Mesoporous carbon molecular sieve as well as preparation method and application thereof

Abstract

The invention belongs to the field of inorganic materials, and particularly relates to a mesoporous carbon molecular sieve and a preparation method and application thereof. The method comprises the following steps: taking a carbon molecular sieve as a precursor, putting the precursor into a tubular furnace, and introducing nitrogen to completely replace oxygen in a pipeline; and introducing a mixed gas of ammonia gas and nitrogen gas into the tubular furnace, heating to 500-900 DEG C, calcining, and cooling to room temperature after calcining to obtain the mesoporous carbon molecular sieve. The mesoporous molecular sieve can be used for removing trace thiophenic sulfur in styrene. The mesoporous carbon molecular sieve has good mechanical stability and cannot be damaged when being mechanically stamped by fluid, and the adsorbent has a unique pore structure, can effectively and physically adsorb trace thiophenic sulfur in styrene, does not chemically react with styrene, and can be used for adsorbing thiophenic sulfur in styrene. And the adsorbent is long in cycle service life, high in adsorption selectivity and easy to regenerate, and has relatively high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, specifically relating to a mesoporous carbon molecular sieve, its preparation method, and its application. Background Technology

[0002] Styrene produced by conventional methods is in short supply. Cracked gasoline produced by steam cracking ethylene plants using light hydrocarbons, naphtha, and diesel as feedstocks contains approximately 4%–6% styrene. With the increasing scale of ethylene production plants and the shift towards heavier feedstocks, cracked gasoline production has significantly increased, making the recovery and utilization of styrene possible. However, the sulfur content of the styrene recovered from cracked gasoline is 30–100 ppm, severely impacting the chemical utilization of styrene. Therefore, researching suitable desulfurization processes to reduce the sulfur content in styrene products to below 5 ppm is of great significance.

[0003] Styrene desulfurization methods include hydrodesulfurization, adsorption desulfurization, oxidative desulfurization, biological desulfurization, and extraction desulfurization. Hydrodesulfurization requires high pressure and high concentrations of hydrogen, resulting in high investment and production costs, low desulfurization efficiency, and significant aromatic hydrocarbon saturation, thus it is not commonly used. Oxidative desulfurization technology offers advantages such as high selectivity, deep desulfurization capability, and low equipment investment and operating costs; however, the availability of efficient, inexpensive, and highly selective oxidants is a key factor limiting its industrial application. Biological desulfurization technology offers high selectivity, but its desulfurization rate is low, and its effectiveness varies depending on the sulfur content and type of sulfides in the raw materials. The discovery of effective desulfurizing microorganisms, the improvement of their activity, stability, and selectivity, and the optimization of suitable conditions for desulfurizing bacteria are central to advancements in biological desulfurization technology. Compared with traditional hydrodesulfurization, adsorption desulfurization has milder reaction conditions, significant deep desulfurization effect, and is economically feasible. However, its industrial application is limited by problems such as competitive adsorption of aromatics such as styrene and sulfides due to their similar polarity, large size of adsorption desulfurization equipment, complex desulfurization process, and difficulty in regenerating adsorbents. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a mesoporous carbon molecular sieve and its preparation method, and applies it to the removal of trace thiophene sulfur from styrene. The mesoporous carbon molecular sieve of this invention exhibits good mechanical stability and will not break under mechanical pressure from a fluid. The adsorbent of this invention has a unique pore structure, enabling effective physical adsorption of trace thiophene sulfur in styrene without chemical reaction with styrene. Furthermore, it has a long cycle life, high adsorption selectivity, and is easily regenerated, resulting in high economic benefits.

[0005] The method for synthesizing mesoporous carbon molecular sieves according to the present invention includes the following steps:

[0006] (1) The carbon molecular sieve is used as a precursor and placed in a tube furnace. Nitrogen gas is introduced to replace the oxygen in the pipeline. In this invention, carbon molecular sieve CMS-260 is used as a precursor.

[0007] In this invention, a mixture of ammonia and nitrogen is introduced to modify the surface of carbon molecular sieves and improve their adsorption performance. The volume ratio of ammonia to nitrogen in the mixture is (5-8):(92-95), which effectively modifies the sieve without drastically affecting its structure.

[0008] (2) A mixture of ammonia and nitrogen is introduced into a tubular furnace and heated to 500-900℃ for calcination. After calcination, the temperature is lowered to room temperature to obtain mesoporous carbon molecular sieve.

[0009] In this step, heating to 500℃ at a rate of 5-8℃ / min for calcination for 4-6 hours can maintain the stability of the molecular sieve structure, avoid structural damage caused by excessively rapid heating, prevent pore collapse, balance crystal form and activity, remove volatile components, construct a stable pore structure, and improve mechanical strength and stability.

[0010] The specific process of applying the mesoporous carbon molecular sieve described in this invention to remove trace amounts of thiophene sulfur from styrene is as follows:

[0011] (1) Install the mesoporous carbon molecular sieve in a fixed bed;

[0012] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0013] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0014] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate, and desulfurize the styrene raw liquid.

[0015] During adsorption, the power of the centrifugal pump should be controlled to ensure the flow rate is maintained at 1.2-1.5 m / s. Excessive flow rate can cause mechanical damage to the mesoporous carbon molecular sieve, affecting subsequent adsorption performance and regeneration. The fluid flow time through the fixed bed should be controlled at 10-15 minutes; the adsorption time should not be too long. The feed temperature of the styrene concentrate should be controlled, with 40℃ being optimal. This temperature matches the actual discharge temperature of styrene production, maintaining the continuity of the industrial plant and reducing energy consumption.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) High efficiency desulfurization: The unique pore structure of the mesoporous carbon molecular sieve described in this invention can effectively adsorb trace amounts of thiophene sulfur in styrene, thereby improving the desulfurization efficiency.

[0018] (2) High selectivity: The mesoporous carbon molecular sieve of the present invention has a unique pore structure that does not react chemically with styrene, thus avoiding the problem of competitive adsorption of aromatics. After desulfurization treatment using the present invention, the content of thiophene sulfur in styrene is significantly reduced.

[0019] (3) Good mechanical stability: The mesoporous carbon molecular sieve of the present invention has high strength and compressive strength due to the cross-linked carbon skeleton, high temperature carbonization process and ordered pore design. It has excellent mechanical stability. After continuous adsorption treatment of fluid with a velocity of 1.2-1.5m / s for a week, no mechanical damage is found. Styrene remains clear and transparent, not easily broken, and has a long service life.

[0020] (4) Easy to regenerate: The mesoporous carbon molecular sieve described in this invention is easy to regenerate, has a long service life, reduces operating costs, and improves overall economic benefits. Attached Figure Description

[0021] Figure 1 This is the BET adsorption test curve of mesoporous carbon molecular sieve II in Example 2. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of the invention.

[0023] Example 1

[0024] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0025] (2) With 20 mL min -1 A mixture of NH3 / N2 (5% / 95%) gas was introduced into a tubular furnace at a flow rate of 5℃ / min, and the temperature was simultaneously increased to 500℃. The furnace was then held at this temperature for 4 hours. After calcination, the furnace was cooled to room temperature to obtain mesoporous carbon molecular sieve I.

[0026] Its specific surface area: 326.5835 m² 2 / g, microporous specific surface area: 239.9173m² 2 / g, pore size: 2.6827nm, the presence of a hysteresis loop indicates the presence of mesoporous structures, suggesting an ion exchange process during the treatment of this adsorbent. This adsorbent exhibits stable performance and a large specific surface area. The mesoporous carbon molecular sieve I was applied to remove trace amounts of thiophene sulfur from styrene, and the specific process is as follows:

[0027] (1) Install the mesoporous carbon molecular sieve I in a fixed bed;

[0028] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0029] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0030] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.2m / s, and desulfurize the styrene raw liquid for 15min. The specific results are shown in Table 1.

[0031] Table 1 Desulfurization rate of mesoporous carbon molecular sieve I

[0032]

[0033] Example 2

[0034] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0035] (2) With 20 mL min -1 The flow rate of the NH3 / N2 (5% / 95%) mixture was increased to 700℃ at a rate of 5℃ / min, and then calcined at that temperature for 4 hours. After calcination, the temperature was lowered to room temperature to obtain mesoporous carbon molecular sieve II.

[0036] Its specific surface area: 378.9102 m² 2 / g, microporous specific surface area: 279.1706m² 2 / g, pore size: 3.2163nm, the presence of a hysteresis loop indicates the presence of mesoporous structures, suggesting an ion exchange process during the treatment of this adsorbent. This adsorbent exhibits stable performance and a large specific surface area. The mesoporous carbon molecular sieve II was applied to remove trace amounts of thiophene sulfur from styrene. The specific process is as follows:

[0037] (1) Install mesoporous carbon molecular sieve II in a fixed bed;

[0038] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0039] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0040] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.3m / s, and desulfurize the styrene raw liquid for 15min. The specific results are shown in Table 2.

[0041] Table 2 Desulfurization rate of mesoporous carbon molecular sieve II

[0042]

[0043]

[0044] from Figure 1 The BET adsorption test curve of mesoporous carbon molecular sieve II shows that the adsorption-desorption curve conforms to the characteristics of type III adsorption isotherm. The molecular sieve is mainly composed of mesopores or macropores, and the pore structure is regular and without obvious blockage, which proves that the adsorption process is mainly physical adsorption.

[0045] Example 3

[0046] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0047] (2) With 20 mL min -1 The flow rate of the NH3 / N2 (5% / 95%) mixture was increased to 900℃ at a rate of 5℃ / min, and the temperature was maintained for calcination for 4 hours. After calcination, the temperature was cooled to room temperature to obtain mesoporous carbon molecular sieve III.

[0048] Its specific surface area: 438.2152 m² 2 / g, microporous specific surface area: 321.4561m² 2 / g, pore size: 4.4371nm, the presence of hysteresis loops indicates the presence of mesopores, suggesting an ion exchange process during the treatment of this adsorbent. This adsorbent exhibits stable performance and a large specific surface area.

[0049] The mesoporous carbon molecular sieve III was applied to remove trace amounts of thiophene sulfur from styrene. The specific process is as follows:

[0050] (1) Install the mesoporous carbon molecular sieve III in a fixed bed;

[0051] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0052] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0053] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.5m / s, and desulfurize the styrene raw liquid for 15min. The specific results are shown in Table 3.

[0054] Table 3 Desulfurization rate of mesoporous carbon molecular sieve III

[0055]

[0056] Example 4

[0057] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0058] (2) With 20 mL min-1 A mixture of NH3 / N2 (8% / 94%) was passed through at a flow rate of 8℃ / min, and the temperature was increased to 600℃. The mixture was then held at this temperature for 5.5 hours. After calcination, the temperature was lowered to room temperature to obtain mesoporous carbon molecular sieve IV.

[0059] Its specific surface area: 341.4851 m² 2 / g, microporous specific surface area: 305.7392m² 2 / g, pore size: 2.7542nm, indicating the presence of mesopores, suggesting an ion exchange process during the treatment of this adsorbent. This adsorbent exhibits stable performance and a large specific surface area.

[0060] The mesoporous carbon molecular sieve IV was applied to remove trace amounts of thiophene sulfur from styrene. The specific process is as follows:

[0061] (1) Install the mesoporous carbon molecular sieve IV in a fixed bed;

[0062] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0063] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0064] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.4 m / s, and desulfurize the styrene raw liquid for 10 min. The specific results are shown in Table 4.

[0065] Table 4 Desulfurization rate of mesoporous carbon molecular sieve IV

[0066] Example 5

[0067] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0068] (2) Using 20 mL min -1 A mixture of NH3 / N2 (7% / 93%) was passed through at a flow rate of 7℃ / min, and the temperature was increased to 800℃. The mixture was then held at this temperature for 4.5 hours. After calcination, the temperature was lowered to room temperature to obtain mesoporous carbon molecular sieve V.

[0069] Its specific surface area: 410.3092 m² 2 / g, microporous specific surface area: 297.4529m² 2 / g, pore size: 3.8014nm, indicating the presence of mesopores, suggesting an ion exchange process during the treatment of this adsorbent. This adsorbent exhibits stable performance and a large specific surface area.

[0070] The mesoporous carbon molecular sieve V was applied to remove trace amounts of thiophene sulfur from styrene. The specific process is as follows:

[0071] (1) Install the mesoporous carbon molecular sieve V in a fixed bed;

[0072] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0073] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0074] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.3m / s, and desulfurize the styrene raw liquid for 12 minutes. The specific results are shown in Table 5.

[0075] Table 5 Desulfurization rate of mesoporous carbon molecular sieve V

[0076]

[0077] Example 6

[0078] (1) Isolate the fixed bed unit that has been continuously adsorbing for one week in Example 2;

[0079] (2) The unit ambient temperature is heated to 400℃ by a heater, and high-purity nitrogen is purged at the same time for 10 hours;

[0080] (3) Stop heating and continue to introduce nitrogen gas to cool the bed to near the adsorption operating temperature;

[0081] (4) Remove the adsorption isolation and repeat the operating conditions in Example 2 to continue desulfurization. The specific results are shown in Table 6.

[0082] Table 6. Desulfurization rate of regenerated mesoporous carbon molecular sieve II

[0083] Comparative Example 1

[0084] (1) Using commercial carbon molecular sieve (CMS-260) as a precursor, place it in a tube furnace and pass nitrogen gas through it to replace the oxygen in the tube.

[0085] (2) With 20 mL min -1 A mixture of NH3 / N2 (5% / 95%) was passed through at a flow rate of 5℃ / min, and the temperature was increased to 400℃. The mixture was then held at this temperature for 4 hours. After calcination, the temperature was lowered to room temperature to obtain mesoporous carbon molecular sieve VI.

[0086] Its specific surface area: 263.0951 m² 2 / g, microporous specific surface area: 197.4091m² 2 / g, pore size: 1.7409nm, this adsorbent is unstable and has a small specific surface area. The mesoporous carbon molecular sieve VI was applied to remove trace amounts of thiophene sulfur from styrene. The specific process is as follows:

[0087] (1) Install the mesoporous carbon molecular sieve VI in a fixed bed;

[0088] (2) Turn on the feed pump to deliver the styrene raw material to the raw material storage tank;

[0089] (3) Close the raw material conveying valve, turn on the centrifugal pump, and remove excess gas from the pipeline;

[0090] (4) Observe the actual operation of the device, adjust the centrifugal pump power according to the flow meter, control the fluid flow rate at 1.2m / s, and desulfurize the styrene raw liquid for 15min. The specific results are shown in Table 7.

[0091] Table 7 Desulfurization rate of mesoporous carbon molecular sieve VI

[0092]

Claims

1. A method for synthesizing a mesoporous carbon molecular sieve, characterized by, The method comprises the following steps: (1) placing carbon molecular sieve as a precursor in a tube furnace, and replacing oxygen in the tube with nitrogen; (2) passing mixed gas of ammonia and nitrogen into the tube furnace, and calcining at a temperature of 500-900 DEG C, and cooling to room temperature to obtain mesoporous carbon molecular sieve.

2. The method of claim 1, wherein the mesoporous carbon molecular sieve is synthesized by the following steps of: The carbon molecular sieve CMS-260 is used as the precursor.

3. The method for synthesizing mesoporous carbon molecular sieves according to claim 1, characterized in that, In the mixed gas of ammonia and nitrogen, the volume ratio of ammonia to nitrogen is (5-8):(92-95).

4. The method for synthesizing mesoporous carbon molecular sieves according to claim 1, characterized in that, The temperature increasing rate is 5-8 DEG C / min.

5. The method for synthesizing mesoporous carbon molecular sieves according to claim 1, characterized in that, The calcining time is 4-6 h.

6. A mesoporous carbon molecular sieve characterized by, The method is obtained by any one of claims 1-5.

7. The mesoporous molecular sieve in claim 6 is used for removing trace thiophene sulfur in styrene.

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