Preparation process of carbon molecular sieve

Abstract

The invention discloses a preparation process of a carbon molecular sieve, and belongs to the technical field of carbon molecular sieves, and the key point of the technical scheme is that the preparation process comprises the following preparation steps: S1, crushing flower mud and then pre-carbonizing; s2, carrying out ball milling on the pre-carbonized flower mud material to obtain flower mud powder; s3, carrying out extrusion molding on the flower mud powder, and then carrying out carbonization; s4, the carbonization process is carried out according to the following gradient: in the first stage, the temperature is increased to 600 DEG C from the room temperature, and nitrogen is introduced; at the second stage, nitrogen and ammonia are introduced at the temperature of 600-750 DEG C, and heat preservation treatment is conducted for 1-2 h at the temperature of 750 DEG C; in the third stage, the temperature is increased to 800 DEG C from 750 DEG C, and nitrogen, ammonia gas and carbon dioxide are introduced; in the fourth stage, nitrogen and carbon dioxide are introduced at the temperature of 800-900 DEG C, and heat preservation treatment is conducted for 0.5-1 h; s5, deposition and pore adjustment are conducted, and then cooling is conducted to obtain the carbon molecular sieves. Pyridine nitrogen is introduced to the surfaces of the pores, and stepped carbonization treatment is conducted, so that the oxygen adsorption effect is effectively improved, and effective separation of oxygen and nitrogen is achieved.

Description

Technical Field

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

[0002] Carbon molecular sieve is a corrosion-resistant porous carbon framework 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 many tiny pore structures. The molecular diameter of oxygen is smaller than that of nitrogen. After the gas enters the carbon molecular sieve adsorbent, the diffusion rate of oxygen is faster and it enters the solid phase of the carbon molecular sieve, while nitrogen with a slower diffusion rate enters the gas phase more, thus realizing the separation of oxygen and nitrogen.

[0003] The existing raw materials of carbon molecular sieves include coal, fruit shell, coconut shell, phenolic resin, and flower mud, etc. When using flower mud to prepare carbon molecular sieves, waste resource utilization can be realized, environmental pollution can be reduced. At the same time, after carbonization, flower mud retains a high specific surface area, which is beneficial to gas adsorption. However, the separation efficiency of flower mud carbon molecular sieve for oxygen and nitrogen is relatively low. The reason is that although the carbon structure derived from flower mud can create micropores, the pore size dispersion is as high as ±0.5nm. When some pore sizes exceed 0.43nm, nitrogen has a stronger adsorption than oxygen due to longer-range dispersion forces, which leads to a lower separation efficiency of flower mud carbon molecular sieve for oxygen and nitrogen, and ultimately makes it difficult to reach the ideal level of nitrogen purity obtained. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a preparation process of carbon molecular sieves. By introducing pyridine nitrogen on the pore surface and performing stepwise carbonization treatment in this application, the adsorption effect on oxygen is effectively improved, and the effective separation of oxygen and nitrogen is realized.

[0005] A preparation process of carbon molecular sieves provided by the present invention adopts the following technical scheme: A preparation process of carbon molecular sieves includes the following preparation steps: S1. Crush the flower mud and then perform pre-carbonization; S2. Ball-mill the pre-carbonized flower mud material into flower mud powder; S3. Stir and knead the flower mud powder with a binder and water, extrude it into a shape, and then perform carbonization; S4. The carbonization process is carried out according to the following gradients. The first stage: heating from room temperature to 600 °C while passing nitrogen; the second stage: at 600 - 750 °C, passing nitrogen and ammonia, and holding for 1 - 2 h at 750 °C; the third stage: heating from 750 to 800 °C, passing nitrogen, ammonia and carbon dioxide, and the concentration of ammonia is less than that in the second stage; the fourth stage: at 800 - 900 °C, passing nitrogen and carbon dioxide, and holding for 0.5 - 1 h. S5. Deposition and pore regulation: Heat the primary product obtained in step S4 to 700 - 800 °C under nitrogen protection, pass a regulating agent for pore regulation treatment, and then cool to obtain a carbon molecular sieve.

[0006] By adopting the above technical solutions, in the carbonization process of the present application, gradient heating and introducing different gases in different stages are selected, which helps to maintain the overall structure of the flower mud molecular sieve and avoid disintegration during the heating process. When all nitrogen is introduced in the first stage, nitrogen acts as a carrier gas to carry away pyrolysis tar, reduce carbon deposition and blockage of pores, and at the same time can also prevent the flower mud from oxidizing and burning; 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, thus significantly enhancing the adsorption capacity for oxygen and helping to improve the purity of nitrogen. The third stage is a transition stage, where nitrogen, ammonia and carbon dioxide are introduced simultaneously, and the concentration of ammonia is greatly reduced, avoiding surface structure stress caused by gas mutation. In the third stage, nitrogen and carbon dioxide are introduced for activation, and the etching rate is controllable to avoid pore collapse. The reason is that the electron density on the carbon surface after nitrogen doping increases, inhibiting the excessive erosion of the carbon skeleton by carbon dioxide.

[0007] Therefore, the present application improves the pore size dispersion problem of the flower mud carbon molecular sieve through specific carbonization gradients and deposition and pore regulation steps, improves the separation efficiency of oxygen and nitrogen, and further improves the purity of nitrogen during nitrogen production.

[0008] 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.

[0009] By adopting the above technical solutions, the heating rate in the first stage is controlled at 2 - 5 °C / min to avoid the rupture of the flower mud precursor during the heating process. The heating rate in the second stage is controlled at 10 - 15 °C / min. As the carbonization heating rate increases, the specific surface area, pore volume and micropore volume of the carbon molecular sieve all show a continuous increasing trend. A higher heating rate helps the development of the pore structure and increases the volatilization rate.

[0010] Preferably, the nitrogen flow rate in the first stage, the second stage, the third stage and the fourth stage is 200 - 250 ml / min.

[0011] By adopting the above technical solutions, appropriate nitrogen gas 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.

[0012] Preferably, the ammonia gas flow rate in the second stage is 20 - 50 ml / min.

[0013] Preferably, the ammonia gas flow rate in the third stage is 1.0 - 2.5 ml / min, and the carbon dioxide gas flow rate is 10 - 25 ml / min.

[0014] Preferably, the carbon dioxide gas flow rate in the fourth stage is 40 - 100 ml / min.

[0015] By adopting the above technical solutions, controlling the carbon dioxide gas flow rate at 40 - 100 ml / min in the fourth stage of the carbon molecular sieve preparation process helps to accurately regulate the pore structure of the carbon molecular sieve, improve its separation efficiency of oxygen and nitrogen, enhance the purity of nitrogen during nitrogen production. At the same time, using flower mud for preparation can achieve the resource utilization of waste, reduce environmental pollution, and retain a high specific surface area for gas adsorption.

[0016] Preferably, the particle size of the flower mud powder in step S2 is 5 - 20 μm.

[0017] By adopting the above technical solutions, the pre-carbonized flower mud material is ball-milled into flower mud powder with a particle size of 5 - 20 μm, which is conducive to subsequent full stirring and kneading with the binder and water, ensuring uniform mixing of the materials, providing a good foundation for subsequent extrusion molding and carbonization steps, and helping to improve the performance and quality of the final carbon molecular sieve. The reason is that when the particle size of the flower mud powder is smaller, the pores of the carbide are more developed, and the specific surface area, total pore volume, and micropore volume also increase accordingly. In addition, after the specific surface area increases, the contact area between the gas-solid phases increases, which makes the reaction and mass transfer processes of the solid phase easier, and the volatile matter is more easily removed, so it is easier to activate at high temperatures. However, when the particle size of the flower mud powder is too small, the sintering risk of the flower mud during the carbonization process is high, resulting in the collapse or closure of the micropores, and the binder is more likely to completely coat the fine particles, blocking the micropore entrances. When the particle size of the flower mud powder is too large, the surface layer is over-carbonized and the inside is not fully reacted, resulting in uneven distribution of the microporous structure, too large pore diameters in some areas or ineffective micropores not being formed, thus reducing the separation efficiency of the carbon molecular sieve for oxygen and nitrogen.

[0018] Preferably, in step S3, there are 100 parts by weight of flower mud powder, 35 - 60 parts by weight of binder, and 30 - 40 parts by weight of water.

[0019] Preferably, the binder is composed of cardanol phenolic resin and polyethylene glycol 6000 in a weight ratio of (4 - 8) : (3 - 4).

[0020] By adopting the above technical solution, after stirring, kneading, extruding and carbonizing the flower mud powder, binder and water in a specific proportion, the full mixing and forming of the materials can be ensured, which is beneficial to the smooth progress of the subsequent process and finally improves the overall performance of the carbon molecular sieve. When the proportion of the binder increases, the specific surface area and pore volume both show a trend of first increasing and then decreasing, and the micropore volume shows a continuous decreasing trend. The reason is that the flower peat particles as the main raw material form the adsorption main body, the residual carbon after carbonization of the cardanol phenolic resin as the binder connects the main body particles, and a small amount of pores are also generated by itself. The polyethylene glycol as the auxiliary agent is almost completely decomposed, and the decomposition of the binder and the auxiliary agent generates rapid channel pores, which together with the adsorption main 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 and cause the secondary structure to be not obvious. 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, but when 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.

[0021] Preferably, the deposition and pore adjustment are 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 min; in the second step, the temperature is 800 °C, the water vapor concentration is 4%, and the treatment is carried out for 20 min.

[0022] By adopting the above technical solution, the two-step pore adjustment method using benzene and water vapor can effectively control the pore size of the carbon molecular sieve, thereby improving the separation efficiency of oxygen and nitrogen and increasing the nitrogen concentration during nitrogen production.

[0023] In summary, the present invention has the following beneficial effects: By introducing pyridine nitrogen on the pore surface of the carbon molecular sieve in this application, the adsorption capacity for oxygen is increased. At the same time, by controlling the carbonization process, deposition process and the content of the binder, the pore size of the carbon molecular sieve is effectively controlled, thereby improving the separation effect of the flower mud carbon molecular sieve for oxygen and nitrogen. Specific Embodiments

[0024] The following further details the present invention with reference to embodiments. All reagents without indicating the manufacturer can be obtained as conventional reagent products through commercial purchase.

[0025] Example 1

[0026] A preparation process of a carbon molecular sieve includes the following preparation steps: S1. Crush the flower mud and pre-carbonize it at 350 °C for 0.5 h; S2. Grind the pre-carbonized flower mud material into flower mud powder, and the particle size D50 of the flower mud powder is 5 μm; S3. Knead and extrude 10 kg of flower mud powder, 3.5 kg of binder, and 3 kg of water, and then perform carbonization; the binder is composed of cardanol phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3; S4. The carbonization process is carried out according to the following gradients: The first stage: Heat from room temperature to 600 °C. During this stage, nitrogen is passed through, the nitrogen flow rate is 200 ml / min, and the heating rate is 2 °C / min; The second stage: Heat from 600 to 750 °C. During this stage, nitrogen and ammonia are passed through, the nitrogen flow rate is 200 ml / min, the ammonia flow rate is 20 ml / min, the heating rate is 10 °C / min, and after heating to 750 °C, keep it warm for 1 h; The third stage: Heat from 750 to 800 °C. During this stage, nitrogen, ammonia, and carbon dioxide are passed through, the nitrogen flow rate is 200 ml / min, the ammonia flow rate is 1.0 ml / min, and the carbon dioxide flow rate is 10 ml / min; The fourth stage: At 800, pass through nitrogen and carbon dioxide, the nitrogen flow rate is 200 ml / min, the carbon dioxide flow rate is 40 ml / min, and keep it warm for 1 h; S5. Deposit and adjust pores. Deposit and adjust the pores of the primary product obtained in step S4 under nitrogen protection, the nitrogen flow rate is 400 mL / min, and the deposit and pore adjustment are carried out in two steps. The first step, the temperature is 700 °C, the benzene concentration is 5%, and the treatment time is 40 min; the second step, the temperature is 800 °C, the water vapor concentration is 4%, and treat for 20 min, and then cool to obtain carbon molecular sieve.

[0027] Example 2

[0028] A preparation process of carbon molecular sieve, including the following preparation steps: S1. Crush the flower mud and pre-carbonize it at 350 °C for 0.5 h; S2. Grind the pre-carbonized flower mud material into flower mud powder, and the particle size D50 of the flower mud powder is 5 μm; S3. Knead and extrude 10 kg of flower mud powder, 3.5 kg of binder, and 3 kg of water, and then perform carbonization; the binder is composed of cardanol phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3; S4. The carbonization process is carried out according to the following gradients: The first stage: Heat from room temperature to 600 °C. During this stage, nitrogen is passed through, the nitrogen flow rate is 250 ml / min, and the heating rate is 5 °C / min; The second stage: Heat from 600 to 750 °C. During this stage, nitrogen and ammonia are introduced. The nitrogen flow rate is 250 ml / min, the ammonia flow rate is 30 ml / min, the heating rate is 15 °C / min. After heating to 750 °C, keep the temperature for 1.5 h; The third stage: Heat from 750 to 800 °C. During this stage, nitrogen, ammonia and carbon dioxide are introduced. 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; The fourth stage: At 850 °C, introduce nitrogen and carbon dioxide. The nitrogen flow rate is 250 ml / min, the carbon dioxide flow rate is 70 ml / min, and keep the temperature for 1 h; S5. Deposit and adjust pores. Deposit and adjust the pores of the primary product obtained in step S4 under nitrogen protection. The nitrogen flow rate is 400 mL / min. The deposition and pore adjustment are carried out in two steps. First step, the temperature is 700 °C, the benzene concentration is 8%, and the treatment time is 40 min; Second step, the temperature is 800 °C, the water vapor concentration is 4%, and treat for 20 min, and then cool to obtain carbon molecular sieve.

[0029] Example 3

[0030] A preparation process of carbon molecular sieve, including the following preparation steps: S1. Crush the flower mud and pre-carbonize it at 350 °C for 0.5 h; S2. Grind the pre-carbonized flower mud material into flower mud powder. The particle size D50 of the flower mud powder is 5 μm; S3. Stir and knead 10 kg of flower mud powder, 3.5 kg of binder and 3 kg of water, extrude and form, and then carbonize; The binder is composed of cardanol phenolic resin and polyethylene glycol 6000 in a weight ratio of 4:3; S4. The carbonization process is carried out according to the following gradients: The first stage: Heat from room temperature to 600 °C. During this stage, nitrogen is introduced. The nitrogen flow rate is 250 ml / min, and the heating rate is 5 °C / min; The second stage: Heat from 600 to 750 °C. During this stage, nitrogen and ammonia are introduced. The nitrogen flow rate is 250 ml / min, the ammonia flow rate is 50 ml / min, the heating rate is 15 °C / min. After heating to 750 °C, keep the temperature for 2 h; The third stage: Heat from 750 to 800 °C. During this stage, nitrogen, ammonia and carbon dioxide are introduced. 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; The fourth stage: At 900 °C, introduce nitrogen and carbon dioxide. The nitrogen flow rate is 250 ml / min, the carbon dioxide flow rate is 100 ml / min, and keep the temperature for 1 h; S5. Deposition and pore regulation: The primary product obtained in step S4 is deposited and pore-regulated under nitrogen protection. The nitrogen flow rate is 400 mL / min. The deposition and pore regulation are 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 min. In the second step, the temperature is 800 °C, the water vapor concentration is 4%, and the treatment is carried out for 20 min. Then it is cooled to obtain the carbon molecular sieve.

[0031] Example 4

[0032] A preparation process of 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 others are the same as in Example 3.

[0033] Example 5

[0034] A preparation process of 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 others are the same as in Example 3.

[0035] Example 6

[0036] A preparation process of 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 others are the same as in Example 3.

[0037] Example 7

[0038] A preparation process of carbon molecular sieve, which is different from Example 5 in that in step S3, there are 10 kg of flower mud powder, 5 kg of binder, 3.5 kg of water, and the weight ratio of cardanol phenolic resin to polyethylene glycol 6000 is 2:1, and the others are the same as in Example 5.

[0039] Example 8

[0040] A preparation process of carbon molecular sieve, which is different from Example 5 in that in step S3, there are 10 kg of flower mud powder, 6 kg of binder, 4 kg of water, and the weight ratio of cardanol phenolic resin to polyethylene glycol 6000 is 2:1, and the others are the same as in Example 5.

[0041] Comparative Example 1

[0042] A preparation process of carbon molecular sieve, which is different from Example 3 in that during the carbonization process in step S4, ammonia gas is not introduced in the second stage and the third stage, and the others are the same as in Example 3.

[0043] Comparative Example 2

[0044] A preparation process of carbon molecular sieve, which is different from that of Example 3 in that the carbonization process in step S4 is as follows: under the protection of nitrogen, it is heated to 800 °C at a heating rate of 5 °C / min, then heat-insulated for 1 h, and the nitrogen flow rate is 250 ml / min. Other steps are the same as those in Example 3.

[0045] Comparative Example 3

[0046] A preparation process of carbon molecular sieve, which is different from that of Example 3 in that the addition amount of the binder is 7 kg, and the weight ratio of cardanol phenolic resin to polyethylene glycol 6000 is 2:1. Others are the same as those in Example 3.

[0047] Performance detection

[0048] The physical properties and nitrogen production properties of the carbon molecular sieves obtained from the above examples and comparative examples were detected, and the detection results are shown in Table 1.

[0049] Table 1 Carbon molecular sieve performance detection result table Project <![CDATA[Specific surface area m 2 / g]]> <![CDATA[Total pore volume cm 3 / g]]> <![CDATA[Micropore volume cm 3 / g]]> Nitrogen Concentration % <![CDATA[The 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 Note: The nitrogen concentration, nitrogen production amount and air-nitrogen ratio in the above table are under an air pressure of 0.8 Mpa, and the adsorption cycle is 2×58 s.

[0050] It can be seen from the above table that 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 a relatively 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 amount is above 270, and the air-nitrogen ratio ≤ 3.0, indicating that the carbon molecular sieves obtained in the present application have a good separation effect on oxygen and nitrogen.

[0051] Compared with Example 3, in Examples 4-6, as the particle size of the flower mud powder increases, the specific surface area, total pore volume and micropore volume of the carbon molecular sieve in Examples 4-6 all increase significantly. However, when the particle size of the flower mud powder is 20 μm, the growth rates of the specific surface area, total pore volume and micropore volume of the carbon molecular sieve in Example 6 decrease significantly. It can be speculated 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.

[0052] 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, and at the same time the nitrogen production amount increases and the air-nitrogen ratio decreases. It can be seen that when the binder is within this range, it can effectively ensure the physical properties and nitrogen production effect of the carbon molecular sieve.

[0053] Comparing Comparative Examples 1-2 with Example 3, when pyridine 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 Examples 1-2 are significantly lower than those in 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.

[0054] Comparing Comparative Example 3 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 an excessive amount of binder blocks the pores of the carbon molecular sieve to a certain extent, resulting in a reduction in its various properties.

[0055] The embodiments of this specific implementation manner are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation process of carbon molecular sieve, characterized in that: It includes the following preparation steps: S1. Crush the flower mud and then carry out pre-carbonization; S2. Ball-mill the pre-carbonized flower mud material into flower mud powder; S3. Stir and knead the flower mud powder with a binder and water, extrude and form it, and then carry out carbonization; S4. The carbonization process is carried out according to the following gradients. The first stage: heat from room temperature to 600 °C and pass nitrogen. The second stage: 600 - 750 °C, pass nitrogen and ammonia, and keep it at 750 °C for heat preservation for 1 - 2 h. The third stage: heat from 750 to 800 °C, pass nitrogen, ammonia and carbon dioxide, and the concentration of ammonia is less than that in the second stage. The fourth stage: 800 - 900 °C, pass nitrogen and carbon dioxide, and keep it at a certain temperature for heat preservation for 0.5 - 1 h; S5. Deposit and adjust the pores. Heat the primary product obtained in step S4 to 700 - 800 °C under nitrogen protection, pass a pore regulator for pore adjustment treatment, and then cool to obtain a carbon molecular sieve.

2. The preparation process of 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 preparation process of a carbon molecular sieve according to claim 1, characterized in that: The nitrogen flow rate in the first stage, the second stage, the third stage and the fourth stage is 200 - 250 ml / min.

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

5. The preparation process of a carbon molecular sieve according to claim 1, characterized in that: 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 preparation process of a carbon molecular sieve according to claim 1, characterized in that: The carbon dioxide flow rate in the fourth stage is 40 - 100 ml / min.

7. The preparation process of 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.

8. A preparation process of a carbon molecular sieve according to claim 1, characterized in that: In step S3, 100 parts by weight of the flower mud powder, 35 - 60 parts by weight of the binder, and 30 - 40 parts by weight of water are used.

9. The preparation process of a carbon molecular sieve according to claim 8, characterized in that: The binder is composed of cardanol phenolic resin and polyethylene glycol 6000 in a weight ratio of (4 - 8):(3 - 4).

10. The preparation process of a carbon molecular sieve according to claim 1, characterized in that: The deposition and pore adjustment are carried out in two steps. The first step: the temperature is 700 °C, the benzene concentration is 5 - 10%, and the treatment time is 40 - 50 min. The second step: the temperature is 800 °C, the water vapor concentration is 4%, and the treatment time is 20 min.