KR19980052532A - Carbon dioxide high temperature adsorbent and its manufacturing method - Google Patents

Abstract

Provided is an adsorbent having a high base adsorption capacity and enhanced adsorption capacity for carbon dioxide at a high temperature, and a method of preparing the same. The affinity of the adsorbent surface to carbon dioxide is enhanced by supporting alkali metal or alkaline earth metal oxides, hydroxides or carbonates on a support made of a conventional adsorbent or a substance usable as an adsorbent, thereby increasing the affinity of the adsorbent surface to carbon dioxide at a high temperature of 100 ° C. to 250 ° C. without a cooling step. Carbon dioxide can be efficiently separated and adsorbed from carbon dioxide-containing flue gas.

The adsorbent manufacturing method includes an impregnation method and a synthesis method.

Description

Carbon dioxide high temperature separation adsorbent and its manufacturing method

The present invention relates to an adsorbent used for the separation of carbon dioxide in the flue gas and a method for producing the same, and more particularly, to an adsorbent capable of separating carbon dioxide in a high temperature process flue gas and a method for producing the same.

It is well known that carbon dioxide is a major contributor to global warming, and movements to regulate carbon dioxide emissions are spreading around the world. Various methods have been tried from the viewpoint of disposal, separation, and conversion of carbon dioxide, and double separation methods include absorption method, adsorption method, and membrane method. Until now, the technology of separating and recovering carbon dioxide from mixed gas has been used to absorb potassium carbonate solution or alkanol amine solution. However, the absorption process uses a highly corrosive solution. Adsorption methods have been developed and used for the separation of small and medium-sized carbon dioxide due to high operating costs such as energy consumption and chemical costs for regeneration.

Adsorption method uses selective adsorption of adsorbents on carbon dioxide upon contact with gas containing carbon dioxide and adsorbents. Activated carbon and zeolite molecular sieves with large specific surface area are widely used as adsorbents for carbon dioxide. come.

However, since the conventional adsorbents separate carbon dioxide using only weak physical adsorption force between the carbon dioxide and the adsorbent surface, these adsorbents are rapidly reduced as the temperature rises, and thus the plant exhaust gas having a temperature of 100 ° C-250 ° C. It is not suitable for adsorption and separation of carbon dioxide.

Accordingly, an object of the present invention is to solve the problems of the conventional adsorbent as described above to provide a more improved adsorbent excellent in adsorption capacity even at high temperatures.

Furthermore, another object of the present invention is to provide a method for producing an adsorbent having excellent adsorption capacity even at a high temperature.

The object of the present invention as described above can be achieved by the present invention described below.

1 is a graph comparing the adsorption amount of carbon dioxide at 100 ℃ and 250 ℃ of CaO supported silica gel and unsupported silica gel prepared in Example 1 of the present invention

2 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of CaO-supported activated carbon and unsupported activated carbon prepared in Example 2 of the present invention.

3 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of the CaO-supported carbon black and the unsupported carbon black prepared in Example 3 of the present invention.

4 is a graph comparing the adsorption amount of carbon dioxide at 100 ° C. and 250 ° C. of a CaO supported silica zero gel and an unsupported silica zero gel prepared in Example 4 of the present invention.

5 is a scanning electron micrograph and a Ca distribution diagram by electron probe microanalysis of the adsorbent prepared by the impregnation method prepared in Example 4 of the present invention and the adsorbent prepared by the synthesis method prepared according to Example 5 of the present invention.

Figure 5 (a) is a scanning electron micrograph of the adsorbent prepared according to the synthesis method in Example 5

Figure 5 (b) is Ca distribution diagram of the adsorbent prepared according to the synthesis method in Example 5

Figure 5 (c) is a scanning electron micrograph of the adsorbent prepared according to the impregnation method in Example 4

Figure 5 (d) is a Ca distribution diagram of the adsorbent prepared according to the impregnation method in Example 4

FIG. 6 is a graph comparing carbon dioxide adsorption amounts at 100 ° C. and 250 ° C. of an adsorbent prepared according to the synthesis method of Example 5 and the CaO-supported silica zero gel prepared in Example 4. FIG.

According to the first aspect of the present invention,

There is provided a carbon dioxide adsorbent in which a base is added to a surface of a support made of a conventional adsorbent or a substance usable as an adsorbent.

According to a second aspect of the present invention, a step of dissolving a base or a substance formed of a base by firing in a solvent to form a solution; Impregnating the formed solution with a carrier of a conventional adsorbent or a substance usable as an adsorbent to add a base to the carrier surface; Drying to remove the solvent; And optionally, firing the carrier to convert the base forming material supported on the carrier to a base when a substance that forms a base by firing is used. Provided is a method for producing a carbon dioxide adsorbent by an impregnation method comprising a.

According to a third aspect of the present invention, there is provided a method of preparing a sol, the method comprising: preparing a sol with a whole material capable of sol-gel synthesis; Gelling the sol solution by impregnating and dissolving a base or a substance which forms a base by firing; Drying to remove the solvent; And optionally converting the gel-supported base forming material to a base by firing the gel when using a material that forms a base by the firing; and a method of preparing a carbon dioxide adsorbent by a synthesis method. .

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In general, factors that determine the adsorption capacity of the adsorbent include first, the specific surface area of the adsorbent to which the adsorbent to be adsorbed, and the second, the affinity of the adsorbent's surface to the adsorbent. Here, in room temperature or low temperature adsorption, the specific surface area mainly determines the amount of adsorption, but as the temperature rises, the surface affinity of the adsorbent to the adsorbate acts as an important factor of adsorption.

Therefore, in the separation of carbon dioxide and nitrogen, the present inventors can increase the affinity for carbon dioxide by providing a base on the surface of a conventional adsorbent because carbon dioxide is an acidic gas having a greater polarity and quadrupole than nitrogen. In view of the fact that the adsorption capacity at a high temperature can be improved, studies have been carried out to complete the present invention.

The carbon dioxide adsorbent according to the first aspect of the present invention is obtained by providing a base site on a surface of a carrier made of a conventional adsorbent or a substance usable as an adsorbent.

Common adsorbents or materials usable as adsorbents used as the carrier include activated carbon, zeolites, clays, silica gels, activated carbon fibers, carbon blacks and silica xerogels prepared by sol-gel synthesis. .

The carbon dioxide adsorbent according to the present invention is formed by imparting a base to the surface of the carrier as described above. Examples of the material for providing such a base include bases such as oxides, hydroxides and carbonates of alkali metals or alkaline earth metals. The preferred material is an alkaline earth metal oxide, and more preferably CaO.

Meanwhile, the silica zero gel which can be used as a carrier in the adsorbent of the present invention may be prepared by mixing alkoxides, which are all sol-gel synthesizable substances, with a solvent and a catalyst and gelling them.

The adsorbent according to the first aspect of the present invention as described above is provided with a base such as, for example, CaO on the surface of the carrier to improve the affinity for carbon dioxide, so that the adsorption capacity for carbon dioxide at a high temperature of 100 ~ 250 ℃ It is excellent.

Furthermore, according to the second and third aspects of the present invention, a method for producing the adsorbent of the present invention as described above is provided, respectively, and the method according to the second aspect provides a method for preparing the adsorbent by the impregnation method and the third aspect. The method provides a method for producing an adsorbent by the synthesis method, respectively.

According to a second aspect of the present invention, a method for preparing a carbon dioxide adsorbent by impregnation includes dissolving a base or a substance which forms a base by firing in a solvent to form a solution; Impregnating the formed solution with a carrier of a conventional adsorbent or a substance usable as an adsorbent to add a base to the carrier surface; Drying to remove the solvent; And optionally firing the carrier to convert the base forming material supported on the carrier to a base when a substance is used that forms a base by firing.

The base that can be used in the method is a material that can provide a base as described above, for example, an oxide of an alkali metal or alkaline earth metal, a hydroxide or a carbonate.

However, in the practice of the process of the present invention, when such a base is insoluble in a solvent, these compounds in soluble form may be used. That is, as the substance which forms the smoke by firing, salts thereof which are soluble in alkali metals such as Ca and Mg, acetates, nitrates, and other solvents of alkaline earth metals are preferred. Ca (CH ₃ COO) ₂ .H ₂ O.

The base or the substance forming the base by firing is dissolved in a solvent such as water or an organic solvent to form a solution, and then the solution is impregnated with the carrier as mentioned above.

When the carrier is impregnated with the base solution and stirred for a predetermined time, the base is attached to the surface of the carrier to increase affinity with carbon dioxide.

In the case where the carrier is impregnated with the substance which forms the base by firing instead of the base, the basic forming substance supported on the carrier must be converted to the base by calcining the carrier in the subsequent process.

After impregnating the carrier in the base solution, the used solvent is removed by drying or the like, and such a removing process may use a conventional solvent removing method.

In addition, according to the third aspect of the present invention, a method for preparing a carbon dioxide adsorbent by the synthesis method includes preparing a sol from all materials capable of sol-gel synthesis; Gelling the sol solution by impregnating and dissolving a base or a substance which forms a base by firing; Drying to remove the solvent; And optionally firing the gel to convert the base forming material supported on the gel into a base when using the material forming the base by the firing.

In this method, the sol is first synthesized by mixing the entire substance capable of sol-gel synthesis with a solvent. All materials capable of sol-gel synthesis include alkoxides, and Si (OC ₂ H ₅ ) ₄ is preferable as the alkoxide. The sol solution thus prepared is subjected to gelation by impregnating and dissolving the above-described base or a substance which forms a base by firing.

According to this process, a carrier having a base portion is provided on the surface thereof. In the present invention, as a substance which forms a base by firing, acetates, nitrates of alkali metals or alkaline earth metals, and other substances of the aforementioned kind can be used. The preferred is acetate of alkaline earth metal, more preferably Ca (CH ₃ COO) ₂ H ₂ O.

The amount of the material to be impregnated is preferably less than the saturation amount which is the limit that can be dissolved in the sol solution.

Also, impregnated materials can change the pH of the sol solution to promote gel formation, but too fast gelation can interfere with even dispersal of the impregnated material, so the amount of material impregnated must be properly controlled to ensure that the base is evenly distributed within the carrier. A dispersed adsorbent can be obtained. Thereafter, the synthesized gel is dried to remove the solvent. However, in the present invention, when using a material that forms a base by firing, the material supported in the pores of the gel is converted into a base by firing in a post process.

The base-supported carbon dioxide adsorbent of the present invention prepared by the above method has a significant improvement in carbon dioxide adsorption capacity, particularly at high temperature, as compared with conventional adsorbents which depend only on physical adsorption due to increased affinity for carbon dioxide as well as physical adsorption.

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

The time point of carbon dioxide adsorption performed in all examples of the present invention was carried out by the following method.

The pressure of carbon dioxide was carried out to about 1 atmosphere by the static method. The sample used about 0.1 gram of adsorbent. First, carbon dioxide was contacted with the surface of the sample to weaken the affinity for irreversible strong bases for small dioxide. From the second input of carbon dioxide, the equilibrium pressure was measured and the adsorption amount was determined by the gas equation. As a result of repeating the carbon dioxide adsorption experiment of the sample many times, it was found that reversible adsorption occurred in all examples. Adsorption amount of the adsorbent prepared in each example is summarized in Table 1 below.

Example 1

Silica gel having a specific surface area of 680 m2 / g and an average pore size of 12 Å was impregnated in a saturated aqueous solution of Ca (CH ₃ COO) ₂ · H ₂ O for 5 hours, evaporated moisture in vacuo, and then at 700 ° C. for 2 hours. Calcined for The resulting base adsorbent had a specific surface area of 290 m 2 / g and an average pore size of 13 mm 3. The amount of CaO supported was 2.25 mol of CaO per 100 mol of silica.

1 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of a silica gel containing CaO containing in the present Example and an unsupported silica gel. According to FIG. 1, the adsorption amount of the unsupported silica gel at normal pressure is 0.28 mmol / g and 0.060 mmol / g at 100 ° C. and 250 ° C., respectively, but 0.42 mmol / g and 0.20 mmol / g, respectively, for the CaO supported adsorbent. It can be seen that it shows a high adsorption amount.

Example 2

A base addition adsorbent was prepared in the same manner as in Example 1 using activated carbon having a specific surface area of 3,000 m 2 / g and an average pore size of 11 GPa. Base adsorbent prepared in this manner had a specific surface area of 1,500 m 2 / g and an average pore size of 13 kPa. The amount of CaO supported was 8.19 mol of CaO per 100 mol.

FIG. 2 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of the activated carbon and the unsupported activated carbon prepared in the present Example. The adsorption amount of the unsupported activated carbon at atmospheric pressure was 0.84 mmol / g and 0.15 mmol / g at 100 ° C. and 250 ° C., respectively, and 0.69 mmol / g and 0.21 mmol / g for CaO-supported adsorbent, respectively.

At 100 ° C, the adsorption amount of the unsupported activated carbon is larger because the specific surface area is much larger than that of the CaO-supported adsorbent. However, the adsorption amount of activated carbon carrying CaO was large at a high temperature of 250 ° C.

When the adsorption amount was calculated per specific surface area, the adsorption amount per specific surface area at the atmospheric pressure of the unsupported adsorbent was 0.27 μmol / m 2 and 0.048 μmol / m 2 at 100 ° C and 250 ° C, respectively, and the CaO-supported adsorbent was 0.46μmol / m 2 and 0.14 It is understood that the adsorbent impregnated with CaO has a large adsorption amount at high temperature when the latter has a larger adsorption amount and the specific surface area is the same.

Example 3

A base addition adsorbent was prepared in the same manner as in Example 1 using carbon black having a specific surface area of 225 m 2 / g and an average pore size of 28 mm 3. The base addition adsorbent prepared in this manner had a specific surface area of 141 m 2 / g and an average pore size of 27 kPa. The amount of CaO supported was 7.77 mol of CaO per 100 mol of carbon.

3 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of the carbon black carrying CaO and the unsupported carbon black prepared in the present example. The adsorption amount of carbon black unsupported at atmospheric pressure was 0.20 mmol / g and 0.046 mmol / g at 100 ° C. and 250 ° C., respectively, and 0.16 mmol / g and 0.092 mmol / g for CaO-supported adsorbent, respectively. At 100, the adsorption amount was similar, but at 250, the adsorption amount of carbon black carrying CaO was large.

When the adsorption amount is calculated per specific surface area, the adsorption amount per specific surface area at normal pressure of unsupported adsorbent is 0.882μmol / m2 and 0.204μmol / m2 respectively at 100 ℃ and 250 ℃, and CaO-supported adsorbent is 1.16μmol / ㎡ and As the latter has a large adsorption amount of 0.657 µmol / m 2, it can be seen that when the specific surface area is the same, the adsorbent impregnated with CaO has a large adsorption amount at high temperature.

Example 4

In this embodiment, a silica xgel is prepared by sol-gel synthesis, and an adsorbent for carbon dioxide is prepared by impregnation using the support as a carrier.

_{Si (OC 2 H 5) 4} , n- propanol, water, hydrochloric acid 1: 3: 1: NH were mixed in a molar ratio of 0.0007, and synthesizing the sol that is used with water and a base catalyst for the Si 1 mole here ₄ OH Was added at a molar ratio of 3: 0.001 and gelled, followed by drying to synthesize a silica gel (xerogel). The prepared silica gel had a specific surface area of 530 m 2 / g and an average pore size of 11 mm 3.

A base-added adsorbent was prepared in the same manner as in Example 1 using silica zero gel as a support.

The base addition adsorbent prepared in this manner had a specific surface area of 500 m 2 / g and an average pore size of 13 kPa. The amount of CaO supported was 7.42 mol of CaO per 100 mol of silica.

FIG. 4 is a graph comparing carbon dioxide adsorption amounts at 100 ° C. and 250 ° C. of the silica zero gel carrying CaO and the unsupported silica zero gel. The adsorption amount of the unsupported silica zero gel at normal pressure was 0.21 mmol / g and 0.022 mmol / g at 100 ° C. and 250 ° C., respectively, while the adsorption of CaO was 0.34 mmol / g and 0.13 mmol / g, respectively. Showed the amount.

Example 5

This embodiment relates to a method for producing a carbon dioxide adsorbent by a synthesis method.

The sol was prepared in the same manner as in Example 4. Water and Ca (CH ₃ COO) ₂ H ₂ O were added to the mole ratio of Si at a molar ratio of 7: 0.1, and after gelling and drying, the mixture was calcined at 700 ° C. for 2 hours to prepare an adsorbent. Prepared.

The base addition adsorbent prepared in this manner had a specific surface area of 670 m 2 / g and an average pore size of 19 kPa. Comparing CaO-supported silica zero gel prepared in Example 4 with its morphological characteristics, the silica zero gel mainly developed micropores, whereas the adsorbent prepared by the synthesis method in this example mainly developed mesopores and had a specific surface area and The porosity was large because the pore volume was large.

The amount of CaO supported was 8.25 moles of CaO per 100 moles of silica, which was consistent with the amount of CaO added during the synthesis. In the impregnation method from Example 1 to Example 4, this was found to be an advantage of the synthesis method considering that the amount of the lower impregnation varies with the impregnation time and the adjustment of the impregnation amount is difficult.

FIG. 5 is a scanning electron micrograph of the adsorbent prepared by the synthesis method prepared in the present embodiment and the adsorbent prepared by the incorporation method prepared in Example 4, and the distribution map of Ca by the electron probe microanalysis.

The adsorbents produced by impregnation had a relatively smooth surface and a very even distribution of Ca, while the adsorbents by the synthesis had a rough surface and a relatively even distribution of Ca.

FIG. 6 is a graph comparing the amount of carbon dioxide adsorption at 100 ° C. and 250 ° C. of an adsorbent prepared by the synthesis method of the present example and a CaO-supported silica zero gel prepared in Example 4. FIG. The adsorption amount of the unsupported silica zero gel at normal pressure was 0.21 mmol / g and 0.022 at 100 ° C and 250 ° C, respectively, whereas the CaO-supported adsorbent prepared by the synthesis method was 0.34 mmol / g and 0.24 mmol / g, respectively. It showed a high adsorption amount.

TABLE 1

As described above, the carbon dioxide adsorbent according to the present invention increases the affinity for carbon dioxide by adding a base to the surface thereof, thereby greatly improving the adsorption capacity for carbon dioxide at high temperature.

Claims (22)

Carbon dioxide adsorbent by adding base sites to the surface of the support of ordinary adsorbents or materials usable as adsorbents The adsorbent of claim 1, wherein the support is selected from the group consisting of activated carbon, zeolite, clay, silica gel, activated carbon fiber and carbon black. The adsorbent of claim 1, wherein the support is a silica xerogel prepared by sol-gel synthesis. The adsorbent according to any one of claims 1 to 3, wherein the base-substance giving substance is an oxide, hydroxide or carbonate of an alkali metal or an alkaline earth metal. 5. The adsorbent as claimed in claim 4, wherein the base giving substance is an oxide of alkaline earth metal. The adsorbent of claim 5, wherein the alkaline earth metal oxide is CaO. The adsorbent of claim 1, wherein the adsorbent is prepared by adding a base material or a substance capable of forming a base by firing in a sol state during sol gel synthesis of silica zero gel, and gelling the adsorbent. Dissolving a base or a substance formed by base by firing in a solvent to form a solution; Impregnating the formed solution with a carrier of a conventional adsorbent or a substance usable as an adsorbent to add a base to the carrier surface; Drying to remove the solvent; And Optionally firing the carrier to convert the base forming material supported on the carrier to a base if a substance is used that forms a base by firing; Method for producing carbon dioxide adsorbent by impregnation method comprising a The method of claim 8, wherein the support is selected from the group consisting of activated carbon, zeolite, clay, silica gel, activated carbon fibers and carbon black. The method of claim 8, wherein the support is a silica xerogel prepared by sol-gel synthesis. The method of claim 8, wherein the base is an oxide, hydroxide or carbonate of an alkali metal or an alkaline earth metal. The method of claim 11, wherein the base is CaO. The method of claim 8, wherein the material formed by the firing is a salt of an alkali metal or an alkaline earth metal. The method of claim 13, wherein the material formed as a base by firing is an acetate of an alkaline earth metal. 15. The method of claim 14, wherein the alkaline earth metal acetate is Ca (CH ₃ COO) ₂ H ₂ O. Preparing a sol from all materials capable of sol-gel synthesis; Gelling the sol solution by impregnating and dissolving a base or a substance which forms a base by firing; Drying to remove the solvent; And Optionally, calcining the gel to convert the base forming material supported on the gel into a base when a substance which forms the base by the calcining is used; Method for producing carbon dioxide adsorbent by impregnation method comprising a The method of claim 16, wherein all the materials capable of sol-gel synthesis are alkoxides. The method of claim 17, wherein the entire material capable of sol-gel synthesis is Si (OC ₂ H ₅ ) ₄ . The method of claim 18, wherein the base is CaO. The method of claim 16, wherein the material which forms the base by firing is an acid salt of an alkali metal or an alkaline earth metal. 21. The method of claim 20, wherein the material which forms the base by firing is an acetate of an alkaline earth metal. The method of claim 21, wherein the alkaline earth metal acetate is Ca (CH ₃ COO) ₂ H ₂ O