KR101402125B1 - Carbon dioxide absorbent and fabricating method thereof - Google Patents

Abstract

There is provided a carbon dioxide absorbent comprising a heterogeneous metal oxide porous body formed by uniformly mixing a carbon dioxide absorbing metal oxide and a support metal oxide. Forming a mixed solution of a precursor of the carbon dioxide absorbing metal oxide and a precursor of the support metal oxide for the production of the carbon dioxide absorbent; Reacting the mixed solution with a liquid phase method to obtain a precipitate; And a step of firing the precipitate to obtain a heterogeneous metal oxide porous body.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to carbon dioxide absorbent and fabricating method,

TECHNICAL FIELD The disclosed technology relates to a carbon dioxide absorbent, and more particularly, to a carbon dioxide absorbent that has a high absorption capacity and can be repeatedly reused.

Techniques for collecting and storing carbon dioxide from a large generation source such as a power plant or a steel mill to suppress release into the atmosphere include a chemical wet cleaning method using alkanolamines, an adsorption method using an adsorbent such as zeolite, Methods are not costly or easy to apply to large sources of carbon dioxide. As an alternative to the above methods, a dry absorption method of absorbing carbon dioxide using particles carrying an alkali metal component in a fluidized bed reactor has been highlighted (US 6,387,337 B1). The dry absorption method uses a low-cost, reproducible solid absorbent, and the flexibility and eco-friendliness of the process design makes it likely that it will be selected as a large-scale carbon dioxide capture method in the near future.

In order to increase the absorption capacity per unit weight in the production of the absorbent to be applied to the above-mentioned dry carbon dioxide absorption method, there have been many studies to enlarge the area in contact with the gas by making a porous structure.

According to an aspect of the present invention, there is provided a carbon dioxide absorbent comprising a heterogeneous metal oxide porous body formed by uniformly mixing a carbon dioxide absorbing metal oxide and a support metal oxide.

According to another aspect of the present invention, there is provided a method for producing a carbon dioxide-absorbing metal oxide, comprising: forming a mixed solution of a precursor of a carbon dioxide-absorbing metal oxide and a precursor of a support metal oxide; Adding a neutralizing agent to the mixed solution and reacting to obtain a precipitate; And a step of firing the precipitate to obtain a heterogeneous metal oxide porous body.

According to still another aspect of the present invention, there is provided a method for producing a carbon dioxide-absorbing metal oxide, comprising: forming a mixed solution of a precursor of a carbon dioxide-absorbing metal oxide and a precursor of a support metal oxide; Reacting the mixed solution with a liquid phase method to obtain a precipitate; And a step of firing the precipitate to obtain a heterogeneous metal oxide porous body.

According to another aspect of the present invention, there is provided a carbon dioxide absorbing metal oxide precursor comprising at least one precursor of a carbon dioxide absorbing metal oxide selected from the group consisting of an alkali metal oxide and an alkaline earth metal oxide; There is provided a carbon dioxide absorbent comprising a heterogeneous metal oxide porous body prepared by reacting a precursor of a support metal oxide selected from the group consisting of silicon oxide, transition metal oxide and transition metal oxide.

1 is a process flow diagram illustrating a method for producing a carbon dioxide absorbent according to an embodiment of the present invention.
2 is an X-ray diffraction chart of the absorbent prepared in Examples 1 and 2;
Fig. 3 shows the nitrogen adsorption / desorption isotherms of the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3.
4 shows the distribution of the pore sizes of the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3.
FIG. 5 is a graph showing changes in carbon dioxide absorption amount obtained by carbon dioxide absorption / regeneration experiments using the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3.
6 is a graph showing changes in carbon dioxide absorption amount obtained by performing the absorption / regeneration experiment as in Experimental Example 1 using the absorbent (CAO-im) obtained in Comparative Example 1. Fig.

Hereinafter, the present invention will be described in detail with reference to the drawings.

The carbon dioxide absorbent according to an embodiment of the present invention includes a heterogeneous metal oxide porous body formed by uniformly mixing a carbon dioxide absorbable metal oxide and a support metal oxide.

Generally, a carbon dioxide absorbent for use in a water-gas shift reaction and a methane-reforming reaction is prepared by adding a metal oxide absorbent capable of absorbing carbon dioxide at a high temperature such as magnesium oxide or calcium oxide . Even if a porous absorbent is prepared, the porous structure is destroyed by repeating the absorption / regeneration of carbon dioxide, so that the carbon dioxide absorbing ability drops sharply. It is therefore desirable to have a porous support that does not react with carbon dioxide and does not lose its structure even at high temperatures.

The carbon dioxide absorbing metal oxide may be at least one selected from the group consisting of alkali metal oxides and alkaline earth metal oxides so as to have excellent carbon dioxide absorption characteristics. On the other hand, the support metal oxide may be at least one selected from the group consisting of silicon oxide, transition metal oxide and transition metal oxide so as not to lose its structure even at a high temperature of, for example, 900 ° C or higher.

Specific examples of the carbon dioxide absorbing metal oxide include lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), magnesium oxide (MgO), calcium oxide (CaO), barium oxide . The specific examples of silicon oxide of a support metal oxide (SiO _2), copper oxide (CuO), iron oxide (Fe ₂ O _3), nickel oxide (NiO), zinc oxide (ZnO), aluminum oxide (Al ₂ O _3), oxide Titanium (TiO ₂ ), zirconium oxide (ZrO ₂ ), and the like.

In one embodiment, the carbon dioxide absorbing metal oxide is selected from the group consisting of a precursor of a carbon dioxide absorbing metal oxide selected from the group consisting of an alkali metal oxide and an alkaline earth metal oxide, a silicon oxide, a transition metal oxide, Can be uniformly mixed at the molecular level by reacting the precursor of the one or more selected support metal oxides in a liquid phase.

Since the carbon dioxide absorbing metal oxide and the support metal oxide constituting the porous body of the different metal oxide are uniformly mixed with each other, the carbon dioxide absorbent according to one embodiment of the present invention is excellent in the carbon dioxide absorbability and mechanical strength at high temperature.

In order to have a high carbon dioxide absorbing performance of the carbon dioxide absorbent, it is generally desirable to maximize the contact area with the gas. For this purpose, it is advantageous to use a structure having small pores or mesopores of 50 nm or less in pore diameter. However, since the inside of the fine pore particles is difficult to contact with the outside due to the narrow pore diameter, it is necessary to have a structure having larger pores so that the gas can easily flow into the inside of the particle considering the reaction speed. Therefore, the heterogeneous metal oxide porous body may have a hierarchical porous structure. The hierarchical porous structure means a structure having not only fine or medium pores for widening the contact area with the gas, but also a large pore structure for increasing the gas input / output and speed.

For example, the pores of the fine size may be 2 nm or less, the pores of the medium size may be 2 to 50 nm, and the pores of the large size may have a size (diameter) of 50 nm or more. Preferably, the porous body of the dissimilar metal oxide may have mesopores of 2 to 50 nm in diameter and macropores of 50 to 150 nm in diameter. In addition, the total volume ratio of the fine pores and the medium pores may be adjusted to 30 to 70% in order to exhibit an optimum absorption ability.

On the other hand, the molar ratio of the carbon dioxide absorbing metal oxide to the support metal oxide may be 1: 9 to 9: 1, preferably 1: 2 to 5: 1. In this range, the carbon dioxide absorption performance of the heterogeneous metal oxide porous body and the mechanical strength in which the porous structure is maintained even at a high temperature can be exhibited.

The porous substrate of the dissimilar metal oxide not only has a high absorption capacity but also does not deteriorate its absorption ability even with repeated absorption / regeneration and can maintain an excellent absorption ability. The absorbing ability can be measured under various conditions. For example, the absorption and regeneration of the carbon dioxide is repeated 30 times for the porous substrate of the dissimilar metal oxide, and then 70% by volume of nitrogen, 15% by volume of water and 15% % Of carbon dioxide gas at a rate of 70 mL / min, the weight of carbon dioxide absorbed can be maintained at 10% or more of the total weight.

The carbon dioxide absorbent according to one embodiment of the present invention can be manufactured in various ways.

1 is a process flow diagram illustrating a method for producing a carbon dioxide absorbent according to an embodiment of the present invention. Referring to FIG. 1, in step S1, a mixed solution of a precursor of a carbon dioxide-absorbing metal oxide and a precursor of a support metal oxide is formed. In step S2, the mixed solution is reacted by a liquid phase method to obtain a precipitate. In the next step S3, the precipitate is calcined to obtain a heterogeneous metal oxide porous body.

The liquid phase method is a method of preparing a fine powder by precipitating a metal compound in the form of a solution and pyrolyzing it. When a fine powder is prepared by the liquid phase method, a fine powder with high purity can be obtained, and the composition and particle size of the product can be controlled. In addition, the carbon dioxide absorbing metal oxide and the support metal oxide can be mixed very uniformly in the produced heterogeneous metal oxide porous body. Examples of the liquid phase method include Sol-Gel method, uniform precipitation method, hydrolysis method, solvent evaporation method, coprecipitation method, hydrothermal synthesis method and microemulsion method.

Preferably, the liquid phase method can be a uniform precipitation method. The uniform precipitation method is one of the methods of making precipitates. It is a method of making sediments with a precipitant which is slowly formed due to the hydrolysis reaction of a reagent substance contained in a solution without adding a precipitant separately. When a uniform precipitation method is used, a heterogeneous metal oxide porous body having a hierarchical porous structure can be obtained. Precipitation from metal oxide precursors occurs due to changes in the pH of the solution, which can be largely dependent on the rate of decomposition of the elements contained in the solution or neutralizing agents such as hexamethylenetetramine. For the gradual precipitation to occur from a homogeneous solution, it is preferred to use a precursor of a metal oxide that is completely soluble in the solvent. The precursors can be dissolved in water or an organic solvent.

The precursor of the carbon dioxide-absorbing metal oxide may be at least one selected from the group consisting of a precursor of an alkali metal oxide and a precursor of an alkaline earth metal oxide. For example, as a precursor of a metal oxide which absorbs carbon dioxide, calcium nitrate (Ca (NO ₃ ) ₂ ), calcium chloride (CaCl ₂ ), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ) ₂ SO ₄ ), lithium chloride (LiCl), sodium carbonate (Na ₂ CO ₃ ), sodium nitrate (NaNO ₃ ), sodium chloride (NaCl), potassium carbonate (K ₂ CO ₃ ), potassium nitrate (KNO ₃ ) K ₂ SO ₄ ), potassium chloride (KCl), magnesium nitrate (Mg (NO ₃ ) ₂ ) and magnesium chloride (MgCl ₂ ).

On the other hand, the precursor of the support metal oxide may be at least one selected from the group consisting of a precursor of silicon oxide, a precursor of transition metal oxide, and a precursor of metal oxide after the precursor. For example, zirconium chloride (ZrCl ₄ ), zirconium oxychloride (ZrOCl ₂ ), zirconium nitrate (Zr (NO ₃ ) ₄ ), zirconium oxynitrate (ZrO (NO ₃ ) ₂ ) Zirconium sulfate (Zr (SO ₄ ) ₂ ), zirconium oxysulfate (ZrOSO ₄ ), titanium chloride (TiCl ₄ ), titanium oxychloride (TiOCl ₂ ), titanium nitrate (Ti (NO ₃ ) ₄ ) (NO _{3) 2),} sulfuric acid, titanium _{(Ti (SO 4) 2)} , oxy-sulfate, titanium (TiOSO _4), aluminum chloride (AlCl _3), aluminum nitrate _{(Al (NO 3) 3)} , aluminum sulfate (Al ₂ ( SO ₄ ) ₃ ).

The molar ratio of the precursor of the carbon dioxide absorbing material to the precursor of the support metal oxide is preferably about 1: 9 to 9: 1. A higher proportion of the precursor of the carbon dioxide-absorbing metal oxide may absorb a greater amount of carbon dioxide per unit weight, but as the proportion of the support decreases, the rate of absorption loss increases due to repeated absorption / regeneration processes, Higher proportions of the precursors may increase durability, but may reduce the ability of carbon dioxide to absorb per unit weight. In order to maintain the durability and to exhibit the best absorption ability, a mole ratio of about 1: 2 to 5: 1 is preferable.

When a uniform precipitation method is used, a neutralizing agent is added to the mixed solution and reacted to obtain a precipitate. As the neutralizing agent, urea or hexamethylenetetramine may be used. For example, when a mixed solution containing a metal oxide precursor is dissolved in a certain proportion of urea or hexamethylenetetramine and heated, a precipitate can be obtained. Precipitates are mixtures of oxides and hydroxides, which undergo firing and are all turned into oxides. The element causing the uniform precipitation or hexamethylenetetramine may be used in an amount of about 1 to 10 times the total molar amount of the metal oxide precursors used, but practically, the amount of the metal oxide precursors is 1 to 3 times Is appropriate.

The distilled water, which is a solvent, needs a sufficient amount to dissolve all the reactants and is adjusted in consideration of the precipitation rate of the precipitate. The amount of the solvent is suitably about 5 to 100 times the weight of the whole reactants. The reaction temperature is suitably in the range of 60 to 200 ° C and is controlled in consideration of the precipitation rate.

Precipitated precipitates are calcined at 600 to 900 ° C for 1 to 24 hours to form metal oxides. Since the size distribution and surface area of pores are different depending on firing temperature and time, optimum sintering time and temperature are determined by observing surface area and pore size of metal oxides through electron scanning microscope and BET adsorption experiment. If the firing time is too long and the temperature is too high, unplanned by-products are formed and the pore structure is destroyed.

Instead of a liquid phase method such as a uniform precipitation method, a method of supporting a carbon dioxide absorbing component on a support having fine pores or mesopores may be used. However, since the amount of the carbon dioxide absorbing component supported on the inside of the pore is not large and the small pores are clogged by the supported absorption component, it is difficult to secure the absorption ability as expected.

A precursor of at least one carbon dioxide absorbing metal oxide selected from the group consisting of alkali metal oxides and alkaline earth metal oxides, for example, through the above-described production method; A carbon dioxide absorbent comprising a heterogeneous metal oxide porous body prepared by reacting at least one precursor of a support metal oxide selected from the group consisting of silicon oxide, transition metal oxide, and transition metal oxide. The porous metal oxide may have a hierarchical porous structure, and may have mesopores of 2 to 50 nm in diameter and macropores of 50 nm or more in diameter.

The heterogeneous metal oxide porous body produced by the production method according to an embodiment of the present invention has both intermediate pores having a size of 2 to 50 nm and large pores having a size of 50 nm or more, and thus has a high carbon dioxide absorbing ability. And may include a high proportion of the carbon dioxide absorbing component.

In addition, the above-described carbon dioxide absorbent can absorb carbon dioxide not only at a low temperature of 50 to 70 DEG C but also at a high temperature of 700 DEG C or more, depending on the type of the metal that absorbs carbon dioxide. Therefore, the above-described carbon dioxide absorbent can be used not only for capturing carbon dioxide generated in the carbon dioxide, steel mill and cement plant contained in the power plant exhaust gas but also as a carbon dioxide absorbing agent in the water gas reaction and methane-steam reforming reaction . The hierarchical porous heterogeneous metal oxide prepared in the present invention is suitable for mass production because it can be produced using a low-cost metal oxide precursor and a low-cost organic material such as urea or hexamethylenetetramine.

Hereinafter, the present invention will be described in more detail by way of examples, but the spirit of the present invention is not limited by the following examples.

(Example)

Example 1

1.00 g of calcium nitrate (Ca (NO ₃ ) ₂ .4H ₂ O) and 3.18 g of aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) were dissolved in 50 mL of distilled water. 1.07 g of the component was dissolved in a mixed solution of calcium nitrate and aluminum nitrate, and then the temperature of the mixed solution was gradually raised to 170 DEG C for 30 minutes. The reaction was continued for 5 hours while maintaining the reaction temperature at 170 占 폚.

After cooling the reaction vessel to room temperature, the precipitated solid was filtered and washed with distilled water. The solid containing water was heated at 100 占 폚 for 3 hours and then calcined at 700 占 폚 for 3 hours to obtain 0.82 g of an absorbent (CAO-0.5).

Example 2

2.00 g of calcium nitrate (Ca (NO ₃ ) ₂ .4H ₂ O) and 3.18 g of aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) were dissolved in 60 mL of distilled water. 1.42 g of the component was dissolved in a mixed solution of calcium nitrate and aluminum nitrate, and the temperature of the mixed solution was raised to 170 DEG C for 30 minutes. The reaction was continued for 5 hours while maintaining the reaction temperature at 170 占 폚.

After cooling the reaction vessel to room temperature, the precipitated solid was filtered and washed with distilled water. The solid containing water was heated at 100 DEG C for 3 hours and then calcined at 700 DEG C for 3 hours to obtain 0.96 g of an absorbent (CAO-1).

Example 3

4.00 g of calcium nitrate (Ca (NO ₃ ) ₂ .4H ₂ O) and 3.18 g of aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) were dissolved in 90 mL of distilled water. 2.14 g of element was dissolved in a mixed solution of calcium nitrate and aluminum nitrate, and then the temperature of the mixed solution was raised to 170 DEG C for 30 minutes. The reaction was continued for 5 hours while maintaining the reaction temperature at 170 占 폚.

After cooling the reaction vessel to room temperature, the precipitated solid was filtered and washed with distilled water. The water-containing solid was heated for 3 hours and then calcined at 700 ° C for 3 hours to obtain 1.36 g of an absorbent (CAO-2).

X-ray diffraction diagrams of the absorbents prepared in Examples 1 and 2 are shown in Fig. Referring to FIG. 2, it can be seen that both aluminum oxide and calcium oxide are present from peaks of aluminum oxide and calcium oxide. As the amount of added calcium nitrate increases, the peak of calcium oxide becomes stronger and the peak of aluminum oxide becomes weaker.

Adsorption / desorption isotherms of the obtained absorbents were determined by using BET method at a temperature of 77 K using liquid nitrogen. The amount of adsorbed / desorbed nitrogen per unit weight according to the change in relative pressure was measured and shown in FIG. Fig. 3 shows the nitrogen adsorption / desorption isotherms of the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3.

On the other hand, the specific surface area, pore volume, and pore size distribution of the adsorbent were determined from the adsorption / desorption isotherm of FIG. Table 1 below shows the specific surface area and pore volume of the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3.

Sample Calcium oxide / aluminum oxide Specific surface area (m ² / g) Pore volume (cm ³ / g) Example 1 (CAO-0.5) 0.5 59 0.19 Example 2 (CAO-1) One 40 0.14 Example 3 (CAO-2) 2 22 0.10

From the results shown in Table 1, the specific surface area and pore volume decrease as the content of calcium oxide increases.

4 shows the distribution of the pore sizes of the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3. The abscissa is the pore width and the ordinate is the volume of the pores. 3 and 4, it can be seen that the absorbents (CAO-0.5, CAO-1, CAO-2) have mesopores (2-50 nm) and macropores (50-150 nm) of various sizes .

Comparative Example 1

For comparison with the carbon dioxide-absorbing dissimilar metal oxide of Example 1 produced by the uniform precipitation method, a material carrying a carbon dioxide absorbing component was prepared on a support having pores.

1.00 g of calcium nitrate (Ca (NO ₃ ) ₂ .4H ₂ O) was dissolved in 20 mL of water to carry calcium oxide of the same ratio as CAO-0.5 of Example 1. Next , 0.82 g of aluminum oxide powder having a hierarchical porous structure prepared by the method disclosed in the article ( Cryst. Growth Des. 2010, 10, 3977) was added to the calcium nitrate solution. Water was slowly evaporated using a rotary evaporator to obtain dry powder, which was then dried at 100 ° C for 3 hours and calcined at 700 ° C for 3 hours to obtain 1.04 g of an absorbent (CAO-im) having calcium oxide supported on porous aluminum oxide .

 The surface area and the pore volume of the aluminum oxide having a hierarchical porous structure synthesized and the absorbent CAO-im having calcium oxide supported thereon were obtained by the BET method and are shown in Table 2.

Table 2 below shows the specific surface area and pore volume of the porous aluminum oxide used as a support and the absorbent (CAO-im) obtained in Comparative Example 1.

Sample Calcium oxide / aluminum oxide Specific surface area (m ² / g) Pore volume (cm ³ / g) Porous aluminum oxide 0 75 0.32 Comparative Example 1 (CAO-im) 0.5 43 0.15

From the results shown in Table 2, when the calcium oxide is supported on the porous aluminum oxide support having fine pores or mesopores, the specific surface area and the pore volume of the absorbent (CAO-im) are reduced because the small pores are clogged by the supported calcium oxide.

Experimental Example 1

Carbon dioxide absorption and regeneration reactions according to the temperatures of the solid samples CAO-0.5, CAO-1 and CAO-2 obtained from Examples 1 to 3 were observed using an Autochem-2920 instrument of micromeritics. A mixed gas consisting of 70 vol% of nitrogen, 15 vol% of water and 15 vol% of carbon dioxide was flowed at a rate of 70 mL / min to make contact with 0.3 g of absorbent at 650 ° C, and the change of the amount of carbon dioxide absorbed by the absorbent And the results are shown in Fig. FIG. 5 is a graph showing changes in carbon dioxide absorption amount obtained by carbon dioxide absorption / regeneration experiments using the absorbents (CAO-0.5, CAO-1, CAO-2) obtained in Examples 1 to 3. The absorbent absorbed carbon dioxide was nitrogen at a rate of 70 mL / min at 850 ° C to desorb the carbon dioxide, and the regeneration experiment was repeated.

Referring to FIG. 5, it can be seen that the absorption capacity of CAO-2 having the largest amount of calcium oxide is the highest, and that the absorption amount becomes constant when the absorption / regeneration is repeated 20 times or more.

Experimental Example 2

 The absorption / regeneration experiment as in Experimental Example 1 was carried out using the absorbent (CAO-im) obtained in Comparative Example 1, and the results are shown in Fig. 6, the amount of calcium in the absorbent (CAO-im) prepared by the supported method is equal to CAO-0.5, the surface area of the calcium oxide-supported substance and the volume of pores are similar to CAO-1, It is not distributed evenly on the support. Therefore, the absorption ability thereof is very low and the decrease of the absorption ability due to repetition of absorption / regeneration is very large.

Claims (16)

And a heterogeneous metal oxide porous body formed by uniformly mixing the carbon dioxide-absorbing metal oxide and the support metal oxide,
Wherein the heterogeneous metal oxide porous material has a hierarchical porous structure including mesopores having a diameter of 2 to 50 nm and macropores having a diameter of 50 to 150 nm. The method according to claim 1,
Wherein the carbon dioxide absorbing metal oxide is at least one selected from the group consisting of an alkali metal oxide and an alkaline earth metal oxide. The method according to claim 1,
Wherein the support metal oxide is at least one selected from the group consisting of silicon oxide, transition metal oxide, and transition metal oxide. delete delete The method according to claim 1,
Wherein the molar ratio of the carbon dioxide absorbing metal oxide to the support metal oxide is 1: 2 to 5: 1. The method according to claim 1,
After the absorption and the regeneration of the carbon dioxide were repeated 30 times, the mixed gas consisting of 70 vol.% Nitrogen, 15 vol.% Water and 15 vol.% Carbon dioxide was flowed at a rate of 70 mL / min at 650 ° C. Carbon dioxide absorbent with an absorbed carbon dioxide weight ratio of at least 10% of the total weight. Forming a mixed solution of a precursor of the carbon dioxide-absorbing metal oxide and a precursor of the support metal oxide;
Adding a neutralizing agent to the mixed solution and reacting to obtain a precipitate in which two metal components are uniformly mixed; And
And calcining the precipitate to obtain a heterogeneous metal oxide porous body. 9. The method of claim 8,
Wherein the precursor of the carbon dioxide absorbing metal oxide is at least one selected from the group consisting of a precursor of an alkali metal oxide and a precursor of an alkaline earth metal oxide. 9. The method of claim 8,
Wherein the precursor of the support metal oxide is at least one selected from the group consisting of a precursor of silicon oxide, a precursor of a transition metal oxide, and a precursor of a metal oxide after the precursor. 9. The method of claim 8,
Wherein said neutralizing agent is urea or hexamethylenetetramine. delete delete delete delete delete

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