Core-shell composite for greenhouse gas adsorption and method for preparing same

Abstract

An aspect of the present invention provides a method for preparing a core-shell composite for greenhouse gas adsorption, the method comprising the steps of: (a) immersing activated carbon in a solution containing an organic ligand compound to attach an organic ligand to the surface of the activated carbon; (b) adding a metal source to the solution to thereby obtain a composite in which the surface of the activated carbon is coated with a metal-organic framework (MOF); and (c) carbonizing the composite at a temperature of 900-1200oC for 1-3 hours to thereby obtain a core-shell composite in which a porous carbon layer derived from the MOF is formed on the surface of the activated carbon.

Description

Core-shell composite for greenhouse gas adsorption and method for manufacturing the same

[0001] The present invention relates to a core-shell composite for greenhouse gas adsorption and a method for producing the same, and more particularly, to a porous adsorbent material having improved adsorption capacity for greenhouse gases by utilizing the characteristics of a commercial carbon adsorbent and a metal-organic framework, and a method for producing the same.

[0002] The present invention relates to the project identification number 1711196879 and project number PNK9770, which were carried out with the support of the Korea Institute of Materials Science and Technology with funding from the Ministry of Science and ICT.

[0003] With the recent intensifying discussion on limiting and regulating greenhouse gas emissions, liquefied natural gas (LNG), which emits less carbon dioxide, is being used in ships and other fuels to reduce greenhouse gases. However, a drawback of LNG fuel is the inevitable methane slip issue, which occurs when exposed to ambient temperatures or naturally vaporizes due to wave action, resulting in the generation of boil-off gas, mainly methane (CH4). Capturing methane in advance to reduce methane emissions and reusing it as an energy source can reduce greenhouse gas emissions while simultaneously increasing energy independence, resulting in economic benefits.

[0004] Methane's greenhouse effect is known to be approximately 28 times greater than carbon dioxide, so selectively capturing methane emitted from LNG ships and other sources (at high capacities) could help mitigate climate change. Currently, activated carbon, silica, and zeolite are being studied as greenhouse gas adsorbents. However, it is difficult to regard these as highly selective adsorbents for methane adsorption. Therefore, the development of adsorbents that efficiently adsorb methane is necessary, and research into adsorbents that can achieve the desired methane storage capacity is ongoing. Recently, research is being conducted to improve methane adsorption performance using metal-organic frameworks (MOFs).

[0005] MOFs are crystalline porous materials formed by the coordination bonding of metal ions or clusters with organic ligands. The internal pore diameter of MOFs can be arbitrarily controlled depending on the starting materials and synthesis conditions, resulting in a specific surface area of ​​7,000 m 2 / g or more are known to be possible. MOFs are similar to zeolites in that they have a porous crystal structure, but their applications are broader than zeolites in that they can create crystals with an infinite variety of structures and properties through the combination of metal clusters and organic ligands.

[0006] However, MOFs are vulnerable to moisture and, because they are in powder form, they are difficult to utilize on their own because a type of differential pressure phenomenon occurs in which the internal pressure of the MOF becomes higher than the external atmospheric pressure when gas molecules are adsorbed into the MOF structure.

[0007] Meanwhile, activated carbon is a widely used commercial adsorbent due to its low price, well-developed pores, high specific surface area, and surface chemical properties. However, during the use of activated carbon, delamination can occur, which refers to the separation of activated carbon particles and the subsequent detachment of small particles from the surface. This delamination can be problematic, as it can reduce the performance and durability of activated carbon.

[0008] The present invention aims to address these conventional problems by combining MOF and activated carbon to enhance the mechanical stability of both, and to provide a novel porous adsorption material with high gas adsorption efficiency at a low unit cost and a method for manufacturing the same by reducing the amount of MOF used compared to using the powder itself. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

[0009] According to one aspect of the present invention, a method for manufacturing a core-shell composite for greenhouse gas adsorption is provided.

[0010] The method for manufacturing the core-shell composite for greenhouse gas adsorption comprises the steps of: (a) attaching the organic ligand to the surface of the activated carbon by impregnating the activated carbon in a solution containing an organic ligand compound; (b) adding a metal source to the solution to obtain a composite coated with a metal-organic framework (MOF) on the surface of the activated carbon; and (c) subjecting the composite to a temperature of 900 to 1200° C. o A step of obtaining a core-shell composite in which a porous carbon layer derived from the metal-organic framework is formed on the surface of the activated carbon by carbonizing at a temperature of C for 1 to 3 hours; may include;

[0011] Alternatively, the method for manufacturing the core-shell composite for greenhouse gas adsorption comprises the steps of: (a) attaching metal particles to the surface of the activated carbon by impregnating activated carbon in a metal source-containing solution; (b) adding an organic ligand compound to the solution to obtain a composite coated with a metal-organic framework (MOF) on the surface of the activated carbon; and (c) subjecting the composite to a temperature of 900 to 1200° C. o A step of obtaining a core-shell composite in which a porous carbon layer derived from the metal-organic framework is formed on the surface of the activated carbon by carbonizing at a temperature of C for 1 to 3 hours; may include;

[0012] In one embodiment, the organic ligand compound may be one selected from the group consisting of 2-methylimidazole, imidazole, salicylic acid, benzenetricarboxylic acid, 1,4-benzenedicarboxylic acid, and mixtures thereof.

[0013] In one embodiment, the metal source may include at least one metal selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr).

[0014] In one embodiment, the complex may be a metal-organic framework (MOF) coated to a thickness of 50 to 300 nm.

[0015] In one embodiment, the metal-organic framework may be characterized by having a structure in which a metal and an organic ligand form a coordination bond.

[0016] According to another aspect of the present invention, a core-shell composite for greenhouse gas adsorption is provided, which is manufactured by the method for manufacturing the core-shell composite for greenhouse gas adsorption.

[0017] The core-shell composite for greenhouse gas adsorption may include an activated carbon core; and a shell surrounding the surface of the activated carbon core and formed of a porous carbon layer derived from a metal-organic framework (MOF).

[0018] In one embodiment, the core-shell composite for greenhouse gas adsorption has a specific surface area of ​​300 to 2000 m 2 / g may be.

[0019] In one embodiment, the total pore volume of the core-shell composite for greenhouse gas adsorption is 0.2 to 0.8 cm 3 / g may be.

[0020] In one embodiment, the methane adsorption capacity of the core-shell composite for greenhouse gas adsorption may be 10 to 21 mg / g at room temperature and a relative pressure (P / P0) of 1.

[0021] In one embodiment, the activated carbon core may be characterized in that the shape thereof is maintained when adsorbing greenhouse gases.

[0022] According to another aspect of the present invention, a greenhouse gas adsorbent is provided in which the core-shell composite for greenhouse gas adsorption is provided in a packed structure.

[0023] According to the embodiment of the present invention as described above, by developing a porous adsorbent having excellent adsorption performance for greenhouse gases including methane and improved durability, greenhouse gas emissions generated from energy, industrial processes, agriculture, waste, etc. can be effectively controlled.

[0024] In addition, in manufacturing a porous adsorbent material for greenhouse gas adsorption, a composite can be manufactured in a simple manner without a complexation process by coating MOF on activated carbon, a commercial adsorbent material.

[0025] In addition, economic feasibility can be secured by using relatively inexpensive activated carbon and using less MOF materials, which have relatively high manufacturing costs.

[0026] Of course, the scope of the present invention is not limited by these effects.

[0027] FIG. 1 and FIG. 2 are schematic drawings illustrating a method for manufacturing a core-shell composite for greenhouse gas absorption according to an embodiment of the present invention.

[0028] Figure 3 is an SEM photograph of a complex according to a manufacturing example of the present invention, in which (a) shows activated carbon, and (b) to (e) show the appearance of MOF coated on the surface of activated carbon.

[0029] Figure 4 is an SEM photograph of a core-shell composite according to a manufacturing example of the present invention, in which (a) a shell is formed by first adding an organic ligand solution to activated carbon and then adding a metal solution 30 minutes later, (b) a shell is formed by first adding a metal solution to activated carbon and then adding an organic ligand solution 30 minutes later, and (c) a shell is formed by adding a metal solution to an organic ligand solution and then mixing it with activated carbon 30 minutes later.

[0030] Figure 5 is a graph showing a nitrogen adsorption for measuring the specific surface area and total pore volume of a complex according to a manufacturing example of the present invention (a), and a graph showing the methane adsorption capacity measured and compared at room temperature and a relative pressure of 1 (b).

[0031] Figure 6 is a graph showing nitrogen adsorption for measuring the specific surface area and total pore volume according to the carbonization temperature of MOF according to an embodiment of the present invention (a), and a graph showing methane adsorption capacity measured and compared at room temperature and relative pressure 1 (b).

[0032] Figure 7 is an SEM photograph of the surface of a core-shell composite obtained by carbonizing a composite manufactured according to an embodiment of the present invention.

[0033] FIG. 8 is a graph showing the characteristics of a core-shell composite manufactured according to comparative examples and examples of the present invention, wherein (a) is a nitrogen adsorption graph for measuring specific surface area and total pore volume, and (b) is a graph showing methane adsorption capacity measured and compared at room temperature and relative pressure 1.

[0034] Figure 9 is a photograph showing the results of a drop-off test of a core-shell composite manufactured according to a manufacturing example, comparative example, and example of the present invention.

[0035] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings. These embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. The following embodiments may be modified in various different forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0036] The term "core-shell" used in the present invention means a core and a shell structure surrounding the core, and may also be described as "core@shell" in this specification.

[0037] The term "porous adsorbent" used in the present invention refers to an adsorbent having a structure containing numerous pores within its interior. Because the porous adsorbent has numerous pores within its interior, it has a large surface area and can adsorb gas molecules such as methane (CH4) on its surface and pores.

[0038] Hereinafter, a method for manufacturing a core-shell composite for greenhouse gas adsorption according to an embodiment of the present invention and a core-shell composite for greenhouse gas adsorption manufactured thereby will be described.

[0039] First, a method for manufacturing a core-shell composite for greenhouse gas adsorption will be described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are schematic diagrams illustrating a method for manufacturing a core-shell composite for greenhouse gas adsorption according to an embodiment of the present invention.

[0040] First, prepare activated carbon (AC). Depending on the intended use, activated carbon can be manufactured with different particle sizes, shapes, etc., and powdered activated carbon (PAC) can be used in the present invention. Powdered activated carbon has the advantage of a large surface area, excellent adsorption efficiency, and low price.

[0041] When activated carbon is used alone, the particles may separate, causing small particles to fall off the surface. This delamination can reduce the performance and durability of the activated carbon, making it difficult to achieve sufficient adsorption. Therefore, it is necessary to form a shell by impregnating a material with a porous crystal structure to protect the activated carbon surface, thereby enabling more effective adsorption.

[0042] According to a preferred embodiment of the present invention, by directly growing MOF on the surface of activated carbon to form a shell, the delamination of the activated carbon can be prevented, and the pore structure of the MOF can be utilized to enhance the methane adsorption capacity and improve the adsorption performance of the activated carbon. Examples of the MOF include, but are not limited to, ZIF-67, ZIF-8, MOF-801, and HKUST-1.

[0043] The present invention proposes an efficient and controllable synthesis method for embedding an activated carbon core within a MOF shell. As illustrated in Figure 1, organic ligands are attached to the activated carbon surface and internal pores, followed by the addition of metal ions. This results in the formation of a metal-organic framework having a structure in which metal and organic ligands form coordination bonds on the activated carbon surface. In other words, a core-shell hybrid structure, AC@MOF, is generated.

[0044] In another embodiment, as illustrated in FIG. 2, metal particles are attached to the surface and internal pores of activated carbon, and then an organic ligand compound is added. This forms a core-shell composite (AC@MOF) in which a metal-organic framework is coated on the surface of the activated carbon.

[0045] First, an example for forming an AC@MOF complex will be described with reference to FIG. 1.

[0046] In Fig. 1(a), when activated carbon is supported on a solution in which an organic ligand compound is dissolved in a solvent, organic ligand molecules can be adsorbed on the surface of the activated carbon due to the porosity and large surface area of ​​the activated carbon.

[0047] The organic ligand compound may include various organic ligands used in MOF synthesis, and may include carboxylate, phosphonic acid, sulfonate, pyridyl, imidazolate, and azolate functional groups. For example, the organic ligand compound may be one selected from the group consisting of 2-methylimidazole, imidazole, salicylic acid, benzenetricarboxylic acid, terephthalic acid (1,4-benzenedicarboxylic acid), and mixtures thereof, but is not limited thereto.

[0048] As a solvent for dissolving the above organic ligand compound, solvents with high solubility such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dichloromethane (DCM), acetonitrile, acetone, diethylformamide, ethanol, methanol, and water are used. Since the solvent affects the characteristics of the MOF, it is desirable to select it according to the characteristics of the desired MOF.

[0049] It is preferable to add activated carbon in a ratio of 1 to 3 parts by weight per 100 parts by weight of the organic ligand compound. When the content of activated carbon is within the above range, the organic ligand can be well distributed on the surface of the activated carbon.

[0050] Next, in step (b), a metal source is added to the solution in which the organic ligand compound is dissolved.

[0051] As the above metal source, all alkaline earth metals or transition metal ions that are divalent, trivalent, and tetravalent cations can be used. Preferably, it can be composed of at least one metal selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr).

[0052] For example, as a source containing zinc (Zn), anhydrous zinc salts or hydrated zinc salts can be used. For example, zinc chloride (ZnCl2), zinc nitrate (Zn(NO3)2), zinc sulfuric acid (ZnSO4), or zinc acetate (Zn(OAc)2) can be used. Similarly, metal salts containing other divalent, trivalent, or tetravalent metal ions can be used, such as hydrated cobalt salts, hydrated manganese salts, or hydrated chromium salts. These metal sources can participate in the MOF structure by forming coordination bonds with organic ligands.

[0053] In one embodiment, the metal source is added at a ratio of 0.5 to 7 parts by weight per 100 parts by weight of the solution. When the content ratio of the metal source in the solution is within the above range, organic ligands and metal ions are coordinated to form MOF, and a core-shell structured complex having a metal-organic framework (MOF) shell on the surface of the activated carbon core is formed, and the MOF shell can be well formed in an appropriate size and shape in a controllable manner.

[0054] In this way, an AC@MOF composite can be obtained in the step (b). The MOF shell of the porous microcrystalline structure of the AC@MOF composite has a high specific surface area and small pore size, which can increase the adsorption capacity of greenhouse gases.

[0055] As another embodiment for forming an AC@MOF complex, FIG. 2 is described as an example.

[0056] In Fig. 2(a), when activated carbon is immersed in a solution in which a metal source is dissolved in a solvent, metal particles can be adsorbed on the surface of the activated carbon due to the porosity and large surface area of ​​the activated carbon.

[0057] As the above metal source, all alkaline earth metals or transition metal ions that are divalent, trivalent, and tetravalent cations can be used. Preferably, it can be composed of at least one metal selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr).

[0058] For example, as a source containing zinc (Zn), anhydrous zinc salts or hydrated zinc salts can be used. For example, zinc chloride (ZnCl2), zinc nitrate (Zn(NO3)2), zinc sulfuric acid (ZnSO4), or zinc acetate (Zn(OAc)2) can be used. Similarly, metal salts containing other divalent, trivalent, or tetravalent metal ions can be used, such as hydrated cobalt salts, hydrated manganese salts, or hydrated chromium salts. These metal sources can participate in the MOF structure by forming coordination bonds with organic ligands.

[0059] As a solvent for dissolving the above metal source, solvents with high solubility such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dichloromethane (DCM), acetonitrile, acetone, diethylformamide, ethanol, methanol, and water are used. Since the solvent affects the characteristics of the MOF, it is desirable to select it according to the characteristics of the desired MOF.

[0060] It is preferable to add activated carbon in a ratio of 1 to 3 parts by weight per 100 parts by weight of the solution containing the above metal source. When the content of activated carbon is within the above range, the metal particles can be well distributed on the surface of the activated carbon.

[0061] Next, in step (b) of Fig. 2, an organic ligand compound is added to the solution in which the metal source is dissolved.

[0062] The organic ligand compound may include various organic ligands used in MOF synthesis, and may include carboxylate, phosphonic acid, sulfonate, pyridyl, imidazolate, and azolate functional groups. For example, the organic ligand compound may be one selected from the group consisting of 2-methylimidazole, imidazole, salicylic acid, benzenetricarboxylic acid, terephthalic acid (1,4-benzenedicarboxylic acid), and mixtures thereof, but is not limited thereto.

[0063] In one embodiment, the organic ligand compound is added at a ratio of 0.1 to 3 parts by weight per 100 parts by weight of the solution. When the content ratio of the organic ligand compound in the solution is within the above range, the organic ligands and the metal ions are coordinated to form a MOF, and a core-shell structured complex having a metal-organic framework (MOF) shell on the surface of the activated carbon core is formed, and the MOF shell can be well formed in an appropriate size and shape in a controllable manner.

[0064] As a comparative example that deviates from the manufacturing method of the present invention, if a metal source and an organic ligand are first added to a solvent and then activated carbon is added, it is difficult to uniformly grow MOF to a certain size on the surface of the activated carbon, making it difficult to form an AC@MOF complex with a core-shell structure. In this case, the seed is formed solely by MOF before the MOF is formed as a MOF seed on the surface of the activated carbon core, making it difficult to effectively form a core-shell structure.

[0065] Since the core-shell composite manufactured to achieve the effects of the present invention is not in the form of MOF alone but in the form of activated carbon coated with MOF, it is preferable to attach an organic ligand or metal to the activated carbon and then add the metal or organic ligand in order to form the AC@MOF composite.

[0066] The thickness of the MOF layer coated on the activated carbon surface may range from 50 to 300 nm. When the MOF coating layer is formed as described above, it can be used for greenhouse gas adsorption and removal purposes because it has a large surface area even with a small amount. If the thickness of the MOF layer is less than 50 nm, it is difficult to sufficiently form a porous carbon layer from the MOF, and if it exceeds 300 nm, the manufacturing cost increases, which is not desirable.

[0067] Additionally, in step (c) of FIGS. 1 and 2, the AC@MOF composite is carbonized to obtain a core-shell composite. In the present specification, the carbonized AC@MOF composite (i.e., carbonized AC@MOF) refers to a carbon composite with a core-shell structure.

[0068] The above step (c) is a carbonization process that converts the MOF surface into a carbon layer, thereby controlling the surface properties of the microporous carbon layer derived from the MOF and improving the greenhouse gas adsorption capacity.

[0069] In the carbonization treatment of AC@MOF composite according to the embodiment, 900 to 1200 in an inert gas atmosphere o It is desirable to perform the process at a carbonization temperature of C for 1 to 3 hours.

[0070] Carbonization can be performed in an inert gas atmosphere, such as nitrogen or argon. The inert gas atmosphere prevents oxidation of the MOF and ensures a more uniform carbonization reaction.

[0071] The carbonization temperature can affect the carbonization reaction rate. In one embodiment, the carbonization temperature is 900 to 1200 oC range. Carbonization of AC@MOF composites at high temperatures can form carbides while preserving the high surface area and porous properties of the MOF. Consequently, the carbonized MOF possesses a high surface area and excellent gas adsorption properties. In other words, a shell composed of MOF-derived carbon can be formed.

[0072] According to an embodiment, the structural stability of the MOF shell can be improved by carbonization treatment, which allows for more stable use of the core-shell composite.

[0073] If the carbonization temperature is 900 o If it is lower than C, sufficient carbonization is not achieved, so it is difficult to expect the above benefits due to low porosity, and the carbonization temperature is 1200 o If it is higher than C, carbon crystallization may occur and the porosity may decrease, which is not desirable.

[0074] As an example, the carbonization treatment may be performed in the order of temperature increase, temperature maintenance, and cooling, and the heat treatment process may be divided into primary and secondary stages, etc., as needed.

[0075] The carbonization heat treatment time can also affect the carbonization reaction rate and porosity. In one embodiment, the carbonization heat treatment time is preferably 1 to 3 hours. If the carbonization heat treatment time is less than 1 hour, sufficient carbonization may not occur, and if it exceeds 3 hours, carbon crystallization may occur, reducing porosity, which is not desirable.

[0076] The core-shell composite obtained through the above step (c) can be utilized as a gas adsorption and storage material.

[0077] According to another aspect of the present invention, a core-shell composite for greenhouse gas adsorption is provided, which is manufactured by the method for manufacturing the core-shell composite for greenhouse gas adsorption.

[0078] A core-shell composite for greenhouse gas adsorption according to an embodiment of the present invention is a core-shell carbon composite comprising a shell made of carbon derived from a metal-organic framework (MOF) on the surface of an activated carbon core. This improves the disadvantage of the uneven pore distribution of the activated carbon, which makes it difficult to selectively adsorb methane and other substances.

[0079] The core-shell composite for greenhouse gas adsorption has a structure that can adsorb methane well because the shell has a microporous structure derived from MOF, and has a large surface area and a large total pore volume. Specifically, the specific surface area is 700 to 1300 m 2 / g, and the total pore volume is 0.3 to 0.7 cm 3 It is a structure formed with / g, ​​so methane can be well adsorbed.

[0080] The core-shell composite for greenhouse gas adsorption manufactured by carbonizing the AC@MOF composite according to the manufacturing method of the present invention has an increased gas adsorption capacity and excellent gas adsorption properties. Specifically, the methane adsorption capacity of the core-shell composite for greenhouse gas adsorption can be 10 to 21 mg / g at room temperature and a relative pressure of 1.

[0081] Similarly, the shedding amount of pure activated carbon was approximately 0.15% of the total weight. The shedding amount of activated carbon carbonized after MOF coating according to the manufacturing method of the present invention was almost zero. This is attributed to the stable core-shell structure, meaning that the activated carbon core hardly sheds before and after greenhouse gas adsorption, maintaining its shape. For example, the shedding amount of activated carbon carbonized after MOF coating can be less than 0.01%.

[0082] According to the embodiment of the present invention as described above, by growing MOF on the surface of activated carbon to form a shell, the detachment of activated carbon can be prevented, and by utilizing the micropore structure derived from MOF, the methane adsorption capacity can be improved and the adsorption performance of activated carbon can be improved.

[0083] In addition, the core-shell composite according to an embodiment of the present invention is easy to regenerate due to its structural stability. Regenerating the adsorbent involves separating the adsorbed gas and restoring the adsorbent to its initial state. However, conventional activated carbon has a problem of falling off after repeated adsorption, making regeneration and recycling difficult. However, in the case of activated carbon having a porous carbon layer derived from MOF on its surface according to an embodiment of the present invention, the amount of falling off is significantly reduced and the structure of the core-shell composite is maintained, making recycling easy.

[0084] Hereinafter, preferred examples are presented to aid in understanding the present invention. However, the following examples are provided only to facilitate a better understanding of the present invention, and the scope of the present invention is not limited by the examples.

[0085] Manufacturing Example 1: Preparation of AC

[0086] Powdered activated carbon was prepared using activated carbon (AC).

[0087] Manufacturing Example 2: Synthesis of AC@ZIF-67

[0088] ZIF-67 was synthesized according to the commonly known method for preparing the compound. Briefly, the activated carbon was supported on a solution of 2-methyl imidazole in methanol. A solution of cobalt nitrate hexahydrate in methanol was added. The reaction mixture was transferred to a reactor and synthesized at room temperature for 16 hours. The purple precipitate was collected by centrifugation and washed with ample methanol. Finally, the product was dried at room temperature.

[0089] Manufacturing Example 3: Synthesis of AC@ZIF-8

[0090] ZIF-8 was synthesized according to the generally known method for producing it. Briefly, the activated carbon was supported on a solution of 2-methyl imidazole in methanol. A solution of zinc nitrate hexahydrate in methanol was added. The reaction mixture was transferred to a reactor and heated at 80 o C for 10 minutes. The white precipitate was collected by centrifugation and washed with sufficient methanol. Finally, the product was dried at room temperature.

[0091] Manufacturing Example 4: Synthesis of AC@MOF-801

[0092] MOF-801 was synthesized according to the known method. Briefly, the activated carbon was supported in a solution containing formic acid and fumaric acid. To this, a solution containing zinc chloride octahydrate dissolved in DMF was added. The reaction mixture was transferred to a reactor and stirred at 120 o C for 16 h. The white precipitate was collected by centrifugation and washed with sufficient DMF and ethanol. Finally, the product was dried at room temperature.

[0093] Manufacturing Example 5: Synthesis of AC@HKUST-1

[0094] Benzenetricarboxylic acid was dissolved in methanol and then loaded onto activated carbon. A solution of copper nitrate trihydrate in methanol was added. The reaction mixture was transferred to a reactor and synthesized at room temperature for 3 hours. The blue precipitate was collected by centrifugation and washed with ample methanol. Finally, the product was dried at room temperature.

[0095] Experimental Example 1

[0096] The surface characteristics of the AC@MOF material synthesized according to the above manufacturing example were observed and the physical properties were measured.

[0097] Figure 3 is an SEM photograph of a methane adsorbent manufactured according to (a) Manufacturing Examples 1 to 5, wherein (a) of Figure 3 shows activated carbon according to Manufacturing Example 1, and (b) to (e) of Figure 3 show the state of MOF coated on the surface of activated carbon according to Manufacturing Examples 2 to 5, respectively. As a result of observing Figure 3, it was confirmed that MOF was uniformly formed on the surface of AC@MOF compared to pure activated carbon.

[0098] Table 1 below and FIG. 4 are a characteristic comparison table and SEM photographs showing the effect of the mixing order of materials on shell formation in the process of obtaining AC@ZIF-8 core-shell composites according to the manufacturing examples of the present invention. FIG. 4 (a) shows a shell formed by first adding an organic ligand solution to activated carbon according to Manufacturing Example 3 and then adding a metal solution 30 minutes later; FIG. 4 (b) shows a shell formed by first adding a zinc nitrate hexahydrate solution to activated carbon and then adding a 2-methyl imidazole organic ligand solution 30 minutes later; and FIG. 4 (c) shows a shell formed by adding a zinc nitrate hexahydrate metal solution to a 2-methyl imidazole organic ligand solution and then mixing it with activated carbon 30 minutes later.

[0099] Referring to Fig. 4, Fig. 4 (a) and Fig. 4 (b) show that the core-shell structure is well formed, but Fig. 4 (c) is a comparative example that deviates from the manufacturing method of the present invention. When a metal source and an organic ligand are added to a solvent first and then activated carbon is added, it is difficult to uniformly grow MOF to a certain size on the surface of the activated carbon, and thus the core-shell structured AC@MOF complex is not uniformly formed. In the case of Fig. 4 (c), the seed is formed by MOF alone before MOF is formed as a MOF seed on the surface of the activated carbon core, so the shape of the particle is not uniform. In addition, as shown in Table 1, it can be seen that since ZIF is not uniformly grown on the surface of the activated carbon, the pores of the activated carbon are better maintained, and the specific surface area and total pore volume are high.

[0100] Specific surface area of ​​adsorbent (m) 2 / g)Total pore volume (cm) 3 / g) Fig. 4(a) = Manufacturing Example 3 AC@ZIF-87850.42 Fig. 4(b) AC@ZIF-86230.27 Fig. 4(c) AC@ZIF-88020.35

[0101] Table 2 below, (a) and (b) of Fig. 5 show comparisons of the characteristics of methane adsorbents manufactured according to Manufacturing Examples 1 to 5.

[0102] Specific surface area of ​​adsorbent (m) 2 / g)Total pore volume (cm) 3 / g)CH4 adsorption capacity (mg / g) Manufacturing example 1 AC1, 2910.5715.15 Manufacturing example 2 AC@ZIF-671, 1360.5214.38 Manufacturing example 3 AC@ZIF-87850.4211.76 Manufacturing example 4 AC@MOF-8011, 1140.4716.69 Manufacturing example 5 AC@HKUST-11, 2810.5715.88

[0103] Referring to Table 2, Fig. 5(a), and Fig. 5(b), when MOF was coated on the activated carbon surface, the specific surface area and total pore volume remained the same or even decreased, and the improvement in CH4 adsorption capacity was not evident. This confirmed that the synthesis of AC@MOF without carbonization alone did not sufficiently improve the CH4 adsorption capacity.

[0104] Experimental Example 2

[0105] When AC@MOF is carbonized, a carbonization reaction of MOF occurs, and at this time, changes in the characteristics of MOF according to the carbonization temperature were observed.

[0106] Table 3 below compares the properties of methane adsorbents manufactured by carbonizing ZIF-8.

[0107] MOF adsorbent carbonization temperature ( o C) Specific surface area (m) 2 / g)Total pore volume (cm) 3 / g)CH4 adsorption capacity (mg / g)ZIF-8-7850.4211.768003720.2210.861,0007770.4319.251,2001,1480.7616.98

[0108] Figures 6 (a) and 6 (b) are graphs comparing the characteristics of MOF according to carbonization temperature.

[0109] Referring to Figure 6 (a) and Figure 6 (b), it can be seen that the adsorbent in which MOF is carbonized has superior methane adsorption performance compared to the non-carbonized case. In addition, the carbonization temperature is 800 o 1,200 in C o As C increases, the total pore volume of the adsorbent tends to increase, and the carbonization temperature is 800 o 1,000 in C o As C increases, the methane adsorption capacity increases until 1,200 o It can be seen that when C is reached, there is a tendency to decrease slightly again. Through this, MOF is 900~1200 oIt was confirmed that carbonization in C was the most effective in terms of adsorption performance, and it can be predicted that the same applies to carbonization of AC@MOF.

[0110] Experimental Example 3

[0111] Carbonization of AC and AC@MOF was performed, and the corresponding characteristics were observed.

[0112] Table 4 below shows the adsorbents according to Manufacturing Examples 1 to 5 in an argon atmosphere at 1,000 o The characteristics of methane adsorbents manufactured by carbonization with C are compared and shown.

[0113] Separation adsorbent carbonization temperature ( o C) Specific surface area (m) 2 / g)Total pore volume (cm) 3 / g)CH4 adsorption capacity (mg / g)Comparative Example 1AC1,0001,2910.5715.50Example 1AC@ZIF-671,0001,1250.4919.73Example 2AC@ZIF-81,0001,0650.4720.05Example 3AC@MOF-8011,0001,1310.4919.76Example 4AC@HKUST-11,0001,2500.7017.64

[0114] Fig. 7(a) is an SEM photograph of the surface of core-shell composites for greenhouse gas adsorption manufactured according to Example 1, Fig. 7(b) is an SEM photograph of the surface of core-shell composites for greenhouse gas adsorption manufactured according to Example 2, Fig. 7(c) is an SEM photograph of core-shell composites for greenhouse gas adsorption manufactured according to Example 3, and Fig. 7(d) is an SEM photograph of core-shell composites for greenhouse gas adsorption manufactured according to Example 4. Fig. 8(a) is a graph comparing the total pore volume of core-shell composites for greenhouse gas adsorption manufactured according to Table 4. Fig. 8(b) is a graph comparing the methane adsorption capacity of core-shell composites for greenhouse gas adsorption manufactured according to Table 4.

[0115] As shown in Table 4 and (a) and (b) of Fig. 8, it can be confirmed that carbonized AC@MOF (Examples 1 to 4) has higher methane adsorption performance than carbonized AC (Comparative Example 1).

[0116] Experimental Example 4: Dropout Test

[0117] The results of the drop-off test of the core-shell composite for greenhouse gas adsorption manufactured according to the comparative examples and examples of the present invention are compared and shown in Fig. 9.

[0118] Fig. 9 (a-1) is an AC activated carbon according to Comparative Example 1, and Fig. 9 (b-1) is a photograph showing the amount of detachment after carbonizing AC activated carbon coated with ZIF-8 MOF according to Example 2. A detachment test was conducted by adding ethanol to each sample and performing ultrasonic treatment for 30 minutes.

[0119] Through Figure 9, it was visually confirmed that the amount of dropout in (b-1) was almost zero compared to (a-1). In other words, it can be confirmed that the amount of dropout of activated carbon is reduced due to the MOF coating, and the durability and performance of the adsorbent are improved.

[0120] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. (a) A step of attaching an organic ligand to the surface of the activated carbon by immersing the activated carbon in a solution containing an organic ligand compound; (b) adding a metal source to the solution to obtain a complex coated with a metal-organic framework (MOF) on the surface of the activated carbon; and (c) The above complex is 900 to 1200 o A step of obtaining a core-shell composite in which a porous carbon layer derived from the metal-organic framework is formed on the surface of the activated carbon by carbonizing at a temperature of C for 1 to 3 hours; Method for manufacturing a core-shell composite for greenhouse gas adsorption. 2.(a) A step of attaching metal particles to the surface of the activated carbon by immersing the activated carbon in a solution containing a metal source; (b) a step of adding an organic ligand compound to the solution to obtain a complex coated with a metal-organic framework (MOF) on the surface of the activated carbon; and (c) The above complex is 900 to 1200 o A step of obtaining a core-shell composite in which a porous carbon layer derived from the metal-organic framework is formed on the surface of the activated carbon by carbonizing at a temperature of C for 1 to 3 hours; Method for manufacturing a core-shell composite for greenhouse gas adsorption.

3. In paragraph 1 or 2, The above organic ligand compound is, One selected from the group consisting of 2-methylimidazole, imidazole, salicylic acid, benzenetricarboxylic acid, terephthalic acid (1,4-benzenedicarboxylic acid) and mixtures thereof. Method for manufacturing a core-shell composite for greenhouse gas adsorption.

4. In paragraph 1 or 2, The above metal source comprises at least one metal selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr). Method for manufacturing a core-shell composite for greenhouse gas adsorption.

5. In paragraph 1 or 2, The above complex is, Metal-organic frameworks (MOFs) coated with a thickness of 50 to 300 nm, Method for manufacturing a core-shell composite for greenhouse gas adsorption.

6. In paragraph 1 or 2, The above metal-organic framework is characterized by having a structure in which a metal and an organic ligand form a coordination bond. Method for manufacturing a core-shell composite for greenhouse gas adsorption.

7. Activated carbon core; and A shell comprising a porous carbon layer derived from a metal-organic framework (MOF) surrounding the surface of the activated carbon core; Core-shell composites for greenhouse gas adsorption.

8. In paragraph 7, Specific surface area of ​​700 to 1300 m 2 / characterized by being g, Core-shell composites for greenhouse gas adsorption.

9. In paragraph 7, The total pore volume is 0.3 to 0.7 cm 3 / characterized by being g, Core-shell composites for greenhouse gas adsorption.

10. In paragraph 7, Characterized in that the methane adsorption capacity is 10 to 21 mg / g at room temperature and relative pressure (P / P0) 1. Core-shell composites for greenhouse gas adsorption.

11. In paragraph 7, When greenhouse gases are absorbed, Characterized in that the shape of the activated carbon core is maintained, Core-shell composites for greenhouse gas adsorption.

12. A core-shell composite for greenhouse gas adsorption according to any one of clauses 7 to 11 is provided in a packed structure. Greenhouse gas absorbent.

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