Preparation method and application of carbon-based adsorbent

Abstract

The invention belongs to the technical field of solid adsorbents, and particularly relates to a preparation method and application of a carbon-based adsorbent. The preparation method comprises the following steps: adding phenolic resin-based porous carbon and melamine into a hydroxyl-rich solution, carrying out ultrasonic impregnation, calcining the impregnated product, and carrying out vacuum activation to obtain a carbon-based adsorbent; wherein the hydroxyl-rich solution is a mixture of methanol, ethanol and water. The nitrogen-containing functional group is introduced into the carbon-based adsorbent prepared by the method, so that the electron cloud of the porous carbon framework is changed, the carbon-based adsorbent plays an important role in improving the N2 / H2 separation selectivity, the purity of the recovered H2 is high, and the recovery rate of the H2 is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid adsorbents, and particularly relates to a preparation method and application of a carbon-based adsorbent. Background Art

[0002] With the increasing energy demand, the decreasing fossil fuels, and the worsening environmental pollution, it is crucial to find alternative and efficient energy sources. In recent decades, extensive research has been conducted on renewable energy sources such as solar energy, tidal energy, and wind energy, as well as secondary energy sources such as hydrogen energy. Among them, hydrogen, as a green and clean energy source and industrial raw material, is regarded as one of the most promising clean energy sources to replace fossil fuels due to its advantages of high-efficiency utilization, zero emissions, high combustion calorific value, and clean and pollution-free. As a recognized highly efficient clean energy, hydrogen energy is regarded as the cornerstone of the future energy system, and its development and utilization are conducive to alleviating global challenges such as environmental pollution and energy shortage. The energy generated by the complete combustion of hydrogen is higher than that generated by most fuels of the same mass. The heat generated by the combustion of the same mass of hydrogen is about 2.4 times that of methane, 3 times that of gasoline, and 4.5 times that of coke. From an economic perspective, the application of hydrogen can reduce the cost of energy use and improve the efficiency of the energy industry. The wide application of hydrogen in fields such as fuel cells, energy storage, and chemical engineering helps to reduce carbon dioxide emissions and alleviate the dependence on fossil fuels. However, the efficient enrichment and purification of hydrogen are the key challenges in promoting the hydrogen economy. Currently, relatively mature hydrogen production methods include fossil energy (oil, coal, natural gas) reforming to produce hydrogen, electrolysis of water to produce hydrogen, biomass gasification to produce hydrogen, and industrial by-product gas to produce hydrogen. According to the different preparation methods, hydrogen can be divided into gray hydrogen produced by steam methane reforming (SMR) and industrial by-product gas recovery, blue hydrogen produced by combining SMR with carbon capture and storage technology (CCS), and green hydrogen produced by electrolyzing water using renewable energy. According to the data reported by the International Renewable Energy Agency, the production cost of gray hydrogen is about 9-15 yuan / kg, the production cost of blue hydrogen is about 12-18 yuan / kg, and the production cost of green hydrogen is about 21-46 yuan / kg. Therefore, the advantage of producing gray hydrogen from hydrogen-rich industrial by-products such as coke oven gas, chlor-alkali chemical tail gas, and ammonia synthesis purge gas is that it can not only significantly reduce production costs, reduce environmental pollution, and improve resource utilization rate, but also play a unique role in promoting the realization of the carbon neutrality goal. The effective recovery of H2 in industrial hydrogen-rich tail gases (such as ammonia synthesis purge gas) is of great significance for resource utilization and environmental protection. The composition of ammonia synthesis purge gas in the ammonia production system is approximately N2:H2 = 1:3. Currently, the main difficulty in hydrogen recovery is that most industrial hydrogen-rich tail gases contain different concentrations of N2. Because the molecular diameters of N2 and H2 are too similar, the kinetic diameters of N2 and H2 are 2.89 Å and 3.64 Å respectively, resulting in difficult separation, and it is difficult to balance the purity and recovery rate of product H2 in industrial simulations. Therefore, achieving efficient separation of N2 and H2 is crucial for the separation, recovery, and reuse of industrial hydrogen-rich tail gases. Currently, the relatively mature and reported technologies for separating N2 / H2 mainly include membrane separation and adsorption separation. Among them, the adsorption separation technology has the advantages of simple operation, energy saving, and high degree of automation, and is an ideal gas separation technology.

[0003] At present, as a key factor determining the separation efficiency, the screening and preparation of adsorbents are the core of the research on the separation of mixed gases. The selection of adsorbents is limited by the fact that the adsorbent materials must have high selectivity, cyclic stability, and good mechanical properties. Currently, common solid adsorbents mainly include metal-organic frameworks (MOFs), zeolite molecular sieves, porous organic polymers, porous activated carbon, etc. Among them, resin-based spherical porous carbon has broad application prospects in the adsorption field due to its high mechanical strength, large specific surface area, rich pore structure, strong adsorption performance, acid and alkali corrosion resistance, etc. Although porous carbon is widely used in gas adsorption, its defects such as unsatisfactory pore size distribution and limited surface functional groups limit its high-efficiency selectivity in N2 / H2 separation. To meet the industrial separation requirements, it is necessary to modify and regulate the pore structure and surface chemical properties of activated carbon to improve the adsorption selectivity of gases.

[0004] Chinese Patent CN109908864 A discloses a preparation method of a nitrogen-doped porous carbon-based carbon dioxide adsorbent, which includes the following steps: (1) Put amino acids and pore-forming agents into a reaction pot and mix them evenly; (2) Heat the mixture in a high-temperature furnace, wash and dry the product after cooling to obtain a nitrogen-doped carbon-based carbon dioxide adsorbent. In this patent, it is difficult to achieve the full mixing of the carbon source and the nitrogen source through mechanical stirring, and the contact surface between the two is limited, resulting in the nitrogen source being unable to be evenly and effectively embedded in the carbon skeleton.

[0005] How to solve the problems of high energy consumption and complex process in N2 / H2 separation and efficiently achieve the adsorption separation and purification of N2 / H2 is one of the mainstream research directions for H2 recovery at present. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a carbon-based adsorbent. The prepared carbon-based adsorbent has introduced nitrogen-containing functional groups, changed the electron cloud of the porous carbon framework, and played an important role in improving the separation selectivity of N2 / H2. The recovered H2 has high purity and high H2 recovery rate; the present invention also provides the application of the carbon-based adsorbent to solve the problems of high energy consumption and complex process in the existing N2 / H2 separation methods.

[0007] The preparation method of the carbon-based adsorbent described in the present invention is to add phenolic resin-based porous carbon and melamine to a hydroxyl-rich solution for ultrasonic impregnation, and then calcine and vacuum activate the impregnated product to obtain a carbon-based adsorbent; wherein, the hydroxyl-rich solution is a mixture of methanol, ethanol, and water.

[0008] The volume ratio of methanol, ethanol, and water is 0.5 - 2:0.5 - 2:1.

[0009] The temperature of the hydroxyl-rich solution is 80 - 90°C, and the mass ratio of phenolic resin-based porous carbon to the hydroxyl-rich solution is 10:80 - 150.

[0010] The mass ratio of phenolic resin-based porous carbon to melamine is 10:0.5 - 1.

[0011] The phenolic resin-based porous carbon is preferably spherical phenolic resin-based porous carbon.

[0012] The temperature of ultrasonic impregnation is 80 - 90 °C, the time of ultrasonic impregnation is 1 - 3 h, and the ultrasonic power is 100 - 300 W.

[0013] The calcination is stepwise temperature-rising calcination. Nitrogen is introduced for protection during the calcination process. After rising from room temperature to 150 °C, it is calcined for 0.5 - 2 h. After rising from 150 °C to 250 °C, it is calcined for 0.5 - 2 h. After rising from 250 °C to 300 °C, it is calcined for 0.5 - 2 h.

[0014] The temperature of vacuum activation is 110 - 130 °C, and the time of vacuum activation is 12 - 24 h.

[0015] The carbon-based adsorbent prepared by the present invention contains the following elements by mass fraction: C: 88 - 93%, N: 1 - 6%, O: 5 - 6%.

[0016] The diameter of the carbon-based adsorbent is 2.5 - 4 mm, the porosity is 0.3 - 0.5, and the bulk density is 400 - 600 kg / m 3 , and the sphericity is 0.7 - 0.95.

[0017] The application of the carbon-based adsorbent prepared by the preparation method of the carbon-based adsorbent described in the present invention is the application of the carbon-based adsorbent in the separation and purification of N2 / H2.

[0018] The adsorption pressure for the separation and purification of N2 / H2 is 0.9 - 11.1 bar, and the temperature for the separation and purification of N2 / H2 is 5 - 25 °C.

[0019] The application of the carbon-based adsorbent prepared by the preparation method of the carbon-based adsorbent described in the present invention includes the following steps: (a) The first adsorption tower, the second adsorption tower, the third adsorption tower, and the fourth adsorption tower are all filled with the carbon-based adsorbent; (b) The mixed raw material gas of N2 and H2 enters the first adsorption tower through the raw material buffer tank, N2 is pressurized and adsorbed, and H2 is discharged. Then, vacuum is pumped to desorb and release N2. The mixed gas of N2 and H2 in the first adsorption tower is discharged into the first buffer tank. The first adsorption tower and the second adsorption tower are used alternately; (c) The mixed gas of N2 and H2 in the first buffer tank enters the third adsorption tower to pressurize and adsorb N2. After the adsorption is completed, the obtained mixed gas of N2 and H2 is discharged and returned to the feed pipe. Then, vacuum is pumped in the third adsorption tower to desorb and release N2. The obtained mixed gas of N2 and H2 is discharged. The third adsorption tower and the fourth adsorption tower are used alternately.

[0020] The device used for N2 / H2 separation and purification includes a feed pipe, which is connected to a raw material buffer tank. The raw material buffer tank is respectively connected to a first adsorption tower and a second adsorption tower. The first adsorption tower and the second adsorption tower are respectively connected to an H2 product buffer tank. The H2 product buffer tank is connected to an H2 discharge pipeline. The first adsorption tower and the second adsorption tower are connected to each other. The first adsorption tower and the second adsorption tower are respectively connected to a first vacuum pump. The first vacuum pump is connected to a first buffer tank. The first buffer tank is respectively connected to a third adsorption tower and a fourth adsorption tower. The third adsorption tower and the fourth adsorption tower are respectively connected to a second buffer tank. The second buffer tank is connected to the feed pipe. The third adsorption tower and the fourth adsorption tower are connected to each other. The third adsorption tower and the fourth adsorption tower are respectively connected to a second vacuum pump. The second vacuum pump is connected to the discharge pipeline.

[0021] The beneficial effects of the present invention are as follows: Phenolic resin-based porous carbon and melamine are added to a hydroxyl-rich solution for ultrasonic impregnation and pyrolysis. Ultrasonic impregnation enables melamine to adhere to the surface of the porous carbon through physical dispersion, and promotes the combination of melamine and the carbon wall through hydrogen bonding. The interaction between the microporous wall of the porous carbon and nitrogen atoms is enhanced, and nitrogen-containing functional groups are formed after pyrolysis. Moreover, the boiling points of methanol and ethanol are 64.7°C and 78.4°C respectively, and their volatility is higher than that of water. The rapid escape during the calcination stage will make melamine more concentrated on the inner wall of the pores rather than aggregated on the surface, forming more uniform nitrogen doping sites.

[0022] Reasons why the hydroxy-rich solution used in the present invention does not select alcohols such as propanol and alcohols with more than three carbon atoms: First, propanol has relatively high toxicity and a low flash point (15°C), posing a relatively high risk in high-temperature processes; second, as the carbon chain in the alcohol increases, the solubility of melamine becomes lower and lower. Moreover, during the high-temperature calcination process under nitrogen protection, the pyrolysis of high-carbon-chain alcohols such as propanol and alcohols with more than three carbon atoms will generate hydrocarbons such as propylene and propane, increasing the risk of carbon deposition, damaging the porous structure, and hindering the nitrogen doping reaction of melamine. The present invention selects a mixed solution of methanol, ethanol, and water to form a gradient polarity. Compared with ethanol, methanol has a stronger polarity, but excessive polarity may cause the melamine molecules to aggregate due to overly strong hydrogen bonds. Therefore, it is necessary to adjust the overall polarity through ethanol to prevent the solute from aggregating; the hydrogen bond effect of water is higher than that of methanol and ethanol. After methanol and ethanol dissolve melamine, water forms a hydrogen bond network with methanol and ethanol, fixing the dissolved melamine molecules through the hydrogen bond network to prevent melamine from precipitating due to excessively high local concentration; melamine contains multiple polar amino groups and also contains a weakly polar triazine ring structure. When melamine dissolves in the hydroxy-rich solution, the high polarity provided by methanol helps dissolve the polar group amino of melamine, and ethanol assists in dissolving the weakly polar triazine ring structure of melamine. In the initial stage of pyrolysis under nitrogen protection, methanol and ethanol in the hydroxy-rich solution pyrolyze to form a reducing atmosphere such as CO and H2. Pyrolysis in the reducing atmosphere will reduce the oxidation degree of the carbon material, resulting in a decrease in polarity and an increase in non-polarity. The increase in non-polarity will enhance the adsorption capacity for non-polar gases, and the adsorption capacity for N2 is stronger than that for H2. The carbon-based adsorbent contains more pyridine nitrogen and pyrrole nitrogen. Due to the introduction of nitrogen-containing functional groups, the electrostatic potential on the carbon surface changes, and the electron cloud density decreases, showing strong electrophilicity. The adsorption energy of the carbon-based adsorbent for N2 increases greatly, and the difference in the adsorption energy of the carbon-based adsorbent for N2 and the adsorption energy of the carbon-based adsorbent for H2 increases significantly. The introduction of nitrogen-containing functional groups plays an important role in improving the N2 / H2 separation selectivity. The present invention applies the carbon-based adsorbent in the separation and purification of N2 / H2, effectively separating N2 from H2. The purity of the recovered H2 reaches more than 99.2%, and the recovery rate of H2 reaches more than 85.6%, showing broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the XPS diagram of the phenolic resin-based porous carbon in Example 1.

[0024] Figure 2 is the XPS diagram of the carbon-based adsorbent prepared in Example 1.

[0025] Figure 3 is the gas breakthrough curve diagram of the phenolic resin-based porous carbon in Example 1.

[0026] Figure 4 is the gas breakthrough curve diagram of the carbon-based adsorbent prepared in Example 1.

[0027] Figure 5 It is a schematic structural diagram of the device used for the separation and purification of N2 / H2; In the figure: 1, the first adsorption tower; 2, the second adsorption tower; 3, the third adsorption tower; 4, the fourth adsorption tower; 5, the raw material buffer tank; 6, the feed pipe; 7, the H2 product buffer tank; 8, the second buffer tank; 9, the discharge pipeline; 10, the first buffer tank; 101, the ninth valve; 102, the fourth valve; 103, the seventh valve; 201, the fifth valve; 202, the eighth valve; 301, the seventeenth valve; 302, the thirteenth valve; 303, the fifteenth valve; 401, the fourteenth valve; 402, the sixteenth valve; 501, the second valve; 502, the third valve; 601, the first valve; 701, the H2 discharge pipeline; 702, the tenth valve; 801, the nineteenth valve; 901, the eighteenth valve; 902, the second vacuum pump; 1001, the sixth valve; 1002, the eleventh valve; 1003, the twelfth valve; 1004, the first vacuum pump.

[0028] Figure 6 It is the XPS diagram of the carbon-based adsorbent prepared in Example 2. Detailed implementation manners

[0029] The following further describes the present invention in conjunction with embodiments.

[0030] Example 1 First, 0.5 g of melamine was dissolved in 80 g of a hydroxyl-rich solution at 80 °C, then 10 g of phenolic resin-based porous carbon was added, and ultrasonic impregnation was carried out at a constant temperature of 80 °C for 1 h with an ultrasonic power of 200 W. The impregnated product was sent to a tubular furnace for calcination. During the calcination process, nitrogen protection was introduced. After rising from room temperature to 150 °C, calcination was carried out for 1 h. After rising from 150 °C to 250 °C, calcination was carried out for 1 h. After rising from 250 °C to 300 °C, calcination was carried out for 1 h. The calcined sample was activated at 110 °C for 12 h in a vacuum environment to obtain a carbon-based adsorbent, namely nitrogen-doped phenolic resin-based porous carbon; wherein, the hydroxyl-rich solution is a mixture of methanol, ethanol and water, and the volume ratio of methanol, ethanol and water is 1:1:1.

[0031] XPS characterization was carried out on the phenolic resin-based porous carbon and the carbon-based adsorbent, and the results are shown in Figure 1 and Figure 2 . In order to determine the chemical state of N, the N1s spectrum was respectively fitted to four peaks at about 398.5, 400.0, 401.0 and 405.0 eV. The peak with the N1s binding energy peak at about 398.5 eV can be attributed to the signal of nitrogen in pyridine nitrogen; the peak at about 400 eV can be attributed to the signal of nitrogen in pyrrole nitrogen; the peak at about 401 eV can be attributed to the signal of nitrogen in graphitic nitrogen; and the peak at 405 eV and above can be attributed to the signal of nitrogen in nitro compounds. FromFigure 2 It can be seen that the contents of pyridine nitrogen and pyrrole nitrogen in the prepared carbon-based adsorbent are relatively high.

[0032] Penetration experiment: Under the conditions of 298K and 5 bar, a mixed gas penetration experiment of N2 / H2 was carried out on phenolic resin-based porous carbon and carbon-based adsorbent. The gas composition was N2 / H2 / He = 1:3:6 (volume ratio), and the partial pressures corresponding to the three gases were 0.5 bar, 1.5 bar, and 3 bar respectively. The partial pressure of He as the carrier gas was 3 bar. Since it did not participate in adsorption, the total partial pressure of N2 and H2 was 2 bar. The gas penetration curve of phenolic resin-based porous carbon is shown in Figure 3 , and the gas penetration curve of the carbon-based adsorbent is shown in Figure 4 .

[0033] From Figure 3 it can be seen that the breakthrough point of nitrogen was about 15 s later than that of hydrogen; from Figure 4 it can be seen that the breakthrough point of nitrogen was about 46 s later than that of hydrogen; indicating that the adsorption selectivity of the carbon-based adsorbent for N2 was enhanced, and it had better separation performance than phenolic resin-based porous carbon.

[0034] The application of the carbon-based adsorbent in the separation and purification of N2 / H2 is as follows: As Figure 5 shown, the device used for N2 / H2 separation and purification includes a feed pipe 6, the feed pipe 6 is connected to a raw material buffer tank 5, the raw material buffer tank 5 is respectively connected to a first adsorption tower 1 and a second adsorption tower 2, the first adsorption tower 1 and the second adsorption tower 2 are respectively connected to an H2 product buffer tank 7, the H2 product buffer tank 7 is connected to an H2 discharge pipeline 701, the first adsorption tower 1 and the second adsorption tower 2 are connected, the first adsorption tower 1 and the second adsorption tower 2 are respectively connected to a first vacuum pump 1004, the first vacuum pump 1004 is connected to a first buffer tank 10, the first buffer tank 10 is respectively connected to a third adsorption tower 3 and a fourth adsorption tower 4, the third adsorption tower 3 and the fourth adsorption tower 4 are respectively connected to a second buffer tank 8, the second buffer tank 8 is connected to the feed pipe 6, the third adsorption tower 3 and the fourth adsorption tower 4 are connected, and the third adsorption tower 3 and the fourth adsorption tower 4 are respectively connected to a second vacuum pump 902, and the second vacuum pump 902 is connected to a discharge pipeline 9.

[0035] A first valve 601 is provided on the feed pipe 6, a second valve 501 is provided on the pipeline between the raw material buffer tank 5 and the first adsorption tower 1, a third valve 502 is provided on the pipeline between the raw material buffer tank 5 and the second adsorption tower 2, a fourth valve 102 and a sixth valve 1001 are successively provided on the pipeline between the first adsorption tower 1 and the first vacuum pump 1004, a fifth valve 201 and a sixth valve 1001 are successively provided on the pipeline between the second adsorption tower 2 and the first vacuum pump 1004, a seventh valve 103 is provided on the pipeline between the first adsorption tower 1 and the H2 product buffer tank 7, an eighth valve 202 is provided on the pipeline between the second adsorption tower 2 and the H2 product buffer tank 7, a ninth valve 101 is provided on the pipeline between the top of the first adsorption tower 1 and the top of the second adsorption tower 2, a tenth valve 702 is provided on the H2 discharge pipeline 701, an eleventh valve 1002 is provided on the pipeline between the first buffer tank 10 and the third adsorption tower 3, a twelfth valve 1003 is provided on the pipeline between the first buffer tank 10 and the fourth adsorption tower 4, a thirteenth valve 302 and an eighteenth valve 901 are successively provided on the pipeline between the third adsorption tower 3 and the second vacuum pump 902, a fourteenth valve 401 and an eighteenth valve 901 are successively provided on the pipeline between the fourth adsorption tower 4 and the second vacuum pump 902, a fifteenth valve 303 is provided on the pipeline between the third adsorption tower 3 and the second buffer tank 8, a sixteenth valve 402 is provided on the pipeline between the fourth adsorption tower 4 and the second buffer tank 8, a seventeenth valve 301 is provided on the pipeline between the top of the third adsorption tower 3 and the top of the fourth adsorption tower 4, and a nineteenth valve 801 is provided on the pipeline between the second buffer tank 8 and the feed pipe 6.

[0036] The tower heights of both the first adsorption tower 1 and the second adsorption tower 2 are 3.75 m, and the tower diameters are both 0.75 m; the tower heights of both the third adsorption tower 3 and the fourth adsorption tower 4 are 2.25 m, and the tower diameters are both 0.75 m.

[0037] 565 kg of carbon-based adsorbent is respectively loaded into the first adsorption tower 1 and the second adsorption tower 2, and 339 kg of carbon-based adsorbent is respectively loaded into the third adsorption tower 3 and the fourth adsorption tower 4.

[0038] Open the first valve 601 and the second valve 501, and the mixed raw material gas of N2 and H2 (volume ratio N2:H2 = 1:3) enters the raw material buffer tank 5 through the feed pipe 6. The feed flow rate of the mixed raw material gas of N2 and H2 is 1.4×10 -3mol / s, the feed temperature is 25 °C, and the mixed raw material gas of N2 and H2 in the raw material buffer tank 5 is continuously fed into the first adsorption tower 1 until the adsorption pressure reaches 2.0 bar. Then, the first valve 601 and the second valve 501 are closed for adsorption, and N2 is adsorbed in the first adsorption tower 1; when the first adsorption tower 1 is performing adsorption work, the first vacuum pump 1004, the sixth valve 1001, and the fifth valve 201 are opened to evacuate the second adsorption tower 2. After the first adsorption tower 1 reaches the set adsorption time of 116 s, the seventh valve 103 is opened to discharge H2, and H2 enters the H2 product buffer tank 7; the second adsorption tower 2 continues to perform the evacuation work. After the discharge of H2 from the first adsorption tower 1 is completed, the first vacuum pump 1004, the seventh valve 103, the sixth valve 1001, and the fifth valve 201 are closed, and the ninth valve 101 is opened to allow the gas to flow from the first adsorption tower 1 to the second adsorption tower 2, completing the equalization pressure drop work of the first adsorption tower 1 and the equalization pressure rise work of the second adsorption tower 2. The ninth valve 101 is closed, and the first vacuum pump 1004, the fourth valve 102, and the sixth valve 1001 are opened to evacuate and desorb the carbon-based adsorbent in the first adsorption tower 1 to release N2. The obtained mixed gas of N2 and H2 is discharged from the first adsorption tower 1 and enters the first buffer tank 10, serving as the feed gas for the third adsorption tower 3 and the fourth adsorption tower 4; when the first adsorption tower 1 is being evacuated, the first valve 601 and the third valve 502 are opened, and the mixed raw material gas of N2 and H2 enters the raw material buffer tank 5 through the feed pipe 6. The mixed raw material gas of N2 and H2 in the raw material buffer tank 5 is continuously fed into the second adsorption tower 2 until the adsorption pressure reaches 2.0 bar, and then the first valve 601 and the third valve 502 are closed for adsorption, and N2 is adsorbed in the second adsorption tower 2. After the second adsorption tower 2 reaches the set adsorption time of 116 s, the eighth valve 202 is opened to discharge H2, and H2 enters the H2 product buffer tank 7; the first adsorption tower 1 continues to perform the evacuation work. After the discharge of H2 from the second adsorption tower 2 is completed, the first vacuum pump 1004, the eighth valve 202, the fourth valve 102, and the sixth valve 1001 are closed; the tenth valve 702 is opened, and the product gas H2 (purity 99.5%) collected in the H2 product buffer tank 7 is discharged through the H2 discharge pipeline 701; the tenth valve 702 is closed, and the ninth valve 101 is opened to allow the gas to flow from the second adsorption tower 2 to the first adsorption tower 1, completing the equalization pressure rise work of the first adsorption tower 1 and the equalization pressure drop work of the second adsorption tower 2. Close the ninth valve 101, turn on the first vacuum pump 1004, the sixth valve 1001 and the fifth valve 201, evacuate and desorb the carbon-based adsorbent in the second adsorption tower 2 to release N2. The obtained N2 and H2 mixed gas is discharged from the second adsorption tower 2 and enters the first buffer tank 10, serving as the feed gas for the third adsorption tower 3 and the fourth adsorption tower 4; Open the eleventh valve 1002, continuously feed the N2 and H2 mixed gas in the first buffer tank 10 into the third adsorption tower 3. The feed temperature of the N2 and H2 mixed gas is 25°C. After reaching the adsorption pressure of 2.0 bar, close the eleventh valve 1002 for adsorption, and N2 is adsorbed in the third adsorption tower 3; When the third adsorption tower 3 is performing adsorption work, turn on the second vacuum pump 902, the fourteenth valve 401 and the eighteenth valve 901 to evacuate the fourth adsorption tower 4; After the third adsorption tower 3 reaches the set adsorption time of 86 s, open the fifteenth valve 303 to discharge the N2 and H2 mixed gas (volume ratio N2:H2 = 1:3). The N2 and H2 mixed gas enters the second buffer tank 8; The fourth adsorption tower 4 continues to perform the evacuation work; After the third adsorption tower 3 finishes discharging the N2 and H2 mixed gas, close the second vacuum pump 902, the fifteenth valve 303, the fourteenth valve 401 and the eighteenth valve 901, and open the seventeenth valve 301 to make the gas flow from the third adsorption tower 3 to the fourth adsorption tower 4, completing the equal pressure drop work of the third adsorption tower 3 and the equal pressure rise work of the fourth adsorption tower 4; Close the seventeenth valve 301, turn on the second vacuum pump 902, the thirteenth valve 302 and the eighteenth valve 901, evacuate and desorb the carbon-based adsorbent in the third adsorption tower 3 to release N2. The obtained N2 and H2 mixed gas is discharged from the third adsorption tower 3 and enters the discharge pipeline 9, and the N2 and H2 mixed gas is then discharged from the discharge pipeline 9; When the third adsorption tower 3 is being evacuated, open the twelfth valve 1003, and continuously feed the N2 and H2 mixed gas in the first buffer tank 10 into the fourth adsorption tower 4. After reaching the adsorption pressure of 2.0 bar, close the twelfth valve 1003 for adsorption, and N2 is adsorbed in the fourth adsorption tower 4; After the fourth adsorption tower 4 reaches the set adsorption time of 86 s, open the sixteenth valve 402 to discharge the N2 and H2 mixed gas (volume ratio N2:H2 = 1:3). The N2 and H2 mixed gas enters the second buffer tank 8, and the third adsorption tower 3 continues to perform the evacuation work; After the mixture of N2 and H2 is completely discharged from the fourth adsorption tower 4, the second vacuum pump 902, the sixteenth valve 402, the thirteenth valve 302, and the eighteenth valve 901 are closed, and the nineteenth valve 801 is opened. The mixture of N2 and H2 collected in the second buffer tank 8 (volume ratio N2:H2 = 1:3) enters the feed pipe 6; the nineteenth valve 801 is closed, and the seventeenth valve 301 is opened to allow the gas to flow from the fourth adsorption tower 4 to the third adsorption tower 3, completing the equal pressure increase of the third adsorption tower 3 and the equal pressure decrease of the fourth adsorption tower 4; The seventeenth valve 301 is closed, and the second vacuum pump 902, the fourteenth valve 401, and the eighteenth valve 901 are opened to evacuate and desorb the carbon-based adsorbent in the fourth adsorption tower 4 to release N2. The obtained mixture of N2 and H2 is discharged from the fourth adsorption tower 4 into the discharge pipeline 9, and the mixture of N2 and H2 is then discharged from the discharge pipeline 9.

[0039] After detection, the purity of the recovered H2 is 99.5%, and the H2 recovery rate is 88.4%.

[0040] Example 2 First, 1 g of melamine is dissolved in 150 g of a hydroxy-rich solution at 90 °C, then 10 g of phenolic resin-based porous carbon is added, and the mixture is impregnated by ultrasonic waves at a constant temperature of 90 °C for 2 h with an ultrasonic power of 300 W. The impregnated product is sent to a tubular furnace for calcination. During the calcination process, nitrogen is introduced for protection. After rising from room temperature to 150 °C, calcination is carried out for 0.5 h, after rising from 150 °C to 250 °C, calcination is carried out for 2 h, and after rising from 250 °C to 300 °C, calcination is carried out for 0.5 h. The calcined sample is activated at 120 °C for 24 h in a vacuum environment to obtain a carbon-based adsorbent, namely nitrogen-doped phenolic resin-based porous carbon; among them, the hydroxy-rich solution is a mixture of methanol, ethanol, and water, and the volume ratio of methanol, ethanol, and water is 0.5:2:1.

[0041] The XPS diagram of the carbon-based adsorbent is shown in Figure 6 , from Figure 6 it can be seen that the contents of pyridine nitrogen and pyrrole nitrogen in the prepared carbon-based adsorbent are relatively high.

[0042] The adsorption pressure is 0.9 bar, the feed temperature is 20 °C, and other steps are the same as the application of the carbon-based adsorbent in the separation and purification of N2 / H2 in Example 1.

[0043] After detection, the purity of the recovered H2 is 99.3%, and the H2 recovery rate is 86.4%.

[0044] Example 3 First, dissolve 0.7 g of melamine into 100 g of a hydroxyl-rich solution at 85 °C, then add 10 g of phenolic resin-based porous carbon, and impregnate it by ultrasonic wave at a constant temperature of 85 °C for 3 h with an ultrasonic power of 100 W. Feed the impregnated product into a tubular furnace for calcination. During the calcination process, introduce nitrogen for protection. Heat it from room temperature to 150 °C and then calcine for 2 h, heat it from 150 °C to 250 °C and then calcine for 0.5 h, heat it from 250 °C to 300 °C and then calcine for 2 h. Activate the calcined sample at 130 °C for 20 h in a vacuum environment to obtain a carbon-based adsorbent, namely nitrogen-doped phenolic resin-based porous carbon; among them, the hydroxyl-rich solution is a mixture of methanol, ethanol and water, and the volume ratio of methanol, ethanol and water is 2:0.5:1.

[0045] The adsorption pressure is 11.1 bar, the feed temperature is 5 °C, and other steps are the same as the application of the carbon-based adsorbent in the separation and purification of N2 / H2 in Example 1.

[0046] After detection, the purity of the recovered H2 is 99.2%, and the H2 recovery rate is 85.6%.

[0047] Comparative Example 1 The hydroxyl-rich solution is a mixture of methanol and water, and the volume ratio of methanol and water is 1:1. Other steps are the same as in Example 1.

[0048] After detection, the purity of the recovered H2 is 99.1%, and the H2 recovery rate is 80.6%.

[0049] Comparative Example 2 The hydroxyl-rich solution is a mixture of ethanol and water, and the volume ratio of methanol and water is 1:1. Other steps are the same as in Example 1.

[0050] After detection, the purity of the recovered H2 is 99.1%, and the H2 recovery rate is 81.5%.

[0051] Comparative Example 3 The hydroxyl-rich solution is a mixture of methanol and ethanol, and the volume ratio of methanol and ethanol is 1:1. Other steps are the same as in Example 1.

[0052] After detection, the purity of the recovered H2 is 99.2%, and the H2 recovery rate is 82.4%.

[0053] Selective adsorption performance experiment: The steps of the selective adsorption performance experiment are the same as in Example 1. Using A component: N2 and B component: H2 as the feed gas respectively, conduct selective adsorption performance experiments at different feed temperatures (5 °C, 15 °C, 25 °C) and different adsorption pressures (0.98 - 11.08 bar), and measure the saturated adsorption amount of N2 at different adsorption pressures (unit is bar) (unit is mmol / g), the saturated adsorption amount of H2 at different adsorption pressures Saturation adsorption capacity (unit: bar) (unit: mmol / g), and the adsorption selectivity S of the gas was estimated according to the ideal adsorbed solution theory (IAST). The results are shown in Table 1.

[0054] The calculation formula for the adsorption selectivity S is as follows:

[0055] where S is the selectivity of component A relative to component B.

[0056] The larger S is, the better the adsorption separation selectivity of the two gases is.

[0057]

Claims

1. A method for preparing a carbon-based adsorbent, characterized in that Phenolic resin-based porous carbon and melamine are added to a hydroxyl-rich solution for ultrasonic impregnation, and the impregnated product is calcined and vacuum activated to obtain a carbon-based adsorbent; wherein the hydroxyl-rich solution is a mixture of methanol, ethanol and water.

2. The method for preparing a carbon-based adsorbent according to claim 1, characterized in that The volume ratio of methanol, ethanol and water is 0.5-2:0.5-2:

1.

3. The method for preparing a carbon-based adsorbent according to claim 1, characterized in that The temperature of the hydroxyl-rich solution is 80-90° C., the mass ratio of the phenolic resin-based porous carbon to the hydroxyl-rich solution is 10:80-150, and the mass ratio of the phenolic resin-based porous carbon to melamine is 10:0.5-1.

4. The method for preparing a carbon-based adsorbent according to claim 1, characterized in that The temperature of ultrasonic immersion is 80-90°C, the time of ultrasonic immersion is 1-3h, and the ultrasonic power is 100-300W.

5. The method for preparing a carbon-based adsorbent according to claim 1, characterized in that The calcination is a step-by-step temperature calcination, during which nitrogen protection is introduced. The temperature is raised from room temperature to 150°C and then calcined for 0.5-2h, from 150°C to 250°C and then calcined for 0.5-2h, and from 250°C to 300°C and then calcined for 0.5-2h.

6. The method for preparing a carbon-based adsorbent according to claim 1, characterized in that The temperature of vacuum activation is 110-130°C, and the time of vacuum activation is 12-24h.

7. An application of a carbon-based adsorbent prepared by the method for preparing a carbon-based adsorbent according to any one of claims 1 to 6, characterized in that Application of carbon-based adsorbents in N2 / H2 separation and purification.

8. The use according to claim 7, characterized in that The adsorption pressure of N2 / H2 separation and purification is 0.9-11.1 bar, and the temperature of N2 / H2 separation and purification is 5-25°C.

9. The use according to claim 7, characterized in that The steps include: (a) the first adsorption tower (1), the second adsorption tower (2), the third adsorption tower (3) and the fourth adsorption tower (4) are all filled with a carbon-based adsorbent; (b) the mixed raw gas of N2 and H2 passes through the raw material buffer tank (5) and enters the first adsorption tower (1) to adsorb N2 under pressure and then discharge H2, and then vacuumizes and decomposes to release N2. The mixed gas of N2 and H2 in the first adsorption tower (1) is discharged and enters the first buffer tank (10). The first adsorption tower (1) and the second adsorption tower (2) are used alternately; (c) The N2 and H2 mixed gas in the first buffer tank (10) enters the third adsorption tower (3) to adsorb N2 under pressure. After the adsorption is completed, the obtained N2 and H2 mixed gas is discharged and returned to the feed pipe (6). The third adsorption tower (3) is then vacuumed and analyzed to release N2. The obtained N2 and H2 mixed gas is discharged. The third adsorption tower (3) and the fourth adsorption tower (4) are used alternately.

10. The use according to claim 7, characterized in that The device used for N2 / H2 separation and purification comprises a feed pipe (6), the feed pipe (6) is connected to a raw material buffer tank (5), the raw material buffer tank (5) is respectively connected to a first adsorption tower (1) and a second adsorption tower (2), the first adsorption tower (1) and the second adsorption tower (2) are respectively connected to a H2 product buffer tank (7), the H2 product buffer tank (7) is connected to a H2 discharge pipe (701), the first adsorption tower (1) and the second adsorption tower (2) are connected, the first adsorption tower (1) and the second adsorption tower (2) are respectively connected to a first vacuum pump (1004). The first vacuum pump (1004) is connected to the first buffer tank (10), the first buffer tank (10) is respectively connected to the third adsorption tower (3) and the fourth adsorption tower (4), the third adsorption tower (3) and the fourth adsorption tower (4) are respectively connected to the second buffer tank (8), the second buffer tank (8) is connected to the feed pipe (6), the third adsorption tower (3) and the fourth adsorption tower (4) are connected, the third adsorption tower (3) and the fourth adsorption tower (4) are respectively connected to the second vacuum pump (902), and the second vacuum pump (902) is connected to the discharge pipe (9).

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