio at 0.1MPa and 30°C is 2.66, and the methane / nitrogen separation ratio is 3.61.

[0078] Comparative Example 1

[0079] Different from Example 1, in this comparative example, thiourea was not added, and an undoped carbon material adsorbent was obtained, which was recorded as RFC.

[0080] The adsorption capacity of nitrogen, methane and carbon dioxide of the undoped carbon material adsorbent RFC at 0.1MPa and 30°C is 6.24mL / g, 17.95mL / g and 37.39mL / g respectively. The separation ratio of carbon dioxide to methane at 0.1MPa and 30°C is 2.08 and the separation ratio of methane to nitrogen is 2.88.

[0081] Comparative Example 2

[0082] Different from Example 1, in this comparative example, the nitrogen and sulfur co-doped carbon ball powder was not modified by KOH solution, and the obtained carbon material adsorbent was recorded as RFC-2.

[0083] Adsorption isotherm test results: The adsorption capacity of nitrogen by carbon material adsorbent RFC-2 at 0.1MPa and 30°C is 8.10mL / g, the adsorption capacity of methane is 20.56mL / g, and the adsorption capacity of carbon dioxide is 38.61mL / g. The separation ratio of carbon dioxide / methane of RFC-2 at 0.1MPa and 30°C is 2.15, and the separation ratio of methane / nitrogen is 2.82.

[0084] Figure 4 CO2 of nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 obtained in Example 1 and undoped carbon material adsorbent RFC obtained in Comparative Example 1 2 / CH 4 The adsorption separation ratio curve shows that the carbon dioxide / methane separation ratio of nitrogen and sulfur co-doped carbon material adsorbent TURFC-1 at 0.1MPa is 2.68, and the methane / nitrogen separation ratio is 3.74; while the carbon dioxide / methane separation ratio of undoped carbon material adsorbent RFC at 0.1MPa is 2.08, and the methane / nitrogen separation ratio is 2.88. It can be seen that the carbon dioxide / methane and methane / nitrogen separation performance of nitrogen and sulfur co-doped carbon material adsorbent is significantly better than that of unmodified carbon material adsorbent.

[0085] It can be seen from the above embodiments that the present invention provides a nitrogen and sulfur co-doped carbon material adsorbent and its preparation method and application. The present invention significantly improves the adsorption and separation capacity of the adsorbent by doping nitrogen and sulfur. Through the doping of nitrogen and sulfur, the pore structure of the adsorbent is jointly improved, wherein the nitrogen-containing groups also participate in the formation of the pores, while improving the micropore structure, providing more adsorption sites for methane. Through the modification of KOH, the pore structure of the adsorbent is further improved, the specific surface area and micropore volume of the adsorbent are increased, and it is more conducive to the separation of methane / nitrogen. It can be seen that the present invention solves the problems of irregular structure of carbon-based adsorbents in the prior art, the difficulty in adjusting the pore shape and size, and the resulting problems in the adsorption of binary mixtures of CH 4 / CO 2 and CH 4 / N 2 The technical problem is that the separation ability is not high.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen and sulfur co-doped carbon material adsorbent, characterized in that: The following steps are involved: Step 1), resorcinol, thiourea, citric acid, hexamethylenetetramine and ethanol solution are mixed to obtain a mixed solution; Step 2), subjecting the mixed solution to hydrothermal treatment, and then sequentially subjecting the mixed solution to centrifugation, drying, and heat treatment to obtain nitrogen- and sulfur-co-doped carbon spheres; Step 3), dispersing the obtained carbon spheres in a KOH solution, and then sequentially centrifuging, drying, and heat treating to obtain a nitrogen and sulfur co-doped carbon material adsorbent.

2. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 1, characterized in that: In step 1), the molar ratio of thiourea to resorcinol is 0.5 to 2:1; The molar ratio of resorcinol, citric acid and hexamethylenetetramine is 1:0.1-0.8:0.5-2; In the ethanol solution, the alcohol-water ratio is 0.3-0.

6.

3. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 1 or 2, characterized in that: In step 1), the mixing is carried out while stirring at a speed of 400 to 600 rpm.

4. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 3, characterized in that: In step 2), the temperature of the hydrothermal treatment is 100-150° C., and the time of the hydrothermal treatment is 20-30 hours.

5. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 3, characterized in that: In step 2), the centrifugal speed is 9000-10000 rpm, and the centrifugal time is 3-5 min; The drying temperature is 50-70° C., and the drying time is 12-24 hours.

6. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 1, 2 or 4, characterized in that: In step 2), the heat treatment temperature is 700-900° C., the heat treatment time is 3-6 hours, and the heating rate is 1.5-3° C. / min.

7. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 6, characterized in that: In step 3), the concentration of the KOH solution is 2-4 wt%; The dispersion speed is 600-700 rpm, and the dispersion time is 0.5-2 hours.

8. The method for preparing a nitrogen and sulfur co-doped carbon material adsorbent according to claim 4, 5 or 7, characterized in that: In step 3), the drying temperature is 50 to 70° C. and the drying time is 12 to 24 hours; The heat treatment temperature is 600-700° C., the heat treatment time is 2-5 hours, and the heating rate is 0.5-1.5° C. / min.

9. The nitrogen and sulfur co-doped carbon material adsorbent prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the nitrogen and sulfur co-doped carbon material adsorbent according to claim 9 in the adsorption and separation of binary mixtures CO2 / N2, CO2 / CH4 and CH4 / N2.

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