Method for modifying carbon molecular sieves

Abstract

The present invention relates to a method for modifying a carbon molecular sieve. The method for modifying a carbon molecular sieve according to an embodiment of the present invention can introduce an effective inorganic thin film into the pores of the carbon molecular sieve, and can form a uniform thin film at a lower temperature than the existing CVD process. The method can also adjust the change in adsorption amount depending on the type of gas by finely controlling the pore size of the carbon molecular sieve, thereby increasing separation selectivity depending on the type of gas, minimizing the trade-off of a significant decrease in specific surface area, and maximizing the gas adsorption capacity even if the pore size of the carbon molecular sieve is reduced.

Description

[Technical Field]

[0001] The present disclosure relates to methods for modifying carbon molecular sieves. In particular, the present disclosure relates to methods for modifying carbon molecular sieves to control the pore size of the carbon molecular sieve. [Background technology]

[0002] Carbon molecular sieve (CMS), a special grade of activated carbon (AC), is a carbon material with micropores measuring several to several tens of angstroms in size. Carbon molecular sieves are microporous carbon materials characterized by uniform but narrow pore size distribution, and are attracting attention for their high permeability and selectivity. Carbon molecular sieves are primarily used for gas separation through the pressure swing adsorption (PSA) process, and are used as adsorbents in pellet or powder form. The gas permeability, separation, and adsorption performance of carbon molecular sieves are determined by the size and shape of the micropores present within them.

[0003] Previously, various attempts have been made to control the micropores present in carbon molecular sieves using carbon CVD (CVD) with benzene, methane, etc. However, carbon CVD requires high process temperatures of over 600°C, making it difficult to control the diffusion and reaction inside the pores due to the difficulty in controlling process variables, making the process technically challenging. Thus, precise control of the micropores within carbon molecular sieves is extremely difficult. Furthermore, with existing thermal CVD processes, minimizing the trade-off between pore size control and a significant decrease in specific surface area remains a problem that needs to be solved. Therefore, there is a need for a new concept of pore modification technology that can solve these problems. Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure seeks to provide a modification method that can control the micropore size of carbon molecular sieves. [Means for solving the problem]

[0005] The present invention provides a method for modifying a carbon molecular sieve, the method comprising the steps of: introducing a carbon molecular sieve and a first precursor into a reaction chamber to form a first precursor multilayer in which at least a portion of the first precursor is adsorbed in the pores of the carbon molecular sieve (Step 1); purging the reaction chamber to remove unadsorbed first precursor from the first precursor multilayer to form a first precursor monolayer (Step 2); introducing a second precursor into the reaction chamber to react the first precursor monolayer with at least a portion of the second precursor to form a composite layer (Step 3); and purging the reaction chamber to remove unreacted second precursor from the composite layer to form an inorganic thin film (Step 4), where the above cycles are repeated two or more times.

[0006] According to one embodiment of the present invention, step 1 may include a step of introducing a carbon molecular sieve and a first precursor into a reaction chamber (step 1-1), and a step of impregnating the carbon molecular sieve with the first precursor to form a first precursor multi-layer having at least a portion of the first precursor adsorbed thereon (step 1-2). Step 3 may also include a step of introducing a second precursor into the reaction chamber (step 3-1), and a step of impregnating the carbon molecular sieve having the first precursor monolayer formed in the pores with the second precursor to form a composite layer in which the first precursor monolayer and at least a portion of the second precursor react with each other (step 3-2). In addition, the time for impregnating the first precursor in step 1-2 may be 1 to 630 seconds, The pressure can be between 1 and 10 torr. In addition, the time for impregnating the second precursor in step 3-2 may be 1 to 630 seconds, and the pressure may be 1 to 10 torr. In addition, in step 1, the introduction of the first precursor may be carried out for 1 to 600 seconds. In addition, in step 3, the introduction of the second precursor may be carried out for 1 to 600 seconds. Furthermore, the purging in the stages 2 and 4 can be carried out independently for 1 to 600 seconds. During the cycle, the temperature of the carbon molecular sieve can be maintained at 80 to 300°C. The first precursor may also include one or more selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane. The second precursor may also include one or more selected from the group consisting of H2O, O3, H2O plasma, O3 plasma, and O2 plasma. The gas used for purging in any one or more of the steps 2 and 4 may include nitrogen (N2) or argon (Ar). The cycle can be repeated 2 to 320 times. [Effects of the Invention]

[0007] The carbon molecular sieve modified by the method of an embodiment of the present disclosure may form an inorganic thin film on the surface of the pores. In an embodiment of the present disclosure, the method can adjust the adsorption amount depending on the type of gas by finely controlling the pore size, thereby increasing the separation selectivity depending on the type of gas. The method according to an embodiment of the present disclosure can be performed at a lower temperature than conventional chemical vapor deposition (CVD) methods and allows for precise process control. In an embodiment of the present disclosure, the trade-off of a significant decrease in specific surface area is minimized, and gas adsorption capacity can be maximized even with a reduced pore size. The method of an embodiment of the present disclosure may enable pore control of carbon molecular sieves to effectively sieve various gas molecules according to their sizes. The method of one embodiment of the present disclosure can control the pore size of carbon molecular sieves at the angstrom (Å) level, and can control the pore size distribution, particularly in the micropore region. The method according to an embodiment of the present disclosure can effectively introduce an inorganic thin film into the pores of a carbon molecular sieve and form a thin film more uniformly than the existing CVD process. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows the measured gas adsorption amount in Experimental Example 1. [Figure 2] FIG. 2 shows the pore volume distribution according to the pore width of Experimental Example 1 measured using the HK model. [Figure 3] FIG. 3 shows the pore volume distribution according to the pore width of Experimental Example 1 measured using the NLDFT model. [Figure 4] FIG. 4 shows a graph of the BET surface area of ​​Experimental Example 1. [Figure 5] FIG. 5 shows a graph of the HK median pore width of Experimental Example 1. [Figure 6] FIG. 6 shows the measured gas adsorption amount in Experimental Example 2. [Figure 7] FIG. 7 shows the pore volume distribution according to the pore width in Experimental Example 2 measured using the HK model. [Figure 8] FIG. 8 shows the pore volume distribution according to the pore width of Experimental Example 2 measured using the NLDFT model. [Figure 9] FIG. 9 shows a graph of the BET surface area of ​​Experimental Example 2. [Figure 10] FIG. 10 shows a graph of the HK median pore width of Experimental Example 2. [Figure 11] FIG. 11 shows the measured gas adsorption amount in Experimental Example 3. [Figure 12] FIG. 12 shows the pore volume distribution according to the pore width in Experimental Example 3 measured using the HK model. [Figure 13a] FIG. 13a shows the pore volume distribution according to the pore width of Experimental Example 3 measured using the NLDFT model. [Figure 13b] FIG. 13b shows the pore volume distribution according to the pore width of Experimental Example 3 measured using the NLDFT model. [Figure 14] FIG. 14 shows a graph of the BET surface area of ​​Experimental Example 3. [Figure 15] FIG. 15 shows a graph of the HK median pore width in Experimental Example 3. [Figure 16] FIG. 16 shows the adsorption selectivity of N2 gas and O2 gas in Experimental Example 4. [Figure 17] FIG. 17 shows the gas adsorption data using CO2 in Experimental Example 4. [Figure 18] FIG. 18 shows a graph of the gas adsorption amount in Experimental Example 5. [Figure 19] FIG. 19 shows a graph of the BET surface area of ​​Experimental Example 5. [Figure 20] FIG. 20 shows the pore volume distribution according to the pore width of Experimental Example 5 measured using the NLDFT model. [Figure 21] FIG. 21 shows the pore volume distribution according to the pore width in Experimental Example 5 measured using the HK model. [Figure 22] FIG. 22 shows a graph of the HK median pore width of Experimental Example 5. [Figure 23] FIG. 23 shows the gas adsorption amount and BET surface area of ​​Experimental Example 6. [Figure 24] FIG. 24 shows the pore volume distribution according to the pore width of Experimental Example 6 measured using the NLDFT model. [Figure 25] FIG. 25 shows the pore volume distribution according to the pore width in Experimental Example 6 measured using the HK model. [Figure 26] FIG. 26 shows a graph of the HK median pore width of Experimental Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, terms such as first and second are used to describe various components, and the terms are used only to distinguish one component from another. Furthermore, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly indicated. In this specification, the terms "comprise," "include," "comprise," "have," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood not to preclude the presence or possibility of addition of one or more other features, numbers, steps, components, or combinations thereof.

[0010] Furthermore, in the present invention, when it is stated that each layer or element is formed "on top of" or "on" another layer or element, it means that each layer or element is formed directly on the other layer or element, or that other layers or elements can be additionally formed between each layer, on the object, or on the substrate. The present invention can be modified in various ways and can have various forms, and the specific embodiments will be illustrated and described in detail below, but it should be understood that this is not intended to limit the invention to the specific disclosed forms, and that the invention includes all modifications, equivalents, and alternatives falling within the spirit and technical scope of the invention.

[0011] The term "molecular sieve" is the trade name of synthetic zeolite industrially produced by Linde Corporation in the United States. Molecular sieves have a large number of uniformly sized fine pores and have excellent adsorption power, so as the name implies, they have the function of separating molecules. Currently, the term "molecular sieve" has become a broad term and is used as a scientific and technical term to refer to porous materials with uniformly sized pores arranged in a three-dimensional array. Because molecular sieves exhibit selectivity for molecules of a specific size due to their uniform pore size, they can be widely used as catalysts, catalyst supports, adsorbents, etc.

[0012] Carbon molecular sieves (CMS) are molecular sieves whose primary component is carbon. Compared to metal oxide-based molecular sieve materials such as zeolites, carbon molecular sieves have many advantages, including high thermal and hydrothermal stability, chemical resistance, and organophilicity. Carbon molecular sieves can also be used in a variety of applications, such as catalyst supports, adsorbents, sensors, and electrode materials. The pore size of the carbon molecular sieve determines whether gases are subject to the sieving effect or not. For example, the kinetic diameter of methane is 3.8 Å (0.38 nm), while the kinetic diameter of nitrogen is 3.64 Å (0.364 nm). Therefore, carbon molecular sieves with pore sizes intermediate between these two can be used as the most effective methane / nitrogen molecular sieves. The synthesis process of carbon molecular sieves usually involves a pyrolysis process. In this process, methods have been devised to increase the pore size and porosity by adjusting the pyrolysis temperature and post-treatment with oxygen, etc., but there is a limit to the increase.

[0013] Therefore, the present inventors have attempted to maintain the specific surface area while finely adjusting the pore size of the carbon molecular sieve by applying a separate process, atomic layer deposition (ALD), to the prepared carbon molecular sieve.

[0014] Atomic layer deposition (ALD) offers many advantages over traditional deposition methods. ALD relies on self-limiting surface reactions to provide precise thickness control, excellent conformality, and large-area uniformity. Atomic layer deposition is primarily used in semiconductor wafer processing, where an ALD process involves cycles with the following sequential steps: 1) adsorbing a precursor onto the substrate surface; 2) purging excess precursor molecules in the gas phase; 3) introducing a reactant that reacts with the precursor on the substrate surface; and 4) purging excess reactant. The above steps constitute one cycle, and the number of cycles can be counted to precisely control the deposition thickness.

[0015] According to an embodiment of the present invention, a method for modifying a carbon molecular sieve includes the following steps: (1) introducing a carbon molecular sieve and a first precursor into a reaction chamber to form a first precursor multilayer in which at least a portion of the first precursor is adsorbed in the pores of the carbon molecular sieve; (2) purging the reaction chamber to remove unadsorbed first precursor from the first precursor multilayer to form a first precursor monolayer; (3) introducing a second precursor into the reaction chamber to react the first precursor monolayer with at least a portion of the second precursor to form a composite layer; and (4) purging the reaction chamber to remove unreacted second precursor from the composite layer to form an inorganic thin film. The above cycles are repeated two or more times.

[0016] In step 1, a first precursor is introduced into the reaction chamber together with a carbon molecular sieve. At least a portion of the introduced first precursor is adsorbed into the pores of the carbon molecular sieve, and the unadsorbed first precursor is stacked in multiple layers, thereby forming the first precursor multilayer. Then, in step 2, the reaction chamber is purged to remove the unadsorbed first precursor from the first precursor multilayer, leaving only the first precursor layer adsorbed on the surface of the carbon molecular sieve pores, thereby forming a first precursor monolayer. Next, in step 3, a second precursor is introduced into the reaction chamber, and at least a portion of the second precursor reacts with the first precursor monolayer. The second precursor that does not react with the first precursor monolayer is placed on the reactant, thereby forming the composite layer. Then, in step 4, the reaction chamber is purged to remove the first precursor from the composite layer. The unreacted second precursor that does not react with the monolayer of the first precursor can be removed, thereby forming an inorganic thin film on the surface of the carbon molecular sieve pores.

[0017] Furthermore, in the present invention, the steps 1 to 4 are regarded as one cycle, and this cycle is carried out two or more times. Preferably, the cycle can be performed 2 to 320 times, more preferably 2 to 200 times. If the cycle is performed less than 2 times, there may be a problem that the carbon molecular sieve pores are hardly modified due to insufficient deposition, and if the cycle is performed more than 320 times, there may be a problem that many of the carbon molecular sieve pores are closed, resulting in a very small surface area and low adsorption efficiency.

[0018] According to one embodiment of the present invention, step 1 may include a step of introducing a carbon molecular sieve and a first precursor into a reaction chamber (step 1-1), and a step of impregnating the carbon molecular sieve with the first precursor to form a first precursor multi-layer having at least a portion of the first precursor adsorbed thereon (step 1-2). The impregnation in step 1-2 is performed by interrupting the introduction of the first precursor into the reaction chamber and maintaining the state for a predetermined time. By performing the impregnation step, the first precursor multi-layer can be uniformly formed in the pores of the carbon molecular sieve, and the first precursor multi-layer can also be formed in the pores inside the carbon molecular sieve, providing time for the precursor to be sufficiently transmitted to the fine pores inside the carbon molecular sieve, thereby more effectively and uniformly controlling the pore size of the carbon molecular sieve.

[0019] In this case, the time for impregnating the first precursor may be 1 to 630 seconds, and the pressure may be 1 to 10 torr. Preferably, the time for impregnating the first precursor may be 50 to 600 seconds, and the pressure may be 2 to 8 torr. By satisfying the time and pressure ranges for impregnating the first precursor, the first precursor multi-layer can be uniformly formed in the pores of the carbon molecular sieve, and the first precursor multi-layer can also be formed in the pores inside the carbon molecular sieve, providing time for the first precursor to be sufficiently transmitted to the fine pores inside the carbon molecular sieve, which is more advantageous in terms of more effectively and uniformly controlling the pore size of the carbon molecular sieve.

[0020] According to an embodiment of the present invention, step 3 may include a step of introducing a second precursor into the reaction chamber (step 3-1), and a step of impregnating the carbon molecular sieve having the first precursor monolayer formed in the pores with the second precursor to form a composite layer in which the first precursor monolayer and at least a portion of the second precursor react with each other (step 3-2). The impregnation in step 3-2 is performed by interrupting the introduction of the second precursor into the reaction chamber and maintaining the state for a predetermined time. By performing the impregnation step, a composite layer can be uniformly formed on the first precursor monolayer on the pores of the carbon molecular sieve, and a composite layer can also be formed on the first precursor monolayer on the pores inside the carbon molecular sieve. This provides time for the precursor to be sufficiently transmitted to the fine pores inside the carbon molecular sieve, thereby more effectively and uniformly controlling the pore size of the carbon molecular sieve.

[0021] In this case, the impregnation time of the second precursor may be 1 to 630 seconds, and the pressure may be 1 to 10 torr. Preferably, the impregnation time of the second precursor may be 50 to 600 seconds, and the pressure may be 2 to 8 torr. By satisfying the above ranges of the impregnation time and pressure, a composite layer is uniformly formed on the monolayer of the first precursor on the pores of the carbon molecular sieve, and a composite layer is also formed on the monolayer of the first precursor on the pores inside the carbon molecular sieve. This provides time for the second precursor to be sufficiently transmitted to the fine pores inside the carbon molecular sieve, which is more advantageous in terms of more effectively and uniformly controlling the pore size of the carbon molecular sieve.

[0022] In addition, the introduction of the first precursor in the step 1 may be carried out for 1 to 600 seconds, and the introduction of the second precursor in the step 3 may be carried out for 1 to 600 seconds. Precursor introduction can be carried out for 1 to 600 seconds. Specifically, the precursor introduction times in steps 1 and 3 can be independently 1 second or more, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more to 600 seconds or less, 300 seconds or less, 100 seconds or less, 50 seconds or less, or 20 seconds or less. The pore size of the carbon molecular sieve can be controlled depending on the type of gas selected by controlling the precursor introduction time within the above range. However, if the precursor introduction time is less than 1 second, pore control may be ineffective due to incomplete atomic layer deposition, and if it exceeds 600 seconds, many pores in the carbon molecular sieve may be closed, resulting in a very low surface area and low adsorption efficiency.

[0023] The purge times of the stages 2 and 4 may be independently 1 to 1000 seconds. For example, the purge times of the stages 2 and 4 may be independently 1 second or more, 5 seconds or more, 10 seconds or more, 15 seconds or more, 30 seconds or more, or 60 seconds or more to 1000 seconds or less, 900 seconds or less, 800 seconds or less, 700 seconds or less, or 600 seconds or less. If the purging time is too short, precursor residues may remain, resulting in the deposition of an inorganic oxide thin film that is thicker than intended, and if the purging time exceeds the above range, it may cause a decrease in process efficiency.

[0024] During the cycle, the temperature of the carbon molecular sieve can be maintained at 80 to 300°C, preferably, the temperature of the carbon molecular sieve can be maintained at 90 to 190°C. The pore size of the carbon molecular sieve can be controlled depending on the type of gas to be selected by controlling the temperature of the carbon molecular sieve within the above range. If the temperature of the carbon molecular sieve is less than 80°C, defects may occur in the inorganic thin film formed due to incomplete reaction. If the temperature is more than 300°C, excessive inorganic thin film may be formed in the pores of the carbon molecular sieve, resulting in a very small surface area of ​​the carbon molecular sieve and a low adsorption efficiency.

[0025] By performing the cycle, the inorganic thin film formed in the pores of the carbon molecular sieve may contain at least one of an oxide of the first precursor and a nitride of the first precursor.

[0026] The first precursor may include one or more selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane. Preferably, the first precursor includes trimethylaluminum, which may be advantageous for achieving the effects aimed at by the present invention.

[0027] The second precursor can be any material that can react with the first precursor to form an oxide or nitride of the first precursor, but preferably includes at least one selected from the group consisting of HO, O, HO plasma, O plasma, and O plasma, which may be advantageous in achieving the effects of the present invention.

[0028] The gas used for purging in any one or more of steps 2 and 4 can be any gas commonly used for purging in the art, but may preferably include nitrogen (N2) or argon (Ar). [Example]

[0029] Preferred examples are presented below to aid in understanding the invention, but the following examples are merely for the purpose of illustrating the invention and are not intended to limit the invention thereto. In the following, activated carbon is used as the carbon molecular sieve, and the following experimental cycle is counted as one cycle. We carried out an experimental example.

[0030] Experimental Cycle

[0031] (1st stage) The reaction chamber was maintained at a vacuum state with a base pressure of 40 mTorr or less. An activated carbon (carbon molecular sieve) substrate and trimethylaluminum as a first precursor were introduced into the reaction chamber. Trimethylaluminum was vaporized outside the reaction chamber and introduced into the reaction chamber in gas form (introduction time: 2 seconds). A first precursor multilayer was formed in which at least a portion of the first precursor was adsorbed into the pores of the carbon molecular sieve. (Stage 2) Next, the inside of the reaction chamber was purged with nitrogen (N2) gas for 60 seconds to remove unadsorbed first precursor from the first precursor multilayer, leaving only the first precursor layer adsorbed on the surface of the carbon molecular sieve pores, forming a first precursor monolayer. (Stage 3) Next, a second precursor, HO, was introduced into the reaction chamber, and the first precursor monolayer and at least a portion of the second precursor were reacted to form a composite layer. The second precursor was vaporized outside the chamber and introduced in gas form for 2 seconds. During this process, the second precursor in contact with the first precursor monolayer reacted, and the unreacted second precursor was deposited on the reactant, forming a composite layer. (Stage 4) Next, the inside of the reaction chamber was purged with nitrogen (N2) gas for 60 seconds to remove unreacted second precursor, thereby forming an inorganic thin film (oxide of the first precursor). During steps 1 to 4, the temperature of the activated carbon was maintained at 150°C. In the following experimental examples, the gas adsorption amount, pore volume distribution depending on pore width, BET surface area, HK median pore width, and IAST adsorption selectivity were all measured by the following methods.

[0032] Gas adsorption amount

[0033] To measure the gas adsorption amount, the sample was thoroughly degassed at 300°C for more than 6 hours, and then heated to a relative pressure of 1*e using a Micromeritics 3Flex device with N2 and Ar gas at approximately -195°C and -185°C, respectively. -7Gas adsorption was carried out while changing the pH from 0 to 1, and the amount of gas adsorbed by the sample was measured in volume.

[0034] Pore ​​volume distribution by pore width

[0035] Pore ​​size distributions were determined from adsorption isotherms using nonlocal density functional theory (NLDFT) and the HK (Horvath-Kawazoe) slit pore model.

[0036] BET surface area

[0037] The Brunauer-Emmett-Teller equation was used to calculate the BET surface area from the adsorption isotherms.

[0038] HK median pore width

[0039] The HK (Horvath-Kawazoe) slit pore model was used to calculate the median value from the pore size distribution results to determine the HK median pore width value.

[0040] IAST adsorption selectivity

[0041] In the following experimental examples, IAST adsorption selectivity is the adsorption selectivity of O2 gas relative to N2 gas, and the O2 and N2 gas adsorption amounts were measured using a Belsorp HP device under conditions of 120 kPa and 298.15 K. Then, the O2 and N2 selectivity in air separation (N2:O2 = 79:21) based on the ideal adsorption solution theory (IAST) was calculated using the following equation.

number

number

number

number

number

number

number

[0042] Experimental Example 1: Confirmation of physical properties by changing the number of atomic layer deposition cycles

[0043] The experimental cycle was repeated 1, 30, 100, and 300 times to obtain the modified activity. The gas adsorption capacity, pore volume distribution according to pore width, BET surface area, and HK median pore width of the modified activated carbon were determined using the above methods.

[0044] Referring to FIG. 1, it was confirmed that the more cycles were performed and the more modified, i.e., the more precursors were deposited in the pores of the activated carbon, the less gas was adsorbed compared to the activated carbon before modification. The graph in Figure 2, analyzed using the HK model, shows changes in pore size in the micropore region of 2 nm or less. In particular, there was no significant change in the region of 0.5 nm or less, but in the region of pores larger than that, a general decrease in pore size was observed as the number of ALD cycles increased. Furthermore, the graph in Figure 3, analyzed using the NLDFT model, confirms that as the process cycles increase, pores generally decrease throughout the micro to mesopore region. In particular, the graph zooming in on the micropore region of 2 nm or less shows no significant change in ultramicropores of 0.5 nm or less, but a clear decrease in micropores of 1 nm to 2 nm, indicating that the application of the ALD process reduces larger pores and increases the proportion of relatively small pores. However, when a very thick ALD process of 300 cycles was applied, the ultramicropore region clearly decreased, indicating that excessive Al2O3 film deposition resulted in general pore closure. The BET surface area in Figure 4 also confirmed that the surface area decreased as the number of cycles increased and the material was modified. Furthermore, when calculating the median pore width based on the HK median pore width graph in Figure 5, a decrease in the average width was confirmed with an increase in the number of ALD cycles. When one cycle was performed, there was almost no difference in the specific surface area compared to when no cycles were performed, but the decrease in pore width was significant.

[0045] Experimental Example 2: Confirmation of physical properties depending on precursor injection time

[0046] The same experimental cycle was performed as in the previous experimental cycle, except that the first precursor injection time was 15 seconds, the second precursor injection time was 15 seconds, and the purge time between each precursor injection was 600 seconds. The experimental cycle was performed 10 times to obtain modified activated carbon. That is, although the precursor injection time was significantly increased, the number of cycle repetitions was reduced by 1 / 10, maintaining the overall process time similar to that of the 100-cycle experiment in Experimental Example 1. The gas adsorption capacity, pore volume distribution according to pore width, BET surface area, and HK median pore width of the modified activated carbon were confirmed by the above-mentioned methods.

[0047] As in Experimental Example 1, it was confirmed that the gas adsorption capacity of the modified activated carbon after 10 cycles was lower than that of the unmodified activated carbon (see Figure 6). In addition, even though the total process time and the total amount of precursor injected were similar, it was confirmed that maintaining a longer precursor injection time helps the ALD precursor penetrate deep into the complex porous structure of the activated carbon, and is effective in depositing the precursor into the pores inside the activated carbon. The graph in Figure 7, analyzed using the HK model, shows changes in pore size in the micropore region of 2 nm or less. While there was no significant change in the region of 0.4 nm or less, in the region of pores larger than this, a general decrease in pore size was observed as the number of ALD cycles increased. This indicates that, compared to Experimental Example 1, even smaller pores were significantly reduced in size, making it possible to control pore size over a wider range. In addition, the graph of Figure 8, which was analyzed using the NLDFT model, shows that the volume of micropores and mesopores of 0.5 nm or more is effectively reduced, while the volume of ultramicropores of 0.5 nm or less is maintained. It was also confirmed from the BET surface area in Figure 9 that the surface area of ​​the modified activated carbon was smaller than that of the unmodified activated carbon. In addition, the median pore width was calculated based on the HK median pore width graph in Figure 10. In this case, a decrease in average width was observed in the 10-cycle ALD process similar to that in the 300-cycle process of Experimental Example 1.

[0048] In particular, when comparing Experimental Example 1 and Experimental Example 2, it was confirmed that the change in injection time affected the gas adsorption amount and BET surface area. This was thought to be due to the fact that the longer the injection time, the more uniformly the gas is deposited within the carbon precursor.

[0049] Experimental Example 3: Confirmation of physical properties depending on whether or not the precursor is impregnated

[0050] First, the physical properties of unmodified activated carbon and activated carbon modified by further including a precursor impregnation step in the experimental cycle were compared. The modification method including the precursor impregnation step in this experiment further included (Step 1) introducing the first precursor, increasing the pressure for 24 seconds to reach 5 torr, and then impregnating for 600 seconds, and (Step 3) introducing the second precursor, increasing the pressure for 27 seconds to reach 5 torr, and then impregnating for 600 seconds. The purge time in (Steps 2) and (Step 4) was 10 seconds, and then a step of evacuating the reaction chamber for 60 seconds without purging was added. The method was the same as the experimental cycle. The experimental cycle including the impregnation step was repeated five times to modify the activated carbon. The gas adsorption capacity, pore volume distribution by pore width, BET surface area, and HK median pore width of the modified activated carbon were then determined using the methods described above. In addition, the impregnation pressure was changed from 5 torr to 0.5 torr, 1 torr, and 3 torr, respectively, and the physical properties were measured. The impregnation time was changed from 600 seconds to 0.5 seconds, 300 seconds, and 1200 seconds, respectively, and the physical properties were measured.

[0051] As shown in Figures 11a and 11b, the gas adsorption capacity of the modified activated carbon was confirmed to be lower than that of the unmodified activated carbon through the experimental cycle including the impregnation step. It was also confirmed that the higher the impregnation pressure and the longer the impregnation time, the lower the amount of adsorbed gas. Furthermore, when the impregnation pressure was 0.5 torr and the impregnation time was 0.5 seconds, the difference in the amount of adsorbed gas was minimal compared to when the impregnation was not performed. The graphs in Figures 12a and 12b, analyzed using the same HK model as in Experimental Example 2, show changes in pore size in the micropore region of 2 nm or less. While there are no significant changes in the region of 0.3 nm or less, in the region of pores larger than this, a general decrease in pore size was observed as the infiltration pressure and infiltration time increased. This confirms that, compared to Experimental Example 2, even smaller pores were significantly reduced, enabling pore size control over a wider range. In addition, the graphs in Figures 13a and 13b, which were analyzed using the NLDFT model, show that the volume of micropores and mesopores larger than 0.45 nm is effectively reduced, while ultramicropores smaller than 0.45 nm are maintained. Because the reactants can be efficiently injected into the interior during the impregnation process, it is possible to control the pore size even with fewer cycles (5 cycles), and it was found that the pore size can be controlled by changing the impregnation pressure and impregnation time. The BET surface area of ​​the modified activated carbon (Figures 14a and 14b) also confirmed that the surface area was smaller than that of the unmodified activated carbon. It was also confirmed that the surface area decreased as the impregnation pressure and impregnation time increased.

[0052] In particular, when comparing Experimental Example 2 and Experimental Example 3, it was confirmed that the BET surface area decreased slightly, including the impregnation step, despite the decrease in the number of cycles (see Figure 15). In addition, as the impregnation pressure and impregnation time increased, a decrease in pore width was observed, and the impregnation time In the case of 0.5 seconds, it was confirmed that the reduction in pore width was minimal compared to the case where no treatment was performed (Bare AC1).

[0053] Experimental Example 4: Confirmation of gas adsorption selectivity

[0054] The adsorption degree, IAST selectivity, i.e., adsorption selectivity and adsorption amount, were compared for unmodified activated carbon, activated carbon modified by five experimental cycles including the impregnation step, and activated carbon modified by 100 experimental cycles without the impregnation step of Experimental Example 1. In this experiment, the adsorption selectivity of O2 gas relative to N2 gas was confirmed as shown in Figure 16.

[0055] Referring to FIG. 16, the activated carbon modified by 100 cycles without the impregnation step in Experimental Example 1 exhibited the highest adsorption selectivity, while the activated carbon modified by 5 cycles including the impregnation step exhibited an adsorption selectivity at a similar level to that of the unmodified activated carbon. Furthermore, a more specific inference can be made from the BET results using CO2 in Figure 17. The ultramicropore region of 0.4 nm or less, which cannot be measured by the size of N2 or Ar gas molecules, can be observed by using CO2. The results of 100 ALD cycles showed an increase in the volume of 0.36 nm-sized micropores compared to 5 cycles including the impregnation process. This is inferred to be because in the process including the impregnation process, large pores become smaller and small pores also become smaller, whereas in the process without the impregnation process, large pores become smaller and 0.36 nm ultramicropores are generated, leaving the existing ultramicropores unaffected by the process.

[0056] Experimental Example 5: Confirmation of physical properties by controlling precursor injection time and purging time

[0057] The same experimental cycle as in the previous example was carried out, except that the precursor injection times in (Steps 1) and (Step 3) and the purge times in (Steps 2) and (Step 4) were controlled as shown in the table below. The activated carbon was modified by repeating the precursor injection time and purge time control cycle 100 times, and the gas adsorption capacity, pore volume distribution according to pore width, BET surface area, and HK median pore width were determined.

[0058] [Table 1] The divisions in Table 1 are used in the following graphs. 18, it was confirmed that the amount of adsorbed gas decreased as the introduction time of the first and second precursors increased. In this case, when the precursor introduction time was 0.5 seconds, the difference in the amount of adsorbed gas was minimal compared to when no precursor was introduced (Bare AC1). The BET surface area graph in Figure 19 shows that the surface area is hardly affected by an increase in the purging time, but when the precursor is introduced for a certain period of time or longer, the surface area decreases rapidly, which leads to a decrease in the amount of gas adsorption (5-30-5-30). Furthermore, when the precursor introduction time was 0.5 seconds, the difference in surface area was minimal compared to when no purging was performed (Bare AC1). In addition, the change in pore width, like the BET, is not significantly affected by the change in purging time. Referring to the results in Figures 20a and 20b, it was observed that when the purge time was shortened to 30 seconds compared to the existing 2-60-2-60 cycle, the pore size due to residual precursors became even smaller. Furthermore, when the precursor injection time was reduced to 0.5 seconds, the difference with Bare AC1 was minimal, and when the precursor injection time was increased to 5 seconds, the larger pore size was observed to become smaller, confirming that the precursor injection time has a greater effect on the deposition pattern. The analysis of the results based on the HK model in the graph of FIG. 21 confirmed that, similar to the NLDFT results, more ALD film was deposited as the precursor injection time increased due to the effect of changes in purge time. The calculation results for the HK median pore width in Figure 22 show that the average pore size decreases as the purge time and precursor injection time decrease. However, in the case of 5-30-5-30, the size of pores smaller than 0.5 nm also decreased due to excessive deposition, and the overall downshift of pores reduced the effect of pore size reduction. Furthermore, in the case of 0.5-30-0.5-30, the difference from Bare AC1 was minimal.

[0059] Experimental Example 6: Confirmation of physical properties depending on substrate temperature

[0060] The same method as in the previous experimental example was used, but the substrate temperatures were varied to 90°C, 150°C, and 210°C. This cycle was repeated 100 times each, and the gas adsorption capacity, pore volume distribution by pore width, BET surface area, and HK median pore width of the modified activated carbon were determined. Referring to the graph of BET surface area in FIG. 23, it was confirmed that the surface area tends to decrease as the substrate temperature increases, and similarly, the amount of gas adsorption also decreases. In both the pore size analysis results based on the NLDFT model (Figure 24) and the HK model (Figure 25), a decrease in pore size was clearly observed as the substrate temperature increased, and a significant decrease in micropores was observed, especially when the experimental conditions were 210°C. The calculation results of the HK median pore width in Figure 26 show that the pore size generally decreases with increasing temperature up to 150°C. However, at 210°C, the size of pores smaller than 0.5 nm also decreases due to excessive deposition, and the pore size reduction effect decreases due to the overall downshift of the pores.

Claims

1. Step 1: introducing a carbon molecular sieve and a first precursor into a reaction chamber to form a first precursor multi-layer in which at least a portion of the first precursor is adsorbed in the pores of the carbon molecular sieve; Purging the inside of the reaction chamber to remove unadsorbed first precursor from the first precursor multilayer to form a first precursor monolayer (Step 2); introducing a second precursor into the reaction chamber to react the first precursor monolayer with at least a portion of the second precursor to form a composite layer (Step 3); and and purging the inside of the reaction chamber to remove unreacted second precursor from the composite layer to form an inorganic thin film (Step 4).

2. The step 1 is introducing a carbon molecular sieve and a first precursor into a reaction chamber (step 1-1); and 2. The method for modifying a carbon molecular sieve according to claim 1, further comprising: impregnating the carbon molecular sieve with a first precursor to form a first precursor multi-layer having at least a portion of the first precursor adsorbed thereon (Step 1-2).

3. The step 3 is introducing a second precursor into the reaction chamber (step 3-1); and 2. The method for modifying a carbon molecular sieve according to claim 1, further comprising: impregnating a carbon molecular sieve having a first precursor monolayer formed in pores with a second precursor to form a composite layer in which the first precursor monolayer and at least a portion of the second precursor react with each other (Step 3-2).

4. 3. The method of claim 2, wherein the time for impregnating the first precursor in step 1-2 is 1 to 630 seconds, and the pressure is 1 to 10 torr.

5. 4. The method of claim 3, wherein the second precursor is impregnated for 1 to 630 seconds under a pressure of 1 to 10 torr in the step 3-2.

6. 2. The method of claim 1, wherein the first precursor is introduced for 1 to 600 seconds in Step 1.

7. 2. The method of claim 1, wherein the second precursor is introduced for 1 to 600 seconds in step 3.

8. 2. The method for modifying a carbon molecular sieve according to claim 1, wherein the purging in step 2 and step 4 is performed independently for 1 to 600 seconds.

9. 2. The method for modifying carbon molecular sieves according to claim 1, wherein the temperature of the carbon molecular sieve is maintained at 80 to 300°C during the cycle.

10. 2. The method for modifying a carbon molecular sieve according to claim 1, wherein the first precursor comprises at least one selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane.

11. The second precursor is H ２ O, O ３ , H ２ O plasma, O ３ Plasma and O ２ 10. The method for modifying a carbon molecular sieve according to claim 1, comprising one or more selected from the group consisting of plasma.

12. The gas used for purging in any one or more of the steps 2 and 4 is nitrogen (N ２ 2. The method for modifying a carbon molecular sieve according to claim 1, wherein the carbon molecular sieve is modified with a nitrogen atmosphere.

13. 2. The method for modifying a carbon molecular sieve according to claim 1, wherein the cycle is performed 2 to 320 times.

Images