KR101484173B1 - Nanoporous Carbon Material for Gas Sstorage and Preparation Thereof - Google Patents

Abstract

The present invention relates to a nanoporous carbon material for storage and a manufacturing method thereof and, more specifically, to an economical synthesis method for a nanoporous carbon material for gas storage with a porous structure for oxygen storage in which equivalent adsorption heat is applied. The nanoporous carbon material according an embodiment of the present invention is economical since manufacture costs are able to be reduced by using rice bran silica generated in agricultural residues as an inorganic template in a nano-casting process. The nanoporous carbon material increases average isoelectronic adsorption heat up to 7.3 KJ/mol as compared with most porous carbon materials and metal-organic frame structure preferred for hydrogen storage materials operated at room temperature by being synthesized into pores of a specific slit-shape preferring the adsorption of hydrogen molecules and small molecules similar to the same and significantly increases hydrogen storage capacity in which the whole hydrogen adsorption capacity is 5.7 wt% at 7.3 MPa and 77 k in which the volume contribution of pore is 3.29 wt%.

Description

TECHNICAL FIELD [0001] The present invention relates to a nanoporous carbon material for gas storage,

The present invention relates to a nanoporous carbon material for storage and a method of manufacturing the same, and more particularly, to a method for economical synthesis of a nanoporous carbon material for gas storage having a porous structure for oxygen storage using a porous carbon material, .

Hydrogen is one car or two cars as a fuel that can produce from the energy source, in the case of a fuel cell system using the hydrogen to allow the endless production of hydrogen from water, there is no concern of resource depletion and environmental pollution, such as using carbon dioxide (CO ₂₎ It has the advantage of not emitting any substance at all. However, such a fuel cell system requires a hydrogen storage medium in order to utilize hydrogen, and researches for using carbon materials in recent years as such hydrogen storage medium are under way. However, the carbon material has not been clearly identified at present, and it is urgent to develop it for its technical and economic performance. Because of this, the carbon structure is focused on using the most effective porosity for hydrogen storage.

As a result, nanoporous carbon having a small empty space of 1 nm to several nanometers in diameter has been developed. This material is one of the substances of interest as a hydrogen storage medium. Therefore, a large amount of surface area can be increased, so that materials or gases are contained in the pores. However, since the porous material can be used as a carrier after discharging such substances or gases in a specific environment, . However, when hydrogen molecules are decomposed into hydrogen atoms by chemical adsorption due to small interaction energies between hydrogen molecules and carbon atoms, it is impossible to desorb at ordinary temperature and pressure, which is not suitable for use at room temperature. As a countermeasure to this, a synthesis of nano graphite plate type with hydrogen sorbent storage at 80 K or a layered spacer of 8 Å, organometallic addition of buckyball, and hydrogen storage by Kubas coupling of SWNTs with transition metal But hydrogen storage has a limit that is far below expectations.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an economical synthesis method of a porous carbon material, preferably a nanoporous carbon material for gas storage having an oxygen storage pore structure employing an equimolar adsorption heat.

According to an exemplary aspect of the present invention, there is provided a method of producing a mesoporous carbon material for gas storage,

(a) immersing an inorganic template of rice hull silica nanoparticles (RH-SNP) in a carbon source-sulfuric acid mixture in which a carbon source and an aqueous sulfuric acid solution are mixed;

(b) subjecting the mixture of step (a) to primary drying in a drying furnace at a temperature of 90-110 ° C, followed by secondary drying in an drying furnace at a temperature of 150-170 ° C;

(c) after the step (b), heating the dried material to 800-1000 ° C under argon gas to terminate the carbonization;

(d) removing the RH-SNP template using a basic aqueous solution after carbonization in step (c) to obtain a mesoporous carbon material from which the RH-SNP template has been removed;

(e) filtering and washing the mesoporous carbon material from which the RH-SNP template obtained in step (d) has been removed, followed by drying at a temperature of 60-70 ° C to obtain mesoporous carbon To a method for producing a mesoporous carbon material for gas storage.

According to various embodiments of the present invention, since the nanoporous carbon material of the present invention is synthesized by using rice bran silica produced from agricultural wastes as an inorganic template in a nano-casting process, manufacturing cost can be reduced, The nanoporous carbon material is synthesized with hydrogen molecules and certain slit-shaped voids favoring the adsorption of useful similar small molecules, and compared to most porous carbon materials and metal-organic framework structures preferred as hydrogen storage materials operating at room temperature The average heat of adsorption of electrons increased to 7.3 KJ / mol. In addition, the material significantly increased hydrogen storage capacity at 7.3 MPa and 77 k, with a contribution of 3.29 wt% of total vacancy volume, at 5.7 wt% Effect can be achieved.

1 is a SEM image of (a) RH-SNP and (b) a TEM image of RH-SNP according to an embodiment of the present invention.
FIG. 2 is a schematic view illustrating a method of synthesizing porous carbon using a nanocasting method for RH-SNP masses that are differentially typed with carbon species according to an embodiment of the present invention.
3 is a SEM and TEM micrograph of MCs (a, b) and MCg (c, d) according to an embodiment of the present invention.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

According to an aspect of the present invention, there is provided a method for producing a mesoporous carbon material for gas storage,

(a) immersing an inorganic template of rice hull silica nanoparticles (RH-SNP) in a carbon source-sulfuric acid mixture in which a carbon source and an aqueous sulfuric acid solution are mixed;

(b) subjecting the mixture of step (a) to primary drying in a drying furnace at a temperature of 90-110 ° C, followed by secondary drying in an drying furnace at a temperature of 150-170 ° C;

(c) after the step (b), heating the dried material to 800-1000 ° C under argon gas to terminate the carbonization;

(d) removing the RH-SNP template using a basic aqueous solution after carbonization in step (c) to obtain a mesoporous carbon material from which the RH-SNP template has been removed;

(e) filtering and washing the mesoporous carbon material from which the RH-SNP template obtained in step (d) has been removed, followed by drying at a temperature of 60-70 ° C to obtain mesoporous carbon A method for producing a mesoporous carbon material for gas storage is disclosed.

The nanoporous carbon material according to an embodiment of the present invention is economically effective because it is synthesized using rice bran silica produced from agricultural wastes as an inorganic template in a nano-casting process, thereby reducing manufacturing cost.

According to one embodiment of the present invention, the carbon source of step (a) is characterized by being at least one carbon source selected from sucrose and glycerol.

According to another embodiment of the present invention, the basic aqueous solution of step (d) is an aqueous solution of sodium hydroxide.

In the step (d), when silica is removed using a basic aqueous solution of NaOH, there is an effect that silica residue is not generated at all, unlike the case of removing silica using a strong acid of conventional HF.

According to another embodiment of the present invention, the mesoporous carbon material has a slit-like void structure.

Since the mesoporous carbon material according to the embodiment of the present invention has a narrow and long slit-like void structure, it can form a large surface area to maximize adsorption of hydrogen, and the capillary condensation process is performed by the slit- There is an effect that the gas molecules such as hydrogen can be quickly transported from the outside into the particles by solving the problem of clogging of the pores.

According to another embodiment of the present invention, the mesoporous carbon material has a specific surface area of 600-800 m ² / g, a pore volume of 0.7-1.5 cm ³ / g, and a pore diameter of 4-5 nm do.

The specific surface area of the mesoporous carbonaceous material for gas storage according to the embodiment of the present invention has the greatest effect on improving the gas storage ability, and when the specific surface area is less than 600 m ² / g, the specific surface area is too low There may arise a problem of low gas storage value due to a shortage of contact area with sufficient gas, and when it exceeds 800 m ² / g, there may be a difficult problem of gas storage / release behavior due to a too complicated pore structure .

Further, the pore volume is exceeded it is difficult for gas storage, 1.5 cm ³ / g in accordance with too little space when the gas is practically be a bar, a ^trivalent pore volume 0.7 cm / g with a spatial mean that to be stored is less than The fraction of the micropores becomes too small and the space is wide, but the storage amount of the actual gas is low.

Further, the pore diameter affects the depth of the micropore. When the diameter is less than 4 nm, it is practically difficult to provide micropore. When the diameter exceeds 5 nm, the micropore does not protrude to the outside There is a problem in that it can be formed inside.

According to another embodiment of the present invention, the mesoporous carbon material has an average equivalent electron adsorption heat of 7.3 KJ / mol or more, a total hydrogen adsorption amount of 3-3.5 wt%, a total hydrogen storage capacity at 77 K and 7.3 MPa By weight and 5.5 to 6.5% by weight.

The mesoporous carbon material according to the embodiment of the present invention has a composition of a carbon nanotube having an average electron adsorption heat of 7.3 KJ / mol or higher, a carbon activator such as conventionally activated carbon AX-21_33 (5.53 kJ / mol), Norit R0.8 (5 kJ / mol) -5 (4 KJ / mol), and has a structure with an equi-electron adsorption heat larger than the normal physical adsorption, showing a high hydrogen adsorption amount of 3-3.5% by weight, a temperature of 77 K and a pressure of 7.3 MPa The hydrogen storage capacity of the carbon material can be remarkably increased because the total hydrogen storage capacity is 5.5-6.5 wt%.

According to another embodiment of the present invention, the gas is any one of a gas selected from the group consisting of a hydrogen molecule, an oxygen molecule, a nitrogen molecule, and a helium molecule or a material having a void volume smaller than that of the mesoporous carbon material .

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. In addition, it is apparent that, based on the teachings of the present invention including the following examples, those skilled in the art can easily carry out the present invention in which experimental results are not specifically shown.

Example  1: Using sucrose Siege  carbon( MCs )

The mesoporous carbon material was prepared using sucrose as a carbon source, as reported in the prior art. During the synthesis, a certain amount of inorganic template rice hull silica nanoparticles (RH-SNP) was immersed in an aqueous solution of sucrose and sulfuric acid prepared by dissolving a certain amount of sucrose and H ₂ SO ₄ in 5 g of distilled water. The mixture was dried in an oven at 100 DEG C for 6 hours and further dried at 160 DEG C for 6 hours. After a certain amount of sucrose, H ₂ SO ₄ and 5 g of water were added again to the RH-SNP containing partially polymerized and carbonized sucrose, heat treatment (100 ° C./6 hours and 160 ° C./6 hours ). The termination of the carbonization of the sample was carried out by heating at 900 DEG C (heating rate 2 DEG C / min) for 6 hours in argon gas atmosphere. The RH-SNP template was removed by adding an NaOH aqueous solution to the carbonized material, filtered, and washed several times with water and ethanol to obtain a mesoporous carbon material from which the RH-SNP template had been removed. And dried at a temperature of 24 hours to obtain mesoporous carbon represented by MCs.

Example  2: Using glycerol Siege  carbon( MCg )

The mesoporous carbon material was prepared using glycerol as a carbon source, as reported previously. At the time of synthesis, a certain amount of RH-SNP was added to a solution containing 5 ml of water and a predetermined amount of sulfuric acid. The mixture was dried in an oven at 100 DEG C for 6 hours and further dried at 160 DEG C for 6 hours. The termination of the carbonization of the sample was carried out by heating at 900 DEG C (heating rate 2 DEG C / min) for 6 hours in argon gas atmosphere. The RH-SNP template was removed using NaOH aqueous solution, finally filtered, washed several times with water and ethanol to obtain a mesoporous carbon material from which the RH-SNP template had been removed, and then dried at 65 ° C for 24 hours And dried to obtain mesoporous carbon represented by MCg.

As shown in Figs. 1 (a) and 1 (b), the SEM image of the RH-SNP showed that the nano-porous mass having an RH-SNP average diameter of about 50 nm .

The mechanical properties and porosity of the RH-SNPs were studied using nitrogen adsorption measurements via Brunauer-Emmett-Teller (BET) method. The RH-SNP loaf measured nitrogen adsorption-desorption (nitrogen adsorption-desorption isotherms) is typical Ⅳ type behavior and a burst of H ₃ which is characteristic of methoxy early-porous material with the air gap of the slit shape _- shows a magnetic hysteresis curve. As a result of the capillary condensation process, a narrow pore size distribution with an average diameter of 3.67 nm resulted, and thus the BJH pore diameter of the mesoporous RH-SNP showed typical mesopore size.

The structural characteristics, on the other hand, are based on the isotherm specific surface area based on the BET method, the mesopore volume of the mesoporous RH-SNP based on the Barrett-Joyner-Halenda (BJH) method, the total pore volume, , And t-plot method (see Table 1). As shown in Fig. 2, the mesoporous carbon material was prepared by nano-casting using inorganic precursors other than RH-SNP as an inorganic template.

The reaction was carried out using two different carbon sources with different molecular sizes. Glycerol has a molecular size (0.47 nm) that is three times smaller than that of sucrose, which exhibits excellent mobility over sucrose and can be filled by the easy permeation of glycerol molecules into mesoporous RH-SNPs. An excess amount of sucrose carbon source is required to fill the RH-SNP mesopore and a certain amount of the RH-SNP template. The pore structure of the RH-SNP is obtained by converting the solid wall of the mesoporous carbon, The walls can be pores of the mesoporous carbon produced.

The mechanical properties of the two mesoporous carbon materials, MCs and MCg, using sucrose and glycerol carbon sources were determined by the BET calculation method using specific surface area, total pore volume, mesopore volume, microvoid volume, and mean mesopore diameter (See Table 1).

Nitrogen isotherms of the MCs are the IV-type behavior, which is characteristic of a slit-model pore structure of the mesoporous carbon material obtained from the clay layer of mesoporous carbon formed after the removal of the RH-SNP with the same pore structure of the RH- And a clear H ₃ - type magnetic hysteresis curve.

The starting point of the hysteresis of the MCs migrated to a higher relative pressure (0.6) compared to the RH-SNP template (0.44), which indicated the formation of large diameter pores in the mesoporous carbon after dissolution of the RH-SNP wall. As a result of the capillary condensation process, the mesopore peak of 4.2 nm in diameter represents the wall thickness of mesoporous RH-SNP masses. The total pore volumes and surface areas of the MCs were increased compared to the RH-SNP template and were 0.85 cm ³ / g, 0.39 cm ³ / g, and 644 m ² / g and 226 m ² / g, respectively. Nitrogen isotherms of MCg show IV and clear H ₃ -type hysteresis curves, indicating that the mesoporous carbon material obtained from the mesoporous carbonaceous clay layer formed after removing the RH-SNP to maintain the same pore structure of RH- Is a feature of the slit-shaped void structure.

As shown in Table 1, the capillary condensation process of MCg results in a narrow pore size distribution and a mesopore pore diameter of 5.13 nm in diameter. As shown in Table 1, the MCg has a total pore volume greater than MCs, about 1.44 cm ³ / g, and a surface area of 749 m ² / g. The total pore volume values of MCg were measured using a conventional silica nanopore-sucrose nanocomposite (1.02 cm ³ / g), SBA-16 (0.72 cm ³ / g), SBA-15 (1.3 cm ³ / g) 1.0 cm < ³ > / g), it is appropriate to say that the value is high when compared to the value of the mesoporous carbonaceous material prepared using other types of silica templates.

FIG. 3 shows a microscopic morphology of the previously prepared mesoporous carbon material. As shown in Fig. 3 (a), the shape of MCs containing lumpy carbon particles containing mesopores is shown, and the dissolution effect of the RH-SNP template is reflected in the surface area, resulting in an increase in the micropore volume.

The slit-shaped void structure of the MCs carbon model was clearly shown in the TEM image of FIG. 3 (b). The SEM and TEM images of MCg are shown in Figures 3c and 3d and show a smooth surface of mesoporous sintered carbon mass with mesoporous size larger than MCs, which is consistent with the pore-mechanical properties of MCg.

As shown in Table 1, the hydrogen adsorption capacities of the RH-SNP, MCs and MCg were studied using volume measurements at different pressures and temperatures. The hydrogen uptake measurements were performed at 303 K, high pressures of 77 K, 1.9 MPa, and 7.3 MPa. Hydrogen molecules were adversely adsorbed through the physical adsorption mechanism on the mechanical surface of the RH-SNP mass and the previously obtained mesoporous carbon material model. As shown in Table 1, the hydrogen storage capacities of the RH-SNP, MCs and MCg were 0.34 wt%, 1.42 wt% and 1.61 wt% at 1.9 MPa and 77 K, respectively. The type of carbon precursor plays a crucial role in the hydrogen storage capacity of the mesoporous carbonaceous material and the large pore volume of the MCg is 1.44 cm ³ / g and plays an important role in hydrogen absorption capacity as compared to 0.85 cm ³ / g of MCs . On the other hand, the microvoid volume of MCs is 10 times higher than that of MCg, but the total hydrogen adsorption capacity is controlled by the total pore volume at a low temperature of 77 K. At 77 K, the maximum hydrogen absorption capacity of MCs is 1.42 wt% It was confirmed that there was no absorption capacity. As shown in Table 1, the hydrogen uptake of MCg was 1.61 wt% and 2.41 wt% at 1.9 MPa and 7.3 MPa, respectively, and the graphitization and increased porosity of the mesopores using glycerol precursor were confirmed compared to the sucrose precursors And there is a remarkable effect on the hydrogen adsorption capacity. The hydrogen storage capacity of MCs and MCg was measured at 303 K, at which the micropore volume had a much higher effect on the hydrogen storage capacity. The hydrogen storage capacity was 0.18 wt% for MCs and MCg at 7.3 MPa, 0.15 wt%, and MCg has significantly lower microvoid volume than MCs with larger microvoid volume but much larger than MCV, but affects absorption at 303 K.

As evidenced by the TEM image and mechanical properties, the RH-SNP template stores hydrogen molecules with a maximum capacity of 0.87 wt% at 7.3 MPa and 77 K, which has a slit-shaped pore structure and a meso structure with an average diameter of 3.67 nm Indicating the result of the presence of pores. These results confirm that the slit-shaped pores are a preferred pore shape for the storage of hydrogen molecules and other similar small molecules, and that the capacity depends on the diameter and volume of the pores.

On the other hand, the isosteric heat of adsorption was calculated by measuring the adsorption isotherms at 77 K, 87 K and 195 K using the Clausius-Clapey Theorem. As shown in Table 1, the average adsorption heat of MCg is 6.8 KJ / mol and the MCs are 7.3 KJ / mol. This indicates that the hydrogen uptake decreases when the temperature rises. In particular, the hydrogen adsorption isotherm of the MCs at 1 bar is higher than that of MCg, which is related to the higher hydrogen adsorption rate of MCs compared to MCg, and reflects the isothermal adsorption heat of MCs which is higher than MCg, and MCg (0.15 wt%) at 303 K (0.18 wt%) than that of MCs. MCs can be attributed to more bonding structures, and more microvoid volumes than MCg cause many interactions of hydrogen molecules with slit-shaped micropores in carbon sites.

Crystallization of high isoelectronic coalescence heat at low pressure is due to high hydrogen adsorption power and low dependence on temperature is consistent with the previously reported. It is important that the electron adsorption power, such as the average of MCs and MCg, is higher than the activated carbon AX-21_33 (5.53 kJ / mol), Norit R0.8 (5 kJ / mol), and MOF-5 (4 KJ / mol). This indicates that the heat of adsorption is dependent on the pore structure, and the presence of slit-shaped pore structure in MCs and MCg has a significant effect on adsorption heat as compared to the specific surface area, which is the case for MOF-5, AX-21_33 and Norit R0.8 .

In addition, the void volume plays a crucial role in the total hydrogen storage volume, which consists of excess surface adsorption with the storage of hydrogen molecules in the pores of the solid material. Due to the total hydrogen adsorption amount, the void volume effect was shown at the total hydrogen storage of MCg at 77 K and 7.3 MPa. Compressed hydrogen concentrations were obtained from the American National Institute of Standards and Technology. The pore volume of the MCg was 1.44 cm < ³ > / g, and the total hydrogen adsorption amount was 3.29 wt%, which results in a maximum total hydrogen storage capacity of 77 K and 7.3 MPa at 5.7 wt% Both adsorption and pore volume were included and showed high contribution by pore volume.

division RH-SNP MCs MCg S _BET ^a (m ² / g) 226 664 749 V _tot ^b (cm ³ / g) 0.39 0.85 1.44 V _meso ^c (cm ³ / g) 0.36 0.74 1.43 V _micro ^d (cm ³ / g) 0.03 0.11 0.01 D _BJH ^e (nm) 3.67 4.2 5.13 H ₂ Uptake ^f (wt.%) 0.34 (0.87) ^g 1.42 1.61 (2.42) ^g HOA ^h (kJ / mol) - 7.3 6.8

Claims (7)

A method for producing a mesoporous carbon material for gas storage,
(a) immersing an inorganic template of rice hull silica nanoparticles (RH-SNP) in a carbon source-sulfuric acid mixture in which a carbon source and an aqueous sulfuric acid solution are mixed;
(b) subjecting the mixture of step (a) to primary drying in a drying furnace at a temperature of 90-110 ° C, followed by secondary drying in an drying furnace at a temperature of 150-170 ° C;
(c) after the step (b), heating the dried material to 800-1000 ° C under argon gas to terminate the carbonization;
(d) removing the RH-SNP template using a basic aqueous solution after carbonization in step (c) to obtain a mesoporous carbon material from which the RH-SNP template has been removed;
(e) filtering and washing the mesoporous carbon material from which the RH-SNP template obtained in step (d) has been removed, followed by drying at a temperature of 60-70 ° C to obtain mesoporous carbon A method for producing a mesoporous carbon material for gas storage. The method of claim 1, wherein the carbon source of step (a) is at least one carbon source selected from sucrose and glycerol. The method for producing a mesoporous carbon material for gas storage according to claim 1, wherein the basic aqueous solution of step (d) is an aqueous solution containing at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH) Way. The method of claim 1, wherein the mesoporous carbon material has a slit-like void structure. The mesoporous carbon material according to claim 1, wherein the mesoporous carbon material has a specific surface area of 600-800 m ² / g, a pore volume of 0.7-1.5 cm ³ / g, and a pore diameter of 4-5 nm. A method for producing a mesoporous carbonaceous material. The mesoporous carbon material according to claim 1, wherein the mesoporous carbon material has an average equivalent electron adsorption heat of 7.3 KJ / mol or more, a total hydrogen adsorption amount of 3-3.5% by weight, a total hydrogen storage capacity of 77-6.3 MPa, % Of the total weight of the mesoporous carbon material. The gas storage device according to claim 1, wherein the gas is any one of a gas selected from the group consisting of a hydrogen molecule, an oxygen molecule, a nitrogen molecule, and a helium molecule or a material having a void volume smaller than that of the mesoporous carbon material Method of making mesoporous carbon material.

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