A preparation process of carbon molecular sieve

Abstract

The invention discloses a preparation process of a carbon molecular sieve, which belongs to the technical field of carbon molecular sieves. The key points of the technical solution include the following preparation steps: S1, crushing floral mud and pre-carbonizing it; S2, ball-milling the pre-carbonized floral mud material into floral mud powder; S3, extruding the floral mud powder and then carbonizing it; S4, the carbonization process is carried out according to the following gradient: the first stage: heating from room temperature to 600°C and passing nitrogen; the second stage: 600-750°C, passing nitrogen and ammonia, and keeping warm at 750°C for 1-2 hours; the third stage: heating from 750 to 800°C, passing nitrogen, ammonia and carbon dioxide; the fourth stage: 800-900°C, passing nitrogen and carbon dioxide, and keeping warm for 0.5-1 hour; S5, depositing and adjusting the pores, and then cooling to obtain the carbon molecular sieve. The present application effectively improves the adsorption effect of oxygen by introducing pyridine nitrogen on the pore surface and performing a step-by-step carbonization treatment, thereby achieving effective separation of oxygen and nitrogen.

Description

Technical Field

[0001] The present invention relates to the field of preparation of carbon molecular sieves, in particular to a preparation process of carbon molecular sieves. Background Art

[0002] Carbon molecular sieve is a corrosion-resistant porous carbon skeleton material. Due to its high specific surface area, excellent adsorption capacity and thermal stability, it is widely used in pressure swing adsorption air separation technology (nitrogen generator) for air separation to produce nitrogen-rich gas. The principle is that carbon molecular sieve has a large number of tiny pores. The molecular diameter of oxygen is smaller than that of nitrogen. After the gas enters the carbon molecular sieve adsorbent, the oxygen diffuses faster and enters the solid phase of the carbon molecular sieve, while the nitrogen with a slower diffusion rate enters the gas phase more, thereby achieving the separation of oxygen and nitrogen.

[0003] The raw materials of existing carbon molecular sieves include coal, fruit shells, coconut shells, phenolic resins and floral mud. When floral mud is used to prepare carbon molecular sieves, waste resources can be utilized and environmental pollution can be reduced. At the same time, floral mud retains a high specific surface area after carbonization, which is conducive to gas adsorption. However, the floral mud carbon molecular sieve has a low separation efficiency for oxygen and nitrogen. The reason is that although the carbon structure derived from floral mud can create micropores, the pore size discreteness is as high as ±0.5nm. When the partial pore size exceeds 0.43nm, nitrogen is more strongly adsorbed than oxygen due to the longer-range dispersion force. This leads to a low separation efficiency of floral mud carbon molecular sieve for oxygen and nitrogen, and ultimately makes it difficult for the purity of the produced nitrogen to reach the ideal level. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a preparation process of a carbon molecular sieve. The present application effectively improves the adsorption effect of oxygen and realizes the effective separation of oxygen and nitrogen by introducing pyridine nitrogen on the pore surface and performing a step-by-step carbonization treatment.

[0005] The present invention provides a process for preparing a carbon molecular sieve using the following technical solutions:

[0006] A process for preparing a carbon molecular sieve comprises the following steps:

[0007] S1. Crushing the floral mud and pre-carbonizing it;

[0008] S2. ball-milling the pre-carbonized floral mud material into floral mud powder;

[0009] S3, mixing and kneading the flower mud powder, a binder, and water, extruding and then carbonizing;

[0010] S4, the carbonization process is carried out according to the following gradient: the first stage: heating from room temperature to 600 ° C, passing nitrogen; the second stage: 600-750 ° C, passing nitrogen and ammonia, and keeping warm at 750 ° C for 1-2 hours; the third stage: heating from 750 to 800 ° C, passing nitrogen, ammonia and carbon dioxide, and the concentration of ammonia is less than the concentration of ammonia in the second stage; the fourth stage: 800-900 ° C, passing nitrogen and carbon dioxide, and keeping warm for 0.5-1 hour;

[0011] S5, deposition and pore adjustment: the primary product obtained in step S4 is heated to 700-800° C. under nitrogen protection, a regulating agent is introduced for pore adjustment treatment, and then cooled to obtain a carbon molecular sieve.

[0012] By adopting the above-mentioned technical scheme, the present application selects gradient heating and introduces different gases at different stages during the carbonization process, which helps to maintain the overall structure of the flower mud molecular sieve and avoid disintegration during the heating process. When nitrogen is fully introduced in the first stage, nitrogen is used as a carrier gas to carry away the pyrolysis tar, reduce the clogging of the gaps by carbon deposition, and at the same time avoid the oxidation and combustion of the flower mud; when nitrogen and ammonia are introduced in the second stage, at this temperature, ammonia doping can introduce pyridine nitrogen on the pore surface, and its lone pair electrons form a charge transfer complex with oxygen, thereby significantly improving the adsorption capacity of oxygen and helping to improve the purity of nitrogen. The third stage is a transition stage, in which nitrogen, ammonia and carbon dioxide are introduced at the same time, and the concentration of ammonia is greatly reduced to avoid surface structural stress caused by gas mutation. Nitrogen and carbon dioxide are introduced for activation in the third stage, and the etching rate is controllable to avoid pore collapse. The reason is that the electron density of the carbon surface increases after nitrogen doping, which inhibits excessive erosion of the carbon skeleton by carbon dioxide.

[0013] Therefore, the present application improves the pore size discreteness problem of the flower mud carbon molecular sieve through a specific carbonization gradient and deposition pore adjustment step, thereby improving the separation efficiency of oxygen and nitrogen, and thereby improving the purity of nitrogen during nitrogen production.

[0014] Preferably, the heating rate in the first stage is 2-5°C / min, and the heating rate in the second stage is 10-15°C / min.

[0015] By adopting the above technical solution, the heating rate in the first stage is controlled at 2-5°C / min to avoid the rupture of the flower mud precursor due to the heating process. The heating rate in the second stage is controlled at 10-15°C / min. As the carbonization rate increases, the specific surface area, pore volume and micropore volume of the carbon molecular sieve show a continuous increasing trend. The higher heating rate is conducive to the development of the pore structure and increases the release rate of volatile matter.

[0016] Preferably, the nitrogen flow rate in the first stage, the second stage, the third stage and the fourth stage is 200-250 ml / min.

[0017] By adopting the above technical solution, appropriate nitrogen flow rates are used in each stage to ensure the stability and controllability of the carbonization process, which helps to optimize the microporous structure of the carbon molecular sieve, improve the separation efficiency of oxygen and nitrogen, and the purity of nitrogen during nitrogen production.

[0018] Preferably, the ammonia flow rate in the second stage is 20-50 ml / min.

[0019] Preferably, the ammonia flow rate in the third stage is 1.0-2.5 ml / min, and the carbon dioxide flow rate is 10-25 ml / min.

[0020] Preferably, the carbon dioxide flow rate in the fourth stage is 40-100 ml / min.

[0021] By adopting the above technical solution, the carbon dioxide flow rate can be controlled at 40-100 ml / min in the fourth stage of the carbon molecular sieve preparation process, which helps to accurately control the pore structure of the carbon molecular sieve, improve its separation efficiency of oxygen and nitrogen, and increase the purity of nitrogen during nitrogen production. At the same time, the use of flower mud can realize the resource utilization of waste, reduce environmental pollution, and retain a high specific surface area for gas adsorption.

[0022] Preferably, the particle size of the flower mud powder in step S2 is 5-20 μm.

[0023] By adopting the above technical solution, the pre-carbonized floral mud material is ball-milled into floral mud powder with a particle size of 5-20 μm, which is conducive to the subsequent thorough stirring and kneading with the binder and water, ensuring that the materials are evenly mixed, providing a good foundation for the subsequent extrusion molding and carbonization steps, and helping to improve the performance and quality of the final carbon molecular sieve. The reason is that the smaller the particle size of the floral mud powder, the more developed the pores of the carbide, and the specific surface area, total pore volume and micropore volume also increase accordingly. In addition, with the increase in specific surface area, the contact area between the gas and solid phases increases, which makes the reaction and mass transfer process of the solid phase easier, and the volatile matter is easier to remove, making it easier to activate at high temperatures. However, if the particle size of the flower mud powder is too small, the risk of sintering during the carbonization process is high, causing the micropores to collapse or close, and the binder is more likely to completely cover the fine particles and block the entrance of the micropores. When the particle size of the flower mud powder is too large, the surface is over-carbonized and the interior is not fully reacted, resulting in uneven distribution of the micropore structure, and the pore size in some areas is too large or no effective micropores are formed, which leads to a decrease in the separation efficiency of the carbon molecular sieve for oxygen and nitrogen.

[0024] Preferably, in step S3, the flower mud powder comprises 100 parts by weight, the binder 35-60 parts by weight, and the water 30-40 parts by weight.

[0025] Preferably, the binder is composed of cardamom phenolic resin and polyethylene glycol 6000 in a weight ratio of (4-8): (3-4).

[0026] By adopting the above technical solution, flower mud powder, binder and water are used in a specific proportion for stirring, kneading, extrusion molding and then carbonization, which can ensure that the materials are fully mixed and formed, which is conducive to the smooth progress of subsequent processes and ultimately improves the overall performance of the carbon molecular sieve. When the proportion of the binder increases, the specific surface area and pore volume show a trend of first increasing and then decreasing, and the micropore volume shows a trend of continuous decrease. The reason is that the flower peat particles as the main raw material form the adsorption body, and the residual carbon after carbonization of the cashew phenolic resin as the binder connects the main particles and also produces a small amount of pores itself. The polyethylene glycol as an auxiliary agent Almost completely decomposed, the decomposition of the binder and the additive produces fast channel pores, which together with the adsorption body form the secondary structure of the carbon molecular sieve; if the proportion of the binder is too large, more residual carbon will be formed after carbonization, which will block the pores of the main adsorption particles to a certain extent, resulting in an unclear secondary structure. When the proportion of the binder is small, the residual carbon of the binder is relatively small, the secondary structure of the sample is obvious, and the pore structure is developed. However, if the binder content is too low, disintegration will occur during the particle forming stage. Therefore, when the binder content is controlled within this range, the performance of the carbon molecular sieve can be effectively guaranteed.

[0027] Preferably, the deposition pore adjustment is carried out in two steps. In the first step, the temperature is 700°C, the benzene concentration is 5-10%, and the treatment time is 40-50 minutes; in the second step, the temperature is 800°C, the water vapor concentration is 4%, and the treatment time is 20 minutes.

[0028] By adopting the above technical solution and a two-step pore adjustment method using benzene and water vapor, the pore size of the carbon molecular sieve can be effectively controlled, thereby improving the separation efficiency of oxygen and nitrogen and increasing the nitrogen concentration during nitrogen production.

[0029] In summary, the present invention has the following beneficial effects: the present application increases the adsorption capacity of oxygen by introducing pyridine nitrogen on the surface of the carbon molecular sieve pores, and at the same time effectively controls the pore size of the carbon molecular sieve by controlling the carbonization process, deposition process and the content of the binder, thereby improving the separation effect of the flower mud carbon molecular sieve on oxygen and nitrogen. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the examples. All reagents without manufacturer's indication are conventional reagent products that can be obtained commercially.

[0031] Example 1

[0032] A process for preparing a carbon molecular sieve comprises the following steps:

[0033] S1. Crushed the floral mud and pre-carbonized it at 350℃ for 0.5h;

[0034] S2. Ball-milling the pre-carbonized floral mud material into floral mud powder, wherein the particle size D50 of the floral mud powder is 5 μm;

[0035] S3, 10kg of flower mud powder, 3.5kg of binder, and 3kg of water were stirred and kneaded, extruded and then carbonized; the binder was composed of cashew phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3;

[0036] S4. The carbonization process is carried out according to the following gradient:

[0037] The first stage: heating from room temperature to 600 ° C, during this stage nitrogen was passed through, the nitrogen flow rate was 200 ml / min, and the heating rate was 2 ° C / min;

[0038] The second stage: heating from 600 to 750 ° C, during this stage nitrogen and ammonia are passed, the nitrogen flow rate is 200 ml / min, the ammonia flow rate is 20 ml / min, the heating rate is 10 ° C / min, and the temperature is heated to 750 ° C and then kept warm for 1 hour;

[0039] The third stage: heating from 750 to 800 ° C, during which nitrogen, ammonia and carbon dioxide are passed through, with a nitrogen flow rate of 200 ml / min, an ammonia flow rate of 1.0 ml / min and a carbon dioxide flow rate of 10 ml / min;

[0040] Stage 4: at 800°C, nitrogen and carbon dioxide were introduced with a nitrogen flow rate of 200 ml / min and a carbon dioxide flow rate of 40 ml / min, and the temperature was kept at 800°C for 1 hour.

[0041] S5, deposition pore adjustment, the primary product obtained in step S4 is deposited and pore adjusted under nitrogen protection, the nitrogen flow rate is 400 mL / min, and the deposition and pore adjustment is carried out in two steps. In the first step, the temperature is 700°C, the benzene concentration is 5%, and the treatment time is 40 minutes; in the second step, the temperature is 800°C, the water vapor concentration is 4%, the treatment time is 20 minutes, and then the carbon molecular sieve is obtained by cooling.

[0042] Example 2

[0043] A process for preparing a carbon molecular sieve comprises the following steps:

[0044] S1. Crushed the floral mud and pre-carbonized it at 350℃ for 0.5h;

[0045] S2. Ball-milling the pre-carbonized floral mud material into floral mud powder, wherein the particle size D50 of the floral mud powder is 5 μm;

[0046] S3, 10kg of flower mud powder, 3.5kg of binder, and 3kg of water were stirred and kneaded, extruded and then carbonized; the binder was composed of cashew phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3;

[0047] S4. The carbonization process is carried out according to the following gradient:

[0048] The first stage: heating from room temperature to 600 ° C, during this stage nitrogen was passed through with a nitrogen flow rate of 250 ml / min and a heating rate of 5 ° C / min;

[0049] The second stage: heating from 600 to 750℃, during which nitrogen and ammonia are passed through, with a nitrogen flow rate of 250ml / min, an ammonia flow rate of 30ml / min, a heating rate of 15℃ / min, and after heating to 750℃, heat preservation treatment is carried out for 1.5h;

[0050] The third stage: the temperature is raised from 750 to 800 ° C. During this stage, nitrogen, ammonia and carbon dioxide are passed through. The nitrogen flow rate is 250 ml / min, the ammonia flow rate is 2.0 ml / min, and the carbon dioxide flow rate is 20 ml / min.

[0051] Stage 4: 850°C, nitrogen and carbon dioxide, nitrogen flow rate of 250 ml / min, carbon dioxide flow rate of 70 ml / min, heat treatment for 1 hour;

[0052] S5, deposition pore adjustment, the primary product obtained in step S4 is deposited and pore adjusted under nitrogen protection, the nitrogen flow rate is 400 mL / min, and the deposition pore adjustment is carried out in two steps. In the first step, the temperature is 700°C, the benzene concentration is 8%, and the treatment time is 40 minutes; in the second step, the temperature is 800°C, the water vapor concentration is 4%, the treatment time is 20 minutes, and then the carbon molecular sieve is obtained by cooling.

[0053] Example 3

[0054] A process for preparing a carbon molecular sieve comprises the following steps:

[0055] S1. Crushed the floral mud and pre-carbonized it at 350℃ for 0.5h;

[0056] S2. Ball-milling the pre-carbonized floral mud material into floral mud powder, wherein the particle size D50 of the floral mud powder is 5 μm;

[0057] S3, 10kg of flower mud powder, 3.5kg of binder, and 3kg of water were stirred and kneaded, extruded and then carbonized; the binder was composed of cashew phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3;

[0058] S4. The carbonization process is carried out according to the following gradient:

[0059] The first stage: heating from room temperature to 600 ° C, during this stage nitrogen was passed through with a nitrogen flow rate of 250 ml / min and a heating rate of 5 ° C / min;

[0060] The second stage: heating from 600 to 750℃, during which nitrogen and ammonia are passed through, with a nitrogen flow rate of 250ml / min, an ammonia flow rate of 50ml / min, a heating rate of 15℃ / min, and after heating to 750℃, heat preservation treatment is carried out for 2h;

[0061] The third stage: the temperature is raised from 750 to 800 ° C. During this stage, nitrogen, ammonia and carbon dioxide are passed through. The nitrogen flow rate is 250 ml / min, the ammonia flow rate is 2.5 ml / min, and the carbon dioxide flow rate is 25 ml / min.

[0062] The fourth stage: 900 ° C, nitrogen and carbon dioxide, nitrogen flow rate of 250 ml / min, carbon dioxide flow rate of 100 ml / min, heat treatment for 1 hour;

[0063] S5, deposition pore adjustment, the primary product obtained in step S4 is deposited and pore adjusted under nitrogen protection, the nitrogen flow rate is 400 mL / min, and the deposition and pore adjustment is carried out in two steps. In the first step, the temperature is 700°C, the benzene concentration is 10%, and the treatment time is 50 minutes; in the second step, the temperature is 800°C, the water vapor concentration is 4%, the treatment time is 20 minutes, and then the carbon molecular sieve is obtained by cooling.

[0064] Example 4

[0065] A preparation process of a carbon molecular sieve, which is different from Example 3 in that the particle size D50 of the flower mud powder is 10 μm, and the rest is the same as Example 3.

[0066] Example 5

[0067] A preparation process of a carbon molecular sieve, which is different from Example 3 in that the particle size D50 of the flower mud powder is 15 μm, and the rest is the same as Example 3.

[0068] Example 6

[0069] A preparation process of a carbon molecular sieve, which is different from Example 3 in that the particle size D50 of the flower mud powder is 20 μm, and the rest is the same as Example 3.

[0070] Example 7

[0071] A preparation process of a carbon molecular sieve, which is different from that of Example 5 in that, in step S3, the weight ratio of 10 kg of flower mud powder, 5 kg of binder, 3.5 kg of water, and cashew phenolic resin to polyethylene glycol 6000 is 2:1, and the rest is the same as that of Example 5.

[0072] Example 8

[0073] A preparation process of a carbon molecular sieve, which is different from Example 5 in that, in step S3, the weight ratio of 10 kg of flower mud powder, 6 kg of binder, 4 kg of water, and cashew phenolic resin to polyethylene glycol 6000 is 2:1, and the rest is the same as Example 5.

[0074] Comparative Example 1

[0075] A preparation process of a carbon molecular sieve is different from that of Example 3 in that, during the carbonization process of step S4, no ammonia is introduced in the second stage and the third stage, and the rest is the same as that of Example 3.

[0076] Comparative Example 2

[0077] A preparation process of a carbon molecular sieve, which differs from Example 3 in that the carbonization process of step S4 is as follows: after heating to 800°C at a heating rate of 5°C / min under nitrogen protection, heat preservation for 1 hour, and the nitrogen flow rate is 250 ml / min. The other steps are the same as Example 3.

[0078] Comparative Example 3

[0079] A preparation process of a carbon molecular sieve, which is different from Example 3 in that the amount of binder added is 7 kg, the weight ratio of cashew phenolic resin and polyethylene glycol 6000 is 2:1, and the rest are the same as Example 3.

[0080] Performance testing

[0081] The physical properties and nitrogen production performance of the carbon molecular sieves obtained in the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0082] Table 1 Carbon molecular sieve performance test results

[0083] project <![CDATA[Specific surface area m 2 / g]]> <![CDATA[Total pore volume cm 3 / g]]> <![CDATA[Micropore volume cm 3 / g]]> Nitrogen concentration% <![CDATA[Nitrogen production rate m 3 / h·t]]> Air-nitrogen ratio% Example 1 1022 0.589 0.368 99.5 276 3.0 Example 2 1035 0.621 0.397 99.6 292 3.0 Example 3 1052 0.634 0.404 99.6 295 2.9 Example 4 1078 0.652 0.421 99.7 304 2.8 Example 5 1084 0.674 0.428 99.6 308 2.8 Example 6 1088 0.683 0.431 99.6 317 2.9 Example 7 1135 0.725 0.474 99.8 316 2.6 Example 8 1126 0.698 0.453 99.7 313 2.7 Comparative Example 1 896 0.493 0.282 94.3 278 3.6 Comparative Example 2 860 0.413 0.231 86.3 246 3.9 Comparative Example 3 875 0.514 0.316 88.7 245 3.7

[0084] Note: The nitrogen concentration, nitrogen production and air-nitrogen ratio in the above table are under an air pressure of 0.8 MPa and an adsorption cycle of 2×58 s.

[0085] As can be seen from the above table, the specific surface areas of the carbon molecular sieves obtained in Examples 1-3 of the present application are all above 1000, the total pore volume is above 0.5, and the micropore volume is above 0.3, indicating that the carbon molecular sieves obtained in the present application have high specific surface area, total pore volume and micropore volume. At the same time, when the carbon molecular sieves obtained in Examples 1-3 are used for nitrogen production, the nitrogen concentration is above 99%, the nitrogen production is above 270, and the air-nitrogen ratio is ≤3.0, indicating that the carbon molecular sieves obtained in the present application have good separation effects on oxygen and nitrogen.

[0086] Compared with Example 3, Examples 4-6 show that as the particle size of the flower mud powder increases, the specific surface area, total pore volume and micropore volume of the carbon molecular sieves in Examples 4-6 all increase significantly. However, when the particle size of the flower mud powder is 20 μm, the growth rate of the specific surface area, total pore volume and micropore volume of the carbon molecular sieve in Example 6 decreases significantly. It can be inferred that when the particle size of the flower mud powder exceeds 20 μm, the specific surface area, total pore volume and micropore volume of the carbon molecular sieve will no longer increase and may even decrease.

[0087] Compared with Example 5, in Examples 7-8, as the binder content increases, the specific surface area, total pore volume and micropore volume of the carbon molecular sieve further increase, while the nitrogen production increases and the air-nitrogen ratio decreases. It can be seen that when the binder is within this range, the physical properties and nitrogen production effect of the carbon molecular sieve can be effectively guaranteed.

[0088] Compared with Example 3, when pyridinic nitrogen is not introduced on the pore surface and the gradient carbonization process is omitted, the physical properties and nitrogen production performance of the carbon molecular sieve obtained in Comparative Example 1-2 are significantly reduced compared with Example 3. It can be seen that the carbonization process in this application can effectively improve the physical properties and nitrogen production effect of the carbon molecular sieve.

[0089] Compared with Example 3, when the content of the binder exceeds the limit of this application, the physical properties and nitrogen production performance of the carbon molecular sieve obtained in Comparative Example 3 are reduced. The reason is that the addition of excessive binder blocks the pores of the carbon molecular sieve to a certain extent, thereby causing its various performances to be reduced.

[0090] The embodiments of this specific implementation method are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for preparing a carbon molecular sieve, characterized in that: The method comprises the following preparation steps: S1. Crushing the floral mud and pre-carbonizing it; S2. ball-milling the pre-carbonized floral mud material into floral mud powder; S3, stirring and kneading 100 parts by weight of flower mud powder, 35-60 parts by weight of a binder, and 30-40 parts by weight of water, extruding and then carbonizing, wherein the binder is composed of cashew phenolic resin and polyethylene glycol 6000 in a weight ratio of (4-8): (3-4); S4, the carbonization process is carried out according to the following gradient: the first stage: heating from room temperature to 600 ° C, passing nitrogen; the second stage: 600-750 ° C, passing nitrogen and ammonia, and keeping warm at 750 ° C for 1-2 hours; the third stage: heating from 750 to 800 ° C, passing nitrogen, ammonia and carbon dioxide, and the concentration of ammonia is less than the concentration of ammonia in the second stage; the fourth stage: 800-900 ° C, passing nitrogen and carbon dioxide, and keeping warm for 0.5-1 hour; S5, deposition pore adjustment, the primary product obtained in step S4 is deposited and pore adjusted under nitrogen protection. The deposition and pore adjustment is carried out in two steps. In the first step, the temperature is 700°C, the benzene concentration is 5-10%, and the treatment time is 40-50 minutes; in the second step, the temperature is 800°C, the water vapor concentration is 4%, the treatment time is 20 minutes, and then the carbon molecular sieve is obtained by cooling.

2. The process for preparing a carbon molecular sieve according to claim 1, wherein: The heating rate in the first stage is 2-5°C / min, and the heating rate in the second stage is 10-15°C / min.

3. The process for preparing a carbon molecular sieve according to claim 1, wherein: The nitrogen flow rates in the first, second, third and fourth stages are all 200-250 ml / min.

4. The process for preparing a carbon molecular sieve according to claim 1, wherein: The ammonia flow rate in the second stage is 20-50 ml / min.

5. The process for preparing a carbon molecular sieve according to claim 1, wherein: The ammonia flow rate in the third stage is 1.0-2.5 ml / min, and the carbon dioxide flow rate is 10-25 ml / min.

6. The process for preparing a carbon molecular sieve according to claim 1, wherein: The carbon dioxide flow rate in the fourth stage is 40-100 ml / min.

7. The process for preparing a carbon molecular sieve according to claim 1, characterized in that: The particle size of the flower mud powder in step S2 is 5-20 μm.